First Report of Golovinomyces bolayi Causing Powdery Mildew on Lettuce in Mexico.

In August 2022, powdery mildew symptoms were detected on lettuce (Lactuca sativa) in a commercial field located in Quecholac, Puebla, Mexico. Signs appeared as whitish powdery masses on leaves. Disease incidence was about 100% and signs covered up to 40% of leaf surface. Mycelium was amphigenous forming white patches. Hyphal appressoria were indistinct or nipple-shaped and solitary. Conidiophores (n= 30) were hyaline, erect, arising from the upper surface of hyphal mother cells or lateral, and of 90 to 201 µm long. Foot cells were cylindrical, of 49 to 92 × 10-15 µm, followed by 1-3 shorter cells, and forming conidia in chains. Conidia (n= 100) were hyaline, ellipsoid-ovoid, doliiform-subcylindrical, 27 to 40 × 14 to 20 µm. Conidial germination belonging to the Euoidium type. Chasmothecia were not observed. The morphological characters were consistent with those of Golovinomyces bolayi (Braun et al. 2019). A voucher specimen was deposited in the Herbarium of the Department of Agricultural Parasitology at the Chapingo Autonomous University under accession number UACH451. To confirm the identification of the fungus, genomic DNA was extracted from conidia and mycelium following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region was amplified by PCR using the primers ITS5/ITS4 (White et al. 1990) and sequenced. The resulting 506 bp sequence had 100% identity to those of G. bolayi (LC417109 and LC417106). Phylogenetic analyses using the Maximum Likelihood and Maximum Parsimony methods were performed and confirmed the results obtained in the morphological analysis. The isolate UACH451 grouped in a clade with isolates of G. bolayi. The ITS sequence was deposited in GenBank under accession number OR467546. Pathogenicity was confirmed by gently dusting conidia onto ten leaves of healthy lettuce plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 30 ºC, and relative humidity of 70%. All inoculated leaves developed similar symptoms to the original observation after 10 days, whereas control leaves remained disease free. Microscopic examination of the fungus on inoculated leaves showed that it was morphologically identical to that originally observed. Based on morphological data and phylogenetic analysis, the fungus was identified as G. bolayi. This pathogen has been previously reported causing powdery mildew on lettuce in Argentina, Canada, Chile, Ecuador, Peru, USA and Venezuela (Braun et al. 2019; Mieslerová et al. 2020). To our knowledge, this is the first report of G. bolayi causing powdery mildew on lettuce in Mexico.

Viruses of plant-pathogenic fungi: a promising biocontrol strategy for Sclerotinia sclerotiorum.

Plant pathogenic fungi pose a significant and ongoing threat to agriculture and food security, causing economic losses and significantly reducing crop yields. Effectively managing these fungal diseases is crucial for sustaining agricultural productivity, and in this context, mycoviruses have emerged as a promising biocontrol option. These viruses alter the physiology of their fungal hosts and their interactions with the host plants. This review encompasses the extensive diversity of reported mycoviruses, including their taxonomic classification and range of fungal hosts. We highlight representative examples of mycoviruses that affect economically significant plant-pathogenic fungi and their distinctive characteristics, with a particular emphasis on mycoviruses impacting Sclerotinia sclerotiorum. These mycoviruses exhibit significant potential for biocontrol, supported by their specificity, efficacy, and environmental safety. This positions mycoviruses as valuable tools in crop protection against diseases caused by this pathogen, maintaining their study and application as promising research areas in agricultural biotechnology. The remarkable diversity of mycoviruses, coupled with their ability to infect a broad range of plant-pathogenic fungi, inspires optimism, and suggests that these viruses have the potential to serve as an effective management strategy against major fungi-causing plant diseases worldwide.

First Report of White Mold Caused by Sclerotinia sclerotiorum on Brussels Sprouts in Mexico.

The Brussels sprout (Brassica oleracea var. gemmifera) is a cruciferous vegetable with high health-promoting value and Mexico is one of the most valuable exporters worldwide (Data Mexico 2023). From September to November 2021, white mold symptoms (Rimmer et al. 2007) were observed in Brussels sprouts (cv. Confidant) fields in Tonatico, Estado de México, Mexico. Irregular, necrotic lesions were observed on leaves, whereas abundant white mycelium, and later black sclerotia were produced outside and inside of stems. Disease incidence ranged from 20 to 40% in five fields. For fungal isolation, symptomatic stem pieces were surface sterilized with 2% sodium hypochlorite for 2 min, rinsed in sterilized distilled water twice, placed on PDA medium, and incubated at 25°C in darkness for 3 days. Sclerotinia-like colonies were consistently obtained and six isolates were purified by the hyphal-tip method. Fungal colonies were white and fluffy. Irregular, black, and small (3 to 6 mm diameter) sclerotia were produced at the edge of colonies after 5 days of incubation. The morphological characters were consistent with those of Sclerotinia sclerotiorum (Saharan and Mehta 2008). Two representative isolates were selected for molecular analysis and pathogenicity tests. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi at the Colegio Superior Agropecuario del Estado de Guerrero under the accession numbers CSAEG50 and CSAEG51. For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR and sequenced using the primer pair ITS5/ITS4 (White et al. 1990). The sequences were deposited in GenBank (accession nos. OQ878510 and OQ878511). BLASTn searches in GenBank showed 100% identity with the available sequences of Sclerotinia sclerotiorum (accession nos. OQ891471, OQ891472, HQ833448, and MT177216). A phylogenetic analysis using the Maximum Likelihood method placed isolates CSAEG50 and CSAEG51 in the same clade as S. sclerotiorum. Pathogenicity tests were performed by inoculating 10 healthy Brussels sprout seedlings (cv. Confidant) grown in pots. A mycelial plug was directly placed on the stem of each plant. Five uninoculated Brussels sprout seedlings were used as control. All plants were placed in a moist chamber at 25°C with a 12-h photoperiod for 2 days. White mold symptoms appeared on inoculated plants after 3 days, whereas control plants remained symptomless. The fungi were reisolated from the infected plants and found to be morphologically identical to the isolates used for inoculation, fulfilling Koch's postulates. Pathogenicity test was performed twice with similar results. Sclerotinia sclerotiorum has been previously reported to infect Brussels sprouts in the USA (Campbell 1947). To our knowledge, this is the first report of Sclerotinia sclerotiorum causing white mold of Brussels sprouts in Mexico. The disease is widely distributed in Brussels sprouts fields in the central region of Mexico, therefore additional studies are needed to develop effective disease-management strategies.

First Report of Peach Scab Caused by Cladosporium tenuissimum in Mexico.

Peach (Prunus persica) is one of the most popular stone fruits in the world. From 2019 to 2022, typical scab symptoms were observed on 70% of peach fruits in a commercial orchard in Tepeyahualco, Puebla, Mexico (19°30'38"N 97°30'57"W). Fruit symptoms are black circular lesions of 0.3 mm in diameter. The fungus was isolated from symptomatic fruit pieces that were surface sterilized with 1% sodium hypochlorite for 30 s, rinsed in autoclaved distilled water three times, placed on PDA medium, and incubated at 28°C in darkness for 9 days. Cladosporium-like colonies were isolated. Pure cultures were obtained by single spore culture. Colonies on PDA showed aerial mycelium abundant, smoke-grey, fluffy, and with margin glabrous to feathery. Conidiophores were solitary, long, intercalary conidia narrow erect, macro- and micronematous, straight or slightly flexuous, cylindrical-oblong, olivaceous-brown, and often subnodulose. Conidia (n= 50) catenate in branched chains, obovoid to limoniform, sometimes globose, aseptate, olivaceous-brown, apically rounded, 3.1 to 5.1 × 2.5 to 3.4 µm. Secondary ramoconidia (n= 50) were fusiform to cylindrical, smooth-walled, 0-1-septate, pale brown or pale olivaceous-brown, measuring 9.1 to 20.8 × 2.9 to 4.8 µm. Morphology was consistent to that described for Cladosporium tenuissimum (Bensch et al. 2012; 2018). A representative isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Department of Agricultural Parasitology at the Chapingo Autonomous University under the accession number UACH-Tepe2. To further confirm the morphological identification, total DNA was extracted using the cetyltrimethylammonium bromide method (Doyle and Doyle 1990). The internal transcribed spacer (ITS) region, partial sequences of the translation elongation factor 1-alpha (EF1-α) and actin (act) genes were amplified by PCR, and sequenced using the primer pairs ITS5/ITS4 (White et al. 1990), EF1-728F/986R, and ACT-512F/783R (Carbone and Kohn 1999), respectively. The sequences were deposited in GenBank under the accession numbers OL851529 (ITS), OM363733 (EF1-α), and OM363734 (act). BLASTn searches in GenBank showed 100% identity with available sequences of Cladosporium tenuissimum accession (ITS: MH810309; EF1-α: OL504967; act: MK314650). A phylogenetic analysis using the maximum likelihood method placed isolate UACH-Tepe2 in the same clade as C. tenuissimum. To verify the pathogenicity of the fungus, 20 healthy peach fruits were inoculated with four drops of 15 µl of a conidial suspension (1 × 106 spores /ml). Ten control fruit were treated with sterilized water. All the fruits were kept in a moist chamber at 25°C for 10 days. Circular and necrotic lesions were produced eight days after inoculation, whereas control fruits remained healthy. Pathogenicity test was conducted three times with similar results. Fungal colonies were reisolated from the artificially inoculated fruit, thus fulfilling Koch's postulates. Cladosporium tenuissimum has been previously reported to cause diseases on strawberry, cashew, papaya, and passionfruit in Brazil (Rosado et al. 2019; Santos et al. 2020), as well as diseases on pitaya, hydrangea, and carnation in China (Xu et al. 2020; Li et al. 2021; Xie et al. 2021). Cladosporium carpophilum is reported as the causal agent of peach scab. The environmental conditions for the development of C. carpophilum are 20-30 °C in warm humid areas (Lawrence and Zehr 1982), however, in this case the infection by C. tenuissinum occurred in a temperate semi-dry climate, with temperatures of 5 -15 °C and R.H. less than 50 % with an incidence of 80 %. To our knowledge, this is the first report of Cladosporium tenuissimum causing peach scab in Mexico and worldwide.

First Report of Bacterial Wilt of Eggplant (Solanum melongena) Caused by Ralstonia pseudosolanacearum in Mexico.

Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is a major disease of solanaceous crops worldwide. In May 2022, symptoms of wilting, yellowing, and reduced growth were observed on eggplant (Solanum melongena) cv. Barcelona in a commercial greenhouse located in Culiacán, Sinaloa, Mexico. The disease incidence was recorded up to 30%. Sections of stems from diseased plants showed discoloration of the vascular tissue and the pith. Colonies with typical RSSC morphology were isolated from five eggplant stems on Petri plates containing casamino acid-peptone-glucose (CPG) medium supplemented with 1% 2,3,5-triphenyltetrazolium chloride (TZC), and incubated at 25°C for 48-h (Schaad et al. 2001; Garcia et al. 2019). On CPG medium + TZC, white and irregular colonies with pinkish centers were observed. On King's B medium, mucoid and white colonies were produced. The strains were Gram-negative in the KOH test and were nonfluorescent on King's B medium. Strains were positive using commercial Rs ImmunoStrip® (Agdia, USA). For molecular identification, DNA was extracted, and the partial endoglucanase gene (egl) was amplified by PCR and sequenced using the primer pair Endo-F/Endo-R (Fegan and Prior 2005). BLASTn searches showed 100% identity with available sequences of R. pseudosolanacearum from Musa sp. in Colombia (MW016967) and from Eucalyptus pellita in Indonesia (MW748363, MW748376, MW748377, MW748379, MW748380, MW748382). To confirm the bacterial identity, DNA was amplified with the primers 759/760 (Opina et al. 1997) and Nmult21:1F/Nmult22:RR (Fegan and Prior 2005) to generate 280 and 144-bp amplicons for RSSC and phylotype I (= R. pseudosolanacearum), respectively. A phylogenetic analysis was performed using the Maximum Likelihood method and the strain was distinguished as R. pseudosolanacearum sequevar 14. The strain (CCLF369) is currently preserved in the Culture Collection of the Research Center for Food and Development (Culiacán, Sinaloa, Mexico) and the sequence was deposited in GenBank (accession number OQ559102). Pathogenicity tests were performed by injection of 20-µl of a bacterial suspension (108 CFU/ml) at the base of the stem of five eggplants cv. Barcelona. Five plants inoculated with sterile distilled water were used as control. Plants were kept in a greenhouse at 28/37°C (night/day) for 12 days. All inoculated plants exhibited wilting, chlorosis, and necrosis of leaves between 8 and 11 days after inoculation, whereas control plants remained asymptomatic. The bacterial strain was only isolated from symptomatic plants and confirmed to be R. pseudosolanacearum using the molecular techniques mentioned above, fulfilling Koch´s postulates. Ralstonia pseudosolanacearum has been previously reported to cause bacterial wilt of tomato in Sinaloa, Mexico (García-Estrada et al. 2023); however, to our knowledge, this is the first report of R. pseudosolanacearum infecting eggplant in Mexico. Further studies on epidemiology and management strategies for this disease are required on vegetable crops in Mexico.

First Report of Colletotrichum tropicale Causing Anthracnose on Pitahaya Fruit in Mexico.

Pitahaya (Hylocereus spp.), also called dragon fruit, is a cultivated cactus that is native to Mexico as well as Central and South America. In October 2021, anthracnose symptoms were observed on fruit of pitahaya (Hylocereus costaricensis) in a commercial orchard located in Culiacán, Sinaloa, Mexico. Lesions on fruit were circular, sunken, dark brown and with halo. To fungal isolation, small pieces from adjacent tissue to lesions of symptomatic fruits were surface disinfested by immersion in a 2% sodium hypochlorite solution for 2 min, rinsed in sterile distilled water, and placed in Petri plates containing potato dextrose agar (PDA). The plates were incubated at 25 ºC for 5 days in darkness. Colletotrichum-like colonies were consistently observed on PDA and five monoconidial isolates were obtained. An isolate was selected as a representative for morphological identification, multilocus phylogenetic analysis, and pathogenicity tests. The isolate was deposited as CCLF186 in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa). On PDA, initially white colonies turned grey with abundant orange conidia masses at 8 days after incubation at 25 ºC. Conidia were cylindrical, with ends rounded, aseptate, hyaline, and measuring 15.2 to 18.9 × 4.3 to 6.4 µm (n= 100). Appressoria were terminal, subglobose to clavate, of 7.4 to 11.6 × 5.9 to 8.2 µm (n= 30). Setae were not observed. These morphological characters were consistent with those reported for the Colletotrichum gloeosporioides species complex (Weir et al. 2012). To determine the phylogenetic identity of the isolate CCLF186, genomic DNA was extracted following the CTAB method (Doyle and Doyle 1990), and the internal transcribed spacer (ITS) region, the ApMat intergenic region, as well as partial sequences of actin (act) and glyceraldehyde-3-phosphate dehydrogenase (gapdh) genes were amplified and sequenced using the primers pairs ITS5/ITS4 (White et al. 1990), AM-F/AM-R (Silva et al. 2012), GDF/GDR, and ACT-512F/ACT-783R (Weir et al. 2012), respectively. The sequences were deposited in GenBank under accession nos. OP269659 (ITS), OP302778 (gapdh), OP302777 (act), and OP302779 (ApMat). BLASTn searches revealed high identity with sequences of C. tropicale (CBS 124949) for ITS (100%), ApMat (100%), act (100%), and gapdh (100%). A phylogenetic tree based on Bayesian inference and Maximum Likelihood methods, including published ITS, ApMat, act, and gapdh sequence datasets for isolates in the Colletotrichum gloeosporioides species complex was generated. The phylogenetic analysis based on the concatenated sequences clustered the isolate CCLF186 with the C. tropicale reference isolates. Pathogenicity of the isolate CCLF186 was confirmed on 10 healthy pitahaya fruits without wounds. A drop of a conidial suspension (1 × 105 spores/ml) was placed on two locations on each fruit. Ten control fruits were treated with sterilized water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 8 days. The pathogenicity test was repeated twice. All inoculated pitahaya fruits exhibited sunken and necrotic lesions 6 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation. Recently, C. tropicale causing anthracnose in dragon fruit (Selenicereus monacanthus) was reported from Philippines (Evallo et al. 2022). Now, this is the first report of C. tropicale causing fruit anthracnose in H. costaricensis in Mexico and worldwide. These findings provide a basis for research about the distribution and effective disease-management strategies.

Fungicide Sensitivity of Sclerotinia sclerotiorum from U.S. Soybean and Dry Bean, Compared to Different Regions and Climates.

Fungicide use is integral to reduce yield loss from Sclerotinia sclerotiorum on dry bean and soybean. Increasing fungicide use against this fungus may lead to resistance to the most common fungicides. Resistance has been reported in Brazil (Glycine max) and China (Brassica napus subsp. napus), however, few studies have investigated fungicide sensitivity of S. sclerotiorum in the United States. This work was conducted to determine if there was a difference in fungicide sensitivity of S. sclerotiorum isolates in the United States from: (i) dry bean versus soybean and (ii) fields with different frequencies of fungicide application. We further hypothesized that isolates with fungicide applications of a single active ingredient from tropical Brazil and subtropical Mexico were less sensitive than temperate U.S. isolates due to different management practices and climates. The EC50(D) fungicide sensitivity of 512 S. sclerotiorum isolates from the United States (443), Brazil (36), and Mexico (33) was determined using a discriminatory concentration (DC) previously identified for tetraconazole (2.0 ppm; EC50(D) range of 0.197 to 2.27 ppm), boscalid (0.2; 0.042 to 0.222), picoxystrobin (0.01; 0.006 to 0.027), and thiophanate-methyl, which had a qualitative DC of 10 ppm. Among the 10 least sensitive isolates to boscalid and picoxystrobin, 2 presented mutations known to confer resistance in the SdhB (qualitative) and SdhC (quantitative) genes; however, no strong resistance was found. This study established novel DCs that can be used for further resistance monitoring and baseline sensitivity of S. sclerotiorum to tetraconazole worldwide plus baseline sensitivity to boscalid in the United States.

First Report of Ralstonia pseudosolanacearum Causing Wilt Disease in Tomato (Solanum lycopersicum L.) Plants from Mexico.

Mexico produces more than four million tons of tomato fruits and ranks tenth worldwide. In February 2022, tomato plants in a greenhouse in Culiacan, Sinaloa State, were affected by wilt diseases with an incidence of 20% and irreversible wilt and death of the infected plants (severity up 70%). When cut stems from affected plants, a reddish to brown discoloration of the vascular system was observed and these were disinfected with 1% NaClO for 5 min and then placed in a humid chamber. Characteristic milky-white exudate was obtained. From that exudate, irregular, mucoid, and white colonies with pink centres were obtained on casamino peptone glucose (CPG) plates supplemented with 1% 2,3,5-triphenyl 15 tetrazolium chloride (TZC); these characteristics are typical of the Ralstonia solanacearum species complex (RSSC) (Garcia et al., 2019). Identification of the pathogen was done by PCR using specific primer pairs reported by Paudel et al. (2022), RssC-wF3 (5'-TATATATCCTCGACTTTTCCATGAAGCTGTG-3') - RssCwR3 (5'-CTATATATATACCCCACTTGTTGAGGAACTG-3') and Rpseu-wF5 (5'-TTTTATTTTTTTGGTGTCCGGGCCAAGATAG-3') - Rpseu-wR5 (5'- TTATATTACTCGAACGTGCTGCAAAACCACT-3'), which amplified fragments of 162 and 251 bp for RSSC and Ralstonia pseudosolanacearum, respectively. Additionally, 759 (5'-GTCGCCGTCAACTCACTTTCC-3') - 760 (5'-GTCGCCGTCAGCAATGCGGAATCG-3') (Opina, et al., 1997) and Nmult21:1F (5'-CGTTGATGAGGCGCGCAATTT-3') - Nmult22:RR (5'- TCGCTTGACCCTATAACGAGTA-3') (Fegan and Prior, 2005) were used to generate 282 and 144 bp amplicons for RSSC and phylotype I, respectively. Subsequen to making the specific detection, the representative strain ClnMx was used to generate a sequence for the endoglucanase (egl) gene for separation into sequevars by using the primers Endo-F (5'- ATGCATGCCGCTGGTCGCCGC-3') and Endo-R (5'-GCGTTGCCCGGCACGAACACC-3'), which amplified a fragment of 750 bp (Fegan et al., 1998). The egl sequence (GenBank Access ON542479) showed 100% identity with the well-defined R. pseudosolanacearum sequevar 14, which was isolated from tomato plants from Senegal (UW763, I-14 GenBank Access CP051174) (Steidl et al., 2021), as well as, the strain MAFF 301070 (GenBank Access AB508612) from Japanese tomato. For pathogenicity tests, four 1-month-old tomato plants were infected using an insulin syringe that contained a pure bacterial suspension with approximately 2x108 CFU/mL. For each plant, 20 µL was infiltrated into the axil of the third upper leaf, and for untreated controls, tomato plants were infiltrated with sterile water. All plants were kept at 28°C under greenhouse conditions. Symptoms resembling those observed in the field were observed in inoculated plants six days after inoculation, and the plant pathogen was recovered on TZC medium. To confirm the bacteria identification a PCR using the specific primer pairs mentioned early was carried out. In contrast, water-treated control plants remained healthy. Koch's postulates were carried out twice with similar results. Ralstonia solanacearum species complex (RSSC) causes severe economic losses in many countries of the world because of their capability to infect a wide range of host plants, including potato, tomato, eggplant, tobacco, and, banana, among others. Ralstonia pseudosolanacearum has been reported to cause tomato wilt disease mainly on the Afro-Eurasian continent in areas such as Senegal, Cambodia, and Japan (Klass et al., 2019). To our knowledge, this is the first report of R. pseudosolanacearum causing bacterial wilt diseases in tomato plants from Mexico and because, the control of this bacteria is a challenge by the long survival time in soil, water, and infected plant tissues, the identification of this important pathogen could provide relevant information for developing management strategies.

First Confirmed Report of Rhizoctonia solani AG-7 Causing Potato Stem Canker in Mexico.

Rhizoctonia solani, is the causal agent of black scurf and stem canker of potatoes (Solanum tuberosum L.) throughout the world. In November 2021, stem canker symptoms were observed in two potato fields located in Ahome, Sinaloa, Mexico. The disease incidence was estimated up to 15%. For fungal isolation, fragments of symptomatic stems were surface sterilized with 2% sodium hypochlorite for 2 min, rinsed with sterilized distilled water, and blotted dry on sterile filter paper. Fragments were placed on PDA medium and incubated at 25°C in darkness for 4 days. Rhizoctonia-like colonies were consistently obtained and 12 isolates were purified by the hyphal-tip method. Fungal colonies on PDA were white initially and then turned brown, raised, and with entire or undulate edges. Septate hyphae were hyaline, smooth, and branched at right angles with a septum near the point of branching. Microscopic examination by staining with 1% safranin O and 3% KOH solution showed multinucleate cells. The morphological features of the isolates resembled those of Rhizoctonia solani (Sneh et al. 1991). Four representative isolates were selected for molecular analysis and pathogenicity tests. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa) under accession nos. CCLF267, CCLF274, CCLF277, and CCLF279. For molecular identification, genomic DNA from each of the four isolates was extracted, and the internal transcribed spacer (ITS) region was amplified, and sequenced with the primer pair ITS5/ITS4 (White et al. 1990). The sequences were deposited in GenBank (accession nos. OP784258 to OP784261). Phylogenetic analyses were performed using the Maximum Likelihood method with ITS sequences for anastomosis groups (AG) of Rhizoctonia solani. The phylogenetic tree grouped the four isolates within the R. solani AG-7 clade with high bootstrap support (100%). For pathogenicity tests, certified pathogen-free potato mini-tuber (cv. Fianna) were placed in a polystyrene pot (1 L) filled with a 5 cm layer of a sterile substrate composed of soil and peat moss (2:1 w/w). One rice grain (20 mg) colonized with each isolate was placed 10 mm above the uppermost sprout tip and covered with the sterile substrate (Inokuti et al. 2019). Control plants were inoculated with sterile rice grains. All pots were transferred to a greenhouse where the temperature ranged from 20 to 32°C. Stem necrosis symptoms were observed on all inoculated plants 25 days after emergence, whereas control plants remained symptomless. Pathogenicity test was performed twice with similar results. Fungi were reisolated from the infected stems and found to be morphologically identical to the isolates used for inoculation, thus fulfilling Koch's postulates. The AG-7 has been previously reported to cause potato diseases in South Africa (Truter and Wehner 2004). In Mexico, Carling et al. (1998) reported the presence of an isolate of R. solani AG-7 obtained from a potato tuber-borne sclerotium in Toluca; however, there is no information about the methodology used for the characterization of that isolate. To our knowledge, this is the first confirmed report of R. solani AG-7 causing potato stem canker in Mexico. Our findings improve knowledge about R. solani AGs occurring in potato fields in Mexico. So, further studies should be conducted to investigate the diversity, prevalence, and fungicide sensitivity of AGs distributed in the main potato-producing states in Mexico.

Occurrence and Distribution of Physiological Races of Exserohilum turcicum in Maize-Growing Regions of Mexico.

Turcicum leaf blight (TLB) is a common foliar disease of maize in Mexico that is caused by the fungal pathogen Exserohilum turcicum. The most effective management strategy against TLB is monogenic race-specific resistance. Among the 140 E. turcicum isolates from symptomatic leaves collected from maize fields in Mexico, 100 were obtained from tropical (Veracruz) and temperate areas (Estado de México) between 2010 and 2019, and 40 isolates were obtained from tropical (Sinaloa, Tamaulipas, Veracruz, and Chiapas), subtropical (Nayarit, Jalisco, and Guanajuato), and temperate areas (Estado de Mexico, Hidalgo, and Puebla) collected in 2019. All the isolates caused TLB symptoms on the positive control (ht4), showing that they were all pathogenic. Six physiological races of E. turcicum (2, 3, 23, 3N, 23N, and 123N) were identified based on resistant or susceptible responses displayed by five maize differential genotypes (A619Ht1, A619Ht2, A619Ht3, B68HtN, and A619ht4). The most common was race 23, accounting for 68% of the isolates, followed by races 23N, 123N, 3, 2, and 3N at 15, 8, 6, 2, and 1%, respectively. Race 123N was able to infect the greatest number of maize differential genotypes used in the study. Race 123N was detected in Sinaloa and Estado de México. Race 3 was detected in Nayarit and Jalisco. Race 2 was detected in Jalisco, Estado de México, and Veracruz, and race 3N was detected in Tamaulipas. Race 23 was equally dominant in the tropical, subtropical, and temperate regions, while race 123N was more common in the tropical environment, and race 23N was more common in the tropical and temperate environments. There was no evidence for shifts in the races between 2010 and 2019.

First Report of Fusarium citri Causing Postharvest Fruit Rot of Chayote in Mexico.

In November 2018, symptoms of brown rot were observed on chayote (Sechium edule) var. nigrum spinosum with a 20% disease incidence of 120 harvested fruits in the National Germplasm Bank of Sechium edule, located in the Centro Regional Universitario Oriente (CRUO) from the Chapingo Autonomous University (Huatusco, Veracruz, Mexico). For fungal isolation, pieces from symptomatic fruits were surface disinfected by immersion in a 1.5% NaClO solution for 2 min, rinsed in sterile distilled water, placed in Petri plates containing potato dextrose agar (PDA) amended with kanamycin sulfate, and incubated at 25ºC. Fusarium-like colonies were consistently isolated on PDA and five monoconidial isolates were obtained. A representative isolate was selected for morphological characterization, phylogenetic analysis, and pathogenicity tests. On PDA, colonies exhibited white and fluffy aerial mycelia, with diffused pale brown pigment in the center at 7 days of incubation at 25℃ in darkness. Macroconidia (n= 100) were hyaline, falcate, with 4 to 5 septa, measuring 23.9 to 31.9 × 2.9 to 4.2 µm, and foot-shaped basal cells. Microconidia and chlamydospores were absent. Morphological features were consistent with the description of the Fusarium incarnatum-equiseti species complex (Xia et al. 2019). The isolate was deposited as FUS2 in the Culture Collection of Phytopathogenic Fungi of the Laboratory of Plant Pathology at the Colegio de Postgraduados. For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region, partial sequences of translation elongation factor 1-alpha (EF1-α), and the second-largest subunit of RNA polymerase II (rpb2) genes were amplified, and sequenced with the primer sets ITS5/ITS4 (White et al. 1990), EF1-728F/EF1-986R (Carbone and Kohn 1999), and RBP2-5F/RPB2-7R (Liu et al. 1999), respectively. DNA sequences were edited in BioEdit 7.2 and compared with those in the NCBI nucleotide database. Alignments were implemented in MEGA X using reference sequences from Fusarium spp. A phylogenetic tree, including published ITS, EF1-α, and rpb2 sequence data, was constructed for the Fusarium incarnatum-equiseti species complex (FIESC) based on Maximum Likelihood. The sequences were deposited in GenBank (accession nos. ON878083, ON890421, and ON890420). The phylogenetic analysis grouped the isolate FUS2 within the F. citri clade. Pathogenicity of the fungus was verified on 10 healthy chayote fruits var. nigrum spinosum previously disinfested by immersion in a 1% NaClO solution for 3 min and washed in sterile water. A total of 5 mL of a conidial suspension (1 × 106 spores/ml) was sprayed on each whole fruit. Ten control fruit were sprayed with sterile distilled water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 30 days. All inoculated fruits developed water-soaked brown lesions (3 to 5 cm in diameter) covered with white mycelium at 15 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation, fulfilling Koch´s postulates. Fusarium citri has been associated with Capsicum sp. and mandarin orange in China, Triticum sp. in Iran, alfalfa in Denmark, and lettuce in the Czech Republic and Italy (Farr and Rossman 2022). To our knowledge, this is the first report of F. citri causing postharvest fruit rot of chayote in Mexico and worldwide.

First Report of the Root-Knot Nematode Meloidogyne enterolobii Parasitizing Eggplant in Mexico.

Eggplant (Solanum melongena L.) is an important vegetable cultivated in Mexico and the state of Sinaloa is the largest producer of eggplants with 90% of the country's total production. In April 2022, eggplants cv. Barcelona exhibiting root-knot, stunted growth, and yellowing were detected in a greenhouse in Culiacán, Sinaloa, Mexico. Disease incidence was approximately 10% (1000 plants evaluated). Ten soil samples were collected from the greenhouse. An average of 400 root-knot nematode second-stage juveniles (J2s) were extracted from 100 g of soil for each sample. Roots were washed with tap water and dissected. Females and egg masses were obtained by dissecting galls. Microscopic examination of the perineal pattern of mature females (n= 10) was round to ovoid, with rounded and high dorsal arch. Females (n= 20) were globular to pear-shaped, body length of 645 to 739 µm, body width of 470 to 559 µm; the stylet was dorsally curved, 15.1 to 16.2 µm long, and with rounded stylet knobs; neck length of 195 to 202 µm and the distance from the base of the stylet to the dorsal gland orifice (DGO) was 4.2 to 5.8 µm. Second-stage juveniles were vermiform, annulated, and tapering at both ends. Morphological characteristics of the females and J2s were consistent with those reported for Meloidogyne enterolobii (Yang and Eisenback 1983). For molecular identification, total DNA was extracted from individual females according to the extraction protocol described by Hu et al. (2011), and the ribosomal intergenic spacer 2 (IGS2) was amplified by PCR using the specific primers Me-F/Me-R for M. enterolobii (Long et al. 2006). PCR amplification generated a 236-bp fragment for the analyzed sample and the amplicon was sequenced. The sequence was deposited in GenBank under the accession number OP004802. BLASTn searches showed 100% identity with available sequences of M. enterolobii from the USA (MH800967) and China (KP411228, MT742011). A phylogenetic tree including published IGS2 sequences for Meloidogyne spp. was constructed based on Maximum Likelihood method. The phylogenetic analysis placed the sequence MeCUB in the same clade with Meloidogyne enterolobii. Pathogenicity tests were performed under greenhouse conditions by inoculating 5000 eggs of a pure population of M. enterolobii on 10 healthy eggplants cv. Barcelona (30-day-old) grown in pots with sterilized soil. Five uninoculated eggplants were used as control. Plants were maintained at 26 to 34°C in a greenhouse for 35 days. Stunted growth and root-galling symptoms appeared on inoculated plants after 21 days, whereas control plants remained symptomless. Nematode reproduction factor (final population density/initial population density) was 0.93 and 2.28 at 28 and 35 days after inoculation, respectively. The nematode on the inoculated roots was morphologically identical to that observed on naturally infected roots in the field. The pathogenicity test was carried out twice with similar results. Meloidogyne enterolobii has been previously reported on eggplants in Puerto Rico (Rammah and Hirschmann 1988). To our knowledge, this is the first report of M. enterolobii causing root-knot of eggplant in Mexico. This nematode is widely distributed in Sinaloa affecting other vegetable crops such as tomato (Martínez-Gallardo et al. 2015), chili (Carrillo-Fasio et al. 2020), and cucumber (Gómez-González et al. 2020), so future studies are required to evaluate integrated management strategies.

First Report of Collar Rot Caused by Sclerotinia sclerotiorum on Sesame (Sesamum indicum) in Mexico.

Sesame (Sesamum indicum L.: Pedaliaceae) is the second most cultivated oilseed in Mexico with 80,000 ha per year. The seeds of this crop are used as a condiment, for the extraction of oil, and its medicinal properties. In October 2020, collar rot symptoms were observed in six sesame fields (SOPC-9539 TD variety) located in the Carrizo Valley (26°15'33.1"N; 109°01'37.9"W), El Fuerte, Sinaloa, México. Initially, small brown spots in the basal stem of the infected plants were observed. At advanced stages of the disease, the circumference of stem was necrotic with the presence of white mycelium that extends to the roots. Infected plants were showing symptoms of yellowing, wilting, and finally death. Disease incidence was estimated at 15%, counting the total of diseased plants in five counts done in arbitrary quadrants within the sesame fields. For fungal isolation, stem sections from the symptomatic basal stem were surface disinfected with 1.5% sodium hypochlorite for 2 min, then triple rinsed with sterile distilled water. The tissue sections were dried on sterile blotting paper and plated in Petri dishes with potato dextrose agar (PDA) culture medium. The plates were incubated at 28ºC in darkness for 48 h. Sclerotinia-like colonies were consistently isolated and four isolates from different locations were purified by the hyphal-tip method. Fungal colonies were formed of compact white mycelium, with the formation of sclerotia on the margin of the plate 6 days after inoculating PDA cultures. Sclerotia averaged 3.1 mm in diameter and 0.024 g. One isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of Fuerte Valley at the Sinaloa Autonomous University under Accession no. FAVF654. To confirm identification, genomic DNA was extracted from one isolate, and the internal transcribed spacer (ITS) region was amplified by PCR and sequenced directly using the primer pair ITS5/ITS4 (White et al. 1990). The resulting consensus sequence was deposited in GenBank under accession no. ON401416. BLASTn alignments in GenBank showed 100% identity of our sequence with the sequence of the type strain of Sclerotinia sclerotiorum ATCC 46762 (accession no. JX648201). Pathogenicity of the fungus was demonstrated by inoculating healthy sesame plants (Dormilón and SOPC-9539 TD ies), germinated in plastic pots with sterile substrate. Plants were inoculated with the FAVF654 isolate by applying 3 sclerotia at the base of each of the 12 plants. Twelve plants were left uninoculated, which served as controls. All the inoculated plants, of both varieties, developed the characteristic symptoms of the disease 7 days after inoculation, while the control plants remained symptomless. The pathogenicity test was performed twice with the same result. The fungus was reisolated from all the inoculated plants, thus fulfilling Koch's postulates. Sclerotinia sclerotiorum has been reported on sesame plants in Bulgaria and Korea (Farr and Rossman, 2022). To our knowledge, this is the first report of Sclerotinia sclerotiorum causing collar rot in sesame plants in Mexico and the Americas. This disease considerably reduces the yield of sesame; therefore it is necessary to develop effective disease-management strategies.

First Report of Ceratobasidium sp. (AG-A and AG-G) Causing Root Rot and Stem Canker of Common Bean in Mexico.

Common bean (Phaseolus vulgaris L.), is a grain legume widely cultivated worldwide for its edible dry seeds and pods. In February 2021, root rot symptoms were observed in two common bean (cv. Azufrado Higuera) fields located in Ahome (25º96´19¨N, 109º33´42¨W) and Guasave (25º71´85¨N, 108º78´50¨W) municipalities in Sinaloa, Mexico. Diseased plants showed reduced growth, dark brown canker at the base of the stem, root rot, as well as the absence of secondary roots. The disease incidence was estimated up to 35%. For fungal isolation, symptomatic roots were surface sterilized with 1% sodium hypochlorite for 2 min, rinsed with sterilized distilled water two times, and blotted dry on sterile filter paper. Small fragments of diseased roots were placed on PDA medium and incubated at 25°C in darkness for 3 days. Rhizoctonia-like colonies were consistently obtained and 10 isolates were purified by the hyphal-tip method. Colonies on PDA were white initially and then turned brown after 15 days of incubation. The septate hyphae were 3.9 to 6.3 µm in width and branched at right angles with a septum near the point of branching. Microscopic examination by Safranine-O staining showed two nuclei per cell. The morphological features of the isolates resembled those of Ceratobasidium (Sneh et al. 1991). The two Ceratobasidium isolates were selected for molecular analysis and pathogenicity tests. The isolates were deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of Fuerte Valley at the Sinaloa Autonomous University (Accession nos. FAVF395 and FAVF396). For molecular identification, genomic DNA from each of the two isolates was extracted, and the internal transcribed spacer (ITS) region and partial fragments of the second largest subunit of RNA polymerase II (rpb2) gene were amplified and sequenced with the primer pairs ITS5/ITS4 (White et al. 1990) and RBP2-980F/RPB2-7cR (Liu et al. 1999), respectively. The ITS sequences (accession nos. ON630914 and ON630915) showed 99.66 and 99.01% identity with Ceratobasidium sp. (AG-A) from the USA (OM045887) and Ceratobasidium sp. (AG-G) from China (HM623627), respectively. Whereas, the rpb2 sequences (OM258171 and OM258172) showed 94.10 and 95.74% identity with Ceratobasidium sp. (AG-A) from Serbia (MT1267888) and Ceratobasidium sp. (AG-G) from Japan (DQ301701), respectively. A phylogenetic tree based on Maximum Likelihood and including combined ITS and rpb2 sequences data for Ceratobasidium spp. was generated. The phylogenetic tree grouped the isolates FAVF395 and FAVF396 within the Ceratobasidium sp. AG-A and AG-G clades, respectively. Pathogenicity tests for each isolate were performed by inoculating 10 healthy common bean seedlings (15-day-old) grown in pots. A total of 50 ml of a mycelial suspension adjusted to a concentration of 1 × 105 mycelial fragments/ml were directly placed on the stem base of each plant. Five uninoculated common bean seedlings were used as control. All plants were kept in a greenhouse for 15 days at temperatures ranging from 22 to 32°C. Root rot and stem canker symptoms appeared on inoculated seedlings after 10 days, whereas control plants remained symptomless. Fungi were reisolated from the infected roots and found to be morphologically identical to the isolates used for inoculation, thus fulfilling Koch's postulates. Ceratobasidium sp. has been previously reported as the causal agent of root rot of watermelon in Sonora, Mexico (Meza-Moller et al. 2014; Farr and Rossman 2022). To our knowledge, this is the first report of Ceratobasidium sp. causing root rot of common bean in Mexico. Further monitoring should be performed to quantify yield impacts and develop effective management strategies for this disease.

Efficacy of Biorational Products for Managing Diseases of Tomato in Greenhouse Production.

Gray mold (Botrytis cinerea), late blight (Phytophthora infestans), powdery mildew (Leveillula taurica), pith necrosis (Pseudomonas corrugata), and bacterial canker (Clavibacter michiganensis) are major diseases that affect tomato (Solanum lycopersicum L.) in greenhouse production in Mexico. Management of these diseases depends heavily on chemical control, with up to 24 fungicide applications required in a single season to control fungal diseases, thus ensuring a harvestable crop. While disease chemical control is a mainstay practice in the region, its frequent use increases the production costs, likelihood of pathogen-resistance development, and negative environmental impact. Due to this, there is a need for alternative practices that minimize such effects and increase profits for tomato growers. The aim of this study is to evaluate the effect of biorational products in the control of these diseases in greenhouse production. Four different treatments, including soil application of Bacillus spp. or B. subtilis and foliar application of Reynoutria sachalinensis, Melaleuca alternifolia, harpin αß proteins, or bee honey were evaluated and compared to a conventional foliar management program (control) in a commercial production greenhouse in Central Mexico in 2016 and 2017. Disease incidence was measured at periodic intervals for six months and used to calculate the area under the disease progress curve (AUDPC). Overall, the analysis of the AUDPC showed that all treatments were more effective than the conventional program in controlling most of the examined diseases. The tested products were effective in reducing the intensity of powdery mildew and gray mold, but not that of bacterial canker, late blight, and pith necrosis. Application of these products constitutes a disease management alternative that represents cost-saving to tomato growers of about 2500 U.S. dollars per production cycle ha-1, in addition to having less negative impact on the environment. The products tested in this study have the potential to be incorporated in an integrated program for management of the examined diseases in tomato in this region.

Occurrence of Curvularia pisi and C. muehlenbeckiae Causing Leaf Spot on Guar (Cyamopsis tetragonoloba) in Mexico.

Cyamopsis tetragonoloba (Fabaceae family), known as guar or clusterbean, is a drought-tolerant annual legume cultivated on a commercial scale focused on industrial gum production. In September 2021, symptoms of leaf spot were observed on guar plants in several commercial fields located at Guasave, Sinaloa, Mexico. Symptoms included round to oval, light brown lesions with dark margins. The disease incidence was estimated to be up to 30% in five fields. Curvularia-like colonies were consistently isolated, and 12 monoconidial isolates were obtained. Two representative isolates were selected to use downstream and were deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of Fuerte Valley at the Sinaloa Autonomous University under Accession FAVF643 and FAVF645. On potato dextrose agar (PDA), colonies of both isolates FAVF643 (pale brown margin) and FAVF645 (lobate edge) were dark brown. Conidiophores of both isolates FAVF643 (paler towards apex and 76 to 191 × 3.5 to 5.2 µm) and FAVF645 (80 to 260 × 3.9 to 5.1 µm) were mostly straight, pale brown to dark brown, septate, and simple to branched. Conidia of both isolates FAVF643 (19.9 to 33.3 × 8.8 to 13.5 µm) and FAVF645 (18.5 to 27.1 × 9.1 to 13.1 µm) were curved, rarely straight, brown, with apical and basal cells paler than middle cells being pale brown, and 3-distoseptate. Morphology of both isolates FAVF643 and FAVF645 was consistent with that described for Curvularia (Marin-Felix et al. 2017; 2020). For phylogenetic identification, total DNA was extracted and PCR products sequenced from ITS5/ITS4 primers -the internal transcribed spacer (ITS) region (White et al. 1990) and GPD1/GPD2 - partial sequences of glyceraldehyde-3-phosphate dehydrogenase (gpdh) gene amplification. A phylogenetic tree based on Maximum likelihood including published ITS and gpdh for Curvularia spp. was constructed. Phylogenetic analyses showed that isolate FAVF643 grouped with the type strain C. pisi (CBS190.48) sequence, and the isolate FAVF645 grouped with the type strain C.muehlenbeckiae (CBS144.63) sequence. The resulting sequences were deposited in GenBank as: C. pisi OM802153 (ITS); OM835758 (gpdh), and C. muehlenbeckiae OM802154 (ITS); OM835759 (gpdh). The pathogenicity was verified on healthy guar plants. For each isolate, five plants were inoculated by spraying a conidial suspension (1 × 106 spores/ml) onto leaves until runoff. Five plants sprayed with sterile distilled water served as controls. All plants were kept in a moist chamber for two days, and subsequently transferred to a greenhouse for 12 days at temperatures ranging from 26 to 32°C. All inoculated leaves exhibited necrotic lesions with a dark margin 10 days after inoculation, whereas control plants remained symptomless. The fungi were consistently re-isolated from the diseased leaves and found to be morphologically identical to the isolates used for inoculation, fulfilling Koch´s postulates. Curvularia lunata had been reported as the causal agent of leaf spot on guar in India (Chand and Verma 1968); however, to our knowledge, this is the first report of C. pisi and C. muehlenbeckiae causing leaf spot on guar in Mexico and worldwide.

Viruses of Economic Impact on Tomato Crops in Mexico: From Diagnosis to Management-A Review.

Tomato is the most economically important vegetable crop worldwide and the second most important for Mexico. However, viral diseases are among the main limiting factors that affect the productivity of this crop, causing total losses in some cases. This review provides key information and findings on the symptoms, distribution, transmission, detection, and management of diseases caused by viruses of major importance in tomato crops in Mexico. Currently, about 25 viruses belonging to nine different families have been reported infecting tomato in Mexico, but not all of them cause economically significant diseases. Viruses of economic importance include tomato brown rugose fruit virus (ToBRFV), tomato spotted wilt virus (TSWV), tomato yellow leaf curl virus (TYLCV), pepino mosaic virus (PepMV), and tomato marchitez virus (ToMarV). The topics discussed here will provide updated information about the status of these plant viruses in Mexico as well as diverse management strategies that can be implemented according to the specific circumstances of each viral pathosystem. Additionally, a list of tomato-affecting viruses not present in Mexico that are continuous threats to the crop health is included.

First Report of Colletotrichum chrysophilum Causing Papaya Anthracnose in Mexico.

Anthracnose, caused by Colletotrichum spp., is the most important fungal disease of papaya (Carica papaya L.) worldwide. In March 2020, mature papaya fruit (cv. Maradol) showing typical symptoms of anthracnose were observed in an orchard located in Pinotepa Nacional, Oaxaca, Mexico. Disease incidence of 100 papaya plants surveyed in the orchard was estimated at about 45%. Initially, small and water-soaked lesions appeared on the fruit surface, which later enlarged to circular sunken lesions with translucent light brown margins. On advanced infections, salmon-pink masses of spores were observed on the lesions. Twenty Colletotrichum-like colonies were consistently isolated on potato dextrose agar (PDA) medium at 25°C in the dark for 6 days and 10 monoconidial isolates were obtained. An isolate was selected as representative for further characterization. The isolate was deposited as CPM-H4 in the Culture Collection of Phytopathogenic Fungi of Plant Pathology Laboratory of the CIIDIR-Oaxaca of the Instituto Politécnico Nacional. On PDA, the colonies were initially light grey then later became dark grey with orange conidial masses after incubation for 7 days. Conidia (n= 50) were hyaline, aseptate, cylindrical with rounded ends, and measured 10.2 to 13.6 × 4.1 to 5.3 µm. Appressoria (n= 20) were mostly simple, solitary and smooth-walled, dark brown, and clavate, measuring 6.8 to 14.8 × 5.5 to 7.7 µm. Based on morphology, the isolate was tentatively identified as belonging to the Colletotrichum gloeosporioides species complex (Weir et al. 2012). For molecular identification, total DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), and partial sequences of actin (ACT), ß-tubulin (TUB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and chitin synthase (CHS-1) genes were amplified (Weir et al. 2012), and sequenced. The sequences were deposited in GenBank (accessions nos. OM965612 (ITS), OM959540 (ACT), ON065005 (TUB2), ON065003 (CHS-1), ON065004 (GAPDH). A phylogenetic tree based on Bayesian inference and including published ITS, ACT, TUB2, GAPDH, and CHS-1 sequence dataset for Colletotrichum spp. was constructed. The multilocus phylogenetic analysis clearly distinguished the isolate CPM-H4 as Colletotrichum chrysophilum. Pathogenicity of the fungus was verified on 10 healthy papaya fruits (cv. Maradol) without wounds. A drop of a conidial suspension (1 × 105 spores/ml) was placed on three locations on each fruit. Ten control fruit were treated in the same way but with sterilized water. The fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 8 days. The pathogenicity test was repeated twice. All inoculated papaya fruits developed sunken necrotic lesions 6 days after inoculation, whereas no symptoms were observed on the control fruits. The fungus was consistently re-isolated only from the diseased fruits and found to be morphologically identical to the isolate used for inoculation, fulfilling Koch´s postulates. Colletotrichum chrysophilum has been previously reported to cause anthracnose on mango (Fuentes-Aragón et al. 2020a), avocado (Fuentes-Aragón et al. 2020b), and banana (Fuentes-Aragón et al. 2021) in Mexico; however, to our knowledge, this is the first report of C. chrysophilum causing papaya anthracnose in Mexico. Therefore, it is necessary to explore the diversity of Colletotrichum species associated with papaya in Mexico through subsequent phylogenetic studies as well as to monitor the possible movement and distribution of this pathogen into other Mexican regions.

First Report of Soft Rot of Pitahaya Fruit Caused by Gilbertella persicaria in Mexico.

Pitahaya (Hylocereus spp.), also called dragon fruit, is a cultivated cactus that is native to Mexico as well as Central and South America. In September 2021, soft rot of fruit of H. ocamponis, H. undatus, and H. costaricensis was observed in a commercial orchard located in La Cruz de Elota, Sinaloa, Mexico. The disease occurred on approximately 15% of pitahaya fruit. Lesions on fruits were water-soaked and light brown, extending to the whole fruit and covered with mycelia, sporangiophores, and sporangia. Colonies of a fungus were consistently isolated on PDA medium and 10 isolates were obtained. Three isolates were selected and deposited in the Culture Collection of Phytopathogenic Fungi at the Research Center for Food and Development (Culiacán, Sinaloa) under accession nos. CCLF171-CCLF173. Colonies on PDA medium were initially white and later grayish. Sporangiophores were hyaline to light brown, and aseptate. Sporangia (n= 30) were initially light brown but became black at maturity, globose to subglobose, single, terminal, 65.8 to 117.2 µm in diameter, and longitudinally separated into two halves. Columellae (n= 20) were light brown, obovoid, 33.5 to 72.9 × 31.5 to 69.8 µm, with a distinct basal collar. Sporangiospores (n= 100) were hyaline, globose to ellipsoid, aseptate, 6.9 to 12.8 × 5.1 to 10.9 µm, with polar appendages. Chlamydospores were solitary or in chains, oval or irregular. Zygospores were not observed. Based on the morphological characters, the fungal isolates were identified as Gilbertella persicaria (Benny 1991). To confirm the identity, total DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR using the primers ITS5/ITS4 (White et al. 1990), and sequenced. The ITS sequences were deposited in GenBank under the accession nos. OM301904-OM301906. A BLASTn search of these sequences showed 99.47 to 99.81% identity with the sequence MK301174 of G. persicaria from Hylocereus sp. in Taiwan. A phylogenetic analysis based on Maximum Likelihood method grouped the isolates CCLF171-CCLF173 within the G. persicaria clade. Pathogenicity of the three isolates was verified on healthy Hylocereus spp. fruit. Fruit of H. ocamponis, H. undatus, and H. costaricensis were surface sterilized with 80% ethanol, and dried. For each fungal isolate, five detached fruits were superficially wounded with a sterile toothpick and inoculated by placing 15 µL of a spore suspension (1 × 105 sporangiospores/mL). Sterile distilled water was applied to five healthy pitahaya fruits to serve as controls. All fruits were kept in a moist plastic chamber at 25°C and 12 h light/dark for 6 days. All inoculated fruits developed rot 3 days after inoculation, whereas no symptoms were observed on the control fruits. The experiment was repeated twice with similar results. The fungi were consistently re-isolated from the diseased fruits, fulfilling Koch´s postulates. Gilbertella persicaria has been previously reported to cause stem rot, fruit rot, and wet rot in pitahaya (Hylocereus spp.) in Japan (Taba et al. 2011), China (Guo et al. 2012), and Taiwan (Lin et al. 2014), respectively. To our knowledge, this is the first report of G. persicaria causing soft rot of Hylocereus spp. fruit in Mexico. Additional studies are needed to develop effective disease-management strategies.

First Report of Sclerotium rolfsii Causing Collar Rot of Guar (Cyamopsis tetragonoloba) in Mexico.

Cyamopsis tetragonoloba (Fabaceae), also known as guar or cluster bean, is an annual legume grown mainly for industrial purposes and also as an ingredient for animal feed. In October 2021, collar rot symptoms were observed in five guar fields located in Guasave, Sinaloa, Mexico. Abundant white mycelium, and later brown and small sclerotia were observed at the base of the stems. Diseased plants showed reduced growth, wilting, and drying of the entire plant. Disease incidence ranged from 15 to 40%. Samples were collected from each field at two phenological stages (vegetative and reproductive). For fungal isolation, symptomatic stems pieces were surface sterilized with 2% sodium hypochlorite for 2 min, rinsed in sterilized distilled water two times, placed on PDA medium and incubated at 28°C in darkness for 3 days. Sclerotium-like colonies were consistently obtained and five isolates from five different fields were purified by the hyphal-tip method. Fungal colonies were white, cottony, and often forming fans. Sclerotia (1 to 2 mm diameter) were white at first and then gradually turned dark brown. Microscopic examination showed septate hyphae with some cells having clamp connections. A representative isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Faculty of Agriculture of Fuerte Valley at the Sinaloa Autonomous University under Accession no. FAVF647. For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region was amplified by PCR and sequenced using the primer pair ITS5/ITS4 (White et al. 1990). The sequence was deposited in GenBank (accession no. OM510466). BLASTn searches in GenBank showed 99.21 to 100% identity with the available sequences of Sclerotium rolfsii (accession nos. MK926446, MH854711, and KY175225). A phylogenetic analysis using the maximum Likelihood method placed isolate FAVF647 in the same clade as S. rolfsii. Pathogenicity tests were performed by inoculating 10 healthy guar seedlings (15-day-old) grown in pots. Four sclerotia were directly placed on the stem base of each plant. Five uninoculated guar seedlings were used as control. All plants were placed in a moist chamber at 25°C with a 12-h photoperiod for 2 days. Collar rot symptoms appeared on inoculated plants after 3 days, whereas control plants remained symptomless. Pathogenicity test was performed twice with similar results. The fungus was reisolated from the artificially inoculated plants, thus fulfilling Koch's postulates. Sclerotium rolfsii has been reported on guar plants in Australia, Brazil, Fiji, India, and the United States (Farr and Rossman 2022). To our knowledge, this is the first report of Sclerotium rolfsii causing collar rot of guar in Mexico. The disease is very common in guar fields in Sinaloa, Mexico, therefore additional studies are needed to develop effective disease-management strategies.