Etiology of Foliar Blight of Indian Paintbrush (Castilleja tenuiflora) in Mexico.

Castilleja tenuiflora is a native perennial plant used in traditional Mexican medicine. In June 2022, leaf blight symptoms were observed in a wild population of C. tenuiflora plants. Disease incidence was 80% and disease intensity reached up to 5% of the leaf area. Currently, there are no reports of pathogens causing leaf blight in this plant; therefore, this work aimed to identify the fungi responsible for the disease. The fungi recovered from the diseased tissue were characterized by means of pathogenicity tests and cultural, morphological, and molecular characterization. The information obtained revealed that Alternaria alternata and Alternaria gossypina are the pathogens responsible for the disease. This is the first report implicating species of Alternaria in causing leaf blight of C. tenuiflora in Mexico, as well as the first report of Alternaria gossypina also in Mexico. These pathogens may threaten the in situ conservation of native C. tenuiflora populations and limit their in vitro propagation. Future research lines should focus on determining the effect of these pathogens on metabolite production.

The Need and Opportunity to Update the Inventory of Plant Pathogenic Fungi and Oomycetes in Mexico.

Mexico generates specific phytosanitary regulations for each product and origin to prevent the entry of quarantine pests and/or delay their spread within the national territory, including fungi and oomycetes. Phytosanitary regulations are established based on available information on the presence or absence of these pathogens in the country; however, the compilation and precise analysis of reports is a challenging task due to many publications lacking scientific rigor in determining the presence of a taxon of phytosanitary interest in the country. This review evaluated various studies reporting the presence of plant pathogenic fungi and oomycetes in Mexico and concluded that some lists of diseases and phytopathogenic organisms lack technical-scientific basis. Thus, it highlights the need and presents an excellent opportunity to establish a National Collection of Fungal Cultures and a National Herbarium for obligate parasites, as well as to generate a National Database of Phytopathogenic Fungi and Oomycetes present in Mexico, supported by the combination of morphological, molecular, epidemiological, pathogenicity, symptom, and micrograph data. If realized, this would have a direct impact on many future applications related to various topics, including quarantines, risk analysis, biodiversity studies, and monitoring of fungicide resistance, among others.

Molecular confirmation of Coleosporium plumeriae Causing Rust of Plumeria rubra in Mexico.

Frangipani (Plumeria rubra L.; Apocynaceae.) is a deciduous ornamental shrub, native to tropical America and widely distributed in tropical and subtropical regions. In Mexico, P. rubra is also used in traditional medicine and religious ceremonies. In November 2018-2022, rust-diseased leaves of P. rubra were found in Yautepec (18°49'29"N; 99°05'46"W), Morelos, Mexico. Symptoms of the disease included small chlorotic spots on the adaxial surface of the infected leaves, which as the disease progressed turned into necrotic areas surrounded by a chlorotic halo. The chlorotic spots observed on the adaxial leaf surface coincided with numerous erumpent uredinia of bright orange color on the abaxial leaf surface. As a result of the infection, foliar necrosis and leaves abscission was observed. Of the 40 sampled trees, 95% showed symptoms of the disease. On microscopic examination of the fungus, bright orange, subepidermal uredinia were observed, which subsequently faded to white. Urediniospores were bright yellow-orange color. They were ellipsoid or globose, sometimes angular, echinulate, (21.5) 26.5 (33.0) × (16.0) 19.0 (23.0) µm in size. Morphological features of the fungus correspond with previous descriptions of Coleosporium plumeriae by Holcomb and Aime (2010) and Soares et al., (2019). A voucher specimen was deposited in the Herbarium of the Departmet of Plant-Insect Interactions at the Biotic Products Development Center of the National Polytechnic Institute under accession no. IPN 10.0113. Species identity was confirmed by amplifying the 5.8S subunit, the ITS 2 region, and part of the 28S region with rust-specific primer Rust2inv (Aime, 2006) and LR6 (Vilgalys and Hester 1990). The sequence was deposited in GenBank (OQ518406) and showed 100% sequence homology (1435/1477bp) with a reference sequence (MG907225) of C. plumeriae from Plumeria spp. (Aime et al. 2018). Pathogenicity was confirmed by spraying a urediniospores suspension of 2×104 spores ml-1 onto ten plants of P. rubra. Six plants were inoculated and sealed in plastic bags, while four noninoculated plants were applied with sterile distilled water. Plants were inoculated at 25°C and held for 48 h in a dew chamber, after this, the plants were transferred to greenhouse conditions (33/span>2°C). The experiment was performed twice. All inoculated plants developed rust symptoms after 14 days, whereas the non-inoculated plants remained symptomless. The recovered fungus was morphologically identical to that observed in the original diseased plants, thus fulfilling Koch's postulates. According to international databases (Crous 2004; Farr and Rossman 2023), C. plumeriae has not been officially reported in Mexico, despite being a prevalent disease. Diseased plants have been collected and deposited in herbaria, unfortunately, these reports lack important information such as geographic location of sampling, pathogenicity tests, or molecular evidence, which are essential for a comprehensive study of the disease in Mexico. To our knowledge, this is the molecular confirmation of Coleosporium plumeriae causing rust of Plumeria rubra in Mexico. Rust of P. rubra caused by C. plumeriae has been previously identified in India, Taiwan, Malaysia, and Indonesia by Baiswar et al. (2008), Chung et al. (2006), Holcomb and Aime (2010) and Soares et al., (2019). This disease causes important economic losses in nurseries, due to the defoliation of infected plants.

Ocurrence of Colletotrichum siamense Causing Leaf Spots on Soursop (Annona muricata) in Mexico.

Soursop (Annona muricata L: Annonaceae) is a small tropical fruit tree native to South America (Pinto, 2005). The flesh of its fruits is widely used as a main ingredient of pastries, even young fruits are used as a vegetable. In June 2022, leaf spots symptoms were observed on fifty soursop plants in a commercial nursery located in Juan José Ríos (25°45'20"N 108°50'21"W), Ahome, Sinaloa State. The incidence of the disease was 75%, while the severity was 12%. Symptoms were round, small black necrotic spots, that grew up to 6 mm in diameter with brown or gray color at the center. Fungal isolation was done on potato dextrose agar (PDA) and Colletotrichum-like colonies were obtained. Five isolates were recovered and purified by single spore culture and only a single morphotype was observed. One random isolate was selected for pathogenicity tests, morphological and molecular characterization. The isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Biotic Products Development Center at the National Polytechnic Institute under accession no. IPN 13.0102. Colonies in PDA at 25°C grow at a rate of 9.0-14.0 mm/d. After 14 days, the colony was olive to gray with orange conidial masses, and conidia (n =100) were hyaline, aseptate, cylindrical, and straight with rounded ends, measuring 11.5 to 18.5 and 3.5 to 5.5 µm. Appressoria were melanized and circular or oval in shape, measuring 6.0 to 4.0 µm (n=20). According to the morphological characteristics observed, the isolate was placed tentatively within the Colletotrichum gloeosporioides species complex (Weir et al. 2012). For molecular confirmation, genomic DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), partial sequences of actin (ACT) (Weir et al. 2012) and span style="font-family:'Times New Roman'">glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified and sequenced. Sequences were deposited in GenBank under the accession numbers: ITS, OQ606966; ACT, OQ617292 and GAPDH, OQ617293. A phylogenetic tree including published sequences of the C. gloeosporiodes species complex was constructed according to Talhinhas and Baroncelli (2021) and the isolate IPN 13.0102 was grouped in a clade with the ex-type culture of C. siamense (ICMP18578) and C. pandanicola. However, C. pandanicola was recorded only as an epiphytic fungus occurring on leaves of Pandanus sp. (Pandanaceae) (Tibpromma et al. 2018) and there are no additional reports of this fungus as a plant pathogen on Pandanus or any other plant. Therefore, the isolate IPN 13.0102 corresponds to C. siamense. Pathogenicity was demonstrated by spraying a conidial suspension (1 × 105 conidia/ml) onto four healthy soursop plants, while two control plants were sprayed using sterile distilled water. All plants were kept in a wet chamber for 48 h at 28  2°C and 85% RH. The characteristic symptoms of the disease were observed 14 days after inoculation, while control plants remained healthy. The pathogenicity test was repeated twice obtaining the same results. The morphology of the recovered fungus was consistently identical to that originally isolated from diseased leaves, fulfilling Koch's postulates. Colletotrichum siamense has been previously reported on Anona spp. in Brazil (Costa et al. 2019). To our knowledge, this is the first report of Colletotrichum siamense causing leaf spots on Annona muricata in Mexico. Further studies for monitoring and control strategies of leaf spots on soursop are required.

First Report of Puccinia menthae Causing Leaf Rust on Peppermint (Mentha x piperita) in Mexico.

Peppermint (Lamiaceae) is an aromatic herb with culinary, medicinal, and industrial properties. In June 2022, symptoms and signs of foliar rust were observed in four commercial fields of peppermint (Mentha × piperita) in San Buenaventura Tecalzingo, San Martín Texmelucan, Puebla, Mexico (19°14'34.0"N 98°27'25.4"W; 19°14'16.7"N 98°27'21.4"W; 19°14'37.0"N 98°27'07.7"W; 19°15'00.6"N 98°26'54.7"W). Two diseased plants were collected at each site. The disease was present in 50% of the plants and the damaged foliar tissue was under 17%. Initial symptoms included small chlorotic spots on the adaxial surface of the leaves, which later spread to form a necrotic area surrounded by a broad chlorotic halo. Necrosis developed only in the presence of abundant reddish-brown pustules on the abaxial surface of the leaf, while smaller pustules were observed on the adaxial surface. The signs were detected as numerous reddish-brown pustules on the abaxial surface of the leaves. The infected leaves of all samples showed subepidermal uredinia, erumpent, with hyaline and cylindrical paraphyses. Urediniospores (n = 50) were hyaline to light brown, echinulate, with two germinative pores, obovoid (16.5-26.5 × 11.5-25.5 µm, mean ± SD = 22 ± 1.6 × 19 ± 0.4 µm and 0.6 µm of wall thickness), individually supported on pedicels. Morphological characteristics aligned most closely with the description of Puccinia menthae by Kabaktepe et al. (2017) and Solano-Báez et al. (2022). A voucher specimen was deposited in the Herbarium of the Department of Plant-Insect Interactions at the Biotic Products Development Center of the National Polytechnic Institute under accession no. IPN 10.0115. From one sample, genomic DNA was extracted, and the 28S gene region of rDNA was amplified by a nested PCR using the primer sets Rust2inv (Aime, 2006) and LR6 (Vilgalys and Hester, 1990), and Rust28SF (Aime et al., 2018), and LR5 (Vilgalys and Hester, 1990) for the first and second reactions, respectively. The obtained sequence (GenBank accession No. OQ552847) showed 100% homology (902/1304bp) with the type-specimen sequence of P. menthae (DQ354513) from Cunila origanoides from USA (Aime, 2006). A phylogenetic analysis using Maximum Likelihood including a published 28S dataset for Puccinia species was executed and the isolate IPN 10.0115 was grouped into a clade of P. menthae with bootstrap support value of 100%. Pathogenicity was assessed by spraying a suspension of urediniospores (1×104 spores/ml) of the isolate IPN 10.0115 onto six healthy peppermint plants (Mentha × piperita) that were 30 days old, while six other plants were sprayed with sterile distilled water. All plants were kept in a wet chamber for 48 h at temperatures from 28±2°C and relative humidity of 95%, after which the plastic bag was removed. All inoculated plants developed disease symptoms after 15 days, whereas the control plants remained symptomless. The pathogenicity assay was conducted twice with similar results. The morphology of the pathogen recovered from the pustules of the inoculated plants was identical to that originally recollected, thus fulfilling Koch'postulates. To our knowledge, this is the first report of Puccinia menthae causing leaf rust on Mentha × piperita in Mexico. This species has been previously identified using morphological characteristics in Brazil, Canada, Poland, and USA on Mentha × piperita (Farr and Rossman, 2023). Since the disease defoliates peppermint plants reducing yield, further information on disease management is needed.

Occurrence of Colletotrichum truncatum Causing Foliar Spot on Sesame (Sesamum indicum) in Mexico.

Sesame (Sesamum indicum L.) is an oilseed crop that present agronomic advantages and nutritional contributions in regions where water and soil fertility are limiting. In September 2020 and October 2022, anthracnose symptoms were observed on sesame fields in Mocorito (25°29'04"N;107°55'03"W) and Guasave (25°45'40"N;108°48'44"W), Sinaloa, Mexico. The disease incidence was estimated at up to 35 % (10 has) in five fields. Twenty samples were collected with symptoms on the leaves. On leaves, lesions were irregular and necrotic. Colletotrichum-like colonies were consistently isolated on PDA medium and five monoconidial isolates were obtained. One isolate was selected as a representative for morphological characterization, multilocus phylogenetic analysis, and pathogenicity tests. The isolate was deposited in the Culture Collection of Phytopathogenic Fungi of the Biotic Product Development Center at the National Polytechnic Institute under the accession number IPN 13.0101. On PDA, colonies were flat with an entire margin, initially white, then dark gray with black acervuli and setae. The growth rate was 9.3 mm/day. Conidia (n=100) on PDA were hyaloamerosporae, 17.5- 22.7 × 3.6-4.5 µm, smooth-walled, falcated and pointed at both ends, with granular content. Acervuli showed setae acicular (2-3 septate setae) tapered to the apex. The mycelial appressoria were brown, obclavate and irregular. Morphological features matched those of the Colletotrichum truncatum species complex (Damm et al. 2009). For molecular identification, total DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), and partial sequences of actin (ACT), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes were amplified by PCR (Weir et al. 2012) and sequenced. The sequences were deposited in GenBank under accession nos. OQ214919 (ITS), OQ230773 (ACT), and OQ230774 (GAPDH). BLASTn searches in GenBank showed 100%, 100%, and 100% identity to MN842788 (ITS), MG198003 (ACT), and MF682518 (GAPDH) of C. truncatum, respectively. A phylogenetic tree based on the Maximum Likelihood method and Bayesian Inference including published ITS, ACT, and GAPDH sequence data for C. truncatum species complex was generated (Talhinhas and Baroncelli 2021). In the phylogenetic tree, the isolate IPN 13.0101 was placed in the same clade of C. truncatum. Pathogenicity of the isolate IPN 13.0101 was verified on 15 sesame seedlings leaves (Dormilon variety) (15-day-old) disinfected with sodium hypochlorite and sterile water. Each leave was inoculated with 200 µL of a conidial suspension (1 × 106 spores/mL). Five plants non inoculated served as controls. All plants were kept in a moist chamber for two days, and subsequently transferred to a shade house where the temperature ranged from 25 to 30°C. All inoculated leaves developed irregular and necrotic lesions ten days after inoculation, whereas no symptoms were observed on the control leaves. The fungus was consistently re-isolated from the diseased leaves, fulfilling Koch´s postulates. The experiment was conducted twice with similar results. Colletotrichum spp. has been previously reported (Farr and Rossman, 2023) to cause sesame anthracnose in Mexico (Alvarez, 1976), Thailand (Giatgong, 1980) and Cuba (Arnold, 1986), but this is the first report of C. truncatum causing sesame anthracnose in Mexico. This disease is a recurrent problem in sesame fields in Sinaloa, therefore further studies are required to understand its impact.

Detection of Brasiliomyces malachrae Causing Powdery Mildew on Ornamental Cotton (Gossypium hirsutum) plants in Mexico.

Cotton (Gossypium L.; Malvaceae) is the most important fiber crop worldwide, also as a source of vegetable protein and edible oil. Cultivated species of cotton were apparently domesticated independently in four separate regions, in both the Old and the New World. Due to its economic importance, it is necessary to study the diseases that limit its production. During July of 2020-2022, symptoms of powdery mildew were observed on 80 ornamental cotton plants in a nursery located in Cuautla (18°52'38"N; 98°58'28"W), Morelos, Mexico. Disease incidence was 29%. Signs first appeared as small white colonies, which subsequently developed into abundant mycelial grown mainly on the upper leaf surface. White patches of mycelia were observed on leaves. In advanced stages of the disease, plants exhibited symptoms of yellowing, necrosis, and early defoliation. Microscopic analysis from 10 plant samples showed that mycelia were amphigenous, epiphyllous, in thin patches and evanescent. Hyphae were hyaline, thin walled and hyphal appressoria were simply lobed. Chasmothecia (n=50) were sub-aggregate, generally spherical to subglobose (46-61 µm in diameter), whitish, subhyaline, smooth, with a peridium of a single cell layer and appendages were absent. Three asci per chasmothecia, subspherical, 30-44 × 26-38 µm, with 4-6 ascospores per ascus. Ascospores were hyaline, ellipsoid to ovoid (16-23 × 10-18 µm). The asexual phase was not observed. The characteristics observed correspond to Brasiliomyces malachrae (Braun and Cook 2012; Cabrera et al. 2018). A voucher specimen was deposited in the Herbarium of the Department of Plant-Insect Interactions at the Biotic Products Development Center of the National Polytechnic Institute under accession no. IPN 10.0114. To confirm identification, DNA was recovered from the fungus and the internal transcribed spacer (ITS) from one sample was amplified by PCR, using the primers ITS1/ITS4 (White et al. 1990). The sequence was deposited in GenBank (OQ546720) and showed 100% sequence homology (647/1642bp) with the type sequence of B. malachrae (LC191217) from Malvastrum coromandelianum in Argentina (Cabrera et al. 2018). Pathogenicity was verified through inoculation by gently dusting conidia from infected leaves onto leaves of five healthy cotton plants. Five noninoculated plants served as controls. All plants were maintained in a greenhouse at temperatures from 28±2°C and relative humidity ranging from 80±5%. The experiment was performed twice. Inoculated plants developed powdery mildew symptoms after 14 days, whereas the control plants remained healthy. The fungus on the inoculated leaves was morphologically identical to that originally observed on diseased plants, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Brasiliomyces malachrae causing powdery mildew on Gossypium hirsutum in Mexico and North America (Farr and Rossman 2023). Powdery mildew on G. hirsutum caused by B. malachrae has been previously identified in Venezuela by Hanlin and Tortolero (1984). This disease could be a primary source of inoculum of powdery mildew for commercial cotton plantations, derived from the free movement of ornamental plants.

First Report of Erysiphe betae Causing Powdery Mildew on Chard (Beta vulgaris var. cicla) in Mexico.

Chard (Beta vulgaris var. cicla; Chenopodiaceae) is a vegetable native to the Mediterranean, widely cultivated for its nutritional properties. In June 2020, an outbreak of powdery mildew was detected in a commercial crop of chard in San Martín Texmelucan, Puebla (19°14'37.1"N; 98°27'12.5"W), Mexico. The disease was present in 86% of the plants (n=400) and the pathogen was found to cover up to 95% of the surface of the leaves. Initially, small whitish patches were observed on both sides of the leaves. Subsequently, the patches grew rapidly to cover most of the leaf surface and premature senescence of infected leaves was observed. The signs of the pathogen were observed as abundant whitish masses of conidia. Microscopic analysis of the fungus showed amphigenous mycelia with lobed hyphal appressoria. Conidiophores (n=30) were simple and erect, 93133 × 7.58.5 µm. Foot cells (n=30) were cylindrical, predominately straight, and rarely somewhat curved at the base, 30.036.5 µm, followed by a longer cell and two shorter cells, and the conidium. Conidia (n=100) were hyaline, ellipsoid-ovoid, 3745 × 1416 µm. Germ tubes (n =30) were terminal, short (0.52.0 times the conidial width) and stout. Conidial appressoria (n=30) were mostly lobed, showing from 2-6 lobes. Chasmothecia were not found. The morphological characteristics observed correspond to previous descriptions of Erysiphe betae by Braun and Cook et al. (2012). A voucher specimen (accession no. UACH450) was deposited in the Department of Agricultural Parasitology Herbarium at the Chapingo Autonomous University. To confirm identification, DNA was extracted from the fungus, and the internal transcribed spacer (ITS) and the 28S gene region of rDNA from one sample were amplified by PCR, using the primers ITS1/ITS4 (White et al. 1990) and PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000). The sequences obtained from our specimen were registered to the GenBank under the accession numbers ON157053 and ON157047 for ITS and LSU, respectively. Our sequences shared 100% identity for ITS (KX574674) and 99.8% for LSU (OM033348 and OM368494) with sequences of E. betae in BLAST'n search. Based on phylogenetic analysis using the Maximum Likelihood method including a published ITS + 28S dataset for Erysiphe species, the isolate UACH450 was grouped into a clade with E. betae. Takamatsu et al. (2015) found that E. betae, E. malvae and E. heraclei are phylogenetically indistinguishable (they form the E. heraclei species complex), nevertheless, E. malavae infects Lavatera and Malva (Malvaceae), E. heraclei predominately forms on hosts of Apiaceae and E. betae is commonly found on Beta and Chenopodium (Chenopodiaceae) (Braun and Cook 2012). Pathogenicity was verified by spraying a suspension of conidia (1107 conidia/ml) onto the leaves of six healthy chard plants and six plants were sprayed with sterile distilled water to serve as controls. All plants were maintained at temperatures from 28 2 °C and relative humidity of 802 %. All inoculated leaves developed powdery mildew symptoms after 14 days, whereas the control plants remained symptomless. The pathogenicity test was performed twice, observing the same results. The recovered pathogen showed the same morphological characteristics as the inoculated pathogen, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Erysiphe betae causing powdery mildew on Beta vulgaris var. cicla in Mexico. This pathogen has been previously reported in Iraq (Amano, 1986) and Greece (Vakalounakis and Kavroulakis, 2017) on Beta vulgaris var. cicla. Also, Erysiphe betae has been reported in Mexico on Chenopodium and throughout the world on sugar beet (Farr and Rossman, 2022). This pathogen is a major issue as it can completely cover the leaves of the diseased plants, making them difficult to market.

First Report of Leaf Blight Caused by Colletotrichum karsti on Peppermint (Mentha x piperitavar. citrata) in Mexico.

Spearmint (Mentha x piperita var. citrata (Ehrh.) Briq.: Lamiaceae) is an aromatic herb widely cultivated owing to its industrial properties. In June 2020, symptoms of leaf blight were observed on 1,500 peppermint plants in a commercial nursery located in Cuautla (18°52'18"N 98°57'58"W), Morelos, Mexico. The incidence of the disease was 89%. Symptoms were initially observed as irregular, small black necrotic spots, that grew rapidly until the leaves were blighted. Fungal isolation was done using diseased leaf tissue on potato dextrose agar (PDA) as described by Ayvar-Serna et al. (2020) and Colletotrichum-like colonies were obtained. Six isolates were purified by single spore culture and only a single morphotype was obtained. One isolate was used for pathogenicity tests, morphological characterization, and multilocus phylogenetic analysis. The isolate (accession no. UACH449) was deposited in the Culture Collection of Phytopathogenic Fungi of the Department of Agricultural Parasitology at the Chapingo Autonomous University. Colonies in PDA grow at a rate of 7.0-10.0 mm/d. After 14 days, the colony was white to orange, and conidia (n =100) were hyaline, cylindrical, and straight with rounded ends, measuring 15.0-17.0 × 4.5-6.5 µm. Appressoria were brown and bullet-shaped. In 28-day-old colonies, the formation of perithecia was observed. Asci were hyaline, unitunicate, 8-spored, fasciculate, and cylindrical to clavate. Ascospores (n =100) were hyaline, unicellular, allantoid, inaequilateral, often straight on the inner side, apices rounded, arranged biseriately within the asci, and measured 14-19 × 4.0-7.5 µm. Morphological features of the isolate placed it tentatively within the Colletotrichm boninense species complex (Damm et al. 2012). For molecular identification, genomic DNA was extracted, and the internal transcribed spacer (ITS) region (White et al. 1990), partial sequences of calmodulin (CAL), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and actin (ACT) (Damm et al. 2012) genes were amplified and sequenced. A phylogenetic tree including published ITS, CAL, GAPDH, and ACT data for Colletotrichum species was constructed and the isolate UACH449 was grouped in the clade of Colletotrichum karsti. Sequences were deposited in GenBank under the accession numbers: ITS, OL825605; CAL, OL855890; GAPDH, OL855891 and ACT, OL855889. Pathogenicity was tested by spraying a suspension of 1 × 10^5 conidia/ml, onto eight healthy peppermint plants 30-days-old var. citrata, while eight control plants were sprayed using sterile distilled water. All plants were kept at 25 +/- 2°C and 70% RH. The characteristic symptoms of the disease were observed seven days after inoculation, while control plants remained symptomless. The pathogenicity test was repeated twice. The fungus was consistently reisolated from the eight inoculated plants and was morphologically identical to that originally isolated from diseased leaves, fulfilling Koch's postulates. To date, this pathogen has not been reported on peppermint (Farr and Rossman, 2022). To our knowledge, this is the first report of Colletotrichum karsti causing foliar blight on peppermint worldwide. According to our field observations, this disease is a threat to the production of peppermint plants.

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 Puccinia menthae Causing Leaf Rust on Spearmint (Mentha spicata) in Mexico.

Spearmint (Lamiaceae) is an aromatic herb widely cultivated in Mexico for its culinary, medicinal, and industrial properties. In May 2020, symptoms and signs of rust were observed in a two-ha commercial crop of spearmint in Cuautla, Morelos (18°50'26.6"N 98°57'31.9"W), Mexico. The disease incidence was 85% and the severity was 23%. Initial symptoms included chlorotic spots on the adaxial surface of the leaves. At advanced stages of the disease, necrotic spots surrounded by chlorotic halos were developed, and later the plants were defoliated. The signs were observed as numerous orange to reddish-brown erumpent pustules primarily on the abaxial surface of the leaves. Microscopic examination of the samples revealed the presence of subepidermal uredinia, erumpent, with hyaline and cylindrical paraphyses. Urediniospores (n = 50) were hyaline to light yellow, globose to obovoid, measuring 17-27  11-25 µm, including 0.6-0.7 µm wall thickness, individually supported on pedicels, echinulate, with two germinative pores. Morphological features of the fungus correspond with previous descriptions of Puccinia mentha by Kabaktepe et al. (2017). A voucher specimen (accession no. UACH448) was deposited in the Department of Agricultural Parasitology Herbarium at the Chapingo Autonomous University. To confirm identification, the 28S gene region of rDNA was amplified from one sample by a nested PCR using the primer sets Rust2inv (Aime, 2006) and LR6 (Vilgalys and Hester, 1990), and Rust28SF primers (Aime et al., 2018), and LR5 (Vilgalys and Hester, 1990) for the first and second reactions, respectively. The sequence of our specimen (GenBank accession No. OL878354) showed 100% homology (923/1304bp) with the type-specimen sequence of P. menthae (GenBank accession No. DQ354513) from Cunila origanoides from USA (Aime, 2006). Also, a phylogenetic analysis (Bayesian inference) including a published 28S dataset for Puccinia species was performed and the isolate UACH448 was grouped into a clade with P. menthae. Pathogenicity was demonstrated by spraying five ml of a suspension of urediniospores (1104 spores/ml) recovered from infected leaves onto leaves of ten healthy spearmint plants and ten noninoculated plants served as controls. All plants were maintained at temperatures from 28 to 35°C and relative humidity ranging from 70 to 80%. All inoculated plants developed the characteristic symptoms of the disease after 14 days, whereas the control plants remained symptomless. The pathogenicity test was performed twice with similar disease response. The morphological characteristics of the pathogen recovered from all the inoculated plants were identical to that originally inoculated, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Puccinia menthae causing leaf rust on Mentha spicata in Mexico. This species has been previously identified in Australia (Edwards et al. 1999), New Zealand (Beresford et al. 1982), and USA (Farr and Rossman, 2021) on Mentha spicata. This disease reduces considerably the quality of peppermint plants, so it is necessary to develop management strategies.

First Report of Golovinomyces sonchicola Causing Powdery Mildew on Sonchus oleraceus in Mexico.

Sonchus oleraceus, common sow thistle, is native to Europe, Northern Africa, and Western Asia. This plant has become a common weed throughout the world. In Mexico, this weed has become widely naturalized by replacing indigenous plants and invading many agricultural areas. During the spring of 2018 and 2019, common sow thistle plants showing typical symptoms and signs of powdery mildew, were collected from agricultural fields in Ahome, Sinaloa, Mexico. As much as 30% of plants were diseased and 60 to 95% of the foliage was affected. Mycelium was conspicuous and white-gray, and on stems and both surfaces of leaves. Appressoria were nipple-shaped to crenulate. Conidiophores (n= 30) were hyaline, cylindrical, erect, and up to 150 µm long. Foot-cells (n= 30) were distinctly curved, 47 to 75 × 10 to 13 µm, slightly constricted, followed by 1-3 shorter cells and formed conidia in chains. Conidia (n= 100) were ellipsoid to doliiform to subcylindrical, 28 to 37 × 14 to 19 µm, lacked fibrosin bodies, and germinated from the apex. Chasmothecia were not observed. The morphological characters were consistent with those of the anamorphic state of Golovinomyces sonchicola (Braun and Cook 2012, Jakse et al. 2019). A voucher specimen (accession no. FAVF215) was deposited in the Herbarium of the Faculty of Agriculture of El Fuerte Valley at the Autonomous University of Sinaloa (Juan Jose Rios, Sinaloa, Mexico). To confirm the morphological identification, genomic DNA was extracted from mycelium and conidia, and the internal transcribed spacer (ITS) region and part of the 28S gene were amplified by PCR and sequenced. The ITS region of rDNA was amplified using the primers ITS5/ITS4 (White et al. 1990). For amplification of the 28S rRNA partial gene, a nested PCR was performed using the primer sets PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000) and NL1/TW14 (Mori et al. 2000) for the first and second reactions, respectively. Phylogenetic analyses using the maximum parsimony and maximum likelihood methods (Braun et al. 2019), including ITS and 28S sequences of isolates of Golovinomyces spp. were performed and confirmed the results obtained from the morphological analysis. Isolate FAVF215 grouped in a clade with the other isolates of G. sonchicola. The ITS and 28S sequences were deposited in GenBank under accession numbers MW425872 and MW442972, respectively. Pathogenicity was demonstrated by gently dusting conidia from infected leaves onto leaves of 20 healthy plants and covered with plastic bags for 24 h. Ten non-inoculated plants served as controls. All plants were maintained in a greenhouse at 25 to 35ºC. All inoculated plants developed similar symptoms to those observed in the field from natural infections after 12 days, whereas powdery mildew symptoms and signs were not observed on control plants. The morphology asexual structures of fungus on inoculated plants were identical to those on naturally infected plants, fulfilling Koch's postulates. Inoculation tests were repeated twice with identical results. Based on the morphological data and phylogenetic analysis, the fungus was identified as G. sonchicola. This fungus has been reported causing powdery mildew on S. oleraceus in Germany, The Netherlands, Slovenia, and The United Kingdom (Farr and Rossman 2021). To the best of our knowledge, this is the first report of G. sonchicola causing powdery mildew on S. oleraceus in Mexico. This powdery mildew pathogen may represent an option for the biological control of common sow thistle.

Biological activity of Claviceps gigantea in juvenile New Zealand rabbits.

The Ascomycete fungus Claviceps gigantea infects maize kernels and synthetizes several alkaloids, mostly dihydrolysergamides. There is limited information on the damage these toxins cause in mammals, despite reports from infested areas with 90% presence of the fungus sclerotia. With this background, it was decided to determine the biological activity of chemical compounds present in sclerotia of C. gigantea in rabbits 38 days after weaning. Sclerotia of C. gigantea were collected in fields with high incidence of the disease, ground and analysed for nutrients. Experimental diets were prepared with four treatments, where sclerotial powder was added, substituting for alfalfa flour in increasing proportions [C. gigantea/alfalfa flour (0:100, 5:95, 15:85 and 25:75)]. Total ergot alkaloid content was analysed by high-performance liquid chromatography. Male juvenile rabbits were utilised and distributed in completely randomised design with four replications. Initial weight was recorded in each animal, and experimental diet was offered. In this study, weight of animals, feed consumption and feed conversion were evaluated in individual animals. Blood samples were taken for haemograms, and finally euthanasia was practiced. The consumption of C. gigantea had a negative effect on body weight and feed consumption. The necropsies showed anomalies proportional to the consumption of feed contaminated with the fungus.