Distribution and Pathogenicity of Colletotrichum Species Associated With Mango Anthracnose in Mexico.

Mango anthracnose, caused by Colletotrichum spp., is the most significant disease of mango (Mangifera indica L.) in almost all production areas around the world. In Mexico, mango anthracnose has only been attributed to C. asianum and C. gloeosporioides. The aims of this study were to identify the Colletotrichum species associated with mango anthracnose symptoms in Mexico by phylogenetic inference using the ApMat marker, to determine the distribution of these species, and to test their pathogenicity and virulence on mango fruits. Surveys were carried out from 2010 to 2012 in 59 commercial orchards in the major mango growing states of Mexico, and a total of 118 isolates were obtained from leaves, twigs, and fruits with typical anthracnose symptoms. All isolates were tentatively identified in the C. gloeosporioides species complex based on morphological and cultural characteristics. The Bayesian inference phylogenetic tree generated with Apn2/MAT intergenic spacer sequences of 59 isolates (one per orchard) revealed that C. alienum, C. asianum, C. fructicola, C. siamense, and C. tropicale were associated with symptoms of mango anthracnose. In this study, C. alienum, C. fructicola, C. siamense, and C. tropicale are reported for the first time in association with mango tissues in Mexico. This study represents the first report of C. alienum causing mango anthracnose worldwide. The distribution of Colletotrichum species varied among the mango growing states from Mexico. Chiapas was the only state in which all five species were found. Pathogenicity tests on mango fruit cultivar Manila showed that all Colletotrichum species from this study could induce anthracnose lesions. However, differences in virulence were evident among species. C. siamense and C. asianum were the most virulent, whereas C. alienum and C. fructicola were considered the least virulent species.

Phylogeny, Distribution, and Pathogenicity of Lasiodiplodia Species Associated With Cankers and Dieback Symptoms of Persian Lime in Mexico.

Persian lime (Citrus latifolia Tan.) is an important and widely cultivated fruit crop in several regions of Mexico. In recent years, severe symptoms of gummosis, stem cankers, and dieback were detected in the Persian lime-producing region in the states of Veracruz and Puebla, Mexico. The aims of this study were to identify the species of Lasiodiplodia associated with these symptoms, determine the distribution of these species, and test their pathogenicity and virulence on Persian lime plants. In 2015, symptomatic samples were collected from 12 commercial Persian lime orchards, and 60 Lasiodiplodia isolates were obtained. Fungal identification of 32 representative isolates was performed using a phylogenetic analysis based on DNA sequence data of the internal transcribed spacer region and part of the translation elongation factor 1-α and ß-tubulin genes. Sequence analyses were carried out using the Maximum Likelihood and Bayesian Inference methods. Six Lasiodiplodia species were identified as Lasiodiplodia pseudotheobromae, Lasiodiplodia theobromae, Lasiodiplodia brasiliense, Lasiodiplodia subglobosa, Lasiodiplodia citricola, and Lasiodiplodia iraniensis. All Lasiodiplodia species of this study are reported for the first time in association with Persian lime in Mexico and worldwide. L. pseudotheobromae (46.9% of isolates) was the most frequently isolated species followed by L. theobromae (28.1%) and L. brasiliense (12.5%). Pathogenicity on Persian lime young plants using a mycelial plug inoculation method showed that all identified Lasiodiplodia species were able to cause necrotic lesions and gummosis, but L. subglobosa, L. iraniensis, and L. pseudotheobromae were the most virulent.

First Report of Anthracnose Caused by Colletotrichum spaethianum on Hemerocallis flava in Brazil.

In January 2011, leaves of several daylily (Hemerocallis flava L.) plants in nurseries in Vitória da Conquista, northeastern Brazil, showed typical anthracnose symptoms. Reddish brown lesions with a yellow halo were first observed at the tip leaves. As the disease progressed, the lesions rapidly expanded down the leaves, resulting in severe blight. Small pieces up to 5 mm in diameter were removed from the lesion margins, surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter-1 streptomycin sulfate. Macroscopic colony characters and microscopic morphology characteristics of two isolates were developed after growth on PDA for 7 days at 25°C under a 12-h light/dark cycle. Colonies presented effuse mycelium, initially white and becoming pale gray, with numerous black structures like sclerotia, setae, and acervuli absent in culture media. Conidia were hyaline, aseptate, curved or slightly curved, round or somewhat acute apex, base truncate, 13.4 to 22.7 (18.2 ± 2.16) µm length, and 3.2 to 5.8 (4.24 ± 0.62) µm width, length/width ratio 4.37, and were typical of Colletotrichum spp. DNA sequencing of partial sequence of actin (ACT), chitin synthase (CHS-1), and glyceraldehyde-3-phosphate dehydrogenase (GPD) genes and the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA gene cluster) were conducted to accurately identify the species. Sequences of two daylily isolates were highly similar to those of C. spaethianum (Allesch.) Damm, P.F. Cannon & Crous. A phylogenetic analysis using Bayesian inference and including published ACT, CHS-1, GPDH, and ITS data for C. spaethianum and other Colletotrichum species associated with daylily anthracnose (1,3) showed that the isolated fungi belong to the C. spaethianum clade. Sequences of the isolates obtained in this study were deposited in GenBank (ACT Accession Nos. KC598114 and KC598115; CHS-1 Accession Nos. KC598116 and KC598117; GPDH Accession Nos. KC598118 and KC598119; ITS Accession Nos. KC598120 and KC598121). Cultures are deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco, Recife, Brazil (CMM1224 and CMM1225). Pathogenicity tests were conducted with the two C. spaethianum strains on daylily leaves. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds near the tip leaves. Four detached leaves were inoculated for each isolate, and PDA discs without fungal growth were used as controls. The leaves were maintained in humid chamber for 2 days at 25°C under a 12-h photoperiod. Anthracnose symptoms that closely resembled those observed in the affected nurseries were developed up to 5 days after inoculation. No symptoms developed on the control plants. C. spaethianum was successfully re-isolated from symptomatic plants to fulfill Koch's postulates. C. spaethianum was described from H. fulva and H. citrina in China, Hosta sielbodiana in Germany, and Lilium sp. in South Korea (3), and from Peucedanum praeruptorum in China (2). To our knowledge, this is the first report of C. spaethianum in Brazil and the first report on H. flava. References: (1) U. Damm et al. Fungal Divers. 39:45, 2009. (2) M. Guo et al. Plant Dis. 97:1380, 2013. (3) Y. Yang et al. Trop. Plant Pathol. 37:165, 2012.

First Report of Stem Rot of Papaya Caused by Fusarium solani Species Complex in Brazil.

In October 2010, 2-year-old papaya (cv. Hawaii) trees with high incidence of stem rot were observed during a survey conducted in Rio Grande do Norte state, northeastern Brazil. Stems showing reddish brown-to-dark brown symptoms were collected and small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter-1 streptomycin sulfate. Plates were incubated at 25°C with a 12-h photopheriod for 4 days. Pure cultures with white, fluffy aerial mycelia were obtained by subculturing hyphal tips onto PDA. Identification was made using morphological characteristics and DNA based molecular techniques. Colonies grown on PDA and Spezieller Nährstoffarmer agar (SNA) for 10 days at 25°C with a 12-h photoperiod were used for morphological identification (3). The fungus produced cream sporodochia and two types of spores: microconidia were thin-walled, hyaline, ovoid, one-celled, and 6.8 to 14.6 × 2.3 to 4.2 µm; macroconidia were thick walled, hyaline, slightly curved, 3- to 5-celled, and 25.8 to 53.1 × 3.9 to 5.7 µm. Fifty spores of each type were measured. Rounded, thick-walled chlamydospores were produced, with two to four arranged together. On the basis of morphological characteristics (1), three fungal isolates (CMM-3825, CMM-3826, and CMM-3827) were identified as Fusarium solani (Mart.) Sacc. and were deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco (Recife, Brazil). Single-spore isolates were obtained and genomic DNA of the isolates was extracted and a portion of the translation elongation factor 1-alpha (EF1-α) gene of the isolates was amplified and sequenced (2). When compared with sequences available in the GenBank and Fusarium-ID databases, DNA sequences of the three isolates shared 99 to 100% sequence identity with F. solani species complex (GenBank Accession Nos. JF740784.1, DQ247523.1, and DQ247017.1). Representative sequences of the isolates were deposited in GenBank (Accession Nos. JQ808499, JQ808500, and JQ808501). Pathogenicity tests were conducted with four isolates on 3-month-old papaya (cv. Hawaii) seedlings. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds (0.4 cm in diameter) on the stem (center) of each plant. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (10 each) were kept in a greenhouse at 25 to 30°C. After 2 weeks, all inoculated seedlings showed reddish brown necrotic lesions in the stems. No symptoms were observed in the control plants. The pathogen was successfully reisolated from symptomatic plants to fulfill Koch's postulates. To our knowledge, this is the first report of F. solani species complex causing papaya stem rot in Brazil. Papaya is an important fruit crop in the northeastern Brazil and the occurrence of this disease needs to be taken into account in papaya production. References: (1) C. Booth. Fusarium Laboratory Guide to the Identification of the Major Species. CMI, Kew, England, 1977. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Ames, IA, 2006.

First Report of Mango Anthracnose Caused by Colletotrichum karstii in Brazil.

From April to June 2010, mango fruits (Mangifera indica L.) (cv. Tommy Atkins) showing post-harvest anthracnose symptoms were collected during a survey conducted in São Francisco Valley, northeastern Brazil. Fruits affected by anthracnose showed sunken, prominent, dark brown to black decay spots. Small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter-1 streptomycin sulfate. Plates were incubated at 25°C in the dark for 5 to 7 days and colonies that were morphologically similar to species of Colletotrichum were transferred to PDA (1). Identification was made using morphological characteristics and phylogenetic analysis. Two isolates (CMM 4101 and CMM 4102) presented colonies that had white aerial mycelia and orange conidial mass, varying between colorless and pale orange in reverse. Conidia were hyaline, cylindrical, and aseptate 14.52 (10.40 to 20.20) µm long and 4.90 (3.80 to 6.50) µm wide, length/width ratio = 3.0. Mycelial growth rate was 5.20 mm per day at 25°C. Morphological and cultural characterizations were consistent with the description of Colletotrichum karstii (3). PCR amplification by universal primers (ITS1/ITS4) and DNA sequencing of the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA gene cluster) were conducted to confirm the identifications. Analysis of representative sequences (GenBank Accession Nos. HM585409 and HM585406) suggested that the isolated pathogen was C. karstii. Using published ITS data for C. karstii (3), a phylogenetic analysis was made via Bayesian inference, which shows that the isolated fungi belong to the C. karstii clade. Sequences of the isolates obtained in this study were deposited in GenBank (KC295235 and KC295236), and cultures were deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco (CMM, Recife, Brazil). Pathogenicity tests were conducted with the C. karstii strains on mango fruits cv. Tommy Atkins. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds (0.4 cm in diameter) at the medium region of the each fruit. PDA discs without fungal growing were used as controls. Inoculated fruits were placed in plastic containers lined with paper towels wetted in distilled water. The containers were partially sealed with plastic bags to maintain high humidity and incubated at 25°C in the dark. The plastic bags and paper towels were removed after 24 h, and fruits were kept at the same temperature. The experiment was arranged in a completely randomized design with four replicates per treatment (isolate) and four fruits per replicate. Typical anthracnose symptoms were observed after 10 days in mango fruits. C. karstii was successfully reisolated from symptomatic mango fruits to fulfill Koch's postulates. C. karstii was previously described from Orchidaceae in southwest China and the United States (2,3). To our knowledge, this is the first report of C. karstii causing mango anthracnose in Brazil and worldwide. References: (1) U. Damm et al. Stud. Mycol. 73:1, 2012. (2) I. Jadrane et al. Plant Dis. 96:1227, 2012. (3) Yang et al. Cryptogamie Mycol. 32:229, 2011.

Monosporascus eutypoides, a Cause of Root Rot and Vine Decline in Tunisia, and Evidence that M. cannonballus and M. eutypoides Are Distinct Species.

Three Monosporascus eutypoides-like isolates recovered from cucurbit plants with symptoms of Monosporascus root rot and vine decline in Tunisia were compared to 28 isolates of M. cannonballus from 12 countries for phenotypic, genomic, and pathogenicity characteristics. Morphologically, M. cannonballus and M. eutypoides-like cultures were similar, each producing fertile perithecia in culture containing globose, smooth, dark brown to black ascospores. Nevertheless, all M. cannonballus isolates had one ascospore per ascus, while M. eutypoides-like isolates had mainly two to three ascospores per ascus (rarely one). The employment of the internal transcribed spacer (ITS) of nuclear ribosomal DNA, the elongation factor 1-α (EF-1α), and the ß-tubulin (ß-tub) gene sequence diversity analyses and the resulting phylogenies identified a level of polymorphism that enabled separation of M. cannonballus and M. eutypoides-like isolates. All isolates of M. cannonballus had identical EF-1α and ß-tub sequences irrespective of very diverse geographic origins, which were different from the EF-1α and ß-tub sequences of the M. eutypoides-like isolates (96 and 97% similarity, respectively). Similar results were obtained for the ITS region of rDNA. In addition, of three M. eutypoides-like isolates tested for pathogenicity, all three were pathogenic on watermelon, two were pathogenic on muskmelon, but only one was pathogenic on cucumber. The results demonstrate that the M. eutypoides-like isolates belong to the species M. eutypoides, and that M. cannonballus and M. eutypoides are distinct species.

First Report of Papaya Fruit Anthracnose Caused by Colletotrichum brevisporum in Brazil.

Papaya fruits (Carica papaya L.) (cv. Golden) showing post-harvest anthracnose symptoms were observed during surveys of papaya disease in northeastern Brazil from 2008 to 2012. Fruits affected by anthracnose showed sunken, prominent, dark brown to black lesions. Small pieces (4 to 5 mm) of necrotic tissue were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter-1 streptomycin sulfate. Macroscopic colony characters and microscopic morphology characteristics of four isolates were observed after growth on PDA (2) for 7 days at 25°C under a 12-hr light/dark cycle. Colonies varied between colorless and pale brown in reverse, with orange conidial mass. Conidia were hyaline, aseptate, cylindrical with round ends, slightly flattened, smooth-walled, guttulate, and 13.5 (10.5 to 17.1) µm × 3.8 (2.1 to 4.8) µm (l/w ratio = 3.5, n = 50), typical of Colletotrichum spp. DNA sequencing of partial sequences of actin (ACT) gene and the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA) were conducted to accurately identify the species. Sequences of the papaya isolates were 99% similar to those of Colletotrichum brevisporum (GenBank Accession Nos. JN050216, JN050217, JN050238, and JN050239). A phylogenetic analysis using Bayesian inference and including published ACT and ITS data for C. brevisporum and other Colletotrichum species was carried out (1). Based on morphological and molecular data, the papaya isolates were identified as C. brevisporum. Conidia of the papaya isolates were narrower than those described for C. brevisporum (2.9 to 4.8 µm and 5 to 6 µm, respectively) (1), which may be due to differences in incubation temperature or a typical variation in conidial size in Colletotrichum species (3). Sequences of the isolates obtained in this study are deposited in GenBank (ACT Accession Nos. KC702903, KC702904, KC702905, and KC702906; ITS Accession Nos. HM163181, HM015851, HM015854, and HM015859). Cultures are deposited in the Culture Collection of Phytopathogenic Fungi of the Universidade Federal Rural de Pernambuco, Recife, Brazil (CMM 1672, CMM 1702, CMM 1822, and CMM 2005). Pathogenicity testing was conducted with all four strains of C. brevisporum on papaya fruits (cv. Golden). Fruits were wounded at the medium region by pushing the tip of four sterile pins through the surface of the skin to a depth of 3 mm. Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were placed in shallow wounds. PDA discs without fungal growth were used as control. Inoculated fruits were maintained in a humid chamber for 2 days at 25°C in the dark. After 6 days, anthracnose symptoms developed that were typical of diseased fruit in the field. C. brevisporum was successfully reisolated from symptomatic fruits to fulfill Koch's postulates. C. brevisporum was described from Neoregalia sp. and Pandanus pygmaeus in Thailand (1). To our knowledge, this is the first report of C. brevisporum in Brazil and the first report of this species causing papaya fruit anthracnose. References: (1) P. Noireung et al. Cryptogamie Mycol., 33:347, 2012. (2) B. C. Sutton. The Genus Glomerella and its anamorph Colletotrichum. CAB International, Wallingford, UK, 1992. (3) B. S. Weir et al. Stud. Mycol. 73:115, 2012.

First Report of Mango Dieback Caused by Pseudofusicoccum stromaticum in Brazil.

From September to December 2010, mango (Mangifera indica L.) stems showing dieback symptoms were collected during a survey conducted in São Francisco Valley, northeastern Brazil. Small pieces (4 to 5 mm) of necrotic tissues were surface sterilized for 1 min in 1.5% NaOCl, washed twice with sterile distilled water, and plated onto potato dextrose agar (PDA) amended with 0.5 g liter-1 streptomycin sulfate. Plates were incubated at 25°C in the dark for 14 to 21 days and colonies that were morphologically similar to species of Botryosphaeriaceae were transferred to PDA. Colonies developed a compact mycelium that was initially white, but becoming gray dark after 4 to 6 days of incubation at 25°C in darkness. Identification was made using morphological characteristics and DNA based molecular techniques. Pycnidia were obtained on 2% water agar with sterilized pine needles as substratum after 3 weeks of incubation at 25°C under near-UV light. Pycnidia were large, multilocular, eustromatic, covered with hyphae; locule totally embedded without ostioles, locule walls consisting of a dark brown textura angularis, becoming thinner and hyaline toward the conidiogenous region. Conidia were hyaline, thin to slightly thickened walled, aseptate, with granular contents, bacilliform, straight to slightly curved, apex and base both bluntly rounded or just blunt, 15.6 to 25.0 (20.8) µm long, and 2.7 to 7.9 (5.2) µm wide, length/width = 4.00. According to these morphological characteristics, three isolates (CMM1364, CMM1365, and CMM1450) were identified as Pseudofusicoccum stromaticum (1,3,4). PCR amplification by universal primers (ITS4/ITS5) and DNA sequencing of the internal transcribed spacer (ITS1-5.8S-ITS2 rRNA gene cluster) were conducted to confirm the identifications through BLAST searches in GenBank. The isolates were 100% homologous with P. stromaticum (3) (GenBank Accession Nos. AY693974 and DQ436935). Representative sequences of the isolates were deposited in GenBank (Accession Nos. JF896432, JF966392, and JF966393). Pathogenicity tests were conducted with the P. stromaticum strains on 5-month-old mango seedlings (cv. Tommy Atkins). Mycelial plugs taken from the margin of actively growing colonies (PDA) of each isolate were applied in shallow wounds (0.4 cm in diameter) on the stem (center) of each plant. Inoculation wounds were wrapped with Parafilm. Control seedlings received sterile PDA plugs. Inoculated and control seedlings (five each) were kept in a greenhouse at 25 to 30°C. After 5 weeks, all inoculated seedlings showed leaf wilting, drying out of the branches, and necrotic lesions in the stems. No symptoms were observed in the control plants. P. stromaticum was successfully reisolated from symptomatic plants to fulfill Koch's postulates. P. stromaticum was described from Acacia, Eucalyptus, and Pinus trees in Venezuela (3,4), and there are no reports of this fungus in other hosts (2). To our knowledge, this is the first report of P. stromaticum causing mango dieback in Brazil and worldwide. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , 18 May 2011. (3) S. Mohali et al. Mycol. Res. 110:405, 2006. (4) S. R. Mohali et al. Fungal Divers. 25:103, 2007.

First Report of Papaya Fruit Rot Caused by Colletotrichum magna in Brazil.

Species of the genus Colletotrichum are commonly reported as pathogens of fruits in tropical regions. Papaya fruits (Carica papaya L.), cv. Golden, with typical lesions of anthracnose, chocolate spot, and/or stem-end rot were collected from 18 papaya-producing areas of northeast Brazil in 2007. One hundred and fifty-five isolates of Colletotrichum spp. were obtained from the fruit lesions and cultured on potato dextrose agar. Pathogenicity tests were conducted by placing a 20-µl drop of 105 conidia ml-1 suspension on a wounded area of two healthy fruits of cv Golden at the climacteric stage. Inoculated fruits were placed in a moist chamber at 26°C (±2) for 48 h. After this period, the plastic covers of the trays used to form the moist chamber were removed and the trays were kept at 26°C (±2) for 98 h when symptoms were assessed. The causal agents of fruit rot were recovered from inoculated fruits showing symptoms of anthracnose and chocolate spot. Conidia from fresh lesions were collected and measured. Conidia dimensions were 13.49 × 3.80 µm, length/width ratio = 3.55 µm. Conidia were predominantly cylindrical to bluntly rounded ends and slightly flattened. All isolates were morphologically similar to Colletotrichum gloeosporioides Penz (1). Molecular analyses of the isolates were carried out with taxon-specific primers for C. acutatum J.H Simmonds and C. gloeosporioides (3). Only one amplicon was detected for eight isolates with the C. gloeosporioides primer. All isolates were genotyped using inter-simple sequence repeat (ISSR) primers. Three groups of isolates were found, one containing the eight C. gloeosporioides isolates, a second group comprised of 141 isolates, and a third contained six isolates. The second and third groups were more similar to each other than to the first C. gloeosporioides group. Thirty two representative isolates of the three ISSR groups were sequenced for the internal transcribed spacer (ITS) and glutamine synthetase (GS) (GenBank Nos. HM163181 and HM015847) regions. With molecular phylogenetic analyses, two well-supported clades were formed, one with the C. gloeosporioides isolates and the other with sequences highly similar (99% similarity) to the two ITS sequences available in GenBank (DQ003310 and GU358453) and the GS region of G. magna Jenkins & Winstead (DQ792873). The latter was reported in the United States and Taiwan (2,4). Isolates of C. magna and C. gloeosporioides are morphologically similar and identification needs to be based on molecular analyses. To our knowledge, this is the first report of C. magna causing rot of papaya fruit in Brazil. References: (1) P. F. Cannon et al. Mycotaxon 104:189, 2008. (2) M. Z. Du et al. Mycologia 97:641, 2005. (3) P. Talhinhas et al. Appl. Environ. Microbiol. 71:2987, 2005. (4) J. G. Tsay et al. Plant Dis. 94:787, 2010.

First Report of Monosporascus cannonballus on Watermelon in Brazil.

In 2008 and 2009, vine decline symptoms were observed in three watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) fields located in the municipalities of Mossoró (Rio Grande do Norte State) and Quixeré (Ceará State) in northeastern Brazil. Symptoms included yellowing of crown leaves just prior to harvest and collapse of many of the vines. Mean maximum daily temperatures for the first and second half of the season were 28.6 and 25.1°C, respectively. Affected plants exhibited necrotic root systems and lacked most of the secondary and tertiary feeder roots. Numerous perithecia on the roots contained asci and ascospores characteristics of Monosporascus cannonballus Pollack & Uecker (1,2). Small pieces of primary and secondary roots were surface disinfected and plated onto potato dextrose agar (PDA) medium with 0.5 g liter-1 of streptomycin sulfate and incubated for 7 days at 25°C in the dark. Hyphal tips from all colonies were transferred to PDA and further incubated for 30 to 40 days at 25°C in the dark for subsequent growth and sporulation. Isolations consistently yielded colonies of white mycelium, which became dark grayish after 10 to 15 days, and perithecia with one-spored asci. The internal transcribed spacer regions of ribosomal DNA of isolates 18-5 and 19-1 were sequenced (GenBank Accession Nos. GQ891544 and GQ891545). These sequences were identical to sequences of M. cannonballus (GenBank Accession Nos. AM167936 and AM167937). Pathogenicity of these two isolates was confirmed on watermelon cv. Crimson Sweet in a greenhouse maintained at 25 to 30°C. Inoculum was produced in a sand-oat hulls (Avena sativa) medium (0.5 liter of sand, 46 g of ground oat hulls, and 37.5 ml of distilled water) and incubated at 25°C for 1 month. CFU were quantified by serial dilution using 1% hydroxyethyl cellulose. A sterilized mixture of equal portions (vol/vol) of sand and peat moss was used to fill 17-cm-diameter plastic pots and inoculum was added to produce an inoculum concentration of 20 CFU g-1. Five watermelon seeds planted in each pot were later thinned to one seedling per pot. There were five replicated pots for each treatment with an equal number of noninfested pots. Plants were evaluated for disease 45 days after sowing. All isolates of M. cannonballus were highly aggressive and caused severe root necrosis compared with the noninoculated controls. M. cannonballus was reisolated from symptomatic plants, confirming Koch's postulates. In 2004, M. cannonballus was reported in the same Brazilian cucurbit-growing areas causing root rot and vine decline of muskmelon (Cucumis melo L.) (3), but to our knowledge, this is the first report of M. cannonballus on watermelon in Brazil. References: (1) R. D. Martyn and M. E. Miller. Plant Dis. 80:716, 1996. (2) F. G. Pollack and F. A. Uecker. Mycologia 66:346, 1974. (3) R. Sales Jr. et al. Plant Dis. 88:84, 2004.

Epiphytic bacteria antagonistic to Curvularia leaf spot of yam.

Curvularia eragrostidis yam leaf spot is a serious concern among the northeast Brazilian yam growing areas. In order to study its biocontrol, bacterial isolates from the yam phylloplane were tested against the pathogen. They were evaluated with respect to the following parameters: (1) inhibition of C. eragrostidis mycelial growth by using paired culture and cellophane membrane methods, (2) inhibition of conidium germination by using a paired suspension test, (3) reduction of disease severity and, (4) persistence of antagonistic action, on plants under greenhouse conditions. From a total of 162 bacterial isolates, 39 showed antagonism to the pathogen in paired culture. The bacteria produced extracellular, nonvolatile, and diffusible metabolites in the membrane cellophane test. Seventeen isolates resulted in more than 75% inhibition of C. eragrostidis mycelial growth. Among them, IF-26 showed the greatest antagonism. The isolates IF-82, IF-88, and IF-109 inhibited pathogen conidial germination, with average inhibition levels of 99.2, 98.2 and 96.2%, respectively. Under greenhouse conditions the antagonists were applied at three different time intervals relative to C. eragrostidis inoculation: 3 days before, at the same time, and 3 days after. IF-82 and IF-88 applied at the same time as pathogen inoculation both reduced disease severity 75%. IF-82 showed the best persistence of antagonistic action, with an average of 96.3%. IF-82, identified as Bacillus subtilis, was the best biocontrol agent for the yam leaf spot disease in this study.

Selección de germoplasma de frejol común (phaseolus vulgaris) chicharro (vigna unguiculated) resistentes a rhizoctonia solani / Selection of common beans (phaseolus vulgaris) and cowpea (vigna unguiculata) germoplasms resistant to rhizoctonia solani

Con la finalidad de seleccionar fuentes de resistencia a rhizoctoria solani entre germoplasmas de frejol común y chicharro, se efectuaron evaluaciones en condiciones de invernadero y campo. En la primera situación, 20 germoplasmas de cada leguminosa fueron evaluadas. Las semillas fueron sembradas en suelo esterilizado, previamente infestado con el patógeno, mediante la incorporación de 50 mg de sustrato colonizado (arroz) Kg de suelo. La evaluación de los germoplasmas fue realizada 15 días después de la siembra, mediante una escala de valores numéricos, siendo distribuidas en las categorías de " resistente, moderadamente susceptible (mod. susc.) y susceptible". Tres germoplasmas de frejol (AN 534-534, IPA-5 e IPA-9), se comportaron como resistentes a r.solani, mientras que entre los de chicharro, se observaron reacciones mod. susc. y susceptibles. En las condiciones de campo, en las huertas que contenían suelo previamente infestado por el patógeno (10g m2 de suelo), se evaluaron 7 germoplasmas de frejol y 13 de chicharro. La severidad de la enfermedad fue evaluada 21 días después de la siembra, conforme a la metodología utilizada en invernadero. Todos los germoplasmas de frejol y 3 germoplasmas de chicharro (corujinha, L101.000-2 y L191.006) se comportaron como mod. susc. mientra que los demás fueron clasificados como susceptibles. Los resultados evidenciaron la dificultad en la obtención de germoplasmas con altos niveles de resitencia a r. solani, indicando la necesidad de la implementación de prácticas integradas que conduzcan al control de la enfermedad, en la cual el uso de germoplasmas con resistencia mod. suc. sería uno de los componentes

Influencia de la irrigación en el atizonamiento de las hojas de ñame (dioscorea cayennesis) por curvularia eragrostidis en el n. e. de Brasil / Influence of irrigation on leaf blight of yam (dioscorea cayennensis) by curvularia eragrostidis in the n. e of Brasil

El atizonamiento de las hojas (quema), causado por curvularia eragrostidis, es una de las principales enfermedades del ñame (dioscorea cayennesis) en el noreste brasileño. Por esto se analizó el progreso y patrón espacial de la enfermedad en cuatro áreas con plantaciones comerciales de ñame, dos irrigadas ( A y B) y dos no irrigadas (C y D), localizadas en el municipio de Alinca, Estado de Pernanbuco, Brasil. En las áreas irrigadas, la cantidad inicial y la máxima severidad de la enfermedad, fueron superiores a las verificadas en las áreas no irrigadas. Utilizándo el modelo de Gompertz, no se verificaron diferencias significativas entre las tasas de progreso de la enfermedad, siendo idénticas en las áreas A, B, C y ligeramente inferior en el área D. En las áreas B, C y D, las plantas enfermas presentaron un patrón aleatorio, dentro y entre las líneas de plantación y el área A presentó un patrón agregado, especiamente entre las líneas. Considerándo estos resultados, es posible concluir que la irrigación no tuvo influencia significativa en la severidad de la mancha necrótica de las hojas de ñame ni en la agregación de plantas enfermas dentro de las áreas de plantación

Tratamiento de semillas de algodón con pseudomonas spp. fluorescentes en el biocontrol de rhizoctonia solani / Cotton seed treatment with fluorescent pseudomonas spp. in rhizoctonia solani biocontrol

Fue evaluado el efecto del tratamiento de semillas de algodón con pseudomonas spp. fluorescentes para el control de rhizoctonia solani. Primeramente se seleccionaron 67 cepas de pseudomonas para inocular semillas de algodón de la variedad precoce-1. Las semillas fueron sumergidas en suspensiones bacterianas (10/8 células/ml) preparadas en solución de MgSo40.1M y posteriormente sembradas en bandejas con suelo sin esterilizar e infectado con el patógeno (cepa RS-4), en densidad de 50 mg de sustrato (arroz) colonizado/Kg de suelo. La evaluación de la intensidad de la enfermedad se realizó a los 10 días después de la siembre, utilizándose una escala de valores de 0 a 4, donde 0= sin síntomas y 4= máximo de síntomas. Las cepas de pseudomonas p-8, CR-27, CB-38, CB-33 y P-5, fueron más eficaces en el control de las cepas de r. solani (RS-4, RS-5 y RS-6), con densidades de inóculos de 50, 100 y 150 mg/kg de suelo. La cepa CB-33 ejerció mayor biocontrol que la cepa RS-4 del fitopatógeno, así como las cepas RS-5 y RS-6 respectivamente. Las cepas bacterianas presentaron mayores niveles de control que el fungicida quintozene en todas las condiciones

Hongos fitopatógenos asociados a frutos comercializados en Recife, Pernambuco, Brasil / Phytopathogenic fungi associated with fruits marketed in Recife, Pernambuco, Brazil

En la central de abastecimiento y en tres ferias libres de la ciudad de Recife, PE(Brasil), se analizaron cada tres meses, durante un año, frutos de aguacate (palta), limón, maracuyá-amarillo, pimentón y tomate para detectar la presencia de enfermedades fúngicas. En cada muestra fueron evaluadas 20 unidades de cada tipo de fruto, en cinco puntos diferentes por sitio de colecta, totalizándo 100 frutos/punto de comercialización, la incidencia de enfermedades fúngicas en los frutos de aguacate fue de 38,52 porciento, en maracuyá de 15,48 porciento, en limón de 17,55 porciento, en pimentón de 1,58 porciento y en tomate de 6,5 porciento. El hongo detectado con mayor frecuencia en los frutos de aguacate fue sphaceloma perseae (20,0 porciento), en limón sphaceloma fawcetti (6,2 porciento), en maracuja cladosporium herbarum (10,3 porciento) en pimentón alternaria alternata (0,7 porciento) y en tomate geotrichum candidum (3,2 porciento). Los altos valores de incidencia de enfermedades fúngicas detectados, indican la necesidad de adoptar procedimientos antes y después de la cosecha, para reducir los riesgos de infección, lo que promovería la reducción significativa de pérdidas de postcosecha

Epidemiología de enfermedades fúngicas de postcosecha en frutos de papaya / Epidemiology of postharcest fungal diseases in papaya fruits

Se analizó el impacto de las enfermedades fúngicas en las pérdidas de postcosecha de papaya en la fase de comercialización, evaluando la influencia de la temperatura en la manifestación de las enfermedades de postcosecha y del binomio temperatura-humedad relativa en la severidad de la pudrición causada por Lasiodiplodia theobromae. Cuatro supermercados, en la cuidad de Recife (Estado de Pernambuco, Brasil), fueron analizados en cuanto al impacto de las enfermedades fúngicas postcosecha en las pérdidas de frutos de papaya. Estas fueron las principales causas de descarte, correspondiendo un 98 por ciento al Cultivar Formosa y 90,5 por ciento al Cultivar Sunrise Solo. Los principales hongos involucrados en el proceso de infección fueron Colletotrichum gloeosporiodes, L. Theobromae y Rhizopus stolonifer, agentes causales de la antracnosis, pudrición peduncular y pudrición acuosa, respectivamente. Al analizar la influencia de la temperatura (5, 15 y 30°C) en los frutos con aspecto sano, se constató que las principales enfermedades fueron las mismas observadas en los frutos descartados. A temperaturas de 5 y 15°C, la antracnosis presentó una mayor incidencia en relación con las otras enfermedades, mientras que la pudrición peduncular fue constatada solamente a 30°C, con incidencia superior a las demás. En el análisis de la influencia de la temperatura y la humedad sobre la severidad de la pudrición causada por L. theobromae, no se observaron síntomas de la enfermedad en frutos en humedad relativa inferior o igual al 90 por ciento. En presencia de elevada humedad, sólo a partir de 25°C fue constada la incidencia de la enfermedad, con un aumento en la severidad de la misma con la elevación de la temperatura y del período de humedad relativa.

Influencia de la distancia de plantación y selección de genotipos de mani (arachis hypogaea l.) resistentes a cercosporidium personatum (berk & curt.)deigh. y puccinia arachidis speg / Influence of spacing arrangement and genotype selection of peanut (arachis hypogaea l.) resistent to cercosporidium personatum (berck & curt) deigh and puccinia arachidis speg

La mancha negra y la roya, causadas respectivamente por los hongos cercosporidium personatum y puccinia arachidis, constituyen las principales enfermedades, 15 genotipos de maní fueron analizados con respecto a los niveles de resistencia bajo condiciones naturales de infección. El diseño se efectuó en bloques completos al azar, con 5 repeticiones. La evaluación fue efectuada a los 85 días después de la siembra, midiéndose la incidencia y la severidad de las enfermedades en 45 folíolos por parcela. Los genotipos BR-1, L2IAC2, CNPA Senegal y CNPA 125 AM, se destacaron de los demás al evidenciar los menores niveles de severidad de la mancha negra, mientras en la incidencia de la roya se destacó CNPA Senegal y CNPA Havana. El efecto de los tipos de espaciamientos de siembra fueron de 0,3, 0,5 y 0.7m entre líneas con 5,10 y 15 plantas/m lineal. Los niveles de severidad de las enfermedades fueron analizadas utilizándose el cultivar IAC Tupa. la evaluación fue efectuada 90 días después de la siembra, en 45 folíolos de la linea central de cada parcela. Los resultados no evidenciaron un efecto significativo de los tipos de espaciamientos en la severidad de la mancha negra y de la roya