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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.

El objetivo de este trabajo fue evaluar el comportamiento postcosecha del fruto de mango cv Ataulfo en estado de madurez fisiológica como respuesta a la infección inducida por Colletotrichum siamense y Colletotrichum asianum. Se inocularon mangos con C. siamense y C. asianum y se almacenaron durante 10 días a 28 °C y HR de 85-90%. En los frutos se evaluó la virulencia de Colletotrichum spp. Y su efecto en las variables de calidad físicas, químicas y la respiración. A los 10 días de almacenamiento, C. siamense mostró mayor virulencia que C. asianum en los frutos de mango, con algunas diferencias en el color interno entre los frutos inoculados y los testigos. Los frutos inoculados con C. asianum presentaron mayor actividad respiratoria y menor textura con respecto al testigo. Las variables de calidad físicas y químicas en los frutos mostraron diferencias significativas con respecto al tiempo de almacenamiento, pero no por la presencia del hongo. La infección de los mangos causada por las dos especies de Colletotrichum se manifestó como manchas necróticas en la zona infectada de los frutos, afectando la apariencia y la calidad visual.

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.

Peronospora tabacina is considered the main limiting factor in tobacco production worldwide. In Mexico, information on the genetic diversity of this pathogen is scarce; therefore, the objective of this research was to evaluate 12 microsatellites in 20 isolates collected in the states of Nayarit, Chiapas, and Veracruz. PCR amplification and sequencing of these microsatellites were performed; as well as the alignment and comparison of the sequences deposited in the GenBank database. A total of 19 isolates showed amplification for the 12 microsatellites evaluated, while in one of the isolates, the amplification of two microsatellites was not observed, it being possible to determine that P. tabacina isolates present in Nayarit, Chiapas, and Veracruz are genetically homogeneous. Regions of dinucleotides were observed, most corresponding to (GT)n repeat motifs or (TG)n variations, as well as (AC)n, (CA)n, (AT)n and (AG)n motifs. The isolates analyzed in this study can be considered products of clonal lines, therefore no genetic diversity was found in these isolates.

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.

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 U.S. The work presented here was conducted to determine if there was a difference in fungicide sensitivity of S. sclerotiorum isolates in the U.S. 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 sub-tropical Mexico were less sensitive compared to temperate U.S. isolates due to different management practices and climates. The EC50(D) fungicide sensitivity of 512 S. sclerotiorum isolates from the U.S. (443), Brazil (36), and Mexico (33) was determined using a discriminatory concentration (DC) previously identified for tetraconazole (2.0 ppm; EC50(D) ranged 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, two 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 throughout the world plus baseline sensitivity to boscalid in the U.S.

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.

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.

In November 2018, symptoms of brown rot were observed on chayote (

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.

Eggplant (

Turcicum leaf blight (TLB), is a common foliar disease of maize in Mexico that is caused by the fungal pathogen

Common bean (

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.

Nanche (Byrsonima crassifolia) has great economic importance in the dry and humid tropics in Mexico, where is used for the elaboration of different drinks, foods, and candies; also in the traditional medicine to treat fever and stomach disorders. Since 2021, a high incidence of disease-causing scabby fruit in young nanche fruits has been detected in Las Choapas, Veracruz, Mexico. Disease symptoms were visible on the skin of fruits which progressed as fruits matured. Therefore, the objectives of this study were to identify the causal agent of this scab disease based on morphology and molecular techniques and to determine their pathogenicity. Fifteen isolates were recovered from diseased fruits. Because the isolates presented similar morphology, two of them were selected to determine their identity and pathogenicity. On the basis of colony characteristics, conidial morphology, and phylogenetic analyses of the internal transcribed spacers, partial translation elongation factor 1-α gene, and partial β-tubulin gene sequence the isolates were identified as Neopestalotiopsis australis. Koch's postulates demonstrated the pathogenicity of N. australis on nanche. This is the first report implicating N. australis as a causal agent of Scab Disease on B. crassifolia in Mexico and in the world.

La muerte descendente del limón ‘Persa’ (Citrus latifolia Tan.) causada por Lasiodiplodia spp., es una enfermedad de alta importancia. La intensidad de las podas en limón incrementa la susceptibilidad y la pérdida anual de hasta 35% de árboles, lo que resulta 60% de reducción de la producción. Durante los años 2016 y 2017, en el municipio de Papantla, Veracruz se evaluó la efectividad del control químico y biológico contra Lasiodiplodia spp., después de la poda. Se realizó un diseño de bloques completo al azar, se aplicaron cinco tratamientos: metil tiofanato (1 g L-1), tiabendazole (2.5 g L-1), clorotalonil (3 g L-1) y mancozeb (4 g L-1), Trichoderma harzianum + Trichoderma viridae (20 ml L-1) y un testigo (sin aplicación). Se realizaron dos aspersiones dirigidas a tronco, ramas y follaje hasta punto de goteo. Se evalúo la incidencia y severidad de la enfermedad cada siete días después de la primera aplicación. Con los datos de incidencia se realizó ajuste de modelos epidemiológicos y se calcularon los parámetros descriptivos como: intensidad inicial, tasa de incremento y área bajo la curva del progreso de la enfermedad. El fungicida metil tiofanato tuvo mayor efectividad para el control de la enfermedad, seguido de tiabendazol.

Anthracnose, caused by Colletotrichum spp., is the most significant field and post-harvest disease of mango worldwide and is mainly controlled through the use of systemic fungicides belonging to the methyl benzimidazole carbamate (MBC) class. In Mexico, this disease in mango has been associated with at least seven cryptic species belonging to the C. gloeosporioides complex. In this study, the distribution of sensitivity to MBC (benomyl and carbendazim) and prochloraz fungicides of 101 Colletotrichum spp. isolates obtained from 101 commercial orchards in Mexico’s most important mango-producing states was determined. All Colletotrichum spp. isolates were obtained from commercial mango orchards with applications of MBC fungicides and that had not been exposed to applications of prochloraz, or any other DMI (demethylation inhibitors) class fungicide. Isolates were evaluated using an in vitro test to determine the effective fungicide concentration at which 50% of mycelial growth is inhibited (EC50) for each isolate-fungicide combination. EC50 values for benomyl and carbendazim ranged from 0.0967 to 0.3995 µg mL−1 (median = 0.1923 µg mL−1) and from 0.0880 to 0.1703 µg mL−1 (median = 0.1171 µg mL−1), respectively, while those for prochloraz ranged from 0.0066 to 0.0813 µg mL−1 (median = 0.0253 µg mL−1). Our results revealed a wide distribution in Mexico of Colletotrichum spp. isolates from mango sensitive to MBC fungicides and prochloraz. Data obtained in this study will serve as a source of comparison of the evolution of the sensitivity of Colletotrichum spp. populations obtained from mango to MBC and DMI fungicides in the future.

Pitahaya (

Anthracnose, caused by

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.

Wilt disease complex is one of the most important diseases of tomatillo (Physalis ixocarpa) in the production areas of Mexico. Disease symptoms include wilting, poor growth, discoloration of vascular tissues, root rot, and death of plants. The aims of this study were to identify the fungi associated with wilt disease complex of tomatillo by the combination of phylogenetic analyses and morphological characterization, as well as to determine their pathogenicity and virulence on tomatillo seedlings. A total of 88 fungal isolates were obtained from symptomatic plants from 19 tomatillo fields distributed in northern Sinaloa, Mexico. Subsequently, a subset of 37 isolates representing the range of geographic origin was selected for further morphological and molecular characterization as well as pathogenicity tests. Phylogenetic analyses using Maximum Likelihood were used to identify 15 isolates of Rhizoctonia (ITS sequence data), 14 isolates of Fusarium (EF-1α sequence data), five isolates of Macrophomina (ITS, EF-1α, BT, and ACT sequence dataset) and three isolates of Neocosmospora (EF-1α sequence data) to species level. Pathogenicity tests were performed on tomatillo seedlings (cv. Gran Esmeralda) under greenhouse conditions. Phylogenetic analyses of 37 fungal isolates allowed the identification of Rhizoctonia solani AG 4-HGI (40.5%), Fusarium oxysporum (29.8%), Macrophomina phaseolina (13.5%), F. nygamai (8.1%) and Neocosmospora falciformis (8.1%). All fungal species were found to be pathogenic on tomatillo seedlings but a significant difference in disease severity was observed. To our knowledge, F. nygamai, M. phaseolina and N. falciformis were recorded for the first time infecting tomatillo in Mexico and worldwide.

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. Fil: Tovar Pedraza, Juan Manuel. Centro de Investigación En Alimentación y Desarrollo; México Fil: Mora-Aguilera, Jose Antonio. Instituto de Fitosanidad, Colegio de Postgraduados; México Fil: Nava-Diaz, Cristian. Colegio de Postgraduados. Instituto de Fitosanidad; México Fil: Bernardi Lima, Nelson. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Unidad de Fitopatología y Modelización Agrícola - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Fitopatología y Modelización Agrícola; Argentina Fil: Michereff, Sami Jorge. Universidad Federal Rural Pernambuco; Brasil Fil: Sandoval-Islas, Sergio. Colegio de Postgraduados. Instituto de Fitosanidad; México Fil: Camara, Marcos Paz Saraiva. Universidad Federal Rural Pernambuco; Brasil Fil: Téliz, Daniel. Colegio de Postgraduados. Instituto de Fitosanidad; México Fil: Leyva-Mir, Santos Gerardo. Universidad Autonoma Chapingo; México

El cultivo de avena (Avena sativa L.) es afectado por un amplio rango de enfermedades foliares causadas por hongos patógenos, entre estos los más importantes son las inducidas por Bipolaris spp., los cuales causan severos tizones foliares, principalmente en la zona de los Valles Altos de México. El objetivo de este estudio fue identificar molecularmente los dos aislamientos asociados al tizon foliar en avena y determinar la respuesta de 30 variedades comerciales de avena de la Colección Nacional a la infección por B. victoriae y B. sorokiniana bajo condiciones de invernadero. Un aislado de B. victoriae y un aislado de B. sorokiniana, se incrementaron para inocular plantas de 30 variedades de avena mediante la aspersión de una suspensión de esporas al follaje. El diseño experimental empleado fue en bloques al azar para cada uno de los aislados, se evaluaron 30 tratamientos que consistieron en las variedades analizadas, cada tratamiento constó de 20 plantas con cuatro repeticiones. Se midió el daño foliar como variable de repuesta para determinar la severidad a la enfermedad. Se observó que las variedades AB-177, Cuauhtémoc, Gema, Texas, Nodaway y Pampas se comportaron como las más susceptibles a B. sorokiniana, mientras que, las variedades Teporaca y Nuda mostraron ser moderadamente resistentes a éste patógeno. Para el caso de B. victoriae, se observó que las variedades Juchitepec y Ópalo fueron resistentes, entretanto, las variedades Gema, Bachiniva y Cevamex se comportaron como las más susceptibles a la infección.

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 β-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.

[EN] Lasiodiplodia theobromae is one of the most frequent fungal pathogens associated with dieback, gummosis, leaf spot, stem-end rot and fruit rot symptoms in cashew, mango, papaya and grapevine. In this study, the variation in the genetic diversity of 117 L. theobromae isolates from northeastern Brazil (n = 100) and Mexico (n = 17), which were collected from these four crops, was analysed using microsatellite markers. The results revealed low genetic diversity among L. theobromae populations and the existence of two genetic groups. All Mexican isolates were grouped with Brazilian isolates, suggesting a low level of differentiation between these populations. Furthermore, no evident host or climate-based population differentiation was observed for L. theobromae in Brazil. The populations studied were mostly clonal, but additional studies are needed to better understand the mode of reproduction of the pathogen. The low genetic diversity of L. theobromae populations in northeastern Brazil suggests that resistant cultivars could be used as a durable management strategy to reduce the impact of the diseases caused by this pathogen., This study was financially supported by CoordenacAo de Aperfeicoamento de Pessoal de Nivel Superior - CAPES, 'Ciencia sem Fronteiras - CAPES' (number 88881.132070/2016-01) and the Universitat Politecnica de Valencia. G.E. was supported by the Spanish postdoctoral grant Juan de la Cierva-Formacion. The authors thank Maela Leon and Valentin Garrigues (Universitat Politecnica de Valencia, Valencia, Spain) for laboratory support. The authors declare no conflicts of interest.

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Watermelon is an important vegetable crop in Mexico and produced on 358,105 ha, with nearly 1.5 x 106 tons. In September 2019, brown, irregular shape to round lesions with concentric rings were observed on the leaves and stems of watermelon plants in Sonora State. The surface of the lesions contained abundant cup-shaped sporodochia covered by masses of olive-green to black conidia. Edge sections of symptomatic tissues were cut from the leaves, disinfected in 70% ethanol for 1 min and subsequently washed twice with distilled water. Disinfected tissue samples were transferred to PDA medium and incubated at 27°C for 15 days. White colonies were observed with spordochia arranged in concentric rings with characteristic of greenish-black masses of conidia. Spore masses stained with lactophenol blue were examined microscopically. Conidia were nonseptate and rod-shaped with rounded ends that measured 6.65 ± 0.54 x 1.56 ± 0.25 μm (n = 100). The characteristics of the fungus were similar to those reported for Paramyrothecium foliicola (Rennberger and Keinath, 2020). Molecular identification was performed on a representative isolate. RNA polymerase II second largest subunit (RPB2), calmodulin (CmdA) and the β-tubulin (B-tub) genes were amplified and sequenced with the primer sets RPB2-5F2-RPB2-7cR, CAL228F-CAL737R and Bt2a-Bt2b, respectively. These sequences were submitted to GenBank with the acc. nos. MW116070 for RPB2, MW116071 for CmdA and MW116072 for B-tub. BLASTn analysis of the sequences demonstrated 99.34 to 100% identity with Paramyrothecium foliicola (acc. nos. MN398043, MN593713 and MN398138). Koch's postulates were verified on 15-day-old watermelon seedlings and mature fruit. One point of each of ten watermelon seedlings and six points of each of five fruit were marked for inoculation. A plug of mycelium obtained from a monosporic pure culture (grown for 15 days in PDA) was applied to each point without wounds. PDA only medium was included as the controls. The pathogenicity tests were repeated twice. Treated seedlings and fruit were kept in plastic bags at 27°C for 15 days. The first symptoms appeared 4 days after inoculation on the seedlings and 3 days after inoculation on the fruit. At the end of the test, the symptoms were similar to those observed initially in the field. The pathogen was re-isolated from lesion edges, and the morphological characteristics of the pathogen were determined to correspond with those of the inoculated fungus. Control seedlings and fruits remained healthy. P. foliicola has been reported to cause leaf spot disease on wild rocket and basil (Matić et al., 2019) and, recently, on watermelon in South Carolina (Rennberger and Keinath, 2020). To the best of our knowledge, this report is the first to describe P. foliicola causing leaf spot and stem canker on watermelon in Mexico.

Extraction of eggs of Meloidogyne spp. in sodium hypochlorite (NaOCl) is a helpful procedure to assess the population levels and to obtain inoculum. In this sense, laboratory and greenhouse experiments were done to evaluate the effect of the NaOCl concentration on the viability of M. enterolobii eggs. Additionally, the objective of this investigation was to corroborate the preferable treatments to count populations in cucumber galled roots or to obtain inoculum of M. enterolobii. It was shown that the effect of the NaOCl concentration on the viability of M. enterolobii eggs is potentially detrimental. The NaOCl concentration caused a higher hatching, which in turn, resulted in non-infective larvae. Therefore, the best treatments to obtain inoculum of eggs of M. enterolobii included the 0.75% NaOCl (with 8-min stirring), 0.5% NaOCl (with stirring for 8, 12, and 16 min), and 0.3% NaOCl concentration (with stirring for 8, 12, 16, and 20 min). For a correct estimate of the egg population in roots, we show by several treatments that a concentration of 0.5% NaOCl (with stirring for 8, 12, and 16 min) and 0.75% NaOCl (with 8-min stirring) give the highest results.

From 2018 to 2020, powdery mildew-like signs and symptoms were observed on chayote (Sechium edule var. virens levis) in a commercial field located in Santa Maria del Rio, San Luis Potosi, Mexico. Signs appeared as whitish powdery masses on both sides of leaves and stems. Disease incidence was about 30% and signs covered up to 70% of leaf surface. Ten samples were collected and analyzed. Mycelium was amphigenous, persistent, white, in dense patches. Hyphal appressoria were lobed and solitary. Conidiophores (n = 30) were hyaline, erect, straight, and 62 to 101 μm long. Foot cells were cylindrical and straight, followed by 1-3 shorter cells, and forming conidia in short chains. Conidia (n = 100) were hyaline, surface striate, cylindrical-ellipsoid, doliiform or ovoid, 25.7 to 37.6 × 11.9 to 18.4 μm, without fibrosin bodies, and with germ tubes terminal or subterminal. Conidial appressoria were lobed. Chasmothecia were not observed. The morphological characters were consistent with those of the anamorphic state of Neoerysiphe sechii (Gregorio-Cipriano et al. 2020). A voucher specimen was deposited in the Herbarium of the Department of Agricultural Parasitology at the Chapingo Autonomous University under accession number UACH192. To confirm the identification of the fungus, genomic DNA was extracted from conidia and mycelium, 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, including ITS and 28S sequences of isolates of Neoerysiphe spp. were performed and confirmed the results obtained in the morphological analysis. The isolate UACH192 grouped in a clade with isolates of N. sechii. The ITS + 28S sequence was deposited in GenBank under accession number MZ468642. Pathogenicity was confirmed by gently dusting conidia from infected leaves onto ten leaves of healthy chayote plants. Five non-inoculated leaves served as controls. The plants were maintained in a greenhouse at 25 to 30 oC, and relative humidity of 60 to 70%. All inoculated leaves developed similar symptoms to the original observation after 8 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. The pathogenicity test was repeated twice with similar results. Based on morphological data and phylogenetic analysis, as well as pathogenicity test, the fungus was identified as N. sechii. This pathogen has been previously reported causing powdery mildew on S. edule and S. mexicanum in Veracruz, Mexico (Gregorio-Cipriano et al. 2020). However, to our knowledge, this is the first report of N. sechii causing powdery mildew on chayote in San Luis Potosi (Central Mexico). This pathogen represents a serious threat to chayote production and disease management strategies should be developed.

Tomato (