ABSTRACT In Mexico, Creole corn has presented problems related to seed rot. Therefore, the objective of this study was to determine the frequency of fungi associated with Creole corn seeds. From January to February 2019, 13 Creole corn samples were collected from several localities in Guerrero, Mexico. The samples were processed in PDA culture medium and the frequency of each fungus was estimated based on cultural characteristics and taxonomic keys. Considering symptomatic corn seed samples, Fusarium oxysporum was recorded in eight samples at 97.2%, followed by F. graminearum, isolated from race “Olotillo 1” at 94.4% and from race “Cónico pepitilla” at 58.3%. Phomopsis sp. was isolated at 100% from race “Olotillo 2”. Gibberella moniliformis was isolated from “Elotes Occidental 1” at 83.3%, while the least frequent isolate (19.4%) from “Pepitilla” was Sarocladium strictum, which was recorded in three samples at the low values of 11.1% and 2.8% for races “Arrocillo 2” and “Pepitilla”, respectively; Talaromyces variabilis was found in two samples at 11.1% and 2.8% from “Arrocillo 2” and “Cónico pepitilla”, respectively; Stenocarpella macrospora was isolated at 72.2% from “Pepitilla”. Aspergillus flavus was obtained from “Cónico Pepitilla” at 16.7%, while Setosphaeria turcica and Emericella sp. were less frequently isolated. Considering asymptomatic seeds of race “Cónico pepitilla”, F. oxysporum was isolated at 8.3%, Fusarium acuminatum at 8.3% and Gibberella moniliformis at 41.7%; from asymptomatic seeds of “Olotillo 1” and “Olotillo 2”, Phomopsis sp. was isolated at 50% and Rhizoctonia solani at 50%, respectively. In the present study, the fungi F. oxysporum, Phomopsis sp., G. moniliformis and F. graminearum were most frequently associated with Creole corn seeds.

RESUMO No México, o milho crioulo apresenta problemas de podridão das sementes. Portanto, o objetivo desta pesquisa foi determinar a frequência de fungos associados a sementes de milho crioulo. De janeiro e fevereiro de 2019, 13 amostras de milho crioulo foram coletadas em localidades de Guerrero, México. As amostras foram processadas em meio de cultura BDA e a frequência de cada fungo foi estimada com base nas características culturais e chaves taxonômicas. Nas amostras sintomáticas de sementes de milho, Fusarium oxysporum foi registrado em oito amostras com 97,2%, seguido por F. graminearum isolado na raça de milho “Olotillo 1” com 94,4% e na raça “Cónico pepitilla” com 58,3%. Phomopsis sp., foi isolado 100% na raça “Olotillo 2”. Gibberella moniliformis, foran isolados de “Elotes Occidental 1” com 83,3% e o menos frequente (19,4%) em “Pepitilla” foi Sarocladium strictum registrado em três amostras com valores baixos de 11,1% e 2,8% na raça de milho “Arrocillo 2” e “Pepitilla”, Talaromyces variabilis em duas amostras com 11,1% e 2,8% em “Arrocillo 2” e “Cónico pepitilla”. Stenocarpella macrospora foi isolado em 72,2% da raça de milho “Pepitilla”. Aspergillus flavus em “Cónico Pepitilla” com 16,7%, Setosphaeria turcica e Emericella sp., foi isolado com menor frequência. Em sementes assintomáticas da raça “Cónico pepitilla” foi isolado F. oxysporum com 8,3%, Fusarium acuminatum 8,3%, Gibberella moniliformis em 41,7%, em sementes assintomáticas de “Olotillo 1” e “Olotillo 2” Phomopsis sp., foi isolado em 50% e Rhizoctonia solani com 50%. Neste estudo, os fungos F. oxysporum, Phomopsis sp., G. moniliformis e F. graminearum foram os mais frequentemente associados às sementes de milho crioulo.

RESUMO A doença manchada de vinagreira causada por Corynespora cassiicola afeta a produção de cálice no México. O objetivo deste estudo foi avaliar vinte e dois genótipos de vinagreira contra C. cassiicola em casa de vegetação. Com base nas área abaixo da curva de progresso da doença (AACPD) foi possível detectar genótipos suscetíveis, tolerantes e resistentes. Dada a incidência nas folhas, os genótipos suscetíveis foram Conpoz, Sudlaz, Morcot e Sudigua (valores de AACPD 7379,2 a 5891,7); tolerantes foram Conayu e Chinxal (AACPD 1341,6 e 1313,2). Enquanto isso, pela severidade nas folhas, os suscetíveis foram Sudigua, Conpoz e Morena2 (AACPD de 788,4 a 436,3); tolerantes foram Almatech, Crioxal, Rojatec e Conayu (37,7 a 28,76 de AACPD). Enquanto, avaliando a incidência em cálices, genótipos suscetíveis foram; Morena2, Morena, Conpoz, Descop e Chinayu (AACPD de 6572,1 a 2319,4); para a gravidade suscetível foram Morena2, Descop, Morena, Cabxal, Chinayu e Conpoz (AACPD de 3355,4 a 779,2). A incidência e severidade nos cálices detectaram genótipos resistentes, que foram Almatech, Criolaz2, Criocot, Criolaz, Rojatec, Criopoz, Crioxal, Chinxal e Conayu (0,0 de AACPD). Neste estudo, foram detectados genótipos tolerantes e resistentes à mancha foliar e cálice causada por C. cassiicola em vinagreira.

ABSTRACT Roselle spot caused by Corynespora cassiicola affects calyx production in Mexico. The aim of the present study was to evaluate twenty-two roselle genotypes against C. cassiicola under greenhouse conditions. The area under the disease progress curve (AUDPC) was used to detect susceptible, tolerant and resistant genotypes. Considering the incidence in leaves, susceptible genotypes were Conpoz, Sudlaz, Morcot and Sudigua (AUDPC values of 7379.2 to 5891.7); tolerant genotypes were Conayu and Chinxal (AUDPC 1341.6 and 1313.2). Based on the severity in leaves, susceptible genotypes were Sudigua, Conpoz and Morena2 (AUDPC from 788.4 to 436.3); tolerant genotypes were Almatech, Crioxal, Rojatec and Conayu (37.7 to 28.76 AUDPC). Assessment of the incidence in calyces indicated that susceptible genotypes were Morena2, Morena, Conpoz, Descop and Chinayu (AUDPC from 6572.1 to 2319.4); for the severity in calices, susceptible genotypes were Morena2, Descop, Morena, Cabxal, Chinayu and Conpoz (AUDPC from 3355.4 to 779.2). Incidence and severity on calyces evidenced resistant genotypes, which were Almatech, Criolaz2, Criocot, Criolaz, Rojatec, Criopoz, Crioxal, Chinxal and Conayu (0.0 AUDPC). In the present study, tolerant and resistant genotypes were detected to leaf and calyx spot caused by C. cassiicola in roselle.

Abstract. The importance of native Mexican varieties in agricultural food production is analyzed, discussed and reflected upon, particularly regarding emergency situations such as the pandemic caused by the SARS-CoV-2 virus. The main example used is the tomato, Solanum lycopersicum, comparatively with commercial varieties. Evidence is provided of the higher tolerance of native varieties to pests and diseases. When grafted onto commercial varieties, they maintained their tolerance, but also increased their yield. Before and perhaps during the pandemic, native tomato varieties have been an important food source for several marginalized communities in Mexico. The analysis suggests that the agricultural food production based on native varieties may help solve problems in the supply chain of imported agricultural inputs, while also solving the dependency on agrochemicals, fertilizers and commercial varieties, and promoting family-produced foods. A lower dependence on industrialized inputs would contribute towards self-sufficiency and food sovereignty, with nutritious and innocuous foods. In times of a pandemic, the family production model in marginalized rural settings would help reduce the mobility of people and the risk of contagion, increase food security and reduce SARS-CoV-2 risk factors due to the incidence of chronic diseases, particularly metabolic diseases.

Resumen. Se analiza, discute y reflexiona sobre la importancia de las variedades nativas mexicanas en la producción agroalimentaria, particularmente en situaciones de emergencia como la pandemia ocasionada por el virus SARS-CoV-2. Se ejemplifica con el jitomate, Solanum lycopersicum, comparativamente con variedades comerciales. Se muestran evidencias de mayor tolerancia de variedades nativas a plagas y enfermedades. Cuando se injertaron con variedades comerciales, mantuvieron su tolerancia; pero, además, incrementaron su rendimiento. Antes y probablemente durante la pandemia, las variedades nativas de jitomate han sido fuente importante de alimento para numerosas comunidades marginadas de México. El análisis sugiere que la producción agroalimentaria basada en variedades nativas puede subsanar problemas en la cadena de suministros de insumos agrícolas de importación reduciendo además la dependencia de agroquímicos, fertilizantes y variedades comerciales y favorecer la producción familiar de alimentos. Una menor dependencia de insumos industrializados coadyuvaría a la autosuficiencia y soberanía alimentaria, con alimentos nutritivos e inocuos. En tiempo de pandemia, el modelo familiar productivo en entornos rurales marginados favorecería menor movilidad de personas y riesgos de contagio, seguridad de alimentos y reducción de factores de riesgo al SARS-CoV-2 por la incidencia de enfermedades crónicas en particular las metabólicas.

Abstract. Nacobbus aberrans sensu lato is one of the most important plant parasitic nematodes (PPN) in tomato crop. For the management of this PPN, it is important to study sustainable strategies such as genetic resistance, commonly found in crop wild relatives. In this regard, there was interest in knowing the response of local populations (Michoacán, Mexico) of wild tomato (Solanum lycopersicum var. cerasiforme) to the inoculation with second stage juveniles. Three experiments (E1, E2, and E3) were mounted. Five wild genotypes and one cultivated genotype (cv. Rio Grande) were evaluated. At 7 and 21 days after the inoculation (dai), the number of nematodes within the root was evaluated, and at the 45 and 60 dai root galling was recorded. In the E1 and E2 experiments, at 7 and 21 dai, the J2 and J3-J4 stages were found. In all three experiments, there was root galling, and at 60 dai egg production was evident. N. aberrans s.l. invaded the roots and completed its development and reproduction. These results reveal the suitability of the five Mexican populations of wild tomatoes as hosts of the nematode and suggest the need to explore other wild solanaceae as possible sources of resistance to the nematode.

Resumen. Nacobbus aberrans sensu lato es uno de los nematodos más importantes en el cultivo de jitomate. Para su manejo, es de importancia el estudio de estrategias sostenibles como la resistencia genética, comúnmente encontrada en parientes silvestres de los cultivos. Al respecto, surgió el interés por conocer la respuesta de poblaciones locales (Michoacán, México) de jitomate silvestre (Solanum lycopersicum var. cerasiforme) a la inoculación con juveniles de segundo estadio de N. aberrans s.l. Se montaron tres experimentos (E1, E2, y E3). Se evaluaron cinco genotipos silvestres y uno cultivado (cv. Río grande). A los 7 y 21 días posteriores a la inoculación (dpi) se evaluó el número de nematodos dentro de la raíz, y a los 45 y 60 dpi el agallamiento de raíces. En E1 y E2, a 7 y 21 dpi se encontraron los estadios J2 y J3-J4. En los tres experimentos ocurrió agallamiento, y a 60 dpi la producción de huevos fue evidente. N. aberrans s.l. invadió las raíces, y completó su desarrollo y reproducción. Estos resultados revelan la aptitud de las cinco poblaciones mexicanas de jitomate silvestre como hospedantes del nematodo, y sugieren la necesidad de explorar otras solanáceas silvestres como posibles fuentes de resistencia al nematodo.

Abstract In Mexico, Ficus benjamina L. is mainly used as an ornamental and has been widely accepted because of its low production cost, rapid growth and abundant foliage. Ficus L. is a very broad genus that groups together diverse species native to tropical and subtropical regions. The aim of this research was to morphologically and molecularly identify the causal agent of “branch dieback” in F. benjamina plants. Dieback was observed in Ficus benjamina trees in urban areas and gardens in Sonora during the hottest season (June to September) in 2014. Fungal isolates were obtained from different symptomatic plants. The morphological characteristics of these isolates were similar to each other and their pathogenicity was confirmed by observing necrotic lesions caused by four of these isolates in F. benjamina plants 40 days after inoculation. Concatenated sequences from the internal transcribed spacer region (ITS; KU141333 and KU141334), large subunit (LSU; MF508739 and MF508740) and RNA polymerase II subunit (RPB2; MF508741 and MF508742) of the DNA from two representative isolates were analyzed phylogenetically, showing that the NDFB002 and NDFB003 isolates form a separate clade with several strains of Neoscytalidium dimidiatum. These isolates were previously reported in the National Center for Biotechnology Information (NCBI) GenBank. To our knowledge, this is the first report where N. dimidiatum is designated as a causal agent of branch dieback in F. benjamina plants in Mexico.

Resumen En México, Ficus benjamina L. se usa principalmente como ornamental y ha sido ampliamente aceptado debido a su bajo costo de producción, crecimiento rápido y follaje abundante. Ficus L. es un género muy amplio que agrupa diversas especies originarias de regiones tropicales y subtropicales. El presente trabajo tuvo como objetivo identificar morfológica y molecularmente al agente causal de la “muerte descendente de ramas” en plantas de F. benjamina. Se observó muerte descendente en árboles de Ficus benjamina de zonas urbanas y jardines de Sonora durante la temporada de mayor calor (junio-septiembre) en 2014. Se obtuvieron aislados fúngicos de diferentes plantas sintomáticas. Las características morfológicas de dichos aislados fueron similares entre sí y su patogenicidad se corroboró al observar las lesiones necróticas ocasionadas por cuatro de estos aislados en plantas de F. benjamina a los 40 días después de la inoculación. Las secuencias concatenadas de la región espaciadora interna transcrita (ITS; KU141333 y KU141334), subunidad grande (LSU; MF508739 y MF508740) y ARN polimerasa subunidad II (RPB2; MF508741 y MF508742) del ADN de dos aislados representativos se analizaron filogenéticamente, mostrando que los aislados NDFB002 y NDFB003 forman un clado aparte con varias cepas de Neoscytalidium dimidiatum. Dichos aislados se reportaron previamente en el Banco de Genes del National Center for Biotechnology Information (NCBI). Hasta donde se sabe, este es el primer reporte donde N. dimidiatum se señala como agente causal de muerte descendente de ramas en plantas de F. benjamina en México.

Plants of chilli Capsicum annuum L. CM334 show a high level of resistance to Phytophthora capsici, but are susceptible to Nacobbus aberrans; such resistance has been associated with capsidiol accumulation, a sesquiterpene phytoalexin. In the present study the expression of hydroxymethylglutaryl-CoA reductase 2 gene (HMG2, associated with sesquiterpene phytoalexins biosynthesis) in CM334 chilli roots inoculated with N. aberrans and in combination with P. capsici, was determined by qRT-PCR. The levels of HMG2 transcripts were significantly reduced (p≤0.05) from -1.57 to -1.28-fold in the interaction CM334/N. aberrans; whereas in roots inoculated only with the oomycete, the accumulation of transcripts occurred earlier and at higher levels (1.52 to 3.54-fold). In plants inoculated with both pathogens, the expression was higher compared with those inoculated with the nematode only (p≤0.05), but generally lower than the expression observed in roots of plants inoculated with the oomycete alone. The expression of the HMG2 gene associated with defense was reduced in CM334 chilli plants infected by N. aberrans.

Plantas de chile Capsicum annuum L. CM334 exhiben un alto grado de resistencia a Phytophthora capsici, pero son susceptibles a Nacobbus aberrans; tal resistencia se ha asociado con la acumulación de capsidiol, una fitoalexina sesquiterpé-nica. En el presente estudio se determinó mediante qRT-PCR los niveles de expresión del gen HMG2 (hidroximetilglutaril-CoA reductasa 2, asociado con la biosíntesis de fitoalexinas sesquiterpénicas) en raíces de chile CM334 inoculadas con N. aberrans y en combinación con P. capsici. Los niveles de transcritos de HMG2 fueron significativamente reducidos (p≤0.05) de -1.57 a -1.28 veces en la interacción CM334/N. aberrans; mientras que en raíces inoculadas sólo con el oomiceto la acumulación de transcritos fue temprana e intensa (1.52 a 3.54 veces). En plantas inoculadas con ambos patógenos, la expresión fue alta comparada con aquellas inoculadas sólo con el nematodo (p≤0.05), pero generalmente menor que la expresión observada en raíces inoculadas sólo con el oomiceto. La expresión del gen HMG2 (asociado con defensa) fue reducida en raíces de chile CM334 infectadas por N. aberrans.