ABSTRACT Azotobacter vinelandii is a Gram negative that undergo a morphological and physiological differentiation process to form cysts resistant to desiccation. The main components of a cyst are alkylresorcinols (ARs), phenolic lipids of 21 to 23 C. These lipids are homologous to plant ARs, where they have been reported to have antifungal properties. The objective of this study was to evaluate the antifungal capacities of vegetative cells and cysts of A. vinelandii AEIV. The cysts were visualized by optical microscope and the detection of ARs was performed by thin layer chromatography. Antagonism bioassay were carried out between vegetative cells and cysts against Fusarium brachygibbosum, Aspergillus niger and Colletotrichum gloeosporioides. We confirmed the induction of cysts and the presence of ARs of A. vinelandii AEIV. We observed that using 1×103 cysts reduced up to 76.3% (p < 0.05) the growth of the three phytopathogenic fungi and this result was not observed when using vegetative cells or the strain blocked in the synthesis of ARs. This shows that the cysts exert an antagonistic effect on phytopathogenic fungi and do so through the ARs, considering the development of an effective strategy to control pests in fungi that affect postharvest fruits.

Resumen Por primera vez se registra a la avispa Eupelmus puchriceps (Cameron) como parasitoide del picudo de la espina del nopal Cylindrocopturu sbiradiatus Champion. Además, se presentan nuevos registros de distribución y distribución altitudinal en México así como aspectos preliminares de su biología.

Abstract The wasp Eupelmus puchriceps (Cameron) is recorded for the first time as a parasitoid of the nopal spine weevil Cylindrocopturus biradiatus Champion. In addition, new distribution and altitudinal records from Mexico are presented, as well as preliminary aspects of its biology.

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.

Resumen En actualidad la agricultura se han implementado biofertilizantes o compuestos orgánicos como abono para aumentar el rendimiento de los cultivos de interés comercial y restaurar la fertilidad del suelo. El uso de bacterias promotoras de crecimiento vegetal ha sido una de las mejores alternativas que aumentan el rendimiento y no ocasionan daños al ambiente. Su uso no es totalmente aceptado por los productores por el riesgo que pudieran tener a la salud del consumidor. Por ello en este trabajo se evaluó la efectividad de dos cepas K. variicola PB02, K. quasipneumoniae HPA43 en consorcio con Trichoderma en el rendimiento de Solanum lycopersicum cultivar DT22 una variedad comercializada en el mercado nacional, se observó el aumento significativo (p= 0.003) respecto a otros biofertilizantes comerciales y al grupo testigo. Se evaluó la inocuidad microbiológica de los frutos, la traslocación de estas bacterias por el sistema vascular de la planta hasta llegar a fruto, por medio del perfil clonal de cada uno de los aislamientos, sin encontrar similitudes entre las cepas inoculadas y las cepas aisladas de tejidos endófitos del fruto; sin embargo, es necesario realizar estudios genéticamente para comprobar que estas bacterias no han desarrollado mecanismos que le permitan translocar a sitios anatómicos aéreos de las plantas y fruto, de esta manera garantizar frutos de calidad sin que representen un riesgo a la salud del consumidor y alto rendimiento en la producción de cultivos agrícolas de interés comercial.

Abstract Currently, biofertilizers or organic compounds have been implemented in agriculture as fertilizer to increase the yield of crops of commercial interest and restore soil fertility. The use of plant growth-promoting bacteria has been one of the best alternatives that increase production yield and do not cause damage to the environment. Their use is not fully accepted by producers because of the risk they may have to the health of the consumer. Therefore, this work evaluated the effectiveness of two strains K. variicola PB02, K. quasipneumoniae HPA43 in consortium with Trichoderma in the production yield of Solanum lycopersicum cultivar DT22, a variety highly marketed in the national market, the significant increase (p= 0.003) was observed with respect to other commercial biofertilizers and the control group. The microbiological safety of the fruits, the translocation of these bacteria by the vascular system of the plant until reaching the fruit, was evaluated through the clonal profile of each of the isolates, without finding similarities between the inoculated strains and the strains isolated from endophytic tissues of the fruit, however it is necessary to carry out more genetically specific studies that verify that these bacteria have not actually developed mechanisms that allow them to translocate to aerial anatomical sites of plants and fruit, thus guaranteeing quality fruits without representing a risk to the health of the consumer and a high yield in the production of agricultural crops of commercial interest.

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. Blackberry gray mold, induced by Botrytis cinerea, is a fruit disease that causes important economic losses. The present study evaluated nine fungicides belonging to different chemical groups, alone and in combination with potassium silicate, using the dose recommended on the label for the control of B. cinerea in the field. The incidence and severity of the disease were evaluated, as well as the degrees Brix, silicon concentration, and yield. The experiment was carried out twice. Incidence and severity percentages were converted to area under the disease progress curve (AUDPC). Combined with potassium silicate, the fungicide azoxystrobin significantly reduced incidence and severity, showing the lowest percentages in the last evaluation of these variables. In the first repetition, the incidence and severity values were 4% (AUDPC = 1320) and 0.1% (AUDPC = 298.5), respectively. In the second, 3% (AUDPC = 1099) and 0.1% (AUDPC = 214.5) respectively. The concentration of soluble solids and fruit yield increased (12.4 and 13.6 t ha-1 in the first and second repetition, respectively). The results indicate that potassium silicate enhances the effect of fungicides under field conditions and can thus be considered a management alternative against the gray mold disease in blackberries.

Resumen. El moho gris de la zarzamora causado por Botrytis cinerea, es una enfermedad que afecta los frutos y causa pérdidas económicas importantes. En la presente investigación se evaluaron nueve fungicidas pertenecientes a diferentes grupos químicos, solos y en combinación con silicato de potasio utilizando la dosis recomendada en la etiqueta para el control de B. cinerea en campo. Se evaluó la incidencia y severidad de la enfermedad, además de grados Brix, concentración de silicio y rendimiento, el experimento se realizó dos veces. Los porcentajes de incidencia y severidad se transformaron a área bajo la curva del progreso de la enfermedad (ABCPE). El fungicida azoxystrobin combinado con silicato de potasio redujo la incidencia y severidad significativamente, presentando los menores porcentajes en la última evaluación de dichas variables. En la primera repetición, los valores de incidencia y severidad fueron de 4% (ABCPE= 1320) y 0.1% (ABCPE= 298.5), respectivamente, y en la segunda 3% (ABCPE=1099) y 0.1% (ABCPE=214.5), respectivamente. Por lo tanto, aumentó la concentración de solidos solubles y rendimiento (12.4 y 13.6 t ha-1 en la primera y segunda repetición, respectivamente). Con base en los resultados obtenidos, se determinó que el silicato de potasio potencializa el efecto de los fungicidas bajo condiciones de campo, por lo tanto, puede ser una alternativa de manejo contra el moho gris en zarzamora.

Resumen La especie Solanum lycopersicum L. muestra variación en intensidad de color, forma y tamaño de fruto, hábitos de crecimiento, por lo que es importante identificar variedades sobresalientes en características agronómicas y someterlos a un proceso de mejoramiento genético. El objetivo del presente estudio fue evaluar el efecto de la inoculación con Klebsiella variicola, K. quasipneumoniae y K. pneumoniae en plantas de 19 ecotipos de tomate. Se estableció un experimento en un diseño de bloques completos al azar bajo un arreglo factorial generalizado con cinco repeticiones en condiciones de bioespacio. Las variables evaluadas fueron días a floración, peso fresco de fruto, longitud de raíz, peso fresco de raíz, volumen de raíz, peso seco de raíz y número de semillas. El análisis de varianza mostró diferencias significativas en las fuentes de variación cepas de bacteria y ecotipos de tomate. Los resultados indicaron variación en el sistema radicular, características agronómicas y componentes de rendimiento de fruto con la aplicación de bacterias promotoras de crecimiento vegetal en ecotipos nativos de tomate. Las cepas bacterianas favorecen la producción de frutos de tomate con atributos para ser comercializados.

Summary The species Solanum lycopersicum L. shows variation in intensity of color, fruit shape and size, growth habits, so it is important to identify outstanding varieties in agronomic characteristics and subject them to a genetic improvement process. The objective of this study was to evaluate the effect of inoculation with Klebsiella variicola, K. quasipneumoniae and K. pneumoniae in plants of 19 tomato ecotypes. An experiment was established in a randomized complete block design under a generalized factorial arrangement with five replications under biospace conditions. The variables evaluated were days to flowering, fresh fruit weight, root length, fresh root weight, root volume, dry root weight and number of seeds. The analysis of variance showed significant differences in the sources of variation bacterial strains and tomato ecotypes. Results indicated variation in the root system, agronomic characteristics and fruit yield components with the application of plant growth promoting bacteria in native tomato ecotypes. Bacterial strains favor the production of tomato fruits with attributes to be commercialized.

Abstract The Mexican tea (Chenopodium ambrosioides L.) is an aromatic and medicinal plant. Information on its growth dynamics and mineral nutrition for its production is insufficient, therefore, the objective of the study was to evaluate the effect of three concentrations of the Steiner nutrient solution on the growth and production of Mexican tea grown under green- house conditions. The study was conducted in Cuernavaca, Morelos, Mexico; with the genotype H-1000 (Hortaflor®) grown in tezontle as substrate. Three concentrations (50, 75 and 100 %) of the Steiner nutrient solution were applied to evaluate the growth of the crop by means of destructive samplings at 39, 46, 53, 60, 67 and 74 days after sowing; in each sampling, the following were determined: plant height, leaf area, leaf area index (LAI), weight of fresh matter, weight of dry matter, crop growth rate (CGR), absolute growth rate (AGR), and production per plant. A regression analysis was performed on the variables with the Excel® program, and for the case of production per plant, an analysis of variance and Tukey›s mean test (P ≤ 0.05) were performed. The highest height and production in the Mexican tea crop grown in a greenhouse and with inorganic substrate was obtained with Steiner’s nutrient solution at 100 %, which coincided with the highest CGR, AGR and LAI values, and whose equations were adjusted to a quadratic model. The results obtained suggest the use of Steiner’s 100 % nutrient solution to obtain the best productivity in this aromatic and medicinal plant.

Resumen El epazote (Chenopodium ambrosioides L.) es una planta aromática y medicinal. La información sobre su dinámica de crecimiento y nutrición mineral para su producción es insuficiente, por lo que, el objetivo del estudio fue evaluar el efecto de tres concentraciones de la solución nutritiva Steiner sobre el crecimiento y producción de epazote cultivado en invernadero. El estudio se realizó en Cuernavaca, Morelos, México; con el genotipo H-1000 (Hortaflor®) cultivado en tezontle como sustrato. Se aplicaron tres concentraciones (50, 75 y 100 %) de la solución nutritiva Steiner para evaluar el crecimiento del cultivo mediante muestreos destructivos a los 39, 46, 53, 60, 67 y 74 días después de la siembra; en cada muestreo se determinó: altura de planta, área foliar, índice de área foliar (IAF), peso de materia fresca, peso de materia seca, tasa de crecimiento del cultivo (TCC), tasa absoluta de crecimiento (TAC) y producción por planta. A las variables se les realizó un análisis de regresión con el programa Excel®, y para el caso de producción de epazote por planta se realizó análisis de varianza y prueba de medias de Tukey (P ≤ 0.05). La mayor altura y producción en el cultivo de epazote cultivada en invernadero y con sustrato inorgánico se obtuvo con la solución nutritiva de Steiner a 100 %, lo cual coincidió con los valores más altos de la TCC, la TAC y el IAF, y cuyas ecuaciones se ajustaron a un modelo cuadrático. Con los resultados obtenidos, se sugiere emplear la solución nutritiva de Steiner a 100 % para obtener la mejor productividad en esta planta aromática y medicinal.

Abstract. Several Corynespora cassiicola isolates obtained from roselle (Hibiscus sabdariffa) and nine associated weeds to this crop were morphological and phylogenetically analyzed. The fungal isolates were divided into two groups: group one included 37 isolates obtained from H. sabdariffa and eight obtained from other host plants including Solanum lycopersicum, Chromolaena odorata, Senna alata, Eugenia oerstediana, Passiflora viridiflora, Momordica charantia, Ricinus communis and Gossypium hirsutum; in this case, the predominant colonies were gray, dense texture and polygonal in shape. Group two included two isolates obtained from H. sabdariffa and one from Hyptis suaveolens; in this group the colonies were mainly cream and pale brown, dense and round. Comparative analysis with isolates of C. cassiicola from other countries showed that group one isolates were mainly associated with those isolated from the Solanaceae family, while those from group two were related to those of the Cucurbitaceae family. To our knowledge, this is the first study on the morphological and genetic characterization of C. cassiicola in Mexico.

Resumen. Se analizaron morfológica y filogenéticamente diferentes aislados de Corynespora cassiicola obtenidos de jamaica (Hibiscus sabdariffa) y nueve malezas asociadas al cultivo. Los aislados fúngicos se dividieron en dos grupos: el grupo uno incluyó 37 aislados obtenidos de H. sabdariffa y ocho obtenidos de otros hospedantes como Solanum lycopersicum, Chromolaena odorata, Senna alata, Eugenia oerstediana, Passiflora viridiflora, Momordica charantia, Ricinus communis y Gossypium hirsutum; en este caso, las colonias predominantes fueron de color gris, textura densa y forma poligonal. El grupo dos, incluyó a dos aislados obtenidos de H. sabdariffa y uno de Hyptis suaveolens; en este grupo, las colonias fueron principalmente de color crema y café pálido, densas y redondeadas. El análisis comparativo con aislados de C. cassiicola de otros países mostró que los aislados del grupo uno referidos anteriormente se asociaron principalmente con aquellos aislados de la familia Solanaceae, mientras que los del grupo dos se relacionaron con los de la familia Cucurbitaceae. Para nuestro conocimiento este es el primer estudio sobre la caracterización morfológica y genética de C. cassiicola en México.

Abstract. In recent years, Corynespora cassiicola induced spotted of roselle threatens calyx production. The objective was to determine if some bacterial strains inhibit the development of C. cassiicola in vitro and under biospace conditions. The inhibition of development was due to the dual confrontation of the bacteria: food (20), amphibian skin (41), tailings (22), air (seven) and rhizosphere (10) against the fungus. Plants of jamaican “Creole” variety were sown and artificially inoculated with C. cassiicola. From the beginning of symptoms of the disease, the selected bacterial strains with the highest percentage of inhibition were inoculated. AUDPC was evaluated. Only seven strains inhibited the development of the fungus in vitro from 62.7 to 100%: Klebsiella pneumoniae (M10-1 and M10-10), Acinetobacter lwoffii (A5), Sphingomonas paucimobilis (NF21), Serratia marcescens (M13ACD), S. liquefaciens (M8ACD) and Acinetobacter sp. (5H2). Regarding leaf severity, the M10-1 and M10-10 strains reduced AUDPC by 9.5 and 12.6%, respectively, followed by NF21 (AUDPC 14.5), the control registered the highest levels (AUDPC 45.7). For the severity in calyces, the AUDPC analyzes of all the strains exercised control by reducing severity levels (17.1-8.6 AUDPC).

Resumen. En años recientes, el manchado de la jamaica inducido por Corynespora cassiicola amenaza la producción de cálices. El objetivo fue determinar si algunas cepas bacterianas inhiben el desarrollo de C. cassiicola in vitro y bajo condiciones de bioespacio. La inhibición del desarrollo fue por confrontación dual de las bacterias: alimentos (20), piel de anfibios (41), jales mineros (22), aire (siete) y rizosfera (10) contra el hongo. Se sembraron plantas de jamaica variedad “criolla” y se inocularon artificialmente con C. cassiicola, a partir del inicio de síntomas de la enfermedad se inocularon las cepas bacterianas seleccionadas con mayor porcentaje de inhibición. Se evaluó la ABCPE. Solo siete cepas inhibieron del 62.7 al 100% el desarrollo del hongo in vitro: Klebsiella pneumoniae (M10-1 y M10-10), Acinetobacter lwoffii (A5), Sphingomonas paucimobilis (NF21), Serratia marcescens (M13ACD), S. liquefaciens (M8ACD) y Acinetobacter sp. (5H2). En relación a la severidad en hojas las cepas M10-1 y M10-10 redujeron el ABCPE en un 9.5 y 12.6%, respectivamente, seguido de NF21 (14.5 de ABCPE), el control registró los mayores niveles (45.7 de ABCPE). Para la severidad en cálices, los análisis del ABCPE de todas las cepas ejercieron control al reducir niveles de severidad (17.1-8.6 ABCPE).

Abstract The development of maize genotypes (Zea mays L.) for forage production in rainfed conditions is incipient, because no specific varieties have been disseminated for this purpose. The objective was to identify hybrids with forage potential for rainfed conditions in the state of Guerrero, Mexico. 25 maize genotypes were evaluated under rainfed conditions, under an experimental design of randomized complete blocks with three replications. The experimental unit consisted of four furrows 5 m long, 0.8 m wide between furrows, 0.17 m between plants to obtain a population density of 73 529 ha-1 plants. It was fertilized with the formula 120N-60P-00K. The characters studied were: plant height, cob height, plant weight, cob weight, yield of green, grain and dry fodder. The results indicated highly significant differences in the characters studied. Experimental trilinear hybrids H-H562xHCF2-91, H-H565xHCF2-91, H-H516xHCF2-91, simple cross hybrid 329x97 and control H-564C stood out in green forage yield and single cross hybrids 1275x1277, 1278x1276, hybrids Experimental H-H516xHCF2-91 and H-H565xHCF2-91 expressed higher dry forage yield.

Resumen El desarrollo de genotipos de maíz (Zea mays L.) para producción de forraje en condiciones de secano es incipiente, debido a que no se ha difundido variedades específicas para tal fin. El objetivo fue identificar híbridos con potencial forrajero para condiciones de secano del estado de Guerrero, México. Se evaluaron 25 genotipos de maíz en condiciones de secano, bajo un diseño experimental de bloques completos al azar con tres repeticiones. La unidad experimental consistió de cuatro surcos de 5 m de longitud, 0.8 m de ancho entre surcos, a 0.17 m entre plantas para obtener una densidad de población de 73 529 plantas ha-1. Se fertilizó con la fórmula 120N-60P-00K. Los caracteres estudiados fueron: altura de planta, altura de mazorca, peso de planta, peso de mazorca, rendimiento de forraje verde, de grano y de forraje seco. Los resultados indicaron diferencias altamente significativas en los caracteres estudiados. Los híbridos trilineales experimentales H-H562xHCF2-91, H-H565xHCF2-91, H-H516xHCF2-91, híbrido de cruza simple 329x97 y el testigo H-564C destacaron en rendimiento de forraje verde y los híbridos de cruza simple 1275x1277, 1278x1276, híbridos experimentales H-H516xHCF2-91 y H-H565xHCF2-91 expresaron mayor rendimiento de forraje seco.

Abstract The wild populations of papaya (Carica papaya L.) integrate a biological resource for the genetic improvement of the species. The prediction of the geographical distribution of wild and cultivated populations is a useful tool to determine collection sites for their use and conservation. With the objective of estimating the potential distribution of papaya in Mexico, a database with geo-reference information of wild and cultivated papaya individuals was elaborated, then the maximum entropy algorithm (MaxEnt) was applied with 22 bioclimatic variables as predictors. The total area of potential distribution of the wild specimens was 114 546.5 km2, the high potential areas were located in the Gulf of Mexico (south of Veracruz, Tabasco, Campeche) and on the coast of Chiapas. The cultivated papaya presented a high potential distribution in three zones: south of Veracruz, coast of Chiapas and north of Guerrero, forming 185 396.9 km2. The variables that contributed most in the model to estimate the potential distribution of wild papaya were: average minimum temperature of the coldest period (33%), average annual temperature (20%) and soil moisture regime (13%), for the distribution of cultivars the most important variables were: average minimum temperature of the coldest period (41%), rainiest semester precipitation (19%) and annual precipitation (11%). The environmental factors temperature and rainfall, were common in the prediction of distribution of both types of papaya in Mexico.

Resumen Las poblaciones silvestres de papaya (Carica papaya L.) integran un recurso biológico para el mejoramiento genético de la especie. La predicción de la distribución geográfica de las poblaciones silvestres y cultivadas es una herramienta útil para determinar sitios de colecta para su uso y conservación. Con el objetivo de estimar la distribución potencial de papaya en México, se elaboró una base de datos con información de geo-referenciación de individuos de papaya silvestre y cultivados, posteriormente se aplicó el algoritmo de máxima entropía (MaxEnt) con 22 variables bioclimáticas como predictores. El área total de la distribución potencial de los especímenes silvestres fue de 114 546.5 km2, las áreas de alto potencial se ubicaron en el Golfo de México (sur de Veracruz, Tabasco, Campeche) y en la costa de Chiapas. La papaya cultivada presentó una distribución potencial alta en tres zonas: sur de Veracruz, costa de Chiapas y norte de Guerrero, conformando 185 396.9 km2. Las variables que más contribuyeron en el modelo para estimar la distribución potencial de papaya silvestres fueron: temperatura mínima promedio del periodo más frío (33%), temperatura promedio anual (20%) y régimen de humedad del suelo (13%), para la distribución de cultivares las variables más importantes fueron: temperatura mínima promedio del periodo más frío (41%), precipitación del cuatrimestre más lluvioso (19%) y precipitación anual (11%). Los factores ambientales temperatura y precipitación pluvial, fueron comunes en la predicción de distribución de ambos tipos de papaya en México.

Summary In Mexico, tomato (Solanum lycopersicum L.) is the most exported vegetable, and it is also of utmost importance in local markets; however, silverleaf whitefly (Bemisia argentifolii Bellows & Perring) attacks reduce production from 30 to 70 %. Although Mexican farmers use different technologies to grow tomato plants, irregular ripening is a generalized concern for adequate yield and product quality. Previous reports on tomato irregular ripening (TIR) associate it to the presence of silverleaf whitefly and low temperatures during harvest. Silverleaf whitefly incidence and temperature effects were measured to establish a relationship to TIR at one of the largest Mexican areas of tomato production. Experiments were carried out on 16 tomato hybrids sowed at the INIFAP Experiment Station in the Culiacan Valley, Mexico. Yield and commercial fruits size were measured, as they are important factors that determine commercialization and destination market (e.g. industrial process, export or domestic market). Silverleaf whitefly incidence and temperature effects on TIR were also analyzed on the basis of yield. TIR symptoms, both temporary (TIRt) and permanent (TIRp) were observed. The term TIRt described fruits that resumed their maturation process during the storage after harvest and reached full ripening after 7 d at 25 ºC. Consistent with previous reports, it was observed that TIRt symptoms were associated to low temperatures (≤ 8 ºC) during early harvest dates. TIRp damaged more fruits and associated to the effect of silverleaf whitefly at high population densities (0.77 to 0.93 adults cm-2), to high temperatures during the harvest season and to susceptible tomato genotypes.

Resumen En México, el tomate (Solanum lycopersicumm L.) es el cultivo hortícola de mayor exportación y una hortaliza de gran importancia en el mercado local, pero el ataque de mosquita blanca (Bemisia argentifolii Bellows & Perring) reduce su producción entre 30 y 70 %. Aunque los agricultores mexicanos emplean diferentes tecnologías para cultivar plantas de tomate, la presencia de algunos frutos que muestran madurez irregular es una preocupación generalizada en términos del rendimiento y calidad del producto. Reportes previos en madurez irregular del fruto (MIF) asocian este evento principalmente con la presencia de mosquita blanca (MB) y bajas temperaturas durante la cosecha. La incidencia de MB y efectos de la temperatura se evaluaron para determinar su relación con MIF en una de las mayores áreas de producción de tomate en México. Los experimentos se realizaron con 16 híbridos de tomate plantados en el Campo Experimental Valle de Culiacán, México del INIFAP. Se evaluó el rendimiento y tamaño comercial de los frutos cosechados, con base en su comercio y mercado de destino (e.g. proceso industrial, mercado de exportación o nacional). La incidencia de MB y los efectos de la temperatura sobre la MIF se analizaron en función del rendimiento. Se observaron síntomas de MIF tanto temporales (MIFt) como permanentes (MIFp). El término MIFt se consideró para aquellos frutos que restablecieron su proceso de madurez durante el almacenamiento después de la cosecha y alcanzaron la maduración completa después de 7 d a 25 ºC. En concordancia con reportes previos, se observó que los síntomas de MIFt se asociaron a bajas temperaturas (≤ 8 ºC) presentes durante las fechas de cosecha temprana. MIFp produjo más daños a los frutos y se asoció con el efecto de MB en altas densidades de población (0.77 a 0.93 adultos cm-2), altas temperaturas durante la temporada de cosecha y genotipos de tomate susceptibles.

Abstract Sowing of non-conventional hybrids is a real possibility to increase maize grain yield in areas of medium productive potential from altitudes of 1 200 to 1 700 m of the Guerrero’s mountains and similar regions, where different ecological niches predominate, in which has been difficult to make specific improved material available to farmers. Therefore the INIFAP’s Maize Breeding Program based in Iguala, Guerrero, since 1985 has been working on the use of native populations of subtropical origin per se or in combination with improved maize and experimental lines till the generation of the new ‘HV-240’ varietal hybrid, obtained with native and improved germplasm so that it shows greater adaptation and better plant type than native maize, which is planted in 70% of the area cultivated with maize in the state of Guerrero. The ‘HV-240’ is characterized by a wide adaptation, a biological cycle of 125 days on average, with 64 days to male and female flowering, plant height of 250 to 270 cm, reason why it shows greater resistance to bending, and grain yield from 5 to 6.5 t ha-1.

Resumen La siembra de híbridos no convencionales es una posibilidad real para elevar el rendimiento de maíz en áreas de mediano potencial productivo en altitudes de 1 200 a 1 700 m de la montaña de Guerrero y regiones similares, donde predominan diferentes nichos ecológicos, en los cuales se ha dificultado poner a disposición de los agricultores materiales mejorados específicos. Por ello el Programa de Mejoramiento Genético de Maíz del INIFAP con sede en Iguala, Guerrero, desde 1985 ha venido trabajando en el aprovechamiento de poblaciones nativas de origen subtropical per se o en combinación con maíces mejorados y líneas experimentales, hasta generar el nuevo híbrido varietal ‘HV-240’, obtenido con germoplasma nativo y mejorado con mayor adaptación y mejor que el maíz nativo, que se siembra 70% de la superficie cultivada con maíz en el estado de Guerrero. El ‘HV-240’ se caracteriza por tener una adaptación amplia, un ciclo biológico de 125 días en promedio, con 64 días a floración masculina y femenina, altura de 250 a 270 cm, que presenta mayor resistencia al acame, y un rendimiento de grano de 5 a 6.5 t ha-1.

Abstract Corn is the main source of food and the largest crop cultivated in Mexico. In the state of Guerrero there is great diversity of agro-ecological regions distinguished by its altitude, temperature, soil type, rainfall distribution, where farmers grow hybrid varieties and native population’s of corn under irrigation and rainfed conditions. The objective of this study was to assess the effect of different doses of nitrogen and phosphorus in phenotypic characteristics and yield of three maize genotypes in two environments in the northern region of the state of Guerrero. The experiment was established in Iguala and Apaxtla, Guerrero during the spring-summer cycle - 2013. The genotypes were VS-535, A-7573 and V-537C. Nitrogen doses (100, 150 and 200 kg ha-1) and phosphorus (60, 90 and 120 kg ha-1), under a randomized complete block design with three replications in factorial arrangement. The experimental unit consisted of four rows of five meters length, row spacing 0.80 m. Recording: plant height, ear height, cob health, grain yield. The results indicated that in the four quantified variables, significant effects were detected. In Apaxtla, plant height, ear height, cob health and grain yield were higher than those observed in Iguala, Guerrero. Treatment nine (VS-535 + 200N + 120P) expressed greater cob health and grain yield. V-537C was higher in plant height and grain yield compared to VS-535 and A-7573, and the three genotypes were similar in height and cob health. The application of 200 units of N increased plant height and 90 units of P increased ear height, cob health and grain yield t ha-1.

Resumen El maíz es la principal fuente de alimento y es el cultivo que mayor superficie ocupa en México. En el estado de Guerrero existe gran diversidad de regiones agroecológicas que se distinguen por su altitud, temperatura, tipo de suelo, distribución de lluvias, donde los agricultores siembran híbridos, variedades y poblaciones nativas de maíz bajo condiciones de riego y temporal. El objetivo del presente trabajo fue examinar el efecto de diferentes dosis de nitrógeno y fósforo, en características fenotípicas y rendimiento de tres genotipos de maíz en dos ambientes de la región norte del estado de Guerrero. El experimento se estableció en Iguala y Apaxtla, Guerrero en el ciclo primavera verano - 2013. Los genotipos fueron VS-535, A-7573 y V-537C. Se estudiaron dosis de nitrógeno (100, 150 y 200 kg ha-1) y de fósforo (60, 90 y 120 kg ha-1), bajo un diseño experimental de bloques completos al azar con tres repeticiones en arreglo factorial. La unidad experimental fue de cuatro surcos de cinco metros de longitud, distancia entre surcos a 0.80 m. Se cuantificaron: altura de la planta, altura de mazorca, sanidad de la mazorca, rendimiento de grano. Los resultados indicaron que en las cuatro variables cuantificadas, se detectaron efectos significativos. En Apaxtla, la altura de planta, altura de mazorca, sanidad de la mazorca y rendimiento de grano fueron superiores a los observados en Iguala, Guerrero. El tratamiento nueve (VS-535+200N+120P) expresó mayor sanidad de mazorca y rendimiento de grano. La V-537C fue superior en altura de planta y rendimiento de grano respecto a VS-535 y A-7573, y fueron semejantes los tres genotipos en altura y sanidad de la mazorca. La aplicación de 200 unidades de N aumentó la altura de planta y 90 unidades de P incrementó la altura de mazorca, sanidad de la mazorca y rendimiento de grano t ha-1.