Resumen El estado de Tamaulipas en México es considerado como parte de los centros de origen del maíz nativo, los maíces que ahí se cultivan poseen características agronómicas de importancia y son ampliamente diversos; sin embargo, los estudios de diversidad en el estado han sido pocos. Se analizó la diversidad morfológica y agronómica entre poblaciones de maíz nativo cultivadas en el Altiplano de Tamaulipas. Se establecieron experimentos en los municipios de Jaumave, Tula y Güémez, Tamaulipas, bajo un diseño experimental de bloques completos al azar en los ciclos de siembra otoñoinvierno 2016-2017 y primavera-verano del 2017, con 98 poblaciones de maíz nativo y dos testigos. Se registraron 33 caracteres morfológicos, se sometieron a análisis de varianza combinado; la agrupación de la diversidad se realizó mediante análisis de componentes principales. El análisis de componentes principales explico el 73.96 % de la variación total y mostró que los caracteres fenológicos y de mazorca fueron los que mayormente sustentaron la variación morfológica. El análisis de conglomerados permitió la identificación de dos grandes grupos morfológicos, donde predominó la raza Ratón. La variación del maíz nativo de Tamaulipas es amplia y contínua, en la cual se podrían encontrar alelos de interés para incorporarlos a programas de mejoramiento genético de maíz.

Summary The state of Tamaulipas in Mexico is considered part of the centers of origin of native maize, the maize grown there has important agronomic characteristics and is widely diverse; however, studies on diversity in the state have been scarce. Morphological and agronomic variation among populations of native maize cultivated in the highlands of Tamaulipas was analyzed. Experiments were established in the municipalities of Jaumave, Tula and Güémez, Tamaulipas, under a randomized complete blocks experimental design in the Autumn-Winter 2016-2017 and Spring-Summer 2017 agricultural cycles using 98 populations of native maize and two checks. Thirty-three morphological characters were recorded and subjected to a combined analysis of variance; diversity grouping was carried out using principal component analysis. The principal component analysis explained 73.96 % of the total variation, and showed that the phenological and ear traits were the ones that mainly supported the morphological variation. The cluster analysis allowed the identification of two large morphological groups, where the Raton race predominated. Variation of native maize of Tamaulipas is broad and continuous, in which alleles of interest could be found to incorporate them into maize breeding programs.

ABSTRACT Genomic selection is considered to be an important tool in plant breeding programs. However, its application in the earliness of tomato (Solanum lycopersicum L.) has not been studied. The objective of the present study was to evaluate the prediction performance of six statistical models for six quantitative characteristics related to earliness in tomato. The study used phenotypic and genotypic data belonging to an F2 population consisting of 172 tomato plants. Simple sequence repeat (SSR) markers were obtained using genotypic information, and the genomic values were estimated by the following six different statistical models: Bayesian Lasso (BL), Bayesian ridge regression (BRR), BayesA, BayesB, BayesCπ, and reproducing kernel Hilbert spaces (RKHS) regression. The correlation values ranged from 0.17 to 0.57. The highest association values were found in days to flowering of the third inflorescence and 1000-seed weight, which were greater than 0.5. In general, all the models performed in a similar manner because only slight differences were observed among the correlation values. Specifically, BL, BayesB, and RKHS exhibited the highest Pearson correlation values for most traits. According to the results, genomic selection could be a useful tool to support tomato breeding focused on earliness.

Summary Due to its high fiber quality, earliness and smaller vegetative size, Mexican cotton (Gossypium hirsutum L.) is the most cultivated worldwide, providing almost 90 % of world production. Mexico ranked thirteenth among the main cotton-producing countries, of which India, China, the United States of America, Brazil and Pakistan account for 77 % of world production. In Mexico, transgenic cotton has been planted for more than 20 years because of its tolerance to the attack of the cotton larvae complex and its resistance to herbicides such as glyphosate, ammonium glufosinate and dicamba; however, some farmers consider that transgenic cotton is not profitable and would be willing to plant conventional varieties if they were available in the market. Therefore, in this study, the conventional Cian Precoz, Cian 95, Juárez 91, Laguna 89 and Nazas cotton varieties were evaluated, along with the Delta Pine commercial control, in relation to their productive performance. The production system was in rows 0.76-m apart, and nine plants per linear m, to have a population of 115,000 plants ha-1. Traits such as seed and lint yield, earliness to first harvest, yield components and fiber quality were measured. Significant differences (P ≤ 0.05) were detected between varieties for all the traits due to the wide genetic variation. Delta Pine produced the highest yield (3906.1 kg ha-1); it was also superior to the rest of varieties in lint, seed and lint plus seed weight. Regarding the fiber quality requirements for the textile industry, all the materials evaluated meet the minimum requirements in length, breaking strength and micronaire index.

Resumen Por su alta calidad de fibra, precocidad y menor tamaño vegetativo el algodón mexicano (Gossypium hirsutum L.) es el más cultivado en el mundo, aporta casi 90 % de la producción mundial. México se ubica en el decimotercer lugar entre los principales países productores de algodón, del cual India, China, Estados Unidos de América, Brasil y Pakistán concentran el 77 % de la producción mundial. En México, desde hace más de 20 años se siembra algodón transgénico por su tolerancia al ataque del complejo de larvas del algodonero y por su resistencia a herbicidas como glifosato, glufosinato de amonio y dicamba; sin embargo, algunos agricultores consideran que el algodón transgénico no es rentable y estarían dispuestos a volver a sembrar variedades convencionales si éstas estuvieran disponibles en el mercado. Por lo anterior, en este estudio se evaluaron las variedades convencionales de algodón Cian Precoz, Cian 95, Juárez 91, Laguna 89 y Nazas, junto con el testigo comercial Delta Pine en relación con su comportamiento productivo. El sistema de producción fue en surcos con distanciamiento de 0.76 m y nueve plantas por m lineal, para contar con una población de 115,000 plantas ha-1. Se midió el rendimiento de algodón en hueso y fibra, la precocidad a la primera cosecha, los componentes del rendimiento y la calidad de fibra. Se detectaron diferencias significativas (P ≤ 0.05) entre variedades en todas las variables debido a amplia variación genética existente. Delta Pine produjo el mayor rendimiento (3906 kg ha-1) y fue superior al resto de las variedades en peso de fibra, semilla y peso de fibra y semilla. En relación con los requerimientos de calidad de fibra para la industria textil, todos los materiales evaluados cumplen con los requisitos mínimos de longitud, resistencia al rompimiento e índice de micronaire.

ABSTRACT Commercial tomato (Solanum lycopersicum L.) hybrids can be a good germplasm for obtaining new tomato inbred lines. The present study was aimed to investigate the stability of commercial F1 hybrids under climatic conditions of highlands, to estimate genetic parameters, and evaluate the breeding potential of F1 hybrids based on the agronomic performance of its F3 progeny. We employed a breeding scheme based on pedigree selection for the obtainment of 49 F3 families. Significant differences were found in most of the traits evaluated in both F1 and F3 generations, while in the F2 population only one variable showed significant differences. Heritability ranged from 0.07 to 0.29 for F1, and from 0.16 to 0.45 for F3. Most of the F1 hybrids exhibited values of stability across seasons in at least one trait. However, ‘Loreto’ and ‘Reserva’ only exhibited a high stability for yield. Genetic gains ranged from -8.40 to 72.95. Yield per plant was the traits with the highest gain. Based on genetic gains obtained by the F3 progeny, we concluded that ‘Cid’, ‘Espartaco’ and ‘Loreto’ have a high breeding potential for yield and other traits, which could be exploited by public tomato breeding programs.

RESUMO: No presente estudo investigamos a relação da afiliação etnolinguística com a diversidade genética de variedades locais de tomate na região Centro-Sul do México. Um total de 30 variedades de tomate, coletadas em 18 aldeias com diferentes afiliações etnolinguísticas, foram analisadas. Verificamos que a diversidade genética das variedades crioulas de tomate está associada ao grupo etnolinguístico presente na região estudada. Nossos resultados mostram que existem diferenças morfológicas entre raças cultivadas por diferentes grupos etnolinguísticos. No entanto, também houve evidências de semelhanças morfológicas entre raças de grupos com diferentes afiliações etnolinguísticas. Finalmente, diferentes critérios de seleção, como, principalmente, cor, tamanho e forma dos frutos, desempenham um papel importante na divergência fenotípica entre as variedades crioulas cultivadas em diferentes sistemas agrícolas tradicionais.

ABSTRACT: In the present study, we investigated the influence of social and environmental factors in the genetic diversity of tomato landraces in the South-Central region of Mexico. A total of 30 tomato landraces, collected in 18 villages with different ethnolinguistic affiliations, were analyzed. We reported that the genetic diversity of tomato landraces is associated with the ethnolinguistic group, weather, and soil-type present in the region studied. Our results showed that there are morphological differences between landraces grown by different ethnolinguistic groups; however, there was also evidence of morphological similarities between landraces from groups with different ethnolinguistic affiliations. Finally, different selection criteria, mainly fruit color, size and shape, plays an important role in the phenotypic divergence among landraces grown in different traditional farming systems.

Resumo: O objetivo deste trabalho foi avaliar a diversidade genética de nove raças de milho (Zea mays ssp. mays) do Noroeste do México e uma população de teosinto da raça Balsas (Zea mays ssp. parviglumis). Foram identificados 649 alelos, uma média de 20,9 alelos por locus, utilizando 31 loci microssatélites. Desses, 84,3% eram polimórficos e apresentaram heterozigosidade esperada de 0,49. A representação gráfica da análise de fatores principais (PCoA) mostrou ampla variação e distribuição populacional. O maior valor probabilístico obtido com o critério ΔK confirmou a existência dos cinco grupos populacionais agrupados com o modelo bayesiano. Esse agrupamento coincide com a distribuição populacional observada no gráfico PCoA. As raças de milho examinadas apresentam ampla diversidade genética entre e dentro das populações avaliadas.

Abstract: The objective of this work was to evaluate the genetic diversity of nine maize races (Zea mays ssp. mays) from Northwestern Mexico and one population of teosinte of the Balsas race (Zea mays ssp. parviglumis). A total of 649 alleles were identified, with an average of 20.9 alleles per locus using 31 microsatellite loci; 84.3% of them were polymorphic loci with a 0.49 expected heterozygosity. Graphic representation of principal coordinate analysis (PCoA) showed broad variation and population distribution. The highest probabilistic value obtained with the ΔK criterion confirmed the existence of five population groups clustered by the Bayesian model. This grouping coincided with the population distribution observed in the PCoA graph. Maize races examined retain broad genetic diversity among and within the evaluated populations.

ABSTRACT The flowering time is regarded as an important factor that affects yield in various crops. In order to understand how the molecular basis controlling main components of earliness in tomato (Solanum lycopersicum L.), and to deduce whether the correlation between fruit weight, days to flowering and seed weight, is caused by pleiotropic effects or genetic linkage, a QTLs analysis was carried out using an F2 interspecific population derived from the cross of S. lycopersicum and S. pimpinellifolium. The analysis revealed that most of the components related to earliness were independent due to the absence of phenotypic correlation and lack of co-localization of their QTLs. QTLs affecting the flowering time showed considerable variation over time in values of explained phenotypic variation and average effects, which suggested dominance becomes more evident over time. The path analysis showed that traits such as days to flowering, seed weight, and length of the first leaf had a significant effect on the expression of fruit weight, confirming that their correlations were due to linkage. This result was also confirmed in two genomic regions located on chromosomes 1 and 4, where despite showing high co-localization of QTLs associated to days to flowering, seed weight and fruit weight, the presence and absence of epistasis in dfft1.1 × dftt4.1 and fw1.1 × fw4.1, suggested that the linkage was the main cause of the co-localization.

Yield is a complex trait that is affected by several genetic and environmental factors. Yield is defined as the amount of the part of interest that is harvested from a crop plant in a given area. We investigated the genetic basis of yield in an F2 population derived from a cross between Solatium lycopersicum L. and its most closely related wild species S. pimpinellifolium L. We found that average fruit weight, fruit diameter, and fruit length had a strong effect on yield. In addition, small effects on yield due to soluble solids content and locule number were also observed. A total of 25 different significant quantitative trait locus (QTLs) were detected for six traits (fruit length and diameter, fruit weight, yield, locule number, and Brix degrees). The percentage of phenotypic variation associated with single QTLs ranged from 4.19% to 12.67%. A strong co-location of QTLs among yield and fruit size traits was observed, suggesting that these QTLs play a role in the same expression process controlling yield. We also realized that the effects of soluble solids content on yield could be due to direct effects of fruit size QTLs linked to genes controlling soluble solids content. This result then may suggest that yield in tomato is mainly formed by fruit size QTLs, whereas the remaining factors may play a complementary role in the expression of tomato yield.

Native or landrace tomatoes (Solanum lycopersicum L.) known as "deer eye", "cherry", "kidney" and "pepper-shaped" are widely used in the States of Puebla and Oaxaca, México, where they are cultivated for self-consumption and local commerce. These materials represent an important source of germplasm for tomato breeding programs. To describe the agronomic and morphological diversity of widely used landrace tomatoes in Puebla and Oaxaca, 40 accessions plus the commercial hybrid 'SUN7705' were evaluated in a randomized complete block design with four replications and five plants per replicate. In order to characterize the morphology and agronomy of these genotypes, 20 traits were measured (plant diameter, height at 95 d, height to the first cluster, distance between clusters, days to flowering of the third cluster, number of flowers of the third cluster, days to maturity of the third cluster, number of fruits of the third cluster, total number of clusters, number of leaves, number of petals, cluster length, total number and total weight of fruits, average fruit weight, diameter, length and firmness of the fruit, number of locules, and total soluble solids). Variance was calculated through a combined analysis. Most traits showed significant differences (P ≤ 0.01) among genotypes. A principal component analysis showed that the first two components explained 77.03 % of the variation among collections. Materials with outstanding features in total soluble solids and precocity were identified in some "cherry", "deer eye" and "kidney" type collections, that might be used directly as local varieties or as a source of germplasm. Bell pepper type tomatoes excelled in fruit size, soluble solids, firmness, with characteristics similar to the control hybrid ('SUN7705'), so they also have potential for being used directly as varieties or source of germplasm for genetic improvement in "saladette" tomatoes, which are widely used at the national level.

En algunas regiones de los Estados de Puebla y Oaxaca en México, los tomates (Solanum lycopersicum L.) nativos conocidos como "arriñonados", "chinos criollos", "cuadrados" o "tipo pimiento", "ojo de venado" y "cereza", se usan ampliamente y son cultivados para autoconsumo y comercialización local. Estos materiales pueden ser fuentes de germoplasma para usarse en programas de mejoramiento genético. Con el objetivo de describir la diversidad agronómica y morfológica de tomates nativos de amplio uso local en Puebla y Oaxaca, se evaluaron 40 colectas más el híbrido comercial 'SUN7705' como testigo, en un diseño experimental de bloques completos al azar con cuatro repeticiones y cinco plantas por repetición. Para la caracterización agronómica y morfológica de los genotipos se midieron 20 variables (diámetro de planta, altura a los 95 d, altura al primer racimo, distancia entre racimos, días a floración del tercer racimo, número de flores del tercer racimo, días a maduración del fruto del tercer racimo, número de frutos del tercer racimo, número de racimos totales, número de hojas, número de pétalos, longitud del racimo, número total de frutos y peso total de frutos, peso promedio del fruto, diámetro, longitud y firmeza del fruto, número de lóculos y sólidos solubles totales). Mediante un análisis de varianza combinado se detectó que hubo diferencias significativas (P ≤ 0.01) entre genotipos, para la mayoría de las variables. Los dos primeros componentes principales explicaron 77.03 % de la variación entre las colectas. Se identificaron colectas sobresalientes en sólidos solubles totales y precocidad, en materiales con frutos tipo "cereza", "ojo de venado" y "arriñonados", que podrían utilizarse directamente como variedades de uso local o como fuente de germoplasma. Los tomates con frutos "cuadrados" o "tipo pimiento" sobresalieron en tamaño del fruto, sólidos solubles y firmeza, y sus características fueron similares al testigo ('SUN7705'), por lo que tienen potencial para ser usados directamente como variedades o fuente de germoplasma para el mejoramiento genético de tomates tipo "saladette", los cuales son de amplio uso a nivel nacional.

Most tomato (Solanum lycopersicum L.) seed used in commercial in Mexico crops are acquired from foreign companies; this seed is very expensive. To avoid the expense, smaller farmers try sowing hybrid seeds from early generations (F2 and F3), possibly losing fruit yield and fruit quality. This work evaluated fruit yield per plant (PTF), yield components and some quality related traits of seven Saladette tomato hybrids of indeterminate growth and their respective F2 generations. A randomized completely block design with four replications was employed in plants grown under greenhouse and hydroponic conditions. The analysis of variance of contrasts of averages between F1 vs. F2 detected significant differences for the variable PTF in five out of the seven genotypes ('Sun 7705', 'Moctezuma', 'Cuauhtémoc', 'Reserva' y 'Cid'). In the case of the other two genotypes ('Loreto' and 'Espartaco'), the differences were not significant, thus indicating that the reduction of fruit yield in F2 generations was minimal. These results suggest that inbreeding depression in an F2 generation depends particularly on the genetic constitution of the lines that formed the commercial hybrid. For total fruit number, total soluble solids content, fruit firmness, length and pH, in a general way and for the majority of the genotypes, there were no statistical differences between the averages of the F1 and F2 generations. These findings show that the magnitude of these characteristics remained without change in F2 segregating individuals, some of them being quality related traits.

Casi toda la semilla de tomate (Solanum lycopersicum L.) que se utiliza para siembras comerciales en México proviene de empresas extranjeras, por lo que el costo de dicha semilla es muy alto. Esta situación provoca que en ocasiones el pequeño productor siembre semilla de generaciones tempranas (F2 y F3) de híbridos, con la posible pérdida de rendimiento y calidad de fruto. En este trabajo se evaluó el rendimiento de fruto por planta (PTF), componentes de rendimiento y algunos caracteres de calidad de siete híbridos de tomate tipo Saladette de crecimiento indeterminado, y sus respectivas generaciones F2, bajo un diseño experimental de bloques completos al azar con cuatro repeticiones, en plantas crecidas en condiciones de invernadero e hidroponía. El análisis de varianza de contrastes de los promedios F1 vs. F2 detectó diferencias significativas para la variable PTF en cinco de los siete genotipos ('Sun 7705', 'Moctezuma', 'Cuauhtémoc', 'Reserva' y 'Cid'). En las variedades 'Espartaco' y 'Loreto' las diferencias no fueron significativas, es decir, la reducción del rendimiento en las generaciones F2 fue mínima, lo cual sugiere que la depresión endogámica de una generación F2 depende particularmente de la constitución genética de las líneas que hayan dado lugar al híbrido comercial. Para las variables número total de frutos, contenido de sólidos solubles totales, firmeza y longitud de fruto y pH del jugo del fruto, de manera general y para la mayoría de los genotipos se observó que no hubo diferencias estadísticas entre los promedios de las generaciones F1 y F2, lo cual indica que la magnitud de estas características, algunas de ellas de calidad, se mantiene en individuos segregantes F2.

C. purpurea is the fungus causing the disease called "ergot of wheat" and can affect the yield until 40 %. In the region of Nanacamilpa, Tlaxcala, suspects the presence of C. purpurea; in addition, by the sclerotia size its believes that could be C. gigantea. Some authors argue that for an early diagnosis and differentiation of these two pathogens, the sclerotia size at an early age is a distinctive feature. By extraction of DNA and amplification of the ITS region (Internal Transcribed Spacer), was proved that size is not a distinctive feature for the separation of these two pathogens, besides was observed that the fungus in the region may reach a greater early sclerotia size than average mentioned in the literature. Finally it was confirmed the presence of C. purpurea in the town of Nanacamilpa, Tlaxcala.

C. purpurea es el hongo causante de la enfermedad llamada cornezuelo del trigo y afecta el rendimiento hasta en 40 %. En la región de Nanacamilpa, Tlaxcala, se sospecha la presencia de C. purpurea; además de que por el tamaño de los esclerocios encontrados se cree que podría ser Claviceps gigantea. Algunos autores argumentan que para un diagnóstico temprano y que diferencie a los dos patógenos, el tamaño del esclerocio a temprana edad es una característica distintiva. Mediante la extracción de DNA de esclerocios y la amplificación de la región ITS (Internal Transcribed Spacer) se pudo comprobar que el tamaño no es una característica distintiva para la separación de estos dos patógenos, además se observó que C. purpurea en la región de estudio puede alcanzar un tamaño temprano de esclerocio mayor al promedio que se menciona en la literatura. Finalmente se corroboró la presencia de C. purpurea en el municipio de Nanacamilpa, Tlaxcala.