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.

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 Solanum 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.

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.

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-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 ∆K 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.Index terms: Zea mays, conservation strategies, landraces, microsatellites, plant breeding. Diversidade genética e estrutura das raças de milho nativo do Noroeste do MéxicoResumo -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.Termos para indexação: Zea mays, estratégias conservacionistas, raças nativas, microssatélites, melhoramento vegetal.

The variability in the phytochemical concentrations of Capsicum annuum var. glabriusculum has not been extensively analyzed among wild populations and ecologic niches in its phylogeographic area. This study aimed to determine the variations in the phytochemical and antioxidant contents of the wild Piquin chili. The total flavonoid content of hydroalcoholic extracts (0.06 to 0.70 mg equivalent of quercetin per gram of dry weight (mg QE/g DW)), free radical‐scavenging capacity for 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH.) radicals (0.55 to 8.55 mm TE/g DW), amount of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS+) in aqueous extracts (18.13 to 107.6 mm TE/g DW) and pungency (21,760 to 88,476 Scoville heat units) were highly variable. By analyzing the spatial distribution using the first three principal components, correlations between the phytochemical content and the free radical‐scavenging capacity (in both extracts) and flavonoid and phenolic contents (in the hydroalcoholic extract) were observed. Consistent with the statistical analysis, the spatial analysis showed intraregional differences in composition patterns, with an emphasis on central and coastal areas. Flavonoid contents, polyphenol contents and free radical‐scavenging activity were the phytochemical components that mainly contributed to the diversity of the population.

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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 F 2 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 colocalization 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.