Yield prediction and inbreeding of maize synthetics generated with lines and single crosses : classic probability

reduce costs and labor associated with predicting the genotypic mean (GM) of a synthetic variety (SV) of maize (Zea mays L.), breeders can develop SVs from L lines and s single crosses (SynL,SC) instead of L+2s lines (SynL). The objective of this work was to derive and study formulae for the inbreeding coefficient (IC) and GM of SynL,SC, SynL, and the SV derived from (L+2s)/2 single crosses (SynSC). All SVs were derived from the same L+2s unrelated lines whose IC is FL, and each parent of a SV was represented by m plants. An a priori probability equation for the IC was used. Important results were: 1) the largest and smallest GMs correspond to SynL and SynL,SC, respectively; 2) the GM predictors with the largest and intermediate precision are those for SynL and SynL,SC, respectively; 3) only when FL=1, or m is large, SynL and SynSC are the same population, but only with SynSC prediction costs and labor undergo the maximum decrease, although its prediction precision is the lowest. To determine the SV to be developed, breeders should also consider the availability of lines, single crosses, manpower and land area; besides budget, target farmers, target environments, etc.

Genetic diversity among alfalfa genotypes (Medicago sativa L.) of non-dormant cultivars using SSR markers and agronomic traits

The aim of this study was to assess genetic diversity among 40 alfalfa (Medicago sativa L.) genotypes of different non-dormant (FD=8) cultivars. Biomass yield, regrowth speed and reaction to spring black stem, lepto leaf spot, and rust were evaluated. Analyses of variances were performed using a mixed model to examine the agronomic variation among individuals. A principal component analysis on standardized agronomic data was performed. Agronomic data were also used to calculate Gower's distance and UPGMA algorithm. For the molecular analysis, six SSR markers were evaluated and 84 alleles were identified. The genetic distance was estimated using standard Nei's distance. Average standard genetic diversity was 0.843, indicating a high degree of variability among genotypes. Finally, a generalized procrustes analysis was performed to calculate the correlation between molecular and agronomic distance, indicating a 65.4% of consensus. This value is likely related to the low number of individuals included in the study, which might have underestimated the real phenotypic variability among genotypes. Despite the low number of individuals and SSR markers analyzed, this study provides a baseline for future diversity studies to identify genetically distant alfalfa individuals or cultivars.

Proteómica de la madurez del tomate : identificación de dos estados de madurez del fruto por perfiles proteicos totales del pericarpio en RILs de tomate

Durante la madurez del fruto se producen cambios morfológicos, fisiológicos y bioquímicos provocados por la expresión regulada de diferentes genes. El objetivo de este trabajo fue verificar si la presencia de polipéptidos totales del pericarpio en los estados verde maduro (VM) y rojo maduro (RM) permite caracterizar la madurez del tomate. Se analizaron 18 líneas endocriadas recombinantes obtenidas por selección antagónica-divergente de un cruzamiento entre la cv. Caimanta (Solanum lycopersicum) y la entrada LA722 (S. pimpinellifolium), que fueron incluidas junto a la F1 como testigos experimentales. Los extractos proteicos se obtuvieron de dos muestras independientes de cada estado según el protocolo estándar y se resolvieron en SDS-PAGE. Se analizó la presencia/ausencia de bandas por genotipos y por estado, detectándose 26 en VM y 29 en RM. Algunas bandas fueron comunes entre estados, mientras que otras resultaron propias de VM o RM, respectivamente. Se calcularon las distancias de Jaccard y se realizó un análisis de conglomerados según el método UPGMA. En el dendrograma (correlación cofenética = 0,43) se distinguieron dos grandes grupos definidos por el estado de madurez. Se concluye que los perfiles proteicos del pericarpio son una herramienta postgenómica apropiada para identificar dos estados de madurez del fruto de tomate.

Variación agromorfológica y cambios biofísicos poscosecha en frutos de tomate (Solanum lycopersicum L.)

Se evaluó la variación fenotípica agromorfológica y cambios biofísicos de frutos después de 10 días de almacenamiento a temperatura ambiente, en una colección de tomate de Oaxaca, México. La colección de 57 colectas fue sembrada y caracterizada bajo invernadero. En poscosecha se evaluó pH, grados Brix, pérdida de peso y parámetros de color (L*, a*, b*, cromaticidad y ángulo Hue) a 0 y 10 días después de la cosecha. Las colectas mostraron diferencias significativas (P < 0,01) en todos los caracteres agromorfológicos y también hubo diferencias significativas entre acervos genéticos preclasificados como cultivados, ruderales e intermedios entre cultivados y ruderales. Nueve grupos de diversidad fenotípica fueron conformados. Se determinaron diferencias significativas entre tiempos de almacenamiento (0 y 10 días) para todas las características biofísicas. Después de 10 días de almacenamiento a temperatura ambiente (20,6±5°C y 34±10% HR), se incrementaron los °Brix de 4,1 a 4,6 y pH de 3,7 a 4,3. Entre grupos fenotípicos e interacción tiempo de almacenamiento-grupos, se determinaron diferencias significativas en °Brix, coordenadas de color L* y b*, y ángulo Hue. Los cambios diferenciales poscosecha indican divergencias fenotípicas entre y dentro de acervos genéticos que pueden explotarse en programas de mejoramiento con objetivos regionales.

Gamma irradiation on Alstroemeria aurea G. in vitro rhizomes: : an approach to the appropriate dosage for breeding purposes

Gamma irradiation has been widely used as a breeding technique to obtain new cultivars in ornamental species such as Alstroemeria, where several cultivars have been obtained through rhizome radiation. The optimum dosage for an appropriate induction of mutation must be considered for breeding purposes and it depends mainly on plant susceptibility. Thus in this study in vitro cultured rhizomes of Alstroemeria aurea were irradiated with a gamma source using different dosages to evaluate the direct effect produced. Damage and number of rhizome sprouting were observed and recorded during 61 days after irradiation. At the end of this period, rhizomes were weighted and mortality was evaluated. Both mortality and weight increased depending on dosage. All irradiated rhizomes showed early sprouting in comparison with control (0 Gy) and no significant difference in final number of shoots after 61 days among irradiated treatments was observed. Bleaching and necrosis was observed in all irradiated rhizomes and was more evident at higher doses. LD50 was established at about 40 Gy and the optimum dosage to induce mutation was suggested between 2.5 and 5 Gy, when the growth was reduced in 50%, and probably this dosage could be used for breeding purposes.