Parâmetros genéticos e seleção entre famílias de meio irmãos de Jatropha curcas L.

Abstract

The aim of this study was estimate genetic parameters in a population of 88 half- sib families of Jatropha evaluating vegetative characteristics at three and six months after planting and by evaluation of seed production per plant for four years in Nova Porteirinha-MG. We evaluated the plant height, stem diameter, number of branches per plant and canopy projection at three and six months after planting. The annual harvest of each plant was weighed and stored in paper bags. The quantification of the oil content was performed by NMR seeds from each family. To estimate the genetic parameters and selection of individuals, the Selegen REML/BLUP software were used. The dendrogram was constructed from the genetic distances of Mahalanobis by means of UPGMA. The characteristics evaluated at three and six months showed considerable genetic variability (CVgi higher than 14%), except for plant height at 6 months (CVgi=5,44%). Heritability estimates of the average of progeny reached values above 66%, the heritability estimates at the individual level are above 33% in the first crop year. The half-sib families showed considerable percentage of genetic variation, indicating that there is genetic gain with the selection, including for the vegetative parameters. Observing seed production per plant as the main parameter to perform the selection, the families 23, 36, 44, 73 and 74 are always among the top 20. In the fourth year after planting it was observed a decrease in the production of plants although it was expected some stability of production, contributing to lower values of genetic parameters as a whole, as well as the genetic correlations, but high values of genetic variation allow the gain from early selection of individuals or families. There were positive genetic correlations between: width and length of seed; 100 seed weight and oil content, seed yield per plant and oil content. There is genetic variability for vegetative characters. The average oil content of families was 37,5%, with some stable families, as 36 and 22, have average oil content above the overall mean, around 39%. Early selection of individuals or families can be held in Jatropha based on productivity due to high correlation with the harvest in the first year. The accuracy of measurements of this parameter shows that the repeatability data are reliable ones. The best families selected by BLUP based on the production and stability were 23, 36, 44, 73 and 74. The families selected based on oil yield are 27, 43, 64, 56 and 55. Five heterotic groups were formed based on production data with average genetic distance of 0,88, or 30% of the relative distance. To continue the breeding program is interesting to set a population of cross- pollination with 20 selected families to raise the average yield and oil content in seeds. It is recommended that the top 10 individuals selected for oil and seeds yield are gathered in a population of open-pollination, creating individuals more productive and with higher seed oil content.