Performance de potenciais genitores para um programa de melhoramento de trigo

Abstract

Brazil is one of the largest wheat importers in the world, despite its enormous potential of increasing the production of this cereal. One of the strategies to increase wheat production is the expansion of crop in regions where it is not traditionally cultivated, such as the south of the State of Minas Gerais. Thus, the development and release of cultivars adapted to these environments is essential. In the first part of this study, it is presented a literature review about main points on wheat cultivation in Brazil and Minas Gerais, its genetic variability and the effect and implications of the genotype by environment interaction on wheat crop. In the second part of the study the paper entitled “Performance of Potential Genitors for a Wheat Breeding Program” is presented. It aimed to evaluate the genetic variability of agronomic traits and adaptability of 78 wheat cultivars from different breeding programs for cultivation in the south region of Minas Gerais and based on this evaluation, to choose genitors for a wheat breeding program. The traits plant height, heading date, thousand-seed weight, hectoliter weight and grain yield were assessed. Individual and joint analyses were performed using Henderson's linear mixed model approach. The variance components were estimated by the residual maximum likelihood method, and the significance was verified by the likelihood ratio test at 5% probability. The genetic values of the cultivars were predicted using BLUP predictor. The generalized heritability of Cullis on cultivar-mean basis and the selective accuracy were estimated. The cultivar by location interaction was decomposed into simple and complex fractions according to Robertson's method. The genetic and residual correlations between the traits were estimated. Additionally, a multi-trait selection was performed based on the sum of standardized variables using the Z index. The genetic variance was significant. Finally, the Z index was estimated allowing selection for multiple traits. The genetic variance was significant in both locations for all traits, and the cultivar by location interaction was expressive as well. These results indicate differential responses of cultivars through the locations. The Z index allowed to identify 15 cultivars most adapted to the south region of Minas Gerais and desirable performance for all evaluated traits, which are ORS Guardião, CD 105, Valente, BRS Angico, Tbio Aton, IPR 144, CD 1595, CD 1303, IPR 130, CD 1252, BRS Sanhaço, CD 122, BRS 404, Tbio Tibagi, CD 1104 and Tbio Audaz.