Progresso genético e adaptabilidade e estabilidade de cultivares de milho avaliadas em ensaios de valor de cultivo e uso

Abstract

The open pollinated varieties (OPVs), the intervarietal hybrids (IH) and topcrosses (HTC) have in common the low cost of seeds, making it attractive for family farming. This study had as objectives: (i) estimate the genetic progress (GP) in crop and use value testing (CUP) of maize varieties, coordinated by Embrapa Maize and Sorghum (EMS) in the period from 2010/2011 to 2014/2015; (ii) identify OPV or maize hybrids of low cost of seeds with high adaptability and stability (ideal genotypes) for crops in the normal sowing time, and times with some edaphoclimatic restriction. It was used CUP testing data of maize varieties, coordinated by EMS, between the agricultural years of 2010/2011 and 2014/2015, with a total of 117 environments, of which 95 were evaluated in the first season (regular season) and the remaining 22 environments had some edaphoclimatic restriction. Each planting season had an average of 39 genotypes, some evaluated in more than one crop, totaling 81 different cultivars, which 56 were OPV, 8 IH, 8 HTC and 9 hybrid witnesses, specifically 3 double hybrids (DH), 3 triple hybrids (TH) and 3 single hybrids (SH). The experimental design used was randomized blocks, and have been evaluated the grain productivity. The variance components and genetic values (BLUPs) used to estimate the GP were obtained by means of mixed models. The BLUPs were subsequently submitted to the singular values decomposition to obtain the GGEBiplot graphics. Based on the GP results of advance (GPA) between pairs of years, it was observed that, with the exception of the pair of crops 2012/2013 to 2013/2014, the remaining pairs presented positive GPA, indicating the efficiency of the program in the selection of maize cultivars with high productivity. With the annual GP average of 332 kg.ha-1, one can infer that, in general, selected cultivars as well as the cultivars introduced over the five harvests of study have tended to increase favorable alleles for productivity. The GGE-Biplot of the joint analysis allowed the formation of three megaenvironments. It was possible to identify optimal genotypes for the formed mega-environments, where some of the SH used as controls G22 (BRS1055) and G26 (2B707) were optimal for the first and the second mega-environments, respectively, the HTC G79 (HTCMS707) and the OPV G42 (Sint 10783) the optimal for the third and second largest mega-environment, which includes beyond the environments of normal season of planting, some of the environments conducted with edaphoclimatic restrictions. The testing program of CUP of maize varieties coordinated by EMS presents an annual GP of 332 kg.ha-1. Some OPVs are not only recommended for different environmental strata, as are those with greater adaptability and stability in case of environments with restrictions for the full development of maize crop. There are HTC and IH with compatible adaptability and stability with commercial hybrids, making it very attractive for family farming, for crops in environments with or without edaphoclimatic stresses.