STABILITY AND ADAPTABILITY PERFORMANCE OF DIFFERENT GENETIC CLASSES OF MAIZE

Experiments were carried out in the agricultural years 1992/93 and 1993/94 at twelve locations, totaling 19 environments, to assess the environmental effects, stability and adaptability of 16 maize cultivars. The cultivars were two three-way hybrids (P 3230 and G 500); three double hybrids (C 525, BR 201 and HD 25); seven varieties (OC 202, BR 106, IAPAR 26, IAPAR 50, IAPAR 51, IAPAR 52 and PMI 8601); and four intervarietal hybrids (HI 8901, HI 8902, HI 8735 and HI 8768). The year x location and year x genotype x location interactions were both highly significant (P < 0,01), showing that the assessed genotypes had differentiated responses when tested in different environments. According to the analysis of Eberhart & Russel (1966), the three-way hybrids P 3230, G 500 and the double hybrid BR 201 were responsive and adapted to all the environments while the varieties IAPAR 50, IAPAR 51, IAPAR 52, and PMI 8601 had average responsiveness, but were poorly adapted and cultivar IAPAR 26 had low responsiveness and adaptability. The two-segmented model proposed by Cruz et al. (1989) was used to determine whether the genotypes had different performance in inferior or superior environments. In favorable environments, the intervarietal hybrids HI 8735 and HI 8768 were considered responsive, C 525 was considered little responsive and the others were considered of average responsiveness. Utilizing the model proposed by Cruz et al. (1989) together with the model proposed by Eberhart & Russel (1966), it was evidenced that the genetic classes formed by three-way hybrids and double hybrids, beyond high productivities, showed high adaptability and responsiveness, as on favorable as well as on unfavorable environments, when compared to the genetic classes formed by varieties and intervarietal hybrids evaluated on this experiment