Divergência genética em milho de primeira e segunda safra

Abstract

The objective of this study was to estimate the genetic divergence among 19 corn hybrids growing at the summer and "safrinha" season. Two experiments were carried out in Rio Verde, Goias, in the 2007/2008 and 2008/2008 season. Both experiments were conducted at reduced spacing of 0.5 m, with population density of about 65,000 plants per hectare at summer and "safrinha" season respectively, using a randomized block design with three replications. Were evaluated the following characters: plant height, ear height, length of tassel, leaf area index, number of kernels rows per ear, number of kernels per row, thousand grain weight and grain yield. The genetic divergence was estimated from Mahalanobis dissimilarity and the hybrids were grouped by the methods of Tocher and non-weighted arithmetic averages (UPGMA). The results show greater genetic divergence between hybrids 2A525 and DKB177 and between P30K64 and DKB177 at the summer and "safrinha" season respectively. The indexes of dissimilarity observed in both seasons suggest the achieving of greater heterosis by crossing lines from the hybrids AG8060, P30F35, 2B587, AG7088 and DKB390 with lines from the hybrids AG7000 and DKB177.