Seleção genética para precocidade em uma população segregante de milho (Zea mays L.)

Abstract

Due to the set of changes and factors corn crop has been subjected in the last few decades, earliness became one of the major characters for addition of genetic value and adaptability to currently cultivated corn hybrids. Thus, selection of characters related to earliness has been of large interest to corn breeding programs. The aim of this work was to estimate genetic parameters related to earliness in a tropical corn population adapted to the central region of Brazil. In this study were evaluated 188 F4 testcrosses in an expanded statistical block design at six locations and plant density of 70,000pl ha-1. Significant differences were detected between the testcrosses (G), Location (L) and GxL interaction. The heritability coefficient for these testcrosses varied from 35.25% for stalk and root lodging (TQA) and 68.91% for pollen shed (FM). Genetic gain estimates showed that it is possible to improve each of these characters individually, via direct selection. However, estimates of indirect effect showed that correlated changes, in general, are unfavorable. The estimated genetic parameters suggest that utilization of selection indexes that, besides grain yield, include characters such as grain moisture, pollen shed, silk, stalk and root lodging to select the testcrosses, under normal development condition the crop, can lead to the development of hybrids with high grain yield and earliness, simultaneously.