Heterosis for yield and agronomic attributes in diverse maize germplasm

摘要

Combining ability estimation are important genetic attributes for maize breeders in anticipating improvement in productivity via hybridization and selection. Maize exhibits heterosis for all traits and the extent of heterosis is significantly variable depending on the choice of parents and the trait(s) measured. We developed hundreds of S2 lines in 2009 and out of these S2 lines, several selected lines were crossed with three different testers in three isolations to generate testcrosses (spring 2010). The testcrosses were evaluated in a partial lattice square design with two replications to divulge combining ability and heterosis for particular traits of economic importance (summer-2010). Phenotypic data were recorded for flowering time, morphological traits and total yield to calculate total variability, combining abilities and mid parent (MPH) and better parent (BPH) heterosis. The 87 testcrosses possessed highly significant differences (P ≤ 0.01) for the investigated traits. Proportional contribution of lines, tester and their interaction to the total variability for anthesis silking interval (ASI) was 38.33, 2.34 and 59.33%, respectively. Means yield ranged from 2547.45 to 9842.02 kg ha-1. Maximum yield was observed for CMI-76, using OPV Jalal as a tester, while minimum yield was detected for CMI-190-2, using WD3x 6 as a tester. In general, tester parent OPV Jalal showed better heterotic effect with each line as compared to other testers. Based on these results we conclude that maize unveiled excessive ability for heterotic expression, even several inbred lines exhibit enough variability to find out appropriate genotypes for a successful breeding program and generating stable inbred lines for production of commercial hybrids. Genetic variability and harboring of excessive hybrid vigor makes maize as a model crop for all kind of studies. Furthermore, these results suggested that the input cost of hybrids can easily be minimized by avoiding losses of resources and time in production of desirable inbred lines, as it is obvious that the breeding community always preferred hybrids maize rather than OPV or synthetics varieties because of its high productivity.