Genetic enhancement of inbred lines through pre-breeding in maize

The improvement in the genetic yield potential of maize has led to the development of an extremely large number of maize cultivars across almost all maize-growing countries in the world. In the process, the genetic diversity in the modern maize cultivars has gradually narrowed down. To improve the genetic diversity, there is a need to undertake pre-breeding through wide-hybridization between inbred lines and their wild species, namely Zea mays ssp. Parvigluimis (WS-5) and Zea luxurians (WS-1). In the present study, 69 elite inbred lines were crossed with two wild relatives of maize, Z. mays ssp. Parviglumis and Z. luxurians. The resulting hybrids of wide hybridization showed typical wild species characters like tillering, prolificacy on main tiller and side tillers, and ear characters. This shows the introgression of characters from wild species. Combining ability analysis revealed the presence of a significant amount of variability among parents and crosses for most traits under study. Z. luxurians was a good general combiner for all the traits except tassel length, anthesis silking interval, and days to 75% dry husk based on the GCA effects. Whereas lines, IC0621049 and IC0621565, were good general combiners for all the traits except days to 75% dry husk. Among the crosses, highly significant SCA effects in the desired direction were shown by PFSR-3 x WS-5, EC618215 x WS-1, and IC213122 x WS-1 for plant height, ear diameter, no. of kernel rows per ear, no. of kernels per row, ear weight, and grain yield per ear. Molecular analysis also confirmed the genuine nature of hybrids. Cluster analysis classified all the parents involved in the crosses into two groups, with most of the inbred lines grouping with WS-5, revealing that most of the inbred lines were closely related to WS-5 as compared to WS-1. This may be the reason for the development of more successful crosses with WS-5 as compared to WS-1.