Breeding for Some Quantitative Traits in Common Wheat (Triticum Aestivum L) Using Diallel Crosses.

Abstract

A diallel cross set was carried out among six parents of common wheatwithout reciprocal crosses to study the inheritance of heading date, maturity date, plant height, spike length, number of spikes per plant, number of kernels per spike,1000 grain weight and grain yield per plant using Hayman approach and Jones method. The parental varieties and their possible 15 crosses were sown under two different nitrogen levels i.e.,70 kg /faddan (normal) and 35 kg/faddan (stress) using randomized complete block design with three replicates per each nitrogen level . The diallel cross analysis were carried out using the approaches proposed by Hayman (1954) and Jones (1965). Mean squares for fertilizations were found to be significant for all traits studied except days to maturity and plant height, indicating differences between the two different nitrogen fertilization levels for most characters.Genotypes, parents and the resultant crosses mean squares were found to be highly significant for most traits studied at the two different nitrogen levels and their combined data. The additive genetic variance ( D ) was found to be highly significant for all traits studied at the two different nitrogen fertilizations except number of grains per spike and grain yield per plant at the two different nitrogen levels . The dominance genetic variation1 H  and 2 H  were found to be highly significant for all traits studied at the two different nitrogen fertilizations. Moreover, the estimated values of dominance components 1 H  and 2 H  were found to be greater in their magnitude than the corresponding additive genetic variations ( D  ) for most traits under investigation. Estimates of the ratio of dominant to recessive alleles in the parents (KD / KR) were found to be more than unity for all traits studied at the two different nitrogen levels, except grain yield per plant. Moderate heritability values were detected for heading date, plant height and spike length . For the other traits, low heritability in narrow sense was detected.The additive genetic variance (a) was found to be highly significant for all characters studied at both two nitrogen fertilizer levels. The dominance genetic variation (b) was highly significant for all-characters studied at the different two nitrogen fertilizer levels. The (a) values were found to be larger in magnitude than the corresponding (b) values for most traits studied.