Genetic analysis of plant height and its components in diallel crosses of bread wheat (Triticum aestivum L.)

An incomplete diallel cross study comprising of seven bread wheat (Triticum aestivum L.) cultivars was carried out with parents and F1 progeny to determine heterosis, combining ability, gene action, and correlations for plant height and its components. The results showed that heterosis and heterobeltiosis occurred in plant height, spike length, peduncle length, length of the second internode from the top to bottom, length of the third internode from the top to bottom, length of the second basal internode and length of the first basal internode, but their values varied among crosses and characters. Estimates of the genetic components of variation as well as ratio of GCA/SCA showed that all the characters were predominantly controlled by additive gene action. Plant height and its components were governed by partial dominance with additive type of gene action. Narrow sense heritability estimates for all the characters were higher, varying from 76.62% to 95.08%. Plant height might be controlled by four groups of dominant genes, while its components might be controlled by one or two/ three groups of genes. The correlation analysis showed that lengths of internodes were positively and significantly associated with plant height, and path analysis indicated that peduncle length had the highest effect on plant height, followed by length of the second internode from the top to bottom. The estimates of general combining ability pointed out that the best general combiners for the plant height and its components were Ningmai 8 and Yangmai 9, which appeared to be promising parents for wheat breeding program. Results concluded that selection for plant height and its components would be effective in early generation. The results obtained from this study might be helpful for wheat breeders trying to develop new varieties with semi-dwarf and lodging resistance.