Assessment of genes controlling area under disease progress curve (AUDPC) for stripe rust (P. striiformis f. sp. tritici) in two wheat (Triticum aestivum L.) crosses.

Genetic effects on controlling stripe rust resistance were determined in two wheat crosses, Bakhtawar-92 x Frontana (cross 1) and Inqilab-91 x Fakhre Sarhad (cross 2) using Area under Disease Progress Curve (AUDPC) as a measure of stripe rust resistance. The resistant and susceptible genotypes for crosses were identified by initial assessment of 45 wheat accessions for stripe rust resistance. Mixed inheritance model was applied to the data analysis of six basic populations P1, F1, P2, B1, B2, and F2 in the crosses. The results indicated that AUDPC in cross 1 was controlled by two major genes with additive-dominance epistatic effect plus polygenes with additive-dominance epistatic effects (model E). Whereas in case of cross 2, it was under the control of two major genes with additive-dominance epistatic effect plus additive-dominant polygenes (model E-1). Additive effect was predominant then all other types of genetic effects suggesting the delay in selection for resistance till maximum positive genes are accumulated in the individuals of subsequent generations. Occurrence of transgressive segregants for susceptibility and resistance indicated the presence of resistance as well as some negative genes for resistance in the parents. The major gene heritability was higher than the polygene heritability in B1, B2 and F2 for the crosses. The major gene as well as the polygene heritability was ranging from 48.99 to 87.12% and 2.26 and 36.80% for the two crosses respectively. The highest phenotypic variations in AUDPC (2504.10 to 5833.14) for segregating progenies (BC1, BC2 and F2) represent that the character was highly influenced by the environment.