GENE ACTION AND COMBINING ABILITY IN EARLY GENERATIONS OF DIALLEL CROSS IN BREAD WHEAT .

Abstract

To study combining ability and types of gene action controlled on heritability of yield components in bread wheat, diallel cross with one direction was done among six genotypes of bread wheat , Abu-Graib3, A4.10 , IPA99 , M2 , A3103 , Al- Fatah . In the second season 2006-2007, a field trail was conducted for all crosses with parents using randomized complet block design (RCBD) .Genetic analysis showed that significant differences for GCA and SCA for all studied traits. Average degree of dominance was more than one for all studied traits indicating the effects of over dominance and predominant of non-additive gene action . Heritability in broad sense showed high values while heritability in narrow sense was low values except grain yield per plant in F3- generation reached to 47% . The crosses (M2xA3103) in F1 , (IPA99x M2) in F2 and ( IPA99x A3103) in F3 gave highest grain yield per plant reached to 29.1 , 27.5 , 29.2 g/plant, respectively. The main conclusions from these results, that was a continuous variance in genetic parameters, yield and its components for parents and their crosses in all studied generations because they were a segregate generations and the traits not stabilized well till F5 or F6 , so these crosses must be grown to a successive generations to develop new genotypes with high yielding ability.