HERITABILITY, VARIABILITY, GENETIC CORRELATION AND PATH ANALYSIS FOR QUANTITATIVE TRAITS IN DURUM AND BREAD WHEAT UNDER DRY FARMING CONDITIONS

Abstract

Two field experiments were carried out during the 2009-2010 growing season at the station of Directorate of Agricultural Researches/Erbil under dry farming conditions. The first experiment included 25 strains of durum wheat, and the second included 20 strains of bread wheat. Growth trait, yield and its components were studied, and then data are entered in the statistical genetic analysis, as well as the path coefficient analysis. The results showed high genetic variation, heritability and genetic advance for plant height, number of spikes, 1000 grain weight, biological yield and grain yield in durum wheat. While it was high in all traits in bread wheat. The grain yield was correlated genetically positive and significantly with 1000 grain weight, biological yield and harvest index in durum wheat, while showed genetically positive and significant correlation with all traits in bread wheat. The path coefficient analysis revealed that harvest index and biological yield had the maximum positive direct effects on grain yield in durum wheat reached 0.966 and 0.242, respectively. While the harvest index had the maximum positive direct effect (1.417) on grain yield in bread wheat, which was used as a criterion for the selection of superior genotypes in each group. INTRODUCTION The grain yield is a complex traits which is influenced by many factors, would be plant breeders interested to know the nature of the relationship and the kind between these traits, especially under dry farming conditions, where the water is the main limiting factor in many areas of wheat production around the world due to uneven rainfall distribution during the growing season, so it is important that characterized cultivars cultivated in these areas in the superior performance of grain yield and its components under the limited and non-limited of moisture conditions (Okuyama et al., 2004). Grain yield is the result of many developmental and physiological events that occur during the life cycle of the plant, and grain yield is determined by three main components; the number of spikes/plant, number of grain/spike and weight of grains (Poehlman, 1987). Hochman (1982) and McMaster et al. (1984) referred that the influence of each one of these components on the product of grain depends on the stage of growth that occurs due to water deficit. At elongation stage, the inadequate availability of water or rain affect on the components of grain yield by increasing the number of spikes/plant, grains/spike, and weight of grains/plant, while leading to increased weight of grains during the grain filling stage (McMaster et al.,1984). Simane et al. (1993) reported high correlation between the number of grains/spike and grain yield along the span of