BREEDING WHEAT FOR TOLERANCE TO SOME ENVIRONMENTAL STRESSES

Abstract

The aim of this study was to analyze genetic system govering some drought measurements i.e., leaf temperature (LT), stomatal resistance (SR), transpiration rate (TR), osmotic presser (OP) and water situation defect (WSD), and susceptibility index (SI) for yield and some of its components i.e. number of spikes per plant, number of kernels per spike, 1000-kemel weight, biological yield, grain yield and straw yield of eight parent and their crosses of wheat under stress (one irrigation) and nonstress (normal irrigation) field conditions Phenotypic stability for grain yield was also estimated. Eight parental lines, representing wide range of variability in most of the studied traits, were utilized. These parental varieties or/lines were planted in 1994/1995 season and crossed in all possible combinations without reciprocal to obtain seeds of 28 F, hybrids. In 1995/1996 season the 28 hybrids and 8 parental lines were grown in a randomized complete block design with three replications in both Zarzora and Shebin El-Korn locations. Four adjacent experiments were conducted in each location, the first, second, third and fourth experiments were irrigated one, two, three and four times after planting irrigation, respectively. The susceptibility index (SI) was calculated independently for each environment (the first and fourth experiments in each location) from origin data for yield and yield components before analysis using a generalized formula (Fischer and Maurer 1978). An ordinary analysis of variance was firstly perfonned for each origin susceptibility index values in each location and combined over both locations. Also, combined analysis was performed between the two experiments (stress and normal irrigation) in the individual location for drought measurements, whenever homogeneity of error variance was realized. Heterosis was computed as mean squares