Abstract
Eighteen different genotypes of bread wheat were evaluated for: heat and water stress conditions. These genotypes reprented some families of early generations, i.e. F3 and F5 as well as some of parental varieties. Heat stress was represented by two delayed planting dates, November 27th and December 27th. Water stressed included irrigation each 5, 10 and 15 days starting at booting stage. The experiment was carried out at the Agricultural Research Station in Deirab (24 degrees, 42 N and 46 degrees, 44 E, Alt 600 m), King Saud University, near Riyadh, Saudi Arabia.
Results indicated that planting dates had significant effects on yield characters, biological yield, harvest index, and spike length. However, it showed highly significant effects on Kernel weight (1000 seed), flowering date, days to maturity, and filling period. Yield was reduced from 5.28 Ton/H to 3.19 Ton/H as wheat was planted late in November and late in December, respectively. The reduction of yield associated with December 27th planting was due to heat effect of high temperature during seed filling period.
Water stress (irrigation intervals) exhibited significant effects on yield, biological yield, and kernel weight (1000 seed). While it had significant effects on days to maturity and filling period. Yield was reduced about 15% when wheat was irrigated every 15 days as compared with irrigation every 5 days. Two genotypes out of 18 tolerated both heat and water stress conditions. These genotypes were number 17 and 18 (L.19 - 3 - Y.R. 179 - 2 - 16 - 17 and L. 13 - 9 - Y.R. - 189 -2 - 19 - 18) which produced high yield under both stress conditions.
Significant positive correlations were found between grain yield and each of biological yield, harvest index, kernel weight, days to maturity, anti length of filling period.