Effect of Sowing Date on Growth, Accumulated Heat, Yield and Its Components of Some Bread Wheat Genotypes

Abstract

Significant differences were detected among the studied sowing dates, where; the first sowing date gave the heaviest shoot dry weight and the highest leaf area index at 50, 65 and 80 days in the two studied seasons. The highest value of CGR at 50-65 days at the first sowing date in the first season, also CGR and NAR achieved the highest values at 65-80 days from sowing at 30 November in the second season and at 15 December in the first season. Number of days taken to emergence, tillering and jointing were gradually reduced with wheat planting from 15 December to 1 November, however, number of days to maturity was gradually increased. Moreover life cycle of wheat gradually decreased with delayed planting. Sowing date at 1 st of November achieved the highest values of GDD in tillering, jointing, booting, heading and maturity, while sowing date at 15 th December achieved lowest values of GDD in both studied seasons. The highest chlorophyll content, heat use efficiency, harvest index and heaviest biological and grain yield/ fed were obtained at sowing date 30 November in the two studied seasons. Tested wheat genotypes significantly difference, where Gemmieza 11 cultivar and Line 4 had the heaviest shoot dry weight and highest leaf area index at 50, 65 and 90 days in both seasons. Moreover, at 80-95 days Giza 171 gave the superiority for net assimilation rate in both seasons and for crop growth rate in the second season only, also at 50-65 days Line 3 and 65-80 days Line 4 gave the highest value of CGR in the first season. Moreover, maximum days and accumulated GDD detected for Giza 171 at jointing stage and Line 4 at maturity in the two seasons. Giza 171 gave the highest value for chlorophyll content and 1000-kernel weight in both seasons and HUE, plant height and harvest index in the first season, while biological yield in the second season. The highest number of tillers/m 2 was recorded in Sids 13 cultivar and spike length for Gemmieza 11 in both studied seasons. Also, Line 3 had the highest biological yield in the first season and Line 4 for HI in the second season. The interaction between sowing dates and genotypes had significant, where; in most cases, delayed sowing (15 December) had adverse effects on shoot dry weight, leaf area index, crop growth rate, net assimilation rate, phenological stages and growing degree days but the intensity varied among wheat genotypes. Sustaining the growth in late sown conditions of Shandaweel 1, Giza 171, Line 3 and Line 4 was clear indication of its adaptability measures to terminal heat stress. Planting of Giza 171, Gemmieza 11 and Line 4 on 15 or 30 November seemed the most productive combination. The finding of this investigation may help both physiologists and breeders in determining the sowing dates and genotypes could be selected for good growth and high yield.