INFLUENCE OF SOWING DATE ON DEVELOPMENT, HARVEST INDEX AND YIELD COMPONENTS FOR BREAD WHEAT CULTIVARS HAVING DIFFERENT THERMAL RESPONSES IN MIDDLE EGYPT

Two experiments were conducted in 2010/2011, 2011/2012 at Malawi Agric. Res. Sta., ARC to investigate the effect of sowing date according to the thermal time on developmental traits, yield and its component of four bread wheat cultivars (Triticum aestivum  L) i.e. Giza168, Sids-1, Sids-12 and Shanwel-1 (Hexaploid) in three sowing dates i.e. 21^st November, 10^th December and 30^th December  . The results showed that mean of all the sowing dates and cultivars arrived to anthesis at 88.6 DAS (881.4˚c) and to maturity 141.3 DAS (1671.2˚c) in season 1, however they arrived to anthesis at 98.5 DAS (973.0˚c) and to maturity 152.6 DAS (1986.5˚c) in season 2. Heading date and anthesis were significantly affected by cultivars and sowing dates in both two growing seasons, also the interaction in the second season. Days to maturity were significantly affected by sowing date in two growing seasons and the interaction in the first season. Plant height was differed significantly by cultivars in two growing seasons and by sowing date and their interaction in the second season.
No. spikes/m² was significantly affected by sowing dates in both growing seasons and cultivars in the second season and their interaction in the first season. No. kernels/spike was significantly affected by cultivars, sowing dates and their interaction in the second season only. The weight of 1000-kernels was significantly affected by sowing date in two growing seasons and by cultivars and their interaction in the second  season only.
Grain filling period was significantly affected by sowing dates in two growing seasons and the interaction between cultivars × sowing date in the second season. Grain yield / plot (kg) was significantly affected by cultivars and sowing dates in two growing seasons. Harvest index was significantly affected by cultivars in first season and by sowing date and their interaction in the second season. Mean H.I. of Sids12 was slightly higher than other cultivars. Mean H.I. in sowing dates of optimum was higher than other dates in two growing seasons and their interaction in the second season.
Conclusions: The obtained results revealed that: 1- The tested wheat genotypes were differed significantly among them in accordance to temperature and photoperiod requirements. 2- This study must be continuously arranged with all new released wheat genotypes for determining appropriate planting time for high yield.