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. 21st 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.

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Three experiments were carried out at Bahteem Agricultural Research Station during three successive seasons from 2005/2006 to 2007/2008. In 2005/2006 season using three wheat (Triticum aestivum L.) crosses namely; Gemmeiza 7 x Sids 1, Sakha 94 x Irena and Sids 1 x Sakha 94. Six populations (P1, P2, F1, F2, BC1 and BC2) for each cross were used in this investigation. The data were recorded on an individual guarded plants for number of spikes / plant, number of kernels / spike, 100grain weight and grain yield / plant. Significant heterotic effects were obtained for number of spikes / plant, grain yield / plant and number of kernels / spike in the first cross while, heterotic increase in grain weight, grain yield / plant and number of kernels / spike seemed to be accounted for the heterotic response observed in the second cross. Also, significant heterotic effect was found for number of spikes / plant, grain weight and grain yield / plant in the third cross. Inbreeding depression estimates were significant for all studied attributes except for number of spikes / plant in the first cross. Over dominance towards the higher parent for number of spikes / plant, grain weight, grain yield / plant and number of kernels / spike were observed in the first cross. Meanwhile, over or partial dominance towards the lower parent was obtained for all characters in the third cross. On the other hand, partial dominance was observed for all characters (number of spikes / plant, grain weight, grain yield /plant and number of kernels / spike) in the second cross. F2 deviations (E1) were significant for all studied characters in the three crosses, except for number of spikes / plant in the first and second crosses, and grain weight in the first cross only. Moreover, backcross deviations (E2) were significant for all characters studied in all crosses, except for number of spikes / plant and for grain weight in the first cross, grain yield / plant in the first and the second ones. The additive gene effects were significant for all studied characters in the second and the third crosses, except for number of spikes / plant, grain weight , grain yield / plant and number of kernels / spike in the cross (Gemmeiza 7 x Sids 1). These results suggest the potential for obtaining further improvement in most studied character. In addition, dominance epistasis was significant for some of the studied attributes (number of kernels / spike, grain yield/ plant in the first and second crosses; and grain weight in the first and third ones; and number of spikes / plant in the third one). High to medium values of heritability were associated with high and moderate genetic advance as percentage of F2 mean in most characters. These results indicated that selection for the studied characters could be useful in the early generations.

The present investigation was carried out at Mallawy Agricultural Research Station, El-Minia Governorate, Egypt during the two successive seasons; 2010/ 2011 and 2011/2012. The objective of this investigation was to study the effect of sowing dates expressed in the accumulated temperature on yield and its components of three durum wheat genotypes (Triticum durum), i.e., Beni sweif-1, Beni sweif-4 and Beni sweif-5 in three sowing dates, namely; 21 st November, 10 th December and 30 th December during the two winter growing seasons. The studied characteristics included plant height, and number of spikes/m², number of kernels/spike, 1000-kernel weight, grain yield, straw yield and grain filling period. The results showed that all the sowing dates and cultivars reached to maturity at 140.2 days after sowing (DAS) (1652.2 °C days) in season 1 and at 152.4 DAS (2016.4 °C days) in season 2. Heading date and anthesis were significantly affected by cultivars and sowing dates in both growing seasons, also the interaction in the second season. Days to maturity were significantly affected by sowing dates in the two growing seasons and cultivars in the first season. Plant height was significantly affected by cultivars and sowing dates in both growing seasons; also significant interaction was observed between cultivars and sowing dates in the second season only. Number of spikes/m² was significantly affected by sowing dates in both growing seasons; also cultivars in the second season on spike/m 2. Number of kernels/spike and thousand kernel weight were significantly affected by cultivars, sowing dates and the interaction between cultivars and sowing dates in the second season only. Grain yield/plot was significantly affected by sowing dates in both growing seasons and cultivars in the second season. Straw yield was significantly affected by sowing dates in both growing seasons because the sowing dates (thermal time) was the main limiting factor to straw and grain yield in two growing seasons 2010/2011 and 2011/2012. Grain filling period was significantly affected by sowing date in both growing seasons and the interaction cultivar × sowing date was significant in the second season. The current study showed that the first sowing date was the optimum date for Beni sweif-1 in both growing seasons. These results are discussed in relation to future improvement of yield in respect to the variation of meteorological data in winter season with a spot light on thermal time.