HETEROSIS AND COMBINING ABILITY OF SOME BREAD WHEAT GENOTYPES.

Twenty one wheat hybrids and their seven parental genotypes were evaluated in the research farm of the Faculty of Agriculture ,Ain shams University, Shoubra El-khema, Cairo, Egypt, in 2016/2017 growing season. The genetic analysis was conducted using Griffing( 1956 ,)Method 2, model 1). Significant differences among parent genotypes and their 21 crosses for all the studied traits (days to 50% heading, days to maturity, flag leaf area, plant height, number of spikes/ plant, spike length, number of spikelets/ spike, number of kernels/ spike, 1000-kernel weight and grain yield/ plant) were detected. This indicated that, variability exists among these populations may increase the chance appearance of good new combination that can be isolated in the succeeding generations. Parents versus crosses mean squares as an indication for average heterosis over all crosses were significant for all studied traits. Mean squares of general (GCA) and specific (SCA) combining abilities were significant for all studied traits except spike length trait for SCA which was insignificant. GCA/SCA ratios were more than unity for all studied traits, which indicating that the additive type of gene action is of great importance in the inheritance of these traits. Heterosis over the better parents showed that, the best hybrids were Gemmiza 9xGiza 168, Sakha 93x Giza, 168, Sakha 94x Jawahir-14, Sakha 94x Bob white, Giza 168xAcsad 925 and Jawahir-14x Bob white for grain yield/ plant trait and some of the other studied traits. The best general combiner parents were Sakha 94, Jawahir-14 and Bob white for grain yield/ plant trait and some of the other studied traits. The best SCA hybrids were Gemmiza 9x Sakha 93, Gemmiza 9x Giza 168, Sakha 93x Jawahir-14, Sakha 94xJawahir-14, Sakha 94x Acsad 925, Sakha 94xBob white, Giza 168x Jawahir- 14, Giza 168x Acsad 925, Jawahir-14x Bob white and Acsad 925x Bob white for grain yield/ plant trait and some of the other studied traits. These result could be used in wheat breeding programs. Wheat (Triticum aestivum L.) is one of the leading cereals and staple food in many countries of the world including Egypt. It plays a remarkable role in meeting the food requirements of the country [Barutcular et al 2017; Ljubičić et al 2017; Singh, S.P. and V. Sharma, 2017; Thomas et al 2017 and Tiwari et al 2017]. In Egypt, wheat is the main winter cereal crop used as a staple food for urban and rural societies and the major source of straw for animal feeding [Ismail 2015, Hamda and Ibrahim 2016 and Kandil et al 2016]. However, total wheat consumption has increased drastically due to over population growth by about 2.5 % per year. Egypt imports about 45 % of its wheat requirements. This reflects the size of the problem and the efforts needed to increase wheat production. Thus, increasing production per unit area appears to be one of the important factors for narrowing the gap between wheat production and consumption. Information regarding general and specific combining ability of wheat genotypes is a prerequisite to launch a successful wheat-breeding programs. Diallel mating design has been extensively used to analyze the combining ability effects of wheat genotypes and also to provide information regarding genetic mechanisms controlling grain yield and other traits. Knowledge of general and specific combining ability. influencing yield and its components has become increasingly important for plant breeders in the choice of suitable parents for developing potential possessing varieties in wheat. Many researchers gave reviews, which revealed that both general and specific combining ability were involved in the improvement of yield and its contributing traits in wheat such as [Tiwari et al 2017; Patel, 2017; Ljubičić et al 2017; Kumar et al 2017 and Ahmad et al 2017]. [ABSTRACT FROM AUTHOR]