Identification of a GA-insensitive semi-dwarf locus on chromosomes 2D of wheat (Triticum aestivum) and its relationship with earliness and growth characteristics using selected chromosomal substitution lines

This study was carried out in an unheated greenhouse in order to identify possible GA-insensitive or GA-sensitive genes in semi-dwarf wheat varieties Timstein and Red Egyptian using selected substitution lines of the above varieties and to determine whether these kinds of dwarfness is associated with earliness and some other agronomic traits. According to analyses of variance, it was revealed that significant variations exist among the substitution lines for majority of characters under study. The results also showed that the chromosomes related to the selected substitution lines studied in the current experiment do not have crucial differences with recipient variety for most agronomic traits except line CS(RE-2D) which shows a highly significant difference with its recipient for height. Therefore, chromosome 2D seems to have a locus for reducing height in variety Red Egyptian. Such a locus was not documented in CS(Tim2D) because this line was significantly (12.63 cm) taller than CS(RE-2D). In addition, the height of CS(RE-2D) was not affected by GA application providing a proof that the dwarf locus on chromosome 2D of RE is not sensitive to GA. Finally, the results also indicated that dwarfness caused by the locus on chromosome 2D in substitution line CS(RE-2D) is associated with earliness implying that the locus shortened the growth period of the line by reducing the period of times needed for flowering and maturity. Thus, it can be concluded that this dwarf locus may be used in escaping wheat cultivars from the drought that generally happens at the end of growth season in many parts of the world. However, the correlation analysis indicated that the overall relationship between height and earliness is not significant.