Dwarfing gene Rht4 and its effects on key agronomic and coleoptile traits in bread wheat

The gibberellin sensitive gene Rht4 is a single recessive factor and reduces plant height in wheat. To reveal its potential use in wheat breeding, the effects of Rht4 gene on plant height and other key agronomic and coleoptile traits were investigated and compared using a bi-parental population from a cross between "BSJ-14" (semi-dwarf, Rht4) and Scholar (tall, no known dwarfing alleles) under the rainfed conditions. The presence of Rht4 gene was controlled at the molecular level using SSR marker of Rht4. It was found that 25 out of 72 F4 lines carried Rht4 gene while 36 lines did not possess the gene and 11 lines were heterozygous. Rht4 gene reduced plant height and peduncle length by 5.2% and 5.3%, respectively. Spike length, spikelet number and kernel number per spike were decreased but thousand kernels weight increased in lines with Rht4 gene as compared to tall lines. Reduction in coleoptile length, coleoptile diameter and first leaf length was observed in lines with Rht4 gene by 5.5%, 2.1% and 6.6%, respectively. The increase in thousand kernels weight in plants carrying Rht4, especially in heterozygotes, shows that this gene should be put emphasis on in wheat breeding programs, particularly in the development of hybrid varieties.