Distribution of Allelic variation for vernalization, photoperiod, and dwarfing genes and their effects on growth period and plant height among cultivars from major wheat producing countries
Yang Fang-Ping, Xia Xian-Chun, Zhang Yong, Zhang Xiao-ke, Liu Jian-Jun, Tang Jian-Wei, Yang Xue-Ming, Zhang Jun-Ru, Liu Qian, Li Shi-zhao, and He Zhonghu
To efficiently use exotic resources in Chinese wheat breeding programs, we investigated the heading date, maturity date, and plant height of 100 representative cultivars collected from 14 countries at eight locations in China, and detected the allelic variations of vernalization loci VRN-1 and VRN-B3, photoperiod gene Ppd-D1a,and dwarfing genes Rht-B1b and Rht-D1b by means of molecular markers. The frequencies of vernalization loci were 8.0% for Vrn-A1a, 21.0% for Vrn-B1, 21.0% for Vrn-D1 and 64.0% for vrn-A1+vrn-B1+ vrn-D1, except for the absence of dominant allele Vrn-B3 in all tested materials. Dominant vernalization alleles Vrn-A1a, Vrn-B1, and Vrn-D1 were mainly observed in cultivars from Chinese spring wheat region, Italy, India, Canada, Mexico, and Australia; whereas, cultivars carrying all recessive alleles at the four vernalization loci and vrn-A1+vrn-D1+Vrn-B1+vrn-B3 genotypewere mostly found in cultivars from Chinese winter wheat region, United States (US) winter wheat region, Russia winter wheat region, United Kingdom (UK), France, Germany, Romania, Turkey, and Hungary. All cultivars headed normally when sown in autumn. Cultivars with dominant alleles showed earlier heading date than those with recessive alleles, and genotypes with two or more dominant alleles showed additive effects. Some European and US cultivars with recessive genes at the four vernalization loci could not mature in Yangling and Chengdu. Under spring-sown condition, the cultivars with dominant vernalization alleles showed high heading frequency; in contrast, most cultivars with recessive alleles failed to head. Gene Ppd-D1a was distributed mainly in cultivars from China, France, Romania, Russia, Mexico, Australia, and India with the total frequency of 68%. Most cultivars with Ppd-D1b were from high latitude regions, such as UK, Germany, Hungary, and Canada. The Ppd-D1a genotypes appeared to head earlier than the Ppd-D1b genotypes. Daylight condition had no effect on maturity of most Ppd-D1a genotypes, but short daylight condition resulted in failing mature in most Ppd-D1b genotypes. The frequencies of dwarfing genes Rht-B1b and Rht-D1b were 43.0% and 35.0% in the cultivars tested, respectively. Rht-B1b was mainly observed in cultivars from US, Romania, Turkey, Italy, Mexico, and Australia, while Rht-D1b had high frequency in varieties from China, Germany, UK, Italy, and India. Generally, cultivars from one country contain either Rht-B1b or Rht-D1b, andthe frequencies of Rht-B1b and Rht-D1b were very low in cultivars from high latitude regions. The effect of Rht-B1b, Rht-D1b and Ppd-D1a on reducing plant height was significant, of which Rht-B1b and Rht-D1b exhibited an additive effect.