| Drought is the serious problem of world agricultural production, also the important factor that restricts Chinese agricultural and economic development. Along with increasing of population, reducing of cultivated area, shorting of water resourse and warming of global climate, it is a important breeding objective that further effective utilize rainfall and irrigation water resource, increase wheat drought resistance and yield potential. Wheat mainly growing in arid and semi-arid region is important food crops in China. It is important to wheat cultivars that select prominent drought-resistance wheat varieties, exploit drought-resistance potential completively, reduce water consumption of growth period utilize deep water effectively increase water use efficiency and improve utilize and distribute way of limited water.It plays a key role in improving world wheat production that utilize dwarfing genes such as Rht-B1b,Rht-D1b and Rht8 effectively. The use of dwarfing genes to reduce plant height,enhance lodging resistance,improve harvest index and yield potential has been one of the major strategies in China breeding. Wheat dwarfing varieties primary cultivate in area having better water and fertilizer, however, along with shorting of water resource, 60% area of Chinese wheat production depend on natural rainfall, Therefore, select drawing genes which benefit for improving wheat drought-resistance, and selective breeding varieties suitable for wheat productive utilization of dry land and limited irrigated area, also are important direction of wheat high-yield breeding.The objectives of this study were to determine the presence of three dwarfing genes of Rht-B1b, Rht-D1b and Rht8 in wheat cultivars from major agro-ecological zones in northern China by molecular markers, and their pedigree available, revealing the frequencies and distribution patterns of these three dwarf genes in wheat cultivars from different agro-ecological zones and their relationship with water use efficiency; and further analyzed the effects of those three dwarf genes on traits of related to drought resistance and yield potential,It plays a key role of dwarfing gene to wheat improvement for dry land, and the main results were as follows:1. Dwarfing genes Rht-B1b (Rht1), Rht-D1b (Rht2) and Rht8 in 129 wheat genotypes in Northern region of China have been detected by molecular markers and pedigree analysis. Results indicated that among the 129 wheat cultivars, 58 genotypes with the Rht-B1b, 24 genotypes with the Rht-D1b and 73 genotypes with the Rht8 are respectively detected. None of the three dwarfing genes and Rht-B1b+ Rht-D1b are identified in this study, however there are 35 genotypes with Rht-B1b+Rht8 and 16 genotypes with Rht-D1b+Rht8. Pedigree information confirmed that Rht-B1b in Chinese wheat cultivars is from the Korean introduction Suwon 86 (Rht-B1b+Rht-D1b) and the Italian introduction St2422/464 (Rht-B1b+Rht8). Huixianhong and Suwon 86 are the original sources of Rht-D1b in Chinese wheat cultivars. The original sources of Rht8 are Lovrin 10, St2422/464, Funo, Abbondanza, Villa Glori and Chinese landrace Bima 4.2. Molecular detection and pedigree analysis to 129 wheat varieties show that the three dwarfing genes Rht-B1b,Rht-D1b and Rht8 have different distribution frequency in bred varieties of various ecological regions, and different dwarfing genes in various wheat area. Dwarfing genes Rht-B1b,Rht8 take a dominant position with frequencies of 45.0% and 56.6%, respectively, followed by Rht-D1b with a frequency of 18.6%. Dwarfing genes Rht-B1b,Rht-D1b are mostly concentrated in Yellow and Huai Valley Facultative Wheat Region and Southwestern China Autumn-sown Spring Wheat Region, respectively; Rht8 gene has extensive distribution in various ecological regions. The different distribution of three dwarfing genes in Northern region of China related with utilization of dwarfing genes in wheat breeding and their ecological adaptation. Dwarfing genes Rht-B1b,Rht-D1b are mostly concentrated in Yellow and Huai Valley Facultative Wheat Region and Southwestern China Autumn-sown Spring Wheat Region of more rainfall. Rht8 gene has extensive distribution in various ecological regions, which related with ecological adaptation of Rht8 gene.3. Test on response to GA3 of these cultivars revealed that wheat cultivars with the dwarfing genes Rht-B1b, Rht-D1b, Rht-B1b+Rht8 and Rht-D1b+Rht8 were insensitive to GA3, and those with the dwarfing gene Rht8 were responsive to GA3.4. Analysis of traits of related to drought resistance through dwarfing genes have different sensitivity to gibberellin show that dwarfing genes Rht-B1b,Rht-D1b have strong ability of reduce plant height, at 24.6% and 30.4%, respectively, and have adverse influence in length of coleoptile, flag leaf and the first seeding leaf; Although Rht8 having sensitivity to gibberellin has poor effects in reducing plant height and internode under spike, and has no adverse effects in length of coleoptile, seeding root and the first seeding leaf, which on hand reducing wheat lodging rist, keeping larger biomass, at the same time, increase ability of resisting adverse environment.5. Analysis of yield traits through dwarfing genes have different sensitivity to gibberellin show that And Rht8 has no adverse effects in number of spikelets, effective spikes per plant and 1000-grain weight, meanwhile increases grain number per spike. Compare with other dwarfing genes having insensitivity to gibberellin, the seed setting of Rht8 is high in upper and bottom of spike, so increase the productive potential; Rht-B1b and Rht-D1b have no adverse effects in number of spikelets, effective spikes per plant and 1000-grain weight, meanwhile Rht-D1b increases grain number per spike.To sum up, dwarfing gene Rht8 has no adverse effects in traits of related to drought resistance, and increase the productive potential. Therefore, we consider that dwarfing gene Rht8 having sensitivity to gibberellin is a ideal one used in improvement of dry-land wheat.
|
PDF Full Text Request