Characterization And Physiological And Genetic Analysis Of Phosphorus Efficiency In Winter Wheat Germplasms

Phosphorus (P) deficiency is one of the principal yield-limiting factors in wheat production. Improving P efficiency genetically can be one of the promising ways to deal with this problem.In this study, 216 wheat genotypes were evaluated for their P nutritional efficiency under field condition. Phosphorus nutritional efficiency was measured by P efficiency (yield at low P level) and sensitivity to low P (yield decrease caused by P deficiency). Then some genotypes were chosen to investigate the physiological basis contributing to genetic variations of phosphorus efficiency. The main results were as follows:1 Two high P efficient varieties with high yield potential, CA9325 and Nongdal39, and three low P in-efficient varieties with low yiled potential, Nongdall6, 20120223 and Jimai23, were selected from 216 winter wheat genotypes through two-year field experiments. During the two years tests, only 37.8% of the tested cultivars had stable P efficiency, indicating that, in order to get P efficient germplasm more quickly and more exactly, it was necessary to characterize for several years. The plant height, heading time delayed by P deficiency, and sturcture of yield components were related to P nutritional efficiency. The results also indicated that biomass, leaf area at anthesis and grains per ear at severe P deficient condition (Olsen P=2.4mg-kg-1) or ears per centiare at slight P deficient condition (Olsen P=6.6mg-kg"') may be taken as the secondary criterion in selecting for P efficient cultivars.2 The relationship between P efficiency and P absorption efficiency and P utilization efficiency was analyzed with 12 winter wheat cultivars under field condition. By path analysis, it was found that both P absorption efficiency and P utilization efficiency had direct roles in P efficiency, but the role of P absorption efficiency was greater than P utilization efficiency. The results also indicated P utilization efficiency was important after anthesis, but P absorption efficiency was important during the whole growth period.3 Three cultivars with different P efficiency were used to analyze the physiological base attributed to genotypic variations in P efficiency. The results showed that P efficient cultivars could maintain their predominance in then- yield structure and have three common characters in P deficiency status. They were quick dying of invalid tillers, well-developed ear and more dry matter production after anthesis in P deficiency status. Phosphorus efficient cultivars with different yield structure also had their special physiological characteristics. The cultivar CA9325, with few tillers but big ears, succeeded in maintaining its secondary root growth after anthesis so that it absorbed enough P for grain development in this growth stage. The cultivar Nongdal39, with numerous tillers, accumulated more P before anthesis. After anthesis, P upatke of this cultivar was low while P utilization efficiency was high.4 The broad sense heritability of P efficiency is high (63%) when it was analyzed in the population composed of cultivars. This figure was low (20%) when it was analyzed in the F2 population derived from Linghan 6210 X Jinmai 17. It was supposed that P efficiency is controlled by quantitative genes, and the selection for P efficiency in early generation is ineffcient in breeding for P efficient cultivars.