Analysis Of Root Response Characteristics Under Low Phosphorus And Evaluation Of Agronomic And Economically Traits With More Than 500 Maize Inbred Lines

Maize breeding for improving phosphorus efficiency is based on germplasm resources which has excellent tolerance to low phosphorus. Therefore, the screening of tolerance to low phosphorus on maize germplasm resource is prerequisite of post-genetic research and nutrient efficient breeding, meanwhile it is also one of the keys throughout the experiment. Root is the main organ of nutrient uptake of maize. The ability of the root not only affects the strength and effectiveness of supply of phosphorus, but also disturbs the efficiency of phosphorus utilization and crop productivity. Consequently selecting new varieties with the root of efficiently nutrient absorption and utilization is the vital measure of improving the efficiency of resource use of soil nutrients. Maize germplasm resources provide material support for breeding new varieties, therefore, the narrow genetic basis is the main reason that it is difficult to achieve breakthroughs in maize breeding. China has rich resources of local maize germplasm, of which local varieties account for about 90%, but less than 3% of which are utilized by maize breeding researchers, research and development as well as utilization are still quite inadequate. In addition, the maize germplasm in tropical and subtropical which is one of the the main directions for the use of exotic germplasm has a wealth of excellent adaptation types, such as high quality, disease resistance, lodging resistance and to keep green for a long time.In this study, the experimental materials are the 524 inbred lines which come from CIMMYT, United States and domestic key parental lines. All inbred lines were planted in Sichuan and Yunnan respectively, and agronomic and economic traits are identified, then genetic diversity of test materials were evaluated based on individual level; To screen some important breeding objective traits of the genotype. These can provide a broader utilization of germplasm resources for breeding practice. The differences of nutrient characteristics in 524 copies of the maize germplasm with tolerance to low-P stress morphological and physiological mechanisms characteristics of root in seedling period under the low-P stress are both studied, the screening standard of tolerance to low phosphorus in local maize varieties is also discussed, which establish the theoretical foundation for utilization of local maize with tolerance to low-P stress. The major results are as follows:1. The response of root morphology under low P was found by Phosphorus stress test at seedling stage, and response order showed as Root shoot ratio> Longest root> Forks> Total length> Tips> Crossings> Surfarea> Root volume.2. With the low-p response to define the change rate of Root shoot ratio and longest root, combineing with the yield and the low-p response, screened out 118 materials, such as CY72, DAN598.3. With the 6 traits as indicator which were significantly correlated with the important root traits, Screen out 60 materials per trait, such as (CML-28)-B, (CML-431)-B.4. Compared to the variation of all the agronomic traits, found the variation range in tassel branch number, cob weight, hundred gaint weight, ear height, rows per ear, cobdiameter, ear length, tassel axis length and plant height. Screening of the agronomic traits of the coefficient of variation greater than 0.2, selected 300 materials, Such as HaiO14, (NC350-B)-B.5. Mapping the number distribution of 17 traits, found the most obvious of the changes was growth period between Sichuan and Yunnan. The mean number of tasseling stage, silking stage and loose powder stage in Sichuan are postpone for 26.4 days,26.3 days, and24.3 days.6. The significant differences of growth period, ear height, ear leaf length, tassel axis length, tassel branch number, leaf number, ear width, cobdiameter, ear row number, rows per ear, cob weight, hundred gaint weight between tropical and temperate germplasm were found, by comparing the representation of tropical and temperate germplasm significant difference.7. The Correlation analysis showed that plant height, tassel axis length, ear height, ear leaf width and ear leaf length were significantly correlated with hundred gaint weight; growth period, tassel branch number and leaf number were significantly negatively correlated with hundred gaint weight.