The Adaptive Responses Of Rice Seedling To Phosphorus Deficiency And The QTL Analysis

Seven rice genotypes (Zhenshan97, Minghui63, Shanyou63, IR20, Nipponbare, R64 and IR78877) were employed to investigate the variation of their shoot and root morphological traits and phosphorus use efficiency under different phosphorus levels at seedling stage. By responses of seven genotypes under different phosphorus levels, a certain phosphorus concentration of 0.25 mg/L was selected as the proper concentration which can cause phosphorus deficiency of rice. The following hydroponic culture experiment which adopted the concentration of 0.25 mg/L as the low phosphorus level, in contrast with the normal phosphorus level of 10 mg/L, was conducted to study the effect of phosphorus deficiency on morphological traits of RILs and different rice genotypes and the relationship among shoot, root traits and phosphorus-related parameters. The QTLs for all related traits were also located. The results obtained were summarized as following:1. The different phosphorus levels had a significant inflences on the shoot-, root-related traits and phosphorus use efficiency of seven rice genotypes. The plant height, tiller number, shoot dry weight and total dry weight all decreased significantly as the phosphorus application declined. Contrastly, the root parameters such as maximum root length, total root length, root surface area, root volume, root dry weight and root-shoot ratio all increased significantly, the same as phosphorus use efficiency on the basis of biomass. While the phosphorus concentration and accumulation in both shoot and root showed significantly decline as the phosphorus application decreased.2. There was significant variation shown on the shoot and root morphological traits of RILs and different rice genotypes under two phosphorus levels at seedling stage. The shoot morphological traits under low phosphorus level had inferiority to their conunterparts under normal phosphorus level. While the root growth was significantly stimulated under low phosphorus level. Although there was significantly decline on phosphorus concentration and accumulation under low phosphorus, the phosphorus use efficiency of biomass increased apparently. The different rice genotypes showed the same variation.3. There was significant and positive correlations among shoot morphological traits, root parameters and phosphorus accumulation when suffered phosphorus deficiency. Root parameters were also significantly and negatively related to root phosphorus concentration.4. According to the hierarchical cluster analysis procedure, the total phophorus accumulation, phosphorus use efficiency of biomass and root volume of RILs were classified into 3 clusters (1-3) from high to low, respectively. The mean values of cluster 1 of both total phosphorus accumulation and root volume were larest among 3 clusters, that is the cluster with high phosphorus accumulation has bulky roots. The classification of phosphorus use efficiency of biomass shows the similar performance.5. A total of 68 QTLs were detected under two phosphorus levels, which includes 37 QTLs under low phosphorus level and 31 QTLs under normal phophorus level. That is 13 QTLs were detected for shoot traits,16 QTLs for root tratis and 8 QTLs for phophorus related parameters under low phosphorus level. And 12 QTLs were detected for shoot traits,14 QTLs for root traits and 5 QTLs phophorus related parameters under normal phosphorus level. There were 4 QTLs on chromosome 1,3,6 and 7 detected under both low and normal phosphorus levels. The expression of QTLs can be affected by different phosphorus levels.