Identification Of QTL For Rice Yield Related Components Under Nitrogen Deficiency And For Cd²⁺ Content In Brown Rice

A F9population including167lines, which was came from the cross between theindica variety Zhongyouzao No.8and the japonica variety Fengjin. Main agronomictraits of grains number per spike (GNS), spike length (SL), effect spike (ES), seedsetting rate (SSR),1000-grain weight (KGW) and yield per plant (YD) wereinvestigated in a pot trial with normal nitrogen level and low nitrogen stress. The RILwas analyzed with a genetic linkage map consisting157DNA markers. The statisticsoftware of QTL Network2.0was applied to detect QTL and QTL effect analysis for sixyield traits and nitrogen agronomic use efficiency under normal and low nitrogenconditions in rice. Moreove,a population with188lines of F10(RIL) crossed byNipponbar（japonica）and Luhui99（Oryza sativa L）was employed to map QTL of Cd2+content of brown rice in A and B environment with another genetic linkage map.①Correlation analysis of six yield traits and relative value of traitsThe results showed that effect spike, yield per plant, grains number per spike and spikelength were sensitive to nitrogen stress, So varieties with higher effect spike, yield perplant, grains number per spike and spike length were better picks for low nitrogentolerant varieties. Correlation analysis on agronomic traits showed that yield per plantwas extremely positively correlated with effect spike, grains number per spike and seedsetting rate under normal nitrogen level. However, under low nitrogen stress yield perplant was extremely positively correlated with effect spike, grains number per spike andspike length, and positively correlated with1000-grain weight. The correlationcoefficient between yield per plant and effect spike increased significantly under lownitrogen stress, hence higher effect spike can effectively reduce the loss of production.The relative value of yield per plant was extremely positively correlated with effectspike, grains number per spike, yield per plant, the relative value of effect spike and therelative value of grains number per spike under low nitrogen stress, but negativelycorrelated with agronomic traits under normal nitrogen level. These indicated that theproduction of inbred lines with high yield is not consistent under two conditions, butexist lines of higher relative value of yield per plant, therefore we can filter low nitrogentolerant inbred lines through the low nitrogen stress test.②Identification of QTL for yield related components under two nitrogen levelsThere are altogether thirteen QTLs for yield traits that were detected, but only two QTLs were detected in both nitrogen conditions. Two QTL of nitrogen agronomic useefficiency were detected, explained7.74%and6.67%of the phenotypic variationsrespectively.③Mapping of QTL of Cd2+content in brown riceOnly two QTLs had been detected in environment A, they were located on chromosome7and8respectively. The QTLs explained phenotype variance29.8%and8.87%.Onlyone QTL was detected on chromosome7in environment B, the contribution was8.7%.Environment B have an effect on the expression of the gene. The QTLs of Cd2+content in brown rice are more likely to be expressed in environment with high Cd2+levels, so breeding low Cd2+content rice varieties should be in high Cd2+content soilenvironment.