Cold Tolerance Identification And QTL Analysis Of Indica And Japonica Recombinant Inbred Lines

Low temperature damage is one of the main factors limiting rice yield and geographical distribution.It may be affected by low temperature damage at different stages of rice growth and development,resulting in reduced yield and loss of nutrients.Therefore,improving the cold resistance of rice and cultivating cold-resistant rice varieties are of great significance to meet the food needs of the world’s population.In this study,166 lines derived from crosses of cold-tolerant japonica rice J07-23 and indica rice IR36 were used as experimental materials to identify cold-tolerance indicators at germination,bud stage and seedling stage,and to map cold-tolerant QTLs.The main results are as follows:1.A total of 450 pairs of molecular markers distributed on 12 chromosomes were screened,and 221 pairs of molecular markers were screened out.The Map was constructed with Map Chart 2.2.The genetic linkage map covered the rice genome at 1484.1 c M with an average distance of 6.72 c M.2.Under different low temperature conditions,this study identified the cold tolerance index of parents and populations at germination,bud stage and seedling stage.The results showed that the IR36 was significantly stronger than the cold-tolerant parent J07-23 at germination,and the cold tolerance of IR36 at bud and seedling stage was extremely weaker than J07-23.The cold tolerance index of the population in the three growth and development stages showed a super-parent two-way separation phenomenon,which was close to the normal continuous distribution,and the absolute values of kurtosis and skewness of the BIL population were close to ± 1,which was a typical quantitative trait inheritance.3.Correlation analysis showed that during the germination period,the low temperature germination rate had a very significantly positive correlation with the average germination days,germination coefficient,germination index and mean diurnal germination rate.At the seedling stage,the cold resistance level had a very significantly positive correlation with the dead seedling rate and the dead leaf rate,the dead seedling rate had an extremely significant negative correlation with the dry matter weight.Seedling length had an extremely significant positive correlation with root length and dry matter weight.As far as the study population was concerned,there was no direct relationship between cold tolerance at germination and budding stage,there was a negative correlation between cold tolerance at germination and seedling stage,and there was a significant correlation between cold tolerance at bud and seedling stage.4.At germination stage,locating 48 QTLs related to cold tolerance,7 main QTLs had been identified,and the contribution rate varied from 15.17% to 19.75%.A total of 11 QTLs controlling low temperature germination were detected,q GR11-2 was the main QTL,with a contribution rate of 15.96%.12 QTLs controlling average germination days were detected,and q AGD1-1 was the main QTL,with a contribution rate of 19.75%.A total of 8 QTLs controlling germination coefficient were detected,q GC9-1 and q GC9-2 were the main QTLs with contribution rates of 15.86% and 15.17% respectively.A total of 12 QTLs controlling mean diurnal germination were detected,q MDG1-1 was the main QTL,with a contribution rate of 16.05%.A total of 7 QTLs were detected to control the germination index,q GI1-2 and q GI2-2 were the main effect QTLs with contribution rates of 15.78% and 15.76% respectively.5.At the bud stage,there were 11 QTLs that control the seedling rate,which were located on chromosomes 1,2,3,4,7,and 11 respectively.The contribution rate varied from 1.82% to 17.82%,LOD value varied from 2.54 to 6.26.q SR1,q SR2-2 and q SR3-4 were identified as the main QTL,with contribution rates of 15.66%,17.82% and 16.95%.The alleles of q SR1 and q SR2-2 were derived from cold-tolerant japonica rice J07-23,and the alleles of q SR3-4 were derived from IR36.6.At seedling stage,locating 27 QTLs related to cold tolerance.There were 2 QTLs for controlling cold resistance level,q CRL2-1 was the main QTL with a contribution rate of 16.96%.There were 8 QTLs for controlling dead seedling rate,q DSR2-2 and q DSR11 were the main QTLs,contributing 15.49% and 19.33% to the phenotypeand.There were 8 QTLs for controlling dead leaf rate,q DLR2-2 was the main QTL with a contribution rate of 15.57%.There were 2 QTLs for controlling seedling length,and all synergistic alleles were derived from indica rice IR36.There were 6 QTLs for controlling root length,q RL1 was the main QTL with a contribution rate of 21.32%.Only q DMW4 was detected to control dry matter weight,with a contribution rate of 3.60% to the phenotypic variation,and the allele from the IR36.