The Genome-wide Association Study Of Aluminum Accumulation In Rice(Orazy Sativa L.)

Aluminum is one of the heavy metal pollution elements in soil,which is very toxic to rice growth in acid soil.Over 50%of the potential arable land and about 30%of the land area in the world are acidic.Aluminum toxicity is an important factor limiting the growth and yield of rice.Therefore,it is of great significance to reveal the mechanism of aluminum tolerance in rice and reduce aluminum toxicity to improve rice yield.The results showed that the root tip was the most sensitive part to aluminum stress,and Al3+could combine with pectin components of root cell wall to change the structural properties of cell wall;It can bind to cell membrane,ion channel proteins,enzymes,signal pathway components,cytoskeleton,and DNA.Aluminum stress inhibited root elongation,affected nutrient transport and water absorption of root cells.At present,based on the study of Al tolerance at seedling stage in rice,some resistant varieties or materials have been selected,and several QTLs controlling Al tolerance have been mapped by molecular markers.In this study,GWAS analysis was carried out using two sets of population in the laboratory.Population 1 is the DC1 population of three multi parent high generation cross lines(MAGIC)populations(DC1,DC2 and 8-way)with genetic diversity.The genes related to aluminum tolerance at seedling stage were analyzed,and the phenotypes were identified,including plant height,root length,aboveground dry weight,water content and Al3+ content,whole root dry weight and Al3+ content,Genetic mapping of 55k high-throughput SNP genotypes was performed.Population 2 is 208 natural populations,covering most of Indica and Japonica Rice in Southeast Asia,with genetic diversity.Through the method of positive genetics,association analysis and linkage analysis,we hope to obtain genetic loci related to aluminum absorption and transport.The results are as follows1.Under normal conditions and aluminum stress,there were significant phenotypic variations in aluminum tolerance of four parents of MAGIC-DC1 population,with significant differences in aboveground length,root length,aboveground dry weight and root dry weight,and aluminum ion content,respectively.Parents C and D were more sensitive to aluminum stress than parents a and B.2.In this study,the effects of aluminum stress on root morphology and the response mechanism of rice roots to aluminum stress were investigated in five representative natural populations,namely,Nipponbare、SWR17、CIHERANG-SUBI、IR66、NSIC-RC141 and Yunjing37.The results showed that there were significant differences in Al stress phenotypes among different rice varieties.Root relative elongation of 4 and 6 rice varieties were significantly higher than that of the control under 3 and 7,indicating that short-term treatment with relatively low Al concentration could promote the growth of some rice roots.When the aluminum concentration is 20 μ1,the root growth of Yunjing37 increased,while that of other varieties decreased significantly,and the inhibition degree of root growth increased with the increase of aluminum concentration.3.The Al3+content at seedling stage of MAGIC-DC1 population was determined,and several QTLs affecting the Al3+content in shoot and root and the ratio of A13+concentration between shoot and root were detected.Based on further analysis of a significant QTL on chromosome 1,we selected 61 candidate genes that may be related to aluminum transport.Through qRT-PCR analysis,OsGA20ox2 gene was selected for subsequent functional verification.The results showed that the aluminum tolerance of osga20ox2 gene knockout was decreased and it was more enriched than wild type;The Al3+ content at seedling stage of natural population in Southeast Asia was determined.Several QTLs affecting the Al3+content in shoot and root and the ratio of Al3+concentration between shoot and root were detected.Four aquaporin genes were selected for further analysis of a significant QTL on chromosome 7,Construction of the corresponding CRISPR/Cas9 single knockout and double knockout mutants for subsequent gene function preliminary verification.According to the preliminary identification results of one of the obtained mutants,the mutant ospip2;4-1 and ospip2;4-2 was more tolerant to aluminum stress.