Evolvement Rule Analysis Of Important Agronomic Traits And Genome-Wide Association Study Of Grain Shape In South China Rice Varieties

In China,more than half of the people take rice as the staple food.With the increasing population,decreasing farmland and increasingly harsh environment,the food security of China and even the whole world is facing great challenges.Rice region in south China is one of the main rice-producing areas in China.The rice sown area accounts for about 20% of China’s total area,which has an important impact on China’s food security.Genetic and improvement characteristics of agronomic traits of rice in south China were studied,as well as the composition factors of yield,and the relationship between yield and other agronomic traits was analyzed,so as to provide theoretical basis for the genetic and breeding of higher yield of rice.Rice varieties in south China have obvious selective marks in grain type traits,which are important traits affecting rice yield and quality.Therefore,it is of great significance to locate the QTL for grain type traits in south China for rice breeding in this region.1.Breeding imprinting analysis of important agronomic traits in rice in south ChinaThe purpose of this experiment was to study the evolution of agronomic traits and to analyze the characteristics of rice improvement in south China,so as to find a new method of improving rice yield.Through collecting large area extension rice varieties,backbone parents since dwarfing breeding and landraces before modern breeding from south China and planting them in different ecological regions and investigating total of 18 traits including adaptation,plant type,grain type and yield-related traits,using multiple comparison,correlation and path analysis we found that rice varieties in different ecological regions have a similar evolution and there are great changes between landrace and modern bred varieties in following traits: uniform growth duration,decreased plant height,increased leaf area,more spikelets per panicle and slender grain type,etc.for modern varieties.Growth duration was paid more attention in breeding program before 1980 s,while panicle type and grain type were much emphasized since 1980 s.Biomass is a base of high yield and dwarfing breeding decreased plant height and increased harvest index.Therefore,in order to further improve yield by increasing sink size,it is an important way to improve yield by increasing biomass based on increased effective panicle number which has showed gradually decrease in recent years.2.Genome-wide association analysis of grain shapeUsing the south China rice varieties collected in this experiment as the materials,25 QTLs affecting grain type were identified and located on chromosomes 1,3,4,5,6 and 10,respectively,by GWAS analysis using the second-generation resequencing SNP genotype data and the phenotypic data of grain types collected from multiple sites in the 2017 and 2018.Seventeen important QTLs on chromosomes 3,4,5,6 and 10 were identified by candidate gene association analysis and haplotype analysis.