Analysis of Epistasis among QTLs on Heading Date based on Single Segment Substitution Lines in Rice.

Heading date directly determines the planting districts and seasons, and thus plays an important role for producing and introducing of varieties. Limited to the materials and methodologies, analysis of epistasis still presents an obvious challenge. This thesis estimated effectively four types of epistatic components among dual QTLs on heading date based on eight single segment substitution lines (SSSLs) in rice. The results confirmed that they carried truly with heading date QTLs. Eleven pairs of QTLs were with 50.0% of significant epistatic effects, of which additive-additive, additive-dominance or dominance-additive, and dominance-dominance interaction components occupied 40.9%, 50.0% and 59.1%, respectively. One QTL always interacted with multiple QTLs in various components. Several characteristics of epistasis on heading date were found that 1) different epistatic components had almost consistent directions; 2) dominance-dominance epistasis was perhaps most important in the four epistatic components; 3) epistasis was mostly positive, delaying rice heading; and 4) all epistatic components were seasonal sensitive. Two flowering pathways were further confirmed via a network constructed among these QTLs. These results have further confirmed the prevalence of epistatic interactions, deepened the understanding of genetic and flowering mechanism, and excavated several advantageous genes on heading date in rice.