Abstract:

Sanhuangzhan 2 (SHZ-2) has been considered as a promising blast resistance source in rice breeding in South China because of its durable blast resistance and good agronomic traits. Three major genes responsible for qualitative resistance and five defense genes significantly associated with quantitative resistance to blast in SHZ-2 have been identified and mapped using the candidate resistance gene approach in our previous study. However, its eating quality of kernel is relatively poor because of higher amylose content (AC), and most derived resistant cultivars have the similar shortcoming. To have an insight into the relationship between the strong blast resistance and the higher AC in SHZ-2, a RIL population derived from a cross between SHZ-2 and Lijiangxintuanheigu (LTH) was used to identify the blast resistance genes in SHZ-2 and QTLs for AC in the study. Results revealed that no significant (P<0.05) correlation between blast resistance and AC in the RIL population was found (Table 2). t-test also indicated that there was no significant difference for average AC between highly blast-resistant RI lines and the blast-susceptible RI lines (Table 3). Three QTLs for AC were identified when single-factor analysis of variance and interval mapping were performed. They were mapped on chromosome 5, 6 and 7, respectively. All the three QTLs were from LTH and contributed to the reduction of AC. Comparing the locations of QTLs for AC identified in this study with the locations of previously identified genes (major genes and QTLs) conferring blast resistance in SHZ-2, there was no close linkage among these genes for the two traits (Fig.2). These results suggested that the strong blast resistance are not linked with the higher AC in SHZ-2 and it is possible to combine the two traits and develop a elite cultivar with durable blast resistance and ideal AC by proper selection of parents and marker-asisted selection.

Key words: Blast resistance, Amylose content, Gene mapping, Correlation, Oryza sative L.