Genes/QTLs affecting flood tolerance in rice

The adaptation of deepwater rice to flooding is attributed to two mechanisms, submergence tolerance and plant elongation. Using a QTL mapping study with replicated phenotyping under two contrasting (water qualities) submergence treatments and AFLP markers, we were able to identify several genes/QTLs that control plant elongation and submergence tolerance in a recombinant inbred rice population. Our results indicate that segregation of rice plants in their responses to different flooding stress conditions is largely due to the differential expression of a few key elongation and submergence tolerance genes. The most important gene was QIne1 mapped near sd-1 on chromosome 1. The Jalmagna (the deepwater parent) allele at this locus had a very large effect on internal elongation and contributed significantly to submergence tolerance under flooding. The second locus was a major gene, sub1(t), mapped to chromosome 9, which contributed to submergence tolerance only. The third one was a QTL, QIne4, mapped to chromosome 4. The IR74 (non-elongating parent) allele at this locus had a large effect for internal elongation. An additional locus that interacted strongly with both QIne1 and QIne4 appeared near RG403 on chromosome 5, suggesting a complex epistatic relationship among the three loci. Several QTLs with relatively small effects on plant elongation and submergence tolerance were also identified. The genetic aspects of these flooding tolerance QTLs with respect to patterns of differential expression of elongation and submergence tolerance genes under flooding are discussed. Received: 13 December 1999 / Accepted: 14 March 2000<@head-com-p1a.lf>Communicated by G. Wenzel