Mapping of Quantitative Trait Loci Associated with Resistance to Phytophthora sojae and Flooding Tolerance in Soybean.

Phytophthora root rot (PRR), caused by Phytophthora sojae Kaufm. and Gerd., and flooding injury can limit growth and productivity of soybean [Glycine max (L.) Merr.], especially on poorly drained soils. The objective of this research was to map quantitative trait loci (QTL) associated with flooding tolerance and/or resistance to P. sojae. Mapping was conducted using F7 recombinant inbred lines (RILs) derived from a cross between the flooding-tolerant and PRR-resistant accession PI 408105A and the flooding-intolerant line S99-2281. A genetic linkage map consisting of 613 simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers was developed. Flooding tolerance was determined by measuring both plant injury and flooding yield index. Both Rps gene and partial resistance to P. sojae were measured for each RIL using the hypocotyl and layer tests. Genomic regions on four chromosomes were associated with genetic control of decreased plant injury and higher yield under flooded conditions. Of these, one region near markers Sct_033 and BARC-024569-04982 on chromosome 13 and one near BARC-016279-02316 on chromosome 11 were associated with partial resistance to P. sojae. The results indicate that genes for both flooding tolerance and P. sojae resistance were necessary to reduce injury and yield loss under saturated soil conditions and that these genes can contribute to increasing soybean productivity on soils prone to waterlogging. [ABSTRACT FROM AUTHOR]