Fine Mapping of a Resistance Gene RpsHN that Controls Phytophthora sojae Using Recombinant Inbred Lines and Secondary Populations

Abstract

Phytophthora root rot (PRR), caused by Phytophthora sojae, has negative effects on soybean yield in China and can be controlled by identifying germplasm resources with resistance genes. In this study, the resistance locus RpsHN in the soybean line Meng8206 was mapped using two mapping populations. Initial mapping was realized using two recombinant inbred line (RIL) populations and included 103 F_6:8 RILs derived from a cross of Meng8206 × Linhedafenqing, including 2600 bin markers, and 130 F_6:8 RILs derived from a cross of Meng8206 × Zhengyang148, including 2267 bin markers. Subsequently, a 159 F_2:3 secondary population derived from a cross of Meng8206 × Linmeng6-46, were used to fine map this locus using SSR markers. Finally, the resistance locus from Meng8206 was fine mapped to a 278.7 kb genomic region flanked by SSR markers SSRSOYN-25 and SSRSOYN-44 at a genetic distance of 1.6 and 1.0 cM on chromosome 3 (Chr. 03). Real-time RT-PCR analysis of the possible candidate genes showed that three genes (Glyma.03g04260, Glyma.03g04300, and Glyma.03g04340) are likely involved in PRR resistance. These results will serve as a basis for cloning, transferring of resistant genes and breeding of P. sojae-resistant soybean cultivars through marker-assisted selection.

Keywords: Phytophthora root rot; bins and SSR markers; fine mapping; linkage map; resistance gene; soybean.

FIGURE 1

Dendrogram reflected by UPGMA cluster analysis of the reaction to 8 P. sojae among Meng8206, Zhengyang148, Linhedafenqing, and LinMeng6-46, 15 differentials each had an independent Rps gene: Harlon (Rps1a), Harosoy13XX (Rps1b), Williams79 (Rps1c), PI103091 (Rps1d), Williams82 (Rps1k), L76-988 (Rps2), Chapman (Rps3a), PRX146-36 (Rps3b), PRX145-48 (Rps3c), L85-2352 (Rps4), L85-3059 (Rps5), Harosoy62XX (Rps6), Harosoy (Rps7), YuDou25 (RpsYu25), LuDou4 (Rps9) and the susceptible cultivar Williams.

FIGURE 2

Genetic linkage map and physical map of RpsHN on chromosome 3. Genetic distance (cM) is shown on the left, and markers are shown on the right. (A) Linkage map of RpsHN from the present study. (B) Physical map of SSR and bins markers from the present study. The green line refers to the physical distance between bin249 and bin283, and the red line refers to the fine mapping region. (C) Physical position of the mapped region of RpsHN on chromosome 3 (Lin et al., 2013).

FIGURE 3

Relative expression levels of Glyma.03g04260 (Glyma.03g034800), Glyma.03g04300 (Glyma.03g034900) and Glyma.03g04340 (Glyma.03g035300) in Linmeng6-46 and Meng8206. Seven-day-old soybean seedlings were inoculated with isolate HeN08-35. The sampling times were 0, 12, 36, 48, and 72 hours post-inoculation (hpi).