Studies on the disease resistance of rice restorer lines with Pi9 blast resistance gene produced by dominant genic male sterile

Rice blast is one of the most serious fungal diseases of rice. The most effective strategy for the control of rice blast is to use resistant genes to breed resistant varieties. The resistance gene Pi9 is the first clone of the broad-spectrum resistance gene to rice blast, which has high level resistance to the races of magnaporthe grisea in many countries and regions. In this study, a two-line restorer line R998 with high blast resistance, good grain quality and high combining ability was developed by crossing 08C453-1 carrying Pi9 resistance gene with Yangdao 6. The near-isogenic lines library of dominant genic male sterile (GMS) was established by backcrossing the elite germplasm of two-line restorer lines with GMS materials, the male sterile plants were selected from the library and crossed with R998, and mixed sowing and mixed seed and mixed harvesting was carried out until HF2, then the excellent individual plants with comprehensive traits were selected. Identification and screening techniques of rice blast, such as molecular assistant screening, artificial inoculation and induced selection of disease areas, were used, six restorer lines derived from R998 resistant to rice blast, R1501, anxiang 15, R1032, R1392, R7766 and R8917, were developed. The results showed that 71.5% of R998 and its six derived two-line restorers were moderately resistant. In addition, 9 medium indica varieties were bred by R998 and its 6 derived restorer lines, including 3 in nation and 6 in province. Among them, Moliangyou 1501 composite index was 3.5 grade, the highest loss rate was 2.3 grade, and other varieties composite index was 4.1-5.5 grade, which was 1-3 grade higher than the control, the highest loss rate of other varieties was between 4.5 and 5.5 except for 7.0 in haoliangyou 729, which was 2-4 lower than the control. This study provides an idea for group breeding using dominant genic male sterile polymerized favorable genes.

Automated summary

This study developed a high-yielding two-line restorer line R998 with high blast resistance, good grain quality, and high combining ability. By establishing a library of dominant genic male sterile lines, six restorer lines resistant to rice blast were developed. In addition, nine medium indica rice varieties were bred using R998 and its six derived restorer lines. This study provides an idea for group breeding using dominant genic male sterile polymerized favorable genes.