Improvement of rice blast and brown planthopper resistance of PTGMS line C815S in two-line hybrid rice through marker-assisted selection

Two-line hybrid rice breeding, which plays an important role in ensuring food security in China, is one of important approaches to utilize the heterosis in rice. Breeding of photo-thermo-sensitive genic male sterile (PTGMS) lines of two-line hybrid rice with high resistance to diseases and pests is vital for enhancing rice yield stability, reducing environmental pollution, and increasing rice production efficiency. To breed PTGMS rice with resistance to both rice blast and brown planthopper (BPH), four broad-spectrum blast resistance genes Pi9, Pi47, Pi48, and Pi49 and two BPH resistance genes Bph14 and Bph15 were introgressed into a PTGMS line C815S through backcrossing and gene pyramiding coupled with molecular marker-assisted selection (MAS) in this study. Finally, several improved PTGMS lines of C815S which pyramided 1-3 homozygous rice blast resistance genes and two BPH resistance genes were developed. Evaluation of rice blast resistance showed that the improved PTGMS lines were resistant, while C815S was susceptible or only moderately resistant. Assessment of the BPH resistance showed that C815S was highly susceptible, while the improved lines were resistant. The improved lines had similar major agronomic traits and temperature of fertility transition to C815S, and several traits were even better. The newly developed PTGMS lines can be used for breeding of superior two-line hybrid rice or advanced PTGMS lines.