Evaluation on Effect of Resistance Improvement of Bacterial Leaf Blight and Brown Planthopper for Three Dominant Indica Restorer Lines

Abstract

A novel bacterial blight (BB) resistance gene, Xa23, and brown planthopper (BPH) resistance gene, Bph18(t) were introgressed into three popular restorer lines (Minghui 86, Shuhui 527, and Zhehui 7954) for wild abortive cytoplasmic male sterility by marker-assisted backcross and pyramiding breeding approaches in combination with artificial inoculation and stringent phenotypic selections. The four derived BB resistant restorer lines [Minghui 86-Xa23, Shuhui 527-Xa23, Zhehui 7954-Xa23, and Zheshu-Xa23-Bph18(t)] and their derived hybrid combinations with Ⅱ-32A and Huhan11A demonstrated similar BB resistance spectrum as the donor parent, IRBB23. The three derived BPH resistant restorer lines [Shu 527-Bph18(t), Zhehui 7954-Bph18(t), and Zheshu-Xa23-Bph18(t)] showed resistant or moderate resistant to BPH. The newly developed BB and BPH resistant restorers and their derived hybrids were identical to their respective original versions for agronomic traits especially under disease free condition. However, under severe disease condition, the four BB resistant restorer lines exhibited significantly higher grain weight and spikelet fertility as compared to the respective original restorer lines thus further resulting in BB resistant hybrids with significantly higher grain yields than their respective original hybrids. The results indicated that the Xa23 gene could completely express its dominant resistance in different backgrounds of both restorer and male sterile lines across different growth stages,suggesting its immense breeding value in BB resistance improvement for hybrid rice. However, effect of resistant improvement of Bph18(t) for BPH depends on genetic background. Improvement of resistance of BB and BPH for restorer lines by molecular marker-assisted backcross and pyramiding was deeply discussed.