Molecular Breeding of a Novel PTGMS Line of Wdr for Broad-spectrum Resistance to Blast Using Pi9, Pikh, and Pi5 Genes

Abstract

Background: The two-line method based on the photoperiod and thermo-sensitive genic male sterile (PTGMS) lines is more cost-effective, simple, and efficient than the three-line system based on cytoplasmic male-sterility (CMS). Blast and drought are the most prevalent biotic and abiotic stress factors that hamper rice production, respectively. Molecular techniques demonstrate higher efficacy in the pyramiding of disease resistance genes, providing green performance under the background of water-saving and drought-resistance rice.Results: This work employed molecular marker-assisted selection (MAS), conventional hybridization and high-intensity stress screening to integrate the broad-spectrum blast resistance genes Pi9, Pikh, and Pi5 into Huhan 1S. Subsequently a novel water-saving and drought-resistance rice (WDR) PTGMS line Huhan 74S was developed. The drought resistance of the new PTGMS line Huhan 74S was comparable to that of Huhan 1S. The artificial inoculation of 14 blast strains revealed that the resistance frequency of Huhan 74S was 85.7%. Based on the conditions of natural field induction, Huhan 74S and its hybrid combination revealed satisfactory resistance to leaf and neck blast. The identification outcomes of photo-thermal characteristics showed that the critical point of Huhan 74S fertility conversion had an average daily temperature of 23℃, and the stable sterile period in Shanghai lasted 51 days. The rice quality of Huhan 74S was grade 3 based on standards issued by the ministry. Also, both the agronomic and rice quality performances adhered to the conditions of two-line hybrid rice production.Conclusion: The newly bred PTGMS line Huhan 74S demonstrated a stable and lasting resistance to blast. Moreover, the hybrid combination showed a high yield potential and can be used in the breeding of high-yield, high-quality, disease-resistance two-line hybrid water-saving and drought-resistance rice (WDR), hence promoting sustainable rice production in China.