Background: Rice is one of the most important staple food crops in Asia. Since the first green revolution beginning in 1960s, high-yield semidwarf modern rice varieties have been widely planted; however, traditional rice varieties with tall plant type are still grown in many countries due to their good grain quality and adaptation to local climate and environment. Siputeh, a local rice variety mainly planted in Java and Sumatra islands of Indonesia, produces long grain rice with good cooking and eating quality. However, the variety has low yield with tall plant type and long growth duration and is highly susceptible to biotic and abiotic stress.
Results: Siputeh as the recurrent female was crossed with the donor line WH421, an elite paternal line of hybrid rice containing the sd1, Wx (b), Xa4 and Xa21 genes, followed by backcrossing and self-pollination. TS4, a BC3F4 line derived from the breeding program, was obtained through marker-assisted selection for the sd1, Wx (b), Xa4 and Xa21 loci. TS4 has semi-dwarf phenotype and short growth duration. TS4 conferred disease resistance to multiple Xanthomonas oryzae pv. oryzae (Xoo) strains collected from different countries around the world. TS4 achieved higher grain yield than Siputeh in two field trials conducted in Banda Aceh, Indonesia and Lingshui, China, respectively. Finally, TS4 has better grain quality than Siputeh in terms of degree of chalkiness and amylose content.
Conclusion: An improved rice line, designed as TS4, has been developed to contain semi-dwarf gene sd1, low amylase content gene Wx (b) and bacterial light resistance genes Xa4 and Xa21 through marker-assisted selection. TS4 has semi-dwarf phenotype with reduced growth duration, produces high yield with good grain quality and provides broad-spectrum resistance to Xoo strains. The development of TS4 enriches the diversity of local rice varieties with high yield potential and good grain quality.