Abstract
BackgroundRice 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.ResultsSiputeh as the recurrent female was crossed with the donor line WH421, an elite paternal line of hybrid rice containing the sd1, Wxb, 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, Wxb, 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.ConclusionAn improved rice line, designed as TS4, has been developed to contain semi-dwarf gene sd1, low amylase content gene Wxb 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0033-2) contains supplementary material, which is available to authorized users.
Highlights
Rice is one of the most important staple food crops in Asia
Siputeh as the recurrent female was crossed with the donor line WH421, an elite paternal line of hybrid rice containing the sd1, Wxb, 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, Wxb, Xa4 and Xa21 loci
Summary
Rice is one of the most important staple food crops in Asia. The recessive semi-dwarfing gene, sd-1, is one of the most important genes deployed in modern rice breeding. The different alleles of the sd gene have remained the predominant semi-dwarf genes in modern rice cultivars (Asano et al 2007). There are two different types of starch, amylose and amylopectin, in rice endosperm and the amylose content affects rice eating and cooking quality (Cruz and Khush 2000). Wxa and Wxb are two predominantly distributed functional Wx alleles in rice (Sano 1984; Wang et al 1995). Wxa is widely distributed in indica rice with high amylose content while Wxb is mainly found in japonica rice with low or intermediate amylose content (Sano 1984; Wang et al 1995). Based on the polymorphism at the splicing site of the first intron, a codominant CAPS (cleaved amplified polymorphic sequence) molecular marker PCR-AccI was developed for selection of Wx alleles in rice breeding (Cai et al 2002)
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