Fine mapping of qSTV11(KAS), a major QTL for rice stripe disease resistance.

Rice stripe disease, caused by rice stripe virus (RSV), is one of the most serious diseases in temperate rice-growing areas. In the present study, we performed quantitative trait locus (QTL) analysis for RSV resistance using 98 backcross inbred lines derived from the cross between the highly resistant variety, Kasalath, and the highly susceptible variety, Nipponbare. Under artificial inoculation in the greenhouse, two QTLs for RSV resistance, designated qSTV7 and qSTV11(KAS), were detected on chromosomes 7 and 11 respectively, whereas only one QTL was detected in the same location of chromosome 11 under natural inoculation in the field. The stability of qSTV11(KAS) was validated using 39 established chromosome segment substitution lines. Fine mapping of qSTV11(KAS) was carried out using 372 BC(3)F(2:3) recombinants and 399 BC(3)F(3:4) lines selected from 7,018 BC(3)F(2) plants of the cross SL-234/Koshihikari. The qSTV11(KAS) was localized to a 39.2 kb region containing seven annotated genes. The most likely candidate gene, LOC_Os11g30910, is predicted to encode a sulfotransferase domain-containing protein. The predicted protein encoded by the Kasalath allele differs from Nipponbare by a single amino acid substitution and the deletion of two amino acids within the sulfotransferase domain. Marker-resistance association analysis revealed that the markers L104-155 bp and R48-194 bp were highly correlated with RSV resistance in the 148 landrace varieties. These results provide a basis for the cloning of qSTV11(KAS), and the markers may be used for molecular breeding of RSV resistant rice varieties.

Long-term seasonal forecasting of a major migrant insect pest: the brown planthopper in the Lower Yangtze River Valley.

Rice planthoppers and associated virus diseases have become the most important pests threatening food security in China and other Asian countries, incurring costs of hundreds of millions of US dollars annually in rice losses, and in expensive, environmentally harmful, and often futile control efforts. The most economically damaging species, the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), cannot overwinter in temperate East Asia, and infestations there are initiated by several waves of windborne spring or summer migrants originating from tropical areas in Indochina. The interaction of these waves of migrants and synoptic weather patterns, driven by the semi-permanent western Pacific subtropical high-pressure (WPSH) system, is of critical importance in forecasting the timing and intensity of immigration events and determining the seriousness of subsequent planthopper build-up in the rice crop. We analysed a 26-year data set from a standardised light trap network in Southern China, showing that planthopper aerial transport and concentration processes are associated with the characteristics (strength and position) of the WPSH in the year concerned. Then, using N. lugens abundance in source areas and indices of WPSH intensity or related sea surface temperature anomalies, we developed a model to predict planthopper numbers immigrating into the key rice-growing area of the Lower Yangtze Valley. We also demonstrate that these WPSH-related climatic indices combined with early-season planthopper catches can be used to forecast, several months in advance, the severity of that season's N. lugens infestations (the correlation between model predictions and outcomes was 0.59), thus allowing time for effective control measures to be implemented.

[Detection and analysis of QTL for resistance to the brown planthopper, Nilaparvata lugens (Stål), in rice (Oryza sativa L.), using backcross inbred lines].

A mapping population of 98 BC1F9 lines (backcross inbred lines: BILs), derived from a backcross of Nipponbare (japonica)/Kasalath (indica)//Nipponbare by the single-seed descent methods, was used to detect quantitative trait loci (QTL) for resistance to brown planthopper (BPH), Nilaparvata lugens (Stål). Seedbox Screening Technique (SST) was applied to evaluate the reactions of two parents and 98 BILs to BPH at the seedling stage, and the entries were graded on ratio of dead seedlings. A total of three QTL controlling BPH resistance were detected on chromosomes 2, 10 and 12, respectively. Individual QTL accounted for between 10.4% and 16.6% of the phenotypic variance, and the resistance of all the three QTL came from Kasalath, the moderate resistance parent. These QTL should be useful in breeding of varieties resistant to BPH in marker-assisted selection (MAS) program.