Inheritance and Mechanism of Resistance to Rice Stripe Disease in cv . Zhendao 88 , a Chinese Rice Cultivar

Mechanisms of resistance to rice stripe disease in a Chinese rice cultivar (Oryza sativa L., cv. Zhendao 88) were determined, and molecular markers for the resistance gene were identified. Single tillers at the seedling stage were inoculated with Rice stripe virus (RSV) and its vector, the small brown planthopper (SBPH) Laodelphax striatellus Fallen, to test for non-preference and antibiosis. The inheritance of resistance in the F2 and F2 : 3 lines from the cross cvs Zhendao 88· Wuyujing No. 3 was also examined by single-tiller inoculation. Cv. Zhendao 88 was highly resistant to RSV and weakly resistant to SBPH. The resistance gene was mapped by SSR and RAPD analyses to rice chromosome 11 within 4.7 cm of a SSR marker RM229 and a RAPD marker OPO11. Data and inheritance analysis indicated that rice stripe disease resistance in cv. Zhendao 88 was derived principally from resistance to RSV and controlled by a single dominant gene. Breeding for rice stripe resistance could be accelerated by using cv. Zhendao 88 as a resistant parent if the linked marker for virus resistance were used in a marker-assisted progeny selection programme. Introduction Rice stripe disease first occurred in Jiangsu, China in the 1990s and has since spread rapidly to become the most serious disease of rice (Oryza sativa L.) in the entire middle and lower regions of the Yangtze River (Co-operation Tackle Key Project of Rice Stripe Disease in Jiangsu Province 2003). Rice stripe disease is caused by Rice stripe virus (RSV), long-known as the type species of the genus Tenuivirus (Toriyama and Tomaru 1995). RSV virions are non-enveloped and contain four segments of linear single-stranded RNA designated RNA1, 2, 3 and 4 in order of decreasing molecular size. RNA1 encodes a 337kD protein that is thought to be an RNA-dependent RNA polymerase (Toriyama et al. 1994), whereas RNA2, RNA3 and RNA4 are ambisense in their coding strategy (Zhu et al. 1991, 1992; Takahashi et al. 1993; Xiong et al. 2008, 2009). RSV is transmitted by the small brown planthopper (SBPH), Laodelphax striatellus Fallèn. Once acquired, the virus is transmitted by SBPH in a persistent manner and passed transovarially (vertically) to offspring at a moderate to very high rate (Toriyama 1986). This mode of transmission facilitates rapid and severe disease spread and occurrence. Development of resistant rice cultivars is one of the most economically effective and environmentally sound disease management strategies (Cooperation Tackle Key Project of Rice Stripe Disease in Jiangsu Province, 2003; Ordon et al. 2009). As most of the cultivars of O. sativa ssp. japonica have poor resistance to rice stripe disease in Jiangsu Province (Zhou et al. 2006), the development of RSV-resistant rice cultivars is a very high regional priority. The possible mechanisms of resistance to rice stripe disease can be derived from resistance to the virus, to the vector or to both. The resistance mechanisms to rice stripe disease vary among rice cultivars (Nemoto et al. 1994; Sun et al. 2006). An indica variety, IR50, was found to be moderately resistant to the virus and tolerant to the vector. Two japonica cultivars, Musashikogane and Minamihatamochi, were found to be highly resistant to virus infection but susceptible to the vector. These cultivars displayed very high resistance to rice stripe disease in mass inoculation tests, with cvs Musashikogane and Minamihatamochi displaying more disease resistance than IR50 (Nemoto et al. 1994). The inheritance of rice stripe resistance within rice germplasm has been studied in natural field tests and by inoculation of plants with viruliferous SBPH. Resistance exhibited both qualitative (Washio et al. 1967, J Phytopathol 159:159–164 (2011) doi: 10.1111/j.1439-0434.2010. 01737.x 2010 Jiangsu Academy of Agricultural Sciences