Abstract

Rice stripe disease is caused by rice stripe virus (RSV) and transmitted mainly by the small brown planthopper (Laodelphax striatellus Fallen). The number, the rate of viruliferous and sucking preference of insect, and the rice resistance to the virus and insect determine the grade of the disease prevalent. Since 2001, the disease happened severely every year at Yangtze River Delta in China. It was known that the virus resistance gene Stv-bⁱ, derived from indica cultivar Modan, could control this disease. The previous study had been mapped this gene into a 286kb interval on the long arm of rice chromosome11. 

In this research, we constructed a set of chromosome single segment substitution lines (CSSSLs) with different substituted segments of Teqing in the long arm of chromosome11, respectively, under the genetic background of the susceptible japonica cultivar, Lemont. Total of 52 CSSSLs in the targeted region were developed. Different SSSLs have various substitution segments in length and position but together covered the whole interval containing Stv-bⁱ. These SSSLs were planted 2 years at 2 severely diseased locations with 2 repeats per location. The resistant and susceptible lines could be clearly distinguished and which repeated very well among replicates and years. So, the major resistance gene from Teqing was located in a 69kb region on the long arm of chromosome 11, which was covered by the region containing Stv-bⁱ. This resistance gene was named qStv11^TQ temporarily.

By using MAS, a new cultivar Wulingjing 1 carrying the resistance gene Stv-bⁱ was fleetingly bred through backcross breeding. The recurrent parent Wuyujing 3, highly susceptible to RSV, possesses high yield potential, stable production capability and excellent food-tasted quality and had been planted in Jiangsu province since the nineties of last century with longest cultivated history and largest planted area. The cultivar Zhendao 88 carrying the resistance gene Stv-bⁱ based on the pedigree analysis was used as donor parent. In each backcross generation, we selected the progenies with Stv-bⁱ based on the closely flanked markers. In advanced backcross generations, the marker’s detection for genetic background of selected plants was added, along with the estimate by the eye for the similarity of selected plants to recurrent parent on synthetic agronomic traits. As a result, the new cultivar, Wulingjing 1, was fleetingly bred in BC₃F₄ generation, whose resistance to the disease was significantly increased and main characters especially on excellent food-tasted quality were consistent with those of Wuyujing 3. In resistance identification tests with multiple locations organized by Seed Management Department of Jiangsu Province, the average percent of affected plants of the new cultivar was only 4.4% and significantly lower than that of recurrent parent (53.2%).