Field experiments of mixed- (intercropping) and pure-planting (monoculture) of four rice varieties, representing improved hybrid varieties (Shanyou63 and Shanyou22) and high-quality traditional varieties (Huangkenuo and Zigu) from Yunnan Province, were conducted based on their differences in genetic background and agro-economical characteristics. The results demonstrated that the mixed-planting of the hybrid rice and high-quality traditional rice varieties had a significantly greater effect on controlling rice blast disease than the monoculture of these varieties, particularly the traditional ones. It is evident for the highly susceptible traditional varieties in mixed-planting to achieve disease control, with significant decreases in blast incidences and severity indexes. The blast control efficiency reached up to 83-98% under such planting model. This suggests that an appropriate mixed-planting of rice varieties with diverse genetic background and agro-economical characteristics is an effective approach for rice blast control. In addition, resistance of the traditional rice varieties to lodging was considerably increased in the plots with mixed-planting, compared with the plots with monoculture. The average rate of grain-yield increase ranged from 6. 5 to 9.7% in the plots with mixed-planting.
Genetic diversity of commercial and local rice cultivars in Yunnan Province was studied using the resistance gene analogue (RGA) based on resistance gene conserved sequences. The RGA analysis of 137 cultivars was conducted by PCR amplification using three primers, i.e. S1/AS3, XLRR for/XLRR rev, and Pto-kinl/Pto-kin2, respectively. The results showed that both Indica and Japonica cultivars were genetically highly diverse. All cultivars were divided into 3 lineages according to the DNA band data at 96% dissimilarity, and into 20 lineages at 60% dissimilarity. The lineages were related to their genetic background and blast disease resistance with only a few exceptions. The RGA data can be useful in rice production by mixed-planting of different cultivars in the field and breeding of resistance cultivars by selecting different parental cultivars with great genetic diversity.
SUN Yan, WANG Yun-yue, HE Yue-qiu, FAN Jing-hua, CHEN Jian-bin and ZHU You-yong( Key Laboratory for Plant Pathology of Yunnan Province ,Yunnan Agricultural University, Kunming 650201 ,P.R. China
