Resistance To Small Brown Planthopper And Its Mechanism In Rice Varieties

The small brown planthopper (Laodelphax striatellus Fallen,SBPH) were trended to increase in recent years, due to climatic changes, changes in cultivation practices and loss of variety resistance, and it caused serious damage to rice plant in Jiangsu, Shandong and Henan provinces of China. Planting resistant cultivars is deemed to be the ideal way to control this pest. Mechanism of resistance to small brown planthopper was studied in this study, and the results were as follows:To clarify resistance and its mechanisms of rice variety to small brown planthopper, L. striatellus Fallen, antixenosis and antibiosis of 11 rice varieties to L. striatellus were tested, and relationships between nutrient contents, amount of SiO2 amount of oxalic acid and resistance of rice varieties to L. striatellus were studied. The results indicated that three japonica rice lines, Wujing15, Wuyunjing 7 and Wuyunjing8 were susceptible to L. striatellus. Four japonica vatrieties, such as Zhendao2, Xudao3, Yandao8 and Yangjing9538, and four hybrid rice vatieties Shanyou63, Xieyou63, Xieyou136 and Fengyouxiangzhan exhibited moderate or high resistance to L. striatellus. Behavioral responses of the small brown planthopper to volatiles emitted from resistant varieties Zhendao2, Yangjing9538, Xudao3, Yandao8, Shanyou63 and Fengyouxiangzhan were studied with H-shaped olfactometer. The results showed that resistant rice varieties, such as zhendao 2 showed apparently antixenosis to L. striatellus.There were close correlations between the contents of soluble sugar, starch, total free amino acids, soluble proteins and the survival rate of L. striatellus nymphs. The amount of SiO₂ in leaf sheaths in Zhendao2, Xudao3 and Xieyou136 were 0.1660±0.0027, 0.1530±0.0081 and 0.1401±0.0064 g/g respectively, which were obviously higher than susceptible check. Higher oxalic acid contents in leaves in Yangjing9538 and Zhendao2, which were 56.372±1.086 and 53.763±1.887μg/mL respectively were founded compared with susceptible check. It is suggested that the resistance of tested rice verieties to L. striatellus was caused by lower nutrient contene, higher amount of SiO2 and oxalic acid lead to the resistance in some rice varieties, such as Zhendao2 to L. striatellus.40 components were collected from headspace of rice plants with solid phase microextractrion (SPME), among which 22 components were identified by GC-MS. These were 15 terpenes and its oxygen-containing compounds, 6 alkanes, 3 alcohols, 1 ester. Volatile components were significantly different among tested rice varieties. Nerolidol were only detected in Yangjing 9538 and Zhendao 2. One component, unknown 15 were not found in Wuyujing 3. The constituents of volatiles and the relative concentrations were different in different varieties. Behavioral responses of SBPH to each of 7 compounds such as Limonene, Linalool, Methyl salicylate, Nerolidol, Isocaryophyllene, (-)-Zingiberene, Cedrol and n-Dodecane etc (2 concentrations for each) were measured in H-shaped olfactometer. The results demonstrated that SBPH could be attracted by 6 compounds except (-)-Zingiberene. However, the components causing the antixenosis remain unknown.