Identification of antibiosis and tolerance in rice varieties carrying brown planthopper resistance genes

Brown planthopper (BPH) [Nilaparvata lugens (Stål) (Hemiptera: Delphacidae)] is a major pest in rice [Oryza sativa L. (Poaceae)] production. Identification of resistance genes and development of BPH-resistant varieties is an economical and effective way to control this pest. In this study, BPH honeydew excretion, survival rate, and emergence rate were used as indicators to detect the antibiotic level, whereas the relative growth rates of plant height (RH) and fresh weight (RW), and the number of days until yellowing were used to identify the level of tolerance to BPH in rice varieties. Rice varieties Swarnalata and B5, which showed high levels of antibiosis and tolerance to BPH, thus were highly resistant in the seedling bulk test; Mudgo and T12, which showed moderate resistance to the insects, had a high level of tolerance and moderate antibiosis to BPH. Varieties Rathu Heenati, ARC 10550, and Chin Saba were identified to be susceptible to BPH, showing a moderate level of tolerance and no antibiosis. In comparison to the evaluation methods of BPH resistance, the honeydew excretion and survival rate could be used to detect the antibiotic level, and the RH, RW, or leaf yellowing days could be employed as indicators to evaluate the rice varieties’ tolerance. Overall, a combined application of these indicators can effectively identify the levels of antibiosis and tolerance to BPH in rice varieties, and BPH-resistance levels of the varieties were mainly determined by the antibiosis level. The results should help in understanding BPH-resistance categories of rice varieties and for resistance breeding.