Long-term virulence monitoring of differential cultivars in Japan's immigrant populations of Nilaparvatalugens (Hemiptera: Delphacidae) in 2001-2019

Resistant rice cultivars are an alternative of insecticide control for one of the major rice pests: the brown planthopper, Nilaparvatalugens (Hemiptera: Delphacidae). However, N.lugens has obtained virulence to resistant rice cultivars as same as insecticide resistance. The monitoring of virulence to differential cultivars is important for detections of the breakdown of resistance genes 'BPH' owned by the cultivars. We conducted long-term virulence monitoring (2001-2019) of differential cultivars in N. lugens immigrant populations in Japan. The virulence to the cultivars IR26 (BPH1), Mudgo (BPH1), and ASD7 (BPH2) was higher than that to other differential cultivars. The virulence to Babawee (BPH4) was lower than that to IR26, Mudgo, and ASD7, but it fluctuated over the immigrant years. The virulence to Kanto-PL7 (BPH3), Rathu Heenati (BPH3, BPH17) and Balamawee (BPH27, Three QTLs) was lower than that to other differential cultivars. The immigrant populations have therefore not developed virulence to three differential cultivars. These results suggest that N. lugens continued to develop virulence to differential cultivars that possess BPH1 and BPH2 after the breakdown. However, our results indicate that N.lugens could not break through the efficacy of differential cultivars possessing multiple BPH resistance genes.

Automated summary

The study found that the brown planthopper continues to evolve resistance to different resistant rice cultivars, but certain resistance genes are more effective at resisting the evolution of the pest, making it unable to develop virulence to all differential cultivars.