Detection of Yeast-like Symbionts in Brown Planthopper Reared on Different Resistant Rice Varieties Combining DGGE and Absolute Quantitative Real-Time PCR

SIMPLE SUMMARY: The brown planthopper (BPH) is an important pest that causes huge losses in rice production. The promotion and use of insect-resistant rice varieties is an important way to control BPH. However, in practice, BPH can adapt to resistant rice within several generations. Endosymbionts may be one of the reasons for the rapid adaptation of BPH to resistant rice. The BPH harbor yeast-like symbionts (YLS) in their abdomen, and YLS are essential for the nutrition, development, and reproduction of BPH. Our previous report showed that among the YLS communities detected in BPH, Ascomycetes symbionts, Pichia-like symbionts, and Candida-like symbionts were the three dominant populations of YLS. In this study, PCR-DGGE and absolute quantitative real-time PCR were used to detect the variations of three dominant YLS in BPH across different nymph ages and on different resistant rice varieties. The results showed that the total number of YLS gradually increased from the first instar to adulthood, but decreased in the fifth instar nymph, when BPH were reared on the susceptible rice variety TN1. The rice-resistant varieties, Mudgo, ASD7, and RH have more significant inhibitory effects on the three dominant YLS in the first and second generations of BPH. However, the numbers of the three dominant YLS were all recovered from the third generation of BPH. Ascomycetes symbionts were the most dominant strain among the three YLS. ABSTRACT: The brown planthopper (BPH), Nilaparvata lugens, is a serious pest of rice throughout Asia. Yeast-like symbionts (YLS) are endosymbionts closely linked with the development of BPH and the adapted mechanism of BPH virulence to resistant plants. In this study, we used semi-quantitative DGGE and absolute quantitative real-time PCR (qPCR) to quantify the number of the three YLS strains (Ascomycetes symbionts, Pichia-like symbionts, and Candida-like symbionts) that typically infect BPH in the nymphal stages and in newly emerged female adults. The quantities of each of the three YLS assessed increased in tandem with the developing nymphal instar stages, peaking at the fourth instar stage, and then declined significantly at the fifth instar stage. However, the amount of YLS present recovered sharply within the emerging adult females. Additionally, we estimated the quantities of YLS for up to eight generations after their inoculation onto resistant cultivars (Mudgo, ASD7, and RH) to reassociate the dynamics of YLS with the fitness of BPH. The minimum number of each YLS was detected in the second generation and gradually increased from the third generation with regard to resistant rice varieties. In addition, the Ascomycetes symbionts of YLS were found to be the most abundant of the three YLS strains tested for all of the development stages of BPH.