In silico modeling and interactive profiling of BPH resistant R genes with elicitor molecules of rice planthoppers

Brown planthopper resistant NBS-LRR specific R genes (Bph9, Bph14, Bph18, Bph26) have been reported in rice. BPH specific R genes were clustered with other R genes of rice on chromosome 12 (Bph9, Bph18, Bph26) and 3 (Bph14). Motif analysis of BPH specific R genes showed the predominant motifs as CC, NBS and LRR regions. Bph9, Bph18 and Bph26 R genes exhibited high degree of sequence similarity in their CC and NBS region and are considered as functional alleles of BPH resistance at chromosome 12. LRR region of BPH genes were interacting with the elicitor molecules of planthoppers and are the potential lignad binding site. Bph14 exhibited more number of LRR repeats and were interacting efficiently with all the tested salivary elictor molecules of planthoppers. Bph18 with no LRR region exhibited reduced interaction efficiency with the tested elicitor molecules of planthoppers. Our in silico studies confirms that Bph14 R gene resistance protein to be a promising candidate for providing broad spectrum resistance against planthoppers of rice. The study further provides new avenues to investigate the mechanism of receptor-ligand recognition and signaling mechanism against rice planthoppers.

A rapid multiplex PCR assay for species identification of Asian rice planthoppers (Hemiptera: Delphacidae) and its application to early-instar nymphs in paddy fields

Rice (Oryza sativa L.) is the main cereal crop in many Asian countries. The Asian rice planthoppers, Nilaparvata lugens (Stål) (brown planthopper), Sogatella furcifera (Horváth) (white-backed planthopper), and Laodelphax striatellus (Fallén) (small brown planthopper) (Hemiptera: Delphacidae), are the most economically important pests of rice. These three rice planthopper species often co-occur in the same paddy field. Traditionally, species identification of individuals of the three rice planthopper species has relied on morphological characters, but accurate discrimination of early-instar nymphs is very difficult, even for expert researchers. In this study, we developed a rapid one-step multiplex PCR assay using conserved and species-specific 5.8S-ITS2 rDNA gene primers for simultaneous identification of individuals of the three rice planthopper species. The multiplex PCR results showed that the three rice planthopper species could be identified accurately based on the length of the resultant amplicon, regardless of the individual developmental stage. Furthermore, we applied this assay for the first accurate quantification of early-instar nymphs of each rice planthopper species in paddy fields. Notably, we found that the species composition of early-instar nymphs cannot be extrapolated from that of adults. Thus, the multiplex PCR assay developed here facilitates detection of each rice planthopper species at the beginning of outbreaks in paddy fields.

Infection and transmission of the facultative endosymbiont Arsenophonus in the spider Pardosa pseudoannulata

Background The infection of insect pests and their parasitoids with the facultative endosymbiont Arsenophonus has been well studied, whereas the infection of the predators of insect pests with this symbiont is less well understood. We studied this symbiont in the spider Pardosa pseudoannulata, an important predator of rice planthoppers, collected from rice paddies in 8 geographical regions in China.Results Diagnostic PCR showed that Arsenophonus was present in 4 of the 8 sampled populations of spiders. In these 4 populations, the infection incidence was between 2.1% and 16.7% and significantly differed between the Lishui population and the other three populations. Investigation of symbiont infection in both females and their offspring indicated that Arsenophonus can be vertically transmitted in P. pseudoannulata; the average transmission rate was approximately 25%. Remarkably, Arsenophonus was present in approximately 11% of the offspring of uninfected females, indicating that nonmaternal transmission occurs in this spider.Conclusions Populations of the spider P. pseudoannulata are infected at low rates with the symbiont Arsenophonus. This symbiont can be vertically transmitted from female spiders to offspring but may also be transmitted by male spiders or other vectors. Arsenophonus populations from different geographical regions exhibit genetic differentiation.

Suppression of Rice Planthopper Populations by the Entomopathogenic Fungus Metarhizium anisopliae without Affecting the Rice Microbiota

ABSTRACT Entomopathogenic fungi can regulate insect populations and function as crucial biological control agents against insect pests, but their impacts on nontarget microorganisms are poorly understood. In this study, we investigated the potential of the fungal strain Metarhizium anisopliae CQMa421 to control rice planthoppers under field conditions and its effects on rice microbiota. This fungus suppressed rice planthoppers during this period, and its control efficiency was more than 60% 7 days after application and did not significantly differ from that of the chemical treatment except in 2019. Both treatments showed a smaller population of rice planthoppers than the controls. After application, M. anisopliae was maintained on rice plants for approximately 14 days, showing a decreasing trend over time. Furthermore, the results showed that the bacterial and fungal richness (operational taxonomic units) and diversity (Shannon index) did not significantly differ between the fungal treatment and the controls after application. The major bacterial taxa of Proteobacteria (including Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Deltaproteobacteria), Actinobacteria, Bacteroidetes, and Cyanobacteria accounted for more than 80% of the bacterial community after fungal application, and the major fungal taxa Ascomycota (including Eurotiomycetes, Dothideomycetes, and Sordariomycetes) and Basidiomycota (including Ustilaginomycetes) represented more than 90% of the fungal community. However, the microbial communities of the rice phyllosphere did not significantly change after entomopathogenic-agent application, indicating that the indigenous microbial communities may adapt to fungal insecticide application. Taken together, the results suggest that this fungal agent has good potential for rice planthopper control with no substantial effects on rice microbial communities. IMPORTANCE Entomopathogenic fungi may be used as crucial biocontrol agents for the control of insect pests, but few effective fungal strains have been reported for the control of the rice planthopper, a major pest of rice. More importantly, the impacts of fungal insecticide application on nontarget microorganisms have not been well evaluated, especially under field conditions. Therefore, in this study, we investigated the effects of the fungal strain M. anisopliae CQMa421 on rice planthopper populations from 2017 to 2019 and evaluated its potential impacts on the microbiota of rice plants after application. The results suggested that this fungal agent has good potential for use in the control of rice planthoppers with no significant effects on rice microbial communities, representing an alternative strategy for the control of rice pests.