Jianjun Cheng,Qinghua Chen,Qianshuang Guo,Yongjun Du
Premating behaviors mediated by pheromones play pivotal roles in animal mating choices. In natural populations of the striped stem borer Chilo suppressalis and the rice leaf roller Cnaphalocrocis medinalis in the rice field habitat, we discovered that Z11-16:Ald, a major component of the C. suppressalis pheromone, modulated the premating behavior of C. medinalis . Z11-16:Ald evoked a strong olfactory response in male antennae and strongly inhibited the sex pheromone trapping of male C. medinalis in the field. The functions of three C. medinalis sex pheromone receptor genes ( CmedPR1–3 ) were verified through heterologous expression in Xenopus oocytes. CmedPR1 responded to Z11-18:OH and Z11-18:Ald, as well as the interspecific pheromone compound Z11-16:Ac of sympatric species; CmedPR2 responded to Z13-18:OH and Z13-18:Ald, as well as the sex pheromone compounds Z11-16:Ald and Z9-16:Ald of sympatric species; and CmedPR3 responded to Z11-18:OH and Z13-18:OH, as well as the interspecific pheromones Z11-16:OH, Z9-16:Ald, Z11-16:Ac, and Z11-16:Ald of sympatric species. Thus, CmedPR2 and CmedPR3 share the ligand Z11-16:Ald, which is not a component of the C. medinalis sex pheromone. Therefore, the sex pheromones of interspecific species affected the input of neural signals by stimulating the sex pheromone receptors on the antennae of male C. medinalis moths, thereby inhibiting the olfactory responses of the male moths to the sex pheromones. Our results demonstrate chemical communication among sympatric species in the rice field habitat, the recognition of intra- and interspecific sex pheromones by olfactory receptors, and how insect premating behaviors are modulated to possibly affect resource partitioning.
The sex pheromone of the oriental armyworm, Mythimna separata (Walker), in China has always been confusing. It was initially considered as cis-11-hexadecenal (Z11-16:Ald) or cis-11-hexadecenyl acetate (Z11-16:Ac) and cis-11-hexadecenol (Z11-16:OH), as well as a mixture of these compounds. However, inconsistent results have frequently occurred using these compounds or mixtures in field trapping. Through gland analysis from individual females and nationwide field experiments, we identified two distinct types: Z11-16:Ald (aldehyde type or A type) and a mixture of Z11-16:Ac and Z11-16:OH (ester type or E type). Electroantennography (EAG) results indicated that both strains of males co-existed in the field. A strain of males had a strong EAG response to Z11-16:Ald but weak responses to Z11-16:Ac and Z11-16:OH, whereas E strain males had strong responses to Z11-16:Ac and Z11-16:OH but a weak response to Z11-16:Ald. Z11-16:OH identified in female E strain inhibited the attraction of A strain males to A type pheromones. Both A and E types of sex pheromone were respectively formulated and field evaluation (2014-2021) across > 20 provinces from southern to northern China showed geographic and generational variations. During overwintering, E strain males were predominantly caught in Hainan, Fujian, and Guangdong provinces, while A strain males were mainly trapped in Guangxi, Anhui, Sichuan, Jiangsu, and Jiangxi provinces. Subsequent generations exhibited mixed populations in most regions. These findings suggest regional adaptation and migration-driven hybridization. The study highlights the necessity of strain-specific pheromone blends for effective monitoring and control. This work resolves long-standing ambiguities in M. separata sex pheromone ecology.