Pheromone Analysis of Wild Female Moths with a PBAN C-Terminal Peptide Injection for an Estimation of Assortative Mating in Adzuki Bean Borer, Ostrinia scapulalis

The adzuki bean borer, Ostrinia scapulalis, has distinct genetic variation in the blend of two sex pheromone components, (E)- and (Z)-11-tetradecenyl acetates. This variation is largely controlled by a single autosomal locus with two alleles, E and Z. E-type (EE) females produce a pheromone with a mean E:Z ratio at 99:1 whereas Z-type (ZZ) and I-type (ZE) produce pheromones with mean of 3:97 and 64:36, respectively. Interestingly, in many natural populations of O. scapulalis in Japan, this pheromone polymorphism appears to be stably maintained. We tried to predict the changes in relative abundance of each pheromone type by estimating the pheromone production genotype of wild females and their male mates. The pheromone titer in the wild, mated females was increased without changing the blend ratio by an injection of a peptide with pheromone biosynthesis activating activity (TKYFSPRL-NH2). The frequencies of E-, I-, and Z-types at Matsudo were 15, 52, and 33%, respectively, and did not deviate from the Hardy-Weinberg expectations. The estimated mating patterns were concordant with the assumption that no assortative mating was occurring in this population, and this is suggested as a cause of sustained polymorphism at Matsudo.