Genetic basis of pheromone-mediated sexual communication in the pink bollworm moth, Pectinophora gossypiella (Lepidoptera: Gelechiidae)

Long distance sexual communication in the pink bollworm moth, Pectinophora gossypiella, is based on a female-emitted two-component pheromone ((Z,E)- and (Z,Z)-7,11-hexadecadienyl acetate). The genetic bases of pheromone production and response were examined to assess the potential for the development of resistance to synthetic pheromone used as a mating disruptant. Male response was measured with a still-air wing-fanning bioassay. Heritability (h$\sp2$) of wing-fanning duration was significant for 25 and 44% ZE blends (h$\sp2$ = 0.377 $\pm$ 0.113 and 0.385 $\pm$ 0.095, respectively) but not for a 65% ZE blend (h$\sp2$ = $-0.145\ \pm$ 0.103). Solvent extracts of excised pheromone glands were used to measure pheromone production by females. Heritabilities for pheromone blend and amount were 0.342 $\pm$ 0.08 and 0.410 $\pm$ 0.089, respectively. Selection of females producing pheromone with a higher percentage of the ZE isomer resulted in an increase in mean ($\pm$ SD) blend from 42.9 $\pm$ 1.0 to 48.23 $\pm$ 1.2% ZE after 12 generations. Although significant, this change is small compared to the broad male response spectrum, and may be insufficient for the evolution of resistance to synthetic pheromone. The duration of wing fanning to blends with a high percentage of the ZE isomer was elevated in the female-selected line, demonstrating that signal production and response are influenced by the same or closely linked loci. Selection for females that produce more pheromone resulted in a rapid increase in pheromone titer (24.0 $\pm$ 8.1 to 45.8 $\pm$ 7.9 ng in 6 generations). Selection for greater male responsiveness to a 44% ZE blend yielded an increase in wing-fanning duration from 5.36 $\pm$ 13.65 to 17.40 $\pm$ 26.98 sec after 6 generations. Based on these selection responses, evolution of resistance appears more likely through a change in pheromone amount than through a change in the pheromone component ratio