Primary and secondary plant metabolites determining the suitability of pistachio kernels for the carob moth

Abstract The carob moth, Ectomyelois ceratoniae (Zeller) (Lepidoptera: Pyralidae) is a serious pest of fruit and nut crops worldwide that causes significant losses in Iranian pistachio orchards. In order to assess variation among cultivars is susceptibility to carob moth and biochemical correlates, the present study evaluated the suitability of kernels of 10 pistachio cultivars for E. ceratoniae development and reproductive performance under laboratory conditions: 25 ± 1°C, 65 ± 5% RH and a 16:8 (L:D) photoperiod. The primary and secondary metabolites of nuts were quantified and correlated with life history traits and various metrics of biological performance and indices of relative suitability were calculated. Nut protein content averaged 18.4 ± 0.1% and did not vary significantly among cultivars. Two cultivars yielded significantly slower larval development and lower values for relative growth rate, female longevity and fecundity, relative to all others. Suitability indices calculated from moth life history parameters varied by a factor of 4.66 across cultivars, with values <1 for the two most resistant varieties. The latter cultivars were less consumed by larvae and were lowest in carbohydrate content and efficiency of food conversion, but ranked highest in total phenolics, tannins and flavonoids. Linear regressions indicated that carbohydrate content was positively correlated with kernel suitability for larval development and adult reproduction, whereas total phenolics, tannins, flavonoids and anthocyanins were all negatively correlated. The implications of these findings for integrated management of E. ceratoniae in pistachio orchards, and the possibility of improving pistachio resistance to carob moth, are discussed.