Evaluation of flavonoids inGossypium arboreum (L.) cottons as potential source of resistance to tobacco budworm.

Asiatic cottons [Gossypium arboreum (L.)] have been investigated as a source of resistance to the tobacco budworm [Heliothis virescens (Fab.)] because their diversely colored petals have been presumed to contain various allelochemicals. However, we found that larvae fedG. arboreum squares (buds) grew about equally compared with those fed squares from commercialG. hirsutum lines. The best source of resistance was found in severalG. hirsutum double-haploid (DH) lines. In our investigation of allelochemicals, G.arboreum lines were found to contain much less gossypol in leaves, squares (buds), and petals thanG. hirsutum L. lines. Flavonoids were significantly higher inG. arboreum lines only in petals. Of 22G. arboreum lines from which squares were gathered and fed to tobacco budworm (TBW) larvae in the laboratory, larval growth was not significantly decreased on any, but larval survival was decreased on six. When the square flavonoids were isolated and incorporated in laboratory diets for the TBW, moderate toxicity was observed. However, the estimated toxicities were not greater than those of the same flavonoid isolates fromG. hirsutum lines. The most prevalent flavonoids, all previously found in G.arboreum plant tissues, were gossypetin 8-0-glucoside and gossypetin 8-0-rhamnoside, neither of which were present inG. hirsutum tissue. Quercetin 3-0-glucoside, quercetin-3'-0-glucoside, and quercetin 7-0-glucoside were also present in significant amounts in both species. Gossypetin 8-0-rhamnoside and gossypetin 8-0-glucoside were the most toxic flavonoids tested (the ED50% was estimated to be 0.007 and 0.024) and therefore may prove to be contributing factors of resistance to TBW feeding.