Role of the Epicuticular Wax Locus Bloomless2 in Sugarcane Aphid (Hemiptera: Aphididae) Resistance.

Epicuticular wax on plants can protect the above ground portions of the plant from water loss, ultraviolet light, insects, and fungal pathogens. Yet, beneficial effects have been seen with a reduction of plant epicuticular wax. The sorghum wax mutant, bloomless2 (bm2), and a sparse bloom mutant have displayed resistance to greenbugs [Schizaphis graminum (Rondani)], an aphid. In this study we sought to determine if five bloomless2 mutants in three genetic backgrounds could have enhanced resistance, as compared to the wild-type, to the sugarcane aphid which, since 2013, has become the major pest on sorghum in the United States. Two greenhouse studies with artificial infestation and one field study with natural infestation were conducted. Aphid numbers on the second leaf from the top and the lowest green leaf, plant damage score, and plant growth stage were assessed at weekly intervals. Correlations were seen for sugarcane aphid number and plant damage for the greenhouse and field rating dates. No consistent differences in aphid number or plant damage score were seen between mutant and wild-type pairs. This suggests that the bm2 locus has no role in sugarcane aphid resistance or susceptibility.