The sorghum epicuticular wax locus Bloomless2 reduces plant damage in P898012 caused by the sugarcane aphid

Abstract

Abstract The sugarcane aphid [Melanaphis sacchari] has been rapidly spreading in the southern United States with devastating impacts on sorghum [Sorghum bicolor (L.) Moench]. Previous studies have shown the sorghum epicuticular wax mutants, in particular a bloomless2 (bm2) mutant and a sparse bloom mutant, were resistant to greenbugs [Schizaphis graminum], a type of aphid. In this study we sought to determine if five different genotypes, which all have mutations in the Bm2 locus, differ for sugarcane aphid resistance as compared to their respective wild‐type plants (P954035, P898012, and Tx7078). Two greenhouse studies with artificial infestation and one field study under natural infestation were conducted. Aphid numbers on the second leaf from the top and the lowest green leaf, plant damage, and plant growth stage were assessed at weekly intervals. The Greenhouse Test 2 and the Field test were the most effective at determining plant resistance and susceptibility to the sugarcane aphid. Bm2 mutants in the P898012 background had greater aphid damage than their wild type plants. These findings suggest that the Bm2 locus has a role in reducing aphid damage in the P898012 background yet has a limited role in the Tx7078 and P954035 backgrounds.