Globally-deployed sorghum aphid resistance geneRMES1is vulnerable to biotype shifts but being bolstered byRMES2

Abstract

ABSTRACTDurable host plant resistance (HPR) to insect pests is critical for sustainable agriculture. Natural variation exists for aphid HPR in sorghum (Sorghum bicolor) but the genetic architecture and phenotype has not been clarified for most sources. To assess the threat of a sorghum aphid (Melanaphis sorghi) biotype shift, we characterized the phenotype ofResistance to Melanaphis sorghi 1(RMES1) and contributing HPR architecture in globally-admixed populations selected under severe aphid infestation in Haiti. We foundRMES1reduces sorghum aphid fecundity but not bird cherry-oat aphid (Rhopalosiphum padi) fecundity, suggesting a discriminant HPR response typical of gene-for-gene interaction. A second resistant gene,RMES2, were more frequent thanRMES1resistant alleles in landraces and historic breeding lines.RMES2contributes early and mid-season aphid resistance in a segregating F2population, howeverRMES1was only significant with mid-season fitness. In a fixed population with high aphid resistance,RMES1andRMES2were selected for demonstrating a lack of significant antagonistic pleiotropy. Associations with resistance co-located with cyanogenic glucoside biosynthesis genes support additional HPR sources. Globally, therefore, a vulnerable HPR source (RMES1) is bolstered by a second common source of resistance in breeding programs (RMES2) which may be staving off a biotype shift.HIGHLIGHTThe globally-deployed sorghum aphid resistance gene,RMES1, reduces aphid reproduction and therefore is vulnerable to a biotype shift. A second major gene,RMES2, and cyanogenesis may increase global durability of resistance.