Improving cotton (Gossypium hirsutum L.) plant resistance to reniform nematodes by pyramiding Ren1 and Ren2

Reniform nematode (Rotylenchulus reniformis) has become a major pest of cotton in the mid-south area of the United States. Resistance genes, Ren1 and Ren2 from Gossypium longicalyx and Gossypium aridum, respectively, have been identified and introduced into Upland cotton (Gossypium hirsutum). We developed an F2 population of 184 progeny plants by crossing Ren2 -containing plants with a LONREN-2 plant that had the resistance gene Ren1. The F2 plants were evaluated for their resistance to reniform nematodes in a growth chamber. Microsatellite markers BNL2662 and BNL3279 were analysed to assist the selection of proper parental plants and F1 progeny and to study the segregation of the resistance genes in the F2 population. Our results suggested that Ren1 and Ren2 were duplicate genes with Ren1 residing on chromosome 11 (A subgenome) and Ren2 on chromosome 21 (D subgenome). F2 plants containing either Ren1 or Ren2 had significantly fewer nematodes than the susceptible Upland cotton genotype. No significant difference in nematode resistance was found between plants containing Ren1 and those having Ren2, indicating that these two genes may have similar resistance mechanisms. Plants containing both Ren1 and Ren2 appeared to have higher resistance than those with just one of the genes, and pyramiding these two genes may be a valuable tool to cotton breeders when managing this pest.