**Submitted to:** Journal of Nematology

**Publication Type:** Peer Reviewed Journal

**Publication Acceptance Date:** 11/18/2016

**Publication Date:** 12/1/2016

**Citation:** Stetina, S.R., Erpelding, J.E. 2016. Gossypium arboreum accessions resistant to Rotylenchulus reniformis. Journal of Nematology. 48:223-230.

**Interpretive Summary:** In the southeastern United States, the reniform nematode is a serious pest of upland cotton. None of the cotton varieties available to farmers have resistance to this nematode because there is no naturally-occurring resistance to work with in cotton. However, species that are closely related to upland cotton, including Gossypium arboreum, may have useful levels of resistance that can be transferred into upland cotton by cotton breeders. Therefore, more than 200 different varieties in the G. arboreum collection were evaluated to identify the most resistant ones. The 15 varieties with the fewest nematodes infecting the roots in the first set of tests were evaluated again in longer tests to verify that they could effectively reduce the nematode population. Nine of the varieties (PI 529992, PI 615755, PI 615766, PI 615788, PI 615856, PI 615950, PI 615991, PI 616008, and PI 616159) were as good as the resistant control, and varieties PI 615848 did a better job of suppressing the nematode population than the resistant control. Cotton farmers would benefit if cotton breeders could incorporate the newly-identified resistance from these varieties into upland cotton.

**Technical Abstract:** In the southeastern United States, reniform nematode (Rotylenchulus reniformis) is a serious pest of upland cotton (Gossypium hirsutum), a species which has no naturally-occurring resistance against this nematode. To identify sources of reniform nematode resistance in species closely related to upland cotton, 222 G. arboreum accessions from the U.S. germplasm collection were evaluated in repeated growth chamber experiments. In initial screenings, root infection was measured 4 weeks after inoculation. The 15 accessions supporting the fewest infections (PI 529992, PI 615755, PI 615766, PI 615788, PI 615848, PI 615856, PI 615950, PI 615977, PI 615991, PI 616008, PI 616016, PI 616062, PI 616126, PI 616159, and A2 553) were evaluated again in confirmation tests lasting 8 weeks. The combined totals of nematodes extracted from soil and eggs extracted from roots were analyzed. All 15 accessions tested supported significantly smaller reniform nematode populations than the susceptible controls (G. hirsutum cultivar Deltapine 16 and G. arboreum accession PI 529729). Nine accessions (PI 529992, PI 615755, PI 615766, PI 615788, PI 615856, PI 615950, PI 615991, PI 616008, and PI 616159) supported reniform nematode populations comparable to the resistant control (G. arboreum accession PI 615699), and accession PI 615848 had significantly fewer reniform nematodes than the resistant control. Cotton breeders would benefit from introgressing the newly-identified resistance from these accessions into their upland cotton improvement programs.