Introgression in tetraploid cotton of the resistance to reniform nematode Rotylenchulus reniformis Lind. & Oliveira from the Gossypium hirsutum L. x G. longicalyx Hutch & Lee x G. thurberi Tod trispecific hybrid

In order to develop upland cotton plants resistant to Rotylenchulus reniformis Lind. & Oliveira reniform nematode, a three-species hybrids including Gossypium hirsutum L. (2n = 4 x = 52, (AD)1 genome) was created using G. longicalyx Hutch & Lee as donor parent (2n = 2x = 26, F1 genome) and G. thurberi Tod. (2n = 2x = 26, D1 genome) as bridge species. The morphology and the resistance to reniform nematode of the parents and of thirty plants belonging to the selfed progeny of G. hirsutum x G. longicalyx x G. thurberi (HLT) trispecific hybrid were assessed. G. longicalyx, G. hirsutum x G. longicalyx hexaploid and all the thirty plants issued from the selfing of HLT hybrid were very resistant to reniform nematode unlike G. hirsutum which was very sensitive to it. Cytogenetic studies showed that HLT hybrid and its direct progeny have 52 chromosomes as the main cotton cultivated species. HLT hybrid shows a good pollen fertility and a very high level of chromosome pairing at metaphase I. It is self fertile but presents important incompatibility barriers when crossed as female parent with G. hirsutum. The prospects to develop upland cotton commercial cultivars resistant to reniform nématodes from the available interspecific genetic stocks are discussed.