A genome-wide association study for resistance to Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 in diploid cotton (Gossypium arboreum) and resistance transfer to tetraploid Gossypium hirsutum.

Fusarium wilt, caused by the soilborne fungus Fusarium oxysporum f. sp. vasinfectum (FOV), is a devastating disease affecting cotton (Gossypium spp.) worldwide. Understanding the genetic basis of resistance in diploid cotton and successfully transferring the resistance to tetraploid Upland cotton (G. hirsutum) are crucial for developing resistant cotton cultivars. Although numerous studies have been conducted to investigate the genetic basis of Fusarium wilt in tetraploid cotton, little research has been conducted on diploid species. In this study, an association mapping panel consisting of 246 accessions of G. arboreum, was used to identify chromosomal regions for FOV race 4 (FOV4) resistance based on foliar disease severity ratings in four greenhouse tests. Through a genome-wide association study (GWAS) based on 7,009 single nucleotide polymorphic (SNP) markers, 24 FOV4 resistance QTLs, including three major QTLs on chromosomes A04, A06, and A11, were detected. A validation panel consisting of 97 diploid cotton accessions was employed, confirming the presence of several QTLs. Evaluation of an introgressed BC2F7 population derived from G. hirsutum/G. aridum/G. arboreum showed significant differences in disease incidence and mortality rate, as compared to susceptible and resistant controls, suggesting that the resistance in G. arboreum and/or G. aridum was transferred into Upland cotton for the first time. The identification of novel major resistance QTLs, along with the transfer of resistance from the diploid species, expands our understanding of the genomic regions involved in conferring resistance to FOV4 and contributes to the development of resilient Upland cotton cultivars.