Identification of new genetic sources of resistance to bacterial blight race 18 in diploid Asiatic cotton and resistance transfer to tetraploid cotton (Gossypium hirsutum)

Authors: ABDELRAHEEM, ABDELRAHEEM - New Mexico State University; ZHU, YI - New Mexico State University; Zeng, Linghe; Stetina, Salliana - Sally; Feng, Chunda; WHEELER, TERRY - Texas A&M University; ZHANG, JINFA - New Mexico State University

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2024
Publication Date: 5/9/2024
Citation: Abdelraheem, A., Zhu, Y., Zeng, L., Stetina, S.R., Feng, C., Wheeler, T., Zhang, J. 2024. Identification of new genetic sources of resistance to bacterial blight race 18 in diploid Asiatic cotton and resistance transfer to tetraploid cotton (Gossypium hirsutum). Euphytica. 220:85. https://doi.org/10.1007/s10681-024-03342-1.
DOI: https://doi.org/10.1007/s10681-024-03342-1

Interpretive Summary: Bacterial blight (BB) is a disease that can cause serious yield loss in cotton production. Understanding the genes controlling the disease and transferring the BB resistance from Asiatic cotton into U.S. cotton are critical steps in development of BB resistant cultivars in U.S. cotton production. This study aimed to identify molecular control of BB resistance in 246 Asiatic germplasm lines in the first step. Next, a breeding population was developed from crosses between the resistant Asiatic lines and the susceptible American cultivars for transferring the BB resistance into the American cultivars. Nine major regions in the genome of these Asiatic lines were identified as controlling BB resistance. Greenhouse tests for BB resistance showed that the BB resistance in the breeding population was intermediate between the resistant Asiatic cotton parent and the susceptible American cotton parent. This result indicates that the BB resistance has successfully transferred into the American cotton. The identified major genomic regions for the BB resistance can be used to reveal genes controlling BB resistance and the breeding population can be used by cotton breeders to develop BB resistant cotton cultivars.

Technical Abstract: Bacterial blight (BB) caused by Xanthomonas citri pv. malvacearum (Xcm), poses a significant threat to Upland cotton (Gossypium hirsutum) production worldwide, and Xcm race 18 is the most virulent and widespread race and can cause serious yield loss. Understanding the genetic basis of resistance in diploid Asiatic cotton (G. arboreum) and successfully transferring the resistance to tetraploid Upland cotton are crucial for developing resistant cotton cultivars. This study aimed to identify chromosomal regions for BB resistance through a genome-wide association study (GWAS) using 246 G. arboreum accessions evaluated in two replicated greenhouse tests and to evaluate an introgression BC2F7 population derived from a tri-species hybrid (G. arboreum/G. aridum/G. hirsutum). In response to Xcm race 18 infections after artificial inoculation, 80 % of the accessions exhibited a high level of resistance, including 151 accessions showing immunity with no visible foliar water-soaked lesions. A GWAS based on 7,009 polymorphic SNP markers detected 9 major BB resistance QTLs on chromosomes A01, A02, A05, A06, A10, A12, and A13 in the Asiatic cotton. The tri-species introgression population showed segregation in BB resistance with significantly lower disease incidence of BB than the susceptible check Acala 1517-18 GLS (30.2 vs. 100%), suggesting that the resistance in the diploid species has been successfully transferred into Upland cotton for the first time. The identification of Xcm race 18 resistant diploid Asiatic cotton germplasm and specific chromosomal regions and candidate genes delineated by SNPs for resistance for the first time provides strong evidence that the Asiatic cotton is a new genetic source of resistance to BB. The results will facilitate further genetic and genomic studies toward the eventual identification of resistance genes and their transfer into tetraploid cotton through marker-assisted selection.