Bacterial blight (BB) in cotton (Gossypium hirsutum L.) is caused by the gram-negative bacterium Xanthomonas citri pv. malvacearum (Xcm), and Xcm Race 18 is the most prevalent and virulent bacterium across the U.S. Cotton Belt. The objectives of this study were to investigate the genetic basis of resistance to Xcm Race 18 in U.S. upland cotton (Gossypium hirsutum) as broadly represented by 34 resistant obsolete U.S. upland accessions and 29 resistant commercial cultivars and elite breeding lines spanning a century of breeding efforts. Segregation in resistance was analyzed in F₂ populations from crosses between the resistant parents and one or two susceptible parents (one upland: Acala Ultima or NM 14T1330, and one G. barbadense: NMSI E2032). A total of 111 F₁, 95 F₂, and 23 F_2:3 populations were artificially inoculated with Xcm Race 18 to investigate segregation ratios for BB resistance. All F₁ were resistant, and 65 F₂ populations derived from 52 resistant parents exhibited the expected 3:1 resistant/susceptible ratio for resistance to Xcm Race 18, indicating a dominant resistance gene conferring the resistance. The analysis of DNA markers that are tightly linked to the B₁₂ gene on chromosome c14 (D02) showed that all the resistant germplasms tested possessed the B₁₂ gene and they were co-segregating with BB resistance, indicating that the B₁₂ locus is broadly distributed within the U.S. upland cotton. The results point to the need to discern if these resistant lines carry different B₁₂ alleles or different but tightly linked resistance loci including B₁₂.

中文翻译：

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美国陆地棉抗白叶枯病18种和B12连锁标记分析的遗传分析

棉花 ( Gossypium hirsutum L.) 中的细菌性枯萎病 (BB)是由革兰氏阴性细菌Xanthomonas citri pv.引起的。Malvacearum (Xcm) 和 Xcm Race 18 是美国棉带中最普遍和毒性最强的细菌。本研究的目的是调查美国陆地棉（Gossypium hirsutum）对Xcm Race 18 抗性的遗传基础，广泛代表34 个抗性过时的美国旱地品种和29 个抗性商业品种和跨越一个世纪的育种努力的优良育种系。 . 在 F ₂中分析了电阻中的分离来自抗性亲本和一两个易感亲本（一个高地：Acala Ultima 或 NM 14T1330，以及一个G. barbadense：NMSI E2032）之间的杂交种群。用Xcm Race 18人工接种总共111个F ₁、95个F ₂和23个F _2:3种群以研究BB抗性的分离比。所有 F ₁都具有抗性，并且来自 52 个抗性亲本的65 个 F ₂种群表现出预期的 3:1 抗性/易感比对 Xcm 种族 18 的抗性，表明赋予抗性的显性抗性基因。与B ₁₂紧密相关的 DNA 标记的分析染色体c14（D02）上的基因显示所有测试的抗性种质都具有B ₁₂基因并且它们与BB抗性共分离，表明B ₁₂基因座广泛分布在美国陆地棉中。结果表明需要辨别这些抗性品系是否携带不同的B ₁₂等位基因或不同但紧密相连的抗性基因座（包括B _{12 ）}。