Cotton ( Gossypium spp.) is the most widely-grown natural fiber crop used by the textile industry. Fusarium wilt, caused by Fusarium oxysporum f. sp. vasinfectum (FOV) comprised of eight nominal pathogenic races, is one of the most destructive diseases in cotton. FOV race 4 (FOV4) is an emerging threat to cotton production in the US. In this study, a total of 3258 lines including 3080 Upland ( G. hirsutum ) and 178 Pima ( G. barbadense ) germplasm lines were evaluated in 21 tests under greenhouse or temperature-controlled conditions for resistance to FOV4. A total of 2224 lines from 13 tests were screened in a commercial potting soil in the greenhouse under higher temperature (HT) conditions (24–32 °C), while 1204 lines from 8 tests were screened in a naturally FOV4-infected farm soil at a lower temperature (LT) setting (20–21 °C), both with artificial inoculations. The 170 Pima lines were evaluated in both temperature regimes. The results showed that, at 30 days post inoculation, both temperature regimes produced similar disease incidence (81.2% for HT vs. 86.8% for LT), but LT caused significantly higher disease severity ratings (DSR, 3.86 vs. 1.94) and plant mortality (81.7% vs. 7.5%) than did HT. DSR and morality rate were highly significantly correlated (r = 0.849–0.941) at LT. Significant genotypic variations in DSR were detected in all studies except two, and the broad-sense heritability estimates for DSR were 0.59–0.83 with an average of 0.70 at HT and 0.61–0.72 with an average of 0.69 at LT, indicating that 70% the phenotypic variation in FOV4 resistance was determined by genetic variation. Using the naturally FOV4-infected farm soil and LT to screen 1034 Upland and 170 Pima germplasm lines (with 20–40 plants for each line) with artificial inoculations, 48% showed 100% mortality; 22% had a mortality rate between 70 and 99%; 5% had mortality below 30%; and 0.5% (6 lines) did not display any apparent FOV4 symptoms. The results indicated that many existing available germplasm lines may be heterogeneous for FOV4 resistance and pedigree selection within germplasm may increase frequencies of resistant plants. This study represents one of the first publicly reported large-scale screenings of cotton for FOV4 resistance in the US and provides useful information for breeding cotton with resistance to FOV4.

中文翻译：

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通过在温室或受控条件下筛选 3000 多个种质系来评估四倍体棉花中枯萎病 4 抗性的遗传变异

棉花 (Gossypium spp.) 是纺织业使用的最广泛种植的天然纤维作物。镰刀菌枯萎病，由尖孢镰刀菌f引起。sp. vasinfectum (FOV) 由八个名义致病小种组成，是棉花中最具破坏性的病害之一。FOV Race 4 (FOV4) 是对美国棉花生产的新威胁。在这项研究中，在温室或温控条件下的 21 项测试中评估了总共 3258 个品系，包括 3080 个 Upland ( G. hirsutum ) 和 178 个 Pima ( G. barbadense ) 种质系对 FOV4 的抗性。在较高温度 (HT) 条件 (24–32 °C) 下，在温室商业盆栽土壤中筛选了来自 13 项测试的 2224 条品系，而在较低的温度 (LT) 设置 (20–21 °C)，两者都进行人工接种。在两种温度范围内对 170 条皮马线进行了评估。结果表明，在接种后 30 天，两种温度方案产生相似的病害发生率（HT 为 81.2% 对 LT 为 86.8%），但 LT 导致显着更高的疾病严重程度等级（DSR，3.86 对 1.94）和植物死亡率（81.7% 对 7.5%）比 HT。DSR 和道德率在 LT 中高度显着相关 (r = 0.849–0.941)。除两项研究外，所有研究都检测到 DSR 的显着基因型变异，DSR 的广义遗传力估计值为 0.59–0.83，HT 平均为 0.70，LT 平均为 0.61–0.72，LT 平均为 0.69，表明 70% FOV4 抗性的表型变异由遗传变异决定。使用自然感染 FOV4 的农场土壤和 LT 筛选 1034 个陆地和 170 个 Pima 种质系（每系 20-40 株植物）和人工接种，48% 显示 100% 死亡率；22% 的死亡率在 70% 到 99% 之间；5% 的死亡率低于 30%；0.5%（6 行）没有表现出任何明显的 FOV4 症状。结果表明，许多现有的可用种质系对于 FOV4 抗性可能是异质的，种质内的系谱选择可能会增加抗性植物的频率。这项研究代表了美国首次公开报道的针对 FOV4 抗性的棉花大规模筛选之一，并为培育具有 FOV4 抗性的棉花提供了有用的信息。22% 的死亡率在 70% 到 99% 之间；5% 的死亡率低于 30%；0.5%（6 行）没有表现出任何明显的 FOV4 症状。结果表明，许多现有的可用种质系对于 FOV4 抗性可能是异质的，种质内的系谱选择可能会增加抗性植物的频率。这项研究代表了美国首次公开报道的针对 FOV4 抗性的棉花大规模筛选之一，并为培育具有 FOV4 抗性的棉花提供了有用的信息。22% 的死亡率在 70% 到 99% 之间；5% 的死亡率低于 30%；0.5%（6 行）没有表现出任何明显的 FOV4 症状。结果表明，许多现有的可用种质系对于 FOV4 抗性可能是异质的，种质内的系谱选择可能会增加抗性植物的频率。这项研究代表了美国首次公开报道的针对 FOV4 抗性的棉花大规模筛选之一，并为培育具有 FOV4 抗性的棉花提供了有用的信息。