Fusarium oxysporum f. sp. vasinfectum Race 4 (FOV4) causes high seedling mortality in pima cotton (Gossypium barbadense L.) grown in the western and southwestern U.S. Cotton Belt. The objectives of this study were to analyze the combining abilities and genetic basis of FOV4 resistance in pima cotton using a half-diallel mating design. Thirty-six biparental F₃ and F₄ generations were derived from six commercial cultivars and three elite lines and artificially inoculated with FOV4 for screening for FOV4 resistance in four replicated tests, with two tests for each generation. Disease severity rating (DSR) at 28 d after inoculation (DAI) and the area under the disease progress curve (AUDPC) across 7, 14, 21, and 28 DAI were analyzed via Griffing's Method 2 and Hayman's diallel analysis. ‘Pima S-6’, ‘PHY 76’, and ‘8810’ (resistant parents) were heterogeneous in their responses to FOV4 infections with 20 to 50% disease incidence and mortality rate; and they had significantly lower DSR and AUDPC with negative general combing ability effects compared with the susceptible parents. Variances caused by specific combining ability and nonadditive effects were higher than those caused by additive effects for FOV4 resistance, consistent with the estimates for broad-sense heritability. The results indicated a predominant nonadditive effect for FOV4 resistance within these genotypes of pima cotton. A minimum of one or two genes was estimated for FOV4 resistance based on Hayman analysis. The results represented the first study applying a diallel analysis to investigate the quantitative genetic basis of FOV4 resistance in pima cotton.

中文翻译：

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美国比马棉对枯萎病4号抗性的二等列分析

尖孢镰刀菌f. sp. vasinfectum Race 4 (FOV4) 导致生长在美国棉带西部和西南部的皮马棉 ( Gossypium barbadense L.) 的幼苗死亡率很高。本研究的目的是使用半双列交配设计分析比马棉 FOV4 抗性的配合能力和遗传基础。三十六双亲 F ₃和 F ₄世代来自六个商业栽培品种和三个优良品系，并人工接种 FOV4 以在四次重复测试中筛选 FOV4 抗性，每代测试两次。通过 Griffing 的方法 2 和 Hayman 的双列分析，对接种后 28 天的疾病严重程度等级 (DSR) 和 7、14、21 和 28 DAI 的疾病进展曲线下面积 (AUDPC) 进行了分析。“Pima S-6”、“PHY 76”和“8810”（抗性父母）对 FOV4 感染的反应是异质的，发病率和死亡率为 20% 至 50%；与易感亲本相比，它们的 DSR 和 AUDPC 显着降低，具有负面的一般梳理能力影响。由特定组合能力和非加性效应引起的方差高于 FOV4 抗性的加性效应引起的变异，与广义遗传力的估计一致。结果表明，在这些皮马棉基因型中，FOV4 抗性具有显着的非加成效应。基于海曼分析，至少估计了一个或两个基因的 FOV4 抗性。该结果代表了第一项应用双列分析来研究比马棉 FOV4 抗性的数量遗传基础的研究。