Pedigree selection under field conditions within Acala 1517-08 and its glandless derivatives for development of cotton resistant to Fusarium wilt caused by Fusarium oxysporum f. sp. vasinfectum race 4

Wheeler³

et al. 2021

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Fusarium wilt of cotton (Gossypium spp.) is caused by a soil‐ and seed‐borne fungal pathogen Fusarium oxysporum f. sp. vasinfectum (FOV). Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) is a significant threat to cotton production in the United States. The effect of temperature and soil on disease symptoms in cultivars with a range of susceptibility to FOV4 was examined in growth chamber trials. Three upland (G. hirsutum L.) and three pima (G. barbadense L.) cultivars were planted in three types of soils (potting mix and farm soils with and without FOV4 preinfestation) and maintained at four constant temperature regimes (20, 23, 26, and 29 °C). After seedling emergence, each pot was inoculated with conidial suspensions of FOV4 and scored for resistance based on disease incidence (DI), foliar disease severity rating (DSR), and mortality rate (MR) at 7, 14, 21, and 28 d post‐inoculation (dpi). The area under the disease progress curve (AUDPC) based on DSR across the four evaluation dpi was also analyzed. Among the six cultivars tested, Pima PHY 841 RF, Pima S‐6, and the uplands Acala 1517‐08 and FM 2334GLT were the most resistant, whereas upland PHY 725 RF and Pima S‐7 were the most susceptible. The genotypic responses to FOV4 were not significantly (P > .05) affected by differences in temperature regime or soil type. Cotton seedlings manifested more severe symptoms and higher mortality when maintained at 23 °C, followed by 20/26 °C and 29 °C in descending order. The mycelial growth rate was greater at 23/26 °C, whereas plants grew slower at 20/23 °C. There were no differences (P > .05) in DI, DSR, MR, and AUDPC between the inoculated farm soil (with no FOV4 preinfestation) and the inoculated FOV4‐preinfested farm soil, suggesting the unnecessity of using the latter in artificial inoculations. However, the potting soil produced higher (P < .05) DI and DSR at 7 and 14 dpi but lower (P < .05) AUDPC. This growth chamber study demonstrated that 23 °C produced the highest DI, severity, and plant death, providing an important piece of information for screening cotton for FOV4 resistance in breeding and FOV4 disease management in cotton production.

Section: Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Importance of temperature in evaluating cotton for resistance to Fusarium wilt caused byFusarium oxysporumf. sp.vasinfectumrace 4

Zhang

Wheeler³

et al. 2021

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“…As with most studies on FOV in cotton (Lopez‐Lavalle et al., 2012; Sanogo & Zhang, 2016; Wang & Roberts, 2006), a virulent FOV4 isolate can be used as a representative in artificial inoculations. In rare occasions, a mixture of different isolates or races was used for screening (Abd‐Elsalam et al., 2014; Zhang, Abdelraheem, Zhu, Wheeler, Dever, Elkins‐Arce, et al., 2020). Bell et al.…”

Section: Discussionmentioning

confidence: 99%

“…These resistant germplasms will be useful to breeding cotton for FOV4 resistance. However, they are heterogeneous in resistance, and the genotype frequency and gene frequency for the FOV4 resistance can be increased through repeated pedigree selections under a high FOV4 disease pressure, as shown by Zhang, Abdelraheem, Zhu, Wheeler, Dever, Elkins-Arce, et al (2020).…”

Section: Discussionmentioning

confidence: 99%

“…After the highly virulent FOV4 was first identified in California, genetics and breeding for FOV4 resistance and pathology of FOV4 were primarily conducted in that state. However, since the first published report of FOV4 in the Upper Rio Grande Valley of Texas (Halpern et al., 2018), major efforts in breeding and pathology research have been shifted to the region (Bell et al., 2019; Zhang, Zhu, et al., 2020; Zhang, Abdelraheem, Zhu, Wheeler, Dever, Elkins‐Arce, et al., 2020; Zhang, Abdelraheem, Zhu, Wheeler, Dever, Felichowski, et al., 2020), where fields with as high as 90–100% cotton mortality before midseason were observed (Zhang, Abdelraheem, Zhu, Wheeler, Dever, Elkins‐Arce, et al., 2020). These efforts include, but are not limited to, numerous cotton fields being surveyed and found to be infested with FOV4 (Bell et al., 2019); a FOV4‐specific polymerase chain reaction (PCR) marker and a multiplex PCR being developed to identify different genotypes of the race (Bell et al., 2019); fields with heavy FOV4 infestations being identified and used for screening cotton for resistance and selections (Zhang, Abdelraheem, Zhu, Wheeler, Dever, Elkins‐Arce, et al., 2020); and a virulent FOV4 isolate being used to screen cotton for FOV4 resistance in the greenhouse or temperature‐controlled conditions (Zhang, Abdelraheem, Zhu, Wheeler, Dever, Frelichowski, et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

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Interactions between cotton genotypes and Fusarium wilt race 4 isolates from Texas and resistance evaluation in cotton

Wheeler²,

Dever³

et al. 2021

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Fusarium wilt, caused by the soil‐borne fungus Fusarium oxysporum f. sp. vasinfectum (FOV) race 4 (FOV4), is one of the most destructive diseases in cotton (Gossypium spp.) in the southwestern and western Cotton Belt. However, the virulence of FOV4 is currently unknown. In this study, 17 FOV isolates collected in the Fabens, TX, area were determined to be FOV4 based on FOV4‐specific polymerase chain reaction (PCR) and sequence analysis of three genes encoding for translation elongation factor, β‐tubulin, and phosphate permease. A further multiplex PCR analysis determined that they all belonged to the Tfo1/MULE MT genotype. Based on disease severity ratings (DSR) on two upland and two pima cotton lines in the greenhouse, virulence of the 17 FOV4 isolates differed but was overall congruent on the four lines, and differences among cotton genotypes accounted for 82% of the total variance. Variance in virulence due to FOV4 isolates and FOV4 isolate × cotton genotype interaction each accounted for only 8–11% of the total variance. A virulent MT FOV4 isolate was used to inoculate 104 entries representing 92 cultivars and elite lines in two tests at 21–23 °C. The combined ANOVA detected a significant genotypic variation in DSR with moderate broad‐sense heritability estimates (.62–.69). About 90–91% of the genotypes were susceptible to FOV4, including 100% mortality in 59–91% of the genotypes. Pima PHY 805 RF and three upland cultivars including FM 2334GLT, Acala 1517‐08, and Acala Daytona RF had similar resistance responses to the resistant check pima PHY 841 RF. This study demonstrated that cotton genotypes played a predominant role in determining FOV4 virulence, reinforcing the validity of using a representative isolate to screen cotton for FOV4 resistance.

Diallel analysis of resistance to Fusarium wilt Race 4 in American pima cotton

Dever²,

Wheeler³

et al. 2021

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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.