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

Abstract

AbstractFusarium 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.