|WAGNER, TANYA - Texas A&M University|
|Bell, Alois - Al|
|ALI, AKHTAR - University Of Tulsa|
|FLORES, ORLANDO - Texas A&M University|
Submitted to: Journal of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2022
Publication Date: 4/21/2022
Citation: Wagner, T.A., Bell, A.A., Castles, Z.A., Ali, A., Flores, O., Liu, J. 2022. Detection, genotyping, and virulence characterization of Fusarium wilt race 4 (VCG0114) causing cotton wilt in three Texas fields. Journal of Phytopathology. 170(7-8):492-503. https://doi.org/10.1111/jph.13100.
Interpretive Summary: Fusarium wilt is a world-wide disease of cotton caused by the fungal pathogen, Fusarium oxysporum f. sp. vasinfectum (Fov). One particular strain of the pathogen known as race 4 (Fov4) was first detected in the U.S. in California and had been confined to California since 2001 through extensive quarantine efforts. However, Fov4 was recently detected in several cotton fields near El Paso, Texas. In previous work, we developed molecular methods to differentiate strains of Fov and demonstrated that Fov4 could be further classified into several types. In this study, we obtained diseased plants from the El Paso region and confirmed that the plants were infected with Fov4. Additionally, only the MT type of Fov4 was detected in plants collected from the Lower Valley region of El Paso, whereas only the T type was found in the Upper Valley region of El Paso. Based on disease assays in growth chambers, the MT type was more virulent than the T type, causing much more severe disease in plants. Determining the distribution of the different Fov4 types and monitoring their movement will be of vital importance in optimizing disease management strategies for Fov4 and preventing the further spread of this disease.
Technical Abstract: Fusarium wilt of cotton, caused by the soilborne fungus Fusarium oxysporum f. sp. vasinfectum race 4 (Fov4, VCG0114), is a serious disease that has adversely affected cotton production in California since 2001 and in the Upper Rio Grande Region near El Paso in the border areas between Texas and New Mexico since 2017. Fov4 was isolated from cotton stem samples collected from wilted or asymptomatic plants adjacent to the wilting plants from the El Paso area. The MT genotype was the only Fov4 genotype found in two fields in the Lower Valley of El Paso and the T genotype was the only Fov4 genotype found in one field in the Upper Valley Region of El Paso. No mixed genotypes of Fov4 were detected in any of these fields. Furthermore, the F. oxysporum isolates were exclusively Fov4. The results support the observation that the MT genotype of Fov4 is mainly distributed in the Lower Valley of El Paso and the T genotype of Fov4 is mainly distributed in the Upper Valley Region of El Paso. Virulence of the MT genotype of Fov4 was significantly higher than that of the T genotype. PCR methods previously developed for Fov4 specific PCR detection and multiplex Fov4 genotyping were validated by VCG analyses of the newly obtained isolates. These PCR methods were adapted for the in planta detection of Fov4, but Fov4 genotyping was limited to the detection of T, MT, and MiT genotypes. It is important to continue to monitor dynamic population structure of Fov4 genotypes to prevent the spread of Fov4 and optimize disease control.