|Ellis, Margaret - CALIFORNIA STATE UNIVERSITY|
|Diaz, Josue - CALIFORNIA STATE UNIVERSITY|
|Hutmacher, Robert - UNIVERSITY OF CALIFORNIA, DAVIS|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/25/2019
Publication Date: 5/15/2019
Citation: Ellis, M.L., Diaz, J., Hutmacher, R.B., Ulloa, M. 2019. Evaluation of Fusarium oxysporum F. sp. vasinfectum race 4 as a seedling pathogen and in co-inoculation assays with rihizoctonia solani. National Cotton Council Beltwide Cotton Conference. p. 349-353.
Technical Abstract: Fusarium oxysporum f. sp. vasinfectum (Fov) race 4 is an important wilt pathogen of cotton that has also been known to cause damping off and seedling mortality in infested fields. Fov race 4 is geographically limited, first identified in California in 2001 and confirmed in Texas in 2017. Since the introduction of Fov race 4 in California, it has been a recurring and expanding threat to California’s cotton production. It has also been observed in California that more disease often develops when Fov race 4 and Rhizoctonia solani are present in the same field, thus suggesting a potential interaction between the two fungi. Therefore, the objectives of this study included (1) collecting isolates of Fov and R. solani from commercial and grower fields in California for genotypic and phenotypic evaluations; and (2) evaluating the interaction between Fov race 4 and R. solani in co-inoculation assays. Isolates of Fov were genotyped using two sets of Fov race 4 specific primers. Sixteen isolates were phenotypically characterized for their ability to cause seedling infections using a rolled towel assay. The results found genotypic variations between Fov race 4 isolates. Based on the phenotypic evaluation of Fov race 4 isolates, all isolates produced seedling symptoms on cotton. In greenhouse assay the interaction between Fov race 4 and R. solani was evaluated. There was a significant difference between fungal treatments (P < 0.0001) with more disease development in the co-inoculation treatment, which confirm field observations when both fungi are present in the same field.