Studies of evaluation parameters for resistance to Fusarium wilt in cotton caused by Fusarium wilt race 4 (Fusarium oxysporum f. sp. vasinfectum)

Authors: ZHANG, JINFA - New Mexico State University; ZHU, YI - New Mexico State University; ELKINS-ARCE, HEATHER - Texas A&M University; WHEELER, TERRY - Texas A&M University; DEVER, JANE - Texas A&M University; Whitelock, Derek; HAKE, KATER - Cotton, Inc; WEDEGAERTNER, TOM - Cotton, Inc

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2022
Publication Date: 5/5/2022
Citation: Zhang, J., Zhu, Y., Elkins-Arce, H., Wheeler, T., Dever, J., Whitelock, D.P., Hake, K., Wedegaertner, T. 2022. Studies of evaluation parameters for resistance to Fusarium wilt in cotton caused by Fusarium wilt race 4 (Fusarium oxysporum f. sp. vasinfectum). Crop Science. 62(3):1115-1132. https://doi.org/10.1002/csc2.20744.
DOI: https://doi.org/10.1002/csc2.20744

Interpretive Summary: Fusarium wilt caused by the soil-borne fungus FOV4 is an early season cotton disease, causing seedling wilt and death. Root vascular staining (RVS) is used to evaluate cotton for FOV4 resistance, but there are issues with the use of stem vascular discoloration (SVD). A study was conducted to determine if SVD could be used to evaluate cotton for FOV4 resistance under field conditions and how reliable are evaluations for resistance to FOV4 under greenhouse or controlled conditions compared to field screenings. Results suggested that disease severity measurements based on mortality rate and RVS were most accurate in assessing cotton for FOV4 resistance. Also, disease severity measurements based on mortality rate and SVD can be used in combination with disease severity measurements based on mortality rate and RVS to compare the response of different cottons to FOV4 infections. It was also found that seedling mortality in the greenhouse with artificial inoculations of FOV4 was consistent with mortality rates in the field. Therefore, artificial inoculations with FOV4 and screening under controlled, greenhouse conditions can be used to evaluate cotton for FOV4 resistance. These results will provide new tools and help direct future studies to develop FOV4 disease resistant cottons to reduce the disease’s impact on the cotton industry in the Western U.S.

Technical Abstract: Fusarium wilt caused by Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) is an early season vascular disease with symptoms including seedling wilt and mortality. The objectives of this study were to investigate the relationship between mortality rate (MR) and disease severity rating (DSR) based on root vascular staining (RVS)- DSR (RVS) and stem vascular discoloration (SVD)- DSR (SVD) in the field and the relationship of MR in controlled conditions with MR and DSR in the field. Results from two field tests and two greenhouse tests each with a Latin square design for eight cultivars and two field progeny-row tests were analyzed. In the field, MR from emergence to the late square stage was significantly correlated with both DSR (RVS) and DSR (SVD) at crop maturity, and they were also significantly correlated with DSR based on both MR and RVS- DSR (MR+RVS) and both MR and SVD- DSR (MR+SVD). The results suggest that DSR (MR+RVS) is the most accurate in assessing cotton for FOV4 resistance, and DSR (SVD) and DSR (MR+SVD) can be used in combination with DSR (RVS) and DSR (MR+RVS), or as the substitutes for RVS. MR in the greenhouse tests was significantly correlated with MR and DSR (MR+RVS) and DSR (MR+SVD) in the field, indicating consistency between evaluations under the controlled and field conditions. Furthermore, foliar symptoms-based MR and DSR under controlled-conditions were significantly correlated, with coefficients of variation ranging between 20 and 30%. The results confirm the validity of using the two parameters in greenhouse evaluations for FOV4 resistance in cotton.