Efficiency of selection for resistance to Fusarium wilt race 4 in cotton when conducted in the field versus greenhouse

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; WEDERGAERTNER, TOM - Cotton, Inc; HAKE, KATER - Cotton, Inc; BISSONNETTE, KAITLYN - Cotton, Inc

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2022
Publication Date: 10/27/2022
Citation: Zhang, J., Zhu, Y., Elkins-Arce, H., Wheeler, T., Dever, J., Whitelock, D.P., Wedergaertner, T., Hake, K., Bissonnette, K. 2022. Efficiency of selection for resistance to Fusarium wilt race 4 in cotton when conducted in the field versus greenhouse. Euphytica. 218. Article 165. https://doi.org/10.1007/s10681-022-03117-6.
DOI: https://doi.org/10.1007/s10681-022-03117-6

Interpretive Summary: Upland cotton is the most important fiber crop in the world, and Fusarium wilt caused by the soil-borne fungus FOV race 4 (FOV4) is one of the most destructive cotton diseases. However, progress in breeding for FOV4 resistance in cotton is slow. To address field selection efficiency in a typical pedigree selection process for FOV4 resistance in cotton, a comparative study between field and greenhouse conditions and selections was performed. The results showed that the plant mortality rate in the greenhouse was more than twice of that in the field, suggesting a higher percentage of disease escapes in the field. Also, variability in the results was lower for tests in the greenhouse than in the field. As it is well understood, crop breeding is mostly field based, and new cultivars should be evaluated under different environmental conditions for their performance before their release for commercial production. This process certainly applies to breeding for disease resistance in cotton. However, focusing on field performance of cultivars does not suggest that the entire process in breeding should be exclusively field based. Greenhouse screening of cotton for FOV4 resistance had several advantages over field screening: 1) experimental errors were greatly reduced in greenhouse screening due to uniform and high FOV4 inoculum density from artificial inoculation; 2) greenhouse screening had significantly higher plant mortality rate than that in the field screening; and 3) greenhouse screening required much less space, time and labors to complete the entire evaluation process. These results help verify the accuracy and efficiency of greenhouse evaluations for FOV4 resistance, an important tool used by cotton breeders and pathologists. These results will help speed up and direct future studies to develop cultivars that are resistant to FOV4 disease in U.S. cotton.

Technical Abstract: Upland cotton (Gossypium hirsutum L.) is the most important fiber crop in the world, and Fusarium wilt caused by the soil-borne fungus Fusarium oxysporum f. sp. vasinfectum (FOV) is one of the most destructive diseases. FOV race 4 (FOV4) causes an early season disease with symptoms including seedling mortality and vascular discoloration (VD). However, breeding for FOV4 resistance in Upland cotton is complex. To address plant selection efficiency under field conditions in a typical pedigree selection process for FOV4 resistance in cotton, a comparative analysis between the field and greenhouse evaluations and selections was performed. Single plant selections (SPS) with no or low VD selected in a FOV4-infested field between 2018 and 2021 were progeny tested in both the field and greenhouse. Results indicated that overall mean plant mortality rate (MR) in the greenhouse across the four years was more than three times mortality in the field (81.9 vs. 22.9%) with a much narrower range (75–89% vs. 10–30%), suggesting a higher percentage of disease escapes in the field. Results from 10 replicated tests each with 32 lines and 4 replications confirmed the higher MR (79.8 vs. 30.5%) with a narrower range (72.0–88.9 vs. 22.2–39.5%) in the greenhouse screening which had lower coefficients of variation (28.3 vs. 61.3%, with a range of 18.6–40.5 vs. 46.7–72.8%) than the field screening, although MR between the field and greenhouse screening was significantly and positively correlated. However, MR in progeny rows in the field was not correlated with that in the greenhouse. SPS selected for no or low VD in Acala 1517–08 and Acala 1517–18 GLS in the greenhouse protocol had lower escapes and significantly reduced MR in their progeny compared to those selected in the field and unselected populations. However, SPS in susceptible Pima S-7 selected in field and greenhouse conditions did not decrease MR in their progeny, suggesting no or very low levels of frequencies of resistance gene(s) and resistant genotypes in this cultivar.