Sources, selection and breeding of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4) resistance in Upland (Gossypium hirsutum L.) cotton

Authors: Ulloa, Mauricio; HUTMACHER, ROBERT - University Of California, Davis; SCHRAMM, TERI - University Of California, Davis; ELLIS, MARGARET - California State University; NICHOLS, ROBERT - Cotton, Inc; ROBERTS, PHILIP - University Of California; WRIGHT, STEVEN - University Of California

Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2020
Publication Date: 6/14/2020
Citation: Ulloa, M., Hutmacher, R.B., Schramm, T.L., Ellis, M.L., Nichols, R., Roberts, P.A., Wright, S.D. 2020. Sources, selection and breeding of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4) resistance in Upland (Gossypium hirsutum L.) cotton. Euphytica. 216:109. https://doi.org/10.1007/s10681-020-02643-5.
DOI: https://doi.org/10.1007/s10681-020-02643-5

Interpretive Summary: For over a decade, a soil-borne and seed-borne fungal pathogen named Fusarium race 4 (FOV4) has impacted cotton production in California’s San Joaquin Valley, causing plant wilt and death. This pathogen was identified in 2019 in New Mexico and 2017 in the El Paso area of far west Texas in close proximity to the Texas High Plains, the largest Upland cotton producing region in the USA. Because there is not a known FOV4-resistant or highly resistant Upland commercial variety in the USA, the need to develop resistant Upland cotton varieties has become urgent. Our previous research identified high levels of resistance to FOV4 in the cotton cultivar Pima S-6’ and resulted in the public release of Pima germplasm with improved FOV4 resistance. However, the search for resistant Upland cotton has proved more challenging compared to the effort in Pima. In this study, we performed and extensive evaluation of a large number of Upland varieties to identify new genetic sources for breeding FOV4 resistance in Upland cotton. Our research provides important new information about the status of Upland germplasm in the USDA-ARS and Public University Upland cotton collections, allowing private and public breeders and researchers to make informed decisions regarding the choice of germplasm to use for planting and breeding. In addition, this research has identified and developed potentially new FOV4 resistant Upland germplasm for public release in the near future which can be incorporated into commercial Upland USA cotton varieties. Even though disease expression of plants to FOV4 infection is more severe in susceptible Pima cotton plants, FOV4 can also infect Acala and Upland cottons to a high degree, and if we are not prepared, future economic losses can be severe. Highly tolerant or resistant Upland breeding lines developed as part of this study will be publicly released to reduce the vulnerability of the cotton industry to this pathogen.

Technical Abstract: Diseases such as Fusarium wilt [Fusarium oxysporum f.sp. vasinfectum (FOV)] represent expanding threats to cotton (Gossypium spp.) production around the world. For over a decade, FOV race 4 (FOV4) has impacted cotton production in California’s San Joaquin Valley (SJV) causing plant wilt and death. With this disease formally identified in 2019 in New Mexico and 2017 in the El Paso area of far west Texas in proximity to the largest Upland cotton producing region in the USA, the need to expand the genetic base of Upland (G. hirsutum L.) cotton and develop cultivars resistant or tolerant to FOV4, a soil-borne and seed-borne fungal pathogen, has become urgent. Our previous research in Pima (G. barbadense L) cotton identified high levels of resistance to FOV4 (germplasm ‘Pima S-6’) and publicly released Pima germplasm with improved FOV4 resistance. However, the search for resistant Upland cotton has proved more challenging compared to the effort in Pima. More than 1,000 Upland accessions from the USDA-ARS Cotton Germplasm Collection were evaluated for reaction to FOV4. After FOV4 artificial-greenhouse and naturally infested grower field FOV4 evaluations of these accessions, less than 0.1% were selected to develop highly resistant FOV4 progeny. Two sources (NM12Y1004 - NM12Y1005 and SA-3208) of Asiatic breeding origin were identified with tolerance to FOV4 and used to introgress and increase resistance. Pedigree information from additional parental lines or breeding stocks used to develop progeny revealed their sources to be exotic and wild Upland germplasm - triple/multiple crosses, deriving these SA-obsolete cultivars named ‘Auburn M’, ‘DES 920’, ‘MARSPD202085’, ‘S.N.0503-1’, PD 2165, and ‘Stoneville 14’, among others. There was a range of severity of foliar symptoms, and level of FOV4 plant infection based on vascular root staining (VRS) and plant mortality in these infested fields. In grower infested fields, observations were made under moderate to severe FOV4 inoculum based on susceptible germplasm/cultivar-checks. Many FOV4 infected Upland cultivars typically showed fewer leaf symptoms and much lower plant mortality in early stages of the disease. The genetic inheritance mode of action of FOV4 resistance/tolerance in Upland cotton seems to range from recessive to intermediate, unlike in Pima cotton where resistance seems to be dominant or more complete at the plant host level. Highly tolerant or resistant Upland breeding lines were developed from this breeding research effort and will be publicly released to reduce the vulnerability of the cotton industry to this pathogen.