Project Number: 3096-21000-022-019-A
Project Type: Cooperative Agreement
Start Date: Dec 14, 2018
End Date: May 31, 2022
1.To identify Fusarium wilt (FOV) populations from California and Texas cotton fields. 2.To use representative FOV races for phenotypic evaluation of selected US and Uzbekistan germplasm.
Fusarium wilt of cotton, caused by Fusarium oxysporum f. sp. vasinfectum (FOV), is one of the most important diseases in cotton producing regions throughout the world, causing significant economic losses to cotton farmers. This proposed research is part of a collaborative effort by USDA-ARS and University cooperators in the USA for combating FOV, a serious economic threat for sustainable cotton production in the USA and Uzbekistan. The work to be conducted at California State University, Fresno (Fresno State) will be focused on identifying the most prevalent FOV races and other pathogens in infested fields of the USA and use these representative identified FOV races for phenotypic evaluation of selected US and Uzbekistan germplasm. Candidate germplasm will be evaluated through artificial soil inoculation in the greenhouse following an established protocol. In the last reported large-scale survey of FOV populations in cotton fields in California and other cotton producing states in 2015, only FOV race 4 (FOV4) was identified in California. In 2017, FOV4 was also identified in Texas for the first time. During the 2018 growing season in California, there was substantial stand loss in several commercial resistant/tolerant cultivars in growers’ fields. This loss was seen in fields that were planted with cultivars that are known to have resistance to FOV4. Based on preliminary data collected in seven fields, there seems to be another FOV race that may be interacting with FOV4. This interaction may be able to break the resistance found in some cultivars with high levels of resistance to FOV4. The knowledge from a new survey will be important for the continuation of cotton production in the state and for ongoing field evaluations of FOV resistant germplasm. In addition, plants exhibiting symptoms of FOV will be collected from multiple grower and commercial fields at four of the main growth stages of cotton including: germination and emergence, seedling establishment, leaf area and canopy development, and flowering and boll development. Single spore isolations will be done for all isolates. The collected FOV isolates will be screened using FOV4 race-specific primers. Also, we will further genotype a set of representative FOV isolates using DNA sequencing of several genes (EF-1a, PHO, and BT). The DNA sequences will be aligned using MUSCLE and a phylogenetic analysis will be conducted using Bayesian inference using the MrBayes plugin of Geneious to compare our isolates with known sequences of FOV races. Promising germplasm will also be screened, and evaluation methods will be like those previously described by research done in California. Host-plant resistance is the only cost-effective long-term solution to address the problem of FOV, but its use is seriously impeded by the narrow genetic base of Upland cotton. There is the need to identify and develop Upland cotton resistant/tolerant to FOV4 to make sure that we are prepared to handle its potential threat and spread into other cotton-growing areas in the USA.