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ARS Home » Plains Area » College Station, Texas » Southern Plains Agricultural Research Center » Insect Control and Cotton Disease Research » Research » Research Project #437910

Research Project: Fusarium Wilt of Cotton: Pathogen Population Characterization, Virulence & Resistance Mechanism Determination, Marker Assisted Resistance Breeding

Location: Insect Control and Cotton Disease Research

Project Number: 3091-22000-035-61-R
Project Type: Reimbursable Cooperative Agreement

Start Date: Jan 1, 2020
End Date: Dec 31, 2020

1. Characterize the genetic variation, virulence, and nematode interactions of F. oxysporum isolates. 2. Advance and evaluate tolerance to Fusarium oxysporum f. sp. vasinfectum race. 4 (FOV4) from Gossypium barbadense and G. arboreum sources and introgress resistance genes from such sources into BAR lines that are homozygous for Ren 2&3 and Mi 1&2 which are highly resistant to both reniform and root-knot nematodes, respectively. Identify markers associated with the resistances. 3. Identify FOV4 virulence determinants by transcriptomic analysis. Determine genetic polymorphism among different FOV4 genotypes including the non-pathogenic types and confirm the virulence role of the identified genes by gene knock-outs and subsequent pathogenicity assays. 4. Determine the possible roles of the gossypol and lacinilene pathways on host resistance to the FOVs.

1. Characterize the genetic variation, virulence, and nematode interactions of FOV isolates belonging to the root rot pathotypes (VCG 0113, 0114, and 01111. Determine differential interactions of various vascular competent pathotypes (VCG 0111, 0112, 0117,01120, 0121, and others) with the nematode resistance genes Mi1 and Mi2. 2. Pima S-2, Pima S-4, Pima S-6, Sakel, Seabrook Sea Island 12B2, Gossypium arboreum accession # 190 have been backcrossed into BAR 32 lines to introgress FOV resistance genes. The progenies are being selfed and selected for homozygous resistant and susceptible plants. Lines resistant to both the root rot and vascular competent FOV pathotypes as well as the nematodes will be identified, developed and released. 3. Genetic markers associated with resistance will be identified and mapped using DNA from susceptible and resistant backcross lines. Emphasis will be placed on SSR markers already reported to be associated with resistance to race 3 (VCG 0113) or race 4 (VCG 0114) in the literature. 4. MT genotype Fov4 isolates show greater virulence than do Tgenotype isolates, while one of the N genotype isolates is non-pathogenic. These isolates will be utilized for transcriptomic analysis to identify genetic polymorphism and virulence determinant genes. In the genome of Fov4, DNA transposons such as Tfo1 and mutator like elements are highly active and may be responsible for virulence variation among isolates. Expression of genes affected by these elements will be identified, and the virulence role of the identified genes will be confirmed by gene knock-out approaches and pathogenicity assays. 5. Blocking the gossypol pathway in cotton using RNAi resulted in increased host resistance to Fov, which also resulted in the increased production of lacinilene pathway defense compounds. In order to assess the practical utility of such an approach, we will also assess the reactions to necrotrophic seedling disease pathogens and to the bacterial blight pathogen Xanthomonas citra pv. malvacearum, to which lacinilene terpenoids are highly toxic. Anticipated Tangible Accomplishment: This project will create basic information that can be used to develop technologies and germplasm lines to manage FOVs. Results will support preparation of one of more manuscripts for submission to peer-reviewed journals.