|Bell, Alois - Al|
|KEMERAIT, ROBERT - University Of Georgia|
|ORTIZ, CARLOS - Texas A&M University|
|PROM, SANDRIA - Texas A&M University|
|NICHOLS, ROBERT - Cotton, Inc|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2017
Publication Date: 3/14/2017
Citation: Bell, A.A., Kemerait, R.C., Ortiz, C.S., Prom, S., Quintana, J., Nichols, R.L., Liu, J. 2017. Genetic diversity, virulence, and Meloidogyne incognita interactions of Fusarium oxysporum isolates causing cotton wilt in Georgia. Plant Disease. 101:948-956.
Interpretive Summary: Several outbreaks of Fusarium wilt of cotton in South Georgia raised concerns about the identity and variation of the causal pathogen. Eight different genetic groups of the pathogen were found among 492 isolates collected from 7 fields in 5 counties. All of the isolates caused severe wilt when they occurred with root-knot nematode, but did little damage in the absence of the nematode. Use of highly nematode-resistant cultivars is probably the best approach to controlling the wilt disease.
Technical Abstract: Locally severe outbreaks of Fusarium wilt of cotton (Gossypium spp.) in South Georgia raised concerns about the genotypes of the causal pathogen, Fusarium oxysporum f. sp. vasinfectum. Vegetative complementation tests and DNA sequence analysis were used to determine genetic diversity among 492 F. oxysporum f. sp. vasinfectum isolates obtained from 107 wilted plants collected from seven fields in five counties. Eight vegetative complementation groups (VCG) were found, with VCG 01117B and VCG 01121 occurring in 66% of the infected plants. The newly recognized VCG 01121 was the major VCG in Berrien County, the center of the outbreaks. All eight VCG resulted in significant increases in the percentages of wilted leaves (27 to 53%) and significant reductions in leaf weight (40 to 67%) and shoot weight (33 to 60%) after being stem punctured into Gossypium hirsutum ‘Rowden’. They caused little or no significant reductions in shoot weight and height or increases in foliar symptoms and vascular browning in a soil-infestation assay. Soil infestation with Meloidogyne incognita race 3 (root-knot nematode) alone also failed to cause significant disease. When coinoculated with M. incognita race 3, all VCG caused moderate to severe wilt. Therefore, the VCG identified in this study belong to the vascular-competent pathotype, and should pose similar threats to cotton cultivars in the presence of the root-knot nematode. Use of nematode-resistant cultivars, therefore, is probably the best approach to control the disease in Georgia.