Role of Local Trichoderma spp. Isolates in Reducing Tomato Fusarium Wilt and Increasing Phosphorus Uptake

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Commodities

• Vegetables: tomatoes

Practices

• Crop Production: nutrient management
• Pest Management: biological control

Many Trichoderma isolates are able to parasitize structures of plant pathogenic fungi, can solubilize poorly-soluble soil nutrients such as phosphorus (P), and can induce crop resistance to plant pathogens. There is little information on how Trichoderma-induced benefits to crops interact (i.e., nutrient uptake and disease tolerance) or the magnitude of the nutrient uptake benefit. In objective 1, we will evaluate eight local isolates of Trichoderma (including T. asperellum, T. brevicompactum, T. hamatum, T. harzianum, and T. koningiopsis) for 1) potential to reduce Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici (Fol)and 2) to solubilize poorly soluble forms of soil P. In the first study, Fol-susceptible tomato (Valencia) will be subjected to ten treatments (eight Trichoderma and no Trichoderma control, all inoculated with Fol, and a non-Fol-inoculated control). In the second study, dual culture assays between Trichoderma isolates and Fol will be conducted on Pikovskaya’s media formulated with four P source treatments (aluminum-P, calcium-P, potassium-P, or no added P). In objective 2, twoTrichoderma selected based on obj. 1 will be used in greenhouse studies with five diverse tomato species/genotypes (S. habrochaites, S. pimpinellifolium, S. lycopersicum var. cerasiforme, S. lycopersicum cvs. Valencia & Clementine). Treatments will include two Trichoderma, or a control, and tomato seeded into pots amended with one of three P amendments (phytate, aluminum-P, and super-P). In objective 3, two tomato will be treated with one of two Trichoderma, or a control, and with one of two P amendment rates all with or without Fol inoculation.

1a: Evaluate eight local Trichoderma isolates for suppression of tomato wilt disease caused by F. oxysporum f. sp. lycopersici in a susceptible heirloom tomato cultivar.

Hypothesis: The ability of Trichoderma spp. isolates to reduce symptoms of F. oxysporum f. sp. lycopersici (Fol) on Valencia tomato compared to an Fol-inoculated control will vary among isolates, with some local isolates being equivalent to a non-Fol-inoculated control.

1b: Evaluate eight local Trichoderma isolates for the ability to solubilize Al-phosphate and Ca-phosphate in lab assays, and interactions with Fol in dual-plate assays on media with varying P substrates.

Hypothesis: Trichoderma isolates will vary in ability to solubilize P sources, with local isolates more effective in solubilization of Al- than Ca-phosphate

2: Evaluate two Trichoderma isolates of differing P-solubilization potential on tomato P-uptake in a greenhouse trial of five diverse tomato genotypes/wild relatives and three P substrates.

Hypothesis: High P-solubilizing Trichoderma will increase tomato biomass and P uptake when tomato is grown in low-P availability substrates, but magnitude of effects will differ among tomato germplasm and be more pronounced in tomato wild relatives

3: Evaluate two Trichoderma isolates of differing P-solubilization potential on biocontrol interactions (+/- Fol) with P-uptake in a greenhouse trial with two differing tomato species or genotypes.

Hypothesis: Tomato biomass, performance, and wilt resistance will be greatest when inoculated with high P-solubilizing Trichoderma.