Verticillium klebahnii and V. isaacii isolates exhibit host specificity in biological control of Verticillium wilt caused by V. dahliae

Authors: PURI, KRISHNA - University Of California; HU, XIAOPING - Northwest Agricultural & Forestry University; GURUNG, SURAJ - University Of California; SHORT, DYLAN - University Of California; SANDOYA, GERMAN - University Of Florida; SCHILD, MARION - Swiss Federal Institute; ZHANG, YUAN-YUAN - Inner Mongolian Agriculture University; ZHAO, JUN - Inner Mongolian Agriculture University; Anchieta, Amy; Klosterman, Steven; SUBBARAO, KRISHNA - University Of California

Submitted to: PhytoFrontiers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2021
Publication Date: 4/5/2021
Citation: Puri, K.D., Hu, X., Gurung, S., Short, D.P., Sandoya, G.V., Schild, M., Zhang, Y., Zhao, J., Anchieta, A.G., Klosterman, S.J., Subbarao, K.V. 2021. Verticillium klebahnii and V. isaacii isolates exhibit host specificity in biological control of Verticillium wilt caused by V. dahliae. Phytofrontiers. https://doi.org/10.1094/PHYTOFR-01-21-0001-R.
DOI: https://doi.org/10.1094/PHYTOFR-01-21-0001-R

Interpretive Summary: Verticillium dahliae is a fungus that causes Verticillium wilt disease on many economically important crops, including tomato and lettuce. Control of Verticillium wilt is difficult since the fungus survives in the soil for years and the available soil fumigants are not as effective as once widely used methyl bromide. Alternative disease control approaches are necessary for control of this disease. In this study, two potential biological control agents were tested for their ability to protect eggplant, tomato, and lettuce from V. dahliae. The study revealed that the biocontrol agent Verticillium klebahnii was effective at reducing disease on eggplant and tomato but not on lettuce. Microscopy analyses revealed that the biocontrol agent blocked V. dahliae from entering the vascular system in the plant and therefore may be useful as a treatment to reduce disease in some crops.

Technical Abstract: Verticillium dahliae, the soil-borne fungal pathogen, causes vascular wilt on many economically important crops resulting in significant yield losses. Verticillium klebahnii (isolate PD659) and V. isaacii (isolate PD660), two related species that cause little or no symptoms in some hosts, were evaluated as potential biocontrol agents (BCA) in eggplant, lettuce, and tomato by pre, post, and co-inoculation with a virulent race 1 isolate of V. dahliae (VdLs16). Initial studies demonstrated that the biocontrol efficacy of both BCAs was similar to reference BCA Talaromyces flavus (NRRL15936) across all hosts (a= 0.05). Subsequent experiments with PD659 against V. dahliae isolate Sm113 from eggplant, VdLs16 and VdLs17 isolates from lettuce, and Le1811 isolate from tomato demonstrated a significant biocontrol efficacy in eggplant and tomato but not in lettuce (at 95% CI), suggesting host-dependent effectiveness of V. klebahnii. Confocal microscopy using GFP-tagged tomato V. dahliae isolate Le1811 indicated delayed xylem colonization or lack of pathogen progression into the vascular system in a host-dependent manner on BCAs treated plants. Quantitative analyses of the expression of defense-related genes PR1a, PR5, acidic extracellular b-1,3-glucanase (GlucA), basic intracellular b-1,3-glucanase (GlucB), acidic extracellular chitinase (Chi3), basic intracellular chitinase (Chi9), and cysteine proteases (cysProreases) in tomato in the presence or absence of PD659 suggested an elevated expression of defense-related genes in compatible interaction of V. dahliae-tomato cv. Early Pak. Verticillium klebahnii (PD659) may delay the entry of V. dahliae by competing for space or nutrients during the initial stages of root colonization.