Verticillium

Verticillium is a genus of filamentous, soilborne fungi that are important plant pathogens. The best known species, including Verticillium dahliae and Verticillium albo-atrum, cause vascular wilt diseases in a wide range of crops and ornamentals. Verticillium species form resting structures called microsclerotia that can persist in soil for many years, helping the pathogen survive between growing seasons.

Biology and disease cycle. In susceptible plants, the fungus infects roots and colonizes the xylem vessels, where it disrupts water transport. This leads to wilting, chlorosis, stunting, and vascular discoloration in affected tissues. The pathogen spreads within the plant and can move between plants via infested soil, irrigation water, or contaminated tools. Microsclerotia in the soil germinate to initiate new infections when host roots are present, enabling long-term soilborne pressure.

Hosts and impact. Verticillium affects hundreds of plant species, including many vegetables (such as tomato and potato), woody ornamentals, fruits, and fiber crops. Disease severity depends on the pathogen species, host, climate, and soil conditions, with warm, moist soils often favoring infection. Because microsclerotia remain in soil, outbreaks can be persistent and challenging to eradicate from production sites.

Diagnosis and management. Diagnosis combines field symptoms with laboratory confirmation through fungal isolation or molecular assays. Management emphasizes prevention and long-term strategies: use resistant or tolerant cultivars when available, practice long crop rotations with non-hosts, implement soil solarization or appropriate fumigation where permitted, sanitize equipment, and remove infected plant material. Biological and cultural approaches may help reduce inoculum, though complete eradication is difficult due to soilborne persistence.

Taxonomy notes. Verticillium comprises several species with overlapping host ranges; V. dahliae and V. albo-atrum are among the most economically significant. Most Verticillium species reproduce asexually, forming conidia and resting microsclerotia.