Update on Verticillium dahliae alternate hosts

Abstract

Verticillium wilt continues to be a major economic constraint to cotton production in Australia. Previous glasshouse studies conducted by Department of Primary Industries, Queensland confirmed numerous alternate hosts of Verticillium dahliae, the causal agent of verticillium wilt of cotton. Further testing with isolates of both the defoliating and non-defoliating strains of V. dahliae, confirmed Brassica carinata as another alternate host. Characteristic disease symptoms developed in inoculated plants and the pathogen was able to be reisolated from diseased plants, demonstrating Koch's postulates. This is a relatively new crop option and its disease status to common soil borne diseases of cotton was largely unknown. In addition, results from previously reported glasshouse studies showed that winter cereals, wheat, barley, oats and triticale, were hosts of V. dahliae and the pathogen could be seed-borne in these crops that also supported development of microsclerotia. Growers are often observing little improvement in verticillium disease levels in cotton that follows a winter cereal rotation. Naturally grown wheat, as well as barley residues collected from V. dahliae-infected fields have recently been examined, and findings will be discussed in this presentation. A greater understanding of the relationship between cereals and V. dahliae will allow more informed rotation choices to be made.