Liquid fermentation of Colletotrichum truncatum UFU 280, a potential mycoherbicide for beggartick

Abstract

One isolate of Colletotrichum truncatum was found recently causing severe anthracnose symptoms and leading to the death of beggartick (Bidens pilosa L. and Bidens subalternans DC.), one of the major weeds of Brazilian agriculture. This isolate, namely UFU 280, was selected for development of a mycoherbicide against this weed. Associated of beggartick, one of the, Here, results of a preliminary attempt to develop a protocol for mass production of inoculum (conidia) and fungal biomass of C. truncatum was performed aimed at paving the way for greenhouse and field evaluations of this biocontrol candidate. Isolates of Colletotrichum spp. have been successfully produced in the past to serve as the active ingredients of mycoherbicides. The method of choice has been the production of propagules through liquid fermentation. We assessed the effect of several options of liquid media recipes, type of seeding of medium, pH levels, incubation lengths, incubation temperatures and agitation speeds on the shaking speed on the concentration of conidia obtained per volume of medium. Additionally, a possible effect of the kind of medium utilized over the virulence of the inoculum was also evaluated through an inoculation study. We found that an adequate amount of conidia of C. truncatum (isolate - UFU 280) can be obtained in ME liquid culture medium, adjusted to a pH of 9.0, seeded with a conidial suspension and incubated for 6 days, under a regime of orbital shaking of 150 rpm, at temperatures ranging from 20 to 25 °C. Mortality of beggartick plants using conidia produced in different liquid culture media was of 100%.