Bioherbicidal efficacy of a Myrothecium verrucaria-sector on several plant species

Authors: Hoagland, Robert; Boyette, Clyde; Stetina, Kenneth - Ken; Jordan, Robin H

Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2016
Publication Date: 11/28/2016
Citation: Hoagland, R.E., Boyette, C.D., Stetina, K.C., Jordan, R.H. 2016. Bioherbicidal efficacy of a Myrothecium verrucaria-sector on several plant species. American Journal of Plant Sciences. 7:2376-2389.

Interpretive Summary: Control of weeds is a major concern on a global basis and weeds with tolerance or resistance to herbicides are even more problematic. Many microorganisms that cause diseases in weeds have been evaluated as bioherbicides for potential alternatives to herbicides. Scientists in the USDA-ARS, Crop Production Systems Research Unit and the Biological Control of Pests Research Unit, Stoneville, MS discovered a spontaneous sector (mutant) during growth studies of the bioherbicide, Myrothecium verrucaria (MV strain IMI 361690). The sector (MV-Sector BSH) was isolated, grown as mycelium in pure culture and shown to lack the ability to produce spores. Comparative bioassays and greenhouse tests on mycelial preparations of MV and the sector indicated the sector possessed bioherbicidal activity on sicklepod, hemp sesbania, kudzu and glyphosate-resistant Palmer amaranth at a level equal to, or slightly less than, MV. Comparative protein profiles of cellular extracts of MV and the sector revealed differences with respect to quantity and number of certain protein bands. Results provide important information related to the bioherbicidal activity of MV and suggest additional work should be carried out to further characterize the sector, use it as a tool in comparative studies of MV, and demonstrate if it has potential as a stand-alone bioherbicide.

Technical Abstract: Comparative studies were conducted on mycelial preparations of the bioherbicide, Myrothecium verrucaria (MV) strain IMI 361690 and a recently discovered sector (MV-Sector BSH) of this fungus. The whitish sector was discovered, isolated, grown in pure culture on PDA and found to be a non-spore producing mutant when grown under conditions under which MV produces abundant numbers of spores. Application of MV and MV-Sector BSH mycelial preparations to intact plants (hemp sesbania and sicklepod) and leaf discs (kudzu and glyphosate-resistant Palmer amaranth) showed that the sector efficacy was generally equal to, or slightly lower than MV. Bioassays of MV and this sector on seed germination and early growth of sicklepod and hemp sesbania seeds demonstrated that hemp sesbania seeds were slightly more sensitive to the fungus than sicklepod seeds and that the sector bioherbicidal activity was slightly less than that of MV. SDS-PAGE protein profiles of cellular extracts of MV and the sector and their respective culture supernatants showed several differences with respect to quantity and number of certain protein bands. Overall results showed that the isolate was a non-spore producing mutant with phytotoxicity to several weed (including weeds tolerant or resistant to glyphosate), and that the phytotoxic effects were generally equivalent to those caused by MV treatment. This is the first report of a non-sporulating MV mutant that suggests additional studies on protein analysis, and an extended weed host range under greenhouse and field conditions in order to further evaluate its possible bioherbicidal potential.