TITLE:
Effects of Myrothecium verrucaria on Two Glyphosate-Resistant Amaranthus palmeri Biotypes Differing in Betacyanin Content
AUTHORS:
Robert E. Hoagland, Clyde Douglas Boyette, Robin H. Jordan, Kenneth C. Stetina
KEYWORDS:
Betalain, Bioherbicide, Biological Weed Control, Palmer Amaranth, Pigweed
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.11 No.2,
February
21,
2020
ABSTRACT: Previously we found two biotypes of Amaranthus palmeri (Palmer amaranth) in a population of this economically important weed that were resistant to glyphosate but differed with
respect to pigmentation. One biotype was typically red-pigmented (betacyanin)
while the other was green, with no visual appearance of red hue on any plant
part at any growth stage. We have also reported that a strain of Myrothecium verrucaria (MV) exhibited bioherbicidal activity against several important weeds including
glyphosate-resistant Palmer amaranth. In greenhouse tests, MV was applied to these two biotypes (red and green) at two
ages (3-week- and 6-week-old) and effects of this fungus monitored over a 5-day
time course. Initial symptoms of MV (16 to 24 h after inoculation) were:
epinastic curvature, wilting and development of lesions on leaves and stems.
Generally, the younger plants tended to be more sensitive to MV than older
plants. Bioherbicidal damage increased with time leading to necrosis and plant
mortality and increasing disease progress. Severe loss of fresh weight occurred
in both biotypes as compared to untreated plants. Results indicated that
MV was effective on both biotypes, but effects on growth reduction and disease
progression were more rapid and generally greater in the green biotype, suggesting
that compounds responsible for red pigmentation may be more potent as defense
against pathogen attack.