Eb. King et Jl. Parke, BIOCONTROL OF APHANOMYCES ROOT-ROT AND PYTHIUM DAMPING-OFF BY PSEUDOMONAS-CEPACIA AMMD ON 4 PEA CULTIVARS, Plant disease, 77(12), 1993, pp. 1185-1188
Pseudomonas cepacia strain AMMD applied as a seed treatment has been u
sed for biocontrol of Pythium damping-off and Aphanomyces root rot of
peas. We tested the biocontrol efficacy of this strain on four pea cul
tivars that differed in susceptibility to Aphanomyces root rot. In 199
0 and 1991, seedling emergence, Aphanomyces root rot severity, and pea
yield of biocontrol-treated and nontreated controls were compared in
a field naturally infested with Pythium spp. and Aphanomyces euteiches
f. sp. pisi. In 1991, the experiment also was conducted in an adjacen
t field with no history of pea cropping to evaluate the effect of the
biocontrol agent in the absence of Aphanomyces root rot. Biocontrol ef
ficacy was not limited to a single cultivar. Differential effects of b
iocontrol among cultivars were clearly related to the degree of suscep
tibility of each cultivar to Pythium and Aphanomyces. Seed treatment w
ith P. cepacia AMMD significantly improved emergence of all four culti
vars when disease was severe and improved emergence of two cultivars w
hen disease was moderate. P. cepacia AMMD did not reduce symptoms of A
phanomyces root rot in either year. Bacterial seed treatment increased
yield of three cultivars in the infested field in 1990 when compared
with no treatment but did not increase yield of any of the cultivars i
n the same field in 1991. Bacterial seed treatment increased yield of
one cultivar in the noninfested field. A metalaxyl seed treatment incl
uded in experiments in 1991 to control Pythium increased both emergenc
e and yield.