Eb. King et Jl. Parke, POPULATION-DENSITY OF THE BIOCONTROL AGENT BURKHOLDERIA-CEPACIA AMMDR1 ON 4 PEA CULTIVARS, Soil biology & biochemistry, 28(3), 1996, pp. 307-312
We determined if the biocontrol bacterial strain, Burkholderia cepacia
AMMDR1, introduced as a seed treatment, persisted on pea roots, and h
ow its presence affected populations of both indigenous B. cepacia and
total culturable aerobic bacteria in the rhizosphere. The experiment
was conducted with four pea cultivars to determine if bacterial popula
tions differed among cultivars. Total culturable aerobic bacteria, ind
igenous B. cepacia and introduced B. cepacia AMMDR1 were sampled from
root segments of each cultivar grown from either treated or non-treate
d seed at 1, 2, 4 and 6 wk after planting. The population density of t
he introduced strain did not differ significantly among cultivars, nor
was there a significant cultivar effect on total bacteria at three of
four sampling dates. Cultivars supported different numbers of indigen
ous B. cepacia only at 2 wk after planting. Introduction of the biocon
trol agent, which comprised 1-10% of the total bacteria on each date,
did not increase the total number of culturable aerobic bacteria on ro
ot segments in comparison to no treatment. The number of indigenous B.
cepacia on roots grown from non-treated seeds was similar to that of
the introduced strain by the end of the 6-wk growing season. These res
ults suggest that roots may have a Carrying capacity for bacteria in g
eneral, and also for a specific functional group or species such as B.
cepacia.