Tk. Jana et al., Agglutination potential of Pseudomonas fluorescens in relation to energy stress and colonization of Macrophomina phaseolina, SOIL BIOL B, 32(4), 2000, pp. 511-519
Agglutination potential of 172 isolates of Pseudomonas fluorescens, isolate
d from the rhizosphere soil of chickpea plants, was evaluated in crude aggl
utinin (CA) of Macrophomina phaseolina and on sclerotia and hyphae surfaces
. Eighteen such isolates varied significantly in their agglutination potent
ial (10-73%). Isolates 12 (Agg(+)) and 30 (Agg(1)) showed maximum (73%) and
minimum (10%) agglutination, respectively. Total loss of endogenous C rese
rve did not differ significantly (P = 0.05) from sclerotia incubated with A
gg(+), Agg(1) or Agg(-) (a non-agglutinable Tn5 mutant of wild type 12). Mo
st of the C lost from stressed sclerotia was evolved as (CO2)-C-14 (40%), w
hereas 5% C was lost in the form of sclerotial exudate (residual C). The to
tal C loss was in the order: Agg(+) > Agg(1) > Agg(-) > unsterilized soil.
Germination of sclerotia incubated with Agg(+), Agg(1), Agg(-) cells or in
soil was suppressed both in the presence or absence of C source and such sc
lerotia retained a greater portion of their viability even after 60 d. Loss
of C from the sclerotia incubated with isolates of P. fluorescens was dire
ctly correlated with germination repression (r = -0.89 to - 0.96; P = 0.05)
. Greater colonization of sclerotia by Agg(+) was observed compared to Agg(
1) or Agg(-) isolates. Our findings clearly demonstrate the existence of a
great diversity of P. fluorescens isolates in natural soils in respect to t
heir agglutination potential on M. phaseolina sclerotia. Irrespective of th
e agglutination potential of isolates, they can invariably impose energy st
ress on sclerotia resulting in accelerated loss of C and also elevating the
nutrient requirement for sclerotia germination. (C) 2000 Elsevier Science
Ltd. All rights reserved.