Diversity of potential microbial parasites colonizing sclerotia of Macrophomina phaseolina in soil
1996
Srivastava, A.K. | Arora, D.K. | Gupta, S. | Pandey, R.R. | Lee, M.W.
The colonization of Macrophomina phaseolina sclerotia by microbial parasites was evaluated in unsterilized field soil at different levels of soil moisture (0, -5, and -10 kPa) and temperature (20, 30, and 40 degrees C). The maximum colonization of sclerotia was recorded in soil held at -5 or -10 kPa at 30-40 degrees C. Trichoderma harzianum isolate 25-92 and Pseudomonas fluorescens isolate 4-92 were recorded as potential sclerotial parasites, and they significantly (P=0.05) reduced the germination of sclerotia by 60-63%. Cells of P. fluorescens and buffer-washed conidia of T. harzianum were completely agglutinated at 28 degrees C with crude agglutinin of M. phaseolina. The ability of different antagonists to parasitize the sclerotia were correlated with the agglutination ability of the antagonists. The inhibition of soil-borne pathogens by biological control agents depends on the growth, competence, and ability of these agents to colonize the pathogens in soil. It is also essential to understand the recognition of pathogens by potential antagonists in order to formulate effective biocontrol disease management strategies (Barak et al. 1985; 1986; Barak and Chet 1990). Lectins are reported to be possible sites of recognition on pathogenic propagules which bind the carbohydrate component on the surface of the antagonist (Manocha and Sahai 1992). The objectives of the present study were to screen and select potential antagonists of M. phaseolina from field soil and to evaluate the effect of temperature and moisture on colonization of sclerotia by microbial parasites. The agglutination properties of some selected antagonists and their efficacy in suppressing the germination of sclerotia were also studied.
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