Three isolates of M. phaseolina, differing in their virulence, were included to study interaction on agar plates, competitive saprophytic ability, and tolerance to soil microorganisms.
Results for the interaction on agar plates with 6 fungi, R. solani. F. solani, F. moniliforme, Pythium sp. and S. rolfsii and T. roseum showed different inter¬actions among “M. phaseolina isolates and between iso¬lates and fungi. The virulent isolates of M. phaseolina were more inhibitory than weak isolates.
Studying competitive saprophytic ability (CSA) in¬dicated that the three isolates of M. phaseolina were able to colonize the inoculum-soil discs at all concen¬trations when the inoculum-soil discs were immediately plated on PDA medium. Colonization ratings gradually increased with increase in the amount of inoculant of the isolate in the inoculum-soil mixture. Percentage of colonization differed from one isolate to another; CAS increased with the increase in virulence of the isolate.
Using wastie cellophane method, showed that M. phaseolina did not tolerate soil microorganisms on soil-inoculated plates, when plates were inoculated 24 hrs. before placing the test isolates culture discs. While all isolates gave degree of tolerance to soil micro¬organisms, when the tested isolates culture discs were immediately transferred to the cellophane sheet above the site of soil inoculum.
When streaks of heated soil suspension (namely spore- forming bacteria) were placed opposite to culture discs, inhibition zones were generally wider when competing organisms from the streaks were allowed to grow 24 hour before placement of the disc, the virulent isolate was least sensitive. |
