Biocontrol of seedborne Botrytis cinerea in chickpea with Gliocladium roseum

An isolate of Gliocladium roseum proved highly antagonistic to Botrytis cinerea. Sporulation of B. cinerea on chickpea seed naturally infected or inoculated with B. cinerea was suppressed by seed treatment with conidial suspensions of G. roseum at 10(7) and 10(8) conidia/mL, respectively. Establishment of healthy seedlings in punnets (small trays) 5 weeks after sowing with inoculated seed was increased from 29.2% to 59.7% by treatment with G. roseum at 3 x 10(7) conidia/mL, and from 1.4% to 69.4% with G. roseum at 3 x 10(8) conidia/mL, the latter being equivalent to disease control by Thiram. There was no significant effect of Rhizobium on disease suppression by G. roseum, and treatment with G. roseum at 10(8) conidia/mL did not reduce nodulation. Amendment with culture filtrates of G. roseum did not affect the growth rate of B. cinerea on potato dextrose agar, indicating that constitutive production of an antibiotic is not involved in biocontrol. A selective medium was developed to enumerate propagules of G. roseum on seed recovered from soil. There was no significant change in the population of G. roseum on seed after incubation for 4 weeks in soil to which the isolate of G. roseum was indigenous.