Antifungal properties exhibited by bacteria isolated from agriculturally cultivable soils and their antagonistic nature towards fungal phytopathogen suppression

Soil samples collected from rhizosphere soil, cultivable field soil, Rhizoplane soil of paddy plants and were used to isolate bacteria by culture methods of which thirty two bacterial cultures were identified with diverse colony characteristics on nutrient agar medium and biochemical characterization. Sixteen bacterial isolates were selected for screening fungal antagonism on PDA and were further tested against <italic>Fusarium</italic> and <italic>Rhizoctonia species.</italic> In this study, two <italic>Pseudomonas strains</italic> (RB15, RB30) and <italic>Bacillus cereus</italic> (RB13) were cyanogen producers. Both strains of <italic>Pseudomonas</italic> RB15 and RB30 and <italic>Bacillus cereus</italic> (RB13) were also siderophore producers. Only three isolates showed chitinolytic activity; <italic>Serratia marcesens (RB24), Bacillus cereus (RB13) and Enterobacter cancerogenus</italic> (RB17).

Fungal Antagonism Assessment of Predatory Species and Producers Metabolites and Their Effectiveness onHaemonchus contortusInfective Larvae

The objective of this study was to assess antagonism of nematophagous fungi and species producers metabolites and their effectiveness onHaemonchus contortusinfective larvae (L3). Assay A assesses the synergistic, additive, or antagonistic effect on the production of spores of fungal isolates of the speciesDuddingtonia flagrans,Clonostachys rosea,Trichoderma esau, andArthrobotrys musiformis; Assay B evaluates in vitro the effect of intercropping of these isolates grown in 2% water-agar (2% WA) on L3ofH. contortus.D. flagrans(Assay A) produced 5.3 × 106spores and associated withT. esau,A. musiformis, orC. roseareduced its production by 60.37, 45.28, and 49.05%, respectively.T. esauproduced 7.9 × 107conidia and associated withD. flagrans,A. musiformis, orC. roseareduced its production by 39.24, 82.27, and 96.96%, respectively.A. musiformisproduced 7.3 × 109spores and associated withD. flagrans,T. esau, orC. roseareduced its production by 99.98, 99.99, and 99.98%, respectively.C. roseaproduced 7.3 × 108conidia and associated withD. flagrans,T. esau, orA. musiformisreduced its production by 95.20, 96.84, and 93.56%, respectively. These results show evidence of antagonism in the production of spores between predators fungi.

The role of clp-regulated factors in antagonism against Magnaporthe poae and biological control of summer patch disease of Kentucky bluegrass by Lysobacter enzymogenes C3

A global regulator was previously identified in Lysobacter enzymogenes C3, which when mutated, resulted in strains that were greatly reduced in the expression of traits associated with fungal antagonism and devoid of biocontrol activity towards bipolaris leaf-spot of tall fescue and pythium damping-off of sugarbeet. A clp gene homologue belonging to the crp gene family was found to globally regulate enzyme production, antimicrobial activity, and biological control activity expressed by Lysobacter enzymogenes C3 (Kobayashi et al. 2005). Here, we report on the expansion of the biocontrol range of L. enzymogenes C3 to summer patch disease caused by Magnaporthe poae. The clp– mutant strain 5E4 was reduced in its ability to suppress summer patch disease compared with the wild-type strain C3 and was completely devoid of antifungal activity towards M. poae. Furthermore, cell suspensions of 5E4 were incapable of colonizing M. poae mycelium in a manner that was distinct for C3. Strain C3 demonstrated biosurfactant activity in cell suspensions and culture filtrates that was associated with absorption into the mycelium during the colonization process, whereas 5E4 did not. These results describe a novel interaction between bacteria and fungi that intimates a pathogenic relationship.Key words: lytic enzymes, biosurfactant, turfgrass biocontrol agent, mycopathogenic bacteria.