Inhibitory effect and mechanism of Streptomyces venezuelaevar RL-2 active products on plant pathogenic fungi Antagonistic mechanism of Pseudomonas fluorescens strains against Phytophthora nicotianae and biocontrol effect on tobacco black shank Antagonistic effect of biocontrol fungus, Paecilomyces lilacinus strain NH-PL-03 and its mechanism against Fusarium oxysporum Antagonism and mechanism of action of Trichoderma aureoviride against Pythium aphanidermatum causing turfgrass root rot Antagonistic mechanisms of Trichoderma spp. againstPhytophthora nicotianae