ANTAGONISTIC INTERACTIONS BETWEEN FUNGAL PATHOGENS AND PHYLLOPLANE FUNGI OF GUAVA

Dominant phylloplane fungi of guava (Psidium guajava L.) were screened for their antagonistic activities against the two pathogens, Colletotrichum gloeosporioides and Pestalotia psidii, both in vitro and in vivo. Culture filtrates of Aspergillus niger, Fusarium oxysporum and Penicillium citrinum caused more than 50% growth inhibition of C. gloeosporioides. Filtrates of Cephalosporium roseo-griseum and F. oxysporum were most effective in reducing the growth of P. psidii. Volatiles produced from the cultures of A. niger, F. oxysporum, P. citrinum and P. oxalicum inhibited the growth of C. gloeosporioides, whereas volatiles from C. roseo-griseum, F. oxysporum and Trichoderma harzianum inhibited the growth of P. psidii. The inhibitory effect of volatiles decreased with increase in incubation time. In general, the maximum effect of volatiles was noticed after 48 h incubation. Different grades of colony interactions in dual cultures were recognised between the two pathogens and the phylloplane fungi examined. Maximum inhibition of C. gloeosporioides was caused by Aureobasidium pullulans, Cladosporium cladosporioides, epicoccum purpurascens, F. oxysporum and Myrothecium roridum, whereas Aspergillus terreus, C. roseo-griseum and P. oxalicum significantly reduced the growth of P. psidii. Application of a spore suspension of each test fungus inhibited lesion development of guava leaves caused by the test pathogens in vitro. Inhibition was more pronounced when the spore concentration was increased. A, pullulans, C. cladosporioides, E. purpurascens, F. oxysporum, and T. harzianum were found to be strongly antagonistic to C. gloeosporioides. A. niger, A. terreus, C. roseo-grisem and T. harzianum were strongly antagonistic to P. psidii.