In vitro and in planta assays for biological control of Fusarium root rot disease of vanilla

Abstract

izosphere and phyllosphere organisms isolated from vanilla consisted of predominant colonizers such as Fusarium sp. (24 isolates) and Colletotrichum sp. (20 isolates). Other organisms were Rhizoctonia sp. (two isolates), Trichoderma spp. (seven isolates), Paecilomyces sp. (one isolate), Mucor sp. (three isolates), non-sporulating fungal species (10 isolates) and Pseudomonas fluorescens (three isolates). When tested in vitro, six isolates showed more than 50% inhibition of Fusarium oxysporum f. sp. vanillae. These were two isolates of Trichoderma sp. (53.30-70.58), one isolate of Paecilomyces sp. (65.00%) and two isolates of P. fluorescens (59.15- 62.50%) that were antagonistic to the pathogen. None of the non-pathogenic Fusarium species tested showed promising inhibitory effect on F. oxysporum f. sp. vanillae. The five promising isolates were tested in planta by challenge inoculation. Paecilomyces sp. provided 100 per cent protection against root rot. T. harzianum and P. fluorescens provided 40% protection. Thus the present study indicated the possibility of using Paecilomyces sp. as a potential antagonist for F. oxysporum f. sp. vanillae.