Ampelomyces quisqualis Ces. A Novel Biocontrol Agent for Powdery Mildew
Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore – 3
Ampelomyces quisqualis Ces. is a naturally-occurring biocontrol agentthat protects crops from powdery mildew caused by several obligate pathogenic species like Erysiphe spp., Oidium spp., Blumeria spp.,Sphaerotheca spp., Leveillula spp, Microsphaera spp., Uncinula spp. It is used as an effective foliar spray to combat powdery mildew through hyper parasitism of the pathogenic disease causing fungi.
Ampelomyces quisqualis was first reported by Cesati and described as a hyperparasite of powdery mildew in 1870 by De Bary and in 1930 by Emmons. Yarwood in 1932 was the first to attempt using Ampelomyces quisqualis spore suspensions as a biocontrol for powdery mildew of Red clover caused by Erysiphae polygoni. Odintsova in 1975 obtained some control of apple powdery mildew caused by Podosphaera leucotricha. In 1977 Jarvis and Slingsby obtained control of greenhouse cucumber powdery mildew caused by Sphaerotheca fuliginea. Several researches are on to continuously assess the biocontrol activity of Ampelomyces quisqualis. It was called as Cicinnobolus cesatii byDe Bary which was claimed to be illegitimate by Rogers in 1959 who named the species as Ampelomyces quisqualis
- Competition for space and Nutrients: Ampelomyces quisqualis competes with the pathogens by colonizing a large area of the target site and competes for the plant substrates and nutrients thereby causing the pathogens to starve - Domino effect.
- Mycoparasitism: Ampelomyces quisqualis being a hyper parasite penetrates the pathogen and infects it by forming pycnidia (fruiting bodies) within powdery mildew hyphae, conidiophores (specialised spore-producing hyphae) and cleistothecia (closed fruiting bodies of powdery mildews). It derives nutrition from the target pathogenic fungus protoplasm and spores multiply inside target pathogenic fungus body and eventually kill the mildew colony.
- Enzyme production: Ampelomyces quisqualis produces certain enzymes which dissolve the host cell wall and penetrate and inactivate the host defense mechanism. Extracts of the fungal endophyte Ampelomyces quisqualis is known to produce 6 natural compounds that exhibit antagonistic properties to their host. They are macrosporin-7-O-sulfate, 3-O-methylalaternin-7-O-sulfate, ampelopyrone, desmethyldiaportinol, desmethyldichlorodiaportin and ampelanol