GENETIC-IMPROVEMENT OF FUNGI BY PROTOPLAST FUSION FOR BIOLOGICAL-CONTROL OF PLANT-PATHOGENS

Fungi are being developed in academe and industry for biocontrol of pathogens, weeds, insects, and nematodes. In many cases, limiting factors for commercialization of biocontrol fungi include inadequate production, formulation, and application technologies. For many fungi, however, genetic strain improvement is needed for the promise of biocontrol to be realized. Various techniques are now available for strain improvement; each has advantages and limitations. In this article techniques are compared briefly, and one, protoplast fusion, is discussed in detail. Typically, protoplast Tusion is used to initiate parasexual recombination between dissimilar nuclei. Recent work with Trichoderma has shown that protoplast fusion can be used to create phenotypic diversity, including strains with improved biocontrol capabilities. Surprisingly, parasexuality did not appear to account for the phenotypic diversity created in Trichoderma by protoplast fusion. Mechanisms other than parasexuality may operate in Trichoderma and in certain other fungal systems and may be exploitable for strain improvement.