Host plant genetic strains

Incorporate into plant varieties, perhaps through genetic engineering, specific antifungal genes expressed in the specific plant tissues, e. g. seed tissues contaminated by aflatoxigenic strains (a host-plant resistance approach), and... 

The nodules produced by different strains of bacteria may vary widely in their ability to fix nitrogen, and this is independent of the ability of the bacteria to enter the root and stimulate the host to produce nodules. This variation in effectiveness appears to be a genetic characteristic of the microorganisms but beyond this there is great uncertainty as to the basic causes for the failure of the host plant to produce normal effective nodules. 

There is considerable variation in the life cycles of different Epichloe species and in different host populations (White, 1988 Leuchtmann and Clay, 1997). In some species, stromata are formed invariably on all tillers of infected grass hosts, so that seed production is completely suppressed. This type of symbiosis represents the antagonistic extreme. Other species display both sexual and asexual cycles (balanced transmission) on different tillers of an infected plant, or on different subsets of individuals of a host population where seed transmission is often predominant. These associations are considered to be more mutualistic. In a third category, no stromata are formed on any of the infected plants, and seed transmission is the only means of dispersal. The latter group includes genetically distinct strains derived from sexual Epichloe spp. and all Neotyphodium species. 

Microbial enzymes produced by fermentation under controlled conditions constitute now the most relevant option for enzyme synthesis. Microbial strains can produce not only the enzyme proteins coded by their own genetic information, but also those produced by the expression of foreign genes as recombinant proteins. As analyzed before, microorganisms are ideal hosts for enzyme synthesis and only those glycoenzymes which cannot be properly produced in microbial hosts are to be produced in plant (Ma et al. 2003) or animal cell culture (Altamirano et al. 2004 Wurm 2004). 

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