Comparison of fungal growth and production of extracellular pectin lyase activity by pathogenic and non-pathogenic races of Colletotrichum lindemuthianum cultivated under different conditions

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A comparison between pathogenic (1472) and non-pathogenic (0) races of Colletotrichum lindemuthianum revealed significant differences in terms of growth and production of extracellular pectin lyase activity on different carbon and nitrogen sources in liquid culture. Race 1472 grew faster in media containing glucose or polygalacturonic acid. On the latter, both races secreted comparable levels of pectin lyase activity but race 1472 produced approximately twice the amount of mycelia. On 92%-esterified pectin, race 1472 produced the highest activity detected in this study and this was about two-fold higher as compared with race 0. Cell walls isolated from Phaseolus vulgaris hypocotyls and to a lower degree cellulose sustained growth of both races but induced PNL only in the pathogenic race. On xylan, both races produced substantial and similar enzyme levels but this polysaccharide sustained growth of race 1472 only. Compared with race 1472, race 0 grew much slower on glutamate but produced similar amounts of mycelia in other nitrogen sources. On ammonium chloride, race 1472 produced a five-fold higher activity than race 0. Differences are discussed in terms of their possible relevance in fungal pathogenesis.