Physiologic studies on some entomogenous fungi

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Virginia Agricultural and Mechanical College and Polytechnic Institute

In view of the objects set forth in this thesis, and with analysis of the data obtained, a few points in conclusion may be taken as being reasonably true and evident.

On the basis of consistently different and respectively characteristic physiologic traits it appears that Beauveria B is distinct from Beauveria A, even though they are essentially similar in morphology and pathogenicity. Whether they are distinct species, or are strains of the same species is unsettled.

Physiologic characteristics popular to different species of closely related fungi may be used to supplement morphology and pathogenicity as criteria of classification and reidentification.

In the limited host range studies, the Beauveria species were most cosmopolitan in parasitism. The Entomophthora species were largely uninfective for the insects used and under the conditions obtained, possibly having been in culture so long as to loose virulence. Endosclerotium was highly specific for a single host, the mealy bug.

In this study of entomogenous fungi, embracing membrane of several representative groups, it does not appear that they can be characterized as a group apart from other fungi on the basis of physiology. They grow saphrophytically on a wide range of some 50 different proteins, sugars, nutrient solid media, and organic acids.

In contrasting the physiological characteristics of the slow growing E. saphaerosperma with the other two species of Entomophthora, it can be stated that consistently different physiologic results were correlated with the distinctly different morphology. Further, the near identical physiological behavior by E. apiculata and E. saphaerosperma, paralleled with essentially similar morphology, may prove that these two are one and the same species.

In the case of Endosclerotium, it may be observed that slow growth and cultural inflexibility seem to be correlated with extreme host specificity.

The liquefaction of gelatin and the peptinization of proteins indicate that the Entomophthora species produce proteinase enzymes in abundance.