Biodiversity of Plant Pathogenic Fungi - Kerala Forest Research ...

are divided into 20 sub-types and many further sub-divisions depending upon the floristic
composition. In the present study, eight forest ecosystems including forest nurseries were
selected for investigating the fungal diversity.
Most fungi consist of filaments (hyphae) that increase in length by the deposition of cell
wall material from a growing tip. As these tips expand and produce new growing points,
a network of mycelium develops. Once established, fungal mycelia are capable of
essentially unlimited growth and persistence. The mycelial nature of most fungi affects
the definition and interpretations of fungal diversity and makes the protocols and
assumptions used for estimating fungal biodiversity inherently different from those used
for plants and animals. To understand the limitations associated with estimations of
fungal biodiversity, one must consider methods for counting fungal units used for most
macro-organisms.
The level of cellular aggregations that fulfills the criterion for fungi and other
microorganisms, however, is not very clear. For example, isolates of a single species of
fungus obtained from an infected leaf at spatially disjunctive locations in the foliage may
represent the mycelium of a single individual or the mycelium of several individuals. As
a result, counting individual fungal colonies on an isolation plate, whether the isolate was
obtained from a 1 mm 2 piece of substratum does not represent the same information
obtained from counting plants or insects that occur within a defined area. Thus, one
cannot be sure if fungal isolates of a species from a single habitat have been obtained
from one individual or from several individuals. Although, the latter situation is
common, the former circumstance may also occur.
With these existing limitations, the present investigation focuses on the presence or
absence of a particular fungal species within an ecosystem in order to assess some aspects
of biodiversity. Species richness (Menhinick’s index (R2), Margalef’s index (R1)) and
species diversity indices (Simpson’s index, Shannon index (H’) ) of pathogenic fungi in
these different ecosystems were worked out and an overall picture is given in Table 3.
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