Abstract:
Diplodia pinea (= Sphaeropsis sapinea) is an
endophytic fungus and opportunistic canker pathogen of
Pinus spp. The diversity of this fungus has been studied at
broad geographic scales, but little is known regarding its
population structure at smaller spatial scales such as within
a single tree. This is despite the importance that diversity in
a single tree might hold for understanding the biology of
the fungus, especially the role of the endophytic or
asymptomatic phase in disease development. Moreover
there was not information regarding the distribution of the
fungus within healthy trees and its persistence. The
genotypic diversity of these isolates was investigated using
microsatellite markers. Five polymorphic markers were
developed and these were used together with eight
previously developed markers and vegetative compatibility
tests to study the genotypic diversity of D. pinea isolates. In
this study, D. pinea was isolated for the first time in the
well structured stems of healthy P. patula trees along with
branches and cones. From a total of 44 isolates collected
from five trees, 39 microsatellite haplotypes and 32
vegetative compatibility groups (VCG’s) were identified.
The results indicate high genotypic diversity of D. pinea
within individual asymptomatic trees which will lead to
disease outbreak when trees are physiologically stressed.
