The role of diamondback moth cuticle surface compounds in pre-penetration growth of the entomopathogen Isaria fumosoroseus

Abstract

Transcript patterns elicited in response to hosts can reveal how fungi recognize suitable hosts and the mechanisms involved in pathogenicity. These patterns could be fashioned by recognition of host-specific topographical features or by chemical components displayed or released by the host. We investigated this in three isolates of Isaria fumosoroseus which has shown considerable pathogenic ability against Plutella xylostella. Conidia inoculated to hind wings had the highest germination ability while the conidia inoculated to head regions showed the lowest germination. Conidia applied to diamondback moth wings showed slightly lower rates of germination than those incubated on SDA. Although I. funosoroseus isolates germinated well on crude methanol extracts, only low levels of germination occurred on hexane and dichloromethane extracts. Similarly, poor germination was also observed on diamondback moth hind wing from which cuticular lipids were extracted by using methanol when compared to the untreated hind wings showing that simple polar compounds are required to stimulate germination before the fungus can make effective use of a complex mixture of non-polar lipids. Such studies could address the origin of intraspecies differences and correlate these differences with the underlying metabolic and biosynthetic differences that define different host ranges.