Effects of Pisum sativum L. (Rutales: Fabaceae) surface wax bloom on the efficacy of the fungal pathogen Pandora neoaphidis (Remaudière and Hennebert) Humber (Entomophthorales: Entomophthoraceae) to Acyrthosiphon pisum Harris (Homoptera: Aphididae) were investigated. In the field, observational data show that a higher proportion of P. neoaphidis-killed A. pisum is produced on a reduced wax bloom P. sativum isoline as compared with the normal wax bloom sister line. Individual plant bioassays confirmed the pattern observed in the field. After uniform inoculations, P. neoaphidis killed more A. pisum on P. sativum with reduced as compared to normal surface wax. This suggests that differential infection results from interactions between waxes on the plant surface and P. neoaphidis. Additional experiments demonstrated increased adhesion by conidia to upper leaf surfaces of the reduced as compared to normal wax bloom isoline. Further, conidial germination was increased on upper leaf surfaces of the reduced as compared to normal wax bloom isoline. There was no effect of wax type, or load, on conidial germination upon an amorphous layer of surface wax extract. Together, results show that the plant surface is an important parameter, exerting both direct and indirect influence on the infection dynamic between this entomopathogenic fungus and its aphid host.
Species 1: Entomophthorales Entomophthoraceae Pandora neoaphidis
Species 2: Homoptera Aphididae Acyrthosiphon pisum (pea aphid)
Species 3: Rutales Fabaceae Pisum sativum (pea)
Keywords: tritrophic interactions, extrinsic resistance
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