The effect of resistance to mildew infection on ruminal fermentation of Lolium perenne

In the field, resistance to microbial pathogens increases crop yield.
The work described here was designed to investigate whether the priming
of endogenous anti-microbial defence responses associated with
resistance mechanisms could affect subsequent utilization by the rumen
micro-organisms during colonization and fermentation of the ingested
fresh forage. The non-discriminatory approach Fourier Transform
Infra-Red Spectroscopy (FTIR) was used to profile the entire metabolome
generated during in vitro fermentation of Lolium perenne leaves which
had been previously infected with an avirulent mildew, thus generating
localized lesions of plant-cell death as part of the Hypersensitive
Response defence reaction. Regardless of mildew exposure there was an
effect of incubation time on metabolic profile, with separation becoming
more obvious with increasing fermentation time. Within these individual
timepoints, inoculation with mildew was also seen to affect the
metabolic profile with the profiles of uninfected (control) leaves
clustering away from infected leaves at later timepoints. We therefore
propose that pre-exposure of grass to infection by avirulent mildew
elicits plant defence responses that modify subsequent colonization by
the rumen microbial population. The consequences of this for
fermentation efficiency are currently being assessed.