Microbial life in the grapevine: what can we expect from the leaf microbiome?

Abstract

The above-ground parts of plants, which constitute the phyllosphere, have long been considered devoid of bacteria and fungi, at least in their internal tissues and microbial presence there was long considered a sign of disease. However, recent studies have shown that plants harbour complex bacterial communities, the so-called “microbiome”[1]. We are only beginning to unravel the origin of these bacterial plant inhabitants, their community structure and their roles, which in analogy to the gut microbiome, are likely to be of essential nature. Among their multifaceted metabolic possibilities, bacteria have been recently demonstrated to emit a wide range of volatile organic compounds (VOCs), which can greatly impact the growth and development of both the plant and its disease-causing agents. In particular, these VOCs have been shown to promote root growth and thereby nutrient acquisition and growth, but also to induce plant resistance against diseases [2-4]. Their effects on fungal and oomycete pathogens range from mycelium growth reduction to inhibition of sporulation, zoospore release and even death, although much of these reports are based on experiments performed in controlled laboratory conditions with model plants [5]. Preliminary experiments indicate that these VOCs could also confer protection against oomycete pathogens grown in planta [6]. This presentation will summarize the present state of knowledge in both fields of research, the phyllosphere microbiome and the bacterial emission of VOCs, and highlight the potential these new fields offer for sustainable viticulture.

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