Modulating the phyllosphere microbiome in grapevine using plant biostimulants to enhance protection against biotic and abiotic stress

Abstract

Context and purpose of the study. Climate change scenarios predict ever increasing frequency of drought events and coupled with disease outbreaks poses survival risks to perennial fruit crops such as grapevine. The combination of drought and disease is becoming more widely studied in grapevine research. The use of plant biostimulants is a promising approach as these naturally occurring compounds are non-toxic and are believed to be able to modify the leaf microbiome leading to enhanced plant health and immunity. The motivation of this study is to investigate if 1; plant biostimulants can alter the phyllosphere microbiome and 2; these changes result in enhanced plant health and immunity when challenged by the dual stressors of drought and Botrytis cinerea infection.

Material and methods. one-year-old potted grafted vines Cabernet Sauvignon in glasshouse conditions as a model testing system. The biostimulant solutions prepared was sprayed onto grapevine leaves Phyllosphere microbiome studies will involve using ARISA (automated method of ribosomal intergenic spacer analysis). Control and treated plants will be further divided into those experiencing water stress (due to withholding water) and those challenged with Botrytis cinerea inoculant. Botrytis cinerea will be tested with glycine betaine a major component of the biostimulant used.

Results. Botrytis cinerea grown on glycine betaine showed enhanced sporulation at higher concentrations. In general the glycine betaine had little effect in concentration ranges tested on the necrotrophy. Potted vines were tested using detached leaf disc assays and liquid culture assays for the effects of glycine betaine pre-treatment on grapevine response to infection. To date no difference in infection severity or progression is seen between the control and glycine betaine pre-treatment. ARISA analyses of grapevine leaves pre-treated with glycine betaine is being conducted for fungal and bacterial diversity. Plant biostimulant analyses are currently underway incorporating water deficit experiments and Botrytis cinerea challenge.