Statistical modeling of long-term grapevine response to ‘Candidatus Phytoplasma solani’ infection in the field

Abstract

Bois noir (BN) is the most widespread European grapevine yellows disease caused by 'Candidatus Phytoplasma solani'. Although our knowledge of the mechanisms of interactions of this pathogenic bacteria with host is largely unknown, the plant-pathogen system of BN is commonly used as a model system for studying grapevine yellows diseases. We applied here a conceptual model of general plant pathology -a disease triangle for describing interactions among the host plant, the pathogen and the environment. We generated a proofof-concept statistical model for disease triangle using original experimental data and different statistical and data mining approaches for a selected system of 'Ca. P. solani' infection of cv. 'Chardonnay' grapevine plants. We monitored individual plants from a single vineyard over a period of six years. Phytoplasma content, the expression of 21 selected grapevine genes and environmental conditions were recorded and related to disease severity. Our model predicts that in described conditions BN is a function of the expression of grapevine gene VvDMR6, summer rainfall and abundance of 'Ca. P. solani'. The greatest impact among elements of the disease triangle is attributed to the pathogen, and is independent of the pathogen titer. We showed that this first de facto representation of the disease triangle is useful for showing disease dynamics over several years and could be applied to other plant-pathogen systems. The overall results of this study will contribute to understanding of 'Ca. P. solani' biology and its interactions with grapevine host.

Spatial pattern of Bois noir: case study of a delicate balance between disease progression and recovery

“…For the persistence of symptoms, it is worth noting that only a few of the grapevines persistently showed symptoms, in agreement with Rott et al 47 ; hence, the sanitary status of vineyards infected by BN can be interpreted as a dynamic situation. After the two BN epidemic years (2010, 2011), in 2012 there was initially an increment in symptom remission that was related to the temporary recovered grapevines (tRec; with 1-2 years of recovery).…”

miRVIT: A Novel miRNA Database and Its Application to Uncover Vitis Responses to Flavescence dorée Infection

“…The downregulation of AGO2 here reported in FD condition ( Figure 4 ) could suggest that phytoplasma-infected plants may be more susceptible to virus infection compared to healthy ones. This hypothesis was not confirmed in BNp infected plants, where the presence of phytoplasma did not influence the virus infection ( Rotter et al, 2018 ). However, considering the above-reported differences in molecular and metabolic responses between plants infected by BNp and FDp, we cannot exclude that FDp-infected plants are more sensitive to virus attack, thus opening the venue for future research studies specifically addressed to explore this response.…”

Plant Hormones in Phytoplasma Infected Plants

“…Salicylic acid studies have revealed that several salicylate biosynthetic genes are up-regulated in the midribs or whole leaves of grapevine infected with the phytoplasma ‘ Ca . P. solani’, e.g., VvICS , which encodes isochorismate synthase, and VvSamt , which encodes S-adenosyl-L-methionine: salicylic acid carboxyl methyltransferase, which catalyzes the formation of the volatile ester methyl salicylate from SA (Hren et al, 2009; Dermastia et al, 2015; Paolacci et al, 2017; Rotter et al, 2018). In addition, quantification of SA and its conjugates in the main leaf veins during infections of grapevine with ‘ Ca .…”