Metaboic profiles of grapevines infected with pseudocercospora vitis and agrobacterium vitis

Abstract

In this study, profilings of disease-related metabolites were assessed for characterizing two major grapevine diseases, leaf spot caused by Pseudocercospora vitis and crown gall caused by Agrobacterium vitis, respectively, for both of which GC-MS and multivariate data analysis were applied as the analytical instrumentation and statistical validation. For the leaf spot, a total of 20 metabolites were determined to have their relations with lesion symptoms and the periphery of the leaf spot symptoms, most of which were increased in their contents in the periphery of the symptoms compared with the necrotic lesions. For the crown gall, 13 metabolites increased significantly in relation to the response types, mostly at post-inoculation stages, more prevalently (8 metabolites) at two days after inoculation than other stages, and more related to the susceptible response type (SS) (7 metabolites) than resistant (RR) (3 metabolites) or moderately resistant (SR) (one metabolite) response type. This suggests that most of the disease-related metabolites may be induced by the pathogen infection largely for facilitating gall development except resveratrol, a phytoalexin involved in the resistance response (RR). A total of six metabolites were identified from the comparison of the metabolite profiling between the leaf tissues with and without leaf spot symptoms, including maltotriose, glucoheptonic acid and tartronic acid, a phenolic compound 1-hydroxyanthraquinone and two amino acids aspartic acid and L-threonine. This suggests these may be the disease-related metabolites occurring widely around the infection sites of the leaf tissues with the leaf spot. For the crown gall, most numerous metabolites related to the infection or wound significantly occurred at 2 days after inoculation (DAI) (post-1) (8 for infection in SS, 4 for wound in RR), second-most at 7 DAI (post-2) (3 for infection in SS, 6 and 1 for wounding in SS and RR, respectively), and least at 30 DAI (post-3) (all 3 for infection in RR or SR), suggesting that the responses to the pathogen infection mostly occur in the susceptible grapevines at post-1, and those to wounding (wound healing) occur earlier in the grapevines with RR than those with SS or SR. It also suggests the responses to wounding should be completed and no more wound-related metabolites are detected at post-3. All of the results suggest that plant resistance and wound healing responses are inter-related, enhancing the other responses to increase resistance to the pathogen infection and to speed up the wound healing processes. These disease characteristics revealed by metabolite profiling would provide valuable information and new insights on the understandings of the diseases so as to be used for the development of grapevine disease management strategies.