An investigation of the role of endogenous and exogenous bacteria in grapevine propagation and development

Abstract

There is a perception in the vine nursery industry that the HWT process sterilises both the surface and the wood of cuttings, but results from this research show clearly that many of the micro organisms associated with grapevines, particularly bacteria, are quite robust, not always killed by the high temperature of HWT and sometimes freely sporulating fungi are actually dispersed during the process. It is possible that micro organisms associated with grapevine cuttings may contribute either directly as opportunistic pathogens, or indirectly via toxic metabolites, to the poor performance or failure of cuttings or newly grafted vines, particularly if nursery conditions are stressful and favour the development of the micro organisms over the cuttings.

In this research, neither graft healing or root numbers were affected by HWT, but scion shoot growth was apparently promoted by HWT.

Recommendations from the research, and the experience of the authors, suggest that it would be prudent for nurseries to avoid the use of water in propagation, particularly if it is not treated to control water borne micro organisms. The practice of subjecting cuttings to a pre HWT hydration period should be abandoned, as should the practice of holding cut buds in water. Further commercial trials to assess the value of post HWT cooling of cuttings should be undertaken with a view to also abandoning this practice. It would also be prudent for nurseries to allow saturated cuttings to drain sufficiently to reduce surface moisture before placing them in cold storage to reduce the chances of the proliferation of epiphytic micro organisms.

Summary

Analysis of fungal and bacterial populations on cuttings and influence of nursery practice on surviving microorganisms.