AMF Community Diversity Promotes Grapevine Growth Parameters under High Black Foot Disease Pressure.

Romy Moukarzel,Alexis Guerin-Laguette,Hayley J. Ridgway,Jing Liu,E. Eirian Jones

doi:10.3390/jof8030250

Abstract

Black foot disease is one of the main grapevine root diseases observed worldwide and is especially problematic in New Zealand. Arbuscular mycorrhizal fungi (AMF) have been shown to reduce infection and mitigate the effect of black foot disease on grapevine rootstocks. In contrast to prior studies, which have limited their focus to the effect of one, two or a combination of only a small number of AMF species, this study used whole AMF communities identified from 101-14, 5C and Schwarzmann rootstocks sampled from New Zealand vineyards. The effect of AMF on black foot disease was investigated in a ‘home’ and ‘away’ experiment using three commercial grapevine rootstocks. The study produced some evidence that AMF treatments lowered disease incidence at 5 cm and disease severity in vines by 40% to 50% compared to the vines inoculated with the pathogen only. This work also showed that the presence of high disease incidence may have limited the potential disease protective effect of AMF community. However, despite the high disease incidence and severity, AMF inoculation increased vine growth parameters by 60% to 80% compared to the vines inoculated with the pathogen only. This study is the first to provide an understanding on how young grapevine rootstocks inoculated with their ‘home’ and ‘away’ AMF communities would respond to challenge with a black foot pathogen species mixture. Further research is required to understand the mechanistic effect of AMF colonization on the increase of grapevine growth parameters under high black foot disease pressure.

Highlights

Black foot disease has been commonly associated with soilborne Cylindrocarpon species, based on the recent taxonomic revision of the genus, the species associated with black foot disease of grapevines have been reclassified as either Dactylonectria or Ilyonectria, with several species defined within each group [1–3]
This study showed that disease incidence/severity was not associated with the decrease in growth parameters as seen in other studies [8] and could indicate that the experimental period was too short
This study showed that the high level of disease present in the rootstocks limited the effect of Arbuscular mycorrhizal fungi (AMF) community with only small evidence that AMF treatments lowered disease incidence and severity in vines

Summary

Introduction

Cultivated grapevine varieties are susceptible to diseases caused by fungal pathogens which can limit yield. The symptoms of black foot can be recognized by the development of black necrotic lesions on roots, and brown discoloration in the trunk base of the affected vines [6,7]. These pathogens can persist as resting spores or mycelium in infected root fragments in vineyard and nursery soils [6,8–10]. The black foot pathogens impact young grapevines during field establishment by infecting the root vascular tissues at the basal end of the rootstock contributing to poor growth or death of vines [11,12]. The severity and spread of black foot disease is enhanced by environmental stress, and while management practices can improve the performance of diseased grapevines, there are no proven methods to control or fully eradicate the disease from infected vineyards [6]

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