AMF community diversity identification and their effects on grapevine growth parameters under black foot disease pressure

Abstract

Arbuscular mycorrhizal fungi (AMF) have potentially significant applications for sustainable agricultural ecosystems. AMF have been also shown to reduce infection and mitigate the effect of black foot disease on grapevine rootstocks. However, limited information is available regarding AMF grapevine interactions worldwide and especially in New Zealand. Moreover, most studies to date have researched the effect of one, two or a combination of only a small number of AMF species on fungal pathogens associated with grapevines. Therefore, this work aimed to (i) characterise the AMF community diversity associated with different commercial grapevine rootstocks sampled from New Zealand vineyards, (ii) investigate the beneficial effect of AMF community on grapevine growth parameters, and (iii) evaluate how young grapevine rootstocks inoculated with their ‘home’ and ‘away’ whole AMF communities would respond to challenges with a black foot pathogen species mixture. The AMF communities identified from these rootstocks were assigned to Ambispora spp., Claroideoglomus spp., Funneliformis spp. and Glomus spp. The community analyses demonstrated that rootstock significantly influenced the AMF community composition in all sites. The findings of the second part of experiment showed that the AMF communities had a significant direct effect by increasing plant biomass and nutrient uptake and indirectly by influencing the chlorophyll content in grapevine leaves through the increase of specific nutrients such as K, Mn, and Zn. The outcome of the third part of experiment revealed that high disease incidence and severity did not reduce growth in vines with AMF inoculation compared to vines inoculated with the pathogen only. It also showed that the high level of disease present in rootstocks limited the effect of the AMF community with only little evidence that AMF treatments lowered disease incidence and severity in vines. Further research is required to understand the mechanistic effect of AMF colonisation on plant growth parameter especially under high disease pressure.