Aim Arbuscular mycorrhizal fungi (AMF) are often regarded as non-specific symbionts, but some AMF communities show host preference in various ecosystems including vineyards. Grapevine plants are very responsive to AMF colonisation. Although these fungi have potentially significant applications for sustainable agricultural ecosystems, there is a gap in knowledge regarding AMF-grapevine interactions worldwide and especially in New Zealand. This study focused on identifying AMF taxa colonising grapevines in New Zealand vineyards and investigated the effect of grapevine rootstocks on AMF community diversity and composition. Method and Results Denaturing gradient gel electrophoresis (DGGE) and trap cultures were used to characterise the AMF communities. Grapevine roots from three vineyards and 9 rootstocks were analysed by DGGE and used in trap cultures for AMF recovery. Trap cultures allowed the recovery of six AMF spore morphotypes that belonged to Ambispora sp., Claroideoglomus sp., Funneliformis sp., and Glomus spp. Bands excised, reamplified and sequenced from the DGGE were assigned to Glomus spp., Rhizophagus spp. and Claroideoglomus spp. The AMF community analyses demonstrated that rootstock significantly (p <0.05) influenced the AMF community composition in all sites. Conclusions The study showed that for a comprehensive identification of AMF both results from trap culture and molecular work were needed and that the rootstock cultivar was the main driver of the arbuscular mycorrhizal community colonising the roots. Significance and impact of the study This study provides a firm foundation for future research exploring the beneficial use of AMF in enhancing grapevine production and sustainability.

Introduction: The increase of temperature due to climate change at different phenological stages of grapevine has already been demonstrated to affect accumulation of primary and secondary metabolites in grape berries. This has a significant implication for Pinot noir especially in New Zealand context as these compounds can have direct and indirect effects on wine quality. Methods: This study investigates how varying bunch microclimate through changes in temperature applied at veraison stage can affect: fresh weight, total soluble solids, the accumulation of anthocyanins, total phenolics and amino acids of the grape berries. This was studied over two growing seasons (2018/19 and 2019/20) with Pinot noir vines being grown at two different temperatures in controlled environment (CE) chambers. The vines were exposed to 800 µmol/m2/s irradiance with diurnal changes in day (22°C or 30°C) and night (15°C) temperatures. This experimental set up enabled us to determine the accumulation of these metabolite at harvest (both seasons) and throughout berry development (second season). Results and discussion: The results showed that berry weight was not influenced by temperature increase. The total soluble solids (TSS) were significantly increased at 30°C, however, this was not at the expense of berry weight (i.e., water loss). Anthocyanin content was reduced at higher temperature in the first season but there was no change in phenolic content in response to temperature treatments in either season. The concentrations of total amino acids at harvest increased in response to the higher temperature in the second season only. In addition, in the time course analysis of the second season, the accumulation of amino acids was increased at mid-ripening and ripening stage with the increased temperature. Significant qualitative changes in amino acid composition specifically the α-ketoglutarate family (i.e., glutamine, arginine, and proline) were found between the two temperatures. Significance: This study is the first to provide detailed analysis and quantification of individual amino acids and phenolics in Pinot noir in response to changes in temperature applied at veraison which could aid to develop adaptation strategies for viticulture in the future.

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.

Arbuscular mycorrhizal fungi (AMF) establish symbiotic interactions with the roots of vascular plants, including grapevines. Verifying AMF colonisation routinely requires establishing the presence of hyphae, arbuscules and vesicles. Clearing roots with potassium hydroxide (KOH) followed by staining with trypan blue has been used previously to visualise fungal structures, however visualisation is difficult with darkly pigmented roots, such as those of grapevines so additional steps are required to ensure clear visualisation. Three fixing and clearing processes were evaluated prior to staining with trypan blue: 1) fixing grapevine roots in 70% v/v ethanol overnight; 2) clearing by heating the roots in either 2% or 10% w/v KOH; and 3) clearing the roots in 3% v/v hydrogen peroxide for 10 min. Roots were examined under a compound light microscope for the presence of AMF. A combination of fixing grapevine roots in 70% ethanol overnight and clearing by autoclaving in 10% KOH produced the greatest enhancement in subsequent staining of grapevine roots with trypan blue overnight. The best method tested enabled the discrimination of arbuscular mycorrhizal structures in fresh roots of grapevines without the use of toxic chemical fixatives.

Aims: Arbuscular mycorrhizal fungi (AMF) can perform significant functions within sustainable agricultural ecosystems, including vineyards. Increased AMF diversity can be beneficial in promoting plant growth and increasing resilience to environmental changes. To effectively utilize AMF communities and their benefits in vineyard ecosystems, a better understanding of how management systems influence AMF community composition is needed. Moreover, it is unknown whether AMF communities in organically managed vineyards are distinct from those in conventionally managed vineyards. Methods and Results: In this study, vineyards were surveyed across the Marlborough region, New Zealand to identify the AMF communities colonizing the roots of different rootstocks grafted with Sauvignon Blanc and Pinot Noir in both conventional and organic systems. The AMF communities were identified based on spores isolated from trap cultures established with the collected grapevine roots, and by next-generation sequencing technologies (Illumina MiSeq). The identified AMF species/genera belonged to Glomeraceae, Entrophosporaceae, and Diversisporaceae. The results revealed a significant difference in AMF community composition between rootstocks and in their interaction with management systems. Conclusions: These outcomes indicated that vineyard management systems influence AMF recruitment by rootstocks and some rootstocks may therefore be more suited to organic systems due to the AMF communities they support. This could provide an increased benefit to organic systems by supporting higher biodiversity.