Grape Days: Exploring root stock opportunities

At the Grape Days events, Solomon shared findings that Trichoderma has demonstrated ability to mitigate biotic and abiotic stresses, attaching themselves to roots to create a symbiotic relationship, with potential to mitigate the unpredictability of climate change-induced drought stress.

Solomon inoculated potted vines grown in two different Marlborough soils with Trichoderma then monitored drought stress, stomatal conductance, stem water potential, photosynthesis rates, and root biomass, under controlled conditions in a glasshouse at Lincoln University. The biggest finding was a consistent increase in route biomass in all replicates regardless of the irrigation method.

BRI Knowledge Transfer and Engagement Leader Braden Crosby continued the theme of climate change and applying less irrigation, sharing information on a rootstock project studying the influence of deficit irrigation on a 30-year-old repository of 11 different rootstocks at Pernod Ricard. The project was led by Yuichi Ando, with the help of Dr Mark Krasnow, of Thoughtful Viticulture, and Dr Stewart Field, a lecturer at Nelson Marlborough Institute of Technology (NMIT). “Understanding rootstock performance in a changing climate will be key to ensuring our plantings today are robust for future environments,” Braden said. “Investigating vine water usage and key performance metrics under a stress condition will hopefully lead to a wider array of genetic material planted for these future challenges.”

Central Otago Grape Days included a summary of the data gathered so far by Otago Polytechnic from the clonal repository in Central Otago, run in partnership with Riversun Nursery, which has 12 clones of Pinot Noir. Attendees also heard from BRI Research Winemaker Ngarita Warden on the wines produced from the trials. Mark Naismith, Vineyard Manager at Te Kano, said the Polytech and BRI clonal trial information was enlightening. “To see the clonal traits matching what most Central Otago growers would describe as anecdotal adds verifiable weight to good planning and design. The ongoing wine trials will certainly assist in discussion around desired wine styles and economics.”

Optimal hang time for Pinot quality

A trial comparing the impact of ‘hang time’ on red wine quality was also on the stage at Grape Days. Dr Damian Martin, Science Group Leader at Plant & Food Research’s Marlborough site, covered a 2021 collaboration between Plant & Food Research, a commercial Marlborough winery and NMIT, assessing grape sugar loading and harvest date implications for red winemaking.

Detailed Pinot Noir berry sampling was conducted to determine the end of sugar loading, with three successive harvests – nine, 21 and 28 days after sugar loading – undertaken in the same Marlborough Pinot Noir block. “Sugar loading occurs from berry softening to maximum berry size – about 22 brix – and is reliant on photosynthesis and osmotic potential gradients,” Damian says. “Hang-time is the period from the end of sugar loading until harvest and involves berry dehydration and cell death, so has nothing to do with photosynthesis. You need fast sugar loading to allow enough hang-time for good things to happen before the berry’s ‘use-by’ date expires.”

Both commercial scale ferments and replicated small-scale wines were made, and overall quality, typicality, concentration, body, sweetness, and flavour intensity were rated lowest in the first pick, but not different between the second and third. Astringency was highest in the third pick, while the 21st day pick was softest. Wine anthocyanins were 50% higher in the early pick, while total phenolics were not different between picking dates, Damian said. “Our results indicate that the optimal picking date for Marlborough Pinot Noir in 2021 was about 21 days post sugar loading.”