Evaluation of an indirect method for leaf area index determination in the vineyard: Combined effects of cultivar, year and training system

The performance of the plant canopy analyzer LAI-2000 was evaluated in three seasons to estimate vineyard LAI (leafarea index) in the Bordeaux area. Measurements were made in a vertical-trellised vineyard with 5555 Semillon and Sauvignon blanc vines per ha, and with 2525 lyre-trained Cabernet franc vines per ha. Various LAI-2000 sampling protocols were tested and the data compared with destructive determinations. While the results from single vines a ere not satisfactory, very good relationships were obtained if five consecutive vines were used. In the vertical-trellised vineyard, a very accurate and direct estimate of LAI could be obtained with the LAI-2000 using a combination of "parallel" and "diagonal" sampling protocol. LAI values obtained by direct and LAI-2000 had a 1:1 correspondence and were identical for both, year and cultivar. For the lyre system, a local calibration was required, mainly because of the contribution of shoots, perennial vine parts and posts. This calibration was easily obtained by progressively removing leaves from the vines

The The use of GFV and GSR temperature-based models in emerging wine regions to help decision-making regarding choices in grape varieties and wine styles. Application to Brittany (France)

Viticulture and wine production are facing climate change. While it can be a challenge in some regions, it is an opportunity for others. The aim of this study is to develop a methodology to assess climatic characteristics and potential for viticulture of new areas, through spatial analyses of data from temperature-based grapevine models (the Grapevine Flowering Veraison model -GFV and the Grapevine Sugar Ripeness model -GSR) during current and future periods. A deadline for veraison was set on the 1st of September for dry wine and on the 15th of September for sparkling wine. Different sugar levels were targeted for the production of different wine styles (170 g·L-1 for sparkling wine, 190 g·L-1 and 200 g·L-1 dry white and red wines, respectively) on the 15th of October. The methodology was applied over the region of Brittany (France) to assess the potential to produce different wine styles from 6 grapevine varieties (‘Sauvignon blanc’, ‘Chardonnay’, ‘Chenin’, ‘Pinot noir’, ‘Cabernet franc’ and ‘Cabernet-Sauvignon’). Observed data from the Météo-France weather stations network and an 8-km gridded climate model data from the 2014 EUROCORDEX simulation set (CNRM-CM5/RCA4 climate model) were used over the past (1950-2020) and future periods (2031-2060 and 2071-2100) under two GHG emission scenarios (RCP 4.5 and 8.5). Climatic conditions of this region seem to be increasingly suitable in the future depending on climate scenario, time period projections and targeted types of wine. The methodology can be applied to any emerging winegrowing region with the ability to adjust variety choices, time lines and sugar levels thresholds as desired to meet the needs of a specific region

Viticulture in a changing climate: solutions exist

Grape growers have always cultivated vineyards in challenging environments, adapting their practices to sometimes very difficult local conditions. Climate change, as a new player, is modifying the terroirs’ characteristics rapidly and irremediably, giving viticulturalists major new challenges to face

Estimation de la capacité photoautotrophique de vitroplants de porte-greffe de vigne (var. Gravesac): mise au point d'un système de mesure de la photosynthèse nette de vitroplants

La capacité photosynthétique de vitroplants de vigne (var. Gravesac) a été déterminée à l'aide d'un dispositif de mesures des échanges gazeux en circuit ouvert. L'activité photosynthétique et la respiration de la plante sont importantes en culture in vitro. La photosynthèse nette maximale est de 2 µmol m-2 s-1 a 500 µ11-1 de CO2. A 350 µ11-1 de CO2 la photosynthèse est de 1,6 µmol m-2 s-1. La respiration a l'obscurité est de 0,018 µmol s-1 g-1 de poids sec total. La quantité totale des sucres solubles dans le milieu de culture reste constante pendant les deux mois de culture. Le saccharose est totalement hydrolysé en glucose et en fructose. Les vitroplants de Gravesac ne prélèvent pas de sucres dans le milieu, ce qui confirme leur degré élevé d'autotrophie dans ces conditions de culture. La comparaison entre les échanges gazeux de vitroplants et des plantes cultivées en serre met en évidence une réduction de 80% de l'activité in vitro.Evaluation of the photoautotrophic ability of Vitis plantlets (rootstock var Gravesac): Set-up of a special open flow gas exchange systemThe photosynthetic ability of Vitis rootstock plantlets (var. Gravesac) was estimated in vitro with an open flow system specially designed for in vitro culture. CO2 response curves were established and respiration was also measured. The maximum net photosynthetic rate, reached at 500 µ11-1 of CO2, is 2 µmol m-2 s-1. At 350 µ11-1 CO2 the photosynthetic activity is 1.6 µmol m-2 s-1. The dark respiration rate is 0.018 µmol s-1 g-1 of total dry weight. The total amount of soluble carbohydrates in the medium remains the same whether plantlets were present or not. In the medium with plantlets, the sucrose is entirely hydrolysed in glucose and fructose within two months. No carbohydrate uptake from the medium was recorded indicating an autotrophic behaviour. Measurements of CO2 exchange were also performed at leaves of plants cultivated in a greenhouse. The photosynthetic activity of in vitro plants accounts only for 20% of the level of greenhouse-grown plants

Evaluation of criteria to assist the selection of good quality grafted grapevines prior to their commercialisation

The production of grafted grapevine plant material is a complex process with many steps running over at least one year, from grafting to final sorting in nurseries. To reach the market in France, grafted grapevines must meet three criteria by law: resistance to a manual graft union test (or thumb test), a minimum number of three roots and a woody, lignified stem which has grown from the bud of the scion wood of at least 2 cm long. This study aimed to evaluate the possibility of using visual criteria to select good quality grafted grapevines, without the need to do the thumb test because the thumb test is manual and therefore very subjective; the test depends on the strength applied by the person who realises it. This study was done on 22 scion/rootstock combinations with different degrees of grafting success, i.e., producing different proportions of marketable plants after one year in the nursery. The three legal criteria currently used to select marketable grafted grapevines in France as well as other external and measurable criteria such as the length of lignified stem and diameter, the number of thin and thick roots, and rootstock wood diameter were measured on the 22 scion/rootstock combinations. Variation in the values for these different criteria was observed and correlations between the criteria and the number of marketable plants were studied. This data was then analysed to determine which visible criteria contribute most to identifying marketable grafts. The percentage of marketable grafts was most strongly correlated with the thumb test and positively correlated with the length of the lignified stem. The variables with the highest predictive effect for identifying marketable plants (other than the thumb test) were the number of large roots and the length of the lignified stem. The possibility of using visible criteria to screen for good quality grafted plants is discussed, but no single, or combination of criteria, was sufficiently strongly correlated with the percentage of marketable plants to replace the thumb test

Horticulture Research

Soil microbiota has increasingly been shown to play an integral role in viticulture resilience. The emergence of new metagenomic and culturomic technologies has led to significant advances in the study of microbial biodiversity. In the agricultural sector, soil and plant microbiomes have been found to significantly improve resistance to environmental stressors and diseases, as well as influencing crop yields and fruit quality thus improving sustainability under shifting environments. Grapevines are usually cultivated as a scion grafted on rootstocks, which are selected according to pedoclimatic conditions and cultural practices, known as terroir. The rootstock connects the surrounding soil to the vine’s aerial part and impacts scion growth and berry quality. Understanding rootstock and soil microbiome dynamics is a relevant and important field of study, which may be critical to improve viticulture sustainability and resilience. This review aims to highlight the relationship between grapevine roots and telluric microbiota diversity and activity. In addition, this review explores the concept of core microbiome regarding potential applications of soil microbiome engineering with the goal of enhancing grapevine adaptation to biotic and abiotic stress

A muscadine locus confers resistance to predominant species of grapevine root-knot nematodes (Meloidogyne spp.) including virulent populations

Root-knot nematodes (RKNs) Meloidogyne spp. are extremely polyphagous pests and four species severely affect grapevines throughout the world: M. arenaria, M. incognita, M. javanica and M. ethiopica. Californian populations of M. arenaria and M. incognita are reported to be virulent to widely used rootstocks and to the rootstock ‘Harmony’ in particular. Breeding RKNs-resistant grape rootstocks is a promising alternative to highly toxic nematicides. Muscadine (Vitis rotundifolia syn. Muscadinia rotundifolia) is a resistance (R) source with undercharacterised genetics. To this end, we used a segregating progeny between the RKN-resistant Vitis x Muscadinia accession ‘VRH8771’ from the muscadine source ‘NC184-4’ and the RKN-susceptible V. vinifera cv. Cabernet-Sauvignon. We first phenotyped its resistance to isolates of the i) M. arenaria, ii) M. incognita and iii) M. javanica species, and then to iv) two mixed Harmony-virulent Californian populations of M. arenaria and M. incognita. Finally, we created an isolate of M. arenaria and M. incognita from these Harmony populations and phenotyped the progeny to each of them [v) and vi)], and to vii) an isolate of M. ethiopica. The resistance phenotype of all the progeny’s individuals was independent of the RKN isolates or populations used. Resistance was mapped in a region of chromosome 18 in VRH8771, supporting the hypothesis that it is conferred by a single gene with an unprecedented wide spectrum in grapevine, including Harmony-virulent isolates. This dominant gene, referred to as MsppR1, is linked to the telomeric QTL XiR4 for X. index resistance from the same source. Additionally, plant mortality data showed that MsppR1-resistant material expressed a high-level resistance to the Harmony-virulent isolates. Our results are a first step towards the development of marker-assisted breeding using SSR and SNP markers for resistance to RKNs in accession VRH8771. © 2023, International Viticulture and Enology Society. All rights reserved

Soil composition and rootstock genotype drive the root associated microbial communities in young grapevines

Soil microbiota plays a significant role in plant development and health and appears to be a major component of certain forms of grapevine decline. A greenhouse experiment was conducted to study the impact of the microbiological quality of the soil and grapevine rootstock genotype on the root microbial community and development of young plants. Two rootstocks heterografted with the same scion were grown in two vineyard soils differing in microbial composition and activities. After 4 months, culture-dependent approaches and amplicon sequencing of bacterial 16S rRNA gene and fungal ITS were performed on roots, rhizosphere and bulk soil samples. The root mycorrhizal colonization and number of cultivable microorganisms in the rhizosphere compartment of both genotypes were clearly influenced by the soil status. The fungal diversity and richness were dependent on the soil status and the rootstock, whereas bacterial richness was affected by the genotype only. Fungal genera associated with grapevine diseases were more abundant in declining soil and related root samples. The rootstock affected the compartmentalization of microbial communities, underscoring its influence on microorganism selection. Fluorescence in situ hybridization (FISH) confirmed the presence of predominant root-associated bacteria. These results emphasized the importance of rootstock genotype and soil composition in shaping the microbiome of young vines

Grapevine decline is associated with difference in soil microbial composition and activity

Grapevine decline is a top concern in viticulture worldwide and is often associated with many biotic and abiotic factors. Grape trunk diseases and viruses are some of the most frequently identified causes of vine dieback. However, a decline is sometimes observed when no mineral deficiency or excess, or pathogenic causes can be identified. Soil enzymatic and microbial activities are relevant bio-indicators since they are known to influence vine health. Grapevine associated microbiota, linked to vine fitness, is known to be influenced by soil microbiota coming from the microbial pool inhabiting the vineyard. This work describes the microbial diversity and activity of four different vineyard plots of the Bordeaux region, selected due to the presence of localised declining areas unexplained yet by disease symptoms. Soils were sampled in declining areas and areas within the same plot showing no decline symptoms, during autumn and spring periods. Significant differences in enzymatic activities, microbial biomass and activity were found among soils even if those soils presented quite similar physicochemical characteristics that could not explain these observed declines. The results of enzymatic assays distinguished patterns in autumn and spring periods with an overall greater enzymatic activity in soils from non-declining areas. This work suggests that soils displaying decline symptoms present a dysbiosis in functionality and diversity which is linked to vine health