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

New PCR primers applied to characterize distribution of Botrytis cinerea populations in French vineyards

The phytopathogenic fungus Botrytis cinerea is a complex of two main genetic groups, Group-I and Group-II, the latter including different TE types distinguished by the presence or absence of two transposable elements (TE), Boty and Flipper. In populations from Bordeaux vineyards (n = 470), the frequency distribution into these genetic subdivisions showed that Group-I isolates were rare (2.3 %) whereas, within Group-II, four TE types were identified by dot blot in very different proportions: II-transposa (59.8 %), II-boty (21.3 %), II-vacuma (15.5 %) and II-flipper (1.1 %). To distinguish the TE types by PCR, a first primer pair was designed within the Flipper sequence which yielded a not-expected 2287 bp fragment. The 5’ extremity of this fragment was sequenced revealing a potential genomic insertion site of the Flipper element allowing the design of a new overlapping PCR primer. Detection of the Flipper element by two newly developed PCR tests and a published one (F300-F1550) was consistent with dot blot results in Group-I and II-transposa (concordance rates from 94.6 % to 100 %). However, discrepancies between PCR and dot blot were noticeable especially in II-boty, but also in II-vacuma (concordance rates from 33.3 % to 38.0 % and from 62 % to 81.2 %, respectively). On the basis of TE-type identification strengthened by combining different PCR and dot blot results, the spatiotemporal distribution of the Group-II isolates was assessed according to the developmental stage and the host organ of grapevine. In Bordeaux as in Loire valley vineyards, similar distribution patterns were described showing significant differences between the most sampled TE types. The II-transposa isolates predominated on grape berries at the end of the season, whereas the II-vacuma ones were detected mostly at flowering. Lastly, the II-boty isolates were more often detected on grapevine leaves than on flowers or berries.

Comparison of efficacy and modes of action of two high-potential biocontrol Bacillus strains and commercial biocontrol products against Botrytis cinerea in table grapes

In table grapes (cv. Thomson Seedless), the antifungal activity against Botrytis cinerea was further analysed and compared between two high potential bacterial biological control agent (BCA) strains, Bacillus velezensis BUZ-14 and B. ginsengihumi S38. Two commercial biocontrol products (BPs), served as standards of comparison, Amylo-X (R) and Serenade Max (R), also based on Bacillus BCA strains. The main mode of action quantified for all the strains was antibiosis due to hydrosoluble and volatile metabolites and their combinations. The BUZ-14 strain was the most active BCA strain, demonstrating significant disease reduction exceeding 60 % when used in the culture form grown in 863 medium, including living cells (LCs) and cell-free supernatant (CFS). Both BPs exhibited significantly reduced efficacy of their CFS fraction (< 10 %) compared with that of the two BCA strains, confirming their high antibiosis potential. The novel methodology allowed us to demonstrate the significant effect of the BCA culture medium on volatilome (VOC) antagonist efficacy. The S38 strain achieved the highest disease reduction (90 %) owing to the greatest production of VOCs in the richest MOLP (Medium Optimum Lipopetide Production) culture medium, whereas grape juice was the least favourable medium for VOC efficacy for both bacterial strains (BUZ14 and S38). The overall poor activity of living Bacillus cells in all the BCA and BPs tested is discussed based on the low capacity of the BCA strains to grow in the berry. Then, the presence of living cells is also discussed with the possibility that these cells are not required in field applications of such BCA strains in this genus. Moreover, different environmental suboptimal conditions, including temperature (22 and 27 degrees C) and relative humidity (RH) (100 and 85-95 %), were tested, and BUZ-14 exhibited the highest Botrytis reduction at both temperatures and RH values. However, no significant differences were observed between temperatures or RH values for the same BCA. Further studies in vineyard conditions and applications, such as biofumigation or active packaging, will be performed to confirm the new findings reported in this investigation

A new integrative assessment indicator for damage caused by major pests and diseases in the vineyard

An original and integrative evaluation indicator has been developed to quantify the cumulated damage from major pests and diseases affecting grape bunches: downy mildew, powdery mildew, gray mould and tortricid moths. It made it possible to estimate the associated crop losses and to relate them to the plant protection strategy in different modes of production (organic farming, in-transition, conventional). Thus, overall plant losses were higher in 2012 than in 2011. The in-transition growers’ strategy, with reduced copper doses but increased numbers of sprays, led to a 20% increase in average severity on bunches (essentially due to Downy mildew). The more pragmatic approach of experienced organic growers and conventional ones (higher doses and fewer sprays) reduced the yield losses. The proposed indicator is used for two purposes, i) evaluating the quantitative losses due to pest attacks and ii) differentiating them from other non-pest ones. A more detailed analysis including the impact on performance will be achieved and published soon

New insight about the functionality of oenological tannins; Main results of the working group on oenological tannins

This communication synthetize all the results obtained by the OIV working group on oenological tannins to the current date. The obtained results confirm that oenological tannins really exert a protection effect against grape juice and wine oxidation because they have antioxidant activity, they consume directly oxygen and they exert an inhibitory effect on the laccase activity. Moreover, oenological tannins also exert a copigmentation effect which can improve and protect de color of red wines

Inner necrosis in grapevine rootstock mother plants in the Cognac area (Charentes, France)

The incidence and quantification of decline-associated inner necrosis in grapevine rootstock mother plants have rarely been studied. In an experimental vineyard planted in 1991 at Saintes (Charentes), susceptibility to esca was evaluated in eleven common rootstock varieties. Fifty vines per rootstock variety were used as mother plants producing long canes which were severely pruned every year. No foliar symptoms, typical of grapevine wood diseases, were seen in field inspections conducted in the summer of 1996, 2002, 2003 and 2006. In 2007, nine trunks per variety were randomly selected and were cross-sectioned at the point of greatest diameter. All sections revealed typical esca necrosis, central and/or sector-shaped, indicating that such necrosis is very common. Every section was photographed and the percentage of necrotic area was calculated by either visual assessment or image-analysis. No significant difference was detected between these two calculating methods. Based on the mean percent necrotic area, rootstock varieties were ranked in order of susceptibility from the least susceptible, ‘1103 Paulsen’ (33%), to the most susceptible, ‘101-14 MGT’ (71%). The percent of necrotic area was correlated significantly with i) the incidence of mortality and ii) the percentage of vine sections showing white rot, a type of necrosis indicating an advanced stage of wood deterioration. This study confirmed that necrosis in grapevine wood is not always associated with foliar symptoms, but that it is related positively with grapevine mortality. Furthermore, wood necrosis in mother-plants poses a risk of disseminating associated fungi through propagation material

Environmental conditions affect Botrytis cinerea infection of mature grape berries more than the strain or transposon genotype

Effects of environment, Botrytis cinerea strain, and their interaction on the infection of mature grape berries were investigated. Our data collectively showed that (i) T and RH or WD were more important than strain for mature berry infection by either mycelium or conidia and (ii) the effect of the environment on the different strains was similar. Two equations were developed describing the combined effect of T and RH, or T andWD, on disease incidence following inoculation by mycelium (R2 = 0.99) or conidia (R2 = 0.96), respectively

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

International audienc

The influence of Thrips obscuratus on infection and contamination of kiwifruit by Botrytis cinerea

International audienc