Ajay Kumar Sharma

Influence of canopy management practices on fruit composition of wine grape cultivars grown in semi-arid tropical region of India

Effect of canopy management practices on berry composition of red and white grape cultivars grown in Pune region of India was examined. Cabernet Sauvignon and Sauvignon Blanc vines were selected for the study. Both the cultivars exhibited significant variation in fruit composition parameters in response to various canopy management practices. Combination treatment of leaf removal (LR) either with shoot thinning (ST) or cluster thinning (CT) exhibited high total soluble solids (TSS), lowest acidity (malic acid), lower potassium content and higher anthocyanin content. The vines which received ST+CT+LR treatment and control vines recorded least anthocyanin concentration and phenolic compounds indicating excess light exposure or excess shade to clusters is not congenial for producing better quality fruits. Leaf removal treatment in combination with either shoot thinning or cluster thinning was found to be superior under semi-arid tropical conditions to obtain good quality fruits. Reasons for such variations in fruit composition parameters under different management practices are discussed.

Rootstock Influence on the Biochemical Composition and Polyphenol Oxidase Activity of ‘Thompson Seedless’ Grapes and Raisins

‘Thompson Seedless’ grapes grafted on five rootstocks and own-rooted vines were evaluated for yield, fruit composition, and raisin recovery percentage. Biochemical constituents were analyzed in fresh grapes before drying into raisins and also in raisins. Among different rootstocks, raisin recovery was highest in ‘Thompson Seedless’ grapes grafted on 110 R followed by those on ‘Dogridge’, 1103 P and 99 R. Significant differences were observed in total proteins, reducing sugars, phenol contents, and polyphenol oxidase (PPO) activity in both fresh grapes and raisins made from all rootstock scion combinations. Increase in the content of proteins and reducing sugars was observed in raisins compared to fresh grapes. However, there was a reduction in phenolic concentrations in raisins compared to fresh grapes. PPO activity was highest in ‘Thompson Seedless’ grapes grafted on ‘Dogridge’, while it was least in 110 R.

Effect of Climate Change on Grape and Its Value-Added Products

In India, majority of the grape vineyards are located in semiarid climate. Climate change may aggravate the already serious problems of irrigation water availability and salinity. The elevated CO2 levels may increase productivity in arid and semiarid regions, but the drought stress caused by higher evaporative demand may override beneficial effects of increased CO2 in the atmosphere unless irrigation is increased to compensate the evaporative demand. Higher temperature may advance the ripening of berries and alter the berry composition in both table and wine grapes, thereby affecting the quality of the produce. Developing heat-tolerant grape varieties and salt- and drought-tolerant rootstocks, though essential, requires long period. Until new varieties/technologies are developed to improve water use efficiency and cope up with salinity, the emphasis needs to be given on propagation of existing crop production techniques that can mitigate the impact of climate change. There is also likelihood of change in the incidence and pattern of insect pests like mealy bug, thrips and mites. Similarly the disease incidence pattern is also likely to be affected with the change in climate. This is evidenced by decrease in productivity during the recent years from more than 25 t/ha to 8.3 t/ha during the year 2009–2010 and11.7 t/ha during 2010–2011 due to unseasonal rains which lead to serious downy mildew incidence. Changes in cropping season to adjust to changed climate will bring market competition-related issues particularly for Indian table grape industry in domestic as well as global markets.

Estimation of polyphenols by using HPLC–DAD in red and white wine grape varieties grown under tropical conditions of India

Abstract Grapes are well known for their high content of phenolic compounds. Polyphenols are classified into flavonoids and non-flavonoids by their primary chemical structures of hydroxybenzene. Flavonoids mainly consist of anthocyanins, flavonoids, and flavonols whereas non-flavonoids include hydroxycinnamic and hydroxybenzoic acids. In the present study, sixteen phenolic compounds from ten red and nine white grape wine varieties were quantified using high-performance liquid chromatography. Gallic acid, Vanillic acid, Rutin hydrate, Ellagic acid, Chlorogenic acid, Sorbic acid, Catechin hydrate, Epicatechin, p-coumaric acid, Quercetin, Myricetin, Kaempferol, Piceatannol, and Resveratrol were major compounds found in red wine grapes. Among the varieties, Petit Verdot, Cabernet Franc showed maximum quantitative phenolics, whereas Cabernet Sauvignon, Niellucio, Cinsaut, and Syrah showed least quantitative phenolics in grape berries. Phenolic profile of white wine grapes showed lower concentration of phenolics than that of red wine grapes. The variety Gros Meseng showed maximum phenolics followed by Sauvignon, while the variety Colombard and Chenin Blanc showed least phenolics.