GRAPE ROOTSTOCK - `DOGRIDGE ITS SIGNIFICANCE IN GRAPE CULTIVATION

Grape cultivation is approximately 300 years old in India. It has passed through a series of developments in terms of selection of agro-climatic regions, variety and cultural practices, with particular reference to training and pruning. However, major breakthrough in grape cultivation could be achieved only during the last three decades. Of late, India has emerged as one of the leading producers of world’s finest quality of grapes with highest yield/unit area. One such tool, which is poised to make a significant contribution and play a vital role, is rootstocks.

Vines in India were mostly grown on their own roots as most areas were considered free from soil borne problems. However, interest in grape rootstocks has recently intensified, owing to the problems of salinity, drought and low vine vigour. Due to the severe restriction on the availability of good quality water for irrigation and uncertainty of rains, rootstocks provide an attractive and environmentally sound alternative to manage these twin problems. Rootstock is also an important factor to control scion vigour and to bring an equilibrium between growth and yield.

It is an established fact that rootstocks provide a different root system to the scion. The selective absorption of nutrients by the scions due to changed root system can be profitably employed in eliminating the absorption of toxic elements. Similarly, roots being the sites for the synthesis of cytokinins, which have been demonstrated to be pivotal in fruit bud differentiation, there is scope for manipulating the productivity of vines through rootstocks.

The choice of rootstocks is more difficult than generally believed. This is due to interaction between the rootstock, environment and the scion. Fortunately, for the growers of our country the twin problems of Phylloxera and nematodes and so also the problem of viruses affecting the vine industry elsewhere in the world, does not pose any threat. This situation has helped to a large extent in narrowing down the difficult task of selection.

Among the many rootstocks introduced and tested in India only two have shown their potential. They are Dogridge (Vitis champinii) and Salt Creek (Vitis champinii).

The problem of soil salinity is fast spreading posing a threat to viticulture industry in Maharashtra, Andhra Pradesh and Northern districts of Karnataka. Heavy application of fertilizers, intensive cultivation, faulty management and poor quality of water accentuate the salt problem in grapes. Accumulation of chlorides is two to three times higher in cultivars. Rootstocks exclude the salts even under saline conditions. Proportion of potassium in rootstocks is many folds higher than in popular cultivars on their own roots. Under saline conditions, the symptoms of salt injury appear in the leaves based on the stage of the crop growth, types of soil, variety and environmental factors in relation to the accumulation of chloride and sodium.

Rootstocks Dogridge and Salt Creek have been noticed as best chloride +excluders. These rootstocks today have been used most successfully on soils of low fertility. Their vigorous growth nature is found to be more useful under saline conditions. Performance of Dogridge rootstock especially under black soils and medium black soils has shown lot of promise both in Maharashtra and Bijapur district of Karnataka. Thompson Seedless grafted to this rootstock has shown excellent vigour, resulting in ideal canopy when trained to Y trellis or expanded Y trellis. The leaves of Thompson Seedless or Tas-A-Ganesh have not exhibited the salt injury symptoms even when saline water was being used, when they were grafted on Dogridge or Salt Creek. The tendency of these rootstocks to take up more nitrogen did not affect the productivity of scion cultivar.

Balancing soil fertility and scion vigour with rootstock vigour has thus become very important as a new approach in canopy management of grape vines. Eventhough, many horticultural practices like use of growth retardants, inducing sub canes, modified training systems etc., are very useful and proven tools to check the vine vigour, but imparting vigour to a cultivar to improve the leaf to fruit ratio is possible probably by use of vigorous rootstocks generally bean only recently, so there are few immature vineyards to use as guides in rootstock selection. However, some of the vineyards on Dogridge rootstock which are well managed are showing the promise of giving higher yield, with some of the problems like time of planting, training the rootstocks, grafting procedure, grafting time, etc., being standardized, growers now face fewer problems on these lines. With the standardizing of ideal training system (Y trellis) and spacing to be adopted, when needs to be worked out is the water requirement and nutrient management strategies as these rootstocks are known to possess drought tolerant mechanism in addition to greater nutrient uptake qualities. A balance of these two feature needs to be worked out to evolve a suitable water nutrient input strategy so that with lesser inputs the wide and deep rooting habits of these rootstocks are exploited to the maximum.