अंगूर की उत्पादकता में सुधार कैसे करें।

Among all the horticultural crops, grapes have received a special importance in view of its value addition into raisins. Wine grape area is around 3000 ha and production is estimated about 30000 MT with a productivity of 10MT/ha and wine production is estimated at 15 million liters from this production. Major area in the country is spread in the states of Maharashtra (to the extent of 75 to 80 percent in Nasik, Sangli, Solapur, Satara, Pune and Latur districts) followed by Karnataka (Bijapur, Bangalore, Belgaum, Gulbarga, Raichur districts), Andhra Pradesh (Hyderabad and Ranga Reddy districts) and Tamil Nadu (Theni, Coimbatore and Madurai districts) and small parts in North India states (Punjab, Uttar Pradesh, Haryana, Himachal Pradesh, Jammu & Lashmir) and East and North East states (West Bengal and Mizoram).

In India grape is grown from tropical, subtropical to temperate climate. The major problems faced in tropical region are, ever growing of vines without rest period (dormancy) which is contrary to the scenario in temperate regions. Due to continuous growth and the warm and humid climate, the incidence of insect pests and diseases is more and the requirement of inputs viz., pesticides, manures and fertilizers, growth regulators and labor is almost double as compared to temperate countries.

Further, the climate change in terms of untimely precipitation in annual cycle of crop and stress of heat and cold and other climatic factors also influences productivity and quality of crop.

Productivity refers to inherent capacity of the vines to produce maximum yield in given situation. The productive potential of grape varies from variety to variety and there is a large gap between the productive potential of vine and the actual yield. Hence there is a large scope for reducing the gap between productive potential of vine and the actual yield by adopting various viticultural practices.

Grape Cultivars:

Thompson Seedless and its mutants Tas – A – Ganesh, Sonaka and Manik Chaman are the commercially important table grapes grown in peninsular India. However, Sharad Seedless (Syn; Kishmish Chernyi); Bangalore Blue, Gulabi (Syn: Isabella) and Anab – e – Shahi are some of the other varieties grown in some parts of southern India. 

Manjri Naveen a clonal selection from Centennial Seedless has been selected and released for commercial cultivation which is being cultivated by some of the grape growers in Maharashtra and Karnataka.

Introduction of new varieties is another way to widen the genetic base and to find suitable alternative variety to increase production and productivity. In past few years some of the introduced varieties have been evaluated in different soil and climatic conditions and few of them are found place in domestic and international market which includes Flame Seedless, Red Globe, Crimson Seedless, Italia and Manjri Naveen (a selection from Centennial Seedless). Efforts have also been made to introduce some of the new table varieties such as Autumn Royal, Blush Seedless, Autumn Seedless and Marquis and their evaluation is in progress with respect to their performance under Indian soil and climatic conditions.

Grape Rootstocks

It has been established from several studies that, rootstock can influence the scions behavior in terms of controlling vigor, physiological and biochemical process of scions in bud burst, rate of photosynthesis, fruit quality etc. Bud burst is the main constraint in some of the grape growing region. Use of rootstocks which triggers uniform and quick bud burst is one of the means to improve vineyard production and productivity.

Though Dogridge introduced from USA was the prominent rootstock employed by grape growers in major grape growing regions of the country, over the years there was reduction in the productivity in areas where it was affected by soil salinity. Further it is known to impart more vigor to scions and uneven bud break, thus reducing productivity in long run.

Evaluation of rootstocks has resulted in identifying 110 R rootstock as an alternate rootstock in regions where soil salinity and water scarcity are major constraints in grape cultivation. Rootstock 110 R is known to impart less vigor to Thompson Seedless, imparts uniform and quick bud burst, increases fruitfulness and also restricts uptake of sodium ions from soil thus considered as salt tolerant. Thus use of such rootstocks is also one of the means to increase production and productivity of grape cultivars.

Canopy Management Practices:

Yield is a product of number of fruit bunches / clusters over unit area and the mean weight of cluster. In other words, a fruiting cane/ shoot is the unit of production. Even though, yield per unit area is more in tropical and subtropical regions of India, the cluster/ cane ratio is far less as compared to temperate regions of the world. Over all, the measures to increase productivity of vines are discussed under following headings

1. Increasing the Number of Fruiting Canes per Unit Area (Vines)

As cane is the fruiting unit in grapes, yield depends on number of fruiting canes/unit area. In addition to fruiting cane number, thickness of cane determines the shoot length and number of leaves put forth on the bearing shoot during fruiting season. Optimum cane density of 5 canes per m2 area of canopy is ideal with minimum thickness of at least 8 mm. On the other hand, increased number of canes/unit area has adverse effect on fruitfulness of buds, cane size and cane maturity.

To achieve the desirable number of fruiting canes/unit area proper canopy frame work development is essential in the beginning.

2. Increasing Cluster Cane Ratio

This is one of the measures to increase the productivity of vines. In some of the varieties like Thompson Seedless, it is not possible to increase the number of clusters per unit area by increasing cane density. The cluster/cane ratio is very poor in peninsular India as compared to temperate regions of the world. It is 0.5-0.6 in Thompson Seedless and 1.0 in Anab-e-Shahi as against 10-12 in temperate regions. Such poor cluster/cane ratio is due to poor bud fruitfulness in a cane and poor bud break.

3. Fruit Bud Differentiation

Fruit bud formation takes place for next year on current season growth in temperate conditions and 45 to 60 days after pruning on current season growth in peninsular India. Bud fruitfulness varies with inherent capacity of variety. Studies on fruiting habits of different varieties have shown that first two or three buds from the base contain fewer inflorescence primordia than upper bud.

The proportion of fruitful bud increases progressively towards the middle of cane and falls off towards the tip. Shoot vigour, light and temperature plays a major role in fruit bud differentiation. More the vigour of shoot with respect to its internodal length and weight, less will be the productivity. Experiments have also revealed that light and temperature are the contributory factors for increasing fruitfulness of buds.

4. Mean to Increase Bud Fruitfulness

4.1. Use of growth retardants: Use of appropriated dose of nitrogen and required quantity of water, spraying growth retardants like CCC after back/foundation pruning (March-April) can increase fruitfulness and thickness of canes. These sprays increase bud fruitfulness through:

• reducing vegetative growth
• increasing shoot thickness
• reducing internodal length by counteracting the effect of endogenous ‘GA’
• Increasing endogenous cytokinin levels and consequently ratio of cytokinin/gibberellin congenial for formation of inflorescence primordia.

4.2. Increasing light regime in vine canopy: Orientation of growing shoot should be in such a way that, the buds on them should get maximum available sunlight. Training grape vines to trellis such as T, Geneva Double Curtain, Tatura & ‘Y’ can result in open canopies with diagonal shoot orientation to harvest more sunlight by buds.

4.3. Promotion of cytokinin/GA ratio : Application of 6 BA to shoot apices will prevent the formation of tendril primordia and favours the formation of inflorescence, since cytokinin plays a vital role in controlling the process of inflorescence formation, differentiation of flowers and pistil development. However, 6-BA is yet to have CIB label claims.

4.4. Nutrient management: Nutrition has been considered the major factor in determining the productivity in vines. Appropriate quantity of nitrogen induces the flower initiation through synthesis of proteins and nucleic acids favourable for inflorescence formation. Combination of N, with P and K will induce early flower bud initiation.

5. Bud Break

It is the basic requirement for initiation of new growth by vines. Extent of budbreak refers to percentage of sprouted buds to the total buds on a cane of vine. Budbreak is not a problem after summer pruning in tropics as there will be only one/two buds on spurs and the atmospheric temperature will be high. However, this is problem after forward/fruit pruning (September – October).

In the past, several measures like twisting, ringing and bending of canes were some of the practices followed to increase bud break but, these operations are labour intensive and sometimes it also damages sprouted buds. Hence, use of appropriate and optimum dose of chemicals with CIB label claims is more effective. Among all the chemicals, use of hydrogen cyanamide is the common practice to obtain quick and uniform bud break and also having CIB label claim. Swabbing buds with Hydrogen Cyanamide @ 1.5% with cotton or sponge to the buds within 48 hrs after pruning will enhance bud break.

6. Sub Cane Development

This is one of the means to increase fruit cluster/cane ratio. After foundation pruning March – April), pinching off the shoots after five node at 7 to 8 leaf stage and encouraging one or two buds to grow laterally in addition to apical bud is the process of developing sub canes. Spraying of 500 to 1000 ppm CCC at 5 leaf stage also increases lateral buds.

When these lateral buds reach 5 leaf stage, it is again pinched to arrest the growth of lateral shoots. On maturity, canes and sub canes are pruned to 2 or 3 nodes from the point of origin, since fruit buds are at the first or second node of these laterals and apical shoots.

7. Increasing Fruit Set in Clusters

All the flowers seen at the time of panicle emergence do not develop into fruits/berries. Many flowers fail to set because of poor pollination and fertilization or other causes. Endogenous growth regulator also regulates Berry set. Some of the measures to increase fruit set are:

7.1 Shoot Pinching and Topping

This helps in increasing the fruit set by reducing the food competition for carbohydrates and other organic nutrients between the growing apices and the developing berries, thus reducing the drop of berries due to lack of nourishment.

7.2 Girdling: It consists of removing complete ring of bark 3 to 6 mm wide from the lower part of the trunk or from an arm or a cane below the cluster. This promotes accumulation of carbohydrates in the plants above the girdle; thereby increase the berry set and development. This practice is followed in temperate countries only for production of table grapes.

7.3. Use of Growth Promoters: Use of growth regulators such as gibberllic acid (GA3) and cytokinins (CPPU, 6BA) with appropriate concentration at right stage will increase fruit set and produces good quality bunches. GA3 and CPPU are having CIB label claims.

7.4. Increasing Berry Weight: Sixty per cent of berry weight increases during third stage of its growth after berry softening. This is by influx of sugar and water into the berries. Efficient nutrition and irrigation management practices during this period will improve berry weight. Apart from this, maintaining optimum leaf fruit ratio, girdling, shoot tipping and growth regulator application will increase the berry weight.

7.5. Leaf/fruit Ratio: Leaf area available on bearing shoot during fruiting season has remarkable bearing on the development of bunch, berry size, and dry matter accumulation. The optimum leaf area for proper development of bunch and berries is about 2600 cm2 depending on size of leaves (» 12-15 leaves). Reduction in available leaf area will reduce berry size, its crispness and TSS content. Since the nourishment to the developing bunch is from leaves on the shoot, it is necessary to maintain at least 12 leaves of appropriate size on shoot at the time of fruit set. This is possible only when cane is about 8 mm thickness at fruit pruning (September – October).

Nutrient Management in grapes:

Nutrition is a key component of vineyard management. It has the potential to influence various factors in vine production that includes, fruit set, fruit quality and the processed products such as raisins, wine and juice. Nutrient management is very complex and therefore several variations existing in vineyards needs to be considered.

Some of the important factors are variety, rootstocks, soil type, water quality and its application etc. Use of inorganic fertilizers alone destroys the soil health in the long run and therefore both organic and inorganic sources of the fertilizers should be used since it is not economical to meet the nutrient requirements of the vines through organic sources alone. The organic sources include green manuring crops/cover crops, FYM, wood ashes, composts (vermi-compost and compost prepared from town waste).

Relative nutritional need of vines by petiole testing at different phenological stages

Vine requirements for different nutrients vary at different growth stages. Higher levels of N (nitrogen) are to be applied in the first 30 days after foundation pruning and 40 days after fruit pruning to promote strong shoot growth for achieving desired canopy. Nitrogen needs are less during fruit bud differentiation period.

The requirement of P (phosphorus) is more during the bud formation and bud differentiation period (30-60 days after foundation pruning depending upon the variety). Phosphorous is needed for promoting root growth and fruit bud formation.

Potassium (K) needs are relatively high during 61-90 days after foundation pruning as it makes fruit buds strong and bold, promotes cane maturity and diameter.

Potash requirement is also high during the fruit growth and ripening period.

More Mg (magnesium) is required during the fruit bud differentiation after foundation pruning. Magnesium acts as carrier for P and helps in better P utilization. Magnesium requirement is again higher during 71 – 100 days after fruit pruning to prevent interveinal chlorosis and promote carbohydrate synthesis by leaves.

Zinc (Zn) is essential to normal leaf development, shoot elongation, pollen development and set of fully developed berries.

Pollination and fruit set are physiological processes of the grapevine most sensitive to low boron (B) levels at that time.

Both Fe (Iron) and Mn (Manganese) assist in chlorophyll formation and hence almost all the vine growth stages are sensitive to the deficiencies.

The recommended dose of major nutrients (N,P,K) through fertigation for matured Thompson Seedless vines grafted on Dogridge rootstock is 266.6 N:178.5 P2O5:266.6K2O kg/ha.

Water Management

The need for water varies with different stages of vine growth. For some stages of the vine moisture stress is beneficial and it is harmful for some other stages. During the stage covering the period from foundation pruning to bud differentiation stage (normally mid-April to May) the water requirement is maximum.

Vines should not be water stressed in order to obtain canes of desired thickness (8-10 mm) and sufficient canopy. In the bud differentiation stage, irrigation should be reduced to facilitate better bud differentiation.

Shoot maturity and fruit bud development stages coincides with rainy season but still there is a need to irrigate the vines as the rainfall is highly erratic and whenever its distribution is not uniform.

In the fruit pruning or forward pruning season (normally during the month of October) the vines should receive sufficient irrigation to promote strong shoot growth and adequate leaf area.

Since fruit-set is not a problem in Indian vineyards, mild water stress during berry set to shatter stage helps in reducing berry set which are otherwise avoids thinning. Berry growth to veraison period is most critical stage as cell division and elongation are occurring in the fruit. Water stress at this stage reduces the berry size and yield.

During the period from veraison to harvest the vines should not be over-irrigated in order to avoid berry cracking and delay in harvest. In highly vigorous vineyards the irrigation may be withheld for few days to discourage the new shoot growth. Depending upon the stored water in soil the irrigation may be stopped a week before to increase sugar content in the berries. Moisture stress at this stage however results in berry drop.

There is hardly rest period after harvest (15-30 days) and during this time, the vines can survive on stored soil water in the soils. If the rest period is more than a month, then the vineyard should be irrigated twice or thrice during this period.

Keeping all these points in view, an irrigation schedule based on pan evaporation rate has been developed for black clayey soils, which is known to increase water use efficiency. Apart from this, other moisture conservation techniques such as mulching, spraying anti-transparent chemicals, sub-surface method of irrigation could improve water use efficiency and thus increases vineyard productivity.

Disease and Pest Management:

The main constraint in grape cultivation under tropical and subtropical conditions is the susceptibility of commercially important table grape cultivars to major three fungal diseases such downy mildew, powdery mildew and anthracnose. The occurrence of all the three diseases is highly dependent on weather conditions existing in a region.

Temperature, relative humidity, leaf wetness, wind velocity etc are some of the important factors which influence disease development. Untimely rainfall during critical vine growth stages (flowering / fruiting stage) resulting in occurrence of downy mildew diseases was the prime reason for reduced production and productivity in the past two years.

Due to change in the climate over the years it has been also recorded that there was a shift in the anthracnose causing fungi from Elsinoe ampelina to Colletotricum spp. This might be also one of the reasons for reduced productivity of grapes in past few years as the sprays used to control Elsinoe ampelina must have not controlled Colletotricum spp and therefore, more focused studies in this direction are essential to study the biology and control of this fungus.

Though effective control measures to control these diseases include spray of effective fungicides; prophylactic sprays in advance can reduce the occurrence of disease to a great extent.

This will further help in reducing the residues in table grapes. Experiments conducted in demonstration blocks in different grape growing regions of Maharashtra on use of disease forecasting models in the past two years to reduce the occurrence of disease as resulted in reducing the number of sprays up to the extent of 50% without reduction in the yield and quality of the produce.

Mealy bugs, red spider mites and thrips are the major insect pests causing greater loss to grape production in India. Over use of pesticides to control these pests may result in accumulation of more pesticide residues in harvested produce. Further, extensive use of pesticides can pollute environment and kill natural predators. Need based sprays along with use of environmentally safer chemicals including use of biological control agents based on weather factors can overcome the problems of pesticide residues.

In this direction, an IPM schedule for controlling mealy bugs which includes mechanical, chemical and biological means has been developed and tested effectively in farmers field, which is widely been adopted by grape growers. Efforts are in progress to develop IPM schedule for control of thrips and mites. Occurrence of some of these pests also depends on prevailing weather conditions and therefore development of pest forecasting models based on weather parameters in more precision way similar to that of disease forecasting models, is in the process of development.

Conclusion

The following points are to be followed to improve grape production and productivity

• Production of elite, disease free and true to type planting materials and regularization of nursery policies to produce quality planting materials
• Introducing the varieties of table grape according to the demand and requirements of Foreign markets
• Improvement of the table grape vineyards and cultivation of seedless varieties
• Increasing the productivity of table grape vineyards, by implementation of clones of traditional and new varieties
• Improvement of cultivation technology for a better quality and higher competitiveness of table grapes
• Expansion of area under grape cultivation in non-traditional areas, marginal lands and developing suitable cultivation practices for that region