Write the cultivation practices of grapes in respect of soil and climatic requirements, improved varieties, training and pruning, fruit thinning and plant protection.

Soil and Climatic Requirements

Optimal soil and climatic conditions are crucial for robust grape growth and quality fruit production. Grapes, though adaptable, thrive under specific environmental parameters.

Soil Requirements:

• Type: Grapes can grow in a wide range of soils from sandy loams to sandy clay loams, red sandy soils, shallow to medium black soils, and red loams. However, well-drained, fertile soils with good water-holding capacity are preferred.
• Depth: A soil depth of at least 1 meter is essential for proper root development and vine establishment, with roots typically growing 36 inches or more below the surface.
• pH: Grapes tolerate a wide pH range (4.0-9.5), but soils with a pH between 6.5 and 8.5 are considered ideal. Saline soils are generally not preferred, though grafting on resistant rootstocks like Dog Ridge can mitigate this issue.
• Drainage: Excellent drainage is paramount. Constantly soggy or damp conditions can lead to root diseases and compromised fruit quality.

Climatic Requirements:

• Temperature: Grapes generally require a hot and dry climate during their growth and fruiting periods. An optimal day temperature range of 15°C to 40°C is suitable for vine growth and establishment. Temperatures above 40°C during fruit development can reduce fruit set and berry size, while temperatures below 15°C can impair bud break.
• Rainfall: Grapes flourish in regions with less than 750-900 mm of annual rainfall. Rainfall should ideally not coincide with vine growth after pruning and the bunch ripening phase, as it can promote fungal diseases like downy mildew.
• Humidity: High atmospheric humidity can be detrimental during vegetative growth and fruiting, leading to vigorous vegetative growth at the expense of fruit size and quality, and favoring fungal disease development.
• Sunshine: Abundant sunshine is critical, particularly during fruit set. Low light intensities during active growth and fruit bud formation can adversely affect the crop.

Improved Varieties

India cultivates a diverse array of grape varieties, primarily for fresh consumption, with a growing focus on export-oriented and processing varieties. The selection of a variety depends on the agro-climatic zone and market demand.

Common and Improved Varieties in India:

• Table Grapes:
  • Thompson Seedless and its clones (Tas-A-Ganesh, Sonaka, Sharad Seedless): These are highly popular for fresh consumption and raisin making, especially in Maharashtra and Karnataka. Sonaka Super is known for its sweet taste and large size.
  • Anab-e-Shahi: A vigorous variety, suitable for table purpose, particularly in tropical regions.
  • Perlette: A seedless variety with greenish-yellow berries, known for its sweet-tangy taste.
  • Flame Seedless: A red, seedless variety popular for its sweet taste and crisp texture.
  • Red Globe: Large, bright red, seeded grapes with a sweet taste.
  • Crimson Seedless: A bright red, seedless variety with a crispy texture.
  • Bangalore Blue and Gulabi: These are native varieties, fairly resistant to rain damage, and suitable for juice and table purposes, especially in Karnataka and Tamil Nadu.
• Newer Varieties and under trial: Varieties like Jyoti Seedless, Krishna Seedless, Saritha Seedless, A-18, Manjari Medika (juice), Manjari Kishmish (raisin), Manjari Shyama (table grape), Timco, Timpson, Allison, and Ivory are being introduced and trialed for their export potential, weather resistance, and shelf life.

Training and Pruning

Training and pruning are critical viticultural practices that manage vine vigor, optimize fruit production, improve fruit quality, and facilitate vineyard operations.

Training Systems:

Grapevines require permanent support structures (trellis or arbor). Common training systems in India include:

• Bower System: Highly suited for vigorous varieties like Anab-e-Shahi, Bangalore Blue, and Gulabi, owing to their high productive potential. Vines are trained to grow over an overhead trellis.
• Telephone System (T-trellis): A popular system in many regions, providing good support and canopy management.
• Flat Roof Gable System: Another common system.
• High Cordon System: Often preferred for its relative simplicity in establishment and maintenance. The permanent horizontal arms (cordons) are established along the trellis wires.

Pruning Practices:

Pruning involves the removal of portions of the grapevine to maintain its size, shape, and productivity. It's done when the vine is dormant.

• Dormant Pruning (Winter Pruning): This is the main pruning season, typically in late winter or early spring (December-February in India).
  • One-year-old canes (shoots that have become woody) are pruned back to either short spurs (3-5 buds) for fruiting wood or one-node renewal spurs to produce vegetative shoots for the next year.
  • The "30 + 10" rule is a guide for balanced pruning in some American cultivars: 30 buds for the first pound of prunings removed, and 10 buds for each additional pound.
• Foundation Pruning / Back Pruning (May Pruning): In tropical regions of India (e.g., peninsular India), vines are pruned twice a year, enabling two harvests or one main harvest with better fruit quality.
  • The first pruning (foundation pruning) typically occurs in March-May to develop new canes.
  • The second (forward pruning or fruit pruning) occurs in October-November for fruiting.
  • This "Double Pruning and Double Cropping System" is unique to regions like Tamil Nadu.
• Summer Pruning/Canopy Management:
  • Shoot Thinning: Reduces excess shoot numbers, adjusts crop load, and improves light penetration and air circulation within the canopy. Typically, 1-2 clusters are left per shoot, and weak or unproductive shoots are removed early in the season.
  • Pinching and Topping: Involves removing the tips of growing shoots to control vegetative growth and redirect energy towards fruit development.

Fruit Thinning

Fruit thinning, also known as cluster thinning or crop thinning, is a crucial vineyard management practice that involves selectively removing a portion of the grape clusters or individual berries from the vines. This practice is essential for optimizing grape quality, managing crop load, and ensuring balanced vine growth.

Reasons for Fruit Thinning:

• Enhances Berry Size and Quality: By reducing the number of clusters, the vine's resources are concentrated on fewer berries, leading to larger, plumper, and sweeter fruits with improved color and flavor development.
• Manages Crop Load: Prevents over-cropping, which can stress the vine, reduce its vigor, and negatively impact fruit ripening and overall quality.
• Promotes Uniform Ripening: Thinned clusters receive better sunlight and air circulation, leading to more even ripening.
• Reduces Disease Incidence: An open canopy and less crowded clusters improve air movement, reducing humidity around the berries and thus lowering the risk of fungal diseases like Botrytis bunch rot and powdery mildew.

Timing and Techniques:

• Timing: The ideal time for cluster thinning is typically in early summer, immediately after fruit set when small clusters have formed. Berry thinning (removing individual berries) is done shortly after cluster thinning, once berries are pea-sized.
• Techniques:
  • Cluster Thinning: Involves removing entire clusters that are small, misshapen, overly large, or too numerous on a shoot. Generally, one or two clusters are left per shoot.
  • Berry Thinning: Hand thinning of individual berries within a cluster to prevent overcrowding, rubbing, and promote larger fruit size. This is particularly important for commercial crops to produce tight, well-formed clusters that travel and store well.
  • Use of Gibberellic Acid (GA): In commercial cultivation, GA can be used along with cluster and berry thinning to increase bunch and berry size in seedless varieties.

Plant Protection

Effective plant protection measures are vital to safeguard grapevines from various pests, diseases, and physiological disorders, ensuring healthy growth and sustained productivity.

Insect Pests:

• Flea Beetle: Damages sprouting buds, tender shoots, and leaves. Control involves removing loose bark and applying carbaryl or quinalphos.
• Thrips: Attack blossoms and newly set berries, leading to corky layers on fruits and reduced fruit set. Prophylactic sprays of insecticides like Phosphamidon or Monocrotophos are recommended.
• Mealy Bugs: Cause fruit drop and shriveling, feeding on sap and excreting honeydew. Ants often aid their spread. Integrated approaches include destroying alternate host plants, removing loose bark, applying grease bands, and spraying insecticides like Dichlorvos or Chlorpyrifos. Biological control using predators like Cryptolaemus montrouzieri is also effective.
• Grape Leaf Roller: Caterpillars roll leaves and feed inside, causing defoliation. Control measures include collecting and burning infested leaves and spraying malathion or endosulfan.
• Stem Borer and Root Knot Nematodes: Can cause significant damage. For nematodes, soil application of carbofuran or neem cake is advised.

Diseases:

• Downy Mildew (Plasmopara viticola): A major fungal disease, especially in humid conditions and during rainfall. Symptoms include yellow-green spots on leaves and fuzzy white growth on the underside. Fungicides like Acrobat (Dimethomorph) and Polyram are used for control.
• Powdery Mildew (Erysiphe necator): Characterized by white powdery patches on leaves, shoots, and berries. Can be controlled with fungicides like Sulfur-based products or advanced options like Sercadis Plus.
• Anthracnose: Causes dark, sunken lesions on berries, leaves, and shoots.
• Black Rot: Fungal disease causing black mummified berries.
• Wilt and Leaf Blight: Other common diseases requiring timely treatment.

Physiological Disorders:

• Berry Cracking: Often caused by erratic water supply, especially over-irrigation during veraison to harvest.
• Leaf Chlorosis: Yellowing of leaves due to nutrient deficiencies (e.g., iron, zinc), often linked to soil pH.
• Post-harvest Berry Drop: Can occur due to various factors including moisture stress during specific growth stages.

Integrated Pest and Disease Management (IPM) strategies, combining cultural practices, biological control, and judicious use of chemical pesticides, are crucial for sustainable grape production.