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🧅 Onion — India's Most Important Foreign Exchange Earning Vegetable

Complete guide to onion cultivation covering bulb formation, photoperiod response, pungency compounds, varieties, Maleic Hydrazide for storage, thrips management, and purple blotch disease for competitive exams.

At Lasalgaon in Maharashtra's Nashik district — India's biggest onion market — prices fluctuate daily, influencing the cost of this essential kitchen staple across the entire country. Onion is not just a vegetable; it is a politically sensitive commodity. Maharashtra alone accounts for 23.4% of India's onion area and 27.5% of production, and onion contributes a remarkable 77% of India's total foreign exchange earnings among fresh vegetables. Understanding its cultivation science is critical for both farming and competitive exams.

IMPORTANT

Key exam facts: Day length is more important than temperature for bulb production. Temperature is more important for seed production. Pungency is due to Allyl propyl disulphide. Bolting is caused by low temperature. Spray Maleic Hydrazide @ 2500 ppm to check sprouting in storage.

Onion intro overview showing Maharashtra onion field, Lasalgaon market, bulb-production day length, low-temperature bolting, and sprouting control in storage — This overview sets onion in its real production context while reinforcing the exam anchors of day length, bolting, and sprouting management.

Botanical Identity

Parameter	Detail
Botanical Name	Allium cepa
Family	Alliaceae (previously Liliaceae)
Origin	Central Asia
Rich source of	Vitamin B Complex
Pollination	Highly cross-pollinated (due to protandry)
Pollinator	Honey bees
Inflorescence	Umbellate (umbrella-shaped cluster)
Flower colour	White or bluish
Anthesis time	5-9 am
Season	Cool season crop

India's Position in Onion Production

India's onion production visual showing Maharashtra onion fields, Lasalgaon market, and export context — This production view links Maharashtra field dominance with Lasalgaon market importance and India’s export role in onions.

Parameter	Fact
India's global rank (area and production)	2nd (after China)
India's rank in exports	3rd (12% of world exports)
World's leading onion exporter	Netherlands (21%), followed by Spain
Leading Indian state (area + production)	Maharashtra (23.4% area, 27.5% production)
Biggest onion market in India	Lasalgaon, Nashik, Maharashtra
Share in fresh vegetable forex earnings	77%

Types of Onion

Type	Botanical Name	Key Feature
Common onion	Allium cepa	Single large bulb
Potato/Multiplier onion	A. cepa var. aggregatum	Clusters of small bulbs underground
Tree onion	A. cepa var. viviparum	Produces small bulbils on top of flower stalk

Bulb Formation and Photoperiod

Understanding the interplay between day length and temperature is essential:

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Factor	Importance
Day length	More important than temperature for bulb production
Temperature	More important than day length for seed production
Optimum temperature for bulb development	20-25 degrees C

Compound	Role
Allyl propyl disulphide	Pungency (volatile sulphur compound causing tears)
Quercetin	Colour of outer skin (yellow-brown flavonoid); antioxidant, anti-cancer
Catechol	Phenolic compound with antifungal property; protects outer scales

Method	Rate
Seeds (nursery raised)	8-10 kg/ha
Bulb planting	750 kg/ha (medium-sized bulbs)

Category	Varieties
Largest cultivated type	Orange and Yellow
White (dehydration)	Pusa White Flat, Bhima Shubra
Green onion	Early Grano, Pusa White Flat, Pusa White Round
Small onion (pickling)	Bangalore Rose, Arka Bindu, Agrifound Red
Export quality	Arka Bindu, Agrifound Rose
Selfing variety	Pusa Madhvi (unusual for cross-pollinated onion)

Method	Varieties
Introduced	Brown Spanish, Early Grano, Bermuda Yellow
Selection	Pusa Ratnar, Pusa Red, N-53, Arka Niketan, Arka Kalyan, Arka Pragati, Arka Bindu, Nasik Red, Agrifound Dark Red, Patna Red, Bangalore Rose
Hybrid	Arka Pitambar (White x Red), Arka Kirtiman, Arka Lalima
Male sterile lines isolated in	Pusa Red

🧅 Onion — India's Most Important Foreign Exchange Earning Vegetable

Botanical Identity

India's Position in Onion Production

Types of Onion

Bulb Formation and Photoperiod

Pro Content Locked

Botanical Identity

India's Position in Onion Production

Types of Onion

Bulb Formation and Photoperiod

Pungency and Chemical Compounds

Post-Harvest and Storage

Seed Rate

Important Varieties

By Colour and Use

By Development Method

By Season

Disease-Resistant Varieties

Multiplier Onion Varieties

Pests and Diseases

Thrips — Most Important Pest

Purple Blotch — Major Foliar Disease

Summary Cheat Sheet

Summary Continued

Section Quiz

Season	Varieties
Kharif	Arka Kalyan, Agrifound, N-53, N-241, Arka Pragati (both seasons)
Long day	Brown Spanish, Early Grano (yellow, good for salad)

Concept / Topic	Key Details / Explanation
Botanical identity	Onion is Allium cepa of the Alliaceae family, originated in Central Asia, is a cool-season crop, and is rich in Vitamin B complex.
Flowering and pollination facts	Onion is highly cross-pollinated because of protandry, honey bees are the main pollinators, the inflorescence is umbellate, flowers are white or bluish, and anthesis occurs at 5-9 am.
India's position	India ranks second in area and production after China, third in exports, and onion contributes about 77% of foreign exchange earnings among fresh vegetables; Maharashtra is the leading state and Lasalgaon is the biggest onion market.
Types of onion	Common onion is Allium cepa, potato or multiplier onion is A. cepa var. aggregatum, and tree onion is A. cepa var. viviparum.
Bulb formation vs seed production	Day length is more important than temperature for bulb production, while temperature is more important for seed production; optimum temperature for bulb development is 20-25 degrees C.
Photoperiod classes and bolting	Short-day varieties bulb at 11-12 hours of daylight, long-day varieties need 14-16 hours, and bolting is induced by low temperature.
Pungency and protective compounds	Onion pungency is due to allyl propyl disulphide; quercetin gives outer-skin colour and antioxidant value, while catechol protects outer scales through antifungal action.
Storage and post-harvest management	Sprouting in storage is checked by spraying Maleic Hydrazide @ 2500 ppm about 15-20 days before harvest; zinc improves yield and storage quality, and onion is also associated with relief from sun stroke.

Concept / Topic	Key Details / Explanation
Seed rate	Seed rate is 8-10 kg/ha for nursery-raised crop and about 750 kg bulbs/ha for bulb planting.
Varieties by use and colour	Orange and yellow onions are the largest cultivated group; Pusa White Flat and Bhima Shubra are important white dehydration types; Early Grano, Pusa White Flat, and Pusa White Round are used as green onion types.
Pickling, export, and selfing types	Bangalore Rose, Arka Bindu, and Agrifound Red are used for small pickling onions; Arka Bindu and Agrifound Rose are export-quality, while Pusa Madhvi is notable as a selfing variety.
Varieties by development method	Introduced varieties include Brown Spanish, Early Grano, and Bermuda Yellow; major selections include Pusa Ratnar, Pusa Red, N-53, Arka Niketan, Arka Kalyan, Arka Pragati, Arka Bindu, Nasik Red, Agrifound Dark Red, Patna Red, and Bangalore Rose; important hybrids are Arka Pitambar, Arka Kirtiman, and Arka Lalima.
Seasonal and resistant varieties	Arka Kalyan, Agrifound, N-53, N-241, and Arka Pragati are kharif types; Brown Spanish and Early Grano are long-day types; Arka Kalyan and Nasik Red resist purple blotch.
Multiplier onion varieties	Important multiplier onion varieties are Agrifound Red, CO-3, and CO-4.
Major pest	Thrips tabaci is the most important pest, producing silvery streaks on leaves and reducing bulb size; it is managed with Acephate 1 ml/litre.
Major disease	Purple blotch, caused by Alternaria porri, produces purple elongated lesions on leaves and seed stalks; Arka Kalyan and Nasik Red are resistant varieties.