🧅 Allium & Tuber Vegetables — Onion, Potato, Garlic, Carrot & Radish
Learn onion, potato, garlic, carrot and radish cultivation for CUET Agriculture. Allium crops, tuber vegetables, planting and storage methods.
This lesson covers two important groups of vegetables: the Allium crops (Onion, Garlic) belonging to family Amaryllidaceae, and the root and tuber vegetables (Potato, Carrot, Radish) where the edible parts are modified underground organs. These crops are staples of Indian cuisine and are frequently tested in CUET.
5. Onion (Allium cepa)
Onion (Allium cepa) — Source: Wikimedia Commons (CC)
- Family: Amaryllidaceae (formerly classified under Liliaceae -- this reclassification is important for exams)
- Origin: Central Asia (Afghanistan, Iran, Pakistan region)
- Chromosome number: 2n = 16
- Pungency is due to allyl propyl disulphide, a volatile sulphur compound that evaporates when the onion is cut
- Lachrymatory factor (the chemical that makes your eyes water when cutting onions): syn-propanethial-S-oxide
- Bulb formation is influenced by photoperiod and temperature -- this is a critical concept because different latitudes require different variety types
IMPORTANT
Onion bulb formation depends on day length. Short-day varieties (<12 hrs daylight) are grown in tropical India, while long-day varieties (>14 hrs daylight) are suited for temperate regions. This is why Indian onion varieties differ fundamentally from European ones.
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This lesson covers two important groups of vegetables: the Allium crops (Onion, Garlic) belonging to family Amaryllidaceae, and the root and tuber vegetables (Potato, Carrot, Radish) where the edible parts are modified underground organs. These crops are staples of Indian cuisine and are frequently tested in CUET.
5. Onion (Allium cepa)
Onion (Allium cepa) — Source: Wikimedia Commons (CC)
- Family: Amaryllidaceae (formerly classified under Liliaceae -- this reclassification is important for exams)
- Origin: Central Asia (Afghanistan, Iran, Pakistan region)
- Chromosome number: 2n = 16
- Pungency is due to allyl propyl disulphide, a volatile sulphur compound that evaporates when the onion is cut
- Lachrymatory factor (the chemical that makes your eyes water when cutting onions): syn-propanethial-S-oxide
- Bulb formation is influenced by photoperiod and temperature -- this is a critical concept because different latitudes require different variety types
IMPORTANT
Onion bulb formation depends on day length. Short-day varieties (<12 hrs daylight) are grown in tropical India, while long-day varieties (>14 hrs daylight) are suited for temperate regions. This is why Indian onion varieties differ fundamentally from European ones.
Climate & Soil
- Cool season crop for bulb formation; optimum 15-25 degrees C
- Long-day varieties need >14 hrs daylight (temperate regions); Short-day varieties need <12 hrs (tropical -- India)
- Well-drained sandy loam; pH 6.0-7.0
- Major producing states: Maharashtra (Nashik -- "Onion Capital of India"), Karnataka, MP, Bihar
Important Varieties
| Type | Varieties |
|---|---|
| Red | N-53, Agrifound Dark Red, Arka Kalyan, Arka Niketan, Bhima Super, Pusa Red |
| Light Red | Nasik Red, Pusa Ratnar |
| White | Pusa White Round, Pusa White Flat, Agrifound White |
| Yellow | Arka Pitambar |
| Multiplier (small onion) | Co-4, Agrifound Rose |
| Hybrid | Arka Kirthiman |
Cultivation
- Seed rate: 8-10 kg/ha (transplanted method); 3-4 kg/ha (bulb sets method -- here small bulbs rather than seeds are planted)
- Nursery: 6-8 weeks old seedlings are used for transplanting
- Spacing: 15cm x 10cm -- this is notably closer than most vegetables because onion plants are compact
- Seasons -- onion is grown in three distinct seasons in India:
- Kharif: June-July transplanting; harvest Nov-Dec
- Late Kharif: Sept-Oct transplanting; harvest Feb-Mar
- Rabi: Nov-Dec transplanting; harvest Apr-May -- this is the main season producing the best quality onions with good storage life
Manuring
- 100 kg N + 50 kg P2O5 + 60 kg K2O + 20 tonnes FYM/ha
- Sulphur application at 40 kg/ha improves pungency and storage quality -- sulphur is a key component of the volatile compounds responsible for onion flavour
Harvesting & Yield
- Maturity indicator: Neck fall -- when 50-75% of tops (leaves) fall over at the neck region. This is the most reliable indicator of onion maturity, signalling that the bulb has stopped growing.
- Curing: After harvest, onions are dried/cured in shade for 3-5 days to toughen the outer skin and neck, which reduces storage losses
- Yield: Rabi 20-25 t/ha; Kharif 15-20 t/ha -- Rabi onions yield more because of favourable growing conditions
- Storage: Use well-ventilated structures; spray MH (Maleic Hydrazide) at 2500 ppm on the standing crop 15 days before harvest to prevent sprouting during storage
TIP
Maleic Hydrazide (MH) is a growth retardant that inhibits cell division in the meristematic tissue of the bulb. It must be applied before harvest (not after) to be effective, because it needs to be translocated into the bulb while the plant is still actively growing.
Storage Problems
- Sprouting, rooting, and rotting are the three major storage problems
- Black mould -- Aspergillus niger causes black powdery growth between onion scales
- Irradiation with cobalt-60 or gamma rays can prevent sprouting (a modern post-harvest technology)
- Cold storage at 0-2 degrees C with 65-70% RH extends storage life
6. Potato (Solanum tuberosum)
Potato (Solanum tuberosum) — Source: Wikimedia Commons (CC)
- Family: Solanaceae
- Origin: South America (Peru, Bolivia -- Andes region)
- Chromosome number: 2n = 48 (tetraploid, basic x = 12) -- making potato the only common solanaceous vegetable that is NOT diploid with 2n = 24
- Vegetatively propagated through seed tubers (not true seeds in commercial cultivation)
- Edible part: Modified stem (stem tuber) -- the "eyes" on a potato are actually lateral buds on a compressed underground stem
- India is the second-largest producer after China
NOTE
Despite belonging to Solanaceae like tomato (2n=24), potato has 2n = 48 because it is a tetraploid (4 sets of the basic chromosome number x=12). This is one of the most commonly asked facts in CUET.
Climate & Soil
- Cool season crop; optimum 15-25 degrees C for tuber formation
- Short day length promotes tuberization -- this is why potato is primarily a Rabi (winter) crop in the Indo-Gangetic plains
- Temperature above 30 degrees C inhibits tuber formation because high temperatures promote haulm (shoot) growth at the expense of tuber development
- Well-drained sandy loam; pH 5.0-6.5 (prefers slightly acidic soil)
- Major producing states: UP (largest producer), West Bengal, Bihar, Gujarat, MP
Important Varieties
| Category | Varieties |
|---|---|
| Table/fresh | Kufri Jyoti, Kufri Pukhraj, Kufri Sindhuri, Kufri Badshah, Kufri Bahar |
| Processing (chips) | Kufri Chipsona-1, Kufri Chipsona-3, Kufri Himsona (high dry matter -- essential for crispy chips) |
| Early maturity | Kufri Ashoka, Kufri Chandramukhi, Kufri Khyati |
| Late blight resistant | Kufri Girdhari, Kufri Sheetman |
Why 'Kufri' in Potato Variety Names?
All Indian potato varieties begin with "Kufri" because they are developed at the Central Potato Research Institute (CPRI) headquartered at Kufri, a hill station near Shimla in Himachal Pradesh. This naming convention is unique to potato and is a good exam mnemonic.
Cultivation
- Seed tubers (30-40g size or cut pieces with 2-3 eyes) are used for planting. Each "eye" is a bud that will sprout into a new plant.
- Seed rate: 20-25 quintals/ha -- this is much higher than other vegetables because whole tubers are used as planting material
- Spacing: 60cm x 20cm (ridges and furrows system)
- Planting: October-November (plains of North India); March-April (hills)
- Earthing up is done at 30 and 45 DAP -- this is an essential practice where soil is mounded around the plant base. Earthing up serves two purposes: (1) provides loose soil for tuber expansion, and (2) prevents greening of tubers exposed to sunlight
Manuring
- 25 tonnes FYM + 150-200 kg N + 100 kg P2O5 + 120 kg K2O per hectare
- Nitrogen in 2 splits: 50% basal + 50% at earthing up
- Potato is a heavy feeder of potassium -- potassium improves tuber quality, starch content, and disease resistance
Irrigation
- Critical stages: stolon formation and tuber initiation (30-60 DAP) -- water stress during this period drastically reduces tuber number and size
- Irrigate at 7-10 day intervals
- Stop irrigation 10-15 days before harvesting to allow skin hardening (skin set), which reduces damage during harvest and handling
Harvesting & Yield
- Maturity indicators: haulm (aerial part) turning yellow, skin firmly attached to tuber (does not peel off when rubbed -- this is called skin set)
- Dehaulming -- cutting of plant tops 10-15 days before harvest. This practice promotes skin hardening and helps in uniform maturity.
- Duration: 80-120 days (early varieties: 80-90 days; late: 100-120 days)
- Yield: 25-35 tonnes/ha
Post-Harvest & Storage
- Curing at 15-20 degrees C and 90% RH for 10-14 days -- this allows wound healing (suberization) on any cuts or bruises sustained during harvest
- Cold storage at 2-4 degrees C with 90-95% RH
- CIPC (Chlorpropham) -- a sprout suppressant chemical used in cold stores to prevent premature sprouting
- Green tubers contain solanine, a toxic glycoalkaloid -- tubers exposed to light develop a green colour and accumulate solanine, making them unfit for consumption. This is why earthing up and proper dark storage are essential.
WARNING
Solanine is toxic to humans even in small amounts (causing nausea and digestive problems). Green-skinned potatoes should never be consumed. This is why potatoes must be stored in the dark and earthing up must be done properly during cultivation.
Major Diseases & Pests
- Late blight (Phytophthora infestans) -- the most devastating disease of potato worldwide; caused the Irish Potato Famine (1845) that killed over 1 million people and triggered mass emigration from Ireland
- Early blight (Alternaria solani) -- concentric ring lesions ("target spots") on leaves
- Common scab (Streptomyces scabies) -- raised corky lesions on tuber surface; favoured by high soil pH (above 7.0)
- Black scurf (Rhizoctonia solani) -- black, hard spots (sclerotia) on tuber surface
- Potato tuber moth (Phthorimaea operculella) -- caterpillars mine in leaves and bore into tubers, both in the field and in storage
12. Garlic (Allium sativum)
Garlic (Allium sativum) — Source: Wikimedia Commons (CC)
- Family: Amaryllidaceae (Liliaceae)
- Origin: Central Asia
- Chromosome number: 2n = 16
- Fruit type: Capsule; Edible part: Clove (modified stem -- each clove is a lateral bud enclosed by a fleshy scale leaf)
- Widely used in traditional medicine for blood pressure management and anti-inflammatory properties
IMPORTANT
Garlic is unique among commonly cultivated crops because it does not produce true seed. It is entirely propagated vegetatively by cloves. This means there is no sexual reproduction, and all plants of a variety are genetically identical clones.
Climate & Soil
- Cool season crop; thrives in cold, dry weather during the vegetative growth phase
- Loamy, well-drained soil; pH similar to onion (6.0-7.0)
- Does not produce true seed -- only vegetative propagation by cloves is possible
Key Facts
- Single clove crop -- no seed production; entirely propagated by cloves
- Contains allicin -- the compound responsible for the pungent smell and most of the medicinal properties (antimicrobial, antifungal, cholesterol-lowering)
- The biosynthetic pathway: amino acid alliin is converted to allicin by the enzyme alliinase when garlic tissue is crushed or cut
- Also contains diallyl disulphide, the principal flavour compound
- Seed rate: 400-500 kg/ha (4-5 quintals/hectare) -- this is high because whole cloves are used as planting material
Important Varieties
| Category | Varieties |
|---|---|
| Long day type | Agrifound Parvati (G-313) |
| Short day | Agrifound White (G-41) |
| Other | Jamnagar Local (G-1), Yamuna Safed 1,2,3,4,5, G-282 (largest clove size) |
| Others | Bhima Omkar, Bhima Parpal, Shweta, Pant Lohit |
Diseases
- Purple blotch -- Alternaria porri; causes purple-coloured lesions on leaves. Resistant varieties include Arka Kalyan and Nasik Red.
- Black mould -- Aspergillus spp.; causes black powdery growth, especially in storage
- Bulb and Stem Nematode -- Ditylenchus dipsaci; a serious pest that causes swelling, distortion, and rotting of bulbs
Storage
- Bolting -- premature flowering stalk emergence; caused by exposure to low temperature during early growth. Although garlic does not produce viable seed, it can still produce a flower stalk that wastes plant resources.
- Storage conditions: 0 degrees C at 60-70% RH
- Maleic Hydrazide (MH) at 1500-2000 ppm applied before harvest prevents sprouting during storage (same principle as in onion but at a lower concentration)
13. Carrot (Daucus carota)
Carrot (Daucus carota) — Source: Wikimedia Commons (CC)
- Family: Apiaceae (Umbelliferae)
- Origin: Afghanistan / Western Asia (Central Asia)
- Chromosome number: 2n = 18
- Fruit type: Schizocarp (a dry fruit that splits into two mericarps at maturity)
- Edible part: Swollen tap root -- the fleshy orange part we eat is a modified primary root
- Inflorescence: Umbel (characteristic of the Apiaceae family)
- Pollination: Cross-pollinated due to protandry -- male parts (anthers) mature and shed pollen before the female parts (stigma) of the same flower are receptive, forcing cross-pollination
- Rich source of Vitamin A due to carotene (beta-carotene), the orange pigment that the human body converts to Vitamin A
- Potash (K2O) is essential for good root development; 120 kg/ha recommended
Climate & Soil
- Cool season crop; best root colour development at 15-22 degrees C -- carotene synthesis is optimized at moderate temperatures
- Sandy, deep loamy soil preferred because roots need to grow straight and long without obstruction
- Forking (splitting of the root tip into multiple branches) occurs in hard/stony soils where the root tip meets physical resistance
- Kanji -- a traditional Indian fermented beverage made from black carrot, popular in Punjab during Holi
Varieties
| Type | Subtropical/Asiatic (Red/Orange) | Temperate/European (Orange/Yellow) |
|---|---|---|
| Examples | Pusa Kesar (1st tropical variety), Pusa Vasudha, Pusa Meghali, Pusa Rudhira, Pusa Asita (black/purple) | Pusa Yamdagini (1st temperate variety), Nantes, Early Nantes, Hak Log, Emperor, Chantenay |
| Seed rate | 5-7 kg/ha | 9-12 kg/ha |
| Yield | 5-6 kg/plot | 8-10 kg/ha |
TIP
Remember: Pusa Kesar = first tropical carrot variety (Asiatic type), and Pusa Yamdagini = first temperate carrot variety (European type). Pusa Asita is the unique black/purple carrot, rich in anthocyanins.
Physiological Disorders
- Forking -- caused by hard/compacted soil and calcium deficiency; the root tip splits when it encounters resistance
- Fruit cracking -- caused by boron (B) deficiency and excess moisture (sudden heavy irrigation after drought)
- Cavity spot -- caused by calcium deficiency and K/N nutrient imbalance; appears as small, elliptical depressions on the root surface
- Kadwapan (bitterness) -- develops due to excess soil acidity and high temperature; the root accumulates bitter terpenoid compounds
- Phithiness -- spongy, hollow texture in the root core; caused by delay in harvesting and high temperature -- the root becomes over-mature and lignified
14. Radish (Raphanus sativus)
Radish (Raphanus sativus) — Source: Wikimedia Commons (CC)
- Family: Brassicaceae (Cruciferae)
- Origin: Europe / Mediterranean region (South-Central Asia)
- Chromosome number: 2n = 18
- Fruit type: Siliqua -- the characteristic fruit type of the Brassicaceae (mustard) family
- Edible part: Swollen tap root (similar to carrot, but the swollen portion includes both root and hypocotyl)
- Inflorescence: Racemose
- Pollination: Cross-pollinated
- Good source of Vitamin C and Vitamin A
Climate & Soil
- Cool season crop; best root formation at 10-15 degrees C
- Sandy loam soil preferred for straight, smooth roots
- Pithiness (spongy, hollow roots) develops at higher temperatures -- this is radish's most important quality defect
Varieties
| Type | Subtropical/Asiatic | Temperate/European |
|---|---|---|
| Examples | Pusa Deshi, Pusa Rashmi, Pusa Chetki (for summer sowing), Pusa Sagarika (1st baingan-shaped), Pusa Gulabi, Pusa Jamuni | Pusa Himani (year-round), Scarlet Globe (25-30 days to harvest), White Icicle (round shape) |
| Others | Arka Nishant (multi-disease resistant), Japani White (Oct-Nov sowing) | Rapid Red, White Tip (21 days), Pusa Mridula |
Key Points
- Pusa Chetki -- specially developed for summer sowing (heat tolerant), which is exceptional since radish is typically a cool-season crop
- Scarlet Globe -- one of the fastest maturing vegetables, ready in just 25-30 days; round shape, bright red skin
- Radish requires potash for good root development (similar to carrot)
- Pithiness -- the most common quality problem in radish; spongy, hollow roots caused by late harvesting and high temperature. Always harvest radish at the right stage to avoid this defect.
NOTE
Radish is one of the fastest growing vegetables -- some European varieties like Scarlet Globe can be harvested in just 25-30 days. This makes radish an excellent crop for inter-cropping and short-duration cropping systems.
Summary Cheat Sheet
| Concept / Topic | Key Details / Explanation |
|---|---|
| Onion — family & origin | Family: Amaryllidaceae (formerly Liliaceae); Origin: Central Asia; 2n = 16 |
| Onion — pungency | Due to allyl propyl disulphide; lachrymatory factor: syn-propanethial-S-oxide |
| Onion — bulb formation | Influenced by photoperiod & temperature; short-day varieties (<12 hrs) for tropical India |
| Onion — Nashik | "Onion Capital of India"; Maharashtra is the leading state |
| Onion — seed rate & spacing | 8-10 kg/ha (transplanted); spacing 15×10 cm; Rabi is the main season |
| Onion — maturity indicator | Neck fall — when 50-75% of tops fall over at the neck |
| Onion — storage | MH (Maleic Hydrazide) at 2500 ppm sprayed 15 days before harvest to prevent sprouting; cold storage at 0-2°C, 65-70% RH |
| Onion — storage problems | Sprouting, rooting, rotting; black mould (Aspergillus niger); irradiation with Cobalt-60 prevents sprouting |
| Potato — family & origin | Family: Solanaceae; Origin: South America (Peru, Bolivia); 2n = 48 (tetraploid) |
| Potato — propagation | Vegetatively through seed tubers (30-40g, 2-3 eyes); seed rate 20-25 q/ha |
| Potato — UP | Largest producer in India |
| Potato — earthing up | Done at 30 & 45 DAP; prevents greening (solanine — toxic glycoalkaloid) |
| Potato — manuring | 25 t FYM + 150-200 N + 100 P₂O₅ + 120 K₂O kg/ha; heavy feeder of potassium |
| Potato — storage | Cold storage at 2-4°C, 90-95% RH; CIPC (Chlorpropham) as sprout suppressant; curing at 15-20°C |
| Potato — late blight | Phytophthora infestans — most devastating disease; caused Irish Potato Famine (1845) |
| Potato — varieties | All begin with "Kufri" (from CPRI, Kufri, Shimla); chips: Kufri Chipsona series |
| Garlic — basics | Allium sativum; Family: Amaryllidaceae; Origin: Central Asia; 2n = 16 |
| Garlic — unique trait | Does not produce true seed; entirely propagated by cloves; seed rate 400-500 kg/ha |
| Garlic — active compound | Allicin (pungent smell & medicinal); diallyl disulphide (flavour) |
| Garlic — storage | MH at 1500-2000 ppm; storage at 0°C, 60-70% RH |
| Carrot — basics | Daucus carota; Family: Apiaceae; Origin: Afghanistan; 2n = 18; edible part: swollen tap root |
| Carrot — pigment & vitamin | Rich in carotene (beta-carotene) — source of Vitamin A |
| Carrot — key varieties | Pusa Kesar (1st tropical), Pusa Yamdagini (1st temperate), Pusa Asita (black/purple) |
| Carrot — disorders | Forking (hard soil/Ca deficiency), Cracking (B deficiency), Pithiness (late harvest/high temp) |
| Radish — basics | Raphanus sativus; Family: Brassicaceae; 2n = 18; fruit type: Siliqua |
| Radish — key varieties | Pusa Chetki (summer sowing — heat tolerant); Scarlet Globe (fastest — 25-30 days) |
| Radish — pithiness | Most common quality defect; spongy hollow roots from late harvesting & high temperature |
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