🌾 Seed Production of Self-Pollinated Crops

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Seed Production of Self-Pollinated Crops

Self-Pollinated Crops — Overview

Self-pollinated (autogamous) crops are those where the flower is pollinated by pollen from the same flower or the same plant before the flower opens. Natural cross-pollination is minimal (typically < 5%).

Major self-pollinated crops: rice, wheat, barley, sorghum, groundnut, chickpea, cowpea, soybean, lentil, linseed

Advantages for seed production:

• Natural outcrossing is rare → varietal purity easier to maintain
• Small isolation distances required (physical mixing prevention only)
• Simpler seed production compared to cross-pollinated crops
• Variety remains genetically stable over generations

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General Principles of Seed Production in Self-Pollinated Crops

1. Selection of Seed Plot

• Choose fertile, well-drained, irrigated land with a uniform soil type
• Land must be free from volunteer plants of the same crop species
• Avoid fields with a history of the same crop in the previous season (reduces volunteer plant problem)
• Fields with serious weed problems (especially grassy weeds resembling the crop) should be avoided

2. Isolation Distance

• Foundation Seed: 3 m from other fields of the same crop
• Certified Seed: 3 m from other fields of the same crop
• Isolation in self-pollinated crops is primarily to prevent mechanical mixing (physical admixture from wind, animals, farm machinery) — not to prevent biological cross-pollination
• Exception: pigeon pea (partial cross-pollination): 50 m isolation recommended

3. Source Seed

• Use certified seed of the next higher class as planting material
• Tag of source seed must be preserved and submitted to SCA at time of land registration
• Never use farm-saved seed for certified seed production plots

4. Field Inspection Stages

Inspection is conducted at three stages:

1. Establishment stage: uniformity of stand, volunteer plant check, weed survey
2. Flowering stage: rouging — removal of off-types, diseased plants, volunteer plants
3. Pre-harvest stage: final assessment — disease, off-types remaining, maturity status

5. Roguing

Roguing is the removal of off-type plants, diseased plants, weeds, and volunteer plants from a seed plot to maintain varietal purity.

What to remove:

• Plants differing in height, leaf colour/shape, flag leaf angle, tillering pattern
• Plants showing disease symptoms (especially blast in rice, yellow rust in wheat)
• Volunteer plants (from previous crop seed left in soil)
• Weeds that are difficult to separate from crop seed at processing

When to rogue:

• Multiple rounds: seedling stage, vegetative stage, flowering stage, maturity stage
• Most critical at flowering stage — maximum morphological differences visible

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Rice Seed Production

Rice is India's most important food crop and a major certified seed crop.

Key Standards

Parameter	Foundation Seed	Certified Seed
Isolation distance	3 m	3 m
Off-types (max %)	0.10	0.20
Seed germination (min %)	80	80
Physical purity (min %)	98	98
Moisture content (max %)	13	13

Identification of Off-Types in Rice

Off-types are identified by differences in:

• Leaf characters: leaf width, colour, ligule/auricle presence
• Flag leaf: angle (erect vs. drooping), colour
• Panicle: type (compact vs. open), exsertion level
• Grain: shape (long/short/round), colour (hull, pericarp), presence of awns
• Plant height and maturity duration

Rouging Schedule

• Tillering stage (25–30 days): remove off-types with prominent leaf differences
• Panicle initiation/booting stage (50–60 days): flag leaf angle, plant height
• Flowering stage (65–70 days): panicle type, awn presence, grain colour
• Pre-harvest (90–100 days): final check for remaining off-types

Harvest

• Harvest when 80–85% of panicles are mature (golden yellow)
• Avoid delayed harvest for shattering varieties (e.g., some traditional varieties)
• Avoid threshing different varieties on the same thresher without thorough cleaning
• Dry to ≤ 13% moisture before storage
• Seed yield: 3–4 t/ha (irrigated, well-managed seed plot)

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Wheat Seed Production

Wheat is the second most important cereal; seed production is predominantly in irrigated north India (Punjab, Haryana, UP, MP).

Key Standards

Parameter	Foundation Seed	Certified Seed
Isolation distance	3 m	3 m
Off-types (max %)	0.05	0.10
Seed germination (min %)	85	85
Physical purity (min %)	98	98
Moisture content (max %)	12	12

Rouging in Wheat

• Before ear emergence: remove plants differing in height, leaf colour, tillering habit
• At ear/spike emergence: identify off-types by spike type (awned vs. awnless), grain colour, spike density
• Ear-to-row method used for Breeder Seed production: individual ears grown in rows; entire off-type rows removed

Harvest

• Harvest at physiological maturity (moisture ~25–28%); black layer formation at grain base
• Avoid delayed harvest — causes grain sprouting on the ear in rainy conditions
• Combine harvesting preferred; clean combine thoroughly between varieties
• Seed yield: 2.5–3.5 t/ha

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Pulse Seed Production

Chickpea (Cicer arietinum)

• Self-pollinated; isolation: 10 m (small risk of bee-mediated cross-pollination)
• Roguing at flowering: identify off-types by flower colour (white vs. pink/purple), leaflet shape, pod type
• Harvest when 80% pods are brown/mature; avoid over-maturity (pod shattering)
• Seed yield: 1.0–1.5 t/ha

Pigeon Pea (Cajanus cajan)

• Partially cross-pollinated (5–20% natural crossing); isolation: 50 m
• More roguing rounds needed; strict isolation essential
• Harvest in batches (indeterminate varieties; pods mature over a long period)

Soybean (Glycine max)

• Highly self-pollinated; isolation: 3 m
• Roguing for off-types: leaf shape, pubescence colour, flower colour, pod colour, hilum colour
• Ensure clean thresher — mechanical mixture is the main contamination risk
• Seed yield: 1.5–2.0 t/ha

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Groundnut Seed Production

• Isolation: 3 m
• Off-types identified by: leaf shape/size, branching pattern (bunch vs. spreading), pod reticulation, kernel size
• Harvest pods at physiological maturity — the "sound test" (shake dried pods; rattling sound = over-mature; no sound = just right for seed)
• Dry pods to ≤ 8% moisture before shelling and storage
• Seed yield (kernels): 1.5–2.5 t/ha

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Common Problems in Self-Pollinated Crop Seed Production

Problem	Cause	Prevention
Genetic drift	Natural mutations accumulating over generations	Grow seed from certified source; limit generations
Mechanical mixture	Contamination during sowing, harvest, threshing, storage	Clean equipment thoroughly; store lots separately
Off-types from mutations	Spontaneous mutations in seed plot	Roguing at multiple stages
Volunteer plants	Previous crop seed germinating in soil	Avoid same crop in previous season; early roguing
Seed-borne diseases	Infected seed introduces pathogens	Use healthy source seed; seed treatment

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Steps to Maintain Varietal Purity

1. Start with genetically pure source seed (next higher class)
2. Select clean land with no prior crop of same species
3. Maintain required isolation distance
4. Conduct timely and thorough roguing at all stages
5. Avoid mechanical mixing at every step — sowing, harvesting, threshing, storage
6. Label and store seed lots separately
7. Keep field records (plot map, rouging records, inspection reports)

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Seed Production Standards for Self-Pollinated Crops

Crop	Isolation (m)	Rouging Stages	Typical Seed Yield (t/ha)
Rice	3	Tillering, Flowering, Pre-harvest	3–4
Wheat	3	Pre-ear, Ear emergence, Pre-harvest	2.5–3.5
Chickpea	10	Vegetative, Flowering	1.0–1.5
Pigeon pea	50	Vegetative, Flowering, Pre-harvest	0.8–1.2
Soybean	3	Vegetative, Flowering	1.5–2.0
Groundnut	3	Vegetative, Pre-harvest	1.5–2.5

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Principles and practices of seed production in self-pollinated crops including rice, wheat, pulses, and oilseeds — isolation, rouging, and harvest management.
Section context	Revise this lesson with the rest of Seed Production Technology for stronger conceptual continuity.