Seed Production Techniques in Onion

Onion

Introduction:

1.?? Onion: Allium cepa L.

2.?? Family: Alliaceae

3.?? Origin: Asia

4.?? In India, leading state is Maharashtra

5.?? In India, the average yield per unit area is extremely low: 10.6 t/ha

Onion: Botany:

1.?? Biennial herb

2.?? Tubular leaves

3.?? Attachment of the enlarged leaf base to the subterranean portion of the stem develops into bulbs.

4.?? Flowers developed in the second stage following bulb production.

5.?? Structure of Flower: Umbel

Important Onion Species:

1.?? Allium cepa var. aggregatum (2n = 16)

2.?? Allium cepa var. ascalonicum (2n = 16)

3.?? Allium cepa var. viviparum (2n = 16)

4.?? Allium fistulosum

5.?? Allium cepa (2n = 16)

Types of Onion based on colour:

1.?? Yellow

2.?? Red

3.?? White

Floral Biology:

1.?????? It is a cross pollinated species.

2.?????? Inflorescence is terminal cymose umbel enclosed by beaked spathe, also called as Scape.

3.?????? Flowers are bisexual, actinomorphic, trimerous and bracteates

4.?????? Each flower with five whorls

5.?????? Six perianth, free with imbricate aestivation

6.?????? Six stamens, anthers are oblong and dithecus

7.?????? Superior ovary, axile placentation, tri-carpellary and syncarpous

8.?????? Filiform style, minute stigma

9.?????? Fruit is capsule with six seeds

10.??? Seed is albuminous

11.??? Pollination condition is protandry

Breeding Methods:

1.?????? Introduction

2.?????? Mass Selection

3.?????? Selfing

4.?????? Inbreeding

5.?????? Hybridization

6.?????? Heterosis

Breeding Objectives:

1.?? High yield

2.?? Excellent bulb quality in terms of size, color, firmness, pungency, and dormancy

3.?? High TSS content important for dehydration industry. Skin retention and high dry matter

4.?? Resistance to biotic and abiotic stress

5.?? Development of high yielding varieties

6.?? Development of varieties suitable for export market

7.?? Development of disease resistant F1 hybrids with superior quality of bulbs

Characteristics of Ideal Bulb:

1.?? Bulb attractive, uniform in size, shape, colour and time of maturity

2.?? High pungency

3.?? High dry matter and long storage life

4.?? Intact and attractive skins, thick rings, thin neck, resistant to early bolting, disease, pests

5.?? White bulbs are better for dehydration since people prefer colored dehydrated products. Bulb shape: Globe shape as it leads to reduce waste during tailing and topping

6.?? Size of Bulb: 5.0 – 7.5 cm diameter

7.?? Firms bulbs with high TSS, dry matter

Diseases / Insects:

1.?? Purple blotch

2.?? Stemphyllium blight

3.?? Basal rot

4.?? Maggot

New Breeding Tools:

1.?? Mutation Breeding

2.?? Polyploidy

3.?? Plant Biotechnology

4.?? In-vitro Techniques

5.?? Genetic Engineering

a. Soil type: well drained & loose soil with pH 5.8 to 6.5

b. The ideal temperature for vegetative growth is 12.8 to 23.0 C

c. Ideal temperature for bulb formation is 20 – 25 C

d. Low temperature in early stage cause bolting

e. Average yield:

A. Big size onion: 25 – 30 t/ha

B. Small onion: 16 – 20 t/ha

C. Multiplier onion: 15 – 18 t/ha

Isolation:

1. Foundation seed: 1000 – 1600 m
2. Certified seed: 500 m