Hybrid seed production in Maize

    Hybrid seed production in Maize

Hybrid: –

               Progeny resulting from a cross of two inbreeding parents and this process is called hybridization.

Hybrid plants has more performance than the average of their parents.

AA (inbred line) ×   BB (inbred line)

AB ———– Hybrid

History: –

Hybrid inbreeding started in 1909. GEORGE H. SHULL proposed a method to produce hybrid. Before this, there were many scientists who were working on hybrid production but GEORGE H. SHULL was first who proposed a method to develop hybrid.

In 1909, EDWARD M. EAST was another scientist who was working at Connecticut agriculture station, proposed inbreeding in corn.

Two Theories: –

1. Dominance theory
2. Over dominance theory

Dominance theory :-

Dominance theory states that hybrid vigor results from bringing dominant genes in one plant .

Example :-

AABBccddEE × aabbCCDDee

                 AaBbCcDdEe

Why ?

First theory states that hybrid vigor result in bringing favorable dominant genes in one plant. we all know that Dominant genes always masks the recessive character.

Over Dominance Theory: –

This theory states that hybrid vigor results in heterozygous loci. heterozygous loci contribute more productivity than homozygous.

Why: –

It is due to allelic interaction.

Procedure to develop hybrid: –

1.selection

2.development of inbred lines

3.cross between inbred lines

1.Selection: –

First step to develop hybrid is selection of germplasm. Germplasm lines are collected from

1.naturally open pollinated population

2.F2 results from a cross between two homozygous lines

2.Development of inbred lines

Inbreeding is the process of selfing of a plant which increases the homozygosity. Inbred line is developed by the successive selfing of plant up to 5^th and 6^th generation. it is done by covering the male and female plant parts and during the season of pollination, both parts are exposed and pollens from male part of same plant are crossed on female part. After selfing again male and female parts are covered with paper bags. During development of inbred line its performance is decreased in each generation.

3.Cross between inbred lines: –

Inbred lines are crossed with other inbred lines and hybrids are produced. Hybrids have more outcome than the average of parents.

Hybrid types: –

1.conventional hybrids

2.non conventional hybrids

Conventional hybrids :-

1. Single cross hybrid ( A×B)
2. Double cross hybrid (AB)×(CD)
3. Three way cross (A×B)×C
4. Single modified cross (A×A´) ×B
5. Double modified single cross (A×A´) (B×B´)
6. Modified three ways cross (A× B) (C×C´)

Non-Conventional Hybrids: –

1. Inter-varietal Hybrid: Variety × Variety
2. Top Cross Hybrids: Inbred × Variety
3. Interfamily Hybrid:
4. Top Cross Hybrids: Single Cross × Variety

Muhammad Haroon

Registration number (2014-ag-5484)

Department: PBG

Degree: BSc agriculture

Semester:6^th