Breeding and Seed Production of Ornamental Crops (2+1)

Mutation Breeding

Mutation: A sudden heritable change in characteristics of an organism is known as mutation. The term mutation was introduced by Hugo de Vries in 1900. Since most of the floricultural crops are clonally propagated, mutation breeding has proved to be one of the most effective methods of crop improvement and development of varieties in these crops. It has particularly been used for the induction of variegated characters into different floricultural crops.
Sites for mutation:

• Mutation may be the result of a change in a gene, a change in chromosomes that involves several genes or a change in a plasma gene.
• Mutations produced by changes in the base sequences of genes are known as gene or point mutations.
• Some mutations may be produced by changes in chromosome structure, or even in chromosome number; they are termed as chromosome mutations.
Types of mutations:

1. Spontaneous mutation
2. Induced mutation
1. Spontaneous Mutations:

• The mutations that occur in natural population, are known as spontaneous mutations. Man has no role in this type of variations. The frequency of spontaneous mutations is generally as low as one in 10 lacs, i.e., 10^-6.
2. Induced Mutations:

• When the mutations are artificially induced by a treatment with certain physical or chemical agents; such mutations are known as induced mutations. The agents used for producing them are termed as mutagens.
Mutagens:

• Agents used for the induction of mutations are known as mutagens. Mutagens may be different kinds of radiations known as physical mutagens or some chemicals known as chemical mutagens. The different mutagens may be grouped as follows:
Physical mutagens:
1. Ionising radiations :

a) Particulate radiations, e.g., α-rays, β-rays, fast neurons, and thermal neutrons
b) Nonparticulate radiations (electromagnetic radiations), e.g., X-rays and γ-rays.

2. Non ionising radiations, e.g., ultraviolet radiation (UV).
Chemical mutagens:

• Alkylating agents e.g, sulphur mustards, nitrogen mustards epoxies, ethylene-imines, (e.g., ethylene imine or EI), sulphates and sulphonates (e.g., ethymethane sulp-honate or EMS, methylmethane sulphonate or MMS), diazoalkanes, nitroso compounds, e.g. N'-methyl-N-nitro-N-nitroso-guanidine or MNNG).
• Acridine dyes e.g., acriflavine, proflavine, acridine orange, acridine yellow ethidium bromide.
• Base analogues, e.g., 5-bromouarcil, 5-chlorouracil
• Others, e.g. nitrous acid, hydroxyl amine, sodium azide