Breeding of Fruit and Plantation Crops

Procedure of mutation breeding When mutations are induced for crop improvement, the entire operation of induction and isolation of mutants is termed as mutation breeding. The various steps involved in mutation breeding are as under: Objectives of programme – Objective should be clear cut and well defined Selection of variety for mutagen treatment – Locally accepted best variety in which improvement is needed either in polygenic or monogenic trait. Part of plant to be treated- Seeds, pollen grains or vegetative propagules (buds and cuttings) may be used for mutagenesis. Selection of plant part for mutagenic treatments are based on mode of multiplication / reproduction. In sexually propagated fruit plants, seed treatment is common. Pollen grains may be used, but it has some limitations. It is difficult to collect large amount of pollen grains and pollen survival life is also short. In case of a sexually propagated fruit plant, buds or cuttings are used for mutagenic treatment. Dose of mutagen – An optimum dose is that one which produces the maximum frequency of mutation and causes the minimum killing i.e. LD 50. It is that dose of mutagen which would kill 50% of the treated individual. Dose of mutagen depends upon intensity and time of treatment. Mutagen treatment- Selected plant part is exposed to the desired mutagen dose. The plants are immediately planted to raise M1 plant from them. In case of seed treatment they are pre-soaked for a few hours to initiate metabolic activities and then exposed to mutagen. Treated seeds are sown immediately in field to raise M1 generation. The seeds derived from mutated pollen is considered as M1 and subsequent generations can be derived through selfing or clonal propagation.