Breeding of Fruit and Plantation Crops

Somatic mutations

• These mutations occur in tissues other than the germ track. Most mutations occur somatically, i.e., after the differentiation has set in, when a group of somatic cells is genotypically different from the other cells in the same individual, a somatic mutation may be suspected. The change occurs in the cells of the growing body.


• Hence the new types of cells are not only heterozygous but form a patch. In meristematic tissues of axillary buds and others a mutation often leads to a batch with new characters. Such changes occur more frequently in polyploidy and heterozygous plants and in individuals which have been grown for long as clones.


• If propagated vegetatively the mutated parts give rise to new types of plants. This practice is common in horticulture. The brown colour of the grain in sorghum in some cases is determined by the persistence of the integument in which, the colour is deposited.


• Often mutant patches of white occur in individual grains of panicles from homozygous brown grained line. Anatomical studies have shown the suppression of the integument in such places where the white patch appears and genetical studies have shown that this is only affecting the somatic tissue and does not affect the germinal tissues.


• White grain colour is recessive to brown. In Cosmos sulphureus, plants with yellow petals have often been observed to appear suddenly ; the usual one has orange-yellow coloured petals.


• Sometimes the region affected is half the head and, in such cases, in the progeny, plants with all yellow flowers have appeared. These have bred true. Somatic mutations have been recorded in vegetatively propagated plants like apples, dahlias, chrysanthemum, potato, rose, etc.