In-vitro Techniques and Mutagenesis for the Improvement of Vegetatively Propagated Plants

Abstract

Conventional plant breeding is based on genetic variation and selection of the desired genotypes. The availability of genetic diversity and genetic variation is the starting point of any breeding programme. In most crops, sufficient genetic variation is present among land races, cultivars and their wild relatives. In conventional plant breeding programmes this is followed by several years of selection and field evaluation before a desired genotype is released as an improved cultivar. In many sexually propagated crops, e.g., rice, wheat, maize, barley, the genetic variability is usually recombined through hybridization. The desired recombinants are then selected from the segregating populations in the subsequent generations which are tested, multiplied and released as improved cultivars. However, a number of important crops such as banana, plantain, date palm, citrus, potato, sweet potato, pineapple, apple, and pear are propagated from vegetative parts, and are not amenable to improvement in the same manner as sexually propagated plants. Many of these plants are complex polyploids, take several years to flower and fruit, some are self-incompatible. In others, such as banana and plantain, there is little or no seed formation. Often the propagule size is too big and bulky to handle and to grow large populations. Hence, it is not possible to produce sufficiently large populations required to obtain the desired recombinant in a short duration. In these plants, mutation induction offers the possibility to alter a few characters without disrupting the genome while retaining all the other characters of clones.