In vitro Mutagenesis and Mutant Multiplication

Abstract

Induced mutations technique is a valuable tool not yet fully exploited in fruit breeding. Tissue culture makes it more efficient by allowing the handling of large populations and by increasing mutation induction efficiency, possibility of mutant recovery and speediness of cloning selected variants. Some vegetatively-propagated species are recalcitrant to plant regeneration, which can be a limit for the application of gene transfer biotechnology, but not for mutation induction breeding. Mutagenesis offers the possibility of altering only one or a few characters of an already first-rate cultivar, while preserving the overall characteristics. Traits induced by mutagenesis include plant size, blooming time and fruit ripening, fruit color, self-compatibility, self-thinning, and resistance to pathogens (Predieri, 2001). The combination of in vitro culture and mutagenesis is relatively inexpensive, simple and efficient (Ahloowalia, 1998). The availability of suitable selection methods could improve its effectiveness and potential applications. The molecular marker technology available today already provides tools to assist in mutation induction protocols by investigating both genetic variation within populations and early detection of mutants with desired traits. However, cost still represents a major limitation to their application. Among the techniques and sources of genetic variation available for tissue culture mutation induction, physical mutagens have already shown potential for application in fruit breeding. The types of radiation suitable for mutagenesis are ultraviolet radiation (UV) and ionizing radiation (X-rays, gamma-rays, alpha and beta particles, protons, and neutrons). X-rays and gamma-rays are the most convenient and easiest types of radiation to use with regards to application methods and handling (Sanada & Amano, 1998), and have been both the most widely used ionizing radiation types and the most effective for fruit breeding purposes. Furthermore, physical mutagens