EVALUATION OF INDUCED MUTATION METHODS IN PINOTAGE TO INCREASE GENETIC VARIABILITY

Researcher: P. Burger - 10 Jun 2016

This project aims to develop a method to increase the genetic diversity of Pinotage. Pinotage, South Africa’s locally bred cultivar is considered the country’s flagship red cultivar, however very few clones are available to the industry. Pinotage was only bred in the twentieth century (1925) and can be regarded as a “young” cultivar. This means it has had limited time to give rise to mutations compared to other cultivars that have been around for centuries.

Traditional breeding involves crossing two parent cultivars and since grapevine is a heterozygous crop, their off-spring are unique individuals with characteristics varying from both parent cultivars and from its siblings. Thus traditional cross-breeding is not suited to improve or alter single or limited characteristics of an existing cultivar. Genetic modification provides an ideal solution since specific genes can be inserted into an existing cultivar, but there is a lot of controversy and consumer resistance against this technique. Evidence exists that spontaneous bud-mutations result in the formation of new cultivars and clones while induced mutation has been successfully used to develop new cultivars in a number of crops. Induced mutation alters characteristics at random, but allows for the generation of a large number of variations that can be used for possible selection.

Mutations in grapes have been induced by gamma irradiation of buds, after which plants are established on own roots from the buds, or by grafting single-bud cuttings onto rootstocks. Once the plants are established, potential mutants can be selected based on phenotypic differences.  The sensitivity of cultivars to irradiation differ, some withstanding higher doses than others.

The current pilot study will explore irradiation-based mutagenesis of Pinotage by evaluating irradiation doses and length of exposure to mutagenic agents on different tissues (bud wood, in vitro micro buds and somatic embryos or embryogenic callus).

The study aims to optimise the most appropriate mutagenesis protocol for Pinotage with regard to procedure, plant material used and dose rate. This will help to find the method that is most effective to induce mutation, while ensuring survival and regeneration of plants. This in turn will develop and increase the genetic variability of Pinotage.

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