Producing high quality potato starches with new genetic tools

Neiker-Tecnalia (the Basque Institute of Agricultural Research and Development) is realising a project for obtaining high quality starch in potato tubers (Solanum tuberosum) using new molecular and genetic tools.

The aim of the research is to produce starches which have better physicochemical conditions for its industrial use, as well as for producing healthier and more functional foodstuffs.

In order to obtain new varieties of potato with starches of various qualities, it is necessary to employ new tools, given that it is difficult to achieve genetic improvement with traditional phenotype selection. Different techniques are employed in this project, such as ‘allele mining’, inverse genetics, mapping by association and in vitro assays for evaluating the different starch types.

The overall aim is the modulation of the properties of potato starch (modifying the degree of the ramifications of its amylose and amilopectin components, the length of the polymers and the degree of phosphorylation), as well as analysing the effects of these modifications. To this end, gene alleles of SBE (starch-branching enzyme) with reduced or zero activity are produced and identified, through the application of the Tilling technique (directed mutagenesis) or the ‘allele mine’ (analysis of the biodiversity of SBE genes and other possible genes which influence the quality and quantity of starch). All this enables designing new commercial varieties of potato with starches that have new specific properties.

The “Allele mining” technique

Neiker-Tecnalia researchers have opted for ‘allele mining’, a field of research that aims to identify the allelic variation for relevant traits within a collection of genetic resources. This technique has been employed with commercial varieties and with other germplasm of the Solanum genus, in order to analyse the variability of alleles of genes that codify SBEs with reduced or zero activity. The goal of ‘allele mining’ is to find potato accessions which produce new types of starch with special and enhanced characteristics for industrial and food processes.

In a complementary manner, mutated dihaploid potatoes were produced through inverse genetics, and with which action mechanisms of the genes were studied. Moreover, an in vitro test was used for the rapid analysis of the enzymatic activity of the SBE alleles, in such a way that it was not necessary to obtain homozygotic plants for these alleles and only the alleles of interest form part of the enhancement process.

A drastic reduction of the content of amylopectin means a reduction of the total content of starch. This is an obstacle for genetic improvement, as the greater the dose of SBE alleles induced, the less will be the starch yield. To eliminate this problem, clones were selected with more effective capacity for the biosynthesis of starch. This is achieved with the help of gene-mapping by association. With this technique, alleles with better performances were detected in the starch biosynthesis route. In this way, DNA molecular markers with diagnostic value are sought for the genetic enhancement of varieties of high-yield potatoes.

Production of biomaterials and healthier starches

It is estimated that this project will produce results applicable in the production of biomaterials and bioproducts and in the production of healthier foods. As regards biomaterials and bioproducts, the Neiker-Tecnalia project will help to obtain varieties of potatoes that can produce starch with better physicochemical characteristics for industrial production.

This type of starch will allow obtaining transparent gels without disagreeable odours and, moreover, which have optimum conditions of adhesiveness and reactivity, as well as good qualities for the formation of films. For example, starches with a high content of amylose have better viscosity characteristics and better capacity of union and are found useful in the manufacture of paper, adhesives or in the textile industry. Starches with a high content of phosphate can be used to produce synthetic polymers.

As regards the production of healthier foods, the improvement in the amylose content will optimise their nutritional content and allow obtaining varieties of potato that can be used as functional foods;given that, being fibre-enriched, their calorific power is less, resulting in beneficial effects for the gastrointestinal tract.

European project

The R+D activities are being undertaken within the umbrella of a European ERA-NET project (‘Plant genomics’ section) co-financed by the Spanish Ministry of Science and Innovation within the framework of the Euroresearch (EU2009-04028) programme. Neiker-Tecnalia is working on the project with a number of Spanish and German private companies and research centres: Bioplant (potato breeding company, Germany), IME-Fraunhofer (Institute of Plant Biochemistry and Biotechnology, Germany), Appacale (potato breeding company, Spain) and MPIZ (the Max Planck Institute for Plant Breeding Research, Germany).

The SBE alleles identified by the Neiker-Tecnalia researchers will be able to be used by the enterprises involved in the project, with the goal of obtaining special varieties of fecula for industry and also varieties for human consumption with beneficial effects on health.

Better quality for industrial processes

Starch is a molecule made up of two carbohydrates, amylose and amilopectin, with unique properties. The inactivation of SBEs leads to the formation of starches with different physicochemical characteristics. Thus, the introduction of inactive alleles of the genes that code for these SBEs leads to new varieties with starch content of high quality for various industrial processes.

Potato starch is a product widely used in industrial processes, such as in the manufacturing of paper, glues, building materials, plastics and medicines. It is especially appreciated by the industry, given its low protein and fat content.