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High hopes from new ethylene project

25 August 2011

Reducing energy usage and wastage are the aims of a LINK-funded project that aims to extend the use of ethylene as an effective sprout suppressant. A better understanding of tuber metabolism and cultivar sensitivity will bring better, residue-free sprout control.

Ethylene and its use as a sprout suppressant are to come under investigation in a new industry-funded research project.

The primary aim of the three-year LINK-funded project will be to develop better guidelines for its use in store, reducing the need for refrigeration. But researchers believe it will also give them a better grasp on the processes and genes that influence sprout growth and metabolism during potato storage and could ultimately allow ethylene to be used as a sprout suppressant across all potato storage.

“Ethylene is widely used, especially with other fruit and vegetables, as a way of controlling ripening and suppressing sprout growth,” explains Glyn Harper from Sutton Bridge Experimental Unit (SBEU).

“But we know very little about how it controls sprout growth, or why it works better on some varieties than others. We also need to know more about the relationship between ethylene, respiration and sugar levels within the tuber.”

Understanding this will be crucial if ethylene is to be used for potatoes destined for processing. Currently ethylene is used on around 150,000 tonnes of pre-pack potatoes as a residue-free way to help retain crop quality. But varieties vary in their sensitivity to ethylene, so most need to be held at low temperature for effective sprout control.

What’s more, ethylene’s reported effect of raising sugar concentration in tubers would result in dark fry colours, negating its use in the processed market. This leaves most growers and store managers the single option of chlorpropham (CIPC) to control sprouting. Despite the success of the CIPC Stewardship Group, the use of the chemical in stores is the subject of increasing scrutiny.

“We want to develop a robust and practical alternative to CIPC for processed potatoes. We also want to reduce the reliance on refrigeration to retain crop quality in the pre-pack market – every 1°C increase in average storage temperature achieved will save an estimated eight million tonnes of carbon dioxide emissions every year,” notes Glyn. “Storing at 10°C is also considerably cheaper than storing at 3°C.”

Initially work at SBEU will focus on ethylene concentration needed to effectively control sprout growth in a range of varieties. “Anything over four parts per million has an effect, the industry standard is ten parts per million but the target headspace concentration is up to 50ppm.”

Also under investigation will be a range of other natural chemicals and plant hormones that are known to have an effect on sprouting and tuber metabolism.

“We know there are hormones produced within the tuber that stimulate sprout growth” explains lead scientist on the project Richard Colgan, from the Natural Resources Institute, which is part of the University of Greenwich.

“We’re looking for inhibitors of these hormones and will be combining these with ethylene and studying their effect on tubers. It’s a complex interaction that we want to understand in more detail. Eventually we hope to have a combination of treatments that will suppress effectively and reliably sprout growth that can be taken to commercial trials.”

Throughout the project the effect of the treatments on sugar accumulation within tubers will be monitored in order to evaluate a method of application that preserves crop quality without affecting fry colours.

“We know that ethylene stimulates respiration, and that it stimulates starch breakdown to sugar. But the extent to which the two are linked is not fully determined,” continues Richard. “We hope to shed more light on this complex relationship, which would give growers more control over tuber metabolism and the sugar content of tubers.”

The final aspect of gene marking and cultivar evaluation will be carried out by SCRI, capitalising on SCRI’s advanced transcriptomic and genotyping facilities developed for the potato. “Russet Burbank is particularly sensitive to ethylene, for example. A range of varieties and breeding lines will be tested and we will examine differential patterns of gene expression in cultivars that differ in their reaction to ethylene,” says Richard.

“Once we have established the candidate genes we can take this work forward to inform future breeding programmes. A long-term aim of the project is a potato that will retain its crop quality with the minimum of intervention during storage.”

The £628,000 project started in October 2009 and lasts for three years. It is joint-funded by industry and government under the Sustainable Agricultural – Link programme previously co-ordinated by Defra but now managed by the Technology Strategy Board. Aside from AHDB Potatoes, the industry partners are Greenvale AP, Cygnet, Pepsico, Landseer, and Greenwich University Enterprise.

The 2006 AHDB Potatoes research review The use of ethylene for sprout control can be found here.

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