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Achieving sprout suppression results equivalent to those provided by chlorpropham (CIPC) is ‘within reach' using combinations of existing sprout suppressant technology and new physiologically-targeted treatments, a new study has found.

Dr Mac McWilliam, R&D director at PepsiCo, told the Cambridge University Potato Growers Association (CUPGRA) conference that research from Cranfield University had identified combinations of physiologically-targeted treatments which conferred storage durations equivalent to that of CIPC in processing potatoes.

These included applications of 1-methylcyclopropene (1-MCP) and targeted ethylene to connect the timing of application of ethylene to the physiological status of the tuber, in short- and medium-term storage situations.

Sugar spike

Dr McWilliam said: "Ethylene is low cost with good sprout control but has a risk of increased sugars in many processing varieties. In a number of situations, you see a respiration peak about three days after the onset of the application of ethylene. This means you've essentially woken up the potato, which translates to a sugar spike.

"That sugar spike is where 1-MCP comes in. It's an ethylene inhibitor and it preferentially blocks the pathways leading to conversion of starch to sugars, without impacting the sprout suppression. 1-MCP can block that sugar cascade and we can get that nice bright crisp we're looking for."

Combination

Laboratory and plant-scale experiments conducted between 2015 and 2019 examined commercial processing varieties and assessed sprouting, sugars, fry colour, respiration and weight loss.

By optimising the combination of 1-MCP and ethylene through application timings, the study found by adding 1-MCP after curing (but before pull down within a set temperature range) and then following with physiologically targeted ethylene in the cold storage (applied at the onset of eye movement), respiration was minimised and any impact on sugars was mitigated.

Dr McWilliam said: "By combining the 1-MCP together with the physiologically targeted ethylene we're able to confer three advantageous factors: no sugar accumulation, benefits from sprout control, and a reduction in weight loss equating to about 1% in four months.

"Across three processing varieties, in the low sugar stability variety we were able to show significant benefit in terms of sugar status and sprout control until February. In our mid-term variety with medium sugar stability we got a similar effect."

Benefits

In the long-term storage target, where the single modulator was applied, there were significant benefits, he added.

"In our mid-term variety, we could go right up to the end of May without sugar impact or firmness status, and that outperformed our CIPC control. Similarly, with our long-term variety with the highest sugar stability, that was starting to sprout under CIPC, but in our modified treatment it maintained it all the way through to June."

1-MCP is already used as an ethylene inhibitor in a range of crops in the UK, most commonly in apples, Dr McWilliam said.

"Because of the previous use on other crops, 1-MCP registration could be as close as 2021/2022. There's also opportunity for an emergency permit with enough support, which could bring it forward to next year."