Potato Review

38 POTATO REVIEW JULY/AUGUST 2021 HEAT STRESS e longer the duration of a heat event the greater the impact on crop production, compared to a short higher temperature, he said. Results of the UK’s largest ever biostimulant eld study with Syngenta’s Quantis last season, proved that the stress mitigation it provided under the e ects of heat delivered signi cantly higher potato crop yields. In 30 independently-assessed eld trials that were subjected to leaf temperatures of 25 C for more than four hours on 14 days during a period from the onset of tuber bulking to the end of August, the average yield response from a three-spray Quantis programme was 2.2 t/ha. Reviewing weather data for an area such as the Cambridgeshire Fens, for example, revealed that temperatures that would impact on potato crop performance during that period has occurred every season for the past six years. e frequency that it has occurred has varied from the lowest of eight days in 2015, up to 32 days in 2018 (above, right). On average over the six years, crops would have been subjected to the damaging heat stress conditions on more than 15 days each season. “Using this information gives growers and agronomists a clear indication of where they should focus agronomy on heat stress mitigation,” Dave said. “It also shows, that with the seasonal variability of when heat stress can occur, the importance of preparing the crops’ resilience to the e ects of heat by building Quantis into the programme throughout the tuber bulking phase.” Dave pointed out that temperatures at crop height will typically be higher than modelled for weather records, and within the canopy with little air ow could rise even further. “ at could be having even greater impact of plant health and its ability to cope with stress,” he warned. Independent crop research has shown optimum root growth in potatoes occurs at soil temperatures of 15 C to 20 C, with a fall o when temperatures exceed 20 C. Plant physiological studies that indicate where potatoes are under the e ects of oxidative stresses, such as heat, they are unable to assimilate photosynthates, including sugars and carbohydrates, from leaves down into tubers. In fact, they may even be drawing on plant reserves to counter the stress factors. Syngenta Global Technical & Plant Phenotyping Manager, Nathinee Ruta, warned that can cause a yield reduction in both the number and size of tubers, along with the consistency of quality. “ at’s where the heat stress relief of Quantis is targeted to minimise the damage. “ e major components of Quantis are organic acids, which includes sugars and organic acids, amino acids and some nutrients. With these components, the product is equipped with anti- oxidant properties,” she said. “ ese anti-oxidant e ects are crucial to minimise the toxicity caused by reactive oxygen species (ROS – known as free radicals) in cells in plants under abiotic stress.” Biostimulant specialist Dr Ruta pointed out the strength of Quantis lies in its relatively high proportion of short chain carbon molecules, which are particularly e ective at helping the plant to prevent the creation of ROS during periods of stress. Furthermore, it helps with the scavenging of accumulated ROS, to minimise their adverse e ects. “By lling the organic carbon gap when a plant comes under heat stress, it can activate and enhance the plant’s natural capability to adapt to heat stress, to prevent damage and minimise its e ects to protect tuber yield. “ e multi-function approach to stress relief in potato plants gives the potential for higher yield and better tuber size under heat conditions,” she said. “Anti-oxidant e ects are crucial to minimise the toxicity caused by reactive oxygen species (ROS – known as free radicals) in cells in plants under abiotic stress.” Dr Nathinee Ruta Ely potato growing season heat events with stress e ects 2018. Ely potato growing season heat events with stress e ects, 2015 to 2020.