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Predicting tuber dry matter concentration in potato

Supervisors: Dr David Firman and Dr Mark Stalham (NIAB CUF), Prof. Howard Griffiths (Plant Sciences, University of Cambridge)

Project outline:

The dry matter concentration of potato tubers is an important quality attribute, particularly for the production of crisps and french fries but also for fresh produce. There is considerable variation in the concentration of tuber dry matter at harvest between potato varieties, seasons and sites of production but there is limited understanding of the mechanisms for this variation. Tuber dry matter concentration tends to increase progressively after tuber initiation but differences in water balance of the plant due to water availability from the soil and evaporative demand can have short- and long-term effects on tuber dry matter concentration. Tuber initiation occurs over a short period early in the growing season and the extent to which final tuber dry matter concentration is determined by environmental influences during early development is unclear.

Variation in tuber dry matter concentration between and within tubers is also poorly understood but this variation can affect suitability for processing and cooking attributes of table potatoes. The texture of cooked potato results from an interaction of a number of physical characteristics such as dryness and cohesiveness. Large cells have been associated with high starch content in tubers but it is unclear if differences in the number and size of cells or other structural differences during the early development of tubers influence patterns of dry matter concentration as tubers develop. Cytological evidence indicates that initial tuber growth is primarily due to cell elongation and radial cell expansion in the pith followed by cell division and concomitant cell expansion. The relative contributions of cell division and expansion during later stages of tuber growth appear to differ between potato varieties and could also be influenced by growing conditions. Cell division and expansion rates also vary within tubers and there are differences in cell size between the stolon and apical ends of the tubers which may influence dry matter concentration. Enzymatic blackspot bruising is an additional trait of interest as it has often been associated with high tuber dry matter concentration and although no simple overall relationship is apparent, differences in bruising due to transient dehydration and contrasting cell size have been found.

This studentship will be based with the NIAB CUF Agronomy Research Group and also have full access to university facilities and resources. NIAB CUF has a strong interest in using data from field experiments and commercial crops to inform crop models for predicting yield, water and nutrient use. We are interested in establishing the role of environmental and genetic factors that affect crop growth. Close interaction with members of Cambridge University Potato Growers Research Association provides access to all sectors of the potato industry and enables rapid adoption of research findings into practice.

This project will involve field experiments to examine the changes in tuber dry matter concentration with plant development. Experiments will include factors which result in short- and long-term effects on tuber dry matter concentration and will include varieties with different tuber dry matter concentrations. Findings from these experiments will be used along with a large body of historic data to improve the ability to predict and manipulate the tuber dry matter concentration in commercial crops. The project is an opportunity to develop a broad range of skills in plant physiology, data analysis, modelling and agronomy and to help effect improvements in potato production practices.

This studentship is fully funded by CUPGRA (Cambridge University Potato Growers Association). CUPGRA encourages study and research on potatoes and promotes the interchange of scientific research and field practice for innovative, sound commercial production of potatoes through its association with the Agronomy Research Group at NIAB-CUF.

The closing date for applications is 31 January 2018.

Applications should be sent to David Firman and should include two academic referees.

The studentship will cover a stipend at the standard Research Council rate, research costs and tuition fees at the UK rate.