*EASTBIO CASE* Fruit cell wall physiology and biochemistry to guide breeding the new generation of fruit genotypes

This project targets one of the BBSRC’s four Strategic Priority Areas: Agriculture and Food Security. It comprises novel research that is both of fundamental interest and has industrial applicability. The softening of ripening fruit involves dramatic changes in cell-wall structure. In many species, softening is important because it makes fruit pleasant to eat. On the other hand, excessive softening is detrimental, causing wastage on the supermarket shelf and making crops more vulnerable to pathogens. Slowing the softening process, e.g. in raspberries, would cause less waste when UK crops peak; imported crops, e.g. from Southern Europe and Morocco in winter, could go further; and opportunities would be raised for summer UK exports. Slow-softening fruits would bring less disease and longer picking intervals.

Preliminary data from the applicants’ laboratories: Fry’s lab (Edinburgh) is elucidating novel mechanisms by which fruits soften. This work draws on many years’ experience of cell-wall biochemistry. Collaborators at Edward Vinson Ltd. (Kent), commercial fruit breeders, have a molecular breeding pipeline, e.g. in strawberry, raspberry and blackberry. We aim to link genetic markers (Edward Vinson) to physiological/biochemical processes (Edinburgh), benefiting future breeding efforts. Edward Vinson Ltd. is developing a molecular map for raspberry, so it will be possible to look for relevant genetic markers and use these in marker-assisted selection.

Proposed new research: Available genotypes differ in firmness, e.g. recently developed commercial genotypes versus ‘heritage’ varieties. We will explore the relationship between their genetics and their cell-wall processes. At the Edinburgh laboratory, the student will develop convenient new tools for screening cell-wall ‘softening markers’, including:
• vitamin C secretion and turnover;
• hydroxyl radicals non-enzymically attacking cell-wall polysaccharides in vivo;
• solubilisation and partial degradation of pectic polysaccharides;
• specific pectic enzyme activities and/or action in living fruit—
* pectin methylesterase
* rhamnogalacturonan lyase and pectate lyase (recent evidence suggests these enzymes contribute to softening)
* endopolygalacturonase
* xyloglucan endotransglucosylase and endohydrolase (XTH)

Student’s role (initially working under close guidance): The student will explore the physiological/biochemical processes occurring in softening fruit cell walls. He/she will develop novel, simplified assays for these processes suitable for routine use by plant breeders. This study will employ chromatography and electrophoresis, with detailed practical guidance at Edinburgh. Training/experience will also be provided in preparing seminars, posters, reports and manuscripts; and undergraduate demonstrating.

Student’s role (subsequent opportunities for independent exploration): Later, depending on initial findings and personal interests, the student will be able to devise the best ways forward to fully characterise the processes. This may include in-vivo radiolabelling in Fry’s laboratory, and NMR spectroscopy and mass spectrometry in Edinburgh University’s Chemistry Department.

Industrial liaison: In the fruit breeding laboratory at Edward Vinson Ltd., the student will apply the novel assays he/she has developed, working closely with the molecular breeder and using his laboratory on-site. The student will also look at the novel softening markers in breeding material in the field, potentially linking field measurements of firmness with shelf-life. The period(s) of industrial liaison will provide insight into the opportunities and practicalities of commercial applied biology.

At the Edinburgh labs, the student will develop convenient new tools for screening biochemical cell-wall ‘softening markers’. When developed, the tools will later be trialled in commercially relevant situations: (a) feasibility tests in this direction will be undertaken within the Edward Vinson Ltd. fruit breeding programme by the student who develops the new tools; and (b) it is expected that the new tools will in the future be operated on a higher-throughput basis by Industry personnel.

CASE Studentship: UK students will have their full tuition fees paid for by the BBSRC, and (regardless of citizenship) Edward Vinson Ltd. will contribute towards laboratory consumables plus the student’s additional living expenses during the time in Kent; Edward Vinson Ltd. will also supplement the student’s stipend.