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114R479 Controlling Dormancy and Sprouting

Full Research Project Title: Controlling Dormancy and Sprouting in Potato and Onion

Duration: October 2013 - September 2017

Background

Potato and onion production relies on industrial-scale storage to ensure year round availability, for both fresh and processing sectors. In the UK alone, 4.05 million tonnes of potato tubers and 600,000 tonnes of onions are stored annually. Dormancy properties of potato tubers and onion bulbs are key determinants of postharvest life. Premature sprouting of either organ during storage is accompanied by severe loss of quality. Chemical inhibitors of sprouting (e.g. chlorpropham (CIPC) and maleic hydrazide (MH)) are the UK industry standards; yet they are under threat and concerns about CIPC led to a new EU wide Maximum Residue Level (MRL) for CIPC in 2005 of 10 ppm for potatoes. Furthermore, UK legislation demands regular residue testing. For the potato crop stored in the UK, 44% is treated with CIPC and so there is an urgent need to develop new storage strategies for potato and onion, less reliant on CIPC as well as cold temperature storage. For potato and onion breeders there are no genetic markers that can be used to select for dormancy-related traits. For those involved in all sectors of the supply industries (seed, fresh and processed), predictive models that indicate how a crop may perform in storage are lacking. This project is part funded by the BBSRC’s Horticulture and Potatoes Initiative (HAPI).

- To improve the understanding of dormancy in potato and to use a comparative approach to accelerate our understanding of dormancy in onion.

- To develop a unifying model that can be used to optimise decision making in managing agronomy, storage (e.g. scheduled release), and cultivar assessment.

Objectives:

a) To increase our understanding of the control of dormancy in potato tubers using segregating potato populations that show extensive variation in tuber dormancy to identify genes that control dormancy characteristics.

b) To increase our understanding of the control of dormancy in onion bulbs through the establishment of transcriptome resources for onion that facilitate comparative analysis with potato

c) To develop genetic/molecular/biochemical markers in potato and onion for evaluation of dormancy status in existing and emerging cultivars and to understand the impact of agronomic/storage practices on development of dormancy.

d) To establish a platform for follow-on work, application and engagement with industry.

Approach

There are 3 work packages to this project:

WP1. Genetic basis of tuber dormancy (JHI, GU)

Potato populations that show a great variation in tuber dormancy will be segregated, candidate genes that control those associated dormancy characteristics will be identified.

WP2. Potato and onion transcriptomics (CU, IC, GU)

Unlike potato, the large onion genome has not been sequenced and genetic maps are rudimentary, making progress on identification of QTLs difficult. Genetic transformation is similarly challenging. Instead, we will capitalise on knowledge in potato to drive discovery of potential commonalities between potato and onion that can lead to comparative interrogation at several levels (transcripts, hormones). In the absence of a reference genome, Cranfield University (CU) will perform an onion transcriptome study using RNA-seq.

WP3. Integrative biology of dormancy and sprouting (CU, IC, GU, JHI)

Onset and duration of dormancy and rate of subsequent sprout growth are governed by genetic factors but are also regulated by multiple environmental factors during crop growth and storage, and by internal hormone signalling. The basic science component of this project will integrate physiological, molecular and genetic approaches, to generate more robust models for potato and, where practicable, apply these in onion.

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