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Development of diffuse browning disorder in relation to physiological and biochemical changes in apple fruit during development and storage - FO0308

Research is proposed to identify the underlying cause of diffuse browning disorder, a physiological disorder that develops progressively in Cox apples during storage. This hitherto undescribed disorder has caused significant losses of stored Cox apples over the past 6 years and particularly in 2000-1 and 2004-5. No figures are available to indicate the overall financial losses incurred by the growers but in a recent survey conducted by East Malling Research 26% of Cox growers reported a problem with DBD. The inability to predict the occurrence of DBD in different consignments of apples has resulted in loss of confidence in storing Cox other than for short periods. Moreover, reduced quality due to DBD threatens future sales of Cox and the sustainability of the UK dessert apple industry.

Previous applied research funded by the Horticultural Development Council failed to identify the stress factors that cause DBD. Although storage environment (stress) factors such as sub-optimal storage temperatures may influence susceptibility to DBD they are not the main cause. DBD has emerged as a problem in a period when storage recommendations for Cox have remained unchanged. Since there are orchards that are consistently affected and others with no history of a problem it appears that DBD development is associated with stress factors that operate during fruit development. In specific orchards the application of sprays containing gibberellin inhibitors for growth control has exaggerated DBD development but the upsurge in the problem is not generally related to these chemicals. Attempts to relate DBD occurrence to climatic factors and more specifically to light intensity have not proved successful. In view of the difficulty in evaluating the many potentially causal (stress) factors affecting DBD a more strategic approach to the DBD problem has been adopted. Hypotheses on the likely causal (stress) factors will be developed subsequent to gaining an understanding of events in fruit tissue predisposed to DBD.
Research is planned to identify putative endogenous regulators of DBD susceptibility and to develop hypotheses on the most likely stress factors affecting fruit during their development on the tree. More specifically the objectives are to measure changes in the chemical profile of apples during development and storage and in the physiology of fruit at harvest and during storage and relate these to the development of DBD. Molecular techniques will be used to study the expression of genes known to be involved in regulating stress in plants. It is also proposed to observe changes in the anatomical structure in apple flesh that precedes the development of diffuse browning disorder. The strategic work proposed may provide opportunities to develop and deliver practical methods to avoid or prevent DBD. The analytical work may indicate possibilities for developing diagnostic tests and the physiological studies of fruit ripening and disorder expression may pave the way for methods of screening commercial consignments of fruit at harvest. Analysis of fruit from commercial orchards in order to appropriately market consignments at risk is entirely feasible but will depend on the complexity and cost of any analysis required. Growers currently submit samples of fruit for mineral analysis prior to harvest as a means of estimating storage potential and more specifically the risk of disorders that relate to concentrations of particular elements.

Research to link metabolic changes in developing fruit with subsequent storage behaviour is highly innovative and has more generic implications in that there is the potential to understand how pre-harvest factors affect storage quality of different cultivars of apple and other fruits stored long-term such as pears and kiwifruit.

The research proposed is consistent with Defra policy needs particularly as regards industry sustainability. Where problems occur in fruit scheduled for the fresh market this is likely to result in disposing of the fruit through less lucrative outlets such as juice. At this point the fruit has incurred the cost (and energy use) of storage. Rejection at the point of sale incurs additional costs (and energy use) of grading, packing and distribution. In this case the packaging would be wasted. The research will benefit UK science as little is known about the physiological and biochemical basis for orchard factor effects on post-harvest physiology and storage quality. The results of the research will benefit the fruit industry directly and will therefore help to preserve the rural economy and communities. Many associated industries are dependant on a viable apple industry in the UK and there is a serious risk that Cox will be de-listed by major multiple retailers if the problem is not resolved. Since Cox represents 50% of the UK dessert apple crop the loss of the cultivar would have a major impact on the rural landscape and on the amenity value of the countryside to the UK taxpayer.

Project Documents
• Final Report : Development of diffuse browning disorder in relation to physiological and biochemical changes in apple fruit during development and storage   (768k)
Time-Scale and Cost
From: 2007

To: 2009

Cost: £251,094
Contractor / Funded Organisations
East Malling Research
Allocated - EMR              
Disease Prevention              
Environmental Performance              
Food and Drink              
Food Chain              
Food manufacturing industry              
Food Quality              
Fields of Study
Resource Efficient and Resilient Food Chain