This project represents a multidisciplinary collaboration between Harper Adams, Warwick and Reading Universities. The project aims to reduce post-harvest discolouration in lettuce and will explore the genetic and biochemical regulation of pinking and browning traits.
This research project is part of the work of the Fresh Produce Research Centre at Harper Adams University.
There is a need to improve postharvest quality of lettuce in salad packs to reduce waste and deliver consistently good quality products to consumers. We are proposing breeding lettuce varieties with reduced propensity to discolour as a way to address the problem. To do this we need to understand the genetics and biochemistry of discolouration. We are building on our previous research which identified genetic factors (QTL) controlling the amount of pinking and browning of lettuce leaves in salad packs 3 days after processing. However, we do not know what compounds or which genes are involved and we now intend to find this out by a three year multidisciplinary project funded by the BBSRC Horticulture and Potato Initiative (HAPI) involving the Fresh Produce Centre at Harper Adams[a1], the Wagstaff group at Reading and the Barker group at Warwick a lettuce breeding company (Rijk Zwaan), a lettuce grower (Gs Fresh), a salads processor (Bakkavor) and AHDB Horticulture which started in May 2015.
We have previously produced a set of F7 recombinant inbred lines (RILs) from a cross between the varieties Saladin x Iceberg. We know the RILs show genetics differences for pink or brown discolouration (see Atkinson et al., TAG 126:2737-2752). During summer 2015 the RILs were grown at HAU and processed in a way that mimicked commercial production. They were assessed for the amount of post- harvest discolouration they developed. Significant differences were found between the RILs which is in agreement with our previous findings. The data will be combined with the Saladin x Iceberg linkage map in a QTL analysis for comparison with the analysis carried out by Atkinson et al.
The RILs will undergo metabolomics analysis at Reading and for gene expression at Warwick. Key targets will be metabolites and genes involved in the phenylpropanoid pathway which is thought to be responsible for discolouration but other compounds and genes of interest will be identified through a bulk segregant analysis. Metabolite data will be used for QTL analysis and gene expression data for eQTL analysis. We will associate gene expression patterns and metabolites to the amount of pinking and browning to identify key steps in the genetic and biochemical regulation of discolouration. Once we have done this we will look for naturally occurring versions of the genes involved which give reduced discolouration and also look to see how the genes behave when lettuce plants are grown in different environments
The compounds produced by the phenylpropanoid pathway influence other traits such as pest and disease resistance, taste etc. We will assess lines which show high discolouration or no discolouration for their resistance to aphids, two diseases (Sclerotinia and mildew) and for taste to see if there are any differences.
We will see if the results for lettuce hold true for other crops by seeing how the key genes behave in apple and cabbage and whether this is related to the amount of browning that develops when they are processed.
Biotechnology and Biological Sciences Research Council Horticulture and Potato Initiative (BBSRC HAPI)
Harper Adams University
University of Warwick Crop Centre & Reading University