Lettuce: a genetic approach to improving post-harvest quality

Summary: There is a need to improve the postharvest quality of minimally processed lettuce to reduce waste and deliver consistently good quality products to consumers. The aim of Horticulture and Potato Initiative (HAPI) / AHDB Horticulture Project CP 150 is to breed lettuce varieties with a reduced propensity to discolour, as a solution to the problem. The genetics and biochemistry of discolouration needs to be properly understood. Previous research has identified genetic factors controlling the amount of pinking and/or browning on lettuce leaves in salad packs three days after processing. However, neither the compounds nor the particular genes that are involved were identified. A multidisciplinary approach to find out more is being employed by the three universities (Harper Adams, Reading and Warwick) who are working on this project together with a lettuce breeding company- Rijk Zwaan, a lettuce grower- Gs Fresh, and a salads processor, Bakkavor.

Experimental lettuce lines showing differences in the amount of pink or brown discolouration have been identified in lettuce germplasm held by The University of Warwick. These lettuces will be grown and processed in a way that mimics commercial production after which discoloration developing within salad packs over 3 days will be assessed. The information will be linked with the individual lines DNA profiles to identify genetic factors for discolouration and DNA markers which could be used by plant breeders. The same lettuces will also be analysed for compounds produced by a biochemical pathway called the phenylpropanoid pathway which is thought to produce the pigments that cause discolouration. The researchers will look at how the genes behave in lettuce plants that produce a lot of discolouration and ones that do not discolour. They will also find out how the genes are expressed under different growing conditions as gene expression patterns can be linked to the amount of pinking and browning.  This will help identify the key genes controlling discolouration. When this phase of work is complete the researchers will investigate naturally occurring versions of the genes which give a reduced discolouration, and they will find out how they behave when lettuces are grown in different environments.

The compounds produced by the phenylpropanoid pathway play a part in crop pest and disease resistance, taste etc. Breeding work arising from this project will aim to ensure that lettuce lines that do not discolour are not susceptible to pests and that their taste is not affected. 

Video clips produced by project academic partners:

 CP 150: Lettuce post-harvest quality - project overview

 CP 150: Lettuce post-harvest quality - phenotyping

 CP 150: Lettuce post-harvest quality - genetics

 CP 150: Lettuce post-harvest quality - metabolites