17th-18th March 2008
Warwick HRI Conference Centre, Wellesbourne
Abstract and poster both entitled 'The genetic characterisation of post harvest spoilage in lettuce' was submitted. Please contact L.D.Atkinson@warwick to request copy of poster (due to unpublished results).
My image of tomatoes was runner up for the student symposium booklet cover. See more...
Genetic Characterisation of Post Harvest Spoilage in Lettuce
A major concern in the food industry is post harvest discolouration of fruit and vegetables which generally incites an unfavourable consumer response. The shelf life of cut lettuce salad packs is regularly restricted by enzymatic browning and pinking. Pinking is due to accumulation of anthocyanins through the phenylpropanoid pathway and browning occurs due to oxidation of polyphenols by polyphenol oxidase. The enzyme phenylalanine ammonia-lyase increases polyphenol biosynthesis for oxidation upon wounding of plant tissue. Post harvest discolouration is currently delayed by combinations of post harvest treatment. Production of genetically improved lines with reduced likelihood for discolouration would avoid the need for such treatment. Genetic engineering could be used to manipulate the biochemical pathways, however, currently public opinion opposes this approach; an alternative is to exploit genetic variation in lettuce for post harvest discolouration through a conventional breeding approach. The current project aims to provide resources for breeding improved ‘shelf life’ and an understanding of the genetics of post harvest browning and pinking.
A new improved linkage map based on 94 F7 Saladin x Iceberg RILs has been created using fluorescent AFLPs. 16 EcoRI/MseI primer combinations with 3 base selectivity were used. 108/170 markers mapped resulting in coalescence into 9 linkage groups, with a map length of 380.539 cM at LOD threshold 4.5.
Post harvest discolouration has been induced in a lettuce diversity set and discolouration phenotypically assessed when cut and bagged using an objective scoring system. The F7 mapping parents showed differences for the two discolouration responses and overall discolouration. Iceberg appears more susceptible for browning, whilst Saladin appears more susceptible to pinking. Differences early on are of greater importance to the food processor due to the products limited life on the shelf before the best before date expires. The differences between the parents covers a major part of the range seen in the diversity set so the mapping population is suitable to carry out genetic analysis for these traits.
Post harvest discolouration in the 94 F7 RILs and the two parents will be induced in replicated field trials and assessed as previously. QTL analysis for post harvest discolouration in lettuce will subsequently be conducted to identify potential markers of value in lettuce breeding. Furthermore, relevant selected associated metabolites from the parents and extreme phenotypic F7 RILs will additionally be analysed by HPLC and enzyme assays to aid identification of compounds associated with the discolouration processes.
| Laura Presenting in a Poster Session
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