19th-20th March 2007
Warwick HRI Conference Centre, Wellesbourne
Abstract submitted entitled 'The genetic characterisation of post harvest spoilage in lettuce'. Poster with the same title was also submitted primarily for the Julia Goodfellow, Chief Executive of BBSRC visit.
Genetic Characterisation of Post Harvest Spoilage in Lettuce.
A major concern in the food industry is the post harvest discolouration of fruit and vegetables. The shelf life of cut lettuce is regularly restricted by enzymatic browning and pinking. During storage their organoleptic characteristics are visibly altered which generally incites an unfavourable consumer response. The phenylpropanoid pathway synthesises polyphenols that are subsequentially oxidised by polyphenol oxidase (PPO). PPO is the main agent responsible for enzymatic browning, although a synergistic effect between PPO and peroxidases is possible. Phenylalanine ammonia-lyase is the rate-limiting enzyme of the pathway normally induced upon wounding of plant tissue, thus increasing polyphenol biosynthesis for oxidation. Anthocyanin pigments are secondary phenolic metabolites which sequentially accumulate causing undesirable pinking due to their associated red colour. Post harvest discolouration is currently delayed by combinations of post harvest treatments. A genetic engineering approach would allow regulation of the pathways, avoiding treatment use. However widespread public opinion opposes this type of modification. The current project aims to provide resources for breeding improved ‘shelf life’ through the exploitation of natural allelic variation 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 using fluorescent AFLP markers and EST’s will be produced. Lettuce accessions held within Warwick HRI Genetic Resources Unit will be screened for both types of discolouration, which will aid in determining whether the mapping population is representative of the range of natural variation in lettuce. Post harvest discolouration in the 94 F7 RILs and the two parents will be induced in replicated field trials. Individuals will be phenotypically assessed using an objective scoring system in a controlled environment mimicking that of pre-packed cut salad packs. QTL analysis for post harvest discolouration in lettuce will subsequently be conducted to identify potential markers of value in lettuce breeding. Future plans also include the identification of candidate lettuce EST’s representing genes potentially involved in the pathways and associated gene expression studies conducted. The EST’s will be mapped to determine whether they are positioned within any QTL and results will be utilised to identify genes associated with the two discolouration responses. 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.
Project funded by BBSRC and Rijk Zwaan
My Student Symposium 2007 poster
Student Symposium 2007 booklet
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