Elucidation of the molecular and biochemical mechanisms associated with colour intensity and colour retention in fresh and dry chilli peppers.

Harriet Berry

Research output: ThesisDoctoral Thesis

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The vibrant red colour of chilli powder determines the quality and price of the material and is therefore of highest commercial importance to the plant breeder, seed companies, and retailer. Intense red colour is the desired quality at the point of harvest and throughout storage. Therefore varieties with low colour intensity and retention are less profitable in comparison to high colour intensity and retention. In the present study colour intensity was characterised among accessions within a colour diversity panel. This was carried out by analysing the pigment profiles of 12 chilli pepper lines throughout ripening to provide an insight into carotenoid biosynthesis and accumulation occurring within these lines. These data resulted in the discovery that carotenoid quantity and composition is directly related to the colour intensity phenotype. Identification of components responsible for the colour intensity phenotypes was attained when selected lines were analysed at a gene, transcript, and metabolite level. This revealed the role of phytoene synthase-1 and 1- deoxy-D-xylulose 5-phosphate gene products in the accumulation of carotenoids and regulatory mechanisms associated with this process. Additionally, the subchromoplast location of the carotenoids within the plastids was analysed using a subplastid fractionation techniques. This emphasised differences in sequestration mechanisms which contributed to the colour intensity phenotype. The PSY2 gene was also sequenced and characterised on a gene expression level in chilli pepper. Colour retention was investigated to identify mechanisms responsible for colour loss during storage. A protocol to speed up and monitor colour loss was implemented using an image analysis technique allowing identification of high and low colour retention lines. Volatile analysis revealed possible lipid peroxidation processes occurring in the high and low retention lines and analysis of superoxide dismutase activity highlighted ROS signalling pathways potentially acting in the plastid in low retention lines.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Fraser, Paul, Supervisor
Thesis sponsors
Award date1 Mar 2016
Publication statusUnpublished - 2015


  • Carotenoids
  • Capsicum
  • Plastids

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