title: A multidisciplinary approach providing new insight into fruit flesh browning physiology in apple (Malus x domestica Borkh.).
abstract: In terms of the quality of minimally processed fruit, flesh browning is fundamentally important in the development of an aesthetically unpleasant appearance, with consequent off-flavours. The development of browning depends on the enzymatic action of the polyphenol oxidase (PPO). In the 'Golden Delicious' apple genome ten PPO genes were initially identified and located on three main chromosomes (2, 5 and 10). Of these genes, one element in particular, here called Md-PPO, located on chromosome 10, was further investigated and genetically mapped in two apple progenies ('Fuji x Pink Lady' and 'Golden Delicious x Braeburn'). Both linkage maps, made up of 481 and 608 markers respectively, were then employed to find QTL regions associated with fruit flesh browning, allowing the detection of 25 QTLs related to several browning parameters. These were distributed over six linkage groups with LOD values spanning from 3.08 to 4.99 and showed a rate of phenotypic variance from 26.1 to 38.6%. Anchoring of these intervals to the apple genome led to the identification of several genes involved in polyphenol synthesis and cell wall metabolism. Finally, the expression profile of two specific candidate genes, up and downstream of the polyphenolic pathway, namely phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO), provided insight into flesh browning physiology. Md-PPO was further analyzed and two haplotypes were characterised and associated with fruit flesh browning in apple.
authors.affiliation: Genomics and Crop Biology Department Research and Innovation Centre, Fondazione Edmund, Mach, San Michele all'Adige (Trento), Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Di Guardo
authors.forename: Alice
authors.initials: A
authors.lastname: Tadiello
authors.forename: Brian
authors.initials: B
authors.lastname: Farneti
authors.forename: Giorgia
authors.initials: G
authors.lastname: Lorenz
authors.forename: Domenico
authors.initials: D
authors.lastname: Masuero
authors.forename: Urska
authors.initials: U
authors.lastname: Vrhovsek
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Costa
authors.forename: Riccardo
authors.initials: R
authors.lastname: Velasco
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Costa
mesh_terms: D004156:Catechol Oxidase / Q000235:genetics; D005638:Fruit / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D018745:Genome, Plant / Q000235:genetics; D027845:Malus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics; D040641:Quantitative Trait Loci / Q000235:genetics
chemical_list: D004156:Catechol Oxidase; D010650:Phenylalanine Ammonia-Lyase