Flower colour is inherited as a semi-qualitative trait in azalea and is mainly determined by differences in anthocyanins and flavonols. A two-gene model is used to explain the phenotypic variation between white, brick red and carmine red colour: W in case the flower petals contain anthocyanins and Q if flavonols are present as co-pigments. However, the presence of flavonols in white flowers cannot be detected visually. Also, the existence ofpink flowers is not explained by this two-gene model. Therefore, flower colour was determined on a crossing population using image analysis software and discriminant analysis was used for classification. Carmine red, brick red and white flowers could clearly be separated. Pink flowers were distributed in between the other groups, suggesting that pink can be split up in different classes depending on the pigment types present (pink flowers with or without flavonols). This classification could not be made visually, only pale pink flowers, grouped close to white, can easily be distinguished from the other pink flowers. To elucidate this ‘pink’ problem, integration of the image analysis data as QTLs on a genetic map of the crossing population could be enlightening. A genetic map of 16 linkage groups was constructed. Besides anonymous AFLP and SSR markers also a set of functional markers were used. EST-markers were developed for four genes coding for key-enzymes in the flavonoid biosynthesis pathway. MYB-profiling, a sequence directed technique similar to NBS-profiling, generated in this crossing population fifteen dominant markers functionally related to the MYB gene family. MYB-genes are a large group of transcription factors that are involved in a wide array of cellular processes and also in flavonoid biosynthesis. In this way, phenotypic and genetic data will both be integrated on the genetic map of azalea. In case both are located at the same mapping position, these genes are proven to be directly involved in the creation of the phenotypic variation of the trait. Nevertheless, it is very likely that not the genes themselves but transcription factors are the switches that regulate the phenotype of the trait. In that case, phenotype and genotype will be mapped at different positions, but phenotype is then expected to be mapped together with the true regulators, the transcription factors e.g. MYB markers. To confirm this theory, gene expression profiles of five flavonoid biosynthesis genes are generated in petals of a selection of flowers of the crossing population using qPCR and QTL mapping will again integrate these data with the genetic map. Prelminiary mapping results will be presented.
|Titel||Control of flowering time and applications for plant breeding|
|Status||Gepubliceerd - 2008|
|Evenement||Control of Flowering Time and Applications for Plant Breeding - Salzau, Duitsland|
Duur: 22-sep-2008 → 24-sep-2008