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Identifying genetic regulators of reproductive transitions in evolutionarily-divergent trees to facilitate rapid breeding

Primary supervisors: Dr Andrew Plackett & Dr Graeme Kettles, School of Biosciences

Project title: Identifying genetic regulators of reproductive transitions in evolutionarily-divergent trees to facilitate rapid breeding

University of registration: University of Birmingham

Project description:

The decision of plants to reproduce- at what age and at what time of year- are of fundamental importance to both agriculture and silviculture (forestry). Although this process has been investigated in short-lived annual plants, whether long-lived tree species make these decisions in a similar way is unknown. It is also unclear whether this decision-making process is similar between independent evolutions of the tree growth-habit. This question is becoming of increasing practical relevance to extremely long-lived tree species such as oak, which takes 40-100 years to flower. Any future attempts to improve traits of commercially-valuable trees and the resilience of ecologically-important trees by selective breeding will need to shorten the time it takes trees to flower, and for this an understanding of their underlying decision-making processes will be crucial. This project aims to provide a first outline of these processes in two commercially-valuable and evolutionarily-distant trees, the broad-leafed flowering tree oak (Quercus robur), which provides timber and acorn crops, and the conifer Sitka spruce (Picea sitchensis), a major timber crop. The comparison between these two species will test whether the same decision-making toolkit is likely to be conserved across all tree types.

This project will identify candidate genes controlling the age at which these two species first flower (the juvenile-to-adult transition) and candidate genes that control the annual decision to flower in adult trees. This will be achieved by two approaches: 1) an unbiased investigation of all possible genes involved through next-generation sequencing approaches (RNA-seq and transcriptome bioinformatic analysis), and 2) identifying oak and Sitka orthologs of known flowering genes from the annual plant Arabidopsis thaliana and testing whether expression of these genes is associated with tree flowering using quantitative real-time PCR (qPCR). These orthologs will then be tested for the ability to control flowering in Arabidopsis using genetic complementation assays. Finally, this project will also test whether ‘Speed breeding’ techniques that have been successfully developed for American Chestnut1 and can potentially shorten tree generation time by many years can also accelerate first-flowering of oak and Sitka. Successful outputs of this project will enable targeted breeding programmes in tree species where this is currently impractical.

References:

  1. Baier, K. M., Maynard, C. A., & Powell, W. A. (2012). Early flowering in chestnut species induced under high intensity, high dose light in growth chambers. Journal of the American Chestnut Foundation 26: 8–10

BBSRC priority theme:Sustainable Agriculture and Food: Plant and Crop Science & Understanding the Rules of Life: Plant Science

Contact: Dr Andrew Plackett & Dr Graeme Kettles, University of Birmingham