Delayed bolting in Rocket for improved quality and greater sustainability.

Flowering time in crop plants is agronomically important because it impacts on quality, yield and scheduling of production. Research into the molecular pathways controlling flowering time in the model plant Arabidopsis has progressed rapidly over the past 20 years and has led to a much greater understanding of the genetic regulation of flowering. However, to date there has been little translation of this huge investment in Arabodopsis research into real benefits in crop plants. Premature bolting (flowering) of rocket before it is harvested is a major problem for growers, as secondary metabolites are produced in the leaves which give the plant a bitter and unpleasant taste and render the crop unsaleable. Delayed bolting is a desirable trait in commercial rocket varieties as it preserves the quality of rocket leaves sold for consumption in leafy salads, and increases sustainability by reducing wastage caused by premature bolting of crops in the field. Several genes have been identified which, if mutated, result in delayed flowering in Arabidopsis. These include genes involved in the photoperiodic pathway, the vernalisation pathway, the autonomous pathway, and genes responsible for integrating the floral pathways. Many of these genes have been cloned from Arabidopsis and homologues of some of these genes have been identified in a diverse range of species, including monocots, where they have been shown to have similar, or conserved roles in regulating flowering time. This project will exploit the knowledge of molecular pathways controlling flowering gained from model plants such as Arabidopsis, and also from the knowledge gained about genes controlling bolting in lettuce (which is part of a current BBSRC funded project in the Supervisors lab), to identify novel alleles of flowering time genes that have either been induced through mutagenesis, or have arisen naturally, that can be used to delay bolting in rocket. This will be done through the following approaches; a). An EMS mutagenised population will be screened for late bolting lines that have been created as a result of the mutagenesis treatment. b). Flowering time genes will be identified and isolated from Rocket, this will be done through homology to known flowering time genes in Arabidopsis which is a close relative of Rocket. c). A Rocket diversity set will be screened for natural variation affecting bolting time. d). Sequences of flowering time genes in the late bolting Rocket lines that have been isolated from a). and c). will be analysed to identify polymorphisms that may be the cause of the late bolting phenotype. This may be done through comparing the transcriptome sequence of the late bolting lines with WT lines, and/or PCR-based cloning and sequencing of the target genes. e). Polymorphisms in flowering time genes will be followed through a back-crossing programme to see if they co-segregate with the late bolting phenotype and thus could be causing the late bolting. f). Late bolting Rocket lines will be grown in commercially managed field trials to test the robustness of the late bolting in different field conditions. g). The effect of delayed bolting on senescence in rocket will be investigated through the analysis of the expression of senescence-associated genes in the late bolting lines. The principle objectives/outputs of this research project are; i). The identification of Rocket genes controlling bolting time. ii). The creation of late bolting lines in a commercially relevant Rocket cultivar which can readily be incorporated into breeding programmes to generate new varieties with delayed bolting. iii). The identification of naturally occurring alleles of known flowering time genes that have a robust effect on bolting time in different genetic backgrounds. iv). To examine the advantages conferred by delayed bolting in terms of reduced crop losses and possibly also through effects on leaf senescence.