Delayed bolting in Rocket for improved quality and greater sustainability.

作物的开花时间在农学上是重要的，因为它影响质量、产量和生产调度。在过去的20年里，对模式植物拟南芥中控制开花时间的分子途径的研究进展迅速，并对开花的遗传调控有了更深入的了解。然而，迄今为止，这种对Arabodopsis研究的巨大投资很少转化为作物植物的真实的效益。对于种植者来说，在收获之前过早抽薹（开花）是一个主要问题，因为叶子中产生的次级代谢产物会给植物带来苦味和不愉快的味道，并使作物无法销售。延迟抽苔是商业火箭品种的理想性状，因为它保留了出售用于叶沙拉消费的火箭叶的质量，并通过减少田间作物过早抽苔造成的浪费来提高可持续性。已经鉴定了几个基因，如果突变，会导致拟南芥延迟开花。这些基因包括参与光周期途径、春化途径、自主途径的基因和负责整合成花途径的基因。这些基因中的许多已经从拟南芥中克隆，并且这些基因中的一些的同源物已经在包括单子叶植物在内的多种物种中被鉴定，其中它们已经被证明在调节开花时间中具有相似或保守的作用。本项目将利用从模式植物如拟南芥中获得的控制开花的分子途径的知识，以及从控制莴苣抽薹的基因中获得的知识（这是目前BBSRC资助的Supervisors实验室项目的一部分），以鉴定通过诱变诱导或自然产生的开花时间基因的新等位基因，可以用来延迟火箭的栓接。这将通过以下方法实现：a）。将筛选EMS诱变群体中由于诱变处理而产生的晚抽薹系。B）。将从Rocket中鉴定和分离开花时间基因，这将通过与拟南芥中已知的开花时间基因同源性来完成，拟南芥是Rocket的近亲。（c）。一个火箭多样性集将筛选影响抽薹时间的自然变化。d）。已从a）分离的晚抽薹Rocket品系中的开花时间基因的序列。和c）。将进行分析，以确定多态性，可能是晚抽薹表型的原因。这可以通过比较晚抽薹系与WT系的转录组序列和/或靶基因的基于PCR的克隆和测序来完成。e）。开花时间基因的多态性将通过回交程序进行跟踪，以观察它们是否与晚抽薹表型共分离，从而可能导致晚抽薹。（f）。晚抽薹Rocket系将在商业管理的田间试验中种植，以测试晚抽薹在不同田间条件下的稳健性。g）。通过对晚抽薹系衰老相关基因表达的分析，探讨延迟抽薹对火箭衰老的影响。本研究项目的主要目标/产出是：i）。控制抽薹时间的Rocket基因的鉴定。（ii）。在商业上相关的Rocket栽培品种中创建晚抽薹系，其可以容易地并入育种计划以产生具有延迟抽薹的新品种。（iii）。鉴定已知开花时间基因的天然存在的等位基因，这些等位基因在不同的遗传背景中对抽薹时间具有稳健的影响。iv）。研究延迟抽薹在减少作物损失方面的优势，也可能通过对叶片衰老的影响。

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.