Salentijn Elma M J, Petit Jordi, Trindade Luisa M
Plant Breeding, Wageningen University and Research, Wageningen, Netherlands.
Front Plant Sci. 2019 May 16;10:614. doi: 10.3389/fpls.2019.00614. eCollection 2019.
Hemp, L., is a sustainable multipurpose fiber crop with high nutrient and water use efficiency and with biomass of excellent quality for textile fibers and construction materials. The yield and quality of hemp biomass are largely determined by the genetic background of the hemp cultivar but are also strongly affected by environmental factors, such as temperature and photoperiod. Hemp is a facultative short-day plant, characterized by a strong adaptation to photoperiod and a great influence of environmental factors on important agronomic traits such as "flowering-time" and "sex determination." This sensitivity of hemp can cause a considerable degree of heterogeneity, leading to unforeseen yield reductions. Fiber quality for instance is influenced by the developmental stage of hemp at harvest. Also, male and female plants differ in stature and produce fibers with different properties and quality. Next to these causes, there is evidence for specific genotypic variation in fiber quality among hemp accessions. Before improved hemp cultivars can be developed, with specific flowering-times and fiber qualities, and adapted to different geographical regions, a better understanding of the molecular mechanisms controlling important phenological traits such as "flowering-time" and "sex determination" in relation to fiber quality in hemp is required. It is well known that genetic factors play a major role in the outcome of both phenological traits, but the major molecular factors involved in this mechanism are not characterized in hemp. Genome sequences and transcriptome data are available but their analysis mainly focused on the cannabinoid pathway for medical purposes. Herein, we review the current knowledge of phenotypic and genetic data available for "flowering-time," "sex determination," and "fiber quality" in short-day and dioecious crops, respectively, and compare them with the situation in hemp. A picture emerges for several controlling key genes, for which natural genetic variation may lead to desired flowering behavior, including examples of pleiotropic effects on yield quality and on carbon partitioning. Finally, we discuss the prospects for using this knowledge for the molecular breeding of this sustainable crop a candidate gene approach.
大麻（Cannabis sativa L.）是一种可持续的多用途纤维作物，具有较高的养分和水分利用效率，其生物质质量优异，可用于纺织纤维和建筑材料。大麻生物质的产量和质量在很大程度上由大麻品种的遗传背景决定，但也受到环境因素的强烈影响，如温度和光周期。大麻是一种兼性短日植物，其特点是对光周期有很强的适应性，环境因素对“开花时间”和“性别决定”等重要农艺性状有很大影响。大麻的这种敏感性会导致相当程度的异质性，从而导致意外的产量下降。例如，纤维质量受收获时大麻发育阶段的影响。此外，雄株和雌株在株高上存在差异，所产生的纤维具有不同的特性和质量。除了这些原因外，有证据表明大麻种质间在纤维质量上存在特定的基因型变异。在培育出具有特定开花时间和纤维质量、并适应不同地理区域的改良大麻品种之前，需要更好地了解控制大麻重要物候性状（如“开花时间”和“性别决定”）与纤维质量相关的分子机制。众所周知，遗传因素在这两个物候性状的结果中起主要作用，但参与该机制的主要分子因素在大麻中尚未得到表征。虽然已有基因组序列和转录组数据，但其分析主要集中在用于医疗目的的大麻素途径。在此，我们分别综述了短日和雌雄异株作物中关于“开花时间”、“性别决定”和“纤维质量”的表型和遗传数据的现有知识，并将它们与大麻的情况进行比较。出现了几个控制关键基因的情况，其自然遗传变异可能导致期望的开花行为，包括对产量质量和碳分配产生多效性影响的例子。最后，我们讨论了利用这些知识进行这种可持续作物分子育种的前景——一种候选基因方法。
