苦荞源库协调对结实率的影响及其机理研究

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) is an edible and medicinal crop with rich nutritional health value. As the interest in the use of tartary buckwheat for health benefits is growing, the market demand is increasing greatly. Although there are large flower numbers on inflorescence , the seed setting rate is only 15-35%. The low seed setting rate is one of the important factors that constrains grain yield in tartary buckwheat. Previous studies found the close relationships among photosynthate, source-sink ratio and seed setting rate. This study intends to use 14C isotope tracer technology to study the distribution of photosynthate of different organs and different spatial in different seed setting tartary buckwheat. Through measures like leaf cutting to study the regulation of source sink in different seed setting tartary buckwheat. Through scanning electron microscopy to study pollen viability, germination rate and stigma receptivity on tartary buckwheat in order to clear fertilization and seed development effect on seed setting rate. This research try to use the crop cultivation science, botany, plant anatomy and plant physiology to study the relationships between photosynthate, source, sink and setting rate, and to find the fundamental cause that resulting in low setting rate, and further to reveal the mechanism of source sink coordination affecting seed setting rate in tartary buckwheat. This study has the important theoretical and practical significance on theoretical research of flowering and seed setting and raise yield in tartary buckwheat. It also has great scientifc significance for exploring the mechanism of seed setting rate at the molecular level, cloning functional genes and modifying the cultivar in the future.

苦荞作为重要的药食同源作物，具有丰富的营养保健价值。近年来其功能性制品日益受到消费者的青睐，市场需求量剧增。苦荞单株开花数多，而结实率仅为15-35%，极其低下的结实率已成为限制其高产的关键因素之一。前人研究发现，光合产物、源库比与结实率间紧密联系。本课题拟采用14C同位素示踪技术，研究不同结实能力苦荞材料在不同器官、不同空间的光合产物分配；通过剪叶等措施调控源库，研究不同结实能力材料源库情况；采用电镜分析研究苦荞花粉活力、萌发率及柱头可授性等，明确受精及籽粒发育（早衰）对结实率的影响。采用作物栽培学、植物学、植物解剖及植物生理学相结合的研究方法，通过研究光合产物、源和库与结实率的具体关系，试图找到苦荞结实率低的根本原因，阐明源库协调对结实率的影响及其机理，对苦荞开花结实理论研究和产量全面提升具有重要的理论和现实意义；对下一步从分子水平探讨苦荞结实率、克隆功能基因、改良品种具有重大科学意义。

本项目围绕苦荞结实率低的问题，通过四年研究明确了苦荞结实率低的原因，阐明了源库协调对结实率的影响及其机理，主要结论如下：（1）采用８个苦荞品种，通过田间试验研究了苦荞植株的花和籽粒构成及分布情况，考察其结实特性，发现苦荞初花至成熟期不断开花，收获时有大量败育花(28.0-51.0%)和空瘪粒不能形成饱满籽粒，严重影响结实率。从结实分布看，主茎的结实率高于分枝，比其高6.9-30.2%。植株上部的结实率高于植株下部(9.4-16.9%)，但高结实率品种在各部位的分布无明显差异；（2）通过13C标记同化物去向，发现植株上部的13C同化物自留量(68.2%)显著高于输出量(31.8%)。植株中、下部自留量低于输出量，且苦荞植株自上而下的输出量依次增加，分别为31.8%，64.5%和95.1%。进一步分析发现，上、中、下部叶片产生的13C同化物主要运输到主茎，分别为60.9%、59.1%和73.7%，远高于分枝。（3）通过剪叶等调控源库，发现减库保源可显著提高苦荞结实率，较对照增加18.5-44.1%，减源保库处理组的苦荞结实率均显著低于对照。（4）分析物质积累对结实的调控效应发现苦荞花后根、茎、叶干物重占比整体呈下降趋势，而籽粒的干物重上升。灌浆期高结实率品种籽粒具有更强的物质转运能力；（5）苦荞现蕾期花粉活力较高（90%以上），但之后会逐渐降低，生育后期仅为40-49%，严重影响籽粒形成。籽粒发育过程中，花后苦荞籽粒可溶性糖和淀粉含量逐渐增加，而蔗糖含量逐渐减少。高结实率品种SS和SSS酶活性均高于低结实率品种，比其分别高5.2%-11.6%和6.6%-12.5%。酶活性和蔗糖含量是影响籽粒灌浆和结实率高低的关键，生产上可通过增强源供应，改善源库关系以促进籽粒形成和灌浆，形成更多有效籽粒和强势粒，从而提高苦荞结实率。