The Seed-Setting Characteristic Of Different Tartary Buckwheat Cultivars And Its Response To Source-Sink Regulation

Tartary buckwheat is an important food and drug homologous crop,which has rich nutritional and health value.With consumers'attention to nutrition and health care,Tartary buckwheat and its functional products are increasingly popular,stimulating the market demand of Tartary buckwheat.The yield and quality of Tartary buckwheat cause urgent attention.However,Tartary buckwheat is a typical plant with very low seed-setting rate?15-35%?,which is one of the major limiting factors to yield improvement.In order to clarify the seed-setting characteristic of Tartary buckwheat,pot and field experiments were carried out to study the characteristics of flowering and fruiting,biomass accumulation and distribution,as well as their relationships by adjusting source-sink ratio and labeling ¹³C stable isotope.The aim is to reveal the inherent essence of low fruit setting of Tartary buckwheat and its response to source-sink regulation,to provide theoretical basis and technical support for the high seed setting breeding and high-yield cultivation of Tartary buckwheat.Simultaneously,it would provide theoretical reference for the further study of Tartary buckwheat seed setting rate,functional genes clone and cultivars improvement at the molecular level.The main results are as follows:1.From the initial flowering stage to the mature stage,the Tartary buckwheat bloomed continuously.At harvest,there were a large number of sterile flowers?28-51%?and unfilled grains?25-40%?,which could not develop into seed;this seriously affected the seed setting rate of Tartary buckwheat.The seed setting rates of eight cultivars ranged from 20.7%to 33.6%.All cultivars were divided into three types by clustering analysis:cultivars with high seed setting rate more than 31%?Chuanqiao1,Dianning1?,middle cultivars with seed setting rate between 23.3-29.1%?Xiqiao1,Chuanqiao2,Qianku3,Liuku3?and cultivars with low seed setting rate less than 23.1%?Xiqiao2,Jinku6?.2.According to the component of seed-setting,there was no significant difference in the number of filled grains,unfilled grains and sterile flowers in cultivars with high seed setting rate,while in other types,the number of filled grains is significantly less than unfilled grains and sterile flowers.According to the distribution of seed-setting rate through the whole plant,the seed-setting rate of the main stem was higher than that of the branches?all cultivars varied between6.9-30.2%?,and the seed-setting rate of the upper part of the plant is higher than that of the lower part?9.4-16.9%?.However,there was no significant difference in the seed-setting rate of Chuanqiao 1,which was the cultivar with highest seed-setting rate.3.The network analysis indicated that the seed-setting rate of Tartary buckwheat was significantly positively correlated with the SPAD,net photosynthetic rate and dry matter accumulation at seedling stage,blooming stage and filling stage,while it was significantly negatively correlated with the Fv'/Fm'at all period,?PS?at seedling stage and filling stage.4.The result showed that the self-retention of ¹³C assimilate in the upper part of the plant?68.2%?was higher than its output?31.8%?,while the self-retention of ¹³C assimilate in the middle and lower part of the plant was lower than their output.In addition,the ¹³C assimilate output of Tartary buckwheat from upper part to lower part increased successively,which was 31.8%,64.5%and 95.1%,respectively.Further analysis showed that the upper,middle and lower part of the plant delivered more than55%of ¹³C assimilates to the main stem?60.9%,59.1%and 73.7%,respectively?,far more than the amount delivered to branch.The amount of ¹³C assimilates delivered to flowers and grains mostly came from leaves of middle part,which showed that the leaves of middle part contributed most to the photosynthetic products of flowers and grains.5.The source-sink regulation showed that S₁ treatment?keep whole leaves and two spikelets on the top of main stem,removal other spikelets?significantly improved the seed-setting rate of Tartary buckwheat about 18.5%to 44.1%.The seed-setting rate of S₁ treatment was higher than that of S₂ treatment?keep whole leaves and two spikelets on the bottom branches,removal other spikelites?.The seed-setting rate of S₃treatment?keep whole spikelets and two mature leaves on the top of main stem,removal other leaves?group and S₄ treatment?keep whole spikelets and two mature leaves on the bottom of main stem,removal other leaves?group were significantly lower than that of the control group,except for two cultivars with lowest seed setting rate?Jinku 6 and Xiqiao 2?.However,there was no significant difference between the seed setting rate of S₃ treatment group and S₄ treatment group.