苹果砧穗互作分枝调控机制研究

After applying dwarf rootstocks, the main apple cultivar of Chinese, Fuji, has many problems such as low branches, slow growth and inability to produce fruits after planting for many years, which seriously affects apple yield and economic efficiency. The existing research results showed that promoting effective branching of saplings is an important measure for shortening the fruit tree infancy and increasing yield. Plant growth regulators and artificial buds notching technique are often used in production to promote branching of apple saplings,early fructifying and increasing yield. However, the actual operation wastes a lot of manpower and time, raising production costs. Simultaneously, there are lots of issues such as food safety and ecological environment as well. In the previous study, a multi-branch mutant of Malus baccata (L.) Borkh., rootstock, was obtained, of which has 10 times branches more than that of the wild type, and utilization of this multi-branch rootstock resource may be able to solve the above production problems. However, the effect of this mutant on branching and branching mechanism of scions is not clear. This study intends to use this mutant as an entry point to study the effect of the different combinations of rootstock and scion on the branching of the scion, and evaluate the application prospects of the mutant rootstock to the apple industry. At the same time, the mechanism of branching of mutants has been studied and the molecular markers related to the branches has been screened. The results of this study will provide important scientific and technological support for accelerating the process of molecular marker assisted breeding and solving practical problems in apple production.

目前我国主栽品种富士系应用矮化砧木后，多出现分枝量少、生长缓慢，苗木定植后多年不结果等问题，严重影响苹果产量和经济效益。已有的研究结果表明，促进幼树分生有效分枝是缩短果树童期，提高产量的重要手段。生产中常使用植物生长调节剂和人工刻芽等技术，促进苹果幼树成枝，提早结果和提高产量。但实际操作耗力耗时，提高了生产成本，同时也存在食品安全和生态环境等问题。本研究前期获得了砧木用山定子多分枝突变体，其分枝数量是野生型的10倍以上，利用该多分枝砧木资源也许能解决以上生产问题。但该突变体对接穗的分枝影响及分枝机理尚不明确。本研究拟以该突变体为切入点，通过不同的砧穗组合研究其对接穗分枝性的影响，评价该突变砧木对苹果产业应用前景。同时，研究突变体分枝机制，筛选分枝相关的分子标记。本实验结果将为加快分子标记辅助育种进程，解决苹果生产中存在的现实问题提供重要的科技支撑。

我国是世界上最大的苹果生产与消费国，苹果产业为农业结构调整与农民增收发挥关键作用。随着矮砧集约化栽培模式的推进，富士系嫁接于矮化砧后出现的分枝量少、生长缓慢的问题趋于严重。本研究利用苹果属中一种多分枝芽变（Multi-branched Bud，MB）及其野生型（WT）为材料，结合表型、生理生化参数、激素处理和重测序分析，鉴定了多分枝表型发生的生理和分子机制；鉴定其扦插性能和应用前景，为苹果分枝调控技术提供理论基础。同时，对于该芽变出现的花不育特性进行机理研究，探讨分枝与花育性相互调控作用。取得的主要结果如下：1、MB分枝数量显著增加可达到WT的10倍，而WT未出现分枝或分枝少量极少；MB还表现分枝角度大、节间短、矮化、茎粗、叶色淡、侧枝着生点小、花雌性不育等特征。2、测定激素含量，发现MB不同节间处CTK成分ZR含量显著高于WT，且从顶芽往下逐渐上升；而生长素含量显著低于WT；赤霉素含量无明显差异。3、完成了WT和MB全基因组重测序，两样本间编码区相关的snp差异位点24303个，定位了5072个基因；与编码区相关 inDels 差异891个，定位在596个基因上。KEGG分析显著富集到碳水化合物代谢和植物信号转导，其中与激素信号转导相关基因38个。经MB与富士的杂交后代分析，分枝为一数量性状，且可能多基因控制。通过BSA定位分析，分枝关联区域9.87Mb。在该预测区间内，注释到非同义突变基因328个，激素信号转导相关5个。4、通过观察花发育不同时期的形态特征，MB花发育在第4时期出现停滞现象。通过转录组数据分析，两样本中差异下调基因2105个，上调基因778个，通过GO和KEGG分析，我们推测可能与果胶酶有关。其中MdPME4经RT-PCR验证，与WT相比，有1000多倍的下调趋势。同时，将该基因CDS 在MB与WT中分别克隆测序可知，MB中该基因CDS有23bp的缺失。5、对苹果多分枝芽变的应用前景进行评价，MB 扦插繁殖性能较低，组培繁育较为困难，不适合作为自根砧使用。MB 作为中间砧时，对富士具有矮化性和早花性，枝组分布均匀。