异色菊×菊花脑种间杂种耐旱性的QTL和候选基因定位及功能标记开发

Chrysanthemum is an important traditional flower in China and ranks among the most popular cut flower worldwide, thus having considerable commercial values. Drought is a major abiotic stress that adversely affects chrysanthemum’s production, and the key to solve the problem is to breed drought-tolerant cultivars. Hitherto, great progresses have been achieved in physiologic and molecular mechanisms governing drought tolerance of chrysanthemum, but it is rarely known concerning the genetic determinism, which has hindered the genetic improvement for drought-tolerant chrysanthemum cultivars. Now that analysis on the genetic pattern of many important traits of chrysanthemum has been hampered mainly by its complex backgrounds, i.e. hexaploidy, high heterozygosity, huge and unknown genome, the discovery and use of low-ploidy wild related species of chrysanthemum may open a possibility to dissect the inheritance of these traits. In our early research, a higher level of genetic heterogeneity was found for the two important diploid related species of cultivated chrysanthemum, Chrysanthemum dichrum (drought-tolerant) and C. nankingense (drought-sensitive), and the drought tolerance varied continuously in the interspecific hybrid progenies of the two species, thus laying an important foundation for genetic analysis of drought tolerance. The present study is further set up to investigate drought tolerance of the interspecific F1 mapping population, and to construct high-density genetic linkage maps for the two Chrysanthemum species via high throughout sequencing-based SNP molecular markers, based on which the additive and epistatic QTL effects will be dissected and the major QTL responsible for drought tolerance will be subsequently identified. In the meantime, bulked drought-tolerant and drought-sensitive segregants will be constructed, from the forementioned interspecific F1 mapping population, to identify candidate genes governing drought tolerance by bulked segregant RNA-seqencing (BSR) analysis. Combining the QTL and BSR analyses the candidate genes will be mapped on the high-density genetic maps, and finally some functional molecular markers will be developed for drought tolerance. The findings of this study will add in-depth understanding of genetic mechanism of drought tolerance in chrysanthemum related species, and the mapped candidate genes, along with the developed functional markers, will be of vital importance for future genetic improvement of drought tolerance in chrysanthemum.

菊花是我国传统名花和世界重要切花，观赏和经济价值高。干旱是影响菊花产业发展的主要逆境之一，培育耐旱新品种是解决该问题的关键。目前，菊花的耐旱生理和分子机制研究进展良好，但其遗传机制尚不明晰，严重影响耐旱育种进程。菊花为六倍体物种，遗传背景复杂，不利其性状的遗传解析，而其低倍性近缘种更便于开展相关研究。我们前期发现菊花二倍体近缘种异色菊（耐旱）和菊花脑（不耐旱）的遗传异质性较高，其种间F1群体的耐旱性呈连续变异。本项目拟进一步调查该F1群体的耐旱性，利用SNP标记构建异色菊和菊花脑的高密度连锁遗传图，通过加性和上位性QTL定位获得耐旱性主效QTL，通过转录组水平的集团分离分析（BSR）挖掘耐旱相关基因，综合QTL和BSR分析开展耐旱候选基因定位，并开发耐旱功能型分子标记。研究结果将揭示菊花近缘种植物耐旱性的遗传机制，实现耐旱候选基因定位和功能标记开发，对今后菊花耐旱性的遗传改良具有重要意义。

菊花是我国传统名花和世界重要切花，观赏和经济价值高。干旱是影响菊花产业发展的主要逆境之一，培育耐旱新品种是解决该问题的关键。目前，菊花的耐旱生理和分子机制研究进展良好，但其遗传机制尚不明晰，严重影响耐旱育种进程。本项目连续3次调查了菊花二倍体近缘种异色菊（耐旱）和菊花脑（不耐旱）的种间F1群体9个耐旱相关性状，采用隶属函数值和主成分分析评价了耐旱性，三个环境间有较强的相关性（r ≥ 0.74**，P < 0.01），挖掘耐旱种质11份；明确了耐旱性的杂种优势和主基因遗传效应，各耐旱相关性状均存在超过高值亲本的个体，也存在低于低值亲本的个体，产生了正向和负向的超亲后代；控制抗旱性主要由一对表现为加性和显性的主基因控制，主遗传率为50%，受环境影响较大。基于多位点关联分析方法挖掘到4个SSR位点与地上干重、地下鲜重和萎焉指数等3个耐旱相关指标显著关联（LOD＞2.5），表型变异解释率为4.03 % ~ 15.11 %。使用GACDV.1.2软件，构建了菊花脑和异色菊种间杂交F1群体的高密度遗传图谱，共包含9条连锁群，连锁群长度为137.40~249.09 cM，总长为1859.31cM，平均标记间距为0.278cM。共检测到60个主效QTLs，LOD值介于3.04 ~ 12.182之间，单个 QTL 可以解释 2.76 ~ 16.76 %的表型变异；初步分析发现QTL相关后续基因主要与ABA等植物激素调控、碳水化合物和糖代谢、信号分子调控和氧化还原反应有关。基于QTL关联的SNPs，开发出耐旱性相关的3个KASP功能型分子标记用于后续辅助选择，为今后菊花耐旱性遗传改良奠定了重要基础。

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