Dong Shaoyun, Wang Weiping, Bo Kailiang, Miao Han, Song Zichao, Wei Shuang, Zhang Shengping, Gu Xingfang
Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, China.
Front Plant Sci. 2019 Dec 11;10:1620. doi: 10.3389/fpls.2019.01620. eCollection 2019.
Cucumber ( L.) is an economically important vegetable crop worldwide, but it is sensitive to low temperatures. Cucumber seedlings exposed to long-term low temperature stress (LT), i.e., below 20°C during the day, and 8°C at night, exhibit leaf yellowing, accelerated senescence, and reduced yield, therefore posing a threat to cucumber production. Studying the underlying mechanisms involved in LT tolerance in cucumber seedlings, and developing germplasm with improved LT-tolerance could provide fundamental solutions to the problem. In this study, an F population was generated from two parental lines, "CG104" (LT-tolerant inbred line) and "CG37" (LT-sensitive inbred line), to identify loci that are responsible for LT tolerance in cucumber seedlings. Replicated phenotypic analysis of the F-derived F family using a low-temperature injury index (LTII) suggested that the LT tolerance of cucumber seedlings is controlled by multiple genes. A genetic map of 990.8 cM was constructed, with an average interval between markers of 5.2 cM. One quantitative trait loci (QTL) named on chromosome 5, and two QTLs named and on chromosome 6 were detected. Among them, accounted for 26.8 and 24.1% of the phenotypic variation in two different experiments. Single-nucleotide polymorphism (SNP) variations within the region of were analyzed using two contrasting bulks generated from the cucumber core germplasm. Result showed that 214 SNPs were distributed within the 42-kb interval, containing three candidate genes. Real-time quantitative reverse transcription PCR and sequence analysis suggested that two genes , an auxin response factor, and , an ethylene-responsive transmembrane protein, might be candidate genes responsible for LT tolerance in cucumber seedlings. This study furthers the understanding of the molecular mechanism underlying LT tolerance in cucumber seedlings, and provides new markers for molecular breeding.
黄瓜（L.）是全球一种经济上重要的蔬菜作物，但它对低温敏感。暴露于长期低温胁迫（LT）下的黄瓜幼苗，即白天温度低于20°C且夜间温度为8°C时，会出现叶片黄化、衰老加速和产量降低的情况，因此对黄瓜生产构成威胁。研究黄瓜幼苗耐低温胁迫的潜在机制，并培育具有更高耐低温能力的种质资源，可为解决这一问题提供根本方案。在本研究中，从两个亲本系“CG104”（耐低温自交系）和“CG37”（低温敏感自交系）构建了一个F群体，以鉴定黄瓜幼苗耐低温的基因座。使用低温伤害指数（LTII）对F衍生的F家系进行重复表型分析表明，黄瓜幼苗的耐低温性受多个基因控制。构建了一张990.8 cM的遗传图谱，标记间平均间隔为5.2 cM。在5号染色体上检测到一个名为 的数量性状基因座（QTL），在6号染色体上检测到两个名为 和 的QTL。其中， 在两个不同实验中分别解释了26.8%和24.1%的表型变异。利用从黄瓜核心种质中产生的两个对比混合群体分析了 区域内的单核苷酸多态性（SNP）变异。结果表明，214个SNP分布在42 kb区间内，包含三个候选基因。实时定量逆转录PCR和序列分析表明，两个基因，一个生长素响应因子 和一个乙烯响应跨膜蛋白 ，可能是黄瓜幼苗耐低温的候选基因。本研究进一步加深了对黄瓜幼苗耐低温分子机制的理解，并为分子育种提供了新的标记。
