Li Caixia, Dong Shaoyun, Beckles Diane M, Liu Xiaoping, Guan Jiantao, Wang Zaizhan, Gu Xingfang, Miao Han, Zhang Shengping
State Key Laboratory of Vegetable Biobreeding, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Department of Plant Sciences, University of California, One Shield Avenue, Davis, CA, 95616, USA.
Stress Biol. 2024 Dec 11;4(1):53. doi: 10.1007/s44154-024-00191-9.
Fruit quality and yield are reduced when cucumber (Cucumis sativus L.) plants are exposed to low temperature (LT) stress, yet, the inheritance and genes linked to cold tolerance in adult plants have not been reported yet. Here, the LT-tolerance of 120 cucumber accessions representing four ecotypes were evaluated by GWAS, and also, in 140 recombinant inbred lines (RILs) derived from a biparental cross. Plants were exposed to naturally occurring LT environments in a plastic greenhouse, in winter 2022, and 2023, and a low temperature injury index (LTII) was employed to evaluate plant performance. Genetic analysis revealed that the LT-tolerance evaluated in the adult cucumber plants was a multigenic quantitative trait, and that 18 of the 120 accessions were highly LT tolerant by our LTII assessment. Two loci (gLTT1.1 and gLTT3.1) exhibited strong signals that were consistent and stable in two environments. In addition, two QTLs-qLTT1.2 on chromosome (Chr.) 1, and qLTT3.1 on Chr. 3, were discovered in all tests using RIL population derived from a cross between LT-sensitive 'CsIVF0106', and LT-tolerant 'CsIVF0168'. qLTT1.2 was delimited to a 1.24-Mb region and qLTT3.1 was narrowed to a 1.43-Mb region. Interestingly, a peak single nucleotide polymorphism (SNP) at gLTT1.1 and gLTT3.1 was also found in qLTT1.2 and qLTT3.1, respectively. These loci were thus renamed as gLTT1.1 and gLTT3.1. In these regions, 25 genes were associated with the LT response. By identifying differences in haplotypes and transcript profiles among these genes, we identified four candidates: CsaV3_1G012520 (an ethylene-responsive transcription factor) and CsaV3_1G013060 (a RING/U-box superfamily protein) in gLTT1.1, and two RING-type E3 ubiquitin transferases at CsaV3_3G018440 and CsaV3_3G017700 in gLTT3.1 that may regulate LT-tolerance in adult cucumber. Interestingly, the accessions in which the LT-tolerant haplotypes for two loci were pyramided, displayed maximally high tolerance for LT. These findings therefore provide a solid foundation for the identification of LT-tolerant genes and the molecular breeding of cucumber with LT-tolerance.
当黄瓜（Cucumis sativus L.）植株遭受低温（LT）胁迫时，果实品质和产量会降低，然而，关于成年植株耐寒性的遗传及相关基因尚未见报道。在此，通过全基因组关联研究（GWAS）对代表四种生态型的120份黄瓜种质的低温耐受性进行了评估，同时也对来自双亲杂交的140个重组自交系（RIL）进行了评估。2022年和2023年冬季，将植株置于塑料大棚自然低温环境中，并采用低温伤害指数（LTII）评估植株表现。遗传分析表明，成年黄瓜植株的低温耐受性是一个多基因数量性状，在我们的LTII评估中，120份种质中有18份对低温具有高度耐受性。两个位点（gLTT1.1和gLTT3.1）表现出强烈信号，在两种环境中一致且稳定。此外，在所有试验中，利用对低温敏感的‘CsIVF0106’和耐低温的‘CsIVF0168’杂交产生的RIL群体，在1号染色体（Chr.）上发现了两个数量性状基因座（QTL）——qLTT1.2，在3号染色体上发现了qLTT3.1。qLTT1.2被定位到一个1.24兆碱基（Mb）的区域，qLTT3.1被缩小到一个1.43 Mb的区域。有趣的是，在qLTT1.2和qLTT3.1中也分别在gLTT1.1和gLTT3.1处发现了一个单核苷酸多态性（SNP）峰值。因此，这些位点被重新命名为gLTT1.1和gLTT3.1。在这些区域，有25个基因与低温响应相关。通过鉴定这些基因单倍型和转录谱的差异，我们确定了四个候选基因：gLTT1.1中的CsaV3_1G012520（一种乙烯响应转录因子）和CsaV3_1G013060（一种RING/U-box超家族蛋白），以及gLTT3.1中的CsaV3_3G018440和CsaV3_3G017700处的两个RING型E3泛素转移酶，它们可能调节成年黄瓜的低温耐受性。有趣的是，两个位点的耐低温单倍型聚合的种质对低温表现出最高耐受性。因此，这些发现为鉴定耐低温基因和黄瓜耐低温分子育种提供了坚实基础。
