This research was conducted to evaluate the contribution of four candidate genes — CsABA2 (CsGy5G015450), CsLRR-RPK2 (CsGy5G015660), CsPM5.2 (CsGy5G015960), and CsaMLO8 (CsGy5G026660) — to powdery mildew (PM) resistance in cucumber germplasms. For this purpose, fifty-four germplasms, consisting of thirty-three breeding lines and twenty-one landraces from fourteen diverse origins, were evaluated for PM-resistance at the adult plant stage and genotyped using molecular markers associated with the four PM-resistance-related genes. According to the phenotypic assessment, sixteen germplasms were susceptible, nineteen germplasms exhibited intermediate-resistant, and nineteen germplasms demonstrated resistant to PM. The results from phenotypic evaluation and genotyping analysis indicated that among the PM-susceptible germplasms, 50% of CsLRR-RPK2, 31% of CsABA2, 25% of CsaMLO8, and 18% of CsPM5.2 had inconsistent genotypes. Genotype inconsistencies among PM-resistant germplasms were observed in 16% of CsLRR-RPK2, 16% of CsABA2, 10% of CsaMLO8, and 10% of CsPM5.2. This study showed that the combination of CsPM5.2 and CsaMLO8 alleles is more effective and beneficial for PM-resistance breeding programs in cucumber. And also, this suggests there is a relationship between PM-resistance and the genotype of a combination of PM-resistance candidate genes. The findings of the genotyping and PM-phenotypic evaluation of the current study may improve selection accuracy in breeding for PM-resistance in cucumber.

Pumpkin (Cucurbita moschata) has been increasingly used as bloomless rootstock for cucumber (Cucumis sativus), but it is sensitive to low-temperature, which is the major bottleneck for winter cultivation. Hence, to develop low-temperature tolerant rootstock varieties, it is needed to identify tolerant germplasm from a wide range of genetic resources. For this, we developed a selection criterion for a quick assessment of low-temperature tolerance in pumpkin germplasms from different geographical origins. We considered various indexes for the fast evaluation of low-temperature tolerance, including seedling developmental stage, type of seedling (excised or non-excised), growth space, etc. Under the testing condition (17℃/7℃, 8 hours light/16 hours dark, 150 μmol m^-2s^-1 light intensity), we found a correlation (r=0.71*) in root growth between 3 weeks-cultured excised seedlings and 6 weeks-cultured non-excised seedlings. Therefore, we extrapolate that excised cotyledonary stage seedling treated for 3 weeks is sufficient to differentiate the tolerant germplasms. Using this screening method, we identified the “S81015” could prevail low-temperature stress. Further, we tested grafting compatibility and growth of grafted cucumbers under the low-temperature condition to assess the effect of rootstock and identify low-temperature tolerant and grafting-compatible rootstock germplasm. Upon grafting, we found a high correlation (r=0.97**) between the root fresh weight of 6 weeks-cultured non-excised seedlings and the shoot fresh weight of the grafted cucumbers. In summary, we could identify the low-temperature tolerant pumpkin germplasms by screening at the early developmental stage. Further, as a rootstock, the tolerant pumpkins also fortified the low-temperature tolerance of grafted cucumbers.

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  Journal of Plant Biology.2023; 66(4): 317.     CrossRef

Dehydrins (DHNs) are hydrophilic proteins with conserved lysine-rich K-segment, which belong to Group II of the late embryogenesis abundant (LEA) protein family. DHNs are considered as molecular chaperons playing important roles in abiotic stress tolerance. In this study, DHN genes were identified through genome-wide searches in five Cucurbitaceae species, including cucumber, wild cucumber, melon, watermelon, and bitter gourd. Three to five DHN genes were found in each of the five species, which were further divided into several protein architecture types based on the presence and order of the major conserved motifs such as K-, Y-, and S-segments. In silico expression profiling using RNA-Seq data revealed high expression of SK₃-type DHN gene and low expression of other type DHN genes in cucumber and melon. In silico promoter analysis identified a number of cis-acting element-like sequences related to abiotic stress-response such as DRE and ABRE in 2-kb putative promoter sequences. DHN genes identified in this study will be valuable for understanding the stress response mechanism as well as assisting molecular breeding in Cucurbitaceae crops.

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  Frontiers in Plant Science.2020;[Epub]     CrossRef
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AP2/EREBP gene family consists of transcription factor genes with a conserved AP2 DNA-binding domain and is involved in various biological processes. AP2/EREBP gene families were identified through genome-wide searches in five Cucurbitaceae species including cucumber, wild cucumber, melon, watermelon, and bitter gourd, which consisted of more than 100 genes in each of the five species. The gene families were further divided into five groups including four subfamilies (ERF, DREB, AP2 and RAV) and a soloist group. Among the subfamilies, DREB subfamily which is known to be related to abiotic stress response was more analyzed and a total of 25 genes were identified as Cucurbitaceae homologues of Arabidopsis CBF/DREB1 genes which are important for abiotic stress-response and tolerance. In silico expression profiling using RNA-Seq data revealed diverse expression patterns of cucumber AP2/EREBP genes. AP2/EREBP gene families identified in this study will be valuable for understanding the stress response mechanism as well as facilitating molecular breeding in Cucurbitaceae crops.

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• Knockdown of Gh_A05G1554 (GhDHN_03) and Gh_D05G1729 (GhDHN_04) Dehydrin genes, Reveals their potential role in enhancing osmotic and salt tolerance in cotton
  Joy Nyangasi Kirungu, Richard Odongo Magwanga, Lu Pu, Xiaoyan Cai, Yuanchao Xu, Yuqing Hou, Yun Zhou, Yingfan Cai, Fushun Hao, Zhongli Zhou, Kunbo Wang, Fang Liu
  Genomics.2020; 112(2): 1902.     CrossRef
• Crosstalk between Brassinosteroids and Ethylene during Plant Growth and under Abiotic Stress Conditions
  Petra Jiroutova, Jana Oklestkova, Miroslav Strnad
  International Journal of Molecular Sciences.2018; 19(10): 3283.     CrossRef
• Comprehensive Transcriptome Profiling and Identification of Potential Genes Responsible for Salt Tolerance in Tall Fescue Leaves under Salinity Stress
  Erick Amombo, Xiaoning Li, Guangyang Wang, Shao An, Wei Wang, Jinmin Fu
  Genes.2018; 9(10): 466.     CrossRef