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Cucumber (Cucumis sativus L.) is an agriculturally and economically important vegetable crop worldwide. The thickness of mesocarp is an important quality pertaining to edibility. The development of mesocarp, however, has received little attention. In this study, we selected one thick mesocarp line D8 to analyze the gene expression profiles of mesocarp at 0, 3, 6, and 9 days after pollination (DAP) by RNA sequencing. Genes mainly related to ribosomes, carbon metabolism, biosynthesis of amino acids, and oxidative phosphorylation were up-regulated at 3 DAP. From 3 to 6 DAP, the genes related to oxidative phosphorylation, photosynthesis, and phagosome were highly induced. From 6 to 9 DAP, the genes related to plant hormone signal transduction were highly induced. Differentially expressed genes linked to cyclin, hormone biosynthesis and signaling, carbon metabolism, and transcription factors MYB and WRKY were common up-regulated at 3, 6, 9 DAP in comparison with 0 DAP. The auxin-responsive and cytokinin-responsive genes were significantly up-regulated in mesocarp development. The higher expression levels of the auxin-responsive gene indole-3-acetic acid-amido synthetase 3.6 and the cytokinin response regulator 3/4b in the thick mesocarp cultivar D8 than in the thin mesocarp cultivar XUE1 might have explained the different growth rates of the mesocarp.

Waterlogging usually leads plant cells to shift their metabolism towards anaerobic fermentation pathways due to the hypoxia stress. The roles of two different levels of waterlogging treatments (water level was kept on the base of hypocotyls and on the base of the first true leaf) in induction of fermentation in waterlogged roots of cucumber line ‘Zaoer-N’ (waterlogging tolerant line) were examined. Root activities, numbers of dead cells, transcripts of genes encoding pyruvate decarboxylase (PDC), alcohol dehydrogenase (ADH) and lactate dehydrogenase (LDH), and activities of the PDC, ADH, and LDH enzymes, concentrations of acetaldehyde, alcohol and lactate were quantified during 48 h of waterlogging, and 48 h of subsequent recovery. The results showed that PDC, ADH, and LDH transcripts, activities of PDC, ADH and LDH, and concentrations of acetaldehyde, alcohol and lactate were upregulated or increased during waterlogging, and decreased with recovery time prolonged. The results revealed that waterlogging up to the base of first true leaf responded more severe than waterlogging up to the base of hypocotyls in root activity and numbers of dead cells, which were mainly caused by alcohol fermentation.

This study investigated the effect of root exudates of cucumber varieties, Jinyan 4 (susceptible variety), Jinchun 4 (resistant variety) and Yinnan Black seed squash on fusarium wilt. The results showed that fusarium wilt occurrence of plants treated with the root exudate of Jinyan 4 was earlier. The infection rate was significantly higher 15 days after inoculation, but similar to the control 20 days after inoculation. In contrast, the infection rate of plants treated with the root exudate of Jinchun 4 was significantly lower than that of the control. The plant height and fresh weight of Jinyan 4 treated with its own root exudate were lower than those of the control, and the root vigor decreased but the conductance increased. There was no significant effect of the root exudates from Jinchun 4 and Black seed squash on plant height and fresh mass of Jinyan 4. We found that the root exudate of susceptible cucumber variety stimulated the growth of Fusarium oxysporum pathogen, in contrast, that of resistance variety and Black seed squash suppressed the growth.

Sequence-related amplified polymorphism (SRAP) and Inter-simple sequence repeat (ISSR) markers are both simple and efficient maker systems adapted to many crops and for multiple purposes. In this study a genetic map based on SRAP and ISSR markers was constructed for cucumber (Cucumis sativus L.) based on the segregations of SRAP and ISSR markers in 112 plants of F2 population derived from a cross between two cucumber inbred lines PW0832 and PW0801. In the investigation of polymorphisms with 50 ISSR primers and 132 SRAP primer combinations, 13 (26%) ISSR primers and 26 (20%) SRAP primer pairs were polymorphic generating a total of 109 polymorphic markers of which 48 were ISSR and 61 were SRAP. The average polymorphic bands were four for ISSR and two for SRAP. All the 109 polymorphic markers were scored for segregation of which 86 satisfied the Mandelian segregation ratio of 3:1. These data were used to construct an integrated linkage map for cucumber consisting of 62 loci, distributed in seven linkage groups (LGs) spanning a total of 992.2 cM, with an average distance of 16.0 cM between two adjacent loci. These markers would be very useful tool for marker assisted selection in cucumber breeding as well as for studies in quantitative traits.

Flooding of vegetable crop fields along the Yangtze River basin in China has been an annual occurrence; therefore the cultivation of tolerant varieties has become one of the most promising control strategies. Our objective was to investigate the inheritance of waterlogging tolerance of cucumber at the early stage of growth with two cucumber parents consisting of PW0832 (tolerant) and PW0801 (susceptible). In 2006, 4-weeks-old potted plants of P1, P2, F1, F2, B1 and B2 generations were subjected to one week waterlogged stress, control plants were not flooded. The simple additive model explained the variations of tolerance score (TOL) adventitious root formation (ARF) and waterlogged root dry weight (RDW) while the additive-dominance model explained the control treatment of RDW. Non-allelic interactions were detected for waterlogged vine length (VLH) and root length (RLH). Complementary epistasis occurred in waterlogged VLH while additive × additive, additive × dominance and dominance × dominance epistastic effects were significant for waterlogged RLH. Transgressive segregation was also observed in most of the traits in the F2 generation indicating some alleles are dispersed in the parents used in this study. The estimates of narrow-sense heritabilities for TOL and ARF were moderately high. Backcross of F1 to both parents in ARF, waterlogged SDW and waterlogged RDW showed good convergence of genes in the B2. These results suggest that it should be possible to develop varieties with high levels of tolerance by selecting transgressive segregants in this cross.