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Ting Zhou, Hao Jiang, Donglin Zhang, Junjun Fan, Long Zhang, Guibin Wang, Wangxiang Zhang and Fuliang Cao

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Hao Jiang, Ting Zhou, Junjun Fan, Donglin Zhang, Long Zhang, Yanyan Sun and Wangxiang Zhang

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Lie-Bao Han, Gui-Long Song and Xunzhong Zhang

Traffic stress causes turfgrass injury and soil compaction but the underlying physiological mechanisms are not well documented. The objectives of this study were to investigate the physiological responses of kentucky bluegrass (Poa pratensis), tall fescue (Festuca arundinacea), and japanese zoysiagrass (Zoysia japonica) to three levels of traffic stress during the growing season under simulated soccer traffic conditions. Relative leaf water content (LWC), shoot density, leaf chlorophyll concentration (LCC), membrane permeability, and leaf antioxidant peroxidase (POD) activity were measured once per month. The traffic stress treatments caused a reduction in LWC, shoot density, LCC, and POD activity, and an increase in cell membrane permeability in all three species. Japanese zoysiagrass had less electrolyte leakage, and higher POD activity and shoot density than both kentucky bluegrass and tall fescue. The results suggest that turfgrass tolerance to traffic stress may be related to leaf antioxidant activity. Turfgrass species or cultivars with higher leaf antioxidant activity may be more tolerant to traffic stress than those with lower antioxidant activity.

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Long He, Jianfeng Zhou, Qin Zhang and Manoj Karkee

A study on multipass harvesting using a mechanical harvesting prototype was proposed for mechanical harvesting of fresh market sweet cherries. Fruit damage rate, fruit removal rate, and fruit maturity level were three of the measures used to compare the performance of the multipass harvesting method against single-pass harvesting. The multipass harvesting was conducted in four consecutive days with short duration of 2.5 seconds at each day, while the single-pass harvesting was one-time harvesting with long duration of 10 seconds at a single day. To generate baseline information for comparison, single-pass harvestings were performed on the first and the last days of the multipass harvesting. Fruit maturity level was determined by comparing the fruit skin color against a standard color chart with seven color levels. Field test results showed that the percentage of under-mature fruit (maturity levels ≤ 5) was substantially lower with multipass harvesting than that with day 1 single-pass harvesting. Similarly, the percentage of over-mature fruit (maturity level 7) was noticeably lower with multipass harvesting than that with day 4 single-pass harvesting. Multipass harvesting achieved a fruit removal rate of 83.4% ± 10.3% and a harvest-induced fruit damage rate of 5.0% ± 4.4%. The corresponding fruit removal rates from single-pass harvesting tests were 48.0% ± 16.1% on day 1 and 66.7% ± 16.2% day 4. Harvest-induced fruit damage rates with single-pass harvesting were 20.1% ± 9.9% on day 1 and 11.8% ± 6.0% on day 4. The results supported the hypothesis that multipass of short-duration shaking offer a potential to achieve a higher overall harvesting efficiency with better fruit quality, and therefore could lead to an optimal solution for mechanical harvesting of fresh market sweet cherries. It is noted that comprehensive economic analysis will be necessary to establish commercial viability of the system in comparison with single-pass solutions.

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Qianqian Shi, Xiaoxiao Zhang, Xiang Li, Lijuan Zhai, Xiaoning Luo, Jianrang Luo, Lixia He, Yanlong Zhang and Long Li

Tree peony (Paeonia sp.) is a popular traditional ornamental plant in China. Among the nine wild species, Paeonia rockii displays wide-ranging, deep purple variegation at the base of the petals, whereas Paeonia ostii exhibits purely white petals. Overall, the posttranscriptional regulation involved in tree peony flower opening and pigmentation remains unclear. To identify potential microRNAs (miRNAs) involved in flower variegation, six small RNA libraries of P. ostii and P. rockii petals at three different opening stages were constructed and sequenced. Using Illumina-based sequencing, 22 conserved miRNAs and 27 novel miRNAs were identified in P. rockii and P. ostii petals. Seventeen miRNAs were differentially expressed during flower development, and several putative target genes of these miRNAs belonged to transcription factor families, such as Myb domain (MYB), and basic helix-loop-helix (bHLH) transcription factors. Furthermore, an integrative analysis of the expression profiles of miRNAs and their corresponding target genes revealed that variegation formation might be regulated by miR159c, miR168, miR396a, and novel_miR_05, which target the MYB transcription factors, chalcone synthase (CHS), and ABC transporter. Our preliminary study is the first report of miRNAs involved in Paeonia flower pigmentation. It provides insight regarding the molecular mechanisms underlying the regulation of flower pigmentation in tree peony.

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Ze Li, Kai Shi, Fanhang Zhang, Lin Zhang, Hongxu Long, Yanling Zeng, Zhiming Liu, Genhua Niu and Xiaofeng Tan

As a result of its high photosynthetic efficiency, the tung tree (Vernicia fordii) is a fast-growing heliophile, yielding fruit within 3 years. In addition, tung oil extracted from the fruit seeds is an environmentally friendly paint used widely in China. However, mutual shading inside a tung tree canopy leads to a low yield of fruit because of weak or dead lower branches. In this project, a pot experiment was conducted to understand the growth, physiological, anatomical structure, and biochemical responses of tung trees under various shading levels. Tung tree seedlings were subjected to different light intensities—100% sunlight (no cover), L100; 75% sunlight (25% shading), L75; 50% sunlight (50% shading), L50; and 20% sunlight (80% shading), L20—from June to August. Results indicate that the L75 treatment reduced significantly the net photosynthetic rate (Pn), stomatal conductance (g S), transpiration rate (E), total aboveground and root dry weight (DW), maximum net photosynthetic rate (A max), and maximum rate of electron transport at saturating irradiance (Jmax) compared with the control, although plant height and leaf area (LA) were not reduced. Lower light intensities (L50 and L20) and longer duration of treatment led to greater reduction in growth, leaf thickness, and photosynthetic potential (A max and Jmax). Chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll content were increased in the L50 and L20 treatments compared with L100 and L75. There was no significant reduction in the enzyme activities of ribulose-1,5-bisphosphate carboxylase (Rubisco) and phosphoenolpyruvate (PEPC) of the seedlings using the L75 treatment; however, lower light intensities (L50 and L20) and longer duration of shade treatment resulted in a significant reduction in enzyme activity. In summary, the results suggest that tung trees have greater photosynthetic activity under high light intensity. Shading, even at 20%, especially for the longer term, reduced photosynthetic efficiency and growth. To prevent growth reduction, tung trees should be grown under full sun with a daily light integral (DLI) of ≈46 mol·m‒2·d‒1, and mutual shading should be avoided by proper spacing and pruning.

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Kai-Ge Zhao, Ming-Qin Zhou, Long-Qing Chen, Donglin Zhang and Gituru Wahiti Robert

Chimonanthus praecox (wintersweet) is endemic to China. It has been cultivated there for more than 1000 years as a garden, potted, and cut-flower plant. Many cultivars have been developed during its long history of cultivation, and recently many germplasms were collected in Wuhan and Nanjing, China. The identification and genetic relationship of these resources were studied based mainly on morphological traits. In the current study, intersimple sequence repeat markers (ISSR) and random amplified polymorphic DNA markers (RAPD) were used for the first time to investigate 72 wintersweet clones from the two regions. Eleven ISSR primers amplified 115 bands, 90 (78.26%) of which were polymorphic. Nineteen RAPD primers amplified 165 bands, 105 (63.63%) of which were polymorphic. Either ISSR or RAPD markers were sufficient to distinguish all the clones surveyed. A Dendrogram based on Jaccard's similarity coefficients indicated that the distribution pattern of the 72 clones was coherent with their geographical origins. Most of the genetic variation (85.68% with ISSR data; 86.75% with RAPD data) occurred among clones within each region. However, the difference between Wuhan and Nanjing groups is statistically significant (ΦST = 0.143, P < 0.001, with ISSR data; ΦST = 0.132, P < 0.001, with RAPD data). Morphological variation and classification of wintersweet cultivars were also discussed compared with the genetic relationship based on ISSR and RAPD markers. This is the first report of the partitioning of genetic variability within and between different cultivated wintersweet regions, and it provides useful baseline data for optimizing sampling strategies in breeding. These results are important for future genetic improvement, identification, and conservation of Chimonanthus praecox germplasm.

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Meiling Yang, Fang Li, Hong Long, Weiwei Yu, Xiuna Yan, Bin Liu, Yunxiu Zhang, Guorong Yan and Wenqin Song

As a wild apple species native to central Asia, Malus sieversii (Ledeb.) Roem. is distributed in a wide region covering most of the Tienshan Mountains. Malus sieversii is a useful genetic pool for apple breeding since rich with diversity. In this paper, we first describe the species range of this endangered species. We then describe an in situ reserve that has been established. We also investigated some reproductive characteristics of M. sieversii including pollen germination, seed dormancy, and seed viability. Both stratification and seedcoat removal efficiently released seed dormancy and accelerated seed germination. Pollen germination rate is around 60%. Our data suggest that injurious insects and human activities, rather than reproductive characters, limit the renewal of M. sieversii.

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Long-na Li, Songjun Zeng, Feng Zheng, Zhi-lin Chen, Kun-lin Wu, Jian-xia Zhang and June Duan

Ten polymorphic microsatellite loci were isolated and characterized from an enriched genomic library of Paphiopedilum concolor (Batem.) Pfitzer. The number of alleles per microsatellite locus ranged from three to 11 with an average of 6.4 in a sample of 30 individuals from three populations. The observed and expected heterozygosity ranged from 0.200 to 0.800 and from 0.544 to 0.827, respectively. These microsatellites can be used as tools to investigate the genetic structure of P. concolor populations and relationship patterns with closely related taxa.

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Phu-Long Pham, Ying-Xue Li, He-Rong Guo, Rui-Zhen Zeng, Li Xie, Zhi-Sheng Zhang, Jianjun Chen, Qing-Lian Su and Qing Xia

Dendrobium officinale Kimura et Migo is a famous traditional Chinese medicinal plant. It produces various phytochemicals, particularly polysaccharides, which have nutraceutical and pharmaceutical values. To increase its biomass production and polysaccharide content, our breeding program has generated a series of polyploid cultivars through colchicine treatment of protocorm-like bodies (PLBs). The present study compared two tetraploid cultivars, 201-1-T1 and 201-1-T2, with their diploid parental cultivar, 201-1, in an established in vitro culture system. Tetraploid ‘201-1-T1’ and ‘201-1-T2’ had shorter leaves and shorter and thicker stems and roots, and they produced higher biomass compared with the diploid cultivar. The length and width of stomata significantly increased, but stomatal density decreased in tetraploid cultivars. The PLB induction rates from the stem node explants of the tetraploid cultivars were significantly higher than those of diploid. However, the PLB proliferation of tetraploids was lower than that of the diploid. The mean number of plantlets regenerated from tetraploid PLBs was also lower than that of the diploid after 4 months of culture. Polysaccharide contents in stems, leaves, and roots of 6-month-old tetraploid plantlets were significantly higher than those of diploids. The polysaccharide content in the stem of ‘201-1-T1’ was 12.70%, which was a 2-fold increase compared with the diploid cultivar. Our results showed that chromosome doubling could be a viable way of improving D. officinale in biomass and polysaccharide production.