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Meng Li, Huanhuan Zhi and Yu Dong

This study aimed to evaluate whether preharvest or postharvest application of glycine betaine (GB) has the potential to improve fruit quality [fruit firmness (FF), size, skin color, soluble solids content (SSC), and titratable acidity (TA)] and susceptibility to storage disorders (peduncle browning, pitting, and decay) in ‘Lapins’ or ‘Regina’ sweet cherries, and to determine whether factors such as application frequency or timing impacted the efficacy of GB spraying. Adding 2 or 4 g·L−1 GB to hydro-cooling water (0 °C) as postharvest treatment did not affect fruit size, skin color, SSC, TA, peduncle browning, or pitting development; however, it did result in fruit softening and a low incidence of decay. GB applied preharvest at 2 or 4 g·L−1 once at 1 week before harvest (1WBH) was more effective for retaining FF and less peduncle browning and pitting compared with postharvest treatment. Increasing the preharvest GB application frequency from one time (1WBH or pit hardening) to three times (pit hardening, straw color, and 1WBH) enhanced FF and TA levels and resulted in lower pitting. The reduction in fruit size was observed for ‘Regina’, but not for ‘Lapins’. Changes in the contents of phosphorous (P), potassium (K), and magnesium (Mg) were unaffected by GB at harvest, whereas three GB sprays increased the total nitrogen (N) content. Compared with ‘Lapins’, ‘Regina’ allowed more calcium (Ca) uptake by GB and ultimately had firmer flesh. In conclusion, three preharvest applications of 4 g·L−1 GB showed great potential to improve quality attributes, to reduce the susceptibility to storage disorders, and to increase the Ca content of ‘Regina’ cherries.

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Jia Li, Liyun Liu, Huanqi Zhou and Meng Li

Areca (Areca catechu L.) is a tropical plant with great economic importance. In China, the fruit of areca (betel nut) is produced mainly in Hainan Province. However, the yield of betel nuts was impacted seriously by frequent water deficits in Hainan Province. Drought causes deleterious effects on the growth and development of areca plants, especially on young seedlings, which hampered the extensive planting of areca. In this study, a reagent of a superabsorbent polymer (SAP) was applied into the culture soil and we analyzed its function against drought stress when seedlings were grown under different irrigation levels. We observed that SAP application caused a significant increase in plant weight under severe drought, as well as in the maximum photochemical efficiency of PSII (Fv/Fm) and actual photochemical efficiency of PSII [Y(II)] index of chlorophyll (chl), indicating the photosynthetic efficiency of seedlings under severe drought (D) was enhanced by SAP. The antioxidant enzyme activity of areca seedlings under D was indicated to be enhanced by the increasing activity of superoxide dismutase (SOD) and peroxidase (POD), but not catalase (CAT). In addition, SAP even has slight negative effects on the growth of seedlings under adequate water. Our results provide a theoretical basis to improve the viability of areca seedlings under severe drought using SAP, which is urgently needed for the market.

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Fachun Guan, Shiping Wang, Rongqin Li, Mu Peng and Fanjuan Meng

To analyze the evolutionary level of Prunus mira Koehne (Prunus mira Koehne Kov et. Kpst), 15 kinds of pollen grains from five altitudes were observed using a scanning electron microscope (SEM). This study demonstrates that pollen morphous P. mira has high variation; specifically, individuals from higher altitudes are much more evolved than those from lower altitudes. This is the first time the pollen morphology of P. mira has been systematically illustrated. Furthermore, 12 random amplified polymorphic DNA (RAPD) primers generated clear and repeatable bands among all individuals based on RAPD; 107 bands ranging from 200 bp to 2000 bp were generated with an average of 8.92 bands per primer. Thus, the RAPD technique proved to be a powerful tool to reveal variation on P. mira. This study provides comprehensive information for genetic diversity of P. mira from different altitudes.

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Meng Wei, Aijun Zhang, Hongmin Li, Zhonghou Tang and Xiaoguang Chen

Nitrogen (N) is an essential macronutrient limiting plant growth and quality of leaf-vegetable sweetpotato (Ipomoea batatas Lam). The objective of this study was to investigate the effects of N deficiency and re-supply on growth, physiology, and amino acids in sweetpotato. Two leaf-vegetable sweetpotato cultivars, Pushu 53 and Tainong 71, were subjected to three treatments in hydro-culture: 1) N sufficiency, 2) N deficiency, and 3) N deficiency and subsequently with N re-supply. Compared with N sufficiency, N deficiency caused a decrease in vine growth, carotenoid and chlorophyll content (Chlt), root viability, photosynthesis, and nitrate reductase (NR) activity in both cultivars, but to a great extent in Tainong 71. Whereas N deficiency increased root growth and glutamine synthetase (GS) activity in both cultivars, and the increase in ‘Tainong 71’ was more obvious. Re-supply of N recovered the vine growth, root viability, Chlt, photosynthesis, NR, and GS activity, to a greater extent for ‘Pushu 53’ than for ‘Tainong 71’. N deficiency significantly decreased essential amino acids, including lysine, phenylalanince, isoleucine, tryptophane, leucine, and valine contents and nonessential amino acids, consisting of glutamic acid, aspartic acid, glycine, argnine, and proline content in both cultivars. These results indicated that the light leaf color leafy sweetpotato ‘Tainong 71’ is sensitive to the N availability and the dark green leaf color ‘Pushu 53’ is more tolerant to low N, which appear to reflect the differential response of two cultivars to their different adaptability to N availability.

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Aoxue Wang, Fanjuan Meng, Xiangyang Xu, Yong Wang and Jingfu Li

Leaf mold, caused by the fungus Cladosporium fulvum, is a serious disease of tomato. In the current study, the main physiological races of C. fulvum collected from three northeastern provinces of China were identified using a set of identification hosts. The results showed that the prevalent pathogenic physiological races were 1.2.3, 1.3, 3, 1.2.3.4, and 1.2.4. F1, F2, and BC1 tomato plants were obtained by crossing C. fulvum-resistant cultivar 03748 carrying the Cf-6 gene and susceptible cultivar 03036. Three 10-mer oligonucleotide random amplified polymorphic DNA (RAPD) primers and two simple sequence repeat (SSR) primers were selected for the further molecular marking analysis after 210 RAPD primers and 50 SSR primers were screened using the bulked segregate analysis method. The polymorphic DNA bands were amplified among parents, 10 F1 plants, 184 F2 plants including 145 resistant plants and 39 sensitive plants using three RAPD primers and two SSR primers so that three RAPD molecular markers and two SSR molecular markers linked to the Cf-6 loci were identified. Three RAPD markers were linked to the Cf-6 resistant locus separated with 8.7 cM, 20.3 cM, and 33.4 cM. Also, one RAPD codominant marker S374619/559 was found. The locations of the two SSR markers were 12.6 cM and 9.7 cM away from the Cf-6 locus. After cloning and sequencing two specific DNA fragments closely connected to the Cf-6 resistant and susceptible alleles respectively, in the RAPD codominant marker S374619/559 and one codominant sequence characterized amplified region marker S674619/559 was converted from RAPD marker S374619/559. In the RAPD marker S374619/559, the length difference of two specific fragments, 619-bp fragment and 559-bp fragment, is the result of one insertion (60 bp) in the 619-bp fragment. These markers will facilitate the selection of resistant tomato germplasm containing the Cf-6 gene and cloning of Cf-6 to breed new C. fulvum resistant tomato cultivars.

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Fanjuan Meng, Ruoding Wang, Mu Peng, Chao Wang, Zhongkui Wang, Fachun Guan and Yajun Li

Inter simple sequence repeat (ISSR) were used to evaluate the genetic diversity of Kongpo Monkshood (Aconitum kongboense L.) in Motuo, Tibet Plateau. From 70 accessions of three populations, 10 out of 100 informative ISSR primers were chosen for polymorphism analysis. Percentage of polymorphic bands was 50% to 66.67% with a mean of 58.42%. The effective number of alleles (Ne) was between 1.545 (population 3) and 1.586 (population 2), and the mean value was 1.564; the Nei’s gene diversity (h) ranged from 0.315 to 0.327 with the average value of 0.320; the value of Shannon’s information index (I) ranged from 0.459 to 0.478, with the mean of 0.469. Based on molecular data, cluster analysis classified the 70 cultivars into three groups. Most accessions were related to the geographical origin and their genetic backgrounds. Bayesian structure and PCoA analysis were consistent with the dendrogram result. Based on the analysis, it will provide a reference for Kongpo Monkshood breeding purposes and contribute to identification, rational exploitation, and conservation of germplasms.

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Rengong Meng, Tony H.H. Chen, Chad E. Finn and Yonghai Li

Experiments focusing on plant growth regulators' concentrations and combinations, mineral salt formulations, and TDZ pretreatment formations were conducted to optimize in vitro shoot regeneration from leaf and petiole explants of `Marion' blackberry. Optimum shoot formation was obtained when stock plants were incubated in TDZ pretreatment medium for 3 weeks before culturing leaf explants on regeneration medium (Woody Plant Medium with 5 μm BA and 0.5 μm IBA) in darkness for 1 week before transfer to light photoperiod (16-hour photoperiod at photosynthetic photon flux of ≈50 μmol·m-2·s-1) at 23 °C ± 2 °C for 4 weeks. Under these conditions, ≈70% of leaf explants formed ≈40 shoots per petri dish that could be harvested and rooted to form plantlets. Chemical names used: N6-benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); gibberellic acid (GA3); indole-3-acetic acid (IAA); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA); N-phenyl-N'-1,2,3-thidiazol-5-ylurea [thidiazuron (TDZ)].

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Zongchang Xu, Meng Wang, Jinhui Zhou, Han Liu, Chengsheng Zhang and Yiqiang Li

Sword-leaf dogbane (Apocynum venetum) is a traditional Chinese herb with increasingly recognized potential to enhance health, but no study of stable reference genes in this herb has been reported. Based on a homologous cloning strategy, we have successfully cloned five candidate reference genes from sword-leaf dogbane: glyceraldehyde-3-phosphate dehydrogenase (AvGAPDH), beta tubulin (AvbTUB), polyubiquitin (AvUBQ), elongation factor 1-alpha (AvEF1α), and actin (AvACTIN). Three distinct algorithms, geNorm, NormFinder, and BestKeeper, were used to estimate the expression stability of candidate reference primer pairs. We found that AvACTIN-2 and AvACTIN-3 presented the highest stability of expression in different tissue samples, and AvGAPDH-2 was most stable under salinity stress. In addition, we illustrated the application of these new reference genes by assaying the expression levels of two hyperoside biosynthesis terminal enzyme genes, flavonoid 3′-hydroxylase (F3′H) and flavonol synthase (FLS), under salinity stress. Our study is the first to report stable expression of internal reference genes in sword-leaf dogbane in multiple experimental sample sets.

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Chen Chen, Meng-Ke Zhang, Kang-Di Hu, Ke-Ke Sun, Yan-Hong Li, Lan-Ying Hu, Xiao-Yan Chen, Ying Yang, Feng Yang, Jun Tang, He-Ping Liu and Hua Zhang

Aspergillus niger is a common pathogenic fungus causing postharvest rot of fruit and vegetable, whereas the knowledge on virulence factors is very limited. Superoxide dismutase [SOD (EC 1.15.1.10)] is an important metal enzyme in fungal defense against oxidative damage. Thus, we try to study whether Cu/Zn-SOD is a virulence factor in A. niger. Cu/Zn-SOD encoding gene sodC was deleted in A. niger [MA70.15 (wild type)] by homologous recombination. The deletion of sodC led to decreased SOD activity in A. niger, suggesting that sodC did contribute to full enzyme activity. ΔsodC strain showed normal mycelia growth and sporulation compared with wild type. However, sodC deletion markedly increased the cell’s sensitivity to intracellular superoxide anion generator menadione. Besides, spore germination under menadione and H2O2 stresses were significantly retarded in ΔsodC mutant compared with wild type. Further results showed that sodC deletion induced higher superoxide anion production and higher content of H2O2 and malondialdehyde (MDA) compared with wild type, supporting the role of SOD in metabolism of reactive oxygen species (ROS). Furthermore, ΔsodC mutant had a reduced virulence on chinese white pear (Pyrus bretschneideri) as lesion development by ΔsodC was significantly less than wild type. The determination of superoxide anion, H2O2, and MDA in A. niger-infected pear showed that chinese white pear infected with ΔsodC accumulated less superoxide anion, H2O2, and MDA compared with that of wild type A. niger, implying that ΔsodC induced an attenuated response in chinese white pear during fruit–pathogen interaction. Our results indicate that sodC gene contributes to the full virulence of A. niger during infection on fruit. Aspergillus niger is one of the most common species found in fungal communities. It is an important fermentation industrial strain and is also known to cause the most severe symptoms in fruit during long-term storage (Pel et al., 2007). Meanwhile, plants activate their signaling pathways to trigger defense responses to limit pathogen expansion. One of the earliest host responses after pathogen attack is oxidative burst, during which large quantities of ROS are generated by different host enzyme systems, such as glucose oxidase (Govrin and Levine, 2000). ROS such as singlet oxygen, superoxide anion, hydroxyl (OH), and H2O2 are released to hinder the advance of pathogens (Gara et al., 2003). ROS can react with and damage cellular molecules, such as DNA, protein, and lipids, which will limit fungal propagation in the host plant (Apel and Hirt, 2004).