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  • Author or Editor: Qin Zhang x
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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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Rhododendron delavayi Franch. is an important ornamental plant and often plays a role in natural hybridization with other sympatric species in Rhododendron subgenus Hymenanthes. Fifteen microsatellite loci were developed and characterized in this species. The average allele number of these microsatellites was four per locus, ranging from three to six. The ranges of expected (HE ) and observed (HO ) heterozygosities were 0.0365 to 0.7091 and 0.0263 to 0.9512, respectively. Cross-species amplification in R. agastum and R. decorum showed that a subset of these markers holds promise for congeneric species study. These sets of markers are potentially useful to investigate the genetic structure and gene flow of R. delavayi and other congeneric species.

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Response of Toyonoka strawberry to AgNO3 was studied. Types and combinations of plant growth regulators had significant effects on shoot regeneration efficiency. Explants cultured for 10 days in shoot regeneration medium in the presence of AgNO3 not only enhanced shoot regeneration efficiency but also expedited the initiation of adventitious buds. Highest regeneration (87.38%) and number of shoots per explant (11.67) were achieved in shoot regeneration media containing 1.5 mg·L–1 TDZ, 0.4 mg·L–1 IBA and 1.0 mg·L–1 AgNO3. Half-strength MS containing 1.0 mg·L–1 AgNO3 was an optimum medium for rooting. AgNO3 advanced root emergence and increased percent rooting, root length, dry weight and activity. Lower concentrations of AgNO3 inhibited ethylene production and promoted shoot regeneration and growth. It had a significant stimulatory effect on chlorophyll, soluble protein contents and antioxidant enzyme activities. Chlorophyll and soluble protein contents, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were increased in the presence of AgNO3 and reached maximum at 1.0 mg·L–1 AgNO3. Root water content, superoxide free radicals (O2 .-), malondialdehyde (MDA) content, proline accumulation and IAA-oxidase activity in leaves were increased while (IAA) content was decreased in the presence of AgNO3. Chemical names used: indole-3-butyric acid (IBA); silver nitrate (AgNO3); thidiazuron (TDZ); N6-benzyladenine (BA); 2,4-dichlorophenoxy acetic acid (2,4-D); indole-3-acetic acid (IAA); α-naphthalene acetic acid (NAA); gibberellic acid (GA3); bovine serum albumin (BSA); 2,3,5-triphenyl-2H-tetrazolium chloride (TTC).

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MicroRNAs (miRNAs) related to phytohormone signal transduction and self-incompatibility may play an important role in the xenia effect. However, associated research in this area is still lacking in rabbiteye blueberry (Vaccinium ashei). In this study, we identified miRNAs, predicted their target genes, performed functional enrichment analysis of the target genes, and screened for miRNAs related to phytohormone signaling and self-incompatibility. A total of 491 miRNAs were identified, of which 27 and 67 known miRNAs as well as 274 and 416 new miRNAs were found in the rabbiteye blueberry cultivars Brightwell and Premier, respectively. Compared with ‘Premier’, 31 miRNAs were upregulated and 62 miRNAs were downregulated in ‘Brightwell’. Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analysis indicated that the 4985 target genes predicted were involved in biosynthesis of amino acids, plant–pathogen interaction, and spliceosome pathways. A total of 10, one, one, five, two, five, and two candidate miRNAs related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling, respectively, in rabbiteye blueberry pollen were identified. Further analysis indicated that novel_miR_49 was a candidate miRNA related to self-incompatibility, and their target gene was maker-VaccDscaff21-snap-gene-21.37. In addition, the KEGG enrichment analysis of the target genes of novel_miR_49 showed that they were involved in the ribosome, aminoacyl-tRNA biosynthesis, and glycosylphosphatidylinositol-anchor biosynthesis pathways. The results revealed that the microRNAs of rabbiteye blueberry pollen regulated to phytohormone signal transduction and self-incompatibility signal transduction based on related to auxin, cytokinin, gibberellin, abscisic acid, ethylene, brassinosteroid, and salicylic acid signaling. Results suggest that more research of the effects of miRNAs on regulation of hormone signal transduction and self-incompatibility is necessary for elucidating the molecular mechanism of the xenia effect.

Open Access

Ascorbic acid (AsA) is a major antioxidant and redox buffer in plants. Dehydroascorbate reductase (DHAR; EC 1.8.5.1) catalyzes the conversion of dehydroascorbate (DHA) to AsA and is crucial for AsA regeneration. In this study, we developed transgenic tomato plants that overexpressed PbDHAR2 to investigate whether PbDHAR2 could limit the deleterious effects of salt and chilling stresses. These transgenic plants contained significantly higher AsA levels than the wild-type (WT) plants. Overexpression of PbDHAR2 increased the expression of the AsA-glutathione (GSH) cycle genes in transgenic lines under salt and chilling stresses. In addition, the transgenic lines subjected to salt and chilling stresses showed higher levels of antioxidant enzyme activity, lower malondialdehyde (MDA) levels, and higher chlorophyll contents than the WT. Thus, our results demonstrate that the regulation of PbDHAR2 during AsA regeneration contributes to enhanced salt and chilling tolerance in tomato.

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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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Genetic diversity of Narcissus was systematically studied on both morphological and molecular levels. Twenty-four characteristics of nine narcissi were observed and their differences evaluated by clustering method. The results showed that nine narcissi can be divided into two subclusters: one comprised by Narcissus pseudonarcissus, the other by Chinese Narcissus. The morphological diversity among five cultivars of N. pseudonarcissus is higher than that among four ecotypes of Chinese Narcissus (Narcissus tazetta var. chinensis). There are seven morphological characteristics in N. pseudonarcissus presenting obvious variations with coefficients from 33.33% to 91.67%. Only five morphological characteristics in Chinese Narcissus present certain variations with coefficients from 37.04% to 51.79%. On DNA level, two clusters are distantly related too. Based on the random amplified polymorphic DNA (RAPD) markers, 13 out of 40 random primers yielded scorable polymorphisms between samples. Wide variations in banding profiles between cultivars or between ecotypes were observed with nearly every primer tested. Among 95 band positions that were scored for all the 9 narcissi, 81 are polymorphic (85.26%). Cluster analysis of the calculated similarity matrix revealed that the genetic diversity between these individuals within the same section is low. However, the genetic diversity between two sections is obviously higher. Taken together, the methods combined morphological characteristics and RAPD technique allow a deep evaluation of the variation of Narcissus on both section level and cultivar/ecotype level.

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The xenia effect refers to the phenomenon whereby the pollen genotype directly affects seed and fruit development during the period from fertilization to seed germination, which leads to different characteristics in phenotypic traits. The xenia effect can create differences in the endosperm and embryo formed after double fertilization and can also alter various fruit parameters, such as the fruit-ripening period; the fruit shape, size, and color; the flavor quality, such as sugars and acids; as well as the nutrient quality, such as anthocyanins. The xenia effect manifests in various ways, playing an important role in increasing the yield of fruit trees, improving fruit appearance and internal quality, as well as in directional breeding. Compared with other pomology research areas, our understanding of the xenia effect is still in its infancy. Currently, xenia is classified into two types: xenia and metaxenia. In the former, the direct effects of the pollen genotype are exhibited in the syngamous parts of the ovules; that is, the embryo and endosperm only. In the latter, the effects of the pollen genotype are demonstrated in structures other than the embryo and endosperm; that is, in tissues derived wholly from the mother plant material, in seed parts such as the nucellus and testa, as well as in the carpels and accessory tissues. However, the current classification has various shortcomings. In the present study, we propose a novel classification based on whether the appearance of xenia results from the tissue formed by double fertilization. Three xenia types are proposed: double-fertilization xenia, non–double-fertilization xenia, and combined xenia. The new classification has great theoretical and practical significance for future studies on the xenia effect and its mechanisms and also provides a more effective, broader application of xenia in improving the yield and quality of fruit trees.

Open Access