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  • Author or Editor: Peng Wang x
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Physiological, biochemical and anatomical indexes were investigated for rose hardiness. It was found that bound/free water ratio, proline accumulation, photosynthetic rate, palisade/spongy tissue ratio, and lignification of winter-acclimated stems were heavily influenced by the temperature causing stem browning. Spongy cell volume and stem tenderness were inversely related to winter hardiness. Data generated from this research demonstrated that catalase stability, TTC reduction rate at 0°C, total photosynthetic rate, stem pith ray number, and leaf wax thickness are good indicators for rose hardiness to freezing temperatures. Two compound indexes were developed through the main component analysis. Based on the results obtained from 12 tested cultivars, these indexes are ideal to quantify hardiness of rose germplasm.

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Cold tolerance/resistance of 41 hazelnut hybrid strains was investigated by evaluating electrolyte seepage velocity, recovering growth, and tissue browning for the tested cold temperatures. Results demonstrated that electrolyte seepage velocity of all tested strains was faster as temperatures dropped down. The S curve relationship was found between seepage velocity and temperature. Turning point temperature used as the half deadly injured index (LT50) was developed using a logistic equation. The mean LT50 and temperature causing tissue browning were excellent indexes to predict cold tolerance/resistance. After treated at –30 or –35 °C and then evaluated for their recovering growth, 10 cold-resistant hybrid hazelnut strains were developed. These hybrids are being tested for regional adoption and will be released as commercial cultivars.

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Based on our investigation of hazelnut germplasm and Thompson's evaluation system for European hazelnuts, an in-depth study on character description of hazelnut germplasm was conducted from 1991 to 1994. Eighty characters were evaluated for the 58 tested species. It was found that eight characters should be eliminated from Thompson's system, such as annual branch length and hair, lentical color, and serration depth. The best leaf sampling position, sample volumes for quantitative characters, and scoring standards were also determined. Therefore, an advanced evaluation system for hazelnut germplasm was developed. The advanced system is easier and simpler, and will significantly expedite systematical studies of hazelnut germplasm.

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Citrullus lanatus (watermelon) is an excellent daily source of dietary lycopene and β-carotene. To investigate the transcriptional regulation of carotenoid biosynthesis genes relative to lycopene and β-carotene accumulation in watermelon fruit, six watermelon accessions with different flesh colors were examined in this study: white-fleshed PI 459074, pale-yellow-fleshed ‘Cream of Saskatchewan’, light-pink-fleshed PI 482255, orange-yellow-fleshed ‘WM-Clr-1’, and red-fleshed ‘LSW177’ and ‘MSW28’. The expression patterns of eight genes (PSY1, PSY2, PDS, ZDS, CRTISO, LCYB, NCED1, and NCED7) involved in lycopene and β-carotene biosynthesis and biodegradation were analyzed. The results confirmed the accumulation of large quantities of lycopene in red-fleshed ‘LSW177’ and ‘MSW28’, reflecting the elevated expression of PSY1 and the low transcriptional expression of NCED1. The relative expression levels of NCED1 likely play an important role in the color development of the light-pink-fleshed PI 482255, whereas the reduced transcriptional expression of PSY1 and the increased expression of NCED1 appear to be the main factors contributing to the formation of white flesh in the fruit of PI 459074. Low transcriptional expression of PSY1 results in the pale-yellow flesh of the ‘Cream of Saskatchewan’ fruit.

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Selenium (Se) fertilizer has a good effect on many field crops, but there are few reports on the application of Se fertilizer on citrus. We investigated the effects of 0 mg/L (CK, water treatment), 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L sodium selenite aqueous solutions on the growth, nutrition, and fruit quality of 15-year-old citrus unshiu (Citrus reticulata Blanco cv. Succosa). The results showed that a low concentration of Se fertilizer promoted the growth and development of the citrus plan, and a high concentration of Se fertilizer was found to slightly inhibit the growth and development of the plant. Among the different treatment groups, 150 mg/L selenium fertilizer showed have the best effect on these evaluated parameters. The results thus suggest that 150 mg/L of Se fertilizer promotes the formation of chlorophyll in the leaves of the test plant and increases the longitudinal and transverse diameter of the fruits and weight of single fruit, significantly enhancing the activity of antioxidant enzymes in the leaves, promoting the absorption of nutrients in the leaves, increasing the contents of total sugar and vitamin, and decreasing the acidity in the fruits and the pericarp thickness. It also promoted the accumulation of the total selenium content in the leaves and fruits and consequently improved the quality of the fruits. These results showed that appropriate concentration of Se treatment can improve the activity of antioxidant enzymes to enhance plant stress resistance, regulate the content of sugar and acid in fruits, and improve the quality of fruits.

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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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Cytosine methylation plays important roles in regulating gene expression and modulating agronomic traits. In this study, the fluorescence-labeled methylation-sensitive amplified polymorphism (F-MSAP) technique was used to study variation in cytosine methylation among seven pecan (Carya illinoinensis) cultivars at four developmental stages. In addition, phenotypic variations in the leaves of these seven cultivars were investigated. Using eight primer sets, 22,796 bands and 950 sites were detected in the pecan cultivars at four stages. Variation in cytosine methylation was observed among the pecan cultivars, with total methylation levels ranging from 51.18% to 56.58% and polymorphism rates of 82.29%, 81.73%, 78.64%, and 79.09% being recorded at the four stages. Sufficiently accompanying the polymorphism data, significant differences in phenotypic traits were also observed among the pecan cultivars, suggesting that cytosine methylation may be an important factor underlying phenotypic variation. Hypermethylation was the dominant type of methylation among the four types observed, and full methylation occurred at higher levels than did hemimethylation in the pecan genomes. Cluster analysis and principal coordinate analysis (PCoA) identified Dice coefficients ranging from 0.698 to 0.778, with an average coefficient of 0.735, and the variance contribution rates of the previous three principal coordinates were 19.6%, 19.0%, and 18.2%, respectively. Among the seven pecan cultivars, four groups were clearly classified based on a Dice coefficient of 0.75 and the previous three principal coordinates. Tracing dynamic changes in methylation status across stages revealed that methylation patterns changed at a larger proportion of CCGG sites from the 30% of final fruit-size (30%-FFS) stage to the 70%-FFS stage, with general decreases in the total methylation level, the rate of polymorphism, and specific sites being observed in each cultivar. These results demonstrated that the F-MSAP technique is a powerful tool for quantitatively detecting cytosine methylation in pecan genomes and provide a new perspective for studying many important life processes in pecan.

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Scion wood of ‘Caddo’ and ‘Desirable’ pecan (Carya illinoinensis) was grafted onto the epicotyl of 1-month-old, open-pollinated ‘Shaoxing’ pecan seedlings for evaluation as a grafting technique to reduce the time to produce grafted trees. The results showed that seedlings grafted with “base scions” had higher survival than those grafted with “terminal scions” for both ‘Caddo’ and ‘Desirable’. Also, grafting with paraffinic tape could achieve greater success rate than that with medical tape. The most ideal time to perform this grafting was late April in Nanjing, China, when pecan seedlings were about 35 days old. This study demonstrated that the technique yielded successful epicotyl grafting of >70%, and it could thus be applied in practice.

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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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