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  • Author or Editor: Yang Li x
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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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An efficient biolistic transformation system of banana combined with a liquid medium selection system was developed during this study. An embryogenic cell suspension (ECS) of Musa acuminata cv. Baxi (AAA) was bombarded with a particle delivery system. After 7 days of restoring culture in liquid M2 medium, embryogenic cells were transferred to a liquid selection M2 medium supplemented with 10 μg/mL hygromycin for resistance screening. The untransformed cell clusters were inhibited or killed, and a small number of transformants proliferated in the liquid selection medium. After the 0th, first, second, and third generation of antibiotic screening, there were 0, 65, 212, and 320, respectively, vitality-resistant buds obtained from a 0.5-mL packed cell volume (PCV) of embryogenic cell suspension. The β-glucuronidase (GUS) staining, polymerase chain reaction (PCR) analysis, and Southern blot hybridization results all demonstrated a 100% positive rate of regenerated resistant seedlings. Interestingly, the number of buds obtained through third-generation screening was almost equal to that obtained from the original ECS in M2 medium without antibiotics. These results suggested that the liquid medium selection system facilitated the proliferation of a positive transgenic ECS, which significantly improved the regeneration rate of transformants. This protocol is suitable for the genetic transformation of all banana genotypes and is highly advantageous to varieties with low callusing potential.

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Zinc finger-homeodomains (ZF-HDs) are considered transcription factors that are involved in a variety of life activities in plants, but their function in regulating plant salt stress tolerance is unclear. The SL-ZH13 gene is significantly upregulated under salt stress treatment in tomato (Solanum lycopersicum) leaves, per our previous study. In this study, to further understand the role that the SL-ZH13 gene played in the response process of tomato plants under salt stress, the virus-induced gene silencing (VIGS) method was applied to down-regulate SL-ZH13 expression in tomato plants, and these plants were treated with salt stress to analyze the changes in salt tolerance. The silencing efficiency of SL-ZH13 was confirmed by quantitative real-time PCR analysis. SL-ZH13-silenced plants wilted faster and sooner than control plants under the same salt stress treatment condition, and the main stem bending angle of SL-ZH13-silenced plants was smaller than that of control plants. Physiological analysis showed that the activities of superoxide dismutase, peroxidase, and proline content in SL-ZH13-silenced plants were lower than those in control plants at 1.5 and 3 hours after salt stress treatment. The malondialdehyde content of SL-ZH13-silenced plants was higher than that in control plants at 1.5 and 3 hours after salt stress treatment; H2O2 and O2 - accumulated much more in leaves of SL-ZH13-silenced plants than in leaves of control plants. These results suggested that silencing of the SL-ZH13 gene affected the response of tomato plants to salt stress and decreased the salt stress tolerance of tomato plants.

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The availability and cost of agricultural labor is constraining the specialty crop industry throughout the United States. Most soft fruits destined for the fresh market are fragile and are usually hand harvested to maintain optimal quality and postharvest longevity. However, because of labor shortages, machine harvest options are being explored out of necessity. A survey on machine harvest of blueberries (Vaccinium sp.) for fresh market was conducted in 2015 and 2016 in seven U.S. states and one Canadian province. Survey respondents totaled 223 blueberry producers of various production sizes and scope. A majority (61%) indicated that their berries were destined for fresh markets with 33% machine harvested for this purpose. Eighty percent said that they thought fruit quality was the limiting factor for machine-harvested blueberries destined for fresh markets. Many producers had used mechanized harvesters, but their experience varied greatly. Just less than half (47%) used mechanical harvesters for fewer than 5 years. Most respondents indicated that labor was a primary concern, as well as competing markets and weather. New technologies that reduce harvesting constraints, such as improvements to harvest machinery and packing lines, were of interest to most respondents. Forty-five percent stated they would be interested in using a modified harvest-aid platform with handheld shaking devices if it is viable (i.e., fruit quality and picking efficiency is maintained and the practice is cost effective). Overall, the survey showed that blueberry producers have great concerns with labor costs and availability and are open to exploring mechanization as a way to mitigate the need for hand-harvest labor.

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Albino tea plants are mutants that grow albino young leaves owing to lack of chlorophylls under certain environmental conditions. There are two types of albino tea plants grown in production, i.e., light- and temperature-sensitive albino tea cultivars. The former grows albino leaves in yellow color under intensive sunlight conditions and the later grows albino leaves with white mesophyll and greenish vein as the environmental temperature is below 20 °C. Both albino teas attract great attention because of their high levels of amino acids and the “umami” taste. There have been many studies focusing on the temperature-sensitive albino tea plants, whereas little attention has been given to the light-sensitive albino tea cultivars. The characteristics of the albino tea cultivars and the mechanism underlying them were reviewed in the present article based on the published literatures, including chemical compositions, morphological characteristics, and molecular genetic mechanism.

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