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  • Author or Editor: Lei Zhao x
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Different pollinators exhibit different adaptability to plants. Here, we compared the performance in visiting frequency and pollination efficiency among three bee pollinators (Bombus terrestris, Apis cerana, and Apis mellifera) on greenhouse-grown northern highbush ‘Bluecrop’ blueberry plants and evaluate their effects on yield and fruit quality. Our results indicated that the duration of daily flower-visiting of B. terrestris was 24 and 64 minutes longer than that of A. cerana and A. mellifera, respectively, and the visiting time of a single flower for B. terrestris was substantially shorter than the other two bee species, and pollen deposition on the stigma from single visit by B. terrestris was twice and three times that of A. cerana and A. mellifera, respectively. The yield of individual plants pollinated by B. terrestris showed an increase of 11.4% and 20.0% compared with the plants pollinated by A. cerana and A. mellifera, respectively, with the rate of Grade I fruit (>18 mm diameter) reaching 50.8%, compared with 32.9% and 22.5% for A. cerana and A. mellifera groups, respectively. Moreover, the early-to-midseason yield of plants pollinated by B. terrestris was higher, and the ripening time was 3 to 4 days earlier. An artificial pollination experiment demonstrated that seed set of high (≈300), medium (90–110), and low (20–30) pollination amounts were 43.0%, 42.5%, and 10.5%, respectively, and the corresponding mean weights of single fruits (related to the seed number inside) were 2.8, 2.7, and 1.2 g, respectively. The highly efficient pollination of B. terrestris was attributed to its behavior of buzz-pollination. Therefore, it is preferential for pollination of ‘Bluecrop’ blueberry in the greenhouse.

Open Access

Cold hardiness evaluation is important for screening woody species in cold areas. We compared cold hardiness by estimating the 50% lethal temperature (LT50) using electrolyte leakage test (ELLT50) and triphenyltetrazolium chloride test (TTCLT50) for 26 woody species in the Bashang region of China. One-year-old shoots were collected in January and exposed to five subfreezing temperatures in a programmable temperature and humidity chamber. LT50 was estimated by fitting relative electrolyte leakage and percentage of dead tissue against test temperature. For all tested species, triphenyltetrazolium chloride (TTC) staining of the pith was weak and the cambium TTCLT50 was lower than the extreme minimum temperature (−37 °C) recorded in the region. The cambium TTCLT50 and the sd were lower than that for the phloem and xylem. The phloem TTCLT50 was lower than the xylem TTCLT50, and the two sds were similar. The ELLT50 showed no significant correlation with any TTCLT50. For most species, the ELLT50 was higher than the cambium and phloem TTCLT50 and was not significant different with the xylem TTCLT50. The ELLT50 showed higher sd than any tissue TTCLT50. Based on results obtained in this study, when choosing cold hardiness of single stem tissue as an indicator for screening woody species, the xylem should be considered first, followed by the phloem; the cambium and pith were unsuitable. The cold hardiness estimated by ELLT50 was more suitable as indicator for screening woody species than that of stem tissue in winter estimated by TTCLT50.

Open Access

Apple replant disease (ARD) causes enormous economic loss and threatens the survival of apple industry worldwide. Fusarium solani is one of the pathogens that has been proven to cause ARD. Samples were collected at different time periods to investigate the mechanism of defense responses of apple to F. solani infection by monitoring the biomass, reactive oxygen species (ROS), and antioxidant enzyme activities of the apple rootstock ‘M.9T337’. In addition, the abundance of transcription of four pathogenesis-related (PR) proteins involved in antifungal defense was monitored. The results showed that the apple root system was normal and had small brown areas. However, there is a rapid burst of ROS during the early infection stage, and the activities of antioxidant enzymes and transcription of PRs increased during this period. With the extension in infection time, the infected root tissues displayed dark brown necrosis, and the activities of antioxidant enzymes and abundance of transcription of PRs decreased gradually after reaching their peak. Eventually, the plant biomass decreased, and the plant died. In conclusion, the levels of ROS and activities of antioxidant enzymes played an active role during the early stage of resistance of ‘M.9T337’ apples to infection by F. solani. Infection by F. solani can destroy the ROS scavenging system, causing oxidative damage and inhibiting the growth of apple rootstocks.

Open Access

Ventilation and soil moisture influence greenhouse cultivation. Experiments were conducted at Xinxiang Irrigation Research Base of the Chinese Academy of Agricultural Sciences, Henan Province, China, to identify how ventilation and irrigation affected the greenhouse microenvironment. To develop ventilation and irrigation protocols that increase crop yield and improve the quality of drip-irrigated tomatoes grown in the greenhouse, three ventilation modes (T1, T2, and T3) were developed by opening vents in different locations in a completely randomized pattern. T1 had open vents on the north wall and roof of the greenhouse. T2 had open vents on the north and south walls and the roof. T3 had open vents on the north and south walls. Three irrigation treatments (W1, W2, and W3) were designed based on the accumulated water surface evaporation (Ep ) of a standard 20-cm evaporation pan. The irrigation quantities were 0.9×Ep (W1), 0.7×Ep (W2), and 0.5×Ep (W3). The spatial and temporal distributions of temperature and humidity were analyzed for different combinations of ventilation and irrigation to identify their effects on tomato yield and fruit quality. Major results were as follows: 1) In addition to solar radiation, ventilation had an important influence on Ep and, on a daily scale, ventilation had a significant effect on Ep (P < 0.05). 2) Ventilation had a significant effect on indoor wind speed, but the effect varied during different growth stages. During the flowering and fruit setting stage, wind speed for T2 significantly differed from those of T1 and T3 (P < 0.01). During the harvest stage, the three ventilation treatments had significantly different effects (P < 0.01). A correlation analysis showed high correlation between T2 wind speed and T3 wind speed (R = 0.831), but low correlation between T2 wind speed and T1 wind speed (R = 0.467). 3) The effect of ventilation on greenhouse humidity and temperature was greater than the effect of irrigation. The differences in air temperature among various combined treatments of ventilation and irrigation were significant for the flowering and fruiting stages (P < 0.05), but they were not significant for the late harvest stage (P > 0.05). There were significant differences in humidity on sunny days (P < 0.01), but no significant differences on cloudy or rainy days (P > 0.05). Air temperature at 2 m was greater than canopy temperature, but humidity at 2 m was less than that at canopy level. 4) Irrigation water quantity was positively correlated with tomato yield and negatively correlated with the fruit quality indicators total soluble solids, vitamin C content, organic acid content, and soluble sugars content. Ventilation had an effect primarily during the harvest period; it had no significant effect on yield (P > 0.05). However, it had a significant effect on vitamin C content and the sugar:acid ratio (P < 0.01). The combination treatment of T2W2 is recommended as the optimal treatment for greenhouse tomatoes using drip irrigation to produce an optimal combination of crop yield and fruit quality. This study provides theoretical and technical support for the improvement of greenhouse climate control by optimizing greenhouse ventilation and irrigation techniques to promote tomato yield and improve fruit quality.

Open Access

‘Suzhouqing’ is a unique landrace of nonheading Chinese cabbage [Brassica rapa var. chinensis (Linnaeus) Kitamura] with a long history of cultivation in Suzhou of Jiangsu Province, China. However, transitional and overlapped morphologic traits make it difficult to authenticate this accession from other nonheading Chinese cabbages. Genetic relationship between ‘Suzhouqing’ and the related 10 popular accessions in the Yangtze River Delta were analyzed using two well-studied single-copy nuclear genes—ARGONAUTES 7 (AGO7) and BcMF15; the molecular identification of ‘Suzhouqing’ was determined based on the intersimple sequence repeat–sequence-characterized amplified region (ISSR-SCAR) marker. The results indicated that ‘Suzhouqing’ could be identified specifically from the other 10 accessions based on 21 specific nucleotide variations of the AGO7 gene. Sequence variations show a strong correlation with leaf morphology, suggestive of partial causal links between the two. Genetic relationship analysis showed that five accessions with close geographic locations had a very close genetic relationship, whereas the genetic relationship of the other five accessions was related to their morphologic similarity. One exception, ‘AJH’, might undergo a special evolutionary process. Furthermore, ISSR-880 was screened as the specific primer to identify accession ‘Suzhouqing’, and a specific discrimination ISSR-SCAR marker was explored, which amplified no target band in any other accessions. The development of molecular markers for the specific identification of ‘Suzhouqing’ in 11 popular accessions in the Yangtze River Delta could provide a theoretical basis for the protective identification of other agricultural crops.

Free access

A field experiment was conducted over three growing seasons (2012–14) to study the effect of the foliar application of different potassium (K) fertilizers [potassium phosphate monobasic (KH2PO4), potassium nitrate (KNO3), and humic acid potassium (HAK)] on the fruit growth rate, yield, and quality of ‘Kousui’ japanese pear (Pyrus pyrifola) trees. Except the first year of study, foliar application of K fertilizers generally led to an increase in the concentration of fruit total soluble sugar, titratable acidity (TA) and sweetness, along with an elevated K accumulation in leaf and fruit at maturity. In 2013 and 2014, compared with the control, KNO3 treatment led to an average 16% higher yield, and HAK led to an average 15% higher soluble solid content (SSC). Furthermore, HAK resulted in 26% higher yield in 2014. KNO3 treatment showed 19% higher leaf K concentration, 38% leaf K accumulation, and 43% fruit K accumulation in maturity than the control in 2014. Different effects were found on the concentration of specific types of sugar and organic acid, of which fructose and malate were consistently increased by the K application. With regard to the amino acids, KNO3 and HAK treatments led to a significant increase in the concentration of aspartic acid, which was 12% and 22% higher than the control, respectively. In conclusion, foliar application of KNO3 is an efficient way to increase ‘Kousui’ japanese pear fruit yield, whereas spraying HAK is an effective way to improve the fruit quality.

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