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  • Author or Editor: Wei Zhou x
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Luculia pinceana Hook. (Rubiaceae) is a typical distylous species with dimorphic and long-styled monomorphic populations. Within this study, we developed 13 microsatellite markers from L. pinceana using a modified biotin–streptavidin capture method. Polymorphism of each locus was assessed in 30 individuals from four dimorphic populations and one monomorphic population. The average allele number of these microsatellites was 4.153 per locus ranging from three to seven. The observed and expected heterozygosities were from 0.040 to 0.840 and from 0.571 to 0.769, respectively. Additionally, all 13 identified microsatellite markers were successfully amplified in its related species, L. yunnanensis, 10 of which showed polymorphism. These microsatellite markers could provide a useful tool for further study of the breeding system and the population genetic structure in this species and within other Luculia species.

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Harvested nectarine fruit [Prunus persica (L.) Batsch `Flavortop'] were held for 5 days at 20 °C, or stored at 0 °C either immediately (control), or after 2 days at 20 °C (delayed-cooling). Observations were conducted after removal from storage for 1, 3, or 5 weeks and a shelf life of 5 additional days at 20 °C. After 5 weeks storage, 87% of control fruit developed woolliness (mealiness in texture accompanied by dry tasting fruit as a result of reduced juice content), while only 7% of delayed-cooling fruit showed signs of woolliness. Firmness of fruit in the delayed-cooling treatment was less at the beginning of ripening than control fruit, but after shelf life in both treatments, fruit reached the same final softness. Expressible juice was lower in woolly fruit (46%) than in healthy fruit (65%). Along with woolliness, viscosity of the resuspended alcohol insoluble residue (cell wall material) of expressed juice increased, implying accumulation of large molecular-weight polymers. The high performance liquid chromatography profile confirmed there were more large pectin polymers (2000 to 76 Ku) in the cell wall components of juice from woolly fruit and a lower arabinose content in these polymers reflected greater side chain removal from pectins in the juice of woolly fruit. Accumulation of larger sized pectin polymers along with high viscosity correlated with lower polygalacturonase activity in woolly fruit. Degradation of soluble pectin released into the juice of woolly fruit may have been impeded by repressed polygalacturonase activity.

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This study aimed to understand the effects of meteorological factors on the ‘Fuji’ apple quality in the Circum-Bohai and Loess Plateau apple production regions of China and to guide apple production based on local climate. Fruit samples of the ‘Fuji’ apple and meteorological data were investigated from 132 commercial ‘Fuji’ apple orchards covering 44 counties in the two aforementioned production regions (22 counties per region). The partial least-squares regression (PLSR) method was first used to screen major meteorological factors that greatly affected fruit quality; these were subsequently used to establish the regression equation of fruit quality attributes and major meteorological factors. Linear programming was used to estimate optimum meteorological factors for good apple quality. The results showed that in the Circum-Bohai production region, many meteorological factors (total annual precipitation, total precipitation from April to October, lowest temperature from April to October, sunshine percentage from April to October) were significantly higher than those in the Loess Plateau production region; however, the temperature difference between day and night from April to October was significantly smaller than that in the Loess Plateau production region. The soluble solids content and skin color area of apples from the Loess Plateau production region were significantly greater than those from the Circum-Bohai production region. The same fruit quality factor of ‘Fuji’ apple was affected by different meteorological factors in the two production regions. The monthly mean temperature and monthly highest temperature from April to October of the Circum-Bohai production region had relatively larger positive effect weights on fruit quality, whereas the total annual precipitation, monthly mean relative humidity from April to October, and total precipitation from April to October of the Loess Plateau production region had relatively larger positive effect weights on fruit quality. The major influencing meteorological factors of the fruit soluble solids content were total precipitation from April to October (X 7), mean annual temperature (X 1), and the monthly highest temperature from April to October (X 5) in the Circum-Bohai production region; however, it included the monthly mean temperature difference between day and night from April to October (X 6), total annual precipitation (X 2), and total precipitation from April to October (X 7) in the Loess Plateau production region. In the Circum-Bohai production region, the optimum meteorological factors for ‘Fuji’ fruit quality of vigorous apple orchards were the mean annual temperature (13.4 °C), total annual precipitation (981 mm), monthly mean temperature (16.8 to 22.4 °C), lowest temperature (11.9 °C), highest temperature (19.5 to 26.8 °C), temperature difference between day and night (12.3 °C), total precipitation (336–793 mm), relative humidity (55.7% to 70.7%), and sunshine percentage (42.3% to 46.1%) during the growing period (April–October). In the Loess Plateau production region, the optimum meteorological factors for ‘Fuji’ fruit quality of vigorous apple orchards were the mean annual temperature (5.5 to 11.6 °C), total annual precipitation (714 mm), monthly mean temperature (13.3 to 19.9 °C), lowest temperature (7.9 to 9.3 °C), highest temperature (19.6 to 27.3 °C), temperature difference between day and night (7.1 to 12.4 °C), total precipitation (338–511 mm), relative humidity (56.1% to 82.4%), and sunshine percentage (37.3% to 55.9%) during the growing period (April–October). The restrictive factors for high-quality ‘Fuji’ apples of the Circum-Bohai production region were the smaller monthly mean temperature difference between day and night, higher monthly mean lowest temperature, and larger monthly mean relative humidity during the growing period; however, those of the Loess Plateau production region were drought or less precipitation from November to March, lower monthly mean temperature, and higher monthly mean highest temperature during the growing period.

Open Access

Heat treatment induces resistance to low temperature in horticultural crops. Changes in soluble protein and heat-stable protein (HSP) contents, the total soluble solids (TSS), titratable acidity (TA), reducing sugar, weight loss and firmness of honey peach (cv. Hujingmilu) during heat treatment and refrigerated storage were investigated. Low-temperature storage alone led to decreasing of TA and reducing sugar and caused severe fresh mealiness. The hot-air treatment before low temperature combined with the use of a plastic bag (thickness of 0.03 mm) could counteract this effect. Heat treatment before refrigerated storage increased both soluble protein and HSP contents, and the ratio of heat-stable to soluble protein. The most favorable effect was obtained with 46 °C for 30 minutes. In addition, heat treatment before storage retarded the increase in fruit firmness, maintained the highest contents of the TSS and reducing sugar and inhibited the decline of TA during refrigerated storage. Treatment for 30 minutes at 46 °C before low-temperature storage in combination with a 0.03-mm plastic bag might be a useful technique to alleviate chilling injury (CI) and maintain honey peach fruit quality during cold storage.

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Free amino acid (FAA) profile is an important indicator of the quality of fruit and fruit product. Foliar nutrient diagnosis has been used for crop yield prediction for decades but not for fruit quality evaluation. Concentrations of 11 leaf nutrients including N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, and B at stages of terminal shoot maturation and fruit development and fruit FAA profile at harvest were examined in longan in South China. The relation between leaf nutrient and fruit FAA was then investigated by multiple stepwise regression analysis. Foliar N content was greatest among the nutrients among the detected elements at both stages. Twenty-nine FAAs were determined in longan flesh, with alanine (19.9%), γ-aminobutyric acid (17.5%), glutamic acid (15.2%), and asparagine (10.7%) as the main components. Flesh individual FAA, essential amino acid (AA), umami-, and sweet and bitter taste AA strongly depended on foliar nutrients. However, the relation between flesh FAAs and foliar nutrients varied with FAA species. Leaf N was the dominant indicator for most pulp FAAs at two growth stages, while other nutrients (e.g., B, Zn, P, K, Ca, Mg) also played versatile roles on flesh FAAs. This work provides a novel tool to predict fruit FAAs via foliar nutrient diagnosis, which supports the practicality of producing specific target fruit or improving fruit quality through regulation of fertilization strategies in fruit production.

Open Access

Impacts of drought stress on crop production can significantly impair farmer’s revenue, hence adversely impacting the gross national product growth. For cowpea [Vigna unguiculata (L.) Walp.], which is a legume of economic importance, effects of drought at early vegetative growth could lead to substantial yield losses. However, little has been done with respect to breeding for cowpea cultivars withstanding drought at early vegetative growth. In addition, previous investigations have focused on how plant morphology and root architecture can confer drought tolerance in cowpea, which is not sufficient in efforts to unravel unknown drought tolerance–related genetic mechanisms, potentially of great importance in breeding, and not pertaining to either plant morphology or root architecture. Therefore, the objective of this study was to evaluate aboveground drought-related traits of cowpea genotypes at seedling stage. A total of 30 cowpea genotypes were greenhouse grown within boxes and the experimental design was completely randomized with three replicates. Drought stress was imposed for 28 days. Data on a total of 17 aboveground-related traits were collected. Results showed the following: 1) a large variation in these traits was found among the genotypes; 2) more trifoliate wilt/chlorosis tolerance but more unifoliate wilt/chlorosis susceptible were observed; 3) delayed senescence was related to the ability of maintaining a balanced chlorophyll content in both unifoliate and trifoliate leaves; and 4) the genotypes PI293469, PI349674, and PI293568 were found to be slow wilting and drought tolerant. These results could contribute to advancing breeding programs for drought tolerance in cowpea.

Free access

Most `Flavortop' nectarines [Prunus persica (L.) Batsch (Nectarine Group)] that were placed directly into 0 °C storage developed chilling injury after removal, while preconditioning fruit for 2 days at 20 °C (delayed storage) reduced chilling injury substantially. Chilling injury was expressed as the development of a dry, woolly flesh texture during ripening. Delayed-storage fruit were as firm as control fruit when placed in storage, but softened more during storage. Analysis of cell wall components showed that in woolly fruit a higher percentage of pectin was retained in the sodium carbonate fraction, although during ripening polymers in this fraction decreased in molecular mass (Mr). In the guanidine thiocyanate hemicellulose fraction of woolly fruit, the associated pectin and hemicellulose remained as large polymers, while in delayed-storage fruit they decreased in Mr during ripening. Endo-polygalacturonase (PG), pectin esterase (PE), and endo-glucanase (EGase) activities of delayed-storage fruit were the same as control fruit at the beginning of storage, although exo-PG was higher. However, differences were observed at the end of storage. Endo-PG activity was lower in control than delayed-storage fruit at the end of storage while PE activity was higher, and exo-PG and EGase activities were similar. These differences in activity were not reflected in the mRNA abundance of the respective enzymes. Endo-PG and PE message was similar in all fruit at the end of storage and increased during ripening, while EGase message was low at all times except in control fruit after storage and development of woolliness. Prevention of chilling injury by delayed storage appears to be due to the ability of the fruit to continue a progressive, slow cell wall degradation in storage which allows normal ripening to proceed when the fruit are rewarmed. Regulation of the softening process did not appear to be by enzyme synthesis, since mRNA levels of the enzymes did not correspond with enzyme activity.

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Lagerstroemia indica (crape myrtle) is a popular Chinese landscape plant with a long flowering period that contributes to its gorgeous flowers and high ornamental value, which motivate L. indica breeding. We found a wild acarpous individual of L. indica that did not bear seeds after flowering and had a significantly longer flowering period than fructiferous L. indica. This study identified differences in floral organ morphology, and stamen and pistil structure between fructiferous and acarpous L. indica through observation, paraffin sectioning, and scanning electron microscopy (SEM). The flowering time of each acarpous L. indica inflorescence lasts as long as 18 to 25 days. When a single flower withers, it falls from the pedicel without any fruit. The abortion in the floral organ of acarpous L. indica is characterized by sterile and undehisced anthers, pollen abortion, and deformed and irregularly arranged filament cells. Acarpous L. indica features short and loosely arranged papilla cells in the stigma, a flat style and narrow stylar canal, loosely arranged epidermal cells, and no obvious nuclei. No embryo sac cavity is found in acarpous L. indica ovules. In some nucelli, the egg apparatus structure can be observed indistinctly but without cell contour. In others, the egg apparatus structure is completely absent, and only flocculent tissue is observed. This study may provide a theoretical foundation for future studies on the molecular mechanisms of the mutations in acarpous L. indica.

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Previous investigations showed that accumulations of Na+ and Cl in leaves resulted in reductions in chlorophyll content, thereby affecting photosynthesis. Understanding how chlorophyll content evolves over time will help plant breeders to select cowpea genotypes with better tolerance to salinity by allowing them to choose those with more stable chlorophyll content under salt stress. The objective of this study was to assess how the chlorophyll content of cowpea genotypes changed over the course of 24 d of salt stress at the seedling stage. A total of 24 cowpea genotypes with different salt responses were used in this study. The experiment used a split-plot design with salt treatment as the main plot and cowpea genotypes as the subplot. In the main plot, there were two salt treatments: 0 mm (ionized water) and 200 mm NaCl. In the subplot, the cowpea genotypes were arranged as a completely randomized design with three replicates per genotype. The results revealed that: a1) the time × genotype interaction was significant under conditions with and without salt; 2) chlorophyll content slowly decreased in the salt-tolerant genotypes; 3) chlorophyll content slightly increased on day 6 and day 9 of salt stress in both moderate and sensitive genotypes, but it decreased at a faster rate than in the salt-tolerant genotypes; and 4) salt-sensitive genotypes were completely dead on day 24 of salt stress, whereas the salt-tolerant genotypes were able to maintain a significant amount of chlorophyll content. These results can be used to advance breeding programs for salt tolerance in cowpea.

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Soil acidification and boron (B) starvation are two dominant abiotic stress factors impacting citrus production in the red soil region of southern China. To evaluate the combined effects of low pH and B deficiency on plant growth, gas exchange parameters, and the concentrations of B and other mineral nutrients, ‘HB’ pummelo seedlings were treated under B deficiency (0 μM H3BO3) or adequate B (23 μM H3BO3) conditions at various low pH levels (4.0, 5.0, and 6.0). The seedlings were grown with modified half-strength Hoagland’s solution under greenhouse conditions for 12 weeks. Plant biomass, leaf area, seedling height, and root traits were remarkably inhibited by low pH and B deficiency stresses, and these parameters were extremely reduced with the decrease in pH levels. After 12 weeks of treatment, typical stress symptoms associated with B deficiency in citrus leaf were observed, with more severe symptoms observed at pH 4.0 and 5.0 than at pH 6.0. Leaf gas exchange parameter measurements showed that leaf photosynthesis was significantly inhibited under both low pH and B-deficient conditions. Notably, the lower the pH level, the greater the inhibition under both normal and deficient B conditions. Further investigations of the mineral nutrient concentrations showed that under both low pH and B deficiency, the concentrations of B and other mineral nutrients were influenced remarkably, particularly at pH 4.0 and 5.0. The physiological and nutritional results of the ‘HB’ pummelo seedlings indicated that low pH can exacerbate the effects of B deficiency to a certain extent.

Open Access