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.
Periodic drought, irrigation requirements, and the enforcement of mandatory watering restrictions have posed a challenge for homeowners and landscape managers to maintain acceptable turf quality during dry periods. Information regarding irrigation requirements and performance of common turfgrass species used for residential and commercial landscapes in the southeastern United States would be valuable. A Linear Gradient Irrigation System (LGIS) provides an efficient way to measure cultivar responses to variable moisture regimes. Nine commercially available cultivars from three turfgrass species: ‘Argentine’ bahiagrass (BH) (Paspalum notatum Flügge); ‘Common’ and ‘TifBlair’ centipedegrass (CP) [Eremochloa ophiruoides (Munro) Hack.]; ‘Captiva’, ‘Classic’, ‘Floratam’, ‘Palmetto’, ‘Raleigh’, and ‘Sapphire’ st. augustinegrass (STA) [Stenotaphrum secundatum (Walt.) Kuntze.] were evaluated during naturally occurring dry periods in 2010 and 2011 for visual quality, color, and density and chlorophyll index. An irrigation gradient ranging from 0% to 120% of reference evapotranspiration (ETo) was provided by LGIS. Centipedegrass and BH had less demands on supplemental irrigation to maintain acceptable quality during periodic drought compared with STA. ‘Argentine’ BH performed similar to ‘Common’ CP for its visual quality except at the irrigation level of 40% ETo. Among STA cultivars, ‘Palmetto’ performed poorest in its relative drought response than other cultivars. ‘Sapphire’ STA needs further study to better characterize its drought response. The irrigation level of 120% ETo decreased turf quality except for ‘Argentine’ BH, and the irrigation replacement at 40% to 80% ETo, depending on turfgrass species and cultivar, may provide enough supplemental moisture to maintain acceptable turf quality during short-duration drought (≈2 weeks) in north Florida regions.
Drought has become an important factor limiting crop yields in China. As an important greenhouse horticultural crop in China, the research of tomato (Solanum lycopersicum L. cv. Jinpeng No.10) is of great theoretical and practical significance. In the study, four different relative soil moisture contents (74% to 80%, 55% to 61%, 47% to 52%, and 25% to 30%) were used to induce drought stress. We investigated changes in photosynthetic gas exchange, chlorophyll fluorescence, and other related physiological parameters in response to different relative soil moisture contents. Drought inhibited the photosynthesis of tomato significantly, as shown by a clear decline in the net photosynthetic rate. Our results indicated stomatal limitation and nonstomatal limitation were responsible for the photosynthesis reduction.
The relationship of assimilate supply to grape (Vitis vinifera L.) berry growth and development was studied with a seeded (`Kyoho') and a seedless (`Seedless Wuhehong') cultivar. A single shoot girdling between the second and third nodes below the basal cluster at the end of Stage I of berry growth shortened Stage II (the lag phase) of `Kyoho' grape berries by 10 days, and eliminated Stage II in `Seedless Wuhehong' grape berries. Double shoot girdling between the second and third nodes below the basal cluster and above the upper cluster, respectively, at the same time at the end of Stage I, advanced Stage II by 3 days in both cultivars. Normal accumulation of dry weight in the `Kyoho' grape berry is in a double sigmoidal pattern, but it became a single sigmoidal pattern in response to a single basal girdling. The highest percent moisture in berries was at 20 days after full bloom. Rapid changes in berry pectin substances lagged behind those of soluble solids and titratable acidity, and behind the onset of berry softening at veraison in `Kyoho', but not in `Seedless Wuhehong', for which the three processes were concurrent. It is suggested that the slow growth of the berries during Stage II is a result of a decrease in the rate of water accumulation on a whole berry basis and a decrease in accumulation of dry matter in the skin and flesh (pericarp) due to assimilate competition within grapevines and within berries. The relationships between levels of endogenous hormones (IAA, GA3, zeatin, zeatin riboside, and ABA) and berry growth were also studied with `Kyoho' grapes. The results showed that the slow growth of grape berries during Stage II was associated with assimilate competition between the skin-flesh (pericarp) and seeds, and with peak shifts of concentrations of IAA, GA3, zeatin and zeatin riboside. Changes in ABA levels were closely associated with ripening and senescence during late Stage III.
Heavily shaded environments often limit the performance and persistence of hybrid bermudagrass (Cynodon dactylon × C. transvaalensis), therefore a field-based shade study was performed to determine whether different mowing heights (0.5 and 1.5 inch) or two trinexapac-ethyl (TE) growth regulator management treatments (control and 2 oz/acre) allow either ‘TifSport’ or ‘TifGrand’ hybrid bermudagrass to persist under 77% shade. Turfgrass quality (TQ), green cover, normalized difference vegetation index (NDVI), and dark-green color index (DGCI) were evaluated on the two cultivars under a shade structure in Tifton, GA, during 2010 and 2011. Neither of the cultivars maintained acceptable TQ throughout the entire year under 77% shade, although ‘TifGrand’ displayed adequate TQ at the higher mowing height (1.5 inch) and demonstrated more shade tolerance than ‘TifSport’, as indicated by TQ, green cover, and NDVI. The TE application did not enhance the turf performance of ‘TifSport’ under 77% shade when mowed at 0.5 inch, but it improved turf performance of ‘TifGrand’ at the same height. The effect of TE application was cultivar and mowing height dependent under this heavily shaded environment, which warrants future study to determine the best management practices of these cultivars as well as continued efforts to develop new, shade-tolerant bermudagrass hybrids.
Estimating chilling requirements is crucial for identifying appropriate cultivars for a given site, for timing applications of dormancy-breaking chemical agents, and for predicting consequences of climate change. For temperate-zone fruit species such as japanese apricot, productivity is reduced when chilling requirements are not adequately satisfied. In our study, we obtained chilling and heat requirements for flowering of six japanese apricot cultivars, which spanned the range of flowering times in this species for three successive years. Different methods for determining chilling requirements were evaluated and compared, and correlations among chilling requirements, heat requirements, and flowering date were established. The dynamic model proved to be the best for determining the chilling requirements of japanese apricot. The results showed a range of chilling requirements ranging from 26.3 to 75.7 chill portions and a narrow range of heat requirements, from 1017.7 to 1697.3 growing degree-hours (GDH). A very high correlation (R = 0.9797) between flowering date and chilling requirements and a low correlation (R = 0.4298) between flowering date and heat requirements suggest that flowering date in japanese apricot is mainly a consequence of the chilling requirements of the different genotypes, whereas heat requirements contribute a limited effect to the variation in flowering dates. Chilling requirements and heat requirements were positively related with a low correlation coefficient (R = 0.4211).
By using a modified biotin-streptavidin capturing method, a total of 20 polymorphic microsatellite markers were developed from Moringa oleifera Lam. (Moringaceae), a useful multipurpose tree. Twenty-four domesticated individuals, with germplasms of India and Myanmar, were used to screen polymorphism of these 20 microsatellite markers. The number of alleles per locus ranged from two to six. The expected and observed heterozygosity varied from 0.3608 to 0.7606 and from 0.0000 to 0.8750, respectively. Seven loci were significantly deviated from Hardy-Weinberg equilibrium. The availability of these microsatellite primers would provide a powerful tool for aspects of detailed population genetic studies of M. oleifera.
The role of the walnut (Juglans regia L.) shell in nut development, transportation, cleaning, and storage is often ignored. The shell suture seal and thickness are directly associated with kernel characteristics. In the present study, shell differentiation and microstructure were observed with an optical microscope using paraffin-sectioning and cryosectioning. The results showed that the parenchymal cells of the endocarp began to differentiate into sclerenchymal cells from 49 d after flowering (DAF), and the entire process continued until fruit maturation. The mature shell consists of three parts, including the sclereid layer (L1), sclerenchymal cell layer (L2), and shrunken cell layer (L3), from the outside to the inside. The shell thickness, suture seal grade, and mechanical strength were evaluated, as well as the lignin, cellulose, and phenolic compounds of the shell. Suture seal grade was positively correlated with lignin content, shell thickness, and L1 thickness and negatively correlated with shell cell diameter. Similarly, the mechanical strength of the shell was positively correlated with lignin content and L1 thickness. ‘Qingxing’ fruits were subjected to two treatments, namely, 30% shading and 70% shading, from 10 d after anthesis to maturity, with no shading used as control. After harvesting in September, nutshell sections showed thinner shells, with decreased contents of lignin and polyphenols, obtained under shaded conditions, and two of the three parts of the shell changed dramatically. The thinning of L1 and thickening of L3 eventually led to a thinner shell. The aim of this study was to evaluate the relationship among the shell structure, cellular components, and physical properties and provide a theoretical basis for cultivar breeding, rational planting density, and regulation of shell development.
Acer truncatum seeds are an excellent source of beneficial natural compounds, including high levels of unsaturated fatty acids (UFAs), that promote health. Recently, A. truncatum has emerged as an oil crop. Therefore, the transcriptomes of A. truncatum seeds at 70, 85, 100, 115, 145, 180 days after flowering (DAF) were analyzed to gain a better understanding of the transcriptional and translational regulation of seed development and oil biosynthesis. A total of 28,438 genes were identified, and 3069/2636, 3288/3438, 1319/2750, and 5724/5815 upregulated/downregulated genes were identified when comparing different samples with 85 DAF seeds. Sixteen lipid metabolism pathways with 754 differentially expressed genes (DEGs) were identified, including 34 DEGs associated with UFA biosynthesis. A phylogenetic analysis revealed that six putative fatty acid desaturase (FAD) genes clustered into five FAD groups. A quantitative real-time polymerase chain reaction analysis indicated that the temporal expression patterns of oil biosynthesis genes and transcription factors were largely similar to the RNA sequencing results. The results of this study will enhance the current understanding of oil metabolism in A. truncatum seeds and allow new methods of improving oil quality and seed yield in the future.