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.
Jing Zhang, J. Bryan Unruh, and Kevin Kenworthy
Guoting Liang, Junhui Liu, Jingmin Zhang, and Jing Guo
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.
Jing Wu, Qi He, Caihong Zhang, and Gui Wang
Nian Wang, Zhang Chang Qin, Jun-bo Yang, and Jing-li Zhang
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.
Zhi-Hong Gao, Zhi-Jun Shen, Zhen-Hai Han, Jing-Gui Fang, Yu-Ming Zhang, and Zhen Zhang
Sequencing amplification fragments produced using simple-sequence repeat (SSR) primer pairs pchgms2 and UDP96008 in `Dayezhugan' japanese apricot showed that SSRs obtained included a microsatellite locus originally identified in peach. The microsatellite sequence homogeneity between UDP96008 in japanese apricot in this study and UDP96008 in the peach in GenBank was 98%. Twenty-four japanese apricot genotypes originating in diverse geographic areas had been identified with 14 SSR primer pairs developed in different species of Prunus. In total, 129 alleles were obtained and per primer pairs detected 2.5 alleles on the average. The results from cluster analysis showed that the genetic distance between `Nanhong' and `Zhonghong' was the closest, and cultivars from China and from Japan could not be separated completely.
Xue Li, Chen Zang, Hang Ge, Jing Zhang, Donald Grierson, Xue-ren Yin, and Kun-song Chen
Loquat (Eriobotrya japonica) is a model fruit for investigating flesh lignification during storage and response to chilling injury. However, the investigations of enzymes and coding genes and loquat fruit lignification under low-temperature storage are still limited. Here, the activity and transcript levels of up-stream enzymes of the phenylpropanoid pathway, including l-phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate:coenzyme A ligase (4CL), were investigated. The results indicated that activity of these enzymes was positively correlated with loquat fruit lignification and suppression of these increases by heat treatment (HT) and low-temperature conditioning (LTC) significantly alleviated loquat fruit lignification. Coding genes for these enzymes were subsequently isolated based on information from an RNA-seq database and expression of Ej4CL1 was found to be the most responsive to low temperature and inhibition by HT and LTC treatment, whereas the other genes were less responsive to these treatments. Furthermore, function of Ej4CL1 was analyzed by transient overexpression in tobacco leaves, where it stimulated lignin accumulation. Ej4CL1 may be a key candidate that involved in CI-related loquat fruit lignification.
Maria P. Fuentealba, Jing Zhang, Kevin E. Kenworthy, John E. Erickson, Jason Kruse, and Laurie E. Trenholm
Irrigation for commercial and residential turf is becoming limiting, and water scarcity is one of the long-term challenges facing the turfgrass industry. Potential root development and profile characteristics of turfgrass provide important information regarding their drought resistance mechanisms and developing drought-resistant cultivars. The objective of this study was to determine the potential root development and root profile characteristics of two bermudagrass species and two zoysiagrass species using experimental lines and commercial cultivars. The species evaluated in the study were: African bermudagrass (Cynodon transvaalensis Burtt-Davy), common bermudagrass (CB) [Cynodon dactylon (L.) Pers. var. dactylon], Zoysia japonica (ZJ) (Steud), and Zoysia matrella (ZM) L. Plants were grown outdoors in clear acrylic tubes encased in poly vinyl chloride (PVC) sleeves. The experimental design was randomized complete block design with four replications. Rates of root depth development (RRDD) during the first 30 days were obtained. Root length density (RLD) in four different horizons (0–30, 30–60, 60–90, and 90–120 cm) was determined 60 days after planting. Specific root length (SRL, m·g−1) was also calculated dividing total root length by total root dry weight (RDW). The root depth in four turfgrass species increased linearly during the first 30 days after planting. Common bermudagrass (CB) had high RRDD and uniform RLD in different horizons, while ZM accumulated the majority of its roots in the upper 30 cm. Z. matrella had higher RLD than CB in the upper 30 cm. African bermudagrass had higher SRL than CB. There was limited variation within the two African bermudagrass genotypes studied except at the lowest horizon (90–120 cm). Two genotypes in CB and ZJ, respectively, including ‘UF182’ (ZJ), which consistently ranked in the top statistical group for RRDD, and RLD for every horizon, and ‘UFCD347’ (CB) demonstrated greater RLDs in the lower horizons in comparison with the commercial cultivars.
Zhihong Gao, Weibing Zhuang, Liangju Wang, Jing Shao, Xiaoyan Luo, Binhua Cai, and Zhen Zhang
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).
Jiang-Chong Wu, Jing Yang, Zhi-Jian Gu, and Yan-Ping Zhang
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.
Brian Schwartz, Jing Zhang, Jonathon Fox, and Jason Peake
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.