Substantial difference of selenium tolerance was found between the tall fescue (Festuca arundinacea Schreb.) and white clover (Trifolium rapens L.) An inverse relationship between Se accumulation and Se tolerance suggests an exclusion mechanism that restricts Se uptake by the plant with greater Se tolerance. A positive relationship between the increase of protein Se concentration and growth inhibition in the plants suggests that assimilation of Se into protein is responsible for the reducing Se toxicity at the protein level. No evidence of a Se exclusion mechanism which exclude Se from incorporating into protein plays any major role of Se tolerance in this two species.
Zehuang Zhang, Qihua Lin and Qiuzhen Zhong
To identify the dynamic differences in transcriptome and gene expression in chinese bayberry flowers of different sex types, the female ‘Fugong-1’ (WT) and its monoecious mutant (MT) were used as experimental materials. Using Illumina HiSeq™ 2500, flowers at the inflorescence germination, inflorescence elongation, and initial flowering stages were sequenced by RNA-seq technology and 6 libraries were obtained. After sequence assemble, 84,945 unigenes greater than 200 bp were found and the total length was 71.66 Mb. Transcriptomic expression analysis of the six libraries indicated that there was only 297 genes showed different expression at the inflorescence germination stage between MT and WT, the difference of which was the minimum. At the elongation stage and the initial flowering stage, such numbers increased to 787 and 2722, respectively. Gene ontology (GO) functional enrichment analysis revealed that the enriched differentially expressed genes (DEGs) included those related with transcription in DNA-templated (GO: 0006355), pollen exine formation (GO: 0010584), plasma membrane (GO: 0005886), sequence-specific DNA binding transcription factor activity (GO: 0003700), and 2-alkenal reductase [NAD(P)] activity (GO: 0032440) GO categories, etc. Among these processes, pollen exine formation plays an important role in pollen cell wall synthesis and sporopollen participates in the biosynthesis of sporopollenin. High expression levels of these related genes were closely related to the MT’s male flower traits during the initial flowering stage, which resulted in the male characteristics in MT flower. This study provides important foundation for further mining important genes and regulating factors controlling the sex differentiation of flowers in chinese bayberry.
Ze Li, Xiaofeng Tan, Zhiming Liu, Qing Lin, Lin Zhang, Jun Yuan, Yanling Zeng and Lingli Wu
Camellia oleifera Abel. is one of four major woody oil plants in the world. The objective of the current study was to evaluate the effect of different plant growth regulators (PGRs) and concentrations on direct organogenesis using cotyledonary nodes, hypocotyls, and radicle explants. High induction frequency of adventitious shoots were obtained from cotyledonary nodes, hypocotyls, and radicle explants (85.2%, 73.6%, and 41.0%, respectively) when cultured on half-strength Murashige and Skoog (1/2 MS) medium containing 2.0 mg·L−1 6-benzylaminopurine (BA) and 0.1 mg·L−1 indole-3-acetic acid (IAA). Microshoots from cotyledonary nodes, hypocotyls, and radicle explants were then transferred to 1/2 MS medium containing 2.0 mg·L−1 BA and 0.05 mg·L−1 indole-3-butyric acid (IBA) for shoot multiplication, resulting in 6.9 shoots per explant. The shoots were transferred to Woody Plant Medium (WPM) supplemented with various α-naphthalene acetic acid (NAA) and gibberellic acid (GA3) for shoot elongation. The mean length of shoots and the number of leaves per shoot were 3.7 and 6.6 cm, respectively, in WPM supplemented with 0.5 mg·L−1 NAA and 3.0 mg·L−1 GA3. The highest rooting of shoots (90.2%) or the number of roots per shoot (7.2) was obtained when elongated microshoots were transferred to 1/2 MS medium supplemented with 3.5% perlite, 1.0 mg·L−1 IBA and 2.0 mg·L−1 NAA. The rooted plantlets were successfully acclimatized in the greenhouse with a survival rate of 90.0%. The in vitro plant regeneration procedure described in this study is beneficial for mass propagation and improvement of C. oleifera through genetic engineering.
Long-na Li, Songjun Zeng, Feng Zheng, Zhi-lin Chen, Kun-lin Wu, Jian-xia Zhang and June Duan
Ten polymorphic microsatellite loci were isolated and characterized from an enriched genomic library of Paphiopedilum concolor (Batem.) Pfitzer. The number of alleles per microsatellite locus ranged from three to 11 with an average of 6.4 in a sample of 30 individuals from three populations. The observed and expected heterozygosity ranged from 0.200 to 0.800 and from 0.544 to 0.827, respectively. These microsatellites can be used as tools to investigate the genetic structure of P. concolor populations and relationship patterns with closely related taxa.
Ji-Yu Zhang, Zhong-Ren Guo, Rui Zhang, Yong-Rong Li, Lin Cao, You-Wang Liang and Li-Bin Huang
This study examined the ability to vegetatively propagate 1-year-old pecan (Carya illinoinensis) through the rooting of hardwood cuttings. Cuttings were treated with varying concentrations of different auxins and different combinations of media and ambient temperatures. Under different temperature conditions, all auxin treatments induced the rooting of cuttings but did not promote sprouting. The effectiveness of the induction of adventitious roots was as follows: 1-naphthalene acetic acid (NAA) > indole 3-butyric acid > indole 3-acetic acid. The base of the parent shoot treated by NAA at a concentration of 0.09%, planted in substrate with bottom heat was the most effective, with 82% rooting, 8.3 roots/cutting and root lengths of 7.3 cm. These findings suggested that auxin and substrate/air temperature differences are both indispensable in the process of adventitious roots formation in pecan. This study revealed that the propagation of hardwood cuttings derived from branches of 1-year-old pecan is possible.
Jian-Feng Geng, Cheng-Song Zhu, Xiao-Wei Zhang, Yan Cheng, Yuan-Ming Zhang and Xi-Lin Hou
Brassica rapa L. ssp. chinensis (L.) Hanelt, known as nonheading chinese cabbage in China, is an important vegetable in eastern Asia and its genetic improvement requires a genetic linkage map. The first genetic linkage map of nonheading chinese cabbage using 112 doubled haploid lines derived from a released F1 hybrid cultivar Shulü between two lines SW-3 and Su-124 was constructed in this paper. One hundred thirty-eight molecular markers were mapped into 14 linkage groups. Among these markers, there were 77 sequence-related amplified polymorphism markers, 27 simple sequence repeat markers, 21 random amplification polymorphic DNA markers, and 13 intersimple sequence repeat markers. Chi-square tests showed that 54 markers are distorted from Mendelian segregation ratios, and the direction of the distortion is mainly toward the maternal parent SW-3. The distortion affects not only the estimation of genetic distance, but also the order of distorted markers on a same linkage group. Given a specific marker order, the authors proposed a multipoint approach to correct the linkage map in an unbiased manner in an F2 population while considering distorted, dominant, and missing markers. A new method was used to correct the linkage map in the doubled haploid population mentioned earlier considering new, distorted, and missing markers. The total length of the corrected linkage map was 1923.75 cM, with an average marker spacing of 15.52 cM. The map will facilitate selective breeding and mapping of quantitative trait loci.
Ze Li, Kai Shi, Fanhang Zhang, Lin Zhang, Hongxu Long, Yanling Zeng, Zhiming Liu, Genhua Niu and Xiaofeng Tan
As a result of its high photosynthetic efficiency, the tung tree (Vernicia fordii) is a fast-growing heliophile, yielding fruit within 3 years. In addition, tung oil extracted from the fruit seeds is an environmentally friendly paint used widely in China. However, mutual shading inside a tung tree canopy leads to a low yield of fruit because of weak or dead lower branches. In this project, a pot experiment was conducted to understand the growth, physiological, anatomical structure, and biochemical responses of tung trees under various shading levels. Tung tree seedlings were subjected to different light intensities—100% sunlight (no cover), L100; 75% sunlight (25% shading), L75; 50% sunlight (50% shading), L50; and 20% sunlight (80% shading), L20—from June to August. Results indicate that the L75 treatment reduced significantly the net photosynthetic rate (Pn), stomatal conductance (g S), transpiration rate (E), total aboveground and root dry weight (DW), maximum net photosynthetic rate (A max), and maximum rate of electron transport at saturating irradiance (Jmax) compared with the control, although plant height and leaf area (LA) were not reduced. Lower light intensities (L50 and L20) and longer duration of treatment led to greater reduction in growth, leaf thickness, and photosynthetic potential (A max and Jmax). Chlorophyll a (Chl a), chlorophyll b (Chl b), and total chlorophyll content were increased in the L50 and L20 treatments compared with L100 and L75. There was no significant reduction in the enzyme activities of ribulose-1,5-bisphosphate carboxylase (Rubisco) and phosphoenolpyruvate (PEPC) of the seedlings using the L75 treatment; however, lower light intensities (L50 and L20) and longer duration of shade treatment resulted in a significant reduction in enzyme activity. In summary, the results suggest that tung trees have greater photosynthetic activity under high light intensity. Shading, even at 20%, especially for the longer term, reduced photosynthetic efficiency and growth. To prevent growth reduction, tung trees should be grown under full sun with a daily light integral (DLI) of ≈46 mol·m‒2·d‒1, and mutual shading should be avoided by proper spacing and pruning.
X.E. Yang, X.Y. Lin, Y.S. Zhang and E.W. Stover
Citrus is a major fruit crop in the acid red soils (Ultisol) of hilly areas in Southeast China. These soils are normally deficient in P, K, and other elements. Integrated nutrient management is important for sustainable production of citrus in these areas. In this study, a systematic approach was used to identify the limiting factors for plant growth, using sorghum as a test species. Long-term field experiments were conducted with seven different P and K supply levels to determine optimal application rates for citrus (cv. Ponkan), following alleviation of other limiting factors. The primary nutritional limitations to plant growth in red acid soils included: severe deficiencies in N, P, and K, and moderate deficiencies in Ca, Zn, and B. With increasing application of P and K to field soil, N concentrations in citrus leaves decreased up to 60% due to dilution from increased growth, whereas P and K concentrations increased 2-3 fold. After 2 years of fertilizer application, the N: P: K ratio in leaves reached 1:0.5:1 for the optimal P and K treatment. The available P and K in the soils, measured after harvest each year, increased with increasing P and K application rates. However, within each treatment, increase in P and K with additional years of fertilization was modest. Citrus fruit yields generally increased with increasing P and K and reached a maximum at P and K rates of 125 kg P2O5/ha and 500 kg K2O/ha. In 3 years of successive field experiments, the highest net income was obtained by a balanced NPK fertilization practice using N: P2O5: K2O input of 450: 125: 500 kg/ha per year.
Xuelin Shen, Yanmei Zhang, Zhao Lei, Yibo Lin, Minxu Cao, Yueyu Hang and Xiaoqin Sun
‘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.
Yumei Zhang, Runfang Hu, Huawei Li, Haisheng Zhu, Jinming Zhao, Na Guo, Han Xing and Guoqiang Lin
Vegetable soybean is an important economic and nutritious crop. In this study, 48 differentially expressed proteins were identified from filling seeds of soybean (Glycine max) cv. Mindou 6 by using two-dimensional electrophoresis (2-DE) combined with liquid chromatography electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Among them, 25% were related to protein destination and storage, 42% to energy and metabolism, 15% to disease/defense, 6% to transporters, 4% to secondary metabolism, 4% to transcription, 2% to protein synthesis, and 2% to cell growth/division. Along with the maturity of seeds, the number of unchanged abundance proteins decreased, while that of both upregulated and downregulated proteins increased. Both downregulated expression of caffeic acid O-methyltransferase (COMT) and upregulated expression of sucrose-binding protein (SBP) 2 precursor may contribute to increase in digestibility, nutritional value, and eating quality of vegetative seeds at suitable picking period. The pattern of unchanged proteins during the whole seed-filling stage may be also beneficial to the quality of vegetable soybean.