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  • Author or Editor: Chen Wang x
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The embryo abortion rate of Ziziphus jujuba Mill. ‘Zhongqiusucui’ is high, which hinders cross-breeding. Research to identify the causes of embryo abortion is urgently required. To determine the embryo abortion pattern and create a foundation for further research, the embryo abortion characteristics of Z. jujuba Mill. ‘Zhongqiusucui’ were observed during this study. The results indicated that Z. jujuba Mill. ‘Zhongqiusucui’ was a cultivar with a high embryo abortion rate. Furthermore, there were some differences in the embryo abortion rates of jujube fruits in different batches. There was no significant difference between the first and second batches of jujube fruits. Large jujube fruits had a relatively low embryo abortion rate. Small jujube fruits had a relatively low kernel content rate and high embryo abortion rate. Most of the jujube fruits contained a single kernel, and some contained double kernels. The third batch of jujube fruits differed greatly from the first and second batches. The third batch had the highest degree of embryo abortion and all contained kernels were single. The embryo abortion degree of jujube fruits on the lignified bearing shoot was higher than that on the nonlignified bearing shoot, and the probability of jujube fruit with double kernels on the nonlignified bearing shoot was higher than that of the fruit on the lignified bearing shoot. The embryo abortion rates of jujube fruits with a smaller fruit shape index and larger fruit shape index were lower, and that of the medium (fruit shape index range, 1.30–1.60) was higher. The embryo abortion rates of globose, oblong globose, and long cylinder jujube fruits were lower, whereas that of cylindrical fruits was higher. Cracked jujube fruits did not contain normal seed kernels and their embryo abortion rate was 100%.

Open Access

Salvia splendens is a widely used ornamental bedding plant; however, the limited propagation method has decreased its quality and yield. Through years of selection, we have obtained a new variety of S. splendens with weak apical dominance and named it as ‘Cailinghong’. To establish an effective method for regeneration of S. splendens ‘Cailinghong’, different explants, including leaves, receptacles, petioles, stem nodes, and stem segments were used for adventitious bud induction. Next, various combinations of plant growth regulators (PGRs) were selected for bud and root induction, which were assessed by adventitious bud initiation rate and proliferation rate, as well as root induction rate. Meanwhile, the survival rate of transplanted plantlets was also calculated. As a result, stem nodes were found easy to be induced to form buds, and the optimum medium component was 1/2 Murashige and Skoog (MS) medium supplemented with 0.45 µM naphthalene acetic acid (NAA), 8.88 µM 6-benzylaminopurine (6-BA), and 2.46 µM 3-indolebutyric acid (IBA) for plantlets induction, whereas 1/4 MS medium supplemented with 2.23 µM NAA for root induction. Furthermore, the survival rate of transplanted plantlets was up to 80%, and all regenerated plantlets were normal in phenotype. Therefore, cultured in 1/2 MS medium with combined PGRs, whole plantlet of S. splendens ‘Cailinghong’ could be regenerated directly from stem node.

Free access

Marigold (Tagetes erecta) is an important commercial plant because of its ornamental, industrial, and medicinal values. Male-sterile two-type lines are important for heterosis utilization and breeding of marigold. Mining of fertility-related genes may help to elucidate the mechanisms underlying male sterility. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) is a popular and useful tool for analyzing the expression level of a specific gene. Notably, identifying a suitable reference gene is important for data normalization because it affects the accuracy of quantitative analysis. However, at present, no reference genes are available for marigold. During the current study, 10 candidate reference genes were selected and their expression levels in different samples were analyzed by qRT-PCR. The expression level of each gene was analyzed across different developmental stages of male-sterile and male-fertile flower buds by four software programs (geNorm, NormFinder, BestKeeper, and RefFinder). The results showed that different reference genes are required for male-sterile and male-fertile samples, even if they belong to the same line. For male-sterile samples, the ribosomal protein S5/18S ribosomal RNA (RPS5/18S) gene pair was the best reference for qRT-PCR normalization, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) could be used as an alternative. For male-fertile samples, elongation factor 1-alpha (EF1α) and RPS5 were the most suitable reference genes, and Ubiquitin-conjugating enzyme (UBC) could be used as an alternative. Beta-actin (ACTB), tubulin beta (TUB), and phenylalanine ammonia-lyase (PAL) should not be used as reference genes because they were the most unstable genes in flower buds of marigold. The results of the current study may facilitate the selection of reference genes for analyzing the expression patterns of genes involved in flower development related to male sterility in marigold.

Open Access

Screening salinity-tolerant plants is usually time intensive and only applicable to a limited number of salinity levels. A near-continuous gradient dosing (NCGD) system allows researchers to evaluate a large number of plants for salinity tolerance with multiple treatments, more flexibility, and reduced efforts of irrigation. Rose of sharon (Hibiscus syriacus), ninebark (Physocarpus opulifolius), and japanese spirea (Spiraea japonica) were irrigated using an NCGD system with eight electrical conductivity (EC) levels ranging from 0.9 to 6.5 dS·m–1. At 11 weeks after irrigation was initiated, there were no significant differences among EC levels in terms of visual score, growth index [(Height + Width 1 + Width 2)/3], stem diameter, number of inflorescences, and shoot dry weight (DW) of rose of sharon. However, the root DW, relative chlorophyll content (SPAD), and net photosynthesis rate (Pn) of rose of sharon decreased linearly as EC levels increased. Ninebark and japanese spirea had increased foliar salt damage with increasing EC levels. The growth index, stem diameter, number of inflorescences, shoot and root DW, SPAD, and Pn of ninebark decreased linearly as EC levels increased. The growth index and SPAD of japanese spirea decreased quadratically with increasing EC levels, but its stem diameter, number of inflorescences, shoot and root DW, and Pn decreased linearly with increasing EC levels. The salinity threshold (50% loss of shoot DW) was 5.4 and 4.6 dS·m–1, respectively, for ninebark and japanese spirea. We were not able to define the salinity threshold for rose of sharon in this study. However, rose of sharon was the most salinity-tolerant species among the three landscape plants.

Open Access

High temperature (HT) is a major environmental stress limiting oversummer production of nonheading Chinese cabbage (NHCC, Brassica campestris ssp. chinensis Makino). In the present study, the effects of HT on photosynthetic capacity, including light reaction and carbon assimilation, were completely investigated in two NHCC, ‘xd’ (heat-tolerant), and ‘sym’ (heat-susceptible). The two genotypes showed significant differences in plant morphology, photosynthetic capacity, and photosynthate metabolism (carboassimilation). HT caused a decrease in photosynthesis, chlorophyll contents, and photochemical activity in NHCC. However, these main photosynthetic-related parameters, including net photosynthetic rate (P N ), maximal photochemical efficiency of PSII (Fv/Fm), and total chlorophyll content in ‘xd’, were significantly higher than those of ‘sym’ plants. The antioxidant contents and antioxidative enzyme activities of ascorbic acid-reduced glutathione cycle in the chloroplast of ‘xd’ were significantly higher than those of ‘sym’. Microscopic analyses revealed that HT affected the structure of photosynthetic apparatus and membrane integrity to a different extent, whereas ‘xd’ could maintain a better integrated chloroplast shape and thylakoid. Inhibited light reaction also hampered carbon assimilation, resulting in a decline of carboxylation efficiency and imbalance of carbohydrate metabolism. However, larger declined extents in these data were presented in ‘sym’ (heat-susceptible) than ‘xd’ (heat-tolerant). The heat-tolerant genotype ‘xd’ had a better capacity for self-protection by improved light reaction and carbon assimilation responding to HT stress.

Free access

Weigela florida (Bunge) A. DC. is a popular flowering shrub adapted to a wide range of environmental conditions. Efficient methods for micropropagation of this species have not been well developed. The present study established a protocol for in vitro shoot culture of W. florida ‘Tango’ after a systematic evaluation of different culture media, cytokinins, and auxins on axillary shoot induction. Single-node stems were cultured on Driver and Kuniyuki Walnut (DKW) medium for initial production of axillary shoots. The shoots were used as explants and cultured on DKW medium supplemented with 8.88 μm 6-benzylaminopurine (BA) and 0.27 μm naphthaleneacetic acid (NAA), resulting in the production of more than six axillary shoots per explant. The axillary shoots could either be used as explants for additional shoot production or be cultured on ½ DKW medium supplemented with 0.25 μm indole-3-butyric acid (IBA) for rooting. Plantlets were transplanted into a substrate with 99% survival rate in a shaded greenhouse. This established method could be used for rapid propagation of W. florida to speed the introduction of new hybrids or cultivars for commercial production.

Free access

Soil salinity influences plant growth and crop yield significantly. Former studies indicated that uneven salt distribution in the root zone could relieve salt stress. But, how uneven salt distribution influences Na+ and Ca2+ concentration in the stem, leaf, and fruit and whether this influence would bring effects on fruit blossom-end rot (BER) still needs to be further studied. Under consideration of this, pot experiment with four treatments, T1:1, T1:5, T2:4, and T3:3, was conducted by setting the upper soil layer salinity at 1‰, 1‰, 2‰, and 3‰ and the lower soil layer at salinities of 1‰, 5‰, 4‰, and 3‰, respectively. Compared with the uniform salt concentration in the root zone (T3:3 treatment), the incidence of BER in the T1:5 and T2:4 treatments decreased by 60% and 35%, respectively. The fruit Na+ concentration and Na+/Ca2+ ratio were positively correlated with the incidence of BER. The value of the upper-root selective absorption Ca2+ over Na+ (SCa/Na(upper root)) for T1:5 was 0.8 times more than that of T1:1. The results showed that the incidence of BER was positively correlated with root dry matter and SCa/Na(root) weighted mean salinity. The overall results suggested that uneven salt distribution in the root zone could promote the Ca2+ absorption, Ca2+/Na+ ratio, and selective absorption Ca2+ over Na+ and consequently decrease the incidence of BER in tomato fruit.

Free access

Crown gall disease caused by Agrobacterium tumefaciens affects a wide range of horticultural plants, and has no effective treatment. During the evaluation of crown gall resistance of peach germplasm resources, we observed enhanced resistance to subsequent invasion that was activated by virulence of A. tumefaciens in two peach cultivars. To further verify the phenotype observed in field experiments, systemic acquired resistance (SAR)-related salicylic acid (SA) and PR1 genes were investigated. The levels of SA were elevated in two cultivars, and these high levels were maintained for 35 days postinoculation. Compared with mock-inoculated controls, eight of the 22 candidate PpPR1 genes in A. tumefaciens-inoculated samples were significantly upregulated and three were downregulated in response to inoculation with A. tumefaciens. These data suggested that SA-induced SAR was activated in two peach cultivars by virulent A. tumefaciens infection. In addition, the eight induced PpPR1 genes can be used as molecular markers in defense studies in peach.

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Grafting has been widely used in orchard management because the rootstock can make the tree more tolerant to environmental stresses. Iron deficiency is one of the major limiting environmental factor in apple production worldwide. Systematic research has been made about iron-deficiency adaptive responses in the level of organs, cells, and subcells, whereas the interactions between Fe and other divalent cations in tissue level are little known. Synchrotron radiation X-ray fluorescence (SR-μXRF) was used to map the location of selected elements Fe, Zn, Mn, Ni, and Co in the longitudinal and latitudinal root samples of Malus xiaojinensis. Iron deficiency induced a significant increase in the relative contents of five micronutrients in epidermis and cortex. The ratio of element contents of roots under Fe-deficient condition and Fe-sufficient condition at same position increased obviously in the section of 1000- to 2000-μm distance from the root tip in xylem. Expression analysis of iron absorption- and transport-related genes in roots showed that MdNramp3 and MxCS1 increased significantly. These results indicated that iron deficiency promoted the long-distance transport of micronutrients in xylem, and MdNramp3 and MxCS1 might play an important role in this process. Importantly, this study directly provides visual divalent metals distribution in tissue level for an improved understanding of metal absorption process in apple rootstock.

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