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  • Author or Editor: Feng Zhou x
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Gummy stem blight incited by the fungus Didymella bryoniae is a major disease of melons worldwide. The objectives of the present study were to critically evaluate melon (Cucumis melo L.) germplasm for resistance to D. bryoniae and to characterize the genetics of resistance in the resistant accessions. Two hundred sources of germplasm (plant introduction accessions, cultivars, breeding lines, landraces, and wild relatives) were screened against a single highly virulent isolate (IS25) of D. bryoniae in a plastic tunnel. The genetics of resistance to D. bryoniae was studied in three crosses between plant introductions 157076, 420145, and 323498, resistant parents that were fairly adapted (flowering, fruiting, powdery mildew tolerance) to Nanjing conditions, and plant introductions 268227, 136170, and NSL 30032 susceptible parents, respectively. Six populations of each cross (susceptible parent, resistant parent, F1, F2, the two reciprocal backcrosses) were analyzed for their responses to D. bryoniae. Seedlings in both studies were inoculated with a spore suspension (5 × 105 spores/mL−1) of D. bryoniae at the four to six true-leaf stages and assessed for leaf and stem damage at 7, 14, and 21 d postinoculation. Results of germplasm screening indicated most germplasms reported as resistant elsewhere were confirmed resistant under our conditions. However, some plant introductions identified as highly resistant elsewhere were susceptible under our conditions, the most interesting being plant introduction 482399. This plant introduction that was considered resistant was highly susceptible in our study. We also identified other sources of resistance not reported previously, for example, JF1; a wild Cucumis from the highlands of Kenya was rated highly resistant. Analysis of segregation of F1, F2, and backcross generations of the three crosses indicated that each of the three plant introductions carry a single dominant gene for resistance to the D. bryoniae.

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To investigate the characteristics of photosynthetic physiological changes in leaves of Mangifera indica L. cv. Guifei under enhanced ultraviolet (UV)-B radiation, natural light-exposed trees were used as controls and 96 kJ·m−2·d−1 enhanced UV-B radiation was artificially simulated in the field. The changes in fruit maturity and quality, the leaf net photosynthetic rate (Pn), photosynthetic pigment contents, photochemical reactions, the activities of photosynthetic enzymes and related gene expression levels were determined. Compared with the control, the percentage of mature fruits under the treatment significantly increased, and fruit quality improved. The net photosynthetic rate (Pn), photosynthetic pigment content, Hill reaction activity, and photochemical quenching coefficient (qP) of the treated leaves showed significantly higher values than those of the control leaves. The activities of Rubisco and Rubisco activating enzyme (RCA) and the expression levels of the Rubisco large subunit and Rubisco small subunit were significantly increased. Treatment with 96 kJ·m−2·d−1 enhanced ultraviolet-B radiation improved Rubisco activity by increasing the expression of the Rubisco large and small subunit genes, thereby enhancing the CO2-fixing capacity and dark reaction capacity of leaves. Thus, the net photosynthetic rate of leaves increased, which promoted the early maturity of ‘Guifei’ mango by the rapid accumulation of photosynthetic products.

Open Access

The structure and chemical properties of strontium and calcium are similar. To study the interplay between calcium and strontium in plants, different concentrations of SrCl2 (0, 1, 4, and 10 mmol·L−1) were added to the Hoagland nutrient solution with 4 mmol·L−1 Ca2+ (normal level Ca2+) or 0.4 mmol·L−1 Ca2+ (low-level Ca2+), which were used to cultivate Chinese cabbage seedlings. Under the low-level calcium condition, strontium not only did not promote the growth of Chinese cabbage but showed more severe toxicity compared with that under the normal calcium condition. Under normal calcium condition, although the growth of Chinese cabbage was significantly inhibited by 4 mmol·L−1 strontium, strontium did not show significant toxicity. However, under the low-level calcium condition, 1 mmol·L−1 strontium caused a significant decline of plant biomass and photosynthetic activity. Sr2+ showed a competitive inhibitory effect on the absorption of Ca2+, and strontium was more easily absorbed by Chinese cabbage. Under the low-level calcium condition, strontium aggravated the inhibition of calcium absorption. The inhibitory effect of strontium on plant growth was significantly related to the calcium content in Chinese cabbage. Strontium cannot replace the function of calcium in plants under calcium-deficient conditions.

Open Access

The database of grape transcription factors (DGTF) is a plant transcription factor (TF) database comprehensively collecting and annotating grape (Vitis L.) TF. The DGTF contains 1423 putative grape TF in 57 families. These TF were identified from the predicted wine grape (Vitis vinifera L.) proteins from the grape genome sequencing project by means of a domain search. The DGTF provides detailed annotations for individual members of each TF family, including sequence feature, domain architecture, expression information, and orthologs in other plants. Cross-links to other public databases make its annotations more extensive. In addition, some other transcriptional regulators were also included in the DGTF. It contains 202 transcriptional regulators in 10 families.

Free access

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is one of the most toxic polybrominated diphenyl ethers (PBDEs). The toxic effects of BDE-47 on Chinese cabbage seedlings were analyzed in this study. After a 30-day hydroponic exposure to BDE-47 at different concentrations (25, 50, 75, and 100 µg·L−1), the fresh weight of Chinese cabbage seedlings was significantly decreased, whereas their root:shoot ratio was increased, indicating that BDE-47 inhibited the growth of the plant, especially the overground parts. The water content, chlorophyll content, and protein content of Chinese cabbage leaves also markedly decreased with the increase of the BDE-47 concentration. In addition, BDE-47 weakened the photosynthetic capacity of the leaves, which was supported by the decreased photosynthetic parameters [net photosynthetic rate (P n) and stomatal conductance (g S)]. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves were enhanced after exposure to BDE-47, the increased malondialdehyde (MDA) content attested to the existence of membrane lipid peroxidation. The increased plasma membrane permeability and the decreased chlorophyll fluorescence parameters [the maximum quantum yield of PSII photochemistry at t = 0 (F v/F m), photosystem II (PSII) reaction centers (RCs) per cross section (CS) (RC/CS), absorption energy flux per CS (ABS/CS), trapped energy flux per CS (TR o/CS), electron transport flux per CS (ET o/CS), performance index on the absorption basis (PI abs), and driving force for photosynthesis (DF)] further proved that the plasma membrane and photosynthetic membrane were damaged by BDE-47. Our study demonstrated the phytotoxicities of BDE-47 to Chinese cabbage, which can provide valuable information for understanding the toxicity of BDE-47 on vegetables.

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Rose (Rosa L.) is an economically important ornamental genus that has been cultivated for its scent for the perfume industry since antiquity. However, most modern roses have lost their fragrance during the later stages of the breeding process. Here, 59 species of Rosa, including 24 wild Rosa species, 20 Chinese old garden roses, and 15 modern roses, were examined by headspace solid-phase microextraction and gas chromatography–mass spectrometry. Fifty-three volatile organic compounds (VOCs), including terpenoids, benzenoids/phenylpropanoids, and fatty acid derivatives, were detected with qualitative and quantitative analyses. Thirteen common components, including geraniol, citronellol, 2-phenylethanol, 3,5-dimethoxytoluene, 1,3,5-trimethoxybenzene, germacrene D, and cis-3-hexenyl acetate, were found. Furthermore, different wild species or cultivars showed different characteristic compounds. 3,5-Dimethoxytoluene and 1,3,5-trimethoxybenzene were the main compounds in Rosa odorata and Rosa chinensis, which are the original parents of modern roses. 2-Phenylethanol, citronellol, and geraniol were the main aromatic compounds in Rosa damascene and Rosa centifolia. Methyl salicylate, eugenol, methyl eugenol, and benzyl acetate were lost during domestication and breeding of wild Rosa species to Chinese old garden roses and then to modern cultivars. Geranyl acetate, neryl acetate, and dihydro-β-ionol were gained during this time and showed higher amounts across the rose breeding process. Natural and breeding selection may have caused volatile compound gains and losses. These findings provide a platform for mining scent-related genes and for breeding improved ornamental plants with enhanced flower characteristics to develop new essential oil–producing plants.

Open Access