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  • Author or Editor: Jun Zeng x
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White rust (causative pathogen Puccinia horiana) is a destructive disease of commercial chrysanthemum crops. A panel of 19 accessions of commercial chrysanthemum near-relatives (four Ajania species, 11 Chrysanthemum species including five accessions of Chrysanthemum indicum) were screened for their reaction to white rust infection in separate greenhouse trials carried out at two independent sites in eastern China, one in 2010 and the other in 2012. The reaction of the accessions to artificial inoculation ranged from immune to highly susceptible. Accessions of Chrysanthemum indicum, C. yoshinaganthum, C. makinoi var. wakasaense, C. nankingense, C. vestitum, C. lavandulifolium, C. crassum, and Ajania tripinnatisecta were immune, and strong resistance was present in C. japonense, C. × shimotomaii, and A. przewalskii. Most of the accessions behaved similarly in the two trials, but two of the C. indicum accessions produced inconsistent results, each being highly resistant in one trial but susceptible in the other. Because wide crosses are relatively easy to achieve in the chrysanthemum complex, these immune and highly resistant accessions represent promising germplasm for white rust resistance breeding.

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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.

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Nothodoritis zhejiangensis Z. H. Tsi is a rare and endangered epiphytic orchid restricted to a narrow distribution in China. The species is threatened with extinction as a result of loss of suitable habitats. An efficient propagation system is part of this species’ conservation plan. Seed germination reached 64.7% on Knudson's C (KC) medium containing 1.0 mg·L−1 α-naphthaleneacetic acid (NAA), 10% coconut water, and 0.1% activated charcoal. After 50 days culture, most callus (71.3%) from seed-derived protocorms formed on KC medium with 1.0 mg·L−1 2,4-dichlorophenoxyacetic acid and 10% coconut water. Callus could be subcultured 12 times during ≈2 years with more than a 3.0-fold increase from the third to the twelfth subculture. Furthermore, 84% of callus from the tenth sub-culture on KC media supplemented with 1.0 mg·L−1 NAA, 5% coconut water, and 0.1% activated charcoal formed protocorm-like bodies (PLBs). Many (57%) protocorms on KC medium containing 1.0 mg·L−1 6-benzylaminopurine and 10% coconut water formed PLBs. Both callus and PLBs formed simultaneously from different protocorms on KC medium containing 0.01 to 1.0 mg·L−1 thidiazuron and 10% coconut water. PLBs were incubated 12 times during ≈2 years with an approximate 2.4-fold increase per sub-culture. Both callus and PLBs maintained their competence to regenerate plantlets. Hyponex N026 medium supplemented with 1.0 mg·L−1 NAA, 50 g·L−1 banana homogenate, and 0.1% activated charcoal was suitable for plantlet formation and growth of 95.5% of plantlets that developed from PLBs. The roots of plantlets 2 cm in height or taller were wrapped in Chilean sphagnum moss and fixed to a fir bark block; 69.3% of plantlets survived after 180 days in a greenhouse. This protocol is an efficient means for the large-scale propagation of this endangered orchid.

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