First Report of Fusarium subglutinans Causing Leaf Spot Disease on Cymbidium Orchids in Korea

In 2006~2010, leaf spot symptoms, that is, small, yellow spots that turned into dark brown-to-black lesions surrounded by a yellow halo, were observed on Cymbidium spp. in Gongju, Taean, and Gapyeong in Korea. A Fusarium species was continuously isolated from symptomatic leaves; in pathogenicity testing, isolates caused leaf spot symptoms consisting of sunken, dark brown lesions similar to the original ones. The causal pathogen was identified as Fusarium subglutinans based on morphological and translation elongation factor 1-alpha sequence analyses. This is the first report of F. subglutinans as the cause of leaf spot disease in Cymbidium spp. in Korea.

Molecular Identification of Mycorrhizae of Cymbidium kanran (Orchidaceae) on Jeju Island, Korea

A fungal internal transcribed spacer region was used to identify the mycorrhizae of Cymbidium kanran. The family Russulaceae was found to be the most frequently occurring group in both root and soil samples. In phylogenetic analyses, the majority of the Russulaceae clones were clustered with Russula brevipes and R. cyanoxantha. Therefore, C. kanran may form symbiotic relationships with the genus Russula.

Development of cDNA-derived ssr markers and their efficiency in diversity assessment of cymbidium accessions

Cymbidium spp. are popular flowering plants. Assessment of the genetic diversity in cultivated Cymbidium facilitates conservation of germplasm and subsequent cultivar improvement. Thus, it is important to develop more efficient polymorphic DNA markers. Although more motifs (403) were identified and more primers (206) were designed in the genomic library compared to the cDNA library, a larger number of successful primers were obtained from the cDNA library (59.9 percent) than from genomic DNA library (51.1 percent). However, higher PIC and gene diversity were identified in genomic SSRs. The average allele number per locus was also higher in genomic SSRs (7.3) than EST-SSRs (5.2), among the 24 evaluated Cymbidium accessions. AT/TA was comparatively high in EST-SSRs, while this motif was not as common in genomic SSRs. The CTT/AAG/TCT/AGA/TTC/GAA and TGC/GCA/GCT/AGC/CTG/CAG motifs were the most abundant tri-nucleotide sequences in EST-SSRs, while GTT/AAC/TGT/ACA/TTG/CAA was the most frequent in genomic SSRs. The number of repeats ranged from 3 to 12 in EST-SSRs. Currently, 52 novel polymorphic SSR markers have been evaluated, which will be useful for germplasm assessments, core set construction, evaluation of genetic diversity, and marker assisted selection (MAS) based Cymbidium breeding.

First Report of Sclerotium Rot on Cymbidium Orchids Caused by Sclerotium rolfsii in Korea

Sclerotium rot was found on Cymbidium orchids at Seosan-si, Chungcheongnam-do, Korea, in July, 2010. Symptoms occurred on low leaves, which turned yellowish, after which the entire plant wilted. Severely infected plants were blighted and eventually died. White mycelial mats and sclerotia appeared on pseudobulbs. Based on the mycological characteristics and pathogenicity, the causal fungus was identified as Sclerotium rolfsii. This is the first report of new Sclerotium rot on Cymbidium spp. caused by S. rolfsii in Korea.

Central nervous system depressant effects of the ethanolic extract of Cymbidium aloifolium (L.).

The ethanolic leaf extract of Cymbidium aloifolium (L.) was intended to evaluate the effect on the central nervous system (CNS) using a number of neuropharmacological experimental models in mice. The extract, at the dose of 200 and 400 mg/kg body weight, were shown to have CNS depressant activity by the reduction of locomotor and exploratory activities in the open field and hole cross tests. These results suggest that the extract possess CNS depressant activity. The results of statistical analysis showed that the plant extract had significant, (p<0.001) dose dependent, CNS depressant activities when compared to the control.

A Study on Mycorrhizal Microstructure of Wild Cymbidium ensifolium / 广州中医药大学学报

The microstructure of mycorrhiza of wild Cymbidium ensifolium, collected from the mountains of north Guangdong was studied. The results showed that this species possesses the typical mycorrhizal structure of orchid plant. Mycorrhizal fungi invaded the cortex parenchyma by velamen and exodermis, and then, form pelotons and expanded part of area of cortex. The intracellular mycelium was digested and absorbed with clumps of digested material in some cells.

Isolation of the Orchid Mycorrhizal Fungi from the Korean Native Orchids in Cheju

The eleven isolates were isolated from the roots of Cymbidium goeriingii inhabited in the island of Cheju and from Cypripeium calceolus inhabited in the mountains around ChungPuk. The isolates were inoculated to the plantlets of commercial orchids and evaluated to be symbiotic with the orchids. Also, their genomic DNA was extracted from the cultures on the agars and reacted with the primers selected, understanding their biological relations with the pathogenic fungi. Out of eleven isolates, three were observed to stimulate the growth of the orchid plantlets and to be biologically related to the orchid symbiotic fungi, as based on the analyses of PCR-RAPD. Otherwise, the others were observed to decline the growth of orchid plantlet, compared with those of control, and to be grouped with the pathogenic. As based on the results of this work, the roots of C. goeriingii were found to be frequently infected with the pathogenic fungus rather than with symbiotic fungus in natural systems. Further, the infection of the commercial orchid with the pathogens was believed to be abundant without any inoculation of symbiotic fungus under the conditions of greenhouse.