ng Hyeon Ka

Diversity of arbuscular mycorrhizal fungi and their roles in ecosystems.

Abstract Arbuscular mycorrhizal fungi (AMF) have mutualistic relationships with more than 80% of terrestrial plant species. This symbiotic relationship is ancient and would have had important roles in establishment of plants on land. Despite their abundance and wide range of relationship with plant species, AMF have shown low species diversity. However, molecular studies have suggested that diversity of these fungi may be much higher, and genetic variation of AMF is very high within a species and even within a single spore. Despite low diversity and lack of host specificity, various functions have been associated with plant growth responses to arbuscular mycorrhizal fungal colonization. In addition, different community composition of AMF affects plants differently, and plays a potential role in ecosystem variability and productivity. AMF have high functional diversity because different combinations of host plants and AMF have different effects on the various aspects of symbiosis. Consequently, recent studies have focused on the different functions of AMF according to their genetic resource and their roles in ecosystem functioning. This review summarizes taxonomic, genetic, and functional diversities of AMF and their roles in natural ecosystems.

Phylogenetic relationships of Korean Sparassis latifolia based on morphological and ITS rDNA characteristics

Recent studies based on morphological characteristics and molecular analyses have revealed that the characteristics of Sparassis crispa from Asia are not concordant with those of collections from Europe and North America. Consequently, the Asian isolate was redefined as Sparassis latifolia. This study is the first report of Sparassis latifolia collected in Korea. The taxonomic relationships and replacement of Sparassis species were inferred from a comparison of the morphological characteristics and by molecular sequence analysis of the internal transcribed spacer (ITS) rDNA regions. In particular, this study focused on the phylogenetic relationships inferred from the biogeographical distribution of isolates within the genus Sparassis.

Determination of Glucan Contents in the Fruiting Bodies and Mycelia of Lentinula edodes Cultivars

Abstract Shiitake mushrooms (Lentinula edodes) containing β-glucans may be beneficial for human health; they have been used in the treatment of cancer, hypertension, and high cholesterol levels. The objective of this study was to determine the β-glucan content in different sections of the fruiting bodies and mycelia of ten shiitake mushroom cultivars. The measured β-glucan content ranged from 20.06 ± 1.76% to 44.21 ± 0.13% in the pileus sections, and from 29.74 ± 1.40% to 56.47 ± 4.72% in the stipe sections. The results of this study indicate that the variance in β-glucan content dependent on the shiitake cultivar, and that the β-glucan content is higher in the stipe than in the pileus.

Spore Dispersion of Tricholoma matsutake at a Pinus densiflora Stand in Korea

The spore of Tricholoma matsutake is considered to be the starting point of the mushroom growth cycle, but the mechanism of mycelial development from the spore stage is not yet clarified. In this study, we tried to measure how far the spores of T. matsutake disperse from a fruiting body located at a Pinus densiflora stand in Korea. We established 16 slide glasses coated with glycerin near a fruiting body in four directions separated by four different distance intervals within a mushroom productive stand after removing all other fruiting bodies from three plots. The number of dispersed spores increased with time from the first day (475 spores/cm2) to the fourth day (836 spores/cm2) after the pileus opened. The number of spores dispersed downward was about 1.5 times greater than that dispersed toward the ridge. The number of dispersed spores decreased exponentially as the distance from each fruiting body increased. More than 95% of the spores dropped within a meter from the fruiting body, with 75% dropping within 0.5 m. Even so, the number of spores dispersed over 5 m from the fruiting body was more than 50 million when considering the total number of spores produced by a fruiting body is about 5 billion.

Effect of Chitosan Acetate on Bacteria Occurring on Neungee Mushrooms, Sarcodon aspratus.

Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom’s appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were 3 × 10−4 and 1.4 × 10−3 after 24 h, and 2 × 10−4 and 7 × 10−4 after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were 1 × 10−2 and 6.9 × 10−3, respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for 2~3 second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures.