Phylogeny and a new species of Polylobatispora.

During surveys conducted on freshwater fungi from Vietnam, a new aquatic anamorphic fungus was isolated from decaying leaves in Vietnam. The fungus produced phialidic, swollen conidiophore and conidiogenous cells with one-celled conidia with four very tiny lobes. Based on its conidial development and other morphological characteristics, we confirmed that this is a novel fungus and described it as P. ambigua sp. nov. Phylogenetic analyses of P. ambigua based on the LSU nrDNA sequences showed that this fungus clusters in a single clade with the two known Polylobatispora spp. with 97% bootstrap value which is sister with Pseudoprobiscisporaceae. The Polylobatispora clade is nested in the Attracrosporales, Sordariomycetes. Furthermore, in this study two known species of Polylobatispora (P. deltoidea and P. quinquecornuta) were also isolated and illustrated.

Biological control of Xanthomonas Oryzae pv. Oryzae causing rice bacterial blight disease by Streptomyces toxytricini VN08-A-12, isolated from soil and leaf-litter samples in Vietnam.

A total of 2690 actinomycete strains were screened as potential biological control agents in controlling rice bacterial blight (BB) in Vietnam. From these microorganisms, seventeen actinomycete strains were found to be capable of inhibiting all 10 major Xoo races isolated from Xoo-infected rice leaves. One strain, namely VN08-A-12, contained effective characteristics in selectively inhibiting all 10 races in vitro, but did not inhibit most of the other tested microorganisms. Therefore, VN08-A-12 was subsequently selected for rice field trials for two seasons on two rice cultivars SS1 and KD18. Results showed VN08-A-12 was not only able to reduce Xoo lesion lengths in the two rice cultivars (lesion length reduction of up to 38.3%), but it also significantly reduced Xoo-related yield loss in infected rice cultivars from the field (yield loss reduction of up to 43.2%). Interestingly, the culture of this strain also increased the rice yield in healthy rice cultivars (from 2.66% to 16.98% for SS1 and from 3.11% to 5.94% for KD18 cultivar). The strain VN08-A-12 was shown to be identical to Streptomyces toxytricini. To our knowledge, this is the first study reporting S. toxytricini as a beneficial biological agent for the control of BB in rice.

Streptomyces catbensis sp. nov., isolated from soil.

Strain VN07A0015(T) was isolated from soil collected on Cat Ba Island, Vietnam. The taxonomic position of strain VN07A0015(T) was near Streptomyces aomiensis M24DS4(T) (98.5% 16S rRNA gene sequence similarity) and Streptomyces scabrisporus NBRC 100760(T) (95.6%), and it clustered within them; however, this cluster was distant from the type strains of other species of the genus Streptomyces. The aerial mycelia of strain VN07A0015(T) were greyish and formed imperfect spiral spore chains (retinaculiaperti type) with smooth-surfaced spores. The morphological features of strain VN07A0015(T) were different from those of the type strains of S. aomiensis and S. scabrisporus. The chemotaxonomic characteristics of strain VN07A0015(T) were typical for all members of the genus Streptomyces, which possessed ll-type diaminopimelic acid, menaquinone MK-9(H6, H8) and the major fatty acids iso-C(16 : 0) and iso-C(15 : 0). DNA-DNA relatedness between strain VN07A0015(T) and S. aomiensis NBRC 106164(T) was less than 30%. In addition, some physiological and biochemical traits differed from those of S. aomiensis. Therefore, we propose that strain VN07A0015(T) be classified in the genus Streptomyces as a representative of Streptomyces catbensis sp. nov. (type strain VN07A0015(T) = VTCC-A-1889(T) = NBRC 107860(T)).

The production of ß-glucosidases by Fusarium proliferatum NBRC109045 isolated from Vietnamese forest.

Fusarium proliferatum NBRC109045 is a filamentous fungus isolated from Vietnamese forest due to high production of ß-glucosidases. Production of the enzyme was studied on varied carbon source based mediums. The highest activity was obtained in medium containing 1% corn stover + 1% wheat bran (3.31 ± 0.14 U/ml). It is interesting to note that glucose (0.69 ± 0.02 U/ml) gave higher activity and just followed by cellobiose among the di- and mono-saccharides, which is generally regarded as a universal repressor of hydrolases. We improved the zymogram method to prove that in response to various carbon sources, F. proliferatum could express various ß-glucosidases. One of the ß-glucosidases produced by F. proliferatum growing in corn stover + wheat bran based medium was partially purified and proved to have high catalytic ability.