First report of rust caused by Puccinia paullula on Monstera deliciosa and M. adansonii in Japan.

Monstera deliciosa Liebm. and M. adansonii Schott. (Araceae) have been cultivated for the commercial production in Hachijo Island, Tokyo, Japan, since the 1950s. A rust disease producing uredinial sori was found on the leaves of M. deliciosa and M. adansonii in the fields on Hachijo Island in February 2021. Symptoms were first observed on the leaf surfaces as small chlorotic spots, which expanded and became brown to reddish-brown, and produced uredinia with abundant urediniospores. The disease occurred on the whole island including the farm land, symptom incidence ranged from 5 to 30%. To confirm the pathogenicity of this rust fungus, ten plant species of Araceae (M. deliciosa, M. adansonii, Alocasia macrorrhizos, Anthurium andreauum, Dieffenbachia maculata, Epipremnum mirabile, E. pinnatum, Philodendron scandens, Spathiphyllum sp., Syngonium podophyllum) were inoculated with urediniospores obtained from infected samples on M. deliciosa and M. adansonii. Urediniospores were suspended in distilled water (1 × 106 conidia/ml) and sprayed on healthy plants. The inoculated plants were kept in a dark chamber at about 25°C for 48 h, and then transferred to a greenhouse. After 40 days, uredinia were reproduced only on M. deliciosa and M. adansonii. Morphological characteristics of the urediniospores obtained from inoculated monstera plants matched those obtained from the field plants and used as inoculum, thus fulfilling Koch's postulates. No symptoms were observed on the other plant species inoculated. For identification of the rust fungus, dry specimens obtained from both naturally infected plants and inoculated plants were used for morphological observations. Urediniospores with pedicels emerging from the stomata were densely aggregated, globose, and 24.8-29.3 µm (n = 30). Their walls were brown, echinulate, and 1.4-2.2 µm thick. Telia were found in the specimens collected in July and August. The teliospores with pedicels emerging from the stomata were two-celled, ellipsoid, and 21.3-27.5 × 19.5-23.4 µm. Their walls were pale yellow, smooth, and 1.0-1.9 µm thick. Morphological differences among the specimens on M. deliciosa and M. adansonii were not observed. These morphological characteristics were consistent with the description of P. paullula (Sydow and Sydow 1913). For molecular identification, the large subunit (LSU) rDNA and cytochrome oxidase III (cox3) were amplified. LRust1R, LR3, and LR5 (Vilgalys and Hester 1990) primers were used for sequencing of LSU region. Cox3_F (5'-GTTCAGTATGTTATTTTAACG-3') and cox3_R (5'-ATAGGAATAGTCAAACAACATC-3') primers were constructed here based on the P. paullula sequences (KX999927) for the cox3 region. The sequences were deposited in the GenBank as accession numbers OK509070, OK509071, LC663719 and LC663720. BLAST analysis showed that LSU and cox3 sequences shared 98.8% (902/913 nts) and 100% (632/632 nts) identities with P. paullula, KX999886 and KX999927 (Marin-Felix et al. 2017). This is the first report of a rust disease of M. deliciosa and M. adansonii caused by P. paululla in Japan. The rust fungi has been reported as the pathogen on the species of Amorphophallus, Rhaphidophora and Monstera (Sydow and Sydow 1913, Shaw 1991, Chen et al. 2009). The occurrence of this disease should be monitored because it can reduced yield and commercial value of monstera plants. All the specimens used in the experiments were deposited in the National Museum of Nature and Science, Japan (TNS-F82068-82077).

Globisporangium oryzicola sp. nov., causing poor seedling establishment of directly seeded rice.

A new species, Globisporangium oryzicola, was isolated from directly seeded rice seedlings, and from soils of paddy fields and an uncultivated field. Despite their different origins, five of the seven isolates studied caused poor seedling establishment of rice in a laboratory inoculation experiment. The species is characterized by oogonia with smooth-walled or sometimes one projection, with one to two antheridia, and aplerotic oospores. Hyphal swellings were rarely observed. Phylogenetic analyses based on the internal transcribed spacer region of the ribosomal RNA gene and mitochondrial cytochrome c oxidase subunit 1 and 2 genes confirmed that the species differed from other Globisporangium species. This novel species is described and illustrated in detail.

Rice Bran Amendment Suppresses Potato Common Scab by Increasing Antagonistic Bacterial Community Levels in the Rhizosphere.

Potato common scab (PCS), caused by pathogenic Streptomyces spp., is a serious disease in potato production worldwide. Cultural practices, such as optimizing the soil pH and irrigation, are recommended but it is often difficult to establish stable disease reductions using these methods. Traditionally, local farmers in southwest Japan have amended soils with rice bran (RB) to suppress PCS. However, the scientific mechanism underlying disease suppression by RB has not been elucidated. The present study showed that RB amendment reduced PCS by repressing the pathogenic Streptomyces population in young tubers. Amplicon sequencing analyses of 16S ribosomal RNA genes from the rhizosphere microbiome revealed that RB amendment dramatically changed bacterial composition and led to an increase in the relative abundance of gram-positive bacteria such as Streptomyces spp., and this was negatively correlated with PCS disease severity. Most actinomycete isolates derived from the RB-amended soil showed antagonistic activity against pathogenic Streptomyces scabiei and S. turgidiscabies on R2A medium. Some of the Streptomyces isolates suppressed PCS when they were inoculated onto potato plants in a field experiment. These results suggest that RB amendment increases the levels of antagonistic bacteria against PCS pathogens in the potato rhizosphere.

Four new Pythium species from aquatic environments in Japan.

Four new species of Pythium s.str., namely Pythium utonaiense, Pythium brachiatum, Pythium biforme and Pythium junctum, were described based on their morphology and molecular phylogeny. These species were isolated from freshwater samples collected from aquatic environments (pond and lake) in Japan. They were identified as belonging to the genus Pythium s.str. by their morphology, such as filamentous hyphal inflated structures, and molecular phylogenetic analyses based on the internal transcribed spacer region of the ribosomal RNA gene and mitochondrial cytochrome c oxidase subunit 1 gene. The new species are compared to closely related Pythium species regarding their phylogenetic positions and morphological features.

NIASGBdb: NIAS Genebank databases for genetic resources and plant disease information.

The National Institute of Agrobiological Sciences (NIAS) is implementing the NIAS Genebank Project for conservation and promotion of agrobiological genetic resources to contribute to the development and utilization of agriculture and agricultural products. The project's databases (NIASGBdb; http://www.gene.affrc.go.jp/databases_en.php) consist of a genetic resource database and a plant diseases database, linked by a web retrieval database. The genetic resources database has plant and microorganism search systems to provide information on research materials, including passport and evaluation data for genetic resources with the desired properties. To facilitate genetic diversity research, several NIAS Core Collections have been developed. The NIAS Rice (Oryza sativa) Core Collection of Japanese Landraces contains information on simple sequence repeat (SSR) polymorphisms. SSR marker information for azuki bean (Vigna angularis) and black gram (V. mungo) and DNA sequence data from some selected Japanese strains of the genus Fusarium are also available. A database of plant diseases in Japan has been developed based on the listing of common names of plant diseases compiled by the Phytopathological Society of Japan. Relevant plant and microorganism genetic resources are associated with the plant disease names by the web retrieval database and can be obtained from the NIAS Genebank for research or educational purposes.

De novo sequence assembly of Albugo candida reveals a small genome relative to other biotrophic oomycetes.

BACKGROUND: Albugo candida is a biotrophic oomycete that parasitizes various species of Brassicaceae, causing a disease (white blister rust) with remarkable convergence in behaviour to unrelated rusts of basidiomycete fungi. RESULTS: A recent genome analysis of the oomycete Hyaloperonospora arabidopsidis suggests that a reduction in the number of genes encoding secreted pathogenicity proteins, enzymes for assimilation of inorganic nitrogen and sulphur represent a genomic signature for the evolution of obligate biotrophy. Here, we report a draft reference genome of a major crop pathogen Albugo candida (another obligate biotrophic oomycete) with an estimated genome of 45.3 Mb. This is very similar to the genome size of a necrotrophic oomycete Pythium ultimum (43 Mb) but less than half that of H. arabidopsidis (99 Mb). Sequencing of A. candida transcripts from infected host tissue and zoosporangia combined with genome-wide annotation revealed 15,824 predicted genes. Most of the predicted genes lack significant similarity with sequences from other oomycetes. Most intriguingly, A. candida appears to have a much smaller repertoire of pathogenicity-related proteins than H. arabidopsidis including genes that encode RXLR effector proteins, CRINKLER-like genes, and elicitins. Necrosis and Ethylene inducing Peptides were not detected in the genome of A. candida. Putative orthologs of tat-C, a component of the twin arginine translocase system, were identified from multiple oomycete genera along with proteins containing putative tat-secretion signal peptides. CONCLUSION: Albugo candida has a comparatively small genome amongst oomycetes, retains motility of sporangial inoculum, and harbours a much smaller repertoire of candidate effectors than was recently reported for H. arabidopsidis. This minimal gene repertoire could indicate a lack of expansion, rather than a reduction, in the number of genes that signify the evolution of biotrophy in oomycetes.

Draft Genome Sequences of the Oomycete Pilasporangium apinafurcum Strains JCM 30513 and JCM 30514, Formerly Classified as Pythium apinafurcum.

Pilasporangium apinafurcum, formerly classified as Pythium apinafurcum, is a unique oomycete that infects plants asymptomatically. Here, we present the draft genome sequences of two variants of P. apinafurcum, JCM 30513 and JCM 30514, isolated from uncultivated field soil in Wakayama Prefecture, Japan.

TMV-Gate vectors: gateway compatible tobacco mosaic virus based expression vectors for functional analysis of proteins.

Plant viral expression vectors are advantageous for high-throughput functional characterization studies of genes due to their capability for rapid, high-level transient expression of proteins. We have constructed a series of tobacco mosaic virus (TMV) based vectors that are compatible with Gateway technology to enable rapid assembly of expression constructs and exploitation of ORFeome collections. In addition to the potential of producing recombinant protein at grams per kilogram FW of leaf tissue, these vectors facilitate either N- or C-terminal fusions to a broad series of epitope tag(s) and fluorescent proteins. We demonstrate the utility of these vectors in affinity purification, immunodetection and subcellular localisation studies. We also apply the vectors to characterize protein-protein interactions and demonstrate their utility in screening plant pathogen effectors. Given its broad utility in defining protein properties, this vector series will serve as a useful resource to expedite gene characterization efforts.