Keiko T. Natsuaki

The simultaneous differentiation of Potato virus Y strains including the newly described strain PVYNTN-NW by multiplex PCR assay

New recombinant strain and genotype of PVY, designated as PVY(NTN-NW) and SYR-III, respectively, shared properties with PVY(NTN) and PVY(N)W has been reported recently. PVY(NTN-NW) predominated in potato fields in Syria and was able to induce potato tuber necrotic ringspot disease (PTNRD). Due to the rapid spread of the recombinant strains of PVY which might be the case of PVY(NTN-NW), a specific and reliable detection method is an essential step to control this strain and minimize its spread. The shared properties of PVY(NTN-NW) and SYR-III with PVY(NTN) and PVY(N)W, however, complicate their identification involving multiple detection methods. Therefore, a multiplex polymerase chain reaction (PCR), that relies on a combination of previously published and newly designed primers was developed for the detection and identification of PVY(NTN-NW) and SYR-III in single or mixed infections with the main PVY strains, PVY(O), PVY(N), PVY(NTN) and PVY(N)W. In addition, the present PCR assay was able to detect the recombination points in the P1 region enabling the differentiation of the variable genotypes of the recombinant strains PVY(NTN-NW), PVY(NTN) and PVY(N)W. The reliability of this PCR assay was confirmed using a significant number of well characterized PVY isolates collected from Syria and Japan including those of PVY(NTN-NW), SYR-III, PVY(O), NA-PVY(N), PVY(N)W and PVY(NTN).

Inhibitory influence of inorganic salts on banana postharvest pathogens and preliminary application to control crown rot

Lasiodiplodia theobromae, Thielaviopsis paradoxa, Colletotrichum musae, C. gloeosporioides, Fusarium verticillioides, and F. oxysporum were screened in vitro for sensitivity to Na2CO3, NaHCO3, CaCl2, NaCl, and NaClO. The spore germination of all pathogens was completely inhibited by Na2CO3 4 g/l, NaClO 5 g/l, and NaHCO3, CaCl2, and NaCl 6 g/l each. Dipping the bananas for 10–15 min in these concentrations reduced the incidence of crown rot (compared with the untreated fruits) 17 days after harvest in fruits treated with NaClO by 67%, with NaHCO3 by 62%, with NaCl by 38%, and with CaCl2 by 33%. Na2CO3-treated fruits had the same incidence of crown rot as untreated fruits.

Relationships between the Cryptic and Temperate Viruses of Alfalfa, Beet and White Clover

Small isometric virus particles containing double-stranded RNA have been independently reported in Europe and Japan from apparently healthy alfalfa (Medicago sativa), beet (Beta vulgaris), and white clover (Trifolium repens). They have been called cryptic viruses in Europe and temperate viruses in Japan. Serological comparison using immunoelectron microscopy, and polyacrylamide gel electrophoresis of the RNAs indicate that alfalfa cryptic and temperate viruses are the same, beet cryptic virus is probably a mixture of two different viruses, one of which is similar to or the same as beet temperate virus, and white clover temperate virus is a mixture of at least three different viruses, two of them indistinguishable from white clover cryptic viruses 1 and 2, respectively, and the third very likely the same as white clover cryptic virus 3.

Characterization and genetic status of Banana bunchy top virus isolated from Okinawa, Japan

Isolates of Banana bunchy top virus (BBTV), which causes bunchy top disease in bananas, were collected in field surveys on seven islands in Okinawa Prefecture, Japan. From 44 banana samples, one isolate from each island was selected, and the DNA-1 and DNA-3 components were sequenced. Analysis of the major common region of DNA-1 showed that BBTV in Okinawa belongs to the Asian group of BBTV. DNA-1 and DNA-3 analysis revealed that Okinawan BBTV had a closer relationship with isolates from Taiwan and the Philippines than with some isolates from China and Vietnam. All the Okinawan BBTV isolates had high homology in the nucleotide sequences of DNA-1 and DNA-3 (%) because of a single, recent BBTV invasion of this area.

The Occurrence of Potato Viruses in Syria and the Molecular Detection and Characterization of Syrian Potato virus S Isolates

Potato virus Y (PVY) is the main potato virus in Syria but no information is available on the prevalence of other potato viruses. A survey was conducted by ELISA using specific antibodies to nine potato viruses. PVY, Potato virus S (PVS), Cucumber mosaic virus and Potato leafroll virus were detected with infection rates of 54.2, 8.4, 3.7 and 0.9%, respectively. The overall virus infection rate was as high as 72.9% in ware potato fields. A preliminary characterization was carried out on PVS isolates. Syrian PVS isolates infected Chenopodium amaranticolor only locally and therefore were classified as PVSO. Phylogenetic analysis of the coat protein gene showed that PVS comprised two main clusters, cluster-O and cluster-A, which contained the ordinary and Andean strains respectively. Cluster-O was separated into two subclusters, O1 and O2. Two Syrian PVS isolates, PVS3-5 and PVS6-2, fell into the O1 subcluster. PVS3-5 coat protein, however, shared the highest nucleotide identity with European isolates of the O1 subcluster, whereas PVS6-2 was closely related to Asian isolates of the same subcluster. Owing to the high incidence of PVY and PVS in Syria, a duplex reverse-transcription PCR was developed to detect these two viruses in a single PCR.

Characterization of Two Viruses Isolated from Patchouli in Japan

Two sap-transmissible viruses were isolated from patchouli (Pogostemon patchouli) in Japan. The virus source plants showed faint mosaic, mottling, or no symptoms. In electron microscopic examinations, however, elongated (760 nm in length) or spherical (27 nm in diameter) viruslike particles were found. The spherical virus, designated patchouli mild mosaic virus (PaMMV), infected plants in seven families and was found to be serologically related to, but different from, broad bean wilt virus. The elongated virus, named patchouli mottle virus (PaMoV), had a narrower host range and was identified as a member of the Potyviridae on the basis of particle morphology, formation of cytoplasmic inclusions, and a distant serological relationship with turnip mosaic potyvirus

New canker diseases of Abies veitchii and Acer crataegifolium caused by Neonectria castaneicola

New perennial canker diseases of Abies veitchii and Acer crataegifolium are described. Pathogenicity of the causal fungus was confirmed on stems of young Abies and Acer trees using two monoascospore isolates from the perithecia from the two tree species. The causal fungus, producing Nectria-state-teleomorph and Cylindrocarpon-anamorph, was identified as Nectria castaneicola. It was then transferred to the genus Neonectria, as N. castaneicola (W. Yamam. et Oyasu) Tak. Kobay. et Hirooka, comb. nov. followed by the recent concept of Nectriaceae.

The aerial and fruit surface populations of fungi in nonchemical banana production in the Philippines

The fungal population in the air and on developing fruit on a nonchemical banana farm in the Philippines was estimated from January 1998 to December 2001 to follow the source, determine the origin, and establish the population dynamics of various fungi associated with postharvest diseases of banana. Forty fungal genera were found in the air on a nonchemical banana farm and 26 were found on developing fruit. Spore density in the air and on the surface of developing fruit varied with seasonal patterns. Fungi of various species were detected on the farm and on developing banana fruit, but it has not been established as to when a specific fungus arrived at the farm and on the fruit. The results suggest that the source and origin of fungi associated with postharvest diseases of banana fruit in Japan imported from the Philippines were the farm itself, and the fungal association with banana fruit began at flower emergence.

Neonectria amamiensis and Cylindrocarpon amamiense, a new nectrioid fungus and its sporodochial anamorph on Pinus luchuensis from Japan

A new nectrioid fungus with its sporodochial Cylindrocarpon anamorph, collected on dead bark of Luchu pines (Pinus luchuensis) in the southern part of Japan (Kagoshima and Okinawa), having perithecia slightly constricted just below the papilla and conidia with a strongly hooked and acute apical cell, belongs to the genus Neonectria according to the recent concept of the Nectriaceae (Hypocreales). Molecular phylogenetic analysis based on the tub2 region of β-tubulin genes also supports the morphological consideration. This fungus is described as Neonectria amamiensis (anamorph: Cylindrocarpon amamiense).

Cylindrocladium brown leaf spot on Howea belmoreana caused by Calonectria ilicicola (anamorph: Cylindrocladium parasiticum) in Japan

Brown leaf spot disease caused by Cylindrocladium was found on Howea belmoreana on Hachijojima Island, Tokyo, Japan, in December 2001. Typical symptoms were incited after artificial inoculation. A culture of white mycelia, isolated from leaf spot symptoms, produced reddish perithecia of a nectriaceous fungus. Based on morphological and molecular analyses, this fungus was identified as Calonectria ilicicola (anamorph: Cylindrocladium parasiticum). Pathogenicity of this fungus on five plants cultivated on Hachijojima Island was confirmed by artificial inoculation. This report is the first on Cylindrocladium brown leaf spot of H. belmoreana caused by C. ilicicola (anamorph: Cy. parasiticum).