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To study the precise mechanisms underlying the chlorosis caused by plant viruses, we previously established a synchronous experimental system using transgenic plants expressing Cauliflower mosaic virus multifunctional protein, Tav (transactivator/viroplasmin), under the control of an artificially inducible promoter. Shortly after the induction of Tav expression, pathogenesis-related protein (PR) 1a gene expression is upregulated in the transgenic tobacco lines, which show visible chlorosis within a week. The present study showed that the expression of Tav also induces some salicylic acid (SA)- and ethylene-responsive PR genes. In contrast to transiently expressed Tav, which suppressed Agrobacterium-induced and SA-induced PR1a expression, the artificial induction of Tav from the transgene did not affect SA-induced PR1a expression, rather it alone induced PR1a expression. In a deletion analysis, chlorosis and PR1a induction function in transgenic tobacco were mapped to a region in Tav that had been shown to have a role in pathogenesis in a susceptible host, elicitation of the hypersensitive response in a resistant host, suppression of RNA silencing, and the suppression of Tomato bushy stunt virus P19-mediated cell death in tobacco. The results suggest that Tav-induced chlorosis results from a host response, which accompanies PR1a induction, to pathogenic function of Tav.

Phylogenetic analysis of sugarcane rusts based on sequences of ITS and the 5.8 S rDNA revealed two highly divergent ITS groups among isolates of Puccinia sp. sensu Muta, 1987 and P. kuehnii specimens. Although there is sufficient divergence (exceeding normal intraspecific variation) between the ITS regions of the two groups to support separation into different species, unusually high homology of the ITS group I sequences with those of members of Cronartium and identical sequences of the D1/D2 regions of the LSU rDNA for all the isolates of “Puccinia sp.” and P. kuehnii that otherwise exhibited different ITS sequences, suggest that the two highly divergent sequences may have resulted from abnormal genetic events leading to non-orthologous, intraspeciflc polymorphisms. The other sugarcane rust, P. melanocephala and the grass rusts, P. miscanthi and P. rufipes, were separated from “Puccinia sp.” and P. kuehnii and from each other in D1/D2 region analyses, indicating that D1/D2 region sequences may more correctly reflect phylogenetic relationships in these rusts than do the ITS regions. Further studies to examine differences in patho-genicity or finer morphological features within P. kuehnii that may be correlated with the high divergence in ITS sequences and experiments to determine if these two sequence types represent intraspeciflc polymorphism are necessary.

When an elicitor is applied to plants to induce resistance, one of the first detectable events is the efflux of ions from the treated tissue. Here we are the first to demonstrate that an elicitor from Mycosphaerella pinodes evokes leakage of Na+ and K+ ions from isolated cell walls of pea and cowpea in vitro, as observed for epicotyl tissues. Pharmacological experiments showed that this elicitor-stimulated leakage was sensitive to vanadate and N-(3-methylphenyl)biphenyl-4-sulfonamide (NGXT-191), that inhibit a cell wall-associated ATPase (apyrase). Vanadate or NGXT-191 suppressed elicitor-induced superoxide generation and expression of defense genes in vivo. On the basis of these results, we assume that the leakage of these ions, probably associated with an ATP-dependent process(es) in the cell wall, is likely associated with induced defenses of pea and cowpea.

Leaf spots were found on Christmas rose (Helleborus niger) in Yamagata Prefecture, Japan, in October 2006. The morphology of the causal fungus was very close to that of Colletotrichum truncatum. Classifying the species from the sequences of the internal transcribed spacer regions of ribosomal DNA was inconclusive, and the isolates were identified only as Colletotrichum sp. Artificial inoculation confirmed the pathogenicity of isolates to the host plant and some legumes. We propose the name anthracnose of Christmas rose for this disease by Colletotrichum sp.

Morphological and molecular analyses of 25 actinomycete isolates from five commercial earthworm castings in Thailand indicated that all isolates belonged to the genus Streptomyces. From primary screens of spore suspensions and culture filtrates of the isolates for in vitro effects on egg hatch and juvenile mortality of Meloidogyne incognita, 12 isolates that gave significant control of M. incognita were confirmed to reduce root penetration by M. incognita in a secondary screen using green bean. The 12 isolates were also evaluated for their efficiency against root-knot disease on chili in the greenhouse. Streptomyces sp. KPS-E004 reduced the egg hatch rate the most (by 55.8 % using spores, 62.4 % using culture filtrate) and increased the juvenile mortality rate the most (by 63.9 % with spores, 73.9 % with culture filtrate). In the secondary screen, all infective second-stage juveniles of M. incognita treated for 72 h with a spore suspension of KPS-E004 lost the ability to penetrate plant roots. Moreover, this strain had the highest root-knot disease control efficiency on chili (71.2 %). Thus, Streptomyces sp. KPS-E004 has potential as a biocontrol agent to control root-knot disease in organic and sustainable agricultural systems.

Since the first report of the tobamovirus tomato brown rugose fruit virus (ToBRFV) in 2014, it has become globally distributed. Its rapid spread has been primarily attributed to seed-borne transmission. Here, the seed-borne nature of ToBRFV transmission was investigated in different cultivars of tomato, bell pepper, and eggplant. In situ hybridization to localize the virus in reproductive organs of ToBRFV-infected tomato plants revealed that the virus was not present in shoot apices, flower buds, or in ovules during flower opening, indicating the virus may be restricted to the outer integument and transported in the vascular bundles during seed development. However, during early fruit development, the virus was present in the integuments in the ovule. Seeds of tomato cultivars with or without tobamovirus resistance gene Tm-22 transmitted the virus to the progeny seedlings at rates that reflected the ineffectiveness of the gene against ToBRFV. Seeds of bell peppers transmitted ToBRFV at higher rates than tomato seeds, but a bell pepper cultivar that has resistance gene L3 was not systemically infected, and its seeds did not harbor the virus. Three eggplant cultivars were systemically infected with ToBRFV but without showing any obvious symptoms, and even though ToBRFV was present in their seeds, the seedlings were not infected. ToBRFV was detected in the seed coats of contaminated tomato and bell pepper seeds, but not in eggplant seed coats. These results indicate mechanistic differences in seed-borne transmission among the three Solanaceae crops.

In July 2003, a new disease occurred on leaves of highbush blueberry (Vaccinium corymbossum L.) in Iwate, Japan. Leaves initially had brownish spots, which subsequently developed into large lesions with concentric rings, resulting in premature defoliation. Teardrop-shaped conidia infecting leaves were visible by the naked eye as small protuberances in the center of lesions. Star-shaped conidia were sporadically produced on large lesions. The causal fungus was identified as Valdensinia heterodoxa, based on cultural, morphological and genetic studies. Inoculation tests showed that the fungus reproduced lesions on detached young leaves of highbush blueberry. A field survey in 2009 indicated that symptoms initially appeared on the lower leaves of basal shoots in late May, and the disease rapidly progressed on leaves of basal shoots, eventually spreading to lateral shoots from late June to late July. Removal of all basal shoots in late June significantly reduced disease incidence on lateral shoots in late July.