Juveniles of threadsail filefish, <Emphasis Type="Italic">Stephanolepis cirrhifer</Emphasis>, can survive and grow by feeding on moon jellyfish <Emphasis Type="Italic">Aurelia aurita</Emphasis>

We conducted feeding experiments on threadsail filefish Stephanolepis cirrhifer juveniles for 16 days to evaluate the efficacy of moon jellyfish Aurelia aurita as a prey item. Four treatments, each with 40 individuals, were prepared to compare fish growth performance. The treatments consisted of filefish that were starved (control) (S), fed only jellyfish (J), fed only krill (K), and fed both jellyfish and krill (JK). Fish in the S treatment exhibited a 50% mortality rate and reduced body weight, whereas the J treatment exhibited a zero mortality rate and increased body weight. Fish in the JK treatments showed a significantly faster growth than those in the K treatment. Filefish consumed as much as 24 and 13 times their own body weight in jellyfish per day in the J and JK treatments, respectively. This is the first report showing that growth can be sustained by feeding a marine fish only jellyfish, and indicates the potential of jellyfish as a fish prey in both nature and captivity.     

Value-per-recruit analysis of bighand thornyhead <Emphasis Type="Italic">Sebastolobus macrochir</Emphasis> caught off the Pacific coast of northern Honshu,Japan

The yield-per-recruit (YPR) analysis has been used to assess growth overfishing of exploited fish stocks. Since the ex-vessel price per weight widely depends on the size of the fish, the result of the YPR does not imply the revenue. The value-per-recruit (VPR) analysis, which is an economic expansion of the YPR analysis, was conducted for bighand thornyhead Sebastolobus macrochir caught off the Pacific coast of northern Honshu, Japan. The results showed that, for the current age at first capture (t _c = 3), the current fishing mortality (F = 0.12) was close to the optimum level. However, for the current F, optimum t _c in the VPR model was 8 years and would lead to a 47% increase compared to the current revenue. The maximum YPR was obtained at t _c = 6 years, but the revenue at t _c = 6 only gave a 20% increase in the maximum revenue. The difference was caused by the size dependency of the ex-vessel price per weight. The VPR model would generate fisheries management plans with both economical and biological consideration and would help in making general consensus of fisheries management strategies.     

Amberjack <Emphasis Type="Italic">Seriola dumerili</Emphasis> interleukin-10 negatively suppresses host cell-mediated immunity

Interleukin-10 (IL-10) is an anti-inflammatory cytokine and negatively regulates cell-mediated immunity (CMI) induction by inhibiting cytokine production in type 1 T helper cells. IL-10 genes have been isolated from several fish, and inflammatory cytokine inhibition by IL-10 has been well examined. However, a CMI regulator of IL-10 in fish has not yet been identified. In this study, we cloned the IL-10 gene in amberjack Seriola dumerili and analyzed its function using its recombinant protein (rIL-10). In an in vitro culture experiment, gene expression of inflammatory cytokines was suppressed in leukocytes incubated with rIL-10 compared with cells that only received Nocardia seriolae stimulation. This result suggests amberjack IL-10 has conserved function as an inflammatory cytokine inhibitor. Bactericidal activity of amberjack cells against intracellular pathogen stimulation was decreased in a rIL-10 dose-dependent manner. Furthermore, a significant reduction in the T-bet/GATA-3 ratio was observed in N. seriolae living cell (LC)?+?rIL-10-injected fish. Taken together, these results suggest amberjack rIL-10 suppresses CMI induction both in vitro and in vivo. In addition, the number of IgM⁺ cells among spleen leukocytes in N. seriolae?+?rIL-10-injected fish was higher than in only N. seriolae LC, suggesting that Th2-dominant immunity was induced by adding rIL-10.     

A putative RNA silencing component protein FoQde-2 is involved in virulence of the tomato wilt fungus <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">lycopersici</Emphasis>

RNA silencing pathways in filamentous fungi are composed of multiple component proteins and known to be involved in vegetative growth, virulence or sexual reproduction. We found that the tomato wilt fungus, Fusarium oxysporum f. sp. lycopersici (Fol), carries four homologues genes of Qde-2, an argonaute protein gene and one of the main component protein genes in Neurospora crassa. Gene targeting revealed that FoQde-2, one of the Qde-2 homologues in Fol, is involved in virulence to tomato but not in vegetative growth.     

Breeding efforts to mitigate damage by heat stress to spikelet sterility and grain quality

Global warming is predicted to aggravate the risk of unstable crop production. It is of great concern that damage to rice spikelet sterility and grain quality will increase, resulting in yield and economic losses. To secure the global food supply and farmers’ income, the development of rice cultivars with heat resilience is a pressing concern. Regarding spikelet sterility, rice cultivars with heat tolerance at different growth stages have been identified in recent years. The early-morning flowering (EMF) trait is effective in heat escape because it shifts the time of day of flowering to earlier in the morning when it is cooler. Although varietal differences are very small, there are some genetic resources for EMF in wild rice accessions. Regarding heat-induced grain chalkiness, heat-tolerant japonica cultivars for mitigating white-back type of chalky grains (WBCG) were found. Quantitative trait loci for heat tolerance at flowering, EMF, and for WBCG in grain quality have been mapped on the rice chromosomes. Further genetic efforts have been successfully connected to the development of near-isogenic lines for each trait with tagged molecular markers. These breeding materials are quite unique and useful in facilitating marker-assisted breeding toward the development of heat-resilient rice in terms of spikelet sterility and grain quality.     

Two new species,Phytophthora nagaii sp. nov. and P. fragariaefolia sp. nov., causing serious diseases on rose and strawberry plants,respectively, in Japan

A new disease of rose was noticed in Chiba Prefecture of Japan in 1968, and the pathogen was initially identified as Phytophthora megasperma based on morphological characteristics. Similar Phytophthora isolates have since been collected from rose plants in Chiba, Kanagawa, and Shizuoka Prefectures. In 2005, several Phytophthora isolates were recovered from crowns of strawberry plants in Hokkaido Prefecture. These were considered to be members of a new species. In this study, we re-examined all these isolates using morphological and physiological studies and a multilocus phylogenetic analysis. The rose and strawberry isolates were mostly similar morphologically and physiologically, with some exceptions. The rose isolates differed significantly from P. megasperma sensu stricto and other related Phytophthora species. The rose and strawberry isolates had external proliferation of sporangia, characteristic funnel-shaped oogonia, predominantly paragynous antheridia, and fast growth rates of 10.5 mm/24 h at an optimum temperature of 28 °C. In the multilocus phylogenetic tree constructed using sequences from the rDNA ITS regions, rDNA LSU, and the translation elongation factor 1-α, β-tubulin and coxI genes, they formed a distinct monophyletic group in clade 7 with strong bootstrap support. The rose and strawberry isolates separated into two distinct groups. The results indicate that the rose and strawberry isolates constitute two separate species, designated here as Phytophthora nagaii and P. fragariaefolia.     

Mechanism of the rice hull‐induced germination of Monochoria vaginalis seeds in darkness

The seeds of Monochoria vaginalis require light to germinate. However, they are able to germinate in darkness in the presence of rice hulls. The mechanism of this phenomenon was investigated in this study, in which only the unsterilized seeds of Monochoria were induced to germinate by the presence of a rice hull extract. The rice hull extract was able to be replaced by either a mixture of amino acids and phosphate or a yeast extract. The culture media in which germination was observed always showed turbidity, indicating the propagation of bacteria, which were identified as Bacillus sp., Pedobacter sp., Pantoea sp. and Sphingomonas sp. Treatment with the individual bacterial species or combinations of these bacteria induced Monochoria seed germination when added to the media containing the rice hull extract. It was concluded that the rice hull extract accelerates the propagation of bacteria, which in turn digest the seed coat of Monochoria, facilitating its germination.     

Experimental evidence of a pathogenic change caused by homologous recombination between endogenous and introduced dysfunctional Avr-Pita genes in Pyricularia oryzae

To provide experimental evidence that somatic homologous recombination (HR) is involved in the instability and diversification of the avirulence gene Avr-Pita in Pyricularia oryzae, we generated a dysfunctional Avr-Pita homolog and integrated it into strain Hoku-1 containing Avr-Pita. In the transformants, the occurrence of somatic HR events between Avr-Pita and the dysfunctional homolog was confirmed by PCR–RFLP. Germlings from conidia from the HR-positive transformants had lost the avirulence function, which enabled it to infect rice cultivar Yashiromochi containing the corresponding resistant gene Pi-ta. These results suggested that genetic mutation caused by somatic HR is one of the mechanisms responsible for virulence diversity.     

Bacterial leaf blight of sweet pepper (Capsicum annuum) caused by Pseudomonas cichorii in Japan

Sweet peppers (cv. Tosajishi beauty) with leaf blight symptoms were observed in Kochi Prefecture, 2003. Initially, small spots formed on leaves, and later enlarged to brown to dark brown spots, and eventually blighted leaves fell. Several bacteria that caused the same symptoms were isolated and subsequently reisolated. These bacteria were identified as Pseudomonas cichorii on the basis of bacterial characteristics and the 16S rRNA gene sequence. This is the first report of bacterial leaf blight in the sweet pepper in the world.