Molecular markers for genotyping anastomosis groups and understanding the population biology of Rhizoctonia species

Soil-borne Rhizoctonia fungi cause serious diseases in several plant species. For the classification of these fungi, the number of nuclei in a hyphal cell and the anastomosis reaction are important criteria. Although Rhizoctonia spp. has a wide host range, the causal agents have been reported to be selective for host plant families or species and lead to severe disease. Reports of new diseases, particularly in new host plants, and severe damage in agricultural fields incurred by subdivided or newly found groups of Ceratobasidium and Waitea circinata (a varied teleomorph of Rhizoctonia) have been increasing in recent years. The food production environment is altering because of climate change, introduction of potential new host plants, and heavy use of chemicals that reduce microbial diversity. These changes favor the occurrence of new diseases incurred by undefined anastomosis groups (AGs) or subgroups of Rhizoctonia spp. On the basis of the phylogenetic relationships of AGs and subgroups in Rhizoctonia spp., molecular markers for discriminating the groups of the Rhizoctonia species complex have been developed. The application of genetic markers, in the form of microsatellites or simple sequence repeats (SSR), has become increasingly important in fungal genetics. The analyses of population genetics for Rhizoctonia spp. using SSR markers elucidated the modes of sexual and asexual reproduction, phylogeographical distributions, and global migrations associated with adaptation to agroecosystems.     

Influence of volcanic ash sediments on spore adhesion of the red alga Gelidium elegans from the coastal seabed around Miyakejima Island, Japan

The populations of red alga Gelidium elegans along the coast of Miyakejima Island were severely damaged by a volcanic eruption in 2000. The effect of this volcanic eruption has been long lasting, and populations of this red alga still have not recovered. We investigated the effect of seabed sediment particles derived from volcanic ash on the substrate adhesion of G.?elegans spores. The analysis provides evidence that increasing amounts of sediment particles result in lower adhesion rates of G.?elegans spores, and that smaller sediment particles have a greater influence on adhesion. The amount of seabed sediment particles around Miyakejima Island was 9.3?C1815.4?mg/cm². This amount has changed greatly from year to year. The adhesion rate of G.?elegans spores in water around Miyakejima Island was 0?% at all points in 2008 and 2010, but it was estimated as 6.3?C38.6?% in 2009. These results suggest that there is significant inhibition of algal spore adhesion by seabed sediment particles derived from volcanic ash around Miyakejima Island.     

Effects of spiracle-blocking insecticides and microbial insecticides on the predator mirid bug, Nesidiocoris tenuis (reuter) (heteroptera: miridae)

Spiracle-blocking insecticides and microbial insecticides are widely used for Integrated Pest Management (IPM) in Japan while Nesidiocoris tenuis is used for the control of thrips and whiteflies in Kochi Prefecture, Japan. However, the effects of the insecticides mentioned above on N. tenuis were unclear. This study investigated the effects of five spiracle-blocking insecticides and two microbial insecticides on the nymphs and adults ofN. tenuis. Propylene glycol fatty acid monoester was slightly harmful to both the nymphs and adults. Hydroxypropyl starch was slightly harmful to the nymphs, while sodium oleate was slightly harmful to the adults. Decanoyloctanoylglycerol and hydrogenated starch hydrolysate were not harmful to either the nymphs or adults. Beauveria bassiana was extremely harmful to the adults and was moderately harmful to the nymphs. Lecanicillium muscarium was slightly harmful to the adults. Therefore, decanoyloctanoylglycerol and hydrogenated starch hydrolysate can be used in combination with N. tenuis to establish an IPM program.     

Tetrodotoxin--distribution and accumulation in aquatic organisms, and cases of human intoxication

Many pufferfish of the family Tetraodontidae possess a potent neurotoxin, tetrodotoxin (TTX). In marine pufferfish species, toxicity is generally high in the liver and ovary, whereas in brackish water and freshwater species, toxicity is higher in the skin. In 1964, the toxin of the California newt was identified as TTX as well, and since then TTX has been detected in a variety of other organisms. TTX is produced primarily by marine bacteria, and pufferfish accumulate TTX via the food chain that begins with these bacteria. Consequently, pufferfish become non-toxic when they are fed TTX-free diets in an environment in which the invasion of TTX-bearing organisms is completely shut off. Although some researchers claim that the TTX of amphibians is endogenous, we believe that it also has an exogenous origin, i.e., from organisms consumed as food. TTX-bearing animals are equipped with a high tolerance to TTX, and thus retain or accumulate TTX possibly as a biologic defense substance. There have been many cases of human intoxication due to the ingestion of TTX-bearing pufferfish, mainly in Japan, China, and Taiwan, and several victims have died. Several cases of TTX intoxication due to the ingestion of small gastropods, including some lethal cases, were recently reported in China and Taiwan, revealing a serious public health issue.     

柔嫩艾美耳球虫感染对鸡盲肠中一些正常厌氧微生物菌群动态的影响

通过对鸡感染柔嫩艾美耳球虫时盲肠中常见正常厌氧微生物的变化情况进行检测研究发现:鸡在感染球虫后第7、10、14天时盲肠中类杆菌(Bacteriodes)的数量显著减少(P<005),而梭状芽孢杆菌(Clostridium)则显著增多;在球虫感染后的第7、10天时,盲肠中的消化球菌(Peptostreptocuccus)和真杆菌(Eubacterium)呈显著下降(P<005)。上述结果从一个方面阐明了柔嫩艾美耳球虫感染导致对某些其它感染抵抗力下降的机制。     

Factors influencing enhanced Salmonella typhimurium infection in Eimeria tenella-infected chickens

To investigate a possible mechanism involved in the enhancement of Salmonella typhimurium infection in chickens concurrently infected with Eimeria tenella, S typhimurium was given orally to chickens 7 days after E tenella inoculation. The number of viable S typhimurium decreased in the ceca of chickens not inoculated with E tenella, whereas the number gradually increased in the ceca of chickens inoculated with E tenella. Cecal contents were analyzed for pH value, oxidation-reduction potential, and amounts of short-chain fatty acids and bile acids. In the ceca of E tenella-inoculated chickens, the oxidation-reduction potential significantly (P less than 0.05) shifted to the oxidative phase, and the concentration of volatile fatty acids (acetic acid, propionic acid, and butyric acid) significantly (P less than 0.05) decreased. In both aerobic and anaerobic incubations, the number of viable S typhimurium in vitro decreased as the molar concentration of fatty acids increased. Experimental evidence indicated that multiplication of S typhimurium in the ceca of E tenella-inoculated chickens was associated with decreased concentrations of volatile fatty acids.     

Control of tomato bacterial wilt and root-knot diseases by Bacillus thuringiensis CR-371 and Streptomyces avermectinius NBRC14893

Ralstonia solanacearum and Meloidogyne incognita are two soilborne pathogens that cause serious damage and great losses in the production of tomato. For this purpose, a bacterial isolate, Bacillus thuringiensis CR-371, and an actinomyces isolate, Streptomyces avermectinius NBRC14893, were examined for their ability to protect tomato from root-knot nematode and bacterial wilt diseases under glasshouse conditions. Treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 followed by challenge inoculation with R. solanacearum and M. incognita significantly decreased disease severity of bacterial wilt alone, root-knot nematode alone, or mixed infection by both pathogens compared to the control. Furthermore, pretreatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 significantly reduced bacterial proliferation of R. solanacearum both in pathogen alone inoculated plants and in plants co-inoculated with R. solanacearum and M. incognita. In conclusion, our results suggest that the treatment of tomato roots with B. thuringiensis CR-371 and S. avermectinius NBRC14893 simultaneously suppresses bacterial wilt and root-knot nematode diseases. Therefore, B. thuringiensis CR-371 and S. avermectinius NBRC14893 could provide new options for integrated pest management strategies against plant diseases, especially against bacterial-nematode disease complexes that cause synergistic yield losses.     

The influence and impact of tsunamis on the microorganism assembly of Nagatsura-Ura Lagoon,Miyagi, northeastern Japan

Fisheries Science - Two sediment cores were collected from two sites in Nagatsura-Ura Lagoon, the mouth of which was destroyed in the 2011 Tohoku-oki tsunami. Although sediment conditions differed...     

Estimation of breeding values from large‐sized routine carcass data in Japanese Black cattle using Bayesian analysis

Volumes of official data sets have been increasing rapidly in the genetic evaluation using the Japanese Black routine carcass field data. Therefore, an alternative approach with smaller memory requirement to the current one using the restricted maximum likelihood (REML) and the empirical best linear unbiased prediction (EBLUP) is desired. This study applied a Bayesian analysis using Gibbs sampling (GS) to a large data set of the routine carcass field data and practically verified its validity in the estimation of breeding values. A Bayesian analysis like REML‐EBLUP was implemented, and the posterior means were calculated using every 10th sample from 90 000 of samples after 10 000 samples discarded. Moment and rank correlations between breeding values estimated by GS and REML‐EBLUP were very close to one, and the linear regression coefficients and the intercepts of the GS on the REML‐EBLUP estimates were substantially one and zero, respectively, showing a very good agreement between breeding value estimation by the current GS and the REML‐EBLUP. The current GS required only one‐sixth of the memory space with REML‐EBLUP. It is confirmed that the current GS approach with relatively small memory requirement is valid as a genetic evaluation procedure using large routine carcass data.     

Ratio of rice reflectance for estimating leaf blast severity with a multispectral radiometer

 Rice reflectance was measured to determine the spectral regions most sensitive to leaf blast infection with a multispectral radiometer. As disease severity increased, reflectance also increased in the 400–500 nm (blue), 570–700 nm (red), and 900–2000 nm regions but decreased in the 500–570 nm and 700–900 nm regions. The increased reflectance in the blue and red regions may be attributed to decreased chlorophyll and carotenoid contents in response to the blast infection. The maximum and minimum reflectance differences occurred at 680 nm and 760 nm for the nondiseased and diseased rice, respectively. The spectral location of maximum sensitivity was 675 nm regardless of disease severity. Rice reflectance ratios were evaluated as indicators of leaf blast severity. Two ratios, R550/R675 (reflectance at 550 nm divided by reflectance at 675 nm), and R570/R675 quantified the significant disease severity. These wavelengths were selected based on the sensitivity minima and maxima. The ratios of nondiseased rice plants varied depending on growth stage. The variation in ratios must be considered when they are used to estimate leaf blast severity. Received: April 2, 2002 / Accepted: August 12, 2002