Evaluation of fecal samples from mares as a source of Rhodococcus equi for their foals by use of quantitative bacteriologic culture and colony immunoblot analyses

OBJECTIVE: To determine whether mares are a clinically important source of Rhodococcus equi for their foals. SAMPLE POPULATION: 171 mares and 171 foals from a farm in Kentucky (evaluated during 2004 and 2005). PROCEDURES: At 4 time points (2 before and 2 after parturition), the total concentration of R equi and concentration of virulent R equi were determined in fecal specimens from mares by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively. These concentrations for mares of foals that developed R equi-associated pneumonia and for mares with unaffected foals were compared. Data for each year were analyzed separately. RESULTS: R equi-associated pneumonia developed in 53 of 171 (31%) foals. Fecal shedding of virulent R equi was detected in at least 1 time point for every mare; bacteriologic culture results were positive for 62 of 171 (36%) mares at all time points. However, compared with dams of unaffected foals, fecal concentrations of total or virulent R equi in dams of foals with R equi-associated pneumonia were not significantly different. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that dams of foals with R equi-associated pneumonia did not shed more R equi in feces than dams of unaffected foals; therefore, R equi infection in foals was not associated with comparatively greater fecal shedding by their dams. However, detection of virulent R equi in the feces of all mares during at least 1 time point suggests that mares can be an important source of R equi for the surrounding environment.     

Acidic soil conditions suppress zoospore release from zoosporangia in <Emphasis Type="Italic">Olpidium virulentus</Emphasis>

Lettuce big-vein disease, caused by Mirafiori lettuce big-vein virus and Lettuce big-vein associated virus, is suppressed when the pH of field soil becomes acidic. Therefore, we evaluated the effect of soil pH on the activities of Olpidium virulentus, the vector of the viruses. We found that acidic soil, pH less than 6.0, significantly reduced O. virulentus infection of the root and influenced the detection rate of zoospores released in the surrounding water. We concluded that acidic soil suppresses zoospore release from zoosporangia.     

Biochemical,physiological, and molecular characterization of <Emphasis Type="Italic">Dickeya dianthicola</Emphasis> (formerly named <Emphasis Type="Italic"> Erwinia chrysanthemi</Emphasis>) causing potato blackleg disease in Japan

The taxonomic assignment of Japanese potato blackleg isolates of Dickeya spp. has not been confirmed after the changes in their former name, Erwinia chrysanthemi. Therefore, we investigated and identified 23 representative isolates of Dickeya spp. from symptomatic stems of potatoes in Japan, with biochemical tests and phylogenetic sequence analysis using recA, dnaX, rpoD, gyrB, and 16S rDNA sequences. Results of our biochemical tests showed that all isolates can be assigned to phenon 5 and biovar 1, which are associated with D. dianthicola. Based on the recA, dnaX, rpoD, gyrB, and 16S rDNA sequences, all isolates are in the same clade with D. dianthicola and were clearly distinguished from D. chrysanthemi, D. dadantii, D. dadantii subsp. dieffenbachiae, D. solani, D. zeae, and D. paradisiaca. Therefore, we conclude that Dickeya spp. isolated from potatoes with blackleg symptoms in Japan are D. dianthicola.     

Water supply from pearl millet by hydraulic lift can mitigate drought stress and improve productivity of rice by the close mixed planting

The authors have proposed the close mixed planting technique using mixed seedlings of two different crop species that results in close tangling of their root systems. Especially, the combination of drought-adaptive upland crops (e.g. pearl millet or sorghum) and flood-adaptive lowland crop of rice would be beneficial to overcome the drought and flood conditions and to reduce the risks of crop failure. In our previous studies, we found that upland crop yield losses by flood stress was mitigated by mix-cropped rice, owing to the oxygen gas released from the rice roots into the aqueous rhizosphere. In the present study, we conducted two experiments to assess whether mixed cropping a drought-resistant cereal, pearl millet, would improve the performance of co-growing drought-susceptible crop, rice under drought conditions. In the field experiment, some grains were obtained from the rice plants mix-cropped with pearl millet under drought condition. However, no rice matured in the single cropping system. In the model experiment using deuterium analysis, it was confirmed that water absorbed by pearl millet roots from deep soil layer was utilized by rice, suggesting that mix-cropped rice could withstand drought stress and complete grain filling using water released into the upper soil layer by hydraulic lift.     

Furosemide loading test in a case of homozygous solute carrier family 12, member 1 (SLC12A1) mutation (g.62382825G>A,p.Pro372Leu) in Japanese Black cattle

Hydrallantois is the excessive accumulation of fluid in the allantoic cavity in a pregnant animal and is associated with fetal death. We recently identified a recessive missense mutation in the solute carrier family 12, member 1 (SLC 12A1 ) gene (g.62382825G>A, p.Pro372Leu) that is associated with hydrallantois in Japanese Black cattle. Unexpectedly, we found a case of the homozygous risk‐allele for SLC 12A1 in a calf, using a PCR ‐based direct DNA sequencing test. The homozygote was outwardly healthy up to 3 months of age and the mother did not exhibit any clinical symptoms of hydrallantois. In order to validate these observations, we performed confirmation tests for the genotype and a diuretic loading test using furosemide, which inhibits the transporter activity of the SLC 12A1 protein. The results showed that the calf was really homozygous for the risk‐allele. In the homozygous calf, administration of furosemide did not alter urinary Na⁺ or Cl^? levels, in contrast to the heterozygote and wild‐type calves in which these were significantly increased. These results demonstrate that the SLC 12A1 (g.62382825G>A, p.Pro372Leu) is a hypomorphic or loss‐of‐function mutation and the hydrallantois with this mutation shows incomplete penetrance in Japanese Black cattle.     

Nitrogen promotes water consumption in seedlings of Cryptomeria japonica but not in Chamaecyparis obtusa

To evaluate the influence of excessive N deposition on the water consumption of a Japanese plantation forest, 1-year-old seedlings of major plantation trees, Cryptomeria japonica (Japanese cedar) and Chamaecyparis obtusa (Hinoki cypress), were treated with combinations of two N levels (Moderate N and High N) and two soil water conditions (Dry and Moist) for 4 months. The High N treatment received five times as much N as in the Moderate N treatment; the total amount of N added in the High N treatment was roughly 25 times the annual N deposition in precipitation. An increase in soil N availability increased the needle transpiration rate, needle biomass, and needle N content of C. japonica under the Moist treatment, whereas those of C. obtusa were not significantly affected by soil N treatment at either soil water level. Needle N content in C. japonica was positively related to needle photosynthetic rate and transpiration rate. Our results suggested that excessive N deposition has the potential to enhance water consumption in C. japonica stands on moist soils. However, the effects of increased N deposition would be insignificant for C. japonica grown on dry sites. Unlike in C. japonica, water consumption in C. obtusa would be unlikely to respond to excess N deposition, regardless of the soil moisture level. Moreover, the significant reduction in the fine root to needle ratio observed with excessive N application in C. japonica under both Dry and Moist treatments suggests that excessive N deposition is likely to cancel out the tree's morphological adaptation to drought.     

Bacterial antagonists and their cell-free cultures efficiently suppress canker disease in citrus lime

Journal of Plant Diseases and Protection - Proliferation of citrus canker disease caused by Xanthomonas citri subsp. citri (Xcc) has increasingly become a serious threat and has resulted in a...     

The influence of rearing density on stress response and disease susceptibility of ayu (Plecoglossus altivelis)

The impact of coldwater disease caused by Flavobacterium psychrophilum is a recent important problem in the farming of ayu (Plecoglossus altivelis). We hypothesized that stress from high-rearing densities predisposes fish to disease by reducing their immunocompetence, and we sought to reduce fish losses by introducing an alternative culture regime. Fish enclosed at three densities (1250 fish or 8.0 kg, 400 fish or 2.6 kg and 100 fish or 0.6 kg/m³) were examined. Fish in the high-density treatment exhibited more elevated serum cortisol concentrations and more suppressed serum immunoglobulin M (IgM) concentrations accompanied by higher mortality, possibly caused by coldwater disease, than those in the medium- and low-density treatments. These results indicate that high-rearing densities stress fish and evoke subsequent physiological responses which have maladaptive effects. We propose that coldwater disease may be prevented by improving the disease resistance of fish by using moderate stocking densities.