Amphibian virology.

Amphibians are a diverse group of species; much work remains to be done to elucidate the viruses of amphibians. Viral diseases may play an important role in wild and captive amphibian populations. Iridoviruses are a leading cause of wild amphibian mortality events in the United States and are a common cause of amphibian mortality events worldwide. In addition to frank viral diseases, viral infections may play a role in the establishment of bacterial, fungal, and parasitic diseases and are an underlying cause of neoplasia. It is important for the amphibian clinician to recognize disease syndromes and pathology that are consistent with viral etiology.     

Lymphoid follicular cloacal inflammation associated with a novel herpesvirus in juvenile alligators (Alligator mississippiensis).

Multifocal hyperemic nodules and plaques associated with the cloacal mucosa of juvenile alligators (Alligator mississippiensis) at a public aquarium were investigated. Grossly, pale pink to dark red multifocal, circular lesions of varying degrees of severity were identified on the cloacal and, in males, phallus mucosa. Cloacal mucosa biopsies were obtained from 2 of the alligators. These samples were examined histologically and by polymerase chain reaction (PCR) using consensus primers targeting a conserved region of the herpesvirus polymerase gene. Microscopically, the lesions were characterized as submucosal lymphoid follicles with hyperemia and hemorrhage. No inclusion bodies were observed. Minimal to no anisokaryosis was present, and no etiologic agents were identified. Through PCR, a band consistent in size with herpesvirus was observed. Tissues showing similar clinical, histopathologic, and PCR findings were collected from animals at an alligator farm several months later. Sequencing of the PCR amplicon resulted in a 180-base pair sequence that shared 85% sequence identity with tortoise herpesvirus-1.     

Dissemination of Information About Management Strategies and Changes in Farming Practices for the Exploitation of Resistance to Leptosphaeria maculans (Phoma Stem Canker) in Oilseed Rape Cultivars

The management of phoma stem canker (blackleg disease, caused by Leptosphaeria maculans) is an integral component of oilseed rape production. In this paper, we discuss the information about management strategies that is disseminated in Europe and Australia. New cultivars have been introduced with improved resistance to disease, but sometimes this resistance has been overcome as new races of the pathogen have emerged. When cultivars with single major gene resistance have been introduced into areas with high inoculum concentrations, significant economic damage has been caused by new races of L. maculans within 2–3 years. Quantitative or polygenic resistance has also been used successfully against stem canker and offers more durable disease resistance if plant breeders and farmers deploy this resistance more effectively. Strategies to improve the durability of resistance need to be developed and tested in practice. New information on the occurrence of virulence and avirulence genes in populations of Leptosphaeria maculans and modelling of the durability of resistance provide opportunities for plant breeders, specialist technical organisations, cooperatives, advisory services and farmers to collaborate and better exploit cultivar resistance. Changing economic and environmental factors influence cropping practices and, if to be considered successful, management strategies must show clear financial benefits. Technology transfer will need to address all aspects of managing stem canker and other diseases of oilseed rape and using effective written, verbal and electronic methods of communication.     

Effects of temperature on germination and hyphal growth from conidia of Ramularia rhei and Ascochyta rhei, causing spot diseases of rhubarb (Rheum rhaponticum)

Rhubarb leaf and petiole spot disease, caused by Ramularia rhei and Ascochyta rhei , has gradually become more noticeable in the UK field crop. Conidial germination and subsequent colony growth of R. rhei and A. rhei were investigated under in vitro conditions on potato dextrose agar and in vivo on leaf discs. Results indicated that the two fungi responded differently to temperature. Ramularia rhei was better adapted to temperatures ≤ 25°C, with an optimum around 20°C, whereas A. rhei was more adapted to temperatures ≥ 15°C, with an optimum > 25°C. Overall, conidia of R. rhei germinated and subsequent colonies grew at greater rates than those of A. rhei on leaf discs at temperatures ≤ 25°C. These results indicated that it is important to identify the causal agent of leaf and petiole spot diseases in rhubarb field crops in order to estimate disease risks accurately.     

Population structure of Solanum carolinense along the Takano River in Kyoto, Japan as determined by amplified fragment length polymorphism analysis

Areas infested with Solanum carolinense, an introduced perennial weed, have increased quickly in Japan. The genetic structure of a S. carolinense population along the Takano River in Kyoto, Japan was investigated using amplified fragment length polymorphism (AFLP) analysis to reveal how introductions and local spread have contributed to the development of this population. Along a terrace beside the river and an adjacent roadside, we defined a cluster of above‐ground shoots in the population as a subpopulation and 60 subpopulations were identified. Seventeen of these were selected and 165 shoots were analyzed by AFLP analysis using three primer pairs. The AFLP profiles revealed 69 genotypes and the presence of several clones, i.e. genotypes that were present in more than one individual. In total, 19 clones, comprising 2–34 identical genotypes, could be identified in the population. Each of these clones, except one, was allocated within each of the subpopulations. Clustering of the subpopulations was supported by high bootstrap values in all cases. Therefore, introductions from distant regions have mainly contributed to the development of this population, and local spread by seed or vegetative reproduction has rarely been important. The most likely introduction route of S. carolinense to this population was via planting associated with construction works.     

Magneto-opto-electronic bistability in a phenalenyl-based neutral radical

A new organic molecular conductor, based on a spiro-biphenalenyl neutral radical, simultaneously exhibits bistability in three physical channels: electrical, optical, and magnetic. In the paramagnetic state, the unpaired electrons are located in the exterior phenalenyl units of the dimer, whereas in the diamagnetic state the electrons migrate to the interior phenalenyl units and spin pair as a pi-dimer. Against all expectations, the conductivity increases by two orders of magnitude in the diamagnetic state, and the band gap decreases. This type of multifunctional material has the potential to be used as the basis for new types of electronic devices, where multiple physical channels are used for writing, reading, and transferring information.     

In vitro gas production measurements to evaluate interactions between untreated and chemically treated rice straws, grass hay, and mulberry leaves

In vitro gas production was measured to investigate associative effects of untreated and chemically treated rice straw (RS) and of RS and grass hay or mulberry leaves (ML). The RS was treated with NaOH, urea, or (NH4)HCO3. Cumulative gas production was recorded at 2, 4, 6, 8, 12, 16, 24, 36, 48, 60, 72, and 96 h of incubation, and the Gompertz function was used to describe the kinetics of gas production. Treatment with NaOH, urea, and NH4HCO3 increased (P < 0.05) gas production at 48 h by 55, 52, and 37% and the maximum rate of gas production of RS from 0.64 to 1.51, 1.27, and 1.13 mL/h, respectively. The inclusion of treated straws, hay, and ML in a mixture with RS at increasing proportions (25, 50, 75, 100%) elevated cumulative gas production and its rate. Maximum gas production was not different between the RS and its mixtures with the treated straws, but inclusion of hay into RS or NH4HCO3-treated RS increased the maximum gas production. Associative effects were defined as the difference between the observed gas production for the mixtures and the sum of the individual component feeds. The NaOH-treated RS, included at higher proportions, had positive associative effects at all times of incubation < 96 h; effects were negative or absent at 96 h. No effects were observed with mixtures of RS with urea-treated RS. The NH4HCO3-treated RS mixture tended to have negative associative effects at all three levels. Positive associative effects (P < 0.05) were observed for both RS and NH4HCO3-treated RS at almost all inclusion levels of hay or ML after 12 to 96 h of incubation. The response was more pronounced with ML than with hay. Associative effects generally declined with duration of incubation. We conclude that positive associative effects on in vitro gas production occurred more consistently when RS was incubated in mixtures with hay or ML than when incubated in mixtures with chemically treated RS.     

Heterozygosity for genes influencing a quantitative trait

Choosing families to sample for a quantitative trait locus mapping experiment is a critical component of experimental design because only heterozygous families contribute information to the analysis. Additive genetic variance of a paternal half-sib family can be partitioned into two parts: a variance component of maternal source that is constant across different families and a variance component of paternal source that is defined as an index of heterozygosity of a sire. This index is shown to be an upper limit of variance among marker genotypes of a half-sib family and can be used to identify highly heterozygous sires, thus improving the power of detecting QTL in detection studies. Simulated progeny phenotypic data were used to estimate sire's heterozygosity index via an ANOVA method, and accuracy of the estimation was evaluated with the correlation coefficient between the true and estimated index summarized both as the correlation and by the correct ranking of results as measured by the ratio of the true average heterozygosity index of experimentally selected parents to average heterozygosity of all sires. Positive but small correlation can be achieved in the estimation of a sire's heterozygosity when based on the daughters' phenotypic data, and accuracy was improved when progeny-tested sons were used to estimate their grandsire's heterozygosity index, depending on the genetic model of a trait and the size and structure of families.     

The effect of lean growth rate on puberty attainment in gilts

Two hundred sixteen prepubertal Genex Manor hybrid F1 gilts were used to determine the impact of lean growth rate on sexual development of gilts. This study was composed of two experiments (Exp. 1 and Exp. 2). In Exp. 1, at approximately 96 d of age and 54 kg weight, gilts were allocated with respect to growth rate and litter origin to one of two dietary treatments: 1) a diet formulated to maximize lean growth potential (LP; n = 84) or 2) a diet formulated to produce a lower lean growth rate (LL; n = 84). In Exp. 2, at approximately 88 d of age and 50 kg weight, gilts were allocated with respect to growth rate and litter origin to one of two dietary treatments: 1) a diet formulated to maximize lean growth potential (LP; n = 24) or 2) a diet formulated to restrict lean growth further than was achieved in LL in Exp. 1 (RL; n = 24). All gilts were fed treatment diets for ad libitum consumption and housed in groups of six. Weight, backfat depth and loin depth, and feed intake were measured weekly. Starting at 135 d of age, gilts received 20 min of direct daily exposure to a boar as a pen group for pubertal stimulation. Puberty attainment was determined as the day gilts first exhibited the standing reflex in response to contact with a boar. At pubertal estrus, body weight, backfat depth, and loin depths were recorded. Diet affected (P < or = 0.05) estimated fat-free lean gain (LP, 424 vs LL, 347 g/d, Exp. 1; LP, 397 vs RL, 376 g/d, Exp. 2) during the growth period (start to stimulation). However, age at puberty was not affected by diet (LP, 157.3 vs LL, 157.6, Exp. 1; LP, 166.7 vs RL, 167.3, Exp. 2) or overall lean growth at stimulation (P > or = 0.05 in both experiments), confirming that innate variability in sexual development of commercial genotypes, rather than growth performance, determines onset of sexual maturity. A negative correlation between age at puberty and growth rate from 50 kg until puberty (P < or = 0.05) (LP, r = -0.40, LL, r = -0.36, Exp. 1; LP, r = -0.64, RL, r = -0.48, Exp. 2) was a consequence of reduced lean tissue growth during the stimulation period in later-maturing gilts.