Genetic Variations in Populations from Farms and Natural Habitats of Asian Green Mussel,Perna viridis,in Singapore Inferred from Nine Microsatellite Markers

The Asian green mussel, Perna viridis, has been widely cultured in Southeast Asia as delicious seafood depending on natural spat. We analyzed the genetic diversity and population structure of three populations (two from Singapore and one from Malaysia) from natural habitats and two from Singapore farms, by genotyping a total of 262 adult individuals using nine polymorphic microsatellites. In all five populations, high allelic (number of alleles A = 11.0–14.4,allelic richness Ar = 10.4–13.9) and gene diversity (expected heterozygosity He = 0.73–0.77) were observed, whereas deficiency of heterozygosity (inbreeding index f = 0.08–0.12) was detected in all populations. Genetic differentiation among populations was low (pairwise fixation index ranged from 0.003 to 0.088), but statistically significant. The usefulness of the information about genetic variations for genetic resource management of the populations in wild habitats and farms to keep genetic variation and setting up a breeding program of Asian green mussel was discussed.     

Rickets in alpacas (Lama paces) in New Zealand

Rickets was diagnosed in two weaner alpacas from a flock showing ill thrift and lameness during the winter of 1992. Both animals had abnormally shaped ribs with occasional healing fractures, irregular thickening of growth plates and metaphyseal haemorrhages. The mean serum phosphorus concentrations of the alpacas fell during June and July, even though lambs grazing the same pasture had normal serum phosphorus concentrations and the phosphorus concentration of the pasture was considered adequate. Vitamin D deficiency may also have contributed to the osteodystrophy. The alpacas had a thick fleece during the winter, and diurnal Vitamin D₃, synthesis resulting from solar irradiation is likely to have been minimal, especially considering the reduced sunshine hours recorded during the 1992 winter. Surviving alpacas recovered after treatment with monosodium phosphate and an oral Vitamin D supplement. It is possible alpacas are more susceptible to deficiencies of phosphorus and Vitamin D than other grazing animals in New Zealand.     

Climate influences the leaf area/sapwood area ratio in Scots pine

We tested the hypothesis that the leaf area/sapwood area ratio in Scots pine (Pinus sylvestris L.) is influenced by site differences in water vapor pressure deficit of the air (D). Two stands of the same provenance were selected, one in western Scotland and one in eastern England, so that effects resulting from age, genetic variability, density and fertility were minimized. Compared with the Scots pine trees at the cooler and wetter site in Scotland, the trees at the warmer and drier site in England produced less leaf area per unit of conducting sapwood area both at a stem height of 1.3 m and at the base of the live crown, whereas stem permeability was similar at both sites. Also, trees at the drier site had less leaf area per unit branch cross-sectional area at the branch base than trees at the wetter site. For each site, the average values for leaf area, sapwood area and permeability were used, together with values of transpiration rates at different D, to calculate average stem water potential gradients. Changes in the leaf area/sapwood area ratio acted to maintain a similar water potential gradient in the stems of trees at both sites despite climatic differences between the sites.     

Magnetic resonance imaging used for the evaluation of water presence in wood plastic composite boards exposed to exterior conditions

Abstract

Two wood plastic composite (WPC) boards, one experimental and one commercial, were exposed to exterior conditions and evaluated non-destructively using a clinical magnetic resonance imaging (MRI) unit for moisture content (MC) and distribution. The experimental board was exposed in Vancouver, British Columbia, for more than 8 years, and the commercial board was exposed near Hilo, Hawaii, for 2 years. Both boards were characterized in terms of wood content, density, water uptake properties and voids content. The experimental board was additionally destructively analysed for water absorption of the WPC and MC calculated based on the wood content for verification of MRI results. MRI detected the presence of free water and its distribution in both of the WPC boards. Fibre saturation in the experimental board was found to be about 22–24%, in comparison to 25–30% present in most wood species. There was good correlation between the detection of free water by MRI and by destructive testing. Magnetic resonance images showed various major points of water entry in the WPC boards such as the support area, the cut ends, the dripping edge and the sides of the boards. For the experimental board, significant water entry also occurred at the upper exposed surface.     

Micropropagation of mature Calabrian pine (Pinus brutia Ten.) from fascicular buds

Dormant meristems of fascicles explanted from 10-year-old, field-grown trees of Pinus brutia Ten. were cultured in vitro. Browning of cultured fascicles was reduced by including 150 mg l(-1) sodium diethyldithiocarbamate (SDD) in a cytokinin-containing medium. The stage of development of fascicles when placed in culture affected both shoot-bud production and the degree of browning. Only fascicles at an advanced stage of development had a high rate of shoot-bud production. Fascicles cultured for 6 weeks in initiation medium containing 150 mg l(-1) SDD and then for 4 weeks in initiation medium containing 1 mg l(-1) insoluble polyvinylpolypyrrolidone showed the highest rate (23%) of shoot-bud development and the lowest rate (15%) of browning. Elongation of activated shoot buds was considerably enhanced by reducing the concentration of cytokinin in the culture medium. Only shoots >/= 20 mm in height were capable of producing further crops of buds and shoots. When treated with a combination of auxin and cytokinin, only 16% of the elongated shoots produced roots.     

Selection for Pathogenicity to Strawberry in Populations of Colletotrichum gloeosporioides from Native Plants

ABSTRACT Colletotrichum gloeosporioides causes a serious crown rot of strawberry and some isolates from native plants are pathogenic to strawberry. C. gloeosporioides from lesions on wild grape and oak were sampled at two sites adjacent to commercial strawberry fields in Florida and two distant sites. Random amplified polymorphic DNA (RAPD) marker data and restriction enzyme digests of amplified rDNA were used to determine whether isolates were from the same C. gloeosporioides subgroup that infects strawberry. There were 17 to 24 native host isolates from each site that clustered with a group of strawberry crown isolates based on RAPD markers. Among strawberry isolates, there were two rDNA genotypes identified by restriction enzyme analysis. Both genotypes were present among native host isolates sampled from all four sites. There was some evidence that the different rDNA genotypes differentiated two closely related subpopulations, although the proportion of pathogenic isolates from native hosts among the two different genotypes was not different. The incidence of isolates pathogenic to strawberry was greater at sites close to strawberry fields relative to sites distant from strawberry fields for isolates with a BstUI(-)/MspI(+) rDNA genotype (44 versus 13%), a BstUI(+)/MspI(-) genotype (57 versus 16%), or when both genotypes were analyzed together (46 versus 15%). Based on these results, it appears that the C. gloeosporioides subgroup that causes crown rot on strawberry is widely distributed in Florida and that selection for pathogenicity on strawberry occurs in the area where this host is grown in abundance.     

Peri-parturient rise of Cryptosporidium oocysts in cows: New insights provided by duplex quantitative real-time PCR

In order to clarify if a peri-parturient rise of Cryptosporidium parvum oocysts occurs in cows, faecal samples from 42 cows on two farms were collected. These samples were taken during the pre-parturient, the peri-parturient and the post-parturient periods. Two methods were used to detect the oocysts, a nested-PCR coupled with sequencing and a duplex real-time PCR (qPCR) that quantified Cryptosporidium spp. DNA concentration. The qPCR results were adjusted using a hierarchical Bayesian model taking into account within and between run variation. Generalised Estimating Equation models (GEE) were used to determine if peri-parturient cows were at greater risk of being infected than pre- or post-parturient cows. Fourteen dairy cows exhibited a peri-parturient and post-parturient rise in the excretion of Cryptosporidium spp. oocysts, other than the zoonotic C. parvum. The cows in the suckler beef farm were the only ones infected with the zoonotic species C. parvum at calving. Due to the low concentration of oocysts excreted mainly from species other than C. parvum, it would appear unlikely that cows act as a source of infection for their calves or contribute significantly to environmental contamination.