The role of the seed tuber in determining partial resistance to potato blackleg caused byErwinia spp.

In 1991 and 1992, 12 potato cultivars were screened at two locations for resistance to blackleg, after vacuum infiltration of the seed withErwinia carotovora subsp.atroseptica orE. chrysanthemi. Cultivar differences for resistance toE.c. subsp.Atroseptica andE. chrysanthemi were found which were consistent over locations and years. Seed tubers of the same cultivars were also screened for resistance to bothErwinia spp. by using a tuber slice inoculation method. Correlation coefficients for comparisons between resistance to blackleg in the field and tuber tissue resistance under aerobic or anaerobic conditions were not significant. This could partly be explained by drastic changes in relative tuber tissue resistance of the cultivars within a 5 weeks period after planting in the field. Presprouting of seed tubers in diffuse daylight had a less pronounced effect on relative tuber tissue resistance than planting in the field. Monitoring the process of mother tuber decay during the growing season of 1993 after vacuum infiltration withE.c. subsp.atroseptica andE. chrysanthemi revealed that cultivars differed in the extent to which these bacteria enhanced the process of mother tuber decay. These differences partly explained the cultivar differences for resistance to blackleg in the field.Abbreviations Eca Erwinia carotovora subsp.atroseptica - Ech Erwinia chrysanthemi - NOP Noordoostpolder - Wag Wageningen     

EX VIVO COMPUTED TOMOGRAPHIC EVALUATION OF MORPHOLOGY VARIATIONS IN EQUINE CERVICAL VERTEBRAE

Diagnostic imaging is one of the pillars in the clinical workup of horses with clinical signs of cervical spinal disease. An improved awareness of morphologic variations in equine cervical vertebrae would be helpful for interpreting findings. The aim of this anatomic study was to describe CT variations in left–right symmetry and morphology of the cervical and cervicothoracic vertebrae in a sample of horses. Postmortem CT examinations of the cervical spine for horses without congenital growth disorders were prospectively and retrospectively recruited. A total of 78 horses (27 foals, 51 mature horses) were evaluated. Twenty‐six horses (33.3%) had homologous changes in which a transposition of the caudal part of the transverse process (caudal ventral tubercle) of C6 toward the ventral aspect of the transverse process of C7 was present (n = 10 bilateral, n = 12 unilateral left‐sided, n = 4 unilateral right‐sided). There was one horse with occipito‐atlantal malformation, two horses with rudimentary first ribs bilaterally, and one horse with bilateral transverse processes at Th1, representing homeotic (transitional) vertebral changes. Chi‐square tests identified no significant differences in the number of conformational variations between the group of mature horses with or without clinical signs (P = 0.81) or between the group of mature horses and the group of foals (P = 0.72). Findings indicated that, in this sample of horses, the most frequently identified variations were homologous variations (transposition of the caudal part of the transverse process of C6–C7) in the caudal equine cervical vertebral column. Homeotic (transitional) variations at the cervicothoracic vertebral column were less common.     

Clinical experiences of treating septic arthritis in the equine by repeated joint lavage: a series of 39 cases

The condition of septic arthritis was treated in 12 foals with 21 affected joints (Group I) and in 27 adult horses. The adult horses were divided into three groups, based on aetiology of the condition: haematogenous (Group II, n = 6), iatrogenic (Group III, n = 6), and perforating trauma (Group IV, n = 15). The treatment consisted of an initial systemic antibiotic that anticipated the microbial agents that were considered most likely per group, repeated through-and-through joint lavages every other day and non-steroidal anti-inflammatory drugs. The antibiotics were adjusted to the results of bacteriological culture and susceptibility tests. Joint lavages were continued until the white blood cell count dropped below 15 G/l and bacteriological culture was negative, after which a single dose of a short-acting corticosteroid was administered intra-articularly. Joint recovery rate in group I was 71%. Patient recovery rate of the foals, however, was lower (42%). Three foals were killed for reasons other than arthritis; one foal because of an arthritis-related problem and three foals because of persistent arthritis. Overall joint recovery rate, equalling patient recovery rate, in the adult horses was 81%. The expected predominance of Streptococcus spp. in haematogenous arthritis in adult horses was not confirmed, indicating that in these cases also, an initial antibiotic treatment with a broad-spectrum combination is preferable. It is concluded that with intensive treatment, the prognosis of septic arthritis in the adult horse can be classified as fair to even good. Results in the foals are not as good, but this seems to be more due to the specific problems surrounding the equine neonate than to unresponsiveness to the treatment.     

A critical assessment of a desk study comparing crop production systems: The example of the ‘system of rice intensification’ versus ‘best management practice’

When assessing hypotheses, the possibility and consequences of false-positive conclusions should be considered along with the avoidance of false-negative ones. A recent assessment of the system of rice intensification (SRI) by McDonald et al. [McDonald, A.J., Hobbs, P.R., Riha, S.J., 2006. Does the system of rice intensification outperform conventional best management? A synopsis of the empirical record. Field Crops Res. 96, 31–36] provides a good example where this was not done as it was preoccupied with avoiding false-positives only. It concluded, based on a desk study using secondary data assembled selectively from diverse sources and with a 95% level of confidence, that ‘best management practices’ (BMPs) on average produce 11% higher rice yields than SRI methods, and that, therefore, SRI has little to offer beyond what is already known by scientists.     

The inheritance of chemical phenotype in <Emphasis Type="Italic">Cannabis</Emphasis><Emphasis Type="Italic">sativa</Emphasis> L. (IV): cannabinoid-free plants

A genetic factor that blocks the cannabinoid biosynthesis in Cannabis sativa has been investigated. Crosses between cannabinoid-free material and high content, pharmaceutical clones were performed. F₁s were uniform and had cannabinoid contents much lower than the mean parental value. Inbred F₂ progenies segregated into discrete groups: a cannabinoid-free chemotype, a chemotype with relatively low cannabinoid content and one with relatively high content, in a monogenic 1:2:1 ratio. In our model the cannabinoid knockout factor is indicated as a recessive allele o, situated at locus O, which segregates independently from previously presented chemotype loci. The genotype o/o underlies the cannabinoid-free chemotype, O/o is expressed as an intermediate, low content chemotype, and O/O is the genotype of the high content chemotype. The data suggests that locus O governs a reaction in the pathway towards the phenolic cannabinoid precursors. The composition of terpenoids and various other compound classes of cannabinoid-free segregants remains unaffected. Backcrossing produced cannabinoid-free homologues of pharmaceutical production clones with potential applications in pharmacological research. A new variant of the previously presented allele ‘B ₀’, that almost completely obstructs the conversion of CBG into CBD, was also selected from the source population of the cannabinoid knockout factor.     

Variation in performance of western flower thrips populations on a susceptible and a partially resistant chrysanthemum cultivar

Variation in host plant performance among populations of a phytophagous insect pest is a potential threat to the durability of host plant resistance. Aggressive biotypes may overcome the protective properties of formerly resistant cultivars. Therefore, it is of interest to study such variation in breeding programs for host plant resistance to insects. In the present study, the performance of ten populations of Frankliniella occidentalis, the western flower thrips, was determined on a susceptible and a partially resistant cultivar of chrysanthemum, Dendranthema grandiflora. Damage, reproduction, and adult survival were determined using an excised leaf assay. Significant differences between the two cultivars and among the ten populations were found for all three characteristics. In general, damage, reproduction and adult survival were reduced on the resistant cultivar when compared to the susceptible cultivar. Some populations showed, in comparison to the reference population from the Netherlands, much higher damage and reproduction on one or both chrysanthemum cultivars. But also in these populations performance on the resistant cultivar was poor compared to the susceptible cultivar. This revised version was published online in August 2006 with corrections to the Cover Date.     

Dietary Inclusion of Wheat Bran Arabinoxylooligosaccharides Induces Beneficial Nutritional Effects in Chickens

In vivo experiments were conducted to verify whether arabinoxylooligosaccharides (AXOS) obtained as low molecular mass compounds by enzymic hydrolysis from wheat bran arabinoxylan (AX) can exert nutritional effects. Two feeding trials were performed on chickens fed diets with either wheat or maize as the main component. Supplementation of bran AXOS at either 0.5% (w/w) to the wheat‐based diet or at 0.25% (w/w) to the maize‐based diet diets significantly (P < 0.05) improved the feed conversion rate without increasing the body weight of the animals, thus pointing to improved nutrient utilization efficiency. The positive effect of bran AXOS supplementation on feed utilization efficiency was similar to that obtained by adding an AX‐degrading xylanase directly to the wheat‐based diet. No significant effect on feed utilization efficiency was obtained with another type of nondigestible oligosaccharide such as fructooligosaccharides (FOS) derived from chicory roots. Bran AXOS significantly increased the level of bifidobacteria but not total bacteria in the caeca of the chickens, an effect not observed with either xylanase or FOS addition. These data suggest that bran AXOS have beneficial nutritional effects and may act as prebiotics.     

Species-dependent effects of habitat degradation in relation to seasonal distribution of migratory waterfowl in the East Asian–Australasian Flyway

Landscape Ecology - Migratory species’ resilience to landscape changes depends on spatial patterns of habitat degradation in relation to their migratory movements, such as the distance...     

Aluminium toxicity with sorghum genotypes in nutrient solutions and its amelioration by magnesium

Effects of Al toxicity and interaction of Al and Mg on growth of twelve sorghum (Sorghum bicolor (L.) Moench) genotypes have been studied in nutrient solutions (pH 4.2). Aluminium at 30 μM decreased biomass (dry matter yield) of the individual genotypes by factors between 1.27 and 7.36, with identical sensitivity grouping of genotypes as obtained in an earlier pot experiment with an acid soil. Resembling acid-soil stress, Al toxicity was simultaneously expressed in two independent ways, i.e. impairment of root development and induced Mg deficiency. The effect of Al on total dry matter production of the genotypes was correlated more closely with changes in specific root length (m g⁻¹ dry root) than with changes in internal Mg status. Increased Mg concentrations in the solutions (2.5 and 7.5 instead of 0.25 mM) not only decreased Al-induced Mg deficiency but also reduced the concentrations of Al in/on the roots and its damaging effect on root development. Therefore, the sorghum genotypes were less sensitive to Al at the higher Mg levels. At a high Mg concentration in the solution (7.5 mM) dry matter yield of two genotypes was even stimulated by Al.