Chitosan Stimulates Defense Reactions in Grapevine Leaves and Inhibits Development of Botrytis Cinerea

Chitosan (β-1,4-linked glucosamine oligomer) derived from crab shells conferred a high protection of grapevine leaves against grey mould caused by Botrytis cinerea. Under controlled conditions, it was shown to be an efficient elicitor of some defense reactions in grapevine leaves and to inhibit directly the in vitro development of B. cinerea. Treatment of grapevine leaves by chitosan led to marked induction of lipoxygenase (LOX), phenylalanine ammonia-lyase (PAL) and chitinase activities, three markers of plant defense responses. Dose-response curves show that maximum defense reactions (PAL and chitinase activities) and strong reduction of B. cinerea infection were achieved with 75–150 mg l⁻¹ chitosan. However, greater concentrations of chitosan did not protect grapevine leaves with the same efficiency, but inhibited mycelial growth in vitro. Present results underlined the potency of chitosan in inducing some defense responses in grapevine leaves which in turn might improve resistance to grey mould.     

Cytochrome P-based resistance mechanism and pyrethroid resistance in the field Anopheles albimanus resistance management trial

The relative rates of cytochrome P⁴⁵⁰ selection in southern Mexican Anopheles albimanus populations were investigated during a 3 years indoor residual house spraying intervention with a pyrethroid (PYR) or DDT, a mosaic of organophosphate (OP)-PYR, and the annual rotation of OP-PYR-carbamate (CARB). This insecticide resistance mechanism, initially evenly spread in the mosquito population, correlated with PYR resistance during the second treated year, when cytochrome P⁴⁵⁰ contents increased in most villages of the PYR, rotation and mosaic schemes. However, by the third year, mean cytochrome P⁴⁵⁰ contents declined to susceptible levels in mosquitoes of the rotation and one mosaic group but not in the PYR-treated villages. In DDT-treated villages, a continuous decrement of cytochrome P⁴⁵⁰ levels occurred since the first treatment year, and susceptible levels were observed at the end of the intervention. Most correlations of cytochrome P⁴⁵⁰ levels and PYR resistance were lost during the third year, indicating that another mechanism evolved in resistant mosquito populations.     

Distribution and retention of spermatozoa with acrosomal and nuclear abnormalities in the cow genital tract

Two experiments were conducted to evaluate the fate of sperm following uterine insemination. In Exp. I, five pairs of Holstein cows were inseminated with egg yolk-Tris extended semen (approximately 1.0 X 10(9) sperm; .5 ml) from five ejaculates from a single bull that had high levels (approximately 70%) of morphologically abnormal sperm. Cows were slaughtered 12 h after insemination. The genital tracts were removed and promptly clamped into defined regions. Sperm were recovered by flushing with 2.9% sodium citrate buffer. Proportions of abnormal sperm in the various regions were compared with those in the inseminate. Sperm numbers were also determined from each region. Regions of the tract varied in number of sperm (P less than .001), proportions of knobbed acrosomes (P less than .001), tapered heads (P less than .001), protoplasmic droplets (P less than .001), tail abnormalities (P less than .029) and total abnormalities (P less than .002). A total of 63.5 +/- 6.4 X 10(6) sperm was recovered. These sperm were distributed throughout the tract as follows: vagina, 91.8%; cervix, 5.4%; uterine horns, 2.7%, and uterotubal junctions-isthmi, .04%. No sperm were recovered from ampullae. Because retrograde movement of sperm from the uterus occurred in Exp. I, we conducted Exp. II to determine the extent of sperm loss from the genital tract following insemination. Three pairs of Holstein cows were inseminated with .42 X 10(9) sperm (.5 ml; egg yolk-Tris extender) from the same bull used in Exp. I (three ejaculates). All discharged mucus and urine was collected for 12 h after insemination for recovery of sperm. Aspirates (approximately 1 ml) of mucus from the vagina were evaluated during the 12-h post-insemination period for numbers of sperm and leucocytes. Sperm were also recovered from the tract following slaughter (approximately 12 h) to determine retention. Overall, 73 +/- 3.7% of inseminated sperm were recovered. Components were: inseminate lost from the genital tract in discharged mucus, 60 +/- 4.6%; lost in urine, .06 +/- .02%; aspirated from the vagina, 4.4 +/- 1%; adhered to equipment, 1.3 +/- .3%, and retained in the genital tract, 6.5 +/- 1.6%. Predicted numbers of sperm contained in discharged mucus 2 h post-insemination were greater (P less than .009) than at subsequent hours.(ABSTRACT TRUNCATED AT 400 WORDS)     

Utilization by growing goats of diets that contain monensin and low or excess crude protein: comparative slaughter experiment

Monensin was added at 0 or 23 mg/kg dry matter to low (8.3%) or high (17.5%) crude protein diets (2 X 2 factorial arrangement) that were fed to 28 growing wether goats for 194 to 256 d. Average daily gain increased 24% with monensin and 20% with higher crude protein (P less than .05). Feed conversion was improved by both monensin and higher crude protein (P less than .001). During the experiment, digestion and metabolism trials were conducted twice (Periods I and II) with each goat. Apparent dry matter and gross energy digestibility coefficients were not affected by monensin in either period. Digestibility of dietary N was enhanced 7% by monensin in Period II (P less than .01) and tended to be improved in Period I. Higher dietary protein increased all digestibility coefficients (P less than .001). Nitrogen retention was not affected by monensin but was greater (P less than .001) for high-protein-fed goats. Potential changes in empty body composition were assessed by comparative slaughter balance. No effects of dietary treatments on percentage composition of empty body were noted, except a trend for higher protein in monensin-fed goats compared with controls (P less than .1). Empty body protein gain as a percentage of protein intake improved 41% with monensin and decreased 37% with higher dietary protein content (P less than .05). Monensin increased conversion of dietary energy to body ether extract energy (12%, P less than .05), to protein energy (35%, P less than .001) and to total body energy (23%, P less than .001). Magnitude of improvement tended to be greater with low than high dietary protein treatments, suggesting a protein-sparing effect of monensin as determined by comparative slaughter method. However, N retention, measured by intake-excreta balances, was not affected by monensin, suggesting that these point estimates are less than adequate to evaluate true body protein gain.     

Effect of meclofenamic acid on the response of parasite-naive lambs and adult sheep to Ostertagia circumcincta

Meclofenamic acid was used to inhibit prostaglandin synthesis in lambs challenged with Ostertagia circumcincta. It lowered the number of parasites which established in treated animals but not significantly. In treated animals plasma pepsinogen values were elevated at the time of parasite emergence but had dropped below the values achieved in control lambs towards the end of the experiment when parasites were at the adult, lumenal dwelling stage. Meclofenamic acid administered to adult immune ewes during challenge with third stage O circumcincta larvae did not significantly affect the establishment of the parasites, nor did it affect the rise in pepsinogen concentration associated with the challenge.     

Interspecific and environmentally induced variation in foliar dark respiration among eighteen southeastern deciduous tree species

We measured variations in leaf dark respiration rate (Rd) and leaf nitrogen (N) across species, canopy light environment, and elevation for 18 co-occurring deciduous hardwood species in the southern Appalachian mountains of western North Carolina. Our overall objective was to estimate leaf respiration rates under typical conditions and to determine how they varied within and among species. Mean dark respiration rate at 20 degrees C (Rd,mass, micromol CO2 per kg leaf dry mass per s) for all 18 species was 7.31 micromol per kg per s. Mean Rd,mass of individual species varied from 5.17 micromol per kg per s for Quercus coccinea Muenchh. to 8.25 micromol per kg per s for Liriodendron tulipifera L. Dark respiration rate varied by leaf canopy position and was higher in leaves collected from high-light environments. When expressed on an area basis, dark respiration rate (Rd,area, micromol CO2 per kg leaf dry area per s) showed a strong linear relationship with the predictor variables leaf nitrogen (Narea, g N per square m leaf area) and leaf structure (LMA, g leaf dry mass per square m leaf area) (r squared = 0.62). This covariance was largely a result of changes in leaf structure with canopy position; smaller thicker leaves occur at upper canopy positions in high-light environments. Mass-based expression of leaf nitrogen and dark respiration rate showed that nitrogen concentration (Nmass, mg N per g leaf dry mass) was only moderately predictive of variation in Rd,mass for all leaves pooled (r squared = 0.11), within species, or among species. We found distinct elevational trends, with both Rd,mass and Nmass higher in trees originating from high-elevation, cooler growth environments. Consideration of interspecies differences, vertical gradients in canopy light environment, and elevation, may improve our ability to scale leaf respiration to the canopy in forest process models.     

Hendersonia acicola on pine needles infected by Lophodermella sulcigena

Hendersonia acicola normally infects only needles already infected, in July-August of their first year, by Lophodermella sulcigena. Secondary infection, by H. acicola, occurs at the base of the L. sulcigena lesion either in August-October of the first year (early secondary infection) or after fruiting of L. sulcigena in June-July of the second year (late secondary infection). Early secondary infection prevents fruiting of L. sulcigena. An intercellular matrix forms at the base of the L. sulcigena lesion in response to both early and late secondary infection and rapid tissue disorganisation and disintegration ensues. Secondary infection decreases with increase in height up the tree and often results in needle breakage.     

Classifying tree planters and non planters in a subsistence farming system using a discriminant analytical approach

Since the 1970s tree planting has been promoted to meet the multipurpose needs of subsistence farmers and to arrest deforestation in many developing countries. Financial support and extension systems were developed as tree growing outside the forest became more important. The limited success of the forest extension approaches used in the 1980s has been attributed to the failure to ascertain householders' priorities and attitudes to tree growing. Although the broader theoretical paradigm of factors influencing householders' planting of trees has been discussed household and regional level analyses are rare. This study used discriminant analysis to assess the extent to which social and economic factors affect smallholder farmer tree planting in Orissa, eastern India. The validity of the predictive model to define the different groups was tested by assessing the accuracy of classification. The significance of the factors was probed using the identified variables in the discriminant functions developed for smallholder farmers in the coastal and inland zones of Orissa. The results contradicted some common assumptions that only large landowners with a substantial income are innovators. The likelihood of adopting agroforestry is dependent on the progressive attitude of farmers, membership of village organisations, their wealth status and, more importantly, their perceived risk concerning agricultural production. This approach enables tree planters and non-planters to be characterised and hence give better targetting of planning and social forestry programmes.This revised version was published online in November 2005 with corrections to the Cover Date.     

Potential long-term growth gains from early clump thinning of coppice-regenerated oak stands

A study was established in the Missouri Ozarks to evaluate coppice regeneration of oak. Five years after a 32-year-old stand was clearcut and regenerated naturally through stump sprouts, the dominant sprout on each stump was identified based upon height. Treated plots were thinned to the single dominant sprout on each stump whereas control plots were not thinned. Twenty-five years later the largest 247, 371, 494, and 618 stems per ha were examined and height of the dominant sprout at age 5 was found to be strongly related to dbh at age 30 in both thinned and unthinned plots. However, in the thinned plots, the largest 494 stems per ha were on average 11%, 28%, and 58% greater, respectively, in height, dbh, and volume compared to similar dominant sprouts in unthinned plots. Logistic regression analysis was used to develop curves for the evaluation of potential gains from clump thinning. In this analysis, the average height of a stand at age 5 was used to estimate thinning gains at age 30.