Stem Damage Research Articles

Economic value production of trees as a criterion of their maturity in an uneven-aged forest

Abstract Tree maturity of the four main tree species that are most frequent in the uneven-aged forests of the Western Carpathians was analysed. The maturity was determined on the base of the economic value production in relation to tree diameter. We derived mean timber values of spruce, fir, pine, and beech trees (€ m−3) depending on their diameters, quality and stem damage, and in the case of beech also depending on tree age. The assortment structure was calculated using the models of tree assortment tables that account for the stated tree parameters. The assortment prices were taken from the price list of logs in assortment and diameter classes of the Forests of the Slovak Republic, state enterprise, for the year 2016. Trees are mature when their mean timber monetary value is at maximum. Results show, that the highest mean value production of the majority of beech trees of average and above-average stem quality is 70 - 80 € m−3 for trees with diameters between 45 and 55 cm. Monetary values of spruce and fir trees with diameters above 60 to 90 cm are 80 - 95 € m−3, while the monetary values of pine trees with the same diameters are approximately 70 - 115 € m−3. The value production of trees is reduced if the stems are of worse quality or damaged, but in the case of beech it also decreases with greater diameter or tree age.

The Performance of Mixed Manufacturer Metal On Metal Total Hip Replacements

Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components may not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints. The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem were no different to levels published for manufacturer matched joints and in many cases were lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to -0.116, Adept-CPT: 0.101 to -0.056) were within the range of other studies and manufacturer matched clearances (0.134 to -0.149).Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints.

Biology of stem borer, Euzophera perticella (Lepidoptera: Pyralidae) and association of endoparasitoid Pristomerus euzopherae (Hymenoptera:Ichneumonidae) in grafted and ratoon brinjal crop

The present study envisages the bionomics of brinjal stem borer, Euzophera perticella on eggplant and occurrence of its prominent endoparasitoid, Pristomerus euzopherae under Varanasi, Uttar Pradesh condition. Affected plants can easily be visualized by their appearance as light yellow in colour, completely drooped, withered and wilted with stunted growth, reduced plant vigour, lowered fruit bearing capacity and detected in patches across the plot. Damage is more severe in near maturing, ratoon and grafted brinjal crop. Its incidence was observed from the second fortnight of February onwards (13.5% stem damage) which increased gradually with 29.75, 51.5, 76.5 and 89.7% stem damage during March, April, May and June, respectively and where almost all the plants were affected by this borer during July. Oviposition, incubation, larval and pupal periods of E. perticella ranged from 4-11, 3-9, 29-47 and 7-14 days, respectively, whereas adult longevity were 4-8 days for male and 5-13 days for females. An Ichneumonid endoparasitoid, Pristomerus euzopherae was recorded associated with this stem borer. Incidence of this parasitoid was noted during second fortnight of April (1.91% parasitization) with highest parasitization (12.48%) during July followed by June (7.73%).

Stem damages caused by heart rot and large poplar borer on hybrid and European aspen

Abstract Solid wood production of hybrid aspen requires relative longer rotation periods, thus increasing risk of wood damages by pests and diseases. We compared damages by heart rot and poplar borer of 48 years old hybrid (Populus tremuloides Michx. × P. tremula L.) and European aspen in a progeny trial located in Eastern part of Latvia. Trees were harvested and rot patches and galleries were recorded and measured at a stump level. The number of galleries had positive relation on number of patches and total area of rot. The susceptibility of the rot and poplar borer was similar for both hybrid and European aspen. Yet, some differences among families were detected. No effect of pathogens damage was observed on the tree growth. Larger trees had smaller proportion and incidence of rot and galleries per unit of area as well as wider outer rot-free wood layer.

Growth and cold hardening of European aspen seedlings in response to an altered temperature and soil moisture regime

During the autumn, plants undergo a physiological process of cold hardening to limit damage caused by the low temperatures of winter. Under a warming climate, plants may be less cold hardened and hence more susceptible to the effects of a sudden temperature drop. During the growth season of 2010–2011, growth and cold hardening of European aspen (Populus tremula L.) seedlings from native wild populations were examined under ambient and projected climate scenarios in greenhouses at the Haapastensyrjä research station in Southern Finland. Using locally obtained seedlings, we manipulated temperature and soil moisture during the normal growth period and then subjected them to an artificial freezing treatment during September–November 2010. At the end of the experiment, we determined seedling height, survival and the extent of stem damage, and analysed their variation with mixed effect models.Among the treatments tested, temperature was the main factor affecting survival, cold hardening, and frost damage to seedlings. The higher temperature (4°C increase) of the 2100 future climate regime was associated with a 35% decrease in seedling survival (from 66 to 31%) during the growing period. Increased irrigation had a positive, but considerably weaker effect on seedling survival (improved survival by ca. 8%). Height of seedlings after the first growth season was enhanced by increased soil moisture and temperature, but these effects were negated the following spring by increased frost damage caused by warmer growth conditions. Although cold hardiness increased as the season progressed, increase of temperature by 1 and 4°C severely diminished it, and survival after the freezing dropped from 55% (control) to 48% and 14%, while stem damage increased from 58% (control) to 90% and 96%, respectively. These results suggest that regeneration of north European aspen might become burdened in a warmer climate. Although survival was clearly affected, several seedlings grown under the future climate regimes survived freezing and overwintered with negligible damage, suggesting an adaptive capacity of the local population. The intraspecific competition that occurred as a side effect of the experimental setup also affected cold hardening, suggesting that stand structure might be managed to improve the resilience of aspen to frost damage.

English

The African elephant (Loxodonta africana Blumenbach) is a keystone species and ecosystem engineer. Elephants can cause serious damage to important trees, with only certain species being targeted such as Marula (Sclerocarya birrea A. Rich. Hoscht). High levels of elephant utilization may to some extent, compromise the viability of some woody plant populations leading to vegetation changes coupled with a possible loss of species diversity and/or structural diversity. In order to quantify their effect a study was initiated in 2014 to investigate their effect on tree height, degree of branch damage, the extent of debarking, and degree of stem damage. This was done within elephant’s frequently and non–frequently used sites, and a neighbouring enclosure (control site). One hundred and fifty (50 per site) mature S. birrea trees were randomly selected within each site. Tree height was recorded using clinometers, degree of branch damage, extent of debarking (circumference debarked using different percentages of intensity) and degree of stem damage were assessed using different categories. Results indicated that the type elephant damage in both the frequently and non–frequently used sites was different, varied in intensity. A high proportion of Marula trees had been damaged. The size distributions of the trees showed that there was no regeneration. Furthermore, this study also demonstrated that elephants are able to damage Marula trees in several ways, the most destructive being bark stripping and pushing over trees. It is concluded that elephant impact is a powerful mechanism in shaping the structure and composition of Marula woodlands in the Atherstone Collaborative Nature Reserve. The findings of this study provide valuable baseline data and acts as a starting point for the introduction of adaptive management principles in small savanna reserves. This can be achieved by an intensive management programme responding to slight changes in the vegetation and would necessarily involve controlling elephant numbers.   Key words: Crown diameter, damage, elephant, herbivory, marula.

The effect of surface fire on tree ring growth of Pinus radiata trees

Pinus radiata trees showed significantly reduced basal area increments and increased latewood/earlywood ratios, when their stem was charred by surface fires even if no needle damage occurred. An interaction of fire damage and precipitation on growth was observed. Heat from forest fires is able to penetrate beyond the bark layer and damage or completely kill a tree’s cambium. Short-term growth reductions following surface fires have been reported for some species. However, most studies have in common that they describe a compound effect of stem and foliage damage. This study investigated the impact of surface fires on the radial growth of Pinus radiata, where only the stem of trees was charred, while no needle damage was recorded. Tree ring measurements were performed on cores obtained at breast height. Analysis of variance and tests, based on annual basal area increment values were calculated to quantify pre- and post-fire growth differences of tree ring width and latewood/earlywood ratios. The analysis revealed significant growth reductions following a surface fire on P. radiata in the year on which the fire occurred as well as in the following year. As a consequence of the fire, basal area increment and latewood/earlywood ratios were significantly reduced. An interaction of fire damage and precipitation on growth was observed. The obtained results show how fires without crown damage can affect growth and tree ring structure of P. radiata trees and indicate that stem char could be associated with a significant decrease in ring width and latewood/earlywood ratio.

Etiology and management of Fusarium crown and root rot (Fusarium oxysporum) on greenhouse pepper in Ontario, Canada

Infection of greenhouse pepper plants (Capsicum annuum L.) by Fusarium oxysporum was observed in two commercial operations in Ontario, causing plant death and yield losses. The pathogen was identified based on cultural, morphological and pathogenicity tests supplemented by PCR amplification of TEF primers. Following inoculation, symptoms of mild stunting occurred within 5–6 weeks, followed by more severe stunting later. Other symptoms, such as chlorosis, wilting and necrosis of the lower foliage, did not become readily evident until about 60 days after inoculation. At 77 days after inoculation, there was considerable brown-black discolouration and decay of crown tissue but little internal stem discolouration or damage beyond the crown portion was observed. Roots were dark brown to black, severely decayed, and easily separated from the surrounding rock wool medium. The fungus was not pathogenic to greenhouse tomato, cucumber or eggplant, nor to field crops such as bean, chickpea or zucchini squash. There were no significant differences in virulence among isolates but differences in resistance/susceptibility among pepper cultivars were observed. The fungicides Medallion® (fludioxonil) and Senator® (thiophanate-methyl) were as effective as bio-control products Mycostop® (Streptomyces griseoviridis) and Prestop® (Gliocladium catenulatum) in limiting Fusarium crown and root rot in greenhouse pepper. Aspects of an integrated disease management strategy are discussed.

Titling indigenous communities protects forests in the Peruvian Amazon

Developing countries are increasingly decentralizing forest governance by granting indigenous groups and other local communities formal legal title to land. However, the effects of titling on forest cover are unclear. Rigorous analyses of titling campaigns are rare, and related theoretical and empirical research suggests that they could either stem or spur forest damage. We analyze such a campaign in the Peruvian Amazon, where more than 1,200 indigenous communities comprising some 11 million ha have been titled since the mid-1970s. We use community-level longitudinal data derived from high-resolution satellite images to estimate the effect of titling between 2002 and 2005 on contemporaneous forest clearing and disturbance. Our results indicate that titling reduces clearing by more than three-quarters and forest disturbance by roughly two-thirds in a 2-y window spanning the year title is awarded and the year afterward. These results suggest that awarding formal land titles to local communities can advance forest conservation.

Performance Evaluation of a Harvesting Robot for Sweet Pepper

This paper evaluates a robot developed for autonomous harvesting of sweet peppers in a commercial greenhouse. Objectives were to assess robot performance under unmodified and simplified crop conditions, using two types of end effectors (Fin Ray; Lip type), and to evaluate the performance contribution of stem‐dependent determination of the grasp pose. We describe and discuss the performance of hardware and software components developed for fruit harvesting in a complex environment that includes lighting variation, occlusions, and densely spaced obstacles. After simplifying the crop, harvest success significantly improved from 6% to 26% (Fin Ray) and from 2% to 33% (Lip type). We observed a decrease in stem damage and an increase in grasp success after enabling stem‐dependent determination of the grasp pose. Generally, the robot had difficulty in successfully picking sweet peppers and we discuss possible causes. The robot's novel capability of perceiving the stem of a plant may serve as useful functionality for future robots.

Effects of Four Base Cutter Blade Designs on Sugarcane Stem Cut Quality

Abstract. The cut quality of sugarcane stems during harvesting is of considerable importance, as any damage inflicted on the stems and root systems affects ratooning and reduces yield. In current conventional cutting systems for sugarcane, relatively little attention has been paid to optimizing the cutting dynamics by investigating various blade designs and configurations. One limitation of impact cutting methods is the relatively rapid blunting of the blade edges through wear, leading to stem damage. This study aimed at investigating the effects on sugarcane cut quality of four base cutter blade designs: a conventional straight blade, a 30° angled blade, a serrated blade, and a straight blade with laser cladding on its underside. Blades of each type were installed at a 45° angle on a base cutter fitted to a John Deere 3520 sugarcane harvester. Stem damage, root system damage, and stubble height were considered as cut quality indicators, and blade wear was evaluated as the percentage of metal mass loss after completing each harvesting operation. In this study, the extent of stem and root system damage was classified into nine categories: (1) undamaged stem, not uprooted, (2) undamaged stem, partially uprooted, (3) undamaged stem, uprooted, (4) partially damaged stem, not uprooted, (5) partially damaged stem, partially uprooted, (6) partially damaged stem, uprooted, (7) severely damaged stem, not uprooted, (8) severely damaged stem, partially uprooted, and (9) severely damaged stem, uprooted. The highest percentage of stems damaged during harvesting (approx. 38%) and the highest percentage of root systems damaged (approx. 36%) occurred with the angled blade. The percentages of undamaged stems for the straight, angled, serrated, and laser clad blades were 76.9%, 62.1%, 83.1%, and 72.3%, respectively; partially damaged stems were 11.25%, 21.97%, 11.29%, and 17.73%, respectively; and severely damaged stems were 11.9%, 15.9%, 5.65%, and 9.9%, respectively. Except for the angled blade, all the blades cut almost 80% of stems without affecting the root system, and only 5% of stems were uprooted. Indices for stem damage and uprooting damage were calculated to evaluate the cut quality on a scale from -1.00 (least damage) to +1.00 (greatest damage). For both indices, the serrated blade had values closest to the target value of -1.00, implying the least damage to stems and root systems. Greater stubble heights (110 mm) were observed for the angled blade, with 76% of cut stems above the target 75 mm threshold, which was selected based on the farmer’s suggestion. Comparatively less stubble height was obtained with the serrated and laser clad blades, and roughly 60% of stems were cut in the ideal range (<75 mm). Blade wear percentages per ha of harvested area, based on metal mass loss, were found to be 0.76% for the laser clad blade, 0.83% for the serrated blade, and 0.84% for the straight blade. No mass loss data were collected for the angled blade as it caused such a high level of stem damage that its test was discontinued. The results of this study classified the levels of stem and root system damage occurring in the field during harvesting and their effects on ratooning for four base cutter blade designs. Fundamental guidelines for optimal blade configurations associated with sugarcane harvesting are provided. Keywords: Blade wear, Stem damage, Stubble height, Sugarcane harvester.

GRAFTING FOR THE RECOVERY OF YELLOW PASSION FRUIT STEM IN ORGANIC SYSTEM

ABSTRACT The aim of the present study was to evaluate the effect of stem repair grafting on the recovery of damaged plants, yield and quality of yellow passion fruits in organic system. The experiment was conducted simulating five stem damages (treatments) in randomized complete block design with four replications of four plants each. After reaching on average 7.3 ± 1.2 mm in stem diameter, plants were perforated at 20, 40, 60 and 80% of the stem diameter with the aid of a steel drill. The reduction in plant stand treatment with 80 % damage reduces plant productivity. Then, bridge-type grafting was performed by connecting the top and bottom of the injury. The grafting success percentage ranged from 81.3 to 95.8% and did not differ between treatments, but the survival rate of plants was lower in treatments with 40 and 80% of injuries. There were no statistically significant differences between treatments for the following variables: number of fruits per plant, average fruit weight, total soluble solids (TSS), total titratable acidity (TTA) and (TSS/TTA) ratio. Recovery stem grafting allows injured plants to maintain the same productivity by up to 60% compared to plants without injuries.

Subclavian steal syndrome

Literature data on the etiology, clinical picture, diagnostic variants and treatment of subclavian steal syndrome are reviewed. Different clinical variants and neurological symptoms of the syndrome are described. Multispiral computed tomography, along with ultrasound examination, is important in the diagnosis of the syndrome and its causes. The use of other methods is necessary for more accurate diagnosis and prevention of perioperative complications. The character of damage of subclavian arteries and brachiocephalic stem should be taken into account in the choice of an optimal method of surgical treatment.

Field test of different end-effectors for robotic harvesting of sweet-pepper

This paper focusses on field experiments with two different types of endeffectors for robotic harvesting of sweet-pepper fruits. One of the major issues is to reach, grasp and detach the fruit efficiently, without damaging it, while avoiding obstacles in the environment. End-effectors for harvesting fruit must be able to adapt to different fruit sizes and geometries. Two types of end-effectors were designed and realized. The first one had four fingers which utilized the Ray effect to grip the fruit. A scissor-like cut mechanism on top of the fingers was used to cut through the fruit peduncle. The second, a lip-type end-effector first stabilized the fruit using a suction cup after which two rings enclosed and cut the peduncle with a circular blade integrated in the upper lip. Both end-effectors had integrated miniature cameras with a LED illumination system: one Time of Flight camera and the other a colour camera. To study the performance of the end-effectors a number of harvesting experiments were performed in commercial sweet-pepper greenhouses. Special attention was paid to the following aspects: positioning at the target fruit, separation of the fruit from the plant, fruit damage, leaf damage and plant stem damage. Both end-effector designs had their strengths and weaknesses. The Fin ray type end-effector harvested a maximum of 80% of the fruits on the plant, the lip-type end-effector a maximum of 76% of the fruits. In none of the experiments more than 64% of the fruit could be harvested without fruit damage.

Does Surface Topography Play a Role in Taper Damage in Head-neck Modular Junctions?

There are increasing reports of total hip arthroplasty failure subsequent to modular taper junction corrosion. The surfaces of tapers are machined to have circumferential machining marks, resulting in a surface topography of alternating peaks and valleys on the scale of micrometers. It is unclear if the geometry of this machined surface topography influences the degree of fretting and corrosion damage present on modular taper junctions or if there are differences between modular taper junction material couples. (1) What are the differences in damage score and surface topography between CoCr/CoCr and CoCr/Ti modular junctions? (2) How are initial surface topography, flexural rigidity, taper angle mismatch, and time in situ related to visual taper damage scores for CoCr/CoCr couples? (3) How are initial surface topography, flexural rigidity, taper angle mismatch, and time in situ related to visual taper damage scores for CoCr/Ti couples? Damage on stem and head tapers was evaluated with a modified Goldberg score. Differences in damage scores were determined between a group of 140 CoCr/CoCr couples and 129 CoCr/Ti couples using a chi-square test. For a subgroup of 70 retrievals, selected at random, we measured five variables, including initial stem taper machining mark height and spacing, initial head taper roughness, flexural rigidity, and taper angle mismatch. All retrievals were obtained at revision surgeries. None were retrieved as a result of metal-on-metal failures or were recalled implants. Components were chosen so there was a comparable number of each material couple and damage score. Machining marks around the circumference of the tapers were measured using white light interferometry to characterize the initial stem taper surface topography in terms of the height of and spacing between machining mark peaks as well as initial head taper roughness. The taper angle mismatch was assessed with a coordinate measuring machine. Flexural rigidity was determined based on measurements of gross taper dimensions and material properties. Differences of median or mean values of all variables between material couples were determined (Wilcoxon rank-sum tests and t-tests). The effect of all five variables along with time in situ on stem and head taper damage scores was tested with a multiple regression model. With 70 retrievals, a statistical power of 0.8 could be achieved for the model. Damage scores were different between CoCr/CoCr and CoCr/Ti modular taper junction material couples. CoCr/CoCr stem tapers were less likely to be mildly damaged (11%, p=0.006) but more likely to be severely damaged (4%, p=0.02) than CoCr/Ti stem tapers (28% and 1%, respectively). CoCr/CoCr couples were less likely to have moderately worn head tapers (7% versus 17%, p=0.003). Stem taper machining mark height and spacing and head taper roughness were 11 (SD 3), 185 (SD 46), and 0.57 (SD 0.5) for CoCr/CoCr couples and 10 (SD 3), 170 (SD 56), and 0.64 (SD 0.4) for CoCr/Ti couples, respectively. There was no difference (p=0.09, p=0.1, p=0.16, respectively) for either factor between material couples. Larger stem taper machining mark heights (p=0.001) were associated with lower stem taper damage scores, and time in situ (p=0.006) was associated with higher stem taper damage scores for CoCr/CoCr material couples. Stem taper machining marks that had higher peaks resulted in slower damage progression over time. For CoCr/Ti material couples, head taper roughness was associated with higher stem (p=0.001) and head taper (p=0.003) damage scores, and stem taper machining mark height, but not time in situ, was associated with lower stem taper damage scores (p=0.007). Stem taper surface topography was related to damage scores on retrieved head-neck modular junctions; however, it affected CoCr/CoCr and CoCr/Ti couples differently. A taper topography of circumferential machining marks with higher peaks appears to enable slower damage progression and, subsequently, a reduction of the reported release of corrosion products. This may be of interest to implant designers and manufacturers in an effort to reduce the effects of metal release from modular femoral components.

Short and long term effects of some bio-insecticides on Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) and its coexisting generalist predators in tomato fields

Tomato leaf miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), is one of the most destructive pests of tomato in many parts of the world including Iran. Field studies were conducted to determine the short and long term effects of Bacillus thuringiensis var Kurstaki (Bt), azadirachtin (AZ), a mix of AZ + Bt, and indoxacarb, as a current chemical insecticide, on T. absoluta larvae. Also, effects of the insecticides were studied on the coexisting generalist predators, Coccinella septempunctata L., Chrysoperla carnea Stephens and Syritta sp. Sampling of T. absoluta and its coexisting generalist predators were performed 1 day before treatment (DBT) and one, 5, 8, 14 and 19 days after treatment (DAT). The results indicated significant short term effect of indoxacarb on the pest larvae. Indoxacarb reduced T. absoluta density and damages. Bt, AZ and mixture of them significantly suppressed the larval density at 19 DAT and caused significant reduction in leaf, stem and fruit damage. The highest long term effect on the pest abundance and damage were observed in Az + Bt caused 100% reduction in fruit and foliage damage compared to the control. The highest and lowest adverse effects on C. carnea, C. septempunctat and Serrita sp. were observed in indoxacarb and Bt treatments, respectively. Findings of this study imply that the mixture of Az + Bt has the highest selective toxicity on the pest and the lowest effect on its coexisting generalist predators.

Effects of suppression history on growth response and stem quality of extant northern hardwoods following partial harvests

In uneven-aged stands, tolerant hardwood trees often sustain various degrees of suppression before they recruit to the merchantable tree layer. Whether this suppression influences stem quality development and growth potential of the trees in the future is still largely unknown. Using a retrospective approach, we assessed the influence of suppression history on tree growth response and the probability of stem damage following different intensities of partial harvest. Sugar maple and yellow birch samples were obtained from uneven-aged stands in northwestern New Brunswick, Canada. Results indicated that the likelihood of a tree possessing stem damage increased with length of suppression but decreased with increasing residual stand basal area (SBA) and site quality. Basal area increment (BAI) of both sugar maple and yellow birch was negatively influenced by period of suppression. BAI of yellow birch was higher than for sugar maple. Also, BAI increased with year since treatment but decreased with SBA for trees with diameter at breast height (DBH) larger than the subject tree’s DBH for both species. BAI increased in small-to medium-sized trees (10–35cmDBH), reached a maximum at 35cmDBH, and then declined for larger trees (DBH>35cm) in both species. Generally, trees on better quality sites had higher growth. However, we observed a significant effect of site quality on BAI for sugar maple only. Hence, we conclude that the partial harvesting system that is designed to provide growing space for intermediate or sub-canopy trees that have shorter suppression history would increase growth rate of residual trees while maintaining stem quality at the northern limit of tolerant hardwoods.

Comparative behavior of root pathogens in stems and roots of southeastern Pinus species

Root diseases are expected to become a greater threat to trees in the future due to accidental pathogen introductions and predicted climate changes, thus there is a need for accurate and efficient pathogenicity tests. For many root pathogens, these tests have been conducted in stems instead of roots. It, however, remains unclear whether stem and root inoculations are comparable for most fungal species. In this study we compared the growth and damage caused by five root pathogens (Grosmannia huntii, Grosmannia alacris, Leptographium procerum, Leptographium terebrantis, and Heterobasidion irregulare) in root and stem tissue of two Pinus species by inoculating mature trees and tissue amended agar in the laboratory. Most fungal species tested caused greater damage in roots of both pine hosts following inoculation. The relationship between root and stem damage was, however, similar when most combinations of pathogens were compared. These results suggest that although stem inoculations are not suitable for determining the actual damage potential of a given species, they may be viewed as a useful surrogate for root inoculations when comparing the relative pathogenicity of multiple species. When grown on amended agar, fungal species generally had greater growth in stem tissue, contrasting with the findings from tree inoculations.

Seed fall, seed predation, twigging and litter fall of Cascabela thevetia (L.) Lippold

Cascabela thevetia (L.) Lippold is a garden ornamental in northern Australia and two biotypes, the peach and the yellow, are recognised. In some areas it has naturalised and now has environmental and economic effects. As part of a broader research program into the ecology of C. thevetia, a field study was undertaken in northern Queensland to quantify seed fall and seed predation (by avian wildlife) of the peach biotype. The amount of twigging caused by birds while they fed on the seeds and the level of litter production were also recorded. Seed fall, seed predation, twigging and litter production occurred in all months of the year. Seed fall increased slowly over late spring and summer before peaking in mid- to late autumn (April–May) and then declining until October. Mean (± s.e.m.) estimated total annual seed fall was 19140 ± 2880 and 17030 ± 2930 seeds ha–1 in the first and second years respectively. Seed predation by birds was substantial, with 57% of all seeds predated. Birds also chewed an average of 600 twigs ha–1 year–1. Litter production varied from 430 to 950 kg dry weight (DW) ha–1 month–1. In total, 7900 ± 640 and 7390 ± 1420 kg (DW) litter was produced during the first and second years respectively. Although seed production of C. thevetia is less than a lot of other rangeland weeds, seed predation by birds further reduces the number of seeds entering the soil seed bank. The stem damage that occurred in conjunction with seed predation contributed to overall litter production and warrants further investigation in terms of its effect on plant growth.

Mapping of quantitative trait loci underlying resistance to cassava anthracnose disease

SUMMARYCassava (Manihot esculenta Crantz) is an economically important root crop in Thailand, which is ranked the world's top cassava exporting country. Production of cassava can be hampered by several pathogens and pests. Cassava anthracnose disease (CAD) is an important disease caused by the fungus Colletotrichum gloeosporioides f. sp. manihotis. The pathogen causes severe stem damage resulting in yield reductions and lack of stem cuttings available for planting. Molecular studies of cassava response to CAD will provide useful information for cassava breeders to develop new varieties with resistance to the disease. The current study aimed to identify quantitative trait loci (QTL) and DNA markers associated with resistance to CAD. A total of 200 lines of two F1 mapping populations were generated by reciprocal crosses between the varieties Huabong60 and Hanatee. The F1 samples were genotyped based on simple sequence repeat (SSR) and expressed sequence tag-SSR markers and a genetic linkage map was constructed using the JoinMap®/version3·0 program. The results showed that the map consisted of 512 marker loci distributed on 24 linkage groups with a map length of 1771·9 centimorgan (cM) and a mean interval between markers of 5·7 cM. The genetic linkage map was integrated with phenotypic data for the response to CAD infection generated by a detached leaf assay test. A total of three QTL underlying the trait were identified on three linkage groups using the MapQTL®/version4·0 program. Those DNA markers linked to the QTL that showed high statistically significant values with the CAD resistance trait were identified for gene annotation analysis and 23 candidate resistance genes to CAD infection were identified.