Responses in the bark of Cupressus sempervirens clones artificially inoculated with Seiridium cardinale under field conditions

By 70 days after inoculation, resistant and tolerant clones of field-grown Cupressus sempervirens restricted penetration of the bark by Seiridium cardinale, forming ligno-suberized boundary zones which included four to six layers of cells with suberized cell walls. This response contrasted with that in susceptible clones, where only two to four layers of suberized cells were formed in discontinuous bands around inoculation sites. Detection of multiple layers of thin suberized boundary zones in susceptible clones indicated repeated penetration of the wound/infection-induced barrier by S. cardinale during a single growing season. The methods described will be valuable in the development of rapid, early and accurate screening programmes for durable resistance to Seiridium canker in Cupressus species.     

Pathogenicity of Heterobasidion annosum (Fr.) Bref. sensu stricto on coniferous tree species in Turkey

Two‐year‐old seedlings of Pinus brutia, P. brutia var. eldarica, Pinus pinea and 3‐year‐old seedlings of Pinus radiata, Pinus sylvestris, Pinus nigra and Cedrus libani were inoculated on the lower stem with isolates of Heterobasidion annosum s.s. collected from the Black Sea and Mediterranean regions of Turkey. In total, 315 seedlings were inoculated in April 2014 and incubated in a growth chamber for 7 weeks at 18–20°C. All isolates were pathogenic on the seven different hosts and had the ability to grow in living sapwood. The isolates had a greater growth on C. libani, P. sylvestris and P. radiata seedlings compared to plants of the other species tested. The least affected species were P. brutia and P. nigra. The isolates originating from the Black Sea region caused longer lesions on the hosts. Overall mortality during 7 weeks of incubation was 4%.     

Role of plant defense in the utilization of native browse in southern Ethiopia

Browse is an important forage in pastoral systems, especially during dry seasons, because it is high in nitrogen and digestibility. However, browse palatability may be reduced by possible plant defenses such as tannins and physical attributes. Chemical and physical properties of 20 browse species were correlated with the feeding preference of camels, sheep and goats during wet and dry seasons in a densely wooded, semi-arid savanna. Preference was assessed by comparing relative use with abundance of browse species. Chemical components included nitrogen, available nitrogen, acid-detergent fibre, in vitro digestibility, total tannins and condensed tannins. Physical defenses included thorns, hooks, spines, and leaf surface properties. Animal preference was negatively related to chemical and physical defense factors, positively related to N content, and unrelated to fibre and digestibility with results depending on animal species and season. Understanding the physical and chemical factors which influence browse selectivity aids in identifying promising forage resources.     

Effect of processing on the displacement of whey proteins: applying the orogenic model to a real system

Atomic force microscopy (AFM) has been used to investigate the displacement of a commercial whey protein system and the behavior as compared to that of beta-lactoglobulin (Mackie, A. R.; Gunning, A. P.; Wilde, P. J.; Morris, V. J. Orogenic displacement of protein from the air-water interface by competitive adsorption. J. Colloid Interface Sci. 1999, 210, 157-166). The whey protein isolate (WPI) was displaced from an air-water interface by the surfactants Tween 20 and Tween 60. Displacement data obtained were compared with data obtained for pure beta-lactoglobulin and have shown that WPI was more resistant to displacement from the air-water interface than native beta-lactoglobulin. This was related to the greater surface elasticity of WPI at higher surface stresses. In the presence of Tween 20, WPI was observed to remain on the interface at surface pressures up to 8 mN/m greater than the surface pressure at which complete displacement of beta-lactoglobulin was observed. Displacement of WPI and beta-lactoglobulin films by the surfactant Tween 60 showed similar results. However, because of the lower surface activity of Tween 60, it was not possible to reach surface tension values similar to those obtained for Tween 20. Despite the lower surface activity of Tween 60, WPI was still observed to be present at the interface at surface pressure values greater than those by which beta-lactoglobulin had been completely displaced.     

Developing effective sampling designs for monitoring natural resources in Alaskan national parks: An example using simulations and vegetation data

Monitoring natural resources in Alaskan national parks is challenging because of their remoteness, limited accessibility, and high sampling costs. We describe an iterative, three-phased process for developing sampling designs based on our efforts to establish a vegetation monitoring program in southwest Alaska. In the first phase, we defined a sampling frame based on land ownership and specific vegetated habitats within the park boundaries and used Path Distance analysis tools to create a GIS layer that delineated portions of each park that could be feasibly accessed for ground sampling. In the second phase, we used simulations based on landcover maps to identify size and configuration of the ground sampling units (single plots or grids of plots) and to refine areas to be potentially sampled. In the third phase, we used a second set of simulations to estimate sample size and sampling frequency required to have a reasonable chance of detecting a minimum trend in vegetation cover for a specified time period and level of statistical confidence. Results of the first set of simulations indicated that a spatially balanced random sample of single plots from the most common landcover types yielded the most efficient sampling scheme. Results of the second set of simulations were compared with field data and indicated that we should be able to detect at least a 25% change in vegetation attributes over 31 years by sampling 8 or more plots per year every five years in focal landcover types. This approach would be especially useful in situations where ground sampling is restricted by access.     

Physical and chemical responses of Sitka spruce (Picea sitchensis) clones to colonization by Heterobasidion annosum as potential markers for relative host susceptibility

Forty-one 2-year-old clones of Picea sitchensis (Bong.) Carr. from three full-sib families (14 clones from each of two families and 13 clones from a third family) were either wounded and inoculated with an isolate of Heterobasidion annosum (Fr.) Bref. or wounded without inoculation. Lesion lengths on the inner bark from the point of inoculation varied among clones 35 days after treatment. There was no relationship between lesion length and relatedness within families. Two clones (21342 and 25202) with the shortest lesions, tentatively designated as less susceptible to H. annosum, and two clones (21176 and 27166) with the longest lesions, designated more susceptible, were selected for comparison of host anatomical and chemical responses to infection. The position and structure of the ligno-suberized boundary zone (LSZ) in the bark of the clones suggested that the less susceptible clones formed thicker layers of suberized cells in the LSZ following wounding plus inoculation. No LSZ was observed in two ramets of the more susceptible Clone 27166 following wounding and inoculation with H. annosum. Compared with more susceptible genotypes, clones of P. sitchensis with low susceptibility to H. annosum had high relative proportions of (+)-alpha-pinene, (-)-beta-pinene and one unidentified terpene constituent (Unknown-15) in cortical resin sampled 25 cm from the lesions. In contrast, more susceptible clones had higher relative proportions of (-)-limonene, Unknown-16, Unknown-18 and Unknown-19. In the secondary resin produced in bark tissues surrounding the lesions, proportions of several monoterpene constituents varied; these changes included a decrease in the relative amount of beta-phellandrene and corresponding small increases in some minor constituents. The concentrations of the monoterpenes, except a few minor constituents, increased in the infected tissues. Wounding plus inoculation with H. annosum resulted in varied monoterpene responses, with distinct differences between less susceptible and more susceptible clones. In less susceptible clones, Unknown-19 increased following wounding plus inoculation, whereas in more susceptible clones, concentrations of delta-3-carene and Unknown-13 and Unknown-16 increased. Differences in both constitutive and induced resin monoterpene profiles may provide useful markers for resistance to H. annosum in selection and breeding programs.     

Responses of Sitka spruce of different genetic origins to inoculation with Heterobasidion annosum: lesion lengths,fungal growth and development of the lignosuberized boundary zone

Three genetically distinct groups of Sitka spruce, open‐pollinated Queen Charlotte Island provenance, A13 selected seed and M0044 half‐sib mixture, were wounded alone or wounded and inoculated with Heterobasidion annosum sensu stricto on the lower stems. Growth of the pathogen and lesion formation was compared in the three genetic groups after treatment. No differences in the rate of colonization of the three genetic groups were observed over a 40 day period; lesion lengths in the bark and sapwood correlated closely. Moreover, lesions were considerably longer in inoculated plants than in those which were wounded only. No correlations were found within or between host genetic groups in the numbers or total areas of resin canals present in the first 18 mm from the wound in bark tissues for the three host genetic groups. Formation of the ligno‐suberized boundary zone (LSZ), however, was inhibited in the bark of inoculated plants, being first detected later and at a greater distance from the wound/inoculation point in the presence of H. annosum than in plants that were wounded only. Thickness of the suberin cell layers within the LSZ of M0044 plants was greater in wounded and inoculated, than in wounded only plants. The significance of these findings in relation to detecting spruce genotypes potentially resistant to H. annosum is discussed.