Population structure of Chrysoporthe austroafricana in southern Africa determined using Vegetative Compatibility Groups (VCGs)

Chrysoporthe austroafricana is one of the most damaging pathogens of Eucalyptus trees in southern Africa. It also occurs on non‐native Tibouchina granulosa trees and native Syzygium species. Additional isolates of the pathogen from previously unstudied countries in the region have become available from survey studies. The aim of this study was to use VCGs to consider the diversity in populations of isolates collected in various countries in southern Africa (Malawi, Mozambique, Namibia, South Africa and Zambia) and from different hosts. We also wanted to determine whether there are shared VCGs among these countries and hosts in southern Africa and establish a VCG tester strain database. Results showed a high diversity amongst isolates from different countries and hosts, but suggested little movement of VCGs among countries or hosts based on the available isolates. A total of 108 VCG tester strains were identified for southern Africa.     

First records of soilborne Phytophthora species in Swedish oak forests

Thirty‐two oak stands in southern Sweden, 27 with predominantly declining trees and five with a higher proportion of healthy trees were investigated regarding the presence of soilborne Phytophthora species. Phytophthora quercina, an oak‐specific fine root pathogen, was isolated from rhizosphere soil samples in 10 of the 27 declining stands. Additionally, P. cactorum and P. cambivora were recovered from one stand each. No Phytophthora species were isolated from the healthy oak stands. The soil conditions at the sites from which Phytophthora spp. were recovered ranged from mesic sediments to moraines, with clayey to silty textures and with soil pH (BaCl₂) between 3.5 and 5.0. The results show that P. quercina is geographically widespread in oak stands in southern Sweden and indicate that this pathogen may be one of the factors involved in oak decline in Northern Europe as has already been shown for western, Central and parts of southern Europe.     

Host range, distribution, and natural enemies of Bemisia tabaci ‘B biotype’ (Hemiptera: Aleyrodidae) in Turkey

The whitefly Bemisia tabaci (Gennadius) has caused notable damage to vegetable and cotton crops in the eastern Mediterranean region since about 1994, and has become particularly problematic in southern Turkey beginning in 2000. The development of squash silverleaf symptoms in Cucurbita species and the unprecedented high population levels in the region suggested that the B biotype, notable for the latter phenotypes, had been introduced. To test this hypothesis and determine the host distribution of the suspect introduced B biotype and its associated natural enemies, B. tabaci immature instars and adults, and the associated natural enemies were collected from cultivated and uncultivated plant species. From the southern Turkey collections, B. tabaci was found to colonize 152 species from 43 plant families. Of the plant species upon which B. tabaci was found to reproduce, 152 of them were reported as hosts of B. tabaci in Turkey. Five species of predators and two species of parasitoids were identified as natural enemies of the B biotype of B. tabaci in southern Turkey. Using the mitochondrial cytochrome oxidase I gene all B. tabaci were identified as the B biotype of the B. tabaci complex, at 96–100% shared identity with reference B biotype sequences. Results indicate that this invasive biotype has displaced the local Turkey-cotton haplotype that was known to occur previously in southern Turkey.     

A preliminary report on decay and canker of Acacia richii caused by Inonotus rickii in China

An epidemic wood‐decaying fungus, Inonotus rickii, originating from South America, has spread to the Mediterranean area and southern China. We report the first observation of this fungus on Acacia richii in Panzhihua, southern China. It causes serious canker and decay on urban trees in the investigated area. In addition, phylogenetic analysis showed that the fungus from Panzhihua is closely related to isolates from Europe, South America, Mianyang and Hainan of China. Moreover, it was concluded that the isolates of the species previously reported from the USA do not belong to I. rickii.     

Using non-destructive testing to assess modulus of elasticity of Pinus sylvestris trees

Abstract

This study assessed variation in modulus of elasticity of trees and logs of Scots pine (Pinus sylvestris) trees. The study used 192 sample trees (c. 90–150 years) selected from 24 clear-felling forests in central and southern Sweden. Modulus of elasticity (MOE) assessed with transit-time technology on standing tree stems at 0.5–2.0m on the southern and northern side of each tree varied from 8.6 to 17.6 GPa. No systematic MOE difference was found between the southern and northern side of tree stems. The sometimes large MOE variations seen in some individual trees are probably a result of wood variation and wood defects. MOE assessed with resonance-based technology varied between 7.4 and 14.1 GPa for logs cut at similar height (<6.0 m). Models of MOE variation were derived from factors related to growth conditions at stand and tree level, with an R ² _adj of c. 0.46–0.62. The models indicate that growth and tree attributes associated with and/or creating less stem taper would yield trees with higher MOE.     

Flexural properties of southern yellow pine small beams loaded on true radial and tangential surfaces

Values of moduli of rigidity (G _LR andG _LT), obtained from static bending tests of small southern yellow pine beams with square cross sections and true radial and tangential surfaces, are not significantly different. Values of moduli of elasticity and rupture of small southern pine beams at span-to-depth ratio of 14: 1 loaded on a true radial surface are not significantly different from values obtained from matched beams loaded on a true tangential surface.     

Investigations on Heterobasidion annosum s.lat. in central and eastern Asia with the aid of mating tests and DNA fingerprinting

To investigate the taxonomy of Heterobasidion in Eurasia, 49 specimens belonging to H. annosum sensu lato from Asia were identified with the aid of mating tests. Most of the specimens originated from north‐eastern and south‐western China and from the Altai region in southern Siberia, but a few isolates from Kirghizia, Japan and India were also tested. In addition to mating tests, the material from China was investigated with DNA fingerprinting. Heterobasidion annosum sensu stricto was identified only from the Altai region. Homokaryotic isolates from other specimens, except the Indian ones, were sexually compatible with H. parviporum, but they also showed a high degree of compatibility with H. abietinum and with the North American S group. The isolates from SW China (eastern Himalayas) mated with about equal frequency with the European strains of H. parviporum and H. abietinum. However, the DNA fingerprinting showed that these isolates were more closely related to H. parviporum, and hence they were tentatively included in this species. The North American S group was more distant from these Eurasian taxa. Four old isolates from India mated only weakly with the members of the H. annosum s.lat. According to the species concept presented, the distribution of H. parviporum extends from western Europe through southern Siberia to northern China, Japan and the eastern Himalayas. H. annosum s.str. is so far identified only from the Altai region outside Europe, and H. abietinum only from Europe.     

Genetic variation in survival,growth, and stem form of Pinus leiophylla in Brazil and South Africa and provenance resistance to pitch canker

Pinus leiophylla is a relatively common pine that occurs in the mountains of western and central Mexico. Between 1987 and 1990, Camcore, North Carolina State University, sampled 11 populations and 309 mother trees of the species to determine patterns of genetic variation in survival, growth and stem form. Fifteen provenance/progeny trials were established in southern Brazil and South Africa across a wide range of sites and assessed at 3, 5 and 8 years of age for height, diameter and stem form. Results indicated that average productivity ranged from 5 to 19m³ ha^?1 y^?1 depending on the site and that performance was not as competitive as P. patula (South Africa) and P. taeda (Brazil) controls. Provenances from central Mexico (Michoacán) were statistically better in productivity than those from the southern part of the country (Oaxaca), which in turn were superior to those from the northern part of the country (Durango). However, provenances from northern Mexico exhibited superior survival to seed sources from other locations in Mexico when grown on cold sites (winter minimums –10 to 5°C) in South Africa and superior stem form across all locations. Seedlings from the original 11 provenances were screened for resistance to the pitch canker fungus (PCF; Fusarium circinatum). Results indicated that generally P. leiophylla is as susceptible to PCF as P. patula (stemkill = 85%) with the exception of two fast-growing, moderately resistant populations from Michoacán, La Pinalosa (stemkill = 44%) and Ario de Rosales (stemkill = 73%). The future potential of P. leiophylla might be in hybrid combination with P. patula in the seasonally dry areas of southern Africa where fires are common and pitch canker is a problem.     

Yield Potential of Quercus robur Stands in Finland

Yield potential of common oak (Quercus robur L.) stands in Finland was examined by estimating the site index value with a Swedish model of a sample of 23 existing stands in southern Finland, and studying its correlation with site fertility and geographical location. Stand structure and yield parameters were compared with those suggested by the Swedish management regimes to assess their condition and potential for quality oak production. External wood quality and sawlog volume were examined in sample tree data. The study stands scored high site index values on the reference site index curves from southern Sweden. The most fertile sites showed an average site index value of H ₁₀₀=28-30 m, and the common Oxalis-Myrtillus type H ₁₀₀=24-26 m. In the absence of thinning and pruning, the external quality of the trees was poor. Defects had reduced the sawlog proportion on average by 40% from the estimated maximum allowed by tree dimensions.     

Southern pollen sired more seeds than northern pollen in southern seed orchards established with northern clones of Pinus sylvestris

Abstract

Contamination by southern pollen is a considerable problem in Scots pine (Pinus sylvestris L.) seed orchards established with northern clones. This study investigated whether the contamination was due to the competitive superiority of southern pollen by carrying out competition trials using mixtures of pollen from northern and southern populations of Scots pine. Trials were performed in a southerly seed orchard established with clones originating from northern populations. Seed paternity (siring) was determined through the analysis of allozyme variation. Southern genotypes sired significantly more seeds (76%) than their northern competitors and across all mixed-pollen crosses. Maternal genotype had no effect on seed siring success. The mean flower abortion rate was lower in southern pure-pollen crosses and mixed-pollen crosses than in northern pure-pollen crosses. The results show that local pollen may induce high levels of background pollination in southern seed orchards composed of northern genotype grafts. These results must be taken into account when aiming to produce suitable reforestation material for northern areas.     

Diplodia scrobiculata found in the southern hemisphere

Diplodia scrobiculata, a latent pathogen of Pinus spp. and other conifers with a limited distribution in the United States, Mexico and southern Europe, has not been reported previously in the southern hemisphere. This is unlike its close relative Diplodia pinea that is found in most parts of the world where pines are native or have been introduced. During an intensive D. pinea survey conducted in Pinus patula plantations in eastern parts of South Africa, a small number of isolates atypical of D. pinea were found. Morphological studies and DNA sequence comparisons showed that these isolates represent D. scrobiculata. Microsatellite analyses suggest that the South African isolates of D. scrobiculata might have originated from California. Pathogenicity tests showed that some of the D. scrobiculata isolates were as pathogenic as those of D. pinea on Pinus radiata and Pinus elliottii.     

Soil carbon dynamics and residue stabilization in a Costa Rican and southern Canadian alley cropping system

Agroforestry systems can play a major role in the sequestration of carbon (C) because of their higher input of organic material to the soil compared to sole crop agroecosystems. This study quantified C input in a 19-year old tropical alley cropping system with E. poeppigiana (Walp.) O.F Cook in Costa Rica and in a 13-year old hybrid poplar (Populus deltoides × nigra DN-177) alley cropping system in southern Canada. Changes in the level of the soil organic carbon (SOC) pool, residue decomposition rate, residue stabilization efficiency, and the annual rate of accumulation of SOC were also quantified in both systems. Carbon input from tree prunings in Costa Rica was 401 g C m⁻² y⁻¹ compared to 117 g C m⁻² y⁻¹ from litterfall at the Canadian site. In southern Canada, crop residue input from maize (Zea mays L.) was 212 g C m⁻² y⁻¹, 83 g C m⁻² y⁻¹ from soybeans (Glycine max L.) and 125 g C m⁻² y⁻¹ for wheat (Triticum aestivum L.), and was not significantly different (p < 0.05) from the sole crop. The average yearly C input from crop residues in Costa Rica was significantly greater (p < 0.05) in the alley crop for maize (134 g C m⁻² y⁻¹) and Phaseolus vulgaris L. bean crops (35 g C m⁻² y⁻¹) compared to the sole crop. The SOC pool was significantly greater (p < 0.05) in the Costa Rican alley crop (9536 g m⁻²) compared to its respective sole crop (6143 g m⁻²) to a 20 cm depth, but no such difference was found for the southern Canadian system. Residue stabilization, defined as the efficiency of the stabilization of added residue (crop residues, tree prunings, litterfall) that is added to the soil C pool, is more efficient in southern Canada (31%) compared to the alley cropping system in Costa Rica (40%). This coincides with a lower organic matter decomposition rate (0.03 y⁻¹) to a 20 cm depth in Canada compared to the Costa Rican system (0.06 y⁻¹). However, the average annual accumulation rate of SOC is greater in Costa Rica (179 g m⁻² y⁻¹) and is likely related to the greater input of organic material derived from tree prunings, compared to that in southern Canada (30 g m⁻² y⁻¹) to a 20 cm depth.     

First report on the Dutch elm disease pathogen Ophiostoma novo‐ulmi from Latvia

During 2017, Dutch elm disease was investigated on 67 Ulmus glabra and 29 Ulmus laevis samples from 28 sites in Latvia. The presence of Ophiostoma novo‐ulmi was detected in 61.2% of the samples from U. glabra and in 34.5% of the samples from U. laevis. In 11% of cases, hybrids between subsp. novo‐ulmi and subsp. americana were identified, particularly in the sites in the southern part of Latvia. This study presents the first verified record of Ophiostoma novo‐ulmi and its subspecies in Latvia.     

Effect of growing site on the fundamental wood properties of natural hybrid clones of <Emphasis Type="Italic">Acacia</Emphasis> in Vietnam

We investigated clonal and site variations in wood fiber length, microfibril angle, and specific gravity of seven natural hybrid clones of Acacia (Acacia mangium × Acacia auriculiformis) grown in northern and southern Vietnam. Fiber length did not differ between clones or between sites. The microfibril angle of the S₂ layer did not significantly differ between clones but significantly differed between sites. Clone and site significantly affected specific gravity. The significant effects of genetic × environmental interactions on wood properties indicated the difference in the response of clones to different growing conditions. The trends of changes in fiber length, microfibril angle, and specific gravity from the vicinity of the pith to near the bark were similar for all clones at each site; however, variations in fiber length, microfibril angle, and specific gravity were more visible in northern Vietnam than in southern Vietnam, with a significant effect of genetic factors. This difference may be attributable to winter, which is experienced in northern Vietnam but not in southern Vietnam. For clone selection for plantation in the northern region, combining growth rate with wood properties was recommended. On the other hand, for plantation in the southern region, clone selection depends mainly on the growth rate, taking into consideration the specific gravity.     

Comparing agroforestry systems’ ex ante adoption potential and ex post adoption: on-farm participatory research from southern Malawi

Agroforestry (AF) systems have been the focus of numerous research and development projects in southern Africa, yet their adoption rate generally remains low. Employing on-farm, participatory research techniques in southern Malawi, we compared the suitability of three AF-based systems that relay crop the dominant staple, maize (Zea mays), with the perennial legumes Sesbania sesban, Tephrosia vogelii, and Cajanus cajan (pigeonpea). Our secondary objective was to compare two methodologies employed to investigate AF adoption: farming systems based ex ante adoption potential and ex post adoption analysis. Nineteen percent of farmers preferred S. sesban, 26% T. vogelii, and 55% pigeonpea. Between 2001 and 2003, S. sesban adoption ranged from 3 to 6%, T. vogelii from 16 to 20%, and pigeonpea from 76 to 100%. Pigeonpea and T. vogelii were primarily preferred and adopted for their immediate livelihood benefits—a secondary food source in the case of pigeonpea and a fish poison in the case of T. vogelii. Though S. sesban was the most promising in terms of biophysical impacts, many farmers found it labor intensive and its lack of immediate livelihood benefits was a deterrent to adoption. With food insecurity a pervasive hardship in the region, farmers will likely continue to focus on satisfying immediate livelihood needs before prioritizing longer-term soil-quality improvement techniques. Both ex ante adoption potential and ex post adoption analysis contributed distinct and valuable data, and relying on either exclusively would have limited our understanding of the AF systems.     

Potential use of visible and near-infrared spectroscopy for pine species discrimination by examination of needles

The correct identification of pine species is necessary for proper application of wood in forest?based industries, since the quality of each species’ wood depends on factors intrinsic to the material. The aim of this study was to evaluate the potential use of near?infrared and visible spectroscopy in the discrimination of pine species planted in southern Brazil. Needles of Pinus clausa, P. glabra, P. kesiya, P. oocarpa, P. palustris, P. pseudostrobus, P. rigida, P. roxburghii and P. serotina were collected from experimental plantations located in the region of Rio Negro, Paraná, Brazil. The needles were dried and milled for analysis. The evaluation was performed with a spectral range of 400–750?nm (visible) and 1 000–2 500?nm (near?infrared). Analysis using the visible spectra resulted in two principal components explaining 95% of the variation between the needle samples. In the near?infrared analysis, it was possible to discriminate between all nine pine species studied using only two principal components, where the first explained 99% of the variation between species. Spectroscopy based on needles can be used for pine species discrimination, using the original data without mathematical treatment, in southern Brazil.     

Abies sibirica in the Ural region is attacked by the S type of Heterobasidion annosum

Specimens of Heterobasidion annosum were collected in seven mixed stands of Abies sibirica and Picea abies in Yekaterinburg and Perm regions on the western side of the Ural Mountains, Russia. Pure cultures were isolated from 60 collections and identified in mating tests. Only the S intersterility group was found, attacking both fir and spruce. Based on the appearance of clamp connections in matings, the compatibility of 12 homokaryons from the Ural area with 14 S group homokaryons from western Europe was 100%, with 13 F group homokaryons from southern Europe 76% and 9 P group homokaryons from western Europe 3%. The results show that A. sibirica, in contrast to A. alba, is very susceptible to the S type H. annosum.     

Presence of longitudinal cracks in planks from storm-felled pine (Pinus sylvestris L.) and spruce (Picea abies (L.) Karst.)

Abstract

After the severe storm Gudrun in southern Sweden in 2005, a quantitative study was done in order to investigate the presence of lengthwise crack on planks taken from storm-felled trees in southern Sweden, compared to planks from standing trees not subjected to this storm (central Sweden). The main yield from each log was examined. In total, 1087 pine (Pinus sylvestris) planks and 3626 spruce (Picea abies) planks from the storm-struck area were investigated and compared to 1953 spruce and 2000 pine planks from trees outside the storm-struck area. The examination of cracks was done visually on dried planks. For pine, 51.7% of the planks from storm-felled trees had a total length longer than 0.5 m, compared to 7.3% for the reference material. As for spruce, 11.0% of the planks from storm-felled trees had a total crack length of more than 0.5 m, compared to the reference material where 2.2% had cracks longer than 0.5 m. The results show that the storm-felled trees had more longitudinal cracks than the reference material and that pine was more likely to develop storm-related cracks than spruce.     

Damage by Neonectria neomacrospora and Adelges piceae in provenance trials of subalpine fir (Abies lasiocarpa) in Denmark

Field trials of Abies lasiocarpa were undertaken with the aim of assessing the potential for Christmas tree production in Denmark. Twenty‐six provenances originating from Alaska to New Mexico were tested. Damage by the insect Adelges piceae and the fungus Neonectria neomacrospora was recorded for the first time 8 and 12 years after the initial planting. Damage from N. neomacrospora increased rapidly in the period 12–15 years after planting. Trees from the northern provenances and humid climates exhibited less damage than those from southern ones. Previous attack by A. piceae had a minor effect on N. neomacrospora infection. Greenhouse tests showed that detached shoots from healthy Abies lasiocarpa can be used to rank provenances for resistance to N. neomacrospora, but results varied according to host subspecies.     

Genetic variation of Heterobasidion abietinum in Southern Europe and the Mediterranean Basin

Heterobasidion abietinum causes root and butt rot on Abies species occurring in central Europe and the Mediterranean Basin in a distribution extending from Spain in the west to Turkey and Caucasia in the east. To investigate the genetic diversity within H. abietinum, 95 isolates from different regions were analysed with 61 polymorphic molecular markers. The markers showed genetic differentiation amongst the H. abietinum populations. The most diversified population is that on A. pinsapo in southern Spain, which is isolated from gene flow with other populations. Lower but still significant differences were found amongst other European populations. Isolates from Turkey showed little diversification compared with the south European isolates from east of the Alps. The genetic structure of the H. abietinum populations in relation to postglacial recolonization of Abies is discussed.