Screening of Corymbia and Eucalyptus species for resistance to Calonectria pteridis leaf blight

Calonectria leaf blight (CLB), caused by Calonectria pteridis, is a major foliar disease of eucalypt plantations in warm and high rainfall regions in Brazil. The use of resistant genotypes is the best method for disease control in the field, so identification of sources of resistance is strategic for the long‐term genetic breeding programmes of eucalypt. In this study, resistance of 13 species of Eucalyptus and 3 species of Corymbia to CLB was evaluated by spray inoculation of a spore suspension (1 × 10⁴ conidia ml^?1) of the pathogen, under controlled conditions. Eucalyptus brassiana, E. saligna, E. scias and E. agglomerata were the most resistant, while E. robusta, E. urophylla, E. camaldulensis, E. longirostrata and C. toreliana were moderately resistant and E. cloeziana, E. pellita, E. tereticornis, E. pilularis, C. maculata, E. grandis, E. dunnii and C. citriodora were the most susceptible. The broad inter and intraspecific variability of the species tested demonstrates the potential for introgression of resistance genes into valuable genotypes as a strategy for the breeding programmes and commercial plantation of eucalypt.     

Development and evaluation of a real‐time PCR seed lot screening method for Fusarium circinatum,causal agent of pitch canker disease

Fusarium circinatum is a serious pathogen of Pinus spp. worldwide, causing pitch canker disease. F. circinatum can contaminate seeds both internally and externally and is readily disseminated via contaminated seed. Many countries require screening of pine seeds for F. circinatum before they can be imported. The currently accepted screening method is based on culturing the pathogen on a semi‐selective medium and identifying it using morphological traits. This method is time‐consuming and does not allow for accurate identification of the pathogen to the species level. A bulk DNA extraction and real‐time PCR procedure to screen seeds for the presence of F. circinatum were developed in this study. The real‐time PCR method resulted in the detection of F. circinatum in 5 of 6 commercial seed lots tested and has a lower detection limit of 1 × 10^?5 ng of F. circinatum DNA per PCR. The culture‐based method detected Fusarium spp. in four of six of the same seed lots. The real‐time PCR method can be used to screen multiple seed lots in 2 days, whereas the culture‐based method requires a minimum of 1–2 weeks. This new real‐time PCR seed screening method allows for fast, sensitive and accurate screening and can be adapted to handle larger volumes of seeds.     

Diseases on Eucalyptus species in Zimbabwean plantations and woodlots

Zimbabwe embarked on planting Eucalyptus species in the early 1900s. Based on a robust breeding programme, it has become a major source of seed for other countries in and outside Africa. Tree health surveys conducted on Eucalyptus in some east and southern African countries over the past two decades have revealed several important fungal diseases that were previously not known in the region, but little is known regarding these problems in Zimbabwe. The aim of this study was to identify important Eucalyptus diseases across Zimbabwe's agroclimatic regions. Morphological characteristics and DNA sequence data were used to identify pathogens collected to species level. Widespread stem canker diseases, caused by species belonging to the Botryosphaeriaceae and Teratosphaeriaceae, and leaf spot diseases caused by fungi in the Capnodiales, were identified. Armillaria root and stem rot was restricted to a single site in the Eastern Highlands. Fungi that could cause canker or blue stain of timber were isolated from recently harvested stumps and included species of Ceratocystis and Ophiostoma. This study is the first to identify Eucalyptus pathogens to species level in Zimbabwe and we report for the first time the presence of the stem canker pathogen T. gauchensis in southern Africa. The results will provide a foundation for the formulation of future disease management strategies in the country.     

Phosphorus,nitrogen and potassium nutrition on Calonectria leaf blight in eucalypt plants

Calonectria pteridis causes Calonectria leaf blight (CLB), and consequently severe defoliation in eucalypt plantations, which results in losses in wood volume. To reduce the negative impacts of this disease in eucalypt, this study aimed to assess the application of different doses and combinations of the macronutrients N, P and K on the percentage of symptomatic leaf area (SLA) and defoliation induced by the pathogen. Cuttings of a clone of Eucalyptus grandis were transplanted to pots containing soil that received different dose combinations of N, P and K, according to an incomplete factorial design. At 200 days after transplanting, leaf samples were analysed for N, P and K contents, and then, the plants were inoculated. Forty‐five days post‐inoculation, SLA and percentage of defoliation were quantified. Potassium doses above 75 mg/dm³ of soil significantly reduced SLA and defoliation. The influence of N and P on defoliation was dependent on K doses, but both reduced symptomatic leaf area. The best control of the disease, expressed by decreased defoliation and symptomatic leaf area, was achieved with leaf content of N, P and K of 9.8, 0.8 and 10.4 g per kg leaf, respectively, obtained with doses of 55, 82.5 and 143 mg/dm³of soil, respectively. Therefore, N, P and K nutrition can be a component of an integrated management programme for the control of CLB in eucalypts.     

Serpula himantioides,Heterobasidion annosum and Calocera viscosa as butt rot fungi in a Danish Douglas‐fir stand

A scattered wind fall of 50 trees in a 46‐year‐old stand of Douglas‐fir (Pseudotsuga menziesii) revealed Serpula himantioides, Heterobasidion annosum and Calocera viscosa as decay causing fungi. Sixty‐four percent of the stumps had visible rot on the stump surface. Mainly, a central brown rot was seen, caused by either S. himantioides or C. viscosa combined with eccentrically placed spots of incipient H. annosum rot. Subsequently, the appearance of fruitbodies disclosed that in total 76% of the wind thrown trees were associated with one or more of the three decay fungi. S. himantioides was present in a surprisingly large number of trees (54%), and the rot column extended up to 2 m into the stem. This investigation represents the first known incidence of S. himantioides and C. viscosa causing root and butt rot in living conifers in Denmark.     

Populus tremuloides Michx. postfire stand dynamics in the northern boreal-cordilleran ecoclimatic region of central Yukon Territory, Canada

Postfire vegetation development among 8–185-year-old stand was assessed based on 100 relevés from the northern boreal-cordilleran ecoclimatic region (61–63°N) in the central Yukon Territory, Canada. Vegetation sampling included only stands thought to have originated from postfire Populus tremuloides Michx. regeneration that occurred on well drained and low gradient sites. Seven vegetation types were recognized based on cluster analysis and Kruskal–Wallis testing. Relevé ordination using Detrended Correspondence Analysis (70% explained variance) indicated six of the vegetation types represented a secondary successional chronosequence, based on their juxtaposition and a strong correlation of the primary axis with stand age (r = 0.89, P < 0.001). No correlation (P > 0.05) occurred between stand location and age. The youngest vegetation (8–11 years) had a moderate cover of P. tremuloides and Salix spp. up to 5 m tall, with a ground cover of Ceratodon purpureus (Hedw.) Brid. and Bryum caespiticium Hedw. This vegetation was expected to result in P. tremuloides, mixed P. tremuloides and Picea glauca (Moench) Voss, and P. glauca/Hylocomium splendens forest stands with increasing age, respectively. P. tremuloides//Calamagrostis purpurascens—Arctostaphylos uva-ursi stands formed the mid-seral vegetation. Along the chronosequence, total tree, P. tremuloides, shrub, and herb cover peaked 50–70 years after stand initiation; P. glauca cover, total and nonvascular species richness, and dominance concentration gradually increased (P < 0.001); vascular plant richness decreased; bryophytes had a U-shaped abundance pattern; and total plant cover was constant through time (125%). Richness totalled 113 species with averages of 13–18 per relevé. Coarse woody debris was most abundant (maxima 100–223 m³/ha) during the first 20 years of stand development then declined to <50 m³/ha. Successionally, a stem exclusion stage occurred (years 8–18), but with a delayed peak of 2–4 years and reduced densities (1.47 stems/m²) relative to southern boreal stands. No understory suppression, and therefore, no reinitiation stage occurred. Following stem exclusion, an accelerated canopy transition stage occurred relative to southern boreal forests due to early establishment rather than better height-growth rate of P. glauca relative to P. tremuloides. P. glauca tended to equal the cover of P. tremuloides 95–100 years after stand initiation. The oldest vegetation type in the chronosequence more closely resembled old-growth than a gap dynamic stage of development, possibly because of its youthful average age of 125 years. A modification was proposed for the canopy transition stage (Chen–Popadiouk stand development model) to account for the “forced” replacement of P. tremuloides by P. glauca. Differences in stand development were attributed to the cold northern climate.     

Quantitative Genetic Variability in Picralima nitida (Stapf) from Seven Sources in Nigeria

Intraspecific variation in useful tree species is a requirement for any improvement program. Fruits of P. nitida were collected from seven different sources along its geographic range in Nigeria; metrical traits of seeds and resulting seedlings were assessed as well as the biomass. There were significant (p ≤ .05) differences in seed metrical traits of length, width, and weight. Seeds from J4 had the highest germination percentage of 95%, while Ore had the lowest percentage of 70. Highest mean values of 2.22 g, 3.11 cm, and 95 for weight, length, and number of seeds per pod, respectively, were obtained from Edo seeds. There were significant (p ≤ .05) differences in seedlings height, collar diameter, number of leaves, internodes, stem dry weight, root dry weight, leaf dry weight, total dry weight, and leaf area among the sources. The highest mean values of 4.33 cm (collar diameter), 2.31 cm (internodes length), were obtained from Edo collection. Other seedling traits and biomass indices were highest in J4 provenance. J4 seedlings had the highest average relative growth rate (RGR) values of 0.0450 gg^?1 wk^?1 while Etemi seedlings had the highest average net assimilation rate (NAR) value of 0.0063 g² wk^?1. J4 propagule had the best overall performance and is therefore recommended as a seed source for the improvement and conservation of Picralima nitida.     

Growth and nutritional qualities of three ocimum species as affected by methods of propagation

Ocimum species are well known for their medicinal values and this has increased demand from individuals and the pharmaceutical industry. In order to meet the demand for this plant species three different Ocimum species (Ocimum basilicum, Ocimum gratissimum and Ocimum americanum) were propagated by two methods (stem cutting and seed) and their morphometric characteristics were evaluated after six and eight weeks. The chlorophyll content, proximate composition and phytochemical content of the plants were determined. The results obtained showed that the stem cutting propagated Ocimum species performed better than the seed propagated species. The results also revealed that there was a strong correlation between plant height and other morphometric characters. Also, it was discovered that the Ocimum species propagated by seed contained more phytochemicals than those propagated by stem cutting. However, gratissimum species propagated by stem cutting appeared to perform better than two other Ocimum species in terms of plant height, leaf number, stem girth and number of branches.     

Mycosphaerellaceae and Teratosphaeriaceae associated with Eucalyptus leaf diseases and stem cankers in Uruguay

Mycosphaerella leaf diseases represent one of the most important impediments to Eucalyptus plantation forestry. Yet they have been afforded little attention in Uruguay where these trees are an important resource for a growing pulp industry. The objective of this study was to identify species of Mycosphaerellaceae and Teratosphaeriaceae resulting from surveys in all major Eucalyptus growing areas of the country. Species identification was based on morphological characteristics and DNA sequence comparisons for the Internal Transcribed Spacer (ITS) region of the rDNA operon. A total of ten Mycosphaerellaceae and Teratosphaeriaceae were found associated with leaf spots and stem cankers on Eucalyptus. Of these, Mycosphaerella aurantia, M. heimii, M. lateralis, M. scytalidii, Pseudocercospora norchiensis, Teratosphaeria ohnowa and T. pluritubularis are newly recorded in Uruguay. This is also the first report of M. aurantia occurring outside of Australia, and the first record of P. norchiensis and T. pluritubularis in South America. New hosts were identified for Kirramyces gauchensis, M. aurantia, M. marksii, M. lateralis, M. scytalidii, P. norchiensis, T. molleriana, T. ohnowa and T. pluritubularis. Interestingly K. gauchensis, which has been known only as a stem pathogen, was isolated from leaf spots on E. maidenii and E. tereticornis. The large number of Mycosphaerellaceae and Teratosphaeriaceae occurring in Uruguay is disturbing and raises concerns regarding the introduction of new pathogens that could threaten not only Eucalyptus plantations but also native forests.     

Pathogenic fungi associated with pre‐ and post‐emergence seedling blight of pine and cypress in Fars Province,Iran

Seed and root rot of pine and cypress seedlings cause heavy annual losses to forest nurseries in Fars Province. Root and crown samples of various species of conifers, such as Tehran pine (Pinus eldarica), brutia pine (Pinus brutia), Arizona cypress (Cupressus arizonica), Shirazian cypress (Cupressus sempervirens var. fastigiata), common cypress (C. sempervirens var. horizontalis) and oriental arborvitae (Thuja orientalis), showing chlorosis, necrosis, stunted growth, defoliation and root and crown rot symptoms were collected from pine and cypress nurseries across Fars province at various time intervals. Infected tissues were washed and cultured on acidified potato dextrose agar (PDA) and corn meal agar (CMA) amended with Delvocide and ampicillin, with and without surface sterilization, respectively, and incubated at 25°C for 3–5 days. Decaying seeds of all plant species were also collected from nursery seed stocks and cultured on PDA. Hyphal tip isolates were used for further studies. Species of Phytophthora, Pythium, Rhizoctonia and Fusarium were isolated from symptomatic seedlings of pine and cypress at different times during the growing season. Pathogenicity of isolates of Phytophthora, Pythium and Rhizoctonia was confirmed on seedlings of all plant species, whereas Fusarium sp. isolated from the seeds of Tehran pine was only pathogenic on seedlings of Tehran pine and Arizona cypress. Virulent isolates identified as Phytophthora nicotiana var. parasitica, Pythium ultimum, Pythium paroecandrum, Rhizoctonia solani and binucleate Rhizoctonia‐like fungus caused root and crown rot of pine and cypress seedlings. Pathogenic isolates of Fusarium identified as Fusarium proliferatum also caused pre‐emergence seed decay of pine and cypress. Isolates of Phytophthora and Pythium were the most virulent of these fungal isolates.     

盐胁迫对红楠幼苗生长及Na+、K+吸收和分布的影响

In order to explore the salt tolerance mechanism of Machilus thunbergii, the effects of salt stress on seedling biomass, root morphology, sodium and potassium absorption and distribution were studied. The results showed that the above-ground biomass increased slightly under lower salt stress conditions, while the below-ground biomass, root length and root surface area showed a downtrend. The above-ground growth was limited under high concentration salt stress, while the under-ground growth was not subject to significant restrictions. The absorption of Na⁺ in root increased under salt stress, but that of K⁺ decreased. The ability of Na⁺ transporting from root to leaf and stem was weakened. The accumulation of Na⁺ in stem and leaves was less. With the decreased absorption of K⁺, the ratio of Na⁺/K⁺ also continuously increased. With the increased concentration of salt stress, the ability of K⁺ absorption in roots increased. The ability of K⁺ transporting from root to leaf and stem was enhanced, which resulted in significant increase of K⁺ in the leaves and stem. The accumulation of Na⁺ in the under-ground was significantly greater than that in above-ground, while the K⁺ content in above-ground increased significantly, which played a key role in maintaining normal growth and metabolism of M. thunbergii.     

First report of the brown root rot disease caused by Phellinus noxius,its distribution and newly recorded host plants in the Amami Islands,southern Japan

To determine whether the brown root rot disease caused by Phellinus noxius is present in the Amami islands, which are situated near Okinawa, we conducted six field surveys from 1999 to 2005. The brown root rot disease was found in 22 tree species in 17 plant families at 25 different sites in all the islands surveyed. Sixteen of these species were newly recorded as host plants of P. noxius. The disease was more common in the low elevation plains and on hills less than 100 m above sea level than in mountainous areas. This is the first report of the brown root rot disease caused by P. noxius in the Amami Islands, Japan, and Ohshima Island is currently the northern‐most distribution point of the disease in the northern hemisphere.     

Effects of oak root pruning in forest nurseries on potential pathogen infections

Despite the general practice of root pruning, little is known about the potential impact of reducing shoot/root systems of oak seedlings in this way on their future susceptibility to pathogens, for example Cylindrocarpon spp., Fusarium spp., Ilyonectria spp., Pythium spp. Phytophthora spp. or Rhizoctonia spp. In this study, root‐pruned and non‐pruned seedlings of Quercus robur grown under controlled conditions were inoculated with aggressive and less‐aggressive pathogens. Results indicated, in contrast to our initial assumption, that pathogens significantly reduced lateral root biomass more in non‐pruned seedlings, the extent of the response depending on the pathogens species. In response to pathogen pressure, pruned seedlings tended to attain a higher dry stem mass fraction, but lower dry leaf mass fraction. Pathogens also suppressed leaf mass in total root dry mass fraction (dry leaf mass/total root dry mass ratio, in g × g^?1) more in pruned than in non‐pruned seedlings. These results suggest differences in growth between non‐pruned and pruned seedlings in response to pathogen stress. In nurseries, root pruning of oak trees may enhance the reduction in leaf mass in lateral roots mass fraction resulting from pathogen infections, which may decrease seedling quality. It is therefore important to ensure a low level of inoculum of soil‐borne pathogens to minimize the risk of seedling infection.     

Management of fungal root‐rot pathogens in tropical Acacia mangium plantations

Acacia mangium is a fast‐growing tree species. It is mainly planted in large monocultures for pulpwood in South‐East Asia. Root rot has become the most economically damaging disease of this species with high tree mortality rates observed during second and third rotations. Two main types of root rots have been found in A. mangium, viz. brown root‐rot and red‐root disease caused by Phellinus spp. and Ganoderma spp., respectively. To assess the future management options for root rot of A. mangium, we review past and current disease‐management strategies for root rot in different temperate and tropical industrial tree crops. The efficacies of a wide range of silvicultural, chemical and biological options are detailed, and their potential utilization in managing root rot of A. mangium is discussed. We conclude that the current gaps in knowledge regarding identification, biology and disease epidemiology of the root‐rot pathogens will need to be addressed so that effective management options can be developed.     

Early growth differentiation among Prosopis flexuosa D.C. provenances from the Monte phytogeographic province,Argentina

Early-growth differentiation among seven provenances of Prosopis flexuosa (algarrobo dulce) from the Monte phytogeographic province, Argentina, was studied by comparing their height growth; whole-seedling dry mass gain; allocation to root, stem and leaves; leaf number and leaf area in a common garden. Differentiation among provenances was detected for all the seedling characters examined except leaf number. Family variation within provenances was significant for height growth and leaf number. Variation on the provenance level was related to the elevation, geographic location, and some abiotic conditions of the seed source such as mean annual temperature and frost free period. Latitudinal clines were evident for almost all the growth traits. They were more pronounced for height and aboveground mass, and moderate for total plant mass and leaf area per plant. In addition, a good correspondence in growth traits between young seedlings and older trees of this species (studied by others authors) was also assessed. This fact would permit an early selection and genetic advances in the short term in breeding programs.     

Growth and nutrient concentration of two native forage legumes inoculated with Rhizobium and Mycorrhiza in Missouri, USA

The Center for Agroforestry at the University of Missouri has tested numerous native legumes for potential use in agroforestry and selected Illinois bundleflower (Desmanthus illinoensis (Michaux) MacMillan ex Robinson and Fern.) and panicled tick clover (Desmodium paniculatum (L.) DC.) for further testing. Our objective was to document the effect of arbuscular mycorrhizae (AM) (Glomus spp.) and Rhizobium on growth and nutrient concentration of these legumes. Seeds were planted in a greenhouse and inoculated with one of two species of AM and/or one of two strains of Rhizobium. Plants were harvested after 80 d and data taken on leaf and stem dry weight, root fresh weight, stem height, nodulation, AM colonization, and N, P, K, Ca, and Mg concentration. Inoculation with Rhizobium did not affect plant growth in Illinois bundleflower, but colonization by Glomus intraradices increased all plant growth variables except stem height. Nutrient concentration was unaffected by the presence of either endophyte. In contrast, inoculation of panicled tick clover with Rhizobium str. 41Z10 increased leaf dry weight (32%) compared to the control and root fresh weight (41%) compared to str. 32Z3, and colonization by G. intraradices increased leaf dry weight (35%) and stem height (26%). Both species of AM increased P and K concentration (41% and 55%, respectively) in panicled tick clover. Our results suggest that the growth of these legumes can be improved by the use of proper AM species and/or Rhizobium strains. However, additional research to identify the best Rhizobium and AM inoculates for these plant species is important in developing strategies for their use in agroforestry. This revised version was published online in June 2006 with corrections to the Cover Date.     

新疆杨元素含量与生物量研究

新疆杨(Populus bolleana Lauche)在我国新疆栽培最早,尤以和田、喀什地区生长最好。青海、甘肃、宁夏亦早有栽培,近十余年在陕西、内蒙、山西、辽宁、吉林诸省和北京市也有引种,是我国干旱、半干旱地区农田防护林及人工丰产林的优良树种。为进一步利用新疆杨资源,研究其生物量将具有实际应用价值。     

Nutrient element contents of cutting seedlings of hybrid species （ Liriodendron chinense x tulipifera）

The cutting seedlings ofLiriodendron chinense xtulipifera were treated with the different concentrations of auxin (treatment₁: IBA of 50 g·kg⁻¹+NAA of 300 g·kg⁻¹; treatment₂; IBA of 100 g·kg⁻¹+NAA of 300 g·kg⁻¹). The biomass nutrient element contents for different organs (root, stem, leaf) of cutting seedling ofLiriodendron chinense xtulipifera were measured by the dry method, Kjeldahl method and Atomic Absorption Spectroscopy method. The result showed that the biomass of root, stem, and leaf of the cutting seedling treated with auxin was all remarkably increased. The contents of element C in root, stem and leaf had no significant difference between the control and auxin treatments, while the contents of N, P, K and Ca in stem were much lower than that in leaf and root. Variance analysis showed that for the same organ with different concentration treatment of auxin, the four nutrient elements (N, P, K, and Ca) had no significant difference in contents, while there existed significant or very significant difference in contents of the four nutrient elements in different organs with the same concentration auxin treatment. The N, P, K and Ca contents were very low in cutting seedlings; as a result, additional fertilizer should be applied to the seedlings when they were planted in the field. Foundation item: This paper was supported by Jiangsu Province Science Foundation (BE96350). Biography: ZHANG Xiao-ping, (1972-), female, Ph. Doctor in Nanjing Forestry University. Nanjing 210037, P. R. China. Responsible editor: Zhu Hong     

Anchorage of mature conifers: resistive turning moment, root-soil plate geometry and root growth orientation

Eighty-four mature Norway spruce (Picea abies L. Karst), silver fir (Abies alba Mill) and Scots pine (Pinus sylvestris L.) trees were winched over to determine the maximum resistive turning moment (M(a)) of the root-soil system, the root-soil plate geometry, the azimuthal orientation of root growth, and the occurrence of root rot. The calculation of M(a), based on digital image tracking of stem deflection, accounted not only for the force application and its changing geometry, but also for the weight of the overhanging tree, representing up to 42% of M(a). Root rot reduced M(a) significantly and was detected in 25% of the Norway spruce and 5% of the silver fir trees. Excluding trees with root rot, differences in M(a) between species were small and insignificant. About 75% of the variance in M(a) could be explained by one of the four variables--tree mass, stem mass, stem diameter at breast height squared times tree height, and stem diameter at breast height squared. Among the seven allometric variables assessed above ground, stem diameter at breast height best described the root-soil plate dimensions, but the correlations were weak and the differences between species were insignificant. The shape of the root-soil plate was well described by a depth-dependent taper model with an elliptical cross section. Roots displayed a preferred azimuthal orientation of growth in the axis of prevailing winds, and the direction of frequent weak winds matched the orientation of growth better than that of rare strong winds. The lack of difference in anchorage parameters among species probably reflects the similar belowground growth conditions of the mature trees.