Cultural and PCR‐based detection of Septoria musiva in inoculated hybrid poplar stems

The fungal pathogen Septoria musiva can be difficult to isolate from cankers that result from its colonization of poplar stems, and its persistence in these cankers has not been well studied. In order to compare cultural and polymerase chain reaction (PCR)‐based assays for detection of S. musiva in cankers, stems of susceptible hybrid poplar clone NC11505 were wounded and inoculated in August 2003. At 8, 16, 24 and 32 weeks after inoculation (October and December 2003, February and April 2004, respectively), 110 inoculated stems (plus controls) were harvested and a semiselective culture medium was used in attempts to detect the pathogen in bark and wood. Six chips of bark and six chips of underlying wood from one half of each canker were incubated on the semiselective medium for 2 weeks until pycnidia and conidia of S. musiva could be identified. The number of positive cankers and positive chips (out of six attempts per tissue per canker) was recorded. The remaining halves of cankers from subsets of 70 inoculated stems (plus controls) of those harvested in October 2003 and April 2004 were tested using a PCR‐based assay. Three chips of bark and three chips of underlying wood were ground, and DNA was extracted and then amplified using S. musiva‐specific primers designed from the internal transcribed spacer (ITS) region of nuclear rDNA repeats. The number of positive cankers and positive chips (out of three attempts per tissue per canker) was recorded. For both assays, the number of positive cankers and the number of positive chips per canker decreased with time. Using either assay, however, the pathogen was still detected from at least 49% of cankers at 32 weeks after inoculation.     

Studies of microconidia of Marssonina brunnea and apothecia of Drepanopeziza tremulae

Microconidia of M. brunnea were induced in the laboratory on 15 % V8 juice agar and poplar leaf discs. Apothecia of Drepanopeziza tremulae and stromata containing conidia were formed on naturally infected leaves and leaf-discs. The influence of temperature on apothecial development was investigated. The morphology of apothecia and stromata is described.     

Genomewide identification and development of microsatellite markers for Marssonina brunnea and their applications in two populations

Marssonina brunnea is an important pathogen that causes Marssonina leaf spot disease of poplar (MLDP) in various poplar species. Resistance breeding is considered as the main method for preventing this disease and requires information on genetic diversity and population structure. However, molecular markers that may be utilized in the identification of this fungus are limited. This study investigated the distribution of microsatellites in the M. brunnea genome. A total of 15,356 microsatellite markers (excluding mononucleotide repeats) were isolated from 50.1 Mb of genomic sequence. Eight M. brunnea isolates were evaluated in terms of 102 loci, followed by the selection of markers that could be utilized in investigating the population structure of 47 M. brunnea isolates from two populations. Twenty‐four polymorphic microsatellite markers were developed for M. brunnea. The number of alleles per locus ranged from two to eight (average: 3.75). The polymorphism information content (PIC) of these loci ranged from 0.0408 to 0.6492. The average Shannon's information index of these loci in the two populations was 0.3819 and 0.5351, respectively. Using these markers, M. brunnea isolates were mainly divided into two distinct clusters based on the relatedness of the sampling sites. These results indicate that the selected markers could be effectively utilized in investigating the population genetic structure of M. brunnea. This is the first report on microsatellite markers in M. brunnea.     

杨树与杨盘二孢菌激发子互作进程中活性氧的释放及膜脂过氧化

用杨盘二孢菌的激发子粗提液,与高度抗黑斑病的Ⅰ-72杨和高度感染黑斑病的加杨悬浮细胞互作,测定杨树悬浮细胞的生物化学变化.结果表明:Ⅰ-72杨在活性氧的释放和△pH的变化两方面均明显高出加杨;膜脂过氧化过程,从量的方面看,二者几乎没有差异,只是Ⅰ-72杨的膜脂过氧化高峰期要早于加杨1 h.这些研究可以为杨树的抗病机理和杨树抗病基因的研究提供基础.     

In vitro and in vivo germination of spores of Marssonina brunnea (Ell. et Ev.) P. Magn

A water soluble inhibitor of germination is present on the surfaces of freshly collected spores of Marssonina brunnea (Ell et Ev.) P. Magn. Spores of this pathogen have a high potential for germination even in the absence of external substrates. Among the poplar clones examined there was no correlation between spore germination on leaf discs and the disease reaction of the discs under controlled conditions. However under these conditions the disease development on leaf discs taken from clone I-69/55 was correlated with the high resistance of this clone to Marssonina leaf spot in the field.     

The development of Lophodermium pinastri in conifer nurseries and plantations in North America

The recent outbreak of Lophodermium needlecast in North America first appeared in 1966 in forest nurseries on red pine (Pinus resinosa) and Scotch pine (P. sylvestris). Dispersal of infected nursery stock throughout North America has created a serious needlecast problem in Scotch pine Christmas tree plantations. Two biotypes of L. pinastri are present. The pathogenic strain may be a recent introduction. The fungicides maneb and chlorothalonil are being used for control.     

Genetic control of fiber properties and growth in triploid hybrid clones of Populus tomentosa

To better understand the genetic control of fiber properties (fiber length [FL], fiber width [FW] and coarseness [C]) and growth traits (tree height [H], diameter at breast height [DBH] and stem volume [SV]) in triploid hybrid clones of Populus tomentosa carr., genetic relationships among selected fiber properties with growth traits were examined in five-year-old clonal field trials located in Yanzhou, Gaotang and Xiangfen, China. In total, 180 trees from 10 clones were sampled from the three sites. The site had a moderate effect on FW, C and tree growth, and a highly significant (P<0.001) effect on FL and fiber length/width (FL/W). Clonal effects were also significant (P<0.05) for all studied traits except for the DBH and SV. Clone×site interactions were significant for all studied traits (except for FL). The estimated repeatability of clonal mean for FL (0.91) was higher than for FW (0.88), C (0.77), FL/W (0.74), H (0.62), DBH (0.61) and SV (0.55). Intersite genetic correlation estimates indicated that fiber properties were more stable than growth traits. Positively insignificant genetic correlation estimates between FL and growth trait and negatively insignificant genetic correlation estimates between C and growth traits were observed. This suggests that in the triploid hybrid poplar, clones selection for growth traits will not result in a significant increase or reduction in the fiber properties.     

Damage caused by the fungus Scleroderris in plantations and nurseries in Europe and North America

This communication deals with the damage caused by Scleroderris lagerbergii in nurseries as well as in plantations of Europe and North America. Roughly a two million dollar damage which easily may be higher, has been estimated by the author.     

柳蝙蛾在苗圃的发生规律及防治

柳蝙蛾 Phassus excrescens Butler在哈尔滨市 1年发生 1代 ,危害杨、柳大苗树干中部和根。文中介绍了该虫的生物学特性 ,发生规律及防治技术 ,为生产防治提供依据     

Biology of Litosermyle ocanae in Colombian Pinus patula plantations

Plantations of Pinus spp. in Colombia are severely damaged by various phasmid (Phasmatodea: Diapheromeridae) insects. Of these, Litosermyle ocanae is one of the most serious defoliators. Since 1988, several outbreaks have been recorded in Pinus patula plantations, resulting in substantial economic losses. The aim of this study was to determine the life cycle of Litosermyle ocanae in P. patula plantations in Colombia. In addition, we assessed the population levels of L. ocanae and the presence of natural enemies of L. ocanae in these plantations. The development of L. ocanae was monitored under controlled conditions, and population fluctuations and the presence of natural enemies was assessed from field-collected eggs and field observations. The results showed a total life cycle of 225 d and 235 d for males and females, respectively, and a complete fourth instar nymph cycle of 121 d and 116 d for males and females, respectively. The sex ratio was 1:1.7 female to male. Females laid an average of 112 eggs. The number of eggs peaked in November and the most dominant natural enemy observed was a parasitoid wasp Adelphe sp. (Hymenoptera: Chrysididae). The results provide important information for the management of L. ocanae in P. patula plantations.     

猕猴桃细菌性溃疡病综合防治技术

从检疫、栽培管理、化学及物理防治等方面对猕猴桃细菌性溃疡病的综合防治技术进行了阐述 ,论述了冻害与猕猴桃细菌性溃疡病发生的关系 ,提出了以预防冻害为基础 ,从而防止猕猴桃细菌性溃疡病发生的预防措施。     

Considerations on the cause of conifer damage in plantations attributed to the Scleroderris canker

From observations, made in Quebec, in red pine, jack pine and white pine plantations, evidence is provided showing that extensive damage, noticed in 1967, was directly caused by summer frosts during the most critical growth period, as had been demonstrated 20 years before in another plantation in the same area. Similar losses recorded and studied in Canada and in the Northeastern United States, since 1935 appear, in most cases, to be the result of the same unfavourable conditions and not due to the primary attack of Scleroderris lagerbergii Gremmen that should be considered a saprophyte or a secondary parasite on any dead or dying pine branches and stem lesions. Although a disease, attributed to the same fungus in Europe, on pines planted outside their natural range, exhibited different symptoms, its etiology is also questioned.     

Susceptibility of Eucalyptus hybrid clones to Botryosphaeria canker in Uganda

ABSTRACT

The study assessed the susceptibility of the nine commonly grown Eucalyptus clones to Neofusicoccum species associated with Botryosphaeria canker in Uganda. The inoculation trials indicated that susceptibility of Eucalyptus hybrids differed significantly (p = .000), clones GU609, GU7, GC578, and GC796 exhibiting a higher tolerance than GC784, GC550, GU8, GC514, and GC540. The results further revealed that N. parvum was more pathogenic than N. kwambonambiense. The generated information can be exploited in sustainable forest management by expanding the growing of tolerant hybrids in areas with high Botryosphaeria canker disease pressure.     

塔里木河下游胡杨树腐烂病病原鉴定

对新疆塔里木河下游胡杨树Populus euphratica腐烂病病原菌进行分离和鉴定。从新疆巴音郭楞蒙古自治州铁门关市采集胡杨树腐烂病典型病样12份,采用组织分离法分离获得12个分离物,根据科赫氏法则测定致病性,结合形态学观察和18S r DNA-ITS,β-tubulin两个基因序列分析,将其鉴定为金黄壳囊孢Cytospora chrysosperma。     

Competition control in juvenile hybrid poplar plantations across a range of site productivities in central Saskatchewan,Canada

The response of hybrid poplar plantations established on former agricultural land in Saskatchewan to competition from weeds on a range of site productivities was studied. The short-term impact of competition control on the growth of juvenile trees and how tree responses to competition control differed across the productivity gradient was of particular interest, as was the determination of which resource was most highly competed for and was most important in determining tree growth. Eight sets of paired plots in juvenile hybrid poplar plantations were established in central Saskatchewan across a range of site productivities. In each pair, one plot had complete weed control (weed-free) while in the other plot weeds were allowed to grow. The best soil predictor of tree growth was soil texture, represented by a combination of the percentage silt and clay, with finer textures showing better growth. Competition control significantly increased tree growth on all sites with the benefit being greatest on the higher productivity sites. Soil water appeared to be highly competed for between trees and weeds and was a dominant resource controlling growth. For soil nutrients, nitrogen and phosphorous were highly competed for between trees and weeds. However, leaf phosphorous concentration of the weed-free plots had a strong positive relation to tree growth while nitrogen did not, indicating that when trees are free of competition they can access sufficient nitrogen from these soils.     

Newly recognized bacteria involved in trunk scab and canker of white and hybrid poplars

In a 4‐year‐old collection of native Italian Populus alba, growing in the eastern Po valley, many trunks showed severe symptoms characterized by brown spots, similar to trunk scab and/or by cankers. Canker‐like growths, often with gall‐like‐formations in the earlier developmental phases were also found on some clones of P. trichocarpa and their hybrids, as well as on P. deltoides growing in several Northern Italian nurseries. Bacteria and fungi present in the affected tissues and potentially involved in the disease were examined. No fungi were detected, however, several species of bacteria were isolated and identified: Pseudomonas mendocina and Erwinia herbicola group, from the brown spots; Erwinia carotovora sub sp. carotovora and, occasionally, E. herbicola group, from cankers. Only E. carotovora sub sp. carotovora produced clear symptoms of canker when artificially inoculated on young plants of different poplar species. This is the first time this symptomology on poplar species has been clearly related to E. carotovora sub sp. carotovora.     

First report of Cryptosphaeria pullmanensis as causal agent of Cryptosphaeria canker of Populus nigra in Iran

A diatrypaceous fungus was isolated consistently from cankers on Populus nigra trees showing dieback symptoms in Kohgiluyeh Boyer‐Ahmad, Zanjan and Esfahan provinces in Iran. Morphological characteristics and phylogenetic analyses of the ITS region of the rDNA identified the taxon as Cryptosphaeria pullmanensis. Pathogenicity tests conducted in potted 3‐month‐old cuttings of P. nigra confirmed Koch's postulates and revealed that C. pullmanensis caused canker on this host. This is the first report of C. pullmanensis causing a canker disease on P. nigra in Iran.     

Maximising growth and sawlog production from Acacia hybrid plantations in Vietnam

New Forests - Management options to optimise sawlog production from Acacia hybrid (A. mangium?×?A. auriculiformis) combining thinning and fertiliser treatments were applied at six...     

Nutrient transfer associated with precipitation in plantations of eastern cottonwood (Populus deltoides)

Determinations of pH and annual atmospheric inputs of total N, P, K, Ca, and Mg were made in a 7-year-old plantation of eastern cottonwood (Populus deltoides Bartr.) located on the floodplain of the Mississippi River near Greenville, MS. Concentrations and quantities of P, K, Ca, and Mg in precipitation and throughfall showed pronounced seasonal patterns, generally being greater in summer than winter. However, there was little difference between precipitation and throughfall N regardless of season. Relative to foliar element content, nutrients were leached in the order K>Mg>P>Ca with 47.3, 6.7, 3.1 and 31.2 kg/ha, respectively, being transferred to the forest floor. These quantities are generally higher than those reported for other forest species. The pH of precipitation increased upon contact with the summer canopy; however, the presence of acid precipitation (pH<5.6) was found in only eight of the 54 rainfall events monitored. Quantities of precipitation intercepted by the cottonwood stand exhibited no seasonal differences.     

Activation of stress-responsive mitogen-activated protein kinase pathways in hybrid poplar (Populus trichocarpa x Populus deltoides)

Plant mitogen-activated protein kinase (MAPK) cascades are important amplifying modules that can rapidly transduce stress signals into various appropriate intracellular responses. Several extracellular regulated kinase (ERK)-type MAPKs involved in plant defense signaling have been identified in herbaceous species, but no MAPK cascade has yet been characterized in a tree species. We examined the signal transduction events that lead to activation of defense mechanisms in poplar, a major forest species of economic and ecological importance which is becoming the model tree system for studying stress and adaptation responses. We show that, in poplar cell suspensions and leaf tissue, chitosan, a non-host-specific elicitor, and ozone, a strong oxidant and atmospheric pollutant, induce rapid and transient activation of at least two myelin basic protein (MBP) kinases with apparent molecular masses of 44 and 47 kD. The chitosan- and ozone-activated kinases have characteristics of MAPKs-they preferentially phosphorylate MBP, require tyrosine and threonine phosphorylation to be activated and are specifically recognized by anti-ERK and anti-pERK antibodies. Moreover, activation of these poplar MAPKs by chitosan or ozone is dependent on the production of reactive oxygen species; the influx of calcium ions via membrane channels; the activation of an upstream, membrane-localized component; and a cognate MAPK kinase (MAPKK). These data suggest that biotic and abiotic challenges activate MAPKs in poplar, as in herbaceous species, which then function as a convergence point for pathogen defense and oxidant stress signaling cascades.