木材白腐机理研究进展

白腐菌是木材的主要腐朽菌之一，白腐菌菌丝在细胞内形成多种降解酶主要是木素降解酶，次则是纤维素降解酶及半纤维素降解酶，以降解细胞壁物质中的木素、半纤维素及纤维素，作为木腐菌的营养。由于这些木材组成的降解，必然改变木材的化学及物理性质。近年来，在白腐菌的营养需求、降解酶传递途径，对木材主要组成酶降解机理及对材性的影响，产酶的分子遗传等领域的研究均取得一定进展，可望不久将来能利用生物工程改变白腐菌基因，     

Stocks and decay dynamics of above- and belowground coarse woody debris in managed Sitka spruce forests in Ireland

Coarse woody debris (CWD) has become recognised as an important component of the carbon (C) pool in forest ecosystems. In Ireland, managed Sitka spruce (Picea sitchensis (Bong) Carr.) forests account for 52.3% of the total forest estate. To determine the stock and decay dynamics of above and belowground CWD, field surveys using fixed area sample plots, were conducted in six even-aged Sitka spruce stands, representing the young, intermediate and mature stages of a typical commercial rotation. The volume, mass, density loss and C:N ratio of all CWD types (logs, stumps, and coarse roots) were determined using a five-decay class (DC) system. The decay rates and half life of CWD was also determined. To estimate CWD coarse root mass; roots associated with stumps classified in different decay classes were excavated. The coarse roots were categorised into small (2-10 mm), medium (10-50 mm) and large (>50 mm) diameter classes.CWD C-mass ranged from 6.98 to 18.62 Mg ha⁻¹ and was highest in an intermediate forest (D35), while the aboveground volume varied from 6.31 to 42.27 m³ ha⁻¹. Coarse roots accounted for 21% to 85% of the total CWD C-pool in the surveyed stands. The total CWD C-mass was poorly correlated with the number of thinning events (R² = 0.29), when data from D35 was excluded. The density loss was significant in logs (45%), stumps (58%), and small- (38%), medium- (50%) and large roots (38%) as decay progress from DC 0 to 4. There was a 46%, 41%, 51%, 72% and 57% decline in C:N ratio of logs, stumps, small-, medium- and large roots, respectively, as decay progressed from DC 0 to 4. The density decay rates were 0.059, 0.048 and 0.036 kg m⁻³ year⁻¹ for logs, stumps and coarse roots, respectively. The size classification of roots did not significantly affect their decay rate. The half life (50% decomposition) of CWD was estimated has 12-, 14- and 19 years for logs, stumps and roots of Sitka spruce. Regression curves showed a strong correlation between the density and C:N ratio (R² = 0.69, 0.74 and 0.93 for logs, stumps and coarse roots, respectively). The long term storage of C and its slow rate of decomposition make CWD a vital structural and functional component of the CWD C-pool and a major controller of forest ecosystem C-retention.     

Predicting sapstain and degrade in fallen trees following storm damage in a Pinus radiata forest

Storm damage in production forests constitutes a major source of economic loss world wide, yet the retrieval of salvageable timber remains problematic. In particular, an inability to anticipate when sapstain and degrade will appear hampers the planning of log recovery operations. A study was conducted to monitor the deterioration of fallen trees following two winter storms causing wind and snow damage in a Pinus radiata plantation forest in the upper South Island of New Zealand. Percentage sapstain, incidence of basidiomycete decay fungi, and frequency of bark beetle infestation increased, while percentage sapwood moisture content decreased, over a period of 1 year. These changes proceeded more rapidly in fallen trees that were severed at stump height, to simulate breakage, than in those that were left partially rooted. There was little beetle activity at the time of the storms, but Arhopalus ferus (Coleoptera: Cerambycidae), and Hylastes ater, Hylurgus ligniperda and Pachycotes peregrinus (Coleoptera: Curculionidae: Scolytinae), were collected in flight traps during the following spring and summer. The predominant fungal species associated with sapstain was Diplodia pinea, while Ophiostoma piceae and Grosmannia huntii were isolated near the end of the period. The main decay fungi obtained were Phlebiopsis gigantea, Stereum sanguinolentum, and Schizophyllum commune. A generalized linear mixed model was constructed to predict the development of sapstain in fallen trees for conditions prevailing during the study after a storm at the same time of year. According to the model, a 10 m long butt log of 22 cm mid length diameter will have minimal stain (<10% of the cross sectional area affected) when cut from severed stems up to 4 months after the storm; if taken from still-rooted trees this period will extend to 1 year. However, because of large between-tree variation, economically productive log recovery will also depend on the proportion of trees that lie below an acceptable sapstain threshold. Further research is needed to determine regional and seasonal influences on the development of sapstain in fallen trees.     

Efficacy of radio frequency treatment and its potential for control of sapstain and wood decay fungi on red oak,poplar, and southern yellow pine wood species

The effectiveness of radio frequency (RF) treatment in the control of wood decay fungi (Gloeophyllum trabeum, Ganoderma lucidum, and Irpex lacteus) and sapstain fungus (Ceratocystis fimbriata) in red oak (Quercus spp.), poplar (Populus alba), and southern yellow pine (Pinus spp.) was evaluated in the laboratory as an alternative to methyl bromide (MB) treatment. Wood samples (15.5 x 10 x 10 cm) were inoculated with fungi from a 7-day culture by dipping them to a depth of one face deep (2 cm) into inoculum and incubating them at 25°C for 14 days. Identical wood samples were left uninoculated as controls. Subsequent to incubation, the wood blocks were exposed to RF radiation in an industrial 40-kW dielectric oven at temperatures between 60° and 70°C for 2 min. The test fungi were recovered and reisolated from all of the control wood blocks but not from RF-treated wood blocks. RF treatment resulted in complete inhibition of the fungus in 98%-100% of the wood samples. Moisture content loss (≥1%) was noted after wood had been exposed to RF treatment. Moisture content may be an important factor to consider with RF treatments. RF treatment can, therefore, potentially provide an effective and rapid quarantine treatment as an alternative to MB fumigation for certain pathogen-wood combinations. This article reports the results of research only. Mention of a product does not constitute an endorsement or recommendation by USDA for its use.     

不同树种木粉/PVC复合材料天然耐腐性对比研究

选用5种不同树种木粉与PVC制备木塑复合材料,通过人工模拟加速试验对比研究不同组别复合材料对采绒革盖菌和绵腐卧孔菌的天然耐腐性差异,采用扫描电镜(SEM)和水分吸附测试深入分析腐朽菌对复合材料微观形貌及界面结合的影响,结果表明:不同组别复合材料对彩绒革盖菌耐腐性排序为:杉木/PVC马尾松/PVC白千层/PVC枫香/PVC尾巨桉/PVC复合材料;对绵腐卧孔菌耐腐性排序为:杉木/PVC尾巨桉/PVC、白千层/PVC、马尾松/PVC枫香/PVC复合材料。腐朽菌菌丝可通过木粉和PVC树脂界面结合空隙处进入试样内部进行侵蚀,从而降低复合材料间的界面结合,使其水分吸附率明显增加。     

Host ranges of North American isolates of Penicillium causing blue mold of bulb crops

Single isolates of four Penicillium species belonging to series Corymbifera (Penicillium allii, Penicillium hirsutum, Penicillium tulipae, Penicillium venetum) plus an isolate of Penicillium polonicum, all from North American sources, were inoculated individually into Crocus sativus (crocus), Allium sativum (garlic), Allium cepa (onion), Allium stipitatum (ornamental onion), Iris hollandica (iris), Ornithogalum umbellatum (grass lily), and varieties of Gladiolus (gladiolus), Tulipa (tulip) and Narcissus (daffodil). All isolates were pathogenic to garlic and onion (but none to ornamental onion), and all but P. polonicum to Tulipa, although virulence varied considerably. Additionally, P. hirsutum was pathogenic to Crocus, Gladiolus and Iris; P. tulipae to Narcissus, Crocus, Ornithogalum and Iris; P. venetum to Gladiolus, Ornithogalum and Iris; and P. polonicum to Iris. Nomenclature and taxonomy of series Corymbifera are summarized, the above results compared to similar investigations in Europe, and management implications provided.     

Chitosan applications pre- or postharvest prolong raspberry shelf-life quality

Raspberries are fruit with high metabolism that makes them very perishable, impairing their storage and shelf-life. Chitosan coatings have the potential to improve their postharvest life by reducing water loss, respiration rate and decay incidence. The purpose of this work was to study the effect of different concentrations of chitosan, applied pre- or postharvest, on the retention of quality attributes of fresh raspberries. The chitosan concentrations tested were 0 (control), 0.5, 1.0 or 2.0%. The postharvest treatment was applied immediately after harvest, dipping the fruit in the solutions for 5 min. The pre-harvest treatment was done with one hand-spray application per week for three weeks, starting when the fruit were just turning pink. In both experiments the fruit were stored at 0 °C and 90% RH. Pre- or postharvest use of chitosan at 1 or 2% was effective in maintaining titratable acidity and retarding respiration and ethylene production, weight loss and decay incidence. Application by both means resulted in the highest chitosan concentrations accelerating a reduction of ascorbic acid contents. Firmness was maintained only when the fruit were treated pre-harvest at 2%. Thus, application of chitosan at 1 or 2% postharvest and 2% pre-harvest was able to retain key raspberry quality attributes for 15 and 12 days, respectively.     

暖冬条件下播种密度和施氮水平对皖北地区小麦群体叶面积的影响

[目的]研究暖冬条件下播种密度和施氮水平对皖北地区小麦群体叶面积的影响。[方法]设施氮水平和播种密度2个因素,均设4个水平。施氮量在165～255kg/hm2,基本苗在90万～270万/hm2。肥料运筹氮肥按基肥∶拔节肥∶孕穗肥=6∶2∶2,磷肥∶钾肥=1.0∶0.6进行,（NH4）2HPO4用量为225kg/hm2,K2SO4用量为135kg/hm2。磷钾肥分基肥、拔节孕穗肥按7∶3施用。[结果]暖冬年份生育后期小麦群体叶面积下降过快,容易早衰。所设定的中密中氮水平组合群体叶面积下降较慢,高效叶面积率、有效叶面积率高。[结论]该研究为实现暖冬趋势下小麦的高产稳产提供科学依据。     

木腐菌及其腐朽机理研究进展

木腐菌可以有效地改善针叶材心材的渗透性,可用于辅助阔叶材散孔材年轮的鉴定,木腐菌及其所分泌的酶还可作为生物技术应用于木材工业,如生物制浆预处理、生物漂白以及木材酶解为糖的预处理等领域。本文从褐腐、白腐、软腐、竹材及人造板等几个方面出发,对国内外腐朽机理的研究现状进行了较为系统、全面的介绍,旨在使学者了解真菌选择性地降解木竹材的化学成分和细胞各部分的知识,为木竹材的保护和合理利用提供参考。