Citrus replant problem in Iraq I. Possible role of soil fungi and nematodes

The role of soil fungi and nematodes in citrus replant problems was investigated. Several pathogenic and non-pathogenic fungi and the nematodeTylenchulus semipenetrans were isolated in about equal abundance from soils which displayed or did not display replant problems. However, in almost all trees showing evidence of decline, infection by the fungusPhytophthora citrophthora had advanced through the roots until it had reached the tree crown. Fumigation of old citrus soil with methyl bromide greatly increased the growth of sour organe. The application of Nemacure, Benomyl and Ridomil 5G confirmed the important role of pathogenic and non-pathogenic fungi and nematodes in the citrus replant problem. Inoculation of methyl bromide-treated soil with the pathogenic and non-pathogenic fungi separately or in combination further confirmed the previous experiments and also revealed an important role ofP. citrophthora andFusarium solani when replanting citrus in old citrus orchards.     

Citrus replant problem in Iraq II. Possible role of allelopathy

The role of allelopathy in citrus replant problems was investigated in Iraq. The failure of citrus seedlings to grow normally in old citrus orchards was not caused by differences between old and non-citrus soils in electrical conductivity, pH, organic matter, soil texture and those minerals tested. Extracts of soil collected from old citrus orchards significantly reduced the growth of sour orange seedlings. Extracts and decaying sour orange roots reduced the growth of sour orange seedlings as did extracts of non-senescent sour orange leaves and decaying senescent leaves. Thus it appears that allelopathy is at least partly involved in the citrus replant problem.     

Effects of soil extracts from repeated plantation woodland of Chinese-fir on microbial activities and soil nitrogen mineralization dynamics

Effects of soil extracts from repeated plantation woodlands of Chinese-fir on soil fungi growth, the activities of microbial communities, and rates of net soil nitrogen mineralization were investigated. Soil extracts from replanted woodlands significantly inhibited soil non-pathogenic fungi growth, reduced soil respiration activities, and net soil nitrogen mineralization rates. However, soil extracts from replanted woodland increased the growth of pathogenic fungi. The combination of soil extracts and pathogenic fungi did not significantly reduce the growth of Chinese-fir seedlings when compared to the soil extracts alone. The combination of soil extracts with pathogenic and non-pathogenic fungi significantly increased the growth of Chinese-fir seedlings when compared to the combination of soil extracts and pathogenic fungi. The results suggest that the allelochemicals from soil extracts, rather than pathogenic fungi, are the key factor regulating the productivity and nitrogen cycling in repeated plantation woodlands.     

中国柑橘菌物病原名录

我国是世界上最大的柑橘生产国,柑橘产业在我国农业生产中占有重要地位.菌物病害是制约我国柑橘产业效益的重要因素.在过去一百余年里,我国植物病理学家和菌物学家描述和记载了大量柑橘上的病原菌物.然而随着分子系统学在菌物分类鉴定中的广泛应用,以及菌物命名法规的变化,一些菌物的分类地位和拉丁学名发生了较大的变化.为了方便使用者了...     

Potential role of allelopathy in the soil and the decomposing root of Chinese-fir replant woodland

The role of allelopathy in the Chinese-fir (Cunninghamia lanceolata) replant problem was studied. The failure of Chinese-fir seedlings to grow normally in Chinese-fir replant woodland was not only caused by the depletion of nutrients and the deterioration of the structure of replant woodland soil, but also by biotic factors and allelopathy. Extracts of soils collected from replant woodlands significantly reduced the growth of Chinese-fir seedlings. Extracts and decomposing root residues also significantly inhibited the growth of Chinese-fir seedlings. Extracts of the replant soil and of the decomposing roots from Chinese-fir replant woodland were both toxic to other plants. The combination of the decomposing root residues and the pathogenic fungi reduced the growth of Chinese-fir seedlings the most when compared to the decomposing root residue alone and the control. It appears that allelopathy is at least partly involved in the Chinese-fir replant problem. ei]Section editor: R Rodriguez-Kabana     

Effects of nematodes,fungi and bacteria on the growth of young apple trees grown in apple replant disease soil

Growth, dry root weight of seedlings and root score of apple seedlings cv. McIntosh were reduced when soils were inoculated with Pratylenchus penetrans, Penicillium janthinellum, Constantinella terrestris, Trichoderma sp., and 4 strains of Bacillus subtilis. Trichoderma sp., and B-1 and B-26 strains of B. subtilis alone reduced plant growth but the combination of Trichoderma sp. + B. subtilis (B-1) and Trichoderma sp. + B. subtilis (B-26) increased plant height. Plant height, root weight and root score were significantly reduced when P. penetrans plus B. subtilis or P. penetrans plus fungi plus bacteria were present in the soil. It is suggested that fungi, bacteria, nematodes alone or their combinations such as nematodes plus bacteria or nematodes plus fungi plus bacteria may contribute towards the occurrence of apple replant disease.Contribution number 700.Contribution number 700.     

芽孢杆菌菌肥和菌剂对连作条件下桃幼树生长和土壤环境的影响

研究向桃树连作土壤中添加芽孢杆菌菌肥和菌剂对再植幼树生长、土壤养分、酶活性和真菌群落的影响,可为缓解桃树连作障碍提供理论依据.在盆栽条件下,以一年生普通桃'圆梦'和连作10年的桃园土壤为试材,设置8个处理,即连作土常规处理(RS)、客土常规处理(NS)、连作土常规处理基础上分别添加1％、4％、8％的芽孢杆菌菌肥(BF1...     

甲壳素对连作条件下平邑甜茶幼苗生长及土壤环境的影响

研究在苹果连作土壤中添加甲壳素对苹果幼苗生长、土壤酶及土壤真菌群落结构的影响,探讨甲壳素缓解苹果连作障碍的可能性,为防控苹果连作障碍提供依据。盆栽条件下,以平邑甜茶幼苗为试材,在苹果连作土壤中分别添加0,0.5,1.0和2.5g/kg的甲壳素,测定了连作土壤中添加不同量的甲壳素后,幼苗生物量、根系保护酶活性、土壤主要酶(蔗糖酶、脲酶、磷酸酶等)活性以及土壤中真菌群落结构的变化。9月份结果表明,与对照相比,1.0 g/kg的甲壳素处理连作土,可显著提高平邑甜茶幼苗株高和干鲜重,分别比对照增加了36.8%、82.1%和100.8%;甲壳素处理能增加幼苗根系保护酶活性,其中1.0 g/kg甲壳素处理SOD、POD和CAT活性最高,其次为0.5 g/kg,而2.5 g/kg甲壳素处理显著抑制了幼苗根系保护酶活性。1.0 g/kg甲壳素处理可提高土壤中细菌/真菌值,并且提高了土壤中蔗糖酶、脲酶、蛋白酶、磷酸酶、过氧化氢酶和多酚氧化酶活性,分别比对照提高了8.6%、40.5%、81.1%、15.3%、18.7%和49.8%,2.5 g/kg甲壳素处理则降低土壤酶活性或者使土壤酶活性与对照相当。根据T-RFLP的图谱中OUT的数量、种类及丰度,分别计算了不同处理土壤的真菌多样性,发现1.0 g/kg甲壳素处理的连作土具有最高的多样性、均匀度和丰富度指数,分别比对照增加了52.2%、8.0%和87.1%。主成分分析(PCA)结果显示,不同剂量甲壳素处理的连作土壤中真菌被PC2分成了两部分,其中0.5 g/kg和1.0 g/kg的甲壳素添加量分布在PC2的负方向上,而CK和2.5g/kg的甲壳素处理分布在PC2的正方向上,这说明添加不同量的甲壳素对连作土壤真菌群落多样性有显著影响,添加量太多或者太少均会造成土壤真菌多样性下降,只有适量的甲壳素可提高真菌群落结构多样性。实验结果表明1.0 g/kg的甲壳素可提高连作平邑甜茶幼苗生物量,改善连作土壤环境,有效缓解平邑甜茶的连作障碍。     

Evaluation of monoammonium phosphate and bacterial strains to increase tree growth and fruit yield in apple replant problem soil

The long-term effects of biological agents alone and in combination with monoammonium phosphate on tree growth and fruit production of apple trees planted on apple replant soil was studied for five years. Application of monoammonium phosphate (MAP) in the year of planting increased shoot growth, cross-sectional trunk area and fruit yield of McIntosh on M.26 rootstock for the first two years. The application of bacterial agents alone were not effective in increasing young tree growth except BACT-1 in 1987. None of the bacterial agents increased fruit yield when applied alone. The addition of certain bacterial agents to MAP application increased young tree growth in various years. The combination of bacterial agent B-10 and MAP reduced young tree growth and yield compared with the MAP treatment alone. These results suggest that the application of MAP alone may be sufficient to alleviate the replant problem and the addition of BACT-1, EBW-4 or B8 bacterial agents to this treatment may be beneficial to increase tree growth in some years. Contribution number 822. Contribution number 822.     

新疆石河子地区甜樱桃采后腐烂致病真菌的分离鉴定

【背景】甜樱桃果实柔软多汁,采后腐烂率高。石河子是新疆新兴的甜樱桃种植地区之一,但由于采后储运不当造成巨大的经济损失。【目的】鉴定石河子地区的甜樱桃果实腐烂病原菌,以期提高该地区甜樱桃的采后品质、延长货架期。【方法】从石河子136团种植的甜樱桃腐坏组织中分离真菌菌株,根据柯赫氏法则将分离得到的菌株重新接种到健康的甜樱桃果实上确定其致病性;结合形态学和真菌核糖体转录间隔区(r DNA-ITS)序列分析对致病真菌进行鉴定。【结果】从石河子地区甜樱桃腐烂的果肉中分离出5类丝状真菌,其中3类是甜樱桃果实的致病真菌,转录间隔区序列比对确定3类真菌中代表菌株分别为易脆毛霉(Mucorfragilis)、镰刀菌(Fusariumsp.)和干酪青霉(Penicillium camemberti)。【结论】导致新疆石河子地区甜樱桃果实腐烂的致病真菌主要有易脆毛霉(Mucor fragilis)、镰刀菌(Fusarium sp.)和干酪青霉(Penicillium camemberti)。     

银叶杜鹃和繁花杜鹃根部真菌的多样性

植物根系与真菌形成菌根, 在自然生态系统的物质能量循环中具有重要的生态功能。作者在四川省的中国杜鹃园选取银叶杜鹃(Rhododendron argyrophyllum)和繁花杜鹃(R. floribundum), 通过直接扩增杜鹃花根部真菌rDNA-ITS区片段, 来揭示该地区杜鹃花属植物根部真菌的多样性。ITS序列分析结果表明: 从两种杜鹃的根部共检测到41个真菌分类单元, 分别属于子囊菌纲的柔膜菌目(Helotiales)、散囊菌目(Eurotiales)、盘菌目(Pezizales)、假球壳目(Pleosporales)和担子菌纲的蜡壳耳目(Sebacinales)、伞菌目(Agaricales)、Erythrobasidiales、线黑粉菌目(Filobasidiales)。银叶杜鹃和繁花杜鹃根部真菌种类丰富, 包括了杜鹃花类菌根真菌、外生菌根真菌和其他类型真菌, 其中担子菌纲的蜡壳耳目和子囊菌纲的柔膜菌目占有较大比例。     

北京城市公园常见乔木土壤真菌群落特征及影响因素

快速城市化引起的城市环境污染问题日趋严重,由城市中心到城郊往往呈规律性递变趋势。北京城市公园作为城市绿地主体,不仅是城市居民重要的休闲游憩场所,也能在一定程度上反应环境污染,如土壤重金属污染的作用规律。以北京市这一典型大城市为研究区域,根据不同城市公园的建成时间、所处位置和距离市中心的远近选择六个公园作为研究样点,选取公园常见6种乔木下土壤,通过对土壤重金属含量、土壤理化性质以及土壤真菌群落测定和测序,旨在探讨城市公园植被下土壤真菌群落特征（多样性和群落结构组成）以及影响因素。研究结果表明：北京城市公园乔木下的土壤真菌群落多样性、群落组成以及优势类群受到土壤pH值、土壤养分和水分以及重金属铅的调控。其中公园土壤重金属铅含量增加会降低土壤真菌多样性、显著影响优势类群子囊真菌（占真菌群落73%）以及土壤真菌功能类群病原真菌群落组成。研究揭示了北京城市公园土壤真菌群落特征及调控因素,特别是重金属铅对土壤真菌群落的影响,这对提高城市公园科学管理和环境健康具有积极的应用价值。     

高原湿地沼泽化草甸土壤真菌与理化性质的关系

以高原湿地纳帕海沼泽化草甸为研究对象, 采用稀释培养结合形态鉴定比较分析0—20 cm、20—40 cm土层的土壤真菌多样性及群落结构组成, 以及土壤理化性质对土壤真菌多样性及群落结构组成的影响。结果表明: 0—20 cm和20—40 cm土层中的真菌数量、Shannon-Wiener多样性指数(H')、均匀度指数(JSW)和丰富度指数(DMA)均表现为0—20 cm土层> 20—40 cm土层; 分别分离得到土壤真菌12属和10属, 其中木霉属、青霉属、腐霉属、曲霉属同为沼泽化草甸两个土层的优势类群, 表现出较高的相似性, 同时20—40 cm未发现枝孢菌属和壳囊孢属, 又表现出一定的差异性。经RDA冗余分析, 土壤有机质、全氮、速效钾、速效磷、pH、容重和自然含水率可能是影响沼泽化草甸土壤真菌群落结构组成的主要因子。     

柞树林下菌根真菌对碳、氮营养的利用

研究了柞树林下菌根真菌对Ｃ、Ｎ营养的利用状况．结果表明,供试菌种对Ｃ源的利用较为广泛,葡萄糖、果糖为其最适碳源,平均生长量比对照高出４．４倍;供试菌种对有机氮的利用优于无机氮,平均生长量比无机氮源高出１．６倍,硝态无机氮源中平均生长量为对照的２．５倍,对铵态氮的利用较差,平均生长量仅为对照的２．２倍     

Influence of resource unit distribution and quality on the activity of soil fungi in a particulate medium

Experiments were set up to assess the relative impacts of grass lamina fragment density, size and quality on the activity and growth of four fungi in a particulate soil-like matrix. The fungi studied were Cladosporium cladosporioides , Fusarium lateritium , Phoma exigua and Trichoderma viride , all of which are common inhabitants of UK upland grassland soils. Resource quality was varied by using three contrasting grasses as sources of lamina fragments: Lolium perenne , Agrostis capillaris and Nardus stricta . All the fungi were able to forage effectively through the soil-like matrix (at a rate of 1–2 ml matrix d⁻¹) and colonize and partially decompose available lamina fragments (up to 40% d. wt loss). Foraging rates (ml matrix d⁻¹) were affected by lamina fragment species but not by fragment density or size. In general, F. lateritium and T. viride foraged at a faster rate than the other species. Mycelial activity in the soil-like matrix was directly proportional to total lamina fragment availability and was unaffected by fragment size. Biomass production on solid media was also directly related to substrate (carbohydrate) availability. The results indicate that these fungi can adjust their growth patterns in response to fragment density so as to maximize foraging efficiency (energy acquired per unit exploratory biomass production). Differences in lamina fragment species were responsible for up to 50% reduction in mycelial activity.     

Diversity and community structure of ectomycorrhizal mycorrhizal fungi in roots and rhizosphere soil of Abies koreana and Taxus cuspidata in Mt. Halla

In this study, the roots and rhizosphere soil of Abies koreana and Taxus cuspidata were collected from sites at two different altitudes on Mt. Halla. Ectomycorrhizal fungi (EMF) were identified by Illumina MiSeq sequencing. The proportion of EMF from the roots was 89% in A. koreana and 69% in T. cuspidata. Among EMF in rhizosphere soils, the genus Russula was the most abundant in roots of A. koreana (p < 0.05). The altitude did not affect the biodiversity of EMF communities but influenced fungal community composition. However, the host plants had the most significant effect on EMF communities. The result of the EMF community analysis showed that even if the EMF were isolated from the same altitudes, the EMF communities differed according to the host plant. The community similarity index of EMF in the roots of A. koreana was higher than that of T. cuspidata (p < 0.05). The results show that both altitude and host plants influenced the structure of EMF communities. Conifers inhabiting harsh sub-alpine environments rely strongly on symbiotic relationships with EMF. A. koreana is an endangered species with a higher host specificity of EMF and climate change vulnerability than T. cuspidata. This study provides insights into the EMF communities, which are symbionts of A. koreana, and our critical findings may be used to restore A. koreana.     

Synergistic interaction of Rhizobium leguminosarum bv. viciae and arbuscular mycorrhizal fungi as a plant growth promoting biofertilizers for faba bean (Vicia faba L.) in alkaline soil

Egyptian soils are generally characterized by slightly alkaline to alkaline pH values (7.5–8.7) which are mainly due to its dry environment. In arid and semi-arid regions, salts are less concentrated and sodium dominates in carbonate and bicarbonate forms, which enhance the formation of alkaline soils. Alkaline soils have fertility problems due to poor physical properties which adversely affect the growth and the yield of crops. Therefore, this study was devoted to investigating the synergistic interaction of Rhizobium and arbuscular mycorrhizal fungi for improving growth of faba bean grown in alkaline soil. A total of 20 rhizobial isolates and 4 species of arbuscular mycorrhizal fungi (AMF) were isolated. The rhizobial isolates were investigated for their ability to grow under alkaline stress. Out of 20 isolates 3 isolates were selected as tolerant isolates. These 3 rhizobial isolates were identified on the bases of the sequences of the gene encoding 16S rRNA and designated as Rhizobium sp. Egypt 16 (HM622137), Rhizobium sp. Egypt 27 (HM622138) and Rhizobium leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The best alkaline tolerant was R. leguminosarum bv. viciae STDF-Egypt 19 (HM587713). The effect of R. leguminosarum bv. viciae STDF-Egypt 19 and mixture of AMF (Acaulospora laevis, Glomus geosporum, Glomus mosseae and Scutellospora armeniaca) both individually and in combination on nodulation, nitrogen fixation and growth of Vicia faba under alkalinity stress were assessed. A significant increase over control in number and mass of nodules, nitrogenase activity, leghaemoglobin content of nodule, mycorrhizal colonization, dry mass of root and shoot was recorded in dual inoculated plants than plants with individual inoculation. The enhancement of nitrogen fixation of faba bean could be attributed to AMF facilitating the mobilization of certain elements such as P, Fe, K and other minerals that involve in synthesis of nitrogenase and leghaemoglobin. Thus it is clear that the dual inoculation with Rhizobium and AMF biofertilizer is more effective for promoting growth of faba bean grown in alkaline soils than the individual treatment, reflecting the existence of synergistic relationships among the inoculants.     

接种AM菌对西部黄土区采煤沉陷地柠条生长和土壤的修复效应

以采煤沉陷区柠条为宿主植物,研究接种丛枝菌根真菌(arbuscular mycorrhizal fungi,简称AM菌)对柠条生长和根际土壤的改良效应。结果表明:8月份接种AM菌比不接菌柠条的株高、冠幅和地径显著增加了29.11%,29.83%和14.81%,9月份接菌区柠条的根长、平均直径、根表面积和根体积分别比对照区增加了151.0%,34.2%,116.0%和129.3%。接种AM菌增强柠条的抗逆性,接菌区的柠条叶片可溶性糖含量和过氧化氢酶活性分别比对照区增加了13.4%和111.1%。8月份接种AM菌改善了土壤的生物理化性质,接菌区有机质、碱解氮、速效磷和速效钾比对照区分别增加7.06g/kg,140.0 mg/kg,1.82 mg/kg和16.72mg/kg,接种AM菌显著增加了根际土壤中真菌、放线菌、细菌数量和酸性磷酸酶活性。总之,接种AM菌促进采煤沉陷区柠条的生长和土壤的改良。