Haustorial morphology of Cronartium conigenum in naturally infected cones of three Pinus species from Guatemala1

Haustorial morphology of the cone-rust pathogen, C. conigenum, was investigated among naturally infected female strobili of three Guatemalan pines, P. maximinoi, P. pseudostrobus, and P. oocarpa. Among the three pine species, haustorial shapes and sizes were more variable in P. maximinoi and P. oocarpa than in P. pseudostrobus. The haustorial shapes and sizes were more variable in parenchyma cells of the cortex, xylem, and pith than in the cells in the phloem, xylem rays, and tracheids. The haustoria were also present in larger numbers in the parenchyma cells of the cortex, xylem, and pith than in phloem parenchyma cells and tracheids. In living cells, the tips of some haustoria were appressed to the host nuclei.     

Histology of Diplodia pinea in diseased and latently infected Pinus nigra shoots

Diplodia tip blight is a serious disease of >30 conifer species worldwide. Symptoms are particularly severe on non‐native, two‐needled Pinus species, and typically include stunted, necrotic needles and shoots and a general decline of the tree. Latent Diplodia pinea infections occur in current‐year shoots of some symptomless pines, and in some apparently healthy current‐year shoots of diseased pines. Latent infections also occur in symptomless terminal buds. A histological approach was used to investigate the nature of latent infections in shoot stems and terminal buds of landscape Pinus nigra. Fungal colonization was compared in healthy, diseased and latently infected tissues. A nested‐PCR technique that is specific for D. pinea was used to differentiate latently infected tissues from uninfected ones. Latent D. pinea infections were localized in the outer stem cortex, usually in the vicinity of needle scales at leaf axes. In contrast, pathogenic D. pinea infections were characterized by fungal colonization throughout the shoot stem tissues, even very early in symptom development. The presence of necrophylatic periderms in two of the latently infected samples suggests that host defences play a role in the production and maintenance of latent stem infections. Latent infections of terminal buds appeared to originate from the distal bud scales of axillary buds in the terminal bud cluster, and not from the subtending shoot. Fungal tissues were never observed inside asymptomatic, PCR‐negative shoots.     

Susceptibility of provenances and families of Pinus maximinoi and Pinus tecunumanii to frost in South Africa

The future of South Africa’s most important pine species, Pinus patula, is threatened by the pitch canker fungus, Fusarium circinatum. Pinus maximinoi and P. tecunumanii represent two subtropical species that provide an alternative to planting P. patula on the warmer sites of South Africa. Extending the planting range of P. tecunumanii and P. maximinoi to include higher and colder altitude sites will reduce the area planted to P. patula and the risk of F. circinatum. During 2007 progeny trials of P. tecunumanii and P. maximinoi were planted on a sub-tropical and sub-temperate site. Shortly after the establishment of these trials, unusually cold weather conditions were experienced across South Africa (?3°C at the sub-temperate site) resulting in severe mortality. This provided the opportunity to assess the variation in survival as a measure of frost tolerance within these two species to determine whether it could be improved upon through selection. Results indicated that the variation in survival was under genetic control in P. tecunumanii (h _(0,1) ²  = 0.16, h _L ²  = 0.27) and P. maximinoi (h _(0,1) ²  = 0.11, h _L ²  = 0.23) at the sub-temperate site. Correlations in provenance ranking for survival across sites were high for both species. Moderate correlations in family survival for P. tecunumanii (r = 0.52) were found at the two sites. Improvements in cold tolerance can thus be made in both species extending their planting range to include greater areas planted to P. patula thereby limiting the risk of F. circinatum.     

木蠹象对受疱锈菌侵染华山松树皮挥发物的EAG和行为反应

采用触角电位仪和"Y"型嗅觉仪分别研究了茶蔗生柱锈菌锈孢子、感疱锈病树皮、华山松健康树皮挥发性成分对华山松木蠹象的触角电生理和引诱活性.羽化3 d的木蠹象对3种挥发性成分在各浓度下都有明显的EAG反应,锈孢子的EAG反应值最大,健康树皮次之,感病树皮最小,且明显小于前二者.同时,嗅觉生测结果证明,锈孢子挥发性成分对木蠹象的引诱活性最低,平均引诱率不超过20%;同样,感病树皮挥发性成分除浓度为1:15外,其余引诱率都低于35%,二者对该虫总体表现出驱避活性;而健康树皮挥发性成分则有明显的引诱活性.EAG反应值与行为反应的趋向率具有一致性.     

油松落针病的发生与土壤条件关系的分析

文章对辽宁东部地区油松落针病的发生与土壤条件的关系进行了研究分析,结果表明:在7个县的油松发病林分内共有4种森林土壤类型,分别为石质棕色森林土、暗棕色森林土、草甸棕色森林土、生草棕色森林土。石质棕色森林土类型发病率(86.34%)和发病指数(50.01)最高。土壤肥力测定显示共同规律是随着土壤中速效氮、速效磷、钙和镁含量的减少而油松落针病均呈现病情加重的趋势,速效氮含量比正常下降了87.73%,表现最明显。发病林分的土壤pH值皆呈弱酸性,林分病情随着土壤的pH值减小而加重。     

Anatomical and cellular responses of Pinus monticola stem tissues to invasion by Cronartium ribicola

White pine blister rust (Cronartium ribicola) causes extensive damage to white pines and their associated ecosystems across North America. The anatomical and cellular characteristics of C. ribicola colonization in Pinus monticola branch and stem tissues were studied as a basis for understanding host tree reactions that may be related to resistance. Samples examined showed typical fusiform swelling and some had produced aecia. The reaction of phloem and xylem tissues was compared with non-infected tissue using light and electron microscopy. Cortical parenchyma and phloem polyphenolic parenchyma cells underwent mitotic division, cell swelling, and ca sixfold greater accumulation of phenolic compounds in colonized vs. control stems. In the cortex and secondary phloem, haustoria were common in parenchymatous cells, and hyphae were abundant in the intercellular spaces, but cell death was rare, unless aecia had ruptured the stem cortex. Hyphae were also common in xylem rays, tracheids and between tracheids. Disease-induced changes in the cambial zone included development of cambium-derived xylem traumatic resin ducts. Results demonstrate that diverse host defence responses were activated in the bark of apparently susceptible trees, but lack of mechanical damage by C. ribicola to the phenol-containing host cells and the resin duct system allowed extensive colonization and development of aecia despite elicitation of these stem defences. Interactions between P. monticola and C. ribicola are discussed and compared with other conifer–fungus pathosystems.     

Short-term Effect of Thinning on Pinus sylvestris Damage and Sporulation Caused by Cronartium flaccidum

The short-term effect of thinning on cronartium rust on Scots pine ( Pinus sylvestris L.) was investigated in a stand of Scots pine (artificially seeded and in the pole-stage) severely infected by the stem-rust fungus Cronartium flaccidum (Alb. & Schwein) G. Winter. The disease rate (the number of old and fresh infections) was recorded before thinning, after which all trees with a resin-top as well as all individual branches with sporulating lesions were removed from the thinned plots, while the comparison plots remained non-thinned. The numbers of sporulating lesions were recorded on the plots annually for 2-5 yrs after thinning. Thinning had no significant short-term effect on the year-to-year relative number of sporulating lesions. The relative number of sporulating lesions, however, increased in both thinned and nonthinned trees, varying significantly from year to year. Thinning had no significant effect on the year of formation of the shoot bearing annual sporulating lesions, the duration of sporulation or the growth of the fungus along the infected shoot in perennial lesions during the first 5 yrs after the treatment.     

Hyphalike haustoria of the haploid stage of Cronartium ribicola in Pinus monticola observed with the scanning electron microscope1

Haustoria of the haploid stage (n stage) of Cronartium ribicola in bark cells of Pinus monticola were studied with the aid of the scanning electron microscope. The morphology of mature haustoria in all kinds of bark cells was consistently filamentous or elongate (hyphalike). Only immature haustoria are short and globose or reniform. Immature and mature haustoria are constricted at the point of passage through the host cell wall. N stage C. ribicola hyphae are characterized as having haustoria that are morphologically similar to intercellular hyphae.     

Histopathology of Pinus taeda needles infected by Ploioderma lethale

The histopathology of the host/parasite relationship of Pinus taeda needles infected by the Ascomycete Ploioderma lethale and the morphology of the fructifications of the pathogen were investigated. Amphigenous elliptical teleo‐ and anamorph stromata developed only on dead portions of affected needles. Insertion of the teleo‐ and anamorph stromata in the host needle tissue was subepidermal, and the stromata were covered by a shiny to dull black clypeus. Teleomorph stromata frequently coalesced. Abnormal host tissue was primarily confined to tissues external to the endodermis in the symptomatic portion of affected needles, where a collapse of the mesophyll cells was exhibited. An obvious narrowing of affected needles was observed at the distinct juncture of dead and green tissue. Inter‐ and intracellular hyphae colonized the collapsed mesophyll cell regions, endodermal, transfusion, vascular tissues, and resin ducts. Intercellular hyphae and an interface were present in the living mesophyll cells of the green needle tissue subtending the dead terminal portion of affected needles.     

A Reappraisal of the Importance of Cronartium ribicola on Pinus strobus in Great Britain

Because of the possibility of serious infection by Cronartiumribicola (White pine blister rust), Pinus strobus, the Weymouthpine, is now very rarely planted in British forests. An assessment,in 1962, in a number of experimental forest plots of P. strobusestablished in 1953 and 1954 showed that initial infection ofthe trees while growing in the nursery may be an important factorin causing later damage and losses in the forest. The resultsalso indicated that the risk of infection in plantation cropsas a result of spore dispersal from black currants in the localityis much lower than is generally thought. It is suggested thatif P. strobus is raised in nurseries which are relatively isolatedfrom currants and if protective chemical spraying against thedisease in the nursery is carried out, the incidence of infectionin plantations at least half a mile from the nearest currantsis likely to be low. The disease cannot spread within a pinecrop by direct transmission from tree to tree.     

Growth of axenic cultures of Cronartium flaccidum on callus tissue from Pinus nigra var. laricio and Pinus sylvestris

The callus-fungal method was employed to test the response to C. flaccidum of the highly susceptible P. nigra var. laricio and the resistant P. sylvestris, and to ascertain whether results obtained with this method matched in planta observations. Calli were inoculated with axenie cultures of C. flaccidum obtained by incubating basidiospores on modified Schenk and Hildebrandt medium. Several parameters were evaluated. Colony growth was more rapid on P. nigra var. laricio. Colonies were dense on P. nigra var. laricio, but sparse on P. sylvestris. Aerial hyphae growth was abundant on P. nigra var. laricio, but less frequent on P. sylvestris. Hyphal branching began after 18 h on P. nigra var. laricio and after 45 h on P. sylvestris. Necrosis of the host cells set in after 24 h on P. nigra var. laricio, and after 70 h on P. sylvestris. The number of cells with plasmolysis was much larger in P. nigra var. laricio than in P. sylvestris. These results were consistent with the known resistance of the two species on whole plants.     

松材线虫染病黑松上钻蛀性昆虫生态位的研究

2006年8月和10月,在浙江省舟山市和安徽省滁州市的松材线虫病典型发生区调查了黑松上的钻蛀性害虫的种类,分析了衰弱木上优势虫种的生态位宽度、生态位相似性和生态位重叠值。结果表明:在感染松材线虫病的黑松上共发现7种昆虫,其中钻蛀类害虫5种,天敌2种。在两地生活于松树主干上的昆虫种类不尽相同,而且具有各自不同的生态位宽度,存在不同程度的生态位重叠,对空间和营养资源的利用有不同比例的相似性。依据其各自生物学特性和生活习性的不同达到竞争的平衡和共存。     

Cronartium flaccidum on Pinus spp.: relation of inoculum concentration to symptom development

An experiment on the effect of eight inoculum concentrations of basidiospores of Cronartium flaccidum, on development of symptoms on P. nigra spp. nigricans var. austriaca, P. nigra ssp. italica, P. nigra ssp. laricio var. calabrica (from Calabria and Corsica) showed that 60000 basidiospores/ml was the optimum concentration and P. nigra ssp. laricio was the most sensitive.     

樟子松疱锈病重寄生菌的分离鉴定

樟子松疱锈病是樟子松枝干上的主要病害,为利用重寄生菌对樟子松疱锈病进行生物防治,对其病原菌松芍柱锈菌Cronartium flaccidum(Alb.et Schw.)Wint.的重寄生菌进行了分离和鉴定,得到重寄生菌拟枝孢镰刀菌Fusarium sporotrichioides Sherb.、深绿木霉Trichoderma atroviride,并测定ITS序列,获得基因登录号。经显微观察发现接种重寄生菌后锈孢子受到不同程度的破坏,且存在两种不同的作用机理。     

Niche of insect borers within Pinus massoniana infected by pine wood nematode

In November 2003 and June 2004, the insect borers and their spatial distribution within Pinus massoniana were investigated in Zhoushan City, in East China’s Zhejiang Province, where pine wood nematode (Bursaphelenchus xylophilus) are typically found. The niche width, proportional similarity of niche and the niche overlap of dominant species of dying trees were computed. Results show that five insect species infect and damage Pinus massoniana, which had been infected by pine wood nematodes, among which four are wood boring beetles and one termite. Species within host trees vary from winter to summer and all the species have their own niche width, proportional similarity of niche and the niche overlap. They can achieve competitive equilibrium and coexistence according to their biological characteristics and life habits. __________ Translated from Journal of Beijing Forestry University, 2005, 27(6): 108–111 [译自: 北京林业大学学报, 2005, 27(6): 108–111]     

Influence of female cones on the vegetative growth of Pinus contorta trees

Branches of Pinus contorta Dougl. bearing two-year-old female cones initiated fewer lateral buds than vegetative branches. However, the number of lateral shoots that differentiated and grew was not reduced on female cone-bearing branches. Neither the number nor the weight of female cones influenced the length of the terminal shoot. The total length of all lateral shoots was positively associated with the weight of two-year-old female cones. Branch units with two-year-old female cones produced significantly more total dry weight in the current year than vegetative branch units. There was, however, no significant reduction in the dry weight of terminal and lateral shoots. Branches bearing female cones allocated between 17 and 45% of the current year's dry weight to two-year-old cones and between 1 and 5% was allocated to one-year-old female cones. Female cones therefore apparently do not reduce the photosynthetic potential of trees. The influence of female cones compared with male cones on the growth of trees is discussed.     

In vivo interspecific pollination success between Pinus radiata,P. maximinoi,P. oocarpa and P. tecunumanii

The objective of the study was to investigate in vivo interspecific pollination success between Pinus radiata, P. maximinoi, P. oocarpa and P. tecunumanii. Pinus radiata was control pollinated with pollen lots of P. maximinoi, P. oocarpa and P. tecunumanii in a P. radiata seed orchard at Karatara (Southern Cape, South Africa). Pollination success was determined by counting the number of visible ovules, pollen grains inside and outside P. radiata ovules, as well as pollen tubes visible inside P. radiata ovules. Conelets were harvested and studied at eight time intervals, including 24 h after pollination, and weekly for 7 weeks after pollination. Histology studies with a standard fixation-dehydration-embedding sequence and paraffin wax method were used to determine the number of visible pollen grains inside versus outside the ovules and number of pollen tubes. Results indicated that pollen grains did sift through the cone scales within 24 h after pollination. However, P. radiata differed significantly (time by type of cross interaction) from the other three hybrid combinations in terms of number of visible ovules, visible pollen grains inside and outside of the ovules as well as pollen tubes, confirming limited interspecific hybridisation success. Future studies need to determine the percentage of fertile ovules in cross combination as a tool in predicting pollination success.     

Finnish Cronartium ribicola does not infect alternate hosts of Cronartium flaccidum

Susceptibility of the main alternate hosts of Cronartium flaccidum, Vincetoxicum spp. and Melampyrum spp., to C. ribicola was investigated by artificial inoculations on detached leaves in the laboratory and on whole plants in the greenhouse. Neither uredinia nor telia developed on the leaves of either Vincetoxicum hirundinaria, Vincetoxicum nigrum, Melampyrum sylvaticum, Melampyrum pratense, Melampyrum nemorosum, Melampyrum arvense, Melampyrum cristatum or Melampyrum polonicum following inoculation by the 26 aeciospore sources collected from Pinus strobus, Pinus monticola, Pinus flexilis and Pinus peuce in 2000–2003. The results suggest that Finnish C. ribicola does not infect the main alternate hosts of C. flaccidum. Cronartium ribicola and C. flaccidum can thus be identified reliably by inoculations on their main alternate hosts.     

Effects of infection by Cronartium flaccidum (Alb. et Schw.) Wint. on inorganic solute concentrations in Pinus pinaster Ait. and Pinus pinea L. seedlings

Three years after artificial inoculation by Cronartium flaccidum, significant differences in accumulation or loss of ccrtain inorganic solutes resulted in needle and bark tissues of seedlings of Maritime and Italian stone pine.     

Comparative study on the mRNA expression of Pinus massoniana infected by Bursaphelenchus xylophilus

Pine wilt disease(PWD)is a devastating disease affecting the growth of Pinus massoniana,often leading to withering and death.To reveal the changes involved during disease progression,we investigated the mRNA expression profile of P.massoniana infested by Bursaphelenchus xylophilus.The infestation resulted in the downregulation of genes involved in interactions with pathogenic pathways such as disease resistance gene,CC-NBS-LRR resistancelike protein,and the gene encoding a putative nematode resistance protein.Increased infestation pressure(number of nematodes inoculated)caused a continuous decline in the gene expression of stem samples.An infestation of P.massoniana also resulted in a pathway enrichment of genes involved in phenylpropanoid metabolism and flavonoid biosynthesis,which in turn reduced the levels of total phenols and total flavonoids.A downregulation of auxin responsive family protein was observed in infested samples,which resulted in a suppression of plant growth.Thus,upon B.xylophilus infestation,a downregulation of genes associated with the recognition of pathogens,PWD resistance,and growth regulation was observed in P.massoniana,together with a decrease in the levels of phytoalexinlike secondary substances,all of which resulted in withering and ultimately death of P.massoniana.