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.     

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.     

Resistance of improved Pinus monticola and some other white pines to the blister rust fungus,Cronartium ribicola,of Hokkaido,Japan

Resistant progenies of Pinus monticola, improved in the northwestern USA, and Asian and European white pines were inoculated with the blister rust fungus, Cronartium ribicola, of Hokkaido. No resistance was observed in P. monticola but the other pines remained healthy. This shows that the resistance of white pines to the blister rust fungus is limited to a particular pathogenic race and a different race of the rust fungus exists in Hokkaido.     

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.     

Susceptibility of Pedicularis spp. to Cronartium ribicola and C. flaccidum in Finland

Aeciospores of Cronartium ribicola and C. flaccidum were collected from several locations in Finland and used to inoculate Pedicularis spp. and some known and suspected alternate hosts in 2008–2009. In all trials, C. ribicola formed uredinia and telia on leaves of Ribes nigrum. No uredinia or telia of C. ribicola formed on older leaves of Pedicularis spp. but both uredinia and telia were found on young leaves of P. palustris ssp. palustris. Cronartium flaccidum produced uredinia and/or telia on leaves of P. palustris ssp. palustris, P. lapponica, Vincetoxicum hirundinaria and Melampyrum sylvaticum. Neither rust infected P. sceptrum‐carolinum, Vaccinium myrtillus, Calluna vulgaris or Ledum palustre. Similar to rusts in Asia and North America, the results showed that European C. ribicola exhibit more variable host reactions and wider alternate host ranges than earlier described. Pedicularis palustris may play a role in the spread of Cronartium in natural forests.     

Histology of Pinus maximinoi cones infected by Cronartium conigenum1

Apparently healthy and C. conigenum infected female strobili of Pinus maximinoi, collected in Guatemala, were histopathologically studied by light microscopy. Scales from infected cones were fused and fertile scales had aborted seeds. Infected cone scales lacked fibre cells in the cortex, which are abundant in healthy cone scales. Intercellular spaces of cortex contained abundant hyphae compared to phloem and xylem. The cell walls of infected tissues in the ovules were darkly stained, while those of comparable healthy tissue were colourless under Pianeze's IIIB stain. Infected ovules of different developmental stages with nucellus, or nucellus plus spongy tissue, were observed. The cells of each tissue type contained many haustoria and did not develop into female gametophyte and embryo. Ovule colonization by hyphae appeared after pollination and subsequently caused their early abortion.     

Incidence of Cronartium ribicola in Finnish botanical gardens and five-needle pine plantations in northern Finland

Abstract

Stump removal procedure increases the extent of exposed mineral soil in the clear felled areas. In this study, our aim was to find out whether the early growth and mycorrhization of Norway spruce (Picea abies (L.) Karst.) seedlings differ between stump removal and mounding sites. Stumps were harvested from five one-hectare study sites and other five sites were mounded after clear felling. Twenty seedlings were planted on mounds at each study site. Although the height of spruce seedlings did not differ between the treatments after three growing periods, their mean growth was ca. 10% higher at the stump removal sites. The community of ectomycorrhizal (ECM) in the seedling roots did not differ between the treatments. The high mycorrhization rate in the nursery still remained after two and three growing seasons in the field and diversity of ECM community slightly increased during the first years. Our results indicate some positive although rather small and transient effects of stump removal on the performance of planted spruce seedlings. Longer-term studies are needed to fully understand the effects of stump removal on the later seedling development and their symbiotic interactions with mycorrhizal fungi.     

Pedicularis and Castilleja are natural hosts of Cronartium ribicola in North America: a first report

White pine blister rust disease, caused by the introduced pathogen Cronartium ribicola, has severely disrupted five‐needled pine ecosystems in North America. A 100‐year effort to manage this disease was predicated in part on the premise that the pathogen utilizes only species of Ribes (Grossulariaceae) as alternate hosts on this continent. The current study presents the first conclusive demonstration that some species in the family Orobanchaceae (Pedicularis racemosa and Castilleja miniata) are functioning as alternate hosts in a natural ecosystem of North America. This finding has implications for improving our understanding of epidemiology, pathogen adaptation and host–pathogen interactions within white pine blister rust.     

Aeciospores of Cronartium flaccidum,C. ribicola and Endocronartium pini show no differences in morphology

The morphology of the aeciospores of the pine stem rust fungi Cronartium flaccidum, Cronartium ribicola and Endocronartium pini, collected from nine locations in Finland, Sweden and Italy, was compared. Surface structures of 900 aeciospores were visually classified using a scanning electron microscope, and dimensions of 1100 aeciospores were measured from micrographs. The data grouping was tested with discriminant analysis. The spores had well-defined smooth areas and annulate warts on their surface. E. pini, C. flaccidum and C. ribicola could not be distinguished by the surface structures of the spores. The grouping of spores by dimensions into sample locations was statistically significant by one discriminant function, while the grouping into species was not. The observed similarities corroborated the current views on the close relationship of C. flaccidum and E. pini.     

云南松直干、弯干材木材结构比较观察

利用光学显微镜对云南松直干、弯干材木材构造进行解剖学观察，结果表明：弯干材在解剖结构上跟直干材基本保持一致。与直干材相比，弯干材的早材比直干材的早材窄，树脂道多；早、晚材管胞的长度、壁厚、弦向直径差幅分别为：0．14、0．63、4．4、13．56、-0．46、0．81；最大交叉场纹孔数和最大单列射线细胞个数比直干材分别多1个和2个；纺锤形射线高度超出直干材的51．73％。弯干材具有右旋扭转纹。另外，两种材料都是较好的造纸原料，且以弯干材为优。     

Castilleja and Pedicularis confirmed as telial hosts for Cronartium ribicola in whitebark pine ecosystems of Oregon and Washington

The primary objective of this research was to determine whether native species of Castilleja and Pedicularis are naturally infected by Cronartium ribicola in whitebark pine ecosystems of the Oregon and Washington Cascade Range, USA. Secondary objectives were to monitor the phenology of aecial and telial hosts to determine whether there is sufficient time for C. ribicola to complete its life cycle within high‐elevation stands and to evaluate the variety of susceptible native host species within these genera through field and growth chamber inoculation. These objectives were approached through fieldwork in 2008 and 2009 in whitebark pine ecosystems at Mt. Rainier, Mt. Adams, Mt. Hood, Mt. Bachelor, Tumalo Mtn. and Crater Lake. Forty‐nine observational study plots were established and monitored. Natural C. ribicola infection was detected on 84 Pedicularis racemosa plants and five Castilleja plants (C. applegatei, C. miniata and C. parviflora). Field observation provided evidence that there is sufficient time for C. ribicola to complete its life cycle on hosts within high‐elevation whitebark pine stands. In 2009, 18 field inoculation plots were established at Mt. Rainier and Crater Lake. Field inoculation confirmed the susceptibility of two additional species within these genera, C. arachnoidea and P. bracteosa. All four Castilleja species inoculated in the growth chamber developed infection, with an overall infection incidence of 62% (167 out of 270 plants). The identity of the rust species on field specimens as C. ribicola was verified through PCR and sequencing of the ITS1‐5.8S‐ITS2 region of DNA. Improved understanding of the role of these newly recognized hosts in white pine blister rust epidemiology should be used to prioritize sites for the restoration of ecologically valuable whitebark pine.     

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.     

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.     

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.     

Relationship between vigour and susceptibility of Austrian pine (Pinus nigra) to blister rust (Cronartium flaccidum)

In a 13-year-old plantation of Austrian pine no apparent relationship between vegetative vigour expressed as height and as stem circumference, and susceptibility to blister rust due to Cronartium flaccidum was found. Under conditions which favour the development of the disease, it is possible to select vigorous and blister rust resistant Austrian pines.     

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。     

Microculture of western white pine (Pinus monticola) by induction of shoots on bud explants from 1- to 7-year-old trees

We developed a protocol for the production of shoots from bud explants from 1- to 7-year-old trees of western white pine (Pinus monticola Dougl.). The best explant was a 2-mm-thick cross-sectional slice of the early winter bud. Genotype of the donor tree was a significant factor affecting shoot production, but more than 80% of the genotypes tested produced shoots. Of the media tested, bud slices from 1- to 3-year-old trees grew best in Litvay's medium containing N(6)-benzyladenine in the range of 1 to 30 micro M, whereas bud slices from older trees grew best in Gupta and Durzan's DCR medium with zeatin riboside. Up to 400 shoots more than 3 mm in height were obtained from 100 bud-slice explants taken from 7-year-old western white pine trees.     

Responses of foliar delta13C, gas exchange and leaf morphology to reduced hydraulic conductivity in Pinus monticola branches

We tested the hypothesis that branch hydraulic conductivity partly controls foliar stable carbon isotope ratio (delta13C) by its influence on stomatal conductance in Pinus monticola Dougl. Notching and phloem-girdling treatments were applied to reduce branch conductivity over the course of a growing season. Notching and phloem girdling reduced leaf-specific conductivity (LSC) by about 30 and 90%, respectively. The 90% reduction in LSC increased foliar delta13C by about 1 per thousand (P < 0.0001, n = 65), whereas the 30% reduction in LSC had no effect on foliar delta13C (P = 0.90, n = 65). Variation in the delta13C of dark respiration was similar to that of whole-tissues when compared among treatments. These isotopic measurements, in addition to instantaneous gas exchange measurements, suggested only minor adjustments in the ratio of intercellular to atmospheric CO2 partial pressures (ci/ca) in response to experimentally reduced hydraulic conductivity. A strong correlation was observed between stomatal conductance (gs) and photosynthetic demand over a tenfold range in gs. Although ci/ca and delta13C appeared to be relatively homeostatic, current-year leaf area varied linearly as a function of branch hydraulic conductivity (r2 = 0.69, P < 0.0001, n = 18). These results suggest that, for Pinus monticola, adjustment of leaf area is a more important response to reduced branch conductivity than adjustment of ci/ca.     

Analysis of bark proteins in blister rust-resistant and susceptible western white pine (Pinus monticola)

We compared bark proteins from four contrasting (blister rust-resistant versus susceptible) half-sib seedling pairs of western white pine (Pinus monticola D. Don). Pooled proteins from resistant and susceptible groups (four trees per group) were separated by two-dimensional gel electrophoresis, silver stained, and analyzed with the aid of a laser scanner interfaced with a computerized gel documentation system. Qualitative and quantitative protein differences were observed between resistant and susceptible groups. The number of proteins unique to a group was greater in the susceptible category than in the resistant category. Biosynthesis of some common proteins was enhanced near lesioned areas of susceptible seedlings. Many proteins shared similar charge and mass characteristics with those of pathogenesis-related (PR) proteins. Two protein bands were isolated and partially characterized by N-terminal amino acid sequencing: a 10.6-kDa band that was selectively enriched in all resistant individuals, and a 26.0-kDa band that was enriched in some susceptible individuals. The significance of these protein differences and the possible use of selected proteins as disease or resistance markers are discussed.