Spruce wood degradation by Pleurotus abieticola in comparison with Phlebiopsis gigantea and Heterobasidion parviporum: in vitro experiments with isolates

The objective of this study was to evaluate the in vitro mycelium growth of Pleurotus abieticola and its competitive ability to decompose sapwood and heartwood wood, as compared to the activity of Phlebiopsis gigantea and Heterobasidion parviporum. Over the last several decades, P. gigantea has routinely been used for biocontrol of the conifer pathogen Heterobasidion annosum s.l.; however, its protective effect on Norway spruce stands was recently demonstrated to be not satisfactory. P. abieticola was proposed instead, as a promising species that might successfully compete with H. parviporum. We investigated the growth of mycelium and the ability of P. abieticola isolates to decompose wood of Norway spruce, in the experiment with isolates of P. gigantea and H. parviporum. Heartwood was better decomposed than sapwood by the majority isolates used in the experiment. Linear growth of the investigated fungi showed a more rapid mycelium development for P. gigantea and H. parviporum, compared to that of P. abieticola. In dual cultures, H. parviporum was overgrown only by P. gigantea. All the tested isolates of P. abieticola showed weaker wood decomposition than those of P. gigantea and H. parviporum. Further study is required to better understand the role of P. abieticola for the protection of spruce stands.     

Revisiting Bergmann's rule for saguaros (Carnegiea gigantea (Engelm.) Britt. and Rose): stem diameter patterns over space

Aim The influence of winter temperatures and other climate variables are explored to determine which variables are associated with saguaro stem diameter and to determine if Bergmann's rule is applicable to saguaros. Location The northern Sonoran Desert in Arizona, USA. Methods Thirty saguaro populations were sampled (height, diameter, number of branches), and after adjustment for population height structure, mean relative thickness of saguaros was calculated for each plot (population). Fifty‐seven climate variables were calculated for the thirty populations. Regression was run to determine which variables (cold winter, hot summer and precipitation) best predict relative thickness. Previous studies have demonstrated a significant positive relationship between winter precipitation and saguaro branching ( Drezner, 2003 , Ecography, in press). To determine if relative thickness may be an artefact of branching (branches), partial correlation analysis was employed. Results Mean March precipitation best predicts relative thickness. When only winter temperature variables are considered, none are significantly related to relative thickness. Relative thickness is not an artefact of branches. Main conclusions (1) Rainfall, not temperature, best predicts saguaro stem thickness. In addition, despite the focus on summer rains in the literature, winter precipitation is the best predictor of thickness. (2) Bergmann's rule is not applicable to saguaro populations as has been previously suggested [e.g. Niering et al. (1963) Science 142 , 15], as thickness does not increase significantly with latitude. In addition, the suggested mechanism for Bergmann's rule, cold winter temperature, does not significantly predict saguaro stem diameters over the area studied. In some populations that experience high winter rainfall as well as cold temperatures, individuals likely derive thermal benefits from a larger stem diameter; however, the trend is not observed over the area studied and it does not appear to be adaptive.     

Cytogeography of Solidago gigantea (Asteraceae) and its invasive ploidy level

Aim Newly formed polyploids experience problems of establishment and spread similar to those faced by newly introduced alien species. To understand the significance of polyploidy in biological invasions, we mapped the distribution of ploidy levels in Solidago gigantea Aiton in its native range in North America, and in Europe and East Asia where it is invasive. Location North America, Europe and East Asia. Methods Flow cytometry was used to measure ploidy levels in a total of 834 plants from 149 locations. Together with data from contributors and a literature review, ploidy‐level data were assembled for 336 locations. Cytogeographical maps from North America and Europe were prepared, incorporating new and previously published ploidy‐level data. Results In the native range, diploid, tetraploid and hexaploid plants were found, and also one triploid and one pentaploid plant (2n = 3x and 2n = 5x, respectively, each being new reports for this species). There was a high degree of geographical separation among the ploidy levels, and populations with mixed ploidy were rare. However, four zones were identified where plants of different ploidy could come into contact. In Europe and East Asia, only tetraploid plants were found. Main conclusions The geographical pattern in North America suggests that the ploidy levels are ecologically differentiated, although further investigations are needed to identify the nature of these differences. Alien populations appear to be exclusively tetraploid, but it is not clear whether this is because tetraploids were selectively introduced or because diploids were unsuccessful. In any case, comparisons between native and introduced populations need to account for ploidy level.     

Impact of the biological control agent Phlebiopsis gigantea on its resident genetic structure in the Baltic Sea area

The basidiomycete Phlebiop sis gigantea (Fr.) Jülich has been used in Swedish forestry as a biocontrol agent against the root and butt-rot pathogen Heterobasidion annosum s.l. on freshly cut Picea abies stumps since the early 1990s. Until 2005, the commercial preparation of this biological stump treatment, Rotstop®, has been based on a single strain of P. gigantea that has been applied on more than 47,000 ha annually in Fennoscandia. This paper reports on the spread of genetic material from the Rotstop® biocontrol strain of P. gigantea to resident populations of P. gigantea. We conclude that the inoculated fungus remained to a large extent restricted to the treated plots and did not spread to the adjacent areas, dominated by the natural spore deposition from resident populations of the fungus. Furthermore, the study demonstrates high genetic diversity and low geographic differentiation in P. gigantea populations in the geographical area around the Baltic Sea.     

Control of Seven Grasses with a Mixture of Three Fungal Pathogens with Restricted Host Ranges

Three fungi indigenous to Florida, Drechslera gigantea, Exserohilum longirostratum, and E. rostratum, were isolated from large crabgrass (Digitaria sanguinalis), crowfootgrass (Dactyloctenium aegyptium), and Johnsongrass (Sorghum halepense), respectively. In greenhouse trials, these pathogens controlled the following seven grasses: crowfootgrass, guineagrass (Panicum maximum), Johnsongrass, large crabgrass, southern sandbur (Cenchrus echinatus), Texas panicum (Panicum texanum), and yellow foxtail (Setaria glauca). Four-week-old seedlings were inoculated with spore suspensions of each pathogen (2 × 10⁵ spores/ml) or a mixture of the three pathogens (1:1:1 by volume; total 2 × 10⁵ spores/ml). The spore suspensions as well as the control (water only) were amended with 0.5% Metamucil and the seedlings were sprayed, incubated in a dew chamber for 12 h at 28°C, and then held in a greenhouse. All seven grasses were susceptible to each of the pathogens and the pathogen mixture, each with 100% disease incidence. Two weeks after inoculation, disease severity ranged from 83 to 100% for the different grasses. In a host-range trial, 52 plant species were tested, and all nontarget plant species were safe from the individual pathogens and the pathogen mixture inoculum amended with 0.5% Metamucil. An emulsion-based inoculum preparation of the pathogen mixture was also not injurious to the crop species tested (21 species). Thus, D. gigantea, E. longirostratum, and E. rostratum and a mixture of these pathogens were nonpathogenic to the crop species tested, including Poaceae members. It is preferable to have more than one or even two pathogens in the grass pathogen mixture to achieve a broad spectrum of weed control and provide insurance against any possible failure of one or even two of the pathogens in any given combination under field conditions. More pathogens (at least three instead of two) with different modes of action and/or sites of action in a combination have a much greater chance of reducing potential risk of development of resistance in weed populations than a single pathogen used repeatedly. The use of a mixture of these pathogens appears to have the potential to be developed further as a bioherbicide system to control weedy grasses.     

兰科火烧兰属Epipactis若干种类的增补与修订

讨论了北美火烧兰 Epipactis gigantea、卵叶火烧兰 E．royleana和大叶火烧兰 E．mairei之间的异同。过去被许多作者认为是北美火烧兰 E．gigantea和卵叶火烧兰 E．royleana的中国植物实际上应是大叶火烧兰 E.mairei。卵叶火烧兰在中国仅局限于西藏东南部。     

Interaction between Chondrostereum purpureum and Phlebiopsis gigantea in mixed suspensions and their biocontrol efficacy in spruce logs and birch stumps

As the same machinery might be used in applying biocontrol agents Chondrostereum purpureum and Phlebiopsis gigantea to tree stumps, we studied whether the efficacy of one agent is affected by traces of the other present in the treatment suspension. Our results revealed that the same machinery can be used for both biocontrol agents.     

Triterpenoids from Rosa odorata Sweet var. gigantea (Coll.et Hemsl.) Rehd.et Wils and their chemotaxonomic significance

Thirty-three reported compounds were obtained for the first time from Rosa odorata Sweet var. gigantea (Coll.et Hemsl.) Rehd. et Wils and were all identified as triterpenoids. The structure of these compounds was determined by physicochemical constants and spectral analyses (NMR, MS). This is the first report on four compounds (7, 9, 10 and 22) from the family Rosaceae and thirteen compounds (2, 3, 4, 11, 17, 19, 20, 23, 24, 26, 29, 31 and 33) from the genus Rosa. Finally, the chemotaxonomic significance of these compounds is discussed.     

The circadian clock‐associated gene gigantea1 affects maize developmental transitions

The circadian clock is an internal timing mechanism that allows plants to make developmental decisions in accordance with environmental conditions. In model plants, circadian clock‐associated gigantea (gi) genes are directly involved in control of growth and developmental transitions. The maize gigantea1 (gi1) gene is the more highly expressed of the two gi homeologs, and its function is uncharacterized. To understand the role of gi1 in the regulatory networks of the maize circadian clock system, gi1 mutants were evaluated for changes in flowering time, phase change and growth control. When grown in long‐day (LD) photoperiods, gi1 mutants flowered earlier than non‐mutant plants, but this difference was not apparent in short‐day (SD) photoperiods. Therefore, gi1 participates in a pathway that suppresses flowering in LD photoperiods, but not in SD. Part of the underlying cause of early flowering was up‐regulated expression of the FT‐like floral activator gene zea mays centroradialis8 (zcn8) and the CONSTANS‐like flowering regulatory gene constans of zea mays1 (conz1). gi1 mutants also underwent vegetative phase change earlier and grew taller than non‐mutant plants. These findings indicate gi1 has a repressive function in multiple regulatory pathways that govern maize growth and development.