摘要:

Isolates of different species of the conifer pathogenGremmeniella, including some cultures from western Canada and some endophytic isolates, have been characterized by pectic enzyme patterns. Pectinase isozyme patterns are in good agreement with results of electrophoresis of mycelial water-soluble proteins. The North American and European races ofG.abietinavar.abietinacan be distinguished on the basis of a cathodal polygalacturonase band present in all isolates of the former but absent in the latter. Another band, present in all isolates, shows polymorphisms related to the host from which the isolates are derived, thus making it possible to group them on a pathogen race – host genus basis. Sixteen isolates originating from western Canada that were previously found to belong to the North American race with a water-soluble protein assay were also found to belong to that race following the analysis of pectic enzymes. It was not possible using our assay to distinguish between isolates ofBrunchorstia pineavar.cembraeand others derived from otherPinusspp. Among the endophytic isolates, thePinus cembraendophytes show the same polygalacturonase profile as those from diseased pines.Key words: ascomycetes, diagnostic tools, electrophoresis, plant pathology, taxonomy.

ISSN:0008-4026    

DOI:10.1139/b94-114

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The inflorescence structure of Begoniaceae was analyzed taking into account their degree of symmetry. Qualitative and quantitative analyses of 71 species led to the recognition of nine architectural models. When the whole plant is considered, the inflorescence of Begoniaceae is a thyrse. Comparative analyses of the models allowed to determine at what level symmetry or asymmetry is found. There is a correlation between the total lengths of axes and between flower numbers on the best and least developed sides of an inflorescence. For the whole family, the difference between the two sides of the inflorescence is significant for the former, and not for the latter. Divergence angles on the best developed side do not differ from those on the least developed one for a same ramification, and likewise between successive levels of ramification. Thus, the inflorescence appears asymmetrical if total length of axes is considered. These results tend to support the hypothesis that the Begoniaceae are fundamentally asymmetrical. Inflorescence symmetry is found in some groups by stabilization and compensation of different asymmetric components at the global and local levels. Nevertheless, inflorescence asymmetry does not seem to be related to plant architecture, although it seems to be related to the degree of foliar asymmetry.Key words: Begoniaceae, inflorescence, cyme, inflorescential architecture, structural asymmetry.

ISSN:0008-4026    

DOI:10.1139/b94-115

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The genetic structure ofPyrenophora teres, an ascomycete fungus that causes net blotch of barley, was examined using random amplified polymorphic DNA (RAPD) markers. Twenty-seven random oligonucleotide primers were screened against DNA from 16 isolates ofP.teresof diverse geographic origin. Five primers gave scorable, reproducible DNA products (bands) suitable for population genetic studies. Genetic analyses of bands produced by two of the primers revealed single locus segregation in three of four crosses, indicating that these RAPDs can be interpreted as alleles at genetic loci. Allele frequencies were determined for 10 putative RAPD loci from five primers in 22–35 isolates of P.teressampled from each of five geographically separated populations in Canada, Germany, and the U.S.A. Eight RAPD loci were polymorphic in at least one population and two loci were monomorphic in all five populations. Variation in allele frequencies (allelic diversity) among the five populations was partitioned into within- and among-population components using Nei'sGST. AGSTvalue of 0.46 was obtained among all populations indicating that approximately 46% of the total genetic variability detected was due to differentation among populations compared with 54% within populations. AGSTvalue of 0.33 was obtained among the North American populations only. From five to nine multilocus genotypes were found in each population. Nine genotypes occurred exclusively in the German population and four exclusively in the New York population. The other populations had one or two unique genotypes. Gametic disequilibrium values (nonrandom associations of RAPD loci) were calculated among all pairs of polymorphic loci within each population. Eleven of 49 values were significantly different from 0 (P < 0.05); 8 of the 11 significant gametic disequilibrium values occurred in the New York population. Highly significant gametic disequilibrium was detected between the same two RAPD loci in three different populations, suggesting that these loci are genetically linked. Two different multilocus analyses revealed that the genetic structures of the Alberta, North Dakota, and German populations but not the New York population were consistent with random sexual reproduction occurring in these populations.Key words: polymerase chain reaction, population genetics, fungi, genetic differentiation.

ISSN:0008-4026    

DOI:10.1139/b94-116

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

The major problems (bad anchorage, water stress, and root disease) with the cropping of the rubber tree (Hevea brasiliensis) are related to the architecture of its root system. So, the morphogenetic properties of the various roots that emerge during the development of the young seedlings are described to improve our understanding of the dynamics of root system architecture. In this study, the development of the root system of 12 seedlings grown for 40 days in root observation boxes has been recorded on a daily basis and analysed. Additional observations were also made on plants grown in pots or in the field for a 60-day period. This analysis of the sequential differentiation of the root system allowed us to distinguish five different root types according to their spatial and temporal location at emergence: (i) taproot, (ii) early first-order lateral roots, (iii) acropetal first-order lateral roots, (iv) late first-order lateral roots, (v) second-order lateral roots. Large variations and close relationship were found within the growth and branching characteristics on one hand, and within anatomical characteristics on the other (number of xylem poles, external diameter, and stele diameter). These between-type variations were also observed, to a lesser extent, among roots from the same type. The continuity of these development characteristics, which were shown to be acquired early, led us to characterize a morphogenetic gradient. This gradient is a reference scale to understand the morphological plasticity of the root system growing in other mediums.Key words: root system, development, morphogenesis, anatomy, root observation box,Hevea brasiliensis.

ISSN:0008-4026    

DOI:10.1139/b94-117

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

A newPenicilliumspecies,P.tricolor, morphologically similar toP.aurantiogriseumand allied species, was isolated from red spring wheat and durham wheat grains in Saskatchewan and Manitoba.Penicillium tricoloris classified inPenicilliumsubg.Penicilliumand is characterized by the following combination of diagnostic characters: tuberculate conidiophore stipes, greyish turquoise smooth conidia, orange-brown exudate droplets and colony reverse, and production of the mycotoxins xanthomegnin, viomellein, vioxanthin, terrestric acid, and the alkaloids rugulosuvine, leucyltryptophanyldiketopiperazine, verrucofortine, puberuline, and asteltoxin.Key words:Penicillium tricolor, taxonomy, wheat, mycotoxins.

ISSN:0008-4026    

DOI:10.1139/b94-118

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies ofN.communefound on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction inN.commune(2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arcticN.communebut lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpinaandGleotrichiasp.),N.communehad higher rates of nitrogen fixation.Key words:Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosy

ISSN:0008-4026    

DOI:10.1139/b94-119

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Twelve leaf litters belonging to 10 Mediterranean species of coniferous and broad-leaved trees and shrubs and grass species were incubated in microcosms in the laboratory at 22 °C and constant humidity for 14 months. Samples were collected at 0.5, 1, 2, 4, 6, 10, and 14 months, the remaining dry weight being measured at each sampling time. At the end of 14 months, the litters had lost between 52 and 74% of their original mass. The comparison of regressions fitted to the various functions showed that for the species studied, the litter mass loss in relation to incubation time best fitted a double-exponential decay function. The mass loss therefore resulted from the simultaneous decomposition of two main compartments, a labile compartment that decreased rapidly (half-life of 20 – 60 days under the experimental conditions) and a resistant compartment that depending on the species, either did not decrease significantly or decreased 10 to 20 times slower than the labile compartment (half-life of 320–630 days). The litters studied could be categorized according to the relative importance of these two compartments. This was related to the initial content of water-soluble substances and of carbon in the litters. It was also strongly correlated with the spectral information of the initial litters obtained by near-infrared reflectance spectroscopy. In contrast, the rate at which the labile and resistant compartments decreased was related to the permeability of the leaves for the former and to their thickness and mass per surface area for the latter. Near-infrared reflectance spectroscopy provides new perspectives for characterizing the capacity of litters to decompose.Key words: litter, decomposition, near infrared reflectance spectroscopy.

ISSN:0008-4026    

DOI:10.1139/b94-120

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Penicillium nodositatuminfects the roots of alder trees and induces the formation of structures called myconodules, which are similar to young actinorhizae. Root infection ofAlnus incanabyP.nodositatumas well as myconodule development were studied by light and electron microscopy and observations were compared with those described for the infection byFrankiaspp. We have established an obvious homology between the early steps of the infection caused by both microorganisms. The presence of the fungus near the roots induces deformation of root hairs. The infection site is probably localized in a folding of a deformed hair. As soon as hyphae penetrate into the hair, they become enclosed in a polysaccharide matrix. Initially,P.nodositatumcolonizes a region near the infected root hair that may correspond to a slightly developed prenodule. Then a nodular primordium is initiated at some distance from the initial contact and the new nodular cortex is invaded by the fungus. The zone of infection is limited to the cortical cells by a barrier of tannins. Myconodules remain small and unilobed and have an outer morphology similar to that of an incompatibleFrankianodule.Key words:Alnus, myconodule formation,Penicillium, root hair infection.

ISSN:0008-4026    

DOI:10.1139/b94-121

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

Since 1970, the architectural analysis of woody plants has given much information about structural and functional organization of tree crowns, their development, and reiteration patterns. In this study, we have extended this method to tree root systems. We describe the whole architecture of three species and we compare their root system and crown architectural patterns.Key words: architecture, tree, root system, crown, whole plant.

ISSN:0008-4026    

DOI:10.1139/b94-122

出版商:NRC Research Press    

年代:1994

数据来源: NRC

摘要:

F.L. Stevens (1925. Bernice P. Bishop Mus. Bull. No. 19) published the first comprehensive list of fungi in Hawaii, recognizing 7 species of endemic rusts and 10 species probably indigenous. Stevens considered this small number of rusts particularly noteworthy in comparison with the rust floras of other areas with which he was familiar. He ascribed the scarcity to the geographic isolation of the Hawaiian Islands from significant land masses. Currently, of the more than 74 rusts in Hawaii, 22 are considered native, of which 13 are endemic and 9 indigenous. The rust flora, like other groups of native organisms of Hawaii, provides interesting examples of biological colonization and adaptation to remote insular environments.Key words: endemic, Hawaii, indigenous, rusts.

ISSN:0008-4026    

DOI:10.1139/b94-123

出版商:NRC Research Press    

年代:1994

数据来源: NRC