摘要:

In addition to the well-known sessile vesicular zoosporangial type of oöspore germination inAlbugo candida(Lév.) Kuntze, a second type is described. This consists of an exit tube one to two and a half times the length of the diameter of the oöspore and about one quarter of its width, at the end of which the vesicular zoosporangium is produced. Best results were secured by soaking the oöspores for 7 to 10 days in water at 10° to 12 °C and then changing to fresh water. The oöspore material came from hypertrophied inflorescences of rape (Brassica napusL. var.annuaKoch).

ISSN:0008-4026    

DOI:10.1139/b59-015

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The following paper is an evaluation of the taxonomic and ecological status of the genusXanthiumL. A review of its systematics demonstrates that many so-called "species" described on material from Europe actually have their origin in America, except one,X. strumariums. str., which seems to have a Mediterranean–European center of dispersal. Another conclusion drawn is thatXanthiumconsists of only two distinct species:X. spinosumL. andX. strumariumL. The former is a relatively stable species, the latter an enormously variable one readily subdivided into a number of minor taxonomic entities.Ecologically, in eastern North America at least,Xanthiumis primarily a beach plant, which prefers open habitats and succumbs to crowding. The seeds are most often dispersed by water and wind. It enters easily into ruderal habitats, but only as long as these are open and unshaded.The generalized short-day flowering response in this genus supports our hypothesis thatXanthiumhas a tropical–subtropical origin, and we feel that it has its center in Central and/or South America, whence it has spread over the continents north and southward.There is no evidence for any sterility barriers separating the entities ofX. strumarium, but we feel that an intense inbreeding with an occasional outbreeding is responsible for the enormous variation, often resulting in small, local, but unstable taxa.

ISSN:0008-4026    

DOI:10.1139/b59-016

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The authors report the chromosome numbers of 25 taxa of the genusSolidagowhich had not yet been studied from this standpoint, and review the literature. The chromosome numbers of 42 taxa have now been published. The basic number of the genus is nine. Thirty-three taxa are diploid (2n = 18), five are tetraploid (2n = 36), three are aggregate taxa containing both diploid and tetraploid cytodemes, and one is hexaploid (2n = 54). Polyploidy has thus contributed to the evolution of the genusSolidagobut it seems that most of the species have differentiated gradually.S. decemfloraDC. of western North America differs fromS. nemoralisAit. of the same continent by morphological characters, its geographical distribution, and its chromosome number, the first taxon being tetraploid and the second diploid; the two are thus good species and not only varieties of the same species. TheS. rigidaof authors is an aggregate made up of two entities which are distinguished not only by their morphology and geographical distribution but also by their chromosome numbers; the eastern one (S. rigidaL.) is tetraploid, whereas the western one (S. parvirigidaBeaudry) is diploid. The bog and marsh goldenrods,S. PurshiiandS. uliginosa, also possess different chromosome numbers, the first being diploid and the second tetraploid.

ISSN:0008-4026    

DOI:10.1139/b59-017

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

A close correlation was found to exist between the development of the willow bark canker, caused byCryptodiaporthe salicina(Curr.) Weh., and the moisture content of the bark. When this was expressed as a percentage of the amount of water required to saturate the sample under experimental conditions, relative turgidities of 80% or more inhibited canker development which, however, occurred normally at lower percentages. Studies of the epidemiology of this disease in the Vancouver area afforded evidence in support of the limiting effect of bark moisture on canker development. Thus during the dormant season of 1957–58 the monthly average temperature was significantly higher than the minimum temperature for the growth ofC. salicinaon potato dextrose agar and the relative turgidity did not reach the inhibiting value of 80%. Cankers continued to develop throughout this period. During the growing season while temperatures were still more favorable for fungus development no extension of cankers occurred, apparently because, during the growing period, the relative turgidity was in excess of 80%. Canker development was prevented during the winter by placing dormant twigs in water, which likewise increased the moisture content of the bark above the 80% level.

ISSN:0008-4026    

DOI:10.1139/b59-018

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Leaves of Khapli wheat which are normally resistant to race 15B-1 ofPuccinia graminis triticibecome susceptible when detached and floated on water. This breakdown of resistance can be reversed by floating the detached leaves on a solution of benzimidazole. The effect of benzimidazole, however, can be nullified by a supply of exogenous glucose or 5,6-dimethylbenzimidazole. Furthermore, the resistance can again be restored by the presence of cobalt ion combined in solution with glucose and benzimidazole or with glucose and 5,6-dimethylbenzimidazole. Cobalt ions alone, or in combination with glucose, or with benzimidazole, or with 5,6-dimethylbenzimidazole separately have no effect on rust development. In contrast, nickel ion alone or in any combination has a profound inhibitory effect on the development of rust in detached leaves. Other chemicals were also included in this study, and their effect on rust development is discussed. It is speculated that benzimidazole or a derivative of it and cobalt may form a vitamin B12-like factor which is required by the host to maintain its normal metabolic activities.

ISSN:0008-4026    

DOI:10.1139/b59-019

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

F. oxysporumf.cubenseexists in diseased rhizomes and pseudostems of Gros Michel bananas in two major clonal groups or cultivars designated 'Odoratum' and 'Inodoratum' because of the presence or absence of a pronounced distinctive odor from cultures after 4 to 8 days on various media. Three clones of the 'Inodoratum' cultivar, difficult to distinguish morphologically on peptone dextrose agar, were distinguishable by cultural interaction and pathogenicity tests in the field. Some clones of the 'Inodoratum' and 'Odoratum' cultivars were shown to differ quantitatively in pathogenicity in the field. Clone C from Honduras, which is limited in distribution, induced the most rapid disease spread and destruction of banana mats, followed by clone E from Panama. There was an association between the 'Inodoratum'and 'Odoratum' cultivars and the syndromes induced in Honduras. The former usually induced strong yellowing of erect leaves whereas the latter usually induced leaf collapse at the petiole with little or no leaf yellowing.

ISSN:0008-4026    

DOI:10.1139/b59-020

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

The present investigation was commenced in 1932 and has been continued annually since that time with the object of determining the identity, host range, and geographic distribution of theFusariumspecies in Canada. Approximately 9000 isolates ofFusariumwere studied. These isolates were obtained from 173 species and botanical varieties of plants, 14 species of insects, and 4 of fungi. Of the various species and botanical varieties of plants from which isolates were obtained, 19 were cereals and grasses, 19 were vegetable crops, 15 were fruit crops, 13 were field crops, 52 were ornamental plants, 31 were trees and shrubs, and 24 were common weed plants. Less than 1% of the total isolates was obtained from insects and fungi. Although most of the isolates originated in Manitoba, some were obtained from each of the other provinces of Canada except Newfoundland.A total of 18 species, 3 varieties, and 18 formae ofFusarium, classified in nine sections of the genus, were identified among the isolates from plants, insects, and fungi. These species, varieties, and formae are:F. chlamydosporumWr. & Rg.,F. poae(Pk.) Wr.,F. sporotrichioidesSherb. (section Sporotrichiella); F.arthrosporioidesSherb.,F. avenaceum(Fr.) Sacc. (Roseum);F. concolorRg.,F. semilectumBerk. & Rav. (Arthrosporiella);F. acuminatum(Ell. & Ev.) Wr.,F. eauiseti(Cda.) Sacc. (Gibbosum);F. culmorum(W. G. Sm.) Sacc,F. graminearumSchwabe,F. heterosporumNees emend. Raillo,F. sambucinumFuckel,F. samb. var.coeruleumWr.,F. samb. f. 6 Wr. (Discolor);F. moniliformeSheld.,F. moniliformevar.subglutinansWr. & Rg. (Liseola);F. lateritiumNees (Lateritium);F. oxysporumSchl. emend. S. & H.,F. oxysporumvar.redolens(Wr.) Gordon,F. oxysporumf.betae(Stewart) S. & H., f.callistephi(Beach) S. & H., f.cepae(Hanz.) S. & H., f.conglutinans(Wr.) S. & H., f.dianthi(Prill. & Del.) S. & H., f.fabaeYu & Fang, f.gladioli(Massey) S. & H., f.liliiImle, f.lini(Bolley) S. & H., f.lycopersici(Sacc.) S. & H., f.melonisS. & H., f.narcissiS. & H., f.pini(Hartig) S. & H., f.tuberosiS. & H. (Elegans);F. solani(Mart.) App. & Wr. emend. S. & H.,F. solanif.eumartii(Carp.) S. & H., f.phaseoli(Burk.) S. & H., f.pisi(Jones) S. & H.,F. coeruleum(Lib.) Sacc. (Martiella).F. chlamydosporum, F. heterosporum, F. moniliformevar.subglutinans, as well as 14 formae ofF. oxysporumand 3 formae ofF. solani, are reported to occur in Canada for the first time in this series of papers.The six species isolated most commonly, as indicated by the number of hosts from which they were obtained, areF. oxysporum, F. acuminatum, F. solani, F. equiseti, F. avenaceum, andF. poae.The conidia and chlamydospores ofF. chlamydosporumandF. heterosporumare illustrated by drawings.

ISSN:0008-4026    

DOI:10.1139/b59-021

出版商:NRC Research Press    

年代:1959

数据来源: NRC

摘要:

Studies were begun to assess the significance and interrelationships of five fungi consistently associated with the deterioration of balsam fir trees killed by the spruce budworm, and to explain the succession pattern of the fungi in that process. A yeast andOphiostoma bicolorDavidson and Wells were the only fungi consistently isolated from the discolored cambium of dying or recently killed trees;Stereum chailletiiPers. and an unidentified hyphomycete,Fungus F, were the principal fungi isolated from the stained sapwood of trees dead less than one year; andPolyporus abietinusDicks, ex Fries was the only fungus consistently associated with the rotted sapwood of trees dead for more than one year. A gradual and fairly regular lowering of the moisture content, pH, and strength of balsam fir sapwood from the healthy, living state through the various stages of deterioration was recorded. There was no evidence of marked inhibition or antagonism among the fungi tested in pure culture. Although the most vigorous growth ofP. abietinusoccurred in liquid media adjusted at pH 4.5, compared with 6.5 forFungus FandS. chailletii, balsam fir sticks of about pH 6.0 were readily infected byP. abietinusin the laboratory. Sticks artificially infected withS. chailletiiorP. abietinusdeveloped a pronounced reddish stain and showed significant reductions in toughness, and the pH of aqueous extracts of these sticks was markedly reduced. The same properties of sticks infected withFungus Fdiffered very little from those of the check sticks. There was no evidence that eitherFungus ForS. chailletiiwas inhibited by the presence of the other in balsam fir sapwood, or that the presence of either had any effect upon the deteriorating capacity ofP. abietinus. It is suggested that the principal explanation for the succession pattern of fungi in the deterioration of balsam fir lies in a dependence upon changes in certain properties of the wood substrate, particularly in the moisture content of the sapwood.

ISSN:0008-4026    

DOI:10.1139/b59-022

出版商:NRC Research Press    

年代:1959

数据来源: NRC

ISSN:0008-4026    

DOI:10.1139/b59-023

出版商:NRC Research Press    

年代:1959

数据来源: NRC