摘要:

Changes in host cell permeability induced by fungus parasites selected from several distinctive types of disease relationship were studied by plasmolytic methods.Puccinia graminis Triticirace 21 causes an increase in permeability to cells of the susceptible wheat varieties, Mindum and Little Club.Resistance of Mindum wheat to race 36 is associated with a local decrease of host cell permeability.Narcotization of Mindum wheat increases permeability and renders this variety more susceptible to race 36 ofPuccinia graminis Tritici. This information, together with a hypothesis, already expounded, explaining mechanisms involved in food uptake by rusts, was used in the formulation of a theory illustrating a basic component of the factors responsible for rust resistance. This theory seems to interrelate the two main contrasting theories hitherto propounded.Permeability increase is also demonstrated as an effect of tissue invasion byBotrytis cinerea,Sclerotinia Sclerotiorum, andPhytophthora infestanson their respective susceptible hosts. This fact is allied with other information to explain the characteristic symptoms associated with the diseases caused by these fungi, and to propose an accessory role of permeability increase in the parasitism of these organisms.The probable cause of wilting induced by hadromycotic fungi is discussed, and the role of a permeability increase demonstrated for leaf cells of tomato subjected to the action of a filtrate of a culture ofFusarium Lycopersiciis discussed in this connection.A decrease found in the permeability of tissues of swede "root" near the margin of a necrotic lesion caused byPhoma lingamwas interpreted as being a change in accord with Brown's suggestion that a dry rot is determined by the ability of the host plant to restrict the amount of water reaching the parasite and so arrest the progress of its enzymic activity at some intermediate stage.

ISSN:1923-4287    

DOI:10.1139/cjr42c-027

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

The species description ofXanthomonas translucens(J. J. and R.) Dowson is emended to include five closely related organisms, which are distinguishable chiefly by differences in pathogenic capabilities on wheat, oats, barley, and rye. One of these organisms,X.translucens(J. J. and R.) Dowson, is given new rank asX.translucensf. sp.hordei; another,Phytomonas translucensf. sp.undulosa(S. J. and R.) Hagborg, is transferred to the genusXanthomonas; still another,Phytomonas translucensvar.secalis(R. G. and J.) Bergeyet al., is given new rank and also transferred to the genusXanthomonasasX.translucensf. sp.secalis; the remaining two,X.translucensf. sp.hordei-avenaeandX.translucensf. sp.cerealis, are described for the first time.The results of non-determinative comparative studies in physiology and serology of the second and last two of the above-mentioned special forms ofXanthomonas translucens(J. J. and R.) Dowson emend, are given; these show their close similarity in characters other than pathogenicity. These studies also show the presence of some variation between different isolates of the same special form. Parallel studies, made at the same time, on cultures ofPseudomonas atrofaciens(McC.) Stapp,P.coronafaciens(Elliott) Stapp, andP.medicaginisvar.phaseolicola(Burkh.) Stapp and Kotte, were used as controls on the methods.

ISSN:1923-4287    

DOI:10.1139/cjr42c-028

出版商:NRC Research Press    

年代:1942

数据来源: NRC

摘要:

Burrillia anomalaCrowell forms irregularly elongated spots on the leaves ofSparganium diversifoliumGraebner var.acaule(Beeby) Fernald & Eames. The spore-ball of this smut is composed of readily disjoined spores, an occurrence reported in only one other species of the genus, namely,B.acori. Both of these species are recorded only from Ontario.Entyloma peninsulaeCrowell forms linear sori on leaves ofZizania aquaticaL. It differs fromE.lineatum(Cooke) Davis in having much longer sori and considerably smaller spores.E.peninsulaeis recorded only from the type locality in New Glasgow, N.S.

ISSN:1923-4287    

DOI:10.1139/cjr42c-029

出版商:NRC Research Press    

年代:1942

数据来源: NRC