A New Physiologic Race ofPhytophthora megaspermaf. sp.glycinea

Plant Disease ◽  
1984 ◽  
Vol 68 (7) ◽  
pp. 626 ◽  
Author(s):  
B. L. Keeling
Keyword(s):  
Physiologic Race

THE ORIGIN OF A NEW PHYSIOLOGIC RACE OF CROWN RUST VIRULENT ON THE OAT VARIETIES VICTORIA AND SAIA

1963 ◽  
Vol 41 (12) ◽  
pp. 1613-1615 ◽  
Author(s):  
George Fleischmann
Keyword(s):  
Host Resistance ◽  
Crown Rust ◽  
Puccinia Coronata ◽  
Racial Composition ◽  
Physiologic Race ◽  
Close Relationship ◽  
Selective Forces ◽  
Canadian Provinces ◽  
New Race

A new physiologic race of crown rust, Puccinia coronata Corda f. sp. avenae Erikss., was isolated from oats collected in four Canadian provinces in 1962. This race, 332, is one of the first reported that is capable of attacking both the differential oat varieties Victoria and Saia. A close relationship exists between race 332 and race 216, which suggests that the former may have arisen from the latter by mutation. The evolution of this new race has occurred in the absence of any known Saia type resistance in current commercial varieties, and its survival points up the operation of selective forces other than host resistance on the racial composition of the pathogenic population.

PHYSIOLOGIC RACES OF OAT CROWN RUST ISOLATED FROM AECIA ON BUCKTHORN AND THEIR RELATION TO THE RACIAL POPULATION ON OATS IN SOUTHEASTERN ONTARIO AND MANITOBA

1964 ◽  
Vol 42 (9) ◽  
pp. 1151-1157 ◽  
Author(s):  
George Fleischmann
Keyword(s):  
Crown Rust ◽  
Santa Fe ◽  
Rhamnus Cathartica ◽  
Physiologic Race ◽  
Alternate Host ◽  
Oat Crown Rust ◽  
Standard Set ◽  
Physiologic Races ◽  
New Races ◽  
Differential Varieties

The physiologic race composition of isolates of oat crown rust, Puccinia coronata Corda f. sp. avenae Erikss., from aecia on buckthorn, Rhamnus cathartica L., was correlated with the races isolated from oats, Avena saliva L., in southwestern Ontario and Manitoba respectively. Among the races isolated from aecia in each region, predominant were virulent races which were isolated also from infected oats growing in the buckthorn areas. This suggests strongly that the alternate host is important in initiating crown rust epiphytotics.Races virulent on Landhafer and Santa Fe oats comprised 52% of the isolates from oats and 45% of the isolates from buckthorn in Manitoba. Isolates from oats and buckthorn in Ontario were also correlated, with the most prevalent races being those virulent on Victoria and Bond. They comprised 55% and 45% of the isolates from the principal and alternate hosts respectively.Eight races of crown rust recently discovered in Canada are described in terms of their reactions on the standard set of differential varieties. It is suggested that hybridization on the alternate host would adequately account for the origin of these new races.

New Physiologic Race ofPhytophthora megaspermaf. sp.glycinea

Plant Disease ◽  
1986 ◽  
Vol 70 (6) ◽  
pp. 500 ◽  
Author(s):  
Alice C. Layton
Keyword(s):  
Physiologic Race

Cochliobolus carbonum. [Descriptions of Fungi and Bacteria].

1972 ◽  
Author(s):  
M. B. Ellis
Keyword(s):  
Zea Mays ◽  
Geographical Distribution ◽  
New Caledonia ◽  
Seed Infection ◽  
Ear Rot ◽  
Physiologic Race ◽  
Cochliobolus Carbonum ◽  
Race 1 ◽  
Race 2 ◽  
Leaf Symptoms

Abstract A description is provided for Cochliobolus carbonum. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Zea mays. DISEASE: Leaf spot of Zea mays. Leaf symptoms differ according to the physiologic race. Race 1 gives oval to circular, straw-coloured, dry and papery lesions which become zonate with light to purplish-brown margins; they are abundant, up to 1.5 × 2.5 cm and often coalescent. Race 2 gives oval, chocolate-brown spots, sometimes irregular, up to 0.5 × 2.5 cm and less abundant than those of race 1. Both races cause ear rot, a black, felt-like growth over the kernels giving a charred appearance (23: 293). GEOGRAPHICAL DISTRIBUTION: Central and southern Africa, S.E. Europe, India (E.), Cambodia, China, Australia (NSW, Qd); New Caledonia, Canada (Ontario), USA (E.), Argentina and Colombia (CMI Map 380, ed. 2, 1969). Additional records not mapped are: Costa Rica, Guatemala, Salvador. TRANSMISSION: Seed infection is often deep seated (47, 3058); also air-dispersed through the conidia.

Gene-for-gene relationships in the Avena: Puccinia graminis host–parasite system in Canada

1970 ◽  
Vol 48 (5) ◽  
pp. 969-975 ◽  
Author(s):  
J. W. Martens ◽  
R. I. H. McKenzie ◽  
G. J. Green
Keyword(s):  
North America ◽  
Resistance Genes ◽  
Stem Rust ◽  
Host Population ◽  
Puccinia Graminis ◽  
Physiologic Race ◽  
Host Genotype ◽  
Physiologic Races ◽  
Host Parasite ◽  
Gene For Gene

The results of 48 years of oat stem rust physiologic race surveys are interpreted in terms of the prevailing host genotype. Changes in the frequencies of genes that govern virulence in the pathogen can be explained only in part by changes in the resistance genes carried by the host population. Genes for virulence on newly released types of resistance have spread very quickly through the rust population, after initial 'breakdown' of the resistance. The most successful physiologic races carry genes for virulence in excess of those required for successful parasitism in North America. Many races carry genes for virulence on types of resistance that have never been used on this continent.

Spontaneous variability of single isolates of Phytophthora infestans. II. Pathogenic variation

1970 ◽  
Vol 48 (5) ◽  
pp. 897-905 ◽  
Author(s):  
C. E. Caten
Keyword(s):  
Growth Rate ◽  
Generation Time ◽  
High Growth ◽  
High Growth Rate ◽  
R Gene ◽  
Physiologic Race ◽  
Pathogenic Variation ◽  
Resistant Varieties ◽  
Selection For ◽  
Physiologic Races

The variation in two aspects of pathogenicity, aggressiveness and virulence (physiologic race), among single zoospore cultures from three wild isolates has been examined. Two components of aggressiveness were measured, rate of growth on tubers and generation time on detached leaflets. Virulence was assessed from the pattern of compatible and incompatible reactions to members of the R gene differential series. Extensive variation in aggressiveness was detected in samples of zoospore cultures from all three isolates. The level of aggressiveness ranged from a high, equivalent to that of the parental wild isolates, to a complete lack of pathogenicity; as much as 45% was of the latter type. No instance of a change in virulence was found among 104 cultures tested.The significance of the observed pathogenic variation is discussed. It is concluded that zoospore variation is not important as a source of new physiologic races or strains adapted to particular, horizontally resistant varieties. Comparison of populations of zoospore cultures with samples of wild isolates suggests that directional selection for high growth rate and high and rapid sporulation operates in nature. The correlations between a number of cultural and pathogenic characters are examined, and an association between abundant sporulation in culture and high aggressiveness demonstrated.

THERMAL STABILITY OF STEM RUST RESISTANCE IN OAT SEEDLINGS

1967 ◽  
Vol 45 (4) ◽  
pp. 451-458 ◽  
Author(s):  
J. W. Martens ◽  
R. I. H. McKenzie ◽  
G. J. Green
Keyword(s):  
Stem Rust ◽  
Avena Sativa ◽  
Low Temperatures ◽  
Rust Resistance ◽  
Thermal Sensitivity ◽  
Stem Rust Resistance ◽  
Puccinia Graminis ◽  
Physiologic Race ◽  
Plant Genotype ◽  
Thermal Stability Of

Six of the identified genes for stem rust (Puccinia graminis Pers. f. sp. avenae Erikss. and Henn.) resistance in oats (Avena sativa L.) are divided into three categories of thermal sensitivity: resistance conferred by genes A and D is stable; that conferred by genes H and F 'breaks down' at intermediate temperatures; and that conferred by genes B and E breaks down at relatively low temperatures. Studies of oat lines carrying single or several resistance genes indicate that thermal sensitivity of the reactions conditioned by the genes conferring labile resistance is not affected by the presence of genes conferring stable resistance or by the rest of the host plant genotype. The critical temperature of breakdown varies with physiologic race.

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