Some new races ofPuccinia striiformis

Abstract

In the Netherlands in 1961 three new field races were found of Puccinia striiformis, the causal fungus of yellow rust on wheat. Two of these, viz. the 'Falco' race and the 'Opal' race, together with the already known 'Etoile de Choisy' race, constitute the so-called Nord-group of races, which is now deafly distinguished from the so-called Rubis-group. Most dangerous and interesting is the third of the new races. This so-called 'Cleo' race proved to be the first to break both resistance to the Nord-group and resistance to the Rubis-group. On wheat seedlings in the greenhouse all three new races behaved like greenhouse race 'W(ageningen) 8' = 'B(raunschweig) 55'.

A valuable source of yellow rust resistance in Israeli populations of wild emmer,Triticum dicoccoides Koern.

“…tritici) is closely associated with the phenomenon of continuous adaptation of the pathogen to its host, resulting in the appearance of new races . In The Netherlands, where the race population is determined annually, ten new races appeared during the period from 1955 to 1967 inducing epiphytotics on recently developed varieties that until then had been resistant (ZADOKS, 1961 ;UBELS et al ., 1965 ;STUBBS, 1967) . In 1968 another new race (race 60A) appeared, overcoming the resistance of the variety Flevina (Hope/Timstein//Heine's VII), which was one of the few remaining resistant varieties in The Netherlands .…”

The Occurrence of Two New Physiologic Races of Puccinia striiformis Westend. in Britain

“…Since race 3/55 Opal was not able to infect Heines VII the isolates were tested on further supplementary cultivars. Results indicated that the isolates were similar to, but not identical with, race 3/55 Opal and 3/55 Cleo (Ubels et al, 1965) and the name 'race 3/55D' is therefore proposed for this new race. The reactions of race 3/55D, 3/55 Opal and 3/55 Cleo are given in Table 1 In 1967 an isolate was obtained from the resistant cultivar Maris Beacon at the Plant Breeding Institute, Cambridge.…”

“…Seventeen isolates were identified as being similar to race 3/55 Opal (Ubels et al, 1965) but with added virulence on Heines VII. Since race 3/55 Opal was not able to infect Heines VII the isolates were tested on further supplementary cultivars.…”