6.27

VIRULENCES GENES OF LATVIAN POPULATION OF COMMON BUNT TILLETIA CARIES (DC.)TUL.

I PRIEKULE
State Stende Plant Breeding Station, p/o Dizstende, Talsi region LV 3258, LVA

Background and Objectives

The common bunt Tilletia caries (DC.)Tul. is one of the most harmful and serious wheat Triticum aestivum L. diseases in the Baltic region. Spread of the fungus increased sporadic in Latvia. 8 % of wheat areas were infected in 1966-1967, but last years a severity of disease had been reached even 21-63 % in some regions of Latvia. Determination of effective resistance genes to common bunt is very important for successful wheat breeding. Only incomplete research of virulence of the Latvian bunt population had been done in 70thies [1]. Purpouse of this work was to investigate a virulence/avirulence of pathogen population at present.

Materials and Methods

Teliospores of T. caries were collected on wheat breeding fields of the State Stende Plant Breeding Station. The pathogen population, used as inoculum, was a mixture of spores from different wheat varieties. The standart set of differentials - isogenic wheat varieties and and lines, carried resistance genes Bt1...Bt10, was used [1]. Inoculation of differentials was carried out by shaking of seeds with teliospores for 1 min (the ratio of spores/seeds - 1:100). Inoculated seeds were sown in last week of September (late sowing time) in the field in two 1 m rows 0.15 m apart (in three replications). Percentage of infected ears were determined. In terms of virulence of the pathogen, infection level 0-10% were classified as avirulent, 11-100 % - as virulent.

Results and Conclusions

In years 1994, 1996, 1997 the population of common bunt , spread on the Stende Plant Breeding Station, was investigated. The results of estimation showed, that only three isogenic lines have resistance to the patogen infection. The bunt population had effective virulence against Bt1, 2, 3, 4, 5, and 6. The resistance genes Bt8, 9 and 10 were noted as effective, able to insure wheat varieties against pathogen infection. The gene Bt7 showed unclear reaction, variable in years. In 1971 three races of common bunt had been presented in Latvia: T-1, T-5 and unnamed race [2] (according to Krivchenko - 3.(7/1.2.3.4.5.6.8.9.10), 11.(1.2.7./3.4.5.6.8.9.10), 27.(1.3.4.5.7./2.6.8.9.10), virulence/avirulence against Bt genes).All these mentioned above races have the virulence to the resistance gene Bt7. Therefore it can be concluded, that resistance gene Bt7 can't be resistant in Latvian conditions. Resistance genes Bt 4,5 and 6 lost their previous effectivity. Results of our investigations showed, that pathogen populations, spread on the State Stende Plant Breeding Station, activitu can be characterised by formula of virulence/avirulence - 1.2.3.4.5.6.7./8.9.10.

References

1. Krivchenko VI, 1984. Smuts and bunts of cereals, 304p. (Russian) 2. Hoffmann JA, Metzger RJ, 1976. Phytopathology 66,657-660.