Abstract only

Wheat rusts are found in Georgia from the most ancient times and represent serious danger to crops. The most effective and environmentaly safe method of wheat protection from rusts is the cultivation of rust-resistant cultivars. The genetic analyses of the virulence spectrum of the pathogen population bear the decisive role in implementation of the breeding programs aiming at the development of rust-resistant wheat forms. The aim of this study was determination of the virulence gene pool of the wheat rust pathogens with the help of isogenic lines carrying almost all identified resistance genes (Dyck, 1987; McIntosh, 1985; 1987). 236, single-aecio-and uredinial isolates of Pgraminis, 220 uredinial isolates of Precondita and 110 single isolates of P striiformis have been analyzed during the last two years. The initial samples of the disease were collected from production fields in the different areas of Georgia. The isolation and reproduction of pathogen and identification of virulence structure of its population have been carried out according to established international methods (Knott, 1989; Roelfs et al., 1992). Representation and frequencies ofvirulence genes of stem rust, leaf rust and yellow rust pathogens are shown in Table 1. Analysis ofthe representation of the virulence genes of wheat stem rust pathogen, carried out on the set of 35 isogeneic lines, has shown that the population incorporates the majority ofthe virulence genes. The following pp genes were not registered inthepopulation:8,9b, 11,13,22,24,25,26,27,31, 33,35 and pp genes 7, 7a, 21, 32 were rarely enco- untered. Virulence structure of p recondita incorpo- rates 30 virulence genes out of36 analyzed ones. 18 virulence genes are continually represented in the population. Content of the genes: p2a, p2b, p 15, p18, p20, p21, p23,p25,pl, 27+31,p32,p36 varies within21, 6-91,6%.ppgenes: 9, 19,24,28,29,10+23 were not represented in the population as previously. Virulence towards the formerly effective Lr2a, Lr2b genes increased from 3% to 80% (Sikharulidze Z. et all, 1993). Virulence structure of yellow rust p strifo- rmis is represented by the following genes: 2a, 3, 3a,6,7,8,9, II, 12, 15, 17, I8,24,26,SK,SD,J(R) and A(S), however, virulence towards YrI2, YrI 5, Yr24, Yr26 genes was encountered very rarely; pp genes p I, p5, p 10, pSP were not registered in the population. Compared to the previous data (Naski- dashvili G. et al. 2001) virulence of the population has significantly increased. Thus, analyzing virulence structure of Georgian populations of all three wheat rusts, we can make a conclusion that the monitored populations are highly virulent and differ from the populations in other countries (Anpilogova, Volkova ,2000; Kolmer, 2002; Harder. et al., 2001).

English

0409|AGRIS 0401|AL-Wheat Program

Juan Carlos Mendieta

CIMMYT Publications Collection