VARIATION IN THE RESISTANCE SPECTRA OF ETHIOPIAN WHEAT CULTIV ARS TO STEM RUST (PUCCINIA GRAMINIS F. SP. TRITICl) AND ITS EPIDEMIOLOGICAL IMPLICATION

Abstract

Multipathotype test was conducted to study the resistance spectra of Ethiopian
hexaploid and tetraploid wheats to stem rust (Puccinia graminis f.sp. tritici) infection. Seedlings of 14
.durum (Triticum durum), 10 emmer (T. dicoccan), 15 bread (T. aestivum) wheat cultivars and access;ions,
and 33 stem rust differential lines were inoculated with 18 different stem rust races in the greenhouse
experiment. The observed Wection types ([TS) were categorized as low infection type (1.11) and high
infection type (HIT). The number of LlTs (resistance spectrum) exhibited by each variety and accession
was described in terms of low infection type frequency (LIT}). The results obtained indicated that three
bread wheat varieties, KBG-OI, Bobitcho, Megal and one durum wheat variety, Ude possess widest
resistance spectrum (urf = 18, resistant to all the 18 races) while three bread wheat varieties, Ketar,
Galama, Shinna and one durum variety, Gerado exhibited the narrowest spectrum (tnt = 7 and 8). ACC~
213155-2 of emmer wheat type showed r~sistance to 16 races while Acc-212883-3 was resistant to 11
races. The highest range of variation in the resistance spectrum was observed among durum wheat
genotypes while variation recorded among emmer varieties was the least. LITf values of each variety
gave clues to the epidemiological relationship between tITfvalues and pathogen co-evolution. In cases
where gene-for-gene interaction works, varieties with highest LlTf values exert higher ~lection pressure
on the pathogen population than thos<' varieties with lower LITf values and consequent upon this
hypothesis the importance of assessing values of each variety in designing and implementing
vertical resistance management strategy is discussed