'Plant Breeding: Sustaining the Future' Abstracts of the XVIth EUCARPIA Congress, Edinburgh, Scotland, 10-14 September 2001 GENETICS OF BARLEY SOMACLONAL LINES RESISTANCE TO COMMON ROOT ROT L.G. TYRYSHKIN, N.N. SOLOVIEVA, N.M. OVTCHAROVA NI Vavilov Institute of Plant Industry, St Petersburg, Russia

Seedling resistance to common root rot, caused by Bipolaris sorokiniana Shoem, was assessed in R₂ of 1500 regenerated lines of 5 spring barley varieties. Constant segregation for resistance was observed in the progeny of resistant lines in subsequent generations. Only in R₇ it was possible to select constantly resistant lines: 3 - of variety Golden Promise, and 1 - of Roland. Three hypotheses were verified about genetic nature of the trait: partial penetration of resistance in most identified lines, constant reversion of mutations to alleles for susceptibility, polygenic control with cumulative action of minor genes. Analysis of F₂ and F₃ from crosses of resistant lines with susceptible cultivars revealed polygenic control of high level of resistance to root rot; at least some genes are expressed in adult plants.