Epidemiological Effects of Combining Different Sources of Leaf-Rust Resistance in Winter Rye Synthetics

Economically important rye (Secale cereale L.) cultivars are highly susceptible to leaf rust caused by Puccinia recondita f.sp. secalis in Germany. Presently, only race-specific resistances are available, which are likely to lose their effect after prolonged application. To study possibilities of increasing the durability of resistance, a three-year field experiment was initiated in 2000. Seventeen differential lines, three susceptible standards, 30 segregating populations with one to four resistance sources and two full-sib families were grown at six locations under a high level of natural infection. All segregating populations were significantly more resistant than the susceptible standards. The resistance level, however, was under these conditions moderate only. The two full-sib families from Russia showed high resistance. Strong genotype × location interactions were observed indicating different race compositions of the local leaf rust populations.