Rusts epidemics and their implications in wheat breeding and research in the Czech Republic

Rust epidemicsStem rust of rye.In the early 1950s, a severe stem rust epidemic developed on rye in southern Bohemia.The role of an alternate host, barberry bushes occurring in the hilly area of Šumava, was investigated.Of cerealicolous Puccinia graminis subspecies only stem rust that attacks rye was found on barberries.The infection of barberries originated from rust infected couch-grass growing under them.If it grew closer to a field of rye, an infected barberry bush would have a very distinct effect on the spread of stem rust in the field.Barberries were not eradicated after the epidemic, nevertheless, no large-scale outbreak of stem rust on rye has ever appeared since then.Obviously, the incidence of barberry bushes was too low to be the main source of inoculum for severe rust outbreaks.The epidemic in the 1950s probably developed due to a long-distance aerial transfer of inoculum.Of the assortment of rye cultivars and land races tested under severe stem rust infection pressure, landraces from Austria, northern Bohemia and eastern Moravia showed lower disease severity, but insufficient yields (Bartoš & Bareš 1960).Yellow rust of wheat.In the 1960s yellow rust was the most important rust species.None of the cultivars registered at that time was resistant at the seedling stage to all determined yellow rust races.However, many showed resistance at the adult plant stage.Research on yellow rust supported the decision of the State Board for the Registration of Cultivars that only cultivars possessing yellow rust resistance in field tests should be registered in future.This regulation has initiated a consistent breeding for yellow rust field resistance and thus has avoided possible losses that could be caused by yellow rust at that time.The high yellow rust infection on temporarily introduced cultivars Zlatna Dolina and Sava from the former Yugoslavia showed that the risk of yellow rust was high.The last yellow rust epidemic occurred in 1999 and in subsequent years as a part of the epidemic extending from Western Europe over Central Europe to Hungary.Wheat and triticale suffered considerable losses.Stem rust of wheat.The year 1972 was a season with a severe stem rust epidemic on wheat.Resistance governed by Sr5 in cvs.Bezostaya 1, Yubileynaya 50, Aurora and Kavkaz offered good protection against the major part of the stem rust population till 1972.Aurora and Kavkaz possess Sr31 in addition to Sr5.Resistance gene Sr31 remained effective in the epidemic and has been effective until now, whereas virulence to Sr5 has prevailed in the stem rust population after the epidemic in 1972epidemic in (Bartoš 1975)).Mironovskaya 808 with Sr Tmp was another important cultivar grown at that time.This gene governed an intermediate level of resistance to the stem rust population.Since 1972 no epidemics of stem rust have occurred, only a local incidence was recorded.Leaf rust of wheat.