Achievements and prospects of wheat breeding for disease resistance

Abstract

The development of disease resistance breeding is closely linked with the development of genetics, plant pathology and the progress of plant breeding methods. First crosses of wheat based on Mendels genetic principles , aiming to transfer disease resistance, were carried out by BIFFEN (1905). He found monogenic inheritance of yellow rust resistance in wheat. Such inheritance has been later confirmed in other crops and pathogens. The discovery of physiologic races in cereal rusts (STAK-MAN 1914) enabled exact genetic analyses of resistance. Studies on sources of resistance, particularly of wild relatives of crops, were performed by VAVILOV (1919, 1935) who also described geographic centres of origin of cultivated plants and resistance sources. Besides studies of inheritance of resistance, also the genetics of vir-ulence was studied, which was often found monogenic (FLOR 1942). From his results on genetics of resistance in flax and virulence in flax rust FLOR (1956) developed the gene for gene hypothesis. PERSON (1959) demonstrated practical applications of this hypothesis, e.g. for the postulation of resistance genes using pathogen races with known virulence. Polygenic resistance became more popular when VANDERPLANK (1963) published his analysis and conclusions on vertical and horizontal resistance. Durability of disease resistance (defined by JOHNSON [1981]) attracted attention particularly in the last decade when several conferences were devoted to this aspect of resistance. Finally, recent development of molecular biology opened many new prospects for the resistance breeding. SOURCES OF RESISTANCE In the USA breeding for stem rust resistance in wheat was practised already in the first decades of the last century , when crosses with resistant bread wheat accessions were made. Apart of the use of resistance sources from bread wheat, the first interspecific crosses were carried out also in the USA. Of historical as well as of practical importance are the crosses: Jumillo (Triticum durum) × Marquis (Triticum aestivum), from which cv. Marquillo has been developed, and Yaroslav Emmer (Triticum di-coccum) × Marquis, from which the cvs Hope and H 44-24 were derived. Abstract: Achievements and prospects of wheat breeding for disease resistance in the world and in the Czech Republic are reviewed. Attention is paid to rusts, powdery mildew, leaf blotch, glume blotch, tan spot, fusarium head blight, common and dwarf bunt, eyespot, barley yellow dwarf virus on wheat and wheat dwarf virus. Genes for resistance to rusts and powdery mildew in the cultivars registered in the Czech Republic are listed. Promising resistance genes and sources of resistance to the above mentioned diseases are reviewed. Prospects of resistance breeding including application of methods of molecular genetics and development of synthetic hexaploids are outlined.