Reduced height genes in the bread wheat breeding programme

The frequencies of insensitive (Rht+), less insensitive (Rht+-) and sensitive (Rht-) genotypes (generation F5-F7) were evaluated in the bread wheat breeding programme by means of a seedling GA (gibberellic acid) response test. Important characters were determined in 20 winter crosses. The GA insensitive dwarfing genes originated either from British (Rht2) or Czechoslovak varieties and advanced breeding lines (Rht 1 or unidentified genes). Of 20 crosses, 11 outyielded both check varieties. On 1-9 scale the average frost resistance of lines was 4.88, resistance to powdery mildew: 7.17, and resistance to stripe rust: 6.75. A high performance in the examined traits was obtained in genotypes with average plant height of 116 cm (about 100 cm in many years). Shorter crosses (usually both parents with GA insensitive Rht genes) were lower yielding. Longer genotypes are needed for increasing 1000-grain weight and content of protein and wet gluten. The percentage of genotypes with insensitivity or mild sensitivity to GA was 41.8 per cent. No clear global effect of reaction to GA on the performance of examined traits has been found. Results of selection were highly determined by parental genotypes. The selection of insensitive genotypes appears to be reasonable when parents with good bread-making quality are used for crossing. A sufficient quality is required also in donors of GA insensitive Rht genes (e. g. Avalon). Conditions to reach a high grain yield (in addition to quality) are created by the incorporation of Nordin 10 dwarfing genes that positively influence ear and plant yields. What breeders in the Central Europe may effectively use GA insensitive Rht genes with less effect on plant height reduction (e. g. Rht 1, Rht 1S), particularly if these genes are on the background of adapted, good grain quality genotypes.