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The phenomenon of mutant heterosis was studied in barley using F1 hybrids developed from crosses involving two mutants derived from the same parent variety (067AR × 032AR). or frotn crosses of mutants with their parent varieties (Diva × 228DV: 437MG × Mg 4170). The agronomic performance (plant height, tillers per plant, kernel number and weight per plant) of F1, hybrids was evaluated in relation to the corresponding parent variety used for mutant development. Wide-space sowing (0.06 m2/plant) was applied to allow the full expression or hybrid vigour. The hybrids significantly exceeded their parent varieties in various yield parameters in each year of the experiment. Depending on the cross, the level of heterosis ranged from 39.45% to 82.1% for kernel number and from 44,45% to 91.2% for kernel weight, as an average of observations over three years. The increased yield of hybrids was accompanied by an increase in spikes/plant, without significant changes, in most cases, in yield components such as kernels/spike and 1000- kernel weight. The height of F1, plants remained similar to the corresponding parent variety. Doubled haploids (DH) were developed through anther culture from three F1, hybrids to determine whether the heterotic effect could be fixed, even partly, in homozygous lines. Twenty-eight, 42. and 68 DH lines per cross were produced, and evaluated in [he field, space-planted at 0.06m2/plant. together with hybrids and parent varieties. The best-performing DH tines were evaluated again the following season in a conventional field trial. We were able to select 1.5 14.3% of F1'performing' DH lines per heterotic cross combination, which, in two years of studies, reached the yield of heterotic hybrids and significantly out-yielded the parent variety in plot. The yield potential of DH lines was better expressed under a wide sowing density, but even under normal growing conditions, the yield of the best selected DH lines surpassed their corresponding parent varieties by 17.7-30.1%. [ABSTRACT FROM AUTHOR]

The influence of carbon source and growth regulator composition in induction medium on anther culture response was investigated using spring barley genotypes. Anthers were cultured on BAC3, Ficoll-containing medium, supplemented with one of the following carbohydrates: sucrose, maltose, cellobiose and melibiose (6 % w/v). The use of either maltose or cellobiose resulted in a significantly higher anther response, calli and/or embryoid production and green plant regeneration compared to the incubation of anthers on a medium containing sucrose. Contrary to these results, the replacement of sucrose by melibiose in BAC3 medium, drastically reduced the efficiency of anther culture. As an average for the three genotypes tested, the frequency of green plants per 100 anthers plated was 9- to 22-fold higher on medium supplemented with sucrose or cellobiose than on medium containing melibiose as a sole carbohydrate. Among the growth regulators tested, the combination of auxin NAA (2 mg/l) and cytokinin BAP (1 mg/l) performed much better than the employment of auxin 2,4-D combined either with zearin riboside or BAP as cytokinins. The beneficial effect of medium supplemented with NAA and BAP was associated with better embryoid formation compared to the other growth regulator combinations tested. The hormone-free combination gave a similar anther response and production of calli as any medium supplemented with growth regulators, but the regeneration capacity of calli produced on hormone-free medium was much lower, resulting in the drastic reduction of the number of both total and green regenerants. [ABSTRACT FROM AUTHOR]