Symmetric somatic hybrids were produced by electrofusion of protoplasts of two dihaploid tuber-bearing potato (Solanum tuberosum L.) lines and Solanum brevidens Phil., a diploid non-tuber-bearing wild potato species. A total of 985 plants was obtained. Verification of nuclear hybridity of putative hybrids was based on additive RAPD patterns, general morphological characteristics and chromosome counts. 53 (90%) calli regenerated into plants which were identified as somatic hybrids. Most of the hybrids were aneuploids at the tetraploid (4 x) or hexaploid (6 x ) level. The 20 hybrids tested expressed a high level of resistance to potato virus Y (PVY N) characteristic of the S. brevidens parent. Resistance to late blight (Phytophthora infestans (Mont.) de Bary) varied between hybrids, but was on average better than that of the fusion parents. Resistance of hybrids to bacterial stem rot (Erwinia carotovora subsp, atroseptica (van Hall) Dye) was not superior to that of commercial potato cultivars.

Genetic similarities among 20 spring and 22 winter accessions of agronomically different ryes from fourteen countries were estimated by employing random amplified polymorphic DNA (RAPD) techniques. Cluster analysis of genetic distance data showed that 42 genotypes were readily classifiable into two main groups: spring and winter groups. Within the spring group, cultivars fell into a North European and an American-Chinese group. Cultivars of winter rye fell into four groups: Northern European, Russian, American and Chinese lines. A UPGMA-dendrogram based on genetic distances of cultivars of rye within the winter and spring groups showed that the clusters corresponded well to their geographical locations. The results indicated that isolation has played an important role in the evolution of rye, and that temporal isolation has influenced the genetic diversity of rye more than geographical isolation. In this experiment, RAPD proved to be a rapid, reliable and practicable method of revealing polymorphisms in rye populations.

Five known varieties and five local strains of red clover from the latitudes 60 to 66°N were studied in greenhouse conditions. Photoperiods during the growing period were 12,16 and 20 h day, night temperatures 17°and 14°C and light intensity 21.2 klux. The plants were cut three times. Flowering, height development and shoot DM yield were assessed at each harvest. The number of shoots and leaves per plant and leaf area per plant were determined at the second harvest and root size at the third harvest. After the second harvest one replicate of each strain under the three light regimes was placed at +4°C under an 8-h light regime at 10 klux for 26 days. For assessment of plant response to hardening conditions, chemical analyses were performed on roots for TNC, long-chain fatty acids and proline.The study showed that the adaptation of red clover to certain daylength conditions influences plant behaviour with respect to its growth, development and hardening. The present study on daylength and growth together with developmental and chemical analysis are useful for breeding.

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The main goals of the wheat androgenesis experiment were to study the main phenomena of in vitro androgenesis in anther culture of Fj populations (10) and their parents (6), to compare the usage of P-4 and G-17 media for the formation of embryo/callus and to demonstrate a new plant regeneration system.The P-4 induction medium was found to be significantly better than the G-17 in the number of responsive anthers (RA) and calli induced (GI) at the 1 % and 0.1 % level, respectively. Genotypic effect was evident in both RA and GI. The yields of F2 populations in RA and GI were significantly higher than those of their parents regarding both media. The data confirmed the existence of heterosis for RA and GI in F2 populations.The ratio of green/albino plant regeneration was more favourable in the G-17 derived embryo/calli than in the P-4 derived ones.The frequency of plantlet regeneration was enhanced in the group of unresponsive calli by the application of the multiple-step regeneration system. In this system the calli lacking well developed morphogenic structure were transferred to a new regeneration medium, containing a higher concentration of the same cytokinin, other cytokinin or basic medium, before the occurrence of irreversible changes in their physiology.