IMPROVEMENT OF IN VITRO MICROPROPAGATION OF BLACK CURRANT 'ČAČANSKA CRNA'

Upon the establishment of asceptic culture and initiation of rosettes, shoots of black current ‘Čačanska Crna’ (Ribes nigrum L.) were multiplied on Murashige and Skoog (MS) basal medium of different hormonal compositions. As signs of chlorosis were traced on regenerated shoots, shoots were transferred on MS medium containing double-strength FeSO₄ x 7 H₂O. However, low multiplication capacity and low quality of shoots were recorded. To overcome the problem, the effect of different explant orientation (vertical, horizontal and inverted positions) on axillary shoot proliferation was examined. The highest multiplication index (3.1) was obtained in horizontally oriented explants, nonetheless low-quality shoots, incapable of further growing, were also observed. Further examination showed that shoots growing on a medium without cytokinins (MS medium with 0.1 mg/L IBA and 0.1 mg/L GA₃) were long, well developed and could be subcultured by nodal transplantation – they were cut into micro-cuttings (shoot tips and single-node stem segments) and placed on the same medium. The average number of micro-cuttings/shoot was 3.3, whereas the highest recorded number of micro-cuttings/shoot was 6.0. Shoots were long, well developed, with wide dark green leaves and long petioles. Shoots grown on the medium above also showed high rooting ability, their rooting rate reaching 100% by 28^th day. Well developed root system and high-quality rooted plants induce high acclimatization and adaptation rates (100% in both) under ‘mist’ system in greenhouse. Therefore, the process of micropropagation of this cultivar was considerably accelerated by simultaneous performance of both multiplication and rooting at the same stage.