IN-VITRO TECHNIQUES FOR SELECTING WHEAT (TRITICUM-AESTIVUM L) FOR FUSARIUM-RESISTANCE .2. CULTURE FILTRATE TECHNIQUE AND INHERITANCE OF FUSARIUM-RESISTANCE IN THE SOMACLONES

Calli of resistant, intermediary and susceptible wheat (Triticum aesti vum L.) varieties were selected using culture filtrates of Fusarium gr aminearum and F.culmorum and the regenerants were evaluated for resist ance up to R(3). Czapek-Dox broth medium was inoculated with mycelia o f Fusarium isolates and incubated for 2-6 weeks. Filtrates were added to MS callus growing medium, then 5 weeks-old calli were transferred o nto this medium (MST) for 4-5 weeks. MST containing 30% filtrate was f ound to be suitable for selection. Resistant calli were transferred ag ain to fresh MST for further two selection cycles. The surviving calli produced less fertile regenerated lines (R(0)) than the non-selected ones. Among 18 R(1) lines tested for Fusarium-resistance in the seedli ng stage by artificial inoculation in the greenhouse, two (11.1%) were significantly more resistant, one (5.6%) was more susceptible than th e original cultivar and the rest (83.3%) behaved similarly to the dono r plants. Among unselected R(3) lines of three varieties, practically the same number of resistant plants were found as among the related se lected ones. When the R(3) selfed generations obtained through double- layer and culture filtrate selection techniques were tested for Fusari um-resistance, 35.7% of the lines were found to be more resistant than the original cultivars, none was more susceptible and 64.3% had a rea ction similar to that of the source materials. Thus, inheritance of th e disease reaction was not stable in all cases. Success of in vitro se lection for Fusarium-resistance depended also on the genotype, and tox in analysis showed that although being effective, the selective media contained deoxynivalenol only exceptionally. In selecting wheat for Fu sarium-resistance in vitro, the culture filtrate technique proved bett er than the double-layer procedure.