CHLOROPLAST GENOME BREAKDOWN IN MICROSPORE CULTURES OF BARLEY (HORDEUM-VULGARE L) OCCURS PRIMARILY DURING REGENERATION

Southern blot analyses of DNA from microspore cultures of the barley v ariety Alexis suggested that plastid genome deletions/rearrangements c ausing albinism occur primarily during regeneration. The Alexis variet y responded to microspore culture largely by production of ill-defined embryoids and callus from which plants could be regenerated with a lo w frequency. Only 0.06 green and 0.61 albino plants were regenerated p er anther in contrast to the Igri variety, which formed well-defined e mbryoids that readily regenerated 11.7 green and 0.1 albino plants per anther. In Alexis, the plastid genomes appeared to remain intact duri ng the microspore culture but started to break down in the structures that underwent regeneration. This development accelerated in parallel with differentiation and leaf formation. In Igri microspore cultures, callus and albino plant formation could be induced by elevated tempera tures and in particular during the first 10 days of culture and during the regeneration phase.