Chloroplast Genome Breakdown in Microspore Cultures of Barley ( Hordeum vulgare L.) Occurs Primarily during Regeneration

Abstract

Southern blot analyses of DNA from microspore cultures of the barley variety Alexis suggested that plastid genome deletions/rearrangements causing albinism occur primarily during regeneration. The Alexis variety responded to microspore culture largely by production of ill-defined embryoids and callus from which plants could be regenerated with a low frequency. Only 0.06 green and 0.61 albino plants were regenerated per anther in contrast to the Igri variety, which formed well-defined embryoids that readily regenerated 11.7 green and 0.1 albino plants per anther. In Alexis, the plastid genomes appeared to remain intact during 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 temperatures and in particular during the first 10 days of culture and during the regeneration phase.