In vitro chromosome doubling of nineZantedeschia cultivars

Tetraploid plants have been produced from nineZantedeschia cultivars usingin vitro colchicine treatment. Rapidly-multiplying shoot cultures were treated on a medium containing 0.05% colchicine for 1, 2 or 4 days to induce chromosome doubling. Following the treatment, most shoots were killed but the surviving shoots were multiplied for several subcultures. These shoots were then rootedin vitro and transferred to a greenhouse. Plants were screened 2 months later by measuring stomatal length, and 110 out of 565 plants were selected as putative tetraploids with a stomatal length significantly greater than in diploid control plants. Chromosome counts were carried out on root tips from 44 plants and confirmed that 38 were tetraploids, 2 were chimeras (predominantly tetraploid with a few octoploid cells), and 4 were diploids. Stomatal length has been rechecked in mature tetraploid plants of the cultivar Black Magic, demonstrating that stomatal length is a good indicator of ploidy level inZantedeschia. This study has shown that multiplying colchicine-treated shootsin vitro for several subcultures prior to transfer to soil produced very few chimeras. The stomatal length measurements are non-destructive and allow the rapid screening of a population for tetraploids.