POLYPLOID INDUCTION VIA COLCHICINE TREATMENT IN LOQUAT

Tetraploid and triploid seedlings of ‘Algerie’ loquat were obtained using colchicine. Colchicine treatments at different doses and exposure times were applied to shoot apex, whole plants and non-germinated seeds. No stable tetraploids were obtained by treating the shoot apex of 30-days-old in vitro-grown seedlings with one drop of 0.01 and 0.05% (w/v) colchicine solution during one, two or three consecutive days. In vitro whole plants totally submerged in 0.1% (w/v) colchicine solution during 15, 30, 45 or 60 min promoted the highest percentage of tetraploid induction. During the acclimation stage, plants turned necrotic and finally died. Non-germinated seeds immersed in 0.5% (w/v) colchicine solution for 24 and 48 h resulted in two triploids and one tetraploid, respectively. Nuclear DNA content was analyzed by flow cytometry using leaf samples, and five biological replicates per plant. Chromosome counts using samples taken from fully developed leaves and root tips confirmed the ploidy obtained. A minimum of five metaphases per leaf or root, and a minimum of five leaves and roots were observed in each plantlet. The chromosome number of a diploid loquat plant is 2n=2x=34. Chromosome counts were 2n=3x=51 in triploids 2n=4x=68 in tetraploids.