Somaclonal variation in banana (Musa acuminate colla cv. Valery) regenerated plantlets from somatic embryogenesis: histological and cytogenetic approaches

Abstract

Banana (Musa spp.) is the world’s fourth most important food crop after rice, wheat and maize. The Valery banana cultivar is imported in Iran and well known as economic bananas in southern Iran. Shoots (with 2–3 cm stems) of the “Valery” cultivar of banana (Musa sp.) were selected, and meristematic tissue explants were isolated and cultured. Following embryo development, germination and differentiation, samples of regenerated plantlets were randomly taken and fixed in Formaldehyde, Glycial Acetic Acid, Alchol Ethylic (FAA) solution. Serial sections (10 μm) were prepared and stained in hematoxiline and eosine. An aqueous solution of 8-hydroxyquinoline was used to pre-treat the root tips. A solution of absolute ethanol and glacial acetic acid was used to fix the root tips. The mitotic cells identified with metaphase or prometaphase stages were used for chromosome counting. The meristematic tissue segments became swollen two weeks after cultures were initiated. Calli of the embryogenic line were kept separately; these tissues released embryogenic cells. The highest number of embryos (globular, torpedo and mature) were obtained with embryogenic medium (BM). The mature embryos and regenerated plantlets were cultured on regenerated medium (GM). The percentage of germination and development of completely regenerated banana plants was 90–96%. Histological study of regenerated shoots showed that there were many vascular tissues but of a small size; also that the vascular bundles were large and dispersed. The chromosomes were aggregated in metaphase. The regenerated plants from somatic embryos showed 60% triploidy, 10% diploidy and 30% aneuploidy and the chromosomes are more contracted and spread around the cell.