The Experimental Formation of Polyploidy and its Effect in the Genus Musa

Abstract

Polyploidy was induced in two Musa species and their hybrid by means of immersing newly germinated diploid seedlings in 0.5% aq. colchicine solution. Tetraploid M. balbisiana plants were taller and more robust but had slower growth rate, droopier leaves, fewer suckers, and scantier root systems than the diploids. Tetraploidy affected fruit size and shape in M. balbisiana and in M. acuminata. Tetraploidy did not affect bunch size (the number of fruit‐bearing nodes) in M. acuminata banksii but caused great reduction in bunch size of M. acuminata microcarpa ‘Zebrina.’ Doubling of the chromosome number resulted in doubling of the anthocyanin concentration in the leaves of the pigmented banana plants. Colchicine‐induced female sterility was detected in a treated diploid plant of M. acuminata subsp. microcarpa. A number of either female or male, or both female and male sterile plants were encountered in colchicine‐induced tetraploid M. acuminata species. Only one secondary M. balbisiana tetraploid plant was found to be partially female sterile. Colchicine treatment of the seedlings resulted in chromosomal irregularities at mitosis. Chromosomes appeared as open chains, rings and multiple configurations at metaphase. In the majority of cases doubled chromsomal complements reverted to their original number. However, there were cases in which diploids were induced to tetraploidy and later reverted to triploidy instead of diploidy. Also, there were cases in which triploids were doubled to hexaploidy and later reverted to tetraploidy instead of triploidy. From the close morphological similarity between a number of triploid and tetraploid M. balbisiana plants and some edible triploid cultigens belonging to the “ABB Group,” it is suggested that the karyotype of some of these cultigens could be “BBB” rather than “ABB” which contains one “A” M. acuminata genome. New pathways and additional evolutionary possibilities are incorporated into Simmonds’ scheme on the evolution of edible bananas.

Biotechnology of the Banana: A Review of Recent Progress

“…Simmonds (1954 [143] ) classified the Cavendish group of bananas for plant breeding. Chromosomes of Musa are small and difficult to work with (Vakili, 1967 [157] ). The potential advantages of a breeding scheme to overcome the undesirable characters of tetraploids and to incorporate a second diploid male into the recombination process have been reported (Rowe and Richardson, 1975 [130] ; Rowe, 1984 [131] ; Stover and Buddenhagen, 1986 [148] ).…”

Bananas and Plantains

“…were studied by Simmonds (1948a,b). Vakili (1967) reported that colchicine derived tetraploids from M. balbisiana were taller and more robust but had slower growth rate, more droopy leaves, fewer suckers and scantier root systems than diploids. Diploids tended to have a right lamina half-broader than the left, while the reverse holds true for polyploids.…”

“…Colchicine treatment, which results in a doubling of the chromosome number (Vakili, 1962(Vakili, , 1967 has been extensively used on diploid seedlings. For this purpose parental lines were selected to maximize both heterozygosity and the combination of appropriate resistances, quality factors and agronomic characters.…”

“…The use of improved plantain/banana diploids may result in a more adapted plantain progeny. Vakili (1967) proposed that colchicine treatment could be used to double the chromosome number of many of the improved diploids and then to intercross these synthetic tetraploids with other improved diploids. Stover and Buddenhagen (1986) proposed a method to recreate the original plantain clones but with disease resistance and develop novel triploid clones from diploid stock.…”

Nuclear DNA content and base composition in 28 taxa of Musa

“…Therefore, flow cytometry was introduced, to establish DNA amounts in numerous plants and, hence, determine their ploidy levels. For example, the technique has been used to determine ploidy levels in new Musa clones resulting from treatment with polyploidizing agents such as colchicine (Vakili 1967), from culture tissue (Van Duren et al 1996), and from crossing between different species (Dolezel et al 1997). Moreover, flow cytometry has often been used in studies of the systematics and evolution of different species within a genus (Maxted et al 1991;Godelle et al 1993;Martel et al 1997;Le Thierry d'Ennequin et al 1998).…”