Cytotaxonomical studies on banana cultivars

Abstract

Variability in banana are wide and complex with different degrees of expression of the characters of the parental species, Musa acuminata and Musa balbisiana. Commercial cultivars are many, ranging in levels of productivity and quality characters. Investigations were conducted at the College of Horticulture, Kerala Agricultural University, Vellanikkara, Trichur during 1981-83 on 100 cultivars of banana to study the cytotaxonomical aspects. Studies on morphological characters, taxonomic scoring and chromosome number revealed that many of the cultivars were identical and ultimately the cultivars were confined to 64 distinct ones. The taxonomic scoring did not indicate the ploidy. Eight cultivars with the scores of triploids, were identified as diploids. The quantitative, quality and pollen characters showed a significant variation among the cultivars. The characters were influenced by the ploidy and the genomic constitution. The presence of ‘B’ genome increased plant height and girth, leaves per plant, leaf area per plant and petiole length. Musa balbisiana (BB) recorded the highest values for all the above characters. The triploids were more vigorous than the diploids and the tetraploids as indicated by their higher growth rates. The triploids were also better than the other groups for bunch and finger characters. Among them, the triploids of hybrid origin were better for bunch characters while the Musa acuminata triploid group (AAA) was superior to the other groups for finger characters. Longer pedicel was a characteristic feature of Musa balbisiana( BB). The genomic constitution of the cultivars influenced the contents of total soluble solids, sugars and acids in fruits, more than the ploidy. Musa acuminata group AAA, had the highest sugar/acid ratio. Studies on pollen viability, size and production in cultivars revealed the possibility of including a few of them as male parents in the banana hybridization programme. Forty of the cultivars studied were polleniferous. Pollen viability and production were more in pure Musa acuminata and Musa balbisiana groups than in groups of hybrid origin. Musa acuminata cultivars had larger pollen grains than cultivars belonging to the other genomic groups.Estimates of genotypic and phenotypic coefficients of variation, heritability in the broad sense, genetic advance and genetic gain for the 26 characters indicated the scope for selection among the cultivars. Petiole length, pulp/peel ratio on volume basis, weight and volume of fruit showed higher heritability values combined with high genetic gain. Estimation of genetic divergence among the cultivars showed that the cultivars ‘Mannan’ and ‘Pacha chingan’, belonging to the genomic group AAB, were the closest and a Musa acuminata cultivar, ‘Harichal’ (AAA) and Musa balbisiana (BB) were the farthest. The 62 cultivars were grouped into eight homogeneous clusters. Similar clustering pattern was obtained in the canonical analysis also. The study revealed the predominance of the cultivars of the hybrid origin, with different degrees of expression of the characters of the parental species, in the South Indian bananas. The taxonomic scoring system was not always appropriate to find out the ploidy of the cultivars. The study also indicated the scope for selection among the cultivars and the possibility of inclusion of the cultivars with viable pollen as male parents in the hybridization programme.