Effect of ploidy on stomatal and other quantitative traits in plantain and banana hybrids

Ploidy polymorphism occurs in the hybrid offspring derived from interspecific crosses between triploid plantains (Musa spp. AAB group) and diploid bananas (M. acuminata). Therefore, Musa breeders are interested in the determination of ploidy and its effects on phenotypic expression of quantitative traits. The aim of this research was to examine the reliability of stomatal and other phenotypic traits to determine ploidy in segregating plantain-banana hybrid families. Stomatal density and size were significantly correlated (P < 0.01) with ploidy, although the correlation coefficients were not high (r = -0.49 and r = 0.47, for stomatal density and size, respectively). High density of small stomata was correlated with low ploidy level, and vice versa. However, stomatal size and density were also influenced by a significant genotype effect (P < 0.001) within the same ploidy level. Ploidy had an important effect on fruit traits and plant height in the hybrids of 'Obino l' Ewai' x 'Calcutta 4', but this was not so clear in 'Bobby Tannap' x 'Calcutta 4' hybrids. 'Obino I' Ewai' derived tetraploids have medium to tall plants with large bunches and big fruits. Most of the tetraploids derived from 'Bobby Tannap' have short stature due to the gene action of the dwarf, dw, allele. Also, a few selected diploids derived from 'Bobby Tannap' out yielded their non-selected tetraploid full-sibs. In conclusion, chromosome counting remains the only accurate proof of ploidy levels in Musa germplasm

Induction and identification of polyploids in Cattleya intermedia Lindl. (Orchidaceae) by in vitro techniques

The effect of colchicine on the protocorm-like bodies of Cattleya intermedia L. (Orchidaceae) cultured in vitro was studied. Different concentrations of the drug (0.00, 0.05, 0.10 and 0.20%) as well as two times of culture (4 or 8 days) were tested to determine the best treatment for the induction of tetraploid plants. Of the 3 colchicine levels applied, 0.05 and 0.10% of drug treatments appeared to be effective on the production of mixoploids and tetraploids and could be further used in breeding programs. The suitability of stomatal area and stomata density as criteria for the distinction between diploids and tetraploids was also tested. The results suggested that tetraploid plants could be identified with a fair amount of certainty when the screening was based on the density of stomata