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Genetic variation in great yam cultivars (Dioscores alata L.)

Lebot V.. 1996. In : I Congresso Latino Americano de Raizes Tropicais e IX Congresso Brasileiro de Mandioca, 7 a 10 de outubro de 1996, Sao Pedro, Brasil. Programa et resumos. Sao Paulo : UNESP, 1 p.. numero_rapport: N° 112. Congresso Latino Americano de Raizes Tropicais. 1, 1996-10-07/1996-10-10, Sao Pedro (Brésil).

Morpho-agronomic variation was studied for 131 cultivars originating from New Caledonia using 31 morphological descriptors. Four polymorphic enzyme systems (MDH, PGI, 6-PGD and SKDH) revealed 27 zymotypes, each uniquely characterized by the presence or absence of 27 electromorphs. No correlations and agreement could be found between morphological patterns (petiole colour, lamina shape, tuber fresh pigmentation, tuber shape) and banding patterns. Multivariable analyses of the Isozyme data did not differentiate morphotypes groups and did not reveal patterns of association within groups. The data obtained would suggest that many New Caledonian cultivars are the result of somatic mutations. 138 cultivars were subsequently introduced in vitro from than Caribbean, South America, Africa and Asla and their isozyme variation was studied using the same enzyme systems. Overall, 66 distinct zymotypes were identified but no correlations could be found between zymotypes and geographical origins. Multivariate analyses of the Isozyme data indicated that cultivars constitued a continuum of clusters rather that well differentiated groups. Dioscorea alata cultivars appear to have a narrow genetic base and were most likely distributed throught the world as clones unable to reproduce sexually. The species is believed to be derived from human selection of forms a common origin. (Texte intégral)
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