MOLECULAR DIVERSITY AND GENOME STRUCTURE IN MODERN SUGARCANE VARIETIES

RFLP analysis was performed on 40 sugarcane cultivated varieties. Twen ty-two maize low copy DNA clones located on different regions of the 1 0 maize chromosomes were used as probes to survey variability among th e sugarcane varieties. A total of 425 fragments, 411 of which were pol ymorphic, were identified for 22 probe/enzyme combinations. Each varie ty; displayed an average of 7.28 fragments per combination, revealing the complex polyploid origin of modern sugarcane varieties. The averag e genetic similarity between sugarcane varieties was 0.61. Although cu ltivated varieties appear closely related to S. of officinarum clones, the genes of S. spontaneum seem to constitute the principal component of varietal diversity. A very weak global structuring among the 40 va rieties is observed, in agreement with the profuse exchanges of parent al materials between sugarcane breeding stations. Traces of linkage di sequilibrium can be attributed to the distribution of S. spontaneum ch romosomes among sugarcane varieties. The possibility of using modern v arieties as a population for detecting associations between molecular markers and agronomic traits is suggested.