CAUSES AND CONSEQUENCES OF DNA CONTENT VARIATION IN ZEA

Cytogenetic evidence indicates that Zea, which comprises maize (Z. mays ssp. mays) and its wild relatives, is an allopolyploid genus. Our research group has carried out numerous cytogenetic studies on Zea species, mainly focused native Argentinian Bolivian landraces. We found a wide inter- intraspecific genome size variation in the genus, with mean 2C-values ranging between 4.20 11.36 pg. For landraces studied here, it varied 6.75 The objectives of this work are to analyze causes discuss their adaptive value Zea. This attributed differences heterochromatin located knobs amount interspersed DNA from retrotransposons. Polymorphisms presence or absence B-chromosomes (Bs) population frequency Bs also source variation, doses one eight analyzed here. Correlation analysis revealed percentage positively correlated size. In addition, populations cultivated at higher altitudes, known be precocious, have smaller sizes than do those growing lower altitudes. information, together positive correlation observed length vegetative cycle heterochromatin, led us propose role. On other hand, negative relationship heterochromatic allowed existence intragenomic conflict these elements. hypothesize optimal nucleotype may resulted such intranuclear conflict, where adjustments suitable for across altitudinal clines. Key words: B chromosomes, knobs,