EFFECT OF MAGNESIUM ON CHIASMA FREQUENCY IN MAIZE (ZEA-MAYS L)

Five S7 maize lines were cultivated on soil containing three different levels of magnesium (Mg I, Mg II and Mg III). Chiasm frequency per mi crosporocyte and interstitial chiasma frequency were evaluated. Variat ions in both frequencies were detected among lines, among magnesium le vels and among magnesium levels within the sam line. A significant eff ect of Mg II and Mg III levels on chiasm frequency per microsporocyte and on interstitial chiasma frequency was observed in some lines. Thes e results suggest that the rate of genetic recombination can be increa sed in some genotypes in th presence of increased magnesium levels in soil. On the other hand, the excess of magnesium employed at the Mg II I level caused morphological and cytological abnormalities, as well as decline in vigor and death of some plants.