The Male Meiotic System in Three South American Species of Vicia (Fabaceae).

Abstract

Male meiosis of 3 South American species of the genus Vicia (V graminea Sm., V. macrograminea Burk., V. epetiolaris Burk.) was studied. The early meiotic prophase I was characterized by a “bouquet stage” or synizesis. All 3 species showed regular pairing with 7 bivalents per cell at diakinesis and metaphase I. V. macrograminea and V. epetiolaris presented similar meiotic configurations at both stages, with higher values of total chiasmata per cell and a lower proportion of terminal chiasmata. V. graminea was significantly different in chiasmata behaviour since the populations studied presented lower chiasma frequency and distal localization. The number of ring bivalents per cell in metaphase I was lower in V. graminea but not significant.The distribution of chromosomes to the poles in anaphase I as well as the course of the second meiotic division were regular in all 3 species, though bridges without fragments were occasionally observed in anaphase I. These side-arm bridges generally resolve successfully, since the fertility is high (>90%) in all cases. The occurrence of these bridges in species of Vicia from the north hemisphere and in the South American species studied, suggests that non-disjunction could have play a role in the evolution of the basic number of the genus, where the earliest basic number is regarded as x=7, from which x=6 and x=5 arose.