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.