Chromosome number and meiosis in populations of Senna species (Caesalpinioideae – Fabaceae) from Southeast Brazil

Abstract

Senna Mill. is one of the most representative genera of Caesalpinioideae, with wide geographical distribution. Some species have been cytogenetically characterized, but there is no information on population level. Therefore, the present work had the objective of characterizing and comparing chromosomal number and meiotic behavior of 39 accessions belonging to 11 species of Senna Mill. from southern Minas Gerais state, Brazil. Meiotic preparations were obtained by cell suspension technique and stained with 10% Giemsa solution. All meiotic phases were analyzed and the meiotic index was obtained. The species showed different chromosome numbers (n = 12, 13, 14, and 28). Meiotic behavior of four species is described for the first time. The chromosomal numbers reported for most species coincide with those described for populations from either Southern Brazil or from state of Pará. Intraspecific variation for chromosome number was observed in S. rugosa (G. Don) H. S. Irwin & Barneby (n = 14 and n = 28). This variation along with multivalent occurrence suggests polyploidization as an important event in the evolution of this species, as described for many others, mainly in Caesalpinioideae. Most of the analyzed species showed regular meiotic behavior, despite the occurrence of some irregularities.