Cytogenetics of Crotalaria

II. Male meiosis in 8 species of Crotalaria

Abstract

Detailed meiosis was studied in eight species. All the species are diploid (n=8, 2n=16). Meiosis in C. brevifolia and C. brownei is reported for the first time. When taken in conjunction with other data, there is an overwhelming evidence that the basic number of the genus is eight.
C. juncea, C. intermedia, C. brevifolia, C. brownei, C. burhia, C. verrucosa show regular 8 bivalents in majority of the cells. The univalents when present, are in low frequency, ranging from 0-2 per cell. C. lanceolata was characterized by the presence of an average 4.56 univalents per cell. Their range was from 2 to 10. In C. intermedia and C. lanceolata few trivalents and quadrivalents were observed. Anaphase I otherwise normal in other species, showed bridges with or without fragments, precocious division of univalents, unequal disjunction, lagging bivalents in C. lanceolata and C. retusa. As many as three bridge fragment configurations were observed in C. retusa. Recombination index is highest in C. verrucosa and lowest in C. lanceolata.
Heterozygosity is mainly due to features like reduced pairing, reduced chiasma frequency, paracentric inversions, and/or breakage reunion bridges and localized chiasmata. Much of the evolution in this genus, in nature, appears to have taken place through gene mutations at diploid level. Polyploidy has not played a dominant role.