Genome Differentiation Patterns in Diploid Species of Elemine (Poaceae)

Three species of Eleusine viz. E. indica, E. tristachya (both annual), and E. floccifolia (perennial)are wild diploid taxa (x = 9) that display nine bivalents at diakinesis/metaphase I of meiosis and high pollen fertility and seed set. Interspecific F1 hybrids, E. indica ×E. floccifolia and E. tristachya ×E. indica, were analysed to investigate species genome affinity and crossing barriers. In E. indica ×E. floccifolia F1, the mean chromosome pairing was 0.38I + 8.78II + 0.008III + 0.004IV, and nearly 81% of the pollen mother cells contained nine bivalents, suggesting that genomes of E.indica and E. floccifolia are homologous/similar. Despite the regular meiosis, F1s were seed sterile. In E. tristachya × E. indica F1, the mean chromosome pairing was 0.191 8.87II % 0.0IIV, and about 89% of the pollen mother cells exhibited nine bivalents, and the F1s were partially fertile, indicating that genomes of E. tristachya and E. indica are also largely homologous. These pieces of cytogenetic information suggest that these three diploid species form a close genetic assemblage within the genus Eleusine. Barriers for gene exchange between these taxa, in nature, are discussed considering the available literature.