Genome interrelationship in the genus Eleusine (Poaceae) as revealed through heteroploid crosses

Genome interrelationship in the genus Eleusine (Poaceae) has always been a matter of considerable interest for plant breeders whose major objective was to attain genetic improvement in E. coracana (finger millet), an important crop of Africa and south Asia. E. coracana and E. africana are the two major amphidiploid species of Eleusine with AABB genome (2n=4x=36). In attempt to identify the A and B genome donor species, heteroploid crosses were made involving these two tetraploid species and four diploid species viz. E. intermdia, E. indica, E. floccifolia, E. tristachya (all with 2n=2x=18). The resultant F, hybrids were investigated for cytomorphological details. Male meiosis studies in pollen mother cells showed regular occurrence of expected 9II+9I at diakinesis/metaphase I in majority of the cells indicating the existence of complete and/or partial homology among crossing parents. The occurrence of occasional quadrivalents had apparently no bearing on the course of meiosis owing to their scant number. Anaphase I and II were characterized by unequal distribution and micronuclei leading to drastic reduction in pollen stainability (2-8%) and complete seed seterlity. Our observations suggest that E. indica with AA genome is the pivotal donor species in the evolution of E. africana and E. coracana while E. intermedia (A(im)A(im)) and E. tristachya (A(t)A(t)) belong to A genomic group of diploid Eleusines. Further these three species form a close genetic assemblage within the genus Eleusine. The assumption that E.floccifolia is a definite B genome donor species is now widely accepted while E. tristachya might also be a candidate for BB genome is completely ruled out there by leaving the question wide open regarding identity of the other B genome donor species, if any.