Abstract
Assessment of phylogenetic relationships is an important component of any successful crop improvement programme, as wild relatives of the crop species often carry agronomically beneficial traits. Since its domestication in East Africa, Eleusine coracana (2n = 4x = 36), a species belonging to the genus Eleusine (x = 8, 9, 10), has held a prominent place in the semi-arid regions of India, Nepal and Africa. The patterns of variation between the cultivated and wild species reported so far and the interpretations based upon them have been considered primarily in terms of nuclear events. We analysed, for the first time, the phylogenetic relationship between finger millet (E. coracana) and its wild relatives by species-specific chloroplast deoxyribonucleic acid (cpDNA) polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and chloroplast simple sequence repeat (cpSSR) markers/sequences. Restriction fragment length polymorphism of the seven amplified chloroplast genes/intergenic spacers (trnK, psbD, psaA, trnH-trnK, trnL-trnF, 16S and trnS-psbC), nucleotide sequencing of the chloroplast trnK gene and chloroplast microsatellite polymorphism were analysed in all nine known species of Eleusine. The RFLP of all seven amplified chloroplast genes/intergenic spacers and trnK gene sequences in the diploid (2n = 16, 18, 20) and allotetraploid (2n = 36, 38) species resulted in well-resolved phylogenetic trees with high bootstrap values. Eleusine coracana, E. africana, E. tristachya, E. indica and E. kigeziensis did not show even a single change in restriction site. Eleusine intermedia and E. floccifolia were also shown to have identical cpDNA fragment patterns. The cpDNA diversity in Eleusine multiflora was found to be more extensive than that of the other eight species. The trnK gene sequence data complemented the results obtained by PCR-RFLP. The maternal lineage of all three allotetraploid species (AABB, AADD) was the same, with E. indica being the maternal diploid progenitor species. The markers specific to certain species were also identified.
Highlights
The wild relatives of crop species often carry beneficial alleles that are effective against various biotic and abiotic stresses
Robust amplification products were obtained for all seven genes/intergenic spacers from the nine Eleusine species and an outgroup species, D. aegyptium
The present results further indicate that E. indica with the AA genome might be the maternal parent for all three tetraploid species, viz. E. coracana, E. africana and E. kigeziensis
Summary
The wild relatives of crop species often carry beneficial alleles that are effective against various biotic and abiotic stresses. They hold the key to successful crop improvement. The genus Eleusine is a member of the tribe Eragrosteae, subfamily Chloridoideae and the family Poaceae. It is a small genus of nine species, which includes six diploid (2n 1⁄4 2x 1⁄4 16, 18, 20) and three polyploid (2n 1⁄4 4x 1⁄4 36, 38) species (Bisht and Mukai 2002; Liu et al 2011). East Africa is considered to be the centre of diversity for the genus (Bisht and Mukai 2002)
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