Amaresh Chandra
(Corresponding
author)
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Crop Improvement Division, Indian Grassland and Fodder Research
Institute,
Jhansi - 284 003, India
e-mail: amaresh62@yahoo.com
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Publication Data
Paper received:
11
December 2008
Revised
received:
31
March 2010
Accepted:
19 April 2010
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Abstract
In general tropical forage
legumes lack microsatellites or simple sequence
repeat (SSR) markers. Development of genic SSR
markers from expressed sequence tagged (EST) database is an alternate and
efficient approach to generate the standard DNA markers for genome analysis
of such crop species. In the present paper a total of 816 EST-SSRs containing perfect repeats of mono (33.5%), di (14.7%), tri (39.3%), tetra (2.7%), penta (0.7%) and hexa (0.4%)
nucleotides were identified from 1,87,763 ESTs of Medicago truncatula.
Along with, 70 (8.5%) SSRs of a compound type were
also observed.? Seven primer pairs of
tri repeats were tested for cross transferability in 19 accessions of forage
legumes comprising 11 genera.? At two
different annealing temperatures (55 and 60oC) all primer pairs
except AJ410087 reacted with many accessions of forage legumes. A total of 51
alleles were detected with six M. truncatula
EST-SSRs primer-pairs against DNA from 19 accessions
representing 11 genera where number of alleles ranged from 2 to 13. The
cross-transferability of these EST-SSRs was 40.6%
at 55oC and?
32.3% at 60oC annealing temperature. 24 alleles of
the total 50 (48%) at 55oC and 27 of 51 (53%) at 60oC
were polymorphic among the accessions. These 27 polymorphic amplicons identified could be used as DNA markers. This
study demonstrates the developed SSR markers from M. truncatula
ESTs as a valuable genetic
markers and also proposes the possibility of transferring these markers
between species of different genera of the legumes of forage importance. It
was evident from the results obtained with a set of Desmanthus
virgatus accessions where Sequential
Agglomerative Hierarchical and Nested (SAHN) cluster analysis based on Dice
similarity and Unweighted Pair Group Method with
Arithmetic mean Algorithm (UPGMA)? revealed significant variability (24
to 74%) among the accessions.? High
bootstrap values (>30) supported the nodes generated by dendrogram analysis of accessions.
Key
words
Forage legume, EST-SSRs, Genetic resources, Medicago
truncatula, Transferability
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