TITLE:
Confirmation of Pearl Millet-Napiergrass Hybrids Using EST-Derived Simple Sequence Repeat (SSR) Markers
AUTHORS:
Charlie D. Dowling, Byron L. Burson, Jamie L. Foster, Lee Tarpley, Russell W. Jessup
KEYWORDS:
Pennisetum glaucum; Pennisetum purpureum; Bulked Segregant Analysis; Marker-Assisted Selection; Marker-Assisted Breeding; EST-SSR; Expressed Sequence Tag; Simple Sequence Repeat; Microsatellites; Biofuel; Biofuels; Pearl Millet × Napiergrass; Pearl Millet; Napiergrass; Interspecific Hybrid; PCR; Polymerase Chain Reaction; Comparative Genomics
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.4 No.5,
May
29,
2013
ABSTRACT:
Prospects for deploying perennial grasses that are currently considered
leading candidates for dedicated energy crops over large acreages are debatable
because of several limitations, including vegetative propagation or small seed
size, low biomass production during the first growing season, and incomplete assessments
of crop invasiveness risk. Pearl Millet-Napiergrass hybrids (“PMN”; Pennisetum glaucum [L.] R. Br. × P. purpureum Schumach.), in contrast, are large-seeded, sterile
feedstocks capable of high biomass production during establishment year. Novel methods
are warranted for confirmation
of PMN hybrids, as traditional morphological observations can be inconclusive
and chromosome number
determination using cytological methods is laborious and time consuming. Six
putative PMN lines were produced in this study, and 10 progeny from each line
were evaluated using morphological traits, seed fertility, flow cytometry, and
expressed sequence tag-simple sequence repeat (EST-SSR) markers. All putative
hybrid lines were sterile and
failed to produce seed. The PMN hybrids could not be distinguished from either
parent using flow cytometry due to highly similar nuclear genome DNA contents. A
number of paternal napiergrass-specific EST-SSRs were identified for each PMN line, and four
paternal-specific EST-SSRs conserved across all napiergrass accessions were selected
to screen the putative PMN hybrids. These EST-SSRs confirmed that all F1 individuals analyzed were PMN hybrids. The use of paternal-specific markers
therefore provides a valuable tool in the development of both “Seeded-yet-Sterile” biofuel PMN feedstocks and
additional PMN cultivar-and
parental species-specific markers.