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United States Department of Agriculture

Agricultural Research Service

Research Project: Improved Forage and Alternative Use Grasses for the Southern U.S.

Location: Crop Germplasm Research

Title: Marker-assisted verification of Kinggrass (Pennisetum purpureum Schumach. x Pennisetum glaucum [L.] R. Br.)

Authors
item Dowling, Charlie -
item Burson, Byron
item Jessup, Russell -

Submitted to: Plant Omics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 10, 2014
Publication Date: April 3, 2014
Citation: Dowling, C.D., Burson, B.L., Jessup, R.W. 2014. Marker-assisted verification of Kinggrass (Pennisetum purpureum Schumach. x Pennisetum glaucum [L.] R. Br.). Plant Omics. 7(2):72-79.

Interpretive Summary: Napiergrass was crossed with pearl millet to produce hybrids to be used as a bioenergy crop. The seed produced were either hybrid seed or self-pollinated napiergrass seed. The seed were germinated and the seedlings and resulting plants could not be identified as hybrids by their appearance because they resembled napiergrass. The hybrids could be identified by counting their chromosomes, but this is a difficult, time consuming approach. A quicker approach is to measure the DNA content in the nuclei of the offspring and both parents using a flow cytometer. Unfortunately, this approach did not work because the amount of DNA in both parents was very similar and the hybrids could not be distinguished from either parent. Another approach was used to quickly identify the hybrids, and that was the development and use of molecular markers that are present in only the male parent (pearl millet) and not in the female parent (napiergrass). Two markers were specific only to pearl millet. Tissue from the plants recovered from the crosses was analyzed to determine if male-specific pearl millet markers were present, and those seedlings with the markers were true hybrids. This approach accurately and quickly identifies the hybrids and will significantly increase progress in identifying napiergrass x pearl millet hybrids that have potential as high biomass crops that pose no threat as an invasive weed because of seed sterility.

Technical Abstract: While combining improved sustainability over annual crops with high biomass potential, perennial grasses currently being considered for large-scale deployment as biofuel feedstocks have raised concerns regarding their weediness from either or both seed- and rhizome-derived propagules. Kinggrass (napiergrass [Pennisetum purpureum Schumach.] x pearl millet [Pennisetum glaucum {L.} R. Br.]), by comparison, is unique as a seed sterile crop without rhizomes that is perennial and capable of high biomass production beginning during the establishment year. In addition to propagation via axillary nodal buds similar to commercial sugarcane, kinggrass can be planted using seed derived from its fertile maternal napiergrass parent pollinated by pearl millet and the resulting F1 hybrids planted in feedstock production fields will be seed sterile. Confirming the successful production of true kinggrass hybrids can be accomplished utilizing morphological traits, seed fertility measurements, and cytological methods; however, these approaches are time-consuming and laborious. Molecular markers offer a more time- and resource-efficient alternative for hybrid verification. In this study, purported novel napiergrass x pearl millet interspecific hybrids were surveyed with expressed sequence tag-simple sequence repeat (EST-SSR) markers. Two paternal, pearl millet-specific markers, as well as 7 codominant markers, were identified and utilized to screen putative kinggrass hybrids. Both paternal-specific EST-SSRs were present in all F1 individuals, and each codominant EST-SSR fit expected transmission ratios in the F1 population. These EST-SSRs therefore confirmed that all individuals analyzed were true kinggrass hybrids, and they provide valuable molecular tools towards more rapid development of elite biofuel kinggrass feedstocks.

Last Modified: 7/23/2014
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