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United States Department of Agriculture

Agricultural Research Service

Research Project: GENETIC IMPROVEMENT OF PERENNIAL FORAGE AND TURF GRASSES FOR THE SOUTHERN UNITED STATES

Location: Crop Germplasm Research

Title: Molecular characterization of non-flowering perennial Sorghum spp. hybrids

Authors
item Jessup, Russell -
item Whitmire, D -
item Burson, Byron

Submitted to: American Journal of Experimental Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2011
Publication Date: January 1, 2012
Citation: Jessup, R.W., Whitmire, D.K., Burson, B.L. 2012. Molecular characterization of non-flowering perennial Sorghum spp. hybrids. American Journal of Experimental Agriculture. 2(1):9-20.

Interpretive Summary: Even though sorghum is an important food and feed crop throughout the world, it recently has received considerable attention as a feedstock source for bioenergy purposes. Seven unique sorghum plants were found growing in the wild and these plants were collected because of their ability to survive the winter (overwinter), size, vigor, and flowering behavior. Since these plants looked different from grain sorghum and johnsongrass, it was assumed they were natural hybrids. In this study, molecular tools were used to determine the parents of these plants. It was found that all hybrids in fact were natural hybrids between grain sorghum and johnsongrass. Four of the hybrids had 40 chromosomes and produced more forage than either parent. The remaining three hybrids had 30 chromosomes and they did not flower but remained vegetative throughout the growing season. The reason all seven hybrids can overwinter is because they have rhizomes that were inherited from johnsongrass. Their rhizomes are not as strong and vigorous as those of johnsongrass which means these hybrids are not as weedy as johnsongrass. The lack of flowering in the three non-flowering hybrids is a trait of interest to sorghum breeders because it could be used to eliminate pollen spread from genetically modified plants. So these plants could be useful in the development of perennial sorghums for biofuels and yet they reduce the risks of invasiveness and the spread of undesirable traits from pollen flow.

Technical Abstract: Seven perennial Sorghum species hybrids were discovered growing in the wild and were collected because all had specific traits, specifically vigor and flowering response, that could be of value in breeding sorghum for bioenergy purposes. Because of the potential of these plants, the objective of this study was to use molecular tools to identify their parentage. Using flow cytometry, it was determined that three of the putative hybrids were triploids (2n=3x=30) and the other four were tetraploids (2n=4x=40). Bulked segregant analysis (BSA) of S. bicolor SSRs effectively identified species-specific alleles in S. bicolor and S. halepense, as well as confirmed that the putative Sorghum species hybrids in this study were derived from natural interspecific hybridization between S. bicolor and S. halepense. These hybrids in fact have a similar lineage as Columbusgrass. These findings will enhance Columbusgrass breeding strategies to incorporate a non-flowering trait identified in this study. Future dissection of the genetics underlying this trait offers potential for novel sources of floral suppression. Whether the mechanism suppressing flowering in these hybrids is controlled by novel alleles or altered expression of previously characterized genes in floral induction pathways, its characterization and exploitation offers great potential towards designing environmentally benign transgenic sorghums as well as perennial biofuel sorghums with greatly reduced invasiveness risks.

Last Modified: 8/1/2014