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Title: Elimination of a reproductive barrier facilitates intergeneric hybridization of Sorghum bicolor and Saccharum

item HODNETT, GEORGE - Texas A&M University
item Hale, Anna
item PACKER, DAN - Texas A&M University
item STELLY, DAVID - Texas A&M University
item DA SILVA, JORGE - Texas Agrilife Research
item ROONEY, WILLIAM - Texas A&M University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/20/2009
Publication Date: 6/7/2010
Citation: Hodnett, G.L., Hale, A.L., Packer, D.J., Stelly, D., Da Silva, J., Rooney, W.L. 2010. Elimination of a reproductive barrier facilitates intergeneric hybridization of Sorghum bicolor and Saccharum. Crop Science. 50:1188-1195.

Interpretive Summary: Growing interest in green-fuels has turned much attention toward sorghum and sugarcane as biomass feedstocks. The ability to cross these two species and produce offspring with attributes from both crops has the potential to fill a need in the growing biofuels industry as well as contribute to existing uses for these crops (e.g. sorghum could contribute to drought tolerance in sugarcane). A rare mutation in sorghum was previously bred into a variety adapted to the southern U.S. and this variety was used to produce 1371 sorghum/sugarcane offspring. The male-sterile sorghum was used as the female parent, and sugarcane pollen was used to generate hybrid offspring. These offspring, each unique from one another, have characteristics of both sugarcane and sorghum. They have much higher sugar levels than the grain-sorghum parent and when genetic material (chromosomes) is examined under a microscope, it is evident that they have inherited DNA from both parents. For years, breeders have been attempting to create offspring that are a combination of the two crops, but this is the first large-scale successs. The ability to consistently produce large numbers of sugarcane-sorghum hybrids has the potential to enhance the genepool of both species. It is possible, that hybrids resembling sugarcane could be planted from seed in the future, reducing sugarcane planting costs (the most expensive part of sugarcane farming). There is potential to increase the wide adaptation of sugarcane using sorghum genes, and to produce a perennial sorghum crop. Furthermore, the presence of the mutation that made this possible could allow for crossing with additional species. The number of offspring produced using this technique affords the opportunity to select superior hybrid material to further trait enhancement in two different species.

Technical Abstract: Growing interest in bioenergy production has increased efforts to breed for greater biomass through intra- and inter-generic hybridization. Both sorghum (Sorghum bicolor) and sugarcane (Saccharum spp.) are now being bred to enhance the quantity and quality of biomass while maintaining or improving biotic and abiotic stress tolerances. The ability to consistently hybridize these species would facilitate the introgression of complementary traits that increase adaptability, yields, and sustainability of each species. Previous efforts to hybridize these crops have had limited success, but the discovery of a specific trait in sorghum has eliminated at least one prezygotic barrier to fertilization. Techniques to produce a significant amount of seed from crosses between sorghum and sugarcane are described. Using these methods, our programs have grown 1,371 sorghum/saccharum intergeneric hybrid plants. Seed set frequency in the intergeneric crosses was affected by sugarcane pollinators, implying that breeding and selection of sugarcane pollen parents could further enhance successful hybridization. The Sorghum x Saccharum hybrids described in this paper are now being used for introgression of traits into both species. Unlike previous attempts to hybridize these two genera, sufficient quantities of seedlings were produced to impose selection criteria with the goal of developing a new intergeneric cultivar with potential to be used for sugar or as a biomass feedstock. The long-term objective is to combine desirable traits of both sorghum and sugarcane.