Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 28, 2010
Publication Date: November 16, 2010
Citation: Yang, S.H., Lamb, J.F., Jung, H.G., Samac, D.A., Vance, C.P., Gronwald, J.W. 2010. Using genomics to develop alfalfa as a biomass crop [abstract]. In: 2010 Minnesota Forage Research Symposium, November 17-18, 2010, St. Cloud, Minnesota. p. 23. Technical Abstract: Alfalfa is frequently overlooked as a biomass feedstock for cellulosic ethanol production. However, alfalfa has a number of advantages compared to other potential feedstocks. Alfalfa is a perennial, non-food crop that fixes atmospheric nitrogen, improves soil quality, and provides environmental benefits. And biomass alfalfa cultivars could easily be incorporated into a rotation with corn. The model that we propose involves using the leaves as a protein supplement for livestock and the stems as a feedstock for cellulosic ethanol production. Scientists at the USDA-ARS Plant Science Research Unit at St. Paul, MN, have developed a large-stemmed, non-lodging, biomass-type alfalfa experimental germplasm. When this germplasm is grown under a biomass management system, biomass production increased by 40% and theoretical ethanol yield doubled compared to hay-type alfalfa grown under a hay management system. An important next step in developing alfalfa as a cellulosic feedstock is modifying the composition of the cell walls in stems. Alfalfa stems that have more cellulose and less lignin in their cell walls will yield more ethanol. However, because alfalfa is a perennial with a large, complex genome, selecting for these traits in a conventional breeding program is a slow process requiring many years of selection. The time required to improve alfalfa as a cellulosic feedstock could be shortened if we were able to identify key genes regulating cellulose and lignin production in stems. However, finding these genes is difficult because alfalfa is estimated to have more than 40,000 genes. Our functional genomic approach involves examining gene expression in alfalfa clonal lines that exhibit distinct differences in lignin and cellulose content in stems. To measure differences in gene expression, we are using gene arrays and ultra high-throughput sequencing (RNA-Seq). From the analysis of the results obtained using these genomic tools, we have identified candidate genes whose expression is correlated with desirable changes in cellulose and lignin content of stems. The next step is to evaluate the relative importance of these candidate genes by using transgenic approaches to determine the effect of up-regulation and down-regulation on cellulose and lignin content in alfalfa stems. From the evaluation of candidate genes, we will select those that hold the most promise for increasing cellulose and decreasing lignin in alfalfa stems. Knowledge of these genes can be used to speed up selection of high cellulose/low lignin cultivars in our conventional breeding program. In addition, we can use the tools of molecular biology to genetically engineer alfalfa cultivars to increase expression of key cellulose genes and decrease expression of key lignin genes. Both approaches should shorten the time required to develop a biomass alfalfa cultivar that yields higher levels of ethanol.