Panicum

Abstract: The nature of the interaction between plants ant their soil community was investigated by testing for differential responses of four old—field perennial plant species to inocula derived from soil communities that had been grown with ("cultured by") one of these four plant species. The differentiation of the soil communities was evident in measurements of plant survival, phenology, growth, and root—shoot ratios. Effects on survival and growth suggest negative feedbacks between these species and the soil communities that they culture. Survival rates of Krigia dandelion were significantly reduced when grown with their own" soil community. Considered as a whole, the three other species (all grasses) had significantly lower growth and root—shoot ratios when grown with soil communities started with their own inocula compared to soil communities started with the inocula of other species. However, the significance of this effect on growth rate and root—shoot ratios was due primarily to the pairwise comparison of Anthoxanthum odoratum and Danthonia spicata and of Anthoxanthum and Panicum sphaerocarpon, respectively. Pairwise comparisons of Danthonia and Panicum do not suggest differential responses to each other's soils in growth rate or root—shoot ratios nor do soil communities appear to affect the relative competitive ability of these two species. While the components of the soil community responsible for these effects have not been identified, similar although less pronounced patterns were observed in experiments using inocula consisting of washed live root segments as compared to experiments using whole soil as inoculum, suggesting that root pathogens are one important agent.

Abstract: Agriculturally important grasses such as sugar cane (Saccharum sp.), rice (Oryza sativa), wheat (Triticum aestivum) sorghum (Sorghum bicolor), maize (Zea mays), Panicum maximum, Brachiaria spp., and Pennisetum purpureum contain numerous diazotrophic bacteria, such as, Acetobacter diazotrophicus, Herbaspirillum spp., Azospirillum spp. These bacteria do not usually cause disease symptoms in the plants with which they are associated and the more numerous of them, for example, Herbaspirillum spp. and A. diazotrophicus, are obligate or facultative endo-phytes that do not survive well (or at all) in native soil; these are thought to be spread from plant generation to plant generation via seeds, vegetative propagation, dead plant material, and possibly by insect sap feeders. By contrast, Azospirillum spp. are not wholly endophytic but are root-associated, soil-dwelling bacteria that are also often found within plants, probably entering host plants via seeds or via wounds/cracks at lateral root junctions. Endophy...

Abstract: Foxtail millet ( Setaria italica ) is a small diploid C4 panicoid crop species, whose genome is being sequenced by the Joint Genome Institute (JGI) of the Department of Energy. The rationale for sequencing foxtail millet is that it is closely related to the bioenergy grasses switchgrass ( Panicum

Abstract: Summary Switchgrass (Panicum virgatum L.) has been developed into a dedicated herbaceous bioenergy crop. Biomass yield is a major target trait for genetic improvement of switchgrass. microRNAs have emerged as a prominent class of gene regulatory factors that has the potential to improve complex traits such as biomass yield. A miR156b precursor was overexpressed in switchgrass. The effects of miR156 overexpression on SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) genes were revealed by microarray and quantitative RT-PCR analyses. Morphological alterations, biomass yield, saccharification efficiency and forage digestibility of the transgenic plants were characterized. miR156 controls apical dominance and floral transition in switchgrass by suppressing its target SPL genes. Relatively low levels of miR156 overexpression were sufficient to increase biomass yield while producing plants with normal flowering time. Moderate levels of miR156 led to improved biomass but the plants were nonflowering. These two groups of plants produced 58%‐101% more biomass yield compared with the control. However, high miR156 levels resulted in severely stunted growth. The degree of morphological alterations of the transgenic switchgrass depends on miR156 level. Compared with floral transition, a lower miR156 level is required to disrupt apical dominance. The improvement in biomass yield was mainly because of the increase in tiller number. Targeted overexpression of miR156 also improved solubilized sugar yield and forage digestibility, and offered an effective approach for transgene containment.