Browsing by Subject "tiller"

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    Natural genetic variation and gene expression patterns underlying lateral shoot (tiller) development in barley (Hordeum vulgare L)
    (2018-12) Haaning, Allison
    The main shoot and other above-ground tissues develop from the shoot apical meristem (SAM), including axillary meristems (AXM) from which lateral branches develop. In barley, lateral branches called tillers contribute directly to grain yield and define shoot architecture. Two studies were completed to gain a better understanding of the genetic control of tiller development. One focused on characterizing natural phenotypic and genetic variation in tiller number throughout development in a large, diverse germplasm collection; and the second focused on identifying meristem-specific genes and characterizing gene expression patterns that varied by meristem type (SAM or AXM) and morphological stage. Results from the first study revealed that correlations between tiller development (tillering) and factors previously shown to influence tiller development, like photoperiod response and spike row-type, varied depending on environment and genetic background. Furthermore, no major trade-offs existed between tiller number and other traits, and natural genetic variation associated with tillering largely overlapped variation associated with days to heading and spike row-type. Results of the second study revealed a set of genes upregulated in most meristems compared to non-meristem tissues, many of which have been characterized in other species and are likely important for general meristem maintenance or function. Results also suggested that gene expression was primarily differentiated by genotype, meristem type, and morphological stage; however, expression profiles of SAM and AXM were very similar at later developmental stages. A small number of genes were only expressed in SAM or AXM, and clustering based on expression across all meristems revealed genes upregulated in AXM that may be important for tiller development, as some, like UNICULME4 and INTERMEDIUM-C (TEOSINTE BRANCHED 1 ortholog) have already been implicated in tiller development. Genes that were upregulated in ligules compared to leaves were also identified, and clustering of these genes revealed some that were expressed more highly in ligules and AXM that may, as in other species, have dual functions in leaf and tiller development.
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    Understanding rhizome and tiller traits as an approach to improve fine fescue sod
    (2024) Mihelich, Nicole
    Rhizomes and tillers are important morphological features for many turfgrasses and are traits deserving of more focus for cool-season turfgrass breeding. These two types of stems can allow for resilience and competitiveness in a lawn. Rhizomes and tillers are helpful for sod production which requires turf to be able to quickly form a thick mat of interlocking plant material that can hold together during harvest and transplanting. Kentucky bluegrass (Poa pratensis L.) has the ability to form rhizomes, and is the predominant sod species in Minnesota and the surrounding states. However, consumers would benefit from increased availability of species which require fewer inputs such as fine fescue (Festuca L. spp.) sod for lawns and roadsides. Strong creeping red fescue (Festuca rubra L. subsp. rubra Gaudin) displays robust rhizomatous growth that parallels Kentucky bluegrass and shows promise as a low-input sod option. However, strong creeping red fescue breeding has not been improved for rhizome production or improved sod characteristics. For my dissertation, I pursued breeding and genomics approaches to assess fine fescues of the Festuca rubra complex for sod improvement with a focus on strong creeping red fescue stem growth and development as components of sod formation. I characterized diversity of available germplasm via molecular genetic markers, phenotypes in the growth chamber and field environments, and evaluated the effect of photoperiod on rhizome and tiller production. This investigation of rhizome and tiller traits of these fine fescue taxa could help plant breeders develop new low-input cultivars with enhanced sod forming ability.