Browsing by Subject "Oat"

Now showing 1 - 3 of 3
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    Deciphering lodging resistance in oat and other cereal crops
    (2019-08) Susko, Alexander
    Lodging impedes the successful cultivation of oat and other cereal crops in the upper midwestern United States. Lodged cereals not only possess reduced grain yields, but also decreased grain quality. This dissertation first conceives of a camera system to capture plant movement in the wind in the field via a 360-degree field of view camera, followed by a video analysis pipeline to quantify the frequency and amplitude of cereal stem movement under varying wind conditions in the field. The natural oscillating frequencies and amplitudes of stems were dependent on wind speeds and at the cultivar, crop level. Nonetheless, the substantial environmental effects in the field that induce lodging make discovering specific morphologies that confer lodging resistance difficult. Next, in seeking to better identify promising morphological targets for breeding and selecting lodging resistance in cereal crops, a diverse panel of 38 cereal cultivars (oat, wheat, barley) were subjected to replicated testing in a wind tunnel. Wind tunnel testing revealed that a cereal ideotype consisting of low total biomass, high stem strength, and high stem elasticity should confer increased lodging resistance. A field study using the camera system to quantify aspects of plant movement and correlated these phenotypes with physical plant traits is presented next, which indicated that patterns of plant movement are spatially independent in a randomized complete block design of 16 cereal cultivars and that the relationships between plant height, heading date, and plant movement vary among the major cereal crops. Finally, a GWAS and QTL validation study is presented on lodging in oat, which revealed significant marker trait associations for plant height, heading date, and stem snapping, though only QTL for plant height and heading date were successfully validated in derived biparental populations.
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    Expression of maize genes on a specific chromosome in the presence of a foreign genome.
    (2009-09) Cabral, Candida Braga
    Oat-maize addition (OMA) lines are derived from oat x maize sexual hybrids in which individual maize chromosomes have been retained in embryo-rescued plants containing a full complement of oat chromosomes. The maize Affymetrix microarray was used to analyze transcripts from three independently derived OMA lines containing chromosome 5 from the B73 maize inbred line in order to assess the prevalence of maize gene expression in an alien background. Despite the lack of gross morphological changes, we found that 26% of the maize genes that are normally expressed in maize seedlings are also expressed in OMA seedlings. All three OMA lines show very similar gene expression patterns. While there was evidence for expression for many of the maize genes on chromosome 5, there were also numerous chromosome 5 genes that are normally expressed in maize but expression was not detected in OMA lines. The expression, or lack thereof, of a maize chromosome 5 gene was not correlated with chromosomal position, gene annotation or DNA methylation. Although there is a correlation between expression levels of the maize chromosome 5 genes expressed in OMA and maize, the expression levels are generally lower in the OMA background. The basis for maize gene expression in the maize donor but not in the OMA lines likely reflects whether maize genes can be efficiently controlled by oat transcriptional machinery.
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    The oat-crown rust pathosystem: an interaction of a plant, a pathogen, and time
    (2020-12) McNish, Ian
    Plant diseases are often described as the interaction of a plant, a pathogen, and the environment. For a disease to develop, there must be a susceptible plant, a virulent pathogen, and an environment amenable to disease. This concept is useful to explain the presence or absence of a disease, but many important questions and ideas in plant pathology, plant genomics, plant phenomics, and plant cultivar development are also dependent on time. A pathogen population changes over time, by a process of selection, to defeat the resistances deployed in crop cultivars. The genetic architecture of disease resistance changes as a plant grows from a seedling to an adult plant, matures, and dies. The visual and spectral signature of plant stress and disease also changes as the plant grows and the disease develops. Finally, plant breeders attempt to limit the damage diseases cause by quickly improving plant populations and deploying disease resistant plant cultivars. The dimension of time has been well-explored in some areas of plant science such as gene expression, but time is often overlooked in plant breeding, quantitative genetics, and phenomics. Crown rust, caused by the fungal pathogen Puccinia coronata f. sp. avenae Erikss. (Pca), is a dynamic and devastating disease of cultivated oat (Avena sativa L.). In this research, I found that the North American Pca population has gained many virulences over the past thirty years and that the Pca isolates collected in recent years are capable of defeating a surprisingly high number of crown rust resistance genes. I found that the genetic architecture of crown rust resistance changed throughout the growing season. Many resistance loci were detected briefly, sometimes just for a couple of days, and few loci were detected at many points in time. I found that the spectral signature of disease and plant stress changed throughout the season and that the predictive value of the collected data was greatest for adult plants before senescence. Finally, I found that quantitative resistance to crown rust could be rapidly improved in an oat population, but the race-specificity of that resistance was difficult to determine. If plant breeders understand how time influences the composition of pathogen populations, the observations they make, the analyses they perform, and the technologies they develop, then they will be more capable of improving complex plant traits like disease resistance.