Barley (Hordrium sp.) is the most important spring sown cereal crop in Utah, both in acreage and in yield of total digestible nutrients per unit area. It also rates high as a feed crop in the United States. For this reason it is important that varieties are available which are high in yield, high in quality, and disease resistant, along with other desirable characteristics. In order to work toward this end most efficiently, it is first necessary that the genetics of the barley plant be worked out. Barley offers the plant breeders and geneticists a valuable material to use in the study of genetics. The fact that it has many easily distinguishable characters, that it is easy to grow large F2 populations, and that it has a low chromosome number make it desirable for this type of study. That all interspecific crosses are fertile make it all the more desirable for the plant breeder. This study is a by-product of the cereal breeding and improvement program being carried on at the Utah Experiment Station. Recently the study of translocations induced by X0rays and other means has gained wide interests among plant breeders, geneticists, and cytologists alike. Translocations or interchanges consist of the exchange of segments of non-homologous chromosomes. As a result semisterility occurs in plants which are heterozygous for the interchange. the objective of this study is to calculate any linkage which may be found in different crosses involving translocated stocks in barley in order to determine which linkage groups are involved in the translocation; and to note any characters now linked as a result of a translocation which were not linked in normal barley stocks. The ratios and interactions which occur in any of the characters found in this study will be calculated.

The objective in wheat hybridization primarily is to obtain new varieties which are of a greater agronomic value than existing varieties. Frequently, however, crosses which obviously will not produce superior commercial types are made and studied in order to obtain genetic information which may be useful to the breeder. This latter phase of breeding, i.e., the accumulation of genetic information, provides the basis for this study.

The development of new and better varieties of plants through plant breeding is essential to meet certain needs of a changing world. Genetics and a knowledge of its principles are the basis for such improvement. Barley has been used rather extensively in linkage relations studies. Its desirable characteristics are: (1) interspecific fertility and relative ease of hybridization, (2) numerous characters that are easily differentiated, (3) its commercial importance as a crop and (4) there are seven chromosome pairs in each of the four cultivated species.

Genetic consistency within varieties is essential to quality assurance for any agricultural product. While the Australian coffee industry targets high quality coffee, there is observed morphological variation within coffee varieties in New South Wales plantations. This variability may result from environmental, genetic and/or management factors. Genetic factors can be tested by molecular markers which can also shed light on the questions concerning crop quality management. A review of the literature showed low genetic variation in C. arabica. Hence four different molecular marker systems were used in this study to detect possible genetic variation within and between varieties of local coffee grown in Northern New South Wales (NNSW), Australia. Genetic variation in eighty-four seed propagated coffee (C. arabica) accessions, mainly from two commercial varieties (K7 and CRB) in NNSW, were tested using various PCR-based marker systems (RAPDs, ISSRs, SSRs and AFLPs). Eleven accessions from Central Highland, Vietnam, were used as reference material. While RAPD and ISSR did not distinguish intra-varietal molecular variation, SSR and AFLP data revealed the degree of genetic variability and the relationship among individuals within and between coffee varieties. Despite observed morphological variation within supposedly single variety plantations in NNSW, the genetic variation, measured by genetic distance, revealed in this study was very low (K7: 0.193; CRB: 0.205). There exists genetic variation between different farms sharing the same cultivar (K7) which suggests differences in the management of plantation establishment and sourcing of trees. The genetic variability is not aligned with off-type individuals observed in K7, but is with off-type CRB plants which is probably due to inter-varietal hybrids from unintentional outcrossing. The mean level of genetic identity between cultivars derived from the two distinct types of C. arabica is moderate (0.641). Although genetic variation within and among arabica cultivars is low, sufficient DNA polymorphism was found among some C. arabica accessions to allow differentiation. The results in this study suggested that even the elite cultivars, which have been exposed to intensive selection, still show a certain degree of genetic variation amongst individuals within each cultivar even though C. arabica is a predominantly selfing species and has a narrow genetic foundation. The congruence between AFLP and SSR data sets suggests that either method individually, or a combination, is applicable to genetic studies of coffee. SSR alone clearly distinguished and revealed inter-varietal heterogeneity but were more powerful when combined with AFLP.

Genetic consistency within varieties is essential to quality assurance for any agricultural product. While the Australian coffee industry targets high quality coffee, there is observed morphological variation within coffee varieties in New South Wales plantations. This variability may result from environmental, genetic and/or management factors. Genetic factors can be tested by molecular markers which can also shed light on the questions concerning crop quality management. A review of the literature showed low genetic variation in C. arabica. Hence four different molecular marker systems were used in this study to detect possible genetic variation within and between varieties of local coffee grown in Northern New South Wales (NNSW), Australia. Genetic variation in eighty-four seed propagated coffee (C. arabica) accessions, mainly from two commercial varieties (K7 and CRB) in NNSW, were tested using various PCR-based marker systems (RAPDs, ISSRs, SSRs and AFLPs). Eleven accessions from Central Highland, Vietnam, were used as reference material. While RAPD and ISSR did not distinguish intra-varietal molecular variation, SSR and AFLP data revealed the degree of genetic variability and the relationship among individuals within and between coffee varieties. Despite observed morphological variation within supposedly single variety plantations in NNSW, the genetic variation, measured by genetic distance, revealed in this study was very low (K7: 0.193; CRB: 0.205). There exists genetic variation between different farms sharing the same cultivar (K7) which suggests differences in the management of plantation establishment and sourcing of trees. The genetic variability is not aligned with off-type individuals observed in K7, but is with off-type CRB plants which is probably due to inter-varietal hybrids from unintentional outcrossing. The mean level of genetic identity between cultivars derived from the two distinct types of C. arabica is moderate (0.641). Although genetic variation within and among arabica cultivars is low, sufficient DNA polymorphism was found among some C. arabica accessions to allow differentiation. The results in this study suggested that even the elite cultivars, which have been exposed to intensive selection, still show a certain degree of genetic variation amongst individuals within each cultivar even though C. arabica is a predominantly selfing species and has a narrow genetic foundation. The congruence between AFLP and SSR data sets suggests that either method individually, or a combination, is applicable to genetic studies of coffee. SSR alone clearly distinguished and revealed inter-varietal heterogeneity but were more powerful when combined with AFLP.

Three crosses were used to study the inheritance of the sedimentation properties in hard red winter wheat. The parents of the three crosses were the variety Delmar, and the breeding lines 217-61- 7-14 and 217 - 19- 5. Delmar has high sedimentation properties, 217-6 1-7-14 is intermediate, and 217-19-5 has very poor sedimentation qualities. Sedimentation tests were run on five replications of the parents and 300 samples of the F3 populations in each cross. A semi-micro sedimentation test (a one-fourth scale test) was run on 200 F2 plants and the F1's from each cross. The distributions from each cross were analyzed and the type of gene action and possible number of genes involved were estimated. There were two general trends apparent in the progeny of all three crosses. (1) In the F2 generation there were more low parental types than high parental types recovered. This situation was reversed in each of the F3 populations where more high parental types were recovered than the low parental types (2) All three F3means were about 10 units higher than their respective F2 means. The type of gene action appeared to be mainly additive but with some partial dominance for the high parent in each cross . Depending on the cross, from one to three genes were estimated to be functioning in the determination of the sedimentation properties.

The assignment of genetic factors to definite loci in the hereditary mechanism has been a great step in the progress of biology. Of the cereal crops, barley (Hordeum sp.), a crop of economic importance, offers a superior opportunity for genetic studies. Its adaptation to wide varieties of conditions, with a wealth of easily differentiated characters and only seven pairs of chromosomes, the barley plant provides excellent material for linkage studies. Although there is a vast amount of literature dealing with inheritance in barley, yet knowledge of the subject is still very limited. The mode of inheritance of about one hundred characters has been studied and linkage relations of nearly thirty-five characters have been made. The location of a relatively large number of them is still unknown. All the seven linkage groups are established and distinct viable characters are available in six of them, although but few in some cases. The desirability of making further studies in this crop is quite apparent. This manuscript contains the results of observations and experiments with sixteen characters which include three new characters not reported in the literature. All character pairs in each cross studied were checked for possible linkages or independence. The importance of such a study in the future improvement of the barley crop needs no emphasis.

Understanding of grass genome structure and evolution has been significantly advanced through comparative genomics. The genomes of most cool-season forage and turf grasses, belonging to the Pooideae subfamily of the grasses, remain understudied. Creeping bentgrass (Agrostis stolonifera) is one of the most important cool-season turfgrasses due to its low mowing tolerance and aggressive growth habit. An RFLP genetic map of creeping bentgrass using 229 RFLP markers derived from cereal and creeping bentgrass EST-RFLP probes was constructed for a comparative genome analysis. This genetic map was compared with those of perennial ryegrass, oat, wheat, and rice. Large-scale chromosomal rearrangements between the map of creeping bentgrass and the respective maps of the Triticeae, oat, and rice were observed. However, no evidence of chromosomal rearrangements between the maps of creeping bentgrass and perennial ryegrass was detected, suggesting that these recently domesticated species might be closely related than expected. Further comparative genome analysis of creeping bentgrass was performed with the genome sequences of Brachypodium distachyon using sequences of the above-mentioned RFLP mapped markers and 8,470 publicly available A. stolonifera EST (AgEST) sequences. A total of 24 syntenic blocks were identified between the Agrostis linkage groups and the B. distachyon chromosomes. Orthologous loci of AgESTs (678) were identified in the B. distachyon genome, and these loci can be utilized in further comparative mapping of Pooideae species. Insights from comparative genomics with B. distachyon will be useful for genetic improvement of Agrostis spp. and provide a better understanding of the evolution of the Pooideae species.

Doubled haploidy (DH) is a plant breeding technique that is often utilized by plant breeders to minimize the time required to reach homozygosity in breeding lines. The first objective of this study was to compare two methods of generating DH lines in tobacco (Nicotiana tabacum L.). Inbred burley tobacco varieties TN 90LC and GR 149LC were used to produce both androgenic derived doubled haploids (ADDH) and maternally derived doubled haploids (MDDH). The relative agronomic performance of TN 90LC and GR 149 LC ADDH and MDDH lines was compared when used either as pure-line cultivars or when used for the production of the KT 204LC and TN 97LC hybrid cultivars, respectively. The ADDH method was more efficient than the MDDH method in generating large numbers of haploid plants. On average the ADDH TN 90LC population was statistically inferior to the inbred TN 90LC for several agronomic traits; this inferiority of the ADDH method was not observed in the GR 149LC populations. For both genotypes, the MDDH populations were comparable to the inbred parental genotypes. The ADDH method was inferior for TN 90LC, but several individual TN 90LC ADDH lines were equal or superior to the inbred source. The agronomic variability observed in both ADDH and MDDH lines was decreased when they were used to produce hybrid cultivars. Less variation was observed in the DH-derived hybrids KT 204LC and TN 97LC compared to the ADDH and MDDH TN90LC and GR149LC parental lines, respectively. The significant inferiority of ADDH TN 90 lines in comparison to inbred TN 90LC was not observed in the ADDH derived KT 204 population compared to KT 204LC. The second objective of this study was to compare DH Lines derived from an F1 breeding population versus DH lines derived from a segregating F2 population where plants used for DH were pre-screened for quantitatively inherited resistance to soil-borne diseases black shank (Phytophthora nicotianae) and/or Fusarium wilt (Fusarium oxysporum f. nicotianae). There was a clear difference in susceptibility to black shank between the F1 and F2 derived DH populations, both in terms of average disease incidence, and more importantly, in the percentage of individual lines displaying high disease resistance. For two different burley crosses, DH lines derived from the F1 generation were considerably more susceptible to black shank than DH lines derived from the F2 generation. No differences in the incidence of Fusarium wilt were observed between DH lines of F1 and F2 generations; this was likely due to low overall disease incidence. Although delaying the DH process in tobacco from the F1 to the F2 generation could add time to the development of homozygous breeding lines, the delay may be offset by having to screen fewer finished DH lines to identify superior lines.

Plant cell walls are complex structures that must not only constrain cellular turgor pressure but also allow for structural modification during the dynamic processes of cell division and anisotropic expansion. Cell walls are composed of highly glycosylated proteins and polysaccharides, including pectin, hemicellulose and cellulose. The primary cell wall polysaccharide is cellulose, a polymer composed of high molecular weight !- 1,4-glucan chains. Although cellulose is the most abundant biopolymer on Earth, there is still a lot to learn about its biosynthesis and regulation. This research began by applying a variety of analytical techniques in an attempt to understand differences in cell wall composition and cellulose structure within the plant body, between different plant species and as a result of acclimation by the plant to different environmental conditions. Next, a number of different Arabidopsis thaliana lines possessing mutations affecting cell wall biosynthesis were analyzed for changes in cellulose structure (crystallinity) and biomass saccharification efficiency. One of these mutants, isoxaben resistance1-2 (ixr1- 2), which contains a point mutation in the C-terminal transmembrane region (TMR) of cellulose synthase 3 (CESA3), exhibited a 34% lower biomass crystallinity index and a 151% improvement in saccharification efficiency relative to that of wild-type. The culmination of this research began with a chemical screen that identified the molecule quinoxyphen as a primary cell wall cellulose biosynthesis inhibitor. By forward genetics, a semi-dominant mutant showing strong resistance to quinoxyphen named aegeus was identified in A. thaliana and the resistance locus mapped to a point mutation in the TMR of CESA1. cesa1aegeus occurs in a similar location to that of cesa3ixr1-2, illustrating both subunit specificity and commonality of resistance locus. These drug resistant CESA TMR mutants are dwarfed and have aberrant cellulose deposition. High-resolution synchrotron X-ray diffraction and 13C solid-state nuclear magnetic resonance spectroscopy analysis of cellulose produced from cesa1aegeus, cesa3ixr1-2 and the double mutant shows a reduction in cellulose microfibril width and an increase in mobility of the interior glucan chains of the cellulose microfibril relative to wild-type. These data demonstrate the importance of the TMR region of CESA1 and CESA3 for the arrangement of glucan chains into a crystalline cellulose microfibril in primary cell walls.