D. D. Stuthman

Association of a major groat oil content QTL and an acetyl-CoA carboxylase gene in oat

Abstract Oat groats are unique among cereals for the high level and the embryo-plus-endosperm localization of lipids. Genetic manipulation of groat quality traits such as oil is desired for optimizing the value of oat in human and livestock diets. A locus having a major effect on oil content in oat groats was located on linkage group 11 by single-factor analysis of variance, simple interval mapping and simplified composite interval mapping. A partial oat cDNA clone for plastidic acetyl-CoA carboxylase (ACCase), which catalyzes the first committed step in de novo fatty acid synthesis, identified a polymorphism linked to this major QTL. Similar QTL and ACCase locus placements were obtained with two recombinant inbred populations, ‘Kanota’בOgle’ (KO) and ‘Kanota’בMarion’ (KM), containing 137 and 139 individual lines, respectively. By having a common parent these populations provide biological replication of the results in that significant genomic regions should be evident in analyses of multiple cross combinations. The KO population was mapped with 150 RFLP loci distributed over the genome and was grown in five diverse environments (locations and years) for measurement of groat oil content. The KM population was mapped with 60 RFLP loci and grown in three environments. The QTL linked to AccaseA on linkage group 11 accounted for up to 48% of the phenotypic variance for groat oil content. These results provide strong support for the hypothesis that ACCase has a major role in determining groat oil content. Other QTLs were identified in both populations which accounted for an additional 10–20% of the phenotypic variance.

Evaluation of Components of Partial Resistance to Oat Crown Rust Using Digital Image Analysis

Digital image analysis is an objective and nondestructive method potentially capable of providing accurate and precise estimates of disease resistance components. This study was conducted to quantify components of partial resistance to crown rust through the analysis of sequential digital images of inoculated leaves of adult oat plants, and to compare components found in two sources of resistance unrelated genetically. Uredinium density, relative infection frequency, latent period, days to first pustule appearance, uredinium size, and disease progress rates were assessed on three oat lines (RS-line 3W-C2R-9-3b, MN-841801, Starter) in two greenhouse experiments. Resistant lines had fewer and smaller uredinia, and these appeared later than in the susceptible check. Relative infection frequency, latent period, and uredinium size were equally important components in the expression of the partial resistance to crown rust, and the two sources of resistance could not be differentiated by any of the variables studied. The analysis of sequential digital images of diseased leaves produced precise estimates of partial resistance components and disease progress rates.

Continued response through seven cycles of recurrent selection for grain yield in oat (Avena sativa L.)

Long-term selection experiments provide germplasm to study the effects of selection in a closed population. Recurrent selection to enhance grain yield in oat has been ongoing at the University of Minnesota since 1968. The objectives of this study were: (i) estimate the GCA and SCA effects for three agronomic traits in the seventh cycle of selection, (ii) assess the effect of the current methods of selection on parental contribution and unselected traits, and (iii) determine the direct and indirect responses to seven cycles of recurrent selection for grain yield. Progeny of the Cycle 6 parents and parents for Cycles 0 through 7 were grown in two separate tests. Grain yield, heading date and plant height were evaluated in each test. Grain yield was increased by 21.7% after seven cycles of selection. Evaluation of Cycle 6 progeny showed that GCA effects were significant for all three traits studied, and SCA effects were significant only for grain yield. Four Cycle 6 parents did not have any progeny selected as Cycle 7 parents. Results from this study indicate that long term recurrent selection has continued to increase grain yield. Alternative selection strategies may be necessary to maintain the genetic variability in this population, particularly when improvement of secondary traits is required.

Micronuclei frequency and character coherence inAvena sativa L./A.fatua L. crosses

SummaryThe use of micronuclei frequency per microspore quartet (MF) has been proposed to indicate the relative reduction in chromosome homology among interspecific oat (Avena L.) hybrids. Hybrids with lower MF would presumably undergo greater genetic recombination, providing greater opportunity for breaking linkages that contribute to association, or coherence, of desirable and undesirable characters in progenies. Microspore quartets from 63A. sativa/A. fatua hybrids were observed. Character coherence was examined in progenies of the four hybrids with the highest MF (2.22 to 2.82 micronuclei/quartet) and four hybrids with the lowest MF (0.23 to 0.31 micronuclei/quartet) to determine whether a relationship existed between MF and character coherence. Coherence of seed disarticulation with quantitative characters that differentiate the parental species was more frequent in high MF crosses as was expected if high MF is indicative of reduced recombination. However, incidence of coherence between seed color and the quantitative characters was not related to MF differences among the crosses. Likewise, the degree of coherence among the quantitative characters, as measured by coefficients of concordance, was not associated with differences in MF among the crosses. Thus, coherence of the characters studied was not associated consistently with differences in MF.

Development of Oat Breeding Methods

My topic is the development of oat and plant breeding methods. I will start with a short history of important ideas and reports, laying the ground work for current oat breeding approaches. The bulk of my report will describe and discuss, in a critical way, the philosophies and approaches currently in use and the technology that may become available to the breeder in the future.

Land: Hybrid Corn

Crop plant modification through both breeding and genetic engineering have the potential for both improving human welfare and causing problems for people as well as the environment.

Mass (Gravimetric) Selection in Diseased Nurseries

Since its beginning more than 25 years ago, the Mexican oat breeding programme has utilised pedigree selection. The programme began by importing germplasm from the USDA and testing it at three sites, Chapingo, Celeya (winter crop) and Chihuahua. Priority traits include stem rust resistance, earliness, kernel quality and grain yield. As oat acreage increased in the Mexico City area (near Chapingo), stem rust became a serious problem because inoculum is always present and climatic conditions in the area are usually very favourable for stem rust development.