Arnel R. Hallauer

Expanding the genetic map of maize with the intermated B73 x Mo17 (IBM) population.

The effects of intermating on recombination and the development of linkage maps were assessed in maize. Progeny derived from a common population (B73 × Mo17) before and after five generations of intermating were genotyped at the same set of 190 RFLP loci. Intermating resulted in nearly a four-fold increase in the genetic map distance and increased the potential for improved genetic resolution in 91% of the intervals evaluated. This mapping population and related information should connect research involving dense genetic maps, physical mapping, gene isolation, comparative genomics, analysis of quantitative trait loci and investigations of heterosis.

Compendium of recurrent selection methods and their application

Recurrent selection is a breeding method that has been used for the genetic improvement of germplasm. Although recurrent selection methods were suggested over 40 years ago, there use has not been as extensive as the other classical plant breeding methods. Recurrent selection is used for the improvement of traits inherited in a quantitative manner, and the primary objective of the method is to gradually increase the frequency of favorable alieles and maintain genetic variability for future selection. Different methods of recurrent selection have been suggested, depending on the types of gene action considered important in the inheritance of the traits under selection, relative efficiency of selection, and the complexity of the trait under selection. Most methods of recurrent selection include three phases conducted in a repetitive manner; development of progenies, evaluation of progenies in replicated trials, and recombination of the superior progenies based on the evaluation trials. Most information sugge...

Use of index selection in recurrent selection programs in maize

SummaryPhenotypic and genotypic correlations were examined for four traits in seven populations of maize (Zea mays L.) undergoing recurrent selection. Correlations among grain yield and percentage of grain moisture, root lodging, and stalk lodging were low (|r|<0.3) except for the correlation between grain yield and stalk lodging, which was high and negative. The phenotypic and genotypic correlations agreed well from cycle to cycle within populations. Variation of correlations among populations was not significantly larger than variation among cycles. Heritabilities of these traits generally were high (h2>0.5). Two indices, one that used heritabilities as index weights and one that used relative economic weights (base index) as index weights, were compared with the Smith-Hazel index (optimim index). Relative efficiencies of the two indices, in terms of predicted gains for the individual traits and the composite trait, compared with the Smith-Hazel index, were high. The use of an index in which heritabilities were used as index weights was recommended because:1) the heritabilities were the same as the optimum weights when the traits were uncorrelated, and for the data examined the correlations were low; and 2) heritabilities were computed in routine data analyses and were available at no additional cost.

Frequency of the transposable element Uq in Iowa stiff stalk synthetic maize populations

The Uq transposable element is one of two transposable elements consistently found in maize (Zea mays L.) populations. Populations developed from two independent recurrent selection programs initiated in the Iowa Stiff Stalk Synthetic (BSSS) maize population were tested for the frequency of Uq transposable elements to determine how Uq frequency has changed with cycles of recurrent selection. In the first programme, 13 cycles of half-sib and S2progeny recurrent selection [BSSS(S)C13] have been completed and 10 of the 13 cycles were assayed for active Uqelements. In the second programme, 11 cycles of reciprocal recurrent selection [BSSS(R)C11] have been completed and five of the 11 cycles were assayed for active Uq elements. The frequency of Uq was different for the two recurrent-selection programmes. The percentage of plants containing active Uq elements increased from 19% (BSSS) to 91% [BSSS(S)C13] at a linear rate after 13 cycles of half-sib and S2 progeny recurrent selection, whereas the percentage of plants containing active Uq elements decreased from 19% (BSSS) to 0% [BSSS(R)C11] after 11 cycles of reciprocal recurrent selection, with extinction of the Uq element occurring between the fifth and sixth cycles of selection. Our data suggest that the increase in frequency of Uq with half-sib and S2 progeny recurrent selection was predominantly due to random genetic drift coupled with a selective advantage possibly associated with a region of the genome linked to Uq. Neither replicative transposition or chromosome assortment and segregation can be invoked to explain the change in frequency of Uq in these populations. The extinction of Uq after reciprocal recurrent selection was best explained by random genetic drift. Disciplines Agricultural Science | Agronomy and Crop Sciences | Plant Breeding and Genetics Comments This article is published as Lamkey, K. R., P. A. Peterson, and A. R. Hallauer. 1991. Frequency of the transposable element Uq in Iowa Stiff Stalk Synthetic maize populations. Genetical Research 57:1-9. doi: 10.1017/S0016672300028962. Rights Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. This article is available at Iowa State University Digital Repository: http://lib.dr.iastate.edu/agron_pubs/263 Genet. Res., Camb. (1991), 57, pp. 19 With 5 text-figures Primed in Great Britain Frequency of the transposable element Uq in Iowa stiff stalk synthetic maize populations KENDALL R. LAMKEYt, PETER A. PETERSON AND ARNEL R. HALLAUER Cereal and Soybean Improvement Research Unit, USDA-Agricultural Research Service, Department of Agronomy, Iowa State University, Ames . IA 50011 , USA (Received 16 March 1990 and in revised form 9 May 1990)

Effective Population Size and Response to S1-Progeny Selection in the BS11 Maize Population

Research supported by Dep. of Education of the Autonomous Government of Galicia (project XUGA40301B95

Evaluation of maize varieties for their potential as breeding populations

SummaryA 7-variety diallel of synthetic varieties that have not had selection for yield improvement and a 10-variety diallel of synthetic varieties that either resulted from recurrent selection for yield improvement or from the introgression of exotic germ plasm into adapted varieties were evaluated in six environments for yield and five other agronomic traits. The specific objective was to determine the relative potential of the synthetic varieties as germ plasm sources for breeding programs.Recurrent selection improved population yield in ‘BSSS CO’, ‘BSK CO’, and ‘Alph CO’ in the varieties and also in crosses with other varieties. ‘BSSS(R)C6’ and ‘BSSS(HT)C7’ yielded 11.4% and 16.1% more than ‘BSSS CO’, and the variety crosses of ‘BSSS(R)C6’ and ‘BSSS(HT)C7’ yielded 21.6% and 22.0% more than the variety crosses of ‘BSSS CO’. Recurrent selection also improved stalk-lodging resistance for ‘BSSS(R)C6’ and ‘BSSS(HT)C7’, but root lodging for ‘BSSS(HT)C7’ was significantly higher. ‘BS15’ had 61.0% higher yields than ‘Alph CO’, with 9.3% less stalk lodging. Average heterosis of the 10-variety diallel was 1120 kg/ha (19.6%) and ranged from 800 kg/ha (13.7%) for ‘BSK(S)C5’ to 1770 kg/ha (39.4%) for ‘BS12(HI)C5’. The heterosis expressed among individual variety crosses ranged from 4.3% for ‘BSK(S)C5’ x ‘BSTE(FR)C1’ to 37.6% for ‘BSSS(R)C6’ x ‘BS12(HI)C5’, which approached the yield of the two highest yielding single-cross checks.In the 7-variety diallel of unselected varieties, ‘BSTE CO’ and ‘Late Rootworm Synthetic’ were superior as varieties and in crosses for yield and stalk quality. Average heterosis for the 7-variety diallel was 950 kg/ha (18.5%). Stalk lodging was important in the performance of varieties with poor stalk quality.Although recurrent selection improved yield, development of superior breeding populations also will require selection for general agronomic performance. The performance of ‘BS16’ and the yields of ‘BSTL’ and ‘Teozea’ and their crosses suggest that exotic germ plasm should receive greater attention.

Testers and Combining Ability

The inbred–hybrid concept was created in the public sector with the direct influence of Darwin, Festetics, Mendel, and Vilmorin. East related those biological principles to the more practical plant improvement studies to achieve his goals (Hayes, 1956). The progeny test was defined by Allard (1960) as ‘a test of the value of a genotype based on the performance of its offspring produced in some definite system of mating.’ It was used as early as 1850 by Vilmorin in France, and it proved to be a highly effective procedure for the improvement of sugar content of sugar beets (Beta vulgaris). This method of line selection with progeny testing was known as the ‘Vilmorin method’ or ‘Vilmorin isolation principle’ and was introduced in several plant breeding programs in the latter part of the 19th century. The progeny test in maize was first used in 1896 by Hopkins, starting the well-known program for half-sib recurrent selection of maize oil and protein content (e.g., the ear-to-row half-sib selection procedure).

Evolution of plant breeding

Plant breeding is considered one of the longest ongoing activities undertaken by humans, who select plants more productive and useful to themselves and the animals for at least 10,000 years ago. The evolution of civilizations paralleled the success of plant breeding, although this has not been recognized by the public. The reason may be lack of understanding of what plant breeding encompasses. The concept of plant breeding evolved, depending on the time it was formulated, but without losing the essence of being art and science of manipulating plants for man. This review discusses the evolution of the concepts and the methods of plant breeding, here divided arbitrarily into selection based on phenotypes, breeding values and genotypes. No matter how big the pool of genetic information in recent years, the phenotype will continues to be important in the present and future.

Evaluation of Iowa Stiff Stalk Synthetic for resistance to gray leaf spot

Gray leaf spot (GLS) of maize (Zea mays), caused by Cercospora zeae-maydis, has become an increasing disease problem in the United States. Resistance to this pathogen is generally higher in inbred lines of Lancaster origin compared to lines derived from Iowa Stiff Stalk Synthetic (BSSS). This study was conducted to determine whether recurrent selection for yield had altered the level of GLS resistance in BSSS and to identify BSSS(R)C11 S 1 lines that combine GLS resistance with high yield. The distribution of GLS ratings for S 1 lines derived from BSSSC0 and BSSS(R)C11 were very similar, indicating that selection for yield had not altered GLS resistance levels (.)

Genetic Architecture of Ear Fasciation in Maize (Zea mays) under QTL Scrutiny.

Maize ear fasciation Knowledge of the genes affecting maize ear inflorescence may lead to better grain yield modeling. Maize ear fasciation, defined as abnormal flattened ears with high kernel row number, is a quantitative trait widely present in Portuguese maize landraces. Material and Methods Using a segregating population derived from an ear fasciation contrasting cross (consisting of 149 F2:3 families) we established a two location field trial using a complete randomized block design. Correlations and heritabilities for several ear fasciation-related traits and yield were determined. Quantitative Trait Loci (QTL) involved in the inheritance of those traits were identified and candidate genes for these QTL proposed. Results and Discussion Ear fasciation broad-sense heritability was 0.73. Highly significant correlations were found between ear fasciation and some ear and cob diameters and row number traits. For the 23 yield and ear fasciation-related traits, 65 QTL were identified, out of which 11 were detected in both environments, while for the three principal components, five to six QTL were detected per environment. Detected QTL were distributed across 17 genomic regions and explained individually, 8.7% to 22.4% of the individual traits or principal components phenotypic variance. Several candidate genes for these QTL regions were proposed, such as bearded-ear1, branched silkless1, compact plant1, ramosa2, ramosa3, tasselseed4 and terminal ear1. However, many QTL mapped to regions without known candidate genes, indicating potential chromosomal regions not yet targeted for maize ear traits selection. Conclusions Portuguese maize germplasm represents a valuable source of genes or allelic variants for yield improvement and elucidation of the genetic basis of ear fasciation traits. Future studies should focus on fine mapping of the identified genomic regions with the aim of map-based cloning.