bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Markers Associated with Maize Kernel Oil Concentration in an Illinois High Protein × Illinois Low Protein Cross
Authors: Goldman Irwin L. , Rocheford Torbert R. , Dudley John W.
Published: July 2010

The Illinois Long Term Selection Strains offer a unique opportunity to investigate the quantitative genetic basis of kernel chemical traits. This study was conducted to determine the number and magnitude of quantitative trait loci (QTL) influencing kernel oil concentration and kernel weight in a maize (Zea mays L.) population derived from a cross of Illinois High Protein (IHP) × Illinois Low Protein (ILP). The parental strains had been divergently selected for protein concentration for 76 cycles, yet varied in oil concentration from 29 g kg−1 (ILP) to 54 g kg−1 (IHP) and in 300 kernel weight from 76.5 (ILP) to 41.1 g (IHP). One hundred polymorphic RFLP loci spaced throughout the maize genome were scored in a segregating population of 100 S1 families. Kernel oil concentration and kernel weight were obtained from replicated field trials grown during 1990 and 1991. Significant (P < 0.05 level) QTL associations of 25 marker loci on chromosome arms with oil concentration and 18 marker loci on 10 chromosome arms with kernel weight were identified. These results demonstrate the effectiveness of identification of QTL for oil concentration in strains divergently selected for protein concentration for 76 cycles. Clusters of two or more marker loci in the same chromosomal region were significantly associated with oil concentration at four different chromosomal locations and with kernel weight at four chromosomal locations. The detection of relatively few clusters of marker loci associated with genomic regions controlling oil concentration suggests the development of high oil maize germplasm via RFLP marker‐assisted selection may be feasible.
Assessment of Western Canadian Barleys of Historical Interest: II. Morphology and Phenology
Authors: Jedel Patricia E. , Helm James H.
Published: July 2010

Assessment of morphological and phenological traits is essential if these traits are to be used as selection criteria in breeding programs. The purpose of this study was to evaluate the role several morphological and phenological traits play in the productivity of spring barley (Hordeum vulgare L.) cultivars released from 1910 to 1987 in western Canada. We were interested in evaluating these traits for use in a barley ideotype for the western Canadian prairies. Twenty 6‐ and 2‐rowed feed and malt barley cultivars were tested at Botha, Lacombe, and Olds, Alberta, Canada, in 1989 and 1990. Modern cultivars had shorter intervals between tiller appearance, were shorter in stature, and had later stem elongation, anthesis and maturity than older cultivars. The interval between tiller appearance decreased by 0.02 to 0.06 d yr−1. Plant height decreased by 0.14 to 0.29 cm yr−1. Spike length increased by 0.015 to 0.018 cm yr2212;1, although significant increases were not expressed in all location‐years. Days‐to‐stem‐elongation increased by 0.06 to 0.11 d yr−1; days‐to‐anthesis, by 0.04 to 0.10 d yr−1; and days‐to‐maturity by 0.04 to 0.22 d yr−1. Two‐ and six‐rowed cultivars were morphologically distinct but were phenologically similar. Future improvements in western Canadian spring barleys may be achieved through lengthening the prestem elongation period, and increasing culm diameters. In two‐rowed cultivars, increasing leaf widths may also be advantageous. Morphological and phenological traits have changed in association with historical yield increases and may be used to help define a barley ideotype for the western Canadian prairies.
Identification of RFLP Markers Linked to Crown Rust Resistance Genes Pc 91 and Pc 92 in Oat
Authors: Rooney William L. , Rines Howard W. , Phillips Ronald L.
Published: July 2010

Crown rust, caused by the fungal pathogen Puccinia coronata Cda. f. avenae (Eriks & E. Henn.), is recognized as a major diseasee of cultivated oat (Avena sativa L.). Control of the pathogen has relied on the identification of resistance genes (designated Pc genes) and their incorporation into oat cultivars. However, the limited durability of single genes conferring high levels of resistance to the disease has depleted the number of such resistance genes. New genes and ways to deploy them are needed to ensure adequate resistance in future oat cultivars. Our objectives were to characterize crown rust resistance from two unadapted Avena germplasms and to identify RFLP markers linked to the respective Pc genes. In this study, Pc 91 and Pc 92 were identified from the hexapioid germplasms Amagalon and Obee/ ‘Midsouth’, respectively. At each locus, crown rust resistance was conditioned by the presence of a single dominant allele. In backcross‐derived lines, RFLP markers putatively linked to Pc 91 and Pc 92 were identified, and map distances were calculated using segregating F2 populations for each gene. RFLP probe UMN 145 identified a sequence 4.5 cM from Pc 91 and RFLP probe OG 176 identified a sequence 13.6 cM from Pc 92. Using aneuploid stocks to map the location of RFLP markers, Pc 91 was localized to Chromosome 18, while Pc 92 could not be localized to a chromosome probably because of the lack of the corresponding aneuploid stock. The RFLP markers for these genes may be useful in pyramiding Pc genes in an effort to increase the durability of resistance.
Diallel Analysis of Adult‐Plant Resistance to Powdery Mildew in Wheat
Authors: Das M. K. , Griffey C. A.
Published: July 2010

Adult‐plant resistance (APR) to powdery mildew [Blumeria graminis (DC.) E. O. Speer f. sp. tritici Em. Marchal] in wheat (Triticum aestivum L.) has been documented as being more durable than hypersensitive resistance. However, little is known about the inheritance and diversity of this resistance. Combining abilities and gene effects for APR to powdery mildew were studied in a diallel cross involving one susceptible and six APR cultivars. Parents, F1, and F2 populations were evaluated in replicated field trials under natural epidemics of powdery mildew. Area under the disease progress curve (AUDPC) was used to measure disease severity over time. Significant differences in AUDPC were observed among parents, F1 crosses, and F2 populations. Comparisons of AUDPC values of parents, midparents, and F1 crosses involving susceptible and APR parents indicated that resistance is partially dominant. Non‐additive effects of the resistance genes were also evident from significant contrasts between parents and F1 crosses. While nonadditive gene effects were involved, additive gene effects were predominant in the inheritance of APR to powdery mildew in the materials evaluated. General combining ability (GCA) and specific combining ability (SCA) for mildew resistance were significant in both F1 and F2 generations. GCA was more important than SCA as suggested by large ratios of GCA and SCA variance components [σ2g /(σ2g + σ28)] in F1 (0.75) and F2 (0.86) generations. The wheat cultivars Maris Huntsman, Massey, and Coker 983 had high negative GCA effects and should be promising parents in breeding programs for enhancement of powdery mildew resistance.
Genetic Improvement for Yield and Fertility of Alfalfa Cultivars Representing Different Eras of Breeding
Authors: Holland James B. , Bingham E. T.
Published: July 2010

Alfalfa (Medicago sativa L.) exhibits inbreeding depression for forage yield and also tends to set fewer seeds following self‐pollination than following cross‐pollination. The objectives of this study were to estimate changes in yield potential, inbreeding depression for yield, and self‐ and cross‐fertilities of alfalfa cultivars adapted to Wisconsin and representing different eras of breeding from 1898 to 1985. In addition, two University of Wisconsin‐Madison experimental cultivars with well‐known breeding histories were included in the study. The S0 and S1 populations derived from each cultivar were evaluated for 3 yr for forage yield. Self‐ and cross‐fertilities of some S0 populations were measured in a greenhouse study. Both S0 and S1 populations of modern (Era 3) cultivars yielded greater than those of the oldest (Era 1) cultivars. Era 3 S0 populations generally yielded more than those of cultivars released in the 1940s and 1950s (Era 2) but this was not true for S1 populations. These results suggest that favorable alleles have accumulated in modern alfalfa cultivars but that this mostly occurred between Eras 1 and 2. Inbreeding depression decreased between Eras 1 and 2 and increased between Eras 2 and 3. Increased heterozygosity or exploitation of nonadditive genetic effects may account for much of the improvement in cultivar yield potential that occurred between Eras 2 and 3. Era 3 cultivars had a significantly lower ratio of self‐fertility to cross‐fertility than Era 1 cultivars. Therefore, modern cultivars appear to have improved capacity to produce high proportions of cross‐pollinated seed when nonself pollen is available, compared with older cultivars.
Genotypic Variation for Nitrogen Uptake by Maize Kernels Grown In Vitro
Authors: Czyzewicz Juliann R. , Below Fred E.
Published: July 2010

The role of N in controlling kernel growth of maize (Zea mays L.) is difficult to determine at the whole plant level, especially with regard to genotypic differences. The in vitro kernel culture technique can be used to investigate this problem because it minimizes environmental and maternal influences during grain fill. Therefore, the objective of this study was to characterize genotypic variation in the growth and N content and concentration of in vitro cultured kernels in response to varying N supply. Kernels of eight single‐cross hybrids and four inbreds were grown to maturity in vitro on media containing 0 to 50 mM N and analyzed for dry weight and N composition. Distinct differences in the level of N required to achieve maximum kernel weight were observed for both hybrids and inbreds with the optimum external concentration ranging from 10 to 50 mM. For all genotypes, the pattern of kernel N accumulation in response to N supply was relatively similar, and the N concentrations required to obtain maximum kernel N were greater than those needed for maximum dry weight. Although kernel N concentration increased with increases in N supply, the relative genotypic rankings were similar except at the lowest levels of medium N. These findings indicate that maize genotypes differ in the level of N needed to achieve maximum kernel weight in vitro, which may be due to differences in how kernels utilize N for starch deposition and growth.
Condensed Tannin Relationships with In Vitro Forage Quality Analyses for Birdsfoot Trefoil
Authors: Miller Perry R. , Ehlke Nancy J.
Published: July 2010

Condensed tannins (CT) in birdsfoot trefoil (Lotus corniculatus L.) are associated with reduced degradation of protein and dry matter digestibility by ruminant animals. The objectives of this study were to isolate the effect of CT concentration on in vitro degradable crude protein (IVDCP) and in vitro digestible dry matter (IVDDM) in birdsfoot trefoil herbage containing diverse CT concentrations, to determine the relative influence of IVDCP compared with IVDDM, and to determine minimum CT concentrations effecting reductions in IVDCP and IVDDM. Twelve birdsfoot trefoil clones, genetically diverse for CT concentration, were harvested at St. Paul and Rosemount, MN. Herbage samples with uniform fiber concentrations were arrayed in five tannin groups (n = 3) at regular intervals from minimum to maximum CT concentrations at both locations. Herbage samples were compared for differences between polyethylene glycol (PEG) and control treatments for IVDCP and IVDDM analyses. The protease ficin was used to determine IVDCP. As CT concentration increased, the difference between PEG and control treatments increased for IVDCP and IVDDM (R2 = 0.91 and 0.69, respectively). For tannin groups with mean CT concentrations ≥7.0 g catechin equivalent (CE) kg−1 DM, the PEG and control treatments differed for IVDCP compared with tannin groups containing minimum CT concentrations at both locations. For the tannin group with the maximum CT concentration at Rosemount (85.3 g CE kg−1 DM), the PEG and control treatments differed for IVDDM compared with the tannin group containing the minimum CT concentration. It was concluded that paired‐subsample comparisons between PEG and control treatments was a convenient and consistent method for separating the effect of CT concentration from other sources of variation. These data imply that CT concentrations in the range of 25 to 85 g CE kg−1 DM may reduce ruminal protein degradation, with little or no corresponding reduction in dry matter digestibility.
Evaluation of Wheat Wild Relatives for Resistance to Septoria Tritici Blotch
Authors: McKendry A. L. , Henke G. E.
Published: July 2010

Septoria tritici blotch (STB), caused by the fungus Mycosphaerella graminicola (Fuckel) Schroeter (anamorph: Septoria tritici Roberge in Desmaz), is a major disease of wheat (Triticum aestivum L. em. Thell) world wide. The susceptibility of most commercial cultivars to STB has led to the need to identify new sources of resistance to this disease. Although the wild relatives of wheat have provided a valuable source of many new resistance genes, they have not been widely screened for resistance to STB. The objectives of this study were to identify new sources of STB resistance from the wild relatives of common wheat and to examine relationships among frequency of STB resistant accessions and ecogeographieal parameters. Two hundred and fifty‐four accessions, with genomes homologous to those of hexaploid wheat, were inoculated in the greenhouse with a spore suspension of a mixture of 14 S. tritici isolates collected in Missouri. Accessions with a mean disease reaction <1 on a 0 to 9 scale, ranging from no visible symptoms (0) to complete necrosis of the inoculated leaf (9), were considered resistant. Pearson product‐moment correlation coefficients were determined for seedling disease susceptibility scores and environmental variables measured at the site of collection of each accession. Eighteen of the 19 resistant accessions identified were from T. speltoides and T. tauschii. The frequency of resistant accessions was highest in areas of high rainfall and temperature. Targeting areas with these environmental conditions should facilitate future collection of STB resistant germplasm.
Screening Tropical Maize Populations to Obtain Semiexotic Forage Hybrids
Authors: Bosch Lluís , Casañas Francesc , Ferret Alfred , Sánchez Esther , Nuez Fernando
Published: July 2010

In mild Mediterranean irrigated zones, it is possible to grow late forage maize hybrids (900–1000 United Nations Food and Agriculture Organization [FAO]). These late hybrids should give higher yields than available commercial hybrids (700–800 FAO). This study was conducted to (i) assess whether semiexotic (adapted × tropical) materials would be a viable source of high‐yielding late forage hybrids, (ii) determine the most suitable exotic populations for a breeding program, (iii) evaluate the most important production‐and/or quality‐related traits for selection. Testcrosses of 44 tropical populations by B73 and Mol7 adapted inbreds were evaluated. Field trials, which included three sets of top crosses, were carried out in Northeast Spain. The hybrids B73 × Mo17 (700 FAO) and ‘Pioneer 3183’ (800 FAO) were used as common checks. Twenty‐seven semiexotics yielded more total digestible dry matter than did B73 × Mo17, and seven semiexotics outyielded Pioneer 3183. Higher stover yields, good ear production, and similar stover digestibility are responsible for these results. The B73 testcrosses performed better than Mol7 testcrosses for total digestible dry matter, mainly because of better ear yield. The best‐performing semiexotics included Tuxpeño and Cateto germplasm. Correlations and multiple regression analysis showed that total digestible dry matter depends mainly on ear yield, to a lesser extent on stover production, and little on stover digestibility. The low genetic variability among populations for stover digestibility is probably responsible for the low influence on total digestible dry matter. Increases in stover digestibility should be possible without reducing biomass production because production traits and stover digestibility were not correlated.
Crossing and Morphological Relationships among Native Clovers of Eastern North America
Authors: Taylor N. L. , Gillett J. M. , Campbell J. J. N. , Berger Sandra
Published: July 2010

The Trifolium species of eastern North America now occupy a much reduced area in comparison to their earlier range. These species include T. reflexum L. (buffalo clover), T. stoloniferum Muhl. ex Eaton (running buffalo clover), T. carolinianum Michx. (carolina clover), T. virginicum Small ex Small and Vail (Kate's mountain clover), T. bejariense Moric., and a recently discovered species, T. calcarium Collins and Wieboldt. These species all have some potential for use as pasture, and may have desirable qualities for transfer to more widely used forages, such as T. repens L. (white clover). These species were examined to determine morphological and breeding system relationships in comparison with T. repens, and because several are threatened with extinction, to gain information that may optimize management schemes for their long‐term conservation. Based on morphological characteristics, breeding systems, crossing relationships, chromosome numbers, and forage yields, it was concluded that all species are quite distinct and unrelated to T. repens. All the native species had 16 somatic chromosomes. Two annual species, T. carolinianum and T. bejariense, are autogamously self pollinated, as is another annual, T. reflexum, but which may also be cross pollinated to a limited extent in nature. Trifolium stoloniferum set fewer seeds by selfing than by crossing, but self seed set was adequate to maintain the species in nature. Trifolium calcaricum also produced seeds via self‐pollination. One self population of T. stoloniferum produced less biomass than other self and cross populations, suggesting that inbreeding and subsequent loss of vigor may be a possible cause of its near extinction. However, there is insufficient reason to implicate factors other than habitat destruction and competition with other forage species as primary causes of near extinction.
Selfing in an Alfalfa Seed Production Field
Authors: Brown D. E. , Bingham E. T.
Published: July 2010

Purple‐flowered genotypes of alfalfa (Medicago saliva L.) that were simplex at the P locus (Pppp) were spaced planted and open‐pollinated within a seed production field of Blazer XL alfalfa. Self‐pollination in the field environment was estimated by the frequencies of purple‐ and cream‐flowered progeny from simplex plants. Natural purple‐flower color avoided pollinator preferences found with recessive flower colors. The background level of cream gametes (pp) in Blazer XL and the spaced simplex plants was 5% based on cream progeny of two cream (pppp) male‐sterile clones also planted in the field. Selfing averaged 28% based on greenhouse classified with no competition. Based on progeny that were transplanted in the field, selfing averaged 25% while selfing based on progeny seeded in the field averaged 13%. Direct seeding resulted in fewer cream progeny reflecting decreased survival in competition with hybrid progeny. We observed lower selfing percentages than previous estimates which used recessive flower color markers, but our results were similar to a recent allozyme study.
Genetic Base for North American Public Soybean Cultivars Released between 1947 and 1988
Authors: Gizlice Ziya , Carter T. E. , Burton J. W.
Published: July 2010

A negative consequence of four decades of modern soybean breeding is the evolution of cultivars with complex pedigrees that tend to obscure the genetic base of applied breeding. A result is that the genetic base of North American soybean [Glycine max (L.) Merr.] has never been described fully. We attempt here to define the genetic base as sets of genotypes that contain 99% of the genes found in modern cultivars. For clarity, the base is defined both in terms of the original plant introductions (ancestors) used for hybridization and in terms of the progeny derived from them. In a first analysis of pedigree data, 80 ancestors were identified and their fractional genetic contributions to 258 cultivars were computed using coefficient of parentage (r) estimates. In a second analysis, six breeding lines and 133 cultivars were identified as first progeny of the 80 ancestors, and their contributions as parents to modern cultivars were computed using r. This analysis revealed that 91 first progeny constituted 99% of the genes found in modern cultivars. Lincoln and Harosoy in the North and Lee and its full sib (D49‐2491) in the South contributed nearly 40% of the genes to North American cultivars. Nearly 75% of the genes in modern cultivars trace to 17 first progeny released before 1960, indicating that breeders have remained dependent upon this early genetic core of breeding material. For practical study of the genetic base of North American soybean, we propose using a combination of the results from the two analyses described here. Twenty‐eight ancestors and seven first progeny were identified which contribute 95% of the genes found in modern soybean cultivars. This group of 35 genotypes would be a useful core collection for evaluating the presence, absence, or distribution of a trait in North American soybean cultivars.
Recurrent Selection for Tolerance to Bean Yellow Mosaic Virus in Arrowleaf Clover
Authors: Pemberton I. J. , Smith G. R. , McLaughlin M. R.
Published: July 2010

Arrowleaf clover (Trifolium vesiculosum Savi) is an important forage crop in the southeastern USA, but production and persistence of arrowleaf can be limited by virus diseases. We conducted five cycles of recurrent phenotypic selection from 1986 through 1991 for tolerance to bean yellow mosaic virus (BYMV) isolate KY 204‐1 in arrowleaf clover. Six‐week‐old seedlings were mechanically inoculated with BYMV and evaluated at 100 d of age. From 300 to 1100 plants were screened per cycle, and the most tolerant 1 to 4% were hand‐crossed and their progeny advanced to the next cycle. Seedling dry weights and virus disease ratings were used to estimate the level of virus tolerance of each plant. Rating methods were modified during evaluation of Cycle 5; growth parameters and chlorophyll levels were used as selection criteria. Results were compared with those from the susceptible cultivars, Yuchi, Meechee, and Amclo. Field evaluations compared survival of inoculated Cycle 3A germplasm (1991), and survival, yield, and flowering of Cycles 3A and 5 germplasm (1992), with those of the three susceptible cultivars and non‐inoculated controls. Five cycles of recurrent phenotypic selection in arrowleaf clover resulted in a population possessing tolerance to BYMV. A lethal wilt gene was eliminated from the population, and field survival and dry matter production under disease pressure greatly improved. Tolerant plants maintained normal chlorophyll levels and near normal flowering rates when infected with BYMV, thus ensuring successful seed production.
Selection to Maximize Gross Value per Hectare within Three Soybean Populations
Authors: Orf J. H. , Helms T. C.
Published: July 2010

The value of the soybean [Glycine max (L.) Merr.] to processors is primarily determined by the protein and oil content of the seed, while the value to the producer is determined by the yield. Breeders need to consider how selection for yield can be combined with selection for protein and oil to maximize gross value per hectare (GVH). Previous research has not compared selection criteria within segregating populations to identify lines with the highest GVH. The objective of this study was to select lines from segregating populations for yield, protein, oil, the sum of protein and oil, total kg of protein and oil per hectare, and GVH to determine which criterion identified lines with the highest GVH. Experimental lines selected from three populations were evaluated for GVH, based on three protein to oil price ratios. GVH of lines selected for yield was equal to that of lines selected for a combination of yield, protein, and oil content. Based on this study it appears that soybean breeders who have a goal of maximizing GVH can select solely for yield and avoid expensive protein and oil testing. The lines that were high in protein, oil, or sum of protein and oil content, were low yielding and low in GVH at all three protein to oil price ratios. The higher value per kilogram seed of lines selected for protein, oil, or the sum of protein and oil content, did not compensate for the lower yield.
Relationships among European Barley Germplasm: II. Comparison of RFLP and Pedigree Data
Authors: Graner Andreas , Ludwig Werner F. , Melchinger Albrecht E.
Published: July 2010

Information about the genetic relationships among genotypes is of great importance to breeders of barley (Hordeum vulgare L.) and other self‐pollinated crops. In the past, genetic similarity was mainly estimated by Malécot's coefficient of coancestry (f). However, estimates of f may not always reflect the true relationship between genotypes because of selection, random genetic drift, and other causes. In this study, we analyzed 24 winter and 24 spring barley cultivars from the European barley germplasm by means of restriction fragment length polymorphism (RFLP) and pedigree analyses. Our main objective was to compare genetic similarity (GS) based on RFLP data of 136 clone‐enzyme combinations (CEC) with coancestry (f) for their ability to quantify the degree of relatedness among barley genotypes. Rank correlations between GS and ffor related (f ≥ 0.10) pairs of cultivars were weak for both winter (rs = 0.21) and spring barley cultivars (rs = 0.42). Based on linear regression of GS on f, coancestry explained 6 and 14% of the variation in GS for related (f ≥ 0.10) pairs of winter and spring barley cultivars, respectively. The weak correlations can be explained primarily by (i) unrealistic assumptions in calculation of f and (ii) substantial variation in GS estimates of unrelated cultivars. In conclusion, coancestry seems less suited than RFLP‐based GS estimates to quantify the genetic relationships among barley cultivars for many applications in breeding.
Inheritance of Glycinebetaine Deficiency in Sorghum
Authors: Grote E. M. , Ejeta G. , Rhodes D.
Published: July 2010

Glycinebetaine (N,N,N‐trimethylglycine; betaine) accumulates in many species of the Poaceae and Chenopodiaceae. This accumulation is thought to be a metabolic response to osmotic stress which protects enzymes during heat and dehydration. Glycinebetaine deficient mutations have been identified and their genetic control elucidated in cereal crops including barley (Hordeum vulgare L.) and maize (Zea mays L.) The objective of this study was to determine the mode of inheritance of newly identified glycinebetaine deficient lines of sorghum [Sorghum bicolor (L.) Moench], Crosses were made between three high glycinebetaine (>20 μmol gfw−1) and three glycinebetaine deficient (<1 μmol gfw−1) varieties from which F1, F2, and backcross progenies were generated. A colorimetric assay was used to screen leaf samples collected from field grown parental, F1, and segregating progenies for glycinebetaine levels. Reciprocal F1 plants in each cross were not significantly different from each other. Approximately one‐fourth of the F2 plants in each cross exhibited the glycinebetaine deficiency, supporting the theory of single gene inheritance. Backcrosses to deficient parents segregated 1:1 for deficiency, further supporting this hypothesis. Gene action was primarily additive based on generation mean analysis of high and low parents, F1 progenies, and backcrosses to the respective parents. A small degree of dominance for glycinebetaine production was exhibited in the F1 generation.
Waterlogging Effects on Yield and Photosynthesis in Eight Winter Wheat Cultivars
Authors: Musgrave M. E.
Published: July 2010

Winter wheat (Triticum aestivum L. emend. Thell.) yields in Louisiana are consistently below the national average because of a combination of biotic and abiotic environmental factors prevailing in the Gulf Coast region. This study was undertaken to estimate the yield loss for wheat that is attributable to soil waterlogging and to compare physiological performance under waterlogging‐stressed conditions by cultivars grown in Louisiana. In a 3‐yr pot study conducted in a greenhouse, waterlogging stress was imposed by raising the water level to the soil surface. This treatment reduced the soil redox potential in the pots from an average of 409 to 149 mV, indicating an absence of free oxygen in the rootzone. Compared with a well‐drained control treatment, grain weight was depressed 37 to 45% by waterlogging in the eight cultivars tested. In a field experiment with ‘Coker 9877’, grain weight was depressed 51% in poorly drained plots compared with well‐drained plots. Yield depression was due to reduced kernel number and kernel weight rather than to an effect on stand establishment. In the greenhouse experiments, flag‐leaf photosynthesis correlated well with grain weight in the cultivars tested. Waterlogging caused only a small suppression of flag‐leaf photosynthesis and leaf conductance, and there were no significant interactions between treatment and cultivar. These commercially available cultivars showed an equally poor tolerance of waterlogging stress. The results emphasize the need for identification of waterlogging tolerance in wheat cultivars developed for the Gulf Coast states.
Kura Clover Seed Production when Intercropped with Wheat
Authors: Steiner J. J. , Snelling J. P.
Published: July 2010

Kura clover (Trifolium ambiguum M. Bieb.) is a slow‐establishing rhizomatous perennial that has lower seed yields the year after establishment than in subsequent years of production. For new forage crops such as kura clover to be utilized, adequate seed supplies must be available. The objective of this research was to determine whether ‘Rhizo’ kura clover grown for seed can be established with intercropped wheat (Triticum aestivum L.) to increase seed grower net income. Kura clover was planted in spring 1989 and 1990. The clover was grown alone (sole‐cropped) and intercropped with companion‐planted wheat in 15‐ and 30‐cm rows and with relay‐planted wheat in 20‐ and 40‐cm rows. The clover was established with sprinkler irrigation. Sole‐crop kura clover establishment was superior to clover intercropped with wheat. When clover was grown with intercropped wheat, establishment was superior with wide‐spaced compared to narrow‐spaced wheat. The delay in clover establishment from spring‐planted clover relay‐intercropped with fall‐planted wheat was similar to spring‐planted clover companion‐intercropped with wheat. Kura clover was more tolerant of relay‐ than companion‐intercropping because clover seedlings were allowed to establish before the onset of wheat crop competition. Spring‐planted kura clover relay‐intercropped with fall‐planted wheat in 40‐cm rows had the greatest economic return of all treatments. Depending on seed price, all kura clover production systems could be made profitable. However, none of the profitable clover production systems had net income returns equal to wheat grown alone.
Nitrogen Fertilizer Affects Amino Acid Composition and Quality of Spring Barley Grain
Authors: Bulman Patrick , Zarkadas Constantinos G. , Smith Donald L.
Published: July 2010

High N rates used to raise yields and the grain protein concentration (GPC) of cereal crops may lower the nutritional value of the grain by reducing the proportion of essential amino acids in the grain protein. Since spring barley (Hordeum vulgare L.) is an important feed grain for monogastric animals in eastern Canada, a 2‐yr field experiment was conducted to determine N fertilization effects on the amino acid composition of the grain protein. Two cultivars, Leger (adapted feed type) and Argyle (unadapted malting type) were grown with four fertilizer treatments. The four fertilizer treatments were 0 or 100 kg N ha−1 applied as ammonium nitrate at seeding, or with 100 kg N ha−1 at seeding plus 50 kg N ha−1 applied at awn emergence as broadcast ammonium nitrate (not included in 1988) or foliar‐applied urea. Amino acid analyses were conducted by ion exchange chromatography. Nitrogen treatments increased protein per grain in both years, but increased GPC in 1988 only. In 1987, N treatments decreased the proportion of lysine in the grain protein but did not affect other amino acids. In 1988, increased N rates reduced the proportion of aspartic acid, threonine, glycine, lysine, and arginine but increased the proportion of glutamic acid and proline in grain protein. Higher N rates reduced the proportion of cyst(e)ine in grain protein in Leger only. Cultivar differences in amino acid composition were inconsistent between years. Higher rates of N fertilizer increased protein per grain and GPC but lowered the nutritional value of barley grain.
Isozyme Evidence Supporting a Single Geographic Origin for Domesticated Tepary Bean
Authors: Garvin David F. , Weeden Norman F.
Published: July 2010

Crop domestication and evolution studies can provide valuable information about genetic diversity. The domestication pattern of tepary bean, Phaseolus acutifolius A. Gray, which is recognized as a possible source of genes for improving common bean (Phaseolus vulgaris L.), has yet to be resolved. We used starch gel electrophoresis to examine aconitase allozyme variation in seeds from 263 accessions of wild and domesticated tepary bean. Gene frequency data for wild and domesticated tepary bean were then compared in an attempt to clarify tepary bean domestication. Two ACO isozymes were detected. Whereas ACO‐1 was monomorphic, two allozymes were detected for ACO‐2. The allele encoding the slower migrating ACO‐2 allozyme was present in domesticated tepary bean at a frequency of 0.997, whereas the frequency of the fast allele in wild tepary bean was found to be 0.96. This pattern of ACO‐2 allozyme variation suggests that tepary bean was domesticated in a single geographic region, and predicts a genetic bottleneck during tepary bean domestication. Based upon our results, the Mexican states of Jalisco and Sinaloa are two potential geographic origins of domesticated tepary bean. This confirms the results of some previous studies and suggests that broad surveys of tepary bean germplasm for specific traits should focus on wild rather than domesticated forms of the species. In contrast, well‐documented characteristics of tepary bean such as drought tolerance may be transferred to common bean by choosing only a few domesticated tepary bean parents that cross well with common bean.
Protein Degradability in a Diverse Array of Alfalfa Germplasm Sources
Authors: Skinner D. Z. , Fritz J. O. , Klocke L. L.
Published: July 2010

The shortcomings of alfalfa (Medicago sativa L.) as a high quality forage include extensive ruminal degradation of the forage protein, sometimes with concomitant loss through ammonia formation. This study was conducted to determine if significant differences exist in the degradability of forage protein among nine basic alfalfa germplasm sources, and germplasms with epidermal glandular hairs from M. glandulosa David or M. glutinosa M.B. Inter‐ and intrapopulation variation of protein degradability was assessed by an in vitro test based on the extent of degradation by the proteolytic enzyme ficin. The rates of degradation were significantly different among the alfalfa lines, but the proportions of protein lost were equivalent after a 2‐h digestion. Intrapopulation variation, assessed with 10 plants from each of 10 sources, was quite high, suggesting that adapted cultivars with decreased protein degradability could be developed through conventional breeding methods, if selections were carried out on an individual plant basis.
Genetic Changes Associated with Different Methods of Recurrent Selection in Five Maize Populations: I. Directly Selected Traits
Authors: Stojšin Duška , Kannenberg L. W.
Published: July 2010

Several methods of recurrent selection have been developed in maize (Zea mays L.), but information is lacking on which is most effective. A confounding factor is that progress may be hindered by inbreeding depression associated with random changes of allelic frequencies due to the constraints of small effective population sizes. The objectives of this study were to (i) compare the effectiveness of four selection methods in five maize populations (CGSynA, CGSynB, CGG, CGN, and CGW) improved for performance indices involving grain yield, grain moisture, and plant lodging, (ii) separate effects of selection from those due to random drift, and (iii) estimate additive and dominance gene effects contributing to response to selection. Four selection procedures were compared: modified ear‐to‐row (ME) in CGSynA, CGSynB, CGG, and CGN; half‐sib family (I‐IS) in all five populations; seffed progeny (S) in all five populations; and reciprocal recurrent selection (RRS) in CGSynA and CGW. In general, performance indices increased with concomitant increases in yield and decreases in moisture and lodging. Generally, S was the most effective selection procedure and HS was second best. Response to selection was attributed to changing the frequencies of alleles with mostly (i) dominance effects. in ME selection, (ii) additive effects in S and, (iii) either dominance or additive effects in HS and RRS. Estimates of genetic drift effects were predominantly of the opposite sign from the direction of response to selection. The S procedure resulted in the greatest genetic drift in three of the five populations, whereas HS suffered minimal genetic drift effects. This study indicated that there is no selection method that is best under all circumstances.
Increasing Assimilate Reserves Does Not Prevent Kernel Abortion at Low Water Potential in Maize
Authors: Schussler J. R. , Westgate M. E.
Published: July 2010

Water deficits during anthesis cause maize (Zea mays L.) kernels to abort soon after fertilization. Inhibition of photosynthesis accounts for much of the kernel loss, but lack of assimilate reserves might also limit kernel development. We tested whether varying the level of C and N reserves prior to anthesis affected kernel set of plants pollinated at low water potential (Ψv). Plants were grown in sand/soil media in pots in the field under one of three light environments: Control, 75‐cm rows, 4.3 plants m−2; Shade, same as Control except under 55% shade cloth from V6 until maturity; or Isolated, 122‐cm rows, 0.7 plants m−2. These treatments produced a 3.3‐fold range in total extractable carbohydrate (TEC) and a 1.7‐fold range in total Kjeldahl nitrogen (TKN) per plant at silk emergence. Water was withheld at silk emergence and plants were pollinated by hand with excess pollen 4 d later when silk Ψw was = −1.1 MPa, leaf Ψw was = −1.8 MPa, and photosynthesis was completely inhibited. Plants were rewatered 2 d after pollination and remained well watered until physiological maturity. The brief water deficit decreased kernels per ear by 45% in the Controls, 72% in the Shade treatment, and 49% in the Isolated treatment. Lower kernel set in the Shade treatment was associated with low levels of TEC and TKN in the vegetative stalk, leaves, and reproductive stalk, compared with Control plants. However, accumulation of TEC and TKN in excess of Control values in the Isolated plants did not prevent kernel loss. Kernel set in all three treatments was more closely related to the rate of photosynthesis prior to imposing the water deficit than to the level of reserves accumulated prior to flowering. These results suggest that selection for high levels of reserves at pollination will not improve kernel set at low Ψw in maize.
Tillering Response of Barley to Shifts in Light Quality Caused by Neighboring Plants
Authors: Davis Michael H. , Simmons Steve R.
Published: July 2010

Tillering is important in establishing the yields potential of spring barley (Hordeum vulgare L.). Two field experiments were conducted for 3 yr to test if early season shifts in the red/far‐red ration (R/FR) modulate barley tillering patterns. Experiments were designed to determine (i) the extent to which shifts in light quality associated with the presence of neigboring plants modulate barley tillering patterns in the absence of shading and competition for soil resources, (ii) barley responses to sudden changes in light quality during the tillering phase, (iii) the influence of plant spacing on response to shifts in light quality, and (iv) the impact of the response to shifts in light quality on productivity. Plans within treatment rows were grown 18 cm from densely sown border rows of barley. Barriers set into the soil assured negligible competition between border and treatment rows for soil resources during the early growing season. The borders functioned to reflect light, especially far‐red (FR), which reduced R/FR within the treatment rows without shading them. Tiller production was reduced in bordered plants relative to unbordered controls. The removal of borders at 20 d after emergence (DAE) caused an increase in treatment row tiller production, whereas the imposition of boreders at 20 DAE halted tillering. Shoot survival was increased by the presence of borders. Border effects on final spike number, biomass production, and grain yield per plant were inconsistent during the experiments. We conclude theat early season shifts in light quality associated with FR refelection from neighboring plants contribute to modulating barley tillering under field conditions.
Soybean Seed Discoloration and Cracking in Response to Low Temperatures during Early Reproductive Growth
Authors: Srinivasan Ancha , Arihara Joji
Published: July 2010

Prevalence of low temperatures during the flowering adversely affects appearance and quality of soybean [Glycine max (L.) Merr.] seeds at maturity. Our objective was to describe the nature of damage and factors influencing seed quality in a sensitive soybean cv. Kitakomachi and examine genotypic variation in tolerance to discoloration and cracking. The damage was most evident in plants exposed to 15°C (day/night) for 2 to 3 wk commencing from anthesis or 1 wk thereafter. Kitakomachi was sensitive to both discoloration and cracking, whereas Tokei 795 and Tokei 782 were tolerant to discoloratoin and cracking, respectively. Discoloration was first seen when seeds were about 70 to 80% of maximum size. Qualitative histochemical tests indicated a greater presence of phenolics in the palisade layer of the discolored seet coat. Cracking was confined to the upper layers of the seed coat and was associated with damage to osteosclereids. More damage to parenchyma in the funiculus and to osteosclereids in the seed coat was noticed in sensitive genotypes following exposure to cold stress. Within a pair of isolines differing in nodulation, the nodulating line showed more damage than the non‐nodulating line. Additional N fertilization showed varied effects on discoloration depending on duration of chilling and genetpe, but it increased cracking. In contrast, excess soil water status incresed discoloration. Further improvements in crop tolerance and agronomic practise are necessary to produce quality soybeans in cool climates.
Variation for Preharvest Sprouting Resistance in Durum Wheat
Authors: Clarke John M. , DePauw Ronald M. , McLeod J. Grant , McCraig Thomas N.
Published: July 2010

Preharvest sprouting may reduce end‐use quality and is thus an important grading criterion in all market classes of wheat (Triticum spp.). There are few reports in the literature of genetic variation in preharvest sprouting resistance in durum wheat (T. turgidum L. var durum), and the only apparent attempts to breed sprouting resistant durums have been to transfer resistance from red common wheat (T. aestivum L.). Use of resistance sources within the durum species would be easier, so this study was undertaken to assess the variation for sprouting resistance in durum. Sprouting resistance of 185 durum genotypes was evaluated in 1990. Unreplicated samples of 10 spikes from each genotype were evaluated in an artificial rain chamber. Sixty of these genotypes were re‐evaluated in a replicated study in 1991. The 1990 study indicated that the durums had a similar range in sprouting score (spikes out of 10 showing visible sprouts) to the common wheat checks. The sprouting scores of the red (5.8 ± 3.7, n = 30) and white (6.5 ± 3.0, n = 149) genotypes were not different (P < 0.05). Sprouting score measured in 1991 was correlated with that of 1990 (r = 0.55, n = 60). We conclude that there is considerable genetic variation in sprouting resistance in durum that can be more easily exploited by durum breeders than common wheat sources of resistance.
Mowing of Three Fescue Species for Low‐Maintenance Turf Sites
Authors: Dernoeden P. H. , Carroll M. J. , Krouse J. M.
Published: July 2010

While Festuca spp. are suited to low management,there is little information regarding their performance with little or no inputs of irrigation, fertilizer, or herbicides. In this 3‐yr field study, the quality of ‘Bighorn’ blue fescue [Festuca ovina L. spp. glauca (Lam.)W.D.J. Koch], ‘Aurora’ hard rescue (F. longifolia Thuill.), and ‘Silverado’ and ‘Rebel II’ tall rescue (F. arundinacea Schreber) were compared under three mowing regimes. Turf received no supplemental irrigation or fertilizer following seedling emergence. The three mowing regimes were mowing as needed to a height of $.5 cm (Regime I); monthly mowing to a height of 8.0 cm (Regime H); and monthly mowing initiated following seedhead senescence to a height of 8.0 cm (Regime HI). Initially, both tall rescue (TF) cultivars exhibited very good quality. Within I yr of seeding, however, Bighorn and Aurora quality surpassed that of both TF cultivars. Both TF cultivars were more rapidly and extensively invaded by smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb.] and white clover (Trifolium repens L.) than either Bighorn or Aurora following a spring drought in the second year of study. By the second summer and thereafter, Bighorng enerally received the highest quality ratings followed by Aurora. Turf maintained in Regime I was generally of higher quality, but seasonal quality ratings during the latter 2 yr of the study were similar for Regimes I and II. Lowest turf quality was most often associated with Regime III, particularly during spring and summer. Herbicide use in the final study year was important in improving the quality and cover of the TF cultivars but only slightly improved Bighorn or Aurora quality. Hence, in a 3‐yr absence of irrigation or fertilizer inputs, Bighorn and Aurora maintained better quality and better resisted weed invasion compared with the TF cultivars evaluated.
Pollen Storage in Frostless and Conventional Frost‐Forming Freezers
Authors: Hanna Wayne W.
Published: July 2010

Pollen storage allows more effacient use and handling of germplasm. This study was conducted for 3 yr to determine if longevity differed for pollen stored in screw‐cap glass vials or reclosable plastic bags in a conventionaol r a frostless freezer. Viability of pearl millet [Pennisetum glaucum (L.) R. Br.] pollen stored in reclosable plastic bags was maintained for more than 1 yr in a frastless freezer, whereas pollen viability was lost within 1 yr when stored in a conventional frostforming freezer due to buildup of pollen moisture. Viability of pollen stored in screw‐cap glass vials was maintained equally wall in both freezer types and lasted for more than 2 yr.