bluuebunny/crossref_metadata_2025 huggingface dataset:
β‐Glucan Content and Its Relationship to Agronomic Characteristics in Elite Oat Germplasm
Authors: Peterson David M. , Wesenberg Darrell M. , Burrup Dave E.
Published: July 2010

Oat (Avena sativa L.) cultivars with nigh β‐glucan concentration may be useful as a specialty crop for human food. The objective of this study was to evaluate elite oat germplasm, as represented by the 1988–1991 Uniform Midseason Oat Nursery (UMON) and Uniform Early Oat Nursery (UEON) grown at Aberdeen, ID, and the Uniform Northwestern States Oat Nursery (UNSON) grown at Aberdeen and Tetonia, ID, for β‐glucan concentration. Relationships between β‐glucan concentration and other agronomic traits were examined. The stability of β‐glucan concentration among environments was determined. The β‐glucan concentrations of entries in the three nurseries ranged between a low of 30 to 47 g kg−1 and a high of 61 to 70 g kg−1 depending on the year and were different among genotypes. Tnirty‐three genotypes were common to all nine environments of the UNSON. The majority of correlations between environments on a pair‐wise basis were low, but significant, and stability parameters varied among genotypes. Correlations between β‐glucan concentration and agronomic traits were generally nonexistent or inconsistent across years or nurseries for the UMON and the UEON. For the UNSON, there were consistent significant positive correlations between β‐glucan concentration and test weight, protein percentage, and groat percentage and negative correlations with heading date. We concluded that genotypic variation for β‐glucan concentration is sufficient to enable breeding progress. Because β‐glucan concentration was not consistently correlated with other traits, concurrent undesirable shifts in other traits should not hinder breeding progress.
Forage Yield and Quality of a Brown Mid‐Rib Mutant in Pearl Millet
Authors: Degenhart N. R. , Werner B. K. , Burton G. W.
Published: July 2010

Pearl millet (Pennisetum glaucum L.) is used extensively as forage for livestock, and any improvement in forage digestibility may enhance feeding value. The effect of a pearl millet brown mid‐rib gene (bmr) on forage quality and yield was evaluated using near‐isogenic lines. An F1 and two backcrosses were made to an inbred line (T85DB) incorporate the bmr gene into a non‐bmr background. From this crossing scheme, random F2 plants were selfed to produce F3 lines that were planted in a randomized complete‐block yield trial in Tifton, GA, during 1990 and 1991. Random F2 plants from the same cross were planted in 1989 and 1991 to evaluate forage yield and quality differences of leaf sheath, leaf blade, and stem fractions from normal and brown mid‐rib plants. Brown mid‐rib lines yielded 77% as much forage as normal F3 lines. Forage in vitro dry matter digestibility was 5 percentage units greater for brown mid‐rib lines compared with normal lines. Brown mid‐rib F2 plants produced 73% as much stem biomass as the normal phenotype. Stem fraction digestibility of brown mid‐rib plants was 11 percentage units greater than that from normal plants. The digestibility of leaf blade, leaf sheath, and head fractions were only 2.4, 3.6, and 3.6 percentage units, respectively, greater for brown mid‐rib plants vs. normal plants. Negative pleiotrophic effects attributed to the bmr gene on forage yield for the genotype in this study may offset any advantages gained in forage digestibility.
Inheritance of Tolerance to Manganese Deficiency in Soybean
Authors: Graham M. J. , Nickell C. D. , Hoeft R. G.
Published: July 2010

Manganese deficiency is a recurring problem in soybean [Glycine max (L.) Merr.] grown on high pH soils. Presently, the application of chemical fertilizers is used to alleviate yield losses associated with this deficiency. Because chemical control is often ineffective, genetic tolerance could be used in areas where Mn deficiency is a problem. The development of soybean genotypes tolerant to Mn deficiency is facilitated if the mode of inheritance is understood. The F2 and F2:3 progeny of the tolerant germplasm line A14 and the intolerant cultivar Pride B216 were evaluated in the field for tolerance to Mn deficiency. The observed wide range in progeny response to Mn deficiency suggested digenic inheritance. This model was supported by the results of a cluster analysis applied to the F2:3 family mean ratings and variances. Low estimates of narrow sense heritability (h2 = 0.19) in the F2 generation indicated that F2 phenotypic differences were largely due to environmental variation, thereby making yield selection for tolerance to Mn deficiency in the F2 generation difficult. Estimates of narrow sense heritability based on F2:3 family means were greater (h2 = 0.70), indicating that selection based on F2:3 family means should be effective.
Selection Response for Seedling Root Length and Coleoptile Length in Pearl Millet
Authors: M'Ragwa L. R. F. , Watson C. E. , Gourley L. M.
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] production in semiarid areas is primarily limited by poor seedling emergence and poor stands, which result in low yields. The objectives of this study were to measure selection response for seedling root length and coleoptile length, and to compare the effectiveness of greenhouse and laboratory screening procedures for these traits. Divergent phenotypic recurrent selection for seedling root length and coleoptile length was practiced within each of two populations, Tift #2 S1 (TIFT2) and Nebraska Early Dwarf Synthetic (NPM2). The parental and respective selected populations were evaluated in sand in the greenhouse and in paper germination towels in the laboratory. Significant genetic variation was found for seedling root length in the genetically diverse TIFT2 population, but not in the NPM2 population. The TIFT2 subpopulation selected for long seedling root length in sand had significantly longer seedling root length than the subpopulation selected for short seedling root length. Genetic variation for coleoptile length was high in both populations. There were significant responses to selection in the TIFT2 population for seedling root length evaluated in sand and coleoptile length evaluated in germination towels. Selection response for long seedling root length in the TIFT2 population was greater when root length was evaluated in sand than when evaluated in germination towels. Realized heritabilities of TIFT2 subpopulations selected for long and short seedling root length in sand were 0.23 and 0.29, respectively. Realized heritabilities of TIFT2 populations selected for long and short seedling root length in paper germination towels were 0.0 and 0.33, respectively. Sand was a better selection medium than germination towels. Realized heritabilities for long and short coleoptile length were 0.21 and 0.55, respectively, for the TIFT2 population. For the NPM2 population, realized heritabilities for long and short seedling root length were 0.60 and 0.0, respectively, in sand and 0.0 and 0.26, respectively, in germination towels. Realized heritabilities for long and short coleoptile length were 0.0 and 0.90, respectively, for the NPM2 population. Pearl millet coleoptile and seedling root lengths were heritable and further selection gains should be possible.
Performance of Exotic × Temperate Single‐Cross Maize Hybrids
Authors: Godshalk E. Brent , Kauffmann Keith D.
Published: July 2010

Maize (Zea mays L.) hybrids were produced by crossing exotic and temperate inbred fines. A total of 12 exotic lines, four from each of three exotic groups (Argentine flint, ETO, and Tuxpeno), were crossed with 16 temperate inbred lines, four from each of four temperate inbred groups (B37, B73, OH43, and MO17). The hybrids were evaluated in 1992 at Leesburg, GA, and Oglethorpe, GA. This study was conducted to identify superior combinations of temperate and exotic heterotic groups. Generally, hybrids with either B73‐derived or Tuxpeno lines had high yield, high grain moisture, high root lodging, and moderate stalk lodging. The B73 × Tuxpeno hybrids had the highest mean yield. Yield of B73 × exotic hybrids was not significantly different from the mean of the checks, whereas the remaining exotic‐temperate combinations had yield significantly less than the checks. Argentine flint lines combined well with B37 and B73 lines, whereas ETO lines produced high yield when crossed with B73 and OH43 lines. Overall, Tuxpeno lines demonstrated higher combining ability with temperate lines than did the Argentine flint or ETO derived lines. Results from this study suggest considerable potential for exploiting exotic germplasm to improve temperate material, especially the MO17 and OH43 derived lines.
Patterns of Variation in a Collection of Perennial Ryegrass Accessions
Authors: Casler M. D.
Published: July 2010

Perennial ryegrass (Lolium perenne L.) is a relatively new crop in temperate North America. Cultivars for use in this region have been introduced from temperate regions of Europe, Australia, or New Zealand. Because environmental conditions of these areas differ from those of temperate North America, currently used cultivars may not be the most appropriate for this latter region. The objectives of this study were to (i) estimate and describe quantitative genetic variation in the USDA perennial ryegrass collection, (ii) use this information to develop recommendations for future germplasm exploration, and (iii) initiate development of a core collection. Plants of 375 accessions, representing the entire collection to date, were evaluated at two Wisconsin locations for seedling vigor, leaf width, reaction to crown rust (Puccinia coronata Corda), and forage yield in 1991 and 1992. Accessions collected from cultivated sources averaged 6% greater seedling vigor, 6% wider leaves, 22% lower incidence of crown rust, and 20% higher forage yield than those from naturalized (cultivar adaptation to a local ecosystem) sources. Genotypic and phenotypic variance estimates were similar for both naturalized and cultivated groups. Thus, more than 60 yr of intensive ryegrass breeding has not greatly reduced genotypic variation among cultivated populations. Based on principal components analysis, expansion of the collection should focus on the Mediterranean Basin if the goal is to preserve natural variation, or on Eastern Europe and New Zealand if the goal is to collect germplasm with maximum forage yield for environments similar to southern and central Wisconsin. Cluster analysis was useful in identifying groups of accessions with superior performance for four traits and in classifying accessions to identify a core collection which preserved most of the phenotypic variation found within the entire collection.
Estimation of Genetic Parameters for Resistance to Erwinia Soft rot, Specific Gravity, and Calcium Concentration in Diploid Potatoes
Authors: Wolters Petra J. C. C. , Collins Wanda W.
Published: July 2010

Tubers of clones from a diploid Solarium phureja Juz. & Buk.‐S. stenotomum Juz. & Buk. hybrid population were evaluated for Erwinia resistance, specific gravity, Ca concentration, size, shape, eye depth, skin color, and overall appearance. Clones from four different steps in a selection process for high specific gravity were used. The first step consisted of clones with no selection for high specific gravity, and the fourth step consisted of the most advanced clones in the selection process for high specific gravity. Half‐sib families of these clones were grown, and tubers were evaluated for the same traits as the parent clones (except for Ca concentration). Parent clones and half‐sib families of Step 2 were planted on two different dates. Heritability estimates were determined for Ca concentration, tuber size, tuber shape, eye depth, skin color, and overall tuber appearance. Broad‐ and narrowsense heritability were estimated for each selection step and date separately. Estimates for broad‐sense heritability were high for all traits except for tuber shape. Narrow‐sense heritability (averaged across five estimates) was highest for skin color (0.51) and eye depth (0.52). The average narrow‐sense heritability estimates were moderate to low for tuber appearance (0.27) and near zero for tuber size and shape ( & 0.03 and 0.06, respectively). Results indicate that genetic improvement of the population should be possible for skin color, eye depth, and tuber appearance. The low to moderate estimates of narrow‐sense heritability suggest that family selection is needed for improvement. The low to moderate genotypic correlation coefficients between traits indicate that simultaneous selection for Erwinia resistance, specific gravity, Ca content, and overall tuber appearance is feasible.
Evaluation of Maize Populations as Sources of Favorable Alleles for Improvement of Two Single‐Cross Hybrids
Authors: Stojšin Duška , Kannenberg L. W.
Published: July 2010

Adapted and selected populations are expected to be good sources of favorable alleles for immediate improvement of an elite hybrid. We studied 17 maize (Zea mays L.) populations from recurrent selection programs based on performance indices (involving grain yield, moisture, and lodging). These populations represented initial (CO) and advanced selection cycles (Cn) in five sources: CGSynA, CGSynB, CGG,C GN, and CGWT. he objectives of this study were to (i) identify populations that are the best sources of favorable alleles to be used for improving two single‐cross hybrids (CG28 × CO265 and CGKX86 × CO265); (ii) estimate relationship values to determine which inbred parent should be improved; and (iii) determine if the inbred x population cross should be backcrossed to the inbred line prior to selfing. Generally, there were few significant differences among the 17 populations as potential sources for improving the two hybrids. This suggests that either the genetic method was not sensitive enough to detect differences among the populations or that in fact there were no real differences among them as sources of favorable alleles for the two single‐cross hybrids. Generally, CGSynA(HS)C10 and CGW(RRS)C4 were the best sources of favorable alleles, whereas CGNC0 was the worst for improving performance indices and grain yield in the two hybrids. CGSynA,C GG, CGN, and CGW could be used for improving CG28 and CGKX86, whereas CGSynB would be a suitable source of favorable alleles for CO265. Generally, selfing would be the preferred method of developing improved inbred lines for most selected populations; backcrossing to the inbred line prior to selfing should be done if unadapted and/or unselected populations are used as sources of favorable alleles for improving hybrids.
Mowing Height and Vertical Mowing Frequency Effects on Putting Green Quality
Authors: Salaiz T. A. , Horst G. L. , Shearman R. C.
Published: July 2010

Lowering mowing heights to increase creeping bentgrass (Agrostis palustris Huds.) putting green speed (i.e., ball roll distance) is a common practice. This practice can increase turfgrass susceptibility to heat and drought stress. Other cultural practices might be used to improve putting green quality and speed without additional stress. In this study, vertical mowing was used as a grooming technique to potentially improve putting green quality and speed. A ‘Penncross’ creeping bentgrass turf, established in 1986, was mowed daily at 3.2, 4.0, and 4.8 mm in combination with vertical mowing frequency treatments of 1 and 2 times per month, and a check of no vertical mowing. Mowing height and vertical mowing frequency effects on ball roll distance, turfgrass color and quality, and root production were evaluated in this study during 1989 and 1990. Vertical mowing treatments did not affect ball roll distance, turfgrass color and quality, or root production. Ball roll distance decreased by 0.2 m in 1989 and 0.4 m in 1990 as mowing height increased from 3.2 to 4.8 mm. Relative putting green speeds were rated as fast (i.e., > 2.6 m) across mowing height in 1989, and medium‐fast to fast (i.e. 2.3–2.6 m) in 1990. Turfgrass color, quality, and root production increased with mowing height in 1989 and 1.0 unit in 1990. Turfgrass quality increased by 0.4 rating unit per mm increase in mowing height in 1989 and 1.0 unit in 1990. Root production at two soil depths of 75 to 150 mm and 150 to 225 mm increased with mowing height in 1990.
A Co‐Dominant PCR‐Based Marker for Assisted Selection of Durable Stem Rust Resistance in Barley
Authors: Horvath David P. , Dahleen Lynn S. , Stebbing Jo‐Ann , Penner Greg
Published: July 2010

Screening individual barley plants for resistance to stem rust is difficult and time consuming. The objective of this work was to develop PCR‐based markers for assisted selection of stem rust resistance in barley. Near isogenic barley lines (backcrossed 29 times) differing at the Rpg1 locus (where the gene that confers resistance to the stem rust pathogen Puccinia graminis t. sp. tritici is located) were screened for random amplified polymorphic DNAs (RAPDs) with 10 base primers. A total of 540 different primers were screened, and one was identified which amplified a DNA fragment closely linked to Rpg1. The DNA fragment was cloned, mapped, and sequenced. Specifically amplifying primers (SAPs) were designed to amplify related polymorphic DNA in other barley cultivars. The SAPs act as a co‐dominant marker suitable for marker assisted selection of the Rpg1 gene. Three different amplification patterns were observed in the various cultivars tested. Surprisingly, no specific banding pattern is diagnostic for the presence or absence of Rpg1, despite the demonstrated linkage. Of the three amplification patterns, only one (the 500‐bp banding pattern) was present in recently developed resistant cultivars. A similar amplification pattern is also found in many of the susceptible lines that have the cultivar Betzes in their pedigree. RFLP analysis can be used to differentiate the resistant and susceptible cultivars with this amplification pattern.
Mechanisms of Genic Male Sterility
Authors: Horner Harry T. , Palmer Reid G.
Published: July 2010

For normal sexual reproductive development, coordination must occur between both male and female organ ontogeny. An abnormality at any point in this process may lead to sterility. Classification of sterility can be divided into heritable and nonheritable sterility. Numerous schemes for mechanisms controlled by nuclear genes (genic male sterility) have been devised to identify the timing and location of the inception of sterility. These schemes are divided into structural (gross organ changes) and functional. The latter may be divided into abnormal changes occurring in the male cells or surrounding anther tissues during microsporogenesis. Even though sterility can be produced by chemicals, ionizing radiation, genetic engineering, etc., the primary examples presented here will be of naturally occurring systems. The objectives of this paper are to review heritable genic male sterility, give examples of naturally occurring genic male sterility systems, and identify their uses and proposed applications in plant breeding.
Quantitative Trait Loci for Flowering, Plant and Ear Height, and Kernel Traits in Maize
Authors: Berke Terry G. , Rocheford Torbert R.
Published: July 2010

The inheritance of quantitative traits is not well understood. A study was conducted to determine the number and chromosomal locations of quantitative trait loci (QTL) controlling male anthesis date; plant and ear height; kernel weight; and kernel protein, oil, and starch concentration in maize (Zea mays L.). Two hundred S1 lines were derived from a single F1 plant from a cross of Illinois High Oil (IHO) by lllinois Low Oil (Early Maturity) [ILO(EM)]. Restriction fragment length polymorphism (RFLP) analysis was performed to determine RFLP genotypes of the 200 S1 families at 80 polymorphic loci spaced on average 24 centimorgans throughout the genome. The 200 S1 families were measured for phenotypic traits in replicated field trials during 1992 and 1993. Analysis of variance detected significant (P < 0.05) associations between several RFLP loci and each phenotypic trait. A total of 16 marker loci clustered in eight chromosomal regions were significantly associated with male anthesis date, 18 marker loci clustered in II regions were significantly associated with plant height, 14 marker loci clustered in nine regions were significantly associated with ear height, 27 marker loci clustered in II regions were associated with kernel weight, 16 marker loci clustered in eight regions were associated with protein concentration, 31 marker loci clustered in II regions were associated with oil concentration, and 28 marker loci clustered in 13 regions were associated with starch concentration. A number of QTL were detected in chromosomal regions where known gene loci of biological relevance are located.
Effect of a 1R(1D) Chromosome Substitution on Two Spring Wheat Cultivars
Authors: Abadie T. E. , Busch R. H. , Gustafson J. P.
Published: July 2010

The effect of a 1R(1D) chromosomal substitution on the spring wheat (Triticum aestivum L.) cultivars Wheaton and Marshall was studied to determine if the yield advantage, found in preliminary trials with ‘Anza’ in California, would be expressed in different environments and genetic backgrounds. Three experiments were conducted at two locations in Minnesota, from 1989 through 1991, with populations with and without the rye chromosome substitution developed in each cultivar background: (i) F2 derived F6 bulks; (ii) F4 derived random lines; and (iii) paired F6 lines derived from the same F3 plant. Although, frequently, test weight was the only trait significantly reduced by the presence of the substitution, the 1R(1D) bulks and lines also tended to have lower grain yield but higher grain protein content. In Experiments 2 and 3, the 1R(1D) lines tended to have shorter vegetative cycle and taller plants. Kernel weight was rarely affected by the substitution, but when there was an effect, it was increased. Considerable genetic variability among bulks and lines within the 1R(1D) and normal wheat groups in all the populations was observed. This allowed the identification of 1R(1D) lines that were similar to the parental check cultivars for grain yield. The random lines detected effects of the rye chromosome substitution with most resolution, probably because the lines were more homogeneous than the bulks and more random lines were tested than paired lines.
Maximum Parsimony Accurately Reconstructs Relationships of Elite Sorghum Lines
Authors: White P. S. , Gilbert M. L. , Nguyen H. T. , Vierling R. A.
Published: July 2010

Parsimony analyses have been shown to be effective for estimating the branching sequences of evolution. Because pedigree estimation is equivalent to phylogeny estimation, our objective was to examine the usefulness of maximum parsimony in estimating relationships based on restriction fragment length polymorphisms (RFLP). Eighteen sorghum [Sorghum bicolor (L.) Moench] lines, with known relationships were used in this study. Sorghum DNA was cut with various restriction enzymes and hybridized with 76 maize RFLP probes. The RFLP data were scored with a binary and multi‐state coding system. In the binary coding system, each polymorphic band was a separate character. In the multi‐state coding system, each probe‐enzyme combination was a separate character. Binary characters were analyzed with Wagner, unrooted Dollo, and threshold (T = 2, = 3, = 4) methods and multi‐state characters were treated as unordered. Wagner, unrooted Dollo, and threshold (T = 4) parsimony of binary characters correctly reconstructed known relationships. The Wagner and threshold (T = 4) models gave the highest degree of resolution. Parsimony analyses are effective tools for estimating plant breeding pedigrees and provide breeders with new tools for the analysis of germplasm variation, investigations of line origin, and determination of relationships in complex phylogenies or pedigrees.
Population Means and Genetic Variances in Selected and Unselected Iowa Stiff Stalk Synthetic Maize Populations
Authors: Holthaus Joel F. , Lamkey Kendall R.
Published: July 2010

Recurrent selection is a cyclical breeding procedure that focuses on improving the mean performance of a population by increasing the frequency of favorable alleles while maintaining adequate genetic variability for continued selection response. Iowa Stiff Stalk Synthetic (BSSS) is a maize (Zea mays L.) population that has undergone continuous recurrent selection for more than 50 yr as the base population for two independent selection programs (intra‐ and inter‐population). This study was designed to estimate the mean performance and genetic variances in BSSS after seven cycles of half‐sib (HS) progeny selection, six cycles of S2‐progeny selection, and 11 cycles of reciprocal recurrent selection (RRS). A Design II (factorial) mating design was constructed to give direct estimates of additive and dominance variance in the individual populations. Fourteen sets of four male × four female matings for each of the four populations were evaluated in a randomized incomplete block experiment grown in six environments. Half‐sib progeny and RRS methods have produced the most effective mean performance responses for grain yield in the populations per se, 0.076 and 0.104 Mg ha−1 cycle−1, respectively. The S2‐progeny selection procedure in BSSS, with a response of 0.052 Mg ha−1 cycle−1, has not performed up to theoretical expectations. Genetic variance component estimates for grain yield supported the suggestion that dominance variance is important in BSSS germplasm. Although additive variance decreased slightly, high heritability estimates suggest that further improvement in population means should be achieved by each selection method. Mean performance and estimated genetic variability for other important agronomic traits (grain moisture, root and stalk lodging, and ear height) generally showed favorable response to selection.
Host Suitability of Forage Grasses and Legumes for Root‐Lesion Nematode Pratylenchus penetrans
Authors: Thies J. A. , Petersen A. D. , Barnes D. K.
Published: July 2010

Pratylenchus penetrans reduces the productivity of many forage crops in northern USA and eastern Canada. Our objective was to determine the host suitability of forage grasses and legumes for P. penetrans in greenhouse, growth chamber, and field environments. In the greenhouse and growth chamber environments, P. penetrans reproduced on all forage grasses (17) and legumes (12). Both the legumes and grasses varied (P < 0.05) for numbers of nematodes and eggs in the roots. The most suitable hosts included kura clover (Trifolium ambiguum M. Bieb.), alsike clover (Trifolium hybridum L.), white clover (Trifolium repens L.), oat (Avena sativa L.), and rye (Secale cereale L.). The least suitable hosts included pearl millet [Pennisetum glaucum (L.) R. Br.], tall fescue (Festuca arundinacea Schreber), perennial ryegrass (Lolium perenne L.), forage sorghum [Sorghum bicolor (L.) Moench], sudangrass (Sorghum sudanense Pers.), sudex (Sorghum sudanense ✕ S. bicolor), sweetclover (Melilotus alba Desr.), crownvetch (Coronilla varia L.), and MNGRN‐16alfalfa (Medicago sativa L.). Twelve legumes and 9 grasses were transplanted into a field infested with P. penetrans and one‐half the plants were treated with carbofuran (2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranol methylcarbamate). Pratylenchus penetrans reproduced on all entries. Numbers of nematodes per gram fresh root of entries in the greenhouse‐growth chamber and field tests were correlated for both the control (r = 0.60, P< 0.05) and carbofuran treatment (r = 0.48, P < 0.05). We concluded that many forage species are hosts for P. penetrans, but a few legumes and grasses are poor hosts and may be useful in forage rotations to reduce nematode populations.
Drought Resistance Aspects of Turfgrasses in the Southeast: Evapotranspiration and Crop Coefficients
Authors: Carrow Robert N.
Published: July 2010

Water‐use data obtained under the climatic and soil conditions typical of the southeastern USA are very limited. Seven of the most commonly used turfgrasses in the Piedmont region of the humid Southeast were evaluated in a field study under edaphic stresses common to the region for seasonal evapotranspiration (ET) and development of Class A weather pan coefficients (kp) and FAO Penman crop coefficients (k) for irrigation scheduling. Time‐domain reflectrometry (TDR) was used to determine ET for each turfgrass (i.e., ETc) during soil dry‐down periods in 1989 and 1990. Estimated ET by the weather pan and Penman methods was used with ETc to develop crop coefficients. Grasses were Tifway bermudagrass (Cynodon dactylon ✕ C. transvaalensis), common bermudagrass [C. dactylon (L.) Pers.] Meyer zoysiagrass (Zoysia japonica Steud.), common centipedegrass [Eremochloa ophiuroides (Munro.) Hack.], Raleigh St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze], and Rebel II and Kentucky‐31 tall fescue (Festuca arundinacea Schreb.). Average summer ET rates were common bermudagrass (3.03 mm d−1), Tifway bermudagrass (3.11 mm d−1), Raleigh St. Augustine (3.28 mm d−1), Meyer zoysiagrass (3.54 mm d−1), Rebel II tall fescue (3.57 mm d−1), Kentucky‐31 tall fescue (3.69 mm d−1), and common centipedegrass (3.80 mm d−1) with the latter two being significantly higher than the bermudagrasses ET rate. Observed ET values were 40 to 60% lower than reported for the same genotype from arid and semi‐arid regions under nonlimited soil moisture. Under humid environments, ranking grasses for drought resistance based on relative ET does not correlate well with field observations of drought resistance based on wilt and leaf firing. Crop coefficients for the same species were generally higher than those reported under less humid conditions. Warm‐season species exhibited different coefficients and could not be grouped together for a common coefficient. All grasses had substantial changes in coefficients over the growing season; thereby indicating the need for seasonal adjustments when using these for irrigation scheduling.
Marker‐Based Pedigrees and Graphical Genotypes Generated by Supergene Software
Authors: Boutin S. R. , Young N. D. , Lorenzen L. L. , Shoemaker R. C.
Published: July 2010

Merging pedigree analysis with the use of genetic markers is likely to have a major impact on the characterization and development of crop varieties. Here, we present a computerized method for drawing pedigrees in terms of color graphical genotypes. The software transforms numerical marker data into map‐based images representing linkage groups. Different alleles as well as heterozygotes are represented at each marker locus via colors or patterns. Numerical data records (up to 200 markers and 335 individuals) are stored in a spreadsheet‐like table, which consists of the cultivar name, the name of the cultivar's parents, and the score at each marker locus and corresponding map location. The software does not actually calculate linkage maps, which must be generated prior to use as a basis for constructing graphical representations. The software can draw a pedigree for a single linkage group or the entire genome, as well as a graphical representation of the same linkage group of selected individuals. The software, which is free upon request, runs on any Macintosh or Power PC computer with at least four megabytes of random access memory.
Hybrids of Crosses between Oat and Andropogoneae or Paniceae Species
Authors: Matzk Fritz
Published: July 2010

Plant breeders are interested in enlarging the genetic variability within a species of interest and in improving breeding strategies. A wide hybridization program was conducted from 1990 to 1994 in Germany to determine the prospects for sexual gene transfer or haploid production in oat (Avena sativa L.). Five cultivars of oat were pollinated with pearl millet [Pennisetum americanum (L.) Leeke], eastern gamagrass [Tripsacum dactyloides (L.) L.], and maize (Zea mays L.; 2x and 4x) in the greenhouse. Exogenous auxin application, embryo rescue, and early colchicine‐mediated doubling of chromosomes were used to overcome postzygotic barriers. The recovered plants were analyzed cytologically and phenotypically under greenhouse and field conditions. Depending on the pollinator species, the embryo frequencies varied from 0.4% (Z. mays 4x) to 9.8% (pearl millet). In embryo rescue, initial growth occurred frequently, but many plantlets died. Chromosomes of the pollinator species were lost late in embryo and plant development. One to four chromosomes of the pollinator species were found at the tillering stage in root tip cells. Overall, four viable plants were produced, among them hybrids with pearl millet and eastern gamagrass for the first time. The efficiency of haploid production (<0.1%) was too low in all combinations for application in plant breeding programs; however, the transfer of genes or chromosomes appears promising in crosses of oat with maize and pearl millet.
Relationships among International Testing Sites of Spring Durum Wheat
Authors: Abdalla Osman S. , Crossa José , Autrique Enrique , DeLacy Ian H.
Published: July 2010

Knowledge of the relationships among international test sites is valuable information for effective targeting of germplasm exchange. Five years of grain yield data from the Elite Durum Yield Trial (EDYT), consisting of 132 trials from 32 locations in 22 countries, were studied. Pattern analysis, the combination of ordination and cluster analysis, was used to identify groupings of international test sites that represent similar selection environments and compare location association with the mega‐environment designations of the International Maize and Wheat Improvement Center (CIMMYT) breeding program. Two main environmental groups and six subgroups were identified for durum wheat (Triticum turgidum L. var. durum). The major determinants of the groupings were latitude and moisture supply. Biotic and abiotic stresses influenced further delineation of the clusters. Discrepancies between mega‐environment designation and pattern analysis results warrant further investigations of the underlying causes. The relationships among test sites documented in this study should provide a framework for effectively targeting germplasm and information exchange between comparable programs.
Influence of Day and Night Temperature on Soybean Seed Yield
Authors: Gibson L. R. , Mullen R. E.
Published: July 2010

Growth temperature influences the seed yield of soybean [Glycinemax (L.) Merr.]. Most studies have concentrated on the effects of concomitant increases in day/night temperature during the entire life cycle of soybean. A better understanding of the influence of combinations of high day and night temperature imposed during different reproductive growth phases on soybean seed yield would be beneficial in identifying yield limiting factors. Day/night temperatures of 30/20, 30/30, 35/20, and 35/30°C were imposed during flowering and pod set (R1‐R5), seed fill and maturation (R5‐R8), and during the entire reproductive period (R1‐R8). Increases in day temperature resulted in decreased seed formation when plants were exposed during flowering and pod set and decreased seed growth when exposed during flowering and pod set or seed fill. Seed growth reductions in plants exposed to the high day temperature were accompanied by decreased photosynthetic rates. The largest yield reduction in this study was 27% and occurred when 35°C occurred for 10 h per day from flowering to maturity. No significant losses in yield occurred at high night temperature at any reproductive growth phase. The only significant interaction between day and night temperature for the yield components was for seed weight per plant during flowering and pod set. Night temperature stress did not occur at 30°C and a night temperature of 20°C did not reduce the yield loss from daytime high temperature stress. This study suggests that soybean seed yield reductions from high temperatures are primarily a response to day temperature and moderate to high night temperatures have a small affect on soybean seed yield components.
Phaseolus acutifolius A. Gray is More Heat Tolerant than P. vulgaris L. in the Absence of Water Stress
Authors: Lin Tsai‐Yun , Markhart Albert H.
Published: July 2010

Field observations suggest that Phaseolus acutifolius A. Gray is more heat and drought tolerant than P. vulgaris L. Since high temperature stress and water stress are difficult to separate in field experiments, we do not know if P. acutifolius is more high temperature tolerant than P. vulgaris. The goal of our research was to determine whether P. acutifolius is more heat tolerant than P. vulgaris in the absence of water stress. Plants grown at 25°C for 13 d in controlled environment chambers were separated into two groups; one group was maintained at 25°C for 8 d and the other at 32°C for 8 d. Air vapor pressure deficit at the two temperatures was maintained at 1.1 kPa. Phaseolus vulgaris growth was significantly decreased at 32°C compared with growth at 25°C. The decrease included total leaf area, total dry weight, root weight, and net assimilation rate. Phaseolus acutifolius grew similarly at both temperatures. Separate experiments investigated the effects of temperature on seed germination and early seedling growth. Seed germination of both species was reduced by about 11% at 32°C compared with germination at 25°C. Initial P. vulgaris radical growth was inhibited at 32°C whereas radical growth of P. acutifolius was not affected. Our results indicate that at the tissue level P. acutifolius is more heat tolerant than P. vulgaris.
In Vitro Development of Inflorescences from Switchgrass Nodal Segments
Authors: Alexandrova K. S. , Denchev P. D. , Conger B. V.
Published: July 2010

Immature inflorescences are an important explant source for initiating in vitro cultures in gramineous species. The objective of this study with switchgrass (Panicum virgatum L.) cv. Alamo was to produce axenic inflorescences from nodes cultured in vitro. The top nodal segments from tillers in the two to four node stage of greenhouse grown plants were surface sterilized, split longitudinally, and plated with the cut surface in contact with Murashige and Skoog (MS) medium containing 30 g L‐1 maltose. 6‐Benzylaminopurine (BAP) was added in concentrations of 0.0, 5.0,12.5, or 25.0 µM. After 2 to 5 wk culture, panicles were produced with fully developed spikelets and perfect terminal florets. Panicles produced on medium without BAP were between 5 and 9 cm long and the number of spikelets ranged between 50 and 200. Panicles produced on medium with 5.0 to 25.0 µM BAP had a shorter rachis (2–5 cm) and branches, but contained more spikelets (200–700). Young spikelets obtained after 20‐ to 30‐d culture of nodes, were used as explants for regeneration experiments. Calli were initiated from spikelets plated on MS solid medium with 30 g L‐1 maltose, 22.5 µM 2,4‐dichlorophenoxyacetic acid (2,4‐D) and 5.0 µM BAP. They were later transferred to MS medium without growth regulators, where thousands of regenerants developed through somatic embryogenesis and organogenesis. The procedure is highly efficient for producing multiple sterile explants from a single genotype for use in various in vitro culture experiments.
Rhizomatous Lotus corniculatus L.: I. Taxonomic and Cytological Study
Authors: Beuselinck P. R. , Li B. , Steiner J. J.
Published: July 2010

Wild, putative Lotus corniculatus L. accessions from Morocco differ distinctly from domesticated L. corniculatus in that they produce rhizomes. Rhizomes may be useful in increasing stand persistence of domesticated L. corniculatus. The objective of this study was to identify to species the wild Lotus accessions from Morocco (G31272, G31273, G31276, G31298, and G31317) that present rhizomatous growth. Comparative morphological and cytological analyses and intercrossing with L. corniculatus were used in this study. Six morphological characters that distinguish L. corniculatus and L. uliginosus Schkuhr. (the only species in the genus Lotus recognized as producing rhizomes) were used to categorize taxonomically the Moroccan accessions. The Moroccan accessions were morphologically similar to L. corniculatus with the exception of the rhizome trait. The accessions were tetraploid with 2n = 4x = 24 somatic chromosomes. Karyotype analyses detected more similarities than differences between the Moroccan accessions and Norcen. Progeny were produced from intercrosses between L. corniculatus cvs. Norcen and AU Dewey and the Moroccan accessions. Hybridity of progeny was verified by morphological and random amplified polymorphic DNA (RAPD) analyses. A sample of reciprocal F1 progeny were tetraploid, fertile, and consistent in their production of rhizomes. A combination of morphological, chromosome, and karyotype analyses confirmed accessions G31272, G31273, G31276, G31298, and G31317 as L. corniculatus. This is the first description of L. corniculatus with rhizomes.
Screening the Alfalfa Core Collection for Acid Soil Tolerance
Authors: Bouton J. H.
Published: July 2010

Since previous work indicated U.S. alfalfa (Medicago sativa ssp. sativa L.) cultivars are limited as genetic sources of acid soil tolerance, new germplasm needs to be identified and used. The objective of this paper was to screen the PI Core Collection for acid soil tolerance in the greenhouse. Initially, 192 of the 200 PIs in the core collection were screened during 1992 and 1993 in Georgia using replicated cups containing a lower zone of unlimed, unfertilized subsoil with an upper seed germination zone containing the same soil, but limed and fertilized. Acid soil tolerance of each PI was estimated by recording the root dry weight entering the unlimed layer and comparing it with an acid soil tolerant check, GA‐AT. A repeat study using the same screening procedure with 14 PIs was then performed during 1994. Among these 14, seven had initially shown superior root growth to GA‐AT, while seven demonstrated poorer root growth than GA‐AT. None of the seven superior PIs were found to possess better root, crown, or top growth compared with GA‐AT, while the poor rooting PIs remained inferior to GA‐AT for all measured variables. Within the limits of this screening procedure, these findings indicated that germplasm with exceptional acid soil tolerance will be difficult to isolate from the alfalfa PI collection.
Heritability of Carbon Isotope Discrimination and Correlations with Harvest Index in Cowpea
Authors: Menéndez Cristina M. , Hall Anthony E.
Published: July 2010

Breeding for drought adaptation by selecting only for grain yield is slow. Carbon isotope discrimination (Δ) may be a useful selection criterion because of its correlation with transpiration efficiency. However, effectiveness of indirect selection will depend on the realized heritability of Δ and genetic correlations with other traits contributing to grain yield. Heritabilities and genetic correlations between Δ and harvest index (HI), grain yield, and biomass were estimated in two cowpea [Vigna unguiculata (L.) Walp.] crosses. Broad‐sense heritability estimates were intermediate for Δ (0.33 and 0.47) and HI (0.58 and 0.30). Selection based on F2> single‐plant values was performed for high and low Δ, and high and low HI and selection responses were evaluated in the F3 and F4 generations. Realized heritabilities were low for Δ (0.06 and 0.19) and low to intermediate for HI (0.14 and 0.42) and were higher for upward than downward selection for both traits. Heritabilities estimated from parent‐offspring regression with 50 random lines were significant for Δ only in one of the crosses. Heritabilities of HI were significant only from F2:F3 regression suggesting that nonadditive effects were present in the expression of that trait. Low to moderate positive correlations existed between Δ and HI, indicating possible genetic association. No consistent correlations were found between grain yield and Δ, but a positive genetic correlation was present between HI and grain yield. Selection would be more efficient for low Δ in families in advanced generations rather than with single F2 plants and could result in some indirect selection for low HI.
Anatomical and Physiological Mechanisms of Resistance to Brown Leaf Spot in Smooth Bromegrass
Authors: Sherwood R. T.
Published: July 2010

Smooth bromegrass (Bromus inermis Leysser) germplasm PL‐BDR1 and two seed increase generations derived from it are highly resistant to brown leaf spot caused by Pyrenophora bromi (Died.) Drechs. [Drechslera bromi (Died.) Shoemaker, conidial state = Helminthosporium bromi Died.)]. Lesions are about one‐half the width and one‐tenth the area of spots on susceptible cultivars. Physiological or anatomical mechanisms of resistance have not been identified, but they could have a bearing on stability of resistance and on forage quality components. This study was conducted to determine whether certain resistance mechanisms identified in other leaf spot diseases of grasses operate in PL‐BDR1 germplasm. The three resistant generations were compared with susceptible cultivars Belmont, Radisson, and Saratoga for fungal penetration, halo formation, and leaf vein architecture. Susceptible leaves supported higher numbers of penetration attempts and successful penetrations. No effect of plant line was found for appositional wall formation (=papilla formation), initial colonization rate, distance between parallel veins, proportion of large vascular bundles, or girdering of vascular bundles. Resistant lines had wider vascular bundles than susceptible cultivars indicating a possible role for strength of the vascular framework in restricting lateral spread. Extensive cell necrosis and chlorotic halo formation in susceptible cultivars indicated possible involvement of a fungal phytotoxin. Resistant lines had few halos, and reduced sensitivity to toxins may be involved in resistance of PL‐BDR1 to brown leaf spot.
Plant Genetic Study of Restricted Nodulation in Soybean
Authors: Qian Daqi , Allen F. L. , Stacey G. , Gresshoff P. M.
Published: July 2010

The displacement of indigenous Bradyrhizobium japonicum in soybean [Glycine max (L.) Merr.] nodules in favor of a more effective inoculant strain has been suggested as an approach to enhance soybean productivity. The objectives of this study were to (i) screen additional soybean genotypes for ones which restrict nodulation by certain B. japonicum strains, and (ii) investigate at which stage nodule development is blocked. Preliminary screenings of 23 soybean accessions, including Glycine soja Sieb. & Zucc., indicated that ‘TN 4—86‘, BARC‐2(Rj4), and PI 468.397 showed restricted nodulation with B. japonicum strain 61A101C. Cultivar Essex gave effective nodulation. Segregation in the F2 of Essex × PI 468.397 showed no significant difference (P ≤ 0.05) from a 3 nodulation :1 restricted nodulation ratio. The results indicate that the nodulation response of PI 468.397 with strain 61A101C is controlled by a single recessive gene. In contrast, the restricted nodulation response in TN 4–86 is controlled by a dominant gene which is allelic or closely linked to gene Rj4. The kinetic study of nodule development following inoculation with strain 61A101C indicated that the blockage of nodule development on BARC‐2(Rj4), TN 4–86, and PI 468.397 did not occur during root hair curling, but during the stage of cortical cell division. Information of this nature might be useful in distinguishing among different types of nodulation restriction genes based on the stage that blockage occurs. This study suggests that accessions of G. soja should be viewed as potential sources of additional genes that restrict nodulation of soybean with specific strains of Bradyrhizobium. Introgression of such genes could result in soybean cultivars that exclude some of the indigenous strains and become nodulated with commercial strains that are more efficient at fixing nitrogen.