bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth, Osmotic Adjustment, and Cell‐Wall Mechanics of Expanding Grape Leaves during Water Deficits
Authors: Schultz Hans R. , Matthews Mark A.
Published: July 2010

The responses of growth, components of leaf water potential, and mechanical properties of leaves to ontogeny and soil water deficits were investigated in wine grape Vitis vinifera L. Vines were cultured in soil in controlled environments, and water deficits were imposed by withholding water. Osmotic adjustment of several hundred kilo‐pascals maintained turgor at or above that of controls, but growth was completely inhibited. The bulk modulus of elasticity increased almost twofold, from 8.1 MPa for a rapidly expanding leaf to 14.7 MPa for a similar leaf in which growth had ceased after withholding water for several days, and continued to increase to 20.3 MPa 2 d after growth had ceased. Stress‐strain relationships of isolated leaf strips were determined with the Instron analyzer. Total extension (elastic and plastic components) under 20‐ or 30‐g loads was linearly related to the rate of leaf expansion determined prior to sampling. Total extension of well‐watered leaves exhibited a diurnal pattern, with a minimum extensibility near midnight and high extensibility in the light. Plastic extensibility was estimated as the difference in extension in successive load cycles. Plastic extension was linearly related to the rate of leaf expansion. The results indicate that the extensibility (as determined by Instron analysis) of grape leaf tissue decreases concomitant with the rate of expansion as leaves age. Similarly, plastic and elastic extensibility decrease when growing leaves are exposed to water deficits. The results are consistent with the hypothesis that decreased cell‐wall extensibility contributes to the inhibition of leaf expansion caused by water deficits.
Tall Fescue Sward Dynamics: II. Influence of Four Plant Growth Regulators
Authors: Spak David R. , DiPaola Joseph M. , Lewis William M. , Anderson Charles E.
Published: July 2010

Very little is known about the influence of plant growth regulators (PGRs) on turfgrass sward dynamics (including shoot development and mortality) and reproductive development. PGR‐induced growth suppression might increase assimilate supply to axillary buds, resulting in their release. A 2‐yr study was conducted to determine the impact of four PGRs applied in late March on the sward dynamics of ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.). Maleic hydrazide [1,2‐dihydro‐3,6‐pyridazinedione] and mefluidide N‐(2,4‐dimethyl‐5‐[([trifluoromethyl]‐sulfonyl)amino]phenyl)acetamide], two PGRs that suppress vegetative and reproductive growth, were applied at 4.48 and 0.56 kg ha−1, respectively. Flurprimidol [α‐(1‐methylethyl)‐α‐[4‐(trifluoromethoxy)phenyl]‐5‐pyrimidinemethanol] and paclobutrazol [(R*,R*)‐(±)‐β‐[(4‐chlorophenyl)methyl]‐α‐,(1,1dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol], two PGRs that suppress vegetative growth only, were each applied at 1.12 kg ha−1. Twenty shoots were labeled at random in each plot and observed 3, 6, 10, 14, 19, and 31 weeks after treatment (WAT). Maleic hydrazide and mefluidide treatments caused 75% shoot mortality (55% greater than the control) by 10 WAT; however, stand density was unaffected by maleic hydrazide and mefluidide, due to the release of axillary buds beginning 2 WAT. Maleic hydrazide and mefluidide induced a postinhibition growth response, with proliferation of new shoots and rapid growth of shoots surviving chemical treatment. Leaf and crown total nonstructural carbohydrates (TNC) declined during the postinhibition response from 4 to 6 WAT. Flurprimidol and paclobutrazol, despite effective foliar growth suppression, failed to influence shoot mortality, axillary bud release, or TNC levels. Patterns of TNC partitioning in response to PGRs, though different, did not appear to be the result of the effectiveness of seedhead suppression.
Leaf Nitrogen Content and Minimum Temperature Interactions Affect Radiation‐Use Efficiency in Peanut
Authors: Wright Graeme C. , Bell Michael J. , Hammer Graeme L.
Published: July 2010

Reproductive development in peanut (Arachis hypogaea L.) is generally characterized by progressively declining leaf N content. A nonnodulating genotype and three nodulating cultivars were grown at two locations contrasting primarily in night temperature to derive critical levels of leaf N necessary for maintenance of dry matter (DM) accumulation rates. Nonnodulating plants were grown in field plots with four N treatments ranging from 0 g N m−2 (with 1.0 kg m−2 finely chopped cereal straw) to 26.0 g N m−2. The accumulation of DM and N were monitored for two sowing dates in the cooler environment and at a single sowing in the warm environment. Early sowing in the cool environment (early‐cool) resulted in the nonnodulating genotype accumulating similar levels of DM at high N to the comparable treatment in the warm environment (early‐warm), but crop duration in SD1 was 31 d longer. Crop development and DM accumulation were restricted in the second sowing in the cool environment (late‐cool) due to a frost. Slower DM accumulation in early‐cool was related to both reduced interception of incident photosynthetically active radiation, due to slow leaf area development, and to a 20% lower conversion efficiency of intercepted radiation to DM (RUE). The lower RUE in the two cool environments may have been caused by the low minimum temperature. Responsiveness of RUE to the total amount of N per unit leaf area (SLN) was negligible in the two cool environments. Nodulating cultivars grown at the same locations and sowing dates had similar SLN and RUE values as the non‐nodulating genotype grown under the high N treatment.
Genotypic Comparison of Heat Shock Protein Synthesis in Sorghum
Authors: Jorgensen Julie A. , Rosenow Darrell T. , Nguyen Henry T.
Published: July 2010

High temperature stress is an environmental factor limiting sorghum (Sorghum bicolor (L.) Moench) productivity. We determined the optimum heat‐shock protein (HSP) induction temperature in sorghum leaves and investigated intraspecific genetic variability in HSP synthesis among inbred lines RTx430, SC599‐6, and SC326‐6. One dimensional electrophoresis indicated an optimum 42 °C synthesis temperature in seedling leaves. Analysis of genetic variation by two‐dimensional electrophoresis showed only three genotype‐specific but many common HSPs. Sixteen of the common HSPs were synthesized in control samples; however, synthesis during high temperatures was dramatically enhanced. The results suggest limited variation in HSP synthesis and predominant constitutive HSP synthesis among these sorghum lines.
F2 Hybrids of Host Plant Germplasm and Cotton Cultivars: I. Heterosis and Combining Ability for Lint Yield and Yield Components
Authors: Tang Bing , Jenkins Johnie N. , McCarty J. C. , Watson C. E.
Published: July 2010

Although pest‐resistant cotton (Gossypium hirsutum L.) germplasm is available, it is generally not equal to adapted cultivars and other elite germplasm in yield. Cotton F2 hybrids could provide a means to combine beneficial traits of high‐yielding adapted cultivar (elite) germplasm with those of pest‐resistant germplasms. In the F2 heterosis and combining ability were studied for lint yield and the primary yield component boll number as well as for the secondary yield components of lint percentage and boll weight. These F2 hybrids were produced following a North Carolina Design II mating scheme involving four cultivars as female parents and 16 germplasm lines as male parents. The 64 F2 hybrids and 20 parents were evaluated in four environments. General combining ability (GCA) effects for various parents differed significantly. ‘Delcot 344’ gave significant, positive GCA effects for all traits studied. Significant, positive specific combining ability (SCA) effects were smaller and less significant than GCA effects. Heterosis of the F2 over the high‐parent was observed in six (9% of all F2 hybrids) F2 hybrids. In the terms of combining ability for yield, the best two parents were Delcot 344 and ‘Coker 315’. The heterosis for yield of F2 hybrids resulted mainly from increased boll number, boll weight, or a combination of both, rather than increased lint percentage. Interaction of GCA and SCA with environments indicated that F2 hybrids must be evaluated separately in each environment in which they are to be grown. These results suggest that high yielding F2 cotton hybrids can be developed that may contain acceptable levels of pest resistance.
Independent Inheritance of Striga and Alectra Resistance in Cowpea Genotype B301
Authors: Atokple I. D. K. , Singh B. B. , Emechebe A. M.
Published: July 2010

Cowpea [Vigna unguiculata (L.) Walp] is a major food legume the semi‐arid region of Sub‐Saharan Africa. Recently, two parasitic weeds, Striga [Striga gesnerioides (Willd.) Vatke] and alectra [Alectra vogelii Benth.] have become a major threat to cowpea cultivation in this region. A landrace of cowpea from Botswana, B301, is resistant to both parasites and genetic studies have revealed a single dominant gene for striga resistance and duplicate dominant genes for alectra resistance. This study was undertaken to ascertain whether the genes controlling resistance to these parasitic weeds are independent of each other. Genotype B301 was crossed to a susceptible variety, IT84S‐ 2246‐4, and F1, F2, and backcross plants were screened for joint infection by pot culture technique. Roots of each plant were washed free of soil 10 wk after planting and examined for the attachment of striga and alectra. All plants of B301, and F1 and backcross plants involving B301, were completely free of striga and alectra attachments, whereas all plants of IT84S‐2246‐4 were infected by both parasites. The F2 generation segregated into 349 resistant to both, 118 susceptible to striga and resistant to alectra, 15 susceptible to alectra and resistant to striga, and 8 susceptible to both striga and alectra, which fit a trigenic segregation ratio of 45: 15:3:1. Backcross F1 plants involving IT84S‐2246‐4 segregated in a ratio of 3:3:1:1. The data indicated that genes conferring resistance to striga and alectra in B301 are non‐allelic and independent of each other.
Evaluating Rye Inbred Lines Per Se and in Euplasmic and Alloplasmic Crosses for Triticale Suitability
Authors: Geiger H. H. , Oettler G. , Marker R. , Utz H. F. , Wehmann F.
Published: July 2010

The production of primary triticales (× Triticosecale Wittmack) is laborious and the performance of the resulting amphidiploids has been mostly unsatisfactory. It is, therefore, desirable to have criteria to assess wheat and rye lines as suitable triticale parents. This study investigated the genotypic variation and covariation caused by 15 rye (Secale cereale L.) inbred lines per se and as parents of testcrosses, euplasmic and alloplasmic (Triticum turgidum L. and T. aestivum L. cytoplasm) rye F2 populations, and hexaploid and octoploid primary triticales in order to assess rye lines for their “triticale suitability.” All materials were evaluated in drilled yield trials at two locations and in 2 yr. Genotypic variances between rye lines were generally greater than those due to rye parents in testcrosses, F2 populations, and primary triticales. The variances of hexaploid and octoploid triticales, when significant, were of similar magnitude. Correlations between the two ploidy levels were moderate to high for all traits. Relationships between triticales and corresponding rye materials were inconsistent and frequently negative for yield and yield component traits. The prediction of triticale performance based on rye line and cross performance was possible for days to heading, but was without prospect for the yield complex. Rye lines which proved favorable as parents of hexaploid triticales were superior at the octoploid level as well.
Control of Supernodulation in Intergeneric Grafts of Soybean and Common Bean
Authors: Hamaguchi Hideo , Kokubun Makie , Yoneyama Tadakatsu , Hansen Alexander P. , Akao Shoichiro
Published: July 2010

Understanding how nodulation is controlled should provide the basis for improving symbiotic N2 fixation in legume crops. Intergeneric grafting was carried out between soybean [Gylcine max (L.) Merr.] and common bean (Phaseolus vulgaris L.) to investigate whether the autoregulation mechanism operates identically in two species which belong to different genera and which host different microsymbionts. Soybean cultivar Enrei and its supernodulating mutant En6500 as well as common bean cultivar OAC Rico (Rico) and its respective mutant R32BS15 (RBS15) were reciprocally grafted. Subsequently, the degree of nodulation of the grafted plants was determined and compared. when I‐shaped grafts were used, only plants which were grafted intraspecifically with the mutants expressed supernodulation. Plants which were grafted intergenerically did not supernodulate. Both Y‐shaped and X‐shaped grafting procedures were used to graft and additional scion to the supernodulating mutant stocks. Suppression of supernodulation was observed only when wild‐type scions were of the same species as the stock. These results support the hypothesis that the mechanism controlling nodulation or substances involved in autoregulation are different between soybean and common bean.
A SAS Program for Analyzing Augmented Randomized Complete‐Block Designs
Authors: Scott R. A. , Milliken G. A.
Published: July 2010

The augmented design usually is useful for testing many genotypes in early generations when valid statistical analyses are needed with seed supplies too limited to permit replication. Practical use of this design necessitates computer data analysis. Researchers need an easy way to analyze augmented design data with minimal hand computations, and with the fewest possible computer operation steps. This paper presents a SAS program useful for analyzing augmented randomized complete‐block design (ARCBD) data. An actual augmented experiment is used to show construction of the design and analysis of the data. Since SAS can handle large data sets, this program can be used to obtain useful information on large numbers of genotypes where numbers of seeds are insufficient for adequate replication.
Cytogenetic Activity and Mode of Action of the Pairing Homoeologous (Ph1) Gene of Wheat
Authors: Feldman Moshe
Published: July 2010

The Ph1 (pairing homoeologous) gene of common wheat, the main factor responsible for the eytological diploid‐like behavior of this polyploid species, has been a subject of intensive Cytogenetic studies in the last three decades. This paper reviews the effects of Ph1 on chromosomal pairing and spindle microtubule dynamics. It presents data supporting the hypothesis that this gene exerts its effect at presynaptic stages, affecting the premeiotic alignment of homologous and homoeologous chromosomes, and thereby controls the regularity and pattern of pairing at meiosis.
Agronomic Performance of Tall versus Short Semidwarf Lines of Spring Wheat
Authors: Busch R. H. , Rauch T. L.
Published: July 2010

Plant height and grain yield have been positively associated in many studies of wheat (Triticum aestivum L.). The introduction of semidwarf genes changed this relationship by enhancing grain yield as well as reducing plant height. A strategy to select for tall dwarfs was proposed to exploit the positive correlation between yield and plant height observed without semidwarf genes, yet use the advantages of semidwarfism. The objective of this study was to evaluate the proposed model in spring wheat by comparing the yield potential of tall vs. short semidwarf lines. Randomly derived semidwarf lines from four crosses were assigned to tall and short groups based on their piant height. These groups were tested in a total of five environments in Minnesota from 1986 through 1988. The selected trait, plant height, differed between groups in all crosses. The tall‐line group did not differ from the short‐line group for grain yield within or across environments for Crosses I, 2, and 3. The tall‐line group of Cross 4 exceeded the short‐line group for grain yield in the two higher yielding environments, and across environments. The tall group was later in days to head in Crosses 1 and 4. Correlations among traits were generally nonsignificant. The lack of a positive association between plant height and grain yield in three of four crosses indicated that sufficient evidence was not found to Support the application of the tall dwarf model in this hard red spring wheat germplasm.
Heritability of Creeping Bentgrass Shoot Water Content under Soil Dehydration and Elevated Temperatures
Authors: Lehman V. G. , Engelke M C.
Published: July 2010

Improvement of resistance to heat and moisture stress in creeping bentgrass (Agrostis stolonifera var. palustris Huds.) would enable increased planting and use in warmer environments. The objectives of these studies were to: (i) determine the association of shoot water content with survival of creeping bentgrass under elevated soil temperatures, (ii) estimate the heritability of shoot water content in creeping bentgrass, and (iii) determine the relationship of shoot water content under soil temperature stress with shoot water content under soil dehydration stress. ‘Seaside’ creeping bentgrass plants and plants selected from Seaside (Population A) that survived soil temperature stress were subjected to soil temperature stresses ranging from 29 to 37 °C for 4 wk. Water content, measured as (wet weight — dry weight)/ dry weight) of shoot tissue, was found to be 10% higher in the Population A plants. Ten parental clones of creeping bentgrass and 20 half‐sib progeny of each were exposed to 1, 2, 4, and 6 wk of soil temperature stress. Parent and progeny were significantly correlated in water content under soil temperature stress after 2 and 4 wk. Canopy temperature of the 10 parental clones of bentgrass was significantly correlated with water content under soil temperature stress. Narrow‐sense heritability of water content of shoot tissue was estimated between 0.98 and 1.0 using parent‐progeny regression in these creeping bentgrass populations.
Pink Flower Color Associated with Increased Protein and Seed Size in Soybean
Authors: Stephens P. A. , Nickell C. D. , Vodkin L. O.
Published: July 2010

Most soybean [Glycine max (L.) Merr.] cultivars and plant introductions have either purple (Wl) or white (wl) flowers. Pink (wp) flower color results when the homozygous wp alleles are combined with Wl. This study was conducted to determine the effect of pink flower color on agronomic traits in soybean. Pink and near‐isogenic purple‐flowered lines were derived from an F4 plant. Seven homozygous pink‐flowered, three homozygous purple‐flowered, and two lines segregating for pink and purple flower color were evaluated at three locations in Illinois for 2 yr. When pink‐flowered lines were compared to purple‐flowered lines no differences were found for yield, maturity, height, lodging, or seed quality, while significant (P < 0.05) differences were found for seed weight, protein, and oil concentration. Pinkflowered lines averaged 22% higher in seed weight, 4% higher in protein, and 3% lower in oil compared to the purple‐flowered lines. The pink flower trait represents unique germplasm in soybean that can be used in the development of high yielding cultivars with increased seed protein.
Clustering Cultivars into Groups without Rank‐Change Interactions
Authors: Cornelius P. L. , Van Sanford D. A. , Seyedsadr M. S.
Published: July 2010

Crossover (i.e., rank‐change) interactions (COIs) are of particular interest in the interpretation of cultivar yield trial data. The shifted multiplicative model (SHMM) was used to search for subsets of cultivars in which cultivar COIs could be regarded as insignificant or small in a 1985 Kentucky wheat (Triticum aestivum L.) trial with 41 cultivars and seven locations. The first step was to obtain a dendrogram by complete linkage (farthest neighbor) cluster analysis with the “distance” between a pair of cultivars defined as the residual sum of squares when SHMM with one multiplicative term (SHMM1) is fitted subject to a constraint that the fitted model be free of COIs. Statistical tests were computed on subsets of cultivars suggested by branching of the dendrogram to identify subsets in which a constrained SHMM, would account for the variation. Five clusters of five cultivars each and four smaller clusters were found satisfactory. Six cultivars did not cluster with any other cultivar. Analysis of all 2 × 2 interactions indicated that the method effectively assigned cultivars involved in large COIs to different clusters. Only 6% of COIs within clusters were significant as compared to 29% among clusters. Clustering would allow breeders and growers to restrict selection of cultivars to the better ones in each cluster.
Dehydration Stress‐Induced Changes in Translatable Rnas in Sorghum
Authors: Cheng Y. , Weng J. , Joshi C. P. , Nguyen H. T.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] is a drought‐resistant crop species. The main objective of this work was to study the dehydration stress‐induced changes in mRNA accumulation in sorghum. Ten‐day old seedlings were dried in a closed chamber for 6, 10, 14, 18, and 22 h. Poly(A)+ RNAs, isolated from control and dehydration‐stressed shoots, were translated in vitro in the presence of 35S methionine and the translation products were separated by two‐dimensional polyacrylamide gel electrophoresis. Four types of polypeptides which exhibited significant changes during the time course were distinguished. Northern blot analysis using a eDNA encoding a dehydration‐induced protein (dehydrin) revealed a rapid induction and increased accumulation of dehydrin mRNA species throughout the drought stress process. These results suggest that sorghum seedlings, similar to other plant species, exhibit altered gene expression patterns in response to the length of drought stress period.
Prometryn Tolerance in Glanded versus Glandless Isolines of Cotton
Authors: Foster J. David , Verhalen Laval M. , Murray Don S.
Published: July 2010

Cotton (Gossypium hirsutum L.) cultivars normally have lysigenous glands conditioned by two dominant, independently inherited alleles, Gl2 and Gl3. Glandless (gl2gl2gl3gl3) isogenic lines are now available for a number of those cultivars. Such lines allow a decisive test for the relationship formerly proposed between accumulation of the herbicide prometryn [N,N′‐bis(1‐methylethyl)‐6‐(methylthio)‐l,3,5‐triazine‐2,4‐diamine] in the lysigenous glands and increased crop tolerance to that pesticide. Experiments were conducted in a growth chamber to compare the prometryn tolerance of glanded vs. glandless ‘Empire 61 (WR)’ and ‘Westburn M’ isolines. Two intermediately glanded Empire isolines (Gl2Gl2gl3gl3 and gl2gl2Gl3Gl3) were also available for analysis. Ratios derived from leaf chlorophyll fluorescence measurement curves established that the photosynthetic inhibition caused by prometryn in glanded cotton seedlings was of less intensity and shorter duration than in glandless plants within the same genetic background. Comparisons involving the intermediately glanded Empire isolines sugo gested that Gl2 enhances seedling tolerance more than does Gl3. Glanded vs. glandless isolines in five genetic backgrounds (i.e., Empire 61 (WR), Westburn M, ‘Delcot 277’, ‘TH 149’, and ‘Stoneville 213’) plus the two intermediate Empire isolines were also evaluated for prometryn tolerance in the field. Visual crop injury ratings and measured lint yields support the growth chamber data. The treated glanded isoline on each background displayed less injury (20–56%) and higher yield (44–60%) than the corresponding glandless isoline. Again, Gl2 showed less injury than Gl3 though differences in lint yield were not significant. Clearly, lysigenous glands enhance prometryn tolerance in cotton, and higher gland density is directly associated with higher photosynthetic rates and reduced crop injury.
Red Clover Seed Production: I. Crop Water Requirements and Irrigation Timing
Authors: Oliva R. N. , Steiner J. J. , Young W. C.
Published: July 2010

Information about water management and crop stress response for red clover (Trifolium pratense L.) seed production is limited. This study determined red clover seed crop water requirements and evaluated crop water stress index (CWSI) and fraction of available soil‐water used for timing supplemental irrigation. Experiments were conducted at Corvallis, OR, on a Woodburn silt loam (fine‐silty, mixed, mesic Aquultic Argixeroll) in 1990 and 1991. Six irrigation treatments were used to assess within‐ and between‐crop season water requirements. As a consequence of root disease in 1991, the fraction of availables oil water used by plants in the different treatments was generally less in 1991 than 1990. Also, seed production water‐use efficiency was lower in 1991 than 1990. Two distinct non‐stressed baselines for canopy‐air temperature differences versus vapor pressure deficit were identified that were related to increasing leaf senescence and crop aging. The CWSI values across all treatments were negatively associated with plant water potentials (r = −0.87). The CWSI values were similar within similar treatments in both years indicating that root rot damage rather than available soil‐water was limiting plant water uptake in 1991. The CWSI generally increased faster than fraction of available soil‐water used. Unlike fraction of available soil‐water used, CWSI integrated the total plant environment, detecting changes due to root disease in 1991. Under the conditions of this experiment, a single irrigation filling the actives oil profile at CWSI ≈0.28 substantially increased seed yield compared with the nonirrigated control. The CWSI was a useful indicator of red clover water stress status and can be used to schedule clover seed irrigations under typical western Oregon climatic conditions.
DNA Marker Analysis of Loci underlying Resistance to Soybean Cyst Nematode (Heterodera glycines Ichinohe)
Authors: Concibido V. C. , Denny R. L. , Boutin S. R. , Hautea R. , Orf J. H. , Young N. D.
Published: July 2010

Inheritance of resistance to soybean cyst nematode (SCN, Heterodera glycines Ichinohe) is oligogenic and complex. DNA markers, such as restriction fragment length polymorphisms (RFLPs), can be used to identify loci associated with complex genetic characters, including SCN resistance. To uncover these associations, 56 F2 lines from a crass between a susceptible (M83‐15) and a resistant (M85‐1430) soybean [Glycine max (L.) Merr.] inbred line were mapped for DNA marker polymorphisms. F3 lines derived from these F2 individuals were assayed for SCN disease response in the greenhouse to a field isolate of SCN from Minnesota that tested as Race 3. The F2 genotypic classes for each of 43 DNAm arkers were then contrasted with SCN disease response to identify marker loci associated with SCN resistance. Two unlinked RFLP markers, pA85 and pB32, were found to be significantly associated with SCN disease response, together accounting for 51.7% of total phenotypic variation. Based on RFLP analysis, individual F2:3 lines that retained either one or both resistance loci were identified. Lines that possess both resistance loci could be valuable in developing resistant soybean lines free of linkage drag, while lines that have just one of the resistance loci may be useful as single‐gene differentials for SCN race determination.
Incidence and Viability of Acremonium Endophytes in Tall Fescue and Meadow Fescue Plant Introductions
Authors: Holder T. L. , West C. P. , Turner K. E. , McConnell M. E. , Piper E. L.
Published: July 2010

Assessment of the infection status and viability of endophytic Acremonium spp. in USDA plant introductions (PI) of Festuca spp. would aid in identifying potentially desirable endophyte strains for improving pasture and turf species. The PI collection of tall fescue (F. arundinacea Schreb.) and meadow fescue (F. pratensis Huds.) was screened to determine Acremonium infection rate and viability. For tall fescue, 20 seed from each of 565 regenerated seedlots were microscopically examined for endophyte. Seventy‐nine accessions contained endophyte with an average infection frequency of 67.4%. Leaf sheaths of seedlings from the infected accessions were then examined to determine endophyte viability. Fifty‐five of the 79 infected accessions contained viable endophyte at an average infection frequency of 41.2% in the seedlings. The decline in the number of infected accessions and in their infection frequency suggested that loss in endophyte viability may have occurred in storage. More intensive analysis of 15 tall fescue accessions showed that endophyte infection declined from 68.4% in originally collected seed to 42.7% in regenerated seed to 23.6% in the seedlings from the regenerated seedlots, indicating diminishing endophyte occurrence and viability between the time of deposition of seed in the germplasm system and release of regenerated seed for general distribution. In meadow fescue, 29 of 198 accessions contained endophyte at 42.4% infection frequency in the seed and 31.6% infection frequency in the seedlings, indicating a proportionally lesser decline in endophyte viability than in tall fescue. While existing germplasm collections of Festuca spp. can provide Acremonium germplasm for study, newly collected Festuca germplasm will offer a greater diversity of Acremonium genotypes.
Evaluation of Cateto Maize Accessions for Grain Yield and Other Agronomic Traits in Temperate and Tropical Environments
Authors: Hameed Abdul , Pollak Linda M. , Hinz Paul N.
Published: July 2010

The temperate maize (Zea mays L.) race Cateto may have potential for improving grain quality in temperate breeding programs. Temperate germplasm may also be useful in tropical breeding programs for improving yield, agronomic traits, and grain quality. The objective of our study was to assess the yield potential of Cateto race accessions testcrossed with two Corn Belt inbreds for grain yield and other agronomic traits in both temperate and tropical environments. Exotic inbreds representing Cateto, intermediate, and non‐Cateto races were crossed to two U.S. Corn Belt inbreds (Mo17 and B73). Testcrosses (F1s), their F2 and backcross generations, and four checks were evaluated in 1989 through 1991 at three temperate (two in Iowa and one in Missouri) and two tropical (Florida and Zimbabwe) locations. Data were recorded for grain yield, harvest moisture content, days to tassel, ear height, stalk lodging, and root lodging. The testcross‐by‐generation interaction was significant for all traits, except grain yield, whereas the testcross‐by‐tester interaction was significant for ear height, stalk lodging, and root lodging. B73 contributed more favorable alleles for improved standability and grain yield than did Mo17. Although the testcross by location interaction was significant for all traits, the tropical and temperate environments ranked testcrosses similarly. The tropical locations had both the highest and the lowest mean grain yields. The best testcrosses identified in temperate locations may have potential for introgression in the tropics.
A Core Collection for the United States Annual Medicago Germplasm Collection
Authors: Diwan Noa , Bauchan Gary R. , McIntosh Marla S.
Published: July 2010

The United States National Plant Germplasm System contains 3159 accessions from 36 species of annual Medicago. Although there is increasing interest in the annual medics for use in sustainable agriculture, the U.S. collection is under utilized because of lack of agronomic information. Development of a core collection could facilitate easier access to the germplasm collection and enhance its use. The core collection should consist of a sample of accessions that represents the range of variability within the germplasm collection with minimum redundancies. To select a core collection of annual Medicago species, a subset of 1240 accessions was evaluated during the summer of 1990 for 16 agronomic and morphological traits. Accessions within species were grouped by cluster analysis utilizing an unweighted pair group method with arithmetic averages. Intraspecific phenotypic diversity determined the number of accessions for that species selected for the core collection. One accession per cluster was selected for each species for the core collection. Accessions were chosen within a species to represent the greatest diversity in geographical regions. The selected core collection of 211 accessions was reevaluated during the summer of 1991. The core collection was found to represent the variability of the germplasm collection and to remain stable between the two evaluation years. This study can be used as a model method for selecting a core collection for multispecies germplasm collections.
Development of Anther‐Derived Dihaploids to Combine Disease Resistance in Maryland Tobacco
Authors: Walker D. R. , Aycock M. K.
Published: July 2010

Anther culture can reduce the amount of time required to develop completely homozygous lines of tobacco (Nicotiana tabacum L.). The objectives of this study were to determine the value of anther culture in combining resistance to three diseases in dihaploid lines of Maryland tobacco and to evaluate the agronomic performance of these lines relative to the parent cultivars. ‘MD 609’, which is resistant to black shank (Phytophthora parasitica var. nicotianae), was crossed with ‘MD 341’, which is resistant to tobacco mosaic virus (TMV) and wildfire (Pseudomonas syringae pv. tabaci). Anthers from the F1 were cultured to produce approximately 2000 haploid plantlets. The haploids were screened for resistance to TMV and wildfire, and midveins from 315 resistant plants were cultured to generate 133 dihaploids. These 133 dihaploids were then screened for black shank resistance, and 16 (12%) had levels of resistance similar to MD 609. In a 2‐yr field study involving 24 dihaploids, the average dihaploid was inferior to the midparent mean for price and quality index, had longer internodes, and flowered 6% later. These results indicate that whenever possible, screening for desired traits should be conducted at the haploid level to maximize efficiency. Although reduced yields were frequently observed with the dihaploids, certain lines with desirable levels of disease resistance equaled, and occasionally exceeded, the midparent value for yield and other agronomically important traits.
Recurrent Selection for Regeneration Capacity from Immature Embryo‐Derived Calli in Maize
Authors: Rosati Carlo , Landi Pierangelo , Tuberosa Roberto
Published: July 2010

Two cycles of recurrent selection to improve regeneration capacity from immature embryo‐derived calli were implemented in the maize (Zea mays L.) double cross [(A188 × W64A) × (A634 × B79)]. The total number of shoots regenerated per embryo (TNSE) in two consecutive subcultures was the selection criterion. After two cycles of selection, TNSE increased from 0.82 to 1.50 (+83%). A significant but lower increase (from 37.5–46.3%) was also noticed for the percentage of callus surface with embryo‐like structures (PCE) at 4 wk after explaining, while no response was observed for callus fresh weight (CFW). These results indicate that recurrent selection can be successfully utilized in maize to improve regeneration capacity and, indirectly, the proliferation of embryogenic callus. The selection process did not lead to a decline in variability among progenies of the selected populations for TNSE, CFW, and PCE, suggesting that these traits are controlled by polygenic systems. For TNSE the mean value of parental lines was very close to the mean value of the A188 × W64A and A634 × B79 F2 generations and to the mean value of the source populations, indicating that the trait is mainly controlled by additive gene action. The limited indirect response to selection observed for PCE and CFW as well as low correlations of PCE and CFW with the trait under selection (TNSE) indicate that different sets of genes are likely involved in controlling expression of PCE and CFW.
Gamete Selection for Simultaneous Improvement of Multiple Traits in Common Bean
Authors: Singh Shree P.
Published: July 2010

A successful crop improvement program depends upon the ability of breeders and geneticists to effectively and efficiently create, identify, and select recombinant genotypes with a maximum number of desirable traits in the shortest time possible. Therefore, alternative methods of gene recombination and selection need to be studied. My objective is to describe a method of gamete selection for simultaneous improvement of multiple traits in common bean (Phaseolus vulgaris L.). Gametes election is based on the premise that (i) multiple‐parent crosses are required for simultaneous improvement of multiple traits; (ii) the male parents of the final crosses are heterozygous and hence heterogametic;( iii) each zygotic seed is a product of a separate, independent fertilization event; (iv) further chromosomal and genic recombination is limited to genetic material contained within each initial zygote; and (v) early generation (i.e., F1, F2, F3, and F4) testing and selection are an essential part of the methodology. Thus, eventually, plant‐to‐plant pairwise pollination is done between the elite female and beterogametic male parents (selected a priori for desirable dominant and codominant alleles), followed by harvesting and sowing resultant hybrid seeds from each hybridization event in separate plots to obtain F1‐derived families. These are subsequently evaluated in separate, replicated complementary nurseries for seed yield and other agronomic traits, including reactions to diseases and insects, low soil fertility, and/or drought. This permits identifying promising populations and families within populations possessing genes for multiple desirable traits in early generations for further evaluation, selection, and development of improved cultivars.
Heritability and Repeatability of Enhanced N2 Fixation in Early and Late Inbreeding Generations of Soybean
Authors: Herridge David F. , Rose Ian A.
Published: July 2010

Moderate to high levels of soil nitrate suppress nodulation and N2 fixation in soybean [Glycine max (L.) Merr.], resulting in some instances in a net loss of N from the soil when the high‐protein seed is harvested. Development of nitrate tolerance, i.e., the ability to nodulate and fix N2 in the presence of soil nitrate, in cultivars of soybean is desirable. Our objectives were to (i) combine, through hybridization, the reported nitrate tolerance of Korean genotypes 464, 466, 468, and 469 (Commonwealth of Australia Plant Introduction nos CPI66126, CPI66141, CPI66157 and CPI66159, respectively) with the agronomic and seed traits of cultivars Valder, Reynolds, Forrest and Bossier; (ii) assess heritability and repeatability of N2 fixation between individual F2 plants and F2‐derived F3 lines, and F3‐derived lines in the F6 and F7 generations; and (iii) examine correlations of N2 fixation with agronomic and seed traits. Individual plants and lines were evaluated during five seasons between 1986–1987 and 1990–1991 on alkaline vertisol soils (Typic Pellustert) at Breeza and Narrabri, Australia, and in glasshouse culture at Narrabri. The xylem ureide technique was used to estimate N2 fixation activity of individual F2 plants, and of F2‐derived F3 lines and F3‐derived F6 and F7 lines. Data from F2 and F3 generations showed that relative ureide‐N values for the individual F2 plants was of low heritability. We concluded that single‐plant selection for N2 fixation in the F2 generation was largely ineffective. Data from F6 and F7 plot trials, however, indicated that repeatability on a plot basis for relative ureide‐N was about 0.5 (P< 0.01). Phenotypic correlations between relative ureide‐N in xylem sap and other plant and seed traits were variable and generally non‐significant. The selection of site was vital for detecting enhanced N2 fixation. Sites with low soil nitrate did not allow discrimination among genotypes. Three F3‐derived lines, D22‐8, K78‐1, and A46‐4, which were identified in the F6 and F7 trials at the high‐nitrate sites, had the N2 fixation characteristics of the Korean parents and near‐commercial yields (75–83% of that of the highest yielding cultivar, Forrest.
Modified Recurrent Selection for Barley Yellow Dwarf Virus Tolerance in Winter Wheat
Authors: Bauske Ellen M. , Kolb Frederic L. , Hewings Adrianna D. , Cisar Gordon
Published: July 2010

Barley yellow dwarf virus (BYDV) causes an economically important disease of small grains. We evaluated tolerance to BYDV in a winter wheat population resulting from modified recurrent selection. Chemical hybridizing agents (CHAs) were used to facilitate recombination, and selection was based on tolerant genotypes producing more seeds under disease pressure. Seventeen parents, selected for BYDV tolerance, were mated in a partial diallel, with equal amounts of seed from F1 plants constituting the original population. Bulked seed from F1 plants was planted in rows in the field. Female rows were sprayed with a CHA (either RH‐0007 or MON 21200) and inoculated with BYDV‐PAV‐IL. Seed was harvested from female rows. Our objectives were to determine if BYDV tolerance increased over cycles, if plant height and heading date were affected by the selection scheme, and if environmental effects were greater than genotypic effects for symptom expression. For evaluation, the original parents and S1:2 lines from Cycles 2, 3, and 4 were planted in paired hills (one hill in each pair was inoculated with BYDV) in a randomized complete block design. The experiment was repeated with S2:3 lines. No consistent improvements occurred over cycles in early or late disease ratings or yield of inoculated hills. Stunting was reduced from 6.0% in the parent population to 0.8% in Cycle 3 in the S2:3 lines. In comparison with Cycle 2, average heading date in Cycle 4 was delayed by about 2 d. The modified recurrent selection scheme used was not effective in increasing the level of tolerance to BYDV, perhaps because of the limited genotypic variability among the parents, or the use of indirect selection for the number of seeds produced under disease pressure rather than BYDV symptoms.
Reproductive‐Resource Allocation in Rhizoma Peanut
Authors: Williams M. J.
Published: July 2010

Partitioning of energy reserves between sexual (flower and seed) and asexual (rhizome) reproduction in rhizoma peanut (Arachis glabrata Benth.), a perennial, tropical‐forage legume, appears to be affected by environmental stress. If so, seed production may be enhanced by manipulating the growing environment. To investigate this possibility, the effect of defoliation frequency on the energy‐allocation balance of sexual vs. asexual reproduction of rhizoma peanut was determined. Four defoliation frequencies (nondefoliated, weekly, every 4 wk, and every 8 wk) were imposed on ‘Florigraze’ rhizoma peanut. Aboveground and rhizome biomass were sampled prior to treatment initiation (6 June 1988 and 15 June 1989) and every 4 wk until frost (24 wk in 1988 and 16 wk in 1989). During the first 8 wk, aboveground biomass of the non‐defoliated treatment nearly doubled. Concurrently, aboveground biomass of all defoliated treatments remained the same or declined. Rhizome biomass of all treatments declined during the same period but in most cases, recovered by the latter part of the growing season. Generally, aboveground biomass ranked (P < 0.05) 1 wk < 4 wk ≤ 8 wk < nondefoliated, and rhizome biomass ranked (P < 0.05) 1 wk = 4 wk = 8 wk < nondefoliated. Flowering was synchronous for all treatments, but sexual reproductive effort constituted <0.5% of total‐plant biomass because seeds were never produced. Defoliation positively affected (P < 0.05) both flower dry matter (DM) production and sexual:asexual ratio with treatments generally ranked nondefoliated = 1 wk < 4 wk = 8 wk. This study indicates that the partitioning of energy to sexual or asexual reproduction in rhizoma peanut can be altered in response to stress.
Relationships between Vegetative Growth Rate and Flower Production in Flax
Authors: Dean Dybing C. , Grady Kathleen
Published: July 2010

The physiological factors that regulate flower production are not well understood for flax (Linum usitatissimum L.) and other field crops, in spite of the fact that flowers are directly related to seed yield through the fruits that form from them. The objective of this research was to relate total flower production (FTOTAL), length of the flowering period (FPERIOD), and flower production rate (FRATE) of flax to (i) growth rates in several environments, and (ii) plant characteristics measured before and during the flowering period. Growth, flower production, seed yield, and the components of yield of 18 genotypes representing three plant types were measured in five plantings (18 May 1984; 1 May 1989; and 2, 10, and 29 May 1990) at Brookings, SD. Differences in growth, flower production, and yield were large for the five plantings and small for genotypes grouped by plant type. Length of the vegetative period and concentration of N in the tissues at midbloom or last flower were the only traits with significant positive correlation for all three flower production traits and all three plant types. Consideration of growth in shorter periods in three plantings showed that associations with FRATE, FPERIOD, and FTOTAL were negative for the vegetative period and positive for the flowering period for most plant characteristics. Factors producing significant statistics in multiple regression with flower production traits included leaf weight or growth in leaf weight, length of the vegetative period, N concentration, total nonstructural carbohydrate (TNC) concentration, and stem weight. Path coefficient analyses for FRATE, FPERIOD, and FTOTAL revealed indirect effects through leaf and stem growth rates for length of the vegetative period and N concentration. We conclude that FRATE, which had been considered to be a growth function relating vigor during flowering to seed yield at harvest, may be adversely affected by rapid vegetative growth, and that similar effects may occur for FPERIOD and FTOTAL.
Pre‐Induction Age and Post‐Induction Temperature Effects on Meadowfoam Flowering
Authors: Seddigh Majid , Jolliff Gary D.
Published: July 2010

The ability to predict meadowfoam (Limnanthes alba Hartweg ex. Benth.) phenology could help in commercial production management, and control of flowering date is also useful for managing crossing schedules in controlled environments. Effects of four pre‐induction ages (30, 45, 60, and 90 d from seeding) and four post‐induction temperature regimes (constant 12, 18, and 24 °C, and 24/12 °C day/ night) on days from induction to first flower (f) in ‘Mermaid’ meadowfoam (L. alba subsp. alba] were investigated. Post‐induction temperature had a greater effect than pre‐induction age on progress towards flowering (1/f). The relative responsiveness to post‐induction temperature (slope of the function) increased as pre‐induction age increased to 60 d. Post‐induction temperatures did not affect l/f in plants induced at 90 d, and these plants maintained a high 1/f even at the lowest temperature treatment. For pre‐induction ages up to 60 d, 1/f was estimated using a multiple linear regression model, which included only the additive effects of both pre‐induction age and post‐induction temperature. Post‐induction base temperature when 1/f equaled zero was about 5 °C regardless of pre‐induction age. For all pre‐induction ages, thermal sum from both seeding and photoinduction to first flower increased linearly as temperature increased to 20 °C and then decreased. As pre‐induction age increased, thermal sum from photoinduction to first flower decreased, whereas thermal sum from seeding to first flower increased. It was concluded that the effect of post‐induction temperature on progress towards flowering depends on plant age at induction and the differences become larger at higher temperatures.