bluuebunny/crossref_metadata_2025 huggingface dataset:
Recurrent Selfed Progeny Selection for Yield in Soybean Using Genetic Male Sterility
Authors: Burton J. W. , Koinange E. M. K. , Brim C. A.
Published: July 2010

The value of recurrent S1 line selection using genetic male sterility to achieve intercrosses has been questioned because of reduced seed set on male‐sterile S1 progenies, which can affect the precision of yield measurements. Recurrent S1 progeny selection for yield was practiced in two soybean [Glycine max (L.) Merr.] populations (designated II and III) that segregate for genetic male sterility. Recombination of selected lines was accomplished through insect pollination, and yield evaluations of S1 families disregarded the occurrence of male‐sterile plants in the plots. This study determined (i) rates of progress from four cycles of selection on seed yield in both populations and (ii) effects of selection for yield on other agronomic traits. Yield of Population II increased 76.6 ± 23.8 kg ha‒1 cycle‒1 (b ± SE), for a 2.1% yr‒1 increase; plant height increased 5.9% and lodging decreased 8.9% over the four cycles. Selection in Population III did not produce a significant (P > 0.05) linear increase in seed yield (only 37.7 ± 55.7 kg ha‒1 cycle‒1) and there were no significant (P > 0.05) changes in other traits. The success of selection for yield in Population II but not in Population III was most likely due to differences in genetic variability and heritability between the two. Because yield improvement was significant in Population II, it was concluded that segregation of male sterility in the S1 families was not a serious impediment to the evaluation of their relative yield potentials. Thus, genetic male sterility proved to be a useful tool for recurrent yield selection because of the ease with which selected lines are intermated.
Yield Components, Morphology, and Forage Quality of Multifoliolate Alfalfa Phenotypes
Authors: Volenec J. J. , Cherney J. H.
Published: July 2010

Forage quality of alfalfa (Medicago sativa L.) maybe improved by increasing the proportion of leaves to stems. Our objective was to examine the influence of the moltifoliolate leaf trait on morphology, yield components, and forage quality of alfalfa. Multifoliolate plants selected for production of five, seven, or nine leaflets per leaf were compared to trifoliolate plants selected for rapid (RSER) and slow (SSER)shoot elongation rate that also exhibited low and high leaf/stem ratios, respectively. Herbage from field‐grown plants was sampled twice in each of two years. Leaves of multifoliolate plants averaged. 4.4, 6.2, and 6.8 leaflets per leaf for phenotypes FIVE, SEVEN, and NINE, respectively. In 1987 multifoliolate plants produced fewer shoots per plant (x̄ = 26) but phenotypes FIVE and SEVEN consistently produced larger shoots (x̄ = 2.0 g shoot−1) than the RSER phenotype(x̄ = 59 shoots plant−1, 1.3 g shoot−1. Leaf/stem ratio was lowest for phenotype RSER (0.63), while leaf/stem ratio of SSER (1.27) equalled that of phenotypes SEVEN (1.20) NINE (1.30). In vitro dry matter disappearance (IVDMD) of herbage of multifoliolate phenotypes and SSER was greater(P < 0.10) than that of phenotype RSER in 1986, while in 1987 IVDMD of herbage of phenotypes NINE and SSER exceeded that of RSER. Herbage N concentrations of multifoliolate plants were not consistently greater than that of phenotype RSER, and were associated with lower leaf N concentrations in multifoliolate plants. The multifoliolate plants used in this study had high leaf/stem ratios, but this trait was not consistently associated with improved forage quality. Environment,along with other plant characters, also influenced IVDMD and N concentrations of herbage of these plants.
Identification and Inheritance of Inefficient Zinc Absorption in Soybean
Authors: Hartwig E. E. , Jones W. F. , Kilen T. C.
Published: July 2010

Two experimental soybean [Glycine max (L.) Merr.] lines that had produced nearly similar seed yields when grown at Stoneville, MS, differed widely when grown at Newton, MS. This study was conducted to identify the cause for the low seed yield of one line at Newton. Previous studies at this location on soils limed to a pH of 7.0 had shown that ‘Forrest’ soybean increased in yield when fertilized with zinc. Data are not available to show that soybean genotypes differ in efficiency of Zn absorption, so studies were initiated to determine whether Zn concentration in the foliage was different between the two experimental soybean lines. Fully developed trifoliolate leaves were taken from the upper part of the plant at the R1 growth stage and analyzed for concentration of Zn. The low‐yielding line D82‐3298 contained 18 to 25 μg g‐1 of Zn, while D77‐6056, the high yielding line, had 48 to 56 μg g‐1 of Zn. These results indicated that the two did differ in efficiency of Zn absorption. Three hundred thirty F3 lines from the cross D77‐6056 × D82‐3298 were grown along with parents in the same area the following year. The mean Zn concentration for the parental lines was 18.8 ±; 1 μg‐lfor D82‐3298 and 36.9 ± 2.6 μg g‐1 for D77‐6056. The distribution of F3 lines for Zn concentration suggests that only a few genes control Zn absorption efficiency or inefficiency. In additional plantings, D82‐3298, D77‐6056, and Forrest were grown with and without Zn fertilization. D82‐3298 gave a significant (P < 0.05) increase in foliar Zn concentration and seed yield when fertilized with ZnSO4 at Newton, but not at Stoneville. D77‐6056 and Forrest gave no response at either location.
Stomatal Limitation to Carbon Dioxide Assimilation in Nitrogen and Drought‐Stressed Wheat
Authors: Heitholt J. J. , Johnson R. C. , Ferris D. M.
Published: July 2010

Both stomatal and metabolic factors have been shown to limit gas exchange rates in leaves. Two growth chamber experiments using two levels of N supply and two levels of water supply were conducted to determine the effect of N nutrition on the regulation of CO2as similation rate (A) and stomatal limitation to A under drough stress. Wheat (Triticum aestivumL.) plants were soil grown under controlled conditions and subjected to no stress, N limitation, drought stress, or both N limitation and drought stress treatments when 4 wk old. After the plants were 6 wk old, A at varying CO2 concentrations (from 0 to 550 L−1), A at 20 mL O2 L‐1, stomatal conductance intercellular CO2 concentration (C1), leaf water potential (LWP) leaf N concentrationt, stomatal limitation to A, and ribulose bisphosphate carboxylase (rubisco) activity were determined. Drought stress reduced LWP (from‐ 0.73 to ‐1.65 MPa) and N stress reduced leaf N concentration (from > 30 to < 20g N kg‐1), A, and rubisco activity. The stomatal limitation to A and water use efficiency (WUE) was lower and C1 higher in the leaves of plants exposed to both N limitation and drought stress than those exposed to N limitation or drought stress alone or to those unstressed. High C1 in the N ‐ limited, drought‐stressed leaves did not appear to be explained by lower rubisco activity or by photorespiration. Determining other nonstomatal factors might be necessary to explain the low WUE of N‐limited drought‐stressed leaves compared to non stressed leaves.
Metabolic Characteristics Associated with Starch, Protein, and Oil Deposition in Developing Maize Kernels
Authors: Doehlert Douglas C. , Lambert Robert J.
Published: July 2010

The physiological processes that control relative starch, protein, and oil concentration of maize(Zea mays L.) kernels are not well defined. In this study, associationS between Metabolic Characteristics of developing kernels and specific storage product accumulation in mature kernels were identified. In a field experiment, kernels of maize genotypes with widely divergent chemical composition were harvested 50 days post pollination (DPP) to compare starch, protein, and oil concentrations with enzyme activities, sugar,and aminoc acid levels of kernels harvested 20 DPP. Mature kernels starch concentrations were correlated with immature kernel sucrose concentrations and ADP‐glucose pyrophosphorylase activities. Amino acid concentrations in immature kernels were correlated with the activities of phosphoglucoisomerase, Phosphoglucomutase, pyrophosphate: fructose 6‐ phosphalt 1‐phosphotransferase, and aldolasea and with mature kernel protein concentrations, but negatively correlated with starch concentrations. Oil concentrations were positively correlated with mature embryo dry weights and with malate dehydrogenase activities in isolated embryos harvested 20 DPP. The results suggest a complex interaction of sugars and amino acids supplied to the kernel by the plant affecting enzyme activities and storage product accumulation the developing kernel. High‐starch genotypes supplied more sucrose to their kernels, had higher ADP‐glucose pyrophosphorylase activity, and greater starch accumulation. High‐protein genotypes supplied more amino acids to their kernels, and had enhanced expression of a number of enzymes that may contribute to the greater protein accumulation. These data suggest that nutrient supply interacts with expression of enzyme activities in developing kernels to determine starch and protein concentrations in mature kernels.
Shade Effects on Growth of Tall Fescue: I. Leaf Anatomy and Dry Matter Partitioning
Authors: Allard G. , Nelson C. J. , Pallardy S. G.
Published: July 2010

Irradiance influences plant growth through photosynthetic activity and developmental responses. Our objectives were to determine the effect of irradiance on leaf anatomy and dry matter partitioning of tall rescue (Festuca arundinacea Schreb.). Plants were grown outdoors for 10 wk during summer 1986 and autumn 1987 with or without screencloth to give irradiances of 30% (low), 60% (medium), or full (high) sun. Data were similar for both years, although daily air temperatures averaged 25°C in 1986 and 12°C in 1987. Production of total plant dry matter was reduced at low irradiance, primarily due to fewer tillers per plant. Shoot/root ratio and leaf area ratio (leaf area per plant dry weight) were higher for plants grown at low irradiance than for those grown at high irradiance. Recently developed leaf blades on plants at low irradiance were 54 or 650/0 longer and had 56 or 77% more leaf area, but were 12% thinner and had 18 or 25% lower specific leaf weight than did those grown at high irradiance. Blade width was not affected. Total stomatal density at low irradiance was 17 or 24% lower than at high irradiance, with a larger reduction on the adaxial than on the abaxial epidermis. Proportional cross‐sectional areas of epidermis and bulliform cells, vascular bundle and fiber cap cells, and mesophyll cells were similar over treatments. Blades grown at low irradiance had ≈25% more air space than did those at high irradiance. At low irradiance, partitioning of dry matter among plant parts and developmental processes within the leaf blade were shifted to favor production of leaf blade area per unit of dry matter with no influence on forage quality.
Hay Curing and Water Soaking: Effects on Composition and Digestion of Alfalfa Leaf and Stem Components
Authors: Collins Michael
Published: July 2010

Progress toward improved hay harvesting technology is limited by a lack of information on the sources of yield and forage quality losses that occur during curing of alfaffa (Medicago sativa L.) hay, especially with exposure to rain. Two trials were conducted to determine the relative contributions of separate leaf and stem components to losses in yield and quality and to changes in dry matter and cell‐wall digestibility of alfalfa during hay curing and soaking with water. Concentrations of N, ash, in vitro dry matter disappearance (IVDMD)1 and neutral (NDF) and acid (ADF) detergent fibers were measured for leaf and stem components from alfalfa herbage just after harvest, and for field‐cured and water‐soaked hay. Leaf concentration averaged 386, 330 and 280 g kg‐1 in herbage, dry hay, and soaked hay, respectively. Neither hay treatment affected component N concentrations but whole‐shoot N concentration was reduced in both hays due to reduced leaf concentrations. Increased component fiber concentrations and reduced leaf concentration in soaked hay both contributed to large NDF and ADF increases on a whole‐shoot basis. The extent and rate of NDF disappearance were reduced in soaked hay compared with herbage. Leaf accounted for 78% or more of the respiration and shatter losses of DM, N, ash, and in vitro digestible dry matter (IVDDM) and 60% or more of the soaking losses of the same constituents. Onethird of the leaf N content was lost in soaked hay compared with 10% of the stem N content. Leaf and stem each lost 3% of their NDF content. Ash content losses during soaking exceeded 50% for leaf and 30% for stem. Because nearly all of the respiration and shatter losses, and most of the soaking losses, of chemical constituents came from the leaf component, reducing leaf loss offers the greatest opportunity for reducing alfalfa hay harvesting losses. Productive value of hay might be impacted more by severe wetting than constituent concentrations alone would indicate becaus extent and rate of fiber digestion are reduced.
Interactions among Loci Conferring Photoperiod Insensitivity for Heading Time in Spring Barley
Authors: Gallagher L. W. , Soliman K. M. , Vivar H.
Published: July 2010

The inheritance of extreme earliness for heading time, as measured by days to awn appearance (DAA), in ‘Super Precoz (2H)’ (SP), a photoperiod‐insensitive spring barley (Hordeum vulgare L.), was investigated in field studies under short daylengths at Davis, CA, and Ciudad Obregón, Sonora, Mexico, to obtain additional information on gene action. The DAA data from parental, F1, F2, F3, and F4 generations indicated that extreme earliness in SP was conferred by a single locus when homozygous recessive. Data from 75 F3 families evaluated for DAA in a field study and by starch gel electrophoresis of seedling‐plumule extracts indicated that the locus conferring extreme earliness was linked to Est 1 and Est 3 on the long arm of Chromosome 3 with ≈2% recombination. The locus was assigned gene symbol Easp. The dominant allele Easp suppressed the recessive allele easp and permitted the expression of other unidentified Ea loci conferring relative lateness. Allelism tests indicated recessive epistatic interactions between the Easp locus and the Eak and Ea7 loci. The easp recessive homozygote suppressed numerous other Ea maturity loci and headed earlier than the other three recessive homozygotes (i.e., eak, ea7, or eac), which were phenotypically similar.
Upland and Pima Cotton as Pollen Donors for Male‐Sterile Upland Seed Parents
Authors: Waller Gordon D. , Mamood Amed N.
Published: July 2010

The development of an interspecific hybrid cotton has been hampered by a serious problem with pollination. A field study was conducted to compare Pima cotton (Gossypium barbadense L.) with upland cotton (G. hirsutum L.) as a pollen source for hybrid seed production using male‐sterile upland seed parents. Male‐sterile cotton flowers were hand pollinated with either upland or Pima cotton pollen. The number of pollen grains per stigma and the resulting number of seeds per boll were evaluated using covariance analysis. In each of 3 yr the bolls produced from pollen of upland cotton produced more seeds per boll than did those produced from Pima pollen. Adjusted least square means indicate an advantage of four to seven seeds per boll with upland pollen. The conclusion is that more pollen grains per stigma are needed to set an equal number of seeds when using Pima pollen compared with using upland pollen.
New Allele at the Fan Locus in the Soybean Line A5
Authors: Rennie B. D. , Tanner J. W.
Published: July 2010

The soybean [Glycine max (L.) Merr.] line A5 has a low content of linolenic acid in the seed oil. Our objective was to determine if alleles at the Fan locus were influencing this trait in A5. To reduce environmental influences, the study was conducted indoors. Crosses were made between A5 and the low linolenic acid lines C1640 (fan/fan) and N78‐2245 (Fan/Fan). The F2 progeny of A5 ✕ N78‐2245, N78‐2245 ✕ A5, and N78‐2245 ✕ C1640 segregated in bimodal patterns for linolenic acid content, each consistent with a 3:1 ratio. The F2 patterns were confirmed by assays of F3 progeny. There was no segregation for linolenic acid content in the F2 progeny of A5 ✕ C1640. These observations indicated that A5 ✕ N78‐2245, and N78‐2245 ✕ A5 segregated for alleles at the Fan locus. The pattern of low linolenic acid content showed that the Fan and Idh2 loci were linked at distances of 25.2 ± 3.5 units for A5 ✕ N78‐2245, 24.3 ± 3.4 for N78‐2245 ✕ AS, and 24.7 ± 3.5 for N78‐2245 ✕ C1640. These results were all consistent with an allele at the Fan locus being the primary factor responsible for the low linolenic acid content in A5. The allele in A5 has been designated fan(AS). The fan(AS) allele appeared to be in two F4 lines from A5 ✕ N78‐2245 that were characterized by a mean linolenic acid content <25 g kg−1 when grown under 16 h daylength at 28/22°C day/night. The complete genetic basis of this phenotype is receiving further study.
Comparison of Mite Resistance for Control of Wheat Streak Mosaic
Authors: Conner R. L. , Thomas J. B. , Whelan E. D. P.
Published: July 2010

The wheat curl mite (Eriophyes [Aceria] tulipae Keifer) is the vector of wheat streak mosaic virus (WSMV), which incites wheat streak mosaic (WSM), a disease that causes serious yield losses winter wheat (Triticum aestivum L. em. Thell.). Several sources of resistance to mite colonization have been identified. Our objective was to determine the relative effectiveness of four sources of mite resistance in controlling the spread of WSMV. A series of controlled environmental tests showed that the incidence of WSMV tended to be lowest in ‘Rescue’‐Agropyron elongatum (Host) P. Beauv. chromosome substitution, addition, or translocation lines involving Chromosome 6 from A. elongatum. Disease incidence was significantly lower in the wheat‐rye (Secale cereale L.) translocation line KS80H4200 and in the ‘Norstar’‐Aegilops squarrosa L. backcross line NST*4/CMC1 than in the mite‐susceptible wheat cultivars Norstar and Rescue. The incidence of WSM was usually higher in the cultivar TAM 107, which carries a wheat‐rye translocation, than in other mite‐resistant entries and was not always significantly different from the mite‐susceptible winter wheat Norstar, even though TAM 107 reduced the incidence of symptoms of mite feeding. All entries tested were highly susceptible to WSMV when mechanically inoculated. In the field, following a light natural infestation of the wheat curl mite, lines from the cross NST*4/CMCI contained 40% fewer WSMV‐infected plants than lines without mite resistance. This study demonstrated that the mite resistance derived from A. elongatum was more effective in limiting the spread of WSM than was mite resistance originating from either rye or Ae. squarrosa.
Genetic and Linkage Analysis of Aconitate Hydratase Variants in Soybean
Authors: Kiang Y. T. , Bult C. J.
Published: July 2010

Genetic markers and chromosome linkage maps are useful in genetic research and plant breeding. Soybean [Glycine max (L.) Merr.], plants were grown in the greenhouse and field to obtain Ft, F2, and F3 seeds, and starch gel electrophoresis was employed to determine inheritance of several aconitate hydratase isozyme variants and the relative position of the Aco3 locus in soybean Linkage Group 1. Genetic data show that the Aco1 null variant (acol‐n) is allelic to Acol‐a, the Aco2‐c variant is allelic to Aco2‐a, and the Aco4‐d variant is allelic to Aco4‐c. The Aco5 locus has three alleles Aco5‐a, Aco5‐b, and aco5‐n. Recombination values were 12.4 ± 0.8% between the Aco3 and Spl (Am3), 33.6 ± 3.7% between Aco3 and yl2, 39.2 ± 2.1% between Aco3 and t, 13.2 ± 1.2% between Spl and y12, and 29.6 ± 1.3% between Spl and t. The gene order of these markers was thus determined as Aco3‐Spl‐yl2‐t. Based on these five aconitate hydratase isozymes, genetic variation was calculated for both wild and cultivated soybean. No significant differences in the level of genetic variation [gene diversity (heterozygosity) and number of alleles per locus] between wild and cultivated soybean were observed. The values for gene diversity and number of alleles per locus in soybean are comparable to those observed in other autogamous annual plant species.
Defoliation Effects on Grain Fill, Stalk Rot, and Lodging of Grain Sorghum
Authors: Rajewski J. F. , Francis C. A.
Published: July 2010

Yield response to defoliation in grain sorghum [Sorghum bicolor (L.) Moench] can be influenced by time and intensity of leaf removal. Limited information is available for defoliation ✕ environment interactions and the defoliation response of yield‐related traits, stalk rot, and basal stalk lodging. This study was conducted to examine the effect of time and extent of defoliation on hybrid grain sorghum in three eastern Nebraska environments in relation to yield components, duration and rate of grain filling, nonsenescence period, stalk rot, and lodging. Four levels of defoliation (0, SO, 95, and 100%) were applied to plants at 10 d preanthesis, anthesis, 10 d post anthesis, and 20 d post anthesis. Defoliation significantly decreased yield components, grain‐fill duration, grain‐fill rate, and the nonsenescence period, while increasing the occurrence of stalk rot. The most pronounced effects on all traits occurred when plants were defoliated prior to or during anthesis. Significant defoliation level ✕ time interactions and environment ✕ defoliation treatment interactions were observed for all traits. Variance component estimates indicated that environmental interaction comprised 18 to 25% of total variation for the yield components, 5% for stalk rot, and 50% for lodging. Use of defoliation in a limited number of environments may not prove effective in evaluating tolerance to lodging. Small environmental interactions for the stalk rot response suggest that observations from only a few environments are necessary for its evaluation.
Response to Divergent Selection for Anthesis Date in Tall Fescue
Authors: Watson C. E. , McLean S. D.
Published: July 2010

Date of anthesis is the major factor controlling the seasonal distribution of forage yield and quality in tall fescue (Festuca arundinacea Schreb.). The objective of this experiment was to evaluate the response to divergent selection for anthesis date in three cultivars of tall fescue that differ for date of anthesis. Three cultivars, Fawn, Alta, and Kentucky 31, were evaluated for date of anthesis in the field from 1981 to 1983. There was a strong juvenile requirement for some genotypes within each cultivar; however, this tended to be more of a problem with the earlier‐maturing cultivars, Fawn and Alta. Correlations of establishment year data (1981) with mature plant data (1982 and 1983) were low; consequently, establishment year data were not utilized in selecting for anthesis date. Selections for both earlier and later anthesis were made within each population based on mature plant data. The six selected populations and the three unselected parent populations were evaluated as mature plants in the field for 2 yr. All populations exhibited a significant response to selection except for the Fawn population that was selected for earlier anthesis date. Realized heritabilities for later anthesis were higher (0.71–0.79) than for earlier anthesis (0.18–0.38) within each cultivar. The variance for anthesis date within each cultivar was increased by selection for later anthesis and decreased by selection for earlier anthesis. There appeared to be sufficient residual variation for further selection in all populations, with the possible exception of the Fawn population that was selected for earlier anthesis.
Differential Responses to Defoliation of Grain Sorghum Yield Components and Yield‐Related Traits
Authors: Rajewski J. F. , Francis C. A. , Eastin J. D.
Published: July 2010

Leaf removal can significantly reduce yield of grain sorghum [Sorghum bicolor (L.) Moench]. Genotype ✕ defoliation interactions for yield have been reported in other crops, but limited information is available in sorghum. This study was conducted on eight sorghum hybrids to evaluate hybrid responses of yield components and grain‐fill traits to N application and post‐anthesis defoliation. A factorial arrangement of three defoliation levels and three N fertilization rates was used in experiments conducted in five Nebraska and Kansas environments. Defoliation treatments (0, 50, and 100%) were applied at 10 d post anthesis. Removal of 50 and 100% of the leaves caused curvilinear reductions in all measured traits. Significant N effects were not observed in all environments. Defoliation ✕ N interactions did not occur for the traits studied. Genotype ✕ defoliation interactions occurred for grain yield, seed weight, seed number, duration of grain fill, and rate of grain fill, indicating that hybrids did not respond the same to defoliation treatments. Hybrids with higher seed number and longer preanthesis period maintained higher grain yields with defoliation. Responses of seed number to N application were similar for all hybrids. Genotype ✕ defoliation ✕ environment interactions were observed for all traits. Environmental interactions need to be considered when using defoliation to differentiate among hybrids in their components of yield and the relationships of these traits to grain yield.
Preference of Root‐Lesion Nematode for Alfalfa and Forage Grasses Growing in Binary Mixtures
Authors: Petersen A. D. , Barnes D. K. , Thies J. A.
Published: July 2010

Most forage crops are hosts for the root‐lesion nematode, Pratylenchus penetrans (Cobb) Filipjev & Schur‐Stekhoven. The objective of this research was to compare the preference of P. penetrans for two alfalfas (Medicago sativa L.) and 14 forage grasses or small grains when grown in binary (two species) mixtures. The two alfalfas included the susceptible cultivar Baker, and MNGRN‐16, an experimental population with field resistance to P. penetrans. The grasses included 12 species: barley (Hordeum vulgare L,), Kentucky bluegrass (Poa pratensis L.), smooth bromegrass (Bromus inermis Leyss.), oat (Avena sativa L.), orchardgrass (Dactylis glomerata L.), pearl millet (Pennisetum glaucum L.), perennial ryegrass (Lolium perenne L.), quackgrass [Elytrigia repens (L.) Nevski], reed canarygrass (Phalaris arundinacea L.), tall fescue (Festuca arundinacea Schreb.), timothy (Phleum pratense L.), and wheat (Triticum aestivum L.). Two seedlings of each grass entry and one alfalfa seedling were planted into a polyethylene tube containing a 1:1 sand/soil mixture. Eight tubes (replicates) were each inoculated with 90 nematodes; non‐inoculated tubes were used as controls. Six weeks after inoculation, fresh root weight and dry shoot weight were recorded and numbers of nematodes in the roots were determined by staining with acid fuchsin. Among the grasses, the oat, reed canarygrass, and quackgrass had the greatest number of nematodes, whereas pearl millet, perennial ryegrass, tall fescue, and timothy had the least. Alfalfa was the preferred host of P. penetrans when grown in combination with grasses. Baker and MNGRN‐16 alfalfa each supported 75% of the total number of nematodes compared with all grass‐alfalfa combinations. These results suggest possibilities for developing cropping systems including forage species that can tolerate or reduce root‐lesion nematode populations.
Classification of Diverse Bread Wheat‐Growing Environments Based on Differential Yield Responses
Authors: Yau S. K. , Ortiz‐Ferrara G. , Srivastava J. P.
Published: July 2010

Bread wheat (Triticum aestivum L.) environments in West Asia, North Africa, and Mediterranean Europe are highly variable in terms of moisture, temperature, and biotic stresses. The present study attempted to divide this region into relatively uniform subregions by cluster analysis, to reduce the large magnitude of genotype (G) ✕ environment (E) interaction. Grain yield data of 21 to wheat lines in 2 yr were analyzed by a hierarchical agglomerative program with the correlation coefficient as a distance measure and average linkage as the clustering strategy. The large and significant entry ✕ trial interaction detected in the region implied that breeding for wide adaptability for this region would be difficult. Based on differential yield responses of the wheat lines, the cluster analysis showed the differences between the irrigated/high‐rainfall (IHR) and rainfed low‐rainfall (RLR) sites. Besides moisture supply, winter temperature of the sites appeared to be another determinant of the clusters. The IHR clusters consisted of sites with milder temperature than sites in the RLR clusters. The presence or absence of diseases also influenced the delineation of the clusters, but photoperiod of the sites did not appear to have a large influence. The greater variability in RLR sites relative to IHR sites indicated that breeding for RLR environments would be more difficult. We conclude that different breeding strategies should be followed within IHR and RLR environments.
Effects of Gene ant13 on Agronomic and Malt Quality Traits of Barley
Authors: Horsley R. D. , Schwarz P. B. , Foster A. E.
Published: July 2010

Haze formation in beer can be retarded by use of proanthocyanidin‐free barley (Hordeum vulgare L) malt. Lack of production of proanthocyanidins in barley is controlled by a single recessive gene, such as the ant 13 and ant 17 genes. Many of the proanthocyanidin‐free lines developed have had undesirable agronomic and malt quality. The objective of this study was to observe effects of the ant 13 gene of DM582 on agronomic traits and malt quality of backcross‐derived lines using ‘Azure’, ’Glenn’, and ‘Hazen’ as recurrent parents. Gains were made in reducing plant heights and number of days to heading and increasing kernel plumpness, fine grind extract, and soluble protein of BC1 lines as compared with the donor line, DM582. No significant increases in mean grain yield and test weight of Hazen BC1 lines were observed compared with that of DM582. However, individual lines from each population could be selected that had grain yield, 200‐kernel weight, and test weight similar to that of the recurrent parents. This indicates that with selection of superior lines for these traits and using them as parents in a backcross program, proanthocyanidin‐free cultivars with acceptable agronomic performance, malt extract, and soluble protein can be developed. Due to the large negative effects of the ant 13 gene of DM582 on several traits, however, DM582 is not an acceptable source of germplasm to produce proanthocyanidin‐free cultivars with acceptable malt quality that are adapted to the midwestern barley‐growing region of the USA.
Relationships among 70 North Amerian Oat Germplasms: II. Cluster Analysis Using Qualitative Characters
Authors: Souza E. , Sorrells M. E.
Published: July 2010

Analysis of genetic relationships in crop species can provide a relative measure of genetic diversity, an index for parental selection, and structure for stratified sampling of populations. This research was to study the genetic relationships among 70 recent and historical North American oat cultivars using an estimate of the similarity of alleles for polymorphic allozymes, prolamine seed proteins (avenins), and simply inherited morphological characters. Clusters were formed by sequentially dividing groups of cultivars using factor analysis. The first division split cultivars into fall and spring‐planted groups. A modified Shannon‐Weaver information statistic (I'), which is inversely related to genetic diversity, was estimated for each of the six large clusters formed. The I' value for cultivars in the fall‐planted clusters was 0.35, while the spring clusters' value was 0.37. The two clusters representing most of the cultivars from Canada and the midseason spring oat region had a collective I' value of 0.50. This study of qualitative characters indicated that fall‐ and spring‐planted oat cultivars are genetically divergent groups. The fall‐planted oat cultivars are more genetically diverse than the spring‐planted cultivars adapted to the economically important growing regions of the upper North American central plains.
Genetic Variation for Selenium Content in Tall Fescue
Authors: McQuinn S. D. , Sleper D. A. , Mayland H. F. , Krause G. F.
Published: July 2010

Selenium is an element necessary for good animal health. No information is available on inheritance of Se concentration in tall fescue (Festuca arundinacea Shreb.). Therefore, the purpose of this investigation was to determine the nature of genetic variation of Se concentration in tall fescue. To accomplish this objective, 15 parental clones were randomly chosen from a broad‐based population, and their half‐sib (HS) progenies were generated using a polycross mating design. Selenium analysis was determined flourometrically by digesting dried, ground herbage samples in 3:1 HNO3/HClO4. Significant genetic variation was observed among HS families in the fall for Se concentration. Heritability, calculated using parent‐offspring (PO) regression, gave estimates of 18% for summer and 68% for the fall. Heritability and genetic gain estimates were maximized in the fall, as compared with the summer, largely because of a large environmental component. Genetic gain, expressed as a percentage of the mean of parents, predicted an advance of 19% for fall herbage. Progress in selecting for improved concentrations of Se in the fall in this population of tall fescue is likely.
Introgression of Genes for Small Seed Size from Glycine soja into G. max
Authors: LeRoy A. R. , Fehr W. R. , Cianzio S. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] cultivars with a seed weight of <100 mg seed−1 are preferred for some food products. The wild species Glycine soja Sieb. & Zucc. has a seed weight of <30 mg seed−1, but undesirable agronomic characteristics prevent its direct use in commercial production. The feasibility of transferring the genes for low seed weight from G. soja into high‐yielding cultivars of G. max through backcrossing was studied. For three G. max ✕ G. soja crosses, selection between backcross generations for low seed weight was compared with no selection during backcrossing. For each cross, 40 F2‐derived lines from each backcross generation from the BC0 to BC3 were evaluated in two replications at two locations for seed weight, seed coat color, lodging, petiole retention, and maturity. Selection resulted in backcross progeny with smaller seed weights than those obtained from backcrossing without selection. Of the BC3F2‐derived lines, 37% had seed weights of ≤100 mg seed−1 in the populations obtained by selection, compared with 18% of those obtained without selection. From each cross, BC3F2‐derived lines were evaluated for yield. An average positive correlation of 0.44 was found between seed weight and yield among selected populations and 0.54 among unselected populations. Up to 89% of the yield of the recurrent parent was exhibited by lines with seed weights of 100 mg seed−1 or less.
Genetic Linkage of the Phytophthora Resistance Gene Rps2 and the Nodulation Response Gene Rj2 in Soybean
Authors: Devine T. E. , Kilen T. C. , O'Neill J. J.
Published: July 2010

Genome mapping of the agronomically important genes in soybean, Glycine max (L.) Merr., is as yet in a primitive stage. In this study we tested the Rps2 locus controlling resistance to phytophthora root rot (induced by Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin) for genetic linkage to the Rj2 locus controlling ineffective nodulation with certain strains of Bradyrhizobium japonicum. The line BARC‐4 (Rj2) carrying the Rj2 and Rps2 alleles was hybridized with ‘Clark 63’ carrying the rj2 and rps2 alleles. The F2 plants were characterized for the Rj2 vs. rj2 phenotypes by inoculating seeds in growth‐tray culture with a strain (USDA 7) defining for the Rj2 locus. The F3 progeny derived from F2 plants assayed for the Rj2 gene were screened to determine the genotype at the Rps2 locus. The F3 seedlings were evaluated in hydroponic culture inoculated with Race 4 of P. megasperma. Analysis of data indicated a significant (P < 0.0001) chi‐square for linkage. The maximum likelihood estimate for linkage indicated a very tight linkage with 2.7 ±1 genetic map units separating these loci. The Rps2‐Rj2 linkage is designated Linkage Group 19.
Lipid Content and Composition of Soybean Somatic Embryos
Authors: Dahmer M. L. , Collins G. B. , Hildebrand D. F.
Published: July 2010

The extent of morphological similarity between soybean [Glycine max (L.) Merr.] somatic embryos and immature zygotic embryos is often correlated with their ability to germinate and has been used to estimate somatic embryo quality. Biochemical markers, such as the accumulation of seed storage proteins or lipids, offer more objective means of assessing embryo quality than morphological traits alone. The influence of various somatic embryo induction and maturation media on the accumulation and composition of seed storage lipids was determined. Mean lipid concentrations in somatic embryos ranged from 2.4 to 40.3 g kg−1 dry weight and were always much lower than those measured in mature seed (184.6 g kg−1 dry weight). Prior to transfer to maturation media, somatic embryos had significantly higher levels of palmitic acid and linolenic acid than mature seed, but lower levels of oleic acid and linoleic acid than were in the mature seed. Reducing or completely removing auxin during maturation increased germination and also increased the similarity between the lipid compositions of somatic embryos and mature seeds, suggesting that lipid composition may have potential as a diagnostic marker of somatic embryo quality. Differences between somatic embryo axis and cotyledon lipid compositions were identified; however, the differences between the lipid compositions of somatic and zygotic embryos were not fully explained by differences in the relative contribution of axis and cotyledon tissues.
Desiccation Tolerance in Maturing Maize Seed: Membrane Phospholipid Composition and Thermal Properties
Authors: Chen Y. , Burris J. S.
Published: July 2010

Membrane phospholipids play an important role in acclimation of plants to environmental stresses. Phospholipid composition and thermal properties in maturing maize (Zea mays L.) seed were studied to relate high‐temperature desiccation tolerance to membrane stabilization. A preconditioning process (treatment at 35 °C prior to high‐temperature drying) was used to induce the high‐temperature desiccation tolerance. Phosphatidylcholine (PC) accumulated, resulting in an increase in the PC/phosphatidylethanolamine (PE) ratio from 3.6 to 8 within 48 h as the high‐temperature desiccation tolerance was induced during preconditioning. The increase in PC/ PE ratio coincided with a decrease in both phase transition temperature and enthalpy of transition, indicating more stable membranes. The improved stability could be related to the high‐temperature desiccation tolerance and membrane function after preconditioning. A shift in the fatty acid composition of the membrane lipids from linoleic acid (18:2) to oleic acid (18:1) during preconditioning indicates a more saturated fatty acid composition. This shift in fatty acids may result in membranes that more easily cope with high‐temperature desiccation, as contrasted to a low‐temperature effect. The results suggest that alterations in phospholipid molecular species and changes in fatty acid composition to a more saturated composition in maize seed during preconditioning and maturation could be common mechanisms in high‐temperature desiccation tolerance.
Chemical Efficacy of Early Square Removal and Subsequent Productivity of Superokra‐Leaf Cotton
Authors: Kennedy C. W. , Smith W. C. , Jones J. E.
Published: July 2010

Delaying fruit set of superokra‐leaf cotton (Gossypium hirsutum L.) can potentially improve yields and provide an excellent trap‐crop system for boll weevil (Anthonomus grandis Boh.) management if a practical means of early‐season square removal could be obtained. We determined the efficacy of ethephon (2‐chloroethylphosphonic acid) applications on removing early squares, effectiveness of Ag+ at reducing damaging effects of ethephon on plant terminals, and subsequent effects of these treatments on the reproductive development of field‐grown superokra‐leaf cottons. All square‐removal treatments caused a significantly greater number of early squares to abscise than occurred normally in untreated plots, but ethephon treatment results were variable. Side‐directed applications of 8 or 12 mM ethephon at 0.28 kg ha−1 and 20 mM ethephon at 0.68 kg ha−1 removed an average of 124% more squares than manual square removal in 1986. In 1987 and 1988, however, 0.28 kg ha−1 ethephon removed 16 and 24% fewer squares than manual methods, respectively. A 200‐mg L−1 AgNO3 pretreatment on plant terminals significantly reduced the number of squares abscised in the ethephon treatments by 20 and 36% in 1986 and 1988, respectively, and did not consistently improve yield or earliness. Removal of early squares delayed the initiation of fruiting, which continued into a delayed crop maturity. Fruiting occurred more rapidly in square‐removal treatments than controls, but the fruiting period still extended later into the growing season, regardless of the accelerated rate. The effect of square removal on seedcotton yield was variable. Square‐removal treatments averaged 2261, 1914, and 2652 kg ha−1 of seedcotton in 1986, 1987, and 1988, respectively. Controls averaged 2585, 1546, and 2839 kg ha−1 in the same respective years. A difference in environmental conditions during fruiting was considered an important factor in yield differences. Although side‐directed applications of ethephon were effective in removing early squares, the variability in yield and the delay in crop maturity offset any potential advantages it may have in a boll weevil trap‐crop system.
Inheritance of Reaction to Strawbreaker Foot Rot in Two Wheat Populations
Authors: Allan R. E. , Roberts D. E.
Published: July 2010

Strawbreaker foot rot (Pseudocercosporella herpotrichoides), the most important soilborne disease of fall‐sown wheat (Triticum aestivum L.) in northwestern USA, can best be controlled by host resistance. ‘Cerco’ and VPM germplasm are important sources of resistance. This study was conducted to determine genetic control of their reaction to the fungus and devise breeding strategy to exploit their resistance. Intermediate to high heritability (h2) values (0.57 to 0.84) were obtained for lesion indices assessed on calms of mature plants of F2 derived F3, F4, and F5 progenies of the crosses VPM/ ‘Moisson’ 421 (resistant)//Sel.101 (susceptible) and VPM/Moisson 951 (resistant)//Cerco (moderately resistant). The cross between VPM derivative and the susceptible parent concurred with other studies indicating that a single dominant gene controlled the expression of strawbreaker lesion index. The lesion index segregation patterns of the VPM/Moisson 951//Cerco cross revealed that the resistances of the two parents were genetically different. Some progeny may exceed VPM/Moisson 951 for resistance. Significant associations were measured between lesion index and six agronomic traits in one or more generations of both crosses, however, only percent lodging and a rating of strawbreaker symptoms had value as correlated responses with lesion index. A recommended approach would be to select for absence of lodging and strawbreaker symptoms in early generations among lines grown under strawbreaker conditions and limit scoring of lesions to advanced lines.
Reciprocal Full‐Sib Recurent Selection in Maize: I. Direct and Indirect Responses
Authors: Eyherabide Guillermo H. , Hallauer Arnel R.
Published: July 2010

Interpopulation recurrent selection methods can be used for developing new heterotic patterns and enhancing those identified previously. The objective of this research was to estimate the direct and indirect responses to eight cycles of reciprocal full‐sib recurrent selection in maize (Zea mays L.) populations BS10 and BS11. The populations and their crosses corresponding to Cycles 0, 2, 4,6, and 8 were evaluated at two levels of inbreeding (F = 0 and F = 0.5), and populations also were testcrossed to the respective Cycle 0 populations and unrelated inbred lines. Entries were evaluated in eight environments. Eight cycles of selection were effective for increasing grain yield of the population cross (6.5% cycle−1), BS10 (3.0% cycle−1), and BS11 (1.6% cycle−1). Standability, prolificacy, and grain moisture also were changed in the desired directions, and, in most instances, the responses were linear across cycles of selection. Direct responses were greater than indirect responses for grain yield and Standability. The selected populations also performed better than did the unselected populations in crosses with unrelated testers. Changes in inbreeding depression and heterosis were associated with selection. Rates of direct and indirect responses for grain yield in the inbred populations tended to be greater than the rates of responses in the noninbred populations. Reciprocal full‐sib selection increased the frequency of homozygotes for favorable alleles in the BS10 and BS11 populations, which would be improved sources of vigorous inbred lines with good general combining ability. Reciprocal full‐sib selection seems to have increased the frequency of heterozygotes in the population crosses.
Carbon Costs of Dinitrogen Fixation Associated with Dry Matter Accumulation in Alfalfa
Authors: Twary S. N. , Heichel G. H.
Published: July 2010

Dinitrogen fixation of modulated legumes theoretically may limit crop yield because of nodule needs for products of photosynthesis; however, this concept is poorly supported by experimental evidence. To determine how nodule C use might limit legume dry‐matter accumulation, the C costs of N2 fixation of alfalfa (Medicago sativa L.) were investigated in the glasshouse daring two harvest‐regrowth cycles. Plants were inoculated with either of two contrasting rhizobiai strains and grown in nil‐N hydroponics to provide differing symbioses. Dry matter accumulation, total reduced N accumulation, and nodule gaseous exchange (respiration and nonphotosynthetic CO2 fixation) were measared, and C costs were calculated. Dinitrogen fixation and nodule gaseous exchange varied with plant development and harvest. Plants nodulated by Strain I02F51 averaged a 68% higher rate of N2 fixation on a unit nodule‐mass basis than those nodulated by strain P207. Total N2 fixation per plant, however, was similar due to the contrasting nodulation characteristics of the two symbioses. Nodule CO2 fixation on a unit nodule‐mass basis was greater in nodules formed by strain I02F51 than in those formed by strain P207; nodule CO2 fixation per plant was similar for the two symbioses. Nodule CO2 fixation apparently assimilated 25 to 30% of the CO2 respired by nodules. Over the course of the experiment, the average C cost of N2 fixation in nodules formed by strain P207 (9.4 mol C mol ‐~ N) was 59% greater than that of nodules formed by strain I02F51 (5.9 mol C mol−1 N). Total dry matter accumulation during the experiment by plants nodulated by Strain P207 (with higher C costs) was 21% greater than that of plants nodulated by Strain I02F51 (with lower C costs). The results indicated that, in our experimental system, dry matter accumulation was unrelated to the C costs of N2 fixation. These results contrast with what theory suggests, despite the association between specific activity of N2 fixation and C costs. The results have implications to understanding symbiotic limitations to legume productivity and to transforming nonlegumes to fix N2.