bluuebunny/crossref_metadata_2025 huggingface dataset:
Weed‐Crop Competition Models and Response‐Surface Analysis of Red Rice Competition in Cultivated Rice: A Review
Authors: Pantone Dan James , Baker John B.
Published: July 2010

Models that predict crop yield based on crop and weed densities are valuable for estimating yield losses and devising weed control strategies. Field experiments were conducted in 1987 and 1989 to evaluate a model describing the competitive interaction between red rice (Oryza sativa L), a weedy variety, and the commercial cultivar, Mars. The response‐surface model consisted of nonlinear yield‐density equations where average per‐plant yield was the dependent variable and the densities of the competing plant varieties were the independent variables. Yield was measured as both grain yield and the number of seeds. The model predicted the maximum yield of an isolated plant, the area associated with the maximum yield per plant, and competitive ability. Each year, the predicted maximum yield of an isolated red rice plant was greater than that for Mars. Similarly, the parameter describing the area associated with maximum yield per plant was larger for red rice. Red rice was the dominant competitor; the model indicated that it took approximately three Mars plants to have the same effect on the grain yield of Mars as only one red rice plant. With respect to red rice, competition was primarily with plants of the same variety, whereas for Mars, competition with plants of the other variety was more important.
Biomass Heterosis and Combining Ability in Interspecific and Intraspecific Matings of Grain Amaranths
Authors: Lehmann J. W. , Clark R. L. , Frey K. J.
Published: July 2010

To develop a practical foundation for breeding higher‐yielding grain amaranths (Amaranthus spp.), 32 amaranth accessions from the World Germplasm Collection were hybridized to produce 87 Fl's, which were subsequently evaluated for biomass heterosis and combining ability in three factorial mating designs. On average, interspecific matings of A. cruentus L. and A. hypochondriacus L., in comparison with their parents, produced highly significant (P < 0.01) biomass increases. When crossed with A. cruentus African vegetable accessions as females, male parents of both species showed significant (P ≤ 0.05) general combining ability (GCA). Mid‐parent heterosis for biomass ranged from −13 to 88% and high‐parent heterosis ranged from −24 to 40%. Late flowering of interspecific matings was associated with larger biomass yields. Preliminary experiments utilizing intraspecific matings within both A. hypochondriacus and A. cruentus gave no indication of high‐parent heterosis. Interspecific hybridization seems to be a promising way to increase biomass productivity of Amaranthus spp. for use as forage, energy feedstock, or a vegetable.
Stability of Alkaloid Production in Flue‐Cured Tobacco
Authors: Bowman D. T. , Weeks W. W. , Wilkinson C. A.
Published: July 2010

Alkaloid production in flue‐cared tobacco (Nicotiana tabacum L.) genotypes must be within an established acceptable level for the genotypes to be released as cultivars. The objectives of this study were to examine the stability of alkaloid production in cultivars and advanced breeding lines relative to standards set in the Regional Minimum Standards Program. Stability of alkaloid production was examined using data from the Regional Farm Test entries (1986– 1988) and the North Carolina Official Variety Tests (1979–1983). Averaged across 55 environments, the two check cultivars did not differ in nicotine or nornicotine production; however, ‘NC 95’ produced higher levels of anabasine and anatabine and had a higher ratio of total secondary alkaloids to total alkaloids (TSA/TA) than ‘NC 2326’. As indicated by the coefficients of variation, there were stability differences for nornicotine, anabasine, and anatabine production as well as TSA/TA in the Regional Farm Tests but none for nicotine production. In the North Carolina Official Variety Tests, there was a significant cultivar ✕ year interaction for nicotine production and a significant location effect for nornicotine production. The unstable production of secondary alkaloids suggests that TSA/TA should be examined across both years in which the entries are in the program before rejection or acceptance.
Nodulation Interaction of the Soybean Allele Rj2 with Asiatic Isolates of Bradyrhizobium japonicum
Authors: Devine T. E. , Kuykendall L. D. , O'Neill J. J.
Published: July 2010

The dominant allele Rj2 in soybean, Glycine max (L.) Merr., restricts nodulation with Bradyrhizobium japonicum (Jordan) strains USDA 7, USDA 14, and USDA 122, while the recessive allele rj2 permits normal nodulation. To determine the frequency of nodulation restriction by the Rj2 allele of soybean, 89 bradyrhizobial isolates from Asia were tested in Leonard jar culture for nodulation response with near isogenic plant lines differing at the Rj2 locus. Fifty‐one percent of the isolates tested elicited the nodulation restriction of the Rj2 allele. No geographic pattern in the occurrence of Rj2‐restricted strains was discerned. Nearly half (47%) of the isolates restricted by the Rj2 allele were from Serogroup 6. Twenty‐one of 25 Serogroup 6 strains were restricted by the Rj2 allele. Since some strains in Serogroup 6 were not restricted by the Rj2 allele and some strains not in Serogroup 6 were restricted, specific serological reaction per se is not essential or necessary for eliciting the action of the Rj2 allele. It appears that the Rj2 rejection is not as related to serotype as had been assumed.
Genetic Relationships between Loci Controlling Palmitic and Linolenic Acids in Soybean
Authors: Nickell A. D. , Wilcox J. R. , Cavins J. F.
Published: July 2010

Three mutagen‐derived soybean [Glycine max (L.) Merr.] lines have been identified with unique levels of fatty acids. Levels of linolenic acid (18:3) in C1640 and palmitic acid (16:0) in C1726 C1727 are controlled by alleles with additive effects at three loci. If these loci are independent, soybean strains could be developed with unique and useful combinations of both linolenic and palmitic acids. The primary objective of this study was to determine the genetic relationships between loci controlling levels of palmitic acid and the locus controlling linolenic acid. Additionally, effects of altered levels of linolenic and palmitic acids on total fatty acid composition were determined. Fatty acid composition of F2 seeds from crosses of C1640 (low 18:3) with both C1726 (low 16:0) and C1727 (high 16:10) were determined by gas chromatography. Chi‐square analyses of the data demonstrated that the fan locus controlling low 18:3 was inherited independently from both the fap1 and fap2 loci controlling low and high levels of 16:0, respectively. There was no indication of an interaction among alleles at these loci. The decreases in palmitic acid due to fap1 and increases due to fap2 were associated primarily with changes in oleic and linoleic acids. Decreases in linolenic acid due to fan were associated primarily with increases in linoleic acid.
Carbon Isotope Discrimination, Gas Exchange, and Water‐Use Efficiency in Crested Wheatgrass Clones
Authors: Read John J. , Johnson Douglas A. , Asay Kay H. , Tieszen Larry L.
Published: July 2010

Carbon isotope discrimination (Δ) has been proposed as a criterion in selecting for water‐use efficiency (WUE) in C3 crop species. This study was conducted to determine associations among Δ, leaf instantaneous WUE (WUEi), and shoot WUE (WUE3) in clones of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] previously selected for low, medium, and high Δ. Nine clones (three in each Δ class) were grown in a greenhouse in pots weighed every third day and brought to either 0.03 or 0.12 kg kg−1 gravimetric water content. Leaf gas exchange rates and water potentials were determined at 2‐wk intervals until plant harvest at 12 wk. Under drought, the ranking of Δ classes for stomatal conductance agreed with previous and present Δ classifications, and midday leaf water potentials averaged ≈0.4 MPa lower in the low than in the medium or high Δ class. Shoot dry weight and Δ decreased with drought and were correlated positively under well‐watered conditions (r = 0.77*, df = 7, P < 0.05), but not under drought. Although Δ and leaf intercellular CO2 concentration of individual clones were correlated positively at each water level, the expected differences between Δ classes in Δ, WUEi, and WUE3 were obtained only under drought. A lower Δ in low than high Δ class under drought was associated with greater shoot dry weight, WUE3, and WUEi. Across water levels, large negative correlations were found between Δ and WUEi (r = ‐0.95**, df = 16, P < 0.01) or WUE3 (r = −0.89**, df = 16). These results indicate that selection for low carbon isotope discrimination will improve water‐use efficiency in crested wheat‐grass under drought.
Dinitrogen Fixation Potential and Yield of Hypernodulating Soybean Mutants: A Field Evaluation
Authors: Wu S. , Harper J. E.
Published: July 2010

Soil N is a major deterrent to increased N2 fixation by soybean [Glycine max (L.) Merr.]. Three hypernodulating mutants (NOD1‐ 3, NOD2‐4, and NOD3‐7) were compared with a nonnodulating mutant (NN5) and the ‘Williams’ parent in a field study in 1988 and 1989 to determine nodulation and agronomic response to 0 and 200 kg N ha−1 applied as urea. Nodule activity was determined by acetylene (C2H2) reduction activity of nodulated roots and relative ureide abundance in vacuum‐extracted xylem sap. In the absence of N fertilizer, two years of data based on the C2H2 reduction assay indicated that all hypernodulating mutants had greater N2 fixation potential than did Williams in early growth stages. Among them, NOD1‐3 had higher N2‐fixing potential (about 10%) than the other two mutants. Both the relative ureide abundance assay (comparing NN5 with other lines in 1989) and the C2H2 reduction assay during the 2‐yr study indicated that N2 fixation by Williams was completely inhibited by N fertilizer through the initial sampling date, while the three hypernodulating mutants showed detectable N2 fixation activity. The relative ureide abundance assay indicated that both NOD1‐ 3 and NOD2‐4 lines were more tolerant of added N fertilizer than was Williams in 1989. In the absence of N fertilizer and at later stages of plant development, N input from N2 fixation by Williams was very similar to that of the three hypernodulating mutants. Seed yields from the hypernodulating mutants were 10 to 30% less than that from Williams in both years. In general, the small differences among soybean lines in seed protein and oil concentrations in both years were not significant. Therefore, total N in harvested seed was less for the hypernodulating lines than for Williams. The results indicate that these hypernodulating mutants are currently inferior to Williams from an agronomic standpoint.
Osmia lignaria propinqua Cresson: An Alternative Pollinator for Meadowfoam, in Cages
Authors: Jahns T. R. , Jolliff G. D.
Published: July 2010

Meadowfoam (Limnanthes alba Hartweg ex Benth. cv. Mermaid) is an entomophilous winter‐annual oilseed crop with an unstable seed yield history. A 2‐yr study was undertaken to test the efficacy of adult, female Osmia lignaria propinqua Cresson bees as meadow‐foam pollinators. Ten, 35, and 60 of these bees were compared with a 4000 honey bee (Apis mellifera L.) standard, and a 4000 honey bee + 35 O. lignaria propinqua bee treatment. Cages were used to isolate treatments. A noncaged treatment, containing eight honey bee colonies per hectare, served as the control. No significant seeds per flower differences on individually spaced plants were found among any of the caged pollinator treatments in 1986 or 1987. Sixty O. lignaria propinqua bees produced similar solid stand yields to all caged honey bee treatments in both years. No significant differences in seed‐oil content existed between any of the caged pollinator treatments in either year. While >60 O. lignaria propinqua bees may be required to maximize meadowfoam seed set in cages, O. lignarla propinqua showed potential as an alternative pollinator of meadowfoam.
Ureides and Amides as Nitrogen Sources for Soybean Seed Growth and Maturation in Vitro
Authors: Wettlaufer Scott H. , Obendorf Ralph L.
Published: July 2010

While ureides and amides can be utilized for soybean [Glycine max (L.) Merr.] tissue growth in situ, their nutritional effectiveness for seed growth in vitro is not fully characterized. Therefore, the ureides allantoin and allantoate at 31 mM, and the amides asparagine and glutamine at 62 mM, were evaluated as the sole N source for seed growth and maturation in vitro with and without pods. Small and large isolated seeds (50–70 and 300 mg fresh wt.) and small (50 to 70 mg fresh wt.) seeds in detached pods were cultured separately in liquid medium with no or one N source, 1.2 or 0.1 mM P, and 147 mM sucrose, minerals, and vitamins. Allantoin or allantoate did not support seed growth as well as glutamine with isolated seeds or detached pods, and resulted in rapid yellowing of tissues, less dry matter accumulation, and a higher water concentration at harvest. Glutamine and asparagine were equivalent as N sources in supporting growth of 300‐mg seeds with 1.2 mM phosphate, but glutamine was superior to asparagine with 0.1 mM P and also with isolated 50‐ to 70‐mg seeds in both 1.2 and 0.1 mM P. In contrast, glutamine and asparagine were comparable for growth of 50‐ to 70‐mg seeds in detached pods. Phosphate at 0.1 mM with either glutamine or asparagine resulted in increased fresh weight, retention of green color, a higher water concentration, and tissue blackening, but no change in dry matter accumulation during culture of isolated 50‐ to 70‐mg seeds. Glutamine supported soybean seed growth and maturation in all three in vitro systems, while asparagine was a suitable N source for seeds cultured in detached pods or as isolated 300‐mg seeds. Neither ureide was an effective substitute for the amides as the sole N source for seed growth in vitro with or without pods.
Smooth Bromegrass Digestibility Tests: Fungal Cellulase vs. In Vitro Rumen Fermentation
Authors: Casler M. D. , Sleper D. A.
Published: July 2010

Improvement of forage nutritional value is an important objective of many forage grass breeding programs. Both in vitro rumen fermentation and fungal cellulase techniques are widely used to estimate forage digestibility. The objective of this study was to compare in vitro rumen fermentation and fungal‐produced cellulase techniques for use in estimating digestibility for smooth bromegrass (Bromus inermis Leyss.) breeding. Eighteen smooth bromegrass genotypes were grown as replicated spaced plants for 2 yr in the field at Arlington, WI. Forage was harvested at the heads‐emerged growth stage of l‐yr‐old plantings in 1982 and 1985. Duplicate determinations were made for in vitro digestibility of dry matter (IVDMD) and cell wall constituents using rumen fluid from a fistulated cow (Bos taurus) and dry matter using a prepared fungal cellulase solution with a neutral detergent solution pretreatment (NDSPCS). The IVDMD and NDSPCS techniques had a high phenotypic correlation coefficient (r = 0.81, P < 0.01), similar relationships to lignin concentration and other cell wall constituents, and similar patterns of genotypic and error variation. This study provides no evidence that accuracy or precision should be an issue in deciding between rumen fermentation or NDSPCS techniques for estimating digestibility in a smooth bromegrass breeding program.
Geographical Patterns of Variation in the USDA Soybean Germplasm Collection: II. Allozyme Frequencies
Authors: Perry M. C. , McIntosh M. S. , Stoner A. K.
Published: July 2010

Allozyme frequencies can be used as quick and inexpensive measures for determining patterns of diversity in germplasm collections. Our objective was to describe the extent of geographical diversity present in five enzymes controlled by seven variable protein loci (13 alleles) for 2236 accessions of Glycine max (L.) Merr. in the USDA soybean germplasm collection. These accessions represent the entire range of geographical origins in the collection. Countries of origin were grouped into 15 regions based on geography and number of accessions. Assays were performed for leucine aminopeptidase, malate dehydrogenase, superoxide dismutase, phosphoglucoisomerase, and 6‐phosphogluconate dehydrogenase. Each locus had two alleles, except that Sod2 had three and MDH was monomorphic. Total gene diversity was low for all loci except Pg12 and Pgd1. The proportion of the total diversity between regions was relatively high for Sod2. Canonical discriminant and cluster analyses resulted in five clusters, each containing a single region (Africa, Central China, Southwest Central Asia, India, or the New World) and one cluster that contained I0 regions (Chungchong, Korea; Cholla, Korea; Europe; Japan, Jilin, China; Kyonggi, Korea; Kyongsang, Korea; Korea; North China; and Southeast Asia) and 85% of all accessions. This indicates that allele frequencies at these loci were poor discriminators of phenotypic diversity. Additional enzyme loci and other morphological and physiological characters should be used to assist in the further description of this collection.
In Vitro Assay for Evaluation of Phytophthora Rot on Soybean Taproots
Authors: Smith M. A. L. , Wagner R. E. , Anderson J. S. , Spomer L. A.
Published: July 2010

Root lesions indicate soybean [Glycine max (L.) Merr.] cultivar resistance to phytophthora rot, caused by the soilborne fungus Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin (Pmg). The type and degree of resistance to Pmg was rapidly, decisively gauged by monitoring lesion expansion and branch root proliferation in a microculture assay. ‘Williams 82’ soybean, containing the resistance gene Rps1‐kexhibited a dark, discrete lesion on taproots within 12 h after inoculation. In the absence of an effective Rps gene, light‐brown water‐soaked lesions on taproots continued to expand with time. Cultivars with different levels of rate‐reducing resistance could be distinguished by measuring lesion size and rate of expansion.
Breeding for Salinity‐Stressed Environments: Recombinant Inbred Wheat Lines under Saline Irrigation
Authors: Kelman Walter M. , Qualset Calvin O.
Published: July 2010

Disposal of saline drainage water poses a difficulty in some cropping systems. This study investigated the reuse of such water for irrigating winter‐planted spring wheat (Triticum aestivum L.) in the San Joaquin Valley of California. Uniform salinization with a controlled degree of salinity presents a new target cropping system for plant breeding. Our objectives were to measure genetic and environmental variance components for agronomic traits and stress susceptibility index (S), using 43 recombinant inbred lines (RILs) and their parents, ‘Anza’ and ‘Cajeme 71’, grown under three saline irrigation treatments (control, 0.6; intermediate, 7.0; and high, 14.0 dS m‐1) and two N fertilization rates (160 and 260 kg N ha‐1) in 2 yr. Soil water conductivities at harvest time were 1.2, 4.4, and 9.4 dS m‐1 (2 yr means) after the three irrigation treatments. Grain yield reductions after the 7.0 and 14.0 dS m‐1 treatments were 5 and 19% in the first year and 36 and 68% in the second year. In both years genetic variances were significant and genotype ✕ environment interaction variances were not significant for grain and biomass yields and harvest index. Broad‐sense heritabilities estimated each year were low for grain yield (0.30 and 0.10) and biomass (0.07 and 0.02). Differences in S, based on grain yields in the low and intermediate salinity treatments, were nonsignificant in both years among RIL, but indicated a higher salinity tolerance of Anza than Cajeme 71. It was suggested that selection in low salinity environments would produce cultivars with high yield potential for environments with moderate salinity stress (soil conductivity of ≈7 dS m‐1), as may be prescribed with a controlled saline irrigation cropping system for wheat.
Observed Gains from Three Recurrent Selection Regimes for Increased Groat‐Oil Content of Oat
Authors: Schipper H. , Frey K. J.
Published: July 2010

Increasing the groat‐oil content (GO) of aot (Avena sativa L.) could increase the profitability of oat when grown as an oilseed crop or for high‐energy feed grain. In this study, three recurrent selection regimes for increasing GO of oat were evaluated and compared with predicted responses. For Regime 1, selection for GO was practiced among S0 plants grown in the field; for Regime 2, selection occurred among S0 plants grown in the greenhouse; and for Regime 3, selection among field‐grown S0 plants was followed by selection among among and within S0:1 progenies grown in the greenhouse. Gains from selection for GO via the three regimes were evaluated in field experiments by using random lines from each selection for GO via the three regimes were evaluated in field experiments by using random lines from each selection cycle of each regime. Groat‐oil contents increased significantly in Regimes 1 and 3, but not in Regime 2. Annual gains in GO were 6.04, 5.85, and 11.98 g kg‐1 in Regimes 1, 2, and 3, respectively, whereas the predicted gains were 9.69, 4.92, and 11.60 g kg‐1, respectively. Selection among S0 in the field and among and withing S0:1 progenies in the greenhouse both contributed to the increased GO in Regime 3. In each regime, the genetic variance of GO remained significant. Line M022‐4‐5 with a mean GO of 162.85 g kg‐1 had the largest GO in the evaluation experiment. Selection for groat‐oil content on the basis of data from greenhouse‐grown oat plants can be successfully incorporated into a recurrent selection program.
Ammonia‐Labile Bonds in High‐ and Low‐Digestibility Strains of Switchgrass
Authors: Fritz J. O. , Moore K. J. , Vogel K. P.
Published: July 2010

Improvement in the forage quality of switchgrass (Panicum virgatum L.) through phenotypic selection for increased in vitro dry matter digestibility (IVDMD) has been demonstrated. This study tested the hypothesis that genetic improvement of fiber digestibility in switchgrass has been achieved by selection for a strain with a decreased quantity of ammonia‐labile bonds. Tissue samples of a high‐digestibility (high‐lVDMD) and a low‐digestibility strain (low‐IVDMD) of switchgrass were ammoniated at rates of 0, 10, 20, and 40 g kg‐1 dry matter. Fiber composition and in vitro rate and extent of neutrai‐detergent fiber (NDF) digestion were determined on control and ammoniated samples. The high‐IVDMD strain had lower (P < 0.05) concentrations of NDF and acid‐detergent lignin (ADL) than the Iow‐IVDMD strain. Lignin concentrations averaged 53 and 71 g kg‐1 for the high‐ and low‐IVDMD strains, respectively. The high‐IVDMD strain had a greater (P < 0.05) extent of NDF digestion when compared with the low strain; however, the rate of NDF digestion did not differ (P > 0.05) between strains. Increased digestibility of the high‐IVDMD strain was primarily attributed to increased cell‐wail (NDF) digestibility. Ammoniation at 20 and 40‐ g kg‐1 resulted in small decreases (P < 0.05) in NDF concentrations when compared with the control; however, ammoniation had no effect on hemicellulose, cellulose, or ADL concentrations. Ammoniation increased (P < 0.05) both the rate and extent of NDF digestion. Extent of NDF digestion averaged 0.395 for the control and 0.465, 0.498, and 0.493 for the 10, 20, and 40‐g kg‐1 treatments, respectively. Strain ✕ ammoniation rate interaction was not significant for rate and extent of digestion, suggesting that genetic improvement in digestibility of switchgrass was not related to the number of ammonia‐labile bonds.
Seed Protein Content and Delivery of Assimilates to Soybean Seed Embryos
Authors: Hanson W. D.
Published: July 2010

Increasing seed protein content in soybean [Glycine max (L.) Merr.] is associated with reduced seed yields. The objectives Of this study were to investigate the effects of seed protein content on the capacity to deliver dry matter and amino acids to the seed embryo and to identify possible yield‐limiting factors. Fifteen soybean genotypes representing 0.42 to 0.51 g g‐1 seed protein content were grown in the greenhouse during the winter season. High seed‐protein content did not limit specific dry matter accumulation rates. Removing side leaflets to reduce assimilate availability reduced assimilate uptake rates 21%. The reduced uptake rates were not associated with seed protein content. The modified seed structure associated with increased seed protein content did not limit rate of assimilate uptake by the seed. Thus, high seed protein content did not reduce sink activity. Genotypes with high seed protein content had higher rates of increase in seed density than the cultivar Ransom, indicating possible increased seed maturation rates for these genotypes. Rates of amino acid unloading from opened seed coats into a collection medium were associated With the seed protein content. The ratio of rate of amino acid unloading from opened seed coats to rate of dry matter delivery to the embryo was similar to the seed protein content. On the average, selecting for high seed protein content increased the capacity for amino acid production and transport and for amino acid unloading from the seed coat; however, additional factors were involved in the control, of seed protein content. A possible yield‐limiting factor, which is supported by the data on changes in seed density, is the capacity for amino acid unloading from the seed coat.
Spring Dead Spot and Burmudagrass Quality As Influenced by Nitrogen Source and Potassium
Authors: Dernoeden P. H. , Crahay J. N. , Davis D. B.
Published: July 2010

Little is known about the influence of cultural practices on spring dead spot, SDS, (Leptosphaeria korrae J.C. Walker & A.M. Smith) of ‘Tufcote’ and other bermudagrass [Cynodon dactylon (L.) Pers.) cultivars. The primary objective of this study was to assess NaNO3, (NH4)2SO4, NH4C1, CO(NH2)2, KCI, and the N sources plus KC1 in growth‐chamber and field studies for their influence on SDS. In the growth chamber, Tufcote inoculated with L. korrae and fertilized with (NH4)2SO4 or KC1 exhibited a 24% increase in survivability when compared with unfertilized, inoculated plants. Field studies were initiated at Denton and Silver Spring, MD, in 1986. At Denton, improved SDS recovery was observed mid‐June 1987, and enhanced spring green‐up occurred in May 1988 where (NH4)2SO4, (NH4)2SO4 + KC1, and NH4Cl + KC1 were applied. Tufcote was established in 1986 at Silver Spring, but significant levels of SDS did not appear until 1988. In 1988, none of the treatments improved spring green‐up, but all N treatments helped to speed turf recovery from SDS. NH4Cl + KCl enhanced spring green‐up by >75% at Silver Spring in 1989 and 1990, and reduced SDS by >41% from late May to late June 1989 when compared with CO(NH2)2‐treated or unfertilized plots. Other NH4‐N treatments were equivalent to NH4C1 + KCI in improving spring green‐up and reducing SDS in 1989 and 1990. A negative correlation between soil pH and spring green‐up occurred at Denton (1988) and Silver Spring (1990), whereas percent of plot area injured by SDS was positively correlated with soil pH at Silver Spring in 1989. Data indicate that acidification of soil by NH4‐N reduced the severity of SDS over time.
Genetic and Phenotypic Path Analyses in Sugarcane: Artificially Created Relationships
Authors: Kang Manjit S. , Tai Peter , Miller Jimmy
Published: July 2010

In sugarcane (Saccharum spp.) studies, tonnes per hectare of sugar (THS) is generally computed by multiplying tonnes per hectare of cane (THC) and sugar per tonne of cane (S/T). Because of this multiplication, artificial relationships are created between THS and THC and between THS and S/T, but their effect on the relative importance of THC and S/T in determining THS in path analyses is not known. This study examined the possible effect of the artificially created relationships on the relative importance of THC and S/T in determining THS in genetic and phenotypic path analyses. Four cases, two representing nonindependent measures (artificial relationships) and two representing independent measures of THS and THC, were examined. At the phenotypic level, an artificial relationship tended to inflate the relative importance of THC and lower that of S/T, but at the genetic level, the artificial relationship did not greatly inflate or decrease the relative importance of THC and S/T. Multiplying THC and S/T to obtain THS reflects spurious associations in the phenotype that can be circumvented by using genetic correlations in path analyses.
Inheritance of Resistance to Soybean Mosaic Virus in ‘Buffalo’ and HLS Soybean
Authors: Bowers G. R. , Paschal E. H. , Bernard R. L. , Goodman R. M.
Published: July 2010

Soybean mosaic virus (SMV) is a major disease problem in soybean [Glycine max (L.) Merr.] production in several regions in the world. The disease is controllable with plant resistance. This study was undertaken to elucidate the genetics of SMV resistance in the cultivar Buffalo and in the breeding line HLS so they can be used effectively in breeding programs. Buffalo and HLS were crossed to the SMV‐susceptible cultivar Jupiter and with each other. Portions of the F1, F2, and F2:3 populations from each cross were inoculated with one of seven SMV strains (G1∓G7). Virus inoculations were done in the field or greenhouse using an air‐brush technique. Chi‐square analysis of the segregation ratios of populations from the Buffalo × Jupiter cross show that Buffalo's resistance to SMV strains Gl to G7 is under monogenie control, and exhibited dominance under the conditions of this study. Results of the HLS × Jupiter cross show that resistance in HLS to SMV strains G5, G6, and G7 is also conditioned by a single dominant gene. When inoculated with SMV strain G5, G6, or G7, populations of F2 plants from the cross Buffalo × HLS segregated in the ratio of 15 resistant to 1 susceptible. This result, supported by the F2:3 segregation data, suggests that the SMV resistance genes in Buffalo and HLS are located at different loci.
Mutation Studies of an Oilseed Spurge Rich in Vernolic Acid
Authors: Pascual M. J. , Correal E.
Published: July 2010

Euphorbia lagascae Spreng., a wild spurge native to southeastern Spain, is being evaluated as a potential new oilseed crop. It has high seed oil content, with 58 to 62% vernolic acid, a long‐chain unsaturated fatty acid with several applications for the chemical industry. Seed dehiscence is a common problem of all 62 accessions collected to date. The objective of this work was to use chemically induced mutagenesis to develop nonshattering lines. Self‐pollinated M2, M3, and M4 plants were observed in the field in Spain. Three indehiscent mutants were found in the M2 and M3 generations of ethyl methanesulfonate‐treated seed, together with four quatricarpellate mutants containing capsules with >3 seeds capsule−1. The M3 and M4 progenies of mutant plants were studied and the following results were observed: (i) indehiscent plants transferred the character to ≈3.5 and 5% of their M3 and M4 progenies, respectively; (ii) indehiscent plants had on the average 2 seeds capsule−1, one‐third less than normal plants; (iii) M3 quatricarpellate mutants transferred this character, on average, to 40 to 60% of their M4 progeny and produced 10 to 30% more seeds per plant with the same number of capsules.
Agronomic Performance in Acid Soils of Wheat Lines Selected for Hematoxylin Staining Pattern
Authors: Ruiz‐Torres Norma A. , Carver Brett F. , Westerman Robert L.
Published: July 2010

Laboratory screening techniques enable detection of varying degrees of A1 tolerance during seedling development, but their application to crop improvement programs must be verified in the field. The objective of this study was to compare agronomic responses of wheat (Triticum aestivum L. emend. Thell.) lines differing in hematoxylin‐ staining pattern under naturally acidic and limed field conditions. Experiments were conducted on Bethany‐Kirkland (fine, mixed, thermic Pachic‐Udertic Paleustolls) or Grant‐Pond Creek (fine‐silty, mixed thermic Udic‐Pachic Argiustolls) silt loam soil complexes. Four sets of three experimental lines were classified as very susceptible (VS), moderately susceptible (MS), intermediate (I), or tolerant based on hematoxylin staining pattern, and evaluated in limed and unlimed plots as separate experiments in 1988 and 1989. The VS group produced the fewest spikes per square meter and the lowest above‐ground biomass and grain yield in the unlimed treatments; no such reductions occurred in the limed treatments. Differences in agronomic performance were found between groups of VS and MS lines, with relatively little differentiation among MS, I, and T groups. Comparison of two sister lines from the VS and T groups revealed a 12% increase in spike density, 11% increase in biomass, and a 14% increase in grain yield of the tolerant sib under acidic conditions. The two sibs performed similarly under limed conditions, except the VS line was superior in grain yield. The hematoxylin staining procedure shows promise for identifying wheat genotypes with potentially high sensitivity to acidic soils in the southern Great Plains.
Inheritance of Isozyme Variation in Ascochyta Blight‐Resistant Chickpea Lines
Authors: Kusmenoglu I. , Muehlbauer F. J. , Kazan K.
Published: July 2010

Isozymic variation in chickpea (Cicer arietinum L.) crosses involving ascochyta blight [incited by Ascochyta rabiei (Pass.) Lab.] resistant germplasm was studied with the objective of identifying linkages of allozyme variation with ascochyta resistance genes. Such linkages, if found, could allow indirect selection of genes for ascochyta resistance. Eight F2 populations were scored for allozymes of four polymorphic isozyme loci. Five isozymes encoded by the loci Est‐1, Est‐2, Est‐4, Est‐5, Gal‐1, and one previously identified isozyme locus, Pgd‐c, were inherited codominantly. Linkage relationships among isozyme loci and genes for ascochyta resistance, growth habit (hg), and leaf type (slv) were also investigated. No linkage was found among isozyme loci, or between isozyme loci and ascochyta resistance; however, a loose linkage was observed between the gene controlling growth habit (hg) and the gene encoding for the cytosolic form of 6‐phosphogluconate dehydrogenase (Pgd‐c). Linkage of ascochyta resistance with the available isozymic variation was not found in this study. This was not unexpected, due to the limited number of loci segregating in the F2 populations we used. The inheritance of several isozyme loci was determined, however, and a previous report of a gene duplication in the Est‐4/Est‐5 region was confirmed. Hybridization of cultivated chickpea with closely related C. reticulatum Lad., the presumed wild progenitor, might increase the number of polymorphisms that can be used to locate ascochyta resistance genes.
Physiological and Anatomical Features of Two Triticum dicoccoides Wheat Accessions Differing in Photosynthetic Rate
Authors: Kebede Hirut , Johnson Richard C. , Carver Brett F. , Ferris David M.
Published: July 2010

The wild tetraploid species Triticum dicoccoides (L.) Korn has many traits that may be useful to hexaploid wheat (T. aestivum L.). Two accessions of this species (PI 428042 and PI 428109) were found have similar‐sized leaves, but they differ by ≈30% in net CO2 assimilation per unit leaf area (A). We sought to identify physiological and anatomical factors that would explain the difference in photosynthetic rate between the two accessions, and between these accessions and the hexaploid wheat ‘TAM W‐101’. Photosynthetic responses to CO2 (at 20 and 210 mL O2 L−1 air), light, and humidity, and also ribulose bisphosphate carboxylase (rubisco) activity and sucrose concentration, were determined on new fully expanded leaves of each genotype. Anatomical features associated with photosynthesis were determined using light and electron microscopy. PI 428109 showed consistently higher A than PI 428042 at varying levels of CO2, light, and humidity. Higher rubisco activity was observed in leaves of PI 428109 than PI 428042, as also indicated by a greater slope of the initial linear portion of the A vs. ci (intercellular leaf CO2 concentration) curve. A higher sucrose concentration was observed in the leaves of PI 428042 than in PI 428109. No anatomical differences were detected between the two T. dicoccoides accessions. Therefore, photosynthetic differences between the two T. dicoccoides accessions were biochemically, and not anatomically, driven.
Comparative Response of Cultivated and Wild Barley Species to Salinity Stress and Calcium Supply
Authors: Suhayda Charles G. , Redmann Robert E. , Harvey Bryan L. , Cipywnyk Andrew L.
Published: July 2010

Foxtail barley (Hordeum jubatum L.), a wild species that can inhabit highly saline environments, may have more potent salt‐tolerance genes than commercial barley (H. vulgare L.). The objective of this study was to compare the growth and ion relations of the commercial cultivar Harrington with foxtail barley under saline conditions, to determine whether a differential response to salinity stress exists between these species. Seedling performance was evaluated as a function of increasing concentrations of Na2SO4, MgSO4, and CaCl2 (within the electrolyte conductivity range of 0.26 to 1.38 S m−1) and the Ca mole fraction (Camf) of salt treatments in solution culture experiments. The Camf of the salt treatments, defined as the molar ratio of Ca/(Ca + Na + Mg), was maintained at 0.02 or 0.09. Salt treatments at a Camfr of 0.02 significantly reduced leaf area, shoot growth, root growth, and the root‐to‐shoot ratio (R/S) of Harrington seedlings relative to foxtail barley. Growth of Harrington seedlings improved substantially when the Camf was increased from 0.02 to 0.09. The two genotypes differed significantly in root weight and R/S under saline conditions; these differences were independent of the Camf. Evaluation of root and shoot tissue ion contents revealed that H. jubatum seedlings accumulated less Na from the medium than Harrington and preferentially compartmentalized Na in root rather than shoot tissue. The wild species maintained higher levels of Ca, had more favorable K/Na ratios, and maintained higher R/S levels of SO4 than Harrington. Differences between H. jubatum and Harrington in root and shoot ion accumulation suggest that membrane permeability and selectivity properties are controlled by both genotype and Ca supply.
Shoot Nitrogen Dynamics in Tropical Common Bean
Authors: Lynch Jonathan , White J. W.
Published: July 2010

The common bean (Phaseolus vulgaris L.) is an important food crop in the tropics, where its productivity is often limited by low soil N availability. An ideotype for efficient N‐use in bean would distribute N in time and space so that leaf N (and therefore leaf photosynthetic capacity) is optimized with respect to reproductive N sinks. To define parameters and estimate genetic variability for N use, we examined shoot N dynamics in three tropical bean genotypes of similar phenology believed to differ in N acquisition and allocation. Seeds were sown in a high‐N soil in two plantings separated by 20 d. Shoots of BAT 477 acquired considerably more N than Porrillo Sintético, but both genotypes yielded well. G 5059 acquired an intermediate amount of N, partitioned more N to leaves, and matured slightly later, but had a lower final N harvest index (NHI) than the other two genotypes. Time of planting had a substantial effect on shoot N uptake and partitioning. After flowering, N was lost from leaves and stems, rose and fell in young pods and pod walls, and accumulated in seeds. Harvest index (HI) and NHI increased almost linearly from flowering to physiological maturity at the same rate in all three genotypes. Seed N duration dominated post‐flowering shoot N duration. Leaf N duration represented 25% of post‐flowering shoot N duration on average. Leaf CO2 exchange rate (CER) was highly correlated with leaf N content, and both declined during mid and late pod filling. Instantaneous leaf photosynthetic N‐use efficiency (CER per unit leaf N) declined with time. Our data are consistent with the hypothesis that N allocation to seeds limits leaf photosynthesis in bean grown in the tropics. Variation in N translocation patterns was associated with phenology, which must be taken into account in breeding for N‐use efficiency.
Effects of Physical Agitation on Yield of Greenhouse‐Grown Soybean
Authors: Jones R. S. , Mithcell C. A. , Mitchell C. A.
Published: July 2010

Agronomic and horticultural crop species experience reductions in growth and harvestable yield after exposure to physical agitation (also known as mechanical stress), as by wind or rain. A greenhouse study was conducted to test the influence of mechanical stress on soybean yield and to determine if exposure to mechanical stress during discrete growth periods has differential effects on seed yield. A modified rotatory shaker was used to apply seismic (i.e., shaking) stress. Brief, periodic episodes of seismic stress reduced stem length, total seed dry weight, and seed number of soybean [Glycine max (L.) Merr.]. Lodging resistance was greater for plants stressed during vegetative growth or throughout vegetative and reproductive growth than during reproductive growth only. Seed dry weight yield was reduced regardless of the timing or duration of stress application, but was lowest when applied during reproductive development. Seismic stress applied during reproductive growth stages R1 to R2 (Days 3 to 4) was as detrimental to seed dry weight accumulation as was stress applied during growth stages R1 to R6 (Days 39 to 42). Seed dry weight per plant was highly correlated with seed number per plant, and seed number was correlated with the number of two‐ and three‐seeded pods. Dry weight per 100 seeds was unaffected by seismic‐stress treatment. Growth and yield reductions resulting from treatments applied only during the vegetative stage imply that long‐term mechanical effects were induced, from which the plants did not fully recover. It is unclear which yield‐controlling physiological processes were affected by mechanical stress. Both transient and long‐term effects on yield‐controlling processes remain to be elucidated.
Alternative Model for Path Analysis of Small‐Grain Yield
Authors: Dofing S. M. , Knight C. W.
Published: July 2010

The model most widely used for path analysis of grain yield in small grains assumes bidirectional causal pathways between yield components; however, because yield components develop sequentially, it is questionable from a biological standpoint whether a yield component could influence others that develop earlier. The purpose of this research is to describe the theory and application of an alternative model for path analysis of grain yield that takes into account the sequential development of yield components. Path analysis was performed assuming bidirectional and unidirectional causal relationships among yield components of eight spring barley (Hordeum vulgare L.) cultivars grown at Palmer and Fairbanks, AK, in each of two years. Yield and the yield components spikes per square meter, kernels per spike, and kernel weight were estimated. The unidirectional model seems to reflect operative causal pathways more realisitically, and results in simpler estimates that present a clearer picture of the relationships among grain yield and yield components. Of the three yield components, spikes per square meter resulted in the greatest positive contribution to yield, while the effect of kernels per spike on kernel weight was the most negative compensatory response among yield components.
Natural Selection Effects in Wheat Populations Grown under Contrasting Tillage Systems
Authors: Hwu Kae‐Kung , Allan Robert E.
Published: July 2010

Use of no‐till, a conservation‐tillage management system, is increasing in the northwestern USA, to abate the serious soil erosion problem. This study examined the feasibility of improving the adaptation of winter wheat (Triticum aestivum L.) for no‐till by natural selection. Five populations with genetic diversity for several traits, some of which presumably affected fitness of wheat under no‐till, were studied. Two subpopulations were developed for each population by growing them during 1951 to 1985 in plots that had been rotary tilled (till) or directly sown (no‐till) into standing barley (Hordeum vulgare L.) stubble at Pullman, WA. Trait means of the till treatment were always higher than their no‐till counterparts, with the exception of one trait in a single population. Results did not indicate strong or consistent pressure for differential natural selection between the till and no‐till treatments for several agronomic traits in most populations. The population that was putatively the most genetically diverse (Semidwarf Common Wheat USDA Blend) showed significant response to differential natural selection after pooling data across generations; both subpopulations had increased (P ≤ 0.05) biomass and grain yield means in the environments from which they had been derived. Plant height diverged in another population, with tall and short genotypes favored in the till and no‐till environments, respectively. Most populations probably lacked sufficient genetic diversity to respond to differential natural selection for most of the traits; a high proportion of their parentage was derived from locally adapted genotypes that had been selected under conventional tillage. Using no‐till selection pressure on genetically conservative populations that typify most wheat breeding programs probably is unwarranted. However, with populations that have been intentionally developed to achieve a broad genetic base, this approach may be justified.
Identification of Pollenkitt Variation among Alfalfa Germplasm Sources
Authors: Henning John A. , Teuber Larry R.
Published: July 2010

Pollenkitt is the outermost lipid and fatty acid layer of the pollen grain and is thought to contain aroma‐producing volatile compounds that are attractive to pollinators. Honey bee (Apis mellifera L.) nonpreference for alfalfa (Medicago sativa L.) pollen may result from a deficient pollenkitt. This study was conducted to determine if: (i) a pollenkitt is present on alfalfa pollen, (ii) pollenkitt quantity differs among germplasm sources and among plants within germplasm sources, and (iii) pollenkitt measurements (scores) are reproducible over time. Pollen from ≥24 individuals in each of eight germplasm sources were stained for lipids with Sudan IV, observed by light microscopy, and then scored using a five‐point rating system for the presence and amount of pollenkitt. Pollenkitt was present in all eight germplasm sources. Arabian germplasm had greater (P ≤ 0.05) amounts of pollenkitt (mean score 3.77) than all other sources. All sources exhibited within‐population variation. If attractive volatiles are associated with alfalfa's pollenkitt, then breeding for increased pollenkitt may increase honey bee preference for alfalfa pollen.