bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of Adult‐Plant Resistance to Powdery Mildew in Knox 62 and Massey Winter Wheats
Authors: Griffey C. A. , Das M. K.
Published: July 2010

Adult‐plant resistance (APR) to powdery mildew [Blumeria graminis (D.C.) E. O. Speer f. sp. tritici Em. Marchal; syn Erysiphe graminis f. sp. tritici] is more durable than hypersensitive major gene resistance, but little is kown about the inheritance of this type of resistance. Inheritance of APR was studied in four winter wheat (Triticum aestivum L.) crosses. Parents, F1, F2, F3, and backcross populations were evaluated in the field under natural epidemics of powdery mildew. The number of genes governing APR in ‘Massey’ and ‘Knox 62’ wheats was estimated by both qualitative and quantitative methods. Mildew severity was used in the qualitative methods, while are under the disease progress curve was used in quantitative estimates. Results indicate that two to three genes confer APR in these cultivars. Heritability estimates or APR ranged from 0.40 to 0.56 wen standard units and F3/F2 regression methods were used. The variance components method estimated higher heritabilities which ranged from 0.79 to 0.95 Since APR in these cultivars is governed by few genes and heritability estimates are moderate to high, selection for this resistance in early segregating generations should be effective. Powdery mildew resistance in Knox 62 has been effective during its commercial cltivation over 20 yr. Massey has maintained its APR to powdery mildew since its relase in 1981; therefore, APR derived rom these cultivars is expected to be durable.
Influence of Reduced Palmitate Content on Agronomic and Seed Traits of Soybean
Authors: Ndzana Xavier , Fehr Walter R. , Welke Grace A. , Hammond Earl G. , Duvick Daniel N. , Cianzio Silvia R.
Published: July 2010

Soybean [Glycine max (L.) Merr.]genotypes with reduced palmitate content have been developed to improve the nutritional characteristics of the seed oil. The objective of the study was to determine the influence of reduced palmitate on agronomic and seed traits of sobean. Three lines homozygous for the fap1 fap3 alleles (≈ 40g kg−1 palmitate) were crossed to different high‐yielding cultivars (≈110 g kg−1 palmitate). In total, 27 F4‐derived lines with reduced palmitate and 27 lines with normal palmitate content were selected from each of the three single‐cross populations. The lines and parents of each population were grown in separate replicated field tests at three locations in Iowa during 1992. The mean seed yield of the reduced‐palmitate lines was significantly less than that of the normal‐palmitate lines was significantly less than that of the normal‐palmitate lines in two of the three populations. The reduced‐palmitate lines had significantly greater protein content in two crosses and significantly lower oil content than the normal‐palmitate lines in all crosses. The associations of reduced palmitate with agronomic and seed traits could be attributable to pleiotropic effects of the fap1 or fap3 alleles or to possible linkages of the alleles with genes controlling the other traits.
Effect of Russian Wheat Aphid on Wheat Root and Shoot Development in Resistant and Susceptible Genotypes
Authors: Zwer P. K. , Mosaad M. G. , Elsidaig A. A. , Rickman R. W.
Published: July 2010

Genetic resistance is an important management component in the control of Russian wheat aphid (Diuraphis noxia Mordvilko) (RWA). The range of leaf symptoms associated with several resistance sources indicate that differences may occur in seedling development. This study was conducted to determine differences in wheat (Triticum aestivum L.) seedling shoot and root development among resistant and susceptible wheat genotypes infested with RWA. The effectiveness of one resistance source identified in greenhouse seedlings was characterized in field‐grown F2 plants. Visual damage and leaf and root development were measured for 17 lines in the greenhouse. Dry weight, grain yield, and harvest index were studied in infested and noninfested, field‐grown F2 populations generated from ‘Moro’/PI294994 and ‘Hyak’/PI294994. PI48650 and PI294994 had superior seedling shoot and nodal root system development when compared to susceptible genotypes. Visual evaluations were effective in separating susceptible genotypes from potential resistance sources; however, leaf symptoms were not effective in characterizing the most promising RWA resistance resources. Root measurements in conjunction with leaf symptoms identified seedling genotypes least affected by RWA. Russian wheat aphid resistant adult plants produced significantly more dry weight and grain yield and a greater harvest index than susceptible plants in the two populations. Trends for these characteristics were similar for resistant plants in the infested population and plants in the noninfested population.
Yield and Reserve Status of Rhizoma Peanut Growing under Shade
Authors: Johnson S. E. , Sollenberger L. E. , Bennett J. M.
Published: July 2010

‘Florigraze’ rhlzoma peanut (Arachis glabrata Benth.) is a perennial legume of high forage quality, but commercial use has been limited by slow establishment. In the southeast USA, the understory of pine (Pinus spp.) plantations is grazed by cattle (Bos spp.). Because grazing must be deferred during pine establishment, concurrent planting of trees and Horigraze might facilitate use of the legume and improve the quality of forage for grazing. To determine if trials evaluating Florigraze‐pine associations are warranted, preliminary information on Horigraze shade tolerance is needed. A 3‐yr field study was conducted on a Kendrick soil 0uamy, siliceous, hyperthermic Arenic Paleudult) to determine Horigraze growth and reserve status in response to shading and defoliation intensity. Main plots were shade treatments that were defined as percentages of incident photosynthetic photon flux density (PPFD; 34, 54, 78, and 100%); subplots were defoliation stubble heights (4 or 8 cm). Treatments were replicated three times, and plots were harvested four times in 1989, three times in 1990, and once in early summer 1991. Summed across harvests within years, dry matter (DM) yield increased as PPFD increased from 34 to 100% (5.6‐8.8 Mg ha‐1 in 1989 and 3.3‐11.3 Mg ha−1 in 1990). Rate of increase in DM yield was slower as PPFD increased, and yield generally was greater for the 4‐ than 8‐cm clipping height. For 78 and 54% PPFD, annual Florigraze yields were >90 and 70% as great as those for the 100% PPFD treatment in 1989 and 1990. At season end 1989 and 1990, rhizome mass and total nonstructural carbohydrate (TNC) concentration decreased with decreasing PPFD, but values for shaded treatments in 1990 were at least as great as those in 1989. We conclude that rhizoma peanut‐pine associations merit evaluation because Horigraze was productive and persisted well at PPFD levels similar to those observed in pine understories.
White Clover Seed Production: II. Soil and Plant Water Status on Yield and Yield Components
Authors: Oliva R. N. , Steiner J. J. , Young W. C.
Published: July 2010

White clover (Trifolium repens L.) seed yield is reduced by environmental conditions that favor vegetative growth and that consequently reduce flower density. White clover seed yields in western Oregon can be highly variable and often are low. The objective of this study was to quantify the effects of soil and plant water status on white clover flower production, seed yield, and seed yield components. Five supplemental irrigation treatments were applied in 1990 and 1991 to first and second‐year white clover grown on a Woodburn silt loam (fine‐silty, mixed, mesic Aquultic Argixeroll) near Corvallis, OR. Seed yield in 1990 was greatest when water application was delayed until 68% of the available soil‐water was used by the crop. This treatment restricted vegetative growth but maintained an even flush of flower production during the reproductive phase of growth. In 1991, all irrigation treatments yielded the same or less than the non watered control because vegetative stolon growth between the planted rows reduced the number of flowers produced by greater than 50%. In both years, a twice weekly irrigated treatment that matched evaporative demand increased vegetative growth and reduced seed yield. A single irrigation application later than the optimum 68% soil‐water depletion increased total above ground phytomass, but decreased seed yield due to an interruption in flower production compared to irrigation at 68% soil‐water depletion. Flower density was the yield component that most affected seed yield in both years. In 1990, effective control of soil‐water depletion increased seed yield 69% and potential seed yield 4%, compared to the nonirrigated control. Under conditions that promote stolon development prior to the second reproductive season, aggressive vegetation management may be needed to increase inflorescence density and seed yield.
Relative Yield as a Measure of Entry Performance in Variable Environments
Authors: Yau S. K. , Hamblin J.
Published: July 2010

The traditional approach of presenting and analyzing actual (uncoded) yield data from variety trials conducted across sites has drawbacks. The purpose of this paper is to present the theoretical and practical advantages of using relative yield. Both hypothetical and field data were used for illustration. Relative yield was calculated as a ratio of entry yield at each site to the site mean. It was shown that relative yield has three major advantages: (i) conversion of the simple entry variance of yield acrossites to a practical, agronomic stability measure, allowing easy comprehension of the genotype‐by‐environment (G×E) structure, (ii) equal weight given to each site calculating entry means acrossites, and (iii) ease in comparing large numbers of entries tested in different experiments at the same site and year. Plant breeders are encouraged to use routinely relative yield, and to adopt the variance of relative yield across sites as a powerful, yet simple, stability measure.
Inheritance of Reduced and Elevated Palmitate in Mutant Lines of Soybean
Authors: Schnebly Steven R. , Fehr Walter R. , Welke Grace A. , Hammond Earl G. , Duvick Daniel N.
Published: July 2010

The saturated fatty ester content of soybean [Glycine max (L.) Merr.] oil may influence its use in food products. The palmitate content in the seed oil of common soybean cultivars is ≈110 g kg−1. Soybean mutants with reduced or elevated palmitate have been developed. Previous research had shown that the alleles controlling reduced palmitate in C1726 (fapl) and A22 (fapx) were at independent loci, the alleles controlling elevated palmitate in A21 (fap2‐b) and A24 (fap?) were at independent loci, and that A21 and C1727 (fap2) had alleles at the same locus or at tightly linked loci. The objective of this study was to determine if the fapx allele in A22 was at the same locus as fap2 and if the fap? allele in A24 was at the same locus as fapl. The C1726 line was crossed to A21 and A24. The A22 line was crossed to C1727, A21, and A24. The F2 segregation ratio and the segregation of F3 seeds from F2 plants indicated that A22 and A24 have alleles at different independent loci than C1726, C1727, A21, and each other. The temporary designation of fapx for the allele in A22 was replaced by the permanent designation of fap3, and the temporary designation of fap? for the allele in A24 was replaced by the permanent designation of fap4. The study showed that there are at least four independent loci in soybean that control palmitate content.
Genotypic and Environmental Variation for Degree of Cross‐Fertilization in Faba Bean
Authors: Link Wolfgang , Ederer Winfried , Metz Peter , Buiel Hanneke , Melchinger Albrecht E.
Published: July 2010

Faba bean (Vicia faba L.) is a partially allogamous grain legume. Its degree of cross‐fertilization (C) is influenced by genetic and environmental effects. Both sources of variation for this trait were investigated in two experiments using black seed color as a morphological marker. Genotypic variation for C among 48 inbred lines derived from the small‐seeded European faba bean gene pool was evaluated at one location in Germany for 3 yr (Exp. 1). Environmental variation was evaluated with a subset of four inbred lines grown at 17 European locations, with eight locations evaluated for 2 yr (Exp. 2). Mean values for C of genotypes in Exp. 1 ranged from 38.4 to 72.5% and averaged 53.7%. The estimate of the genotypic standard deviation was 7.5% and for heritability it was 0.75. Environmental means of C in Exp. 2 ranged from 42.7 to 73.6% and averaged 53.9%. The standard deviation among locations was 6.3%. In conclusion, selection among genotypes and locations is promising to promote outcrossing in faba beans to better exploit heterosis in the breeding of cultivars.
Post‐Heading Nitrogen Uptake, Retranslocation, and Partitioning in Spring Barley
Authors: Bulman Patrick , Smith Donald L.
Published: July 2010

In cereals, N provided to the developing grains comes from continued N uptake and assimilation after anthesis and from the retranslocation of previously accumulated vegetative N. This study investigated management and cultivar effects on post‐heading N uptake and their relationship with total plant and grain N accumulation and grain protein concentration (GPC). Twenty six‐rowed spring barley (Hordeum vulgare L.) cultivars were grown on a Chateauguay clay soil (fine loamy, mixed nonacid, frigid, Typic Hapludalf) in 1988 under conventional management (recommended N, no fungicide or growth regulator) and on a Bearbrook clay soil (very fine silty, mixed nonacid, frigid, Humaquept) in 1989 and 1990 under conventional and intensive (high N, fungicide and plant growth regulator) managements. Postheading N uptake was generally not related to N concentration and N per plant at awn emergence but was highly correlated with total dry matter accumulation after anthesis and moderately to highly correlated with total plant and grain N per plant at harvest. Postheading N uptake seemed related to the amount of tillering that occurred after anthesis. High‐GPC cultivars did not accumulate more N after heading than low‐GPC cultivars. Nitrogen retranslocation was correlated with total dry matter and N per plant at awn emergence, but the relationship varied with growing season and management. Nitrogen retranslocation and N harvest index were not correlated with GPC. Post‐heading N uptake and N retranslocation were negatively but moderately correlated with each other.
Transgressive Segregation for Palmitic Acid in Seed Oil of Soybean
Authors: Wilcox James R. , Burton Joseph W. , Rebetzke Gregory J. , Wilson Richard F.
Published: July 2010

Palmitic acid is the major saturated fatty acid in soybean [Glycine max (L.) Merr.] oil. Reducing levels of palmitic acid should enhance the nutritive value of soybean oil for human consumption. The low palmitic acid strain C1726 (81 g kg−1 16:0), carrying the fap1 allele, was crossed with two strains developed independently of C1726, N79‐ 2077‐12 and N90‐2013, both with about 60 g kg−1 16:0. Progenies from these crosses were evaluated to determine genetic relationships controlling palmitic acid in these two groups of strains. Palmitic acid concentrations in the oil of F2 seeds, F3 seeds on F2 plants, and seeds from F3 families were determined by gas chromatography. Transgressive segregates averaging 44 and 96 g kg−1 16:0 were identified in the segregating populations. Both F2 plants and F3 families were identified that were either homozygous or heterozygous for loci controlling palmitic acid. Chi‐square analyses for a 1 homozygous P1 type/1 homozygous P2 type/1 homozygous recombinant type (high 16: 0)/1 homozygous recombinant type (low 16:0)/12 plants or families heterozygous at either locus demonstrated that two loci controlling levels of 16:0 were segregating in these populations. A correlation coefficient of 0.97 calculated between palmitic acid values of homozygous F2 plants and their F3 family means demonstrated that the homozygous classes were true breeding for palmitic acid. The locus in C1726 was fapl; the other locus, in N79‐2077‐12 and N90‐2013, has not been designated. These populations provide additional sources of low palmitic acid to enhance the nutritional value of soybean oil.
Genetic Transfer of Gynomonoecy from Diploid to Triploid Eastern Gamagrass
Authors: Dewald C. L. , Kindiger B.
Published: July 2010

Seed yields of eastern gamagrass, Tripsacum dactyloides (L.) L. (Andropogoneae), are limited by scarcity of fertile female florets and excessive maleness in its monoecious inflorescence. Gynomonoecious variants, with sex reversal in formerly male spikelets and reactivation of suppressed female florets, are known that have a greater seed production potential than monoecious forms. Sexual reproduction is exclusively observed in diploid eastern gamagrass, whereas facultative apomictic reproduction is the rule in polyploid forms. This study was designed to combine recessive genes for gynomonoecy from diploids with genes for apomixis from polyploids to develop true breeding (apomictic), prolific seed producing (gynomonoecious) lines. Diploid parents with allele(s) for gynomonoecy were used in each of three generations of interploidy matings to transfer gynomonoecy from diploid to triploid eastern gamagrass. A first generation fertile triploid hybrid and a second generation BIII derived tetraploid hybrid were used as intermediates for genetic transfer. Ninety triploid progeny from the third generation of cytotype intermatings yielded three gynomonoecious individuals, one with relatively good female fertility and two that failed to set seed. The low percentage (3.3%) of triploid progeny that inherited the gynomonoecions trait indicates a strong selection force against gynomonoecy at the triploid level. The breeding strategy employed is considered a practical method to move genes from diploid to higher ploidy levels for subsequent stabilization by apomixis.
Sucrose Synthase and Natural Ripening in Sugarcane
Authors: Lingle S. E. , Irvine J. E.
Published: July 2010

Sugarcane (Saccharum spp. hybrids) cultivars vary in the timing and extent of natural ripening, an increase in the sucrose concentration of stalk juice that increases sucrose recovery in the sugar industry. The present study was conducted to determine (i) what changes sugar accumulation occur in individual internodes during ripening, and (ii) if changes in sucrose synthase (SS) activity accompany natural ripening in sugarcane. Sugar concentrations and SS activities were determined in elongating and sucrose‐storing internodes of two sugarcane cultivars sampled at monthly intervals during the 1989–1990 and 1990–1991 harvest seasons in South Texas. Ripening was indicated by a decrease in elongation rate, increase in total sugar concentration, and increase in sucrose percent of total sugar over successive sampling dates. These changes occurred earlier and to a greater extent in ‘CP 70‐321’, an early ripening cultivar, than in ‘LCP 81‐10’, which ripens later in the season. The specific activity of SS did not change significantly during this same period. In this study, changes in SS activity did not appear to be related to ripening.
Photosynthetic Nitrogen‐Use Efficiency in Relation to Leaf Longevity in Common Bean
Authors: Lynch Jonathan , Rodriguez Nubia S.H.
Published: July 2010

Nitrogen deficiency is an important limitation to bean (Phaseolus vulgaris L.) production in the tropics. The ability of a leaf to utilize N for photosynthetic C assimilation (leaf N‐use efficiency) may be element of genetic adaptation to low N soils. We tested the hypotheses that (i) leaf N‐use efficiency is related to leaf longevity, and (ii) shoot architecture influences the relationship of leaf N‐use efficiency and leaf longevity. Four genotypes that have contrasting shoot architectures (determinate bush, indeterminate bush, indeterminate prostrate, and indeterminate climbing) were grown in duplicate experiments in Colombia. At frequent intervals, the third and eighth leaves to appear on the main stem were analyzed for CO2 assimilation and N content. Daily CO2 assimilation and leaf N content, which were highly correlated, peaked soon after leaf expansion and declined steadily until leaf abscission. Leaf N duration and cumulative leaf CO2 assimilation were highly correlated. Leaf longevity was highly correlated with leaf N duration and significantly correlated with cumulative leaf CO2 assimilation. Leaf longevity was highly negatively correlated with leaf N‐use efficiency expressed as cumulative CO2 assimilation per unit leaf N duration but slightly positively correlated with leaf N‐use efficiency expressed per unit of average leaf N content. Shoot architecture had little impact on these variables and relationships. We conclude that leaf longevity is an important factor in leaf N‐use efficiency but that genetic variation for shoot architecture in common bean is not important in determining the N‐use efficiency of individual leaves.
Oil Treatment and Digestion Depresses Germination of Grass Seed
Authors: Ocumpaugh W. R. , Swakon D. H. D. , Tischler C. R. , Valle L. S.
Published: July 2010

Numerous grasses, including Panicum spp., produce seed that survive passage through the digestive system of livestock and germinate in the feces. Managing livestock to distribute viable seed of desirable plants is a means of revegetating degraded grasslands. Potential germination of grass seeds declines with increased resident time in the gastrointestinal tract. Loss of seed germinability with increased resident time may be caused by indirect effects of secondary metabolites of digestion on the embryo. The cause of the loss of seed germinability is not known, nor is the identity of the secondary metabolites. We hypothesized that coating seed with oil would reduce damage caused by these secondary metabolites. Our objective was to elucidate the effect of oil treatments on germination of Panicum ssp. seed following in vitro and in vivo digestion. TEM‐LD1 kleingrass (P. coloratum L.) and ‘Alamo’ and ‘Sunburst’ switchgrass (P. virgatum L.) seeds were evaluated in a series of trials with and without pretreatment with oil. Corn (Zea mays L.) and mineral oil without subsequent digestion had a small negative effect on germination. Duration of seed exposure to oil or oil type had no effect on seed germination. However, oil pretreatments significantly reduced germination of digested seed of both species in all trials. Mineral oil reduced germination more than corn oil, and increased exposure time to oil prior to digestion further depressed (up to fourfold) seed germination. Apparently, oil treatment solubilized the protective layer of the seed coat, thereby enhancing the digestion effect on the seed embryo. These differential responses may help elucidate the nature of the protective mechanism of the seed against digestion effects. We conclude that oil treatment cannot be used to protect these seeds from digestion effects.
Development of a Model for Marker‐Assisted Selection of Specific Gravity in Diploid Potato across Environments
Authors: Freyre R. , Douches D. S.
Published: July 2010

Dry matter content in potato (Solanum tuberosum L.) is an important factor in processing and is estimated by specific gravity. We performed quantitative trait loci (QTL) analysis for this trait in 2x potato in three environments. A population of 110 individuals was derived from the cross of a hybrid of haploid S. tuberosum (2x) and S. chacoense Bitter, with a S. phureja Juz. & Buk. clone. This population was characterized for 10 isozyme loci, 44 restriction fragment length polymorphisms (RFLPs), and 63 random amplified polymorphic DNA (RAPDs). Field trials were conducted in two locations in Michigan in 1990 with three replications, and in one location in 1991 with 90 individuals and two replications. Specific gravity was determined through air weight/(air weight ‐ water weight). QTLs were mapped separately for each location and for the average across environments by one‐way analyses of variance for each marker locus. A total of 10 putative QTLs was identified over environments and they were localized on Chromosomes 1, 2, 3, 5, 7, and 11. Numbers and effects of QTLs detected varied across environments. The locus with highest R2 value per QTL in each environment was chosen to develop multilocus models, which explained 39 to 45% of the phenotypic variation for specific gravity. Each model was also tested with data from the other environments, and in general, the predictive value across environments was weaker. A model based on average specific gravity across environments explained a consistent proportion of the phenotypic variation for specific gravity when tested across environments. Using multiple environment data to develop models may be more valuable for marker‐assisted selection in a potato breeding program than models based on single environments.
Detection of Somaclonal Variation in Tissue Culture Regenerants of Tall Fescue
Authors: Roylance J. T. , Hill N. S. , Parrott W. A.
Published: July 2010

Clones of tall fescue (Festuca arundinacea Schreb.) regenerated from tissue culture are required for examining interactions between the endophyte, Acremonium coenophialum Morgan‐Jones and Gams, and its host. Somaclonal variation is common among regenerated plants, and could limit the utility of this technology to study the interactions of tall rescue and its endophyte. Various methods are used to detect somaclonal variation, but there is little agreement as to the relative advantages of each. Therefore, the objectives of this study were to determine (i) whether somaclonal variation exists among tall fescue plants regenerated from somatic embryos, and (ii) whether pollen viability, yield, morphological traits, or phenological development give consistent estimates of somaclonal variation. Seven regenerants from non‐infected tall fescue genotype PDN2 and a non‐regenerated PDN2 control were planted in the field in five replications. Plants were screened for somaclonal variation by phenological development, vegetative and flag leaf width/length ratios, total biomass, seed yield, and pollen viability over 2 yr. Although regeneration protocols were designed to minimize somaclonal variation, somaclonal variation of quantitative traits was observed. Total biomass and seed yield of regenerants, used together, were most consistent in detecting somaclonal variation. When using tissue culture to insert endophytes into tall rescue, we found multiple regenerants need to be infected with each isolate of endophyte to ascertain whether differences among response variables are due to endophyte or somaclonal variation.
Species Identification by RAPD Analysis of Grain Amaranth Genetic Resources
Authors: Transue D. K. , Fairbanks D. J. , Robison L. R. , Andersen W. R.
Published: July 2010

The grain amaranths (Amaranthus spp.) were important food staples of ancient American civilizations, and are still important in contemporary Latin America. Because of their nutritional value, the grain amaranths have received significant attention in recent years. Three species predominate among cultivated grain amaranth species: Amaranthus caudatus L., A. cruentus L., and A. hypochondriacus L. Due to variation for morphological characters, accurate classification of amaranth genetic resources is not always possible. The objective of this study was to determine if random amplified polymorphic DNA (RAPD) markers could be used to classify accessions by species. Twenty‐nine previously classified accessions were used as standards. An additional 82 previously unclassified accessions were also investigated. DNA samples from each species were bulked to use as standards for RAPD marker selection. A total of 29 polymorphic RAPD fragments identified in the bulked DNA standards were further tested on all accessions individually. Cluster analysis of RAPD markers separated the 29 known accessions into three distinct groups that corresponded to the morphological species identifications. A species designation was also assigned to all previously unclassified accessions by RAPD analysis. Analysis of 282 polymorphic fragments generated from 80 primers among bulked DNA samples revealed that A. hypochondriacus and A. caudatus are genetically more similar to each other than either species is to A. cruentus. These results suggest that RAPD analysis can be used to efficiently classify grain amaranth accessions by species.
Maize Growth and Yield Following Late Summer Hail
Authors: Dwyer L. M. , Stewart D. W. , Evenson L. , Ma B. L.
Published: July 2010

Leaf damage caused by hail may severely restrict photosynthate production, but estimation of yield loss is hindered by lack of an unaffected control for comparison. A field study was modified in 1990 at Ottawa, Canada, to determine the effect of maize growth stage at the time of hail damage on harvest parameters. Hand‐harvested above‐ground dry matter, grain yield, grain moisture, and harvest index were compared among nine hybrids with maturities ranging from 2350 to 2800 corn heat units (CHU)and planting dates of April, 16 May, and 29 May. A severe hail storm occurred 28 August when some hybrid maturity × planting date treatments were at the milk stage and others were at full dent. A method of analysis was developed using above‐ground dry matter accumulation at tasselling as a pre‐hail indicator of yield potential to calculate the reduction in harvest dry matter and grain yield resulting from the hail storm. The reduction in harvest dry matter and in grain yield was linearly related to the CHU required to reach physiological maturity at the time of the hail storm (P < 0.10). Late‐maturity hybrids were most affected by the hail storm and contributed most to these segressions (P = 0.01 and P = 0.02 for harvest dry matter and grain yield, respectively). Harvest index was not affected by the hail storm (P > 0.10).
Genetic Variances of Agronomic Traits in Tetraploid Crested Wheatgrass under Competitive Conditions
Authors: Ray Ian M. , Frank Albert B. , Berdahl John D.
Published: July 2010

Limited research has been conducted on characterizing the genetic variability of important agronomic traits of forage grasses grown in seeded swards. This study was conducted to estimate the degree of genetic control, i.e., the beritability (h2), of several agronomic, morphological and physiological traits of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes] under sward conditions. Thirty randomly selected half‐sib families from a genetically broad‐based crested whcatgrass population were evaluated at one location for 2 yr in single‐row plots that were spaced 38 cm apart and seeded at a rate of 90 seed m−1. Heritabilities were determined for the following traits based on the progeny means of the 30 families: fresh forage yield, dry matter yield, tiller height, tiller number, flag leaf width, spikelets per spike, proline content, first‐cut vigor, regrowth vigor, and flag leaf pubescence. Heritability estimates of fresh forage yield were similar, i.e, 80 and 82%, when based on 30 and 300 half‐sib families, respectively, indicating that a sample size of 30 families provided a reliable estimate of genetic variance in this crested wheatgrass population. With the exceptions of tiller number and proline content (h2 = 0%), all traits demonstrated moderate to high heritabilities, ranging from 53 to 86%. Confidence interval widths ranged from 14 to 116% as large as the heritability point estimate. Signilicant family × year interactions were detected for some traits that possessed moderate to high heritabilities. The interaction variance components, however, were significantly less than their corresponding genetic variance for all traits except first‐cut vigor. The results indicate that for most traits, evaluation for multiple years would not be needed.
Variation in Parasitic Potential of Heterodera glycines Populations
Authors: Anand S. C. , Sharma S. B. , Rao‐Arelli A. P. , Wrather J. A.
Published: July 2010

A great deal of variation in parasitic potential has been observed among the soybean cyst nematode (SCN) Heterodera glycines Ichinohe populations in the USA. To best utilize sources of genetic resistance to SCN, this variation needs to be characterized. Fifty‐eight populations of the SCN were collected from 10 major soybean producing states. These populations were compared for infraspeeific variation in parasitic potential on soybean [Glycine max (L.) Merr.] genotypes ‘Peking’, ‘Pickett’, Plant Introduction (PI) 88788, PI 90763, and ‘Lee 68’. Race structure, genes for parasitism (capability of a nematode population to produce at least one cyst on a resistant genotype), and levels of parasitism (percentage of cysts that developed on resistant genotypes compared with the susceptible cultivar Lee 68) were assessed. Race was present in 45% of locations; it was the most widespread population. Race 6 was present in 19% of the locations. Frequency of occurrence of other races (Races 1, 2, 5, 9, and 14) ranged between 3 and 9%. On the basis of reproduction on genotypes, 83% of the populations tested had genes to parasitize Pickett. All populations from Arkansas, Florida, Georgia, Iowa, North Carolina, and South Carolina produced cysts on this genotype. Average level of parasitism was greatest on Pickett and lowest on PI 90763; 91% of SCN populations tested had <10% level of parasitism on PI 90763. The SCN gene frequencies demonstrated that nematode populations with predominant genes for parasitism on Pickett and Lee 68 were widespread especially in the southern soybean producing states in the USA. Cultivation of varieties with resistance derived from Peking and Pickett in these regions should not be very effective. For management of SCN‐caused yield losses, cultivation of soybean varieties with resistance derived from P190763, PI 88788, and PI 437654 should be encouraged.
Growth Response of Kenaf Cultivars in Root‐Knot Nematode/Soil‐Borne Fungi Infested Soil
Authors: Cook C. G. , Mullin B. A.
Published: July 2010

The southern root‐knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] is a severe pathogen of kenaf (Hibiscus cannabinus L.) capable of reducing growth, yield, and harvesting efficiency, as well as predisposing kenaf to pathogenic soil fungi. In 1991 and 1992, field studies were conducted to evaluate growth and yield response of six kenaf cultivars grown on a soil naturally infested with RKN and various pathogenic soft fungi. Cultivars included in the studies were Everglades 71 (E71), Talnung 1 (TAD, Cuba (CI08), Indian (IND), SF459, and 117. Early to midscason growth rate differed among culfivars. Across years, culfivars 117 and SF459 grew ≈73 and 55%, respectively, faster than ETI and IND. Total stalk yields differed among cultivars, with 117 and SF459 producing greater yields than the other four cultivars, including a =250% yield increase compared with E71, a widely grown kenaf cultivar in the USA. Based on the presence of root galls, all cultivars appeared to be good hosts for RKN; however, the ability of 117 and SF459 to maintain better plant growth and dry matter accumulation indicated a significant level of field tolerance when grown in the presence of the RKN/soil‐borne fungi complex.
Abscisic Acid Concentration in Leaf and Xylem Sap, Leaf Water Potential, and Stomatal Conductance in Maize
Authors: Tuberosa Roberto , Sanguineti Maria C. , Landi Pierangelo
Published: July 2010

Genetic variation of and the relationships among abscisic acid (ABA) concentration in the bulk‐leaf tissue (L‐ABA) and xylem sap (X‐ABA), bulk‐leaf water potential (Ψ), and stomatal conductance were investigated in eight early‐maturity and seven medium‐maturity maize (Zea mays L.) lines grown under drought conditions in the field. Data were collected in two samplings, 1 wk apart, during flowering. From the first to the second sampling, L‐ABA and X‐ABA increased 34.4 and 71.5%, respectively, Ψ declined 10.5%, whereas SC did not change appreciably. Significant differences (P < 0.05) among lines were found at both samplings for L‐ABA (from 229 to 1025 ng ABA g−1 dry wt.), Ψ, and SC. Significant differences (P < 0.05) for X‐ABA (from 10.3 to 41.1 nmol ABA L−1) were present only among mediummaturity lines at the first sampling. Correlation coefficients computed on a single‐plot and variety‐mean basis (rp and rv, respectively) were generally similar. L‐ABA and X‐ABA were positively correlated. On a variety‐mean basis, SC was more strongly correlated with X‐ABA than with L‐ABA at the first and second samplings (rv of − 0.60* vs. −0.40 and −0.71** vs. −0.19, respectively). The association between Ψ and SC changed markedly from the first to the second sampling (rp from −0.46** to 0.66**; rv from −0.37 to 0.31). An analogous trend was found for the correlations computed on a single‐plant basis within each line: all of the 13 lines characterized by negative correlations in the first sampling showed positive coefficients 1 wk later. The negative relationship between Ψ and SC at the first sampling suggests that SC was controlling Ψ.
Yield, Growth, and Water Use of Conventional and Semileafless Peas in Semiarid Environments
Authors: Martín I. , Tenorio J. L. , Ayerbe L.
Published: July 2010

Terminal water stress is a major factor that reduces field pea (Pisum sativum L.) yield in temperate dry areas. Agronomic practices and plant material should be adapted to these environments to optimize soil water use. In this work, field trials with peas were conducted to study the effect of plant population density and leaf type (conventional or semileafless) upon growth and yield in drought conditions. Experimental plots were grown during the spring of 1990 and 1991. The cultivar Desso (conventional) and a semileafless related breeding line (V‐12) were grown at plant densities ranging from 25 to 200 plants m−2. In both years, yield, yield components, and harvest index were determined. Biomass growth, light interception, and soil water content were also determined for two plant densities during the second year. Seed yield ranged from 1200 to 1700 kg ha−1 in 1990 and from 800 to 1100 kg ha−1 in 1991. Higher plant densities increased straw yield, but plant populations had only a slight effect on seed yield. More populated treatments had a lower harvest index. Vegetative growth before flowering was greater in treatments with higher plant density and, as a consequence, soil water depletion occurred earlier than in the less populated plots. Until flowering, a common linear correlation between aerial dry matter and intercepted photosynthetically active radiation was found for both genotypes, with a slope of 1.43 g MJ−1. At the end of the growth cycle, water deficit progressively decreased radiation use efficiency. Both conventional and semileafless genotypes showed a similar response to variations in plant density and performance under drought conditions.
Methods of Selection for Chilling Tolerance in Nepalese Rice by Chlorophyll Fluorescence Analysis
Authors: Sthapit B. R. , Witcombe J. R. , Wilson J. M.
Published: July 2010

Rice (Oryza sativa L.) yields are frequently low in the high hills of Nepal because of chilling temperatures throughout the growing season. Conventional screening for chilling sensitivity of different rice genotypes in breeding programs relies on visual observations in the field. The screening is subjective, time consuming, and subject to genotype × environment, interactions (e.g., stage of development when chilled). In this study, chlorophyll fluorescence analysis (CFA) was used to test its value in assessing chilling tolerance. Landraces and cultivars with known chilling sensitivities, including chilling‐tolerant landraces and cultivars from Nepal, were compared. Detached leaves from plants of 16 rice genotypes at the tillering stage were chilled in growth cabinets before their photochemical efficiencies (Fv/Fm) were measured by CFA. Genotype differences were examined by three methods: absolute Fv/Fm ratios of excised leaves chilled for 24 to 72 h at 10°C, decline in Fv/Fmratios of excised leaves chilled for 24 to 72 h at 10°C in comparison to unchilled checks, and absolute Fv/Fm ratios of chilled leaves after recovery of up to 72 h at 25°C in the dark. Altitudes of the site of genotype adaptation correlated well with Fv/Fm ratios after chilling for 48 h, whether Fv/Fm values were the absolute values or percentages of corresponding unchilled checks. The absolute Fv/Fm ratios of the chilled plants after 48 h recovery at 25 °C gave the highest correlation with altitude but that correlation was not significantly better than the correlation obtained with the absolute Fv/Fm ratios determined in the absence of a recovery period.
Kernel Set at Low Water Potential Does Not Vary with Source/Sink Ration in Maize
Authors: Zinselmeier C. , Westgate M. E. , Jones R. J.
Published: July 2010

Water deficits during pollination increase the frequency of zygotic abortion in maize (Zea tnays L.). Recent work suggests that reproductive failure occurs because assimilate supply in water‐deficient plants is not sufficient to maintain growth of all newly formed zygotes. We tested this possibility by altering the vegetative source to reproductive sink ratio in the inbred line A188 prior to imposing a water deficit at pollination. Relative assimilate supply was modified by growing plants in 20‐L pots containing 22 kg of amended soil in three environments: (i) the field, (ii) the field under 55% shade, or (iii) a growth chamber. Sink size was modified genetically using a chromosome interchange (reciprocal translocation) mutant (T3‐7c) that is nearisogenic to the wild type (A188WT) but sets only 50% of the fertilized ovaries. Six treatment‐genotype combinations produced a seven‐fold range in photosynthesis per kernel and a four‐fold range in reserve sugars per kernel at silk emergence. Water was withheld on the first day silks emerged and plants were hand pollinated 4 to 7 d later when leaf photosynthesis was <2 μmol m−2 s−1 and silk water potential (Ψw) reached ⊄ ‐ 1.1 MPa. Upon rehydration 2 d after pollination (DAP), leaf Ψw and photosynthesis rapidly recovered to control values. The water deficit decreased kernel number per ear 40 to 70% compared to the controls. Plants with a high source/sink ratio (e.g., T3‐7c, field) were just as sensitive to low Tw at pollination as plants with a low source/sink ratio (e.g., A188WT, growth chamber). These results indicate that assimilate supply per kernel alone does not determine the sensitivity of kernel set to low Tw at pollination.
Nitrate Assimilation in Tobacco Leaves Treated with Maleic Hydrazide to Control Axillary Bud Growth
Authors: MacKown C. T. , Sutton T. G.
Published: July 2010

After removal of the upper stalk containing the developing inflorescence and small expanding leaves (<20 cm) of hurley tobacco (Nicotiana tabacum L.), maleic hydrazide (MH) is used to control axillary bud growth (suckers) and enhance economic yield. Maleic hydrazide has numerous physiological effects on tobacco; many represent delayed or secondary effects on plant metabolism and may affect chemical composition of leaves. The effects of MH level (0, 0.17, 0.34, and 0.68 g plant −1) on the in situ assimilation of nitrate and other selected physiological traits of the second leaf from the top in plants grown in 1989 and 1990 were determined at weekly intervals for 3 wk beginning ⊄10 d after the MH application. Total chlorophyll in laminal tissue decreased as MH level increased; this response to MH became increasingly pronounced with time. The dry weight of the second leaf from the top increased with time, but differences in leaf weight due to treatment were not significant. Leaf total N and nitrate concentrations of the lamina averaged across both years and three sampling dates decreased with increasing MH level. However, in situ assimilation of nitrate was unaffected by MH. Differences in leaf N concentrations due to MH are partly the consequence of greater leaf dry weight accumulation and possibly to decreased uptake and partitioning of nitrate rather than nitrate assimilation. The slightly lower levels of nitrate in the upper leaves of MH‐treated burley tobacco should be a desirable benefit of chemical suppression of suckers, because lower levels of tissue nitrate are often associated with decreased production of nitrosamines in cigarette smoke.
Irrigation during Seedfill and Germinability of Soybean with Impermeable Seed Coat Character
Authors: Heatherly Larry G. , Kenty Michael M.
Published: July 2010

The impermeable seed coat (ISC) trait in soybean [Glycine max (L.) Merr.] is valuable because impermeable seed retain viability longer than permeable seed under adverse conditions such as delayed harvest or lengthy storage. The objective of this study was to determine how drought stress during seedfdling affected the ISC trait. ‘Forrest’, a maturity group (MG) V determinate cultivar with normal seed coat, and D86‐4565, an ISC MG V determinate line, were grown in the field in 1991 (hot, dry season) and 1992 (cool, wet season) at Stoneville, MS. No irrigation or furrow irrigation between beginning seedfill fRS) and full seed (R6) growth stages were used to vary soil water content during seed development. Seed was harvested by hand and machine both years. In 1991, germination of machine‐harvested, unscarified D86‐4565 was increased by irrigation, but the percentage of impermeable seed was not affected. In 1992, irrigation that was started at R5 and continued through R6 increased germination of machine‐harvested, unscarified seed from both genotypes, and significantly decreased impermeability of unscarifled seed of D86‐4565. Unsearified seed from D86‐4565 grown in 1992 had greater germination and higher permeability than seed from 1991. Unscarifled seed from all treatments of D86‐4565 germinated well below the standard of 80%. These results indicate that irrigation of soybean during the seedfilling period can influence the ISC trait and germination of unscarified seed with this trait, but the effect of diverse weather is much greater. Furthermore, adequate moisture during seedfili will not preclude preplant scarification to enhance germination of seed with the ISC trait.
Variability for Temperature of Germination in Sericea Lespedeza Germplasm
Authors: Qiu J. , Mosjidis J. A. , Willliams J. C.
Published: July 2010

Poor and slow seed germination are major problems in growing sericea lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don.]. Knowledge about the temperatures for optimum seed germination is vital to selecting the best seeding date for this forage legume. The objectives of this study were to determine the variability of sericea lespedeza germplasm for germination under several temperatures and the effect of seed weight on percentage and rate of germination. Germination response to temperature of 54 breeding lines and 26 accessions were tested. Mechanically‐scarified seed of each of the 80 genotypes were weighed and germinated in the dark in a germinator at constant temperatures of I0, 15, 20, 25, and 30°C. An additional temperature (35°C) was included to test the germinability of the accessions. Germination counts were recorded daily for 14 d to calculate total percent germination (TPG) and Maguire germination rate index (GRD. Temperature had a significant effect on TPG and GRI. Optimum germination temperature for sericea lespedeza ranged between 20 and 30°C. Thus, seeding time for this species for a particular location should be selected to match the optimum range of soil temperatures provided that adequate soil moisture is available. Mean TPG and GRI were significantly different among the genotypes at each temperature. However, genotypes with a consistently high TPG and GRI at a wide range of temperatures were found. Seed weight was correlated with TPG at I0 (r = 0.401) and 15°C (r = 0.459), also with GRI (r = 0.388‐0.475) at all temperatures for the breeding lines. However, seed weight was not correlated with TPG or GRI for the 26 accessions. The TPG and GRI were highly interrelated, thus, measuring TPG alone should provide adequate information when describing response to environmental stresses in sericea lespedeza.