bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin of Soybean Alleles for Phytophthora Resistance in China
Authors: Lohnes D. G. , Nickell C. D. , Schmitthenner A. F.
Published: July 2010

Since Phytophthora sojae Kauf. & Gerde. is constantly evolving new races that overcome the resistance genes that have been deployed in soybean cultivars [Glycine max (L.) Merr.], the search for new sources of resistance is important in breeding programs involving disease management strategies. No systematic screening of the germplasm collection has been made that would give us an indication of the prevalence and distribution of phytophthora resistance in China. The objective of this study was to examine the distribution of Phytophthora resistant soybean in central China. By means of hypocotyl inoculation in the greenhouse, lines from central China were classified for their reaction to Races 1, 3, 7, and 25 of P. sojae in 1993 and 1994 at Urbana, IL, and Wooster, OH. Resistance was more frequent in the eastern provinces with the origin of Rps1‐d in central China. Any searches for new P. sojae resistance genes in soybean should be focused on the Chinese provinces (Anhui and Jiangsu) with the highest incidence of resistant soybean lines.
Embryo Culture as a Means to Rescue Deteriorated Maize Seeds
Authors: Blackman Sheila A. , Brown Kathryn L. , Manalo Joseph R. , Roos Eric E.
Published: July 2010

Seed germplasm is received and stored at genebanks, such as the National Seed Storage Laboratory, to ensure that genetic diversity is available for future plant breeders. On occasion, low viability seeds are received or seeds may deteriorate unexpectedly between scheduled viability tests, resulting in accessions that cannot be successfully regenerated with routine procedures. In 1993 and 1994, experiments were conducted with the objective of developing procedures to improve the survival of low viability maize (Zea mays L.) seeds and thus avoid the loss of potentially valuable genes. To develop a seed rescue protocol, the effects of various antibiotics, C and other nutrient sources, and hormones were evaluated on the growth of excised hybrid maize embryos in tissue culture. Kanamycin and thiram were effective against bacterial and fungal contamination and improved the growth of aged embryos. Among the C sources tested, only sucrose stimulated growth of isolated embryos but not whole seeds. Complete nutrient mixtures containing macro‐ and micronutrients and vitamins did not stimulate growth of whole embryos, but they stimulated the growth of isolated axes. Among the hormones tested, only gibberellic acid stimulated the growth of the primary root. The seed rescue protocol developed through these experiments was tested on eight endangered maize landrace populations from Argentina. Six of these eight populations contained sufficient seed numbers to compare the embryo culture protocol with whole seed germination. Embryo culture resulted in a twofold increase, on average (range = 0.9–4.0), in plant recovery compared with whole seed germination. This protocol can be used to rescue maize germplasm accessions with a germination percentage below that which results in successful field regeneration.
Pod Inoculation Technique with Phytophthora Sojae to Evaluate Soybean Populations for RPS Alleles in Field Plantings
Authors: Hegstad J. M. , Kyle D. E. , Nickell C. D.
Published: July 2010

The pathogen Phytophthora sojae (M.J. Kaufmann and J.W. Gerdemann) can be injected into soybean pods [Glycine max (L.) Merr.] determine presence of phytophthora root and stem rot resistance. The objective of this study was to use pod inoculation in the field to screen soybean F2 populations segregating for Rps alleles. The potential exists to inject different races of the pathogen into pods at different nodes of a single plant, allowing for multiple screenings at a time. Controlling the amount of Phytophthora sojae pathogen injected into each pod was necessary for accurate scoring of disease progression. Injecting 25 μL of Race 1 or Race 3 mycelium inoculum gave optimal symptom differences. The amount of disease progression up the pod to the point of attachment or the complete lack of rotting was determined to distinguish between susceptible and resistant plants, respectively. The data obtained from scoring pods conformed well to ratios of expected models. This technique provides a rapid and inexpensive field screening for identifying resistant or susceptible progeny early in the selection process.
Results and Biological Interpretation of Shifted Multiplicative Model Clustering of Durum Wheat Cultivars and Test Site
Authors: Abdalla Osman S. , Crossa José , Cornelius Paul L.
Published: July 2010

The examination of crossover interactions (COI) (genotypic rank change) and identification of subsets of homogeneous groups of sites and cultivars without COI are important in the interpretation of cultivar trials in breeding and agronomy. The shifted multiplicative model (SHMM) clustering method was applied to a CIMMYT durum wheat (Triticum turgidum L. var. durum) yield trial consisting of 24 cuitivars grown at 40 international sites during the 1990‐1991 season. The objectives were to identify subsets of sites and cultivars with negligible genotypic rank change and attempt to give a biological interpretation for the resulting clusters. The SHMM with one multiplicative term (SHMM1) provided an adequate fit for seven final groups of cultivars and eight final groups of sites with small numbers of COI. Grouping of cultivars greatly reflected similarity in genetic backgrounds and, consequently, similarity of response to test environments. Differential responses within the same genetic background were attributed to differences in simply inherited traits such as plant height and disease resistance. The observed grouping of sites was generally associated with latitude, while environmental conditions that influenced crop phenology and cropping cycle delineated the final groupings. The results suggest that groups formed based on SHMM clustering methods have valid biological basis. Routine use of SHMM clustering methods could increase selection efficiency through the identification and selection of superior cultivars within clusters having negligible COI. Similarly, groups of test sites that represent similar selection environments could be identified and that would facilitate identification of key test sites as well as decision making concerning exchange of germplasm and information.
Grain Yield and Breadmaking Quality of Wheat Lines with the Leaf Rust Resistance Gene Lr41
Authors: Cox T. S. , Bequette R. K. , Bowden R. L. , Sears R. G.
Published: July 2010

Some of the many disease‐resistance genes transferred into common wheat (Triticum aestivum L.) by interspecific hybridization have been underutilized in agriculture because of associated negative effects on productivity and end‐use quality. The Lr41 gene conferring resistance to leaf rust (caused by Puccinia recondita Rob. ex Desm.) was transferred from the wild diploid goatgrass [Triticum tauschii (Coss.) Schmal], the chromosomes of which recombine readily with those of common wheat (Fritz et al., 1995a). Thus its chromosomesr ecombine readily with those of wheat. This study had three objectives: (i) determine the direct and linked effects of Lr41 on 15 productivity and quality traits in hard red winter wheat under disease‐free conditions; (ii) to determine the effects of resistance conferred by Lr41 under a severe leaf rust epidemic and under a light infection; and (iii) to determine the amount of damage inflicted by diseases other than leaf rust in those environments. Six BC2F2‐derived common wheat lines with Lr41, along with their recurrent parents (hard red winter wheat cultivars TAM 107, TAM 200, and Century), were evaluated in three field experiments with and without fungicide treatment in 1992 and 1994. Lr41 increased grain yield and milling quality under heavy leaf rust infection with no negative effects on those traits in disease‐free plots. However, Lr41 was associated with reduced bake‐mixing time and water absorption in the absence of disease. Effects of other diseases depended heavily upon the genetic backgrounds (i.e., recurrent parents) of backcross lines. There should be no serious impediments to the use of Lr41 in breeding programs.
Relationships among Creeping Bentgrass Cultivars Based on Isozyme Polymorphisms
Authors: Warnke S. E. , Douches D. S. , Branham B. E.
Published: July 2010

An understanding of the genetic variability within a crop species is essential to its improvement. The objectives of this research were to study the utility of isozyme patterns for creeping bentgrass (Agrostis palustris Huds.) cultivar identification and to estimate the relationships between creeping bentgrass cultivars based on isozyme patterns. Seventy to 73 plants from each of 18 creeping bentgrass cuitivars and 25 plants from one plant introduction were scored for 24 isozyme polymorphisms representing six loci. All cultivars except a small group containing the cultivars Pennlinks, Pro/Cup, Southshore, and Lopez were uniquely characterized based on a 20% or greater band frequency in one cultivar versus absence of the band in the most closely clustered cultivar. The isozyme patterns from each plant were used to calculate the genetic distance within a cultivar, and the average band frequency within a cultivar was used to calculate genetic distances between cultivars. The cultivars Pennlinks, Pro/Cup, Southshore, and Lopez had the highest average within‐cultivar genetic distances indicating that additional marker loci will be needed to distinguish these cultivars. The unweighted pair group method with arithmetic average (UPGMA) cluster analysis generated from the between‐cultivar genetic distance matrix divided the cultivars into two groups. One group contains 10 cultivars including the variety Seaside which may have provided initial germplasm for this group. The second group contains the cultivars Pennlinks, Southshore, Pro/Cup, Lopez, and four cultivars with unique allozymes. The plant introduction PI251945 was distantly related to the cultivated U.S. germplasm indicating that European material can be a source of genetic diversity to broaden U.S. bentgrass germplasm.
Herbicidal Effects of the Dipeptide Aianinyl‐Alanine on Perennial Ryegrass (Lolium perenne L.) Seedlings
Authors: Unruh J. B. , Christians N. E. , Horner H. T.
Published: July 2010

Corn gluten meal (CGM), a by‐product of corn (Zea mays L.) wet‐milling, has been shown to be an effective, natural preemergence herbicide and fertilizer for various plant production systems. Alaninylalanine (Ala‐Ala), along with four other dipeptides were isolated from hydrolyzed CGM and identified as being the inhibitory compounds. The herbicidal effects of these natural compounds are seen as growth‐regulating root inhibitors that have minimal effect on shoot growth at low concentrations. However, little is known about the precise inhibitory action of CGM or Ala‐Ala. The objective of this research was to elucidate morphological and anatomical differences in perennial ryegrass (Lolium perenne L.) seedlings treated with Ala‐Ala by means of light and transmission electron microscopy, as well as autoradiographic studies using [3H+]‐Ala‐Ala. Root length was reduced by at least 42% at all treatment concentrations when compared with the control. The treated root tips were observed to be devoid of cellular components, specifically discernible nuclei and mitotic structures, with an overall loss of cytoplasmic integrity. Treated root tips had cell wall abnormalities, including uneven thickening and breakage, especially in the epidermal and the adjacent cortical cells. Autoradiographs suggested that, at treatment concentrations causing epidermal damage, there was minimal inward movement of the dipeptide. At low treatment concentrations, root tip epidermal necrosis was not evident, and inward movement of the dipeptide was not impeded. The herbicidal effects of the dipeptide, Ala‐Ala, on treated perennial ryegrass roots were numerous. Higher concentration levels seemed to cause more of an epidermal necrosis, whereas, lower concentrations produced more subtle effects to the cellular processes.
Screening of Soybean for Pendimethalin Herbicide Induced Stem Damage
Authors: Glover D. G. , Schapaugh W. T.
Published: July 2010

Field‐grown soybean [Glycine max (L.) Merr.] have exhibited stem breakage, lodging, reduced nodulation, and enlarged root tips and hypocotyls (brittle bean syndrome) after treatment with pendimethalin herbicide [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitro‐benzenamine]. Greenhouse and field research was conducted in 1993 and 1994 to develop and evaluate screening systems (herbicide rates, experimental units, and rating methods) to quantify soybean susceptibility to brittle bean syndrome. Both field and greenhouse experiments resulted in injury to soybean plants consistent with pendimethalin‐induced stem damage previously observed in the field. Greenhouse evaluation of cultivars and breeding lines detected significant differences among entries for stem breakage with pendimethalin rates at 0.56, 1.68, and 2.80 kg ha−1. Significant differences among entries for stem breakage were also observed in field trials. Rank correlations among entries for stem breakage at the 1.12 kg ha− field rate vs. the 1.68 or 2.80 kg ha−1 greenhouse rates of pendimethalin were 0.7** and 0.8**, respectively. Although the field and greenhouse evaluations were not in complete agreement, the relative performance of the entries provided evidence that greenhouse screening is an effective tool to characterize genetic variation in soybean for resistance to brittle bean syndrome.
Agronomic Performance of Hybrids between Cultivars and Chromosome Substitution Lines
Authors: Yen Yang , Baenziger P. S. , Bruns R. , Reeder J. , Moreno‐Sevilla B. , Budak N.
Published: July 2010

Previous studies have identified wheat (Triticum aestivum L.) chromosome substitution lines between ‘Cheyenne’ (CNN) and ‘Wichita’ (WI) that contain quantitative trait loci (QTLs) affecting yield and yield components, anthesis date, plant height, and grain volume weight. However, chromosome substitution lines can only identify additive or epistatic gene action. In this study, hybrids between CNN and WI, and between chromosome substitution lines and their recurrent parents were evaluated in four field environments to determine if the QTLs exhibited additive and dominant gene action which could result in heterosis. As expected, the chromosome substitution lines were significantly different for grain yield from their recurrent parents, which indicated the chromosomes contained additive genes. Three of four chromosome substitution line hybrids were not different from the midparent value, which indicated predominantly additive gene action. However, the fourth substitution line hybrid significantly differed from the midparent value for grain yield, which indicated the chromosome contained genes that were heterotic and had dominant gene action. Some hybrids did not significantly differ from one parent, which further indicated the possibility of dominant gene action. Midparent heterosis also was identified in the cultivar hybrid for grain yield. High parent heterosis was not found for any of the measured traits. Hence, genes on these chromosomes exhibited predominantly additive gene action, but also exhibited dominant gene action which may explain some of the heterosis found in the cultivar hybrid.
Analysis of the Diallel Mating Design for Maize Inbred Lines
Authors: Sughroue Jay R. , Hallauer Arnel R.
Published: July 2010

One of the assumptions required to estimate genetic parameters by use of the diallel mating design is that the genes in the parents are independently distributed. The objective of this study was to test the validity of this assumption. Diallel experiments including a fixed sample and a random sample of parents were conducted in maize (Zea mays L.). For the fixed sample, an eight‐parent diailel among selected inbred lines was produced (original diallel). Ninety‐six unselected inbred lines derived from a population, developed by intermating for five generations crosses of the original diallel, were used to produce 12 eight‐parent diallels (random diallels). Diallels were evaluated in replication‐within‐sets randomized incomplete block design in six environments. Estimates of additive (σ2A) and dominance (σ2D) variances from the pooled random diallels were significantly different from estimates of σ2A and σ2D in the original diallel for about half the traits. For six traits, the average level of dominance was overestimated in the original diallel relative to the pooled random diallels. The estimated average level of dominance for grain yield was two times greater in the original diallel than in the pooled random diallels. Estimates of σ2A seemed to be affected more than estimates of σ2D by repulsion phase linkages. Non‐independent distribution of genes causes differences in σ2A and σ2D. The diallel mating design should only be used to estimate genetic parameters when the parents of the diallel have been randomly selected from a population in linkage equilibrium.
Kernel Set and Flower Synchrony within the Ear of Maize : II. Plant Population Effects
Authors: Otegui María E.
Published: July 2010

Kernel number (KN) per plant declines with increasing plant population (PP) in maize (Zea mays L.) and controversy exists about the critical period for spikelet abortion. In this work, the effect of PP (5 and 9 plants m−2) on floral differentiation and kernel set was analyzed for two genotypes of contrasting prolificacy at Grignon, France, (48°51′N). Kernel set variability was tested at Balcarce (37°45′S), Argentina, with three PP (2, 8, and 16 plants m−2) and athinning treatment (from 16 to 2 plants m−2) at silking. Plants were grown with no water or nutrient restrictions. At 9 plants m−2, floral differentiation was delayed in apical ears but almost all spikelets started silk elongation. In subapical ears, 17% of the spikelets of the nonprolific hybrid and 19% of the prolific hybrid had not completed development at silking. At 5 plants m−2 these proportions were reduced to 6%. Significant (P < 0.01) differences were detected in apical ear length after the onset of rapid ear growth (silking −20 d), resulting in reduced ear biomass at silking at high PP. Barrenness occurred at 16 plants m−2 (0.5 ears plant−1), but spikelet abortion took place in all apical ears after silking, except at 2 plants m−2 (control). Kernel number per plant was not related to the degree of floral differentiation reached at silking, but to the amount of intercepted photosynthetically active radiation (KN = 149.5 + 204.6 MJ plant−1 d−1, r2 = 0.92) when the silking −15‐d period was included in the calculations. Presilking limitations to ear growth appear to reduce ear sink strength.
Responses to Root‐Zone CO2 Enrichment and Hypoxia of Wheat Genotypes Differing in Waterlogging Tolerance
Authors: Huang Bingru , Johnson Jerry W. , NeSmith D. Scott
Published: July 2010

Knowledge of wheat (Triticum aestivum L.) responses to CO2 and O2 in the root environment could improve understanding of the mechanisms of waterlogging tolerance and thus help develop waterlogging tolerance wheat plants. This experiment was designed to investigate the responses to elevated CO2 and hypoxia of two wheat genotypes, Bayles and Savannah, which differ in waterlogging tolerance. Plants were grown in a growth chamber in nutrient solutions. Nutrient solutions were bubbled with ambient air (control), N2 containing 5 kPa O2 and ambient CO2 (hypoxia), N2 containing 10 kPa CO2 and ambient O2 (high CO2, ambient O2), and N2 containing 10 kPa CO2 and 5 kPa O2 (high CO2, low O2). Hypoxia alone had adverse effects on net photosynthesis (Pn), stomatal conductance (gs), water relations, chlorophyll (chl) content, and shoot and root growth. The effects were greater for waterlogging‐sensitive Bayles. When compared with the aerated control, the combination of elevated CO2 and hypoxia caused significant reductions in Pn, gs, leaf water potential, and leaf chl content for Bayles, and in shoot and root growth for both Bayles and Savannah. Photosynthetic rate and leaf chi content of Savannah were increased when roots of hypoxic plants were exposed to elevated CO2, but this was not true for Bayles. Root‐zone CO2 enrichment at ambient O2 had no significant effects on shoot growth, but reduced root growth in both genotypes. The results showed that CO2 enrichment under root hypoxia can alleviate some negative effects of hypoxia on Pn, leaf chi content, and shoot growth, the effect being larger for waterlogging tolerance Savannah.
Emergence and Growth of Durum Wheat Derived from Red Smudge‐Infected Seed
Authors: Fernadez M. R. , Clarke J. M. , DePauw R. M. , Lefkovitch L. P.
Published: July 2010

All durum wheat (Triticum turgidum L. var. durum Desf.) cultivars grown in western Canada are susceptible to red smudge of kernels, caused by Pyrenophora tritici‐repentis (Died.) Drechs. This kernel discoloration reduces commercial grade, but its effect on the health and development of the crop when planted is unknown. Seedling emergence, plant growth, and grain yield were evaluated in field and controlled‐environment studies using four cultivars that were established from seed which had 0, 50, or 100% infection. The 2‐yr field study was conducted on a Swinton loam soil (Aridlc Haploborall). Infection resulted in a slower emergence rate and decreased total seedling emergence in both field and controlled‐environment studies. Poor seedling emergence resulted in sparse stands, fewer spikes, less above‐ground dry matter per unit area, and lower grain yield in the field. Seedlings from infected seed required significantly more time to head than those from non‐infected seed; however, plant growth and yield of growth chamber‐grown plants were not affected. Greater yield per plant derived from infected seed than from non‐infected seed in field studies was attributed to reduced interplant competition as a result of poorer emergence. We conclude that red smudge infection has the potential to reduce durum wheat grain yield, although the degree of reduction in a commercial crop will depend on the level of seed infection and on the ability of the crop to compensate for reduced stands. The latter will depend on plant vigor and the growing conditions associated with various seasonal environments.
A High‐Density Soybean Genetic Map Based on AFLP Markers
Authors: Keim Paul , Schupp James M. , Travis Steven E. , Clayton Kathryn , Zhu Tong , Shi Liang , Ferreira Arnaldo , Webb David M.
Published: July 2010

Genetic marker systems have improved dramatically in the past 10 yr. Each new system needs to be evaluated for its distribution of markers on genetic linkage maps to validate its use for genetic analysis. The resulting maps are also useful for establishing the genetic positions of genes affecting important phenotypes. We have constructed a high density map in soybean [Glycine max (L.) Merr.] using a 300 RIL (recombinant inbred line) population from BSR‐101 × PI437.654 by first constructing an RFLP (restriction fragment length polymorphism) “scaffold” map based on the entire population. The RFLP anchored map was then further populated with AFLP (amplified fragment length polymorphism) markers based on only a 42 RIL subset. We report here an 840 marker map consisting of 165 RFLP, 25 RAPD (random amplified polymorphic DNA), and 650 AFLP markers spread over 28 linkage groups representing 3441 cM distance. Although clustering of AFLP markers occurred, markers were mapped to every linkage group and were well distributed relative to other marker systems. The AFLP marker system appears to be a useful approach for generating high density genetic maps in soybean.
Position of the Phytophthora Resistance Gene Rps7 on the Soybean Molecular Map
Authors: Lohnes D. G. , Schmitthenner A. F.
Published: July 2010

For markers to be used when pyramiding resistance genes in soybean [Glycine max L. (Merr.)], it is necessary that resistance genes be placed on the molecular map. The purpose of this study was to place the phytophthora resistance gene Rps7 on the soybean molecular map. A ‘Clark’ × ‘Harosoy’ isoline mapping population that was segregating at the Rps7 locus was classified for reaction to race 12 of Phytophthorasojae Kaufmann & Gerdemann. Mapping analysis placed Rps7 in linkage group 22 of the Clark × Harosoy molecular map. Linkage group 22 corresponds to linkage group N of the public restriction fragment length polymorphism (RFLP) map and these two maps were integrated into the consensus linkage group N.
Influence of Cytoplasms from a Wild Grassy Subspecies on Dry Matter Yields in Pearl Millet
Authors: Hanna Wayne W.
Published: July 2010

Identification of cytoplasmic influences on dry matter yield and other agronomic characters could have a major impact on improving plant performance worldwide since the cytoplasm is contributed by the seed parent to its progeny. The objective of this field study was to determine if cytoplasms from a wild grassy subspecies of pearl millet, Pennisetum glaucum (L.) R. Br. subspecies monodii (Maire) Brunken, influenced hybrid dry matter yield. Thirty near‐isogenic lines with the Tift 23D genetic background but with putatively different cytoplasms (28 from the subspecies, A1 and B1) were pollinated with inbred Tift 383. The 30 Fthybrids were tested for dry matter yields during 1991 and 1992 in Georgia. Differences (P = 0.05) were observed among hybrids and between years. Fifteen of the hybrids yielded significantly more dry matter than the hybrid with the A1 cytoplasm (Tifleaf 1), a commercial hybrid. The hybrid with the highest 2‐yr mean yielded 17% more dry matter than Tifleaf 1. The highest yielding hybrids generally had cytoplasms derived from accessions collected in Senegal, whereas the lowest yielding hybrids had cytoplasms derived from accessions collected in Mall or Niger. However, no significant differences were observed among the mean dry matter yields of hybrids from different countries. Influence of cytoplasms on hybrid dry matter yields were observed, but further studies are needed to distinguish between cytoplasmic and cytoplasmic‐nuclear effects.
Free‐Air CO2 Enrichment Effects on Rate and Duration of Apical Development of Spring Wheat
Authors: Li Ai‐Guo , Trent Anthony , Wall Gerard W. , Kimball Bruce A. , Hou Yue‐Sheng , Pinter Paul J. , Garcia Richard L. , Hunsaker Douglas V. , Lamorte Robert L.
Published: July 2010

Rates and durations of individual phases of wheat (Triticum aestivum L.) apical development are among the most important factors that determine yield components. Because atmospheric CO2 has been increasing steadily, it is important to evaluate the effects of elevated CO2 on wheat development. This study was conducted to determine rates and durations of leaf, spikelet, and floret primordium initiation in a Free‐Air Carbon Dioxide Enrichment (FACE) system. Spring wheat (cv. Yecora Roja) was planted at the University of Arizona Maricopa Agricultural Center. The two CO2 concentrations were 550 (elevated) and 370 (ambient) μmol mol−1 CO2. Individual plant samples were collected every 3 to 4 d. We dissected the main stem (MS), coleoptile tiller (T0), primary tillers (T1, T2, and T3) and secondary tillers (T00, T01, T02, T10, Tll, and T12) and counted primordia. Apex primordium data were fitted to a four‐piece linear‐spline segmented regression model with the SAS proc NLIN. No influence of elevated CO2 (550 μmol−1 on leaf primordium initiation of MS was detected. Nevertheless, CO2 enrichment significantly increased rates of spikelet primordium initiation of MS, T1, T2, T10, and Tll, and diminished the durations of spikelet development phase of MS, TI, T2, T3, T10, and T11. Within the floret phase, CO2 enrichment significantly increased rates of floret primordium initiation of MS, TO, T1, T2, and T3, and diminished the time to the completion of floret primordium initiation of MS, T0, T1, T3, and T11. The information from this study will be utilized to predict wheat apical development and grain production in the elevated atmospheric CO2 environments of the future.
Effect of Repeated Fungicide Applications on Creeping Bentgrass Turf
Authors: Reicher Zachary J. , Throssell Clark S.
Published: July 2010

Though fungicides are regularly applied to creeping bentgrass (Agrostis palustris Huds.) turf throughout a growing season, little is known about possible non‐target effects of these applications on turfgrass growth and metabolism. The objective of this field study was to determine the effect of 3 yr of multiple applications of fungicides to ‘Penncross’ creeping bentgrass maintained under putting green conditions and on a native silt loam soil. Benomyl [methyl‐1‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] at 3.05 kg ha−1, iprodione [3‐(3,5‐dichlorophenyl)‐N‐(1‐methylethyl)‐2,4‐dioxo‐1‐imidazolidinecarboximide] at 3.05 kg ha−1, and propiconazole [1‐(2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2‐ylmethyl)‐1H‐1,2,4‐triazole] at 0.84 kg ha−1 were applied weekly or alternated with chlorothalonil (tetrachloroisophthalonitrile) at 6.36 kg ha−1. Sixteen applications were made in each of 3 yr. Propiconazole applied weekly or alternated with chlorothalonil increased clipping weights, turned bentgrass dark green, and decreased visual quality throughout the study. Chlorothalonil, propiconazole, and benomyl reduced water‐soluble carbohydrate (WSC) concentrations of clippings during the study, this effect was most common in the heat of late summer. Benomyl applied weekly and chlorothalonil applied weekly or alternated with the other fungicides decreased earthworm activity. Propiconazole applied weekly or alternated with chlorothalonil increased damage from pink snow mold (Microdochium nivale Samuels and I. C. Hallett). Chlorothalonil applied weekly and alternated with the other fungicides increased rooting the last year of the study. Fungicides applied frequently did not have serious negative non‐target effects on Penncross creeping bentgrass.
Genetic Diversity among North American Spring Wheat Cultivars: III. Cluster Analysis Based on Quantitative Morphological Traits
Authors: van Beuningen L. T. , Busch R. H.
Published: July 2010

Quantification and classification of diversity in germplasm collections is important for both plant breeders and germplasm curators. Distance measures between collection entries can be based on morphological or biochemical marker traits, pedigree information, or quantitative morphological traits. The objectives of this study were to group spring wheat (Triticum aestivum L.) cultivars into clusters according to their distance as measured by quantitative morphological traits, and to assess the relationship between distance based on quantitative morphological traits and distance based on coefficients of parentage. A broad collection of 289 spring wheat cultivars from the USA, Canada, and Mexico was grown in Minnesota during 1990 and 1991 and evaluated in three environments (two field and one greenhouse). A total of 35 different quantitative morphological traits were scored in one, two, or all three environments, resulting in a data set of 56 variables. This data set was reduced to 16 significant principle components (PCs) that cumulatively explained 80% of the variance. Squared Euclidean Distances based on PC‐scores were used as input for cluster analysis. All but six cultivars could be grouped into 17 major clusters. Major clusters grouped cultivars of common origin, parentage, and/or era of release. Partial agreement with the pedigree data was evident. Many clusters were recognizable across both methods from their most similar subgroups. Regression of the morphological distance on pedigree distance gave an R2 = 0.46 (P < 0.01) when the entire range of pedigree distances was sampled systematically. Quantitative morphological data provided valuable distance measures, and the quality of such measures increased with the number of traits evaluated regardless of whether selected or unselected traits were used. Combinations of distance measures based on pedigree and morphology can provide useful measures of genetic distance, but measurement of morphological traits requires considerable resources.
Convergent‐Divergent Selection for Seed Production and Forage Traits in Orchardgrass: I. Direct Selection Responses
Authors: Casler M. D. , Carlson I. T. , Berg C. C. , Sleper D. A. , Barker R. E.
Published: July 2010

Simultaneous improvement of forage traits and seed yield in orchardgrass (Dactylis glomerata L.) has been problematic because of geographic separation of forage and seed production locations. Most attempts to simultaneously improve both forage and seed traits have relied on a single location. The objective of this study was to conduct and evaluate two cycles of convergent‐divergent (C/D) and local selection for panicle seed weight (PSW) and forage traits. Selection was conducted at four locations (Ames, IA; Mount Vernon, MO; Rock Springs, PA; and Arlington, WI) in four base populations (I79DT, MO2, PLS4, and WO11). Phenotypic selection on a spaced‐plant basis was applied at a 0.25 selection intensity for forage traits, followed by a 0.25 selection intensity for PSW. All populations were evaluated as spaced plants at the Iowa and Pennsylvania locations in 1990 and 1991. Both selection methods were equally effective at increasing PSW, with responses averaging 1.0 to 18.2% cycle−1. Realized heritabilities for PSW were highly variable among the four populations (mean of 0.03–0.23) and were lower for Cycle 2 than for Cycle 1 (mean of 0.02 vs. 0.16). For C/D selection, IA, MO, PA, and WI selection locations increased PSW by 25, 39, 94, and 33 mg panicle−1 respectively. Three of the four populations had significant genetic changes of 2 to 4 d later heading, despite no direct selection pressure for heading dale. There were very few significant and biologically meaningful genotype × location interactions for any trait. Therefore, neither selection method resulted in plants with differential adaptation when evaluated as spaced plants.
Selection for Resistance to Sclerotinia Crown and Stem Rot in Alfalfa
Authors: Pierson P. E. , St. Martin S. K. , Rhodes L. H.
Published: July 2010

Efficient selection methods are needed for improving resistance in alfalfa (Medicago saliva L.) to Sclerotinia trifoliorum Erikss., the causal agent of Sclerotinia crown and stem rot (SCSR). The objective of this research was to determine if SCSR resistance in alfalfa could be improved by recurrent phenol) pic selection. Selections and evaluations were conducted at Columbus, OH, between August 1991 and April 1994 in three alfalfa populations, ‘Armor’, ABI 9023, and ABI 9030. Seedlings were inoculated with the pathogen in the growth chamber and field. Surviving plants were recovered and intermated for each cycle of selection. A standard seedling test was used to measure the progress of selection. Two cycle‐3 populations and the base populations from which they were derived were also inoculated with five additional isolates of S. trifoliorum to examine the durability of resistance in the selected populations. Progeny of populations selected for two or three cycles in the growth chamber a expressed significant (P = 0.05) reduction in disease severity index (DSI). Generally, progeny of one cycle of field selection were not significantly different than the unselected base population. However, in Armor, one cycle of selection in the field (DSI 3.39) was comparable to two or three cycles in the growth chamber (DSI 3.41). Realized heritability estimates for resistance to SCSR ranged from 0.07 to 0.27. Isolates of S. trifoliorum differed in virulence, but there were no isolate by population interactions. The growth chamber selection method developed, using a single isolate of S. trifoliorum, was effective in increasing resistance in three alfalfa populations.
Combined Testcross and S1 Selection for the Improvement of Testcross and Inbred Performances
Authors: Gallais A.
Published: July 2010

In crops where heterosis is high, one of the limiting factors in the development of commercial single‐cross hybrids is the seed yield of the female parent. To improve simultaneously combining ability with the male parent and the seed yield of the female parent, combined testcross and S1 selection has already been proposed by several researchers. In this study, after derivation of the theoretical expression of the relative efficiency of combined testcross and S1 selection, the testcross and S1 correlated responses are compared with those of direct selection with the same number of replications. The genetic advance using an economic index combining testcross and S1 performances is also considered. Combined selection can be more efficient than direct selection for the improvement of testcross performance only with a low testcross heritability, a relatively high S1 heritability, and a high generic correlation between Si and testcross progenies. Combined selection will generally be less efficient in improving testcross performance than direct selection for testcross performance if the same number of plots is used in both methods. Evaluations of selection methods using an economic index that accounts for the cost of seed production demonstrated that combined selection can be more efficient than direct testcross selection. However, the economic weight placed on the S1 value must be relatively high. With the same total number of replications as for testcross selection, combined selection will generally be more justified with unimproved than with elite material.
Genetic Gain for Soybean Seed Yield by Three Recurrent Selection Methods
Authors: Uphoff Michael D. , Fehr Walter R. , Cianzio Silvia R.
Published: July 2010

This study compared genetic gain for soybean [Glycine max (L.) Merr.] seed yield associated with three strategies of recurrent selection in soybean population AP6. For the strategy of a two‐stage test and one intermating generation (2ST‐1IG), 100 F4‐derived lines from 45 single‐cross populations were evaluated in each of three maturity classes, and the 10 highest yielding lines were intercrossed to begin the next cycle. The conventional breeding strategy (CB‐2ST‐IIG) consisted of testing 100 F4‐derived lines from 10 single‐cross populations in each maturity class and intermating 10 selected lines to initiate the next cycle. For the strategy of a two‐stage test and three intermating generations (2ST‐3IG), 100 F4‐derived lines were tested in the midseason maturity class, and 10 selected lines were intermated three generations to form the population for the next cycle. Composites of equal numbers of seeds of the parents for six cycles of 2ST‐1IG and CB‐2ST‐1IG, four cycles of 2ST‐31G, and the individual parents of the most advanced cycles were grown at three Iowa locations during 2 yr. The genetic gain per cycle for seed yield was significantly greater for 2ST‐1IG (53.8 kg ha−1) with one generation of intermating between cycles than for 2ST‐3IG (3.5 kg ha−1) with three intermating generalions. The genetic gain per cycle was greater for 2ST‐1IG than for CB‐2ST‐1IG, although the differences were only significant for the early maturity class. The superior genetic gain for 2ST‐1IG indicated that selection from the largest numbero f single‐cross matingsp ossible should maximize yield improvement from recurrent selection in soybean.
Effect of Specific Leaf Nitrogen on Radiation Use Efficiency and Growth of Sunflower
Authors: Bange M. P. , Hammer G. L. , Rickert K. G.
Published: July 2010

Specific leaf nitrogen (SLN, g/m2) is knownto affect radiation use efficiency (RUE, g/MJ) in different crops. However, this association and importance have not been well established over a range of different nitrogen regimes for field‐grown sunflower (Helianthus annuus L.). An experiment was conducted to investigate different combinations and rates of applied nitrogen on SLN, RUE, and growth of sunflower. A fully irrigated crop was sown on an alluvial‐prairie soil (Fluventic Haplustoll) and treated with five combinations of applied nitrogen. Greater nitrogen increased biomass, grain number, and yield, but did not affect harvest index energy‐corrected for oil (0.4) or canopy extinction coefficient (0.88). Decreases in biomass accumulation under low nitrogen treatments were associated with reductions in leaf area index (LAI) and light interception. When SLN and RUE were examinedto gether, both were less in the anthesis to physiological maturity period, but relatively stable between bud visible and anthesis. However, the effects of canopy SLN on RUE were confounded by high SLN in the top of the canopy and the crop maintaining SLN by reducing LAI. Measurementosf leaf CO2 assimilation and theoretical analyses of RUE supported that RUE was related to SLN. The major effect of nitrogen on early growth of sunflower was mediated by leaf area and the distribution of SLN in the canopy rather than direct effects of canopy SLN on RUE alone. Greater responses of RUE to SLN are more evident later in growth, and may be related to the demand of nitrogen by the grain.
Modeling Carbohydrate Production, Storage, and Export in Leafy and Normal Maize (Zea mays L.)
Authors: Stewart D. W. , Dwyer L. M. , Andrews C. J. , Dugas J. ‐A.
Published: July 2010

The structure of maize (Zea mays L.) canopies influences light interception, photosynthesis, and yield. A recently developed corn phenotype termed Leafy, which has additional leaves above the ear compared with normal phenotypes of the same maturity, is thought to provide a greater source of photosynthates. The objective of this study was to develop a mathematical model to compare hybrid light interception, photosynthesis, carbohydrate storage, and export of carbohydrates from the leaves, based on measured leaf area distribution, leaf photosynthesis, and diurnal changes in leaf sugars and starches. Model simulations were run for two Leafy hybrids and a normal check hybrid, all grown at 6.5 and 3.25 plants m−2. A series of differential equations described how photosynthate was stored as leaf sugar and starch and then exported to stems. Rate coefficients were used to characterize diurnal changes in leaf carbohydrate concentration during early grain filling for different hybrids and planting densities. Model fits to leaf sugar and starch data were good (0.64 ≤ r ≤ 0.89). Model calculations showed that storage of carbohydrates in leaves was relatively small compared with the total amount of leaf photosynthate produced; more than 90% of the photosynthate was exported directly to the stem. Hybrid and planting density comparisons indicated that rate coefficients for the export of photosynthate from leaves increased with total plant dry matter. Leafy hybrids and hybrids grown at the lower plant density had greater plant dry weights, photosynthetic rates, and leaf export rates than the check or hybrids grown at the higher plant density.
Leaf Area Development of Corn as Affected by Windbreak Shelter
Authors: Zhang Hehui , Brandle James R.
Published: July 2010

Windbreaks generally have positive effects on crop yield because of improved growing conditions. To quantify these effects, leaf area and vertical leaf area distribution of corn (Zea mays L.; cv. Wilson 2100) were studied with and without windbreak shelter during 1991 and 1992. Simulation models for leaf area estimation were also evaluated for the two years. Leaf area, length, and width were measured for the whole canopy several times during each growing season. Two types of area prediction models were developed and tested: a simple length‐width model using a correction factor (C) and a statistical model. Although the statistical model gave a slightly better overall estimate of leaf area, the simple model was the preferred choice because of its simplicity and better area predictions when leaves were small. Regardless of windbreak shelter or year, values of C were stable. The average C for this corn hybrid was 0.75, which is consistent with other reported values for corn. Windbreaks did not affect total leaf area nor alter the vertical distribution of leaf area for the two years. With or without shelter, the height of maximal leaf area was at 1/2 of the canopy in 1991 and in the lower 1/3 of the canopy in 1992. This downward shift of maximal leaf area was probably due to lower temperatures and more evenly distributed rainfall in 1992 and may have been positive for plant productivity. The variations of windbreak effect on leaf area development with species and environmental conditions indicate the need of similar future studies on other major crops to formulate an effective strategy for windbreak evaluation.
Monoclonal Antibodies for Detection of Neotyphodium coenophialum
Authors: Hiatt E. E. , Hill N. S. , Bouton J. H. , Mims C. W.
Published: July 2010

A simple endophyte detection system is vital for breeding efforts designed to produce low alkaloid, endophyte‐infected tall rescue (Festuca arundinacea Schreb.) cultivars. The objectives of this research were to generate monoclonal antibodies specific to endophytes for immunochcmical detection purposes. Protein extracts from Neotyphodium coenophialum (Morgan‐Jones and Gains) Glenn, Bacon, and Hanlin comb. nov. isolate EDN11w ere injected into Balb/c mice to elicit an immuner esponse. Hybridomac ell lines were screened for antibody production to the Neotyphodium extract and for cross recognition of protein extracts from N. uncinatum Glen, Bacon, and Hanlin and N. starrii Glen, Bacon, and Hanlin, as well as other fungi in the genera Ciadosporlum, Penicilllum, Fusarium, and Aspergillus. Three hybridomace ll lines produceda ntibodies that reacted to Neotyphodium spp. proteins, but not with proteins isolated from the other fungi. Monoclonal antibody 5C7 was immunochemically tested for specificity to endophyte in leaf sheaths of plant genotype DN11. Fluorescent staining suggested the antibody preferentially bound to the cell wall of the endophyte. Antibodies were tested for affinity to protein extracts from 14 endophyte‐infected and endophyte‐free tall fescue genotypes by an enzyme‐linked immunosorbenta ssay (ELISA) method. Mean absorbance values for the protein extracts from the endophyte‐infected genotypcs differed and ranged from 0.317 to 0.583. Mean absorbance values for the endophyte‐free forms did not differ (P ≥ 0.05). All infected plants had higher absorbance values than non‐infected plants regardless of antibody tested. Monoclonal antibodies can be used in an ELISA to detect Neotyphodium spp. fungal mycelia present in tall fescue.
Effects of Motes on Lint Quality of Interspecific Cotton Hybrids
Authors: Saranga Yeshoshua , Sass Navot , Tal Yechiel , Shimony Carmela , Yucha Rivka
Published: July 2010

Lint of interspecific hybrids (ISHs) of cotton (Gossypium hirsutum L. × G. barbadense L.) tends to contain a high proportion of impurities which reduce the quality of yarn and fabric. Much of these impurities are related to the presence of motes (aborted ovules or seeds) the seed cotton produced by these hybrids. This study was aimed at determining the effect of motes of various sizes and fiber physical properties on the number of neps (tangled fibers) in the lint from ISHs. Lint from 13 ISHs and a control cultivar (G.b. cv. Pima S‐5), grown in the field under either irrigated or dryland conditions, were examined for the number of motes, number of neps, and fiber physical properties. The effects of motes of various sizes and lint properties on nep numbers were examined by means of correlation and multivariate regression analyses. Nep frequency was most closely positively related to the number of medium‐size motes (1‐3 mm in width and 3‐5 mm in length), which was introduced into seven regression equations out of the nine examined cases. Further, nep frequencies were closely negatively related to the percentage of mature fibers, which was introduced into six of the regression equations. R2 values of the resulting equations were between 0.51 and 0.79. Selection for a reduced number of medium motes and a high percentage of mature fibers appears to be a possible approach for improving the lint quality of cotton ISHs.