bluuebunny/crossref_metadata_2025 huggingface dataset:
A System for Genetic Change in Apomictic Eastern Gamagrass
Authors: Kindiger B. , Dewald C.
Published: July 2010

The ability of a species to undergo genetic change is a necessary component of its adaptive evolution, which can lead to the widening or narrowing of its genetic base. In diplosporous apomictic species, change through sexual or meiotic means is limited or omitted entirely. The objective of this study was to investigate the reproductive attributes of tetraploid apomictic eastern gamagrass, Tripsacum dactyloides var. dactyloides (L.) L. One‐hundred progeny generated from an apomictic tetraploid eastern gamagrass accession were evaluated at a phenotypic, cytogenetic, and molecular level by means of random amplified polymorphic DNA (RAPD) procedures to detect their genetic relatedness to the maternal parent and to each other. Differences in phenotype and RAPD‐PCR (polymerase chain reaction) banding profiles, followed by chromosome counts, revealed the generation of new tetraploid variants. The identification of genetic variation in tetraploid progeny would presumably indicate the production of hybrid individuals generated from the fertilization of a reduced egg cell by a sperm nuclei. However, this study indicates the complete omission of hybrid individuals generated from expected normal sexual behaviors and suggests the observed variation is generated by an incomplete or dysfunctional sexual process. The incidence of this behavior was 4%. The detection and generation of genetically variable but cytologically stable tetraploids, from an apomictic eastern gamagrass, suggests the presence of an additional mechanism whereby this species routinely may undergo genetic change without the introduction of new germplasm.
Heterosis of Cuphea lanceolata Single‐Cross Hybrids
Authors: Shajahan Ali M. , Knapp Steven J.
Published: July 2010

Cuphea lanceolata forma silenoides Ait. (Lythraceae) is a self‐compatible, insect‐pollinated, allogamous annual oilseed crop. Our objectives were to develop a set of inbred lines from an open‐pollinated population (LN‐43), estimate inbreeding effects by using differences between an S0 population (LN‐43) and S1 and S2 lines, estimate heterosis effects by using differences between inbreds and single‐cross hybrids, and rank inbred lines as sources of alleles for enhancing single‐cross hybrids of C. lanceolata. Ten groups of S1 and S2 lines were developed by single‐seed descent from the C. lanceolata population LN‐43. All possible single‐cross hybrids were developed among five S5 lines from LN‐43. Plant height, biomass, seed yield, seed oil content, and 500‐seed weight decreased as inbreeding increased. Significant inbreeding depression was observed for every trait. Biomass and seed yield were more severely affected by inbreeding than the other traits. Significant heterosis was observed for every hybrid and trait. Heterosis was greatest for seed yield and least for 500‐seed weight. Mean heterosis was 71.7% for plant height, 79.9% for biomass, 159.0% for seed yield, 36.7% for seed oil content, and 22.3% for 500‐seed weight. A significant positive correlation of 0.72 was observed between line per se and hybrid seed yield, and the highest yielding inbred lines (LN‐97 and LN‐98) produced the highest yielding hybrid (LN‐97 × LN‐98). The seed yield of LN‐97 × LN‐98 might be increased by using LN‐99 as a donor. Although seed yields can be maximized by using single‐cross hybrids, a mechanism for producing hybrid seed has not yet been developed. The heterosis of this species can nevertheless be exploited by using synthetic cultivars.
Field Pea Transpiration and Leaf Growth in Response to Soil Water Deficits
Authors: Lecoeur J. , Sinclair T. R.
Published: July 2010

No quantitative functions exist to describe transpiration rates and leaf expansion rates of drought‐stressed field pea (Pisum sativum L.) plants relative to well‐watered plants. Such functions are especially important in analyses of the effects of water deficit periods on crop yield under a range of field conditions. Pot and field experiments were conducted to develop and evaluate drought‐stress functions for transpiration and leaf area expansion. These functions were obtained in a dehydration cycle where plant response was monitored as the soil dried progressively. The level of water deficit was characterized as the fraction of transpirable soil water (FTSW). Transpiration and leaf area expansion did not change appreciably until FTSW reached = 0.4, and then decreased linearly through FTSW equal to 0. Drought response functions obtained for transpiration and leaf area expansion in a pot study also well represented the results obtained in independent pot and field studies.
Yield and Hard Wheat Quality Attributes in Hard × Soft Red Winter Progeny
Authors: Carver Brett F.
Published: July 2010

Wide genetic distance and proximal adaptation zones of soft (SRW) and hard red winter (HRW) wheat (Triticum aestivum L.) incite intermarket class hybridization and selection for unique gene combinations. Divergent standards for end‐use quality often repress that incentive. This study was conducted to (i) measure mean performance and genetic variability of agronomic and quality traits for HRW × SRW progeny in the context of HRW wheat improvement and (ii) determine the relative merit of single‐cross vs. backcross population development to attain HRW agronomic and quality standards. ‘Century’ and ‘Mustang’ (HRW) were crossed factorially with ‘Coker 983’ and ‘McNair 1003’ (SRW) as single crosses (SC) and as backcrosses (BC) to the HRW parent. A SC of Century and Mustang provided a HRW control population. Field experiments were conducted in three Oklahoma environments with 45 random F4:6 lines per population, the four parents, and ‘Cimarron’ (HRW check). Yield performance was generally higher in the HRW × SRW populations compared with Century × Mustang, but consistent decreases were noted for kernel hardness and flour yield. Backcrossing decreased the yield advantage relative to SC populations, but provided substantial improvement in kernel hardness and moderate improvement in flour yield. Sedimentation volume did not improve in the BC population compared with the SC population. Genetic variances were generally homogeneous between SC and BC populations, except for reduced variance in BC populations for certain flour quality traits. These results support efforts to introgress SRW germplasm into HRW wheat improvement programs. The high proportion of interclass progeny similar to the HRW check for preliminary quality indicators would allow intensive selection pressure for actual breadmaking properties in later generations.
A New Technique for Continous Injection Into Stems of Field‐Grown Corn Plants
Authors: Zhou X. M. , Smith D. L.
Published: July 2010

Chronic addition of nutrients, metabolites, growth regulators, or toxins to intact plants is a useful way to study numerous aspects of plant physiology. However, continuous delivery of large amounts of test solutions into plant tissues has been difficult. Stem infusion methods have proven less destructive and more effective than other methods, such as leaf and root feeding, for supplying nutrients and other materials to developing plants. Infusion into solid‐stemmed plants has been limited by short delivery periods and the damage at the delivery site. A field experiment was conducted to evaluate a new technique for supplying sucrose solutions or water to corn (Zea mays L.) stems. This injection technique delivered pressurized solutions or water through syringe needles sealed to the stem with latex. The pressure was applied to the syringe plunger with ceramic construction bricks. Solutions containing sucrose at 0, 150, and 300 g L‐t were injected over a 32‐d period. The average solution uptake rate was 5.1 mL d−1 plant−1. Distilled water was more easily delivered than sucrose solutions. No difference in uptake rates were observed between 150 and 300 g L−1 sucrose solutions. This injection system is a simple, efficient, and inexpensive method that can be used easily in the field or greenhouse.
Southwestern Corn Borer Growth on Laboratory Diets Containing Lyophilized Corn Husks
Authors: Williams W. Paul , Buckley Paul M.
Published: July 2010

Southwestern corn borer (Diatraea grandiosella Dyar) is a serious pest of corn (Zea mays L.) in the southern USA. Lack of reliable techniques for evaluating resistance after anthesis is a major problem. The objective was to develop a laboratory bioassay for evaluating southwestern corn borer larval growth on diets comprised primarily of lyophilized husks of corn inbred lines. Diets were prepared by adding 15 g of lyophilized busk tissue collected within 3 d after silk emergence to a mixture of 250 mL distilled water, 2400 mg agar, 12.5 mg gentamicin sulfate, 132 mg sorbic acid, and 528 mg ascorbic acid. Larvae were weighed after feeding on the test diet for 21 d. Larvae fed diets containing husks of different inbred lines varied significantly. Because southwestern corn borer larvae that infest corn plants at or after anthesis feed initially on husks, this bioassay is a potentially useful technique for identifying resistant germplasm.
Diallel Analysis of the Stay‐Green Trait and Its Components in Sorghum
Authors: van Oosterom E. J. , Jayachandran R. , Bidinger F. R.
Published: July 2010

Stay‐green in sorghum [Sorghum bicolor (L.) Moench] is an important component of post‐flowering drought tolerance. This research was conducted to describe (i) stay‐green as post‐flowering green leaf area duration (GLAD) and its components [green leaf area (GLA) flowering, timing for onset of senescence, and senescence rate] and (ii) the expression of heterosis for stay‐green in terms of heterosis for its components. The study was conducted during the 1992 to 1993 and 1993 to 1994 post‐rainy season at ICRISAT headquarters near Hyderabad, India. It involved a nine‐parent complete diallel, in two experiments differing in soil‐water availability after flowering. Weekly estimations of % GLA were made on 36 leaves per plot. Relative (%days) and absolute (m2 days) GLAD and their components were derived from a fitted logistic function. The variances in both relative and absolute GLAD were each fully (R2 > 0.96) accounted for by their components. In spite of significant genotype × environment interactions for the component traits, the expression of heterosis for non‐senescence as related to the stay‐green trait was stable across experiments. The inheritance of the onset of senescence was additive, but a slow senescence rate was dominant over a fast rate. Consequently, a large relative GLAD (slow senescence) was partially dominant over a small relative GLAD. Because of the dominance of a large leaf area at flowering, the partial dominance in relative GLAD translated into overdominance for a large absolute GLAD. These results offer an opportunity for improving drought tolerance of sorghum in environments with post‐flowering drought stress.
Fatty Acid Genotypes of Five Virginia‐Type Peanut Cultivars
Authors: Isleib T. G. , Young C. T. , Knauft D. A.
Published: July 2010

Reduction of linoleic acid in the fatty acid profile of Virginia‐type peanut (Arachis hypogaea L.) cultivars is desirable because it would improve the stability and shelf‐life of in‐shell and other peanut products. A low‐linoleate/high‐oleate trait controlled by two recessive genes, ol1 and ol2, has been identified in Univ. of Florida breeding line F435. Most runner‐type cultivars and breeding lines genotyped to date were found to differ from F435 by only one ol allele. Genotypes differing from F435 at two ol loci were Virginia types. The number of genes controlling inheritance of the trait has major implications with respect to the numbers of backcross and F2 test progeny required in an efficient backcross breeding program. To determine the number of genes differentiating F435 from large‐seeded Virginia‐type cultivars, F435 was crossed as a male with five common Virginia‐type cultivars. F4:5 progenies were assayed for fatty acid content by gas chromatography. Progenies were classified as having high or low oleate levels and chi square analysis was applied to the data. Segregation ratios of populations derived from crosses with ‘NC 7’, ‘NC 9’, ‘NC 10C’, and ‘VA‐C 92R’ were consistent with a monogenic model and inconsistent with the digenic model. These cultivars have genotype Ol1Ol1ol2ol2 or ol1ol1Ol2Ol2. Progeny of ‘NC‐V 11’ / F435 followed a ratio consistent with the digenic model and inconsistent with the monogenic model, indicating that NC‐V 11 has genotype Ol1Ol1Ol2Ol2. Oleate levels were elevated by 220 to 280 g kg−1, linoleate levels decreased by 190 to 270 g kg−1, and palmitate levels decreased by 30 to 40 g kg−1 in high‐oleate subpopulations. Other fatty acids exhibited changes that were statistically significant but probably too small in magnitude to significantly alter processing quality or stability of oil.
Genetic Control of Photoperiod Response in Early‐Maturing, Near‐Isogenic Soybean Lines
Authors: Cober E. R. , Tanner J. W. , Voldeng H. D.
Published: July 2010

Photoperiod response is one factor responsible for the regional adaptation of soybean [Glycine max (L.) Merr.] cultivars. Few photoperiod response studies have been carried out with lines containing alleles for late maturity at only one or a few loci. An understanding of the photoperiod response of early‐maturing soybean lines would facilitate cultivar development in short‐season areas. The objectives of this study were to investigate the photoperiod response of early‐maturing ‘Harosoy’ near‐isogenic lines with indeterminate and determinate growth habit and to examine the genetic model for sensitivity to natural day length extended to 20 h with incandescent lamps [incandescent long day length (ILD)]. Harosoy near‐isogenic lines were grown in the field under natural day length and ILD. The same lines were also grown in growth cabinets under 12‐ and 20‐h photoperiods with cool white fluorescent plus incandescent lamps. Under natural day length, E3 and E4 alleles each delayed flowering 5 d and maturity 15 d while the E1 allele delayed both flowering and maturity ≈ 16 d compared with the alternative early‐maturing alleles. The E3 and E4 alleles each delayed flowering 30 d under ILD compared with natural day length. The E1 allele did not delay flowering or maturity under ILD compared with natural day length. Under 12‐h days in a growth cabinet, there were no differences among near‐isogenic lines for flowering or maturity, but the loci responded differently in the 20‐h photoperiods. The E3 allele exhibited the largest photoperiod response, delaying flowering 24 d and maturity 84 d, compared with 12‐h photoperiods. These photoperiod‐sensitivity loci produced differential photoperiod responses that may he useful for short‐season cultivar development.
Isozyme, Protein, and RAPD Markers within a Half‐Sib Family of Buffelgrass Segregating for Apospory
Authors: Gustine David L. , Sherwood Robert T. , Gounaris Yannis , Huff David
Published: July 2010

Isolation of genes controlling apomixis would be useful to plant breeders for fixing hybrid vigor. A single gene codes for aposporous apomixis in buffelgrass [Pennisetum ciliare (L.) Link]. This study was undertaken to assess the feasibility of using isozyme, protein, and random amplified polymorphic DNA (RAPD) markers to detect apospory‐linked sequences within a segregating half‐sib population. Sexual plant B‐2s, five sexual and three aposporous progeny of sexual B‐2s, and cultivar Higgins were studied. Floret and leaf proteins were separated by starch gel electrophoresis, and enzymes in the gel were stained to detect isozyme polymorphisms. Of 22 isozyme systems tested, 12 showed polymorphisms but none cosegregated with apomixis. Two‐dimensional polyacrylamide gel electrophoresis was used to separate steady state proteins of pistils at meiotic and post‐meiotic stages. This technique revealed ≈12% polymorphism within 308 spots, but none of the spots cosegregated with reproductive mode. Genomic DNA was screened for RAPD markers with 111 10‐mer random primers and polymerase chain reaction. Of 569 markers identified, 87% were polymorphic. One marker cosegregated with sexual lines, but none cosegregated with aposporous lines. Analysis of molecular variance examination of the B‐2s parent and the eight half‐sib progeny (Higgins excluded) showed that on the basis of 404 RAPD markers, the aposporous and sexual groups were not significantly different. No RAPD markers were tightly linked with apospory. Additional screening of new primers will allow identification of markers for the gene in full‐sib families.
Fertilizer 15Nitrogen Recovery by Corn, Wheat, and Cotton Grown with and without Pre‐Plant Tillage on Norfolk Loamy Sand
Authors: Karlen D. L. , Hunt P. G. , Matheny T. A.
Published: July 2010

Cropping systems must efficiently use N inputs to be sustainable environmentally and economically. This research was conducted to determine the fate of 15N fertilizer that was applied to corn (Zea mays L.), wheat (Triticum aestivum L.), or cotton (Gossypium hirsutum L.) grown in a 2‐yr, three‐crop rotation on Norfolk (Typic Kandiudult) loamy sand. A total of 48, 2.3‐ by 2.3‐m microplots were established, half into plots that received surface tillage (disked) and half into non‐disked plots. Corn and wheat received a split application of urea [CO(NH2)2] plus ammonium nitrate (NH4NO3) solution (UAN) had a 5 atom percent (ATM%) 15N isotopic label. Cotton was fertilized with NH4NO3 containing a 5 ATM% label. The amounts of 15N removed in the harvested portion of treated and subsequent crops, recycled in crop residues, or remaining in the upper 90 cm of the soil profile were determined. Corn, wheat, and seed cotton yields ranged from 1485 to 7410, 1850 to 2270, and 120 to 2510 kg ha−1, respectively, with significant differences caused primarily by seasonal rainfall or temperature extremes. No‐till significantly increased cotton yield, presumably because of water conservation. Crop removal accounted for 20 to 34% of the fertilizer 15N, while another 20% was accounted for by soil profile analysis to a depth of 90 cm. Approximately 50% of the 15N was apparently lost through denitrification, volatilization, or leaching below the root zone. Most of this loss appeared to occur during the cropping season in which the 15N was applied. This suggests that for optimum fertilizer efficiency and environmental sustainability, crop production practices on Coastal Plain soils must account for all N sources that plants can draw upon, and should accommodate several fertilizer N management options including split applications, injection beneath the soil surface, and/or using less mobile forms.
Production of Red Clover Transgenic for Neomycin Phosphotransferase II Using Agrobacterium
Authors: Quesenberry K. H. , Wofford D. S. , Smith R. L. , Krottje P. A. , Tcacenco F.
Published: July 2010

Genetic variability for resistance to several of the more important diseases of red clover (Trifolium pratense L.) appears to be limited. Incorporation of resistant genes from other species via genetic transformation offers potential. This research was conducted to evaluate methodology for production of transgenic red clover plants via Agrobacterium tumefaciens mediated transformation. The effects of red clover genotypes and Agrobacterium strains on transformation success were evaluated in two experiments. Plants determined to be transgenic for the β‐glucuronidase (GUS) and neomycin phosphotransferase II (NPTII) genes were crossed with normal plants and the inheritance of GUS was determined. Putative transgenic callus and plants were produced on B5 medium containing 50 and 300 mg L−1 kanamycin and carbenicillin, respectively. Both transformation experiments showed significant red clover genotype, Agrobacterium strain, and genotype × strain interactions (P< 0.05) for percentage of petiole pieces regenerating plants. Southern blots of DNA isolated from various GUS+ plants showed evidence of single and multiple copies of the NPTII gene. Petiole pieces from various putative transgenic plants produced near normal amounts of callus when plated on B5 callus induction medium containing 50 mg L−1 kanamycin. Progeny from crossing transgenic with normal plants segregated 1:1 as expected. The protocoloutlined in this paper should be useful for incorporation of genes of agronomic importance into red clover.
Genetic Mapping of Qunatitative Trait Loci in Maize in Stress and Nonstress Environments: II. Plant Height and Flowering
Authors: Veldboom Lance R. , Lee Michael
Published: July 2010

The utility of restriction fragment length polymorphisms (RFLPs) in mapping quantitative trait loci (QTL) has been established in elite maize (Zea mays L.) populations, hut the ability to consistently detect QTL in diverse environments has not been assessed. QTL mapping studies conducted in diverse environments could be a means of locating genes which respond to stress conditions and could provide further understanding of some types of genotype × environment interaction. Our objectives were to investigate the ability to detect QTL for flowering and plant stature traits in two diverse environments and to assess the genetic relationship of QTL for correlated traits. A single‐cross of elite inbreds Mo17 and H99 was used to produce a population of 150 F2:3 lines. Traits were measured on replicated progeny grown in two climatically diverse years at the same location, in which one year was an average environment, and the other year was a stress environment. QTL determinations were made in each environment and the mean of the two environments by using a linkage map of 111 loci. About 50% of all QTL were detected in both environments. The location and parental contribution of these QTL were consistent, hut their effects varied in size. More QTL were identified in the stress environment for anthesis and silk emergence, but the other traits had equivalent numbers of QTL detected in each environment. All QTL identified in the nonstress environment and all QTL identified in the stress environment were also detected in the mean environment. Correlations between traits were generally reflected in the similarity of locations and parental contributions of QTL for these traits. The exception was anthesis and anthesis‐to‐silking interval, which had QTL in common but very poor correlation. The locus of a probe for an1, a plant height mutant, was most closely associated with the QTL having the largest effect on plant height. This finding contributes to the supposition that quantitatively and qualitatively inherited traits share a common set of loci with alleles of varying magnitude of effects.
Identification of Quantitative Trait Loci Associated with Pre‐Flowering Drought Tolerance in Sorghum
Authors: Tuinstra M. R. , Grote E. M. , Goldsbrough P. B. , Ejeta G.
Published: July 2010

Drought tolerance is an important agronomic trait but the genetic and physiological mechanisms that condition its expression are poorly understood. Molecular genetics and quantitative trait loci analysis provide a new and powerful approach to understand better the inheritance and expression of this trait. The purpose of this study was to use molecular markers to identify genetic loci associated with the expression of pre‐flowering drought tolerance in sorghum [Sorghum bicolor (L.) Moench]. Two genotypes with contrasting drought reactions, TX7078 (pre‐flowering tolerant, post‐flowering susceptible) and B35 (pre‐tiowering susceptible, post‐tlowering tolerant), were selected as parents for a sample of recombinant inbred (RI) lines. Ninety‐eight RI lines were evaluated in two different years under conditions of pre‐tlowering drought and full irrigation. This information was used to quantify the drought tolerance of each line. The population was also genotyped with 150 RAPD and 20 RFLP markers that mapped to 17 linkage groups. By means of these markers, six regions of the genome were found to be specifically associated with pre‐flowering drought tolerance. Eight additional regions were more generally associated with yield or yield components under fully irrigated conditions. Several loci were associated with the expression of drought tolerance under both mild and severe drought stress conditions.
QTL Mapping in Tropical Maize: I. Genomic Regions Affecting Leaf Feeding Resistance to Sugarcane Borer and Other Traits
Authors: Bohn M. , Khairallah M. M. , González‐de‐León D. , Hoisington D. A. , Utz H. F. , Deutsch J. A. , Jewell D. C. , Mihm J. A. , Melchinger A. E.
Published: July 2010

Sugarcane borer (SCB), Diatraea saccharalis Fabricius, is a serious pest in tropical maize production areas in the Americas. Little is known about the genetic resistance of maize genotypes to this pest. In this study, we mapped and characterized quantitative trait loci (QTL) affecting resistance to the leaf feeding generation of SCB (1SCB), grain yield under both protection (GYP) and infestation (GYI) with SCB larvae, and plant height (PITT). A total of 171 F2 genotypes derived from cross CML131 (susceptible) × CML67 (resistant) 93 RFLP marker loci were used in QTL analyses. F3 lines were evaluated for the above traits and grain yield reduction (GYR) in field experiments with two replications at two or three tropical environments. Resistance was assessed by rating leaf feeding damage after artificial infestation with SCB larvae. The method of composite interval mapping with selected markers as cofactors was used for detection and characterization of QTL. Resistance to 1SCB was significantly affected by 10 putative QTL on Chromosomes 1, 2, 5, 7, 8, 9, and 10. These showed predominantly additive gene action and explained 65.0% of the phenotypic variance and 93.5% of the genetic variance in a simultaneous fit. Six QTL for GYP, five QTL for GYI with primarily dominant genetic effects, and four QTL for PHT with primarily additive genetic effects were identified, explaining in total about one third of the phenotypic variance for the respective trait. No more than one putative QTL was found to be common between different characters. QTL × environment interaction was found to be significant for 1SCB ratings only. Based on these data, prospects for improving 1SCB resistance by marker‐assisted breeding are promising.
Movement of Certain Herbicides Following Application to Simulated Golf Course Greens and Fairways
Authors: Smith A. E. , Bridges D. C.
Published: July 2010

The objectives of this research were to: (i) determine the movement of pesticides through simulated golf course greens and (ii) determine the potential movement of pesticides from simulated fairways. Lysimeters were developed in the greenhouse and outside containing ‘Penncross’ bentgrass (Agrostis stolonifera L.) or ‘Tifdwarf’ bermudagrass [Cynodon dactylon (L.) Pets. × C. transvaalensis Burtt‐Davy] for collection of leachate from the bases. Simulated ‘Tifway’ bermudagrass fairways were developed with a 5% slope. Only small quantities of 2,4‐D [(2,4‐dichlorophenoxy)acetic acid], dicamba (3,6‐dichloro‐2‐methoxybenzoic acid), and mecoprop [(±)‐2‐(4‐chloro‐2‐methylphenoxy)‐ propanoic acid] were found in the leachate from the greenhouse and outside lysimeters. The concentrations of these herbicides did not exceed 6 μg L−1 and the total quantity to exit the lysimeters was less than 0.9% of the applied herbicide. Over an 8‐d period following treatment, 48% of the simulated rainfall and 9, 14, and 13% of the applied 2,4‐D, dicamba, and mecoprop, respectively, left the simulated fairways. Approximately 75% of the herbicides were transported from the plots during the first rainfall event. The highest concentration of the analytes in the collected runoff water occurred during the first event. These concentrations were 811, 279, and 820 μg L−l 2,4‐D, dicamba, and mecoprop, respectively.
Volatile and Dislodgeable Residues Following Triadimefon and MCPP Application to Turfgrass and Implications for Human Exposure
Authors: Murphy K. C. , Cooper R. J. , Clark J. M.
Published: July 2010

Volatilization can be a major route of pesticide loss following application to turfgrass areas. Consequently, a significant portion of applied pesticide may be available for human exposure via volatile and dislodgeable residues. In this study, volatile and dislodgeable residues were determined following application of triadimefon [1‐(4‐chlorophenoxy)‐3,3‐dimethyl‐l‐(1H‐1,2,4‐triazol‐l‐yl) butanone], and MCPP [( +/−)‐2‐(4‐chloro‐2‐methylphenoxy) propionic acid], to established plot of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.). For each application, a 10‐m radius plot was sprayed and the Theoretical Profile Shape (TPS) method of Wilson was used to estimate volatile flux. Dislodgeable residues were concurrently determined by wiping treated turfgrass with a water dampened piece of cheesecloth. Less than 8% of the total applied triadimefon was measured as volatile residues with nearly all volatilization loss occurring within 5 to 7 d of application. Diurnal patterns of triadimefon volatilization were evident. Mid‐day (1100–1500 h) triadimefon volatile flux on Days 2 (4.6 g ha−2 h−1 ) and 3 (2.4 g ha−2 h−1) was 2 and 1.4 times, respectively, greater than the average of morning and late afternoon volatile flux on these respective days. Less than 1% of the total applied MCPP was measured as volatile residue. Volatile MCPP residues decreased over time to nondetectable levels by Day 5. Both triadimefon and MCPP dislodgeable residues were greatest on Day 1 following application and dissipated over time. By Day 5, triadimefon dislodgeable residues decreased to 0.04% of the initial residue level immediately following application and MCPP dislodgeable residues were nondetectable. Inhalation and dermal exposures to humans were estimated from measured air concentrations and dislodgeable residues, respectively. Hazard quotients (HQs) were calculated for both volatile and dislodgeable residues of each pesticide. Exposures (i.e., doses) divided by reference doses (Rfds) resulted in hazard quotients (HQs). Triadimefon and MCPP volatile and dislodgeable residues resulted in HQs below 1.0 throughout the entire 15‐d experimental period indicating that exposures were below any level expected to cause adverse health effects.
Temperature Dependent Reaction and Selection Response of Two Red Clover Populations to Fusarium Wilt
Authors: Venuto B. C. , Smith R. R. , Grau C. R.
Published: July 2010

Fusarium wilt (caused by Fusarium oxysporum Schlechtend.) has been associated with stand reduction and decreased persistence in red clover (Trifolium pratense L.). Previous research has also indicated that reaction of red clover to isolates of F. oxysporum is temperature dependent. The objectives of this study were to determine if temperature altered the interaction phenotype of two red clover populations inoculated with a single‐conidium isolate of F. oxysporum and to determine if selection at divergent temperatures resulted in a different response for the two populations. Two populations of red clover, C11 and ‘Arlington’, were inoculated in 1992 with a single‐conidium isolate of F. oxysporum and grown in controlled environment chambers (16 and 28°C) at Madison, WI. Resistant phenotypes were selected from each population at each temperature and recombined to form advanced populations for subsequent cycles of evaluation and selection. Three cycles of selection (1992–1994) demonstrated that response to the pathogen was consistently and significantly greater at 28°C for both populations. However, the two red clover populations responded differently to the temperature of the selection environment. Significant population × selection temperature interactions were found for Cycle 1 and Cycle 2 plants. Given the genetic homogeneity of the pathogen, the difference in population response to selection temperature is probably due to the existence of distinct mechanisms of resistance in the host populations. These results have important implications for the development of durable red clover resistance to F. oxysporum.
Grain Fissuring and Milling Yields of Rice Cultivars as Influenced by Environmental Conditions
Authors: Jodari Farman , Linscombe Steve D.
Published: July 2010

Milling quality of rice (Oryza sativa L.) is a primary factor determining its economic value in the U.S. market. It is largely influenced by genotype and environmental conditions prior to harvest. To determine the effect of environment on milling quality of rice genotypes, seven cultivars were evaluated for grain fissuring and milling yield at decreasing grain moisture during 1991 to 1993. Environmental factors, including air temperature, relative humidity, and rainfall, were monitored during grain maturity and drying period. Harvesting was carried out at 2‐ to 4‐d intervals as grain moisture decreased from 270 to 130 g kg−1. High daily minimum relative humidity of 58% and mild temperatures during 1992 caused no significant fissuring until average harvest moisture decreased to 169 g kg−1. Warmer and drier weather during 1993 test period, with 43% daily minimum relative humidity~ caused fissuring to be initiated earlier at a higher grain moisture of 184 g kg−1. With decreasing harvest moistures, head rice yield among all cultivars continued to increase until grain moisture was low enough for fissuring to occur. The optimum harvest moisture with respect to maximum head rice yield among long‐grain cultivars, except for ‘Lemont’, ranged between 179 and 151 g kg−1 during 1991–1993. Within this range, the optimum harvest moisture was highly dependent upon cultivars and environmental conditions. Cultivars with susceptibility to fissuring require higher harvest moistures for maximum milling performance. Optimum harvest moisture among years in grams per kilogram ranged between 200 to 176 for Lemont and 238 to 179 for medium‐grain ‘Bengal’. Despite the strong influence of weather conditions on rice milling yield, certain cultivars, such as ‘Cypress’ and ‘L‐202’, have shown significant resistance to severe environmental fluctuations. Slow drying and fissuring resistance characteristics of Cypress grains provide flexibility in harvesting, transporting, and processing and preserve milling quality.
Improved Resistance to Maize Dwarf Mosaic Virus by Selection under Greenhouse Conditions
Authors: Scott Gene E. , Louie Raymond
Published: July 2010

Maize dwarf mosaic, caused by maize dwarf mosaic virus (MDMV) is the most widespread virus disease of maize (Zea mays L.) in the USA. The objectives of this study were to determine the effectiveness of selecting for resistance to MDMV under greenhouse conditions and to determine if the resistant selections had a gene, presumably Mdm1, for resistance to MDMV that was linked to the endosperm color locus, Y1, on Chromosome 6. One resistant selection was developed from each of six different races of corn crossed with a susceptible hybrid, and two additional resistant selections were obtained out of a synthetic developed in Mississippi. All selections were resistant in field trials in Mississippi. All except one had a higher level of resistance than the field resistant checks in greenhouse tests in Ohio. Three selections had infection levels similar to the highly resistant check inbred, Pa405. Except one, all resistant selections had a gene for resistance linked to the endosperm color locus on Chromosome 6. Apparently, the Mdm1 gene is common in many resistant lines, but the data on one line, Mp92:448, suggest resistance is possible without this gene.
Identification of Field Corn Populations to Improve Sweet Corn for Atlantic European Conditions
Authors: Cartea M. E. , Malvar R. A. , Revilla P. , Ordas A.
Published: July 2010

Sweet corn (Zea mays L.) has been intensively selected for quality and appearance, whereas less effort has gone into improving yield. Acceptance of sweet corn in Europe has increased in the last 10 yr. However, in regions with cool and humid springs and short growing seasons, sweet corn planting is still limited. Identification of donor parents useful for improving sweet corn hybrids would be greatly beneficial for sweet corn breeding programs. The objectives of this study were to identify field corn populations to increase yield in four sweet corn hybrids and to compare different methods for identifying populations with the greatest number of favorable alleles for yield and its components. Ten maize populations were crossed to five sweet corn inbreds. The 50 crosses along with five inbred parents, four sweet corn hybrids, and ten populations were evaluated in two locations in northwestern Spain in 1992 and 1993. Six estimators of relative number of favorable alleles [lp̄1μ′, predicted three‐way cross (PTC), minimum upper bound (UBND), net improvement (NI), probabilities of net gain of favorable alleles given complete dominance, and probabilities of net gain of favorable alleles given partial dominance or complementary epistasis] and general combining ability were calculated. The U.S. synthetic AS‐3(HT)C3 and the northwestern Spanish populations Tuy and Oroso could improve yield and other yield components in sweet corn hybrids. However, European flint corn populations, such as Tuy and Oroso, should have less detrimental effect on kernel quality than U.S. dent populations. Moreover, European flint corn should be better adapted to cool and wet springs and short growing seasons. The lp̄1μ′, PTC, UBND, and NI statistics identified the same populations as the best donors.
Tall Off‐Types in Semidwarf Spring Wheat with Height‐Reducing Genes Rht1 and Rht2
Authors: Storlie E. W. , Xie H. , Talbert L. E.
Published: July 2010

An objective of wheat (Triticum aestivum L.) breeding and seed purification programs is to develop uniform cultivars. However, lack of uniformity may occur due to outcrossing, mechanical mixtures, or aneuploidy. We were interested in the prevalence of aneuploidy resulting in tall off‐types in semidwarf wheat cultivars. Rht1 and Rht2 are the most common height‐reducing genes deployed, and reside on chromosomes 4B and 4D, respectively. In this study, tall off‐types were selected from 11 cultivars representing Rht1 and Rht2 genotypes. The chromosomal constitution of the tall off‐types were determined based on phenotypic and cytogenetic analysis of offspring. Six cultivars with Rht1 genotypes produced an average frequency of 0.15% monosomic 4B plants that averaged from 16 to 22% taller than the height of euploid plants. Five cultivars with Rht2 genotypes produced an average frequency of 0.06% monosomic 4D plants that averaged 12 to 18% taller than the height of euploid plants. Our results indicate that tall off‐types resulting from monosomic 4B and 4D conditions occur in several semidwarf cultivars. However, the frequency and phenotypic effect are greater in semidwarf cultivars with Rht1. Thus, use of Rht2 to cause semidwarf habit may help minimize the problem of tall off‐types.
Effects of Phase Transition on the Development of Lateral Buds in Maize
Authors: Baba Tadashi , Yamazaki Koou
Published: July 2010

Different lateral bud structures are generated along the main shoot axis in maize (Zea mays L.). This study was conducted to show how the structural diversity of the lateral buds is generated. The growth and development of lateral buds of three hybrids were investigated under field conditions at Tokyo, Japan, on a silt loam (Andosols). Six plants per hybrid were harvested as each leaf emerged and the morphological features and the length of each lateral bud were determined. We observed in mature plants that the lateral buds consisted of two discrete populations acropetally along the main stem (i) lower lateral buds that remained in a vegetative state, and (ii) upper lateral buds, including grain‐bearing shoots, that terminated in reproductive organs. Lower lateral buds elongated sequentially up the stem and grew for a specific time interval. The phase transition of the apical meristem to tassel initiation evoked a change in the bud growth pattern. At tassel initiation, the upper lateral buds were still in an incipient state without establishing a complete bud structure. During the reproductive phase that followed, elongation of the upper lateral buds occurred simultaneously. These results suggest that lateral bud growth during the vegetative phase was regulated independently from the reproductive phase during plant development. Lateral buds that are at a certain development state could be responsive to the change in physiological signals during the transition between vegetative and reproductive phase.
Leaf Rust Resistance Gene Lr9 and Winter Wheat Yield Reduction: II. Leaf Gas Exchange and Root Activity
Authors: Ortelli Silvano , Winzeler Michael , Winzeler Hans , Nösberger Josef
Published: July 2010

The introduction of resistance genes from wild relatives into wheat (Triticum aestivum L.) may have detrimental effects on yield. In earlier experiments, we observed a 12% yield reduction in leaf rust (Puccinia recondita Rob. ex Desm. f. sp. Tritici) resistant near isogenic lines (NIL) carrying the resistance gene Lr9 compared with the susceptible recurrent parent Arina. The aim of this study was to find physiological mechanisms for this yield reduction. Two NIL and Arina were investigated in field experiments. In a first experiment, CO2 exchange rate (CER), transpiration, stomatal conductance (gs), and leaf intercellular CO2 concentration (Ci) of the flag leaf were determined after ear emergence. In a second experiment, root activity was estimated from the beginning of stem elongation to early dough stage by the application of Rb and Sr at two soil depths. The NIL and Arina had a similar CER in the morning, but in the afternoon, CER was 7 to 20% lower for the NIL compared with Arina. Differences between the NIL and Arina were larger under dry soil conditions. The CER was closely correlated with gs and Ci indicating that CO2 uptake was restricted by gs. Roots of the NIL took up 15 to 20% less Sr at the 25‐ to 40‐cm soil depth and 12% less Rb at 10‐cm soil depth compared with Arina. The reduced Sr and Rb uptake indicated less root activity for the NIL. It is concluded that lower root activity in the resistant NIL led to water stress and reduced CO2 assimilation. Such stress periods may reduce grain number and grain size of the rust resistant NIL.
Cotton Genotype Response to Early‐Season Cold Temperatures
Authors: Bauer Philip J. , Bradow Judith M.
Published: July 2010

Identifying cotton (Gossypium hirsutum L.) genotypes that are less sensitive to cool temperatures may improve productivity in areas where late‐spring cold fronts are common. Our objectives were to compare commercially available genotypes for relative cold tolerance and to determine whether seedling growth response to cool temperature in a controlled environment was a valid predictor of field performance. Four genotypes, ‘DPL 20’ (early maturity), ‘DPL 50’ (mid), ‘DPL 5690’ (late), and ‘DPL Acala 90’ (late), were studied. Cotyledon area, root and shoot length, and root and shoot fresh weight were measured after 4‐d‐old seedlings were exposed to temperatures of 15, 20, 25, and 30°C for 6 d. The four genotypes were also evaluated in the field in 1991 and 1992 by planting in mid‐April, early‐May, and mid‐May near Florence, SC. Root length was the only seedling trait for which the temperature response was genotype dependent. Root length of DPL 5690 and DPL Acala 90 was the same at all assay temperatures (mean = 4.3 cm). For DPL 20, root length was 9.3 cm at 15 and 20°C, 11.8 cm at 25°C, and 14.3 cm at 30°C. DPL 50 root length was 8.7 cm at 30°C and averaged 6.4 cm at the other three temperature treatments. In the field, when DPL 20 emerged faster than the two late‐maturity genotypes at planting dates that were followed by cold temperatures, it had lower lint yield. The results suggest that measuring the amount of seedling root length inhibition (rather than relative growth differences) caused by suboptimal temperatures may be useful for determining cold sensitivity in cotton.
Allelopathic Effects on Germination and Seedling Growth of Clovers by Endophyte‐Free and ‐Infected Tall Fescue
Authors: Springer T. L.
Published: July 2010

Reports of allelopathy by tall fescue (Festucarundinacea Schreb.) on Trifolium species are inconsistent. Many tall fescue plants are infected with a fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams), which may account for some of the inconsistencies. My objective was to investigate the allelopathic effect of extracts of endophyte‐free (TF − E) and ‐infected (TF + E) tall fescue seeds the seed germination and seedling growth (shoot, root, and root‐hair length and root‐hair density) of five Trifolium species (ball clover, T. nigrescens Viv.; crimson clover, T. incarnatum L.; red clover, T. pratense L.; subterranean clover, T. subterraneum L.; and white clover, T. repens L.). Extracts were prepared by passing 50 g of seed through a pulverizing mill, soaking the milled seed in 500 mL of deionized water, filtering, and sterilizing the solution. Differences among allelopathic effects for seed germination were attributed to legume species. Although the presence of fungal endophyte had no effect on seed germination, germination of ball, crimson, and red clover seed was significantly reduced in extracts of tall fescue seed. Differences among allelopathic effects for shoot and root lengths were attributed to legume species. Seedling shoot length was significantly increased and root length was significantly decreased for clover seedlings grown in tall fescue extracts. Differences among allelopathic effects for root‐hair length and density were attributed to species and substrate (TF − E vs. TF + E) differences. There was a 34% reduction in root‐hair length and a 45% reduction in root‐hair density for clover seedlings grown in seed extracts compared with seedlings grown in water. Seed germination and seedling shoot and root lengths inadequately expressed the subtle allelopathic effects of the fungal endophyte. Micromorphological characters, such as root hairs, may be more sensitive in detecting allelopathic effects.
Two Additional Loci underlying Durable Field Resistance to Soybean Sudden Death Syndrome (SDS)
Authors: Chang S. J. C. , Doubler T. W. , Kilo V. , Suttner R. , Klein J. , Schmidt M. E. , Gibson P. T. , Lightfoot D. A.
Published: July 2010

Severe losses of soybean [Glycine max (L.) Merr.] grain yield occur as a result of the disease sudden death syndrome (SDS), caused by Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burk.) Snyd. & Hans., type A. Selection for resistance to SDS is currently the most efficient means of yield protection. This study was undertaken within adapted soybean germplasm to identify and characterize loci underlying useful field resistance to SDS. One hundred eleven polymorphic DNA markers were compared with SDS disease response among 100 recombinant inbred lines derived from a cross between a durably SDS resistant cultivar, ‘Forrest’, and a SDS susceptible cultivar, ‘Essex’. SDS disease incidence (DI) and disease severity (DS) were determined in replicated, F. solani infested field‐test sites during 4 yr encompassing five locations. Four separate chromosomal segments were strongly associated with mean SDS DI across 5 locations (P < 0.001). In a previous report using the same genetic materials tested in the same environments two of these quantitative trait loci (QTL) had been identified. With the further analysis with 40 additional markers, two more QTL were detected. The two new QTL were stably associated with SDS resistance within each of five F. solani infested locations (P < 0.007). These two loci were identified by RAPD markers OI03450 and OG13490 and by OE04450 and OE021000. The alleles that conferred resistance were both derived from Forrest. Jointly, the four QTL accounted for about 65% of total phenotypic variability in mean DI and 50% in mean DS. DNA markers can be used to define alleles conferring resistance to SDS. Selection for the SDS resistance QTL may allow efficient selection of resistant genotypes with good yield potential in F. solani infested fields.