bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Backcrosses Involving Transgressant Doubled Haploid Lines in Rice under Contrasting Moisture Regimes
Authors: Toorchi Mahmoud , Shashidhar H. E. , Gireesha T. M. , Hittalmani Shailaja
Published: July 2010

Improvement of grain yield in the rainfed lowland rice (Oryza sativa L.) ecosystem is important because that ecosystem covers a considerable area. The objectives of this study were first to find relationship(s) among grain yield and its components, second to assess the influence of root morphological characters on grain yield, and finally to find the relationship of molecular marker heterozygosity with heterosis–performance of yield related characters in rainfed lowland rice. Nine backcrosses involving transgressants for maximum root length in rice from a doubled haploid mapping population of IR64/Azucena along with parents were evaluated simultaneously for grain yield and related characters as well as root traits under contrasting moisture regimes. Grain yield showed maximum reduction under severe moisture stress conditions. Significant negative correlation between drought tolerance index and grain yield was observed in the well‐watered conditions only. Multiple linear regression analysis revealed total dry weight (root + shoot dry weight) as the most significant variable under well‐watered conditions because it could explain as much as 30% of variability in grain yield, followed by root number. Under severe stress conditions, root dry weight explained 20% of variability in grain yield. The relationships between yield and root related characters were determined. General heterozygosity, based on molecular marker data, was found to be correlated with hybrid performance and heterosis of yield related characters. Among the nine backcrosses, P331 × IR64 and P124 × IR64 were selected to map quantitative trait loci for root morphological characters and grain yield.
Photosynthesis and Seed Production under Water‐Deficit Conditions in Transgenic Tobacco Plants That Overexpress an Arabidopsis Ascorbate Peroxidase Gene
Authors: Yan Juqiang , Wang Jing , Tissue David , Holaday A. Scott , Allen Randy , Zhang Hong
Published: July 2010

An underlying mechanism for reductions in crop yield under stress conditions is excessive production of reactive oxygen species (ROS) that can damage lipids, nucleic acids, and proteins, leading to disruption of physiological processes. The aim of this study was to determine whether overexpression of the gene for a peroxisomal antioxidant enzyme, ascorbate peroxidase 3 (APX3), could provide protection of photosynthesis during drought when the potential rises for excessive photorespiratory H2O2 production. Tobacco (Nicotiana tabacum L.) plants were transformed to constitutively overexpress the Arabidopsis thaliana gene for APX3. Following repeated water‐deficit cycles, fruit number and seed mass of transgenic plants were significantly higher than those of control plants. In another experiment, water deficit was developed gradually by reducing, in stages, the extent to which water lost was replenished. Genotypic differences in gas‐exchange parameters were observed at the 25% replenishment stage and at 5 h after severely stressed plants were rewatered. At these times, transgenic plants exhibited greater rates of CO2 assimilation (A), stomatal conductance (gs), and internal CO2 (Ci) to atmospheric CO2 (Ca) concentration than control plants, suggesting that differences in A were controlled by differences in gs Although these data did not support the idea that overexpression of the gene for APX3 enhances protection of the photosynthetic apparatus during water deficit, overexpression of APX3 may affect other cellular metabolisms that result in higher A under moderate water‐deficit conditions and therefore higher seed mass after repeated water‐deficit treatments.
Sources of Variation in the Solvent Retention Capacity Test of Wheat Flour
Authors: Guttieri Mary J. , Souza Edward
Published: July 2010

The solvent retention capacity (SRC) test uses the ability of flour to retain a range of solvents as a means of evaluating economically important aspects of wheat (Triticum aestivum L.) quality: pentosan content, starch damage, gluten strength, and general water retention. Inbred lines from three soft spring wheat populations (‘Vanna’/‘Penawawa’, ‘Kanto 107’/IDO488, and M2/IDO470) were produced in replicated, irrigated trials in 2000 and 2001 to assess variance components for the SRC tests. Milling yield, flour ash, flour protein, and sugar snap cookie diameter for these genotypes were determined. Flour solvent (water, 500 g kg−1 sucrose, 50 g kg−1 sodium carbonate, and 50 g kg−1 lactic acid) retention capacities were measured, and variances estimated for genotype, genotype × environment interaction, and error terms. The variance of genotypes for SRC values in the three populations ranged from 0.67 to 0.97 of the total variance (genotype, genotype × environment, and error) not attributed to main effects of year and replication. Correlations among genotypes were significant and positive for water, sodium carbonate, and sucrose SRC within all three populations (r = 0.70 to 0.92, P < 0.01). In all three populations, these SRC values were negatively correlated with cookie diameter (r = −0.54 to −0.89, P < 0.01). Correlations between lactic acid SRC, a measure of gluten strength, and the other SRC values were complex, as was the correlation between lactic acid SRC and cookie diameter. This suggests that milling and baking quality could be improved through manipulation of flour components using SRC selection.
Genetic Relationship between Kernel Discoloration and Grain Protein Concentration in Barley
Authors: Canci Paulo C. , Nduulu Lexingtons M. , Dill‐Macky Ruth , Muehlbauer Gary J. , Rasmusson Donald C. , Smith Kevin P.
Published: July 2010

Kernel color and grain protein concentration (GPC) are two of the most important attributes of barley (Hordeum vulgare L.) grain intended for use in malting and brewing. Grain with protein levels that are too low or high or that have dark kernel color, which may result from the disease complex of kernel discoloration (KD), is unacceptable for the malting and brewing industries. The purpose of this study was to use molecular markers to map quantitative trait loci (QTLs) for KD and GPC in two recombinant inbred line (RIL) populations. One population was created by means of the high GPC and KD resistant cultivar Chevron. The other population was created from a KD resistant cultivar MNBrite that was derived from Chevron through eight generations of crossing and selection for bright kernels. The traits KD and GPC were evaluated in four and three environments, respectively, using the Chevron population and six environments using the MNBrite population. GPC and KD score were negatively correlated in both populations. A revised genetic map for the Chevron/M69 population, with an additional 45 simple sequence repeat (SSR) markers, was used to identify nine QTLs associated with KD on chromosomes 1(7H), 2(2H), 4(4H), 6(6H), and 7(5H), including two major QTLs on chromosome 6(6H). A single QTL for GPC identified in the Chevron mapping population, accounting for over 55% of the phenotypic variation, was located on chromosome 6(6H) and was coincident with one of the two major QTLs for KD. In this region, the Chevron allele increased GPC and decreased KD score. In the MNBrite mapping population, the same region of chromosome 6(6H) was mapped with SSR markers, and QTL analysis verified that this region was associated with both KD and GPC, indicating that MNBrite inherited this region of chromosome 6(6H) from Chevron. The results of this study suggest that if GPC and KD are controlled by tightly linked genes, then it should be possible to use SSR markers to identify recombinants in this region of chromosome 6(6H) and break the linkage to allow selection for KD resistance without high GPC. Alternatively, if GPC and KD are conditioned by the same gene, then it should be possible to select for KD resistance from Chevron by means of SSR markers and to use phenotypic selection to introgress other genes to reduce GPC to acceptable levels.
Using Line × Tester Interaction for the Formation of Yellow Maize Synthetics Tolerant to Acid Soils
Authors: Narro Luis , Pandey Shivaji , Crossa José , De León Carlos , Salazar Fredy
Published: July 2010

Breeders need more information on selecting testers to identify lines for formation of synthetics and need more user‐friendly methods to study general combining ability (GCA) and specific combining ability (SCA) of genotypes. Forty‐three lines were crossed to two narrow‐based (S3 line and S3 × S3 hybrid) and two broad‐based testers, which were open‐pollinated varieties (OPVs). Topcrosses (line × tester, L × T) were evaluated in eight acid soil environments. The additive main effect and multiplicative interaction (AMMI) and the site regression (SREG) models were used to study the GCA of the testers and lines and the SCA of the L × T interaction. The SREG biplot contains the effect of the lines plus the L × T interaction and displays both GCA and SCA, whereas the AMMI biplot contains the effect of the L × T interaction and displays only the SCA. One synthetic was developed by recombining six lines identified as superior by each tester. The four synthetics were evaluated in 12 acid and nine nonacid soil environments. The synthetic developed with the S3 line as tester yielded the highest and the one developed with an OPV as tester yielded the lowest. The AMMI and SREG models seem to provide an effective tool to visualize and study GCA and SCA of genotypes.
Morphological Comparison of Progeny Derived from 4x‐2x and 4x‐4x Hybridizations of Lotus glaber Mill. and L. corniculatus L
Authors: Beuselinck P. R. , Steiner J. J. , Rim Y. W.
Published: July 2010

Unreduced gametes (2n gametes) from Lotus glaber Mill. (2n = 2x = 12) may aid intercrossing with L. corniculatus L. (2n = 4x = 24) to produce progeny with a greater heterotic advantage than progeny derived from colchicine‐induced {7‐acetamido‐6,7‐dihydro‐1,2,3,10‐tetramethoxybenzo[a]heptalen‐9(5H)‐one} tetraploid (4x) L. glaber The objective of this research was to compare progeny produced from 4x with 2x (4x‐2x) and 4x with 4x (4x‐4x) crosses and determine if 2n gametes had a heterotic advantage over normal gametes derived from colchicine‐induced tetraploids. Vegetative cuttings of the 2n‐gamete‐producing L. glaber genotype 204882‐1 (2x 204882‐1) were treated with colchicine and successfully yielded an autotetraploid (2n = 4x = 24) of 204882‐1 (4x 204882‐1). Three randomly chosen genotypes from the L. corniculatus germplasm MU‐81 were used as maternal parents in crosses to 2x 204882‐1 and 4x 204882‐1. Progeny produced from 4x‐2x crosses were intermediate to or larger than their parents in their leaf and flower morphology. Progeny from 4x‐4x crosses were intermediate to or smaller than their parents in leaf and flower size. Size of leaves and flowers of progeny from 4x‐2x crosses were similar to or larger than 4x‐4x progeny. Morphological comparisons demonstrated that heterotic expression of progeny from 4x‐2x crosses was greater than progeny from 4x‐4x crosses. The results indicate that the generation of interspecific L. corniculatus × L. glaber hybrids via 2n pollen to be effective, but a means of exploiting any heterotic advantage in these cross‐pollinated species needs to be identified.
Identification, Mapping, and Confirmation of a Soybean Gene for Bud Blight Resistance
Authors: Fasoula Vasilia A. , Harris Donna K. , Bailey Matthew A. , Phillips Daniel V. , Boerma H. Roger
Published: July 2010

Bud blight, caused by Tobacco ringspot virus (TRSV; Genus: Nepovirus; Family: Comoviridae), can significantly reduce the seed yield and seed quality of soybean [Glycine max (L.) Merr.]. The identification of resistance genes and the development of resistant cultivars constitute an effective strategy for preventing yield loss. The objectives of this study were to identify and map quantitative trait loci (QTLs) conditioning resistance to bud blight and validate their genomic location with two populations derived from the cross of ‘Young’ (resistant) × PI 416937 (susceptible). One population consisted of 116 F4:7 lines and was used to map restriction fragment length polymorphism (RFLP) markers associated with resistance to bud blight. The lines were grown in one‐row plots in a randomized complete block design with two replications. The plots were naturally infected with TRSV. At maturity, soybean plots were visually scored according to the number of plants that exhibited terminal bud death. A major QTL was identified and mapped on linkage group (LG) F by the RFLP marker K644_1. It accounted for 82% of the variation in bud blight score. To verify the genomic location of the major bud blight QTL, a second population of Young × PI 416937 that consisted of 180 F2:3 lines was evaluated. In this population, simple sequence repeat (SSR) markers on LG F near the putative genomic location of the bud blight QTL were utilized. The major QTL conditioning bud blight resistance was confirmed and found to be closely linked to the Satt510 marker.
Comparison of Two Breeding Strategies by Computer Simulation
Authors: Wang Jiankang , van Ginkel Maarten , Podlich Dean , Ye Guoyou , Trethowan Richard , Pfeiffer Wolfgang , DeLacy Ian H. , Cooper Mark , Rajaram Sanjaya
Published: July 2010

Breeding strategies used by plant breeders are many and varied, making it difficult to compare efficiencies of different breeding strategies through field experimentation. The objective of this paper was to compare, through computer simulation, two widely used breeding strategies, the modified pedigree/bulk selection method (MODPED) and the selected bulk selection method (SELBLK), in CIMMYT's wheat breeding program. The genetic models developed accounted for epistasis, pleiotropy, and genotype × environment (GE) interaction. The simulation experiment comprised the same 1000 crosses, developed from 200 parents, for both breeding strategies. A total of 258 advanced lines remained following 10 generations of selection. The two strategies were each applied 500 times on 12 GE systems. Findings indicated that genetic gain from SELBLK was on average 3.9% higher than that from MODPED, and genetic gain adjusted by target genotypes from SELBLK was on average 3.3% higher than MODPED for a wide range of genetic models. A greater proportion of crosses were retained (25% more) by means of SELBLK compared with MODPED, and from F1 to F8, SELBLK required one third less land than MODPED and produced fewer families (40% of the number for MODPED). For the genetic models considered in our study, computer simulations showed that the SELBLK method resulted in slightly greater genetic gain and significant improvements in cost effectiveness.
Developmental Morphology of Smooth Bromegrass Growth Following Spring Grazing
Authors: Brueland B. A. , Harmoney K. R. , Moore K. J. , George J. R. , Brummer E. C.
Published: July 2010

The timing of initial spring grazing of smooth bromegrass (Bromus inermis Leyss.) pastures affects regrowth potential and subsequent forage yield and quality. This study was conducted to quantify the effects of the timing of the initiation of spring grazing on these factors. A field experiment was conducted at the Rhodes Research and Demonstration Farm in central Iowa from April through July in 1996 and 1997. Treatments were an undefoliated control and four initial dates of defoliation that were applied weekly, beginning when one fully collared leaf per tiller was present. Defoliation was done using two mature cattle (Bos taurus) to quickly (12–24 h) graze the sward to a height of 5 to 10 cm. Regrowth was sampled weekly for 8 wk, staged, and analyzed for forage quality. Early grazing of smooth bromegrass pastures did not delay sward development. Initiation of grazing at the later dates caused short delays in both development and the ability to regrow rapidly, but allowed utilization of a larger quantity of forage for the initial grazing event, with minimally decreased forage quality. Sward development differed between years. Tiller density and mean stage count did not differ among treatments during the 7 wk after defoliation in 1996 but did so in 1997. However, by the end of 8 wk, development was similar for all treatments. On the basis of this study, initiation of grazing when one fully collared leaf per tiller was present, followed by an adequate recovery period before beginning rotational grazing would give producers an early start on pasturing with limited impact on sward yield and health.
Three Microsomal Omega‐3 Fatty‐acid Desaturase Genes Contribute to Soybean Linolenic Acid Levels
Authors: Bilyeu K. D. , Palavalli L. , Sleper D. A. , Beuselinck P. R.
Published: July 2010

Three independent genetic loci have been shown to contribute to soybean [Glycine max (L.) Merrill] seed linolenic acid levels, including the well‐characterized Fan locus. Linolenic acid is the product of omega‐3 fatty‐acid desaturase enzyme activity. The objective of this study was to identify and characterize the family of soybean omega‐3 fatty‐acid desaturase genes and link them to low seed linolenic acid as a tool for the development of molecular markers for low linolenic acid soybean. Using database homology searches and gene cloning, we identified and characterized three soybean microsomal omega‐3 fatty‐acid desaturase genes that contribute to seed linolenic acid levels. Relative expression was characterized by quantitative real‐time RT‐PCR (reverse transcriptase‐polymerase chain reaction). One of the three genes was predominantly expressed in developing seeds. We determined that the low linolenic acid breeding line A5 (fan fan) contains two of the genes, but is missing the third sequence. Therefore, the Fan locus can be definitively assigned to one of the three microsomal omega‐3 fatty‐acid desaturase genes present in the soybean genome. Molecular markers for defects in the three genes will enhance soybean programs breeding for low linolenic acid.
PCR Assays for the Lr37‐Yr17‐Sr38 Cluster of Rust Resistance Genes and Their Use to Develop Isogenic Hard Red Spring Wheat Lines
Authors: Helguera M. , Khan I. A. , Kolmer J. , Lijavetzky D. , Zhong‐qi L. , Dubcovsky J.
Published: July 2010

Rust resistance genes Lr37, Sr38, and Yr17 are located within a segment of Triticum ventricosum (Tausch) Cess. chromosome 2NS translocated to the short arm of bread wheat chromosome 2AS. Characterization of this chromosome segment by 13 restriction fragment length polymorphism (RFLP) markers indicated that the 2NS translocation replaced approximately half of the short arm of chromosome 2A (distal 25–38 centimorgans, cM). The objective of this study was to develop polymerase chain reaction (PCR) assays based on RFLP marker cMWG682 to facilitate the transfer of this cluster of rust resistance genes into commercial wheat (Triticum aestivum L.) cultivars. DNA sequence was obtained from the A‐, B‐, D‐, and N‐alleles of cMWG682 and was used to design N‐allele specific primers. The 2NS fragment amplified by PCR primers cosegregated with the presence of the RFLP‐2NS band in all backcross populations. A cleaved amplified polymorphic sequence (CAPS) was used to develop a marker for the 2A‐allele. This marker can be used to differentiate homozygous and heterozygous plants carrying the 2NS translocation in the final cycle of backcross introgression or in screenings for homozygous plants in segregating populations. Finally, a third PCR assay was developed by means of TaqMan technology as a high‐throughput alternative for selection of the 2NS/2AS translocation in large segregating populations in breeding programs that have access to real time PCR equipment. These molecular markers were used to develop four hard red spring isogenic lines homozygous for the 2NS chromosome segment. One of the isogenic lines, derived from ‘Anza,’ did not show the expected resistance in spite of the presence of all the RFLP markers for the 2NS chromosome segment. Analysis of F1 hybrids suggested that a suppressor of the Lr37 gene is present in Anza. These isogenic lines will provide a valuable tool to test the effects of the large 2NS translocation on quality and agronomic performance.
RAPD Variations in Selected and Unselected Blue Grama Populations
Authors: Phan Anh T. , Fu Yong‐Bi , Smith S. Ray
Published: July 2010

Blue grama (Bouteloua gracilis H.B.K. Lag. ex Steud.) is one of the most widespread native grasses in western North America. Little is known about the genetic diversity of this species and the genetic shift in selected populations. Random amplified polymorphic DNA (RAPD) markers were used to assess the genetic variations of blue grama plants in 11 natural source populations (SPs) in southern Manitoba and two selected populations. Population ‘BMSC’ was a balanced multisite composite of 99 clones selected for higher seed yield from the 11 SPs. Population ‘MSC’ was a mass‐selected composite of 25 clones with higher seed yield from eight SPs. Twelve RAPD primers were used to assay 108 original propagules from the 11 SPs and 96 seedlings from each selected population. A total of 69 polymorphic RAPD bands were detected. No unique RAPD bands were found for any SPs and 97.8% of the total RAPD variation was detected within SPs. Variation in RAPD markers was not associated with geographical distances. Highly significant changes in RAPD band frequency from their SPs were detected in both selected populations, but only MSC displayed the fixation of polymorphic bands. The estimated genetic shifts were small, 0.6% for BMSC and 1.9% for MSC.
COMPARISON OF THERMAL UNITS DERIVED FROM DAILY AND HOURLY TEMPERATURES
Authors: Purcell Larry C.
Published: July 2010

Crop development as a function of thermal time has important applications in crop management and crop modeling. Several reports have indicated that calculation of thermal units on an hourly basis, and averaging these values over 24 h, was superior to calculations of thermal units using the average of maximum (Tmax) and minimum (Tmin) temperatures. In this report, daily and hourly calculations of thermal‐unit accumulation were compared for two sets of cardinal temperatures for representative warm‐season crops. Daily (DTU) and hourly thermal units (HTU) agreed closely except when average temperatures were above 34°C or when close to the base temperature (Tb). Simulations across 43 yr of weather data comparing the time required to cumulate 200°C d were nearly identical for calculations based on DTU and HTU for two sets of cardinal temperatures. For warm‐season crops with similar cardinal temperatures, there is no advantage in hourly calculations of thermal units over daily values.
Inheritance of Seed Color in Flax
Authors: Mittapalli Omprakash , Rowland Gordon
Published: July 2010

Seed color of flax (Linum usitatissimum L.) is used in Canada to identify the two main market types. Traditional, high linolenic acid flax must have brown seed, while solin or zero linolenic acid flax must be yellow‐seeded. The objective of this study was to determine the allelic–gene relationship of the dominant yellow gene, the variegated recessive gene, and various spontaneous and unknown recessive yellow genes in flax. Eleven flax cultivars or lines, four spontaneous recessive yellow seed mutants (YSED2, YSED4, S95407, and S96071), one recessive yellow European line (G‐1186/94), two dominant yellow seed lines (CPI84495 and YSED18), one variegated line (M96006), and three brown lines (‘ED47’, ‘Vimy’, and ‘CDC Bethune’) were crossed in all possible combinations, excluding reciprocals. Test crosses were performed with four USDA‐ARS introductions (‘Minerva’, ‘Bolley Golden’, ‘Crystal’, and ‘Bionda’) possessing the four different seed color genes, to determine which locus controlled the yellow–variegated seed color. Test cross data indicated that YSED2, YSED4, S95407, and S96071 possessed the same recessive allele of the g locus producing yellow seed. The European yellow line, G‐1186/94, had a recessive allele at the d locus producing yellow seed, and a dominant yellow Y1 allele was carried by CPI84495 and YSED18. The variegated seed color was conditioned by a second recessive allele of the b1 locus, designated as b1vg Segregation analysis indicated that all the four loci governing seed color were inherited independently except for a possible weak linkage between g and b1vg The recessive genes (g, d, and b1vg), when homozygous recessive, were epistatic to the other loci carrying dominant alleles.
Evaluation of a QTL for Waterlogging Tolerance in Southern Soybean Germplasm
Authors: Reyna N. , Cornelious B. , Shannon J. G. , Sneller C. H.
Published: July 2010

Water‐saturated soils and flooding (submergence) can greatly reduce soybean [Glycine max (L.) Merr.] yield. Mapping analyses with the simple sequence repeat (SSR) marker Sat_064 have identified a quantiative trait locus (QTL) for tolerance to waterlogging in the cultivar Archer. Our objectives were to evaluate the effect of this QTL on waterlogging tolerance in southern environments and genetic backgrounds, and to assess variability for waterlogging tolerance in Archer derived populations. We used Sat_064 genotype data to create seven sets of NILs from the populations A5403 × Archer and 9641 × Archer. The NILs were grown under waterlogged (water level 70–120 mm above the soil surface for 2 wk starting at flowering) and irrigated control conditions at three environments in 1999 and 2000 and evaluated each for yield and visual waterlogging injury. Waterlogging injury was rated on a 0 (no symptoms) to 9 (>90% severely chlorotic or dead) scale. Checks and select RILs from the same crosses were also tested. Additional RILs from each population were tested for waterlogging injury in 2000. The Sat_064 marker did not account for a significant portion of the variability among the NILs for either waterlogging tolerance based on yield, yield in waterlogged conditions, or waterlogging injury. This may be due to the southern genetic backgrounds and environments in this study as the Sat_064 QTL was originally identified in northern genetic backgrounds and environments. Variation for waterlogging tolerance and waterlogging injury was noted in the RIL populations. The most tolerant RILs suffered a 32% yield reduction from waterlogging and had a waterlogging injury rating of 1.3 while the most susceptible RILs suffered a 77% yield loss and had a waterlogging injury score of 6.8. The populations segregated for waterlogging tolerance independently of the Sat_064 marker. Visual assessment of waterlogging injury was associated with yield‐based assessment of waterlogging tolerance and could be used to select for lines with improved waterlogging tolerance.
Genome Introgression of Festuca mairei into Lolium perenne Detected by SSR and RAPD Markers
Authors: Wang J. P. , Bughrara S. S. , Sleper D. A.
Published: July 2010

The genera of Lolium and Festuca belong to the same tribe Poeae, of subfamily Pooideae, but offer a range of complementary characteristics of agronomic importance. Intergeneric hybridization between the two genera is expected to combine the desirable characteristics of Lolium (good turf quality and good establishment) with Festuca species (drought and heat tolerance and disease resistance) in turfgrass breeding. The use of molecular markers to trace genome introgression in intergeneric hybrids has been reported for many crops, but not for Lolium and Festuca The objective of this study was to use simple sequence repeats (SSR) or microsatellite markers developed from Lolium perenne L. and random amplified polymorphic DNA (RAPD) markers to assess genomic introgression of Festuca mairei St. Yves (Fm) into L. perenne (Lp). Out of the 40 SSR markers tested, nine markers covering seven linkage groups, fully discriminated the Fm and Lp parents and revealed that the Fm genome was transferred into the backcross progenies of Fm and Lp. In 13 backcross derivatives detected by SSR markers, 11 individuals showed that the Fm genome was introduced. Forty‐one RAPD primers were chosen to detect genome introgression of the backcross progeny. A total of 188 parent‐specific markers were obtained. Ninety‐two (49%) are Fm‐specific markers. The 13 backcross progenies showed a range of introgression of Fm‐specific markers (5.4–60.9%). The introgression levels of the backcross progeny revealed by SSR and RAPD markers were significantly correlated (P ≤ 0.0116). The SSRs and RAPD markers were informative and effective in detecting Fm genome introgression into the Lp genome.
How Does Plant Population Density Affect the Forage Yield of Eastern Gamagrass?
Authors: Springer T. L. , Dewald C. L. , Sims P. L. , Gillen R. L.
Published: July 2010

Eastern gamagrass [Tripsacum dactyloides (L.) L.] is a perennial, warm‐season bunchgrass native to the Americas. Although much is known about the effects of fertilization and harvest frequency on the yield of eastern gamagrass, information on the effects of plant density on yield is lacking. Our objectives were to investigate the effects of plant population density on annual dry matter (DM) yield, vegetative shoot density, and basal area of plant crowns of irrigated eastern gamagrass. Cumulative forage DM yield varied significantly with year × density interactions (P < 0.01). Higher plant densities produced greater DM yields with the highest sustained forage yields obtained at a density of 4.8 plants m−2 Variation in number of vegetative shoots per square meter was attributed to year (P < 0.05) and density (P < 0.01). Higher plant densities also had a greater number of vegetative shoots; however, plots with higher initial stand densities reached equilibrium much faster than plots with lower stand densities. Variation in crown area was associated to year × density interactions (P < 0.01). Mature shoots near the edge of the crown probably produce a greater number of tillers until an equilibrium is reached. This is suggested by our data where the number of vegetative shoots per plant increased with decreasing plant density. Most planting recommendations for eastern gamagrass call for seeding into wide rows. These recommendations were developed to enhance seed production stands and facilitate the use of field equipment. Narrower row spacings may facilitate stand establishment while increasing forage production early in the life of the stand.
Improvement of Forage Quality by Downregulation of Maize O‐Methyltransferase
Authors: He Xu , Hall Mary Beth , Gallo‐Meagher Maria , Smith Rex L.
Published: July 2010

Lignin is a complex, aromatic polymer that limits plant cell wall degradation by ruminants and reduces the nutritional value of forages. Genetic engineering, using an antisense strategy, offers the potential to modulate enzymes in the lignin biosynthetic pathway as a way to reduce lignin, thereby improving forage quality and animal performance. We investigated the effectiveness of expressing antisense sorghum O‐methyltransferase gene (omt) to downregulate maize OMT and reduce lignin. Constructs contained a sorghum omt coding region in the antisense orientation driven by the maize ubiquitin‐1 (Ubi) promoter (with the first intron and exon) along with bar, that confers glufosinate herbicide resistance, driven by the CaMV 35S promoter. Twenty‐eight T0 plants regenerated from 17 herbicide‐resistant callus lines from 13 independent bombardments expressed the brown midrib phenotype. O‐methyltransferase activity was significantly lower in T1 transgenics compared with controls, with some plants showing a 60% reduction. Those T1 transgenics with downregulated OMT averaged 20% less lignin in stems and 12% less lignin in leaves compared with controls. On a whole‐plant basis, lignin was reduced by an average of 17% with the greatest reduction being 31%. Digestibility was significantly improved in transgenic plants by 2% in leaves and 7% in stems. Mean whole‐plant digestibility increased from 72 to 76%. This research demonstrates that genetic engineering has the potential to improve forage grass digestibility. This could be important, especially in tropical forage species, which generally have lower quality than temperate species.
Development of SCAR Marker Linked to a Major QTL for High Fiber Strength and Its Usage in Molecular‐Marker Assisted Selection in Upland Cotton
Authors: Guo Wangzhen , Zhang Tianzhen , Shen Xinlian , Yu John Z. , Kohel Russell J.
Published: July 2010

Cotton fiber is a basic raw material in the textile industry. All the changes in spinning technology require unique and often greater cotton fiber quality, especially strength, for processing. On the basis of genetic analysis and molecular mapping, a major quantitative trait locus (QTL) for fiber strength was identified in 7235, an Upland cotton (Gossypium hirsutum L.) germplasm line in our institute, which possesses super quality fiber properties. Eight molecular markers, two simple sequence repeat (SSRs) and six random amplified polymorphic DNA (RAPDs) markers, were linked to the QTL. The objective of this study was to develop rapid and reliable sequence characterized amplified region (SCAR) markers linked to the QTL for marker‐assisted selection (MAS). Two RAPD markers, UBC4311920 and UBC7571365, were converted to SCAR markers after sequencing the two ends of the two polymorphic DNA fragments. Only SCAR4311920 marker detected polymorphism between TM‐1 and 7235, whereas SCAR7571365 showed monomorphism. SCAR4311920 marker was explored to determine its stability in (7235 × TM‐1) F2 with UBC4311920 marker as a control and to screen the major fiber strength QTL of (7235 × Simian 3) BC1F4 population for transferring good fiber quality. The result showed that the specific SCAR4311920 marker could be applied to large‐scale screening for the presence or absence of the major fiber strength QTL in breeding populations.
QTL Associated with Accumulation of Tocopherols in Maize
Authors: Wong Jeffrey C. , Lambert Robert J. , Tadmor Yaakov , Rocheford Torbert R.
Published: July 2010

Tocopherols are a class of fat soluble antioxidant vitamin compounds present in maize (Zea mays L.) that provide health and economic benefits, which potentially could be captured by both producers and consumers to add value to the grain. α‐Tocopherol, δ‐tocopherol, and γ‐tocopherol are the most abundant isomers present in maize. α‐Tocopherol has the highest biological activity for the tocopherols; however, γ‐tocopherol is generally present in much higher concentrations than the other tocopherols in maize kernels. The objectives of this research were to determine levels of tocopherol isomers in maize kernels from two related maize mapping populations and to map quantitative trait loci (QTL) controlling accumulation of tocopherol isomers. Two sets of materials were assayed in this research, a (W64a × A632) F2:4 mapping population and testcross progeny with AE335. Molecular markers were evaluated on the F2:4 mapping population and a linkage map created. Each population was analyzed by high performance liquid chromatography (HPLC) for α‐, δ‐, and γ‐tocopherol. Composite interval mapping (CIM) identified QTL for individual tocopherols and total tocopherols, notably on chromosomes 1 and 5. The ratio of α‐/γ‐tocopherol was analyzed to identify QTL influencing the conversion of γ‐tocopherol to α‐tocopherol. The QTL associated with the largest percentage of phenotypic variation in the study was detected on chromosome 5 for ratio (α/γ) tocopherol. The QTL identified in this study have potential for use in a marker assisted selection program to facilitate increasing levels and ratios of tocopherols in maize grain.
Relationships among Agronomic Traits and Grain Composition in Oat Genotypes Grown in Different Environments
Authors: Peterson David M. , Wesenberg Darrell M. , Burrup Dave E. , Erickson Charles A.
Published: July 2010

Genotype and environment are major determinants of plant phenotype. Economically important quantitative traits include agronomic characteristics and grain composition. This study examined relationships among agronomic traits and grain composition as influenced by genotype and environment. Thirty‐three oat (Avena sativa L.) genotypes were grown in three trials in Idaho (Aberdeen irrigated, Tetonia irrigated, and Tetonia dryland) in three consecutive years (1999–2001). Yield, heading date, kernel physical characteristics, and concentrations of groat protein, β‐glucan, oil, tocols, and avenanthramides were measured. Analysis of the combined data for all environments showed significant genotypic differences for all traits except avenanthramide 2f Most of the variance was associated with genotype for all traits except yield, α‐tocopherol, and the avenanthramides. The genotype × trial interaction was significant only for avenanthramides concentration, whereas the genotype × year interaction was significant for most traits. Principal component analysis biplots illustrate that for protein and oil there was a clear difference between 2000 and the other years. Some genotypes were stable across environments; others responded differently in different environments. Correlation analysis showed several close associations among traits: avenanthramides were correlated with β‐glucan, and oil was negatively correlated with groat physical characteristics and with avenanthramide 2f The results show that knowledge of the relationships among traits and environments can assist breeders in optimizing both agronomic traits and grain composition simultaneously.
Analyses of Acid‐PAGE Gliadin Pattern of Indian Wheats (Triticum aestivum L.) Representing Different Environments and Periods
Authors: Ram Sewa , Jain Nisha , Dawar Vinamrata , Singh R. P. , Shoran Jag
Published: July 2010

Acid‐PAGE analysis of gliadins from 159 Indian wheat (Triticum aestivum L.) cultivars developed during the last five decades was accomplished to identify gliadin band patterns as well as the extent of genetic diversity. Extensive polymorphism [genetic diversity index (H) = 0.875] in gliadin pattern was observed in the cultivars studied. A total of 147 band patterns were identified, of which 45 different mobility bands were in the region of ω gliadins, 42 in the region of γ gliadins, 30 in the region of β, and 29 in the region of α gliadins. Zone‐wise genetic diversity index was highest in North Western Plains Zone (H = 0.904) followed by North Eastern Plains Zone (H = 0.878), Central Zone (H = 0.864), Peninsular Zone (H = 0.844), and Northern Hills Zone (H = 0.836). The α gliadin pattern 1, 8, 11, and 20; β gliadin pattern 21; γ gliadin pattern 15 and 20; and ω gliadin pattern 4, 18, and 38 were specific to cultivars of Northern Zones and α gliadin 20 and β gliadin 22 to Central and Peninsular Zones. Period‐wise highest mean genetic diversity (H = 0.915) was observed in cultivars identified during 1971 through 1980 and lowest (H = 0.868) in cultivars developed after 1990. The reduction in genetic diversity during 1990 onward might be because of enhanced use of 1BL.1RS translocation. This information can be used in breeding programs to maintain genetic diversity within Indian wheat germplasm.
Root Temperature and Aeration Effects on the Protein Profile of Canola Leaves
Authors: Franklin Jennifer A. , Kav Nat N. V. , Yajima William , Reid David M.
Published: July 2010

Canola (Brassica napus L.) is planted in early spring and must survive both low soil temperatures and periods of wet weather. Shoot effects result from both low root temperature and low aeration, but little is known about the interaction between these two environmental factors, particularly with respect to changes in gene products. In this study, canola plants (‘46A65’) were treated in solution culture. Shoot temperatures were maintained at day/night temperatures of 24/18°C, while roots were maintained at an ambient temperature of 24/18°C, or cooled to 10°C. Roots were either aerated, or not aerated to create hypoxic treatments. Plants with roots in cold and hypoxic solution accumulated starch in the root, and had greater reductions in fresh weight and leaf area than those in either cold or hypoxic treatments alone. Twenty‐one changes in protein expression were also found in the cold hypoxic treatment, 17 of which were not found in either cold or hypoxic treatments alone. Gene products up‐regulated in leaves included cytochrome oxidase Subunit I (COX1) in response to hypoxia, elongation factor eEF1 γ chain in plants with cooled roots, and chaperonin 10 when roots were cooled without aeration. Results demonstrate the interaction between multiple stresses on a molecular level, and suggest that flooding under cool soil temperatures will be more detrimental to canola than that which occurs at warmer temperatures.
Ruminant Selection among Switchgrass Hays Cut at Either Sundown or Sunup
Authors: Fisher D. S. , Burns J. C. , Mayland H. F.
Published: July 2010

As a result of photosynthesis, plants typically have greater concentrations of nonstructural carbohydrates at the end of the photoperiod. The preference of ruminants for hays harvested within the same 24‐h period can be greater for plants harvested late in the photoperiod with increased soluble carbohydrate. To test for variation in ruminant preference for afternoon versus morning harvested hays in a C4 grass harvested in the humid east, established fields of ‘Kanlow’ and ‘Alamo’ switchgrass (Panicum virgatum L.) were used to produce hays in 1998, 1999, and 2000 near Raleigh, NC. Harvests were paired so that each cutting in the evening (PM) was followed by a cutting the next morning (AM). We harvested in this manner three times in 1998 to produce six Kanlow hays; twice with Kanlow and once with Alamo at two levels of nitrogen fertility in 1999 to produce eight hays; and three times in 2000 to produce six Alamo hays. The hays were field‐dried, baled, and passed through a hydraulic bale processor. Hays from each year were tested with cattle (Bos taurus L.), goats (Capra hircus L.), and sheep (Ovis aries L.). During an adaptation phase, hays were offered individually. In the experimental phase, all possible pairs of hays were presented. Data were analyzed by multidimensional scaling and by traditional analyses. Multidimensional scaling indicated that selection was based on multiple criteria. The suite of improvements associated with PM‐harvested hays in fiber content, digestibility, and nonstructural carbohydrate observed for alfalfa and fescue hays in the western USA was difficult to reproduce with switchgrass hay in the southeastern USA. This difficulty is likely related to the less favorable environment for haymaking as well as the physiology, anatomy, and morphology of this C4 grass.
Variability for Drought Resistance Related Traits in the Mini Core Collection of Peanut
Authors: Upadhyaya Hari D.
Published: July 2010

Peanut (Arachis hypogaea L.) productivity is low in the semiarid tropics mainly because of drought caused by low and erratic rainfall. Identification of genotypes that have a greater ability to use limited available water is important to enhance productivity of the crop. Water‐use efficiency (WUE) is correlated with specific leaf area (SLA) and soil plant analysis development (SPAD) chlorophyll meter reading (SCMR) and both have been suggested as surrogate traits for selecting for WUE in peanut. The present study was conducted to: (i) identify genotypes with high WUE using SLA or SCMR and (ii) evaluate relationship between and relative stability of SCMR and SLA in these genotypes. The 184 mini core entries, consisting of 37 fastigiata, 58 vulgaris, 85 hypogaea, two peruviana, and one each of aequitoriana and hirsuta and four control cultivars, M 13, Gangapuri, ICGS 44 and ICGS 76 were evaluated for SLA, SCMR, and 19 vegetative, reproductive, and quality traits in the 2001 rainy and 2001–2002 postrainy seasons at ICRISAT Center. Data were analyzed by REML analysis. Seasons were significant for all traits. Variances due to genotypes were significant for SCMR and SLA at 60 and 80 d after sowing (DAS) and other traits except pods per plant, yield per plant, haulm yield per plot, and protein and oil contents. The genotype × season interactions were significant for both SCMR and SLA at 80 DAS only and for all other quantitative traits except number of primary branches, and pod width. The SCMR values at different stages and seasons were more positively correlated with each other than the correlation of SLA values together. SCMR and SLA were negatively correlated. SCMR values were more strongly correlated with pod yield and other economic traits such as 100‐seed weight at both 60 and 80 DAS than SLA. On the basis of higher heritability and lower proportion of genotype × season interaction variance to phenotypic variance, SCMR appeared to be more stable than SLA. On the basis of SLA and SCMR values compared with the control cultivar, five vulgaris and 13 hypogaea accessions were selected. These accessions and control cultivars were grouped by scores of the first 15 principal components (PCs). The clustering by UPGMA method indicated that the selected accessions were diverse from the control cultivars and can be used in the peanut improvement programs to develop cultivars with a broad genetic base.
Linkage Mapping of QTL for Seed Yield, Yield Components, and Developmental Traits in Pea
Authors: Timmerman-Vaughan Gail M. , Mills Annamaria , Whitfield Clare , Frew Tonya , Butler Ruth , Murray Sarah , Lakeman Michael , McCallum John , Russell Adrian , Wilson Derek
Published: July 2010

Seed yield in pea (Pisum sativum L.) is a physiologically complex trait that is strongly influenced by both genotype and environment. Seed yield can be described in terms of its components, which include plant number per unit area, seed weight, and seed number. These yield components show interdependence and plasticity in response to environment; therefore, selection based on a single component is unlikely to succeed in increasing yield in breeding programs. To improve our understanding of the genetic basis of seed yield determination in pea and to identify genetic loci involved, quantitative trait loci (QTL) for yield per se, yield components (seed weight, seed number, and harvest index [HI]) and developmental traits (node of first flower [NFF], number of flowering nodes [NFN], total node number [TNN]) were mapped. The QTL mapping was conducted using F2–derived families of a cross between Primo, a marrowfat cultivar, and OSU442‐15, a blue pea breeding line. Linkage maps containing 108 loci on 11 linkage groups (LGs) were constructed for 227 families derived from this cross. Traits were measured in three replicated field trials conducted in New Zealand during the summers of 1997–1998, 1998–1999, and 2002–2003. The trials were managed to ensure maximum expression of yield potential. The QTL affecting yield‐related traits were associated with 19 genomic regions on LGs I, II, III, IV, VI, and VII. The QTL for different yield‐related traits were colocalized, suggesting some basis for understanding the reproductive plasticity that is observed in pea at the genetic level.