bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Gain in Yield Attributes of Winter Wheat in the Great Plains
Authors: Donmez E. , Sears R. G. , Shroyer J. P. , Paulsen G. M.
Published: July 2010

Knowledge of changes associated with advances in crop productivity is essential for understanding yield‐limiting factors and developing strategies for future improvement. Our objective was to identify plant traits associated with gains in grain yield of winter wheat (Triticum aestivum L.) in the Great Plains. Twelve landmark cultivars and one experimental line were compared with ‘Turkey’ (introduced 1873) at Hutchinson (Clark‐Ost complex soil) and Manhattan (Reading silt loam soil), KS, during 1996–1997 and 1998–1999. Agronomic traits, leaf rust infection (caused by Puccinia recondita Rob. ex Desm. f. sp. tritici), and grain yield and its components were measured. Grain yields ranged from 2718 kg ha−1 for Turkey to 4987 kg ha−1 for the experimental line, with mean genetic gains of 0.16% per year for early genotypes and 0.63% per year for recent genotypes. Kernel number per unit of soil area had the highest phenotypic correlation with grain yield and contributed most to its genetic gain. Gains in spike numbers per unit of soil area and above‐ground biomass also contributed significantly to higher yields of some genotypes. Significant genetic changes over time and correlations with grain yield were observed for early heading, decreased height, and reduced lodging and leaf rust but not for kernel weight. Our results suggested that yield components that form during vegetative phases (spike numbers per unit of soil area and kernels per spike) when conditions for growth are generally favorable are more amenable to genetic improvement than kernel weight, which forms during maturation when moisture and temperature are often unfavorable.
Efforts to Initiate Construction of a Disease Resistance Package on a Designer Chromosome in Tobacco
Authors: Lewis Ramsey S. , Wernsman Earl A.
Published: July 2010

Gene cloning and transformation can be used to circumvent linkage drag effects that can plague conventional interspecific gene transfers. These techniques can also be used to create desirable genetic linkages. Use of Nicotiana glutinosa L. N‐gene mediated TMV (tobacco mosaic virus) resistance in flue‐cured tobacco, N tabacum L., has been limited due to linkage drag effects. Transformation was used to introduce the cloned N‐gene into NC152, a chromosome addition line possessing a chromosome pair from N africana. This chromosome has been proposed to be used as a “designer chromosome” into which numerous transgenes could be inserted to form a desirable linkage package. The system could be used to shuttle a large number of transgenes from genotype to genotype. One hundred thirty‐six primary transformants possessing the N transgene were produced and hybridized with TMV‐susceptible ‘Petite Havana.’ These may serve as valuable TMV‐resistant breeding materials. For each independent transformant, BC1F1 families which segregated for TMV resistance and the addition chromosome were generated. Data from cosegregation, transmission, and molecular analyses were used to conclude that one transformant possessed an insertion of the N‐gene in the addition chromosome. By inserting N in the chromosome, we initiated construction of a disease resistance package by linking the TMV resistance gene with a potyvirus resistance gene(s) native to the chromosome. Occasional loss of the transgene, however, may be evidence of previously undetected interchromosomal recombination, and may have implications for use of this system in cultivar development.
Genotypic Rankings for Aluminum Tolerance of Soybean Roots Grown in Hydroponics and Sand Culture
Authors: Villagarcia M. R. , Carter Thomas E. , Rufty T. W. , Niewoehner A. S. , Jennette M. W. , Arrellano C.
Published: July 2010

Screening methodology remains a practical barrier in the breeding of Al‐tolerant soybean [Glycine max (L.) Merr.]. Our objectives were to (i) develop a repeatable sand‐media culture method for Al tolerance screening of plants, (ii) compare Al response of genotypes in sand culture to a standard hydroponics‐based seedling culture, and (iii) establish a practical guide for the use of hydroponics and sand‐culture screening methods in the selection of Al‐tolerant soybean. We developed a sand‐media culture method and imposed 0 and 450 μM Al3+ activity treatments upon 10 diverse soybean genotypes. The experiment employed a randomized complete block design with nine replications. Root weight and relative root surface area (RRSA) were determined at 18 d after transplanting (DAT). In hydroponics, the genotypes were compared for taproot elongation after 3 d of exposure to 0, 2, and 5 μM Al3+ activity treatments in a split plot design with six replications. Aluminum stress was imposed successfully (approximately 57% of the growth in control) in hydroponics and sand culture, but discrepancies between methods were apparent. The hydroponics‐based seedling screen produced an inflated range of genotypic response and altered Al tolerance rankings in comparison with sand culture. ‘Perry’, which was tolerant to Al in sand culture, was remarkably sensitive to Al in hydroponics. Despite the discrepancies, seedling‐based screening successfully identified three (PI 417021, PI 416937, and Biloxi) of the four genotypes that were most tolerant to Al in sand culture. Results suggested that seedling screens can play a practical role in breeding. However, their application to a specific breeding population should be validated with older plants and solid media. The RRSA appeared to be a promising measure of A1 tolerance for soybean roots.
Flower Abortion Caused by Preanthesis Water Deficit Is Not Attributed to Impairment of Pollen in Soybean
Authors: Kokubun M. , Shimada S. , Takahashi M.
Published: July 2010

A large proportion of flowers in the soybean plant [Glycine max (L.) Merr.] abort during development. Water stress imposed during the development of flowers is a major factor increasing the rate of abortion, and long‐term or frequent water deficits during this period might decrease yield. The physiological mechanism underlying this phenomenon remains unclear. The objectives of this study were (i) to discover whether a water deficit imposed on a soybean genotype IX93‐100 prior to anthesis could cause the abortion of the proximal flowers, which are destined to produce seed‐bearing pods at a high rate under optimal conditions, and (ii) to determine whether the abortion was due to the impairment of the pistil (ovule) or stamen (pollen) function. Water stress caused by restriction of watering for 3 d during the preanthesis stage significantly increased the abortion of the proximal flowers. The pistils of well‐watered plants, pollinated with either stressed or nonstressed pollen, produced pods at a considerable rate, whereas only a small percentage of water‐stressed pistils developed into pods, even when crossed with nonstressed pollen. These results suggest that flower abortion caused by a preanthesis water deficit is not attributed to an impairment of pollen, but was probably due to impairment of ovule function.
Maize Pollen Longevity and Distance Isolation Requirements for Effective Pollen Control
Authors: Luna V. S. , Figueroa M. J. , Baltazar M. B. , Gomez L. R. , Townsend R. , Schoper J. B.
Published: July 2010

Pollen is an important vector of gene flow in maize (Zea mays L.). Experiments were conducted to investigate the duration of pollen viability and the effectiveness of isolation distance for controlling gene flow. Pollen longevity was tested by collecting pollen at dehiscence and exposing it in a thin layer in the open air and sunshine for prescribed time periods before assessing pollen viability by measuring seed set after pollination and scoring visual appearance. Isolation distance efficacy was evaluated by growing 12.8‐m2 plot of maize at various distances from a 4000‐m2 pollen source. The pollinator contained either a genetic leaf or seed marker that allowed pollen flow to be measured. Pollen maintained viability for 1 to 2 h after dehiscence depending on atmospheric water potential. The theoretical, maximum distance viable pollen could move was 32 km, assuming pollen was transported linearly at the maximum average afternoon windspeeds for our location, viability was maintained for 2 h, and pollen settling rate was ignored. Cross pollinations occurred at a maximum distance of 200 m from the source planting, and only a limited number of cross pollinations occurred at the shortest distance (100 m). No cross pollinations occurred at 300 m from the source planting. The results are consistent with conclusions that maize pollen is desiccation intolerant and has a high settling rate. The results indicate isolation distance can be a useful tool for controlling gene flow via pollination in research scale plantings.
Genetic Diversity in Seven Perennial Ryegrass (Lolium perenne L.) Cultivars Based on SSR Markers
Authors: Kubik Christine , Sawkins Mark , Meyer William A. , Gaut Brandon S.
Published: July 2010

An essential prerequisite to cultivar identification is to determine whether cultivars are differentiated genetically. We investigated genetic diversity among and within seven perennial ryegrass (Lolium perenne L.) cultivars (Loretta, Linn, Manhattan II, Affinity, Jet, Pennfine, and Palmer III) using simple sequence repeat (SSR) markers, with the goal of determining whether cultivars could be differentiated on the basis of genetic data. In each cultivar we genotyped 30 individuals with 22 SSR markers, 18 of which had not been reported previously. Our results indicated that each of the seven cultivars contained high but similar levels of genetic diversity. Within cultivar heterozygosity ranged from 0.589 to 0.643. The cultivars could be distinguished by a number of statistical criteria, including: (i) a small but significant proportion (14.6%) of among‐cultivar genetic variation, based on analysis of molecular variance (AMOVA); (ii) significant between cultivar FST values that ranged from 0.065 to 0.197; (iii) separation of individuals in principal component analysis (PCA); and (iv) correct identification of individuals by the genotype assignment test, which is related to discriminant analysis. The genotype assignment test worked particularly well; it correctly assigned all 210 individuals to their cultivar of origin. Sampling analysis indicated that the genotype assignment requires data from at least 15 SSRs to be >99% accurate, suggesting future studies of genetic diversity in perennial ryegrass cultivars should use at least 15 SSR markers. Overall, the SSRs reported in this paper were highly effective for differentiating among cultivars.
Substitutions and Deletions of Genes Related to Grain Hardness in Wheat and Their Effect on Grain Texture
Authors: Tranquilli G. , Heaton J. , Chicaiza O. , Dubcovsky J.
Published: July 2010

The Hardness (Ha) locus on chromosome 5D is the main determinant of grain texture in hexaploid wheat (Triticum aestivum L.). Puroindoline (Pina‐D1, Pinb‐D1) and Grain Softness Protein (Gsp‐D1) genes are tightly linked at this locus. Additional copies of the Gsp‐1 gene are present on chromosomes 5A and 5B. Mutations in the Pina‐D1 and Pinb‐D1 genes have been individually associated with grain hardness, but it is not known if mutations at both loci may further increase hardness or if additional copies may reduce it. In addition, there is no clear evidence of the effect of the Gsp‐1 genes on grain texture. To answer these questions, we compared the effect of different dosages of puroindoline and Gsp‐1 genes on grain texture. Isogenic substitution and deletion lines for homoeologous group 5 in ‘Chinese Spring’ (CS) were evaluated in two replicated field trials with 13 blocks each. Deletions or allelic variants of Gsp‐A1 and Gsp‐B1 did not produce significant effects on grain texture, suggesting that these genes do not have a critical role in grain hardness. Simultaneous deletions of Pina‐D1 and Pinb‐D1 in deletion line 5DS‐2 and substitution line CS (Red Egyptian 5D) resulted in significantly higher hardness index values than all other lines including CS (Timstein 5D) carrying a single Pina‐D1 deletion (P = 0.02). The incorporation of additional copies of Pina‐Am1 and Pinb‐Am1 from T monococcum L. in recombinant substitution line 5A/5Am in CS resulted in significantly softer grains than those from the CS control (P < 0.01).
Reactions of Smooth Bromegrass Clones with Divergent Lignin or Etherified Ferulic Acid Concentration to Three Fungal Pathogens
Authors: Delgado N. J. , Casler M. D. , Grau C. R. , Jung H. G.
Published: July 2010

Increased digestibility of smooth bromegrass is associated with a reduction in lignin concentration or etherified ferulic acid (EthFA) concentration, either of which may reduce host resistance to fungal diseases. The objective of this study was to determine the relationship of lignin and EthFA concentration with disease reaction in smooth bromegrass. Host clones, divergently selected for lignin and EthFA concentration, were challenged by three pathogenic fungi, one biotroph (Puccinia coronata Corda) and two necrotrophs [Pyrenophora bromi (Died.) Drechs., anamorph = Drechslera bromi (Died.) Shoem., and Bipolaris sorokiniana (Sacc.) Shoem]. Significant positive and negative associations were found between lignin or EthFA and host reaction to P. bromi or B. sorokiniana The frequencies of these associations suggested that they arose by chance associations between alleles, rather than tight linkages or pleiotropic (causal) effects. Host reaction to P. coronata was consistently and negatively associated with lignin, less so with EthFA. These associations, together with results from other species, suggest that lignin, and perhaps EthFA, may be important components of rust resistance mechanisms in the Poaceae. If these mechanisms are real, they will cause considerable difficulty for breeders attempting to simultaneously improve both rust resistance and forage nutritional value.
Genetic Characterization of CIMMYT Inbred Maize Lines and Open Pollinated Populations Using Large Scale Fingerprinting Methods
Authors: Warburton Marilyn L. , Xianchun Xia , Crossa Jose , Franco Jorge , Melchinger Albrecht E. , Frisch Matthias , Bohn Martin , Hoisington David
Published: July 2010

The International Maize and Wheat Improvement Center (CIMMYT) currently holds about 17 000 samples of maize (Zea mays L.) and teosinte (Z. mays, several subspecies), a wild relative of maize. Seven CIMMYT populations and 57 inbreds were characterized by simple sequence repeat (SSR) markers. SSRs chosen from almost every bin in the maize genetic map were tested for repeatability, ease of automation in allele calling, and discrimination (information content). Eighty‐five SSRs were found to be repeatable and easily automated, and were run on all material in the study. Fifty‐three of these SSRs were found to be the most discriminatory and will be used in future routine fingerprinting studies. The seven breeding populations clustered as would be predicted on the basis of pedigree and heterotic grouping. Genetic diversity within each population was significantly higher than diversity between populations, indicating that the populations are heterogeneous at the molecular level. The inbreds also showed a high level of genetic diversity, indicating that CIMMYT breeders have successfully incorporated considerable genetic diversity into CIMMYT maize germplasm. Only lines closely related by pedigree clustered together. Population of origin and heterotic grouping were not associated with the clusters formed on the basis of SSR markers, a result consistent with the high level of diversity within source populations of the inbreds. Although this will make it more difficult to assign CIMMYT inbred lines to currently existing heterotic groups by means of markers, the markers may be useful in refining the CIMMYT heterotic groups into additional and more uniform groups.
Development of Redroot Pigweed Is Influenced by Light Spectral Quality and Quantity
Authors: Rajcan Irena , AghaAlikhani Majid , Swanton Clarence J. , Tollenaar Matthijs
Published: July 2010

Light quantity (photosynthetic photon flux density, PPFD) and quality (red:far‐red ratio, R:FR) may affect phenological development of weed species growing under a crop canopy. An indoor study was conducted to quantify the effects of incident PPFD and R:FR on development and dry matter accumulation of redroot pigweed (Amaranthus retroflexusL.). Pigweed was grown in growth cabinets from the one‐leaf stage to the initiation of seed set under three different PPFD/R:FR treatments: (i) high PPFD (550 μmol m−2s−1) and high R:FR (1.4) (HH), (ii) low PPFD (180 μmol m−2s−1) and high R:FR (1.4) (LH), and (iii) low PPFD (180 μmol m−2s−1) and low R:FR (0.8) (LL). The experiment was undertaken at 12‐ and 16‐h daylengths with three replications. Rate of leaf appearance (RLA) was accelerated with an increase in PPFD (HH vs. LH) at both daylengths. The FR enrichment (LL) negated the effect of low PPFD on RLA under the 12‐h but not under the 16‐h daylength. Low PPFD delayed the occurrence of floral primordia, flowering and initiation of seed set. Plant height was a result of the complementary effects of PPFD and R:FR. Total dry matter accumulation and partitioning, with the exception of dry matter accumulation to the stem, were influenced by PPFD only. Results of this study show that both light quality and quantity influence the phenology of pigweed.
Using Satellite and Field Data with Crop Growth Modeling to Monitor and Estimate Corn Yield in Mexico
Authors: Báez‐González Alma Delia , Chen Pei‐yu , Tiscareño‐López Mario , Srinivasan Raghavan
Published: July 2010

The large‐scale monitoring and estimation of crop yield is essential for food security in Mexico. This study developed and validated a method of monitoring and estimating corn (Zea maysL.) yield by means of satellite and ground‐based data. In autumn–winter 1999 and spring–summer 2000, eight locations under irrigated and nonirrigated conditions in corn valleys of Mexico were localized by Global Positioning Systems (GPS) and were sampled every 15 d. Photosynthetic active radiation (PAR), leaf area index (LAI), crop development stage (DVS), planting dates, and grain yield data were gathered from the field. The normalized difference vegetation index (NDVI) was derived from NOAA‐Advanced Very High Resolution Radiometer (AVHRR) images. A growth model was developed to integrate satellite and ground data. Net primary productivity (NPP) was estimated using PAR and NDVI. Dry weight increase (kg ha−1d−1) was determined considering NPP and the partitioning factor. Results indicated that the model accounts for 89% of the variability in yields under irrigated conditions and 76% under nonirrigated conditions. The methodology seems advantageous in large‐scale monitoring and assessment of corn yield.
Influence of Septoria tritici on Yield, Yield Components, and Test Weight of Wheat under Two Nitrogen Fertilization Conditions
Authors: Simón M. R. , Perelló A. E. , Cordo C. A. , Struik P. C.
Published: July 2010

Nitrogen fertilization is required for achieving high yields in wheat (Triticum aestivum L.), but N may enhance the development of leaf blotch (Septoria tritici Roberge in Desmaz., teleomorph Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn). The present study was undertaken to investigate how Septoria leaf blotch affects yield, yield components, and test weight (TW) of different cultivars under different N supplies. Field experiments with six cultivars were carried out in a split‐split plot design during 1996 and 1997. Inoculation treatments were the main plots, N fertilization levels were the subplots, and cultivars were the sub‐subplots. Thousand‐kernel weight (TKW) was higher and TW lower in 1996 than in 1997. Interaction year × inoculation was not significant for any trait; year × fertilization was significant for yield and EPM2, and year × cultivar was significant for all traits except TKW. The separated analysis for each year indicated that additional N increased yield, EPM2, and KPE, but not TKW or TW. Inoculation with S tritici reduced yield and KPE, in both years and TKW, TW, and EPM2 in 1996. Differences between cultivars occurred for all traits except EPM2 in 1996. The percentage reduction in yield, yield components, and TW due to the inoculation was similar in fertilized and nonfertilized conditions, despite the increase in the area under disease progress curve (AUDPC) values by N fertilization in 1996. Cultivar differences in tolerance is suggested.
Turfgrass Evaluation of Native Grasses for the Northern Great Plains Region
Authors: Mintenko A. S. , Smith S. R. , Cattani D. J.
Published: July 2010

A range of native grass species evolved under the environmental extremes of a continental climate in the northern Great Plains, but most have not been evaluated for their suitability as turf. The objective of this research was to evaluate the turfgrass potential of a range of native grasses under three mowing heights. Twelve species (a total of 28 entries) were evaluated under three mowing heights (62, 38, and 18 mm), for turf quality, color, and density at two locations in Manitoba, Canada. The species evaluated included alpine bluegrass (Poa alpina L.), alkali grass [Puccinellia nuttalliana (Schult.) Hitchc.], alpine fescue [Festuca ovina L. var. brachyphylla (Schult. & Schult. f.) Piper, syn. F. brachyphylla Schult. & Schult. f.], blue grama [Bouteloua gracilis (Kunth) Lag. ex Griffiths], buffalograss {Buchloe dactyloides (Nutt.) Engelm. [= Bouteloua dactyloides (Nutt.) Columbus]} Canada bluegrass (Poa compressa L.), fescue spp., fowl bluegrass (Poa palustris L.), Idaho bentgrass (Agrostis idahoensis Nash), marsh muhly [Muhlenbergia racemosa (Michx.) Britton et al.], prairie junegrass [Koeleria macrantha (Ledeb.) Schult.], rough hairgrass {Agrostis scabra Willd. [= A. hyemalis var. scabra (Willd.) H. L. Blomq.]}, side‐oats grama [Bouteloua curtipendula (Michx.) Torr.], and tufted hairgrass [Deschampsia cespitosa (L.) P. Beauv.]. Entries showed similar results across all mowing heights. ‘Bad River’ blue grama, Minnesota ecotype blue grama, and ‘Barkoel’ prairie junegrass entries showed high quality ratings across all years and locations. Blue grama, a warm‐season grass, was drought tolerant and maintained consistent green color throughout the growing season. Although a number of the species showed promise, most entries will require a breeding and selection program before release as low‐maintenance turfgrasses.
Phosphorous Uptake and Concentration of Timothy Genotypes under Varying N Applications
Authors: Bélanger G. , Brégard A. , Michaud R.
Published: July 2010

Improving P uptake in timothy (Phleum pratense L.) would reduce excess soil phosphate while producing forage with greater P nutritional value. A strong relationship exists between N and P concentration in plants, and we hypothesized that genotypes characterized for contrasting N concentration or uptake may also exhibit contrasting P concentration and uptake. Two timothy populations derived from divergent selection for high and low forage N concentration were studied in Experiment 1. These two populations were also studied in Experiment 2, along with seven half‐sib families identified in a field study as having contrasting dry matter (DM) yield and N concentration. In both experiments, a reference population, ‘Champ’, was included and plants were grown in a growth room with varying N rates. Independent of applied N, the genotypes differed for P concentration, P uptake, and P to N ratio (P/N), in forage and total biomass, as well as for leaf P concentration, leaf weight ratio (LWR), root weight ratio (RWR) and efficiency of P uptake for each unit of root biomass (PUPEroot). Averaged across N rates in Experiment 2, forage P concentration among genotypes ranged from 4.1 to 5.1 g P kg−1 DM, while forage P uptake ranged from 10.0 to 14.6 mg P per plant. Variations in P uptake and concentration were related to genotypic differences in DM yield, leaf P concentration, LWR, and RWR. Phosphorus concentration and uptake decreased under N stress. We conclude that variation exists among timothy genotypes for P concentration and uptake.
Plant Density and Environment Effects on Orchardgrass–White Clover Mixtures
Authors: Sanderson M. A. , Elwinger G. F.
Published: July 2010

Earlier research indicated that orchardgrass (Dactylis glomerata L.) cultivars affected white clover (Trifolium repens L.) stolon structure during establishment. We conducted a field study to determine if plant density and environment modified the effect of orchardgrass cultivars on white clover. ‘Dawn’ and ‘Pennlate’ orchardgrasses were established at 10‐, 20‐, or 40‐cm spacings in mixture with ‘Will’ white clover in a systematic plant spacing design. Plots were established in September 1996 on a Hagerstown, Berks, or Rayne soil in central Pennsylvania. Orchardgrass was harvested monthly from May to September 1997 and 1998 to determine yield and tiller number per plant. White clover plants were dug from each plant spacing and site in the fall to determine stolon structure. Orchardgrass cultivar did not affect white clover stolon structure. Orchardgrass and white clover plants were larger and more complex on the Hagerstown soil than on the lower fertility Berks and Rayne soils. The highest stolon densities occurred at the 40‐cm plant spacing on the Hagerstown soil in 1998 with >22 m of main stolon m−2 along with 8 m of first‐order branches and 1 m of second‐order branches. On the Rayne soil, plant spacing had little effect on stolon structure. Weed competition was greater on the Rayne soil (788 plants m−2 from 33 species) than on the higher fertility Hagerstown soil (157 plants m−2 from 19 species). Interspecific competition, edaphic factors, and climate interacted to govern the structure of white clover stolons and overwhelmed orchardgrass cultivar effects.
Molecular Breeding for the Development of Blast and Bacterial Blight Resistance in Rice cv. IR50
Authors: Narayanan N. N. , Baisakh N. , Vera Cruz C. M. , Gnanamanickam S. S. , Datta K. , Datta S. K.
Published: July 2010

The objective of this study was to improve IR50, an elite Indica rice line, by molecular breeding approach involving marker‐aided selection (MAS) and genetic transformation for resistance against blast (BL) and bacterial blight (BB). On the basis of BL pathogen population dynamics and lineage exclusion assays in southern India, the major BL resistance gene Piz‐5 can exclude most Pyricularia grisea Sacc. {= P. oryzae Cavara [teleomorph: Magnaporthe grisea (Hebert) Barr]} lineages. Resistant CO39 near‐isogenic line (NIL) C101A51 carrying Piz‐5 was used as the donor parent and IR50 as the recurrent parent in backcrossing up to four generations. BC4F1 plants were finally selfed to produce BC4F2 seeds. A polymerase chain reaction (PCR)‐based sequence‐tagged site (STS) marker RG64 was used to identify Piz‐5 in the segregating population and the resultant resistant progenies were obtained through phenotypic assays and MAS. To have further resistance to bacterial blight in this cultivar, these blast‐resistant isolines were transformed with Xa21, which is known to confer resistance to all races of Xanthomonas oryzae pv. Oryzae [= X. campestris pv. Oryza (Ishiyama 1922) Dye 1978] (Xoo). Stable integration and inheritance of the Xa21 gene were demonstrated by PCR and Southern blot analysis from three independent transformants. Bioassay data showed that transgenic IR50 is resistant to pathogens, M. grisea and Xoo. Apart from that, pedigree analysis and phenotypic studies with IR50 revealed the endogenous presence of the Xa4 gene, which may show an increased level of resistance to the BB pathogen along with the transformed Xa21 gene. This is the first report documenting the stacking of two major genes (Piz‐5 + Xa21) in rice using molecular breeding through MAS and transformation.
Design and Application of Microsatellite Marker Panels for Semiautomated Genotyping of Rice (Oryza sativa L.)
Authors: Coburn J. R. , Temnykh S. V. , Paul E. M. , McCouch S. R.
Published: July 2010

The objective of this study was to develop a systematic and flexible method for assembling multiplex simple sequence repeat (SSR) marker panels for high throughput genome analysis in rice, Oryza sativa, and to test these panels on a set of cultivated rice germplasm. To do this, 159 microsatellite markers were fluorescently labeled and assembled into 21 multiplex panels for semiautomated genotyping, providing genome‐wide coverage of the 12 rice chromosomes. Panels are comprised of an average of eight markers each, occurring at approximately 11‐centimorgan (cM) intervals throughout the genome. On a standard set of 13 genetically diverse cultivars of Oryza, these markers detected an average of five alleles per locus and had a mean polymorphism information content (P.I.C. value) of 0.67. Polymerase chain reactions (PCR) were optimized on a per marker basis to generate a uniform amount of PCR product and each primer pair was assessed in replicated trials for reliability of allele size estimates. T4 DNA polymerase was used to treat PCR products where the standard deviation of allele molecular weight was greater than 0.5 base pairs (bp). This treatment minimized the variance so that, in the multiplex set reported here, the average std. dev./marker was 0.24 bp, allowing accurate discrimination of alleles that differed by a single nucleotide. The resulting data on allele sizes were then entered into GeneFlow analysis software for the evaluation of polymorphism patterns among diverse rice cultivars. The use of an automated software tool for designing multiplex panels on the basis of both highly polymorphic and more conservative SSR markers resulted in the development of a highly informative semiautomated genotyping system for applications in rice genetics and breeding.
Microsatellite Repeats in Common Bean (Phaseolus vulgaris)
Authors: Gaitán‐Solís E. , Duque M. C. , Edwards K. J. , Tohme J.
Published: July 2010

Phaseolus beans are distributed worldwide and are cultivated in the tropics, subtropics, and temperate zones. The common bean is the most important grain legume for direct human consumption in the world. The objectives of this study were to isolate microsatellite repeats and to establish their discriminatory power (DL) to be used in bean diversity characterization and mapping. We isolated, cloned, and sequenced genomic DNA fragments that contained microsatellite loci from three genomic libraries of Phaseolus vulgaris L. The polymorphism of the microsatellites was evaluated in a panel of 21 P. vulgaris genotypes made up of cultivated and wild beans from the Mesoamerican and Andean pools, and nine genotypes from four Phaseolus species. The number of alleles per microsatellite locus ranged from 1 to 14, with an average of 6 alleles per primer pair. Almost all the microsatellite loci showed high levels of discriminatory power, with the highest value being 0.94. These results indicate that microsatellites can be valuable genetic markers for assessing genetic diversity in the P. vulgaris. The high levels of polymorphism of these new bean microsatellites and their wide cross‐species transportability make these new markers useful for mapping and molecular characterization of Phaseolus species.
Estimation of Genetic Divergence among Elite Cotton Cultivars–Genotypes by DNA Fingerprinting Technology
Authors: Rahman M. , Hussain D. , Zafar Y.
Published: July 2010

Epidemics of cotton leaf curl virus disease (CLCD) was the compelling factor in the decision to devise new strategies for cotton breeding programs of Pakistan. The genetic similarity among the elite cotton (Gossypium spp.) cultivars released before the advent of CLCD epidemics was in the range of 81.5 to 93.41%. New cultivars were developed by crossing the exotic resistant germplasm (LRA‐5166, CP‐15/2, and Cedix) with adapted varieties highly susceptible to CLCD. A study was designed to assess the genetic relatedness or diversity among the newly released, extremely resistant and resistant cultivars. After screening 27 cotton genotypes by different diagnostic methods such as field evaluation, whitefly‐transmission studies, grafting, dot‐blot hybridization, and multiplex PCR using conserved primers sequences, 20 extremely resistant and resistant cultivars were selected for a random amplified polymorphic DNA (RAPD) analysis. The genetic similarity of the exotic germplasm with the elite cultivars was in the range of 81.45 to 90.59%. Similarly, the genetic relatedness among the elite cultivars was in the range of 81.58 to 94.90%. The average genetic similarity among all studied genotypes was 89.55%. We have demonstrated that only cultivar VH‐137 possesses a diverse genetic background. Our study suggests the need to breed for high genetic diversity to serve as a buffer against potential epidemics.
Genetic Diversity of Perilla and Related Weedy Types in Korea Determined by AFLP Analyses
Authors: Lee Ju Kyong , Nitta Miyuki , Kim Nam‐Soo , Park Cheol Ho , Yoon Kyung Min , Shin Young‐Boum , Ohnishi Ohimi
Published: July 2010

Perilla frutescens (L.) Britton var. frutescens is extensively cultivated on a large scale throughout the Korea, whereas var. crispa is not. The weedy types of both var. frutescens and var. crispa are often found along roadsides, waste lands, and around farmers' fields. Although Perilla is one of the important leafy vegetable and oil crops in Korea, systematic analyses on its genetic structure have been limited and are needed for future breeding progress. The objective of this study was to determine genetic diversity and relatedness in Korean accessions of Perilla. Field surveys and amplified fragment length polymorphism (AFLP) analyses were conducted to determine genetic diversity. Analyses of 30 Perilla accessions by seven AFLP primer combinations identified a total of 121 fragments, of which 72 (60%) were polymorphic at the species level. Shanon's index of diversity Hs of the AFLP variations for cultivated type of var. frutescens, weedy type of var. frutescens, and weedy type of var. crispa were 0.63, 2.00, and 1.75, respectively. The weedy type of var. frutescens exhibited the highest variation. Most of the AFLP variation (78%) resided within populations. In the phylogenetic tree, two major clusters were recognized: (i) cultivated type of var. frutescens and weedy type of var. frutescens and (ii) weedy type of var. crispa. Although the wild species of P. frutescens has not been identified, the weedy Perilla is the key taxon for our understanding of the origin of cultivated var. frutescens.
Use of digital image analysis, viability stains, and germination assays to estimate conventional and glyphosate‐resistant cotton pollen viability
Authors: Pline Wendy A. , Edmisten Keith L. , Oliver Tim , Wilcut John W. , Wells Randy , Allen Nina S.
Published: July 2010

Because the success of labor‐intensive hand crosses by breeders is dependent upon pollen viability, quick, simple, and inexpensive methods for viability assessment are of interest. Four such cotton pollen viability assays were compared to determine differences in viability estimates, and relative accuracy by correlation to seed set. The methods compared were Brewbaker & Kwack (B & K) medium, B & K medium plus aniline blue, a fluorochromatic reaction method (FCR), and Alexander's stain. Additionally, digital images of germinated pollen grains were analyzed by means of morphometry software to quantify pollen tube area per pollen grain, as a proposed additional method of assessing viability. Pollen from conventional, nontreated glyphosate‐resistant (GR) and glyphosate‐treated GR cotton (Gossypium hirsutum L.) plants was tested by each method. Glyphosate treatments to GR cotton reduced pollen viability and corresponding seed set in all methods tested. Pollen germination measured by the B & K method was most closely related to seed set per boll, while Alexander's stain gave the highest estimates of viability. The FCR method indicated that many pollen grains from glyphosate‐treated GR cotton were irregularly shaped and only partially flourescein diacetate (FD) stained. All methods tested showed similar high correlation (0.7–0.8) of pollen viability to seed set. Morphometric analysis of digital images of germinated pollen found the greatest pollen tube area to pollen grain ratio with B & K medium + 30 mM sucrose. Because the B & K method most closely predicted the linear magnitude of seed set reduction to reduced pollen viability, allowed the use of morphometry software analysis, and was one of the simplest and least equipment‐demanding methods, it may provide broad utility for those assessing cotton pollen viability.
Genetic Control of Prolificacy and Related Traits in the Golden Glow Maize Population: II. Genotypic Analysis
Authors: de Leon N. , Coors J. G. , Kaeppler S. M.
Published: July 2010

The open‐pollinated maize (Zea mayssubsp.mays) population Golden Glow [GG(MP)] provides excellent material for the study of morphological and genetic changes associated with selection for prolificacy. Late generations of the GG(MP), when planted at low densities, resemble the architecture of teosinte (Z. mayssubsp.parviglumis), the ancestor of maize. Our objectives were (i) to identify molecular markers linked to chromosomal regions that influenced prolificacy and related morphological traits, (ii) to determine whether genes previously shown to influence branching patterns in maize were associated with quantitative trait loci (QTLs) influencing these traits, and (iii) to determine whether epistatic interactions among putative QTLs influenced prolificacy and correlated traits. A mapping population was developed from the cross of inbred A679 and a highly prolific S1plant from Cycle 23 of GG(MP). Simple sequence repeat (SSR) and amplified fragment length polymorphism (AFLP) markers were combined for the linkage map construction. Thirty‐three QTLs were found for 14 of the 16 traits analyzed. A region located on Linkage Group 1 (LG 1) shared similarities with the pattern of development suggested for theteosinte branched1(tb1) mutant. This suggests that genetic control of prolificacy and associated traits in GG(MP) may resemble the genetic changes underlying branching morphology that occurred during maize domestication. No evidence for additive‐by‐additive epistatic interactions was found.
Nonstructural Carbohydrate and Digestibility Patterns in Orchardgrass Swards during Daily Defoliation Sequences Initiated in Evening and Morning
Authors: Griggs Thomas C. , MacAdam Jennifer W. , Mayland Henry F. , Burns Joseph C.
Published: July 2010

Herbage soluble carbohydrate (SC) levels vary diurnally and livestock intake can be higher for herbage harvested or allocated to animals in the evening than in the morning. Few assessments of SC and digestibility patterns have been made during sward depletion in rotationally stocked orchardgrass (Dactylis glomerata L.). We tested the hypothesis that simulated evening daily pasture allocation increases 24‐h mean herbage SC and digestibility levels relative to morning allocation. Total nonstructural carbohydrate (TNC) and in vitro true dry matter digestibility (IVTDMD) levels were compared during 24‐h clipping sequences initiated at 1900 h (PM) and 0700 h (AM). Sward height was progressively reduced from 40 to 8 cm at 6‐h intervals in October, June, and August. Successively lower horizons from defoliation sequences and also from control areas that were not under progressive defoliation were analyzed. Digestibility and TNC levels varied diurnally and seasonally, and were often higher for PM sequences, but differences among 24‐h means were small. Daily mean TNC levels for defoliation sequences initiated in PM and AM were 138 vs. 132, 93 vs. 88, and 72 vs. 60 g kg−1 in October, June, and August, respectively. In all periods, digestibility decreased from approximately 920 to 800 to 890 g kg−1 during sward depletion and displayed similar patterns between defoliation sequences. Patterns of TNC and digestibility during sward depletion may not be represented by those in intact swards, and PM allocation of daily herbage may not increase 24‐h mean dietary TNC density relative to AM allocation. Daily quantities of ingested TNC could be higher for PM herbage allocation if livestock consume proportionately more herbage in the PM than we simulated.
Tetrasomic Linkage Mapping of RFLP, PCR, and Isozyme Loci inLotus corniculatusL
Authors: Fjellstrom Robert G. , Steiner Jeffrey J. , Beuselinck Paul R.
Published: July 2010

Lotus corniculatusL. is a tetraploid (2n= 4x= 24) forage legume which has had limited inheritance studies. The purpose of this research was to develop a genetic map and characterize the genome ofL. corniculatususing molecular markers. A linkage map was constructed forL. corniculatususing information from 217 markers mapped as single‐dose restriction fragment length polymorphism (RFLP), randomly amplified polymorphic DNA (RAPD), inter‐simple sequence repeat (ISSR), sequence tagged site (STS), and isozyme markers and five duplex RFLP markers. Formulas for calculating maximum likelihood estimates of recombination involving codominantly scored duplex loci in tetrasomic species from direct count data are made available. Six composite linkage groups were constructed from the combined data of four homologous linkage groups anchored by shared RFLP loci. Three of the composite groups (Groups 2, 3, and 4) were well defined, two groups (Groups 5 and 6) were poorly discriminated because of apparent marker duplication found between them, and one group (Group 1) was poorly defined because of an apparently high degree of differentiation between its homologous members. This first genetic map forL. corniculatusspans 572.1 centimorgans (cM) and serves to provide a foundation for the genetic analysis of complex traits and marker‐aided selection.
Genetic Mapping of the Or5 Gene for Resistance to Orobanche Race E in Sunflower
Authors: Tang Shunxue , Heesacker Adam , Kishore Venkata K. , Fernandez Alberto , Sadik El Sayed , Cole Glenn , Knapp Steven J.
Published: July 2010

Orobanche cumana Wallr. (= O cernua Loefl., broomrape), a weedy parasitic plant, is a serious pest of cultivated sunflower (Helianthus annuus L.). Breeding for resistance has been crucial for protecting sunflowers from broomrape damage, a challenging task because new races of the pathogen continually emerge and ultimately defeat known resistance genes. Despite several attempts to identify DNA markers tightly linked to Orobanche resistance genes, the closest reported thus far is 5.6 centimorgans (cM) downstream of Or5, a gene for resistance to Race E. The Or5 locus was placed on the simple sequence repeat (SSR) map of sunflower by genotyping and phenotyping 262 recombinant inbred lines (RILs) from a cross between elite inbred lines (PHC × PHD) segregating for resistance to Orobanche Race E. Polymerase chain reaction (PCR) multiplexes were used to screen 78 SSR marker loci, strategically positioned throughout the genome, for polymorphisms between resistant and susceptible bulks of PHC × PHD RILs. The bulks were polymorphic for three of five Linkage Group 3 (LG3) SSR marker loci amplified by the PCR multiplexes. The RILs were phenotyped for resistance to Race E and genotyped for 13 SSR markers from the upper end of LG3. The Or5 locus mapped to the end of LG3 distal to the SSR marker loci (the closest SSR marker locus was 6.2 cM downstream of Or5 The terminal and perhaps telomeric location of Or5 on LG3 sheds light on difficulties, past and present, of identifying flanking DNA markers tightly linked to Or5
Analysis of Genetic Diversity in Crop Plants—Salient Statistical Tools and Considerations
Authors: Mohammadi S. A. , Prasanna B. M.
Published: July 2010

Knowledge about germplasm diversity and genetic relationships among breeding materials could be an invaluable aid in crop improvement strategies. A number of methods are currently available for analysis of genetic diversity in germplasm accessions, breeding lines, and populations. These methods have relied on pedigree data, morphological data, agronomic performance data, biochemical data, and more recently molecular (DNA‐based) data. For reasonably accurate and unbiased estimates of genetic diversity, adequate attention has to be devoted to (i) sampling strategies; (ii) utilization of various data sets on the basis of the understanding of their strengths and constraints; (iii) choice of genetic distance measure(s), clustering procedures, and other multivariate methods in analyses of data; and (iv) objective determination of genetic relationships. Judicious combination and utilization of statistical tools and techniques, such as bootstrapping, is vital for addressing complex issues related to data analysis and interpretation of results from different types of data sets, particularly through clustering procedures. This review focuses on application of statistical tools and techniques in analysis of genetic diversity at the intraspecific level in crop plants.
A Multivariate Method for Classifying Cultivars and Studying Group × Environment × Trait Interaction
Authors: Franco Jorge , Crossa José , Taba Suketoshi , Shands Henry
Published: July 2010

Classification methods are used in genetic resource conservation and plant breeding. The two‐stage Ward‐Modified Location Model (Ward‐MLM) clustering strategy defines initial groups by the Ward method and the MLM is then used to improve those groups. The three‐way clustering strategy considers the same trait measured in different environments as different variables (environment–trait combination), so that the resulting clusters of cultivars have a small group × environment interaction (GEI) for all the traits included in the study. An important component of the GEI is the imperfect genotypic correlation or crossover interaction (COI). This study used the three‐way Ward‐MLM clustering strategy in three different data sets with the objectives of (i) evaluating the ability of the Ward‐MLM methodology for clustering cultivars into groups with low COI, (ii) obtaining a graphical representation of the variables in a low dimensional scatter plot produced by the multidimensional scaling method (MDS) in which the GEI of continuous and categorical traits and environments can be visualized, and (iii) studying how the relationship between a pair of traits changes across environments. The three‐way Ward‐MLM strategy produced groups of cultivars with low levels of COI. The increment of the correlation coefficient values between groups with respect to the total correlation coefficients indicated that the groups formed by the three‐way Ward‐MLM strategy comprised subsets of individuals that had similar trait responses across environments.