bluuebunny/crossref_metadata_2025 huggingface dataset:
Utilization of Phosphorus Substrates by Contrasting Common Bean Genotypes
Authors: Yan Xiaolong , Lynch Jonathan P. , Beebe Stephen E.
Published: July 2010

Phosphorus deficiency limits common bean (Phaseolus vulgaris L.) production in tropical soils, where P may be bound to recalcitrant organic matter, or with aluminum or iron oxides. In a previous study, we showed that P‐efficient genotypes perform well in contrasting soils, suggesting that interactions with specific soil constituents did not account for genetic variation. To confirm this finding, a study was done to determine if contrasting bean genotypes differ in their ability to recover P from different P compounds. Six genotypes were planted in pots of silica sand in which P was supplied at four levels as KH2PO4, CaHPO4, inositol hexaphosphoric acid (IP6), FePO4, or AIPO4. Most results could be explained as a function of relative aqueous solubilities of the P sources. KH2PO4 gave the greatest uptake and growth and FePO4 the least. No differences were observed in the ability of the six genotypes to acquire P from the Al, Fe, or IP6 sources. Andean genotypes, especially the Peruvian landrace G19833, extracted more P from CaHPO4 than Mesoamerican genotypes. G19833 was capable of acidifying the rhizosphere more than other genotypes. We conclude that (i) differential ability to mobilize P from Fe, Al, and organic ligands does not account for genetic variation in P efficiency, and (ii) Andean germplasm has superior ability to mobilize P from Ca sources, which may be useful in utilizing phosphate rock fertilizers.
Comparison of Cotton Genotypes Varying in Canopy Characteristics in 76‐cm vs. 102‐cm Rows
Authors: Heitholt James J. , Meredith William R. , Williford J. Ray
Published: July 2010

Our previous findings with cotton (Gossypium hirsutum L.) indicated that a leaf shape variant with reduced leaf area (okra‐leaf) yielded more in 51‐cm rows than in 102‐cm rows. Yield of a normal‐leaf type was unaffected. The objectives of this study were to determine whether this same response would occur with genotypes varying in canopy characteristics when grown in rows spaced 76 and 102 cm. From 1991 to 1993, seven to 14 genotypes (including two okra‐leaf and one ultra‐short season type) were grown in the field in 76‐ and 102‐cm row spacings. The 1991 part of the study encompassed four soil types and the 1992 and 1993 study was grown on a Bosket fine sandy loam. Irrigation was provided when necessary to minimize water stress. The percentage of photosynthetic photon flux density (PPFD) intercepted and yield were determined. The 76‐cm row spacing intercepted significantly more PPFD than 102‐cm rows up until 80 d after planting. Row spacing did not affect yield in either an excellent environment (1991, 1475 kg ha−1) or in a stressed environment (1993, 905 kg ha−1). However, 76‐cm rows outyielded 102‐cm rows by 15% in 1992 (1280 vs. 1100 kg ha−1). For each year, the genotype × row‐spacing interaction was not significant. However, the combined analysis (1992, 1993) indicated that the P > F for the genotype × row‐spacing interaction was 0.12. This was due to a trend for the cultivars to respond to 76‐cm rows (9% increase) whereas the okra‐leaf types did not respond to 76‐cm rows. Despite genetic differences in morphology and canopy architecture, genotype × row‐spacing interactions may not be important when comparing 76‐ and 102‐cm rows in some U.S. Mid‐South environments.
Expression of Genes Encoding Globulin and Prolamin Storage Proteins in Kernels of Illinois Long Term Chemical Selection Strains
Authors: Bhattramakki Dinakar , Sachs Martin M. , Kriz Alan L.
Published: July 2010

Seed storage protein genes represent an interesting model system to study the structure and function of nuclear genes in higher plants. The Illinois long term chemical selection strains of maize (Zea mays L.) were used in the present study with an objective to investigate the expression of genes encoding seed storage proteins. Analysis of the endosperm proteins by SDS‐PAGE (sodium dodecyl sulfate‐polyacrylamide gel electrophoresis) indicated a general trend in the level of certain polypeptides in different protein selection strains. As percent protein increased as a function of selection, the level of α‐zeins also increased. Embryo protein profiles of IHP (Illinois High Protein) and ILP (Illinois Low Protein) analyzed by SDS‐PAGE and immunoblot analysis indicated that these populations lack detectable globulinl (GLB1) protein. However, PCR (polymerase chain reaction) amplification of DNA from HIP plants and subsequent Southern hybridization with a radiolabeled oligonucleotide probe specific for glb1 intron2 confirmed that the glb1 gene is present in the IHP population. The glbl gene expression patterns were analyzed using embryos from different developmental stages of maize kernels of both IHP and ILP strains. Levels of glbl transcripts were 10‐fold lower in IHP and 30‐fold lower in ILP at 26 DAP as compared with standard functional alleles from maize inbred lines W64A and Va26. In conclusion, we have analyzed a null variant of globulin1 protein in Illinois long term chemical selection strains which would serve as tool to study the molecular basis of gene regulation.
Genetic Control of the Domestication Syndrome in Common Bean
Authors: Koinange Epimaki M. K. , Singh Shree P. , Gepts Paul
Published: July 2010

The marked pbenotypic differences for morphological and physiological traits that distinguish wild progenitors and cultivated descendants (“the domestication syndrome”) and the lack of information about their genetic control have limited the utilization of wild germplasm for crop involvement. This study was conducted to assess the genetic control of the domestication syndrome in common bean (Phaseolus vulgaris L.). A recombinant inbred population resulting from a cross between a wild and a cultivated common bean was subjected to molecular linkage mapping and evaluation in short‐day and long‐day environments. We show that the genetic control of this syndrome in common bean involves genes that can have a large effect (>25–30%) and account for a substantial part of the phenotypic variation observed (>40–50%). The distribution of domestication syndrome genes appears to be concentrations in three genomic regions with a major effect on the syndrome, one of which greatly affects growth habit and phenology, the other seed dispersal and dormancy, and a third, the size of fruit and seed, all of which are important traits in determining adaptation to a cultivated environment. Whereas the influence of genetic background and environment on the expression of some traits will have to be further analyzed, our results suggest, however, that domestication of common bean could have proceeded rapidly (provided that genetic diversity and selection intensity were high) and that evolution can proceed through changes involving a few genes with large effect rather than through a gradual accumulation of changes coded by changes with small effects. They also suggest that adaptation to rapidly changing environmental conditions may involve genes with large phenotypic effects. The information presented here should lead to marker‐assisted selection experiments of introgression of additional genetic diversity into the cultivated common bean gene pool.
A Second Gene for Resistance to Hessian Fly in Iumillo Durum Wheat
Authors: Cambron S. E. , Ohm H. W. , Ratcliffe R. H. , Patterson F. L.
Published: July 2010

Resistance to Hessian fly, Mayetiola destructor (Say), had been reported by other researchers to be transferred from the donor ‘Iumillo’ durum wheat (Triticum durum Desf.) to ‘Marquillo’ spring wheat (T. aestivum L.). We had observed that Iumillo demonstrated a higher proportion of resistant seedlings than Marquillo at temperatures of 21°C and above, and hypothesized that Iumillo may carry a gene(s) that conditions resistance to biotype L of Hessian fly in addition to H18 that had been transferred into Marquillo. Because Iumillo may carry more than one Hessian fly resistance gene, we examined the genetic basis of resistance to Hessian fly of Iumillo. Our objectives were to (i) determine the number of genes for resistance of Iumillo to Hessian fly biotype D at temperatures of 16, 21, 23, and 26°C, tested in a growth chamber, and (ii) determine if the resistance Iumillo to Hessian fly biotype D is inherited independently from H20. A second gene for resistance to Hessian fly biotype D, in addition to gene H18, was identified in Iumillo in backcross (BC) F2 families. Gene H18 had previously been transferred from Iumillo to Marquillo. The second gene is inherited as a dominant or partially dominant, depending on temperature, gene independent of H18 and segregates independently of H20. Unlike H18, which is not effective above 20°C, this second gene of Iumillo is partially effective in the homozygous state at temperatures of 23 and 26°C.
Heritability of Product Fractions from Wet Milling and Related Properties of Maize Grain
Authors: Zehr B. E. , Eckhoff S. R. , Nyquist W. E. , Keeling P. L.
Published: July 2010

Wet milling is an important use of maize (Zea mays L.) grain produced in the USA, and commercial wet millers and hybrid seed companies are increasingly interested in hybrids which have enhanced milling properties. Because of the cumbersome nature of traditional laboratory wet‐milling procedures, relatively little information is available regarding inheritance of wet‐milling product fractions. In this study, the inheritance of maize wet‐milling product fractions was evaluated in grain of 40 full‐sib families from a Design I mating (20 males; two females per male) and a newly developed, rapid, laboratory milling procedure. The narrow‐sense heritability estimate of male‐family means for the starch fraction was 0.73. Predicted gain from selection with a conservative heritability estimate was 7.4 g kg−1 per cycle for the starch fraction. Phenotypic and genetic correlation coefficients between the wet‐milling starch fraction and initial starch concentration, measured by near‐infrared reflectance, were significant (0.79 and 0.89, respectively). Significant phenotypic and genetic correlation coefficients were observed between a wet‐milling index and an index based on near‐infrared reflectance. Relative rankings of check hybrids were significantly different between these two indices. Results from this study indicated product fractions from maize wet milling are heritable, and thus modifiable through selection. Genetic correlation coefficients suggested that selection for increased starch extractability from wet milling could be accomplished by using near‐infrared reflectance to measure starch concentration. Changes in hybrid rank among wet‐milling and near‐infrared reflectance indices suggested that final selections of candidate hybrids for specific milling applications should be based on actual wet‐milling evaluation.
Effect of Unique Cytoplasms in Reciprocal Crosses of Soybean
Authors: Miller Rhonda L. , Shibles Richard M. , Hammond Earl G. , Green Detroy E.
Published: July 2010

Cytoplasmic inheritance studies concerning agronomic characters and seed quality traits have often produced contradictory results. The use of parental lines with similar cytoplasms may explain the seeming discrepancies, since differences among the cytoplasms were not identified in previous studies. Differences among cytoplasms have been identified in soybean [Glycine max (L.) Merr.] by means of chloroplast DNA (cpDNA) restriction fragment length polymorphism (RFLP) terns. This study was conducted to determine if cytoplasmic effects exist in soybean. Ten soybean lines representing five cpDNA cytoplasmic groups were crossed to ‘Harosoy 63’ and ‘Clark 63’ to produce 40 F1 and reciprocal F1 populations. Ten Harosoy 63 F1 and reciprocal F1 populations were advanced to the F2 generation for evaluation in the following year. The parents, crosses, and reciprocal crosses were evaluated for the following agronomic characters: developmental stages, height, leaflet characteristics, and seed size. The population means and variances of each reciprocal cross were examined. Reciprocal cross means were significantly different for agronomic characters in only 8% of the crosses. Reciprocal crosses rarely differed with respect to the variances. Protein, oil, fatty acid, and amino acid composition were examined in composite samples of seed for each line. Significant differences were observed for only a few reciprocal crosses. Protein and oil concentration each differed in only one reciprocal cross. Oleate and linoleate concentration differed the most often, accounting for eight of the 10 significant reciprocal cross differences observed for fatty acid types in the F1 and F2 generations. Reciprocal cross differences involving the aliphatic amino acids were observed in four of the five cytoplasmic groups, but were not consistent with the cpDNA RFLP. groupings. Consistent cytoplasmic effects, based on cpDNA RFLP groupings, were not observed for any of the traits examined. The significant differences that were observed may have been due to nuclear × cytoplasmic interactions, short‐lived maternal effects, or Type I error.
Supplemental Nitrogen Effects on Alfalfa Regrowth and Nitrogen Mobilization from Roots
Authors: Barber L. D. , Joern B. C. , Volenec J. J. , Cunningham S. M.
Published: July 2010

Recent studies suggest that alfalfa (Medicago sativa L.) root carbohydrate concentrations are not correlated closely with shoot regrowth, and that root N reserves may influence shoot regrowth after harvest. The objectives of this greenhouse study were to (i) determine the effects of supplemental N on alfalfa regrowth and N uptake, (ii) quantify N remobilization from roots to regrowing shoots, and (iii) determine if certain root N pools, including vegetative storage proteins (VSPs), were utilized preferentially as N sources during early shoot regrowth. Four cultivars with contrasting fall dormancy reaction were defoliated and supplied with 85 mg N (kg soil)−1 as 15N‐enriched (NH4)2SO4 or KNO3. Samples were taken immediately and once weekly for 28 d. After 28 d, plants were again defoliated and shoots, crowns, and roots of one‐half of the plants sampled immediately. Intact crowns and roots of remaining plants were transplanted into sand, and shoots, crowns, and roots sampled 10 d after transplanting. Taproot N from these samples was partitioned into four specific pools. Nitrate‐N uptake was greater than NH4‐N uptake at 7 and 28 d after N application. Ten days after transplanting, 25% of crown and root total N and 35% of crown and root 15N was remobilized to regrowing shoots. Fifty‐five percent of total root N was soluble in phosphate buffer. The buffer‐soluble N pool was fractionated into a low molecular weight N pool (≈30% of total root N), a non‐VSP protein N pool (≈20% of total root N), and a VSP‐enriched protein N pool (≈5% of total root N). The low molecular weight N and VSP‐enriched protein N pools in roots were utilized preferentially as N sources for regrowing shoots 10 d after transplanting. Accumulation of these root N pools may be important for rapid early shoot regrowth after defoliation.
Response of Three Kentucky Bluegrass Cultivars to Sprayable Nitrogen Fertilizer Programs
Authors: Moore Richard W. , Christians Nick E. , Agnew Micheal L.
Published: July 2010

Developing fertilizer programs that match anticipated maintenance levels for Kentucky bluegrass (Poa pratensis L.) is important because cultivars differ in their response to N management. Our objective was to determine the response of ‘Vantage’, ‘Park’, and ‘Majestic’ Kentucky bluegrass to urea, ureaform, methylene urea, and methylol urea applied at a yearly rate of 1.952 kg N 100 m−2 in three application programs: heavy spring, balanced, and late fall. Data collected included visual quality, clipping yield, thatch depth, shoot density, and root weight. Quality ratings were generally highest for the heavy spring program. Urea produced quality ratings that were equal to or higher than the other N sources. Clipping yields were 20 to 67% lower for Majestic than for Vantage or Park. Thatch development was 23% greater in Majestic than in Vantage in 1987 and 16% more in 1988. Majestic produced 18% more thatch accumulation than Park in 1987 and 26% more thatch in 1988. Majestic had more total root mass than Vantage or Park in the spring of 1986 and in the spring and fall of 1987. In the fall after a severe drought (1988), Majestic had 53 and 43% more total root mass than Park and Vantage, respectively. Plots treated with urea produced 6 to 18% more clippings than the other N sources each year. Quick‐release N sources performed better than slow‐release types. The late fall program resulted in 9% more root mass than the balanced program and 8% more than the heavy spring program at the 0‐ to 5‐cm depth in 1987.
Selective Mapping of QTL Conditioning Disease Resistance in Common Bean
Authors: Miklas Phillip N. , Johnson Elizabeth , Stone Valerie , Beaver James S. , Montoya Carlos , Zapata Mildred
Published: July 2010

Genetic markers linked with quantitative trait loci (QTL) may enable indirect selection of complex disease resistance. Construction of separate linkage maps to identify QTL for each complex disease resistance trait of common bean (Phaseolus vulgaris L.) is unfeasible, however. We investigated whether selective mapping could be used to hasten identification of random amplified polymorphic DNA (RAPD) associated with QTL conditioning bean golden mosaic virus (BGMV) or common bacterial blight (CBB) resistance. The mapping population (‘Dorado’ × XAN 176) consisted of 79 F5:7 recombinant inbred lines. A bulked segregant analysis (BSA) of as few as three individuals and selective genotyping was used. The 101 RAPDs identified between the parents were tested across resistant vs. susceptible bulks for BGMV reaction, combined greenhouse (leaf) and field reactions to CBB, and pod (greenhouse) reaction to CBB. Fourteen of 22 RAPDs selectively mapped because they cosegregated among lines within bulks, were linked with seven of the nine QTL conditioning resistance as identified by QTL mapping using all 101 RAPDs. The two QTL not identified by this approach had minor effects. BSA and selective genotyping required only about one‐third the cost and labor of completely classifying the whole population with each marker and was similarly effective for identifying RAPD markers associated with major‐effect QTL that condition disease resistance in common bean. Two‐locus models (R2), for select environments, explained 60% of the phenotypic variation in BGMV reaction, and 65, 58, and 46% of the phenotypic variation in greenhouse‐leaf, ‐pod, and field reactions to CBB. Repulsion linkages between QTL for BGMV and CBB may complicate the combination of resistance alleles for these two traits.
Fatty Ester Development in Reduced‐ and Elevated‐Palmitate Lines of Soybean
Authors: Schnebly S. R. , Fehr W. R. , Welke G. A. , Hammond E. G. , Duvick D. N.
Published: July 2010

Soybean [Glycine max (L.) Merr.] lines are available that have been genetically modified to reduce and to elevate palmitate content in the seed oil. One objective of this study was to evaluate the changes in palmitate content that occur during seed development of reduced and elevated‐palmitate soybean genotypes. A second objective was to determine the relationship between the palmitate content of the leaves, stems, roots, and seeds of the soybean genotypes. The genotypes evaluated were ‘Elgin 87’, with a normal palmitate content of 110 g kg−1; A18, a reduced‐palmitate line with <45 g kg−1; and A19, an elevated palmitate line with >250 g kg−1. For the first objective, the seeds of each of the lines were harvested at 2‐d intervals from 15 to 39 d after flowering (DAF) and 4‐d intervals from 39 DAF until maturity during 1991 and 1992. Significant differences among the lines for palmitate content of the seeds were observed as early as 19 DAF. The increase in palmitate in A19 was accompanied by a decrease in oleate and linoleate content. The decrease in palmitate in AI8 was accompanied by an increase in oleate content. For the second objective, there was a relationship between the palmitate content in the seed oil and that of the roots, leaves, and stems for each of the lines. A18, which had the lowest palmitate content in the seed oil, had the lowest palmitate content in roots, leaves, and stems. AI9, which had the highest palmitate content in the seed oil, had the highest palmitate content in the vegetative tissues studied. The results indicated that the mutant alleles in A18 and A19 are constitutively expressed.
Managing Large Diverse Germplasm Collections
Authors: Clark R. L. , Shands H. L. , Bretting P. K. , Eberhart S. A.
Published: July 2010

International Agricultural Research Centers and a number of countries have assembled large collections of genetic resources managed in ex situ genebanks. In addition, some countries are managing in situ collections of selected germplasm. Pressure to reduce public funding of all government activities continues to force genebank managers to he more efficient and effective while maintaining quality factors such as high germinability, genetic integrity, and freedom from diseases and insect damage. Quality seed begins in the field at pollination time when flowers of allogamous species are bagged or caged to exclude foreign pollen. Complete seed maturation and drying before harvest provides material that will have optimal storage life. Properly maintained cold room conditions (4°C and 25–30% RH for most seeds) will ensure maximum longevity and reduce the number of regenerations necessary for each accession.
Regeneration of Germplasm Samples: Wild Versus Cultivated Plant Species
Authors: Brown A. H. D. , Brubaker C. L. , Grace J. P.
Published: July 2010

The growth in size and species diversity of germplasm collections held around the world has led to several managerial problems. For dealing with the increasing size of collections, the “core collection” offers one strategy. However, the problems of managing increasing species diversity are only just emerging, particularly in the germplasm collections of wild species. Wild collections encompass those of forest trees, forage plants, medicinal and industrial plants, the wild relatives of cultivated plants, and plant species designated as endangered. Regenerating such collections is a particular problem. In all cases, the accessions of wild species are generally more costly to regenerate than those of cultivated species. This is because of their life history, breeding system, genetic structure, ecology, and lack of domestication. Indeed it is worth asking why bother to regenerate wild accessions at all, and instead rely on resampling conserved sources in situ, or on frozen DNA libraries, or both. Modern empirical studies of the population genetics of wild populations focus on host‐pathogen coevolution, spatial subpopulation structure and dynamics, restricted sampiing strategies, breeding system variation, and colonizing history and molecular divergence and phylogeny. Each of these topics has important lessons for the optimum prioritizing of accessions, or the best methods of their regeneration. Optimum regeneration of wild species requires a clear definition of objectives and priorities among accessions, monitoring of mating system and genetic structure, maintenance of accession purity and associated passport data, and biologically realistic and flexible guidelines for sample size.
Combining Ability Analysis of Resistance of Southern Root‐knot Nematode in Red Clover
Authors: Call N. M. , Quesenberry K. H. , Wofford D. S. , Dunn R. A.
Published: July 2010

Production of red clover, Trifolium pratense L., is reduced in areas infested with root‐knot nematodes (RKN) in the southeastern USA. Although progress has been made in improving RKN resistance in red clover through recurrent selection, little information is available on the mode of inheritance of red clover resistance to any of the RKN species. This study was conducted from 1993 to 1995 in Florida to determine the mode of inheritance and relative importance of general combining ability (GCA) and specific combining ability (SCA) effects in controlling resistance to Meloidogyne incognita (Kofoid & White) Chitwood Race 3 in red clover. By means of a breeding population selected for low root galling and egg mass production when infested with M. incognita, four red clover plants were identified as resistant, three as intermediate, and two additional susceptible individuals were selected from ‘Kenstar’. These individuals were cloned and used as parents in a diallel genetic study. Forty‐eight progeny from each of 36 F1 crosses, without reciprocals, were evaluated under greenhouse conditions during 1995 for response to inoculation with 1500 M. incognita eggs per plant. Eight weeks after inoculation, the number of galls and egg masses on roots of each plant were counted under low power magnification (10–20 ✕). Resistant genotype 119 produced progeny with the least M. incognita reproduction and galling. Crosses involving the two susceptible genotypes, N1 and K4, resulted in the highest numbers of galls and egg masses. The GCA effects were significant for both traits, whereas SCA effects were not significant. These results indicate that for this set of parents, breeding procedures that utilize GCA effects to maximize exploitation of additive gene action should be most effective in improving resistance to M. incognita galling and reproduction.
Combining Ability for Protein Degradability in Alfalfa
Authors: Rooney W. L. , Skinner D. Z. , Fritz J. O.
Published: July 2010

The protein in alfalfa (Medicago sativa L.) forage is degraded extensively and quickly by ruminant animals, and N may be lost through NH3 formation. Recent research has indicated that the degradability of forage protein varies among plants. The objective of this study was to determine the relative importance of additive and nonadditive genetic effects for protein degradability traits in an alfalfa population derived from major germplasm sources. Eight alfalfa plants were intercrossed in a half‐diallel to produce 28 crossed progenies. Three replications of the crosses and parental clones were transplanted and grown in Riley County, Kansas. Protein percentages were estimated with microKjedahl, and protein degradability was estimated by degradation with the proteolytic enzyme ficin prior to microKjedahl digestion. Specific (nonadditive genetic effects) and general (additive genetic effects) combining abilities were determined for crude and soluble protein, buffer‐insoluble and undegradable insoluble protein, and the proportion of undegradable protein/total insoluble protein. Data for each variable on two harvest dates in 1993 and 1994 were used in a combined analysis. Harvest date within years was a significant source of variability for all traits. A significant genotype effect was detected for all traits except undegradable insoluble protein. General combining ability effects were significant for the remaining traits, but specific combining ability effects were significant only for soluble protein. The relative ratios of additive to nonadditive effects were 0.86 for crude protein, 0.70 for soluble protein, 0.74 for insoluble protein, and 0.80 for proportion of undegradable insoluble protein/insoluble protein. The results indicate that genetic effects for alfalfa protein degradability exist and are mostly additive. Recurrent selection procedures should be effective in reducing protein degradability in alfalfa.
Evidence for Homoeologous Linkage Groups in the Soybean
Authors: Lohnes D. G. , Specht J. E. , Cregan P. B.
Published: July 2010

Substantial progress towards the integration of the soybean [Glycine max (L.) Merr.] classical and molecular marker linkage maps recently was achieved by using a 60‐plant F2 population derived from a mating of isolines of the cultivars Clark and Harosoy. However, epistasis limited the completeness of F2 genotyping at two independently segregating loci, D1 and D2, which produced yellow (Y) and green (G) cotyledons in a duplicate recessive fashion (i.e., only the d1d1d2d2 F2 genotype was green). F2 genotypic assignments were obvious for two of the four F2.3 phenotypes (15Y:1G from 1d1D2d2 and all G from d1d1d2d2), but were equivocal for the other two (all Y from D1D1D2D2, D1D1D2D2, D1d1D2D2, D1D1d2d2, or d1d1D2D2; 3Y:1G from D1d1d2d2 or d1d1D2d2). Here, we propose an inferential means of near complete F2 genotyping, by using F2.3 data collected on locus G, which produces G (GG and Gg) and Y (gg) seed coats. Locus G is tightly linked (4.2%) to the D1 locus. Given the repulsion‐phase parental gametes of Gd1 and gD1. we inferred, with a low probability of (recombinational) error, that the GG, Gg, or gg F2 genotypes must be d1d1, D1d1, or D1D1, respectively. Genetically, a F2 plant with all Y or 3Y:1G F2.3 progeny and an inferred GGd1d1 genotype must also be D2D2 or D2d2, respectively, and an inferred GgD1d1 genotype must also be D2D2 or d2d2, respectively. The alleles at D2 could not be inferred from the ggD1D1 genotype. The updated 60‐plant marker data, when subjected to a Mapmaker linkage analysis, revealed that D1 mapped (as expected) to linkage group (LG) 1 and D2 mapped to LG10 of the Clark ✕ Harosoy map. Duplicate genes and homoeologous linkage groups support the hypothesis that the diploid soybean is derived from a tetraploid.
Genome Mapping of Soybean Cyst Nematode Resistance Genes in ‘Peking’, PI 90763, and PI 88788 Using DNA Markers
Authors: Concibido Vergel C. , Lange Douglas A. , Denny Roxanne L. , Orf James H. , Young Nevin D.
Published: July 2010

Several sources of soybean cyst nematode (Heterodera glycines Ichinohe; SCN) resistance have been identified in soybean [Glycine max (L.) Merrill]; yet, the genetic basis of this economically important trait remains poorly characterized. This study was conducted to identify quantitative trait loci that control disease response in three commonly used sources of SCN resistance, Using genetic markers, we analyzed three segregating soybean F2 populations [‘Evans’ × ‘Peking’, Evans × Plant Introduction (PI) 90763, and Evans × P188788] and compared the results with those of a previous study involving PI 209332. for the Peking, PI 90763, and PI 209332 populations, races 1, 3, and 6 were used as SCN inoculum; for the PI 88788 population, only races 3 and 6 were used. To uncover putative resistance loci, F2 DNA marker genotypes at between 63 and 99 loci in each population were contrasted with cyst indices averaged from 12 F2:3 progeny individuals. Four independent partial SCN resistance loci were uncovered at P < 0.0002 (probability per locus). One of these loci, located at the top of linkage group ‘G’ near RFLP locus C006V, was significant at P < 0.0001 in all populations and races tested. Other significant loci included one near RFLP A378H at the opposite end of linkage group ‘G’ from C006V, another on linkage group ‘J’ near marker B032V‐1, and a fourth on linkage group ‘N’ near marker A280Hae‐1. Comparisons between different SCN races indicated that some of the putative resistance loci behave in a race‐specific manner. These results may serve as a resource for SCN researchers and soybean breeders by summarizing a wide range of genetic data on the soybean‐SCN interaction.
Repeatability of Yield Stability Statistics in Soybean
Authors: Sneller C. H. , Kilgore‐Norquest L. , Dombek D.
Published: July 2010

There are many statistics to assess cultivar yield stability: some deal with genotype × environment interaction (GEI) patterns (bi, and interaction principal component scores), some with GEI noise (s2di), some with total GEI sum of squares (
), and others with rank changes [S(1)]. Our objective was to assess the repeatability in soybean [Glycine max (L.) Merr.] of different yield stability statistics. We evaluated nine statistics derived from additive main effects and mnitiplicative interaction (AMMI) analyses, regression coefficients from analyses using either yield‐based or plant height‐based environmental indices, as well as , S(1). Yield data were from Arkansas trials of maturity group V cultivars from 1987 to 1994. Stability analyses were warranted because GEI was significant, partitioning of GEl sum of squares by AMMI or regression techniques was generally significant, and all stability statistics found significant differences among the cultivars. The AMMI‐derived stability statistics produced information on cultivar stability that was similar to that produced by s2di and
. The repeatability of cultivar rankings for s2di,
, S(1), and most AMMI statistics, estimated in different single‐ or two‐year periods were low, indicating that these statistics would not be useful to breeders or growers selecting for stability. The repeatability of two regression coeffacient statistics and one AMMI‐derived statistic were moderate, particularly when estimated over environments from 2 yr. Each of the three statistics relates to a different concept of stability and may be useful to growers and breeders attempting to select cultivars with predictable yield across environments.
Effect of Leaf Rust Resistance Gene Lr34 on Grain Yield and Agronomic Traits of Spring Wheat
Authors: Singh R. P. , Huerta‐Espino J.
Published: July 2010

Leaf rust, caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici, is an important disease of wheat (Triticum aestivum L.) worldwide. The Lr34 gene is known to confer durable resistance. We evaluated the effect of Lr34 on grain yield and other traits in the absence and presence of leaf rust. ‘Jupateco 73R’ and ‘Jupateco 73S’ (near‐isogenic reselections from the Mexican spring wheat cultivar ‘Jupateco 73’ for the presence and absence of Lr34, respectively) and 22 random inbred F6 lines, 11 with and 11 without Lr34 (derived from the cross ‘Jupateco 73R/Jupateco 73S’), were planted in replicated field trials during the 1992–1993 and 1993–1994 seasons in northwestern Mexico. The mean grain yield of Jupateco 73R was 5.9% lower (P < 0.05) than that of Jupateco 73S in protected plots in the 1992–1993 experiment. Significant reductions (P < 0.05) were also observed for biomass, kernels per spike and kernels m‐2. Significant (P < 0.01) reductions of 5% in mean grain yield and 3.7% in mean kernel weight were again evident in one of the two experiments sown during the 1993–1994 season. Comparison of grain yield in protected and non‐protected treatments indicated that though leaf rust could significantly (P < 0.01) reduce grain yield by approximately 15% in the presence of Lr34, the reductions in the absence of Lr34 were substantially higher and ranged between 42.5 to 84% depending on planting date and year. Reductions in all other traits were also significantly higher in the absence of Lr34. We conclude that although the presence of Lr34, which is linked with leaf tip necrosis of adult plants, may carry a slight yield penalty in some disease free environments, its use in leaf rust prone areas could provide substantial protection to grain yield and other traits.
Sites Regression and Shifted Multiplicative Model Clustering of Cultivar Trial Sites under Heterogeneity of Error Variances
Authors: Crossa José , Cornelius Paul L.
Published: July 2010

Previous papers have developed the shifted multiplicative model with one multiplieative term (SHMM1) as a model for clustering yield trial sites or cultivars into groups in which cultivar rank changes are statistically negligible. Properties of SHMM1 are proportionality of predicted cultivar differences within sites, and of site differences within cultivars. The latter constraint is relaxed if the sites regression model with one multiplicative term (SREG1) is used instead of SHMM1. Dendrograms for the two methods are identical, but SHMM and SREG analyses of clusters suggested by the dendrogram may lead to different conclusions concerning acceptability of a particular cluster. This study compared SREG clustering to SHMM clustering in two international maize (Zea mays L.) cultivar trials, when the data to which models were fitted were original unscaled cell means, and, as a way to cope with site to site heterogeneity of error variance, cell means scaled by dividing by the standard error of a cultivar mean within the particular site. Results of both trials confirmed our expectation that SREG clustering would occasionally allow clusters to merge which would not be statistically acceptable under SHMM analysis. This occurred at a cost of a modest increase in percentage and magnitude of significant crossover interactions within the clusters. Both trials exhibited significant site to site heterogeneity of error variances. Scaling of data resulted in more effective removal of significant rank‐change interactions from within clusters, provided that the test criterion was based on the assumption of heterogeneous variance. Besides occasionally allowing larger clusters, advantages for SREG clustering of sites are (i) all solutions (including constrained non‐crossover solutions) exist in closed form and (ii) the analysis of scaled data is equivalent to a weighted least squares analysis, neither of which holds for SHMM.
Selection for Spot Blotch Resistance in Four Spring Wheat Populations
Authors: Sharma R. C. , Dubin H. J. , Bhatta M. R. , Devkota R. N.
Published: July 2010

Spot blotch of wheat (Triticum aestivum L.), caused by Bipolaris sorokiniana (Sacc.) Shoem, is serious constraint in South Asia, and leading cultivars have low levels of resistance. The response to selection for low and high area under disease progress curve (AUDPC) of spot blotch in four wheat populations, involving different Chinese hexaploid parents with high level of resistance and a commercial cultivar moderately resistant to spot blotch, was investigated. Selections were made in the F3 generation for low and high AUDPC of spot blotch and selected progenies evaluated in a replicated field test in the F4 generation at Rampur, Nepal, in 1994. Selection in the F3 for low and high AUDPC was effective in identifying F4 lines with low and high AUDPC, respectively. Low AUDPC resulted in higher biomass and grain yield, higher harvest index, and 1000‐kernel weight. On average, the low AUDPC lines headed later than the high AUDPC lines. Realized heritability estimates for AUDPC were intermediate to high in magnitude (0.48 to 0.76). AUDPC was negatively correlated with biomass (r = −0.195 to −0.451), grain yield (r = −0.169 to −0.452), harvest index (r = −0.256 to −0.597), days to heading (r =−0.319 to −0.570), and 1000‐kernel weight (r = −0.322 to −0.530). Results indicate that selection for low AUDPC of spot blotch in segregating generations would be effective in identifying wheat lines with high levels of resistance and would have positive effects on other characters.
Nutritional Control of Soybean Seed Storage Protein
Authors: Paek Nam C. , Imsande John , Shoemaker Randy C. , Shibles Richard
Published: July 2010

There is interest in increasing the protein concentration of soybean [Glycine max (L.) Merr.] seed. Potentially, this could change its protein composition and perhaps its value as a livestock feed. Our objective was to examine the change in protein composition of soybean seed with change in protein concentration as influenced by nitrogen source supplied. ‘Harper’ soybean was grown in hydroponic culture and supplied with different nitrogen sources (KNO3, NH4NO3N2, urea) during pod filling. Protein quality was monitored as a function of soybean seed storage subunit composition. With N2 fixation as sole N source, the concentration of total seed protein decreased about 6%, storage protein 5%. Each seed storage protein subunit decreased, but the concentration of [β‐conglycinin, especially the sulfur‐poor [β‐subunit, decreased more than glycinin. Seed storage protein concentration was increased up to 4% by substituting reduced‐N for NO−3. The increased protein concentration resulted from a disproportionate increase of the β‐subunit of β‐conglycinin. The relative abundance of α‐ and α′‐subunits was not changed by N form. Thus, N form seems to control, at least in part, the relative portion of the β‐subunit of [β‐conglycinin, and consequently affects the 11S/7S ratio of seed storage protein. This change in composition with increased concentration diminishes the protein quality because the [β‐submit lacks sulfur‐amino acids. It is noteworthy that the concentration of glycinin remained constant while the total seed protein concentration increased. We think these variations in seed storage protein composition result from the relative abundance of S‐ and N‐metabolites available to developing soybean seed.
Change in Virulence of Wheat Curl Mite Detected on Tam 107 Wheat
Authors: Harvey T. L. , Martin T. J. , Seifers D. L. , Sloderbeck P. E.
Published: July 2010

Wheat streak mosaic is the most important wheat (Triticum aestivum L.) disease in western Kansas. The wheat cultivar TAM 107 has been resistant to the wheat curl mite (WCM, Aceria tosichella Keifer), which is the vector of wheat streak mosaic virus (WSMV) and as the most popular wheat cultivar in western Kansas has effectively reduced the incidence of the disease. In 1991, several observations indicated that the incidence of WSMV infection in TAM 107 was much heavier than usual. In 1992, a survey of 10 field collections of WCM showed that one collection from TAM 107 was virulent to that cultivar. In 1995, WCM collections from TAM 107 and ‘Karl’ (susceptible to WCM) were made from 14 western Kansas counties and tested for virulence to TAM 107. All collections of WCM obtained from TAM 107 were adapted to TAM 107, and nine of the 14 collections from Karl were adapted to TAM 107. The high incidence of a WCM strain virulent to TAM 107 may explain the increased losses to WSMV recently observed in that cultivar. TAM 107 probably cannot be relied on in the future to provide protection against WSMV in western Kansas. Lines derived from sources of resistance that are effective against WCM virulent to TAM 107 or that are resistant to WSMV are being advanced in wheat breeding programs and should be deployed in the field as soon as possible.
Megasporocyte Callose in Apomictic Buffelgrass, Kentucky Bluegrass, Pennisetum squamulatum Fresen, Tripsacum L., and Weeping Lovegrass
Authors: Peel Michael D. , Carman John G. , Leblanc Olivier
Published: July 2010

Callose, a β‐l,3‐glucan, is synthesized and deposited in the walls of megaspore mother cells (MMCs) of angiosperms that produce either normal monosporic (>90% of all angiosperm species) or bisporic embryo sacs. Such deposits are absent in angiosperms that produce tetrasporic embryo sacs and were recently shown to be absent in diplosporous Elymus rectisetus (Nees in Lehm.) A. Löve & Connor, Tripsacum L. spp., and Poa nemoralis L. We determined the extent of callose deposits in MMCs of diplosporous weeping lovegrass (Eragrostis curvula Schrad.), several additional diplosporous Tripsacum accessions and aposporous buffelgrass (Pennisetum ciliare (L.) Link), Kentucky bluegrass (Poa pratensis L.), and Pennisetum squamulatum Fresen. Callose deposition was studied in pistils cleared in an aqueous aniline blue clearing medium and observed by means of UV microscopy. Pistils cleared with conventional clearing media were studied by means of interference contrast microscopy. Some pistils were cleared and analyzed in one clearing medium and recleared and reanalyzed in the other. A callosic MMC was observed in only one of 376 appropriately staged pistils taken from diplosporous species. This pistil, one of 89 weeping lovegrass pistils studied, was probably facultatively sexual. An absence of callose during megasporogenesis may be characteristic of most types of diplospory. Though present, the distributions and quantities of callose observed in MMC walls of aposporous apomicts were erratically reduced, possibly as a result of early MMC abortion or early activation of nucellar initials. Callose deficiencies and vacuolization patterns support the following hypotheses: (i) apospory is caused by a moderately precocious gametophytization of nucellar cells, and (ii) bispory, tetraspory, and diplospory are caused by a moderately to extremely precocious gametophytization of the MMC that is nearly complete in the latter case and variably incomplete in the former two cases. Understanding how these precocious gametophytizations evolved and are regulated may be crucial to the eventual transfer of apomixis to major crop species and to its successful manipulation by breeders.
Antioxidant Enzyme and Compound Responses to Chilling Stress and their Combining Abilities in Differentially Sensitive Maize Hybrids
Authors: Hodges D. Mark , Andrews Christopher J. , Johnson Douglas A. , Hamilton Robert I.
Published: July 2010

Chilling sensitive species often have lower antioxidant capacities than do tolerant species. This study was conducted to determine if antioxidant capacities and carbohydrate concentrations would be useful in a proposed screening technique for chilling sensitivity in maize (Zea mays L.). Leaves of 12 maize hybrids exhibiting differential sensitivity to chilling were harvested at the third‐leaf stage under either (i) a constant 25°C control regime or (ii) the control regime plus a short‐term chilling shock of 11°C for 1 d prior to harvesting. Catalase (CAT; EC 1.11.1.6), monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and ascorbate peroxidase (ASPX; EC 1.11.1.11) activities were assessed. Carbohydrate levels were determined as general metabolic indicators of chilling stress. The chill/control ratios of CAT, MDHAR, and ASPX were lowest and concentrations of carbohydrates highest in the most chilling sensitive hybrids. Differences between hybrids in antioxidant capacities to detoxify toxic oxygen compounds may be important in differential chilling sensitivity. The higher chili/control ratios of carbohydrates in the sensitive hybrids after chilling indicated that their rate of assimilate utilization was reduced by the chilling treatment more so than those of the chilling tolerant hybrids. Activities of CAT, MDHAR, and ASPX and concentrations of carbohydrates would thus make excellent indicators of chilling stress in a screening technique for chilling sensitivity of maize.
Comparison of Morphological Development Indexes for Switchgrass and Bermudagrass
Authors: Sanderson M. A. , West C. P. , Moore K. J. , Stroup J. , Moravec J.
Published: July 2010

In 1994, the Crop Science Society of America (CSSA) appointed an ad hoc committee to study various developmental indexes for crops. As part of this committee's activity, our objective was to compare three developmental indexes for use with switchgrass (Panicum virgatum L.) and two indexes for use with bermudagrass [Cynodon dactylon (L.) Pers]. Two cultivars of switchgrass (Alamo and Cave‐in‐Rook at Stephenville, TX, and Kanlow and Cave‐in‐Rock at Ames, IA) were scored once or twice weekly during primary growth according to the Nebraska index, the Texas Agricultural Experiment Station (TAES) index, and the BBCH (European) uniform decimal code. Two hybrids of bermudagrass (Midland and Tifton‐44 at Fayetteville, AR, and Coastal and Tifton‐44 at Stephenville) were scored once or twice weekly during a spring and summer growth cycle according to the BBCH system and an index developed for bermudagrass (West index). The main difference among scales was that the Nebraska and TAES scales were developed for perennial grasses, whereas the BBCH index is a generic scale with some stage descriptors not applicable to perennial grasses. The indexes share several common stage descriptors, but with different decimal codes. For bermudagrass, the main limitation with the BBCH system was that it applied to grass crops having a well‐defined main stem and sideshoots (tillers) and a relatively uniform maturation of the shoots. The BBCH Principal Growth Stages 2 and 3 were difficult to reconcile with the West system, which does not define tillering, whereas subsequent principal stages are reconcilable with minor modifications. We conclude that the BBCH index would require substantial modification to adapt the system for perennial forage grasses.