bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Variation for Biomass and Residue Production in Lentil: II. Factors Determining Seed and Straw Yield
Authors: Kusmenoglu Ismail , Muehlbauer Fred J.
Published: July 2010

Understanding the influence of vegetative and reproductive traits in lentil (Lens culinaris Medik.) on biomass production and seed yield would facilitate cultivar improvement. The objectives of this study were (i) identify and evaluate the morphological changes that have taken place during past cultivar improvement efforts, and (ii) quantify the effect of rainfall on seed and straw production. Seven breeding lines and three checks were evaluated at Pullman and Farmington, WA, and Genesee, ID, from 1993 to 1995 for vegetative growth period (VGP), generative growth period (GGP), crop growth rate (CGR), seed growth rate (Sd.GR), straw growth rate (St.GR), and partitioning coefficients for seed (p) and straw (q). Results indicated that cultivar improvement efforts have achieved higher seed yields by (i) shorter generative and vegetative growth periods, (ii) greater rates of crop and seed growth, (iii) higher seed partitioning coefficients, and (iv) moderate response to rainfall. Greater straw yields have been achieved by (i) longer generative and vegetative growth periods, (ii) greater crop and straw growth rates, (iii) a higher straw partitioning coefficient, and (iv) greater response to rainfall. Simultaneous improvemenotf straw and seed yields is possible within existing lentil germplasm.
Inheritance and QTL Analysis of Field Resistance to Ashy Stem Blight in Common Bean
Authors: Miklas Phillip N. , Stone Valerie , Urrea Carlos A. , Johnson E. , Beaver James S.
Published: July 2010

Ashy stem blight [caused by Macrophomina phaseolina (Tassi) Goid.] can be a serious disease of common bean (Phaseolus vulgaris L.) under drought and high temperature conditions in some regions. The mode of inheritance of valuable sources of resistance is lacking. We studied inheritance of field resistance to ashy stem blight in a recombinant inbred population (‘Dorado’ × XAN 176) consisting of 119 FS:7 recombinant inbred lines (RILs) tested in replicated experiments across 2 yr. A score from 1 to 9 (no disease to severe disease) was used to measure disease reaction. Moderate HNs (0.53 and 0.57) and near‐normal frequency distribution of RILs for mean disease score each year indicated a lack of discrete segregation classes. The phenotypic variation across a subgroup composed of 79 RILs was further investigated with 165 randomly amplified polymorphic DNA (RAPD) markers by one‐way analyses of variance and interval mapping. Five quantitative trait loci (QTL), explaining 19, 15, 15, 13, and 13% of the phenotypic variation for disease score, were detected in 1993. Three of these QTL, explaining 15,12, and 12% of the variation in disease reaction, were detected in 1994. Multiple QTL regression models (P < 0.01) explained up to 47% (four loci) of the phenotypic variation for disease score in 1993 and 28% (three loci) in 1994. The five QTL, all derived from XAN 176, generally showed additive effects. These QTL‐linked RAPD markers may prove useful for indirect selection of field resistance to ashy stem blight derived from XAN 176.
Agronomic and Seed Traits of Soybean Lines Lacking Seed Lipoxygenases
Authors: Narvel James M. , Fehr Walter R. , Welke Grace A.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seeds contain three lipoxygenase isozymes that cause off‐flavors in soy protein‐containing foods. The use of lipoxygenase‐free soybean seed for food applications may be desirable. The objective of this study was to determine the effect of genetically eliminating the lipoxygenase isozymes on agronomic and seed traits of soybean. From the backcross of the three lipoxygenase‐null alleles lx1lx2lx3 into ‘IA2020’, 27 BC1F2‐derived lines lacking the three isozymes( triple‐null) and 27 BC1F2‐derived lines containing the three isozymes (normal) were identified. The lines were evaluated in a replicated test during 1996 at three locations in Iowa. There were significant differences (P < 0.01) among locations for all traits measured, except maturity. No differences (P > 0.05) were found between the mean performance of triple‐null and normal lines for seed yield, maturity, lodging resistance, seed weight, and seed protein content. Mean plant height of normal lines was greater (P < 0.01) than triple‐null lines by 4 cm and mean seed oil content of normal lines was greater (P < 0.01) than triple‐null lines by 3 g kg−1. It will be possible to develop seed lipoxygenase‐free soybean cultivars with desirable agronomic and seed characteristics.
Heterosis and Combining Ability for Callus Growth Rate in Rice
Authors: Kuroda Shigeru , Kato Hiroshi , Ikeda Ryoichi
Published: July 2010

To explain heterosis in rice (Oryza sativa L.) at the cellular level, we studied the inheritance of callus growth rate in seed‐derived calli from a 14‐by‐14 diallel cross that used four japonica, four javanica (the tropical type of japonica), and six indica cultivars. Callus growth rates were calculated from gains in fresh callus weight that were measured after 28 d of culture at 20, 28, 35, and 40°C in the dark. All F1 crosses between subspecies had significantly (P < 0.05) higher callus growth rates than the parental lines. The F1 crosses showed greater tolerance for low temperature than their parents. Analysis of variance of diallel crosses showed that additive and dominance effects on the callus growth rate were both significant (P < 0.01). Variances for general (GCA) and specific combining ability (SCA) callus growth rate were also highly significant. Among crosses between subspecies, japonica × indica showed the most positive SCA effects for callus growth rate at 28 and 35°C, while japonica × japonica and indica × indica showed negative SCA effects at 20 to 35°C. The magnitude of the SCA effects on hybrids at 28°C correlated significantly with that of plant growth in the field from a previous study (r = 0.867, 0.01 < P < 0.05, df = 4). Midparent heterosis for the callus growth rate was clearly positive and significant and was greatest in japonica × indica crosses in the combination groups at 28°C. Heterosis and SCA effects for this trait at 28°C were related to the genetic distance between parental subspecific groups.
Far‐Red Light Affects Photosynthate Allocation and Yield of Tomato over Red Mulch
Authors: Kasperbauer M. J. , Hunt P. G.
Published: July 2010

Plastic mulches are frequently used by both large‐ and small‐scale tomato (Lycopersicon esculentum Miller) growers to conserve water, control weeds, and keep fruit clean. We hypothesized that changing mulch color to reflect more red light (R) and a higher far‐red (FR) to R photon ratio (FR/R) would keep those benefits and improve tomato yield by altering phytochrome‐mediated regulation of photosynthate allocation. Photodegradable and nondegradable forms of red plastic mulch were developed to our specifications. Number, size, and total fruit produced over the red plastic mulches were compared with those over standard black plastic. Photodegradable red mulch (placed over a layer of black plastic) increased fruit yield while it was intact, but yield dropped to that of the black control after the red plastic degraded. Nondegradable red plastic resulted in greater yield. Early crop yield advantage of red mulch was evident whether it was placed directly over soil or over a layer of black plastic. We conclude that increased tomato yield over the new red plastic mulch was caused by reflection of FR to the growing plants and its subsequent phytochrome‐mediated regulation of photosynthate allocation to developing fruit.
Soybean Sulfur and Nitrogen Balance under Varying Levels of Available Sulfur
Authors: Sexton P. J. , Paek N. C. , Shibles Richard
Published: July 2010

Protein quality of soybean [Glycine max (L.) Merr.] seed could be enhanced by increasing the concentration of S‐containing amino acids. The N:S ratio of soybean seed tissue is an indicator of protein quality. The objective of this study was to compare N and S accumulation and distribution in the soybean plant under varying levels of S availability. Soil S levels were varied in two greenhouse trials and tissue S and N contents were monitored. A field experi~nent with 0 and 60 kg ha−1 applied S was also conducted. In the two greenhouse trials, seed yield, rate of dry matter increase, and rate of N accrual by shoots all increased at least five‐fold as S availability increased from less than 15 (zero added S) to 60 mg available S per plant, but showed little response to higher levels of S. Rate of S accrual was strongly related to S availability. In the field trial, there were no responses to added S. Leaf, pod, and seed tissue appeared to accumulate S in proteins, whereas, root and stem tissue appeared to accumulate S as sulfate. Harvest index values for S were consistently less than those for N, indicating S is not remobilized to seed as efficiently as is N. Seed S:N ratio was linearly related to the rate of S versus N accrual on a whole‐plant basis. We estimate that a 50% increase in the amount of S‐containing amino acids in soybean seed may require a 65 to 80% increase in S accrual by shoots to satisfy the increased demand for S.
Identification of Genistein, an Anticarcinogenic Compound, in the Edible Tubers of the American Groundnut (Apios americana Medikus)
Authors: Krishnan Hari B.
Published: July 2010

American groundnut (Apios americana Medikus) is a nitrogenfixing legume that produces edible tubers and seeds. Even though studies have been conducted on the quality of tuber storage compounds, very little is known about compounds that could have beneficial effects on human and animal health. The objective of this study was to investigate the presence of genistein in the tubers. The nodC gene of Rhizobium fredii Scholla and Elkan USDA191 that had been fused with β‐galactosidase was used to detect the presence of genistein in A. americana tubers. The flavonoids from A. americana tubers were purified by C18 reversed‐phase HPLC. The HPLC profile revealed nine UV absorbing peaks. Among them, Peaks 6 and 8 activated the nodC‐lacZ gene fusion about two fold, while the bulk of the inducing activity was associated with Peak 9. The compound in Peak 9 and authentic genistein standard had identical retention times. When A. americana tuber flavonoids were spiked with an authentic genistein standard, Peak 9 coeluted with genistein. In addition, a peak at m/z 271, corresponding to the protonated genistein, was found when the HPLC Peak 9 was analyzed by electrostaticspray mass spectrometry. The results of this present investigation indicate that A. americana tubers contain the isoflavone genistein. The discovery of genistein in A. americana tubers should rekindle interest in this legume as a food crop since genistein has been shown to reduce the incidence of various forms of cancer.
Cotton Responses to Shade at Different Growth Stages: Nonstructural Carbohydrate Composition
Authors: Zhao Duli , Oosterhuis Derrick
Published: July 2010

Photosynthetic irradiance is an important factor affecting cotton (Gossypium hirsutum L.) plant growth, development, lint yield, and fiber quality. A 2‐yr study was conducted to determine the effects of an 8‐d period of shade (63% reduction in photosynthetic photon flux density) at four growth stages [i.e., pinhead square (PHS), first flower (FF), peak flower (PF), and boll development (BD)] leaf photosynthesis, chlorophyll concentration, and nonstructural carbohydrate (hexose, sucrose, and starch) concentrations in leaves, floral bracts, and floral buds of field‐grown cotton plants. At all four growth stages, shade caused a 43 to 55% decrease in leaf photosynthetic rate, and a 14 (on a leaf area basis) or 73% (on a dry weight basis) increase in total chlorophyll concentration, but did not affect leaf dark respiration rate. Starch concentration in leaves and floral bracts decreased sharply under shade, whereas only minor changes in hexose concentration occurred. Shade at the FF and PF stages did not, whereas shade at the BD stage did decrease, the concentration of total nonstructural carbohydrate (TNC) in 20‐d‐old floral buds. Averaged over the four growth stages during the 2 yr, the TNC concentration of shaded cotton decreased 47 to 71% in the leaves, 37 to 48% in the bracts, and 5 to 20% in 20‐d‐old floral buds compared with unshaded control plants. Among the four growth stages, shade at the PF (1994) or BD (1993) stage caused the greatest decrease in leaf TNC concentration; shade at the BD stage resulted in the greatest decrease in the TNC concentrations of bracts and floral buds. Shade during plant reproductive growth significantly reduced leaf photosynthesis and TNC concentrations of field‐grown cotton.
Cell Membrane Thermostability and Whole‐Plant Heat Tolerance of Kentucky Bluegrass
Authors: Marcum Kenneth B.
Published: July 2010

Heat stress is often a major problem in C3 (cool‐season) turfgrasses during summer months, resulting in reduced turf quality and stand loss. Current germplasm screening for heat tolerance relies on field and whole‐plant techniques, which are often inefficient and insensitive due to environmental interactions. A rapid, accurate procedure allowing simultaneous screening of large numbers of genotypes is needed. In vitro cell membrane thermostability (CMT) has been determined for a number of plants. The objectives of this study were to determine if differences in CMT exist among cultivars of Kentucky bluegrass (Poa pratensis L.), and if CMT can predict whole‐plant heat tolerance of these cultivars. CMT was determined by subjecting leaf segments to progressive heat shock exposure times, and deriving cellular electrolyte leakage curves. Whole‐plant heat tolerance was determined by subjecting plants to 41°C day/34°C night at 95% relative humidity for 62 d (Study 1) and 47 d (Study 2) in controlled‐environment chambers. Relative percentage leaf firing and percentage shoot dry weight were determined weekly. CMT was negatively correlated with relative percentage leaf firing (r = −0.80) and positively with relative percentage shoot dry weight (r = 0.75), averaged over two experiments. CMT and whole‐plant heat tolerance used as indicators demonstrated that cultivars BM‐3 and Midnight were more heat tolerant than Lavang, Nugget, and Ryss. This is the first report showing that CMT can predict whole‐plant heat tolerance among turfgrass cultivars. Being rapid, accurate, and requiring little space, CMT may offer turfgrass breeders an ideal method for screening large numbers of genotypes for heat tolerance.
AFLP‐Based Genetic Diversity Assessment among Wheat Cultivars from the Pacific Northwest
Authors: Barrett B. A. , Kidwell K. K.
Published: July 2010

Assessing genetic diversity among adapted, elite germplasm may expedite crop improvement. The objectives of this study were to (i) assess genetic diversity among a representative sample of spring and winter wheat (Triticum aestivum L.) cultivars adapted to dryland production in the Pacific Northwest by amplified fragment length polymorphisms(AFLPs), and (ii) compare genetic diversity estimates (GDEs) generated by methylation sensitive and methylation insensitive restriction enzymes for AFLP analyses. Fifty‐four cultivars and two diploid relatives were included in the study. Sixteen AFLP primer pairs detected 229 polymorphic bands. Mean GDEs (0.51 and 0.58, respectively) detected by PsdI:MseI (methylation sensitive) and EcoRI:MseI (methylation insensitive) AFLP analyses were significantly different (P < 0.0001), indicating greater diversity was detected for methylated sequences. Mean GDEs, based on data from both restriction enzyme combinations, were highest (0.58) for spring vs. winter type pairwise comparisons, intermediate (0.53) within winter type, and lowest (0.49) within spring type. Cluster analysis, ordination analysis, and the analysis of molecular variance suggested genetic diversity among cultivars was hierarchically arranged as cultivars nested within market class, and market classes nested within growth habit. AFLP analysis is an efficient technology for assessing genetic diversity among wheat cultivars.
Introgression of Day‐Neutral Genes in Primitive Cotton Accessions: I. Genetic Variances and Correlations
Authors: McCarty J. C. , Jenkins J. N. , Zhu J.
Published: July 2010

Many of the primitive accessions of cotton, Gossypium hirsutum L., are photoperiodic and not readily useable by plant breeders. Five generations of day‐neutral progenies(F5, BC1F5, BC2F5, BC3F5, and BC4F5) derived from 16 accessions crossed to ‘Deltapine 16’ were evaluatedf or agronomic and fiber traits for 3 yr. Genetic variance components for each trait andc orrelation among these traits were studied. Variation of accessions generation was highly significant for all traits studied. Main effects for accessions and generations were significant; however, the magnitude was relatively small compared witht he interaction variation. The breeding merit of day‐neutral progenies should be evaluated according to specific accessions. Lint yield had significant but small positive phenotypic correlation with lint percentage, boil size, and 2.5% span length, but not with the other traits studied. Highly significant positive correlations were found for effects of accession, generation, and accession × generation between lint yield and lint percentage. With the use of multiple backcrosses to introgress day‐neutral genes in primitive cotton accessions large interaction can be expected between accession and backcross generation; therefore, specific generations should be evaluated for the trait of interest.
Inheritance of the Vernalization Response Determined by Doubled Haploids in Spring Oilseed Rape (Brassica napus L.)
Authors: Murphy L. A , Scarth R.
Published: July 2010

The presence of a vernalization requirement can delay floral initiation until the cold requirement of the plant has been satisfied. Breeders attempting to develop early‐maturing cultivars should be aware and have an understanding of the genetic basis of factors such as vernalization response to assess potential impact on their programs. The ability to generate doubled haploid (DH) lines from oilseed rape (Brassica napus) has led to the use of DH populations in genetic studies. The objective of this study was to determine the mode of inheritance of the vernalization response in spring B. napus with DH lines. A set of Fl‐derived DH lines from crosses between spring oilseed rape parent lines were evaluated for their response to vernalization. The use of DH lines allowed the exposure of the individuals of identical genotype to two differentreatments, vernalization and no vernalization. The vernalization treatment consisted of exposure of germinated seeds for 2 wk at 4°C. Seeds of the non‐vernalized treatment were germinated at 22°C. Comparison between treatments of the final leaf number on the main raceme (FLN) was used to assess the vernalization response. The results indicated that there is a gene for nonresponse to vernalization in the spring oilseed rape cultivar Karat. FLN offers a direct measure of vernalization response, since leaf initiation ceases when floral initiation begins.
Monosomic Alien Addition Lines Derived from Glycine max (L.) Merr. and G. tomentella Hayata: Production, Characterization, and Breeding Behavior
Authors: Singh Ram J. , Kollipara Krishna P. , Hymowitz Theodore
Published: July 2010

Utilization of exotic germplasm (16 wild perennial species of the subgenus Glycine Willd.) to broaden the genetic base of soybean [G. max (L.) Merr.] has been impeded because of extremely low intersubgeneric crossability. Our objective here is to report the production, identification, and breeding behavior of monosomic alien addition lines (MAALs) each with 2n = 40 chromosomes of soybean and one chromosome from G. tomentella Hayata (accession PI 483218, 2n = 78). Glycine tomentella contains genes controlling several economically useful traits such as resistance to soybean rust (Phakopsora pachyrhizi Sydow) and soybean cyst nematode (Heterodera glycines Ichinohe) and tolerance to salt and drought. We have isolated 287 plants with 2n = 41 chromosomes from BC3 and BC4 progenies. On the basis of distinguishing morphological features, these lines were grouped into 22 MAALs and were designated as MT‐I to MT‐XXII. MT denotes max and tomentella. The addition of an extra chromosome of G. tomentella to the 2n soybean complement modified several morphological traits including flowering habit, plant height, degree of pubescence, seed fertility, number of seed per pod and plant, pod and seed color, and seed yield. The female transmission of an extra G. tomentella chromosome in MAALs averaged 36.5% and male transmission averaged 11.7%. This study sets a stage whereby the germplasm treasure harbored in exotic germplasm, the wild perennial relatives of the soybean, which was unexplored and not utilizable in the past, can now be reached by geneticists and plant breeders.
Variability in Protein Composition of Pea Seed Studied by FPLC and Multidimensional Analysis
Authors: Baniel A. , Bertrand D. , Lelion A. , Guéguen J.
Published: July 2010

The nutritional and the functional quality of pea (Pisum sativum L.) seed depends primarily on their protein content and composition. For breeding as well as for industrial uses, efficient methods for analyzing protein composition are of great importance. In the present work, a procedure combining fast protein liquid chromatography and statistical analysis was developed for routine determination of protein composition in pea seed. Chromatographic conditions optimized the resolution and repeatability of peak areas and peak retention times sufficiently for statistical analysis. The analytical procedure was a practical compromise between the time of chromatographic separation and the repeatability of the fractionation. The method utilizes the variability among pea cultivars and the repeatability of their chromatographic profiles and can characterize seed protein composition with sufficient precision to distinguish cultivars.
Waterlogging Effects on Growth and Yield Components in Late‐Planted Soybean
Authors: Linkemer Geoffrey , Board James E. , Musgrave Mary E.
Published: July 2010

A major agronomic problem in the southeastern USA is low yield of late‐planted soybean [Glycine max (L.) Merr.]. This problem is aggravated by the adverse effect of waterlogging on crop growth. Our objectives were to identify soybean growth stages sensitive to waterlogging; identify yield components and physiological parameters explaining yield losses induced by waterlogging; and determine the extent of yield losses induced by waterlogging under natural field conditions. Greenhouse and field studies were conducted during 1993 and 1994 near Baton Rouge, LA, (30°N Lat) on a Commerce silt loam. Waterlogging tolerance was assessed in cultivar Centennial (Maturity Group VI) at three vegetative and five reproductive growth stages by maintaining the water level at the soil surface in a greenhouse study. Using the same cultivar, we evaluated the effect of drainage in the field for late‐planted soybean. Rain episodes determined the timing of waterlogging; redox potential and oxygen concentration of the soil were used to quantify the intensity of waterlogging stress. Results of the greenhouse study indicated that the early vegetative period (V2) and the early reproductive stages (R1, R3, and R5) were most sensitive to waterlogging. Three to 5 cm of rain per day falling on poorly drained soil was sufficient to reduce crop growth rate, resulting in a yield decline from 2453 to 1550 kg ha −1. Yield loss in both field and greenhouse studies was induced primarily by decreased pod production resulting from fewer pods per reproductive node. In conclusion, waterlogging was determined to be an important stress for late‐planted soybean in high rainfall areas such as the Gulf Coast Region.
Root Archutecture Affects Nitrate Leaching from Bentgrass Turf
Authors: Bowman D. C. , Devitt D. A. , Engelke M. C. , Rufty T. W.
Published: July 2010

Understanding the determinants of nitrate leaching should improve nitrogen uptake efficiency and reduce ground water contamination. This column lysimeter study examined the effect of root architecture on NO3 leaching from two genotypes of creeping bentgrass (Agrostis palustris Huds.) differing in rooting characteristics. Ammonium nitrate was applied (50 kg N ha−1) and the columns were irrigated with 1, 2 or 3 cm day−1 (Exp. 1) or irrigation was delayed 1, 3 or 5 d (Exp. 2). In Exp. 1, leachate NO3 concentrations and total N leached from the shallow‐rooted (SR) genotype were approximately twice those from the deep‐rooted (DR) genotype. An average of 38 and 18% of the applied N leached from the SR and DR genotypes, respectively. Cumulative leaching losses increased with irrigation depth. In Exp. 2, NO3 leaching was reduced 90% or more by increasing the time period for immobilization from 1 to 5 d. Recovery of applied 15N in the tissue averaged 87% after 2 mo. Absorption of NO3 and NH4 was measured in nutrient solution culture. The SR genotype had significantly higher uptake rates than DR for both forms of N, expressed on a root weight basis. Collectively these data indicate that a deep‐rooted turfgrass absorbs N more efficiently than a shallowrooted turf, reducing the concentration and total amount of NO3 leached. The effect is apparently not due to differences in N uptake, but rather to rooting patterns. Environmental conditions and management practices that affect rooting depth and density may thus affect N nutrition and NO3 leaching.
Genetic Diversity among Soybean Plant Introductions and North American Germplasm
Authors: Kisha T. J. , Diers B. W. , Hoyt J. M. , Sneller C. H.
Published: July 2010

Elite North American soybean [Glycine max (L.) Merr.] germplasm derives from a limited number of ancestors. Knowledge of genetic diversity patterns in elite germplasm and plant introductions (PIs) is needed to diversity efficiently the elite gene pool. The objective of this research was to study diversity among five gene pools consisting of either ancestral lines (AN), elite lines from northern (NE) or southern (SE) U.S. production areas, and PIs with a northern or southern maturity. The relationship among the pools was evaluated by analysis of 53 restriction fragment length polymorphism (RFLP) loci and by coefficient of parentage (CP). Clustering of lines on the basis of RFLP data was generally consistent with their prior pool classification, though AN lines were dispersed. Greater diversity was noted within the NE than the SE gene pool. The ancestors Mandarin‐Ottawa and PI257435 appeared to be major sources of diversity in the elite gene pool. Diversity among gene pools was primarily due to gene frequency differences and not from the presence or absence of unique alleles. Much of the pattern of diversity in the elite population can be explained by molecular diversity among a few major ancestors, the relationship of these ancestors to the elite lines, and the geographic origin of the ancestors. The correlation of CP and SMC estimates of genetic similarity was 0.61. Selection or drift appeared to have influenced the correlation. The reported diversity pattern may be a guide for finding and incorporating new genes into elite North American soybean.
Heritability of Crown Traits in Alfalfa
Authors: Márquez‐Ortiz J. J. , Lamb J. F. S. , Johnson L. D. , Barnes D. K. , Stucker R. E.
Published: July 2010

The crown is the transitional structure connecting the shoots and roots of alfalfa (Medicago sativa L.) and is associated with the persistence and productivity of the crop. Information on the inheritance of alfalfa crown morpbological traits could facilitate the genetic modification of crown morphology. Our objectives were to estimate heritability of five crown traits and to determine the effect of plant spacing and location on the expression of crown traits. Progenies from design II matings and diallels were evaluated at two Minnesota locations. In October 1991, plants were dug and evaluated for crown depth, crown width, number of crown stems, crown stem width, and number of crown buds. Plant‐spacing effects were determined by evaluating single plants at the ends of the plot separately from plants in the middle. Progenies responded similarly to the extra growing space at the ends of the plots. General combining ability (GCA) effects were important for determining heritability for crown stem width, while both GCA and specific combining ability (SAC) were important for crown width and number of crown stems. Heritability estimates for these crown traits ranged from 22 to 80%. No or few genetic effects were found for number of crown buds and crown depth. Results suggest that selection programs for crown stem width and number of crown stems with uniform plant spacing in one location would be successful. Selection programs for crown width may have limited success, and selection for number of crown buds and crown depth would not be effective.
Genetics and Cytology of a New Male‐Sterile, Female‐Fertile Soybean Mutant
Authors: Ilarslan H. , Horner H. T. , Palmer R. G.
Published: July 2010

Mutants affecting male sterility have potential applications in breeding methodology studies and for commercialization of hybrids. Male‐sterile, female‐fertile soybean [Glycine max (L.) Merr.] plants were observed in an F2 entry. Our objectives were to determine the inheritance, linkage, and allelism of the A94‐JB‐124 male‐sterile, female‐fertile mutant, and to conduct a detailed comparative microscopic study of microsporogenesis and microgametogenesis of fertile and sterile plants. The A94‐JB‐124 male‐sterile, female‐fertile mutant is a single recessive gene, allelic to ms6, and is linked to the W1 (flower color locus) with 4.3 ± 0.3% recombination value based on 988 F2 plants in the couplinglinkage phase. A comparative microscopic study of microsporogenesis and microgametogeucsis of fertile and sterile plants was conducted. The expression of the male‐sterile gene is associated with rapid degenerative changes both in the tapetum and the parietal layer. These changes are initiated at the late sporogenous mass stage. The A94‐JB‐124 mutant was assigned gene symbol Ms6 ms6 (Ames 2) and Genetic Type Collection number T354H. The T295H Ms6 ms6 mutant is now designated Ms6 ms6 (Ames 1). T354H will be useful in the Coscgregation Method to produce hybrid soybean seed.
Resistance to Common Bacterial Blight amongPhaseolus Species and Common Bean Improvement
Authors: Singh Shree P. , Muñoz Carlos G.
Published: July 2010

Common bean (Phaseolus vulgaris L.) is highly susceptible to common bacterial blight (CBB), caused by Xanthomonas campestris pv. phaseoli (Smith) Dye. High levels of cultivar resistance would minimize yield losses, reduce bactericide use and production costs, and facilitate integrated disease‐and‐crop management and the production and distribution of pathogen‐free seed. We aimed to (i) assess the levels of CBB resistance of different Phaseolus species in the tropics, (ii) determine the CBB reaction of resistant cultivars and advanced breeding lines, and (iii) report on CBB resistance of lines developed from P. vulgaris × P. acutifolius (tepary bean) hybridization and gene pyramiding at CIAT. Between 1994 and 1998, we evaluated, in the field, 162 accessions of tepary, scarlet runner (P. coccineus), lima (P. lunatus), and common beans, 119 CBB‐resistant cultivars and advanced breeding lines of common bean, and six lines recently developed by interspecific hybridization and gene pyramiding. For inoculation, we used aspersion, surgical blades, and/or multiple needles. The highest levels (scores of 1.2–2.0) of CBB resistance were found in P. acutifolius accessions, G40029 and G40156, followed by P. lunatus (scores of 4.2–6.2), P. coccineus (scores of 4.8–5.5), and P. vulgaris (scores of 4.5–6.4). Resistance available in P. coccineus and P. vulgaris landraces has already been transferred to common bean. But resistance transferred from P. acutifolius was much lower (scores of 3.8–4.5) than those available. Gene pyramiding produced lines with high CBB resistance (scores of 1.5–2.4), and is thus, a suitable method for developing CBB‐resistant cultivars of different market dasses.
Detection of Epistasis for Protein and Oil Contents and Oil Quality Parameters in Peanut
Authors: Upadhyaya Hari D. , Nigam Shyam N.
Published: July 2010

To improve nutritional quality of peanut (Arachis hypogaea L.), it is necessary to know the importance of genetic effects. Epistasis is not considered in most genetic models. In the presence of epistasis, estimates of additive and dominance variation are biased to an unknown extent. This may affect progress of a breeding program by causing inappropriate breeding methods to be chosen. The objectives of this study were to determine the significance of epistasis in inheritance of protein and oil contents and oil quality parameters, and to estimate additive and dominance variances for the traits not influenced by epistasis. Three testers, Chico (L1), ICGV8 6300 (L2), and their F1 hybrid (L3), were each crossed to 15 cultigens. The experiment was conducted in the 1992‐1993 postrainy and 1993 rainy environments at the ICRISATC Center, Patancheru, India. Characters studied were protein, oil, eight fatty acid contents, and five derived parameters. The deviations, cultigen × L1 + cultigen × L2 − 2 cultigen × L3, were tested to detect epistasis. Environment interacted mores strongly with epistatic gene action than with additive or dominant gene action. Epistasis affected the expression of 11 traits in both environments. The additive × additive epistasis was detected for oleic acid in both environments. Additive gene action was detected for eicosenoic and polyunsaturated/saturated fatty acids (P/S) ratio in the rainy environment. Dominant gene action was detected for P/S in the rainy and for eicosenoic in both environments indicating incomplete dominance for these traits.
Winter Wheat Responses to Bird Cherry‐Oat Aphids and Barley Yellow Dwarf Virus Infection
Authors: Riedell Walter E. , Kieckhefer Robert W. , Haley Scott D. , Langham Marie A. C , Evenson Paul D.
Published: July 2010

Grain yield loss caused by bird cherry‐oat aphid (Rhopalosiphum padi L.) infestation and barley yellow dwarf virus (BYDV) infection may result from direct damage to the winter wheat (Triticum aestivum L.) crop as well as from reduced crop tolerance to stress environments. This greenhouse study measured the effects of R. padi infestation, BYDV infection, or a combination of R. padi plus BYDV on plant height, date of anthesis, yield, and yield components of four winter wheat varieties (‘Roughrider’, ‘Norstar’, ‘TAM 107’, and ‘Vona’) in the absence of additional environmental stresses. Treatments were applied at the two‐leaf growth stage. Early in the pre‐vernalization growth period, R. padi treatment (alone or in combination with BYDV) reduced plant height to about 55 to 60% of the control plant height while BYDY treated plants were about 90% of control. During the post‐vernalization growth period, plant heights attained about 90% of control in the R. padi treatment, to about 80% of control in the BYDV treatment and to about 70% of control in the R. padi+ BYDV treatment. Dates of anthesis were later in the R. padi+BYDV treatments than in the R. padi treatments for Norstar, Roughrider, and Vona but not for TAM 107. Individual kernel weights in the BYDV and R. padi+BYDV treatments were less than control or R. padi treatments for Norstar, TAM 107, and Vona but not for Roughrider. Control or R. padi‐treated plants had a greater number of fertile heads than plants given the BYDV or R. padi+BYDV treatments. Grain yield was strongly associated with kernel number per plant. The number of kernels per plant was reduced 19% by the R. padi treatment, 36% by the BYDV treatment, and 50% by the R. padi+BYDV treatment. Grain yield was reduced 21% by the R. padi treatment, 46% by the BYDV treatment, and 58% by the R. padi+BYDV treatment. With the exception of date of anthesis and individual kernel weight, there were no significant treatment by variety interactions for plant height, grain yield, and yield components. We conclude that R. padi infestation and BYDV infection caused significant yield reductions and that the varieties tested had little difference in their responses to these treatments in the absence of additional environmental stress.
Sustainable Crop Production: Definition and Methodological Approach for Assessing and Implementing Sustainability
Authors: Lewandowski I. , Härdtlein M. , Kaltschmitt M.
Published: July 2010

A method for assessing and implementing sustainable crop production is needed to give practical relevance to the frequently used term “sustainable agriculture”. The objective of this paper is to present such a theoretical procedure. Therefore the terms “sustainability” and “sustainable crop production” are discussed and defined. On the basis of the definitions, an eight‐step procedure for assessing and implementing sustainable crop production is outlined. The steps are (1) identify emissions and other releases linked to different crop production practices, (2) trace each different release from its source (the crop management practice) to its sinks (i.e., agroecosystems and other ecosystems or components of ecosystems directly or indirectly affected by these releases), (3) select indicators that adequately describe the condition of the ecosystem affected directly or indirectly by crop production practices, (4) determine threshold values for the selected ecosystem indicators (i.e., values which should not be exceeded if irreversible changes in the affected ecosystems are to be avoided), (5) transpose the ecosystem threshold values to the farm level by retracing the impact pathways (from Step 2) backward to crop production itself, (6) derive farm‐level indicators that point to separate or combined agronomic practices that could cause irreversible changes in affected ecosystems, (7) determine farm‐level threshold values for management‐induced releases on the basis of ecosystem level threshold values, and (8) identify production schemes that adhere to the framework set by the farm‐level thresholds. From these production schemes the farmer can select those most in line with his available resources and objectives.
Forage Yields of Alfalfa Populations Derived from Parents selected on the Basis of Molecular Marker Diversity
Authors: Kidwell K. K. , Hartweck L. M. , Yandell B. S. , Crump P. M. , Brummer J. E. , Moutray J. , Osborn T. C.
Published: July 2010

It is important to know if forage yields of alfalfa (Medicago sativa L.) cultivars could be improved by using a subset of genetically diverse parents selected from a larger population of parents for a synthetic cuitivar. We used restriction fragment length polymorphisms to assess the level of genetic diversity among 93 alfalfa genotypes previously selected as parents for a potential commercial synthetic cuitivar. On the basis of average pairwise genetic distances between genotypes, four synthetic populations (samples) were developed with 2, 4, 8, 12, 16, or 24 parents selected for genetic dissimilarity (DIS) or similarity (SIM). Resulting synthetic populations were evaluated for forage yield in replicated field trials at three locations for 2 yr. Forage yields of populations with low numbers of parents were highly variable among samples, and as number of parents increased, genetic diversity levels and yield variation decreased. No significant difference (P > 0.05) was detected between forage yields of DIS and SIM groups averaged over parent number and samples; however, yield variation among samples within parent number of DIS and SIM groups was highly significant (P < 0.0001). The SIM group had more sample variation than did the DIS group, and more SIM than DIS populations were among the lower yielding populations. The lack of significant differences between the forage yields of DIS and SIM populations may be due to linkage equilibrium in the population used for selecting parents and the inability to target heterozygosity to specific genome regions affecting yield.
Plant Density‐Dependent Variation in Marketable Yield, Fruit Biomass, and Marketable Fraction in Watermelon
Authors: Duthie James A. , Shrefler James W. , Roberts B. Warren , Edelson Jonathan V.
Published: July 2010

An improved knowledge of effects of density of plants on yield of watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] would help efforts to determine optimal planting density and to anticipate the economic impact of factors that reduce density. We conducted a series of experiments to determine plant density‐dependent rates of change of marketable yield, fruit biomass, and marketable fraction in watermelon cultivar Sugar Baby. In single‐row plots, at least 3.7 m apart, density varied from 0.4 to 4.1 plants m2 (1000‐9000 plants ha−1). Marketable yield per unit area increased at linear rates of 0.5 to 1.1 Mg ha−1 per thousand plants ha−1 because fruit biomass increased at linear rates of 1.1 to 3.2 Mg ha−1 per thousand plants ha−1. The linear effect of plant density explained more than 90% of the increase in fruit biomass per unit area in most experiments. Density did not affect the fraction of fruit biomass that was of marketable quality. The linear rate of change in the marketable fraction did not exceed 3% per 1000 plants ha−1 on average in any experiment. Per plant, marketable yield and fruit biomass, respectively, decreased at curvilinear rates of 0.8 to 8.6 and 1.4 to 10.8 (kg plant−1 per thousand plants ha−1) (plants ha−1)2. These decreases were consistent with a constraint due to intraspecific competition. Our results support the hypothesis that efficiency of commercial production of watermelon could be increased by increasing planting densities.
Mathematical Characterization of Leaf Shape and Area of Maize Hybrids
Authors: Stewart D. W. , Dwyer L. M.
Published: July 2010

Measurement or estimation of leaf area is essential for simulation of light interception and photosynthate production. Leaf shape is an important factor in describing how leaf area is distributed in the canopy. When defined mathematically, leaf shape can be used to calculate leaf area of individual leaves as well as how leaf area varies along the length of the leaf. The objective of this study was to evaluate several methods used to describe leaf shape (the variation in leaf width with distance from the ligule or stem) and to analyze variations in shape coefficients. Measurements of leaf width every 10 cm along fully expanded leaves were made over a number of years, sites, plant densities, and nitrogen treatments with normal, leafy, and reducedstature hybrids. These measurements were fitted to a number of polynomial equations which related leaf width to distance from the ligule. Leaf area was calculated by integrating these equations. In all, 10 methods were used to calculate areas of individual leaves, but one method, based on a second order polynomial equation which could easily be integrated for total leaf area or area along the leaf, was chosen as a standard. All other methods were compared with this standard and leaf area estimates were found to be similar (R2 > 0.98). Planimeter measurements of individual leaf area also compared well with estimates using the standard method (R2 = 0.96) hut planimeter measurements had more scatter than estimated values. The most useful equation was the second order polynomial with two dimensionless shape coefficients using maximum leaf width and total length. Integrating this equation produced the well known length × maximum width × alpha equation for calculating leaf area where alpha was 0.743 for all hybrids and 0.734 for normal hybrids. A method was developed to use this equation for calculating leaf area as a function of leaf length.
Fallow Management and Nitrogen Fertilizer Influence Winter Wheat Kernel Hardness
Authors: Lyon Drew J. , Shelton David R.
Published: July 2010

Kernel hardness is an important grain attribute for wheat (Triticum aestivurn L.) quality and marketing in the USA. The objective of this study was to characterize the effects of fallow management — moldboard plow (plow), subtillage (subtill), and no‐tillage (no‐till) — and N fertilizer (0 and 45 kg N ha−1) on winter wheat kernel hardness, as measured by the Single Kernel Characterization System (SKCS). Rainfed field studies were conducted with ‘Siouxland’ hard red winter wheat from 1995 to 1997 on an Alliance silt loam (fine‐silty, mixed, mesic Aridic Argiustoll) near Sidney, NE. In 1995 and 1996, the kernel hardness index was increased from a 2‐yr average of 46.0 to 55.2 by the addition of 45 kg N ha−1, but N fertilizer treatment had no effect on kernel hardness in 1997 when the average kernel hardness index was 72.9. The effect of fallow management on kernel hardness varied from year to year. Kernel hardness was positively correlated with grain protein in 1995 (r = 0.93) and 1996 (r = 0.94), but no meaningful relationship was observed in 1997. Half of the grain samples analyzed by the SKCS in 1995 and 1996 were classified as either soft or mixed wheat. This study suggests that kernel hardness is affected by a number of factors beyond genetics including N management, tillage system, pest infestations, environment, and their interaction. Growers may find that meeting proposed new grain standards is more complex than merely selecting the right cultivar.
Kernel Number Determination in Maize
Authors: Andrade Fernando H. , Vega Claudia , Uhart Sergio , Cirilo Alfredo , Cantarero Marcelo , Valentinuz Oscar
Published: July 2010

Maize (Zea mays L.) grain yield is closely associated with kernel number at harvest. This yield component is a function of the physiological condition of the crop at a critical period bracketing silking. The objectives of this study were to analyze for that critical period by assessing (i) the relationship between final kernel number and plant or crop growth rate, (ii) the partitioning of dry matter to reproductive structures, and (iii) the effect of duration of this period on kernel set. Kernel number (per plant and per unit area) and growth rates of crops, plants, and ears were measured in 12 field experiments conducted at Balcarce, Argentina, from 1989 to 1996 with hybrid Dekalb 636. Experimental sources of variation included shading, plant density, sowing date, and night temperature. Shading and night temperature treatments were established during a 31‐d period bracketing silking. In one of the density experiments, plant growth rate was estimated for individual plants by means of a non‐destructive methodology based on correlations between dry matter and morphometric measurements. The relationship between kernel number per plant and plant growth rate was curvilinear with threshold values of approximately 1 g d−1 for kernel set and 6 g d−1 for prolificacy. At high and at low plant growth rates during the period bracketing silking, Dekalb 636 set a low number of kernels per unit of plant growth rate. This effect was explained by limited partitioning of biomass to reproductive structures during that period. When duration of the critical period for kernel set was considered by expressing plant growth rate in thermal units, a better estimation of kernel number per plant was obtained.