bluuebunny/crossref_metadata_2025 huggingface dataset:
Cell Wall Composition of Alfalfa Stems at Similar Morphological Stages and Chronological Age During Spring Growth and Summer Regrowth
Authors: Sanderson Matt A. , Wedin W. F.
Published: July 2010

Summer regrowth of alfalfa (Medicago sativa L.) is often more mature and consequently lower in herbage quality than spring‐grown alfalfa of similar chronological age. Alfalfa herbage samples taken at comparable maturity stages have similar quality. Whether cell wall composition is the same, however, is not known. We compared the cellulose, hemicellulose (HC), and lignin (CWL) concentrations in cell walls (neutral detergent fiber) of alfalfa stems at similar chronological ages and maturity stages. Alfalfa was harvested every 10 d during the spring and summer growth periods of 1984 and 1985. Maturity of alfalfa at each harvest was classified on a phenological scale of 0 to 9, and a mean stage number was calculated. Summer‐grown stems of alfalfa were more mature and therefore had a greater concentration of cell walls that were more lignified than spring‐grown stems of the same chronological age. To compare the cell wall composition of alfalfa stems grown in different environments at specific morphological stages, concentrations of cell wall, cellulose, HC, and CWL were regressed on mean stage number. Stem cell wall concentrations [R2 = 0.88, root error mean square (REMS) = 43 g kg−1] and CWL (R2 = 0.71, REMS = 13 g kg−1) increased quadratically, whereas cellulose (r2 = 0.52, REMS = 21 g kg−1) decreased linearly with increasing maturity stage. Cell wall hemicellulose was not related to maturity stage. Stem cell wall concentration and CWL were closely related to alfalfa maturity and could be explained well with a maturity index, whereas cell wall cellulose and HC were not well related to maturity but may have been related to other factors not accounted for in the maturity index.
Responses of Two‐, Three‐, and Four‐Component Barley Mixtures to a Variable Pathogen Population
Authors: McDonald B. A. , Allard R. W. , Webster R. K.
Published: July 2010

Cultivar mixtures have been suggested as a means to control foliar diseases in small grains, but little information is available on how to choose component lines for use in cultivar mixtures. This 3‐yr study tested the ability of two‐, three‐, and four‐component barley (Hordeum vulgare L.) mixtures to control scald disease caused by the fungus Rhynchosporium secalis (Oud) Davis. The mixtures were composed of lines from the parents of Composite Cross II (CCII), a naturally evolving barley population, and from the 45th generation of CCII. The lines differed in resistance or susceptibility to four diagnostic pathotypes of the scald fungus. The results indicate that some barley lines, when grown in mixture, interact to reduce or increase incidence of scald. Lines from the 45th generation of CCII interacted to reduce incidence of scald more often than parental lines of CCII. The largest reductions in sca.ld were observed in mixtures containing lines that were susceptible when grown in pure stand. Genes for resistance to R. secalis were deployed singly in mixtures and also pyramided into single lines. Differences between these methods of gene deployment were nonsignificant statistically. Some two‐component mixtures made up of one resistant and one susceptible line and some three‐component mixtures made up of two susceptible components and one resistant component had no more disease than the resistant component of the mixture grown alone. The results were interpreted as indicating that cultivar mixtures offer an effective strategy for controlling damage due to R. secalis.
Alfalfa Persistence and Yield in High Density Stands
Authors: Rowe D. E.
Published: July 2010

The impact of competition on plant persistence and plot yield has not been well characterized in alfalfa (Medicago sativa L.). In an even aged stand the effects of density, and thus competition, at three levels were elucidated with respect to rate of plant mortality and changes in the plant and plot yields. The genetic materials used were three semidormant alfalfa populations with very different percentages. The replicated experimental plots, each with 483 plants, were space planted in the field, an Orr loam (fine‐loamy, mixed, mesic Aridic Argixeroll), to stand 10, 17.3, and 30 cm on centers. The relative densities were in a ratio of 9:3:1 per unit area. Over 2 yr of data were collected on yield and plant loss, and expressed in terms of the lowest density to adjust for environmental changes over the growing seasons and to isolate genetic differences among the populations from the effects of density. The rates of thinning were linear over the life of the experiment, but different for each density. The yield, when measured on a per plant basis, increased faster than that explained by the rate of thinning for the highest density, and the yield per plot had a net gain for both the medium and high density plantings in all three populations. Thus, it appeared taht competition eliminated some of the less vigorous genotypes; this suggested that selection through competition could be effcetive in a space planted nursery with plants at 17.3 cm on centers or less, and if the trait called competitiveness is heritable.
Sources of Resistance in Maize to Kernel Infection by Aspergillus flavus in the Field
Authors: Scott Gene E. , Zummo Natale
Published: July 2010

Infection of maize, Zea mays L., kernels by Aspergillus flavus Link ex Fr. and subsequent aflatoxin production can be an extremely serious problem; especially in maize grown in the southeastern part of the USA. Maize genotypes that resist attack by this fungus are desperately needed. The objective of these studies was to identify maize inbreds with resistance to kernel infection by A. flavus. Inbreds were inoculated with a pinbar and evaluated for percentage of kernels internally infected by this fungus. Nearly a 5‐fold difference (6 to 30%) among the inbreds tested over a 2‐yr period was found. Five of the inbreds selected as resistant, and five as susceptible, were subsequently tested using a pinbar and two needle inoculation techniques. The pinbar inoculation technique gave the highest level of kernel infection and the greatest separation of the inbreds into their previously classified groups, but all methods of inoculation showed that the two groups of inbreds differed significantly from each other. In a test with 50 inbreds inoculated by the side‐needle inoculation technique, percentage of A. flavus infected kernels ranged from 4 to 62. Resistant (Mp313E, SC54, and Mo18W) and susceptible (T202, T216, and SC212M) inbreds averaged 10 and 44% infected kernels, respectively.
Selenium Accumulation and Selenium‐Salt Cotolerance in Five Grass Species
Authors: Wu Lin , Huang Zhang‐Zhi , Burau Richard G.
Published: July 2010

Selenium is essential for animal health but is toxic at high concentrations. The objective of this study was to determine the pattern of Se accumulation and Se‐salt (NaCl) cotolerance in forage and turfgrass species in order to explore the potential of using these grass species for land and water renovation, and for forage or seed production on land contaminated with Se and/or salt. Five grass species including tall fescue (Festuca arandinaceae Schred.), crested wheatgrass (Agropyron desertorum Fisch.), buffalograss [Buchloe dactyloides (Nutt.) Engelm.], seaside bentgrass (Agrostis stolonifera L.), and bermudagrass [Cynodon dactylon (L.) Pers., Syn.] were studied. Selenium uptake and Se and salt tolerance were examined under nutrient solution culture conditions. Distinct differences in both Se and salt tolerance were detected among the five species under 2 mg Se L−1 or 200 mM NaCl, but no direct association between Se and salt tolerance was found. The species with greater tolerance accumulated less Se thand id the less tolerant species. Tall fescue displayed considerable tolerance under 2 mg Se L−1 or 100 mM salt treatment and accumulated up to 400 μg Se g−1 dry wt. in the plant tissue without growth reduction. Combine Se and salt treatment revealed that Se uptake was increased by addition of salt in the culture solution. However, Na uptake was not significantly affected by the presence of Se. Tall fescue presents a promising potential for use on soils with relatively high levels of salinity and Se.
Heterosis in Upland Cotton. II. Relationship of Leaf Area to Plant Photosynthesis
Authors: Wells Randy , Meredith William R. , Williford J. Ray
Published: July 2010

Heterosis results in a generalized increase in plant growth, yet the involvement of photosynthesis in this response is not well understood. We examined the relationship between leaf area (LA) and canopy photosynthesis of F1, cotton (Gossypium hirsutum L.) hybrids and their parents. The effect of heterosis on leaf apparent photosynthesis (AP) was also studied. Three established cultivars and three F1, hybrid progeny were examined in two field environments. Hybrid progeny had significantly greater leaf area index and canopy photosynthesis rates in both environments during the earliest plant growth stages studied. At the same time, the hybrids and their parent showed no differences in single leaf AP efficiency. Total dry matter was significantly correlated with LA (r = 0.85**, significant at the 0.01 probability level). All measurements during early growth found AP per plant to be significantly associated to LA per plant. Later in growth, the association between AP per plant and LA per plant weakened after mutual shading of leaves had developed. The data indicate that hybrids produced generally bigger plants that intercepted more light than their parents, and hence had increased photosynthesis rates on a per plant basis. Factors that affect early plant growth can result in associated changes in AP per plant and accentuate the need for prudent crop management during early development.
Response to Selection for Time of Flowering in Soybean
Authors: Nelson Randall L.
Published: July 2010

Previous research demonstrated that the duration of the seedfilling period (SFP) in soybean [Glycine max (L.) Merr.) could be genetically modified. Long SFP was associated with early flowering. The objectives of this research were to evaluate the effectiveness of divergent selection for time of flowering while maintaining similar dates of maturity and to determine the influence of such selection on other agronomic characteristics. Genetic male sterility was used to intermate populations selected for time of flowering from a single cross. Pedigree selection was practiced to identify lines with similar maturity and extremes in flowering date. Data from 22 lines were collected on the center two rows of four‐row plots and included dates of R1, R5, R7, and R8, lodging, plant height, and seed yield. In each of 2 yr, the experiment was replicated twice at each of two locations. Selected lines flowered significantly earlier or later than the commercial cultivars in the experiment. Lines with similar time to maturity differed by as much as 24 d in time to flowering. The time from R1 to R5 was a nearly constant proportion of the time from Rl to R7. Because of this relationship changes in duration of SFP were much smaller than changes in time to flowering. The mean SFP (RS–R7) for the six earliest‐flowering lines was 5 d greater than the mean SFP for the six latest‐flowering lines. One line significantly exceeded the SFP and seed yield of ‘Williams’, the higher yielding parent.
Field Evaluation of Early Maturing Soybean Genotypes for Differential Adaptation to Low Night Temperatures
Authors: Seddigh Majid , Jolliff Gary D. , Orf James H.
Published: July 2010

Night temperature has a strong effect on soybean [Glycine max (L.) Merr.] productivity. Successful development of soybean genotypes tolerant to low night temperatures depends on the identification of genetic variation for this trait. Field experiments were conducted at Oregon State University and the University of Minnesota in 1984, 1985, and 1986 to assess genetic variation for adaptation to low night temperature within twenty soybean genotypes of maturity groups (MG) 000,00, and 0 of different origins. All genotypes were grown at Corvallis, OR, and St. Paul, MN, which have mean minimum night temperatures of approximately 10 and 16°C, respectively, during the summer months. Mean maximum temperatures for the same period of the year are similar for the two locations. Both locations are also at about the same latitude (ca. 45° N). Indices for adaptation to cool nights were calculated for seed yield, above ground dry matter (excluding leaves), apparent harvest index, seed weight, and days to maturity. These indices were calculated based on the performance of each genotype for a given trait in Corvallis relative to the mean performance of all genotypes within the same maturity group in Corvallis, as compared to the same value calculated for St. Paul. Genetic variations for adaptation to cool nights were identified for all the traits under investigation. In terms of seed yield, ‘Fiskeby V’ (MG 000), ‘Caloria’ and ‘McCall’ (MG 00), and ‘Dawson’ and ‘Evans’ (MG 0) appeared to be most adapted to low night temperatures, while ‘Maple Presto’ (MG 000), ‘Heike 3’ and ‘Maple Arrow’ (MG 00), and PI 290119 and ‘Ozzie’ (MG 0) seemed to be least adapted to cool nights. It also appeared that different characteristics contributed to the differential adaptation of genotypes to cool nights for seed yield. This information should be useful in breeding programs to develop soybean cultivars less sensitive to variations in night temperature.
Volatile Monoterpenes Collected from the Air Surrounding Flower Buds of Seven Cotton Genotypes
Authors: Chang J. F. , Benedict J. H. , Payne T. L. , Camp B. J.
Published: July 2010

Some volatile monoterpenes released by cotton (Gossypium hirsutum L.) are olfactory cues to boll weevils (Anthonomous grandis Boheman) and some parasites. However, literature examined showed no studies that described or compared the monoterpene odor of different cotton genotypes at different stages of growth or in different environments. The objective of our study was to determine the monoterpene composition of the air surrounding flower buds of five cotton genotypes (‘CAMD‐E’, ‘SP‐37’, ‘STV‐213’, STV‐213 glandless, RDC‐102 glandless, HG‐1, and LEBO) grown under normal agronomic practices at College Station and Corpus Christ!, TX. The monoterpenes were collected from the air surrounding excised buds of each genotype with a Porapak Q effluvial collection system. The quantity of each monoterpene was determined with capillary column gas chromatography utilizing purified standards. The most abundant monoterpenes collected were α‐pinene, β‐pinene, β‐myrcene, d‐limonene, and β‐ocimene. The total quantity of these five monoterpenes was greater for buds of glanded genotypes than for buds of glandless genotypes. Ratios of the five monoterpenes provided a relatively characteristic chemical profile for each genotype. Quantities and ratios of the five monoterpenes collected from buds were dynamic in that they fluctuated with the age of the cotton plant and the environment in which the plants were grown. These results indicate that the five monoterpenes composing, in part, the odor of commercial upland cotton, may differ spatially, temporally, and genetically. This suggests that researchers attempting to identify attractive plant odors should simultaneously compare insect responses and plant odor composition.
Near‐Isogenic Lines—A Potential Resource in the Integration of Conventional and Molecular Marker Linkage Maps
Authors: Muehlbauer G. J. , Specht J. E. , Thomas‐Compton M. A. , Staswick P. E. , Bernard R. L.
Published: July 2010

Near‐isogenic lines (NILs) have been developed in a number crop species via the backcross breeding method. These NILs possess remnant donor parent (DP) DNA, some of which is present in the chromosomal segment linked to and surrounding the introgressed marker. If this DP‐derived DNA contains molecular marker loci (i.e., isozyme variants or restriction fragment length polymorphisms) for which a recurrent parent (RP) and DP possessed allelic contrasts, then DP‐derived molecular alleles may still be present in an NIL and could be detected a posteriori by molecular genetic analysis of specific trio sets of RP/NIL/DP lines. Given this proposition, our objective was to provide a theoretical basis for evaluating the results of such analyses. Using equations derived by previous workers, we calculated that about four of 100 randomly chosen DP‐derived molecular markers would be expected to be retained in a BC5S1 NIL constructed in a hypothetical species with 20 chromosomes of equivalent 50 centimorgan (cM) genetic map lengths. Of these four markers, two or three would be expected to be located on the introgressed marker chromosome. This suggests that a near‐isogenic gene mapping technique would provide a means for subsetting molecular and introgressed markers into presumptive linkage groups. Such a priori information would make traditional methods of integrating both marker types into a single linkage map a much more efficient undertaking. A combined linkage map would be a valuable resource relative to the goal of eventually cloning some of the conventional markers of scientific interest or economic value.
Genetic Variation for Dinitrogen Fixation in Soybean of Maturity Group 00 and 0
Authors: Neuhausen S. L. , Graham P. H. , Orf J. H.
Published: July 2010

Because soybean [Glycine max (L.) Merr.] are generally assumed to be active in N, fixation, their genetic variation in this trait has not been studied to the extent found in other crop legumes. In the few studies undertaken, local cultivars of limited genetic diversity have dominated. This study considered the genetic variation in N2 fixation of 21 Group 00 and 27 Group 0 soybean plant introductions over 2 yr at two Minnesota locations [Hubbard loamy sand (sandy, mixed Udorthetic Haploborall) and Waukegan silt loam (fine‐silty over sandy, mixed, mesic Typic Hapludoll)] differing in available soil N. Traits measured were total N2 fixed (estimated by the difference method using a Clay Maturity Group 0 non‐nodulating line), shoot dry weight at R2 and R6, plant N concentration at R6, the proportion of plant N derived from fixation, and seed yield. All traits except N concentration were positively and highly correlated with total N2 fixed, and therefore have the potential to be used as indirect estimates of N2 fixation for field screening under low to moderate soil N conditions. There were significant differences within both maturity groups for all traits. Some Group 00 lines fixed more N, than ‘McCall’ and as much N, as high N2‐fixing Maturity Group 0 lines. There was sufficient genetic variation to suggest that breeding for improved N2 fixation is feasible in both maturity groups.
Differential Responses of Landrace and Improved Spring Wheat Genotypes to Stress Environments
Authors: Ehdaie B. , Waines J. G. , Hall A. E.
Published: July 2010

Drought and heat stress are major environmental factors reducing grain production of rainfed wheat (Triticum aestivum L.) in semiarid regions. The objective of this research was to identify bread wheats with improved adaptation to hot, dry environments. Field studies were conducted to measure effects of terminal drought and heat stress on duration of developmental phases, grain yield, and yield related traits of day‐length insensitive spring wheats. Fifteen genotypes, including lines from landraces of southwestern Iran and improved cultivars from Iran and California, were grown in a nonstress and three artificially imposed stress environments at Moreno Valley, CA, in 1986. Genotype ✕ environment interactions were significant for grain yield and its components. Stress susceptibility of each genotype was estimated using a calculated index based on grain yield. Landrace genotypes and improved cultivars that were evaluated exhibited a wide range in stress susceptibility and adaptation to stress environments. Landrace genotypes and cultivars did not vary for mean stress‐susceptibility index values. Landrace genotypes generally had lower yield potential than the cultivars. The stress‐susceptibility index identified some genotypes that did not have outstanding yield performance per se in stress environments due to low yield potential and others that had high average yield in stress conditions. Stress susceptibility and yield potential were not associated, indicating that they may be independent components which both contribute to adaptation to stress environments. The stress‐susceptibility index was negatively correlated with number of grains per head, grain weight, grain yield, and harvest index under stress conditions, indicating selection for these characters in stress environments might result in decreased susceptibility to stress.
Genetic Control of Cold Hardiness and Vernalization Requirement in Winter Wheat
Authors: Brule‐Babel A. L. , Fowler D. B.
Published: July 2010

A high level of cold hardiness is essential to ensure consistent overwintering of wheat (Triticum aestlvum L.) in the Northern Great Plains region of North America. Consequently, a clear understanding of the genetic control of cold hardiness would facilitate plant breeding efforts directed at cultivar improvement for this area. Although several genetic studies have been conducted, there is not a general consensus on the mode of gene action controlling the expression of cold hardiness in wheat. This study used one spring and four winter cultivars representing a wide range of cold hardiness potential to investigate the mode of inheritance and interaction of cold hardiness, determined in a controlled environment that allowed for maximum expression of cold hardiness potential, and vernalization requirement in wheat. Differences in growth habit between parental cultivars were controlled by the Vrn1 gene. Cold hardiness, estimated as the temperature at which 50% of the plant population was killed (LT5o), was controlled by genes with either dominant or additive effects. At least one dominant gene was associated with cold hardiness differences between spring and winter wheat, while genes with mainly additive effects determined differences in cold hardiness among cultivars with the winter growth habit. Broad sense heritability estimates for LT5o in the controlled environment considered ranged from 0 to 88% with most estimates exceeding 50%. In the F2‐derived F3 generation, hardy transgressive segregates were most common in crosses between relatively nonhardy cultivars, but no segregates were significantly hardier than the hardiest parental cultivar. Lack of a vernalization requirement did not hinder the development of cold hardiness; however, distribution of F2‐derived F3 lines provided evidence of possible genetic linkage or pleiotropism between the gene segregating for growth habit and a gene or genes controlling cold hardiness.
Interrelationships among and Repeatability of Several Stability Statistics Estimated from International Maize Trials
Authors: Pham H. N. , Kang M. S.
Published: July 2010

Importance and implications of genotype‐by‐environment interaction are well known to breeders and geneticists. Several methods of measuring stability of performance of genotypes across environments have been developed. Some of these methods have been compared empirically and statistically. The purpose of this investigation was to study rank correlations among Eberhart and Russells regression coefficient (bi‐ER) and deviation from regression (sd21); Shuklas σ21, s21, and bi‐Sh; CVi; and S2i statistics. The data used for calculating these statistics were obtained from five international maize (Zea mays L.) trials. Trial 1 involved 14 genotypes tested at 39 locations in 21 countries, trial 2 involved 23 genotypes tested at 46 locations in 27 countries, trial 3 involved 16 genotypes tested at 23 locations in 13 countries, trial 4 involved 18 genotypes tested at 25 locations in 15 countries, and trial 5 involved 12 genotypes tested at 17 locations in 10 countries. The statistic sd2i was highly rank correlated with σ2i and s2i, but not with other statistics. The bi‐Sh and bi — ER statistics were highly correlated (rank) with each other as well as with S2i. None of the statistics was consistently well correlated with mean yield. Stability statistics were also calculated by grouping locations for a trial into high‐yield (top 50%) and low‐yield (bottom 50%) environments. Repeatability of all statistics between the two groups was generally negligible. Repeatability was also negligible between statistics estimated from each of two randomly chosen subsets of environments and from four randomly chosen subsets of environments. The high‐yield environments were characterized by relatively low CVi and the low‐yield environments by relatively high CVi.
Partitioning and Mobilization of Photoassimilate in Alfalfa Subjected to Water Deficits
Authors: Hall M. H. , Sheaffer C. C. , Heichel G. H.
Published: July 2010

Faster regrowth of a stressed alfalfa (Medicago sativa L.) crop compared to an unstressed crop after rewatering has been reported. The bases of this compensatory response are unknown, but they may be important to understanding adaptation to water stress and to developing crop water management strategies. Our objective was to determine the effect of stress induced by water deficit on photoassimilate partitioning and the utilization of stored assimilates during regrowth of alfalfa. Field and greenhouse experiments were conducted using cultivars differing in winterhardiness. Plants were subjected to water stress (plant water potential [ψW > −1.5 MPa), pulse‐labeled with 14CO2, and sampled following 0, 1, 14, 21, and 28‐d translocation periods. Following the 14‐d sampling, herbage was harvested and water stress was removed. Cultivars contrasting in winterhardiness responded similarly to water stress. Stressed and control plants (ψW > −1.0 MPa) contained similar amounts of radiocarbon per unit mass of herbage at the onset of the translocation period. Water stress reduced herbage dry mass and did not alter root dry mass compared to the control. Stressed plant roots contained 73 and 114% more total plant radioactivity (TPR) than the control at the 1 and 14‐d translocation periods, respectively. Water stress significantly increased root starch and TPR percentage in the starch fraction, but had much smaller effects on root soluble‐sugar concentration and TPR percentage of the root sugar fraction. Herbage regrowth mass following harvest and rewatering of the waterstressed plants was similar to that of the control. Compared to the control, water‐stressed alfalfa has greater total nonstructural carbohydrates in the roots, apparently due to increased photoassimilate partitioning to the roots. However, the greater root carbohydrate concentrations did not result in compensatory herbage regrowth following rewatering.
Seed Coat Regulation of Soybean Seed Imbibition
Authors: McDonald M. B. , Vertucci C. W. , Roos E. E.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seeds are prone to imbibitional injury, which may culminate in significant economic losses. This study was designed to investigate the regulation of soybean seed imbibition by the seed coat. The intact seed coat delayed water uptake in the embryonic axis, cotyledons, and whole seed during the first 8 h soaking. The seed coat also assisted in tangential as well as radial displacement of water to the embryo. Scanning electron micrographs revealed a seed coat‐derived radicle pocket surrounding the radicle tip as well as hourglass cells in the seed coat, which decreased in size away from the hilum. The function of the radicle pocket and hour glass cells of the seed coat may be associated with water storage surrounding the embryonic axis. This is substantiated by the large water‐holding capacity of the seed coat compared to its fresh weight. Isolated seed coats absorbed 3.8 times their fresh weight in water. These studies ascribe a significant role to the seed coat in regulating embryo moisture uptake. Initially, the seed coat retards water uptake and/or governs the direction of water penetration to the embryo and eventually serves as a reservoir of water for the hydrating axis.
Legume Compatibility of Reed Canarygrass Clones Related to Agronomic and Other Morphological Traits
Authors: Jones T. A. , Carlson I. T. , Buxton D. R.
Published: July 2010

Legume compatibility, the ability of a forage grass genotype to persist in a legume mixture without losing the legume stand, is needed in genetic materials intended for use in perennial grass‐legume mixtures, but limited information exists about appropriate selection criteria for forage grass compatibility with legumes. Data on nine agronomic and morphological traits of 14 reed canarygrass (Phalaris arundinacea L.) clones grown alone were used to explain their compatibility with alfalfa (Medicago sativa L.) or with birdsfoot trefoil (Lotus corniculatus L.) in binary mixtures subjected to a hay management. A second objective was to choose traits to use as components of a selection index for legume compatibility. Data on the nine traits of the 14 clones grown alone were summarized by principal component analysis. The nine first principal components were then reorganized into three uncorrelated factors, each of which described a different combination of principal components. Clones with high Factor I scores exhibited some combination of high dry‐matter yield (DMY), high tiller weight, early maturity, and height. Clones with high Factor 2 scores exhibited some combination of high DMY, high tiller density, high leaf area per ground area, and low rhizomatous spreading ability. Clones with high Factor 3 scores exhibited some combination of high specific leaf weight, low leaf area per ground area, and erectness of leaves. Factors 1 and 2 were equally important in describing the variability among the 14 clones, and Factor 3 was about 30% less important. Factors 1 and 2 often explained variability for reed canarygrass DMY and legume concentration in alfalfa and birdsfoot trefoil mixtures, but Factor 3 was never significant (P > 0.10). Selection on a spaced‐plant basis for higher DMY, early maturity, increased height, higher tiller density, and lower rhizomatous spreading ability should improve the legume compatibility of reed canarygrass in legume‐dominated stands managed for hay production.
Relationships among Charcoal Rot Infection, Yield, and Stability Estimates in Soybean Blends
Authors: Bowen C. R. , Schapaugh W. T.
Published: July 2010

Charcoal rot [Macrophomina phaseolina (Tassi) Goid] of soybean [Glycine max (L.) Merr.] commonly affects plants grown in the western midwest of the USA. No control measures have been reported. This study measured the effects of cultivar blends and rates of planting on charcoal rot infection and agronomic traits to determine if blends provide a greater protection against the disease and broader adaptation to environments. Six blends and four pure lines in maturity groups III and IV were tested in replicated plots across eight locations. Measurements taken on each plot included seed yield, height, lodging, plant population, and amount of charcoal rot infection. The relationship of these traits with stability estimates were considered. Reducing planting rate from 30 seeds m−1 (387 500 seeds ha−1) to 20 seeds m−1 (258 000 seeds ha−1) significantly lowered infection levels without reducing yield. Stage of reproductive growth was associated linearly with infection level. There was no significant genotype effect for infection when stage of reproductive growth was used as a covariate. Infection levels were correlated with response (bi), relative performance over environments. Response and biological estimates of stability were significantly correlated with one another. Deviations from response, r2, and ecovalance were also significantly correlated. The positive association of growth stage and infection suggests planting full‐season cultivars as a method of reducing charcoal rot. There was no benefit in blending pure lines either in increased yield or decreased charcoal rot infection.
Evaluation of Field Dry‐Down Rates in Early Maize
Authors: Cross H. Z. , Kabir K. M.
Published: July 2010

Field drying of maize (Zea mays L.) is a little‐understood process that greatly influences production costs. This field research was conducted to evaluate ear drying rates of hybrids, to study the breeding potential of parental lines at different drying stages, and to interrelate plant and ear characteristics with rates and stages of drying. Yield, ear moisture, test weight, ears per plant, kernel depth, kernel rows per ear, ear length, and shelling ratio were measured at 11 environments for a late‐maturing diallel set and nine environments for an early maturing diallel set of hybrids. Within each diallel set the individual hybrid moisture contents were regressed against an environmental index (El) to estimate each hybrid's relative rate of moisture loss (RML) and to predict its moisture content at Els of 500 and 200 g kg−1. Phenotypic correlation coefficients (PR) and correlations among general combining ability (GCA) effects (GCAR) were computed for pairs of traits by using hybrid means or GCA effects over environments. Hybrids and inbred GCAs differed significantly for all eight traits in both diallel sets. Mean moisture contents of the 10 hybrids with the lowest predicted moisture at an El of 200 were 14.3 and 5.4 g kg−1 lower than those of the 10 hybrids with the lowest predicted moisture at 500 El for the late and early sets, respectively. The RMLs were higher for the 10‐hybrid groups differed in GCA effects for RMLs, but inbreds with large GCA effects for fast RML did not necessarily have large GCA effects for low moisture when averaged over all environments. The RMLs of hybrids in the late diallel set were negatively correlated with grain yield (r = −0.37*), and there was a significant positive correlation between RML and ear moisture (r = 0.35*). The RML was negatively correlated with kernel depth (r = −0.30*), kernel rows per ear (r = −0.34*), and shelling ratio (r = −0.47*) for the early diallel set, and with ear length (r = −0.42*) for the late diallel set. Test weight was negatively correlated with predicted moisture contents at both 200 (r = −0.71**) and 500 Els (r = −0.59**) for the early diallel but not for the late diallel set. Evaluation of hybrids at very high Els would not identify the same low moisture hybrids as evaluation at low Els; selection for both low moisture and fast RMLs might be more effective than considering either character alone.
Response of Soybean to Air Temperature and Carbon Dioxide Concentration
Authors: Baker J. T. , Allen L. H. , Boote K. J. , Jones P. , Jones J. W.
Published: July 2010

Documented increases in global atmospheric CO2 concentration have stimulated interest in the direct effects of CO2 on plant growth and yield as well as the interactive effects of CO2 with other major climatic variables. This study was conducted to determine the effects and interactions of CO2 concentration and air temperature on the development, growth, total nonstructural carbohydrate (TNC), and final seed yield of soybean [Glycine max (L.) Merr., cv. Bragg] grown season‐long in naturally lit, controlled‐environment chambers. Day/night air temperatures of 26/19, 31/24, and 36/29 °C were maintained in CO2 treatments of 330 and 660 μmol CO2 mol−1 air. Both CO2 enrichment and increasing air temperature decreased main stem plastochron interval, while increasing air temperature increased final main stem node number. Leaf area and above‐ground biomass increased with CO2 enrichment and with temperature from 26/19 °C to 31/24 °C. The nonlinear increase with temperature in leaf area, aboveground biomass, and plastochron interval was attributed to the highest temperature treatment being near or above the optimum for soybean growth and development. Seed yield increased with CO2 enrichment due mainly to an increase in seed number rather than weight per seed. Individual seed weight decreased, while seed number increased with increasing temperature. Leaflet TNC displayed large diurnal variations, while stem TNC was relatively stable throughout the day. Stem TNC was less affected by CO2 than by temperature treatment and decreased with increasing temperature. These results indicate that the response of soybean to elevated CO2 concentration is highly temperature dependent.
Determinate‐ and Indeterminate‐Type Soybean Cultivar Responses to Pattern, Density, and Planting Date
Authors: Parvez A. Q. , Gardner F. P. , Boote K. J.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed yield is influenced by planting date, pattern, and density of seeding, but cultivars differing in growth habit may vary in response to cultural treatments. Narrow‐row compared to conventional wide‐row plantings have consistently produced higher seed yields in the northern USA, where early maturity groups (MG) and indeterminate (INDT) types are commonly used. Positive responses to narrow rows have been less consistent in the southern USA, where late MG and determinate (DT) cultivars are common. Therefore, we hypothesize that this disparity in seed yield response to narrow‐row culture between the two areas is due to inherent differences in DT‐ and INDT‐type canopies resulting from their growth habits. This study, conducted in Gainesville, FL (29 ° 38′N) in 1984 and 1985, employed ‘Duocrop’ (INDT) and ‘Kirby’ (DT), May and July planting dates, 0.91‐, 0.61‐, and 0.30‐m interrow spacings, and 0.18‐ and 0.08‐m intrarow spacings in a Randomized Complete Block (RCB) design. Node and pod numbers, leaf area index (LAI), crop growth rate (CGR), total biomass, and seed yields were significantly increased (per unit land area) with increasing plant population density (PPD) up to a certain PPD, depending on spatial arrangement. The greatest seed yield of both INDT and DT types was from the May planting, narrow‐row culture (0.30 m), and high PPD, but response to PPD was confounded with squareness (ratio of intra‐ to interrow distance among plants) of planting pattern. High PPD (18 to 42 plants m−2 and high squareness values gave higher seed yields than combinations of lower PPDs and lower squareness values. We conclude that seed yield of both DT and INDT soybean in subtropical latitudes is optimized by May seeding, high PPD (40 plants m−2), and use of square planting patterns as approximated by narrow‐row culture.
Effects of Selection for Sugarbeet Purity Components on Quality and Sucrose Extractions
Authors: Smith G. A. , Martin S. S.
Published: July 2010

Soluble nonsucrose constituents in extracted sugarbeet juice are a major concern to sugar processors because they impede crystallization and thus lower extraction of sucrose. Selection response for nonsucrose root extract chemical constituents known to affect sucrose recovery in sugarbeet (Beta vulgaris L.) was determined in a heterogeneous population. The objectives of the research were to determine the direct effects of cyclic selection for specific root extract chemicals and the indirect effects of this selection on other purity determining chemicals. Two cycles of selection for high and low Na+, K+, and amino N were used to develop populations, which were then compared to their common parental population in 3 yr of field testing. Significant population mean shifts for extract chemical composition occurred in the newly synthesized populations developed by high or low selection. Selection for reduced Na+ (one of the three chemical constituents previously identified as important to juice quality) significantly increased purity and extractable sucrose. The effect of selection on other nonsucrose chemicals was often dramatic and not predictable, although a strong positive association was detected between Na+ and CI−. Realized heritability estimates were 0.23, 0.66, and 0.81 for Na+, K+, and amino N, respectively.
Influence of Water Stress on Grain Yield Response to Recurrent Selection in Maize
Authors: Johnson S. S. , Geadelmann J. L.
Published: July 2010

Substantial yield reductions in maize (Zea mays L.) can be attributed to short‐duration drought in rainfed production areas. The objectives of this study were to investigate the effects of moisture stress in selection environments on response to mass and full‐sib recurrent selection and yield stability when selected materials were evaluated in environments with different levels of moisture stress. Five cycles of mass and full‐sib recurrent selection for grain yield were applied to population AS‐A under irrigated and dryland conditions on sandy textured soils. Selected cycles were evaluated as populations per se, S1 bulks, and in testcross combinations in 21 environments that included low, variable, and high moisture stress trials. Selection responses in populations and stability parameters for all materials were estimated. Under irrigated conditions, mass selection (MI) and full‐sib selection (FI), and full‐sib selection under dryland conditions (FNI) resulted in gains in AS‐A of 10.2, 11.0, and 5.8% per cycle, respectively. Mass selection under dryland conditions (MNI) did not result in significant gains per cycle except high moisture stress environments. Selection increased grain yield mainly by increasing responsiveness under low or variable moisture stress. The relative performance of S1 bulks and testcrosses were similar to relative performance of corresponding populations per se. On average, selection for grain yield under irrigated conditions gave results superior to those obtained from selection under dryland conditions. Selection under irrigation was as effective as selection under dryland conditions for increasing yield in moisture‐stressed environments and resulted in greater responsiveness of selected populations to favorable environments.
Genetics of Antibiosis Resistance to Mexican Bean Beetle in Soybean
Authors: Rufener G. K. , St. Martin S. K. , Cooper R. L. , Hammond R. B.
Published: July 2010

A larval antibiosis screening technique was applied to three soybean [Glycine max (L.) Merr.] populations to determine the inheritance of resistance to Mexican bean beetle [Epilachna varivestis (Mulsant)]. The F1, F2, and F3 generations (five F3 plants per F2 plant) of crosses between ‘Williams’ (susceptible) and L76‐0049, L78‐608, and L76‐0328 (resistant) were screened along with the parents. Mean weight of surviving larvae after 10 d of feeding on detached leaves was used as the measure of antibiosis. The resistance of F1 plants was intermediate to that of their parents. Data from the F1 of Williams ✕ L76‐0049 and Williams ✕ L76‐0328 indicated a small degree of dominance for resistance. The distributions of F2 and F3 phenotypes were continuous and unimodal. Skewness toward susceptibility occurred in Williams ✕ L76‐0328, but symmetry was evident in the other crosses. Heritability estimates (single F2 plant basis) ranged from 0.33 to 0.48 when calculated from F3 data, and from 0.11 to 0.22 when calculated from the covariance of F2 plants and their F3 progeny. Estimates of heritability derived from F2 and parental data were larger but had large standard errors. Gene number estimates by the method of moments, and frequency of recovery of parental phenotypes suggested that the number of segregating resistance loci was small. Provided selection was no more intense than 2.5%, expected genetic gain from selection among individual F2 plants was greater if a large number of plants were screened with a single determination per plant than if one‐half or one‐third that number were screened with two or three determinations per plant, respectively.
Source‐Sink Alterations Affect the Number of Cells in Soybean Cotyledons
Authors: Egli D. B. , Ramseur E. L. , Zhen‐wen Yu , Sullivan C. H.
Published: July 2010

The ability of an individual soybean [Glycine max (L.) Merr.] seed to utilize assimilate is an important part of the yield production process. Cotyledon cell number is a major determinant of genetic differences in seed growth rate. Experiments were conducted in the field and greenhouse with ‘McCall’, ‘Williams’, and ‘York’ cultivars to determine if source‐sink alterations would affect cotyledon cell number. Source‐sink alteration treatments (66% defoliation, 80% depodding, and 63% insolation reduction) were applied when tagged fruits were 20 to 25 mm long. Seeds from the tagged fruits were harvested at maturity and cotyledon cells were counted. Defoliation or shading reduced cotyledon cell number by 21 to 55% for McCall and York in the greenhouse and Williams in the field. Depodding increased cotyledon cell number by 26 to 102%. Cotyledon growth rates in an in vitro culture system increased with increasing sucrose concentrations and reached a maximum at 100 to 200 mM. Cotyledon growth rates in vitro with saturating levels of sucrose and asparagine were closely correlated with cotyledon cell number across treatments and genotypes. The data indicate that cotyledon cell number in soybean is influenced by the physiological environment during the cell division phase of seed development and that both cotyledon cell number and assimilate supply are important in determining seed growth rate.
Agronomic Performance of Spring Wheat Isolines Differing for Daylength Response
Authors: Marshall L. , Busch R. , Cholick F. , Edwards I. , Frohberg R.
Published: July 2010

Spring wheat (Triticum aestivum L.) can be either daylength sensitive or insensitive. Sensitive wheat require long days for timely flowering, whereas insensitive wheat mature normally even in short days. The objective of this study was to compare near‐isogenic daylength insensitive and sensitive hard red spring wheat lines to determine whether insensitivity had adverse effects on agronomic traits and grain protein. Eleven pairs of phenotypically diverse hard red spring wheat lines near isogenic for daylength response were evaluated in 25 environments in the upper Midwest. The grain yield for insensitive lines of all pairs was the same as or higher than for the sensitive lines, averaged over all environments. Yield differences between paired insensitive and sensitive lines varied for specific environments, but a general yield disadvantage for insensitive lines was not observed in any environment. Insensitive lines tended to outyield their sensitive counterparts in environments with lower mean yields or shorter grain fill periods. The insensitive lines were earlier in heading than the sensitive lines for most but not all pairs. Grain protein content for insensitive lines was the same as or lower than for sensitive lines, but selection of insensitive lines with adequate protein should not be difficult. The incorporation of insensitivity appears to result in genotypes generally well adapted to the upper Midwest, and may have beneficial effects on some agronomic traits.