bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Response of Leaf Photosynthesis and Canopy Radiation Use Efficiency in Field‐Grown Maize and Sorghum
Authors: Muchow R. C. , Sinclair T. R.
Published: July 2010

The grain yielding capability of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] is dependent on the capacity of the crop to assimilate CO2. Carbon dioxide assimilation can be measured directly at the leaf level (CA) and indirectly at the canopy levels by determining radiation use efficiency (RUE). Since leaf N content per unit leaf area (LN) was expected to influence both of these measures of CO2 assimilation, the primary objective of this study was to obtain field data on CA and RUE in response to differing LN induced by varying the amount of applied N fertilizer. The CA was most responsive to LN at low values of LN, but there was no difference between the species in the hyperbolic relationship between CA and LN. Similarly, RUE increased with LN, but maximum RUE and LN values were higher in maize than in sorghum. In maize maximum RUE was 1.7 g MJ‐1 and maximum canopy LN was about 1.8 g N m‐2, while in sorghum the maximum RUE values were less than 1.3 g MJ‐1 and the maximum canopy LN was less than 1.3 g N m‐2. The experimental increase in RUE with increasing LN, however, was less than expected from published theoretical analyses. It was hypothesized that leaf quantum efficiency per unit incident radiation may also depend on LN such that at low LN, quantum efficiency is decreased and RUE is decreased to less than expected levels.
Near Infrared Reflectance Spectroscopy Prediction of Quality from Masticated Temperate Forage Species
Authors: Cosgrove G. P. , Burns J. C. , Fisher D. S. , Muller J. P. , Pond K. R.
Published: July 2010

Masticated forage provides information related to the quality and fractionation characteristics of a ruminant's diet. This study reports the use of near infrared reflectance spectroscopy (NIRS) to predict the in vitro dry matter disappearance (IVDMD), in vitro organic matter disappearance (IVOMD), and ceil‐wall concentrations of particle size fractions and the whole masticate of temperate forages. Esophageal extrusa samples, with saliva retained, were obtained from fistulated steers (Bos taurus) that were intermittently grazing tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), and ryegrass (Lolium perenne L.). Grazing was initiated at canopy heights of 100, 200, and 300 mm during spring and fall of two consecutive years. Samples were collected at the start of grazing at each canopy height and after defoliation to a 50‐ram residue. Masticates, quickfrozen in liquid N2, were subsequently lyophilized and dry sieved into seven particle size fractions and, along with a whole‐masticate subsample, were scanned for NIRS analyses. A single broad‐based calibration encompassing all experimental factors predicted quality constituents within acceptable limits of precision for this methodology. Standard errors of cross‐validation (SECV) were 6 g kg−1 for organic matter, 16.0 g kg−1 for IVDMD, 16.2 g kg−1 for IVOMD, 14.8 g kg−1 for neutral‐detergent fiber (NDF), and 14.3 g kg−1 for ash corrected NDF. Separate calibrations for each species × sample time combination resulted in little reduction in SECV. Sample numbers used in calibration could be reduced to = 7% of total samples with SECV of 16.3 g kg,−1 for IVDMD. Masticate quality constituents of temperate species were satisfactorily predicted by NIRS when obtained from a wide range of seasonal and plant variation.
Root Size and Distribution of Fieldgrown Wheat Genotypes
Authors: Mian M. A. R. , Nafziger E. D. , Kolb F. L. , Teyker R. H.
Published: July 2010

Extraction of field grown wheat (Triticum aestivum L.) roots is cumbersome, tedious, and labor intensive, whereas the roots of wheat plants grown in hydroponics are dean and easy to extract. To determine if wheat root growth in hydroponics is related to field root growth and grain yield under varying soil conditions, we grew six winter wheat genotypes in three field environments. Genotypes were selected based on the size of their root systems when grown hydroponically: three had large root systems and three had small root systems. Subsurface root length density (SRLD) was measured from soil cores in incremental depths between 13 and 120 cm. Averaged across environments, the root fresh weight in hydroponic culture was correlated with SRLD (r = 0.93**). As group, genotypes with larger root systems in hydroponic culture produced larger SRLD values and higher grain yields than did those with smaller root systems, but for individual genotypes, the correlation between SRLD and grain yield was not significant. Results from this limited number of genotypes indicate that selection for seedlings with large root systems in hydroponic culture may select genotypes capable of producing more roots in the field.
Duration and Rate of Grain Filling in Selected Winter Wheat Populations: I. Inheritance
Authors: Mou Beiquan , Kronstad Warren E.
Published: July 2010

Grain yield of wheat (Triticum aestivum L.) is determined in part by kernel weight, which is a function of the rate and duration of grain fill (GF). The lack of information regarding the inheritance of GF rate and duration prompted this study to determine the relative magnitude of genetic components and combining ability estimates for the GF parameters. Parents and F1 generations resulting from a 4 × 4 diallel mating scheme were grown in space‐planted experiments in 1987 and 1988. The plots were sampled at 2‐ to 3‐d intervals after anthesis to obtain GF data. Significant genotypic variation for GF rate, duration, and kernel weight was observed in both seasons. Genotype × year interaction was not significant for any of the GF traits. General combining ability (GCA) effects for GF rate, duration, and kernel weight were larger than specific combining ability (SCA) effects, with 2GCA/(2GCA + SCA) values of 0.981,0.978, and 0.958, respectively. Both combining ability analyses and estimates of the genetic components from the diallel indicated that a primary part of genetic variability for the GF traits was associated with additive gene action. However, dominance effects also appeared to be involved in the inheritance of GF duration and kernel weight. Narrow‐sense heritability estimates ranged from 0.79 for kernel weight to 0.89 for GF rate. Results suggested that early‐generation selection for both duration and rate of GF and kernel weight should be effective in changing these characters within the material studied.
A Classification of 148 U.S. Maize Inbreds: I. Cluster Analysis Based on RFLPs
Authors: Mumm Rita Hogan , Dudley J. W.
Published: July 2010

Knowledge of relationships among lines is essential to the maize (Zea mays L.) breeder because it directs the exploitation of germplasm in hybrid production. Restriction fragment length polymorphism (RFLP) data should be useful for estimating relationships among inbreds because they reflect differences in the DNA sequence. Cluster analysis, based on RFLPs resulting from 46 probe‐enzyme combinations, was used to reveal associations among 148 U.S. maize inbreds and assign inbreds to heterotic groups. Estimates of genetic relationship between all pairs of inbreds were computed by Gower's Coefficient of Similarity and expressed as Euclidean distances. Then, these estimates were used to assign inbreds to groups by the average linkage method (UPGMA). Differences in the hybridization fragments exhibited lines within and between groups were evaluated to explore the basis for partitioning the fines. In the cluster analysis, inbreds were ordered into two major groups generally coinciding with distinctions between breeding groups derived from ‘Lancaster Sure Crop’ open pollinated variety and from Iowa Stiff Stalk Synthetic. Within these two groups, 11 subgroups were formed, each containing lines associated with an elite inbred (WF9, MO17, C103, PA91, OH43, T8, B14, B73, N28, B37, or OH07). The classification generally agreed with pedigree information and was supported by principal component analysis. Groups differed markedly in the proportions of lines exhibiting particular fragments. However, differences between groups reflected differences in frequencies rather than distinctions between the presence or absence of fragments by the vast majority of the lines in the respective groups.
Assessment of Western Canadian Barleys of Historical Interest: I. Yield and Agronomic Traits
Authors: Jedel Patricia E. , Helm James H.
Published: July 2010

Changes in yield components and agronomic traits may contribute to historical yield advances. The purpose of this study was to determine the yield advances that have been made in spring barley (Hordeum vulgare L.) cultivars released in western Canada from 1910 to 1987 and to evaluate the contribution of yield components and agronomic traits to yield advancement. An important goal was to determine the value of individual traits to an ideotype of barley for the western Canadian prairies. Twenty cultivars of both six‐ and two‐rowed types were tested at Botha, Lacombe and Olds, Alberta, Canada, in 1989 and 1990. Grain yields increased by 12.7 to 41.4 kg ha−1 yr−1 with the greater responses being in the more favourable environments. This increase in grain yield was associated with increased harvest indices of 0.08 to 0.17% per year. Lodging decreased by 0.01 to 0.05 points per year (0–10 scale). Seed protein content decreased by 0.01 to 0.02 g kg−1 yr−1. Test weights responded positively to year of release in the 1990 tests at Botha and Olds. Spike number per square meter and net blotch severity were associated with year of release in some location‐years but response was limited. Vegetative biomass, plant stand establishment, kernel weight, kernels per spike, and response to scald had not changed over years. Increases in grain yield associated with increased harvest indices and reduced lodging have been made in western Canadian barley cultivars. Further efforts to increase vegetative yield, kernel weight and kernel number per spike, while maintaining harvest indices and lodging resistance would appear warranted.
Maize Physiological Traits Related to Grain Yield and Harvest Moisture in Mid‐ to Short‐Season Environments
Authors: Dwyer L. M. , Ma B. L. , Evenson L. , Hamilton R. I.
Published: July 2010

Identification of easily measured physiological traits contributing to yield under specified environmental conditions would benefit genotypic selection for maize (Zea mays L.). A field experiment was conducted to determine relationships between grain yield, harvest moisture, the ratio yield/moisture (Y/M), and 10 maize physiological traits related to development time, vegetative growth, and partitioning to the grain. Nine commercial hybrids, representing three maturity classes from 75 to 95 d, were planted at three sites with zonations, based on cornheat units (CHU), corresponding to the three maturity classes within 100 km of Ottawa, Canada (45° 22′ N, 75° 43′ W), in 1988, 1989, and 1990. Grain yield and harvest moisture were related to hybrid maturity; i.e., late maturity hybrids produced high yields with high grain moisture, but traits related to development time alone did not predict yield and moisture. Traits most highly correlated with grain yield and Y/M for the three maturity classes at the three sites were harvest index, vegetative dry matter (at tasselling), time to develop between silking and maturity (TFILL), and time to develop to silking (TSILK). Traits most highly correlated with harvest moisture were time to develop to maturity, TSILK, and TFILL. Models to estimate grain yield had higher coefficients of determination than those for harvest moisture and models for Y/M had intermediate coefficients. Results suggest that selection for high yielding low moisture hybrids in mid‐ to short‐season production areas should aim to increase (i) the grainfilling period (TFILL); (ii) vegetative dry matter; and (iii) harvest index.
Variability of Seed and Plant Development in Pea
Authors: Dumoulin Véronique , Ney Bertrand , Gérard Etévé
Published: July 2010

Pea (Pisum sativum L.) yields are generally highly dependent on seed number. The objective of the present study was to investigate seed and plant development of 10 contrasting genotypes of pea with differences in seed size (0.1–0.3 g seed−1), foliage type (semi‐leafless and leafed), and number of branches. The periods of seed set and seed filling were studied in the field for 2 yr at two sowing dates. Seed water content (WC) was closely related to seed development. Seed water content at beginning of seed filling and at physiological maturity corresponded to 0.85 and 0.55 g g−1 fresh weight, respectively. The progression of flowering, beginning of seed filling, and physiological maturity along the stem were linearly related to cumulative degree days from the beginning of flowering. The rates of progression of flowering and of beginning of seed filling were not dependent on environmental conditions, but they were significantly different among genotypes. Conversely, the duration of the lag phase, time between flowering and beginning of seed filling at the first node, remained stable in spite of differences in seed size. The onset of physiological maturity was more variable. Duration of seed filling varied among environments, but genotypes had similar durations in spite of differences in seed size. Seed number on the main stem was fixed when the seeds of the last reproductive node began to fill. The delimitation of the seed set period showed genetic variability for the beginning of the period, depending on the first reproductive node number, and its duration.
Maize Internode Elongation Patterns
Authors: Morrison T. A. , Kessler J. R. , Buxton D. R.
Published: July 2010

During maize (Zea mays L.) growth, the stalk elongates in a sigmoidal pattern. This overall pattern arises from the variable growth rates of individual internodes comprising the maize stalk. To discern differences in growth rate among internodes of the stalk, individual elongation rates and patterns were determined in a single‐cross hybrid. When each of 12 aboveground internodes (7 through 18) of growth‐chamber‐grown plants reached approximately 10 mm in length, they were dotted along their lengths with black acrylic paint at 1‐mm intervals and photographed daily over 35 d. Full‐scale photographs documented that all internodes elongated sigmoidally, in a basipetal direction. Elongation began slowly and uniformly throughout the length of the undeveloped internode during the first 2 to 3 d, increased in rate and shifted basipetally from the upper internode region toward the middle, and later, toward the basal region of the enlarging internode. Elongation decelerated in the intercalary meristem region during the final days of internode lengthening. Internodes 8 through 12 elongated similarly with the greatest dally growth rates. Internodes 13 and 14, which supported developing ears, had the longest elongation periods but slower growth rates and shorter final lengths than other internodes. Internode 15 had a rapid rate of growth like I8 through 12, but an elongation pattern similar to I13 and 14. Evidence from this study indicates that the relative position of internodes in the emerging stalk hierarchy and the functional role of internodes in stalk development influences individual internode growth rate, elongation period, and developmental pattern.
Determination of Chitinase Activity in Tall Fescue by Near Infrared Reflectance Spectroscopy
Authors: Roberts C. A. , Marek S. M. , Lei Wang , Karr A. L.
Published: July 2010

New cultivars of pasture‐type tall fescue (Festuca arundinacea Schreber) lack the fungal endophyte, Acremonium coenophialum Morgan‐Jones & W. Gams. Although Acremonium‐free cultivars are less toxic to livestock than Acremonium‐infected cultivars, they are less disease tolerant. Acremonium‐free cultivars may be improved for disease tolerance using a biochemical marker such as chitinase, a defense hydrolase associated with disease resistance in many crops. The objective of this research was to measure chitinase activity in tall fescue seedlings by near infrared reflectance Spectroscopy (NIRS). Ninety‐nine seedling samples were freeze‐dried, ground, and analyzed for total and specific chitinase activity using tritiated chitin as a substrate. Near infrared spectra were recorded for each sample, and an NIRS equation was developed by regressing radiochemical data against spectral data; regression procedures included forward stepwise multiple regression and modified partial least squares (MPLS). In optimum equations, standard errors of calibration and validation were near or below 10% of the mean, similar to errors observed in routine chemical analysis of chitinase. The optimum equation used MPLS to predict specific activity, resulting in a coefficient of determination of 0.90 and a mean and standard error of 88.8 ± 7.2 disintegrations min−1 mg−1 protein. The NIRS‐chitinase procedure is accurate and efficient. Once a spectrophotometer is calibrated, the NIRS procedure is at least 10 tunes faster than chemical procedures, permitting analysis in 60 s per sample.
Inheritance of Aroma in Six Rice Cultivars
Authors: Pinson S. R. M.
Published: July 2010

‘Jasmine 85’, a soft‐cooking aromatic rice (Oryza sativa L.) cultivar, was released in the USA with the objective of displacing imported Thai Jasmine rice in local markets. However, the reduced aroma and off‐white color of its milled rice limit its marketability. The present objective was to determine the number of genes controlling aroma in four rice lines (Jasmine 85, ‘Amber’, a dwarf mutant from ‘Basmati 370’ (PI 457917), and ‘Dragon Eyeball 100’), and to evaluate the allelism of aroma in these four lines and with the single recessive gene known to be in both ‘A‐301’ and Della‐X2. Lack of leaf aroma in aromatic/non‐aromatic F1 hybrids indicated the recessive nature of the aroma in all studied rices. F2 segregation ratios revealed that Jasmine 85 and PI 457917 each contain a single gene for aroma, and the aromatic nature of the F1 leaves from crosses with each other and with A‐301 and Della‐X2 revealed that the aroma genes in all four cultivars are allelic. Amber and Dragon Eyeball 100 each contain two aroma genes, a novel gene plus one allelic to the gene in A‐301, Della‐X2, Jasmine 85, and PI 457917. Incorporation of a novel aroma gene into Jasmine 85 could potentially increase its marketability. No linkage was detected between the two aroma genes in Dragon Eyeball 100 and five morphological characters. High levels of sterility observed in Amber F2 populations may hinder the use of its novel aroma gene.
Relationships among European Barley Germplasm: I. Genetic Diversity among Winter and Spring Cultivars Revealed by RFLPs
Authors: Melchinger Albrecht E. , Graner Andreas , Singh Mahendra , Messmer Monika M.
Published: July 2010

Restriction fragment length polymorphisms (RFLPs) have been proposed for characterizing genetic diversity of barley (Hordeum vulgare L.) germplasm. Forty‐eight (24 winter, 24 spring) cultivars from the European barley germplasm were assayed for RFLPs with 136 clone‐enzyme combinations (CEC) (48 DNA clones, three restriction enzymes). Objectives of this study were to (i) assess the amount variation for RFLPs in these materials, (ii) determine RFLP‐based genetic similarity estimates between unrelated cultivars within and between the winter and spring barley germplasms, and (iii) examine the usefulness of RFLPs for classification of cultivars from different germplasm pools. Thirty‐five DNA clones detected polymorphism with at least one enzyme. For the 62 polymorphic CEC, 58% of all RFLP patterns were common to both winter and spring barley, and about 20% were specific to the cultivars of each group. Genetic similarity (GS) calculated from RFLP data ranged from 0.64 to 0.93 between unrelated pairs of cultivars. Mean GS (MGS) for unrelated cultivar combinations within the group of winter (0.85) and spring (0.84) type cultivars were significantly greater than for winter × spring cultivar combinations (0.76). All winter and spring cultivars except two had a smaller MGS to cultivars from the other group than to unrelated cultivars from the same group. Principal coordinate analysis of GS estimates resulted in a separate grouping of winter and spring cultivars; further subgroups were also apparent for cultivars with a similar pedigree background. Results from our study corroborate the usefulness of RFLPs for the organization of elite barley germplasm.
Association of Grain Protein Concentration and Selected Traits in Hard Red Winter Wheat Populations in the Pacific Northwest
Authors: Costa J. M. , Kronstad W. E.
Published: July 2010

Grain yield and grain protein concentration are often negatively associated in wheat (Triticum aestivum L.). When grain yield increases and grain protein concentration decreases, the milling and baking quality of bread flour can be affected. In the Pacific Northwest region of the USA, grain yield of wheat is usually high and grain protein concentration is low. Parents, F4, and F5 generations of two crosses were solid‐planted in two environmentally diverse but high‐yielding sites in Oregon to study the association of grain protein concentration with grain yield and biological yield, harvest index and related traits in the Pacific Northwest's environment, and to suggest a selection criterion to increase grain yield while maintaining or increasing grain protein concentration. Correlation coefficients showed moderate negative associations between grain protein concentration and grain yield, and also between grain protein concentration and harvest index. Genetic correlations were larger than phenotypic correlations, while environmental correlations were low, suggesting the presence of negative genetic relationships between grain protein concentration with grain yield and with harvest index. Grain yield and harvest index were the most important traits affecting grain protein concentration as estimated by path coefficient analyses. We suggest that selection for high grain yield, while maintaining or increasing grain protein concentration, should not be based on further increases of harvest index, but rather on increasing biological yield.
Variation in Leaf Movements among Common Bean Cultivars
Authors: Kao Wen‐Yuan , Comstock Jonathan P. , Ehleringer James R.
Published: July 2010

Common beans (Phaseolus vulgaris L.) orient their leaves in response to directionality of the sun's direct beam. This study was initiated to test for genetic variability in leaflet orientation, especially variability related to geographic origin. We also determined genetic variability in diurnal, seasonal, and environmental influences on leaflet orientation. The studies included 75 Mesoamerican and Andean common bean lines and two tepary bean (Phaseolus acutifolius Gray) lines at two sites. Cos i (cosine of the angle of incidence to direct sunlight) varied in the order tepary bean > Andean common bean > Mesoamerican common bean. Within sites, variability in seasonal and year‐to‐year patterns of leaf movement was significant, but there were large differences in rankings of lines across sites. Imposed drought decreased cos i, but values of cos i in drought and irrigated treatments remained correlated. Movements of the two lateral leaflets were highly correlated with each other for most of the day, but within many common bean lines were not related to the movements of the terminal leaflet. Thus, at the canopy level the overall impact of the pronounced movements of the terminal leaflet were diminished by movements of the lateral leaflets. The results show substantial genetic variability in both short‐term and long‐term leaflet movements in beans, some of which is related to geographic origin.
Seed Dormancy and Tissue Culture Response in Wheat
Authors: Morris Craig F. , DeMacon Victor L.
Published: July 2010

High levels of seed dormancy in wheat (Triticum aestivum L. em Thell) effect tolerance to pre‐harvest sprouting conditions. An inverse relationship between the level of seed dormancy at maturity and growth of calli derived from immature embryo explants was previously observed among a small group of wheat genotypes. In this study, 24 genotypes representing a diverse genetic base were used to examine the relationship between seed dormancy and tissue culture response in wheat. Immature embryo explants were cultured on a modified Murashige and Skoog medium. Increase in callus fresh weight and subjective callus rating were determined after 30 and 60 d. Cumulative germination curves, percentage germination, a modified Promptness Index, and time to reach 50% germination were evaluated as methods of characterizing the relative level of dormancy among the genotypes. Visual assessment of cumulative germination curves categorized the genotypes into four dormancy groups. Numerical reduction of these curves indicated that genotypes differed most in percent germination and modified Promptness Index after 6 d (PG6 and MPI6, respectively). PG6 and MPI6 were.highly correlated (r = 0.98). Median germination produced a similar ranking of genotypes for seed dormancy with predicted population midpoints of 2.3 to 56 d. After 60 d in culture, calli ranged from an average of 0.29 to 1.00 g, and watery, loose and translucent to friable, compact and yellow‐white in appearance. Callus ratings and weights were all significantly correlated. Wheat genotypes with good tissue culture response exhibited a wide range in mature seed dormancy and no correlation between the two biological phenomena was evident. Therefore, the level of mature seed dormancy and tissue culture response in wheat are largely independent traits, and wheat breeding programs may use tissue culture to develop sprouting‐resistant cultivars.
Germination under Controlled Temperature and Field Emergence of 13 Sorghum Cultivars
Authors: Brar G. S. , Stewart B. A.
Published: July 2010

Temperature and cultivar strongly influence the establishment of dryland sorghum [Sorghum bicolor (L) Moench]. Little is known about the extent of variability in germination and emergence among different sorghum cultivars as affected by temperature. Our objective was to monitor cultivars for germination under different temperature regimes in the laboratory, and subsequently to test their performance in the field for emergence. Sorghum seeds were screened for germination during 10 d in polyethylene growth pouches held in the dark at constant temperatures of 10, 15.5, 21, 26.5, 32, or 37.5°C. In the field study, 13 hybrids were planted on 4, 13, 21, and 26 June 1991, and observed for emergence. Germination percentage significantly (P < 0.05) increased as temperature of treatment increased from 15.5 to 26.5 or 32°C when averaged across the cultivars, with no germination at 10°C. As temperature increased from 15.5 to 37.5°C the average time to germination decreased significantly (P < 0.05). Cultivar Richardson‐9112 had the greatest germination percentage (98%) and DK‐46, well as DK‐42, had the least (79%) when averaged across the five temperatures. For 80% or above of the seeds to germinate, it required 7 d at 15.5, 3 d at 21, 2 d at 26.5 and 32, and 1 d at 37.5°C temperature. An optimum temperature of the cultivars investigated varied between 26.5 and 32°C. Mean field emergence was significantly (P < 0.05) greatest (83%) with Richardson‐9112 and least (36%) with DK‐42Y as well as DK‐46 compared to nine cultivars. Relative mean emergence in the field regressed with relative mean germination in the laboratory yielded a significant (P < 0.05) correlation r2 = 0.77). This study demonstrates the cultivar differences for response to temperature and information concerning variability in germination, and emergence.
Yield Reduction in a Maize Diallel under Infestation with Southwestern Corn Borer
Authors: Thome Catherine R. , Smith Margaret E. , Mihm John A.
Published: July 2010

The southwestern corn borer (SWCB), Diatraea grandiosella Dyar, is an important pest of maize (Zea mays L.) in some parts of the Americas. Germplasm with resistance to leaf feeding by this insect pest was developed at the International Maize and Wheat Improvement Center (CIMMYT) in Mexico, but little is known about the inheritance of resistance or combining ability for yield in this germplasm. A 10‐parent maize diallel cross of eight CIMMYT inbreds and two susceptible public inbreds was evaluated for leaf feeding resistance to SWCB and for yield under both infestation and protection from SWCB. Trials were grown at Tlaltizapdn, Morelos, Mexico, in the dry season of 1989‐1990 and rainy season of 1990. General combining ability (GCA) was the most important source of variation among F1S for leaf feeding damage rating and for yield. The relationship between leaf feeding damage and yield reduction was linear but variable. The most insect resistant lines in this study were selected under infestation with larvae of several species of stalk boring insects but were never directly selected for combining ability for yield. These lines improved GCA for yield only under heavy SWCB infestation. An inbred that was susceptible to leaf feeding had better combining ability for yield than all other lines in the study in both seasons under infestation and protection. The results of this study demonstrate that selecting directly for combining ability for yield across environments may be more useful than selecting directly for insect resistance without selecting for yield.
Selection for Resistance to Fusarium Root Rot, and Associations among Resistances to Six Diseases in Alfalfa
Authors: Miller‐Garvin J. E. , Viands D. R.
Published: July 2010

Fusarium root and crown rot in New York, caused mostly by Fusarium avenaceum (Fr.:Fr.) Sacc., F. oxysporum Sehlechtend.:Fr., and F. solani (Mart.) Sacc., reduces longevity and productivity of alfalfa (Medicago saliva L.). The research objectives were to determine correlations among six alfalfa diseases and progress from recurrent phenotypic selection for resistance to fusarium root rot. From alfalfa half‐sib progenies, phenotypic and additive genetic correlation coetlicients were estimated among resistances to disease caused by the three Fusarium spp. and three common vascular diseases, bacterial wilt (BW) [caused by Clavibacter michiganense subsp, insidiosum (McCall.)], verticillium wilt [caused by Verticillium albo‐atrum (Reinke & Berthier)], and fusarium wilt [caused by F. oxysporum Seh. ex Fr. f. sp. medicaginis (J. L. Weimer)]. Resistances to fusarium wilt (FW) verticillium wilt (VW) were significantly correlated (additive genetic, r = 0.32). Correlations among resistances to the root and crown rot fusaria were moderately to highly positive. Resistances to root rot caused by F. avenaceum and F. solani were moderately and positively correlated with resistance to VW. In two plant populations, two cycles of recurrent phenotypic selection for resistance to root rot species increased levels of resistance by 15 to 44%. Selection for resistance to root rot caused by specific Fusarium species conferred a general resistance to rot caused by all three species, confirming the results of the correlation experiment. Alfalfa populations with resistance to disease caused by the Fusarium spp. can be developed by using an inoculum mixture of all three Fusarium spp., without negative effects on resistances to the vascular diseases.
Genetic Changes Associated with Different Methods of Recurrent Selection in Five Maize Populations: II. Indirectly Selected Traits
Authors: Stojšin Duška , Kannenberg L. W.
Published: July 2010

Recurrent selection in a population can result in changes in traits other than those used directly as selection criteria. Such changes usually are not easily predicted or understood because they do not occur in a consistent manner. This study was conducted to compare changes in indirectly sdected traits (plant height, ear height, tassel branch number, and days to anthesis and silking) in five maize (Zea mays L.) populations (CGSynA, CGSynB, CGG, CGN, and CGW) that were selected for performance indices based on grain yield, grain moisture, and standability. Four selection methods were compared: modified ear‐to‐row (ME) in CGSynA, CGSynB, CGG, and CGN; half‐sib family (HS) in all five populations; selfed progeny (S) in five populations; and reciprocal recurrent selection (RRS) in CGSynA and CGW. Generally, response to indirect selection depended on (i) the selection method used, (ii) the initial mean value of a trait the original population, and (ii) correlations between indirectly and directly selected traits. The combination of these factors seems to determine whether an indirectly selected trait will increase, decrease, or remain constant in advanced cycles of selection. No general trend for response to indirect selection was observed for ear height, plant height, or tassel branch number. Days to anthesis and silking were mainly reduced. This uniform response of days to tlowering was partly due to non‐documented selection against later flowering plants in initial cycles of selection. Genetic drift generally acted in the opposite direction from response to selection, and I‐IS resulted in the least genetic drift. Generally, it seems that the indirectly selected traits changed in the way that would most efficiently contribute to the desirable changes of the directly selected traits.
Alteration of Phenotypic Variances by the Endophyte of Tall Fescue
Authors: Rice J. S. , Ferguson N. H. , Pinkerton B. W. , Stringer W. C.
Published: July 2010

Widespread infection of tall fescue (Festuca arundinacea Schreber) by the endophytic fungus (Acremonium coenophudum Morgan‐Jones and Gams) is responsible for poor performance of grazing animals. Because infection results in changes in phenotypic means for numerous traits, changes in phenotypic variances could also be a result of infection. Phenotypic variances for forage and seed production were investigated in studies of polycross families from endophyte‐infected (El) and endophyte‐free (EF) clones of 20 tall fescue genotypes. No significant phenotypic variance for forage production was detected among El families during the study. In 1989, phenotypic variances for EF were greater than El for both harvests, suggesting that the endophyte can mask plant genotypic variance. Significant phenotypic variances were observed for all seed production traits in both El and EF. Phenotypic variances for total seed weight and seed numbers in 1990 were greater for El than for EF. Estimates of genetic variance for these traits were not greater than twice the standard error in the EF state but were greater than twice the standard error in the El state. The resulting heritability estimates reflected this difference. Endophyte presence could result in overestimates of plant genotypic variance for these traits. Breeding strategies should consider presence or absence of endophyte and the possible effects on variances.
Relative Effectiveness of Hill and Row Plots for Evaluating Alfalfa Yield
Authors: Trimble M. W. , Barnes D. K. , Lamb J. F. S.
Published: July 2010

Plant breeders usually use multiple‐row or broadcast plots grown from 2 to 4 yr to evaluate alfalfa (Medicago sativa L.) populations for yield and agronomic performance. The requirements of land and seed and the cost of evaluation often limit the number of populations that can be evaluated. The objective of this study was to compare the yield of alfalfa populations grown in hill plots planted on either 0.3‐ or 1.0‐m centers and 1‐row (0.5 by 6.1 m) and 6‐row (1.1 by 6.1 m) plots. The study was conducted for 2 yr in Minnesota with 16 alfalfa populations ranging in dormancy, yielding ability, and biological N fixation. The experimental design was a randomized complete block with four replicates at three locations. The strongest association for forage yield between any two plot types was between the 0.3‐m hill plots and the 1‐row plots. Phenotypic and Spearman rank correlations for forage yield between 0.3‐m hill plots and the 1‐row plots in 1984 were 0.73 and 0.67, respectively. No significant correlation was observed in yield between hill plots and 6‐row plots. Yield in 6‐row plots was positively correlated to that in 1‐row plots. A few populations were consistent in rank for forage yield in both years and across all plot types. Forage yield in some populations ranked low in hill plots and high in 6‐row plots, whereas other populations ranked high in hill plots and low in 6‐row plots, illustrating that a population's performance in an evaluation trial could be influenced by the plot type used. Visual estimates of forage yield and actual harvested yield were highly correlated in the hill plots for all three harvests during 1983. These correlations decreased as stands aged, suggesting that use of visual estimates of forage yield would be useful only during the establishment year. Hill plots may be useful in early phases of a breeding program but should not be considered as a replacement for multiplerow yield evaluation plots during the later stages of a breeding program.
Field Performance of Select Tepary Bean Germplasm in the Tropics
Authors: Miklas P. N. , Rosas J. C. , Beaver J. S. , Telek L. , Freytag G. F.
Published: July 2010

Dry edible bean (Phaseolus vulgaris L.), a staple food crop for many tropical countries, is not well adapted to the hot temperatures and low rainfall that prevail during the dry seasons. Cultivated tepary bean (Phaseolus acutifolius A. Gray var. latifolius Freeman), an edible small‐seeded desert annual with extreme tolerance to drought, may be suited to dry‐season production in the tropics. To test this hypothesis, production potential of select cultivated tepary bean germplasm was evaluated in different tropical environments and compared to dry bean. Eleven lines (Neb‐T‐l‐s, Neb‐T‐6‐s, Neb‐T‐Sa‐s, Neb‐T‐15‐s, GN‐605‐s, GN‐610‐s, Pls 321637‐s, 321638‐s, 440788‐s, 440806‐s, and 502217‐s) were field tested from 1989 to 1993 in six trials, two each at Isabela and Fortuna, Puerto Rico, and El Zamorano, Honduras. Locally adapted, high‐yielding dry bean checks included in some trials in Puerto Rico were ‘Dorado’ and ‘Arroyo Loro’. Tepary lines yielded 70% of Dorado in the warm environment of lsabela and 170% of Dorado and Arroyo Loro in the hot environment of Fortuna. Tepary seed weight averaged 30% less than the dry bean cheeks. Seed protein concentration of tepary bean averaged 12% less than Dorado, and the seed protein concentration was inversely related to yield (r − 0.70*). Tepary bean proanthocyanidin (condensed tannin) concentration, an antinutritional factor, was 73% less than Dorado. The tepary bean lines have potential for dry‐season production in the tropics where dry bean traditionally yields poorly.
Harvest Management Effects on Productivity, Dinitrogen Fixation, and Nitrogen Transfer in Birdsfoot Trefoil‐Orchardgrass Communities
Authors: Farnham D. E. , George J. R.
Published: July 2010

Dinitrogen fixation and N transfer need to be quantified to help develop optimum harvest recommendations for legume‐grass mixtures. Field research was undertaken to determine how harvest management (three‐cut vs. six‐cut systems) influenced the productivity, N2 fixation, and N transfer of birdsfoot trefoli‐orchardgrass communities. Four birdsfoot trefoil (Lotus corniculatus L.) cnitivars were seeded in binary mixtures with orchardgrass (Dactylis glomerata L.) Dinitrogen fixation and N transfer were estimated by 15N isotope dilution using pure stands of orchardgrass as a reference. Herbage dry matter yields were greater under the three‐cut system, averaging 8.8 Mg ha−1 compared with 6.4 Mg ha−1 for the six‐cut system (means of cultivars and years). Percentage legume N derived from fixation (%Ndfa) was only slightly greater for the three‐cut system. Mean %Ndfa for the three‐cut system was 98% compared with 95% for the six‐cut system. Total‐season yields of fixed N in birdsfoot trefoil herbage, percentage N in orchardgrass herbage derived from fixation, and total‐season yields of transferred N in orchardgrass herbage generally were not affected by harvest management. We conclude that six‐cut management reduced dry matter yield compared with three‐cut management. Relatively little difference was observed in biological N2 fixation or N transfer, however.
Quantifying Acquired Thermal Tolerance in Winter Wheat
Authors: Porter David R. , Nguyen Henry T. , Burke John J.
Published: July 2010

High temperature stress limits productivity of winter wheat (Triticum aestivum L.) in many environments. Identification of thermal tolerant germplasm is needed to improve plant productivity under heat stress. In this study we used 2,3,5‐triphenyltetrazolium chloride OWC) reduction, an indicator of mitochondrial activity, to characterize cultivar differences for acquired thermal tolerance in winter wheat. Seven‐day‐old seedlings of six hard red winter wheat cultivars grown at 25°C were aeelimated at 37°C for 24 h followed by a 50°C incubation for 2 h. Leaf sections sampled after each temperature treatment were infiltrated with TTC and the resultant formazan was ethanol‐extracted for optical density measuremenatt 530 nm. Under these test conditions, the TTC assay detected differential tolerance (expressed as percent cell viability of the 50°C treated tissue compared to the 37°C treated tissue) which ranged from a low of 6% for ‘Siouxland’, to a high of 72% for ‘TAM 108’. The results of this study show that TTC reduction can be used to measure differences in acquired thermal tolerance in winter wheat.
Prediction of Genotype Performance from Ancestral Relationship in Oat
Authors: Beer S. C. , Souza E. , Sorrells M. E.
Published: July 2010

Coefficient of parentage, the probability that homologous alleles from different genotypes are identical by descent, has been used to estimate genetic similarity. The objective of this study was to determine if the performance of oat (Avena saliva L.) genotypes can be predicted by their coefficient of parentage (rp) values with a particular ancestor. Grain yield, test weight, and height data were gathered for 99 breeding lines from annual Uniform Midseason Oat Performance Nursery (UMOPN) reports. Each line was included in those trials for at least 2 yr from 1979 to 1989. Least‐squares means across environments were derived for each line for each performance variable, from analysis of variance. Coefficients of parentage were calculated for each UMOPN line paired with each of 487 ancestral breeding lines, cultivars, and landraces. For 40 of those ancestors, UMOPN lines were categorized as closely related (0.125 ≤ rp < 1) or distantly related (0 < rp < 0.125). The means of the two parentage categories for each performance variable were compared by a two‐tailed t‐test. For six ancestors, closely‐related UMOPN lines showed increased test weights and depressed grain yields, when compared to distantly‐related lines. The cultivar Hercules enhanced the test weight of its close relatives, with no significant decrease in grain yield. UMOPN lines closely related to ‘Ogle’ or ‘Tyler’ had higher yields but lower test weights, compared to distantly‐related lines. The greatest enhancement in mean yield of closely‐ versus distantly‐related lines was 254 kg ha−1 for ‘Tippecanoe’. However, ‘Clintland 60’ appeared to be the most important ancestor contributing to improved yield without reduced test weight.
Xenia and Maternal Effects on Maize Agronomic Traits at Three Plant Densities
Authors: Seka D. , Cross H. Z.
Published: July 2010

Kernel mass is a primary yield component in maize (Zea mays L.) governed by both xenia and maternal effects. Because kernel growth depends on assimilate supply, we wanted to learn if kernel‐weight genes also affect plant size and agronomic characters. We reciprocally crossed three strains known to differ for rates of grain filling [high (HC), random (RC), and low (LC) R‐nj color] with two kernel‐weight strains [large (LG), and small (SM)] to produce 12 hybrid strains. For 2 yr at two locations, we grew plants of each hybrid at 24 000, 48 000, and 72 000 plants ha−1 in plots arranged so that wind pollinated silks with either LG or SM pollen. Leaf number, leaf width, leaf length, and time to silk were measured to compute leaf area and average leaf expansion rate (ALER). We also measured grain yield and grain moisture concentration at harvest. In one of four environments, hybrids pollinated by the LG strain had 34% higher yields and 24 g kg−1 lower harvest moisture than hybrids pollinated by the SM strain. Increasing plant density delayed silking, increased leaves per plant, and decreased leaf width. Hybrid plants from the LG strain yielded 10% more than hybrid plants from the SM strain. They also had 12% higher grain moisture at harvest, 11% greater leaf surface area (mainly from more and wider leaves), and silked 0.6 d later than SM plants. Hybrid plants from the HC strain produced higher grain yields and greater leaf surface areas than plants from the RC or the LC strains. Leaf surface area was correlated (r = 0.80, P < 0.01) with grain yield. Kernel growth genes influenced yield via xenia effects but mainly by genes in the plant. Although R‐nj color genes only increased yields of specific reciprocal hybrids, in properly planned hybrids these genes may complement genes that increase yield via larger kernels.
Single‐Cross Hybrid Development in Maize by Reciprocal Half‐Sib Selection
Authors: Sfakianakis J. N.
Published: July 2010

Maize (Zea mays L.) inbred lines were developed from two diverse populations, Across‐8045 and GROP‐272, by a reciprocal half‐sib selection scheme for developing single‐cross hybrids. Selection, which was based on half‐sib progenies, was carried out both among and within lines during the So × So through Ss × Ss generations. Genetic gain was measured by comparing progeny yields to the mean of six adapted check hybrids each year. After six generations of inbreeding and selection, gain was 4.0% per generation for Across‐8045 and 6.5% per generation for GROP‐272. The mean yield of the So × So topcrosses was 17% less than that of the checks for Across‐8045 and 30% less than that of the checks for GROP‐272. The mean yield of the best Ss × Ss topcrosses was 11.8% greater than the mean of the checks for Across‐8045 and 15.8% greater than the mean of the checks for GROP‐272. The advantages of the breeding scheme are that it provides abundant half‐sib seed for testing while coupling the development of inbreds and hybrids throughout the process.
Early Maturity Soybean Production System: Genotype × Environment Interaction between Regions of Adaption
Authors: Pfeiffer T. W. , Grabau L. J. , Orf J. H.
Published: July 2010

An early soybean [Glycine max (L) Merr.] production system involves growing soybean cultivars of a maturity group earlier than those that utilize the full growing season. It is proposed as a hedge against drought stress that has contributed to a large reduction in the soybean production area in the southern USA during the last decade. The objective of this study was to compare the magnitude of genotype × environment interactions within and between regions of full season and less than full season adaptation. Thirty‐two Maturity Group I genotypes were evaluated in four environments in both Kentucky (KY) and Minnesota (MN). For yield, within state genotype × environment interactions were significant in both states whereas the genotype × state interaction was not significant. Within and between state interactions were all significant for seed protein and oil concentrations. In all cases, the percentage of possible genotype × environment crossover interactions that were significant was <10%. The yield response in KY to correlated selection in MN was predicted to be 0.94 as efficient as direct selection in KY, and the response to simulated selection at 25% selection intensity was equal for MN and KY selection. In light of this similar genotype performance between states, we recommend not initiating new breeding programs for genotypes specifically adapted to an early soybean production system.