bluuebunny/crossref_metadata_2025 huggingface dataset:
Twelve Cycles of Mass Selection for Prolificacy in Maize I. Direct and Correlated Responses
Authors: Coors J. G. , Mardones M. C.
Published: July 2010

Selection for prolificacy in maize, Zea mays L., has been recommended as an effective method to improve grain yield. The objective of this study was to evaluate selection response from 12 cycles of biparental mass selection for prolificacy in the Golden Glow maize population as measured under different plant densities and fertility levels. Genotypes evaluated were Cycles 0, 3, 6, 9, and 12, along with testcrosses of Cycles 0, 6, and 12 with three inbred lines, A632, W64A, and W9. The evaluation was conducted in 1985 in low‐fertility plots at two locations and three plant densities (38 271, 53 597, and 68 887 plants ha−1). The evaluation was repeated in 1986 at two fertility levels (no added fertilizer and 168 kg N ha−1 with 37 kg K ha−1). Number of ears plant−1 in the cycles per se increased by 2.4 and 3.3% cycle−1 in 1985 and 1986, respectively. Corresponding increases in grain yield plant−1 were 2.0 and 3.0% cycle−1, and increases in grain yield ha−1 were 2.0 and 2.8% cycle−1. Grain moisture, flowering dates, and the period between silk emergence and anthesis decreased with selection for cycles per se. Testcross responses were approximately one‐half those of cycles per se for ears plant−1 and either measure of grain yield. Grain moisture did not change with selection, and days to flowering increased by 1 to 2 d in the testcrosses. The correlations between ears plant−1 and grain yield plant−1 were 0.90 and 0.79 for cycles per se and testcrosses, respectively (both significant at P ≤ 0.05). Response to selection for ears plant−1, as reflected in the regression of ears plant−1 on cycle of selection, was greater under optimum fertility (b = 0.032 ± 0.002) than low fertility (b = 0.022 ± 0.003). Selection response for ears plant−1 was progressively greater as plant density decreased (b = 0.016 ± 0.003, 0.027 ± 0.003, and 0.036 ± 0.003 for 68 887, 53 597, and 38 271 plants ha−1, respectively).
Changes in Agronomic Traits Associated with Recurrent Selection in Two Maize Synthetics
Authors: Nyhus K. A. , Russell W. A. , Guthrie W. D.
Published: July 2010

The agronomic performance of two maize (Zea mays L.) synthetics, BSAA and BSBB, was investigated following four cycles of S1 recurrent selection for resistance to first‐generation European corn borer (Ostrinia nubilalis Hübner) (ECB) and Diplodia (Diplodia maydis (Berk.) Sacc.) stalk rot (DSR). The original and four improved cycle populations (CO–C4), their crosses to a single‐cross tester, crosses between synthetics, and three single‐cross checks were evaluated in five Iowa environments. Artificial infestations of ECB and inoculations of D. maydis were used to assess the ability of genetic resistance to reduce yield losses. Highly significant grain yield reductions were observed in both synthetics per se and averaged 20% from the C0 to the C4 in the absence of disease or insect pressure. Ear length was the main component contributing to grain yield reductions. Changes toward earlier pollen date were closely associated with reductions in plant height observed in both synthetics. The level of resistance achieved in the improved populations of BSBB was sufficient to prevent grain yield losses caused by ECB infestations and D. maydis inoculations relative to a control treatment. Additional genetic studies suggested that the response of most of the agronomic traits evaluated was associated with allelic frequency changes resulting from selection. Inbreeding depression caused by random genetic drift played a small role in most traits, with the exception of grain yield in BSBB.
Soybean Genotype Restricting Nodulation of a Previously Unrestricted Serocluster 123 Bradyrhizobia
Authors: Cregan P. B. , Keyser H. H. , Sadowsky M. J.
Published: July 2010

The displacement of indigenous Bradyrhizobium japonicum strains of serocluster 123 in soybean [Glycine max (L.) Merr.] nodules in favor of a more effective inoculant strain has been suggested as an approach to enhance N2 fixation and thereby increase soybean productivity. We previously identified soybean genotypes that restricted the nodulation and competitiveness of the serotype strain USDA 123, but did not affect the nodulation or competitiveness of many other serocluster 123 isolates. It was the objective of this work to identify a soybean genotype that reduced the nodulation and competitiveness of serocluster 123 isolate MN1‐1c, a strain that nodulated the previously identified USDA 123‐restricting genotypes very well. A total of 850 plant introductions and cultivars were screened in the greenhouse with isolate MNl‐lc. Five soybean genotypes had reduced nodulation when compared with the control cultivars. In two subsequent tests in soil and vermiculite, two of the genotypes, PI 283326 and PI 417566, restricted the nodulation of strains MNllc, USDA 110, and USDA 138. PI 417566 nodulated and fixed N2 effectively with strains USDA 123 and CB1809, while PI 283326 did not. In a test of competition for nodulation, ‘Williams’ soybean and PI 417566 were inoculated with both MNl‐lc and the inoculant quality strain CB1809. Over 90% of the nodules formed on Williams contained MNl‐lc, while less than 10% were occupied with CB1809. In contrast, 70% of the nodules of PI 417566 contained CB1809. Our results demonstrated the ability of PI 417566 to reduce the nodulation and competitiveness of MNl‐lc in favor of the inoculant quality strain CB1809, and indicated that soybean genotypes may be used to exclude specific isolates or subpopulations of serocluster 123.
Twenty‐Four Cycles of Phenotypic Recurrent Selection for Percent Oil in Maize. I. Per Se and Test‐Cross Performance
Authors: Mišević D. , Alexander D. E.
Published: July 2010

Responses and limits to selection are found to differ in various maize (Zea mays L.) populations and traits. Twenty‐four cycles of recurrent selection for high oil concentration have been completed in maize population Alexho Synthetic. The objectives of this study were to determine the response of oil concentration direct selection and correlated responses of fatty acid concentration, grain yield, and other agronomic traits. Cycles 0, 3, 5, 9, 11, 15, 18, 21, and 24 per se, the same cycles crossed to inbreds B73 and R802A, and hybrid check B73 ✕ Mo17, were evaluated in six environments at Yugoslavia and at Urbana, IL in 1985 and 1986. Selection was effective in increasing oil concentration. Total oil concentration increased by 118, 51, and 57 g kg−1 of dry matter in cycles per se B73 and R802A testcrosses, respectively. The rate of response in oil concentration was 4.9, 2.1, and 2.4 g kg−1 cycle−1 for the cycles per se for B73 and R802A testcrosses, respectively. The quadratic response was significant in testcrosses, but not in cycles per se. Thus, oil concentration has not yet shown evidence of plateauing. Oleic and linoleic acid concentration changed with selection for oil concentration in cycles per se −1.39 and 1.39 g kg−1 cycle−1, respectively. Total grain yield of the cycles per se decreased by 1718 kg ha−1, which corresponds to a response of −71.6 kg ha−1 cycle−1. Yield of the testcrosses to inbreds B73 and R802 decreased 19.7 and 15.2 kg ha−1 cycle−1, respectively. Plant height, ear height, 500 kernel weight, ear length, and lodging decreased, while grain moisture and ear row number increased with selection for oil concentration. No change was found in days to silk.
Evaluation of Recurrent Restricted Index Selection for Increasing Yield While Holding Seed Protein Constant in Soybean
Authors: Holbrook C. Corley , Burton Joseph W. , Carter Thomas E.
Published: July 2010

Yield and protein are important traits in soybean (Glycine max L. Merr.); however, genotypic correlations between seed yield and seed protein concentration are often negative, so that selection for one results in a decline of the other. Theoretically, restricted index selection allows maximum genetic gain in one or more traits while restricting genetic gain to zero in another set of one or more traits. The objectives of this study were to evaluate the use of a restricted selection index designed to increase yield while holding seed protein concentration constant; and to examine the efficiency of restricted index selection relative to direct selection for yield, protein concentration, and total protein. Two cycles of index selection resulted in a significant increase in yield and total protein, and no significant change in protein concentration. Cycle 2 parents yielded 171 kg/ha more than Cycle 0 parents and were 93 kg/ha greater in total protein. Linear regression of parental yield on cycle number showed the average increase per cycle for yield to be 86 ± 12 kg/ha. The average increase in total protein was 47 ± 4 kg/ha. These responses were similar to responses expected with use of the index. Selection based on the index was not expected to change oil concentration and no significant changes in oil were observed. In comparing the restricted index with the other selection criteria, direct selection for either yield or for total protein produced the greatest yield response. However, direct selection for yield or total protein is expected to result in significantly lower protein concentration in later cycles of selection. Thus, the use of restricted index selection appears to be the most promising long‐term approach to increasing yield while maintaining high protein concentration.
Drought Effect on Leaf Conductance and Leaf Rolling in Forage Grasses
Authors: Bittman S. , Simpson G. M.
Published: July 2010

Control of water loss is essential for plants growing in the northern Great Plains. The objectives of this study were to examine seasonal changes in leaf conductance (g1) of three forage grasses, smooth bromegrass (Bromus inermis Leyss.) Altai wildrye [Leymus angustus (Trin.) Pilger], and crested wheatgrass [Agropyron cristatus (L.) Beauv. ssp. pectinatum (Bieb.) Tzvel.] growing under contrasting water regimes to relate changes in gL to leaf water status, and to examine the relationship between leaf rolling response and leaf water status in crested wheatgras (CWg). The study was conducted on deep black soil (Melfort silty clay, Typic Cryoboroll) at Melfort, Saskatchewan. Rainout shelters and irrigation were used to impose two contrasting water regimes. Altai wildrye (AWr) generally had higher gL than the other species, while smooth bromegrass (Br) had low gL early in the season when its leaf water potential (ψL) was high. Under favorable moisture, CW8 had lowest proportion of conductance from abaxial surface among the species, although abaxial conductance in Br and AWr declined more rapidly than adaxial conductance under drought. Much of the variation in gL was not accounted for by ψL in all three species. Leaf conductance also changed gradually with leaf pressure potential (ψp) over a wide range of ψp values, particularly in the mornings. In contrast, leaf rolling in CWg was strongly related to both, ψL and ψp. The data suggest that other factors such as the rate of leaf water loss affect stomatal response to tissue water loss.
A Continuous Air‐Exchange Roomette and Gas‐Meting System
Authors: Diesburg K. L. , Christians N. E. , Gladon R. J.
Published: July 2010

Portable, controlled‐environment systems with precise control of airflow rate, gas concentration, humidity, irradiance, and temperature have been constructed with considerable expense and custom design. This roomette exposure system was built from materials common to most laboratories. Desiccators were used for the exposure of hydroponically grown Kentucky bluegrass (Poa pratensis L.) plants to ethylene concentrations of 10 to 3200 µL/L for up to 10 d. Airflow rate and ethylene influx were controlled with separate barostat towers with 1.0‐ and 0.152‐mm inside‐diameter capillary tubes, respectively. An air exchange rate of 7.5 volumes/h and a stirring magnet prevented increased temperatures and moisture condensation while replenishing CO2. Roomette temperature and irradiance were subject to ambient conditions deviating from the mean by 15 and 18%, respectively. Relative humidity was maintained at 85 ± 8% with humidifying stacks. This system can be used for effective, low‐cost, modified‐atmosphere experiments with intact plants as well as plant parts.
Relative Effect of Root and Shoot Genotypes on Yield of Common Bean under Drought Stress
Authors: White J. W. , Castillo J. A.
Published: July 2010

The inherent interactions of roots and shoots make it difficult to determine whether a characteristic such as response to drought is under control of genes expressed in roots, shoots, or throughout the plant. One approach for obtaining such information is to interchange root and shoot genotypes through grafting. In this study, plants of common bean (Phaseolus vulgaris L.) were cleft grafted and then transplanted to the field to evaluate their yield response under drought. Anticipating that the importance of root or shoot genotype would vary with genotypes evaluated, variation in rainfall patterns, and soil conditions, four yield trials with varying sets of genotypes were conducted at two sites with highly contrasting soils. At Palmira, Colombia, the soil was a fertile Mollisol (Aquic Hapludoll, pH = 7.7), and at Quilichao, Colombia, an Oxisol (Plinthic Kandiudox, pH = 5.0), where problem of low pH and high Al saturation were expected to adversely affect root growth. In all trials, root genotype had a significant and usually large effect on seed yield, while shoot genotype had no effect. No root and shoot genotype interaction occurred, and an effect of grafting was only detected in one trial. These results suggest that root characteristics are of primary importance in determining drought response of common bean and, conversely, that shoot characteristics are of much less importance. However, response of specific genotypes varies greatly with environment.
Night Temperature Effects on Soybean Phenology
Authors: Seddigh Majid , Jolliff Gary D. , Orf James H.
Published: July 2010

Knowledge of phenological development in crops as a function of environmental variables can be useful in crop improvement and management. Night temperature is an environmental factor affecting soybean [Glycine max (L.) Merr.] phenology. The objective of this experiment was to determine if accumulated heat units can be used to predict stages of reproductive development (SRD) in soybean grown under different night temperatures. Field experiments were conducted at Oregon State University and the University of Minnesota in 1984, 1985, and 1986. Twenty soybean genotypes of Maturity Groups (MG) 000, 00, and 0 of different origins were grown at Corvallis, OR and St. Paul, MN, which have mean minimum night temperatures of approximately 10 and 15 °C, respectively, during the summer months. Mean maximum temperatures for the same period of the year are similar for the two locations (ca. 26 °C). Both locations are at about the same latitude (ca. 45 °N). Dates for all SRD were recorded at both locations and accumulated heat units (using base and maximum temperatures of 6 and 30 °C, respectively) were calculated from emergence to each SRD for all genotypes. Locations were significantly different for heat units requirements for phenological development of soybean within all three MG. Genotypes within each MG were also significantly different. Location by genotype interaction was not significant. However, location by SRD, and genotype by SRD (except within MG 0) interactions were significant, while location by genotype by SRD interaction was not significant. The results indicate that night temperature has a significant effect on soybean phenology, but its relative effect varies at different SRD, and is genotype dependent. The results further suggest that a degree‐day model may be adequate to predict SRD in early maturing soybeans with the same adaptation characteristics only when grown at a fixed location for which the coefficients have been developed.
Forage Quality of Plant Parts of Perennial Grasses and Relationship to Phenology
Authors: Buxton D. R. , Marten G. C.
Published: July 2010

Limited information exists regarding forage quality variation among plant parts of divergent genetic lines within perennial grass species and its relationship to phenology. This investigation was conducted to determine these relationships in ‘Napier’ and ‘Orion’ orchardgrass (Dactylis glomerata L.), ‘Barton’ and ‘Rebound’ smooth bromegrass (Bromus inermis Leyss.), germplasm of reed canarygrass (Phalarls arundinacea L.) selected for either high or low specific leaf weight, and germplasm of tall fescue (Festuca arundinacea Schreb.) selected for either high or low rate of leaf‐area expansion. These grasses were seeded on a Webster silty clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). Morphological stage determined by the Simon and Park method during spring growth was closely related to accumulated growing degree days (GDD) by using a 5°C base (r2 = 0.97). Within each year, decline in herbage in vitro digestible dry matter (IVDDM) and crude protein (CP) concentration was closely related to calendar day, GDD, and morphological stage, although least to morphological stage. Thus, for morphological staging systems to more accurately predict forage quality, the proportion of reproductive and vegetative tillers in swards will need to be considered as well as their development. Larger cultivar differences in IVDDM occurred within stems of orchardgrass (24%) than within leaves (7%). In smooth bromegrass, Rebound stems were 12% more digestible than those of Barton, but Barton leaves were 6% more digestible than Rebound leaves. There were few genetic differences in CP concentration within any species and no consistent differences in IVDDM within the reed canarygrass or tall fescue germplasms. Thus, cultivar variation for IVDDM was not uniform among plant parts, and selecting grass plants on the basis of specific leaf weight or leaf‐area expansion rate seems to have little effect on forage quality.
A Probit Planes Method for Analyzing Seed Deterioration Data
Authors: Wilson D. O. , McDonald M. B. , St. Martin S. K.
Published: July 2010

Efficient management of seed stocks depends on an accurate description of seed longevity in storage. This work was conducted to study the implementation of the probit analysis method of modeling seed deterioration. Samples of field bean seed (Phaseolus vulgaris L.) were stored at eight temperatures (20‐60°C) and four moisture levels (12–24 g H2MO kg−1) from 0 to 372 d, and evaluated using the standard germination test. Probit analysis was applied to the entire data set simultaneously using nonlinear regression as well as the conventional environment by environment approach. Nonlinear regression was performed on the germination angles using the model statement: germination angle = arcsin√Φ[ki − p/10(Ke−CwLogM−ChT−CqT2)] where Φ is a function that computes the probability that a random variable with a normal (0,1) distribution falls below the argument of the function; Ki is a seedlot constant, and Ke, Cw, Ch, and Cq are species constants. Regression yielded the following parameter estimates: Ki = 6.68 (95.4% initial germination), Ke = 9.08, Cw = 5.20, Ch = 0.0057 and Cq = 0.00079. Use of these parameters resulted in a fit (R2 = 0.83) comparable to that obtained by the conventional environment by environment approach (R2 = 0.80). Persistent lack of fit of deterioration curves to the normal distribution model occurred in both approaches. When probit analysis was performed by environment, specifying the initial germination of the seedlot as the natural response rate, linearity of the probits over time was significantly improved. This suggests that probit analysis of seed deterioration should be performed specifying a natural response rate (6% initially dead seeds in this case) if the initial germination is below 100%
Influence of Cultural Factors on Species Dominance in a Mixed Stand of Annual Bluegrass/Creeping Bentgrass
Authors: Gaussoin R. E. , Branham B. E.
Published: July 2010

Annual bluegrass (Poa annua var. reptans (Hausskn.) Timm.) is a weedy species that is a component of most close‐cut, irrigated fairways. Research was conducted to determine the effect of five management factors and their interactions on the species composition of a mixed stand of annual bluegrass and creeping bentgrass (Agrostis palustris Huds.) maintained at 13 mm. Soil was an Owosso‐Marlette sandy loam (fine‐loamy, mixed, mesic, Typic and Glossoboric Hapludalfs). Management factors investigated for 3 yr were irrigation (daily at 75% open pan evaporation (OPE), triweekly at 110% OPE, and at wilt); clipping treatments (returned or removed); N fertility (98 or 293 kg N ha−1 yr−1); plant growth regulator (PGR) treatments (mefluidide, N‐[2,4‐dimethyl‐5‐[[(trifluoromethyl)‐sulfonyl] amino] phenyl] acetamide, at 0.14 kg ha−1; EL‐500, α‐(1‐methylethyl)‐α‐[4‐(trifluoromethoxy)phenyl] 5‐pyrimidine methanol, at 1.12 kg ha−1 and a control) and ‘Penncross’ creeping bentgrass overseeded (49 kg ha−1 yr−1) or not overseeded). Changes in annual bluegrass (AB) populations for each growing season were determined utilizing the point quadrat method. The effect of clipping removal on AB seed in the soil was determined. Returning clippings increased annual bluegrass 12% over plots in which clippings were removed. Overseeding with creeping bentgrass (CB) increased CB populations 8% compared to plots irrigated daily at 75% OPE and not overseeded. Mefluidide in combination with high N fertility resulted in AB populations 8% higher than control or EL‐500 plots at the same fertility level. Mefluidide also increased AB populations relative to control or EL‐500 treatments when clippings were removed. The greatest significant decrease in AB (28%) occurred with the treatment combination of clippings removed, overseeded, and no PGR. Removing clippings reduced the number of viable AB seeds in the soil by 60%.
Comparison of Different Methods of Identifying Inbreds Useful for Improving Elite Maize Hybrids
Authors: Zanoni Urs , Dudley J. W.
Published: July 2010

The identification of inbred lines (Iw) as sources of favorable alleles not already present in an elite hybrid (I1 × I2) is an essential part of a pedigree corn breeding program. The objective of this study was to compare different methods of estimating the value of an inbred as a parent for improving performance of an elite hybrid. A nonreciprocal diallel of four maize (Zea mays L.) inbreds derived from Stiff Stalk Synthetic (B73, B84, N7A, and H100), five derived from Lancaster (Pa91, Mo 17, H95, H102, and Va26), and five unrelated to Stiff Stalk Synthetic or Lancaster (B77, B57, B75, B79, and N152) was evaluated for grain yield, grain dry matter percentage, earliness of flowering, and plant and ear height at two locations in 1984 and 1985. A minimally biased estimate of the number of favorable alleles present in an inbred but not present in an elite hybrid (μG*) was compared with an earlier biased estimate μG), minimum upper bound estimates (UBND), inbred performance per se, general combining ability (GCA) estimates, and predicted three way performance (PTC). The μG* estimates were highly correlated with PTC and UBND estimates for most traits and with GCA for traits where additive genetic effects are of major importance. Correlations of μG* with the original μG and inbred performance per se were generally low. When the top two lines were selected within each of the 91 hybrids for the magnitude of μG* for grain yield, Pa91 was the line most often chosen followed by B73, B84, and Mol7. Estimates of relative genetic distance of Iw to I1 or I2 agreed well with pedigree information.
Selection for Vegetative Phase and Actual Filling Period Duration in Short Season Maize
Authors: Corke H. , Kannenberg L. W.
Published: July 2010

Optimum use of the limited growing period for maize (Zea mays L.) in short season areas is essential to maximize grain yield. The objective of this study was to evaluate the effects of vegetative phase duration (VPD), i.e., time from planting to silk emergence, and actual filling period duration (AFPD) on grain yield and its components in short season maize germplasm. Eleven random mating populations were subjected to divergent selection to form four subpopulations in each that varied in VPD and AFPD, both measured on an Ontario Corn Heat Units (CHU) basis. The material was evaluated in three environments in Ontario, viz., Innerkip 1981, Woodstock 1982, and Ridgetown 1982. Soil type at each location was a Burford silt loam (Typic Hapludalf). The direct effects of selection, and the correlated responses of other agronomic traits, including grain yield, were significant for most traits. For example, at Ridgetown 1982 average differences between the two extreme subpopulation groups were 200 CHU for VPD, 57 CHU for AFPD, 46 g kg−1 for grain moisture at harvest, and 2.0 Mg ha−1 for grain yield. The joint effect of varying VPD and AFPD on grain yield and components, i.e., kernel number per plant and 1000 kernel mass, was assessed by fitting quadratic response surface models. Increased VPD had positive, significant effects on grain yield; increased AFPD had slight positive effects but these were generally not significant. Differences in kernel number per plant contributed most to grain yield variation within any environment, whereas 1000 kernel mass contributed most to grain yield differences across environments. These results indicate a vegetative size limitation for grain yield of short season maize in the material studied. This should not be interpreted strictly as a source (supply of photoassimilate) limitation during the grain filling period, because preanthesis source size may partly determine kernel number per plant and thus affect sink size.
Genetic Improvement in Milling and Baking Quality of Hard Red Winter Wheat Cultivars, 1919 to 1988
Authors: Cox T. S. , Shogren M. D. , Sears R. G. , Martin T. J. , Bolte L. C.
Published: July 2010

Concern has been expressed that recently released hard red winter wheat (Triticum aestivum L.) cultivars have inferior milling and baking quality when compared with older cuitivars. This concern results from recent experiences in some commercial bakeries, as well as from negative correlations between grain yield and protein concentration commonly reported for cereal crops. We evaluated milling and baking quality traits of 40 hard red winter wheat genotypes, representing the past 70 yr of cultivar release, using grain harvested from replicated experiments at three Kansas locations in 1986 and 1987. Our objective was to determine the direction and magnitude of changes in milling and baking quality traits of hard red winter wheat resulting since breeding efforts were initiated. No significant change over time was detected for floor yield. Mean flour protein was 2 g kg−1 lower for 20 cultivars released between 1976 and 1988 (recent group) than for the 20 released previously (early group); however, regression analysis showed a significant increase since 1976. Absorption, mixing time, loaf volume, crumb grain score,and an overall baking quality index increased 0.1 to 4.6% annually, compared to the mean of ‘Turkey’. Regression coefficients were homogeneous‐over environments for all traits except flour yield. There were few significant correlations between quality traits and grain yield or volume weight. Any deterioration in quality of hard red winter wheat perceived by the baking industry must be caused by nongenetic factors, such as changes in the environment, milling practices, commercial baking methods and formulations, or some combination of these factors.
Sunflower Interspecific Hybrids and Amphiploids of Helianthus Annuus ✕ H. Bolanderi
Authors: Jan C. C. , Chandler J. M.
Published: July 2010

Sterility in F1 sunflower (Helianthus annuus L.) interspecific hybrids limits utilization of wild Helianthus species for the improvement of cultivated sunflower. This experiment was conducted to simplify and improve the effectiveness of the colchicine chromosome doubling technique, to analyze the resultant tetraploids, and to evaluate the role of chromosome doubled sectors of H. annuus ✕ H. bolanderi Gray F1 hybrids in improving backcross seed set. Apical meristems of seedlings were submerged in 150 or 250 mg L−1 colchicine solutions with 0.02 L L−1 dimethyl sulfoxide (DMSO), at pH = 5.4 for 5 h in the dark. Frequency of amphliploids, meiotic chromosome pairing, pollen stainability, and seed set were determined. The 150 mg L−1 colchicine treatment resulted in doubled sectors in 32% of the P21 ✕ H. bolanderi hybrids. Tetraploids had larger disk florets and pollen grains. Gross morphology of the tetraploid plants was similar to their diploid progenitors. Diploid P21 ✕ H. bolanderi hybrids had 5 to 6% pollen stainability and set an average of 4.5 seeds per head upon sib‐pollination. Multivalents at diakinesis involved as many as 14 chromosomes and indicated that P21 and H. bolanderi differ by seven reciprocal translocations. Chromosome doubling increased sib‐pollinated seed set to 61.8 seeds per head. Backcrosses of the amphiploids with P21 and inbred line HA89 set 13.3 and 3.0 seeds per head, respectively. Pollinating P21 and HA89 with pollen from the amphiploid resulted in 45.8 and 38.8 seeds per head, respectively. This seedling colchicine treatment was effective for doubling the chromosomes of the P21 ✕ H. bolanderi hybrids, and the resultant amphiploids had improved fertility and sufficient backcrossed seed set for efficient gene transfer into cultivated sunflower.
Variation in Flowering Response to Photoperiod in Perennial Glycine Species
Authors: Kenworthy W. J. , Brown A. H. D. , Thibou G. A.
Published: July 2010

The wild perennial Glycine spp. offer a potential source of new germplasm for the improvement of soybean [Glycine max (L.) Merr.], but information is needed on useful characteristics in this material. The objective of this study was to determine the flowering response of the wild perennial Glycine species to different daylengths. Twenty‐five accessions of G. tomentella Hayata, one of G. arenaria Tind., and one of G. tabacina (Labill.) Benth. were grown under photoperiods of 8, 12, and 16 h at day/night temperature regimes of 28/24 and 24/20 °C in a phytotron. The accessions represent the latitudinal range within each of five diploid (D1–D5) and five tetraploid (T1–T5) isozymically distinct groups of G. tomentella, and include two previously allied accessions that now have been placed in separate species. The 12‐h daylength was most conducive to cleistogamous and chasmogamous flower development while the 16‐h daylength suppressed flowering. Plants generally took longer to reach comparable phenologicai stages of growth in the cooler temperature regime, but the initial flowers appeared at similar nodes in both warm and cool temperatures. Eight accessions flowered in all three daylengths. The accessions from North Queensland in the D4 (G1300, G1780) and T2 (G1769, G1146) isozyme groups were the least sensitive since they produced both flower types in all photoperiods tested and may be of value in soybean germplasm development.
Genetic Linkage in Soybean: Linkage Group 14
Authors: Thorson P. R. , Hedges B. R. , Palmer R. G.
Published: July 2010

A more extensive genetic map i soybean [Glycine max (L.) Merr.] would be useful in cytogenetic, genetic, and plant breeding studies. The efficiency of mapping studies can be increased by utilizing F2 populations that segregate for morphological and biochemical markers. The objective of this study was to determine if a chlorophyll‐deficient mutant (Y9) was linked to any of three other morphological traits and four biochemical markers. The morphological traits tested were root fluorescence (Fr1, Fr3), hypocotyl color (W1), and pubescence tip (Pb). The biochemical markers were seed coat peroxidase (Ep), isocitrate dehydrogenase (Idh2), aconitase (Aco4), and phosphoglucoisomerase (Pgi2). Linkage was detected between Y9 and Pb, and the pooled recombination value was calculated to be 27.3 ± 1.1%, based on combined F2 and F3 data. No other linkages were detected. This represents a new linkage group (Linkage Group 14) in soybean.
Growth and Nitrogen‐Fixing Responses of Subterranean Clover to Application and Subsequent Removal of Ammonium Nitrate
Authors: Boursier Patrick J. , Raguse Charles A. , Taggard Kenneth L.
Published: July 2010

Considerable variation exists in recommendations for the use of N during establishment of forage legumes. Abundant literature documents the inhibition of N2 fixation by applied N, but few experiments determined the consequences of its subsequent removal. In this study the effects of NH4NO3 on the growth and N2 fixation of subterranean clover (Trifolium subterraneum L.) were investigated. Plants were grown in a greenhouse from seed with a modified Hoagland's solution containing 0, 2, 4, 6, 8, and 12 mM NH4NO3 for 80 d. The plants were then divided into two groups, the N treatments continued for one (+ N) group and the other group given an N‐free Hoagland's solution (−N) for an additional 21 d. Total dry wt. (DM), apparent N2 fixation (ANF), leaf area (LA), and shoot N concentration were measured and levels of photosynthetically active radiation (PAR) were monitored continuously during daylight hours. Per plant DM accumulation increased exponentially over 101 d. Neither DM nor LA accumulation was influenced by NH4NO3 at 50 and 80 d. At 101 d, both DM and LA were greater (P < 0.01) for the 2 mM treatment than for the control, and each declined linearly (P < 0.01 for ± NPM and −NLA; P < 0.05 for +NLA) with increasing NH4NO3 levels. Differences in slopes were not significant (P > 0.05). Leaf area ratio (LAR) was not influenced by NH4NO3 treatments at any of the sampling dates. Nitrogen per plant was greater than the control (P < 0.01) for both ± N at 2 mM, and it declined linearly (P < 0.05 for +N; P < 0.01 for −N) with increasing NH4NO3 levels. A reduction in per‐plant ANF was significant (P < 0.01) over all NH4NO3 levels at 50 and 101 d and over 6 to 12 mM levels at 80 d. Plants previously grown at 6 to 12 mM levels (−N) recovered much of their ANF ability at 101 d, while ANF for + N plants declined (P < 0.01) across all N levels. Expression of ANF on a per unit DM or LA basis improved interpretation of these data. Nitrogen concentration of shoots for all treatments except 12 mM −N was similar to the control at 101 d. Overall, N yields per plant were best explained by DM accumulation from 80 to 101 d. The ability to rapidly recover N2‐fixing ability following depletion of inorganic soil solution N provides opportunity for early season use of N fertilizer in annual range systems.
Bermudagrass Response to Chilling Temperatures as Influenced by Iron and Benzyladenine
Authors: White R. H. , Schmidt R. E.
Published: July 2010

Chilling temperatures (10 to 15 °C down to 0 °C) disrupt photosynthesis, reduce growth, and discolor bermudagrass (Cynodon spp.) turf. We studied the effects of chilling in controlled environments on the CO2 exchange rate (CER), total nonstructural carbohydrate (TNC) content, amylolytic enzyme activity (AEA), chlorophyll content, and turf color in two bermudagrasses to determine the influence of iron and benzyladenine (BA) upon these parameters. Grasses were grown on a Frederick silt loam (clayey, kaolinitic mesic Typic Hapludult) at pH 5.7 with 4.8 g N m−2 month−1. Daytime CER of ‘Midiron’ and ‘Tifgreen’ declined 71 and 82% and night‐time CER declined 55 and 52%, respectively, during 4 d at chilling (10/7 °C day/ night) temperatures. Midiron CER was 70% of the original daytime rate at 30 °C but Tifgreen returned to within only 27% when returned to 30 °C for 2 h after the chilling treatment. In contrast, night‐time CER fully recovered. Tifgreen's low daytime CER was associated with a 25% decrease in chlorophyll content, 60% decrease in AEA, and 160% increase in leaf TNC during chilling. Midiron chlorophyll content was unchanged, AEA decreased 30%, and leaf TNC increased 88% during chilling. The Fe treatments had similar prechill daytime CER. However, 120 mg Fe m−2 as FeDTPA maintained a 23% higher average daytime CER than 0 mg Fe m−2 after chilling and following recovery from chilling. Night‐time CER before and after the chilling regime was not affected by Fe. Average night‐time CER was 28% higher for the 120 than the 0 mg Fe m−2 treatment after the recovery period. Leaf TNC accumulation was similar for the Fe treatments. Darker green turf color was observed for 120 than for 0 mg Fe m−2 after the chilling period although no difference in chlorophyll content occurred. Daytime and night‐time CER, chlorophyll content, TNC, and color scores for the 0 and 12.4 mg BA m−2 treatments were similar at each temperature regime. Although chlorophyll loss and TNC accumulation in leaves are associated with photosynthetic inactivity in chill‐sensitive bermudagrasses, disruption of carbon partitioning and utilization probably contribute to reduced growth and turf quality of bermudagrasses at chilling temperatures. Foliarly applied Fe may facilitate the maintenance of physiological activity and more desirable turf quality of bermudagrass exposed to chilling temperatures.
Pasture Sampling Requirement for near Infrared Reflectance Spectroscopy Estimates of Botanical Composition
Authors: Hill N. S. , Stuedemann J. A. , Ware G. O. , Petersen J. C.
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) has been used predict species composition and plant components in hay and pasture samples. Two measures of error, bias and standard error of prediction (SEP), are important to consider with respect to accuracy of NIRS predictions of laboratory values of samples. Our objectives were to determine how sample size affects the precision and accuracy of the NIRS estimate of the mean of pasture samples. In Exp. I, four grazed pastures of pure and mixed alfalfa (Medicago sativa L.) and tall fescue (Festuca arundinacea Schreb.) were sampled over 12‐d grazing period in July 1987. Samples were separated into percentage of tall fescue, alfalfa leaf, and alfalfa stem and used for development of NIRS calibration equations. The SEP was used to calculate boundary limits, which should contain the NIRS estimates for 1, 5, 8, or 10 pasture samples. Boundary limits decreased from 11.0 to 2.3% units as sample number increased. The increase in accuracy was inversely related to the square root of the sample size. Experiment 2 was similar to Exp. I, except all samples gathered on the first day of grazing within one of the pasture mixtures were used as a verification set for the NIPS calibration equations. Pasture means and standard deviations were similar for laboratory and NIPS values. We conclude that the pasture sample size needed to obtain an acceptable confidence interval of the pasture mean for botanical composition is a sufficient sample size for accurate and precise NIPS prediction of that mean.
Somatic Embryogenesis and Plant Regeneration from Suspension Cultures of Red Fescue
Authors: Zaghmout O. M. F. , Torello W. A.
Published: July 2010

The development of embryogenic cell suspension cultures from which whole‐viable plants could be regenerated on a reliable basis would increase the range of techniques that may be applied by somatic approaches toward genetic modification. The objective of this study was to develop such a cultural system from embryogenic callus tissue of ‘Dawson’ red fescue (Festuca rubra var trichophylla Gaud.). Embryogenic cell suspension cultures were initiated from highly embryogenic callus tissue that had been cultured for over 4 yr. The optimal basal medium for suspension cultures consisted of one‐half strength Murashige and Skoog (MS) salts supplemented with 30 g L−1 sucrose, Gamborgs B‐5 vitamins, 3 g L−1 casein hydrolysate (CH), and 4 mg L−1 of 2,4‐dichlorophenoxyacetic acid (2,4‐D). The addition of CH significantly enhanced culture growth rates as measured by packed cell volumes. Prefiltering newly initiated suspensions through a 31‐μm filter screen was critical in removing relatively faster growing non‐embryogenic (NE) cell types. The use of a discontinuous percoll gradient was as effective as filtering in removing NE cells but was more time consuming. Prolific regeneration of whole, viable plants was attained by transferring embryogenic cell clusters to a hormone‐free, half‐strength MS basal medium supplemented B‐5 vitamins and 8 g L−1 agar.
Partitioning of Blending Ability Using Two‐Way Blends and Component Lines of Soybean
Authors: Gizlice Ziya , Carter T. E. , Burton J. W. , Emigh T. H.
Published: July 2010

Numerous studies have quantified the performance of multiline mixtures or blends in crop species. Few multiline cultivurs, however, have been released for farm use. A primary reason is the lack of efficient methods for identifying genotypes that enhance blend performance. This study was undertaken to evaluate a practical method that describes the relative worth of genotypes in blend combination. Eight adapted soybean [Glycine max (L.) Merr.] genotypes and all two‐way blend combinations were evaluated in eight environments in North Carolina during 1983 to 1985. Genetic effects were partitioned through diallel analysis of two variables: blend yield per se and blend response (BR), the deviation of blend yield from the pure line component average. General blending ability (GBA) and its components, true general competitive ability (TGCA), and general yielding ability (GYA) are defined and related to existing terminology to describe the worth of a genotype as a blend component. General blending ability, statistically analogous to general combining ability, is obtained from diallel analysis of blend yield per se and reflects both the ability of a genotype to affect blend response through competition and its separate ability to yield in pure stand. The TGCA is obtained from diallel analysis of BR and reflects only that contribution of a blend component due to competitive effects. The GYA reflects only the innate yielding ability of a genotype in pure stand and is obtained as the difference between GBA and TGCA. Genotypes in this study differed significantly for GBA, TGCA, and GYA, while components analogous to specific combining ability were nonsignificant. The TGCA and GYA were found to be independent and equally important components of GBA, indicating that both effects must be considered in describing the relative worth of a genotype in blend performance. Results indicate that some genotypes consistently enhance blend performance through competition regardless of the partner genotype involved. This is a novel finding that has implications to the development of superior blends. The GBA, TGCA, and GYA taken together may be used in a practical way to identify desirable genotypes for blending.
Mode of Gene Action for Resistance in Maize to Maize Streak Virus
Authors: Kim Soon‐Kwon , Efron Y. , Fajemisin J. M. , Buddenhagen I. W.
Published: July 2010

Maize streak virus (MSV) transmitted by Cicadulina leafhoppers causes severe yield loss of maize (Zea mays L.) in Africa. This paper summarizes our studies on gene action for resistance to MSV using generation mean analysis. Crosses were made between a resistant inbred (IB32) and four susceptible inbreds (BI4, B68, B73, and Moi7). A total of II 255 plants from the four sets of biparentul crosses, their F2, backcross, and F3 progenies were grown in four experiments under severe artifically induced MSV epiphytotics at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. Severity of streak symptoms on test plants was classified on a five‐point scale based on the amount of streaking of leaves. Under severe artificial infestation inside a screenhouse, average ratings of resistant and susceptible parents were 1.3 and 5.0, respectively. The average F1 rating was 3.13, which was close to the mean midparent value (3.15). The average F2 rating was 2.83, which was 0.3 units more resistant than the F1 value. The average rating of four F1 crosses in the field was 2.22, 0.81 units more resistant than the mean midparental value (3.03). Average rating of the F2 populations was 2.22, which was similar to that of the F1 (2.27). Backcross ratings were close to mean of the F1 and recurrent parent. Individual F3 plants derived from same rating of F2 plants showed considerable variation in ratings. Resistance to MSV from IB32 appeared to be inherited quantitatively with relatively small numbers of genes involved. The symptoms of MSV varied with the genetic background of the susceptible parent. Simple recurrent selection or modified backcross breeding methods could be used to breed for MSV resistance in Africa.
Increasing Stress Resistance by in Vitro Selection for Abscisic Acid Insensitivity in Wheat
Authors: Lu D. B. , Sears R. G. , Paulsen G. M.
Published: July 2010

Abscisic acid (ABA) concentration in wheat (Triticum aestivum L.) plants increases during heat and drought stress and is associated with stomatal closure, low photosynthetic rate, and senescence. This research was conducted to determine if wheat somaclones selected in vitro for ABA insensitivity are resistant to heat and drought stress and to identify traits that contribute to stress resistance as ABA insensitivity is increased. Five ABA‐insensitive somadones and their parental line ND7532 were grown in Hoagland's solution until anthesis, then heat and osmotic stresses were applied through maturity. Heat stress was induced by increasing temperature from 25/20 to 35/25 °C, and osmotic stress (−0.05 MPa) was induced by adding 100 g kg−1 polyethylene glycol‐1000 (PEG‐1000) to the hydroponic solution. An exceptional somaclone KTC86211 and parent ND7532 were grown in 1:1:1 sand: Reading silt loam (fine, mixed, mesic Typic Argiudoil):peat. Heat stress was applied as in the first experiment, and drought stress (−0.5 MPa) was induced by withholding water after anthesis and soil water potential was monitored with a thermocouple psychrometer. The ABA‐insensitive somaclones KTC86211 and KTC86424 had significantly lower stomatal resistance, higher variable leaf chlorophyll fluorescence, longer leaf area duration, and greater kernel wt. and grain yield per plant than the parent in the first experiment. Crop growth rate, grain filling rate, and grain filling duration were higher in the ABA‐insensitive somaclone KTC86211 than in ND7532 in the second experiment, indicating that greater grain yield per plant resulted from rapid assimilation and translocation of nutrients and delayed senescence. We concluded that ABA‐insensitive genotypes may have high growth rates and long leaf area duration under stress and that selection for ABA insensitivity may be an effective approach to improving heat and drought resistance in wheat.
Drought Effects on Water Relations of Three Cultivated Grasses
Authors: Bittman S. , Simpson G. M.
Published: July 2010

Water is the predominant environmental factor controlling yield of forages in the northern Great Plains. This study was conducted to compare the effects of contrasting soil water regimes on the water relations of smooth bromegrass (Bromus inermis Leyss.), crested wheatgrass [Agropyron cristatum (L.) Beauv. ssp. pectinatum (Bieb.) Travel.], and Altai wildrye [Leymus angustus (Trin.) Pilger]. The grasses were grown on deep black soil (Melfort silt)' clay, Typic Cryoboroll) under two soil water regimes: DRY plots were covered by rain‐out shelters beginning at the end of May and IRR plots were watered when soil water potential averaged −0.07 MPa. Measurements of soil water potential (ψs), leaf water potential (ψ/L), osmotic potential (ψ,), and relative water content (RWC) were taken periodically during first and second growths in 1983 and 1984. Crested wheatgrass (CWg) generally had lower ψL and RWC than smooth bromegrass or Altai wildrye. At a specific ψs, ψL of CWg was 0.3 to 0.7 MPa lower than that of Br, possibly resulting from small xylem vessels in CWg. Osmotic adjustment in CWg and smooth bromegrass was similar, but CWg lost more water for a change in pressure potential(ψp), which helped it maintain ψp. Differences in water relations reflected growth patterns and drought resistance strategies previously reported for these species.