bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield and Reproductive Growth of Simulated and Field‐Grown Soybean. II. Dry Matter Allocation and Seed Growth Rates1
Authors: Salado‐Navarro Luis R. , Sinclair Thomas R. , Hinson Kuell
Published: July 2010

A better understanding of the main plant traits that ultimately lead to seed yield in soybean [Glycine max (L.) Merr.] is needed. Objectives were (i) to examine the association among various seed growth traits and yield, and (ii) to compare the stability across environments of dry matter allocation coefficient (DMAC) and seed growth rate on a land area (SGR) and individual seed (ISGR) basis with that for yield. Materials were 45 simulated genotypes generated with a model of soybean reproductive growth, and field evaluations of 88 random (1982) and 17 selected (1983) F7 determinate genotypes from two crosses plus their parents. Randomized complete blocks were used in three field growth analyses performed at Gainesville, FL. Negative correlations (r= −0.44**, significant at the 0.01 probability level) between DMAC and yield were predicted using simulated genotypes and were also found in field‐grown soybean (r= −0.18 to −0.40). Simulations predicted strong negative correlations of DMAC with effective filling period (EFP) (r= −0.92**) and with reproductive period duration (RPD) (r= −0.89**). In most cases field data supported this hypothesis. Correlations of DMAC were r=0.30 to −0.72** with EFP, r= −0.79** to ‐0.85** with RPD, and r= −0.29* (significant at the 0.05 probability level) to −0.60** with the period R5 to R7. Simulations predicted linear yield increases with respect to SGR (r2=0.71**). In all cases, field results showed close agreement with the simulations (r2=0.64** to 0.95**). Correlations of ISGR with yield were low and positive (r=0.03 to 0.39). In simulated genotypes many pathways led to medium yields, but the highest yield was attained by a genotype with the highest biomass at the beginning of seed growth, highest potential maximum net hexose crop growth rate, and the lowest DMAC, which resulted in a high SGR and the longest seed‐filling duration. Highly significant genotype by environment interactions were observed for DMAC and yield but not for SGR and ISGR. Results suggest that high DMAC strongly limited seed‐filling duration and that DMAC estimates the intensity of self‐senescence during seed filling. Yield was mainly a linear function of SGR, and ISGR was poorly associated with yield.
Solar Tracking: Light Avoidance Induced by Water Stress in Leaves of Kidney Bean Seedlings in the Field1
Authors: Berg V. Seymour , Hsiao T. C.
Published: July 2010

Solar tracking by unifoliolate leaves of small red kidney bean (Phaseolus vulgaris L.) seedlings was studied in the field in the summer, using a simple solar‐foliar inclinometer to measure the angle between the leaf surface and the sun's rays. Changes in leaf orientation increased light interception in the morning and late afternoon, while reducing light interception at midday. Light avoidance occurred even in well‐watered plants, but was more marked for plants growing in drier soil. Light avoidance was also observed under diffused but directional light in a growth chamber, where changes in leaf angle were proportional to changes in shoot water potential factors. Temperature differences between leaves of tracking plants in well‐watered soil and those in drier soil were small due to the compensating change in light interception. Holding leaves horizontal increased leaf temperatures in the hottest part of the day slightly above those of tracking leaves for well‐watered plants, but considerably more for plants with lower water potentials. When leaves were held horizontal, water potentials were lower at midday and in early afternoon than they were for tracking leaves. Photosynthesis was enhanced at midday in both wet and dry treatments for leaves held horizontal. At 1600 h horizontal leaves of plants in both treatments, and tracking leaves of plants in the dry treatment, photosynthesized at a low rate, although tracking leaves intercepted more light. Tracking leaves of plants in the wet treatment assimilated at a substantially higher rate.
Nitrogen‐Potassium Fertilization and Soil Moisture Effects on Growth and Development of Drip‐Irrigated Sugarcane1
Authors: Ingram K. T. , Hilton H. W.
Published: July 2010

Because of the lack of N‐K balance in previous experiments and because of the relatively new development of drip irrigation, field research was conducted to determine the effects of N‐K fertilization and soil moisture on the growth and development of drip‐irrigated sugarcane (Saccharum spp. hybrids). Two levels of N‐K fertilization, 575‐551 and 225‐217 kg ha−1, were applied in factorial combination with three soil moisture regimes: (i) maintaining soil moisture tension between 10 and 20 kPa through frequent irrigation (designated 10‐20); (ii) maintaining soil moisture tension between 30 and 40 kPa through frequent irrigation (30‐40); and (iii) alternately allowing soil to dry to 80 kPa tension then irrigating to wet soil to 10 kPa (10‐80). Thus, there were six treatment combinations. The soil was a Molokai silty clay loam (Typic Torrox). Stalk population was 16% greater (P<0.05) in high than low N‐K treatments, whereas there was no significant effect of irrigation treatment on stalk population. In samples taken from 200 to 250 days after planting, leaf area index was about 30% greater in the 575‐551 than 225‐217 kg N‐K ha−1 treatments (P<O.OO1). Soil moisture was directly related to number of green leaves per stalk and inversely related to number of chlorotic leaves per stalk. Respective cane and crop growth (dry matter assimilation) rates were 25 and 24% higher in treatments receiving 575‐551 than 225‐217 kg N‐K ha−1 (P<O.O1). Cane and crop growth rates were 27 and 23% greater for the 10‐20 than 30‐40 and 10‐80 soil moisture treatments, with no significant difference between growth rates of the 30‐40 and 10‐80 soil moisture regimes. Based on sugar yields, N‐K fertilizer use efficiency was greatest for the 10‐20 soil moisture treatments and water use efficiency was greatest for the 575‐551 kg N‐K ha−1 treatments. Thus, we conclude that N‐K and soil moisture inputs should be balanced and at high levels to maximize production and the efficient use of inputs. Furthermore, these results support the management practices of frequent fertilization and irrigation which have been adopted by many growers of drip‐irrigated sugarcane.
Anther Culture of Elite Genotypes of Maize1
Authors: Petolino J. F. , Jones A. M.
Published: July 2010

The use of anther culture as a means of haploid breeding in maize (Zea mays L.) has been limited by the paucity of responsive genotypes. The present study was designed to identify agronomically acceptable germplasm of maize that responds to anther culture. In 1984, 25 related‐line crosses were evaluated for their ability to produce embryoids from cultured anthers. Twelve genotypes responded with at least one anther producing embryoids; with six exhibiting response frequencies of 1.0% or greater. In 1985, 27 genotypes were screened and 17 responded, nine of which displayed frequencies of 1.0% or greater. The most responsive crosses contained the lines H99, FR16, and Pa91. Plants could be regenerated from most responsive genotypes, however, seed production resulting from spontaneous chromosome doubling was low.
Heterosis in Upland Cotton. I. Growth and Leaf Area Partitioning1
Authors: Wells Randy , Meredith William R.
Published: July 2010

There is relatively little information concerning the physiological alterations that are related to heterosis in cotton Gossypium hirsutum L.). To better understand this phenomenon, growth and partitioning of dry matter in four established upland cotton cultivars and their F1 hybrid progeny were monitored in three environments. Total biomass was greater in hybrids than their parents in all environments. Growth analysis found that heterosis greatly affected early development of the hybrids. Although increases in leaf area were greater in the progeny, they were proportional to the dry weight growth of the plant, resulting in similar leaf area partitioning (LAP) coefficients for both parents and hybrids. The greater leaf area index of the hybrids, resulting from greater net assimilation rates but similar LAP values, further stimulates growth via greater interception of light and associated photosynthate production prior to the advent of significant interplant competition.
Inheritance and Combining Ability of Leafhopper Defense Mechanisms in Common Bean1
Authors: Kornegay Julia L. , Temple Steven R.
Published: July 2010

The leafhopper (Empoasca kraemeri Ross and Moore) is a serious pest of common bean (Phaseolus vulgaris L.) in Latin America. Previous studies showed that different leafhopper defense mechanisms were present in bean lines, although all lines suffered considerable damage when leafhopper populations were high. Studies were undertaken to determine the inheritance and combining ability of leafhopper defense mechanisms in beans under field conditions. Bean lines EMP 81 and EMP 82, tolerant to leafhopper feeding damage, and lines EMP 89, EMP 94, and EMP 97, containing antixenosis resistance (a defense mechanism that makes these lines less preferred for leafhopper oviposition) were selected to study. A generation means analysis using EMP 81, EMP 89, and EMP 94, in crosses with a susceptible line, BAT 41, showed that the additive‐dominance genetic model was sufficient to explain the inheritance of tolerance and antixenosis defense mechanisms in these lines. Additive and dominance gene effects were significant for yield of plants under leafhopper attack and feeding damage, although dominance gene effects appeared to be more important in the inheritance of yield. Only additive gene effects were significant for nymphal counts. Similar results were found in the estimation of general and specific combining ability effects in a diallel study of F1 and F2 progeny of crosses among the five resistant bean lines. Certain crosses combining antixenosis and tolerance defense mechanisms resulted in higher F2 yields than would be expected on the bases of the mean performance of their parental lines. The results suggest that transgressive segregation for higher resistance levels may result from crosses among bean lines containing different defense mechanisms.
Developmental Patterns in Five Spring Wheat Genotypes Varying in Time to Maturity1
Authors: Wong L. S. L. , Baker R. J.
Published: July 2010

A better understanding of the developmental aspects of time to maturity may assist in developing early maturing cultivars with acceptable grain yield in spring wheat, Triticum aestivum L. The objectives of this study were to determine the developmental patterns in five spring wheat genotypes as well as the relationships among developmental periods and certain morphological traits. This study was conducted at the University of Saskatchewan in 1982,1983, and 1984. In all field experiments, main shoots of randomly selected plants were used for data collection. ‘Ingal’, ‘Ken 149’, and ‘Potam’ were early maturing genotypes from Alaska, Manchuria, and Mexico, respectively, while ‘Glenlea’ and NB402 were late maturing genotypes from the Canadian Prairies. In general, the difference between the three introduced genotypes and the two Canadian genotypes in time to maturity could be attributed to the difference in duration of the preanthesis period. Ingal required fewer growing degree‐days to reach maturity than Ken 149 and Potam, due to a shorter grain‐filling period. In spite of their diverse origin, Ken 149 and Potam were similar in time to maturity as well as in the other 15 traits evaluated. Glenlea and NB402 were similar in time to maturity. However, compared with NB402, Glenlea spent less time in both the vegetative and spikelet initiation periods and more time in the spike growth period. Differences in developmental patterns among the genotypes were related to differences in number of leaves, number of spikelets, rate of spikelet initiation, spike length, and kernel weight.
Influence of Deep Root Density on Root Pulling Resistance in Rice1
Authors: Ekanayake I. J. , Garrity D. P. , O'Toole J. C.
Published: July 2010

Rooting patterns play an important role in determining the degree of resistance of rice (Oryza sativa L.) cultivars to water stress. Root pulling resistance (RPR) has been suggested as a technique to evaluate genotypic differences in root growth in rice. This work investigated the association between RPR and root length density of the unpulled root component (portion of the root system remaining in the soil after pulling). The rate of increase in RPR among rice cultivars with plant age was also examined. A clamp apparatus connected to a modified spring balance was attached to the base of the plant to measure the pulling resistance. Characteristics of the pulled (portion of the root system removed from the soil) and unpulled root components were assessed in five rice genotypes varying from drought sensitive to tolerant. Two genotypes (IRS2 and MGL2) recorded high RPR, two intermediate (IR 36 and IR442‐2‐58), and one had low RPR (IR20). Genotypes with high RPR were characterized by larger, thicker, and denser root systems. Pulling resistance was significantly correlated with root volume, dry weight, thickness, and the number of thick roots in the pulled root component. Several traits of the pulled root component also had highly significant positive correlations with root length density (RLD) at 0.3 to 0.6 m soil depth. However, RPR was most highly correlated with the RLD of the unpulled component, particularly the RLD from 0.45 to 0.6 m depth (r= 0.88**, significant at the 0.01 probability level). These results suggest that high RPR is strongly related to the ability of the plant to rapidly develop greater root penetration into deeper soil layers. They tend to confirm the utility of RPR as a practical technique in selection for superior root systems in a rice improvement program. Time course analysis of RPR among cultivars showed that genotypic differences increased with plant age. The rate of increase in RPR was low for the first 24 to 25 days after transplanting, but accelerated greatly after this date in tests over two seasons. This change in the rate of increase may correspond with the time at which the root system penetrates into the firm soil layers below the puddled layer. Among the dates used in the study, the optimum sampling date was 33 days after transplanting.
Response of Leaf Growth, Leaf Nitrogen, and Stomatal Conductance to Water Deficits during Vegetative Growth of Field‐Grown Soybean1
Authors: Muchow R. C. , Sinclair T. R. , Bennett J. M. , Hammond L. C.
Published: July 2010

Changes in leaf area development, leaf N content, and stomatal conductance were examined in field‐grown soybean [Glycine max (L) Merr.] in response to soil water deficits imposed during vegetative growth after canopy closure. The consequences of these changes for biomass accumulation were assessed in terms of the amount of photosynthetically active radiation (PAR) intercepted by the crops and the efficiency of its use to accumulate biomass. Mild water deficits decreased leaf expansion more than leaf production, while leaf senescence was similar to that in the well‐watered control. However, the decrease in leaf area development was insufficient to have an impact on PAR interception, but biomass accumulation efficiency was decreased. The decrease in biomass accumulation efficiency was associated with lowered stomatal conductance, while specific leaf N content, a determinant of long‐term photosynthetic capacity, was relatively unaffected. In contrast, severe water deficits decreased both the amount of PAR intercepted and its efficiency of use in biomass accumulation. Accelerated leaf senescence was much more significant in decreasing PAR interception than the decrease in leaf expansion and production. Specific leaf N content actually increased under severe water deficits but, given the extremely low stomatal conductances, had no effect on crop biomass accumulation.
Role of Placental Sac in Endosperm Carbohydrate Import in Sorghum Caryopses1
Authors: Maness Niels O. , McBee George G.
Published: July 2010

An anatomical study of tissues involved with carbohydrate import into developing caryopsis endosperm in three cultivars of sorghum [Sorghum bicolor (L.) Moench] was complemented by determination of the assimilate concentration of placental sac fluids to investigate the role of the placental sac. Individual panicles were tagged daily at anthesis. Caryopses were harvested from anthesis to maturity and from 10 to 20 days postanthesis at 5‐day intervals for microscopic examination and placental sac fluid carbohydrate analysis. Formation of endosperm tissue by 5 days postanthesis coincided with differentiation of transfer cells within the outer surface of endosperm tissue adjacent to the placental region. All caryopsis tissues thought to be associated with carbohydrate movement to the endosperm (vascular tissue, chalazal tissue, remnant nucellar tissue, the placental sac, and aleurone transfer cells) were present in the cultivars by 10 days postanthesis. The role of the placental sac as an apoplastic sink for hexose import into the endosperm was supported by anatomical location and high glucose and fructose concentrations relative to sucrose concentrations in placental sac fluids of all cultivars at 10,15, and 20 days postanthesis. A model for hexose import into the endosperm following vascular unloading in sorghum was developed based on prior findings for maize (Zea mays L.). Results indicate that the placental sac provides an intermediate apoplastic sink for assimilate accumulation from placental tissues and subsequent hexose import by transfer cells of the endosperm.
Improvement in Callus Growth and Plantlet Formation in Creeping Bentgrass1
Authors: Blanche Fe C. , Krans J. V. , Coats G. E.
Published: July 2010

Optimizing callus growth and plantlet formation from somatic callus is advantageous in the recovery of desirable variants using in vitro cell selection methods. Using 24‐week‐old ‘Penncross’ creeping bentgrass (‘Agrostis palustris Huds‘.) stock callus (SC), callus growth and plantlet formation were evaluated from plated SC previously cultured in suspension for 12 and 24 days and SC not previously cultured in suspension. In addition, callus growth and plantlet formation were evaluated from SC plated at aggregate sizes of 0.5‐ to 1.0‐mm and 0.25‐ to 0.5‐mm diam and aggregate densities of 1, 3, and 5 mg.50 mm−2. Callus growth was twofold greater from SC previously cultured in suspension than from SC not previously cultured in suspension. Plantlet formation was inhibited from SC previously cultured in suspension (<10 plantlets/dish) compared to SC not previously cultured in suspension (250 to 450 plantlets/dish). Plated SC aggregates of 0.5‐ to 1.0‐mm diam generally had greater growth than aggregates 0.25‐to 0.5‐mm diam. At both aggregate size dimensions, greatest growth occurred from SC plated at 1 mg.50 mm−2 plating density. Aggregates 0.5‐ to 1.0‐mm and 0.25‐ to 0.5‐ mm diam had the greatest plantlet formation at 1 mg.50 mm−2 and 1 and 3 mg.50 mm−2 densities, respectively.
Triploids and Tetraploids from 4x−2x Crosses in Red Clover1
Authors: Taylor N. L. , Wiseman E. O.
Published: July 2010

The feasibility of broadening the genetic base of tetraploid cultivars of red clover (Trifolium pratense L.) (2n=4x=28) by 4x−x crosses was examined. A white‐flowered nonleafmarked tetraploid clone served as the pistillate parent in bee‐cage crosses with diploid red‐flowered ‘Kenstar’ plants. Among 169 plants produced, 14 died, 119 were selfs (white flowered), and 36 were hybrids (red flowered). Thirty‐three of the 36 hybrids were triploid (3x= 21 or 22), two were tetraploid (4x=28 or 30) presumedly via male gametic restitution, and one was pentaploid, probably from the union of a 2n =4x female gamete and a normal (n=x) male gamete. Pollen stainability of the diploid and tetraploid parents was 96 and 80% respectively. Among progenies, triploids averaged 71%, tetraploid sells 75%, and F1 tetrapioids 88% for pollen stainability. Whole‐plant size differences among ploidy levels were not large, but ploidy levels could be distinguished by leaflet shape. At metaphase I, eutriploids averaged 4.34 trivalents, 2.70 bivalents, and 2.58 univalents. Aneutriploids (3x= 22) had a low frequency of quadrivalents, whereas eutriploids (3x= 21) had none. The F1 tetraploids, produced by 2n gametes, had more quadrivalent associations than two selfed plants of the tetraploid parent, produced by nitrous‐oxide doubling. Crosses with triploids (3x−2x and 2x−3x) yielded viable seeds that should lead to the development of trisomic plants useful for gene mapping. Broadening the genetic bases of tetraploid cultivars using 4x−2x crosses is quite feasible but larger populations may be necessary than for 2x−4x crosses because of the high frequency of triploids produced.
Pollen Viability, Pollen Shedding, and Combining Ability for Tassel Heat Tolerance in Maize1
Authors: Schoper J. B. , Lambert R. J. , Vasilas B. L.
Published: July 2010

High temperatures during maize (Zea mays L.) pollination limit kernel number. Knowledge is limited on the effect of heat stress on both pollen viability and tassel shedding characteristics or of possible heat tolerance sources and testers. The purpose of this research was to determine the tassel response to heat stress, as measured by in vitro pollen viability and shedding characteristics, and the combining ability for these traits using a diallel of four heat‐tolerant and three heat‐intolerant inbreds. Tassels from field‐grown plants were excised at the beginning of anthesis, immediately placed in sufficient water to cover the base, and transferred to growth chambers. The growth chambers were maintained at light period temperatures of 29 and 38°C and dark period temperatures of 24 and 32°C, respectively. In vitro germination, anther emergence, and tassel color were determined after 24 h in the growth chamber. Due to bursting, low levels of germination were obtained, but the percentage of nongerminated pollen increased greatly at the high temperature (65% mean increase). The increase in nongerminated pollen varied among the genotypes, and all except B73 × Mo17 and N28 × Mo17 had statistically significant increases at the high temperature. Mo17 had the most desirable general combining ability (GCA) effect at the high temperature for nongerminated pollen. Specific combining ability effects were significant for nongerminated pollen and accounted for 51% of the genotype and genotype × temperature sum of squares. Anther emergence of the central tassel spike decreased differentially among the hybrids at the high temperature. Mo17 had the most desirable GCA effect for anther emergence. Anther emergence and pollen viability did not always respond the same to high temperature. Results from this study indicate pollen shed and viability must be considered in tassel heat tolerance and hybrids involving Mo17 had the most heat tolerant tassels.
Stress Tolerance and Adaptation in Spring Wheat1
Authors: Bruckner P. L. , Frohberg R. C.
Published: July 2010

Development of stress tolerant cultivars is an objective of many breeding programs, but success has been limited by inadequate screening techniques, and the lack of genotypes that show clear differences in response to well defined environmental stresses. Twenty spring wheat (Triticum aestivum L.) genotypes were evaluated over a range of water and high temperature‐stressed environments (15 location‐years) to establish standards for evaluation of stress tolerance screening techniques and to characterize genotypic stress tolerance and adaptation to stress environments. Overall and postanthesis stress tolerances were determined using grain yield and kernel weight responses, respectively. Stress tolerances were estimated using stress susceptibility indices (S), grain yields and kernel weights predicted for a hypothetical severe‐stress environment from regression parameters, and yields and kernel weights per se in five stress environments. Yield‐based stress tolerance estimates were correlated among all estimation methods. The stress susceptibility index identified stress tolerant genotypes that did not have outstanding yield performance per se in stress environments due to low yield potential, but which minimized yield loss under stress conditions. Kernel weightbased estimates of postanthesis stress tolerance using S were not correlated with predicted kernel weights in a hypothetical severestress environment or with kernel weights per se in five stress environments. Genotypes evaluated in this study exhibited a wide range in stress tolerance and adaptation to stress‐prone environments. Stress tolerant and susceptible genotypes were identified to use in evaluation of stress tolerance screening techniques. Used in tandem, regression analyses of genotype ✕ environment interactions, stress susceptibility indices, and stress performance per se, provided a more complete description of genotypic stress tolerances than did any analysis used alone.
Osmotic Potential and Starch Accumulation in Leaves of Field‐Grown Soybean1
Authors: Cortes P. M. , Sinclair T. R.
Published: July 2010

Although osmotic adjustment in response to a variety of factors has been observed in the leaves of numerous species, the mechanism by which it occurs is still unclear. It has been suggested that, in some cases, enlarging starch granules within leaf cells displace part of the symplasm and result in osmotic adjustment of the remaining osmotic volume. This study tested whether such a mechanism operated in the leaves of field‐grown soybean [Glycine max (L.) Merr.]. Plants of the cv. UFV‐1 were grown in the field on Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Paleudult) and their uppermost, fully expanded leaves were sampled at dawn during midpodfill. In order to vary the amount of leaf starch, the plants were subjected to four treatments; (i) no shading, (ii) intermittent shade without pods, (iii) intermittent shade with pods, and (iv) continuous shading. Leaf osmotic potential was measured with a thermocouple psychrometer and starch concentration was determined for the same leaves by first hydrolyzing the starch and then measuring the resulting glucose. Naturally occurring light fluctuations were found to result in predawn osmotic adjustment, and increases in incident radiation resulted in an increase in starch and an associated decrease in osmotic potential. The changes in osmotic potential could only be partially explained as the result of a physical system in which the volume of starch varied and changed the osmotic volume.
Seed Growth Characteristics of Soybean Genotypes Differing in Duration of Seed Fill1
Authors: Swank J. C. , Egli D. B. , Pfeiffer T. W.
Published: July 2010

Seed growth and development is an important part of the yield production process in grain crops. Experiments were conducted in the field for 2 yr to determine the seed growth characteristics of soybean [Glycine max (L.) Merr.] genotypes that varied widely the duration of seed fill. Fifty‐nine genotypes were grown in 1982 on a Donerail silt loam soil (fine, mixed, mesic Typic Argiudolls) and measurements of seed growth rate (SGR), final seed size (FSS), and effective filling period (EFP) were made. The 59 genotypes exhibited a wide range in SGR, FSS, and EFP. Although SGR and FSS were significantly correlated (r = 0.76**, significant at the 0.01 probability level), subsets of genotypes could be identified that exhibited a wide range in FSS with no variation in SGR. In 1983, seven genotypes (six plant introductions and one cultivar) were selected, on the basis of the 1982 data, to have a relatively similar SGR but a wide range in FSS and EFP. These genotypes were grown on a Maury silt loam soil (fine, mixed, mesic Typic Palendalfs). Fruit samples were taken at weekly intervals to characterize seed development. Cotyledon cell numbers were measured on selected cultivars in 1982 and 1983. For genotypes that differed in EFP, the patterns of dry matter accumulation and seed moisture changes with time were similar to those previously reported. The number of cotyledon cells per unit mass of seed decreased as FSS increased indicating that differences in cell size were associated with the differences in seed size in these genotypes. These data indicate that variation in FSS among genotypes can be associated with either variation in SGR and/or filling period duration.
Field Performance in Soybean with Seeds of Differing Size and Density1
Authors: Hoy Daniel J. , Gamble Edwin E.
Published: July 2010

A 2‐yr field experiment was conducted to determine if separation of soybean [Glycine max (L.) Merr.] seeds by size or density might be effective in improving seedling emergence, speed of emergence, or yield. Eighteen soybean seedlots were separated into four size classes using round—hole screens, and into two density classes by floating low density seeds on sucrose solutions. These seeds were planted in a Typic Hapludalf—grey brown podsolic soil type. Seeds of largest size and seeds of lowest density had the lowest percent emergence and speed of emergence, provided these seeds came from seedlots of intermediate vigor. Seed size and density effects were greater when seeds were subjected to greater field stresses of low temperature and wet or crusted soils. The stand differences due to seed size and density persisted until harvest maturity. If compared to the unseparated control, only the smallest seed size was superior in emergence and speed of emergence, and high density seed did not show any advantage. Seed size had no effect on yield in early or late plantings, but high density seeds outyielded low density seeds in the late plantings. High density seeds did not outyield the unseparated seeds. In general, the effects of seed size and seed density on percent emergence, speed of emergence, and yield indicate that the potential for large scale vigor improvement in soybean seedlots through processing or conditioning is limited.
Introgression of an Exotic Germplasm for Improving an Adapted Maize Population1
Authors: Crossa J. , Gardner C. O.
Published: July 2010

Maize (Zea mays L.) geneticists and breeders in the USA are concerned with the narrow base of Corn Belt germplasm. Numerous experiments using exotic germplasm from other countries have been conducted to broaden the germplasm base. Our study was undertaken to evaluate the potential use of an exotic germplasm source for the improvement of an adapted maize population and to determine the optimum proportion of exotic germplasm to be introgressed. Ninety S1 families from three populations representing three levels of introgression of exotic maize germplasm into an adapted population were developed and evaluated at two locations. The S1 families from the cross (50% adapted germplasm) yielded significantly less than those from adapted (100% adapted germplasm) and backcross (75% adapted germplasm). Both the adapted and the backcross populations were early maturing and yielded similarly. This suggests that major genes for lack of adaptation are acting in the cross population. A significant nonlinearelationship between S1 family means and proportion of adapted material in the base population was noted for all traits. The use of an exotic source has increased the genetic variation in the cross population. With an appropriate effective population size, the cross can be used as a base population in a selection program, if useful genes from the exotic source are at low frequencies.
Gene Frequencies in Mass‐Selected Corn Populatios and in Derived Random Inbred Lines1
Authors: Kling J. G. , Gardner C. O. , Thomas‐Compton M. A.
Published: July 2010

The use of randomly developed lines from a population for estimating genetic variances requires the assumption that gene frequencies are unaffected by natural selection and remain constant with inbreeding. To determine whether gene frequencies were in fact influenced by natural selection, starch gel electrophoresis was used to identify genotypes at 10 isozyme loci in three corn (Zea mays L.) populations and in random lines derived from them. Two of the populations had been improved by 15 cycles of mass selection for increased grain yield. One of these improved populations had received thermal neutron treatments at Cycle 0 and after one cycle of selection. The other population studied was the original open‐pollinated cultivar. Allelic freqencies in random lines derived from massselected populations were affected little by inbreeding. However, natural selection appeared to have more impact on allelic frequencies of lines developed from the original cultivar, suggesting that deleterious recessive alleles were reduced in frequency by mass selection. Changes in allelic frequencies associated with mass selection were noted for Estl and Prx1 in the irradiated and control populations. Gametic phase disequilibrium was not widely detected in the inbred lines, but was common for loci in combination with Mdh2.
Use of Canopy Temperatures of Identify Water Conservation in Cotton Germplasm1
Authors: Hatfield J. L. , Quisenberry J. E. , Dilbeck R. E.
Published: July 2010

Screening crop germplasm for water conserving traits is difficult under dryland environments because of the variability in soil‐water use. Canopy temperatures have been related to crop water stress. This study was designed to evaluate whether cotton (Gossypium hirsutum L.) germplasm differs in canopy temperatures and whether these temperatures could be related to performance under deficit soilwater conditions. Cotton strains (both exotic and commercial) were grown in irrigated and dryland field plots on an Oiton clay loam (fine, mixed, thermic Aridic Paleustoils). The dryland plots were grown under a rainout shelter to exclude any rainfall during the season while the irrigated plots received two irrigations during the measurement period. Canopy temperatures were measured daily between 1330 to 1430 h CST with a hand‐held infrared thermometer. Consistent canopy temperature differences occurred among strains grown in the irrigated plots even though the environmental conditions varied. In the dryland plots, canopy temperatures showed significant strain‐by‐day interactions suggesting that some strains use their available soil water faster than other strains. Calculated nonstressed baselines showed that the strains had a constant slope of −2.00°C kPa−1 and differed only in their intercept. Those strains, which had warmer canopies in the irrigated plots, had the larger biomass in the dryland plots. It is possible to separate cotton germplasm with infrared thermometry.
Analysis of Cell‐Wall Carbohydrates and Starch in Alfalfa by near Infrared Reflectance Spectroscopy1
Authors: Albrecht K. A. , Marten G. C. , Halgerson J. L. , Wedin W. F.
Published: July 2010

Analysis of the structural and nonstructural polysaccharide composition of herbage by conventional techniques is time consuming and difficult to perform on large numbers of samples. This study was conducted to evaluate the utility of near infrared reflectance spectroscopy (NIRS) for analysis of cell‐wall carbohydrates and starch in alfalfa (Medicago sativa L.). The leaves and stems of two alfalfa cultivars grown in two environments and ranging in maturity from vegetative to early seed pod were assayed by conventional means for concentrations of six cell‐wall sugars and starch. Calibration equations were obtained by multiple linear regression of conventional laboratory assay values on NIR spectra from 150 randomly selected samples using a scanning monochromator NIR spectro‐computer system. Calibration equations were verified with 30 additional samples from the original population of 180. From six to nine wavelengths were required to develop the best equations for the various carbohydrate components. The squared coefficients of multiple determination (R2) of the calibration equations ranged from 0.83 to 0.99. The lowest R2 values were associated with cell‐wall sugars having concentrations < 30 g kg‐1 dry weight and small ranges in concentration. With these equations, standard errors of analysis of carbohydrates by NIRS were (in g kg‒1) 8.5 for total structural carbohydrates, 6.6 for glucose, 3.0 for xylose, 1.2 for arabinose, 0.7 for galactose, 1.3 for mannose, and 4.3 for starch. We conclude that NIRS is a rapid and precise means to analyze cell‐wall carbohydrates and starch in alfalfa.
Method for Evaluating Germplasm Response to Chemical Treatment under Field Conditions1
Authors: Deaton W. R. , Mascia P. N.
Published: July 2010

The need for a method that rapidly and accurately evaluates germplasm for response to various chemical treatments while limiting costs led to the development of the technique described and used in this report. This technique involves screening genetic material in the field across several rates of the compound while minimizing space and labor inputs. The results of employing the technique in two experiments evaluating variation among 18 winter wheat (Triticum aestivum L.) cultivars for tolerance to both alachlor [2‐chloro‐2′‐6′‐ diethyl‐N‐(methoxymethyl)acetanilide) and glyphosate [isopropylamine salt of N‐(phosphonomethyl)glycine] herbicides are given. The method produced results that allowed the identification of significant variation among this small, random set of genetic material for tolerance to both the preemergence (alachlor) and the postemergence (glyphosate) herbicides examined. The space, seed, and labor requirements used were minimal compared to those that would be needed for a full‐scale field trial of the 18 cultivars. The technique could also be modified to screen for response to a broad range of other plant growth regulators.
Selection for Heading Date Synchrony in Wild Rice1
Authors: Hayes P. M. , Stucker R. E.
Published: July 2010

Heading date synchrony, the uniform flowering of mainstems and tillers, was characterized and used as a selection criterion in half‐sib family populations of wild rice (Zizania palustris L.). Greater intraplant synchrony would reduce the opportunity for mainstem shattering and increase harvestable yield. Principle objectives were to characterize heading date synchrony, estimate its heritability, and determine its association with other agronomic traits. A secondary objective was to measure the effect of plant density on heading date synchrony expression. Two synchrony indices, synchrony range and synchrony measure, were computed based on mainstem and tiller heading dates of individual plants sampled within half‐sib families. Half‐sib families were evaluated in four replicates of blocks‐in‐replicates designs in paddies at Grand Rapids and Excelsior, MN in 1984 and 1985. The families were derived from single plants: 100 selected for synchrony, 40 for asynchrony and 40 chosen randomly. Compared to reported values for domesticated cereals, wild rice populations showed considerable asynchrony of heading date. Heritable variation for heading date synchrony was not correlated with other agronomic traits. Estimates of predicted gain (3.4 to 6.7% per cycle) indicate that a long‐term selection effort would be required to achieve synchrony in these populations. The random population (control) and the selected population (from one cycle of half‐sib family selection) were evaluated at four plant densities at two locations. Plant density did not have a significant effect on heading date synchrony expression. Comparison of expected gain from selection for yield per se to gain from selection for tiller synchrony favored yield selection as the better choice for long‐term yield gain in wild rice.
Performance and Inbreeding Depression of Populations Representing Seven Eras of Maize Breeding1
Authors: Lamkey Kendall R. , Smith O. S.
Published: July 2010

Improvements in maize (Zea mays L.) yields have been due to improvements in production inputs as well as to cultivars that have improved performance at low levels of inputs and the ability to respond to high levels of inputs used on today's farms. The objectives of this study were to estimate genetic rates of gain and inbreeding depression by evaluating populations representative of each of seven eras of maize breeding. Inbred lines representative of each of the six decades (eras) from 1930 to 1980 were intermated to produce six era populations. A seventh, pre‐1930 era, was represented by the open‐pollinated cultivars (OP) ‘Reids Yellow Dent’ and ‘Lancaster Sure Crop’. These eight entries along with three check populations were evaluated in six Iowa environments. In addition, to assess changes in the rates of inbreeding depression, S1 bulk populations of the six era populations and OP and S2 bulks of the three check populations were also evaluated. The average genetic rate of gain for grain yield was 0.52 ± 0.04 Mg ha‐1 era‐1 when OP was included in the analysis. By assuming 10 yr per era, the yearly genetic rate of gain was 0.052 ± 0.004 Mg ha‐1. The rates of genetic gain for percentage of stalk lodging and grain moisture at harvest were −5.1 ± 0.5% era‐1 and 0.44 ± 0.09% era‐1, respectively. The rate of inbreeding depression for yield increased steadily over eras, and the rate of inbreeding depression for Era 6 was double that for the OP. However, inbreeding depression as a percentage of the So mean showed no directional changes and was similar for all eras. These results indicate that breeders have been effective at selecting lines and hybrids with higher yields and resistance to lodging and the ability to produce higher yields under stress conditions. The increased rates of inbreeding depression for the more recent eras coupled with the increased performance of the S0 and S1 populations suggest that favorable allele frequencies were initially below 0.5 and have been increasing and]or that the more recent era populations are segregating at more loci.
Field Measurement of White Mold Effects upon Dry Beans with Genetic Resistance or Upright Plant Architecture1
Authors: Schwartz Howard F. , Casciano Deanne H. , Asenga Joseph A. , Wood Donald R.
Published: July 2010

White mold of dry beans (Phaseolus vulgaris L.) is caused by the fungus pathogen Sclerotinia sclerotiorum (Lib.) de Bary, which can reduce crop yields 30 to 80% in irrigated regions. To reduce disease‐caused losses, germplasm improvement programs are incorporating sources of genetic resistance and desirable plant architectural traits into commercially acceptable market types. This field study was conducted to develop a small plot research technique to measure white mold effects under differential disease pressure, and to test parental and breeding lines for their potential in controlling disease. Sixteen entries were selected for their known resistance to the pathogen and their diverse plant growth habits. Experiments were conducted in 1982, 1984, and 1985 in a Nunn clay loam (fine, montmorillonitic, mesic Aridic Argiustolls) infested with sclerotia of the pathogen. Small research plots (6 m2) treated with benomyl |l‐(butylcarbamoyl)‐2‐benzimidazolecarbamate] and untreated control subplots effectively and reliably differentiated between cultivars and lines susceptible to and less affected by the pathogen on the basis of disease intensity and yield potential. Plant growth habit was not an acceptable predictor of the ability to escape white mold infection, because some Type I (bush) lines were as susceptible as Type III (prostrate vine) lines. Some Type II (upright vine) entries such as ‘A 51’ and ‘83 VEF MXA 222’ had significantly (P = 0.05) less white mold than did other entries in untreated plots. Resistant entries such as P.I. 169787 performed well despite having a Type I habit with compact canopy. Lines having resistance and desirable plant architecture have been identified and incorporated into the germplasm improvement program at Colorado State University.
Inheritance of a Second Wrinkled Leaf Mutant in American Pima Cotton1
Authors: Turcotte E. L.
Published: July 2010

Leaf morphology mutants arise from time to time in cotton (Gossypium spp.). These mutants are useful as markers for the study of genetic systems and for developmental studies of leaf morphology. One such mutant with wrinkled leaves appeared as a single plant in a 1982 breeding row (82‐748) of American Pima cotton (G. barbadense L.) at Phoenix, AZ. The objectives of the present study were to determine the inheritance of the wrinkled leaf trait and its allelic and linkage relationships with other Gossypium mutants. The wrinkled leaf phenotype is inherited as a monogenic recessive. It expresses on successive leaves beginning with the first sympodial branch produced from Nodes 6 through 8 on field grown plants. The wrinkled leaf trait was not allelic with three other leaf mutant genes nor was it linked with 22 Gossypium mutant genes. The name wrinkled leaf‐2 and the gene symbol wr2 are proposed for the new leaf trait. The new trait should be useful in genetic and developmental studies as an easily scored recessive phenotype affecting leaf morphology.
Genetics of Resistance in Soybean to “Race X” of Soybean Cyst Nematode1
Authors: Hancock J. A. , Hancock F. G. , Caviness C. E. , Riggs R. D.
Published: July 2010

The soybean cyst nematode (SCN), (Heterodera glycines Ichinohe), is a major pest of soybean [Glycine max (L.) Merr.) and new biotypes have been identified in recent years. A new biotype that reproduces on the ‘Bedford’ cultivar has been identified in Arkansas and is designated as “race X”. The objectives of this research were to study genetics of resistance to race X and measure heritability. Crosses and reciprocals were made between PI 90763, a genotype resistant to race X, and three susceptible genotypes, PI 88788, R74‐1001, and PI 209332. Data from F1, F2, and backcross populations indicate that a single recessive gene conditions resistance in these genotypes. There was no evidence of maternal or cytoplasmic inheritance in any of the crosses. Ninety‐four F3 lines were evaluated for reaction to race X and race 4. Lines that are resistant to race X were susceptible to race 4, and the lines resistant to race 4 were susceptible to race X with correlation coefficients of −0.53 and −0.59, respectively. No F3 lines from these crosses were identified as either highly resistant or susceptible to both race 4 and race X of SCN. Narrow sense heritability estimates based on regression of F3 family means on parental plant values ranged from 61 to 64% for the three crosses. The data indicate that the screening techniques used to determine reaction of individual plants were relatively effective for determining resistance.
Effect of Abscisic Acid on Amino Acid Uptake and Effiux in Developing Soybean Seeds1
Authors: Guldan Steven J. , Brun William A.
Published: July 2010

The role of abscisic acid (ABA) in regulating growth of developing soybean [Glycine max (L.) Merr.] seeds is not fully understood. The objectives of this study were to characterize the effect of ABA on the in vitro uptake of asparagine and glutamine by isolated immature cotyledons in three soybean plant introduction (PI) lines with genotypic differences in seed growth rate and final seed weight. Cotyledons were incubated in uptake buffer solutions plus 14C‐asparagine or 14C‐glutamine and treatment concentrations of ABA. The ABA levels in the uptake solutions were 0, 10‐7, 10‐6, and 10‐5 M. The uptake rate of glutamine was approximately three times that of asparagine. Among PI lines, the heavy seeded line had a greater rate of asparagine uptake while the light seeded line had a greater rate of glutamine uptake. For asparagine, 10‐6 M ABA depressed uptake compared to the control. For glutamine, ABA enhanced uptake compared to the control at both 10‐6 and 10‐5 M. In an additional experiment, we observed no effect of ABA and K+ on the release of labeled asparagine from excised soybean seed coats. These data indicate that amino acid uptake rates are genotypically dependent and may be influenced by ABA concentration.