bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Genotypic Response to Drought Stress and Subsoil Aluminum in Soybean
Authors: Goldman I. L. , Carter T. E. , Patterson R. P.
Published: July 2010

Soybean [Glycine max (L.) Merr.] producers in the southeastern USA are often confronted with the problems of drought and toxic levels of subsoil Al. Our objective in this study was to determine the reaction of diverse soybean genotypes to combined effects of these two stress factors. Greenhouse studies were initiated to examine the problem. Two levels of Al saturation in a subsoil layer (6 and 71%), two levels of soil moisture (watered vs. unwatered),three genotypes (‘Forrest’, breeding line N77‐114, and PI 416937), and three sampling dates were used as treatments. Data were collected during a 14‐d drying cycle imposed at early to midpodfilling. Control pots were watered daily. Traits measured were relative water content, water potential, transpiration, diffusive resistance, leaf weight, and stem weight. In the combined presence of drought and Al stress, the Plant Introduction (PI) maintained a substantially higher relative water content, water potential, transpiration, and leaf weight than Forrest or N77‐114. Under drought stress alone, the water status of the PI was inferior to that of Forrest and N77‐114. These data suggest that Al tolerance can impart drought tolerance when subsoil Al is present. In regions where subsoil Al toxicity and drought are common, breeders should consider Al screening of germplasm to efficiently characterize and develop drought tolerant cultivars.
Phosphoenolpyruvate Carboxylase and Pyruvate Kinase Involvement in Protein and Oil Biosynthesis during Soybean Seed Development
Authors: Smith Amy J. , Rinne Robert W. , Seif Robert D.
Published: July 2010

During soybean [Glycine max (L.) Merr.] seed development, sucrose translocated to the seed is metabolized to precursors for protein and oil, the major components of mature soybean seed. while breeders have had success in selecting for increased seed protein or oil concentration, there is little understanding the metabolic events that regulate the partitioning of carbon into these seed components. Enzyme reactions that may determine carbon partitioning to seed protein and oil were examined in six soybean genotypes exhibiting genotypic differences in concentration of seed protein and oil. Developing seed were assayed for the enzymes phosphoenolpyruvate (PEP) carboxylase, pyruvate kinase, malate dehydrogenase, NADP‐malic enzyme, and aspartate and alanine aminotransferases. Correlations between these data and the protein and oil concentrations of each sample were determined. There was no significant difference between the correlation of pyruvate kinase activity with the oil and that with the protein concentration of the seed over development. The correlation of PEP carboxylase activity with protein was generally higher than with oil, suggesting that much of the oxaloacetate (OAA) produced may be used for synthesis of protein precursors. However, the high r values between PEP carboxylase and oil suggested that OAA may also be converted to malate and then to pyruvate (a precursor for oil) via a transhydrogenase system. Therefore, PEP carboxylase and pyruvate kinase activities appeared to contribute to a complex interaction that regulates the metabolic flow of glycolytic carbon into precursors for both protein and oil biosynthesis during soybean seed development.
Genotype‐by‐Environment Interaction in Grain Sorghum. III. Modeling the Impact in Field Environments
Authors: Hammer G. L. , vanderlip R. L.
Published: July 2010

Models of crop growth and development provide tools for examining impacts of changes in physiological traits in field environments. We modified the sorghum [Sorghum bicolor (L.) Moench] crop model, SORKAM, to include effects of genotype‐by‐environment interaction on ontogeny and radiation use efficiency of old and new sorghum hybrids. New hybrids are considered better adapted to more tropical environments. We simulated 40 y of yield data for five sites within the Great Plains from North Platte, NE (41° 9′ N lat.) to Weslaco, TX (26° 10′ N lat.). Simulated crops were fully irrigated and were planted at standard dates at each site. In this way, potential yield estimates were derived for each site. At two locations (Manhattan, KS, and Temple, TX), yield also was simulated without irrigation. Hybrid types differing only in ontogeny yielded similarly in either irrigated or dryland conditions. However, hybrids with enhanced radiation use efficiency at high temperature had increased potential yield at all sites. Average potential yield increased by 3, 18, 23, 26, and 27% for North Platte, Manhattan, Lubbock, Temple, and Weslaco, respectively. The increase was maintained under dryland conditions, but the magnitude was less at low yield level because of the dominating effect of water limitation. The trend in potential yield increase from north to south suggested the effect of temperature on radiation use efficiency was associated with the improved adaptation to more tropical environments shown by the new hybrids. However, the predicted trend was not entirely consistent with previous field studies, suggesting the need for research aimed at understanding what causes enhanced radiation use efficiency. This study demonstrated that modeling has an important role to play in linking physiological research with crop improvement. Modeling can improve relevancy of physiological research and application of that research to crop improvement.
Ultrastructural Techniques to Investigate Cell Wall Degradation and Antiquality Factors in Two Bermudagrass Cultivars
Authors: Woodward J. H. , Akin D. E. , Hoveland C. S.
Published: July 2010

Two bermudagrass (Cynodon dactylon L. Pers.) hybrids, ‘Tifton 78’ (Tilt‐78) and ‘Coastal’ (CBG), differ in dry matter digestibility. The objective of this study was to distinguish factors at the ultra‐structural level which may contribute to the differences in digestibility. Percent tissue types and histological reactions for lignin were similar for both cultivars. Scanning electron microscopy (SEM) leaf blades incubated in rumen fluid or cellulase revealed that non‐lignified tissues were digested to a greater extent in Tift‐78 than in CBG. Pretreatment with 0.1 M HCI or acid‐pepsin augmented cellulase digestion of the more slowly.degraded tissues. Transmission electron microscopy showed that Tift‐78 had a higher number of attached bacteria during incubation with rumen fluid. The ratio of attached Bacteroides to Ruminococcus morphotypes also varied between cultivars. After 24 h, Tift‐78 supported a population of predominantly Bacteroides (74%), whereas CBG had only Bacteroides. By 72 h, the attached population of Ruminococcus and Bacteroides had shifted to 59% and 17%, respectively, for Tift‐78 and 60% and 0%, respectively, for CBG. A SEM‐energy dispersive X‐ray spectroscopic analysis of the elemental composition of parenchymal bundle sheath and epidermal cell walls revealed that CI was significantly higher in untreated tissues of CBG than Tift‐78 but higher in Tift‐78 after cellulase incubation. The higher concentration of CI in CBG may prevent initial colonization of cell walls by specific bacterial morphotypes and reduce the number of attaching bacteria, thus reducing digestibility. Silicon, which has been described as an antiquality factor, did not differ between cultivars. Responses to enzymes indicated that structural carbohydrates in specific cell walls varied in digestibility between bermudagrass cultivars, and differences in cell walls further influenced the adherence of fiber‐digesting bacteria.
Nitrogen Response in the USA and Argentina of Corn Populations with Different Proportions of Flint and Dent Germplasm
Authors: Brun Eduardo L. , Dudley J. W.
Published: July 2010

While N is widely used in the USA for yellow dent corn (Zea mays L.) production, N is rarely used in the Argentine hard flint Corn Belt. Response to N fertilization is common in the USA but usually low and inconsistent in Argentina. To determine the importance of germplasm type on N response in the USA and Argentina, 50 S2's each from corn populations with 100, 75, 50, and 25% of Argentine flint germplasm, respectively, were crossed to a flint and a dent inbred tester. These testcrosses were evaluated under 0 and 280 kg N ha−1 at Champaign, IL and 20 and 300 kg N ha−1 at Havana, IL during 1985 and under 0 and 200 kg N ha−1 in three locations in Argentina during 1986. The relative N response for yield was 15% of the yield at the low N level in both countries. Nitrogen response was not affected by proportion of dent germplasm. Grain yield response per unit N applied also was similar in both countries. Testcross means in both countries for yield at low and high N levels and average yield increased as the proportion of dent germplasm in the population increased. Means for the dent tester were higher than those of the flint tester. Within a country, genetic variances of these populations did not differ significantly for any trait. Unlike results in Argentina, genetic variance for N response was significant in the USA and genetic variances for yield at high and low N levels differed. In both countries, selection in high‐N environments resulted in higher predicted gains in N response and in average performance over both N levels than selection in lower N environments. These results suggests use of higher N levels for selection.
Genetics of Photoperiod Sensitivity and Critical Daylength in Rice
Authors: Poonyarit Monton , Mackill D. J. , Vergara B. S.
Published: July 2010

Photoperiod sensitivity is an important breeding objective for rice (Oryza sativa L.) grown in unfavorable environments. A study was conducted with potted plants in the screenhouse to determine the inheritance of photoperiod sensitivity and date of flowering (critical daylength). The cultivars used were: IR58, a short duration photoperiod‐insensitive cultivar; IR26760‐27, a long duration line with a slight response to photoperiod; Nam Sagui 19 (NS19), a weakly photoperiod‐sensitive cultivar; and Sac Nau (SN) and Puang Rai (PR2), strongly photoperiod‐sensitive cultivars. The regression coefficient for days to flowering on seeding date for the parents ranged from 0.07 in insensitive IR58 to −0.64 in strongly sensitive PR2. In F2 populations, sensitivity ranged from nondominant to partially dominant, except in IR26760‐27 ✕ NS19, where sensitivity was overdominant. Two complementary, partially dominant genes conditioned photoperiod sensitivity. Highly sensitive PR2 and SN had partially dominant alleles for photoperiod sensitivity at both loci; NS19 had the partially dominant allele at the major photoperiod‐sensitivity locus (Se‐1) and IR 26760‐27 had the partially dominant allele at the locus designated Se‐3(t). The locus Se‐3(t) conferred a short critical daylength to genotypes with Se‐1, making them more photoperiod sensitive.
Synthetic Populations of Maize Containing Highland Mexican or Highland Peruvian Germplasm
Authors: Eagles H. A. , Hardacre A. K.
Published: July 2010

Highland tropical germplasm of maize (Zea mays L.) is tolerant of low temperatures but agronomically unattractive in temperate regions. To produce populations which could ultimately be ergonomically acceptable and have tolerance to low temperatures, the synthetic NZS1 was developed from ‘Criollo de Toluca’ ✕ AS32 and the synthetic NZS2 from ‘San Gerónimo’ ✕ BS222. Criollo de Toluca is from the highlands of Mexico, San Gerónimo is from the highlands of Peru, and AS3 and BS22 are elite synthetics from the Corn Belt Dent race of the USA. A third synthetic, NZS3, was developed from selected lines from an International Maize and Wheat Improvement Center (CIMMYT) population developed for highland regions of the tropics and Corn Belt Dent inbred lines. The cytoplasms of NZS1 and NZS2 were from their tropical parents. The five synthetics, NZS1, NZS2, NZS3, AS3, and BS22, were evaluated in a diallel cross, which included reciprocals and the parental synthetics, for grain yield, grain moisture, silking date, and root lodging in New Zealand. The objective of these experiments was to determine the breeding potential of these synthetics in cool, temperate environments. NZS1 and NZS2 silked at the same time as their Corn Belt Dent parents, but NZS1 had higher root lodging and NZS2 had higher grain moisture. NZS1 and NZS2 were lower yielding than their Corn Belt Dent parents, but in some combinations produced yields similar to AS3 ✕ BS22. Therefore, grain yield should not limit the use of NZS1 and NZS2. NZS3 ✕ BS22 was the most desirable cross when all characters were considered, which suggested that NZS3 should be a useful population for short‐term gains. The cytoplasm of Criollo de Toluca delayed silking and increased grain moisture, while the cytoplasm of San Gerónimo reduced grain moisture, suggesting that cytoplasmic inheritance should be considered when utilizing highland tropical populations.
Evaluation of Tall Fescue Plant Introductions for Resistance to Cochliobolus sativus
Authors: Linscombe S. D. , Watson C. E. , Trevathan L. E.
Published: July 2010

Cochliobolus sativus (Ito and Kurib.) Drechsl. ex Dastur is a major foliar pathogen of tall fescue (Festuca arundinacea Schreb.) in the southern USA. Progress in selection for resistance to this pathogen has been slow due to low heritability and low levels of resistance present in adapted germplasm. The objective of this study was to evaluate the world collection of tall fescue plant introductions (PIs) for resistance to C. sativus to identify new sources of germplasm that might have higher levels of resistance. Seedlings of 189 PIs were artificially inoculated with C. sativus in the greenhouse and rated for resistance based on the amount of leaf area covered by lesions in each of 2 yr. There was a significant PI ✕ years interaction resulting from a slightly lower level of disease development in the second year, which had a greater effect on the more susceptible accessions. The most resistant accessions in the collection were almost exclusively of Mediterranean or Asian origin. Only one PI of European origin ranked in the top 35 for resistance to C. sativus. Six of seven Pis identified as having high levels of resistance to C. sativus were of Mediterranean origin. These accessions offer new sources of C. sativus resistant germplasm for tall fescue breeding programs.
Combining Ability for Grain Moisture, Husk Moisture, and Maturity in Maize with Yellow and White Endosperms
Authors: Kang M. S. , Zuber M. S.
Published: July 2010

White‐endosperm (yyy) maize (Zea mays L.) is vital to the maize dry‐milling industry. White maize generally has higher harvest grain moisture content than yellow maize of equal physiological maturity. This increases the grain drying cost of white maize. The objectives of the current field study were to evaluate comparative effects of 2 y, 1 y, and 0 y gene dosages on grain moisture, probe moisture measured via an electronic device, husk moisture, and growing degree days (GDD) to midsilk and to midpollen shed; and to compare the general (GCA) and specific combining ability (SCA) effects from yellow ✕ yellow and white ✕ white endosperm diallels. The yellow and white lines were derived from crosses and backcrosses among Oh7B and Mo14W inbred lines. In the yellow endosperm background, parental lines 4 and 5 contributed positive GCA effects to probe moisture whereas lines 1, 2, and 3 contributed negative effects. In the white endosperm background, parental line 3 contributed positive GCA effects for both probe moisture and grain moisture, and parental line 4 contributed negative GCA effects. Parental line 5 contributed positive GCA effects for husk moisture in the yellow endosperm background. Parental line 1 had a negative GCA effect for husk moisture. White parental line 4 would be conducive to decreasing grain moisture, and the use of this parent could result in earlier maturing white maize with relatively low harvest grain moisture. A few of the SCA and reciprocal effects were significant (p < 0.05). For probe moisture, the 2 y class was significantly higher than the 1 y and 0 y classes. For grain moisture, the 2 y class was significantly higher than the 0 y class. For midsilk GDD and midpollen GDD 2 y > 1 y > 0 y. The y allele might have had a pleiotropic dosage effect on all traits except husk moisture, and it is possible that a gene or a block of genes might be tightly linked to the y allele and be responsible for the later maturity and higher grain moisture content of white endosperm maize germplasm used in this study.
Root vs. Shoot Effects on Herbage Regrowth and Carbohydrate Metabolism of Alfalfa
Authors: Fankhauser J. J. , Volenec J. J.
Published: July 2010

Physiological characteristics mediating shoot growth of alfalfa (Medicago sativa L.) following herbage removal are poorly understood. Our objective was to assess shoot vs. root effects on regrowth of alfalfa using reciprocally grafted and self‐grafted plants of two genotypes selected for contrasting shoot elongation rates (SER). Plants were propagated vegetatively from cuttings severed below the graft union. Plants were sampled weekly in a controlled environment and biweekly in the field during 4 wk of regrowth. Averaged across both environments, SER of plants with scions derived from the rapid SER (RSER) genotype was 88% greater than that of plants with slow SER (SSER) scions. By Week 4 of regrowth in the controlled environment, yield per shoot (YPS) of plants with RSER scions was 54% greater than that of plants with SSER scions. Differences in rates of single‐leaf net photosynthesis and leaf dark respiration were also associated with scion source, and like SER and YPS were not influenced by rootstock. In both environments, quantities of total nonstructural carbohydrates (TNC) in roots of plants with RSER scions were greater than those of plants with SSER scions. In the field environment, root TNC concentrations were 54% greater for plants with RSER scions when compared to plants with SSER scions, irrespective of rootstock. Results indicate that for these genotypes, characteristics of shoot tissues were more influential than root‐borne factors in mediating shoot regrowth and carbohydrate metabolism following herbage removal.
Taproot and Adventitious Root Growth of White Clover as Influenced by Nitrogen Nutrition
Authors: Pederson G. A.
Published: July 2010

White clover (Trifolium repens L.) seedlings form a taproot that persists for only 1 to 2 yr under field conditions. Subsequent growth and persistence depend on adventitious roots formed at stolon nodes. Few studies have attempted to compare characters of taproot with those of adventitious root systems. The objectives of this study were to compare root characters of white clover genotypes grown with taproot and adventitious root systems, and to determine the effect of N source on these characters. A randomized complete block design in a 2 ✕ 3 factorial was used with two N levels (+N and −N Hoagland solution) and three white clover cultivars (‘Regal’, ‘Dusi’, and ‘Louisiana S‐1’) that were inoculated with Rhizobium trifolii. All plants were grown in Cone‐tainers (Ray Leach Cone‐tainer Nursery, Canby, OR) in the greenhouse for 10 wk, with seedlings used for the initial taproot evaluation and stolon tip cuttings used for the subsequent adventitious root evaluation. The + N plants had 55 to 283% and 62 to 208% greater root and shoot dry weights, respectively, than the −N plants. Regal had 10% greater adventitious root dry weights than Dusi, though Dusi was originally selected for large adventitious roots. Louisiana S‐1 averaged 15% smaller diameter roots, 16% fewer fibrous roots, 25% less root dry weight, and 14% more nodule mass than Regal and Dusi. Differences among cultivars for root diameter, secondary root number, fibrous root score, nodule mass, and root dry weight were similarly expressed in both taproot and adventitious root systems. Selection for more fibrous roots in a taproot system should lead to more fibrous roots in an adventitious root system.
Morphology of Alfalfa Divergently Selected for Herbage Lignin Concentration
Authors: Kephart Kevin D. , Buxton D. R. , Hill R. R.
Published: July 2010

Programs to improve alfalfa (Medicago sativa L.) nutritive value have used selection criteria based on total herbage cell‐wall composition. There is only limited information addressing the effect of total‐herbage based phenotypic selection on changes in dry‐matter partitioning of the plant and on the nutritive value of plant parts. The objective of this study was to determine the effects of divergent herbage selection for alfalfa cell‐wall components on plant morphology. Two groups of germplasm were observed. Group 1 consisted of six syn‐2 lines derived from two‐parent combinations, which were randomly selected from ‘Saranac‐AR’ for high (HL) or low (LL) herbage acid‐detergent lignin concentration. Group 2 had HL and 13 LL lines that were full‐sib lines produced on pairs of parents from the Group 1 synthetics. Group 1 was grown for two harvests in a greenhouse and one harvest in the field, and Group 2 was grown for two harvests in the field. Compared with HL lines, LL lines had a greater leaf‐to‐stem ratio, especially in the fraction above the sixth node from the stem base. For LL lines, this ratio in the upper plant fraction was 53, 26, and 18% greater than HL lines for Group I greenhouse, Group 1 field, and Group 2, respectively. When harvested at the same time, LL lines were less mature than HL lines, and, for Group 2, main stem length of LL lines was about 30 mm shorter than HL lines. Dry‐matter yield of HL lines was 17, 28, and 28% greater than LL lines for Group 1 greenhouse, Group 1 field, and Group 2, respectively. Most of the differences between divergent types were related to changes above the sixth node. Thus, selection for improved nutritive value in total herbage of alfalfa may result in marked changes in plant morphology.
Association of Major Seed Components with a Shriveled‐Seed Trait in Soybean
Authors: Honeycutt R. J. , Burton J. W. , Palmer R. G. , Shoemaker R. C.
Published: July 2010

Soybean meal accounts for 70 to 75% of the international trade in high‐protein plant products. Soybean protein is nutritionally deficient in certain amino adds. This deficiency has been associated with major storage protein subunits. The study of mutants affecting major seed components may prove useful in efforts to improve the nutritional value of the soybean [Glycine max (L.) Merr.i. Studies of the association of a shriveled‐seed mutant in soybean with major seed components are presented. Sodium dodecyl sulfate‐polyacrylamide electrophoresis (SDS‐PAGE) analysis of severely shriveled seed of the mutant, 328‐1, showed a reduced level of a polypeptide of 48 kilodalton (Kd) molecular weight subsequently identified the β‐subunit of the 7S storage protein. Densitometer scans of SDS‐PAGE protein gels from normal and shriveled seed confirmed changes in the levels of other proteins. The detectable accumulation of the β‐subunit during seed development occurred later relative to the α and α‐subunits in the mutant genotype than in its parents. Differences in oil content in the mutant and parental genotypes are indicated by nuclear magnetic resonance (NMR) analysis. These differences are due to a genotype ✕ phenotype interaction. Also, it has been shown that genotype effects on total protein content are not significant (P > 0.05).
Converting Alfalfa Development Measurements from Mean Stage by Count to Mean Stage by Weight
Authors: Mueller S. C. , Fick G. W.
Published: July 2010

Mean stage by weight (MSW) precisely quantifies the stage of development in alfalfa (Medicago sativa L.), and it is an established basis for predicting alfalfa quality. Mean stage by count (MSC) eliminates oven drying of separated subsamples as a part of the process of determining the mean stage, but MSC should not be used on samples with a mixture of mature herbage and young regrowth. Conversion of MSC to MSW allows stage comparisons across experiments and use of published quality prediction equations based on MSW without recalibration for MSC. Using field data from central New York State, MSW was accurately estimated from MSC by the equation MSW = 0.456 + 1.153‐MSC (n = 569; r2 = 0.982; RMSE = 0.311). Over the midrange of MSC values (2.0‐5.0), which correspond to stages when most management decisions should be made, the simplified procedure appears to be as accurate as direct measurements of MSW.
Greenhouse Screening of Alfalfa Cultivars for Resistance to Southern Root‐Knot Nematode
Authors: Bouton J. H. , Hussey R. S. , Smith S. Ray
Published: July 2010

Since alfalfa (Medicago sativa L.) is susceptible to southern rootknot nematode [Meloidogyne incognita (Kofoid & White) Chitwood], identification of resistant cultivars is necessary. In this study, the reliability of a greenhouse screening procedure using nematode eggs applied to individual seedlings was compared to the standard procedure of inoculating with juveniles. The level of root‐knot resistance among 12 alfalfa cultivars was also determined using the egg method. The egg method gave more reliable information for galling and reproduction. Cultivars differed for percentage of resistant plants, but all had fewer galls than ‘Lahontan’ (susceptible check) and most were as resistant as ‘Moapa 69’ (resistant check).
Screening for Resistance to Tomato Fruitworm and Cabbage Looper among Tomato Accessions
Authors: Sinha N. K. , McLaren D. G.
Published: July 2010

Tomato fruitworm (Heliothis zea Boddie) and cabbage looper (Trichoplusia ni, Hübner) are two destructive insect pests of the cultivated tomato (Lycopersicon esculentum Mill.). The present investigation was conducted to screen wild (L. Hirsutum Hump and Bonpl., L. hirsutum f. glabratum Mull.) and cultivated tomato accessions for resistance to larvae of these insects, and to evaluate accession by environment (greenhouse vs. field grown plants), and by insect pest (polyphagous H. zea, vs. oligophagous T. ni) interactions for resistance. A petri dish bioassay technique was used, with larval survival on fresh foliage measured every 24 h over a 96‐h period. Mean number of larvae surviving 96 h was taken as a measure of susceptibility of an accession. Number of accessions screened for resistance to H. zea and T. ni were 38 and 33, respectively. Mean larval survival on L. esculentum cultivars ranged from 32 to 52% for H. zea and from 25 to 76% for T. ni. In contrast, six field and three greenhouse grown wild accessions had less than 10% survival of H. zea larvae after 96 h. With few exceptions, all wild accessions were resistant to T. ni, with few or no larvae surviving 96 h. More than 50% of larval mortality occurred in the first 24 h, suggesting the toxic action of phytochemicals as a likely mechanism of insect resistance. Accession by plant growth environment and accession by insect species interactions were both significant. In conclusion, resistance of tomato foliage to insect pest larvae was shown, using a petri dish bioassay procedure, to differ significantly with plant genotype, insect species, and the plant growth environment.
Performance of Single and Double Cross Autotetraploid Maize Hybrids with Different Levels of Inbreeding
Authors: Sockness Bradley A. , Dudley J. W.
Published: July 2010

In autotetraploids (4N's), theory suggests that double crosses (DC) should outperform single crosses (SC) if the parents of the SC's are inbred. To evaluate the importance of this theory, experiments using 4N maize (Zea mays L.) were designed to determine the relative performance of 4N SC's and DC's from parents with different levels of inbreeding. The parental lines were derived from three 4N maize synthetics (B,CD, and OP). The study was divided into three experiments grown in central Illinois in from 2 to 4 environments. In one experiment grown at 2 locations in 1986, between population SC's (B ✕ OP, B ✕ CD, CD ✕ OP)and DC's [(B ✕ OP)(BOP), (B ✕ CD)(B ✕ CD), (CD ✕ OP)(CD ✕ OP)] produced S1 parentalines were compared to within population SC's (B ✕ B, CD ✕ CD, OP ✕ OP) and their between population DC's [(B B)(CD ✕ CD), (B ✕ B)(OP ✕ OP), (CD ✕ CD)(OP a second experiment grown at 2 locations in 1987, the within population SC's and between population DC's produced from S1 lines were compared to the same SC's and DC's produced from S3 parental lines. In a third experiment, within population SC's and DC's produced from 16 essentially homozygous lines from Syn. OP were evaluated. Double cross yields from S2, S3, and homozygous parents were similar, but SC yields decreased as the parents became more inbred. Thus, it may be possible to use relatively inbred parents to produce autotetraploid maize DC's without significant loss of productivity. Results agreed with theory in that for most traits DC's outperformed SC's, the performance was linearly related to the inbreeding coefficient (F), and genetic variancestimates among SC's were larger than among DC's.
Combining Ability Related to Reduced Gene Flow among Maturity Groups within Maize Populations
Authors: Nevado M. E. , Cross H. Z. , Johnson K. M.
Published: July 2010

Little is known concerning the genetic consequences of reduced gene flow among early, medium, and late flowering plants that occurs within maize (Zea mays L.) synthetics. This study was conducted to investigate if genes become stratified into subpopnlations associated with flowering time within synthetics [as indicated by differences in average heterosis of hybrids between plants from various subpopulations and in estimates for their general combining ability (GCA) and specific combining ability (SCA)]. Three independent diallel sets of crosses, each among eight elite synthetics were produced by intercrossing plants of varying maturities within each synthetic: early ✕ late (GI), medium ✕ medium (GIII), and late ✕ early (GIII). Average performance of Gil hybrids (as the standard) was compared to hybrids from GII and GIII. The eight synthetics, which varied in maturity from AES100 to AES400, were evaluated for GCA and SCA by each of the three diallel sets. Field experiments were grown during 3 yr in up to nine environments in North Dakota. The rankings of GCA effects from each diallel were compared using two nonparameteric statistical methods, the Mann‐Whitney test and Spearman rank correlation coefficients. Results indicated that diallels GI, GII, and GIII gave similar average performance for all traits and similar estimates of GCA and SCA for eight of nine traits evaluated. For all traits studied, GCA mean squares were greater than SCA mean squares, indicating a predominance of additive variation. The Mann‐Whitney test indicated that GCA effects for all traits from the three diallels had similar distribution functions, and except for test weight, Spearman rank correlation tests ranked the GCA effects for GI, GII, and GIII in similar orders. Results indicated that gene flow was not greatly restricted among different maturity groups in the synthetics studied.
Effectiveness of Nutrient‐Solution Evaluation for Recurrent Selection for Fe Effeciency of Soybean
Authors: Dragonuk M. B. , Fehr W. R. , Jessen H. J.
Published: July 2010

Recurrent selection for Fe efficiency resulted in a soybean [Glycine max (L.) Merr.] population with a high percentage of segregates that showed little or no yellowing when grown on calcareous soil in the field. Further improvement for Fe efficiency in the AP9 population required the development of an alternative method of enhancingenetic variability. The objective of this research was to determine the effectiveness of nutrient‐solution evaluation in a recurrent selection program for the improvement of Fe efficiency. One hundred random S0‐derived lines of the Cycle 6 (C6) population and the parents of the Cycle 0 (CO) through Cycle 7 (C7) populations were evaluated for Fe efficiency in nutrient solution in the greenhouse and on calcareous soil in the field during 3 yr. Entries were rated for chlorosis on a scale of 1 = no yellowing to 5 = severe yellowing. In the C6 population, the estimated heritability of Fe efficiency on a plot basis was 22 ± 7% for nutrient‐solution and 10 ± 2% for field tests. The rates of observed genetic gain for Fe efficiency in the CO through C7 populations were similar for nutrientsolution and field tests. At a 10% selection intensity, the observed genetic gain was −0.05 score for nutrient‐solution and −0.08 score for field tests when compared with a common field standard. The observed genetic gain was −0.14 score for nutrient solution and −0.11 score for field tests when compared with a common nutrientsolution standard.
Genetic Variability Estimates in Improved ans Nonimproved ‘Iowa Stiff Stalk Synthetic’ Maize Populations
Authors: Helms T. C. , Hallauer A. R. , Smith O. S.
Published: July 2010

Progress from selection is dependent on the additive variance within the population. Selection and genetic drift are two biological processes that can change gene frequencies and thus change the magnitude of the genetic variance of a breeding population over cycles of a recurrent selection program. Our objective was to determine if changes in genetic variance had occurred after recurrent selection primarily for grain yield in two maize (Zea mays L.) selection programs originating from ‘lowa Stiff Stalk Synthetic’ (BSSSCO). One program consisted of reciprocal recurrent selection and the second program consisted of seven cycles of half‐sib followed sequentially by three cycles of S2 per se recurrent selection. Nonselected S2 progenies from each of five populations [BSSSCO, BSSS(R)CS, BSSS(R)C9, BSI3(S)C0=BSSS(HT)C7, and BSI3(S)C3] were evaluated in a replications‐within‐sets experiment conducted in six environments. Average grain yield of the nonselected S2 progenies relative to the original BSSSCO population increased 62% after nine cycles of reciprocal recurrent selection and 81% after seven cycles of half‐sib followed by three cycles of S2 recurrent selection. Evidence suggests that genetic variance decreased in the population improved using reciprocal recurrent selection but not in the population improved by using the sequential half‐sib and S2 recurrent selection methods. Estimates of genetic variance among random S2 progenies decreased in the BSSS(R)C9 population, when compared to the BSSSCO, for stalk lodging; dropped ears; grain yield; and grain moisture at harvest, and increased for root lodging. Genetic variance estimates among random S2 progenies increased for root and stalk lodging, and grain yield, but decreased for dropped ears and moisture at harvest for BSI3(S)C3 relative to BSSSCO.
Inheritance of a Long Terminal Raceme in Soybean
Authors: Kilen T. C.
Published: July 2010

A long terminal raceme of soybean [Glycine max (L.) Merr.], identified in an F5 breeding line, could be useful in studying reproductive abscission levels and in modifying plant architecture. Information on the genetic control of the trait is unknown. Such information would provide new knowledge on the genetics of soybean morphology, and would provide an estimate of the population size needed for selection purposes. The objective of this study was to determine the inheritance of long terminal racemes in soybean. Crosses were made between two breeding lines with long terminal racemes and two commercial cultivars with short terminal racemes. Some F1 plants were grown in a glasshouse to produce F2 populations. Additional F1 plants, parents, and F2 and F3 populations were field grown. Measurements of terminal raceme length and floret number were made on field‐grown plants at the R6 developmental stage. A continuous distribution for terminal raceme length in both the F2 and F3 populationsuggests that the trait is quantitatively controlled, but some dominance for short terminal racemes seemed to be evident. Regression of the mean F3 floret number on F2 terminal raceme length provided an estimate of an increase of 1.8 florets in F3 lines for each 1‐cm increase in terminal raceme length of their F2 parent. Thus, selection for terminal raceme length may be used to indirectly select for floret number per raceme. The standard unit heritability estimate for selection of terminal raceme length on F2 plants was 61%. Only 3% of the F3 lines had a mean terminal raceme length within the range of the donor parent, indicating the need for large segregating populations for recovery of the trait.
Distribution Pattern of Seed Yield in Cowpea
Authors: Kahn Brain A. , Stoffella Peter J.
Published: July 2010

Vertical distribution patterns of seed yield have not been reported for cowpea [Vigna unguiculata (L.) Walp.]. This study was conducted to describe the distribution of seed yield and yield components in several cowpca cultivars and to document possible cultivar differences. Ten cultivars were evaluated in 1985 at Fort Pierce, FL on an Oldsmar fine sand (sandy, siliceous, hyperthermic Alfic Arenic Haplaquods) soil and Bixby, OK on a Severn very fine sandy loam [coarse‐silty, mixed (calcareous), thermic Typic Udifluvent] soil. Nodal groups were created to facilitate interpretation of seed yield (total seed weight per plant) distribution patterns. Cultivars differed in pod number, seeds per pod, and average weight per individual seed at both locations and in seed yield in Florida. Seed yield was equally distributed between main stems and branches on an overall basis, but the nodal grouping analyses revealed cultivar differences. Over 50% of the seed yield came from pods originating from the main stem for ‘Elite’, ‘Crimson Purplehull’, ‘Encore’, ‘Texas Cream 12’, and ‘Pinkeye Purplehull’ at both locations. In contrast, over 50% of the seed yield came from pods originating from branchesm for ‘White Acre’, ‘Mississippi Cream’, ‘Corona’, and ‘Epoch’ at both locations. Except for Crimson PurplehuH in Oklahoma, each cultivar had over 50% of its seed yield originating in Nodal Group I (Nodes 1 to 6 in Florida, Nodes 1 to 7 in Oklahoma). Except for Elite in Oklahoma, most of the seed yield in Nodal Group I came from pods originating from branches. In contrast, most of the seed yield in the upper nodal groups came from pods originating from the main stem for each cultivar at both locations. There was no evidence that seed yield differences were associated with specific differences in plant architecture.
Water Uptake by Cotton Roots during Fruit Filling in Relation to Irrigation Frequency
Authors: Radin J. W. , Mauney J. R. , Kerridge P. C.
Published: July 2010

Yield of irrigated cotton (Gossypium hirsutum L.) increases as the interval between water applications is decreased, even if the total amount of water applied is unchanged. Experiments were undertaken to compare season‐long water relations of high‐frequency dripirrigated cotton (I‐ to 2‐d intervals) to cotton irrigated at approximately 2‐wk intervals. The crop was grown at two locations in central Arizona on a Mohall sandy loam (fine‐loamy, mixed, hyperthermic Typic Haplargid) and an Avondale clay loam (fine‐loamy, mixed, hyperthermic Typic Torrifluvent) soils. In 2‐yr trials at each location, irrigation frequency had inconsistent effects on midday leaf water potential (ψw) during vegetative growth. When the crop developed a heavy fruit load, however, ψw of plants on the longer cycles was much lower than that of drip‐irrigated plants, even after irrigation when ample soil moisture should have been available. Plant hydraulic conductances, estimated from regressions of single‐leaf transpiration rate against ψw, were high in both treatments early in the season. Hydraulic conductance decreased greatly during fruiting in plants on long irrigation cycles but less so in drip‐irrigated plants. Late in the season, after fruit maturation and daring plant regrowth, conductances were again high and similar in the two treatments. The results imply that during heavy fruiting, mild water stress associated with long irrigation cycles triggers deterioration of the root system that is very slow to be reversed. High‐frequency drip irrigation, by preventing cyclical stress, apparently minimized this deterioration during fruit filling.
Morphology and Yield of Isogenic Diploid and Tetraploid Maize Inbreds and Hybrids
Authors: Sockness Bradley A. , Dudley J. W.
Published: July 2010

A potential use of induced polyploidy in maize (Zea mays L.) is to increase total biomass production, for energy or silage production, by capitalizing on the direct consequences of chromosome duplication, i.e., larger cell and plant parts. The objective of this study was to determine the effects of ploidy level per se on morphological traits and grain and stover yields in maize. Three diploid (2n) inbreds were derived as paternal haploids from homozygous autotetraploid (4n) inbreds. The In and 4n inbreds and the three possible hybrids at each ploidy level were evaluated in 1986 and 1987 at each of two different planting dates. In general, 4n inbreds and hybrids had longer, wider leaves, larger stalk diameters, and higher grain and stover moisture than their 2n counterparts. Stover, cob, grain, and total biomass yields were greater for 2n inbreds and hybrids. Significant ploidy ✕ inbred and ploidy ✕ hybrid interactions resulting in reverse rankings at the 2n and 4n levels were found for certain traits. Thus, ranking of genotypes at the In level is not necessarily indicative of their rankings at the 4n level. These results do not support the use of 4n polyploids to increase total biomass production.
Mapping a Second Fatty Acid Locus to Soybean Linkage Group 17.
Authors: Rennie B. D. , Tanner J. W.
Published: July 2010

Alleles at several loci are known to influence the level of specific fatty acids in the seed oil of soybean [Glycine max (L.) Merr.]. However, there have been no reports describing the interaction, or association, of these alleles. The fasa allele is responsible for a high level of stearic acid (18:0), and the fan allele for a low level of linolenic acid (18:3) in soybean oil. Alleles at the Idh2 locus are responsible for specific isozyme patterns following starch gel electrophoresis. Crosses were made between pairs of lines that differed for alleles at the Fan and Fas loci, the Fas and Idhl loci, or the Fan and Idh2 loci. Analysis of the F2 or F3 seeds from heterozygous plants indicated that the Fan and Fas loci are linked at a distance of 21.6 ± 1.7 units. In addition, the Fas and Idh2 loci are linked at a distance of 37.0 ± 2.7 units. The Fan and Idh2 loci have been previously shown to be in Linkage Group 17, and are linked at a distance of 26.2 ± 1.2 units. Linkage Group 17 must, therefore, contain the three loci in the order Fas‐Fan‐Idh2.
Leaf Anatomy and Gas Exchange in Nearly Isogenic Semidwarf and Tall Winter Wheat
Authors: LeCain D. R. , Morgan J. A. , Zerbi G.
Published: July 2010

Although leaf area and photosynthetic cell size have been negatively correlated with leaf CO2 exchange rate (CER) in many studies, the use of diverse genotypes has often confounded interpretation of this relationship. We found leaves of a semidwarf (SD) (Rht1 Rht1 Rht2 Rht2) winter wheat (Triticum aestivum L.) genotype were smaller compared to its nearly isogenic standard height (Tall) (rht1 rht1 rht2 rht2) line, suggesting an interesting system in which to investigate this relationship. Samples from newly expanded leaves of growth chamber‐grown plants were fixed, then embedded in resin for anatomical study using stereological methods. Steady state gas exchange measurements at ambient CO2 concentration were performed on equivalent leaves and, in a follow‐up experiment, at five levels of CO2 for constructing intercellular CO2 (Ci)response curves of CER. Tangential sections revealed that dwarfing genes reduced lamina cell elongation, resulting in smaller and more numerous cells than in the Tall line. A consequence of this response was that total mesophyll surface area/leaf area (Ames/A) was increased by 10% in SD compared to Tall leaves. Leaf CER and conductance to water vapor (g) were also higher in SD plants. Greater stomatal density in the SD line was associated with their higher g, but (Ci)i response curves of CER indicated that higher CER in the SD line was due to greater mesophyll photosynthetic capacity, not to higher g. We conclude that the greater photosynthetic capacity conferred by dwarfing genes results from their anatomical effect on Ames/A.
Chronic Ozone Stress Effects on Yield and Grain Quality of Soft Red Winter Wheat
Authors: Slaughter L. H. , Mulchi C. L. , Lee E. H. , Tuthill K.
Published: July 2010

Chronic O3 stress can limit wheat (Triticum aestivum L.) yields and kernel quality. Field studies were conducted at the USDA Beltsville Agric. Res. Center (BARC) during 1984 and 1985 to assess the effects of low‐level chronic O3 stress during anthesis and kernel fill on soft red winter wheat. Six O3 treatments, ambient air plot control, charcoal‐filtered air (CF), nonfiltered air (NF), NF + 20, NF + 40, and NF + 80 nL O3 L−1, were applied 4 h day−1, 5 day wk−1 beginning 10 d preanthesis through maturity. Biomass, grain yield, kernel weight, kernels per spike, harvest index, flour protein, alkaline water retention capacity, particle size index, and baking quality of four wheat genotypes were examined at physiological maturity. Ambient O3 concentrations were higher and environmental conditions were cool and wet in 1984 compared to 1985. In 1984, NF + 80 nL O3 L−1 treatments significantly reduced all measured characteristics except kernels per spike. In 1985, significant O3 effects were not observed. Significant genotype effects were observed in each year with the exception of harvest index and kernels per spike in 1984. Polynomial regression analyses indicated a decrease in biomass, grain yield, and kernel weight at accumulative oxidant exposure (AOX) values above 5.1 μL L−1 h. The results indicate that brief 4‐h exposure periods above 60 nL O3 L−1 during anthesis and grain fill can reduce yield and kernel quality.
The Pit and Antipit in the Genus Glycine
Authors: Yaklich R. W. , Vigil E. L. , Wergin W. P.
Published: July 2010

The structure of the pit and antipit and their location at the interface of the soybean [Glycine max (L.) Merr] seed coat and embryo were recently discussed in relation to seed development. The prevalence of these two structures in soybean and other Glycine species is not known. This study was undertaken to determine the prevalence of the pit and antipit in G. max, G. soja, G. canescens, G. clandestina, G. falcata, G. tabacina, G. tomentella, and G. latifolia. Seeds were dissected in half, viewed by light microscopy, then sputter coated and viewed by scanning electron microscopy (SEM). Also, images from five accessions of G. max, G. soja, G. latifolia, G. tomentella, G. clandestina, and G. tabacina were projected onto an image analyzer and measurements of the antipit were obtained. The shape of the pit and antipit varied within a species and were either elliptical or triangular. The area, height, and depth occupied by the pit and antipit, respectively, also varied among species. In most accessions, the pit was deeply concave, although, in a few accessions the cotyledon surface was nearly flat. Glycine max, G. soja, and G. tomentella had similar pit cells that were at least twice as long as they were wide. Glycine latifolia had the smallest antipit cells and G. max had the largest. The pit and antipit were prevalent in all the Glycine species examined, indicating that these structures are a common feature in the genus Glycine.