bluuebunny/crossref_metadata_2025 huggingface dataset:
Genotypic Variation for Fatty Acid Content in Selected Glycine max × Glycine Soja Populations
Authors: Rebetzke G. J. , Pantalone V. R. , Burton J. W. , Carter T. E. , Wilson R. F.
Published: July 2010

Modifications in the fatty acid composition of soybean [Glycine max (L.) Merr.] oil may extend its utility to industrial markets currently serviced by other vegetable‐, mineral‐, or fossil‐based oils. However, extension into new markets depends on the development of soybean oils with increased concentrations of saturated, monounsaturated, or polyunsaturated fatty acids. Three wild soybean (G. soja Siebold & Zucc.) accessions possessing unique fatty acid profiles were intercrossed with the reduced saturate and polyunsaturate fatty acid germplasm, N87‐2122‐4, to produce widely segregating populations. Random F2 and F2:3 families from each population were grown, and seed fatty acid contents of individuals within families were analyzed. Genotypic differences for oil quality were significant among populations and families within populations. Individual families produced >140 and 175 g kg−1 palmitic and total saturated fatty acid contents, respectively. No family produced greater oleic acid content than N87‐2122‐4. Some families produced >640 g kg−1 linoleic acid and total polyunsaturates exceeding 720 g kg−1, while selected individuals produced >750 g kg−1 total polyunsaturates in both the F2:3 parental and F2:4 progeny generations. High narrow‐sense heritability estimates for palmitic (h2 = 0.67 to 0.98) and linoleic (h2 = 0.44 to 0.80) acid contents suggested that individual F2 plants can be selected for either trait. However, the smaller heritabilities for oleic (h2 = 0.36 to 0.66) and linolenic (h2 = 0.10 to 0.47) acid contents necessitate selection based on family means. Analyzing these selected wild soybean crosses has demonstrated G. soja may be a useful source of genes to extend genotypic variation for linoleic and total polyunsaturated fatty acid contents. Genes for greater saturate content in PI 424031 may extend variation currently available in mutant soybean germplasm. However, it appears unlikely that G. soja would be useful for increasing oleic acid content above levels in existing soybean mutants.
Marker Effects Estimated from Testcrosses of Early and Late Generations of Inbreeding in Maize
Authors: Eathington S. R. , Dudley J. W. , Rufener G. K.
Published: July 2010

In maize (Zea mays L.) breeding programs, early generation testing allows the discarding of lines with poor combining ability early in the inbreeding process. Molecular markers can be used to locate quantitative trait loci (QTL) and measure marker effects in early generations. For marker assisted selection to be useful in improving the efficiency of early generation testing, marker effects estimated in early generations must agree with marker effects in later generations. However, limited attention has been given to comparing marker effects in different generations of the same cross. Therefore, the overall objective of this research was to compare marker effects estimated from testcross performance of 190 S1 and S4:S5 lines from a maize population (BSll(FR)C7) by inbred (FRMo17) cross. A total of 146 probe‐enzyme combinations were used. To be most useful, correlations between marker effects in different generations need to be higher than phenotypic correlations. For all traits, phenotypic correlations were less than genetic correlations that were less than correlations based on marker effects estimated for the best set of markers from the S1. Except for grain yield, test weight, and days to anthesis, the correlations based on all marker effects were higher than the genetic correlations. As an example, the phenotypic correlation for grain yield was 0.36, the genetic correlation was 0.60, the correlation using all markers was 0.50, and that for the best set of markers was 0.86. Overall, marker effects estimated in S1 and S4:S5 testcrosses had reasonable agreement. Thus, marker information from early generations should improve the prediction of later generation performance.
Soybean Mosaic Virus Resistance Improves Productivity of Double‐Cropped Soybean
Authors: Ren Q. , Pfeiffer T. W. , Ghabrial S. A.
Published: July 2010

Double‐cropped soybean [Glycine max (L.) Merr.], an important production system in the upper south and southeastern USA, has lower productivity than full season soybean. Soybean mosaic virus (SMV) appears to be prevalent in soybean in the upper south of the USA. Yield losses due to SMV infection are greater the earlier infection occurs in relation to soybean developmental stages. Soybean may be infected by SMV at earlier developmental stages when planted late than when planted early, thus double‐cropped soybeans may be more susceptible to yield reduction caused by SMV infection. The objectives of this study were to determine whether SMV resistance provided an average yield benefit in late planting and whether the expression of this benefit was dependent on background genotypes. In 18 resistant/susceptible genotype pairs the resistant genotypes, overall, provided 283 kg ha−1 (12%) resistance benefit for yield over susceptible genotypes in late plantings. This benefit was independent of background genotype and significantly correlated with the difference between early plantings and late plantings in the incidence of SMV infection at growth stage R1 (r = 0.72, P < 0.01). In late planting environments resistance also provided benefits for seed quality traits, i.e., no seed transmission of SMV and low seed coat mottling. We recommend that resistance to SMV should be incorporated into soybean cultivars which will be used in the double‐cropping production system.
Association of Soybean Genes I and T with Low‐Temperature Induced Seed Coat Deterioration
Authors: Takahashi Ryoji
Published: July 2010

Exposure of soybean [Glycine max (L.) Merr.] to chilling temperatures (about 15°C) at flowering (R3–R4 stage) induces browning around the hilum region and cracking of the seed coats. Objectives of this study were to precisely evaluate the effect of chilling treatment on flowers at different developmental stages on the intensity of seed coat pigmentation and to determine the effects of genes T (responsible for pubescence and seed coat color) and I (responsible for the distribution of seed coat color) on seed coat pigmentation and cracking by glasshouse experiments. Tokei‐797, a cultivar with yellow hilum and gray pubescence (I/I, t/t), was exposed to 15°C for 2 wk beginning at 2, 5, 7, 12, 17, and 22 d after anthesis. Pigmentation increased with flower age at the time of treatment and was intense in the treatments, which started from 4 to 11 DAO (days after opening of individual flowers) and decreased thereafter. Harosoy and its two near‐isogenic lines, L67‐38 and L66‐707, were exposed to 15°C for 2 wk beginning at 8 d after anthesis (DAA). Harosoy has yellow hilum and gray pubescence (I/I, t/t). L67‐38 has buff hilum and gray pubescence (i‐i/i‐i, t/t) while L66‐707 has yellow hilum and brown pubescence (I/I, T/T). Seed coats of L67‐38 developed more intense pigmentation around the hilum region than Harosoy. In contrast, pigmentation of L66‐707 was restricted to the hilum. L67‐38 had a higher degree of cracking, while L66‐707 had a significantly lower degree of cracking than Harosoy. The T/t and I/i‐i genes are associated with the degree of pigmentation and cracking in response to chilling temperatures.
Sulfur Availability, Rubisco Content, and Photosynthetic Rate of Soybean
Authors: Sexton P. J. , Batchelor W. D. , Shibles Richard
Published: July 2010

Understanding the role of S in soybean [Glycine max (L.) Merr.] growth is important because a deficiency of the S‐containing amino acids methionine and cysteine limits the nutritional value of soybean protein. As part of a broader study of S uptake and use, our objective was to quantify the effect of S availability on photosynthetic characteristics of soybean. Kenwood soybean was grown in a 3:1 mixture of Ida silt loam [fine‐silty, mixed (calcareous), mesic Typic Udorthent] and acid washed sand with varying amounts of S added as gypsum (CaSO4) in two greenhouse trials. Single‐leaf CO2‐exchange rate (CER), quantum efficiency, dark respiration, leaf S, leaf N, and Rubisco content were determined. There appeared to be a critical level of 35 mg S per kg mixture (about 85 mg S per plant) below which specific leaf S (mg m−2 leaf area) declined linearly with decreases in soil S availability. On average, the most S deficient plants had 70% lower CER, 42% less quantum efficiency, and 50% decline in dark respiration relative to plants receiving adequate S. Total leaf N and Rubisco content were linearly related to leaf S levels, and declined on average 62, and 95%, respectively, as S declined from approximately 120 to 40 mg S m−2 leaf area. There was a linear relation between CER and Rubisco content; however, the amount of nonstructural carbohydrates per unit leaf N increased two‐fold under S deficiency, suggesting that limitations on sink strength were greater than those on source capacity. Carbon dioxide exchange rate was linearly related to leaf S content at all sample dates, with a mean relation of 216 (μmol CO2 g−1 S s−1. The Rubisco fraction declined linearly from nearly 50 to <10% of soluble protein, as leaf soluble protein content declined under S deficiency. We postulate that the decline in the Rubisco fraction may be a function of increased relative importance of housekeeping enzymes for survival as protein levels decline, and/or down‐regulation of Rubisco synthesis in response to a build up of carbohydrates in the source leaves under S deficiency.
Differential Autoradiography and Spin‐Column Purification of Sugars on Activated Charcoal
Authors: Tarpley Lee , Vietor Donald M.
Published: July 2010

Methods utilizing activaled charcoal for separating radiolabeled sugars from each other and from water are described. The first method alleviales a practical limitation for use of tritiated sugars as a tracer in planta. Tritium exchange with waler can now be readily quanlified because lhe method allows a more rapid separalion of sugars and water than has been previously described. A spin column conlaining activaled charcoal and powdered cellulose relained (>99%) sucrose during elution (>99%) of 3H2O in waler rinses. The retained sucrose could then be eluled (95%) from the column by rinsing with aqueous methanol. The second melhod partially resolves anolher limitation in the use of radiolabeled sugars as tracers in planta. We can now ascertain the spatial distribution of various radiolabeled sugars within particular organs. Charcoal filler paper was used to adsorb sucrose and hexose sugars for development of differential autoradiographs of sugars blotted from stem cross‐sections of sorghum (Sorghum bicolor [L.] Moench). The hexose sugars were selectively removed during rinsing of the charcoal paper in water. Autoradiography was performed before and after rinsing. The autoradiographic image obtained before rinsing reflected the presence on the blot of both radiolabeled sucrose and hexose sugars. In comparison, the image obtained after rinsing no longer reflected the presence of radiolabeled hexose sugars. These methods help refine studies of carbon dynamics in plants by enhancing our ability to detect in planta movement of sugars through particular metabolic pathways and to detect lhe spatial distribution within organs of particular radiolabeled sugars.
Factors Affecting Leaf Area Development in Husk Leaf of Flint Corn
Authors: Sato Hideo , Sakurai Naoki , Sendo Sigeyuki , Saneoke Hirofumi , Nobuyasu Hiroyuki , Fujita Kounosuke
Published: July 2010

Some corn (Zea mays L.) genotypes produce husk leaves (laminae extending from the husk) that on a per unit area basis, contribute more photosynthate to grain production than culm leaves. Furthermore, a high correlation between husk leaf area and dry weight has been observed, but little is known about the changes in cell components during development of husk leaves. A field experiment was conducted to quantify methanol (MeOH)‐soluble fraction (cytosol) and incorporation of 13C‐labeled photosynthate in cell walls from 9 d before silking (DBS) to silking. The ear leaf of flint corn (F1 of N‐19 by X‐15) was subjected to 13CO2 eight DBS. Leaf area, dry weight, and photosynthetic activity of the husk leaves, and sugar content of various cell components were measured continuously during the 9‐d period. The husk leaf attained one‐half of its maximum apparent photosynthetic rate (Po) when it had 8% of its maximum leaf area at 4 DBS. At 9 DBS, neutral sugars in the MeOH‐soluble fraction accounted for most of nonstarch carbohydrates within the husk leaf (68%), while hemicellulose and cellulose fractions accounted for <10%. At silking, however, sugars in the hemicellulose and cellulose fractions increased by 23 and 56%, respectively. Results of 13CO2 labeling suggest that during rapid husk leaf development, MeOH‐soluble fraction decreases, while the hemicellulose fraction fluctuates, and cellulose fraction increases.
Characterization and Analysis of North American Triticale Genetic Resources
Authors: Furman Bonnie J. , Qualset Calvin O. , Skovmand Bent , Heaton John H. , Corke Harold , Wesenberg Darrell M.
Published: July 2010

A collection of more than 3000 accessions of triticale (× Triticosecale Wittmack), called the North American Triticale Genetic Resources Collection (NATGRC), was assembled from 10 active and inactive breeding programs in the USA, Canada, and Mexico for the purposes of conservation, characterization, evaluation, and documentation. Since triticale has no wild ancestors and hybrid parentage is often unknown, preservation of unique gene combinations is essential for continued utilization. The origin groups that comprised the whole collection were evaluated in field plots for 2 yr at Davis, CA. Accessions were predominantly secondary hexaploid triticales having spring growth habit. The collection was classified for spike type and 38% had spikes typical of complete (Beagle type) and 30% were substituted (Armadillo type) triticale. The Shannon‐Weaver diversity index (H′), computed for seven qualitative traits, was 1.275 for the whole colleclion. The most diverse group was from Manitoba (1.404) and the least diverse groups were from Oregon (0.822) and CIMMYT (0.867). Overtrait mean coefficients of variation for eight quantitative traits gave similar diversity ratings as H′ for each of the origin groups (r = 0.74*), suggesting that simply scored traits may be useful for assessing overall diversity in large genetic resource collections. Principal components (PC) analysis of quantitative traits showed differentiation, but considerable commonality, among the Canada, Mexico, and USA groups. The CA‐Davis group included hybrid derivatives from CA‐Jenkins × CIMMYT groups that clustered intermediate to those groups, suggesting a genetic basis for the phenotypic clustering. The PC analysis showed that the Beagle and Armadillo types differed in several quantitative traits, showing that this classification is a useful descriptor for hexaploid triticale. The NATGRC is conserved at USDA, Aberdeen, ID, and CIMMYT, Mexico. Researchers are urged to use and contribute to this collection. The formation of a European‐based collection emphasizing winter growth habit is recommended.
Stability of Evapotranspiration Rates in Kentucky Bluegrass Cultivars across Low and High Evaporative Environments
Authors: Ebdon J. S. , Petrovic A. M. , Zobel R. W.
Published: July 2010

In an effort to conserve water applied to irrigated turfgrass sites, it is important to assess the potential for water conservation among turfgrass germplasm. Turfgrass can respond differently in evapotranspiration (ET) rate as climatic conditions change. The objective of this study was to investigate the interaction between the ET response of 61 Kentucky bluegrass (Poa pratensis L., KBG) cultivars (evaluated under controlled environment) and three equally spaced, evaporative environments (temperatures 25, 30, and 35°C, corresponding to 1.263, 1.664, and 2.261 kPa vapor pressure deficit, VPD, respectively). There was a significant interaction (P ≤ 0.001) in ET rate between the 61 cultivars and the three evaporative environments. Simple linear regression models and AMMI (additive main effect and multiplicative interaction) models were used in interpreting cultivar‐environment interactions. There was wide variation in cultivar mean ET (5.36–6.82 mm d−1), in stability of cultivar ET ranking, and sensitivity to evaporative environment characterized by cultivar stability. Cultivar stability (regression coefficients) varied by as much as 60% in the change ET rate, from 1.13 to 3.16 mm d−1 kPa−1. The AMMI model revealed that the high evaporative environment (2.261 kPa VPD) interacted with cultivars in a direction opposite to 1.263 and 1.664 kPa environments indicating that relative ET rankings of cultivars are the most variable between diverse evaporative environments. Compared with ordinary analysis of variance (ANOVA), AMMI was more effective in detecting and interpreting interaction. This study indicated that (i) breeding for water conserving KBG may have limited impact for reducing irrigation requirements because most of the variation in ET (87%) is due to environment and not to the plant's pedigree, and (it) recommendations for use of specific cultivars maybe difficult because of inconsistent water use patterns and intraspecies variation in KBG that were observed in response to diverse evaporative environments that are typical of field conditions.
Inheritance of Flowering Pattern among Four Annual Bluegrass (Poa annua L.) Genotypes
Authors: Johnson Paul G. , White Donald B.
Published: July 2010

Poa annua L. is a turfgrass commonly found on golf course putting greens, as well as many other environments in temperate regions of the world. Although it can produce a very desirable putting surface, the species is usually considered a weed, in part because it is characterized by continuous flowering during the growing season. Flowering at the low mowing heights of a golf green, is detrimental to the putting quality of the green and the stress tolerance of the plants. However, many individuals of P. annua flower only in the spring. We conducted this inheritance study to investigate the genetic control of flowering pattern in four representative genotypes, then relate the information to the ecology of the species in golf course environment, and propose improvements for P. annua breeding. One annual and three perennial tetraploid P. annua genotypes were crossed in all combinations. F1, F2, and in most cases F3 populations were grown and observed in field or greenhouse conditions over 1 to 3 yr. Each plant was rated for flowering pattern during the growing season. A genetic model involving one locus and two alleles with continual flowering completely dominant to seasonal flowering is proposed for control of flowering pattern based on F2 populations exhibiting 3:1 ratios of continual to seasonal flowering pattern types. Three distinct F3 populations are produced from F2 progeny: all continual flowering, all seasonal flowering, and segregating 3:1 continual to seasonal, similar to the F2 generation. There may also be evidence of modifying loci and maternal effects in some populations. This simple inheritance may explain the high heritability of flowering traits and rapid evolution of plant types in golf course turfgrass. Qualitative inheritance also provides the opportunity for efficient selection of desirable seasonal flowering P. annua plants.
Changes in Neotyphodium coenophialum Infestation Levels in Tall Fescue Pastures Due to Different Grazing Pressures
Authors: Gwinn Kimberly D. , Fribourg Henry A. , Waller John C. , Saxton Arnold M. , Smith Marshall C.
Published: July 2010

Infection of tall rescue (Festuca arundinacea Schreb.) with the mutualistic fungal endophyte Neotyphodium coenophialum (Morgan‐ Jones & Gams) Glenn, Bacon & Hanlin results in numerous biochemical and physiological changes that increase host persistence. This study was conducted to determine effects of steer (Bos taurus L.) grazing on changes in endophyte infestation levels of tall rescue pastures. Eighteen 1.2‐ha pastures were seeded in 1992 in 20‐cm drill rows involving combinations of high, medium, or low grazing pressure and ‘Ky 31’ tall fescue infested with N. coenophialum at four levels ranging from endophyte‐free (E−) to 80% infestation (E+). Pastures grazed for about 10 mo. each year from fall 1993 until summer 996, although animals on some of the high grazing pressure pastures occasionally had to be removed because of insufficient forage. Endophyte levels were monitored yearly with protein‐A sandwich enzyme‐linked immunosorbent assay (PAS‐ELISA). Stand density of tall fescue remained satisfactory throughout the study. After 2 yr, endophyte infestation levels in low grazing pressure pastures were at the same level as at the beginning of the study, and E+ levels remained constant in all pastures that started at high E+, regardless of grazing pressure. However, in high and medium grazing pressure pastures, E+ levels increased by 20 to 30%. Based on these data, we conclude that moderate and high grazing pressures influence endophyte infestation level of pastures and must be taken into account when designing pasture management systems.
Forage Quality Variation among Maize Inbreds: In Vitro Fiber Digestion Kinetics and Prediction with NIRS
Authors: Jung H. G. , Mertens D. R. , Buxton D. R.
Published: July 2010

The nutritive value of forage maize (Zea mays L.) may be improved through genetic selection for increased rate of fiber digestion or decreased indigestible fiber concentration. To identify sources of genetic variation, 45 maize inbreds were evaluated for in vitro neutral detergent fiber (NDF) digestion kinetic parameters using stem internode tissue harvested at silking during 2 yr. Near infrared reflectance spectroscopy (NIRS) was also used to estimate NDF digestion kinetic parameters. Maize inbreds varied significantly in NDF concentration and digestion kinetic parameters using either conventional in vitro analysis or NIRS predictions. Using NIRS predictions, inbreds varied in NDF concentration from 497 to 662 g kg−1 dry matter (DM), rate of NDF digestion ranged from 0.037 to 0.077 h−1, and extent of NDF digestion was 525 to 735 g kg−1 NDF. The ranges for NIRS predicted parameters were less than those observed for the calibration data set by conventional analysis. Correspondence between conventional analysis data and NIRS predictions were good, except for lag time. Digestion kinetics calculated from NIRS predicted residues provided more precise predictions of lag time and fractional rate of digestion when compared with observations derived from conventional analyses, than did direct prediction of these kinetic parameters. Correlations between rate of NDF digestion and 18‐h NDF digestibility (r = 0.79) or between potential extent of NDF digestion and 96‐h NDF digestibility (r = 0.95) were large enough that these two fermentation intervals might substitute for conducting complete digestion kinetic studies with eight to 10 fermentation times. The substantial genetic variation among these maize inbreds shows good potential for development of silage hybrids with improved fiber digestion parameters. Year and year × genotype interactions were significant suggesting that identification of superior inbred lines will require evaluations in multiple environments.
Preference for Smooth Bromegrass Clones Is Affected by Divergent Selection for Nutritive Value
Authors: Falkner L. K. , Casler M. D.
Published: July 2010

Selective grazing by sheep (Ovis aries) leads to diet improvement. To learn whether animals select the most nutritious food available, differences in percent consumption were determined among smooth bromegrass (Bromus inermis Leyss.) clones selected for divergent levels of neutral detergent fiber (NDF) or in vitro dry matter disappearance (IVDMD). High‐ and low‐NDF clones from a single population and high‐ and low‐IVDMD clones from four populations were evaluated as spaced plants in separate replicated trials. Preference was determined by offering sheep grazing access to complete blocks comprised of both high and low selections. Pre‐ and post‐grazing plant height and weight were measured and the differences used to calculate percent consumption, which was used as an indicator of preference. Preference and forage nutritive value were determined at three grazing periods in each of 2 yr. High‐IVDMD clones (mean IVDMD = 700 g kg−1) were 12% more preferred (29 vs. 26% of height consumed) than low‐IVDMD clones (mean IVDMD = 690 g kg−1). Low‐NDF clones (mean NDF = 470 g kg−1) were 36% more preferred (34 vs. 25% of height consumed) than high‐NDF clones (mean NDF = 505 g kg−1). Preference was positively correlated with IVDMD in three of four populations and negatively correlated with NDF. Sheep discriminated between equally‐accessible, more‐ and less‐nutritious clones and preferentially selected the more nutritious clones.
Exogenous Cytokinin and Nitrogen Do Not Increase Grain Yield in Narrow‐Leafed Lupins
Authors: Ma Qifu , Longnecker Nancy , Atkins Craig
Published: July 2010

Application of exogenous cytokinin N6‐benzylaminopurine (BAP) to flowers at anthesis increases pod set but not grain yield in lupins (Lupinus angustifolius L). This study aimed to examine whether supplemental nitrogen supply could enhance the fulfilment of enlarged sink capacity induced by BAP application and thus increase seed yield. An abscission‐minus lupin mutant (cv. Danja) was grown in pots under glasshouse conditions. Application of BAP to all flowers produced more pods on the main stem, but not on the lateral branches, with four to 13 more total pods set on the BAP‐treated plants than on the control plants. When BAP was applied to main stem flowers only, the number of pods on the main stem increased from four to 18, but pods on the lateral branches decreased from 19 to 11. In contrast, when BAP was applied to lateral flowers only, the number of pods on the lateral branches increased. However, the increase in pod set induced by BAP caused a decrease in the number of seeds per pod and average seed weight, and as a consequence, plant seed yield was not affected by BAP. Urea fertilizer caused much more shoot N accumulation than did symbiotic N2 fixation, but this shoot N enrichment did not result in an increase in seed yield or seed N content. These findings indicate that there is a limit to grain yield and N harvest index in lupins. Although exogenous application of cytokinin can increase sink strength and cause a redistribution of yield components between the main stem and lateral branches, it did not increase the grain yield of the whole plant under these experimental conditions.
Nitrate Reductase Activities in Rice Genotypes in Irrigated Lowlands
Authors: Barlaan Edward A. , Sato Hiroyuki , Ichii Masahiko
Published: July 2010

Nitrate reductase (NR) is a key enzyme involved in nitrate assimilation in crops. In irrigated lowlands, specific activities of NADH‐ and NADPH‐NR in rice (Oryza saliva L.) have not been investigated. The objectives of this study were to evaluate the nitrate reductase activity (NRA) patterns of rice genotypes with different NRA levels under irrigated lowland conditions, and to determine the effects of NR deficiency on nitrate use, grain yield, biomass, and other agronomic characteristics. Seven cultivars and seven NR mutants were grown under irrigated lowland conditions; bioassayed in vitro for NRA at different growth stages; and evaluated for grain yield, biomass, and other agronomic characters. NADH‐NRA was present at minimal levels in all cultivars before transplanting. At 15 d after transplanting (DAT), NADH‐NRA in all cultivars reached optimum levels and gradually declined until maturity. A similar pattern was observed in most of the NR mutants but with lower levels of activity. NADPHNRA in cultivars and mutants gradually increased from 15 to 45 DAT and then fluctuated between 5 to 10 nmol NO−2 min−1 g−1 fresh weight until maturity. Nitrate availability in the soil may significantly influence NRA and nitrate accumulation in rice in irrigated lowlands. Effects of low or deficient levels of NR on traits evaluated varied among mutants. A decrease of 27 to 73% in grain yield was observed in mutants relative to original cultivars. This study demonstrates that rice assimilates nitrate in anaerobic and flooded conditions, which may have implications for genetic improvement and nitrate or nitrogen management strategies in rice.
Kura Clover Growth and Development during the Seeding Year
Authors: Genrich K. C. , Sheaffer C C. , Ehlke N. J.
Published: July 2010

Information on Kura clover (Trifolium ambiguum Bieb.) development in the seeding year would be useful in developing new cultivars with greater seedling vigor and establishment. Our objective was to study herbage and root biomass accumulation and seedling development of Kura clover following spring and summer planting. Field experiments were conducted on a fine‐silty over sandy, mixed Typic Hapludoll and on a sandy, mixed, Udorthentic Haploboroll. Spring seeded Kura clover had rhizome initials (≤3 cm) 63 d after planting and some spring seeded plants had rhizomes which were 20 cm long with leaves by the end of October. Secondary rhizomes had developed on primary rhizomes of some plants by 98 d after seeding. Summer planted Kura clover plants developed rhizome initials about 100 d after planting but had no rhizomes longer than 3 cm. Pink nodules were observed about 56 d following spring planting and about 42 d after summer planting. Contractile growth was observed about 35 and 46 d after spring and summer planting, respectively. Herbage and root dry weight accumulated at a linear rate following spring and summer plantings until growth was reduced in the fall. By October of the seeding year, spring planted kura clover had average herbage yields of 1672 kg ha−1 and below‐ground mass of 2733 kg ha−1 with 10% of the below‐ground mass consisting of rhizomes. Endura had greater average whole plant and herbage yields than Rhizo, but root yields were similar for the two entries. Since Kura clover seedlings partition a significant amount of dry matter to the root system, increased seedling vigor might be achieved by selecting for increased herbage accumulation.
Isozyme Analysis Supports Allotetraploid Inheritance in Tetraploid Creeping Bentgrass (Agrostis palustris Huds.)
Authors: Warnke S. E. , Douches D. S. , Branham B. E.
Published: July 2010

Inheritance data from tetraploid Agrostis palustris Huds. populations produced by crossing selected plants from cultivated creeping bentgrass varieties is reported. Phosphoglucose isomerase, phosphoglucomutase, glutamate oxaloacetate transaminase, triosphosphate isomerase, anodal peroxidase, esterase, and alcohol dehydrogenase were resolved in a Tris‐citrate/lithium‐borate pH 8.3 buffer system. Acid phosphatase, 6‐phosphogluconate dehydrogenase, aconitase, malate dehydrogenase (MDH), and shikimic acid dehydrogenase were resolved in a histidine‐citrate pH 5.7 buffer system. Four enzyme systems exhibiting polymorphism in the Tris‐citrate/lithium‐borate buffer system were selected for further genetics studies. Segregation data at the Tpi‐l, Tpi‐2, Got‐2, Pgi‐2, and Pgm‐2 loci were used to identify allozymes and distinguish between allo‐ or autotetraploid segregation patterns. Two allozymes were identified at the Pgm‐2 and Tpi‐1 loci, while three allozymes were identified at the Got‐2 and Tpi‐2 loci. The Pgi‐2 locus was highly polymorphic with six different allozymes identified. Fixed heterozygosity at the Tpi‐2 and Got‐2 loci and disomic segregation for a tetraoallelic individual at the Pgi‐2 locus provided strong genetic evidence to support allotetraploid inheritance in creeping bentgrass. Additionally, one parental done that exhibited high levels of self‐fertility was identified and its breeding implications are discussed.
Controlled Freezing as a Indirect Selection Method for Field Winterhardiness in Turf‐Type Perennial Ryegrass
Authors: Waldron B. L. , Ehlke N. J. , Vellekson D. J. , White D. B.
Published: July 2010

Winterhardiness is a complex trait that has been difficult to select for in many Poaceae species. Controlled freezing has been investigated as a selection method to improve winterhardiness; however, most previous reports in perennial ryegrass (Lolium perenne L.) have not provided estimates of genetic parameters. This research was conducted to determine the potential of controlled freezing as an indirect selection method for winterhardiness improvement in perennial ryegrass. Seedlings of perennial ryegrass halbsib families were frozen to −6°C under controlled conditions with freezing tolerance evaluated after 3 wk recovery as visual injury and wet and dry weight shoot regrowth. The same seedlings were subjected to a second freezing treatment of −9°C with freezing tolerance reevaluated. The combination freezing treatment of −6° followed by −9°C was more highly correlated with field winterhardiness than the single freezing treatment of −6°C. Measuring freezing tolerance as wet weight after the combination freezing treatment resulted in the highest genetic correlation (rA = 0.91) indicating that this trait and field winterhardiness were under similar genetic control. Selection using the combination freezing treatment (−6°C followed by −9°C) dry weight evaluation was 58% as efficient as field selection for improving winterhardiness. Ten of the top 15 winter‐hardy families were selected by regrowth evaluation following the combined freezing temperature treatment using a selection intensity of 35%. These favorable results, plus the additional benefit of short cycle time, indicate that controlled freezing can be successfully used as an indirect selection method for increasing winterhardiness in perennial ryegrass.
Relationship between Baking and Noodle Quality in Hard White Spring Wheat
Authors: Lang C. E. , Lanning S. P. , Carlson G. R. , Kushnak G. D. , Bruckner P. L. , Talbert L. E.
Published: July 2010

There is growing interest in the use of hard white wheat (Triticum aestivum L.) for both the production of oriental noodles and making bread. It would be desirable if new hard white wheat cultivars produced flour suitable for both purposes. Our objective was to address the feasibility of developing such dual purpose white wheats. We tested several hard white spring wheat lines grown in three locations in Montana for quality characteristics associated with both end‐use products. The hard white spring wheat lines had bread‐making quality similar to that observed for high quality hard red spring wheat check cultivars. The hard white spring wheat flours differed from Australian Standard White by producing significantly harder noodles that were not as bright, particularly after 24 h of noodle storage. Significant variation existed among the hard white lines for noodle color, suggesting selection during breeding might improve color characteristics. However, superior noodle color was correlated with low protein in two environments and with poor loaf volume in one environment. The challenge facing breeders in the development of dual purpose hard white spring wheats will be to improve noodle characteristics while maintaining good bread‐making qualities.
Evaluation of Near‐Isogenic Sorghum Lines Contrasting for QTL Markers Associated with Drought Tolerance
Authors: Tuinstra M. R. , Ejeta G. , Goldsbrough Peter
Published: July 2010

Drought is the most important constraint on crop production in the world today. Although selection for genotypes with increased productivity in drought environments has been an important aspect of many plant breeding programs, the biological basis for drought tolerance is still poorly understood. We have been conducting a genetic research program directed at developing a better understanding of drought tolerance in sorghum [Sorghum bicolor (L.) Moench]. Several quantitative trait loci (QTL) associated with pre‐flowering and post‐flowering drought tolerance were previously identified in a recombinant inbred mapping population. In the current study, nearisogenic lines (NILs) were developed and used to test the phenotypic effects of three different genomic regions associated with various measures of agronomic performance in drought and/or non‐drought environments. In most cases, NILs contrasting for a specific locus differed in phenotype as predicted by QTL analysis. NILs contrasting at QTL marker tM5/75 indicated large differences in yield across a range of environments. Further analysis indicated that differences in agronomic performance may be associated with a drought tolerance mechanism that also influences heat tolerance. NILs contrasting at QTL marker tH19/50 also differed in yield under drought and nondrought conditions. The analysis of these NILs indicated that these differences may be influenced by a drought tolerance mechanism that conditions plant water status and the expression of staygreen. NILs contrasting at QTL marker t329/132 differed in yield and seed weight. These differences appear to be the result of two QTL that are closely linked in repulsion.
Mapping of Disease Resistance Loci in Barley on the Basis of Visual Assessment of Naturally Occurring Symptoms
Authors: Spaner D. , Shugar L. P. , Choo T. M. , Falak I. , Briggs K. G. , Legge W. G. , Falk D. E. , Ullrich S. E. , Tinker N. A. , Steffenson B. J. , Mather D. E.
Published: July 2010

Using field‐scored data of disease severity under natural infestation, we mapped loci affecting resistance to powdery mildew (Blumeria graminis DC f. sp. hordei Ém. Marchal), leaf rust (Puccinia hordei Otth.), stem rust (Puccinia graminis f. sp. tritici Eriks. & E. Henn.), scald [Rhynchosporium secalis (Oudem.) J.J. Davis], and net blotch (Pyrenophora teres Drechs.). The mapping population included parents and doubled‐haploid progeny of the two‐row barley cross Harrington/TR306. Resistance was affected by two to five loci, explaining 8 to 45% of the phenotypic variance, per disease. All chromosomes, except chromosome 5 (1H), contained regions with at least one disease resistance locus. One region on chromosome 4 (4H) contributed to resistance to stem rust, scald, and net blotch. This region has previously been reported to affect days to heading and maturity. Two known resistance genes in the population, Rpgl and M1g, were mapped to within 3 centimorgans (cM) of their previously estimated genomic locations by simple interval mapping of the field‐scored data. This indicates that the genomic positions of disease resistance genes can be estimated accurately with simple interval mapping, even on the basis of field‐scored data.
Genetic Structure of Regeneration Populations of Annual Ryegrass
Authors: Johnson R. C.
Published: July 2010

Information is lacking concerning how regeneration procedures affect the genetic structure of accessions in germplasm repositories. The objective of this research was to compare the genetic structure of original seed populations with three different regeneration population types in three field grown accessions of Lolium multiflorum Lam. (annual ryegrass). The three regeneration samples were (i) balanced (equal number of seeds per plant combined), (ii) spike (an inflorescence per plant combined), and (iii) bulk (seeds combined proportionally according to seeds per plant). Analysis of 10 loci from eight isozymes was completed on populations of 88 plants for each accession and sampling method. Allelic frequency after the first regeneration in balanced populations deviated from the original at 4% of the polymorphic loci, with differences occurring at 19% of the loci for both spike and bulk populations. For one accession, a second regeneration cycle was completed. The balanced population did not differ from the original but the spike and bulk populations did differ from the original at 33% of the polymorphic loci. The greater deviation from the original allelic frequencies of spike and bulk populations was associated with their variation in progeny numbers per plant, which reduced effective population size (Ne) an average of 27%. After the first regeneration, mean heterozygosity per locus was 0.27, 0.28, and 0.26 for balanced, spike, and bulk populations, respectively, and mean alleles per locus was 2.6 for balanced and spike populations and 2.5 for bulk populations. Thus diversity, measured as heterozygosity and alleles per locus, was maintained nearly as well with bulk or spike samples as balanced samples. The results suggest that the major disadvantage of bulk and spike sampling was the potential for accelerated genetic drift associated with reduced Ne.
Molecular Support for the Hybrid Origin of the Wild Potato Species Solanum × rechei
Authors: Clausen A. M. , Spooner D. M.
Published: July 2010

Twenty‐seven of the 232 wild potato species (Solanum sect. Petota) have been hypothesized to be of natural hybrid origin. Prior molecular data have failed to support hybrid origins involving two other wild potato species, Solanum raphanifolium Cárdenas and Hawkes and S. chacoense Bitter, and hybrid speciation has never been supported with molecular data in sect. Petota. This study was conducted to test the hybrid origin of Solanum × rechei Hawkes and Hjert. It is a locally common and weedy wild potato species from Argentina, occurring at the extreme southern end of the range of S. microdontum Wittm., and near the northern end of the range of S. kurtzianum Bitter, its two putative parents. Solanum × rechei is diploid (2n = 2x = 24) with triploid (2n = 3x = 36) populations, S. kurtzianum is diploid (2n = 2x = 24), and S. microdontum is diploid (2n = 2x = 24), with triploid populations at its extreme southern range. A prior study supported the hybrid origin of S. × rechei by intermediate morphology of natural and synthetic hybrids, reduced pollen stainability of the natural and synthetic hybrids, and distributional evidence. Our studies of new collections and prior germplasm collections fail to support the morphological intermediacy of S. × rechei, but lack of morphological intermediacy is common for many hybrids. Hybrid origin was instead verified by reduced pollen stainability and additive parent‐specific single‐ to low‐copy nuclear restriction fragment length polymorphisms (RFLPs) in S. × rechei. These data suggest that other wild potato species also may be of hybrid origin, which may help explain some of the taxonomic confusion in the group.
Agronomic Performance and Transmission of the Multiple‐Bud Mutation of Sugarcane
Authors: Burner D. M. , Legendre B. L.
Published: July 2010

Few morphological mutations have been identified in sugarcane (Saccharum spp. hybrids), a vegetatively propagated grass with complex, polyploid genetics. The multiple‐bud mutation may increase bud survival at planting and shoot production per unit area. The objectives of this study were to compare yield components and bud germination of single‐bud (normal) cultivars and multiple‐bud mutants, to determine the frequency of multiple buds in mutants, and to assess the sexual transmission of the multiple‐bud trait. Seven multiple‐bud mutants, including one gall‐forming mutant (US 94‐12), were tested with two normal cultivars in plant cane crops for 2 yr in a randomized complete block design with four replications. Transmission was measured for 1 yr in progeny of 19 selfed or single‐cross populations having at least one multiple‐bud parent. Normal cultivars produced one shoot per node in the greenhouse. Most multiple‐bud genotypes produced about two shoots per node, except that US 94‐12 produced 4.5 shoots per node. In field tests, however, numbers of shoots, stalks, and stools of multiple‐bud genotypes tended to be lower than cultivars. The multiple‐bud trait was sexually transmitted to only 2.2% of progeny, lower than previously reported. This may have resulted from stricter screening or intermittent gene expression. Development of a multiple‐bud cultivar will be hindered by the low rate of transmission and, therefore, the large population required for selection. Future studies should be directed toward the identification of commercially acceptable multiple‐bud genotypes having the potential to give stands equal to cultivars at lower planting density, thereby reducing seed cane requirements.
Natural Outcrossing of Sorghum and Sudangrass in the Central Great Plains
Authors: Pedersen J. F. , Toy J. J. , Johnson B
Published: July 2010

Amount of natural outcrossing in a species is one of the primary determining factors in selection of breeding methods. Existing literature on natural outcrossing of sorghum is dated and limited in geographical reference. Experiments were designed to investigate natural outcrossing in contemporary sorghum, Sorghum bicolor (L.) Moench, B‐ and R‐lines, and in sudangrass, Sorghum bicolor (L.) Moench. Four R‐lines and four B‐lines were seeded in rows in isolation at Mead, NE, and allowed to intercross in each of 2 yr. Bulked seed from each row was planted and proportion of offtypes recorded. Outcrossing ranged from 0.1 to 13% in R‐lines, and from 0.5 to 9% in B‐lines. Outcrossing among sudangrass plants with white or green midribs transplanted in isolation in each of 2 yr was estimaled by utilizing the dominant gene for while midrib as a marker. Panicles from green midrib plants were tagged to indicale approximate date of pollination. At maturity, the panicles were divided into top, middle, and bottom thirds and threshed. Seed from each panicle section was planted and proportion of while midrib plants recorded. Outcrossing ranged from 0 to near 100% on individual sudangrass plants and was highly variable. Harvest of panicles pollinated during the middle of the pollination period should maximize outcrossing in sudangrass, but the use of nuclear male‐sterility genes is still recommended for improvement of sudangrass through recurrent selection. For sorghum breeding procedures requiring a high degree of self‐pollination, selfing under pollination bags is recommended.
Estimation of Canopy Photosynthesis in Rice by Means of Daily Increases in Leaf Carbohydrate Concentrations
Authors: Conocono E. A. , Egdane J. A. , Setter T. L.
Published: July 2010

Procedures for rapid measurement of canopy photosynthesis are needed because current methods are time consuming and labor intensive. Our objective was to demonstrate that daily increases in nonstructural carbohydrates of shoots provide a good estimate of daily canopy photosynthesis for rice (Oryza sativa L.). Four cultivars— ‘IR72’, ‘IR64’, ‘IR50’, and ‘YRL39’— were grown in the field on a verlic tropaquept clay soil. Canopy photosynthesis was measured in the field every 2 h from sunrise (0600 h) to sunset (1800 h) and plotted over time to determine daily photosynthesis. Increases in shoot nonstructural carbohydrates per day were calculated by subtracting sunrise concentrations from those at sunset. Highly significant positive relationships between daily canopy photosynthesis and irradiance (r2 = 0.999) and leaf soluble sugars and irradiance (r2 = 0.981) were observed. Coefficients of determination for relationships between daily canopy photosynthesis and daily increases in leaf soluble sugars were high (r2 = 0.987). Growth stage comparisons showed the highest coefficients of determination at panicle initiation because non‐structural carbohydrates in the shoot were dependent on canopy light interception and photosynthesis. Relationships during flowering were intermediate because the spikelet was the main carbon sink. Removal of panicles at flowering increased coefficients of determination to r2 = 0.8. Relationships among cultivars for daily irradiance versus daily canopy photosynthesis or daily increases in leaf soluble sugars had r2 values of 0.7 to 1.0. We conclude that measuring daily increases in leaf carbohydrates can provide a simple, rapid screening procedure for evaluating canopy photosynthesis in rice.