bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Improvement in Large‐Seeded Virginia‐Type Peanut Cultivars since 19441
Authors: Mozingo R. W. , Coffelt T. A. , Wynne J. C.
Published: July 2010

Peanut (Arachis hypogaea L.) yields have increased from an average of 1120 kg ha−‐1 in the 1940s to over 3360 kg ha−‐1 in the 1980s in the Virginia‐North Carolina Production Area. This yield increase may be attributed to the development of new cultivars as well as changes in production practices during this period. In order to measure increases attributed to genetic improvement, a 3‐yr field study (1982–1984) was conducted at the Tidewater Research Center in Suffolk, VA on an Eunola loamy find sand soil (Aquic Hapludults) and the Peanut Belt Research Station in Lewiston, NC on a Norfolk sandy loam soil (Typic Paleudults) using current production practices. The highest yielding cultivar developed during the 1950s, 1960s, and 1970s had an average yield increase of 3.4, 10.2, and 18.5%, respectively, over the standard ‘NC 4’. During the 1970s, breeding emphasis was placed on pest resistance and quality acceptance. Consequently, yields of cultivars released to date during the 1980s have not surpassed the cultivar with the highest yield developed during the 1970s. Results from this study show genetic improvement has been made in large‐seeded Virginia‐type peanut with an 18.5% yield increase attributed to improved cultivars. This genetic improvement has accounted for yearly yield increases of 14.7 kg ha−1.
Inheritance of Resistance to Gray Leaf Spot in Maize1
Authors: Thompson D. L. , Bergquist R. R. , Payne G. A. , Bowman D. T. , Goodman M. M.
Published: July 2010

Gray leaf spot disease (caused by Cercospora zeae‐maydis Tehon and Daniels) of maize (Zea mays L.) has the potential to become an important problem in U.S. maize production. Inheritance of resistance in maize to gray leaf spot disease was investigated using plant ratings from three experiments in naturally occurring field epiphytotics: Generation mean analysis of four populations, diallel analysis of all possible single crosses, and correlation comparison between 16 inbreds per se and their crosses with a common parent. Plants were rated just prior to leaf death on a plot basis utilizing a scale of 1 (resistant) to 5 (susceptible). In the generation mean experiment the susceptible parents, B73 and B73rhm, were rated 4.1 to 4.3 and resistant parents, H99 and NC250, 1.4. For populations from susceptible ✕ resistant parents, estimates of pooled additive effects were large. In the diallel experiment, the eight parents (N28rhm, B73rhm, B73, B73ARB, H99, NC250, Va59, and T234) were rated 4.4, 4.0, 4.1, 2.6,1.4,1.4,1.2, and 1.2 as inbreds per se and 3.3, 3.2, 3.2, 2.5, 2.5, 2.3, 2.3, and 1.8 in crosses, respectively (1985). Mean squares for general combining ability in analyses of variance were significant (P < 0.01) but those for specific combining ability were not (P > 0.05). The 16 inbreds per se were correlated with their ratings in crosses at 0.69 (P < 0.01). Resistance to gray leaf spot in the maize genotypes tested was conditioned mainly by additive effects, was not very complex, could be evaluated effectively using inbreds per se, and may be transferred by usual backcrossing and selection techniques.
Paraheliotropic Leaf Movements in Mature Alfalfa Canopies1
Authors: Reed R. , Travis R. L.
Published: July 2010

The relationship between plant water potential and midday sunavoiding leaf movement was studied in mature alfalfa (Medicago sativa L.) canopies. Diurnal solar tracking patterns were determined for three cultivars representing different germplasm sources: ‘African’, a nondormant type introduced from the arid regions of Africa; ‘Lahontan’, a semidormant type of Turkistan origin; and ‘Norseman’, a dormant type introduced from the Ladak province of northern India. Solar tracking was measureduring four regrowth cycles beginning in early spring and concluding in early fall. Early and late season regrowth cycles for African and Lahontan were typified by patterns in which leaflet surfaces were positioned perpendicular to incident radiation (diaheliotropism) throughout the day. Late spring and midsummer diurnal diaheliotropic patterns were interrupted by midday sun‐avoiding paraheliotropic (PHT) movement in both cultivars. Conversely, diurnal tracking in Norseman was interrupted by PHT movement in all cycles. Leaflet PHT movement is generally presumed to be a stress‐avoidance mechanism induced by changes in plant water status. However, regression analyses of PHT activity data for alfalfa showed no clear relationship between diurnal PHT patterns and xylem water potential (XWP) either among cultivars or with the onset of and recovery from PHT activity. Rather, in all three cultivars, cupping was consistently related to ambient vapor pressure deficit (VPD). African and Lahontan did not exhibit midday leaflet PHT movement during the late season regrowth cycle even when the daily ambient VPD and XWP profiles were similar to the midseason patterns.
Daylength and Sowing Date Responses of Soybean Lines with “Juvenile” Trait1
Authors: Parvez A. Q. , Gardner F. P.
Published: July 2010

Daylength limits adaptation of soybean [Glycine max (L.) Merr.] genotypes to a narrow range of latitudes and sowing dates by affecting vegetative and reproductive growth and development. Photoperiod and sowing‐date experiments were conducted in Gainesville, FL (29.38°N) during 1984 and 1985 to assess the vegetative and reproductive growth of soybean genotypes previously observed to differ in sensitivity to change in latitude and sowing date. ‘Kirby’ and ‘Improved Pelican’ and two breeding lines, F82‐7656 and F84‐1220, selected for adequate vegetative development under short days (“juvenile” trait), were used. Photoperiods included 14‐h, 18‐h, and natural‐winter daylengths between 22 Jan. and 30 Mar. 1984 in a greenhouse experiment, and 10‐h (covered 14 h) and natural‐summer days in 1985 in a field experiment (Jonesville Taxajunct Soil classified as loamy, mixed, thermic Arenic Hapludalf). Sowing dates in the 1984 and 1985 field experiments were monthly from 1 April through 1 August. Improved Pelican, Kirby, F82‐7656, and F84‐1220 ranged from highly to only moderately responsive to the photoperiod and sowing date treatments. In 1984, under natural‐winter days and 14 h, all plants averaged the R1 stage at 30 and 60 days after planting (DAP), respectively. Plants under 18 h were vegetative at 68 DAP, the termination date. Under 10 h in the 1985 field experiment, Kirby, F82‐7656, Improved Pelican, and F84‐1220 were in the R1 stage in 48, 52, 54, and 57 DAP, respectively. Plant height, node number, and DAP to R1 for F84‐1220 were most constant over the range of photoperiods and sowing dates, indicating efficacy of the juvenile trait in extending adaptability.

Improved Pelican in the April and May sowings grew excessively tall (2 m) and aborted its flowers and pods, which indicated not only pre‐, but also postflowering daylength effects. Kirby and F82‐7656 at the August sowing date flowered too early, resulting in severe reduction of vegetative growth and pod number. In the 1 April and 1 August sowings and the 10‐h photoperiod, F84‐1220 was near optimum height and produced more branches, racemes, and pods than the other genotypes. We conclude that the juvenile trait, as demonstrated in line F84‐1220, can improve climatic adaptation of soybean cultivars by buffering photoperiod effects incident to suboptimal latitudes and/or sowing dates.
Juvenile Growth in Pigeonpea, Soybean, and Cowpea in Relation to Seed and Seedling Characteristics1
Authors: Brakke M. P. , Gardner F. P.
Published: July 2010

Pigeonpea (Cajanus cajan L. Millsp.) is characterized by a weak seedling and juvenile growth, and slow establishment. This study evaluated growth parameters influencing seedling and juvenile growth of pigeonpea compared to grain legumes more vigorous in juvenility, viz., cowpea (Vigna unguiculata L.) and soybean [Glycine max (L.) Merr.]. The hypothesis that slow juvenile growth in pigeonpea is due to disproportionate assimilate partitioning to roots resulting in less shoot growth was tested also. Total shoot and root dry matter (DM) and leaf area (LA) were sampled weekly on field‐grown potted plants for 49 days after planting (DAP) in 1983. Dry matter and LA were consistently fourfold to sixfold greater for soybean and cowpea than pigeonpea at each weekly sampling. Shoot/root ratios for the three legumes were similar in trend and magnitude; hence the hypothesis of disproportionate partitioning and root growth was not accepted. Pigeonpea seedlings without exposed cotyledons (hypogenous) had smaller unifoliolate and trifoliolate leaves than the epigenous soybean and cowpea. At 10 DAP, relative leaf area for cowpea, soybean, and pigeonpea was 100, 65, and 20%, respectively. Relative DM yield was 100, 64, and 27%, respectively. However, relative (not absolute) leaf‐ and plant‐growth rates during the time course were significantly greater for pigeonpea than for soybean and cowpea. Nodule formation in pigeonpea was reduced compared to the other legumes. Utilization of seed energy was more rapid in cowpea at 10 DAP than for pigeonpea, but the two were similar at 17 DAP. Seed energy conversion efficiency was similar for cowpea and pigeonpea at both sampling dates. Size of seedling axis was related to seedlingrowth. We conclude that pigeonpea plant type might be improved by larger seeds and cotyledons, epigeal emergence, and larger unifoliolate and trifoliolate lamina during seedling and juvenile growth phases.
Direct Generation of Wheat Haploids via Anther Culture1
Authors: Liang George H. , Xu Aili , Tang‐Hoang
Published: July 2010

Haploids of wheat [Triticum aestivum L.) provide useful materials for obtaining doubled haploids, homozygous lines, and for in vitro mutation research. Wheat haploids generated via anther culture are usually produced by a two‐step procedure: callus induction and plantlet development. To save time, material, and space, we have developed a one‐step procedure by which haploid plantlets are generated from plated anthers without transferring the calluses to a regeneration medium. Regeneration frequency (percent anthers producing plants) with the one‐step procedure varied from 0% for ‘Olaf’ and ‘Waldron’ to 7.31% for ‘Chris’. Two media formulations, both of which contained α‐Naphthaleneacetic acid instead of 2,4‐Dichlorophenoxyacetic acid, produced haploid seedlings directly without transferring calluses to another medium. The plantlets developed by the one‐step procedure appeared about 3 weeks after they were placed on the medium. Albinos and plantlets possessing high polyploid chromosome numbers occasionally appeared among regenerates.
Early Development of Duplication‐Deficiency Ovules in Upland Cotton1
Authors: Contolini Carol S. , Menzel Margaret Y.
Published: July 2010

Viable duplication‐deficiency (dp‐df) products are recovered from heterozygous translocations in Upland Cotton (Gossypium hirsutum L.) with an overall frequency high enough to warrant their use in cytogenetic experiments. The frequencies of dp‐df's from most translocations, however, are considerably lower than predicted from meiotic configurations. Heterozygotes (Tt) of two translocation lines were studied to determine the period of development during which dp‐dfs were lost. In Tt2;14 2B‐l, which normally yields a high frequency of dp‐df's, the frequency of ovule failure was similar to that in TMI controls. Failure of ovules began at 5 days after anthesis in Ttl0;ll 2785. A high percentage of ovules from Ttl0;ll at 5 days postanthesis were found with intact synergids and polar nuclei, indicating that failure may occur daring fertilization. Endosperm failure may also be responsible for some dp‐df loss, because, in 4% of ovules from Ttl0;ll, nucellar cells filled the interior of the ovule and obliterated the space normally occupied by embryo and endosperm. Attempts were made to enhance the recovery of dp‐dfs by culture of 2‐day‐postanthesis ovules. In both lines, the frequency of dp‐dl's was significantly higher (P = 0.001) in the cultured progenies than in controls. In ovulo culture also decreased by 50% the time required to obtain seedlings.
Use of Greenbug Biotype Mixtures in Evaluating Wheat Seedlings for Resistance1
Authors: Tyler J. M. , Webster J. A. , Merkle O. G.
Published: July 2010

Currently, no single source of greenbng [Schizaphis graminum (Rondani)] resistance in wheat (Triticum aestivum L.) germplasm available to wheat breeders provides resistance to all known greenbug biotypes in the field. Therefore, two sources of resistance are being combined in several wheat breeding programs. This requires the evaluation of progeny for reaction to two greenbug biotypes instead of one. Our objective was to test the efficacy of infesting seedlings in the greenhouse with green bugs of two biotypes simultaneously. Such a procedure, if feasible, could economize breeding protocols. OK81322, resistant to biotypes B and C, a ‘Largo’ derivative, resistant to biotypes C and E, and F1, and F2, progeny from the crosses of these genotypes were infested with a 1:1 mixture of biotypes B and E greenbugs. All plants of both parental genotypes were susceptible, all F1, plants were resistant, and the population of F2, plants segregated for greenbug resistance. Results indicated that evaluation of breeding material with mixed greenbug populations is reliable, and this technique should be more efficient than conducting separate biotype tests.
Susceptibility of ‘Tifton 68’ and ‘Coastal’ Bermudagrass to the Mexican Rice Borer1
Authors: Browning H. W. , Hussey M. A.
Published: July 2010

Field observations in 1984 indicated a difference between ‘Tifton 68’ (Cynodon nlemfuensis Vanderyst) and ‘Coastal’ [C. dactylon (L.) Pers.] bermudagrass in susceptibility to the Mexican rice borer, Eoreuma loftini (Dyar). Results from random samples verified the differential susceptibility of these two cnltivars. In replicated 1‐m2 plots, an average of 38% of Tifton 68 stolons were damaged by E. loftini and 15% contained live borers, compared with 0.8% borer damage in Coastal and the absence of live borers in that cultivar. The recovery of pupae and pupal exuviae demonstrated the ability of E. loftini to successfully complete its life cycle on Tifton 68. The transportation of vegetative material of Tifton 68 and its role in the spread of this pest is discussed. Other forage grasses susceptible to damage by E. loftini are listed.
Genotype by Tillage Interactions of S1 Lines from Two Maize Synthetics1
Authors: Newhouse K. E. , Crosbie T. M.
Published: July 2010

Hybrids presently being used for commercial production of maize (Zea mays L.) were developed and evaluated primarily in fields tilled with moldboard plows. In contrast, 37% of the commercial maize hectar age in the USA in 1984 was planted using some type of reduced tillage practice. The effects of using genotypes selected with conventional tillage in reduced tillage field environments are not known. This study evaluated 100 S1 lines from each of two different maize synthetics to examine the consequences of using different tillage systems for field evaluations. The lines were grown in five environments, over a 2‐yr period using no‐till and conventional tillage. The S1 lines from the BS22(R)C1 synthetic had few significant interactions of genotypes with tillage systems and expressed levels of genotypic variance in no‐till equal to or greater than the levels expressed in conventional tillage. The S1 lines from the BS13(SCT)C6 synthetic had significant interactions between genotypes and tillage systems for six of the eight traits reported, and expressed similar levels of genetic variance in each tillage system. Correlations between traits were similar in both tillage systems. Selection efficiency was better in no‐till than in conventional tillage for the BS22(R)C1 synthetic. No obstacles to the use of no‐till systems for evaluation and selection of maize genotypes were observed.
Evaluation of Four Maize Populations Containing Different Proportions of Exotic Germplasm1
Authors: Albrecht Bruno , Dudley J. W.
Published: July 2010

Introgression of exotic maize (Zea mays L.) germplasm into adapted U.S. breeding populations has been proposed as a means for increasing useful genetic variability of quantitatively inherited traits and for enhancing response to selection. However, it is not clear what proportion of exotic germplasms most favorable. The present study was conducted to assess the relative breeding value of four populations with different proportions of exotic germplasm. Two maize populations, Illinois Stiff Stalk Synthetic Composite (RSSSC; adapted to the central Corn Belt) and South African Photoperiod Insensitive Composite II (PIC2;t ropical origin) were crossed and the F1 was backcrossed once to RSSSCT. he F1 and BC1 were randommated to produce the F2, and BC1‐F2 generations, respectively. Random sets of at least 80 to 100 S1 families were derived from the RSSSC, BC1‐ F2, F2, and PIC2 populations (with 0, 25, 50, and 100% exotic germplasm, respectively). These were grown in 1983 and 1984 in replicates‐in‐block designs with two replications at one location. Grain yield, pollen‐shed date, rind puncture resistance, stalk rot and leaf blight severity, and other agronomic traits were evaluated. Genetic variance and covariances were estimated for all traits and all pairs of traits, respectively.M eagnr ain yields for RSSC, BC1‐F2, F2, and PIC2 were 3.31, 3.08, 2.88, and 1.96 t ha−1, respectively. In both years, highest genetic variance estimates for yield were obtained in BC1‐F2. Pollen‐shed in RSSSCw as 10 days earlier than in PIC2 and percentage grain moisture increased linearly with increasing proportion of exotic germplasm. In trogression of PIC2, as expressed in BC1‐F2 and F2, improved stalk rot, leaf blight, and rind puncture resistance of RSSSCP. redictions of gain from selection for grain yield, per se, indicated that the BC1‐F2 would be the most favorable foundation population. However, A desired gain performance index including grain yield, grain moisture, rind puncture resistance, and stalk rot and leaf blight ratings favored the F2 if little weight was given to yield, but ranked RSSSC,BC1‐F2, and F2 as equally valuable foundation of pulations if considerable weight as assigned to yield. The PIC2 population was markedly less valuable mainly due to its lack of adaptiveness.
Genetic Expression of Wheat Streak Mosaic Virus Resistance in Two Wheat‐Wheatgrass Hybrids1
Authors: Stoddard S. L. , Gill B. S. , Lommel S. A.
Published: July 2010

Two intergenic amphiploids wheat (Triticum aestivum) tall wheatgrass (Agropyron elongatum) and wheat ✕ intermediate wheatgrass (A. intermedium) are potential sources of wheat streak mosaic virus (WSMV) resistance. The genetic control of WSMV resistance must be understood before sources can be effectively used in wheat breeding. The amphiploids and the derived disomic addition lines of individual chromosomes in T. aestivum were analyzed to determine chromosome locations, epistatic interactions, and dosage effects of genes for WSMV resistance. The evaluation of resistance was carried out by symptomatology under both growth chamber and glasshouse conditions in conjunction with double antibody sandwich enzyme‐ linked immunosorbent assay (ELISA) and slot‐blot hybridization, which were useful in identifying minor genes for WSMV resistance. The amphiploids were resistant to WSMV infection and remained symptom‐free throughout their growth under both growth chamber and glasshouse conditions. A single chromosome addition line 6E from A. elongatum and L5 from A. intermedium were resistant to WSMV under growth chamber conditions. ELISA and slot‐blot values suggested a minor factor for genetic resistance on another chromosome in both Agropyron species. Apparently, one major factor and at least one minor genetic factor control the resistance observed in these two Agropyron species. Epistatic interaction between chromosomes 5E and 6E in A. elongatum appeared to be involved in genetic expression of WSMV resistance. Moreover, WSMV resistance was hemizygous ineffective as plants with a monosomic addition of 6E were susceptible. The results indicate that resistance in the specific Triticum ✕ A. elongatum amphiploid analyzed here will be difficult to transfer to wheat. The resistance on chromosome L5 of, A. intermedium may be more promising provided one of the ditelosomic lines expresses a level of resistance equal to the L5 chromosome. The hemizygous ineffective nature of WSMV resistance should be taken into account while evaluating breeding lines for resistance. The techniques of ELISA and slot‐blot hybridization proved to be useful in identifying minor genes for WSMV resistance.
Inheritance of Seedling Hydrocyanic Acid Potential and Seed Weight in Sorghum‐Sudangrass Crosses1
Authors: Lamb J. F. S. , Haskins F. A. , Gorz H. J. , Vogel K. P.
Published: July 2010

The hydrocyanic acid potential (HCN‐p) of sorghum [Sorghum bicolor (L.) Moench] plants is recognized as a heritable trait, but previous studies on the mode of inheritance of HCN‐p have produced inconsistent results. The objective of this study was to investigate the inheritance patterns of seedling HCN‐p and also of seed weight in reciprocal crosses of sorghum and sudangrass [formerly S. sudanense (Piper) Stapf]. Both traits were found to be inherited quantitatively. Generation means analysis indicated that additive genetic effects were most important for both seed weight (53% of variation) and seedling HCN‐p (74% of variation). A maternal effect was found for both traits in the F1 and backcross generations. No evidence of this reciprocal effect was found in the F2, suggesting that cytoplasmic inheritance was not involved. A highly positive correlation between seed weight and HCN‐p was found across all entries, across both parents, and in the F1 and backcross generations. However, correlation coefficients between seed weight and seedling HCN‐p for individual entries, the pooled F2'S, or within types of seed parents in the F1 or backcross generations were generally nonsignificant. It was concluded that seed weight per se does not have a large effect on seedling HCN‐p.
Effects of Seeding Rates on Harvest Index, Grain Yield, and Biomass Yield in Winter Wheat1
Authors: Sharma R. C. , Smith E. L.
Published: July 2010

Harvest index (HI) is considered a potential selection criterion for improving grain yield in cereals. Selections are usually made in thinly seeded populations. Therefore, effective selection is dependent upon expression of the traits under selection being consistent in different crop stands. The literature indicates differences in results from selection using HI vs. selection for grain yield per se in thin crop stands. This study was conducted to examine the effects of two seeding rates, standard (67.2 kg ha−1)) and low (16.8 kg ha−1), on HI, grain yield, and biomass yield and to compare the relationship of HI and biomass yield to grain yield in winter wheat (Triticum aestivum L.). Ten hard red winter wheat genotypes were evaluated in replicated field tests in three environments. The field plot design was a split plot with genotypes as main plots and seeding rates as subplots. Results indicate that effects of seeding rate and genotype ✕ seeding rate interactions were significant for grain and biomass yields but not for HI. However, environmental effects and seeding rate ✕ environment interactions were significant for all three traits. The simple and rank correlation coefficients between genotypes grown at the two seeding rates were higher for HI and biomass yield compared to grain yield, which suggests that HI and biomass yield each could have merit as a selection criterion in different crop stands. However, HI and biomass yield in thin crop stands appear to be less effective than grain yield for identifying high grain yielding genotypes.
Salt Increses the Water Use Effeciency in Water Stressed Plants1
Authors: McCree Keith J. , Richardson Steven G.
Published: July 2010

Irrigated crops experience some water stress between irrigations. If poor quality water is used, the crops are also likely to be salinized. Daily C gains and water losses of salinized and nonsalinized sugarbeet (Beta vulgaris L.), and cowpea (Vigna unguiculata L. Walp.) plants were measured continuously, in whole‐plant assimilation chambers, throughout 2 to 3 weeks of water stress under controlled environment conditions. Equivalent data for sorghum plants [Sorghum bicolor (L.) Moench.] were published previously. Even though the three species showed quite different patterns of response to water stress, mild salinization always had the same effect. It reduced the water loss rate per plant, which allowed the length of the irrigation cycle to be increased, which in turn increased the C gain per cycle and the water use efficiency (C gain per unit of water lost).
Nitrate Utilization and Dinitrogen Fixation (Acetylene Reduction) by Nitrate Reductase‐Defecient Mutants of Pea1
Authors: Vigue G. T. , Warner R. L.
Published: July 2010

Three NO−3 reductase pea (Pisum sativum L.) mutants and the ‘Juneau’ control were evaluated for the ability to absorb and accumulate NO−3 from solution, and for growth and N2 fixation (C2H2 reduction) in the presence and absence of NO−3. In short‐term (20 h) hydroponic studies, the mutants absorbed NO−3 at rates similar to Juneau, but accumulated more NO−3 than Juneau in both shoots and roots. Seedlings of Juneau assimilated 63%, while seedlings of mutants assimilated <35% of absorbed NO−3. In long‐term studies with plants grown in vermiculite in the presence of 15 mM NO−3, dry weights of mutants A300 and A317 were <50% of Juneau. However, growth of mutant A334, which had only 6 to 8% of the NO−3 reductase activity of Juneau, was equal to the control. Growth of mutant A300 was not as rapid as the other genotypes when N2 fixation or NH+4 was the only N source. All three mutants and Juneau exhibited good levels of C2H2 reduction activity and growth in the absence of mineral N. Also, the NO−3 reductase mutations did not lessen the inhibition of N2 fixation by NO−3 and the cause of the inhibition remains unclear.
Variation for Activity of Nodule Nitrogen and Carbon Assimilating Enzymes in Alfalfa1
Authors: Jessen D. L. , Barnes D. K. , Vance C. P. , Heichel G. H.
Published: July 2010

The nodule enzymes glutamate synthase (GOGAT) and phosphoenolpyruvate carboxylase (PEPC) are important in the assimilation of symbiotically fixed N in alfalfa (Medicago sativa L.). The objectives of this study were: to evaluate several alfalfa germplasm sources for variability in nodule GOGAT and PEPC activities, and to determine the relationships between N2 fixation and plant yield traits with nodule GOGAT and PEPC enzyme activities. Approximately 160 plants from each of six alfalfa germplasms were grown in sand culture in the glasshouse and assayed for nodule GOGAT and PEPC enzyme activities. Twenty‐four genotypes (four from each germplasm) were selected to represent a range in GOGAT and PEPC activities. These genotypes were evaluated in glasshouse and field clonal studies for GOGAT and PEPC activities per gram nodule fresh weight, acetylene reduction activity (ARA), nodule mass, nodule color, nodule soluble protein concentration, and plant yield. Variability for nodule GOGAT and PEPC activities within each of the six germplasms was large and normally distributed. The 12 high GOGAT genotypes (2 from each germplasm) were 44% greater GOGAT activity than the 12 low genotypes. The 12 high PEPC genotypes were 27% greater in PEPC activity than the 12 low genotypes. Both groups of high enzyme activity genotypes were significantly greater than the low genotypes in ARA, nodule soluble protein concentration, and field shoot yield. Both GOGAT and PEPC activities were positively correlated (r=0.61**, significant at the 0.01 probability level). Also, GOGAT and PEPC were each correlated with ARA (r=0.43*, significant at the 0.05 probability level, and 0.45*, respectively), nodule color score (r=0.46** and 0.73**) soluble protein concentration (r= 0.77** and 0.90**). Plant yield and N2 fixation measured in the field were not correlated with nodule GOGAT and PEPC activities measured in the glasshouse. The relationships between GOGAT and PEPC with other plant traits indicated that these enzymes are associated with the host‐Rhizobium meliloti Dang. symbiosis and should be explored as possible selection criteria to include in an alfalfa breeding program.
Cytoplasmic Effects on Agronomic and Malting Quality Traits in Barley1
Authors: Lee Debra Metzger , Albertsen Nancy , Rasmusson Donald C.
Published: July 2010

The presence of genetic information in organelles of the cytoplasm suggests that certain nucleus‐cytoplasm combinations may be superior in terms of crop productivity or crop quality. The objective of this study was to examine cytoplasmic effects on eight agronomic and seven malting quality traits in six‐rowed malting barley (Hordeum vulgare L.). Backcrossing was used to incorporate the nuclear genome of two malting cultivars, ‘Conquest’ and ‘Dickson’, into six diverse cytoplasms represented by three H. vulgare cultivars and three other Hordeum species. Backcross derived lines and Conquest and Dickson were evaluated in field trials at two Minnesota locations in 1978 and 1983. In all, 15 traits were examined in 12 different nucleus‐cytoplasm combinations. There was little evidence of cytoplasmic effects on the agronomic traits and none for the malting quality traits. The six cytoplasms failed to influence any of the traits in combination with the Conquest nuclear genome. In the Dickson backcrosses, ‘Betzes’ cytoplasm resulted in a slightly earlier heading date, and H. spontaneum var. spontaneum cytoplasm resulted in an earlier heading date and fewer plump kernels. The different performance of the Conquest and Dickson backcross derived lines may indicate a failure to rid the Dickson derived lines of nuclear genes from the cytoplasm donors or be evidence of nuclear‐cytoplasm genotype interaction.
Near Infrared Reflectance Analysis of Total Nonstructural Carbohydrate Concentration in Tropical Grasses1
Authors: Brown W. F. , Piacitelli C. K. , Mislevy P.
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) has been used for the rapid chemical analysis of feed. This research investigated the use of NIRS to analyze total nonstructural carbohydrate (TNC) concentration in stem bases and roots of Cynodon, Hemarthria, Digitaria, and Paspalum tropical grasses from six experiments. Conventional TNC analysis was conducted and NIRS equations were developed from selected samples (85–280) representing all treatments evaluated in an experiment. Standard errors of calibration and analysis ranged from 11.3 to 18.7 g kg‐1 dry matter (DM). Coefficients of determination via NIRS ranged from 0.53 to 0.92. Mean biases ranged from −1.5 to 4.4 g kg‐1 DM. A subset of samples representing all treatments evaluated in each experiment was selected to develop a general NIRS‐TNC equation. Validation results were similar to those from each experiment, indicating that a general NIRS‐TNC equation could analyze TNC concentration of a specific group of samples with the same accuracy as an equation developed from that specific group.
Modification of Methods for Identifying Populations to be Used for Improving Parents of Elite Single Crosses1
Authors: Dudley J. W.
Published: July 2010

One method of utilizing populations (either adapted or exotic) hybrid breeding programs, is to cross a population (Py) to one of the parents (e.g., I1) of an elite F1 (I1 × I2), self in the F2, and attempt to recover a line superior to I1. For a population to be useful in such a program, it must contain favorable alleles not present in the elite F1. A previous method for identifying such populations lacked generality. A modified method was developed that removes the assumption that frequency of favorable alleles in Py. is equal for all classes of loci except those for which the F1 lacks favorable alleles. The modified method provides estimates of gene frequencies (p̄j and p̄k) at loci for which the F1 is heterozygous. These estimates can be used to determine which of the parental inbreds should be improved by crossing to Py and whether to self directly in the F2 or to backcross prior to selfing. Effects of relaxing the assumption of complete dominance are shown. The modified method provided estimates nearer the true values than previously proposed methods when applied to a set of hypothetical data.
Photosynthetic Differences among Triticum Accessions at Tillering1
Authors: Johnson R. C. , Kebede H. , Mornhinweg D. W. , Carver B. F. , Rayburn A. Lane , Nguyen H. T.
Published: July 2010

Flag leaves of many diploid and tetraploid Tritlcum species are known to have higher photosynthesis rates than flag leaves of cultivated hexaploid wheat (Triticum aestivum L.). Yet these differences are reportedly absent or less pronounced on earlier developed leaves. Our objective was to study the relationship between photosynthesis, stomatal conductance, and water‐use efficiency (WUE) in various Triticum acessions at the tillering stage. Net CO2 assimilation per leaf area (A) and associated gas exchange characteristics were measured on newly expanded leaves of 6‐week‐old growth chamber‐grown plants of four wild diploids, six wild tetraploids, and two cultivated hexaploids. Significant variation in A was observed with values ranging from 31.1 μmol CO2 m−2 s−1 in the diploid T. speltoldes to 20.7 in one accession of T. dicoccoides; A for the two hexaploid wheats averaged 22.6. This A range for leaves of plants at tillering is similar to that reported by others measuring A of tlag leaves. Because higher A was associated with higher stomatai conductance (r = 0.86**, significant at the 0.01 probability level), which led to higher transpiration, there was no significant correlation between A and WUE. There was no significant correlation between A and internal CO2 concentration (C1), so differences in A among accessions were not explained by differences in CO2 supply to the mesophyll. Two T. dicoccoides accessions found to differ in A and conductance at tillering also had different flag leaf A and conductance. Comparison of A vs. Ci response curves between these two accessions showed that the higher A was related to a higher capacity for mesophyll photosynthesis rather than stomatal conductance per se. The results show that the variation in A among accessions was to a significant extent attributable to nonstomatal factors and that differences in A among Triticum accessions are detectable at early vegetative growth stages.
Priming Brassica Seed to Improve Emergence under Different Temperatures and Soil Moisture Conditions1
Authors: Rao S. C. , Akers S. W. , Ahring R. M.
Published: July 2010

Germination and emergence of Brassicas under stressful environmental conditions such as adverse soil temperatures and variable soil‐water availability appear to be major obstacles in obtaining suitable stand establishment and subsequent forage production. Primed and nonprimed seeds of ‘Purpletop’ and hybrid ‘Tyfon’ turnip (Brassica rapa L.) and ‘Merlin’ kale (B. oleracea L.) were planted and grown in growth chambers at two temperatures (7.5 and 15°C) and four soil moisture levels (‐10, ‐30, ‐100, and ‐500 kPa). Primed seeds had been treated in aerated solution of polyethylene glycol 8000 (PEG 8000) at 25°C. Individual primed and nonprimed seeds of each cultivar were planted in boxes containing Dale sandy loam (fine silty, mixed, thermic Pachic Haplustolls) that had been equilibrated at each moisture level. Seedling emergence was counted daily until Day 22 after planting. At 7.5°C, priming increased total emergence by 10 and 21% for Tyfon turnip and Merlin kale, respectively. In contrast, Tyfon turnip was the only cultivar with increased total emergence (11%) at 15°C. Purpletop turnip emergence was not affected by priming at either temperature. Priming decreased the time to attain 50% emergence (ETS50) by 1 to 5 days for Tyfon turnip and Merlin kale at 7.5°C, whereas ETS50 for Purpletop turnip increased by 1 to 2 days. At 15°C, priming did not significantly improve the ETS50 except for Merlin kale. These results indicate that priming may reduce the risk of poor stand establishment in cold and moist soils and thus allow earlier planting of slow emerging Brassica cultivars to provide needed forage during the spring forage deficit period.
Cell Wall Carbohydrates of Flaccidgrass Plant Parts. I. Neutral Sugar Composition of Fermented Residues1
Authors: de Ruiter J. M. , Burns J. C.
Published: July 2010

Poor quality subtropical pasture grasses limit animal productivity, especially in mid‐ to late‐summer in the southeastern USA. The fermentability of structural carbohydrates (SC) is an important indicator of quality. Cleavage of the SC into monomers was examined for flaccidgrass (Pennisetum flaccidum Griseb.) plant parts (leaf blade, leaf sheath, and stem) having a range of fiber concentrations. Cleavage was achieved by sequential hydrolysis using 2.0 mol L−1 followed by 0.25 mol L− trifiuoroacetic acid (TFA) of neutral or acid‐detergent extracted cell wall residues (CWR) at 121°C for 1 h at each step. Hydrolysate monomer concentrations were determined by gasliquid chromatography of trimethyisilylated derivatives. Samples at four maturities were fermented in an in vitro rumen fluid bioassay for 0, 20, 40, and 72 h prior to CWR preparation. Plant parts differed widely in their fiber fractions, with neutral detergent fiber ranging from 644 to 817 g kg−1; acid detergent fiber from 336 to 501 g kg−1; hemicellulose from 277 to 353 g kg−1; cellulose from 282 to 383 g kg−1; and lignin from 47 to 112 g kg−1. In vitro dry matter disappearance ranged from 459 to 778 g kg−1. In immature (preheading) plants, the leaf sheaths consistently had a lower disappearance than leaf blades or stems, while mature (postheading) plant stems had the least disappearance. With increasing fermentation time, less SC monomers were hydrolyzed by TFA from the CWR. There was a significant (P ≤ 0.01) linear maturity effect for both the individual (arabinose, xylose, galactose, and glucose) and total neutral sugar concentrations. Significant (P ≤ 0.01) linear and quadratic incubation time responses were found for these variables. Concentrations of SC monomers generally differed among the plant parts. Arabinose, xylose, and galactose in leaf blades were fermented more than in sheaths or stems. Glucose maintained a high level of disappearance, even in mature plants (83 to 93 g kg−1). Xylose fermented the least of the SC monomers (25 to 63 g kg−1 in mature forage). Its resistance to fermentation was a major limitation to the efficient utilization of mature flaccidgrass forage.
Cell Wall Carbohydrates of Flaccidgrass Plant Parts. II. Neutral Sugar Relationships to In Vitro Disappearance and Fiber Fractions1
Authors: de Ruiter J. M. , Burns J. C.
Published: July 2010

The relationship between cell wall (CW) structural composition and in vitro dry matter disappearance (IVDMD) is important in defining a physiological basis for quality differences among subtropical forage grasses. This study was conducted to examine the relationships on a plant part basis between trifluoroacetic acid (TFA)‐ hydrolyzed cell wall monomers of flaccidgrass (Pennisetum flaccidum Griseb.) and the traditional quality estimates of IVDMD, neutral detergent fiber, and hemicellulose. Structural carbohydrate (SC) monomers were determined following TFA hydrolysis by gas chromatography on residues recovered after 0, 20, 40, and 72 h of in vitro fermentation. Neutral detergent extracted cell walls were prepared from flaccidgrass plant parts (leaf blade, sheath, and stem) of four maturities (early season's growth to maturity). A unit increase in IVDMD was associated with a unit decrease in the cell wall concentration (r = −0.98). With increasing fermentation time, less SC monomers (consisting of arabinose, xylose, galactose, and glucose) were hydrolyzed from the CW residues. The CW monomers most strongly related to IVDMD were xylose and glucose (r = −0.94 and −0.87, respectively). In the latter relationship there was a significant quadratic response. The total CW hydrolyzed sugars were also strongly related to IVDMD (r = ‐0.98). These strong relationships were retained when the analysis was performed on 72‐h digested CW residues (r = ‐0.93, ‐0.87, and ‐94 for IVDMD vs. xylose, glucose, and total monomers, respectively). Similarly, the total hydrolyzed sugars of cell walls were good predictors of hemicellulose determined empirically by subtracting acid detergent fiber from neutral detergent fiber (r2 = 0.98). Carbohydrate monomers responsible for variation in IVDMD were identified and the carbohydrate concentration of flaccidgrass cell walls was found to be intricately associated with IVDMD.
Botanical Composition Definition of Tall Fescue‐White Clover Mixtures by Near Infrared Reflectance Spectroscopy1
Authors: Petersen J. C. , Barton F. E. , Windham W. R. , Hoveland C. S.
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) was evaluated for determining botanical composition of preformed mixtures containing ‘Regal’ iadino clover (Trifolium repens L.) and ‘Kentucky 31’ lowendophyte tall fescue (Festuca arundinacea Schreb.) as well as the botanical composition of samples harvested from grazing paddocks. Both species were grown in separate plots, harvested at monthly intervals, and hand‐mixed. This provided combinations from 100% grass to 100% legume, resulting in a total of 60 samples that were used for NIRS calibration. The NIRS calibration equations for percentage tall fescue and white clover resulted in standard errors of calibration of 2.98 and 2.80%, respectively. Synthetic mixtures composed of material from grazing paddocks were used for validation of the equations. Species composition was predicted with excellent precision and accuracy showing biases of ‐1.64 and 1.80%, and standard errors of prediction (SEP) of 3.16 and 3.08% for the tall fescue and white clover equations, respectively. High R2 was also obtained when predicting the percentage of both component species. The NIRS prediction of pasture samples, whose actual composition was determined by hand separation, yielded higher SEP and bias. This additional variation (compared to the prediction of synthetic mixtures) was assumed to be made up of error associated with the hand‐separation procedure and the variation of the prediction samples not present in the calibration set. These data indicate that with the proper selection of calibration samples, wavelengths, and data transformation, NIRS can be used to determine the botanical composition of grass‐legume mixed samples.
Cytology of Sorghastrum nutans, Sorghastrum pellitum, and Their Hybrids1
Authors: Read J. C. , Maika S. D.
Published: July 2010

The use of interspecific hybridization has been used by plant breeders to transfer desirable genes into crop plants. This study was undertaken to determine if Sorghastrum nutans (L) Nash (yellow indiangrass) and S. pellitum (Hack.) Parodi will hybridize, to investigate their cytotaxonomic relationship, and the possibility of using this species in the improvement of yellow indiangrass. Sorghastrum nutans has 40 chromosomes that pair as 20 bivalents during meiosis with no abnormalities, suggesting it is an allotetraploid. Sorghastrum pellitum is a diploid with 20 chromosomes that pair as 10 bivalents during meiosis with no abnormalities. Three triploid interspecific hybrids between hybrids between S. nutans and S. pellitum were produced. Based upon spikelet characteristics, they are morphologically closer to the S. nutans than S. pellitum, female sterile, and the stainable pollen ranged from 0.0 and 2.8%. Chromosome associations during meiosis indicate that S. nutans and S. pellitum have one genome in common and that two homozygous translocations between chromosomes of two genomes in S. nutans may exist.
Plant Traits Related to Productivity of Maize. II. Development of multiple Trait Models1
Authors: Willman M. R. , Below F. E. , Lambert R. J. , Howey A. E. , Mies D. W.
Published: July 2010

Grain yield and stalk lodging are the result of complex interactions of many traits expressed during maize (Zea mays L.) development. A better understanding of the most important traits influencing grain yield and stalk lodging could lead to improved production practices and more efficient breeding programs. To determine the most important combination of plant traits related to maize productivity, multiple regression models using plant trait means as independent variables, and grain yield or stalk lodging means as dependent variables were developed. Four groups of hybrids with different heterotic patterns and maturity were evaluated separately at 11 to 27 locations for grain yield and stalk lodging in 1984. The same groupings of hybrids were evaluated for 21 plant traits at one location (Urbana or St. Joseph, IL) in 1984 and 1985. Regression analysis showed that, dependent on the maturity group, from two to four of the selection traits would account for 46 to 95% of the variability among the hybrids for grain yield and stalk lodging. Across all maturity groups, a four trait model consisting of stalk dry weight at 15 days after anthesis, leaf P concentration at 15 days after anthesis, kernel number at maturity, and percentage of grain protein accounted for 40 to 93% of the variability among hybrids for grain yield. A five‐trait model consisting of plant carbohydrate to N ratio at the seven‐leaf stage, leaf P concentration at 15 days after anthesis, penetrometer readings of stalk rind strength at 40 days after anthesis, the percentage increase in stalk dry weight following ear removal, and the percentage of grain oil together accounted for 44 to 81% of the variability among hybrid means for stalk lodging. Although the role of a given plant trait varied with the particular hybrid, maturity group, and/or environment, the relatively high coefficient of determination values of the models indicates simultaneous measurement of several traits may prove useful in explaining maize productivity in specific hybrid groups.
Dry Matter, Nitrogen Distribution, and Dinitrogen Fixation in Contrasting Alfalfa Symbioses1
Authors: Fishbeck K. A. , Heichel G. H. , Vance C. P.
Published: July 2010

Improving dinitrogen (N2) fixation of alfalfa (Medicago sativa L.) requires combining effective rhizobial strains and host genotypes capable of enhanced N2 fixation. Glasshouse experiments on pot‐grown alfalfa determined how changes in the rhizobial and host genomes associated with N2 fixation affect dry matter and N yields and distribution at vegetative, flower bud, and 30% flowering developmental stages. We compared dry matter and N yield and distribution in a host‐ and a rhizobial‐conditioned ineffective (Fix+) and in a related effective (Fix+) symbiotic combination, and investigated the effect of combined N on N2 fixation and on the distribution of symbolically fixed N2 in two unrelated Fix+ alfalfa germplasms. Dry matter and N yield and response to added N (0, 40, 80 kg/ha) of the host‐conditioned and the rhizobial‐conditioned Fix− combinations were similar. Without combined N, both Fix− combinations distributed relatively less dry matter and N to aerial organs than did the Fix+ combination. Neither the type of Fix− combination nor traits in the Fix+ germplasms supportive of increased N2 fixation altered the relative distribution of dry matter among plant organs; however, N concentration in individual organs varied with supplemental N in the Fix− but not the Fix+ combinations. Dry matter and N yields of the two unrelated Fix+ combinations differed only without combined N. Supplemental N was more inhibitory to N2 fixation by Fix+ germplasm selected for enhanced nitrogenase activity compared with unselected Fix+ germplasm. Either source of ineffective nodulation in Fix− combinations would be appropriate for developing non‐fixing controls for physiological investigations of N2 fixation and for use in programs to evaluate and enhance N2 fixation in alfalfa.