bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Absorption of Soybean Seeds ans Associated Causal Factors1
Authors: Calero Eduardo , West S. H. , Hinson Keull
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed quality in humid environments is related to the amount of water the mature seeds imbibe before harvest and during storage. The mechanism which restricts water uptake by the soybean seed has not been fully determined. The permeability of the seed coat to the passage of water vapor is presumed to be one such mechanism. The purpose of this study was to find genotypes which absorb water slowly and to identify factors associated with low water absorption.

Twelve cultlvars, introductions and breeding lines, and seven progenies from different crosses were used to study the rate of water absorption at 100% relative humidity and 24 C for 8 days and under standard germinating conditions for 8 and 24 hours. Seed coats of selected samples of seed from the water absorption studies were observed using the scanning electron microscope.

A negative correlation between seed size and the percentage of water uptake was found in some materials, but this relationship did not hold for all. A range of water uptake rates was observed. Furthermore, the shape and size of pores present in the seed coat were different for the various materials. Small seeds had a higher percentage by weight of seed coat and large, rounded pores, whereas large and medium seeds had a lower percentage of seed coat with smaller, elongated pores. Waxy material was embedded in different densities into the epidermis. Ecuador 2, Bragg, Ss‐Da‐010 and the progenies from Bragg ✕ (Cobb ✕ PI86490) F4 appear to imbibe water slowly. Small elongated pores and a high density of waxy material embedded in the epidermis were associated with low absorption.
Rhizobium — Host Specificities in Phaseolus coccineus L. and Phaseolus vulgaris L.1
Authors: Hohenberg J. S. , Munns D. N. , Tucker C. L.
Published: July 2010

The introduction of desirable agronomic characteristics into Phaseolus vulgaris L. is being attempted by interspecific hybridization with P. coccineus, but the effects on root nodulation are unknown. Accordingly, cross‐inoculation relationships between P. vulgaris ‘Red Kidney’ and P. coccineus ‘Scarlet Runner’ were tested in the greenhouse with a group of 16 Rhizobium strains effective on Red Kidney and a group of 12 strains effective on Scarlet Runner. Both groups had diverse origins, including commercial sources and isolations from bean fields and other sites in California.

Only six strains, all isolates from Scarlet Runner, were effective on both hosts. Fifty percent of Scarlet Runner isolates were as effective on Red Kidney as the more effective of Red Kidney's homologous strains. Thirty percent of the California isolates tested on Red Kidney were more effective than two commercial inocula.

Strain rejection in Red Kidney was expressed in 75% of all cases as failure to form nodules. In contrast, strain rejection by Scarlet Runner was expressed in 64 to 68% of all cases as ineffective nodulation (nodule malfunction). If Scarlet Runner is representative of P. coccineus in this respect, interspecific hybridization is likely to increase rather than reduce the tendency of P. vulgaris to nodulate with ineffective rhizobia.
Genetic Stability in ‘Pennlate’ Orchardgrass Seed Following Artificial Aging1
Authors: Roos Eric E. , Rincker Clarence M.
Published: July 2010

A single lot of orchardgrass (Dactylis glomerata L. cv. ‘Pennlate’) seed was artificially aged to produce eight levels of germination ranging from 96 to 32%. Field plots were established at Fort Collins, Colo. and Prosser, Washington to evaluate potential genetic shifts resulting from selective deterioration within the seed lot. Populations of each treatment (120 spaced plants) were evaluated for spring vigor, plant diameter, heading date, anthesis date, plant height, number of heads per plant, and stem angle. Artificial aging of seed had no consistent effect on expression of these traits.
Stable Cytoplasmic Male‐Sterile Mutants Induced in Tift 23DB1 Pearl Millet with Mitomycin and Streptomycin1
Authors: Burton Glenn W. , Hanna W. W.
Published: July 2010

Stable cytoplasmic male‐sterile lines are necessary for the commercial production of F1 hybrid seed of important crop plants such as sorghum (Sorghum bicolor L.) and pearl millet [Pennisetum americanum (L.) Leeke.]. The objective of this investigation was to ascertain if streptomycin and mitomycin could help to create stable cms mutants. Seeds of ‘Tilt 23DB1’ pearl millet were soaked in water solutions of 200 and 500 ppm of streptomycin, and 50 ppm of mitomycin at 5 C for 40 hours. Treated seeds were rinsed in tap water, surface dried, and planted in an isolated field along with a check of untreated seed. Head populations of 32,800, 22,300, 18,000, and 13,000 from seed treated with 0, 200, 500 ppm of streptomycin and 50 ppm of mitomycin contained progeny tested stable cytoplasmic male‐sterile (cms) mutants at frequencies of 1 in 16,200, 5,575, 4,500, and 2,600, respectively. The sterility or fertility of ctns mutants crossed with 2 sterility maintainers and 6 fertility restorer inbreds of pearl millet suggests that the induced mutants have sterility maintainer and fertility restorer requirements similar to cms Tilt 23DA, and are similar cms mutants.
Improving the Heterotic Capability of Pearl Millet Lines1
Authors: Burton Glenn W.
Published: July 2010

A population of 180 random F6 lines were developed from a cross between two pearl millet, Pennisetum americanum (L.) Leeke, inbreds T8 and T13. These elite inbreds produce a high yielding F1 forage hybrid when crossed and also demonstrate good heterotic capability (the ability to impart hybrid vigor to their offspring) when crossed on T23A. The forage yields of 156 of these lines when crossed on T23A and of 144 when crossed on T18A were compared with controls in precise 9 ✕ 9 lattice square tests. A number of these single crosses yielded as much as the best control T23A ✕ T8 or T18A ✕ T13, and several yielded significantly more. A number of the F6 lines possessed better seed producing characteristics than either parent. The results suggest that lines with improved heterotic capability can be found in populations from a cross of the two elite lines with heterotic capability that give the highest yielding hybrid when intermated. A yield trial of diallel crosses involving elite lines with high heterotic capability can locate such lines.
Improvement of Yield and Ear Number Resulting from Selection at Allozyme Loci in a Maize Population1
Authors: Stuber C. W. , Goodman M. M. , Moll R. H.
Published: July 2010

Previous studies have shown that alleles at enzyme (allozyme) loci in maize were responsive to directional selection and were associated with changes in grain yield. The purpose of this investigation was to test the hypothesis that manipulation of frequencies of these allozyme alleles in a population of maize would produce responses in correlated quantitative traits. Frequencies of alleles at seven allozyme loci were manipulated in an unselected maize cultivar, ‘Jarvis Golden Prolific’, to generate a population with allelic frequencies virtually identical to those found in the cultivar after 10 cycles of recurrent full‐sib family selection for improvement of grain yield. Field evaluations of this population indicated that selection based solely on the seven allozyme loci produced improvement in grain yield equivalent to one and one‐half to two cycles of full‐sib family selection for yield alone. Selection at the allozyme loci also significantly increased ear number. Possible techniques for the use of allozymes in corn improvement programs were presented.
Photosynthetic Recovery of Peanuts to Defoliation at Various Growth Stages1
Authors: Jones J. W. , Barfield C. S. , Boote K. J. , Smerage G. H. , Mangold J.
Published: July 2010

This experiment was designed to study the response of peanut (Arachis hypogaea L.) canopy carbon dioxide exchange rate (CER) to degrees of foliage loss at different dates throughout the season. Peanut plots were manually defoliated 25, 50, and 75 % on different dates during the season for comparison with control plots (0% defoliation). Weekly, CER was measured on control plots and on plots which had been defoliated at different dates. Canopy CER was initially reduced 45 to 70% after 75 % defoliation reduced leaf area index (LAI) to about 1.0, but subsequent measurements revealed considerable CER recovery. Recovery of CER was related to two mechanisms, leaf area production and re‐adaptation of previouslyshaded leaves to full sun.

The re‐adaptation of leaves to full sun was most apparent from the inability of recently‐defoliated canopies to use all the light they intercepted for CER, but after 1 to 2 weeks, efficiency of utilizing photosynthetically active radiation utilization improved without an increase in LAI. The re‐adaptation process appeared to be related to increasing specific leaf weight. Recovery mechanisms, especially leaf production, diminished as the peanut plants matured and progressed into pod set and pod fill. Leaf area index increased after early defoliations; however, the rate of LAI increase paralleled that of control plots. For defoliations late in the season, leaf growth had ceased and was not stimulated as a result of defoliation.
Blue Saturation Discrimination by Honeybees and its Potential Influence on Cross Pollination1
Authors: Kipp Larry R. , Mason Charles E.
Published: July 2010

Blue saturation discrimination of honeybees (Apis mellifera L.) was investigated using artificial flowers constructed of Munsell standard colored matte paper with blue 7.5 PB 5/10 (Bmax), 7.5 PB 5/6 (Bmed), and 7.5 PB 5/2 (Bmin). Bees trained to Bmax, could distinguish Bmax from Bmin, though discrimination of Bmax from Bmed was not demonstrated. In a test of the reciprocal of the former test, bees trained to Bmin could not discriminate it from Bmax. This and tests with three saturation levels of green suggest that honeybee blue saturation discrimination is inferior to their color discrimination. However, these results indicate that honeybees may not forage randomly among plant genotypes having flowers of the same color with differences in saturation levels beyond Bmax and Bmin, especially when a greater reward is provided by the one with greatest color saturation.
A New Greenbug Biotype1
Authors: Porter K. B. , Peterson G. L. , Vise O.
Published: July 2010

‘Amigo’, a wheat (Triticum aestivum L. em Thell.) germplasm line resistant to the greenbug [Schizaphis graminum (Rondani)], and selections from crosses and backcrosses of wheat to Amigo were evaluated for resistance to greenbug collections made each year from 1977 to 1980. Amigo, its derivatives, and ‘Insave’ rye (Secale cereale L.) were resistant to these field collections of biotype C greenbugs until January 1980 when Amigo and Amigo derivatives failed to survive a greenbug infestation of progeny of a November 1979 field collection at Bushland, Tex. A series of 11 laboratory tests of biotype C‐resistant and C‐susceptible small grain and sorghum [Sorghum bicolor (L.) Moench] lines infested with either biotype C or the Bushland collections clearly showed the Bushland greenbug to be other than the A, B, or C biotype. The Bushlandarea greenbug was designated biotype E. Insave rye, ‘Will’ barley (Hordeum vulgare L.), and biotype C‐resistant oats (Avena sativa L.) were resistant to biotype E. ‘Largo,’ an amphiploid of T. turgidum/ T. tauschii, appeared to have useable resistance for breeding biotype E‐resistant wheats.

Sorghum lines possessing biotype C resistance from tunis grass [Sorghum virgatum (Hack.) Stapf] PI 38108 were susceptible, but sorghums PI 220248 and ‘Capbam’ were resistant to biotype E and should be useful sources of resistance.

Biotype E was the predominanbt iotype in all greenbugc ollections made at Bushland, Tex., between November 1979 and August 1980. Biotype E was found 75 miles north of Bushland in May 1980.
Meiotic Irreglarities in Avena sativa L./A. sterilis L. Hybrids and Breeding Implications1
Authors: McMullen M. S. , Phillips R. L. , Stuthman D. D.
Published: July 2010

The cytogenetic relationships of nine Avena sativa L. (2n = 6x = 42) and seven A. sterilis L. (2n = 6x = 42) genotypes were evaluated by studying microsporogenesis, seed set, and pollen fertility of the lines and their hybrids. A higher frequency of meiotic irregularities was observed in all A. sativa/A. sterilis hybrids relative to the self‐pollinated parental lines or the A. sativa/A. sativa and A. sterilis/ A. sterilis hybrids. Chromosomes of most of the A. sterilis lines clearly differed in their degree of homology with those of A. sativa. Predictions of the chromosome constitutions of individual A. sterilis lines were made based on crosses with A. sativa cultivars, and tested with data from crosses among each other. Univalents and multivalents frequently were observed in meiotic cells of A. sativa/A. sterilis hybrids. The frequency of univalents increased from diakinesis to metaphase I suggesting desynapsis. The univalents ultimately formed micronuclei in the microspore quartets; micronuclei frequency determinations may provide a useful measure of genetically controlled meiotic irregularity in hexaploid oat hybrids. This information may be useful in selecting the most promising parents for gene transfer. Avena sterilis C.I. 8340 appeared to be the most homologous to A. sativa and thus selection among its interspecific progeny will probably more easily separate desirable from undesirable A. sterilis traits.
Location of Nitrate Reduction in Different Soybean Cultivars1
Authors: Hunter W. J. , Fahring C. J. , Olsen S. R. , Porter L. K.
Published: July 2010

The amount of NO3‐ in xylem sap from 11 soybean (Glycine max L. Merr.) cultlvars was examined to determine if nitrate was being reduced in the shoot or root. Rhizobium free plants were grown hydroponically in the greenhouse with NO3‐ as a sole N source. In one study using 5‐week‐old plants, NO3‐—N in the sap was found to vary with cultivar, with NO3‐ accounting for 42 to 79% of the sap N. Presumably a high proportion of NO3‐ in the sap indicates a high reduction of NO3‐ in the shoot. In another study, weekly sap analysis with ‘Tracy’ showed that shoot reduction of the N in the xylem sap dominated in young plants ( 4 to 6 weeks of age), but root reduction dominated in older plants (7 to 14 weeks). A different pattern was seen with ‘Swift’ in which root and shoot NO3‐reduction were about equal in younger plants (4 to 6 weeks), but root reduction dominated in older plants (7 to 13 weeks). A comparison of nitrate reductase enzyme activities in older plants (7 to 13 weeks) showed Swift to have a large amount of activity in the shoot and Tracy to have a large amount in roots. These studies suggested that soybean cultivars differ in the location of nitrate reduction.
The Inheritance of N2 Fixation Efficiency in Crimson Clover1
Authors: Smith G. R. , Knight W. E. , Peterson H. L
Published: July 2010

Host plant genetics of N2 fixation efficiency in the crimson clover‐Rhizobium trifolii symbiosis was investigated using a diallel mating design and mass selection. Dinitrogen fixation was evaluated using the acetylene reduction assay. Plants were grown for 60 days prior to the assay in plastic pouches containing N free nutrient solution. Live plants were assayed using the plastic pouch to contain the gas mixture.

Crosses differed significantly in acetylene reduction rate. In a combining ability analysis, both general and specific combining abillty were significant sources of variation. Only one of the six parental lines showed a significant, positive general combining ability effect. This line uniformly transmitted its high acetylene reducing ability to all but one of its progeny. In terms of variance components, specific combining ability was more important in determining the acetylene reduction rate than general combining ability for all lines tested. After one cyle of mass selection, acetylene reduction rate was increased 8%. The realized heritability of this trait was 63.1%.
Recovery of Heritable Variability in Anther‐Derived Doubled‐Haploid Rice1
Authors: Schaeffer Gideon W.
Published: July 2010

The anther culture technique for the derivation of dihaplolds in rice, Oryza sativa L., has not been applied extensively to commercial cultivars in the United States. The objective of this study was to identify suitable genotypes among U.S. cultivars for the recovery of useful variability from doubled haploid plants regenerated from anther‐derived calli. Six rice cultivars were evaluated for their ability to produce haploids by anther culture. The cultivar ‘Calrose 76’ produced, on the average, anther‐derived calli in more than 2% of the anthers excised. Some haploids recovered from Calrose 76 were shorter than the original cultivar. Second‐generation, colchicine‐doubled and spontaneously doubled dihaploids produced progeny significantly shorter than the original cultivar. The enhanced dwarfness was transmitted to offspring by selfing. Third‐generation plants derived from doubled haploids were 15 to 30% shorter than Calrose 76. Seed and leaf size and seed weight were significantly lower in the third‐generation progeny than in the controls. The work shows that both useful and deleterious variability can be recovered from Calrose 76 anthers, and the technique should be useful to rice breeders for the development of short stature cultivars and other unique characteristics.
Aposporous Apomixis in Schizachyrium (Poaceae: Andropogoneae)1
Authors: Carman J. G. , Hatch S. L.
Published: July 2010

Megasporogenesis and embryo sac development of Schizachyrium sanguineum (Retz.) Alst. var. brevipedicellatum (Beal) Hatch (2n=40) and l00), S. sanguineum (Retz.) Alst. var. sanguineum (2n=80), S. cirratum (Hack.) Woot. and Standl. (2n=20), and S. scoparium (Michx.) Nash var. neomexicanum (Nash) Gould (2n=40) were investigated. Results suggest that S. sanguineum var. brevipedicellatum (2n=40 and 100) are facultative and obligate aposporous apomicts, respectively. All other taxa appeared to be sexual.

It may be possible to manipulate apomixis in the potentially important forage and eonservation species, S. sanguineum var. brevipedicellatum and transfer apomixis from this variety (2n=40) into little bluestem (S. scoparium (Michx.) Nash var. frequens F. T. Hubb.), also 2n=40, through wide hybridization.
Use of Strain Crosses in the Development of Multiple Pest Resistant Alfalfa with Improved Field Performance1
Authors: Elgin J. H. , McMurtrey J. E. , Hartman B. J. , Thyr B. D. , Sorensen E. L. , Barnes D. K. , Frosheiser F. I. , Peaden R. N. , Hill R. R. , Leath K. T.
Published: July 2010

Alfalfa (Medicago sativa L.) forage production is seldom limited by one pest, but by a collectinn of pests. Consequently, alfalfa cultivars need multiple pest resistance (MPR). Crossing alfalfa strains with different types of pest resistances, each with a dominant type inheritance, should result in populations with economlc levels of resistance to the combined pests. Fourteen strain cross populations were produced at Beltsville, Md. and Reno, Nev. and increased to the Syn 3 or Syn 4 generation. Evaluations of the Syn 1 to Syn 4 generations of six of the populatinns were made for resistance to anthracnose, bacterial wilt, common leafspot, rust, root‐knot nematode, stem nematode, pea aphid, spotted alfalfa aphid, potato leafhopper yellowing, and for fall dormancy ratings. In addition, 3‐year forage yield trials of the Syn 2 to Syn 4 of all 14 populations were conducted at Beltsville and Reno. In most cases the pest resistance and dormancy ratings of the six strain cross Populations evaluated were near the mean of the parental strains. In only a few occasions did increasing synthetic generationsignificantly reduce the level of pest resistance or dormancy levels. Forage yields of all 14 populations averaged 108% of the mean of the parent strains and 102% of the best parent. There was a trend for populations with low yielding parents to be lower yielding than populations with high yielding parents. With a few exceptions, yields remained relatively stable between the Syn 2 and Syn 4 generations. The use of strain crosses to produce MPR populations and cultlvars with improved field performance appears to be a promlsing plant breeding method for alfalfa breeders.
Site and Rate of Tissue Digestion in Leaves of C3, C4, and C3/C4 Intermediate Panicum Species1
Authors: Akin D. E. , Wilson J. R. , Windham W. R.
Published: July 2010

Digestion is lower for grasses adapted to tropical regions than for species from temperate areas. These differences in digestibility have been attributed to anatomical structure and to effects of temperature. This research compared the degradation of tissue types in leaf blades of 29 Panicum species of tropical origin having diverse anatomies and representing C3, C4, and intermediate (C3/C4) photosynthetic pathways and grown in identical environments. Blades were incubated in rumen fluid, and tissue degradation was studied by light and scanning electron microscopy. Mesophyll was rapidly degraded in most C4 and C3 species and estimated to be 86 and 80%, respectively, after 20 hours incubation; a few species of each type (e.g., P. effusum and P. laxum) exhibited slower mesophyll degradation than other grasses. However, the mesophyll digestibility in the C3/C4 species was unexpectedly low, averaging only 72% after incubation for 20 hours and only 50% for P. milioides. Epidermal tissues were readily degraded in most species and the average digestibility of the adaxial epidermis tended to be higher (5 to 8 percentage units) than that the abaxial for all photosynthetic types. Parenchyma bundle sheaths were about 90 to 100% digested both in C3 and C3/C4 species, but those of many C4 species were poorly degraded with an average for all species of only 50% after incubation for 20 hours. The outer portion of the sheath cell wall was particularly low in degradation and remained in many C4 species after 48 hours incubation. The low degradation of parenchyma bundle sheath appeared to be a major influence on blade digestibility in C4 species. Vascular tissues were either not degraded or only partially degraded. These results suggest that improved forage quality could result from plant breeding to increase the degradation of limiting tissues, e.g., the parenchyma bundle sheaths of C4 species, without alterations in the basic leaf anatomical structure. Improvement in quality may also be possible by breeding to increase the proportion of mesophyll content, but such a change may not always improve digestibility since the mesophyll of some species was more slowly degraded than that of others.
A Comparison of Leghemoglobins from Five Agriculturally Important Cultivars of Soybean1
Authors: Fuchsman William H.
Published: July 2010

Isoelectric focusing procedures demonstrated that leghemoglobins a, c1, C2, and c3 are all present and apparently identical in the root nodule extracts from five cultivars of soybean [Glycine max (L.) Merr.]. The identity of leghemoglobins rules out the use of leghemoglobin to distinguish among commercially grown soybean cultivars.
Stability of Grain Sorghum Yield Components Across Diverse Environments1
Authors: Heinrich G. M. , Francis C. A. , Eastin J. D.
Published: July 2010

Yields and components of yield of stable and unstable grain sorghum [Sorghum bicolor (L.) Moench] genotypes were evaluated across diverse environments in Nebraska and Kansas in 1978 and 1979 to determine the mechanisms importan to yield stability. From 56 genotypes, three stable and three unstable F1 hybrids were chosen for detailed evaluation across 14 environments. Mean yields of the six hybrids ranged from 9,840 to 5,410 kg/ha, and measured yield components included plants/m2, heads/m2, tillers/plant, seeds/m2, seeds/ head, and seed weight. Although all six hybrids had comparable yield potential in good environments, the stable types were higher yielding in poor environments; thus, the three stable genotypes (with regression of genotype yield on environment mean yield < 1.0) showed that high yield potential in favorable environments and yield stability were not mutually exclusive. In all genotypes, heads/m2 and seeds/ head increased with improved environments, and seeds/m2 correlated closely with yield/ha. There was no correlation between heads/m2 and seeds/head, suggesting in these environments that both were important to yield but were not inversely related. The compensation ratio relating change in seed weight to change in seed number [(b of seed weight)/(b of seeds/m2)], was three to seven times higher in stable than in nonstable genotypes. The stable hybrids had 40% more seeds/ m2 than nonstable hybrids under poor environments. This only partially explained their 70% yield advantage the balance was accounted for by seed size. Sorghum hybrids differ in capacity for yield stability across environments. In this study, the most stable hybrids maintained heads/m2, seeds/head, and seed weight in poor environments. Tolerance of stable genotypes to stress conditions and the maintenance of all yield components at relatively high levels appeared more important than compensation among the components. Breeding for more seeds/head and greater seed weights would be useful according to this evidence. Consistently higher seed weights of stable types seemed to contribute to yield and to stability.
Acceleration of Alfalfa Drying in the Field by Chemical Application at Cutting1
Authors: Wieghart M. , Thomas J. W. , Tesar M. B. , Hansen C. M.
Published: July 2010

Chemicals were sprayed on alfalfa at cutting to reduce the exposure time of cut forage and thereby decrease the risk associated with field drying. Alfalfa (Medicago sativa L.) was sprayed during field mowing with solutions of potassium carbonate alone, but more frequently in combination with methyl esters of long chain fatty acids and an emulsifier (X‐77). Spraying with the three‐component mixture increased mean dry matter (DM) during a 2 to 3 day trial by a factor of 1.09 to 1.40 compared to unsprayed alfalfa. Drying was faster after spraying with the three‐component mixture than with the potassium carbonate solution alone. At the end of the 1st day (8 to 10 hours after spraying) the DM content of the untreated alfalfa ranged from 49 to 59% while alfalfa sprayed with the three‐component mixture had 52 to 82% DM. Mean DM of seed bearing or blooming alfalfa that was sprayed with the three‐component mixture was 1.08 to 1.13 that of unsprayed alfalfa. Seed stage alfalfa had greater drying rate than did blooming alfalfa when both had the same water content. Heavily crimped alfalfa had a mean DM that was 1.04 times that of lightly crimped alfalfa and spraying with the three‐component mixture increased mean DM by factors of 1.08 and 1.11, respectively. This spraying technique hastened the drying of cut alfalfa under various field conditions.
Comparative Physiology and Water Relations of Two Corn Hybrids During Water Stress1
Authors: Ackerson Robert C.
Published: July 2010

The responses of several physiologlcal processes to water stress imposed at three stages of growth were compared in two corn (Zea mays L.) hybrids. One hybrid (XL62AA) was a good drought tolerant commercial hybrid, while the other was an experimental hybrid (LH) derived from a cross of two Latente parents. The hybrids were compared to assess their relative responses to water stress. The LH hybrid exhibited higher rates of leaf photosynthesis than the XL62AA hybrid, but only at high leaf water potentials. Photosynthetic rates of both hybrids decreased as leaves aged. The LH hybrid maintained higher levels of soluble sugars and starch in the leaves as water potentials declined, perhaps owing to higher photosynthetic rates and/or reduced sink demand for photosynthate.The concentration of abscisic acid was also higher in the LH hybrid particularly when plants became waters tressed. Comparisons of the internal water relations between the hybrids indicated that differences in the leaf turgor‐leaf water potentlal relationship existed only during the time tassels were emerging. During this period, the LH hybrid maintained higher turgo pressures at all leaf water potentials compared with the XL62AA hybrid. When stress was imposed during the time of rapid leaf expansion and the told‐grain filling stages of development the leaf turgor‐leaf water potential relatlonships were similar in the two hybrids. The LH hybrid exhibited certain physiological characteristics that may allow greater drought tolerance or resistance when compared with a good drought tolerant commercial hybrid. As such, the LH hybrid may represent an important source of germplasm for developing more drought tolerant hybrids.
Genetic Analysis of Virescent Mutants and the Identification of Virescents υ12, υ13, υ14, υ15 and υ16 υ17 in Upland Cotton1
Authors: Kohel R. J.
Published: July 2010

Nine virescent mutants of cotton (Gossypium hirsutum L.) were tested for allelism with known virescent mutants and with each other in both greenhouse and field plantings. One mutant was allelic to υ1, two were allelic to yg1yg2, and one was allelic to υ10. One mutant gave a positive F1 allelic test with υ2, but segregation in the F2 established that it was a homoeologue of υ2. Of the remaining mutants, three were identified as simply inherited recessive mutants, and one was a duplicate factor recessive residing on the same chromosomes as υ3 and υ6.
Variability for Traits Used to Estimate Silage Quality in Forage Sorghum Hybrids1
Authors: Pedersen J. F. , Haskins F. A. , Gorz H. J. , Britton R.
Published: July 2010

The variation among 49 F] forage sorghum [Sorghum bicolor (L.) Moench.] hybrids from a 7 ✕ 7 cross‐classified design was explored in 1979 and 1980 for the following silage traits: dry matter (DM), crude protein, in vitro dry matter disappearance (IVDMD), neutral detergent fiber, acid detergent fiber, acid detergent lignin, ammonia, lactate, and Brix of the juice from fresh stalks. Wider ranges generally were found for male than for female parental means. Means for most traits were significantly different among entries. Significant differences among hybrid means over males and over females were found for only DM, rVDMD, and Brix. Interactions with years existed for most traits. Genetic ratios calculated from the mean squares indicated that general combining ability was important for DM, IVDMD, and Brix. Simple correlation coefficients between traits measured on silage and on fresh‐dried samples from the same hybrids were all significant. In view of the effort required to make and evaluate silage samples, initial selection for traits used to estimate quality in fresh‐dried samples appears to be the best approach for improving the quality of forage sorghum silage.
Effect of Rhizobium japonicum Mutants with Enhanced N2 Fixation Activity on N Transport and Photosynthesis of Soybeans during Vegetative Growth1
Authors: Thomas Richard J. , Jokinen Kari , Schrader Larry E.
Published: July 2010

The effects of two mutant strains of Rhizobium japonicum with enhanced capacities N2 fixation, on ureide transport, photosynthesis,root respiration, and growth in soybeans [Glycine max (L.) Merr. ‘Wells’] were examined during vegetative growth. Three‐week‐old plants inoculated with the mutants were larger and had higher rates of acetylene reduction, photosynthesis, xylary ureide transport, leaf allantoinase activity and higher concentrations of ureides in shoot tissues than did plants inoculated with the wild‐type strain. The relative composition of xylem sap N was unaffected by Rhizobium strain. Ureides comprised over 90% of the sap N in all treatments. After 5 weeks growth, however, there were no statistically significant differences among treatments in rates of the physiological processes and growth parameters examined. Cross contamination of nodules containing the mutant strains with the wild‐type strain was not responsible for the apparent loss of the initial advantages to the host plant (in terms of N2 fixation and growth) brought about by the use of the mutant strains. The use of modifications in Rhizobium genetics for improving the dependency of the host plant on N2 fixation for its N requirements is briefly discussed.
Progress from Mass Selection for Field Emergence and Seed Weight in a sh2 Population of Maize1
Authors: Bell R. D. , Darrah L. L. , Zuber M. S.
Published: July 2010

The objective of this study was to evaluate progress from 11 cycles of mass selection for increased field seedling emergence and higher seed weight in a shrunken‐2 (sh2) maize (Zea mays L.) population. Evaluation trials included the 11 cycles of mass selection and four commercial checks homozygous for sh2. The evaluation included field tests, and cold and warm laboratory germination tests of the 15 entries. Field tests were done in nine environments with four replications in each environment. All entries were planted in two‐row plots arranged in a randomized complete block design. Selection for increased field emergence among the 11 cycles of the sh2 population resulted in a significant linear gain of 3.3% per cycle, based on cycle zero. Plant and ear height measurements demonstrated significant correlated increases, while date of flowering showed no significant change. Laboratory germination tests included three replications of 100 seeds for both the cold and warm tests performed in 2 years. The cycles of selection showed significant linear increases in germination percentages for both tests. The phenotypic correlation between field emergence and test weight entry means was highly significant [r = 0.86** (**Significant at the 0.01 level.)]. Phenotypic correlations between field emergence and test weight, and laboratory germination test performance were also significant.
Nitrogen Fixation by Soybeans: Seasonal and Cultivar Effects, and Comparison of Estimates1
Authors: Patterson T. G. , LaRue T. A.
Published: July 2010

Nitrogen fixation was estimated by acetylene reduction assays for 21 soybean [Glycine max(L)Merr.] cultivars from five maturity groups. Some cultivars were studied for 2 or 3 years. Fixation by four cultivars was also estimated by the isotope dilution method and by comparing N accumulation to that of a nonnodulating cultivar. Nitrogen fixation was related to maturity group. Late maturing cultivars fixed more N2 than early maturing cultivars. Within maturity groups there was little variation in nitrogen fixing activity. During a season when N2 fixation was low, there was little agreement among three methods of measuring fixation. When available soil N was artifically reduced by amendment with carbohydrate, N2 fixation was higher and there was good correlation among the techniques used. The acetylene reduction assay gave lower values than the other two methods.
Effect of the Brown Midrib‐Allele on Maize Silage Quality and Yield1
Authors: Miller J. E. , Geadelmann J. L. , Marten G. C.
Published: July 2010

High digestible dry matter yield is desired by maize (Zea mays L.) silage producers. The brown midrlb‐3 mutant (bm3) improves the digestibility of maize stover but reduces grain and fodder yields of homozygous bm3 genotypes. Our objective was to estimate the relative genetic potential for improvement of silage quality and yield in bm3 and normal maize populations. A total of 130 bm3 and normal 130 S1 lines were developed from three populations segregating for the bm3 allele. All 260 S1 lines were evaluated at two Minnesota locations in 1978. In 1979, 64 bm3 64 normal S1 lines, and 24 bm3 and 24 normal S1 ✕ S1 hybrids were evaluated at three locations.The bm3 genotypes averaged 77% of the grain yield, 90% of the stover yield and 84% of the fodder yield of the normal genotypes. Some bm3 genotypes produced as much stover as the best normal genotypes. However, no bm3 genotypes produced as much grain or fodder as the best normal genotypes. The normal genotypes yielded 16% more digestible dry matter than the bm3 genotypes. Estimates of genetic variability and predicted genetic gain for digestible dry matter yield were similar for bm3 and normal populations. Even though bm3 germplasm offers a substantial advantage in stover digestibility, our results indicate normal populations of maize may offer more potential for silage breeding programs.
Effect of the Brown Midrib‐3 Allele on Early Vigor and Growth Rate of Maize1
Authors: Miller J. E. , Geadelmann J. L.
Published: July 2010

The brown midrib‐3 mutant (bm3) improves the ruminant digestibility of maize (Zea mays L.) sotver, but homozygous bm3 plants are usually less vigorous than normal plants. Because early season vigor can influence final grain and stover yield, our objective was to investigate the potential for genetically improving the early vigor of bm3 genotypes relative to normal genotypes. A total of 130 bm3 and 130 normal S1 lines were developed from three populations segregating for the bm3 allele and were evaluated in three field environments in Minnesota. Average seedling dry weight of the normal lines was 10% higher than the bm3 lines, but a few bm3 lines had seedling dry weights as high as the best normal lines. Predicted gains from selection among bm3 lines were similar to normal lines of the same population. Dry matter accumulation rates of the normal lines during vegetative growth averaged 13% higher than the bm3 lines, but a few bm3 lines had rates as high as the best normal lines. Two bm3 and two normal S1 lines and their hybrids within bm3 and normal genotypes were evaluated for dry matter accumulation rate over the entire growing season. The average linear accumulation rate of total dry matter was 15% higher in the normal genotypes. The lower rate of grain filling of the bm3 genotypes was somewhat compensated for by a longer effective duration of grain filling. Our results suggest that bm3 populations could be improved to acceptable levels of early vigor and growth rate.
Growth and Yield of Soybean Lines Selected for Divergent Leaf Photosynthetic Ability1
Authors: Ford Duane Merlin , Shibles Richard , Green D. E.
Published: July 2010

One way to enhance net photosynthate production in soybean [Glycine max (L.) Merr.] may be to breed genotypes with accelerated leaf photosynthetic rates. The objective of this experiment was to determine the effects of divergent selection for 14CO2‐uptake rate per unit leaf area, total photosynthesis (TPs), on seed yield and canopy growth. Eighteen F7‐derived lines were grown in the field. These included nine lines previously selected for rapid TPs and nine selected for slow TPs. Total photosynthesis was measured during the seed filling period in 1979 and 1980. The lines were not all at the same growth stage on a given sampling date, so the average TPs rate over the 30 d period after the beginning of seed filling was calculated. This average (MTPs) equals the estimated area under the curve describing TPs as a function of time over the 30 d period, divided by 30 d. The TPs groups differed (P<0.01) in MTPs (2.51 vs. 2.29 nmol/s cm2, averaged over three locations and 2 years). TPs groups did not differ in seed yield, crop growth rate, harvest index, or the duration of seed filling. Seed yield was not correlated with MTPs among the nine lines within either group. Crop growth rate was not consistently correlated with TPs (as measured on any single date) among lines within groups. The TPs groups had similar seed yields in 1981. We concluded that selection for rapid TPs, as measured on a single light‐saturated leaflet, may not lead to greater seed or dry matter yields in soybeans.
Quality Traits in Forage Sorghum Harvested at Early Head Emergence and at Physiological Maturity1
Authors: Pedersen J. F. , Haskins F. A. , Gorz H. J.
Published: July 2010

Information about the extent of variation in quality traits among plants sampled at the same developmental stage but on different dates would be useful to forage researchers. The primary purpose of this study was to obtain such information for five forage sorghum [Sorghum bicolor (L.) Moench] cultivars. Percent dry matter, crude protein, and in vitro dry matter disappearance of leaf, stem, and whole plant samples were determined for field‐grown samples harvested on three different days during early head emergence (EHE) and once during physiological maturity (PM) for each cultivar. Orthogonal comparisons between EHE and PM sampling stages and among the EHE samples were made. Results of the 2‐year study indicated that statistically significant differences existed among EHE samples and between EHE and PM samples. However, differences among EHE samples were generally much smaller than those between EHE and PM samples and may be of little importance for some applications.
Leaf N and Photosynthesis during Reproductive Growth in Soybeans1
Authors: Boon‐Long Preeda , Egli D. B. , Leggett J. E.
Published: July 2010

The redistribution of N from the vegetative plant parts and pod walls to the seed of soybeans [Glycine max (L.) Merr.] during reproductive growth can be a major source of N for the developing seed. It has been suggested that the redistribution of N may be associated with leaf senescence. Experiments were conducted to evaluate the redistribution of N and the changes in photosynthesis in two soybean cultivars that differed in the duration of seed fill. ‘Williams’ and ‘Lincoln’ were grown in the field using conventional cultural practices for 2 years and total N, protein (1 N NaOH extractable), and CO2 uptake rate (measured with a 14CO2 technique) were determined for two leaf positions (last fully expanded and 10th node) during reproductive growth. Total N (mgdm‐2) in the last fully expanded leaves began to decline at growth stage R6 and declined steadily until leaf abscission occurred. Total N in the leaves from the 10th node began to decline sooner but the levels in the leaves at abscission were the same as in the last fully expanded leaves. The decline in protein generally followed a pattern similar to total N. The CO2 uptake rate increased to a maximum during the beginning of seed fill (growth stage R5) and started to decline early in growth stage R6. There was no difference between cultivars in the relationship between CO2 uptake rate and the levels of leaf protein. The earlier senescence of the short filling period cultivar (Lincoln) was associated with more rapid decline in CO2 uptake rate compared with Williams.
Yield Stability in Relation to Maturity in Grain Sorghum1
Authors: Saeed Mohammad , Francis C. A.
Published: July 2010

Yield stability in 54 grain sorghum [Sorghum bicolor (L.) Moench] genotypes in relation to maturity was studied in Nebraska and Kansas across 48 environments. The genotypes were categorized into early, medium, and late maturity groups based on the mean number of days from planting to physiological maturity. A stability analysis was done for each maturity group and for all genotypes ignoring groups. Simple correlation coefficients between stability parameters for yield and stability parameters for yield components were determined. Significant genotype ✕ environment and genotype ✕ environment (linear) interactions were detected for yield and seeds/m2. More than half of the variation in the linear responses of genotypes to environments was attributable to wide differences in maturity among genotypes. Stability analysis of all genotypes ignoring maturity groups showed a significant linear and quadratic relationship between days to flowering and stability parameters, regression coefficient and deviations from regression, respectively, and suggested that differences in yield stability among genotypes were largely a function of relative maturity. Separate stability analysis of genotypes in a maturity group revealed no such relationship in the early and the medium groups. Yield stable genotypes were identified in each group but proportionately fewer in the late group. A combined analysis of genotypes without grouping failed to detect this stability of individual genotypes. When genotypes under test have a wide range of maturity, we suggest a better evaluation for yield stability in groups of genotypes with minimal maturity differences. Early and medium maturing genotypes appeared to be more stable than late maturing genotypes. Stability for yield components such as seed number and seed weight should be considered when breeding for yield stability in grain sorghum.
Estimates of Genetic Parameters in Switchgrass1
Authors: Talbert L. E. , Timothy D. H. , Burns J. C. , Rawlings J. O. , Moll R. H.
Published: July 2010

A population of switchgrass, Panicum virgatum L., consisting of 33 half‐sib families was investigated over 2 years to obtain estimates of genetic parameters for several agronomic and nutritive traits, including height, maturity, dry weight, in vitro dry matter disappearance (IVDMD), and percent N. Dry weight was less heritable than other traits, with an individual narrow‐sense heritability of only 0.25. Narrow‐sense heritability for dry weight calculated on a family mean basis was 0.59. Dry weight and IVDMD were not significantly correlated while the correlation between dry weight and percent N was highly negative. Maturity was also negatively correlated with dry weight. The IVDMD and percent N, both measures of forage quality, had family narrow‐sense heritabilities averaged over three measurements per year of 0.79 and 0.74, respectively. Mean values for both traits were highest early in the season and declined markedly with maturity. The IVDMD and percent N were not significantly correlated. The estimated genetic parameters were used to form several selection indices involving three traits: dry weight, IVDMD, and percent N.
Combining Ability for Yield and Associated Characters in Rice1
Authors: Shrivastava M. N. , Seshu D. V.
Published: July 2010

Combining ability for yield and several related traits in rice (Oryza sativa L.), with a major focus on panicle characteristics, were studied in a 15 ✕ 15 diallel cross (excluding reciprocals). Eleven of the 15 parent cultivars were semidwarfs with broad resistance to various biological and physical stresses and four were traditional talls which still are popular with farmers. Variances for general combining ability (GCA) were significant for all the 16 traits studies; whereas, specific combining ability (SCA) variances were significant only for 12 of these. Specific combining ability was not important for number of spikelets per panicle and per secondary branch, effective length of primary branch, and width of grains. These traits can be utilized in developing highyielding homozygous lines. However, based on ratios obtained by comparing estimates of GCA and SCA variance components, SCA was more important than GCA for three of the characters including grain yield per plant. Heterogeneity of potence analysis confirmed that parental values do not completely predict F1 performance. Parents and cross combinations with high general and specific combining ability for various characters were identified. For grain yield per plant, the cultivars ‘CR1002’, ‘Leb Mue Nahng 111’, ‘IR42’, and ‘RPW617’ were found to be good general combiners, whereas the crosses ‘IR54’/‘PTB33’, ‘IR1060‐90’/‘RPW6‐17’ and ‘IR54’/‘LMN 111’ proved to be good specific combinations. The semidwarfing gene did not seem to limit the expression of some of the panicle traits that are important for further improvements over present yield levels of semidwarfs.