bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reciprocal Recurrent Selection in the BSSS and BSCB1 Maize Populations and Half‐Sib Selection in BSSS1
Authors: Eberhart S. A. , Debela Seme , Hallauer A. R. 
Published: July 2010

Evaluation of progress from five cycles of reciprocal recurrent selection (R) in the BSSS(R) and BSCBI(R) maize (Zea mays L.) populations indicated that the improvement in grain yield of the population cross had been linear at the rate of 2.73 q/ha (4.6%) per cycle. significant changes, however, were detected in the parents. BSSS(R) and BSCBI(R) were developed from Stiff Stalk Synthetic and Corn Borer Synthetic #1, respectively. Topcrosses of improved populations to BSBB did not yield significantly more than topcrosses of the original synthetic populations.Improvement by half‐sib selection with the Iowa 13 double‐cross tester (HT) in BSSS(HT) also had been linear at 1.65 q/ha (2.6%) per cycle. The population cross BSSS(HT)Cn ✕ BSCBI(R)Cn had been improved 2.31 q/ha (3.8%) per cycle, and BSSS(HT) had been proved 0.74 q/ha (1.4%) per cycle, where Cn is the cycle of selection.Heterosis increased from 15% in the CO ✕ CO to 37% for BSSS(R)C5 ✕ BSCBI(R)C5 and to for BSSS(HT)C7 ✕ BSCBI(R)C5. Because only 10 lines were recombined each cycle, the estimated inbreeding of the C5 populations (22%) and the C7 population (29%) probably accounted for part of the increased heterosis and lack of progress in the parental populations.The improvement in yield of the population crosses was obtained with no change in ear height or maturity, and stalk lodging was reduced. Improved population crosses compared favorably with elite single‐cross checks; therefore, BSSS(R)C5, BSSS(HT)C7, BSCBI(R)C5 should be excellent sources of additional inbred lines for developing new improved single‐cross hybrids. Two new lines, B73 and B78, have already been developed from the C5 and C6 of BSSS(HT), respectively; whereas B14 and B37 were developed from the original Stiff Stalk Synthetic.
Genetic Effects Conditioning Resistance to Earworm in Maize1
Authors: Widstrom N. W. , McMillian W. W. 
Published: July 2010

Eleven sweet and 11 dent maize, Zea mays L., inbreds were tested for the types of genetic effects which condition resistance to ear‐feeding injury by the corn earworm, Heliothis zea (Boddie). Parental, F1, F2, and backcross populations were rated to obtain generation means. Variability among means was partitioned by least squares procedures into portions attributable to additive, dominance, and epistatic genetic effects.Additive, dominance, and epistatic sources of variability among generation means were found to be significant with both the sweet and dent corn crosses tested. R2 values, indicating the proportion of variability attributable to various genetic effects, suggested a preponderance of additive effects among sweet corn crosses and dominance effects among dent corn crosses. A comparison of F1 and F2 within plot variances, and the observance of some large parental variances, indicated that earworm injury measurements of individual plants for some generations had a substantial error component. Broad‐sense heritability estimates, on an individual plant basis, of 29% were obtained for both sweet and dent groups. Increasing the general level of resistance within the two population groups tested, and particularly hi the sweet group, should be possible with any of several progeny selection regimes.
Comparison of S1 and Testcross Evaluation after Two Cycles of Recurrent Selection in Maize1
Authors: Genter C. F. 
Published: July 2010

Two populations of maize (Zea mays L.), Virginia Corn Belt‐Southern Synthetic (VCBS) which was developed from a broad genetic base, and Virginia Long Ear Synthetic (VLE) which was developed from intercrosses of seven Corn Belt inbred lines, were advanced two cycles of recurrent selection based on S1 and testcross progeny yield. The 10 populations and their diallel crosses were grown at 3 locations with 6 replications at each location. Significant improvement in population yield and combining ability was achieved only with VCBS.S1 selection in VCBS was more effective than testcross selection in increasing both population yield and combining ability. Testcross selection was effective in increasing the frequency of genes that contribute to yield in crosses but not in populations per se whereas S1 selection increased both combining ability and population yield. The yield of the second‐cycle S1 selection population yielded 9.0 q/ha (11%) more than the second‐cycle testcross population and its mean population cross yield was 1.5 q/ha higher. The two populations derived from VCBS by S1 selection produced significantly higher yields when intercrossed or crossed with VCBS than either population derived by testcross selection. S1 selection in VCBS was as effective as testcross selection in increasing the frequencies of genes that contribute to yield, whether in inbred (derived) or hybrid populations.
Effects of Maize Dwarf Mosaic Virus on Mechanically Inoculated Maize1
Authors: Genter C. F. , Roane C. W. , Tolin S. A. 
Published: July 2010

Effects of maize dwarf mosaic virus (MDMV) on maize (Zea mays L.) were determined by growing selected inbred lines with diallel crosses among them in an area free of johnsongrass (Sorghum halepense L.). Mechanical inoculation with MDMV produced significant effects on grain yield and several other plant traits but the differences were small compared to those observed under natural infection. Two inbred lines, T8 and VaLE8, did not react the same under conditions of natural and mechanical inoculation. Inoculated plants had more gray leaf spot, caused by Cercospora zeae‐maydis (Tehon and Daniels), than uninoculated plants. In paired‐row plots, maximum reduction was 34% for yield and 14% for plant height. Significant mean effects ou yield and moisture content of grain and days to silk were related to time of inoculation. One inbred line, H84, showed severe symptoms when inoculated 10 days after planting but showed mild symptoms when inoculated later. No cross that included Oh07B was measurably affected by MDMV. The most productive hybrid was Oh07B ✕ Oh43, a cross between a very resistant and a very susceptible inbred line. Resistance was dominant in Oh07B, but the intermediate resistance of T8 and VaLE8 was recessive to susceptibility in Oh43 and Pa9l.Stunting, leaf discoloration, barrenness, and severe loss of yield were not induced by mechanical inoculation and subsequent infection with MDMV. We concluded that MDMV is only a moderately destructive virus of maize; therefore, other agents must be contributing to the severely damaging syndrome in maize‐johnsongrass associations.
Seasonal Patterns of Nitrate Reductase Activity and Nitrate Concentration of Two Alfalfa (Medicago sativa L.) Cultivars1
Authors: Eskew D. L. , Schrader L. E. , Bingham E. T. 
Published: July 2010

Studies were undertaken to establish seasonal patterns of nitrate reductase (E. C. 1.6.6.1) activity (NRA) and nitrate concentration in ‘Vernal’ and ‘Saranac’ alfalfa (Medicago sativa L.). A secondary study was conducted to determine the effects of N‐fertilization upon NRA and nitrate concentrations in herbage tissues.In leaflets, NRA and nitrate concentration were high at young vegetative growth stages and declined with maturity during all growth periods, both during year of establishment (1971) and second year of the stand (1972). Nitrate concentrations and NRA were highly correlated over the entire 1972 season (r = 0.80**). Leaflets from the shoot apex were higher in NRA than leaflets lower on the shoots, but nitrate concentrations were similar in both fractions. Stems exhibited low NRA at all sampling dates. Fertilization with 112 kg/ha of N as ammonium nitrate after the second cutting in 1972 increased nitrate concentration in all shoot parts and increased NRA in all leaflet fractions.
Karyology and Phylogenetic Relationships of Phleum pratense, P. commutatum, and P. bertolonii1
Authors: Wilton A. C. , Klebesadel L. J. 
Published: July 2010

Two polyploid and one diploid timothy species are found in North America: Phleum pratense L. (2n = 42), P. alpinum var. commutatum (Gaud.) Koch (2n = 28), and P. bertolonii DC. (2n = 14). Karyotypes and photomicrographs of P. pratense and P. commutatum Gaud. and a photomicrograph of P. bertolonii are presented.Chromosome arm‐length measurements, arm‐length ratios, and other detailed observations showed that P. pratense has three pairs of short acrocentric chromosomes, three pairs of long submetacentric chromosomes, and three pairs of equisized chromosomes with satellites. P. commutatum has two pairs of small acrocentric chromosomes, and one pair of long metacentrics, a slightly shorter pair of submetacentrics, and a pair of satellited chromosomes. This and other data obtained from photomicrographs of cells of commutatum plants from Alaska and Wyoming suggest that P. commutatum has one genome in common with P. pratense. All indications are that P. pratense is an autohexaploid, and P. commutatum is an allotetraploid. The P. bertolonii genome is karyotypically similar to the P. pratense genome.
Breeding Procedures for Panicum maximum Jacq. Suggested by Plant Variability and Mode of Reproduction1
Authors: Burton Glenn W. , Millot Juan C. , Monson Warren G. 
Published: July 2010

In 1970, spaced plants of 158 accessions of guineagrass (Panicum maximum Jacq.), supplied by the USDA Regional Plant Introduction Station, Experiment, Ga., were studied in detail at Tifton, Ga. Great variation was observed in all 12 characters studied. Plant height ranged from 53 to 248 cm and single green plant weight ranged from 0.09 to 6.13 kg. The in vitro dry matter digestibility (IVDMD) of complete culms at the early‐full‐head stage ranged from 41 to 72%. Most accessions set seed well when selfed under bag. Only 1.3% of the spaced plants survived the 1970‐71 winter (–8 C minimum), but 80% of the plants of PI 284764 from the Union of South Africa survived. A study of spaced‐plant progenies from 295 plants in the 1970 planting revealed that 87.8% were highly apomictic (showed no segregation). Facultative apomixis was present in 11.6% of the progenies. These carried 5 to 20% of offtype plants.Two sexual plants, discovered in facultative apomictic introductions PI 277946 and 277922, gave fertile hybrids when crossed with giant short‐day types. Seed shattering was heavy and similar in some 6,000 plants studied. Suggested breeding procedures include screening extensive ecotype collections from Africa and recombining in one or more genotypes (fixed by apomixis) the desirable genes currently available. Suggested procedures for obtaining genes for shatter resistance include mutation breeding, screening selfed progenies of sexual plants and advanced generations of sexual ✕ apomictic hybrids that may release shatter resistance genes hidden in the germplasm, and transferring shatter resistance from other Panicum species by interspecific hybridization.
Estimation of Variability of Quantitative Traits in BSSS by Using Unselected Maize Inbred Lines1
Authors: Obilana A. Tunde , Hallauer Arnel R. 
Published: July 2010

We evaluated 247 S6 unselected maize (Zea mays L.) lines, developed by single‐seed descent from 250 ‘BSSS’ S0 plants, for 21 quantitatively inherited traits in 3 environments. The S6 lines were considered representative of a random group of genotypes from BSSS for the estimation of genetic variances, heritabilities, and correlations among traits.Significant genetic variation existed among the S6 lines for all traits. The estimates of heritabilities, on a mean basis, were high for most traits, indicating that selection would be effective in the desired direction for any of the traits measured. The estimates of the S6 line components of variance, which were about equal to twice the additive genetic variance of the base population, were significant for all traits. After adjustments for inbreeding were made, the estimates of the genetic components obtained by use of S6 lines were very similar to those obtained by using noninbred progenies for seven comparable traits.The genotypic and phenotypic correlations between yield and plant and tassel traits were either very small or zero. The correlations between the ear components and yield generally were higher, with kernel depth having the highest genetic correlation with yield (rG = 0.76). The only plant and tassel traits that showed a relatively high correlation were plant height with ear height (rG = 0.79) and tassel height with tassel‐branch length (rG = 0.55). The genetic correlations among the ear traits ranged from 0.33 to 0.81 and among the root traits from −0.68 to 0.61.
Growth and Seed Production of Nordan Crested Wheatgrass in a Modified Corn Wheel1
Authors: Keller Wesley , Bleak Alvin T. 
Published: July 2010

Studies were conducted with ‘Nordan’ crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult.) for 3 years to determine effects of competition on seed yield, seed size, and plant growth in a corn wheel modified to vary space per plant. Six mature plants were cloned, and these were grown, without irrigation, in two replications in the corn wheel. Five ramets of a single clone were spaced on a logarithmic scale in each pieshaped segment of the wheel at positions from the center of 1.1 m (severe competition) to 5.7 m (little competition).After 3 years, there was a significant interaction for height between clones and degree of competition. The degree of competition had considerably more effect on plant circumference than on height. Significant differences occurred among clones in the mean number of spikes produced, and in the third year the differences in number of spikes by degree of competition was also significant within clones. The six clones differed greatly in total seed yield, and the clone by degree‐of‐competition interaction was significant each year. The six clones differed significantly in weight/100 seeds, which, within each clone, was significantly reduced as competition increased.The corn wheel pattern is suitable for studying the effects of competition on perennial grasses.
Seasonal Patterns and Genotypic Differences in Glucose‐6‐Phosphate Dehydrogenase Activity in a Diallel Cross of Corn1
Authors: Schrader L. E. 
Published: July 2010

Glucose‐6‐phosphate dehydrogenase (G6PD) (E.C. 1.1.1.49) activity was assayed in a four‐parent dlallel cross of corn (Zea mays L.) to determine the level of activity at various stages of development (seasonal patterns) and to look for differences in G6PD activity among inbreds and the F1 progenies. The enzyme was extracted from leaf blades of field‐grown corn every week in 1972 from 2 weeks after seedling emergence until 7 weeks after silking. In 1973, the enzyme was extracted and assayed at 2‐week intervals between 8 and 14 weeks after emergence.Seasonal patterns revealed that G6PD activity in leaves was relatively low in all genotypes during the first 7 weeks after seedling emergence, but activity increased sharply between 7 and 10 weeks in those genotypes with high levels of activity. Activity remained high until 12 weeks after emergence and then decreased rapidly.When seasonal means for G6PD activity were compared, twofold differences in inbreds were observed. Significant genotypic differences were noted for G6PD activity both years at every sampling except at 5 weeks after emergence in 1972. In 1973, all 12 F1 progenies were compared, but no significant reciprocal effects were found. General combining ability for G6PD activity was significant, indicating that the level of G6PD activity in inbreds was reflected in the F1 progenies. Based on general combining ability in 1973 and the close relationship between midparent means and F1 progenies in 1972, assaying G6PD activity in corn inbreds should be adequate to predict the levels of activity in F1 progenies.
Cross‐Pollination of Awned and Awnleted Isogenic Lines of Soft Red Winter Wheat1
Authors: Barnett R. D. , Patterson F. L. 
Published: July 2010

Five pairs of lines of soft red winter wheat (Triticum aestivum L. em Thell.) nearly isogenic except for awns vs awnlets were compared to determine which type would serve as the best pollinator or best female in a hybrid seed production field. Pollen dispersal was measured in the field by pollen collected with adhesive coated slides mounted on wind vanes and by percent seed set on male‐sterile lines. Although the differences were small, awnleted pollinators produced greater pollen loads than the awned, 142 vs 121 pollen grains/10 mm2 in 1968 and 154 vs 120 in 1969; percent seed set from the two pollinator types was not significantly different, 42 vs 40 and 66 vs 63 in the two respective years.Pollen dispersal of awnleted and awned types was also studied in the laboratory by using individual excised spikes placed over pollen traps. Significantly more pollen was collected from the awnleted lines. The 55.2% anther extrusion for the awnleted lines was not significantly greater than the 52.6% for the awned lines. The correlation of percent anther extrusion with number of pollen grains collected gave a coefficient of 0.74 which with 248 degrees of freedom was highly significant.Male‐sterile lines which were segregating for awns vs awnlets were studied to determine which type would serve as the best female. The awned male‐steriles gave 4% higher seed sets.In all phases of this study the differences between the isogenic lines were small or nonsignificant. There seemed to be a tendency for the awnleted type to be the best pollinator and the awned type to be the best female. Cross‐pollination potential is likely to be affected more by other morphological features.
Induced Early‐Maturing Mutation in Sorghum1
Authors: Singh Shree P. , Drolsom P. N. 
Published: July 2010

An early‐maturing Sorghum bicolor (L.) Moench mutant (1030) induced by diethylsulfate is described. The mutant flowered 3 weeks earlier than the parental cultivar, ‘Rox Orange.’ Culm height was reduced by 116 cm. There was a 48% reduction in number of nodes and a 35% reduction in internode length. Segregation data from six crosses suggested that a single gene controllig flowering had mutated from dominant to recessive.Variable magnitudes of additive and dominance ef. fects, and degree of dominance were recorded for days to flower, number of nodes, internode length, and culm height for different crosses. All parental lines and hybrid populations flowered later than the early‐maturing mutant and consequently had a higher number of nodes.
Effect of Plant Age and Inoculum Concentration on Leaf Freckles and Wilt of Corn1
Authors: Calub A. G. , Schuster M. L. , Gardner C. O. , Compton W. A. 
Published: July 2010

The effect of plant age and inoculum concentration on disease reactions in corn (Zea mays L.) was determined following inoculation with Corynebacterium nebraskense Schuster, Hoff, Mandel, and Lazar, the causal organism of the leaf freckles and walt of corn.Resistant and susceptible corn materials were simultaneously inoculated at four different age groups and at four inoculum concentrations for each group. Plant age or maturity played a vital role in differentiating resistant from susceptible lines when the syringe injection technique was used. Susceptible materials were not greatly influenced by plant age. On resistant lines, however, the disease ratings were strongly influenced by plant age. In resistant materials, infection decreased with increased plant maturity, but with the susceptible genotype the greatest infection occurred in plants inoculated at tasseling.Inoculum concentration was a critical factor only in young plants. However, optimum concentration was difficult to define because the results were variable. In tasseling plants, higher concentrations were tolerated without affecting disease reaction.
Growing Degree Days to Black Layer Compared to Minnesota Relative Maturity Rating of Corn Hybrids1
Authors: Sutton Lonnie M. , Stucker R. E. 
Published: July 2010

We evaluated 28 commercial corn (Zea mays L.) hybrids at 2 dates of planting and 24 check hybrids used as standards for establishing Minnesota Relative Maturity (Minnesota RM) at 1 date of planting to determine growing degree days (GDD) to black layer for each hybrid. The hybrids were grown at four locations in Minnesota in 1970 and 1971. Date of 50% black layer formation and percent grain moisture on this date were determined. Growing degree days from planting to black layer were calculated for each plot using the National Oceanic and Atmospheric Administration formula.Hybrids, locations, years, and dates of planting were highly significant sources of variation for GDD from planting to black layer. Hybrid ✕ location and hybrid ✕ year interactions were nonsignificant for growing degree days to black layer and the hybrid ✕ location ✕ year interaction was considered to be negligible in size even though it was statistically significant. The variance for GDD among hybrids within Minnesota RM groups of the check hybrids was highly significant but considerably less than the variance among the maturity groups.The correspondence between growing degree days to black layer and Minnesota RM rating was good on the average for both the commercial and check hybrids, but in a number of instances, hybrids that differed by 10 or more relative maturity units had similar growing degree day ratings. In our opinion, these data cast serious doubt on the usefulness of the GDD to black layer system of rating hybrids for maturity in Minnesota.At black layer, moisture percentage values ranged from 22.6 to 32.9%. The use of GDD from planting to 30% moisture content would tend to increase the range in GDD for the hybrids included in this study.
Gross Morphology and Starch Accumulation in Leaves of Alfalfa Plants Grown at High and Low Temperatures1
Authors: Smith Dale , Struckmeyer B. Esther 
Published: July 2010

Studies have shown that leaves of alfalfa (Medicago sativa L.) plants grown at cool temperatures accumulate more starch than those grown at warm temperatures. The present study was initiated to observe more closely the influence of temperature on leaf development. Plants were grown to first flower at 21/12, 32/24, and 30/30 C day/night temperatures. Leaflet anatomy, and concentration and location of starch grains were observed in fully‐expanded, upper leaves, and measurements of leaf area, dry weight, and carbohydrate composition were made.Upper leaves grown at 21/12C were heavier and larger and had a greater specific leaf weight than those grown at 92/24 or 30/30 C. Leaves grown at 21/12 C contained high amounts of starch at first flower; 40.3% as compared with 6A% at 32/24 C and 12.9% at 30/30 C. Starch grains were confined to chloroplasts. Chloroplasts were distinct in the high‐temperature leaflets, but they could not be identified readily in cool‐temperature leaflets because of the high starch accumulation. Palisade cells were more compact at cool temperatures than at warm temperatures.