bluuebunny/crossref_metadata_2025 huggingface dataset:
A Root Tip Squash Technique for Soybean Chromosomes1
Authors: Palmer R. G. , Heer Hollys
Published: July 2010

A procedure is described for consistently obtaining adequatenumbers of well‐spread metaphase cells from soybean [Glycine max (L.) Merr.] root tips. The salient features are: (i) seeds germinated at alternating temperatures of 30 C for 18 hours and 22 C for 6 hours until roots are 7 to 10 cm long; ii) pretreatment of root tips in saturated paradichlorobenzene at 15 C for 1½ to 2 hours; and iii) fixation in 3:1 for 48 hours at 37 C before hydrolysis and staining in leuco‐basic fuchsin. Tips were incubated in pectinase for 1½ hours at 30 C, and the cells were flattened with a pellet press.
Correlations Between Kernel Plumpness, Lodging, and Other Agronomic Characteristics in Six‐Rowed Barley Crosses1
Authors: Nasr H. G. , Shands H. L. , Forsberg R. A.
Published: July 2010

Phenotypic (rP) and genotypic (rG) correlation coefficients between pairs of several important agronomic characteristics, including kernel plumpness, test weight, lodging resistance, and grain yield, were calculated for 19 populations of seven six‐rowed barley (Hordeum vulgare L.) crosses. Parents used were wide‐kerneled ‘Larker’ and ‘X969‐3,’ medium‐kerneled ‘Dickson’ and ‘X1068.1,’ and thin‐kerneled ‘Fraeg’ and ‘J2458‐1.’ The latter two are short and comparatively stiff‐strawed.

Of 72 significant rP values obtained, 48 values occurred among the six possible character pairs between the four traits listed above. All 48 represented agronomically desirable associations and were equally divided between generations of single and backcrosses. Thus, selection for any one of these desirable characters would be compatible with concurrent selection for the other three. The rG value equalled or exceeded the rP value for 59 of the 72 significant rP values, strengthening the genetic or breeding implications.

The strongest association among six plant and grain characters was between kernel plumpness and test weight. There was a definite trend for taller plants to perform better agronomically.
Changes in Carbohydrate Contents of Germinating Soybean Seeds1
Authors: Hsu S. H. , Hadley H. H. , Hymowitz T.
Published: July 2010

Changes in dry weights, total soluble carbohydrates, and individual sugars in the cotyledons and embryo axes of soybean (Glycine max (L.) Merrill) seeds from a relatively high oil variety, ‘Hawkeye’ (22%), and a low oil line, P.I. 86002 (16%), were determined over a 13‐day germination period. Total dry weights of cotyledons decreased while those of embryo axes increased as the seed germinated. Total soluble carbohydrates accounted for 15% of the total dry weights in cotyledons of ungerminated seeds and decreased more rapidly throughout the germination period than did cotyledon weights. Total soluble carbohydrates of the embryo axes increased steadily during the first 5 days and declined thereafter. Similar patterns of utilization of soluble carbohydrates were observed for Hawkeye and P.I. 86002 even though their cotyledons differed 6% in oil content.

Stachyose, raffinose, and particularly sucrose were the dominant sugars found in ungerminated soybean seeds. Stachyose and raffinose declined rapidly in the cotyledons by day 3 and disappeared by day 9 of germination. Sucrose increased slightly during the first 3 days but decreased steadily after the third day. Fructose and glucose appeared in day‐1 cotyledons, with the former reaching a maximum value on the fifth day and the latter on the ninth. Stachyose, raffinose, and sucrose were also the major sugars found in the 0‐day embryo axes. Stachyose and raffinose were depleted completely by day 3 in the embryo axes of P.I. 86002 and by day 5 in Hawkeye. Sucrose decreased between day 5 and day 13 for P.I. 86002 but showed irregular change in Hawkeye during this period. Fructose and glucose appeared in day‐1 embryo axes, continued to increase through day‐5 of germination, and decreased thereafter.
A Study of Reciprocal Hybrids Between Upland Cotton (Gossypium hirsutum L.) and Experimental Lines with Cytoplasms from Seven Other Species1
Authors: Meyer Vesta G.
Published: July 2010

Genetically or cytoplasmically uniform crops may be vulnerable to disastrous pest infestations. Upland cotton (Gossypium hirsutum L.) cytoplasm is present in most of the cotton cultivars grown commercially in the U.S. However, experimental breeding material has been developed from Upland cotton hybrids with cytoplasms from seven other species of Gossypium. The most uniform and productive progenies within each of these seven cytoplasms were selected for making reciprocal backcrosses to Upland cotton cultivars. Backcrosses with cytoplasm from two tetraploid species (G. barbadense L. and C. tomentosum Nutt.) showed no significant differences from their reciprocal hybrids with Upland cytoplasm, but similar backcrosses with cytoplasm from each of the five diploid species (G. herbaceum L., G. arboreum L., G. anomalum Wawra & Peyr., G. harknessii Brandagee, and G. longicalyx Hutchinson and Lee) differed significantly from their reciprocal hybrids.
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 Trifoliolate and Multifoliolate Phenotypes of Alfalfa (Medicago sativa L.)1
Authors: Ferguson J. E. , Murphy R. P.
Published: July 2010

Twenty‐one multifoliolate alfalfa (Medicago sativa L.) entries were compared with four trifoliolate cultivars for six morphological and growth characters 'at two field locations under spaced plant conditions. All studies were made on the second hay crop during the year after establishment. Numerical counts established a mean value for leaflets per leaf of 4.7 ± 0.05 for the entire multifoliolate population. The percentage leaf was 2% higher at location 1 and 5% higher at location 2 for the multifoliolate population over the trifoliolate cultivars. The percent of plants with multifoliolate leaves in the multifoliolate entries was 99. The percent of leaves per plant that were multifoliolate varied from 55 to 83 among the multifoliolate entries. Within the multifoliolate population, leaflets per leaf and leafiness was positively correlated. Negative correlations between plant weight and plant height with percentage leaf were of a similar magnitude for multifoliolate plants as for trifoliolate ones.
Inbred and Hybrid Effects on Establishment of in Vitro Cultures of Zea Mays L. Endosperm1
Authors: Shannon J. C. , Batey J. W.
Published: July 2010

Zea mays L. endosperm explants from 23 starchy inbred and hybrid lines and several endosperm mutants were tested for their ability to grow in vitro. Explants from two starchy inbreds, two hybrids, and the mutants amylose‐extender, sugary‐1, and shrunken‐2 grew actively and have been maintained in culture for over 2 years. Other lines produced limited growth or no growth following the first transfer. These data demonstrate the importance of testing several different inbreds or hybrids when attempting to establish in vitro cultures of corn endosperm.
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.
Natural Crossing in Cotton (Gossypium hirsutum L.) in the Delta of Mississippi1
Authors: Meredith William R. , Bridge R. R.
Published: July 2010

The glandless trait was used to study the amount of natural crossing in cotton (Gossypium hirsutum L.) in the Delta of Mississippi. We sampled 102 hills of glandless cotton planted in fields of glanded cotton at 11 locations in 1972. Natural crossing varied from. 0.0 to 5.9% and averaged 2.0%. There was only 0.2% natural crossing in the five Central Delta locations. These results indicate that in the Central Delta of Mississippi, cotton is essentially a self‐pollinated crop.
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.
Effect of Daylength Response on Agronomic and Quality Performance of Durum Wheat1
Authors: Lebsock K. L. , Joppa L. R. , Walsh D. E.
Published: July 2010

Durum wheat (Triticum durum Desf.) varieties grown in the United States are not adapted to the short‐day conditions of the middle latitudes (between 28°N and 28°S). Introduction of a gene or genes for daylength insensitivity could broaden the adaptability of these varieties, but the effects of insensitivity on agronomic and quality performance in northern latitudes are not well known. Fifty‐two F3 durum wheat bulks homozygous sensitive to daylength and 52 bulks homozygous insensitive to daylength were selected from 4 crosses between northern varieties and a daylength‐insensitive selection (‘Zenati’/‘Bouteille’) introduced from Israel. These 104 F3 bulks were compared for agronomic and quality performance in North Dakota in 1967 and 1968. Ten pairs of lines, near isogenic except for daylength response, were developed from three of the four crosses by selecting heterozygous plants from F3 through F6. The F6 pairs were compared in a split‐plot arrangement in four environments. Insensitive lines tended to be significantly earlier (1 to 3 days) and shorter (3 cm) than the sensitive lines. Genotype ✕ environment interactions were significant for yield. The insensitive near‐isogenic F6 lines yielded slightly more grain than the sensitive lines in two environments, five of the senstive lines yielded as much as 20 to 40% more grain than the insensitive lines in one environment, and the two response types yielded essentially alike in one environment. We conclude that durum wheats for the North Central States can be converted to the insensitive condition without loss in productivity or quality. Insensitive lines must be thoroughly tested over a wide range of temperature and daylength conditions to assure that only the most stable ones are released for commercial production.
Reaction of Germinating Maize Pollen to Helminthosporium maydis Pathotoxins1
Authors: Laughnan J. R. , Gabay S. J.
Published: July 2010

Pollen from fertile plants of corn (Zea mays L.), with normal and restored male‐sterile cytoplasm (cms), from various sources was assayed for in vitro germination on media containing Helminthosporium maydis pathotoxins extracted from infected leaves. The “pathotoxin” from H. maydis race O inhibited neither germination nor growth of pollen from any of the cms or normal cytoplasm sources tested, as compared with controls. The pathotoxin from H. maydis race T, however, inhibited in vitro germination and growth of pollen from cms‐T and cms‐P plants. Growth of pollen from cms‐C, cms‐S and normal cytoplasm sources was not inhibited by race T pathotoxin. The advantages of a pollen bioassay are discussed, as are possible special applications of this procedure.
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.
Gene Expression in Haploid and Hybrid Progeny from Crosses Between Hordeum vulgare and H. bulbosum1
Authors: Subrahmanyam N. C. , Kasha K. J.
Published: July 2010

Gene expression was examined in haploid and hybrid progeny resulting from interspecific crosses of diploid Hordeum vulgare L. genetic marker stocks with diploid and tetraploid forms of H. bulbosum L. The expression of marker genes on all vulgare chromosomes occurred in the haploid progeny, an observation consistent with the concept that the haploids contain only vulgare chromosomes and that bulbosum chromosomes are selectively eliminated. However, the recessive genes of H. vulgare were masked in diploid and triploid hybrids by H. bulbosum genes, which is indicative of the occurrence of interallelic interactions and genome homology between the species. Gene interaction and expression in interspecific and intergeneric hybrids in relation to alien gene or chromosome transfers is discussed.
Contributions of the Capsule Wall and Bracts to the Developing Cotton Fruit1
Authors: Elmore C. D.
Published: July 2010

Simultaneous exposure of sympodial leaf and fruit of cotton (Gossypium hirsutum L.) to 14CO2 revealed that the bracts were 28% as efficient as leaves for CO2 uptake on a unit‐weight basis, or 20% on an area basis, while the capsule wall was less than 1% as effective as the leaf. Subsequent translocation to the fruit was much more rapid from the leaf than from the bracts. The capsule wall, on the other hand, served as a sink for photosynthate accumulation. Stomatal density was not limiting the uptake capacity of the bracts, since there were more stomata on the outside surface of the bracts (11,325/cm2) than on the lower surface of the leaf (7,187/cm,2). Chlorophyll concentration was three times greater in the leaf than in the bract (2.28 mg, g fresh weight‐1 compared to 0.83). Similarly, the comparatively low rate of CO2 fixation by the capsule wall was not explained by the stomatal frequency on the capsule wall (4407/cm2).
Inheritance of a Yellow‐Leaf Mutant and a Pollen Fertility Restorer in Sugarbeet1
Authors: Roundy T. E. , Theurer J. C.
Published: July 2010

A yellow‐leaf character in sugarbeet (Beta vulgaris L.) was conditioned by a single recessive gene. A genetic pollen fertility restorer in CMS plants, observed in the yellow‐leaf material, was found to be inherited as a single dominant gene. Linkage tests showed that yellowleaf (yl) was independent of monogerm (m), annual growth habit (B), and the restorer gene (Rf3).
Seed Production of Several Strains and Hybrids of Bermudagrass, Cynodon dactylon (L.) Pers.1
Authors: Ahring R. M. , Taliaferro C. M. , Morrison R. D.
Published: July 2010

Seed production of eight strains of bermudagrass (Cynodon dactylon (L.) Pers.) was evaluated along with seven F1 hybrids. All hybrids had a common maternal strain. Seed yields of strains fell into three general groups: low, medium, and high. Yields of hybrids in the low group were greater than those of their male parents. However, both hybrid and paternal strain seed yields from this group were significantly lower than yields of the maternal strain. Hybrids involving three strains, 10978‐b, 9945‐a, and 9959, produced more seed than other hybrids. With the exception of the hybrid involving 9945‐a in 1972, seed yields produced by any one hybrid were never greater than the better parent. Average yield of pure seed for ‘Guymon,’ (an Oklahoma “common,” the maternal parent in all hybrids) was 892 and' 412 kg/ha in 1971 and 1972, respectively. Paternal strains 10978‐b and 9959 produced significantly more seed both years of the study than did Guymon. Direct evidence for percent seed set and indirect evidence for number of seed stalks produced suggests these two factors as being the major components determining seed yields. Compatible cross pollination, a high percentage of self‐fertilization, and favorable environmental conditions appear to be major factors influencing maximum seed set. Regulation of vegetative growth and moisture appears to be the important management area for seed production in the species.
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.
Olfactory Screening of Alfalfa Clones for Uniform Honey Bee Selection1
Authors: Loper G. M. , Waller Gordon D. , Berdel Richard L.
Published: July 2010

An olfactory bioassay procedure is described, and results from testing 28 alfalfa (Medicago sativa L.) clones for honey bee (Apis mellifera L.) olfactory compatibility are reported. Honey bee selection appeared to be based on quantity and quality of flower volatiles. When the honey bees were conditioned to one clone (“normal” alfalfa flower volatiles), bee selection indicated that alfalfa clones could be classified into three categories: compatible, neutral, and incompatible. The difference between compatible and neutral seemed to be based on lower quantities of volatiles produced by the neutral group; however, the one incompatible clone was discriminated against on the basis of olfactory quality. This bioassay procedure could be used as a tool for alfalfa breeders to select parent clones that are olfactorily compatible.
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.
Soil and Symbiotic Nitrogen Requirements for Optimum Soybean Production1
Authors: Harper J. E.
Published: July 2010

Field and outdoor hydroponic studies were conducted to determine the relative potential of soybeans (Glycine max L. Merr.) to utilize nitrate and atmospheric nitrogen as sources of nitrogen. Comparisons of nodulating and nonnodulating isollnes coupled with enzymatic assays of nitrate reductase (in vivo) and nitrogenase (in situ acetylene reduction) were used as indexes. Seasonal profiles indicate maximunmit rate utilization at the full‐bloom growth stage, with symbiotic N2(C2H2) fixation peaking some 3 weeks later during pod fill. Nitrogen fixation estimates based on comparison of nodulating and nonnodulating isolines are not valid under growth conditions of low nitrate levels because growth of the nonnodulated isoline is stunted and nitrate utilization is also impaired. Seed yield of plants totally dependent on atmospheric nitrogen was less than one‐half the yield of plants utilizing both nitrate and atmospheric nitrogen under hydroponic growth conditions. Plants grown on a low nitrate level had higher symbiotic N2(C2H2) fixation rates than those grown on no nitrate. Similarly, seed yield of plants grown in hydroponics on high nitrate levels, which inhibited symbiotic fixation, was less than yield of plants utilizing both nitrate and atmospheric nitrogen. Thus, both symbiotic N2 fixation and nitrate utilization appearede ssential for maximum yield.
Inheritance of a Second Major Gene for Resistance to Phytophthora Rot in Soybeans1
Authors: Kilen T. C. , Hartwig E. E. , Keeling B. L.
Published: July 2010

The inheritance of another gene for resistance to Phytophthora megasperma Drechs. var. sojae Hildeb. in soybeans [Glycine max (L.) Merr.] was studied. This dominant gene, proposed as Rps2, is found in the cultivars ‘CNS’ and derived strains. The results obtained indicated that Rps2 is at a locus different from the Rps, rps2, rps locus. It is suggested that the first locus should now be changed from Rps, rps2, rps to Rps1, rps12, rps1 to distinguish it from the second locus, Rps2 rps2, Rps2 has given a high level of resistance to phytophthora rot in repeated field plantings under conditions favorable for development of the disease. Screening for Rps2 is easily accomplished by growing plants in a liquid culture medium with the pathogen.
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.
Morphological and Physiological Traits in Maize Associated with Tolerance to High Plant Density1
Authors: Buren L. L. , Mock J. J. , Anderson I. C.
Published: July 2010

Maize (Zea mays L.) hybrids were grown at a high plant density (98,800 plants/ha) to determine the influence of several morphological and physiological traits on barrenness, the major factor limiting grain yields at high stand densities. Correlation and multiple regression analyses indicated density‐tolerant maize genotypes would be characterized by rapid completion of silk extrusion, coincidence of pollen‐shed and silk extrusion, rapid growth of the fust ear and first‐ear silk, prolificacy, reduced tassel size, and efficient production of grain per unit leaf area. Breeding populations composed of these “plant types” should allow isolation and development of high‐yielding and density‐tolerant maize genotypes.
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.
Influence of Plant Growth Habit on Peanut Production in Narrow Rows1
Authors: Norden A. J. , Lipscomb R. W.
Published: July 2010

Two peanut (Arachis hypogaea L.) lines, one with bunch growth habit and one runner, were derived from each of two crosses (genetic backgrounds). The four lines were tested at two row spacings [91 cm (conventional) and 46 cm] for 3 years to study relationships between growth habit and seed production with a minimum of confounding by genetic background. While yields of both bunch and runner lines were increased by close rows (16 and 5%, respectively), the increase for the runner lines was not statistically significant. Yield increases from close rows were highest in the more favorable seasons and by the line with the smallest plants. Significant interactions indicated that seasonal variations impose greater problems in isolating superior‐yielding genotypes than the effects resulting from differences in plant growth habit or row spacings. Season and genetic background also had significant effects on seed weight, shelling percent, and percent shriveled seed, whereas row spacing and growth habit had comparatively little effect on these factors. A highly significant genetic background ✕ growth habit interaction was also obtained. Yield was influenced more by genetic background than by growth habit. In one background the bunch line was equal in yield to the runner line, while in the other background the runner line was significantly higher yielding. No significant interactions occurred between row spacing and genetic background for any of the measured characteristics, indicating that superior genotypes selected in normally spaced rows should also be superior in close rows.
Photosynthetic and Respiratory CO2 Exchange of Sugar Beet Leaves as Influenced by Manganese Deficiency1
Authors: Terry Norman , Ulrich Albert
Published: July 2010

Photosynthetic and respiratory CO2 exchange rates were determined for attached leaves of manganese‐deficient or ‐sufficient sugar beets (Beta vulgaris L. cv. ‘F58‐554H1’) cultured hydroponkally in a growth chamber. On withholding Mn from the culture solution, the Mn concentration of the leaf blades decreased from 8 to 10 to about 0.3 meq Mn2+ kg‐1 dry matter and rates of photosynthetic CO2 uptake per unit leaf area decreased to about onethird of the control rates. There was no apparent effect of Mn deficiency on stomatal opening since leaf diffusion resistance (r1’) was unchanged, but mesophyll resistance to CO2 transfer (rm) increased from 2.5 to 10 sec cm‐1 in low Mn leaves. Manganese deficiency decreased rates of photorespiratory evolution of CO2 into CO2‐free air but had no effect on respiration in the dark.
Analysis of the Exponential Growth Equation1
Authors: McKinion James M. , Hesketh J. D. , Baker D. N.
Published: July 2010

Solutions for growth equations that estimate dry matter from photosynthetic, respiratory, and photosynthetic area variables were tested by using field data for cotton (G. hirsutum L. var. ‘Deltapine Smoothleaf’). The equations based on assumptions of exponential leaf area expansion and exponential extraction of light by leaves fitted the data test. A leaf area expansion function that depends upon morphogenetic variables should improve the fit.
Genetic Variability for Net Photosynthesis in Tall Fescue1
Authors: Asay K. H. , Nelson C. J. , Horst G. L.
Published: July 2010

Significant differences in net carbon exchange (NCE) were detected among tall fescue (Festuca arundinacea Schreb.) clonal lines and among their polycross progenies under sward conditions in the field. On dates when differences among parental lines were significant, heritability values ranged from 0.57 to 0.83 in the broad sense, and from 0.22 to 0.44 in the narrow sense. In those instances, expected genetic advance with selection of the upper 5% of the population ranged from 0.77 to 3.13 mg CO2 dm∗2 hr∗1. Genetic variation was from four to six times greater among the parental lines than their polycross progenies. Rates of NCE were significantly increased by irrigation during periods of drought stress. The magnitude of the genetic variability was also greater under more favorable moisture conditions; however, relative differences among genotypes were not consistent under the two moisture regimes. It appears that genetic progress can be made through selection for NCE rate in tall fescue, but the environment must be considered during selection
Morphological Basis for Poor Emergence in Inbred Oh43 Corn
Authors: Tapper Diane Currie , Nevins Donald
Published: July 2010

Studies on the seedling emergence of corn (Zea mays L.) inbred Oh43 indicated that poor stand establishment under field conditions was associated with a structural defect of the coleoptile. The ultimate length of Oh43 coleoptiles is comparable to that of other inbreds, but many of the former develop a longitudinal fissure extending abaxially from near the tip to the coleoptile node. In some seedlings this fissure continues as a dual furrow along the abaxial side of the first internode. Although most (ca. 75%) Oh43 seedlings produce such coleoptiles, this feature was not apparent in other inbreds except one derived from Oh43. Hybrids resulting from crosses with Oh43 showed no evidence of this coleoptile anomaly.
Mutual Balance Between Tester Resistance and Isolate Virulence in the Evaluation of Corn Inbreds for Diplodia Stalk Rot1
Authors: Maxwell James D. , Thompson D. L.
Published: July 2010

Fifty inbred lines of corn (Zea mays L.) in crosses with two single‐cross testers (one relatively resistant, the other susceptible) were inoculated with two isolates of Diplodia zeae (Schw.) Lev. (one highly virulent, the other weakly virulent) and rated for stalk rot. Significant differences among testcrosses were obtained for two combinations: resistant tester‐highly virulent isolate and susceptible tester‐weakly virulent isolate. The results indicate that mutual balance between genotype resistance and isolate virulence can be important for proper discrimination among genotypes.