bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of an Acid Phosphatase and Its Linkage with the Kunitz Trypsin Inhibitor in Seed Protein of Soybeans1
Authors: Hildebrand D. F. , Orf J. H. , Hymowitz T.
Published: July 2010

A soybean [Glycine max (L.) Merrill] seed acid phosphatase exists in the germplasm in three different electro‐phoretic forms. These electrophoretic forms are inherited as codominant alleles at a single locus. The symbol Apa is assigned to the slow (Rf 0.38) form, Apb to the intermediate (Rf 0.42), and Apc to the fast (Rf 0.47) form. Of the 326 cultivars examined, 4 were of the Apa genotype, 296 of Apb, and 26 of Apc. The Ap locus was found to be linked to the Kunitz trypsin inhibitor (Ti) with a crossover frequency of 16.2%.
Carbon Balance of Water‐Deficient Grain Sorghum Plants1
Authors: Wilson D. R. , van Bavel C. H. M. , McCree K. J.
Published: July 2010

Experiments were performed to determine how water deficits affect the rates of production and utilization of photosynthetic substrates in whole plants. Substrate utilization was characterized by two parameters which were estimated from an analysis of the C fluxes into and out of plants during a 24‐hour period. These were the efficiency of conversion of substrate used in growth processes to new plant dry‐matter (Yg, growth efficiency), and the daily substrate requirement per unit dry‐matter for maintenance of existing plant material (m, maintenance coefficient).

Measurements were made on grain sorghum [Sorghum bicolor (L.) Moench cv. RS610] plants at the eight‐leaf growth stage, in which daytime leaf water potentials ranged from −1.4 to −24.6 bars, and nighttime potentials from −1.0 to −10.9 bars. Carbon dioxide exchange rate (CER) measurements were made in an assimilation chamber at air temperature 30 C, dewpoint 22 C, and photosynthetic photon flux density 1,800 µE.sec‐1.m ‐2. Leaf water potentials were measured regularly. Leaf areas and plant dry weights were measured at the end of each test.

Water deficits did not affect Yg, its mean value being 0.71 ± 0.02, comparable to previously reported values for unstressed plants. As water deficits became more severe, m decreased from 60 to 30 mg.g‐1.24hours‐1. The cause of the decrease could not be determined from these experiments.

The dry‐matter accumulation rate of the plants was greatly reduced by water deficit. This reduction occurred for two reasons: (i) the leaf area index was reduced, (ii) the substrate production rate per unit of leaf area by photosynthesis decreased.

The total C efflux rate from the plants in the dark was decreased by water deficit. This decrease was mainly attributable to the reduced quantity of available substrate, as shown by separating the C efflux into growth and maintenance components. Of the 58% reduction of the C efflux rate, 22% was attributable to the reduction of the maintenance component and 36% was caused by the reduction of the growth component.
DNA Heterogeneity Within the C Group of Maize Male‐Sterile Cytoplasms1
Authors: Pring D. R. , Conde M. F. , Levings C. S.
Published: July 2010

Restriction endonuclease fragment analyses of organelle DNAs from five members of the C group of male‐sterile maize (Zea mays L.) cytoplasms revealed three mitochondrial DNA types, while no chloroplast DNA variation was observed. It is proposed that three subgroups of the C group be designated: CI (C cytoplasm); CII (RB, BB, and E cytoplasms); CIII (ES cytoplasm). Heterogeneity within the C group indicates the possibility of broadening the cytoplasmic base of hybrid maize production.
Relation of Seedling Vigor to Semidwarfism, Early Maturity, and Pubescence in Closely Related Rice Lines1
Authors: McKenzie K. S. , Rutger J. N. , Peterson M. L.
Published: July 2010

The effects of independent single genes for plant height, maturity, and pubescence on rice (Oryza sativa L.) seedling vigor in closely related, homozygous F4 lines were studied in laboratory and water‐seeded field experiments. Laboratory seedling height, days to emergence, emergence percentage, emergence index, and 100‐grain weight were measured. Mature plant height and maturity had no significant affect on laboratory seedling height. Pubescent lines as a group exhibited greater seedling vigor than glabrous lines in the laboratory seedling height test, and emerged through the water sooner in the field test. However, several individual glabrous lines exhibited as much vigor as pubescent lines. Tall lines as a group showed a higher emergence percentage than semidwarf lines. There was a significant height ✕ maturity ✕ pubescence interaction for emergence percentage and emergence index. Semidwarf lines with seedling vigor equal to the tall parent were obtained. It appears that moderately high levels of seedling vigor can be attained in high yielding semidwarf rice cultivars.
Comparative Performance of Semideterminate and Indeterminate Soybean Lines1
Authors: Wilcox J. R.
Published: July 2010

Forty semideterminate and 40 indeterminate soybean [Glycine max (L.) Merr.] lines from each of three crosses were evaluated in 0.5‐ and 1.0‐m row spacings for 2 years at Lafayette, Ind. The objectives of the study were to compare the agronomic characteristics of the two plant types and to determine if the plant types responded differently to row spacings.

Yields of the 0.5‐m rows averaged 13% higher than those of the 1.0‐m rows in the 2 years of the study. This response was due primarily to increased yields in the 2nd year of the test.

The indeterminate progenies were an average 5% higher in seed yield, 1 day later in maturity, and 12 cm taller than the semideterminate progenies. Interactions of plant type ✕ row spacing were not significant for any characteristic evaluated except maturity in one cross. These data indicated that both the semideterminate and indeterminate lines responded similarly to the two row spacings used in this study.

Regression of seed yield on plant height for the two plant types showed similar regression coefficients in most of the comparisons, indicating that the increases in seed yield associated with increased plant height were similar for the two plant types. Only half the regression coefficients were significant for lodging scores regressed on plant height for the two plant types. Significant coefficients were similar for the two plant types, indicating that neither plant type resulted in superior lodging resistance. The data indicated that among soybeans adapted to the Midwest, either plant type could be used successfully in a soybean improvement program.
Inheritance of Resistance to Greenbug Toxicity in an Amphiploid of Triticum turgidum/T, tauschii1
Authors: Joppa L. R. , Timian R. G. , Williams N. D.
Published: July 2010

Each year the greenbug (Schizaphis graminum Rondani) causes losses in wheat production having an estimated value of several million dollars. A new source of resistance to greenbug toxin has been found in PI 268210 (Triticum tauschii (Coss.) Schmal 2n=14). The cultivar ‘Langdon’ (T. turgidum L. durum group 2n=28) was used as female in a cross with PI 268210, and an amphiploid with 2n=42 chromosomes was obtained. The amphiploid was crossed with two hexaploid wheat lines, Kt‐C and ‘Little Club’*9/WRT238 (T. aestivum L. aestivum group 2n=42). F2 segregations indicated that resistance to greenbug toxin in the amphiploid was conditioned by a single dominant gene. Chromosome pairing between the D‐genome chromosomes of the amphiploid and the D‐genome chromosomes of the T. aestivum lines appeared to be normal and chromosomal interchanges were not detected.
Relationship of Component Frequency to Compensatory Response in Soybean Blends1
Authors: Fehr W. R. , de Cianzio S. Rodriguez
Published: July 2010

We evaluated the effect of component frequency on the compensatory response of soybean (Glycine max L. Merrill) blends. The component frequency of a blend of ‘Corsoy’ and ‘Amsoy 71’ was varied by 2.5% increments from 100:0 to 0:100. The 41 entries were evaluated for yield at four environments in Iowa during 1973 to 1975.

There were no significant differences among component frequencies for average yield across environments. All deviations of blend yields from the weighted mean of the two cultivars in pure stand were attributed to random error. The environment × component frequency interaction was significant due to changes in rank of entries across environments. The results demonstrate the difficulty of differentiating between random error and true overcompensation or undercompensation in soybean blends.
Water Relations and Carbon‐14 Assimilation of Cotton with Different Leaf Morphology1
Authors: Karami E. , Krieg D. R. , Quisenberry J. E.
Published: July 2010

The purpose of this research was to determine the usefulness of simply inherited genetic differences in cotton (Gossypium hirsutum L.) leaf morphology (normal, laciniate, and superokra) as it relates to drought tolerance or water use efficiency. This initial report describes the leaf water potential components, C02 fixation rates, and the rate of loss of assimilated 14C from various source leaves on plants subjected to soil water stress at select growth stages under glasshouse conditions.

No significant genotypic differences were observed in leaf water potential components or in CO2 fixation rates when the soil water content was near field capacity. Trends did exist for the superokra to be slightly superior to the normaleaf type. Significant differences were observed in both the rate and extent of 14C loss from different source leaves in the various genotypes. The superokra genotype had the highest activity, whereas the normal leaf genotype was the lowest in activity.

As soil water availability began to affect leaf water status, significant genotypic differences existed in all measured physiological parameters. The superokra genotype was able to maintain a more favorable leaf water status through a combination of higher leaf water potential and lower osmotic potentlal than the normal leaf genotypes. Photosynthetic rates were reduced by water stress in all genotypes; however, the magnitude of the reduction varied significantly among the genotypes reflecting specific differences in turgor pressure. The removal of assimilated 14C from various source leaves subjected to water stress also exhibited significant genotypic differences both in the rate of removal and in the total amount of assimilate removed during a 24‐hour period. As water stress intensified the photosynthetic assimilation of 14CO2 was found to be more sensitive than the removal of assimilate from the source leaf.

The results of these experiments indicate a possible advantage of altered leaf morphology when cotton leaves are subjected to soil water stress. The benefits of improved water relations and CO2 assimilatlon to yield in the altered leaf types of cotton remain to be evaluated.
Use of Pod Width for Indirect Selection of Seed Weight in Soybeans1
Authors: Bravo J. A. , Fehr W. R. , de Cianzio S. Rodriguez
Published: July 2010

We evaluated the use of pod width for indirect selection of seed weight in soybeans [Glycine max (L.) Merrill], Each of three experimental lines with relatively small seed was crossed to one of two large‐seeded cultivars, and each F1 was crossed to a different parent with intermediate seed weight. Width of the terminal pod cavity (suture‐to‐suture) and seed weight (g/100 seeds) were measured on individual plants and their progeny for the F1 of the three‐way crosses, F2 and F3 of all crosses, the eight parents, and a control cultivar.

Selection for seed weight was more effective using pod width than was direct selection for seed weight per se on an individual‐plant basis. The phenotypic correlations between the two characters were highly significant (P< 0.01) and ranged from 0.55 on an individual‐plant basis to 0.64 on an entry‐mean basis. The genotypic correlation on an entry‐mean basis was 0.72. Heritabilities based on variance component estimates for pod width were 54% on a plant, 75% on a plot, and 92% on an entry‐mean basis, and for seed weight were 27% on a plant, 41% on a plot, and 71% on an entry‐mean basis. Average genetic response in seed weight obtained from individual plant selection of the top 25% of F1 F2, and F3 plants on the basis of pod width was 50% greater than for seed weight per se.

Use of pod width permits more efficient selection for seed weight in soybean cultivars development. Implications of the results in breeding for seed weight are discussed.
Influence of Chemical Seed Treatments on Germination of Dormant Wild Rice Seeds1
Authors: Oelke E. A. , Albrecht K. A.
Published: July 2010

Wild rice (Zizania palustris L.) seeds have a dormancy period of 3 to 5 months. This dormancy period can be partially broken right after harvest by dehulling the seeds and scarifying them. However, this is time consuming and the resulting seedlings are weak. The purpose of this research was to search for chemical means to decrease the dormancy period and increase the seedling vigor of wild rice.

Seeds which had been stored in water at 3 C for 120 days were soaked in 0, 28, 43, 57, 71, 86, and 95% ethanol for various lengths of time up to 24 hours. Germination was increased from 15% with no chemical treatment to 61% with a 7‐hour soaking in 43% ethanol.

Seeds which had been harvested for 1 week were shaken in 95% ethanol for 15 sec, then in chloroform for 1 min and again for 15 sec in 95% ethanol. After treatment the seeds were stored in water at 3 C and germination samples taken over a period of 180 days. Germination at the end of 60 days was 42% for the treated seed compared to 16% for untreated seed.

Freshly harvested seeds were scarified by tumbling with granite grit for 60 min and then placed for 24 hours in all combinations of 0, 0.005, 0.05, 0.5, and 5.0 mM gibberellic acid (GA3) and 0, 0.063, 0.125, 0.25, and 0.5 mM 6‐benzyl adenine (BA). A combination of the highest concentration of both resulted in the highest germination after 21 days in water; 64% compared to 7% with no chemical treatment. However, seedling survival in the greenhouse, 51 days after treatment, was the highest with the lowest concentration of GA3 and the highest concentration of BA. Treating freshly harvested dehulled and scarified seed with 2.63% sodium hypochlorite for 2 hours increased germination from 2 to 19% and seedling survival from 50 to 87%, compared to no chemical treatment.

Pretreating wild rice seeds with ethanol in combination with chloroform can decrease the dormancy period without dehulling and scarifying seeds. Seedling vigor of scarified seeds can be increased by treating them with GA3 and BA.
Seven Cycles of Reciprocal Recurrent Selection in BSSS and BSCB1 Maize Populations1
Authors: Martin J. M. , Hallauer Arnel R.
Published: July 2010

Reciprocal recurrent selection was proposed as an efficient method of improving the population cross of two broad‐genetic base populations. Seven cycles of reciprocal recurrent selection for grain yield have been completed in ‘Iowa Stiff Stalk Synthetic’ (BSSS) and ‘Iowa Corn Borer Synthetic no. 1’ (BSCB1) maize (Zea mays L.) populations. To determine the effectiveness of reciprocal recurrent selection for grain yield improvement, we evaluated the C0, C1, C3, C5, and C7 of BSSS(R) and BSCB1(R), and the C0 ✕ C0, C5 ✕ C5, and C7 ✕ C7 population crosses in six Iowa environments. Data were collected to determine the direct response to selection for grain yield and the correlated responses for eight other agronomic traits. Observed response for grain yield was compared with computer simulated reciprocal recurrent selection as it was conducted with BSSS and BSCB1. Ten cycles of reciprocal recurrent selection were simulated for starting conditions with three levels of dominance and two initial gene frequencies.

Grain yield of the BSSS(R) ✕ BSCB1(R) crosses increased 1.75 ± 0.37 q/ha per cycle, but yield of the parental populations did not change significantly. Observed midparent heterosis increased from 14.9% for the C0 population cross to 41.7% for the C7 population cross. Mean yield of the population crosses increased from 58.5 q/ha for the C0 population cross to 70.7 q/ha for the C7 populations cross. Estimates of genetic components of variance determined from the yield selection trials for each cycle showed no evidence that genetic variability in BSSS(R) and BSCB1(R) was declining because of selection. The greatest correlation between observed and simulated responses was obtained for the starting condition of complete dominance and equal initial allele (p=q=0.5) frequencies in the simulated populations.
Agronomic Performance of Selected Soybean Morphological Variants in Irrigation Culture with Two Row Spacings1
Authors: Hartung R. C. , Specht J. E. , Williams J. H.
Published: July 2010

Soybean [Glycine max (L.) Merrill] plant morphology can be altered with the use of qualitative genes. These alterations may be useful in deriving high yielding cultivars, particularly in irrigated and/or narrow row cultural environments. Near‐isogenic lines of the soybean cultivars ‘Clark’ and ‘Harosoy,’ which possessed alleles (singly or in combination) conditioning determine (dt1) or semideterminate (Dt2) stem growth, shortened (S) or lengthened (st) stem internode length, narrow (ln) or oval (lo) leaflet shape, five (Lf1) or seven (lf2) leaflet numbers, wavy leaflet margins (lw1), dense (Pd), sparse (Ps), semi‐sparse (Ps6), or appressed (pa1pa2) pubescence, or earlier flowering and maturity (e2), were evaluated for agronomic performance in 18‐ and 71‐cm row spacings under irrigation for 2 years. The Clark‐Dt2S, ‐Dt2Lf1ln, ‐pa1pa2, and ‐Dt2 isolines were significantly greater in yield than Clark, while Clark‐Lf1, ‐lf2, ‐dt1, ‐S, ‐dt1S, and ‐dt1st were significantly lower in yield. The Harosoy‐Pd isoline was significantly greater in yield than Harosoy, while Harosoy‐pa1pa2, ‐dt1S, and ‐dt1 were significantly lower in yield. The interaction of isoline ✕ row spacing was not significant in the combined 2‐year data. There were significant effects of the various alleles on maturity, plant height, lodging, seed quality, and seed weight. Only the Dt2 allele consistently increased yields, but other alleles (e.g., Pd, pa1pa2) increased yields depending upon the cultivar in which these were present. Significant inter‐allelic and allele ✕ genetic background interactions were observed in some cases indicating that allelic ‘worth’ may depend on complementarity with other genes. The alleles Dt2, Pd, pa1pa2, and Dt2S appear to have some potential for yield improvement in soybeans, depending somewhat upon the genetic background in which these are introduced, and warrant consideration by soybean breeders in cultivar development or population improvement.
Ancestry of Improved Cultivars of Asian Rice1
Authors: Hargrove Thomas R. , Coffman W. R. , Cabanilla Victoria L.
Published: July 2010

The 1970 attack of southern corn leaf blight (Helminthosporium maydis, Nisik and Miy.) was conditioned by cytoplasmic uniformity in the U.S. maize (Zea mays L.) crop. Researchers at the International Rice Research Institute (IRRI) studied the genetic diversity of improved Asian cultivars of rice (Oryza sativa L.), focusing on their maternal ancestry because cytoplasmically controlled traits are inherited through the female parents.

All cultivars released by late 1979 under the IR designation trace to the same maternal parent ‘Cina,’ which indicates they might carry similar cytoplasm. Cina is the ultimate maternal parent of 62% of the post‐‘IR8’ cultivars in Bangladesh; 22% in India; 74% in Indonesia; 60% in Korea; 75% in Sri Lanka; and 25% in Thailand. More than half of the Philippines' riceland is planted to maternal derivatives of Cina. Among 79 entries from 10 nations and IRRI in the 1978 International Rice Yield Nursery, 59% trace their maternal ancestry to Cina. From 36 to 92% of the elite materials in other nurseries and IRRI screening trials derive from Cina. Of the 20,000 hybridizations made at IRRI by 1979, 44% of the female parents can be traced to Cina but the trend is declining.

All named IR cultivars, except ‘IR5,’ and virtually all semidwarfs developed in national programs, carry the dwarfing gene from the Chinese dwarf cultivar ‘Dee‐geowoo‐gen.’

The cytoplasmic similarity of modern cultivars, while posing no immediate practical problem, is of sufficient relevance to demand a prompt broadening of the maternal genetic base of improved rice cultivars. Recommendations are made for diversifying the maternal origin and the genetic base of subsequent semidwarfs.
Heritability Estimates for Forage Yield, In Vitro Dry Matter Digestibility, Crude Protein, and Heading Date in Indiangrass1
Authors: Vogel K. P. , Gorz H. J. , Haskins F. A.
Published: July 2010

Space‐planted populations derived from ‘Holt’ and ‘Oto’ indiangrass, Sorghastrura nutans (L.) Nash, were used to obtain heritability estimates for forage yield, in vitro dry matter digestibility (IVDMD), crude protein, and heading date and to determine their genotypic correlations. Heritability estimates were determined by variance component analyses and by parent‐progeny regression. Average narrow sense heritability estimates for the two populations were 0.43, 0.42, and 0.50, for forage yield, IVDMD, and protein, respectively. Narrow sense heritability estimates for heading date were 0.90 or larger. Genotypic correlations of yield and IVDMD were negative for the Holt population but were positive, although low, for the Oto population in 1976. Protein and IVDMD had positive genotypic correlations for both populations. Heading date was positively correlated with yield but was negatively correlated with IVDMD and protein.
Improvement for Accelerated Aging Response of Seed in Maize Populations1
Authors: Scott Gene E.
Published: July 2010

Even though maize (Zea mays L.) seed has a relatively long storage life, improvement for this characteristic is desirable. My objective was to determine if the seed deterioration caused by an accelerated aging process could be reduced in maize populations using a recurrent selection breeding method. The Co, C1, C2, and C3 cycles of two populations were evaluated. Evaluation for differences among cycles of selection was made on seed aged at 42 C and 100% R. H. for either 9 or 10 days. In one population, germination in the C3 cycle was nearly double that of the C0 cycle. Progress in the other population was less.
Flexible Alfalfa Management: Early Spring Utilization1
Authors: Wolf D. D. , Blaser R. E.
Published: July 2010

Providing low‐cost high quality grazing for livestock early in the spring when pasture and hay are limited may increase body weights at economical prices. Current alfalfa (Medicago sativa L.) varieties may be suitable for such grazing if either stands or yields are not greatly reduced by early spring harvests. To evaluate the possibilities of early spring alfalfa grazing, two severities of cutting to simulate grazing were imposed at several spring dates by removing one‐half the leaf area index (LAI) and all the LAI by cutting to a 5‐cm stubble height. Spring utilization dates, based on accumulating 1, 2, 3, and 4 LAI units, occurred on about 9 April, 27 April, 6 May, and 25 May, respectively. During the remainder of the season, harvesting hay at onetenth bloom was considered lenient management for recovery. The 9 April grazing cut, leaving about onehalf the LAI, enhanced the first hay yields as compared with removing nearly all the leaf area. However, at 6 May with an LAI of about 3, leaving one half the leaf area, resulted in lower yields and decreased quality of the following hay harvest as compared with a grazing cut at 5 cm which removed all leaf area. Regrowth from tall stubble remaining after the 6 May grazing cut generally orginated from branches at axillary buds which had smaller stems than those growing from crown buds. Early spring grazing cuts delayed the first hay harvest. This delay is desirable since favorable hay‐making weather is more likely later in the season. Number of regrowth days to one tenth bloom decreased between April and mid‐June and increased thereafter. Regrowth after early August cuts did not flower due to short days of late summer.

Total season yields were similar for all treatments. Residual yields in subsequent years showed no detrimental effects due to date or severity of spring grazing cuts. Utilization of alfalfa in early srping by grazing and taking the first hay harvest about 3 weeks later than normal appears to be a feasible alternative system for flexible alfalfa management.
Root Characteristics of 44 Maize Inbreds Evaluated in Four Environments1
Authors: Jenison J. R. , Shank D. B. , Penny L. H.
Published: July 2010

To study root characteristics, as well as potential tolerance to corn rootworms (Diabrotica spp.) of northern‐adapted genotypes, 44 maize (Zea mays L.) inbreds were evaluated at two locations in both 1974 and 1975 for vertical‐pull resistance at the pretassel and kernel milk stages of plant growth and, for root dry weight and root spread at the later growth stage. The inbreds also were evaluated at one location in 1975 for root‐rot resistance at the kernel dent stage of growth to determine its effect on pull resistance. Highly significant differences existed among inbreds for all characters measured. Although interactions of inbreds with environments were evident, the magnitude of these interactions were relatively small when compared to the differences among inbreds. Highly significant positive rank correlations for inbreds between environments were found for vertical‐pull resistance at both pretassel and milk stages; root dry weight; and nodal root spread. A highly significant simple correlation (r = 0.61) was found between root rot and percent loss in vertical‐pull resistance at the dent stage. The root characteristics measured appear to be relatively stable over environments and effective selection for each should be possible.
Conservation of Inverted Repeats in Chloroplast DNA from the Genus Zea: Teosinte1
Authors: Timothy D. H. , Hu W. W. L. , Levings C. S.
Published: July 2010

Self‐renatured corn (Zea mays L.) and teosinte (Zea spp.) chloroplast DNAs (ctDNAs) were examined by electron microscopy. Molecular conformation was that of one large and one small single‐stranded DNA loop separated by a large duplex region. Within the genus Zea, it is now apparent that the ctDNA genomes contain a sequence repeated once in reverse polarity, that each sequence is approximately 15.5% of the native length of the ctDNA, and that the sequence is highly conserved. Although we have no direct evidence that the inverted ctDNA sequence in teosinte codes for the chloroplast rRNA genes, as in corn, the similarity in the conformation of the corn and teosinte ctDNAs allows the speculation that the teosinte inverted repeat has a similar function to that of corn.
Root Respiration, Nodulation, and Enzyme Activities in Alfalfa During Cold Acclimation1
Authors: Duke Stanley H. , Doehlert Douglas C.
Published: July 2010

This investigation was conducted to determine the effects of hardening conditions (low temperature, short photoperiod) on root respiration, nodulation, and in vitro activities of soluble enzymes in roots of alfalfa (Medicago sativa L.) cultivars which harden or fail to harden. Under hardening conditions in growth chambers root sections of Vernal alfalfa (high hardiness) had higher rates of respiration than did those from Sonora alfalfa (low hardiness). Arrhenius plots of root respiration showed that temperature kinetics for Vernal and Sonora were similar between 4 and 40 C regardless of growth conditions although Vernal had a slightly lower Arrhenius energy of activation (11.2 to 12.6 and 13.8 to 14.4 kcal mole−1, for Vernal and Sonora respectively). Roamer and Vernal (both with high hardiness) grown under hardening conditions nodulated very well and had significant rates of acetylene reduction, whereas Sonora and Caliverde (low and moderate hardiness, respectively) grown under the same conditions nodulated poorly and did not reduce acetylene. Root NAD‐malate dehydrogenase, NADP‐malate dehydrogenase, lactate dehydrogenase, and glutamate oxaloacetatetransaminase activities were highest in hardy plants grown under hardening conditions in growth chambers. Alcohol dehydrogenase activity was usually much higher in all cultivars, hardy and nonhardy, grown under hardening conditions. Studies with six field‐grown cultivars with various degrees of hardiness yielded data similar to that from growth‐chamber plants for the in vitro activities of soluble root enzyme activities. Of 10 enzymes assayed, NAD‐malate dehydrogenase and NADP‐malate dehydrogenase activities correlated best with hardiness and levels of soluble protein. These data indicate that root functions (respiration, the ability to nodulate, and levels of various enzyme activities) increase to a greater extent or are more pronounced in hardy cultivars compared to those with lesser hardiness during the hardening process.
The Manifestation of Dehydration Avoidance in Wheat Breeding Germplasm1
Authors: Blum A. , Gozlan G. , Mayer J.
Published: July 2010

The genetic improvement of wheat for conditions of drought stress requires an evaluation of specific physiological attributes related to drought resistance, as a basis for developing a working screening procedure. An important component of drought resistance is dehydration avoidance.

Dehydration avoidance is defined as plant ability to maintain a relatively higher leaf water potential under conditions of soil moisture stress.

The purpose of this investigation was to document the existance of and variability in dehydration avoidance within a random sample of advanced and well‐adapted wheat (Triticum sp.) genotypes.

Midday leaf water potentials (Ψ1), as a measure of dehydration avoidance, were monitored with a pressure chamber in the various wheat genotypes, simultaneously subjected to soil moisture stress in three different field tests. Leaf diffusive resistance (R1) was monitored with a diffusion porometer in two of the tests.

Genotypes varied significantly in their midday leaf water potentials. About 2 bars of Ψ1 were sufficient to differentiate significantly between genotypes. Variations in Ψ1 were greater than variations in R1 among genotypes. The largest difference in Ψ1 between extreme genotypes, as observed in these tests, reached 12.9 bars.

In one test, where drought stress developed during the spike development stage, leaf water potential (but not leaf diffusive resistance) was correlated with the final number of grains per spike across genotypes of similar phenology.

Linear regressions developed for each genotype between Ψ1 and R1 revealed large variations among genotypes in stomatal response to Ψ1. These relationships lead to the conclusion that dehydration avoidance in only a few of the genotypes may have resulted from stomatal sensitivity and closure at low stress levels. Most of the avoidant genotypes, however, maintained relatively open stomata.
Influence of Phenotype, Season, and Time‐of‐day on Nectar Production in Cotton1
Authors: Waller Gordon D. , Wilson F. D. , Martin Joseph H.
Published: July 2010

Twenty‐five cultivars and breeding stocks of
Gossypium hirsutum L. and two cultivars of G. barbadense L. were studied for rates of flowering and diurnal and seasonal patterns of floral nectar production. Nectar secretion began ca. 0800 hours and production increased linearly until the flowers closed at ca. 1700 hours. In mid‐season, G. hirsutum produced 25 µ1 nectar/flower for at least 5 weeks. Neither nectar volume nor sugar concentration differed significantly among the 25 entries of G. hirsutum. When samples were collected between 1300 and 1700 hours, sugar concentrations were mostly ca. 20%. Flowers of G. barbadense produced about three times this amount of nectar with only slightly lower sugar concentrations. Honeybee (Apis mellifera L.) visits to both species of cotton were negligible, even though we provided nearly 10 colonies/ha during the flowering season.
Agronomic Evaluation of Soybean Genotypes Resistant to Iron Deficiency Chlorosis1
Authors: Niebur W. S. , Fehr W. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] breeders are interested in the development of cultivars with high yield and resistance to iron deficiency chlorosis on calcareous soil. Our objective was to determine if there was a genotype × soil type interaction that would influence selection for yield on noncalcareous or calcareous soils among lines with a high level of resistance to iron chlorosis. Nineteen lines of Maturity Groups I and II with the best available level of resistance to iron chlorosis were evaluated on calcareous and noncalcareous soils at each of three locations in Iowa during 1979. Iron chelate applied to the plants permitted the evaluation of the genotype × soil type interaction in the absence of chlorosis symptoms.

There was no genotype 4 soil type interaction for yield, maturity, height, lodging, seed weight, protein, or oil content. The rank correlation coefficient for mean yield of lines between calcareous and noncalcareous soils was 0.95. The top three lines for yield were the same on the two soil types. The results indicated that selection can be practiced for yield and other agronomic characters among lines resistant to iron chlorosis as effectively on noncalcareous as on calcareous soil.

Significant yield reduction occurred on lines that showed slight yellowing in the absence of the iron treatment. This result indicated that complete elimination of yield loss due to iron chlorosis requires the use of cultivars or agronomic practices that prevent any chlorosis expression.
Simulated Comparisons of Single Seed Descent and Bulk Population Breeding Methods1
Authors: Muehlbauer F. J. , Burnell D. G. , Bogyo T. P. , Bogyo M. T.
Published: July 2010

Two plant breeding methods generally used in breeding self‐pollinated crops, the bulk‐population (BP) and the single‐seed‐descent (SSD) methods, compared by computer simulation to determine which retained the most additive genetic variation after four generations of inbreeding. Various levels of fecundity were simulated in the BP method, and various probabilities of plant survival were used in the SSD method simulation. All simulations were done with a hypothetical crop having seven chromosomes with six loci on each and various degrees of linkage.

In the F6, the additive genetic variance in the BP method was smaller than that in the SSD method; this difference was attributed to losses in genetic variability in BP during generation advance. Within BP a considerable proportion of the total additive variance originated from within‐line variance, as opposed to that which originated from between‐line variance. When the inbreeding coefficient was larger than 0.9, the difference between within‐line and between‐line variances was considerable. In the SSD method, all additive variance must originate from between‐line variance.

Fecundity affected the genetic variability in BP, whereas the probability of individual plant survival was important in SSD. When the standard deviation of fecundity was greater than 25 seeds per plant, progeny from 75% of the original F2 plants were not represented in the population after four generations of advance by BP. About the same number of lines were lost after four generations when seedling survival dropped below 70% in each generation of advance by SSD. Linkage had little effect on additive genetic variance in either system, unless the two lines of the original cross had considerably different sets of alleles.
Seedling Screening for Lysine‐Plus‐Threonine Resistant Maize1
Authors: Phillips R. L. , Morris P. R. , Wold F. , Gengenbach B. G.
Published: July 2010

Over 200 maize (Zea mays L.) strains were evaluated for seedling growth on lysine‐plus‐threonine supplemented media in an attempt to find feedback resistant mutants. Five of 92 inbreds, most of which were developed for use in hybrid production, were resistant (i.e., root length on lysine + threonine medium exceeded 50% of control). Resistant inbreds B37 and B76 were from the Iowa Stiff Stalk Synthetic (BSSS) population. Nine of 103 random line isolates from the BSSS population were resistant. From 16 of the 17 original BSSS component lines tested, only Ill. 12‐E was resistant. Seven broad base maize populations did not yield resistant types.

Resistance was expressed only when seedlings were derived from germinating whole kernels. Seedlings derived from dissected embryos of resistant strains were inhibited. Studies of kernel aspartokinase and homoserine dehydrogenase activities indicated that alterations in the feedback regulation of these enzymes were not the basis of the observed lysine + threonine resistance.

The opaque‐2 version of B37 was inhibited. This observation and amino acid data led to the tentative hypothesis that resistance is a function of the relative amounts of methionine and lysine (M/L ratio) in the kernel with a high M/L ratio leading to resistance and a low M/L ratio leading to inhibition. All three resistant strains analyzed had a high M/L ratio compared with four inhibited strains. Kernels of one strain, BSSS 53, had approximately 21% more total methionine than the other four inbreds analyzed (two resistant, two inhibited) yet retained the typical dent kernel phenotype. Kernels of the resistant strains also tended to have higher percent protein. Specific approaches are suggested for selecting high methionine or high lysine maize.
Expression and Inheritance of Resistance to Hessian Fly in Synthetic Hexaploid Wheats Derived from Triticum tauschii (Coss) Schmal.1
Authors: Hatchett J. H. , Martin T. J. , Livers R. W.
Published: July 2010

Seventeen synthetic hexaploid (SH) wheats, derived from crosses between six tetraploid Triticum species and a diverse group of diploid T. tauschii (Coss.) Schmal., were evaluated for resistance to biotype D of Hessian fly, Mayetiola destructor (Say). Resistance was identified in four of the SH wheats. Based on rections of the tetraploid × diploid crosses and the parental Triticum species to larval feeding, resistance was derived from specific lines of T. tauschii. Other lines of T. tauschii and the tetraploid Triticum species were homozygous susceptible. Resistance of the SH wheats and T. tauschii was expressed as antibiosis in that larvae died in the first instar of development.

Two resistant SH wheats were crossed with susceptible common wheat (T. aestivum L. em Thell.) cultivars ‘Amigo’ and ‘Eagle’ to study the inheritance of Hessian fly resistance derived from T. tauschii. F2 populations segregated in a 3:1 ratio of resistant to susceptible plants, an indication that resistance was conditioned by a single dominant gene. Segregation ratios of F3 lines and F3 plants within segregating lines supported the single‐factor resistance hypothesis. F4 lines derived from homozygous resistant F3 lines bred true for resistance, On the basis of present knowledge of genetic relationships among wheat genes for resistance to Hessian fly, T. tauschii appears to be a new source of resistance that can be readily transferred to hexaploid wheat.
Isoenzyme Polymorphism in St. Augustinegrass1
Authors: Green R. L. , Dudeck A. E. , Hannah L. C. , Smith R. L.
Published: July 2010

St. Augustinegrasses (Stenotaphrum secundatum Walt. Kuntze) were investigated to determine the feasibility of their identification by isoenzyme variability. Several Florida clones of this species are morphologically indistinguishable especially when grown as turfgrasses under high fertility. Adenosine diphosphate glucose pyrophosphorylase, UDP glucose pyrophosphorylase, alcohol dehydrogenase (ADH), and acid phosphatase isoenzymes extracted from leaf tissue of 28 clones were separated by polyacrylamide disc electrophoresis. Gels of all 28 clones were stained for ADP glucose pyrophosphorylase and UDP glucose pyrophosphorylase isoenzyme activity while gels from selected clones were stained for total protein, ADH, and acid phosphatase isoenzymes. Clones could be divided into several groups by quantitative differences of bands with equal electrophoretic mobility of ADP glucose and UDP glucose pyrophosphorylases. St. Augustine grasses grown in Florida could be divided into two groups by either ADP glucose or UDP glucose pyrophosphorylase isoenzyme systems or total protein. These groups could be further subdivided by acid phosphatase and ADH isoenzymes.
Release of Soluble Protein and Nitrogen in Alfalfa. I. Influence of Growth Temperature and Soil Moisture1
Authors: Walgenbach R. P. , Marten G. C. , Blake G. R.
Published: July 2010

The influence of climatic and soil factors during growth on release of soluble protein from alfalfa (Medic ago saliva L.) has not been studied. Herbage proteins soluble in sodium male ate buffer (pH 6.9) have been proposed as possible estimates of ruminant bloat potential in comparative studies. Our objectives were to determine whether growth temperature or soil moisture availability at different growth temperatures would influence concentration of several N fractions released from alfalfa.

‘Ramsey’, ‘Saran ac’, and ‘Desert’ alfalfa cultivates were grown at 18/10, 26/18, and 34/26 C (day/night) with a 16 hour photo period (3 × 3 factorial). Total (TN), total soluble N (TAN), soluble non protein (SPN), and soluble protein N (SPN) were determined.

As the temperature increased, the mean concentration of TN, TAN, and SPN increased in leaves, stems, and total forage. The greatest concentration of SPN in leaves occurred at 26/18 C (x̄ of 11.5 mg/g dry wt), compared to 18/10 C (x̄ of 9.9) or 34/26 C (x̄ of 10.4). The mean SPN concentration in stems increased as temperature increased from 2.7 mg N/g dry wt at 18/10 C to 3.0 mg at 26/18 C and 3.7 mg at 34/26 C. The total forage of any cultivate grown at any temperature contained approximately 6.6 mg SPN/g dry wt, except Desert grown at 18/10 C contained 5.6 mg SPN/g dry wt.

We conclude that the apparent bloat potential, estimated as SPN release, of alfalfa leaves of all cultivates grown at 26/18 C was greater than that of leaves grown at 34/26 and 18/10 C. Little difference in apparent bloat potential occurred in total forage regardless of cultivate or temperature during growth.

Ramsey and Saran ac alfalfa were grown at 18/10 and 26/18 C with a 16 hour photo period. Three soil moisture regimes (R) were imposed at each temperature; soil matrix potentials between −0.1 to −0.5 (R I), −1.0 to −6.0 (R 2), and −6.0 to −15.0 bars (R 3) were established before the soil was restored to field capacity (2 × 3 factorial within each temperature).

With a few exceptions, the concentrations of the N fractions in leaves, stems, and total forage of both cultivates generally increased as the soil moisture content decreased from R 1 to R 3 at each temperature. The leaves, stems, and total forage of both cultivates grown at 26/18 C contained greater concentrations of all N fractions than did those of cultivates grown at 18/10 C, which confirmed results of Experiment I.

Apparent bloat potential, as estimated by SPN release, of leaves, stems, and total forage increased slightly with moistur6 Stress at 18/10 C. At 26/18 C, apparent bloat potential only of stems increased with moisture stress. Insofar as moisture stress occurs in practice more often at warm temperatures, it is not likely to influence alfalfa bloat potentially instigated by soluble protein release.
Diallel Analysis of Leaf Number, Leaf Development Rate, and Plant Height of Early Maturing Maize1
Authors: Rood S. B. , Major D. J.
Published: July 2010

A diallel cross from eight early maturing maize (Zea mays L.) inbreds was used to investigate inheritance and determine combining abilities for leaf number and plant height, two correlates of floweringtime, and leaf development rate (LDR). Dominance for increasing leaf number was almost complete. Apparent “overdominance” for increasing plant height and “overdominance” for decreasing LDR were also observed. Broad‐sense heritabilities were 88, 74, and 78% for leaf number, LDR, and height in the growth room. Narrow‐sense heritabilities were lower, particularly for height. Neither reciprocal effects nor specific combining ability effects were significant for leaf number, LDR, or plant height in field or growth room trials. Thus, hybrid performance was determined by general combining abilities of parental inbreds. Leaf number and LDR were positively correlated with flowering‐time. Leaf number was also correlated with height. Apparent “overdominance” for decreasing LDR explains how dominance for increasing leaf number and incomplete dominance for decreasing flowering‐time may act simultaneously and indicates that heterosis occurs for development in maize.
Theoretical Aspects of Selection for Yield in Stress and Non‐Stress Environment1
Authors: Rosielle A. A. , Hamblin J.
Published: July 2010

The question of choice of selection criterion when lines are grown in stress and non‐stress environments is examined from a theoretical standpoint in this paper. Tolerance to stress is defined as the difference in yield between stress and non‐stress environments, while mean productivity is the average yield in stress and non‐stress environments. Equations are developed for the genetic correlations of tolerance and mean productivity with one another and with yields in stress and non‐stress environments in terms of the ratio of genetic variances and the genetic correlations between yields in stress and non‐stress environments. These equations show that selection for tolerance to stress will generally result in a reduced mean yield in non‐stress environments and a decrease in mean productivity. Selection for mean productivity will generally increase mean yields in both stress and non‐stress environments. Tolerance and mean productivity show negative genetic correlations whent he genetic variance in stress environmentsi s less than the genetic variance in non‐stress environments. This result provides an explanation for the positive correlations often reported between regression coefficient stability and mean productivity; a line with high tolerance to stress normally would have a low regression coefficient stability and genetic variances in stress environments are generally lower than in non‐stress enviornments.
Seed Width to Pod Width Ratio for Identification of Green Soybean Pods that have Attained Maximum Length and Width1
Authors: Rodriguez de Cianzio S. , Frank S. J. , Fehr W. R.
Published: July 2010

Efficient indirect selection for seed weight in a soybean [Glycine max (L.) Merrill] breeding program on the basis of the width or length of green pods requires a rapid technique for determining maximum dimensions of the pods. Our objective was to determine if the ratio of seed width (SW) to pod width (PW) could be used to establish when green pods have attained maximum width and length. Seed and pod development of nine soybean lines differing in seed weight were evaluated in Ames, Iowa, and in two environments at Isabela, Puerto Rico. Width of the seeds and pods were measured from suture to suture and pod length (PL) was measured from the base of the sepals to the tip of the pod.

Differences among lines and environments were statistically significant in the combined analysis of variance for the SW/PW ratio at the earliest time that maximum PW and PL occurred. Among lines and environments, seeds were 28 to 50% as wide as the pods when maximum PW and PL first occurred. Data combined over environments indicated that all lines attained a SW/PW ratio of 50% within 4 days after the earliest time that maximum PW or PL occurred. The results indicated that 50% would be a conservative SW/PW ratio for assuring that a green pod had reached its maximum width and length. Use of the SW/PW ratio is an efficient method of determining the earliest time that green pods can be measured for indirect selection of seed weight in soybeans.