bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of Eight Agronomic Characters in a Winter Wheat Cross1
Authors: Ketata H. , Edwards L. H. , Smith E. L.
Published: July 2010

Parents, F19, F29 and first generation backcrosses (B1 and B2) of a ‘Centurk’ ✕ ‘Bezostaia 1’ cross (Triticum aesti. vum L.) were grown in a space‐planted experiment to obtain genetic information pertaining to grain yield and seven other agronomic characters.

The F1 deviated significantly from the midparent values for heading date, plant height, and kerneis/spikeiet indicating a sizable amount of nonadditive gene action for those traits. Narrow‐sense heritability estimates were very high for heading datea moderately high for kernel weight and plant height, moderate for number of tillers/plant, and low for spikeiets/spike, kernels/spike, kernels/spikelet, and grain yield. Several of those estimates were considered biased upwaxd as epistasis was found to contribute significantly to heading date, plant height, tiller number, kernels/spikelet, and grain yield. No epistasis was detected for spikelets/spike, kernels/spike, or kernel weight, indicating that estimates of gene effects for those characters were free from linkage bias. Duplicate epistasis was detected for heading date and grain yield, suggesting difficulty would be encountered in selecting for earlier maturity or higher yield in this cross. Additive effects were the main source of genetic variation forkernel weight, indicating that early generation selection for higher kernel weight should be effective in this material. The prospects for increasing tiller number were not as favorable as were those for kernel weight.
Inheritance of Sensitivity to Metribuzin in Soybeans1
Authors: Edwards C. J. , Barrentine W. L. , Kilen T. C.
Published: July 2010

Two soybean [Glycine max (L.) Meir.] cultivars, ‘Semmes’ and ‘Hood,’ differing in sensitivity to the herbicide metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazine‐5(4H)one] were studied with their F1, F2, and backcross F2 generations to determine the inheritance of metribuzin sensitivity. The herbicide was added to the nutrient solution in which the plants were growing to insure uniform herbicidal treatment.

The technique was effective for classifying segregating populations. The data gave good evidence that a single recessive gene controlled the metribuzin sensitivity expressed by the cultivar Semmes. The gene symbol hm is suggested for this reaction.
Leaf Water Potential: Comparison of Pressure Chamber and in situ Hygrometer on Five Herbaceous Species1
Authors: Baughn J. W. , Tanner C. B.
Published: July 2010

Leaf water potential was measured on the same leaf with an in situ dewpoint hygrometer of the Neumann‐Thurtell design and with a pressure chamber, for potato (Solarium tuberosum ‘Russet Burbank’), sunflower (Helianthus annuus ‘Russian Mammoth’), pepper (Capsicum annuum ‘California Wonder’), soybean (Glycine max ‘Wells’), and oat (Avena sativa ‘Lodi’). On the average the pressure chamber measurement was within 1.5 bars of the in situ potential, although the scatter in the data was large. The comparisons showed a trend in which the pressure chamber gave lower (drier) leaf water potentials than the hygrometer in the high (wet) potential range, and higher potentials than the hygrometer in the dry potential range. This trend was most distinct in sunflowers, soybeans, and oats. Serious error in the pressure chamber measurement can result if evaporative loss of leaf water is not prevented before and during pressurization or if leaves are stored for an extended period between excision and pressurization.
Relationship of Dwarfing and Hybrid Wheat Mechanisms1
Authors: Godoy Ramon J. , Welsch J. R.
Published: July 2010

The effects of dwarfing genes on the fertility of hybrid wheat (Triticum aestivum L. em Thell) were studied in 36 topcrosses. Three spring wheat cultivars with pollen fertility restorer genes for Triticum timopheevi cytoplasm were crossed with 12 near‐isogenic height lines of the spring wheat cultivars ‘INIA 66’ and ‘Norteno 67.’ The 36 F1,'s were used to pollinate a ‘Noroeste 66’ male sterile line.

The source of major dwarfing segregation used in the near‐isogenic lines came from the cultivar ‘Olesen’ dwarf. Segregation for both height and restoration genes in a male‐sterile cytoplasm was studied. The degree of restoration and sterility was measured by the number of seeds set in one spike/plant. Frequency distributions revealed a larger‐than‐expected proportion of sterile plants in the short height groups and a larger‐than‐expected number of fertile plants in the tall height groups. Correlation studies in seed‐bearing plants showed a weak but positive relationship between plant height and fertility.
Inheritance of Stem Length and its Components in Safflower1
Authors: Abel G. H.
Published: July 2010

Mode of inheritance of two length zones of the stem and their components (internode length and node number) were studied in three crosses of safflower, Carthamus tinctorius L. The purpose was to analyze stem lengths and their components for genetic effects and for their relation to yield.

The dwarf strains were used as females in separate crosses with the tall ones. Two of the tall parents did not differ in internode length or node number. The three dwarfs were similar in number of nodes for the two zones of the plant axis. One of the three dwarfs had slightly longer internodes.

Except for lower stem node number, upper stem internode length, and total upper stem length, a simple additive‐dominance model could not explain the observed results. In those cases where an additive‐dominance model did not fit, the F1 and F2 means were outside the range of the parental means or large differences were observed between the F1 and F2 means. Possible explanations include heterotic effects that involve interactions between loci or variation in estimation of F1 means caused by small sample sizes in this generation. Heterosis, when it was present, tended to increase internode length, decrease node number, and increase stem length in both stem zones

Correlations for yield with lower stem internode length and with upper stem node number were frequently significant; those for yield with upper stem internode length and lower stem node number were generally small and nonsignificant. The correlations indicated that selection for plant height could be conducted without altering yield.
Seed Weight Effects upon Emergence, Leaf Development, and Growth of the Sainfoin (Onobrychis spp.) Seedling1
Authors: Fransen S. C. , Cooper C. S.
Published: July 2010

Selection of legume seedlings with high ratios of cotyledon area to seed weight could result in increased vigor. We studied this relationship and the effect of seed size upon leaf development and seedling growth in 10 sainfoin (Onobrychis spp.) accessions. The accessions did not vary in their ability to distribute seed weight into cotyledon area. Larger seed size was associated with larger embryo axis, leaf primordia, and cotyledon area. Seedlings from large seeds emerged and developed more rapidly than those from small seeds and had larger first and second leaves. Seedling weight at 17 days of age was proportional to seed size. Second leaves, which were all trifoliolate, were larger for seedlings with unifoliolate first leaves than those with trifoliolate first leaves. Frequency of first leaf type was not affected by seed size. We conclude that little progress can be made in selecting plants within a species for greater cotyledon area to seed weight ratios.
Variations in Gossypol Concentation of Flower Buds of Cotton1
Authors: Yang H. C. , Davis Dick D.
Published: July 2010

Gossypol concentration of flower buds (squares) from selected medium to high gossypol lines of upland cotton, Gossypium hirsutum L., was studied both in greenhouse and field conditions.

Gossypol concentration of 20‐day‐old squares generally rose and fell during the growing period. Two cycles of fluctuation occurred in a high gossypol line. The gossypol concentration was independent of square size in the high gossypol line, but was negatively correlated with square size in four medium gossypol lines. Gossypol concentration of squares from greenhouse‐grown plants were strongly correlated with those of squares from plants of the same genotype grown in the field. Samples of 3 to 5 squares/plant, collected during the same 12‐day interval, gave reliable comparisons of the relative gossypol concentration of all lines tested.
New Virescent Cotton Mutant Linked with the Marker Gene Yellow Petals1
Authors: Percival A. E. , Kohel R. J.
Published: July 2010

A new virescent mutant in cotton (Gossypium hirsutum L.), which occurred spontaneously, was found in the Cotton Breeding Nursery at the Texas Agric. Exp. Stn., College Station, Texas. Inheritance tests indicate that the phenotypic expression of this mutant is controlled by a recessive gene at a single locus that, when homozygous, results in virescent foliage. The degree of yellowness expressed by this mutant during its period of maximum expression is comparable to the expression of virescent‐1 (v1) or yellow green (yg1yg2) at College Station. Linkage tests indicate that this new virescent mutant is linked about five crossover units from Yellow petals (Y1), comprising a new linkage group in cotton, and it is independent from 16 other marker mutants tested. It is proposed that this new virescent mutant be named virescent‐10 and assigned gene symbol v10, and the new linkage group be designated Linkage Group XII.
Fertility of 17 Colchicine‐induced Perennial Triticeae Amphiploids Through Four Generations1
Authors: Asay K. H. , Dewey D. R.
Published: July 2010

Seed set and pollen stainability were determined for 17 perennial colchicine‐induced amphiploids (2n=42 or 56) derived from sterile triploid and tetraploid F1 hybrids of Agropyron, Elymus, Hordeum, and Sitanion species. Chromosome doubling restored fertility; however, the level of fertility in the originally doubled hybrids (C0 generation) declined in advanced generations. Fertility stabilized in most hexaploids after the C1 generation, whereas fertility of most octoploids continued to decline. Seed set (seeds/spike) of nine hexaploid amphiploids averaged 17.5, 18.9, and 17.4 in the C1, C2, and C3 generations, respectively. Eight octoploid amphiploids averaged 8.1, 9.1, and 4.2 seeds/spike, respectively, over the same three generations. Synthesis of fertile Triticeae grass species appears to be feasible at the hexaploid level but not at the octoploid level.
Doubling the Chromosome Number of Trifolium Species Using Nitrous Oxide1
Authors: Taylor N. L. , Anderson M. K. , Quesenberry K. H. , Watson Linda
Published: July 2010

To determine the effect of nitrous oxide on chromosome doubling in diploid red dover (Trifolium pratense L.), excised heads were treated at 6 bars atmospheric pressure. Treatment commenced2 4 hours after crossing and continued for the following 24 hours. Of the plants which flowered, 71% were classified as tetraploid based on pollen size. Subsequent root‐tip and PMC chromosome counts of 136 of these plants revealed that 119 were tetraploid, 3 were diploid, and 12 were aneuploid. Two plants died before chromosome counts were made. The technique produced 49 and 79% tetraploids in T. alpestre L. and T. rubens L. respectively. The chromosome numbers of T. noricum Wulf. and T. pallidum Wald. and Kit. were successfully doubled also. Ease and frequency of chromosome doubling was considerably higher and production of mixaploids was lower than in previously‐reported colchicine treatments. The treatment was toxic to T. hirtum All. and T. heldreichianum Hausn.
Leaf Growth, Tuber Growth, and Water Potential in Potatoes1
Authors: Gandar P. W. , Tanner C. B.
Published: July 2010

The objective of this study was to measure the effect of plant water deficit on the growth of potato (Solanum tuberosum L. ‘Russet Burbank’) leaves and tubers. Changes in leaf length, in tuber weight and dimension, and in leaf water potential were measured in glasshouse‐grown potatoes during drying cycles. Leaf elongation rate declined as leaf water potential decreased, and leaf growth ceased at water potentials between −4 and −5 bars. Field measurements of leaf elongation agreed with glasshouse results. Measurements of tuber weight, and of tuber length and diameter, indicated that tuber expansion also ceased at about −4 to −5 bars. These results are discussed in relation to the diurnal changes in leaf and tuber water potentials observed under field conditions.
Chemical Control of Pollination in Wheat and Oats1
Authors: Johnson R. R. , Brown C. M.
Published: July 2010

The objective of this work was to determine if foliar sprays of 3‐(p‐chlorophenyl)‐6‐methoxy‐s‐triazine~2,4‐(1H,3H) dione, triethanolamine salt (DPX 3778) were effective pollen control agent for spring oats (Avena sativa L.) and spring wheat (Triticum aestivum L.). The effect of rate and stage of application was examined in green‐house and field environments. In the greenhouse, treatment with 9 kg/ha active ingredient of DPX 3778 at the early boot stage essentially prevented seed set on six of 11 spring wheat cultivars that were bagged to prevent outcrossing. Treated plants produced pollen that failed to dehisce from the anthers.

‘Protor’ spring wheat or ‘Noble’ spring oats were treated with 0, 4.5, 9, 18, and 27 kg/ha in the field at different growth stages. Increasing chemical rate decreased plant height and reduced seed set on bagged spikes. DPX 3778 at or above 9 kg/ha on Protor wheat appeared sufficient largely to prevent pollen shed when applied at early or late boot. Testcrosses at the 9 kg/ha rate indicated no noticeable adverse effect on female fertility. Seed set on Noble oats was not totally prevented at any rate although 27 kg/ha reduced seed set to less than 10% of the control when applied at early heading or in a split application at early boot plus early heading. In one experiment phytotoxicity was observed on Noble oats at the 18 and 27 kg/ha rates, but 18 kg/ha did not affect this cultivar in a second experiment.

A field experiment revealed genotypic differences in chemical response. Plant height and pollen shed of wheat cultivars were generally reduced more than in oat cultivars. DPX 3778 delayed anther exsertion and floret opening. A sufficient number of wheat cultivars exhibited adequate pollen control to suggest that DPX 3778 may be of potential use in a wheat breeding program.
Leaf and Bract Trichome Density and Boll‐type Influence on Cotton Lint Grade Index1
Authors: Wanjura D. F. , Baker R. V. , Ray L. L.
Published: July 2010

Little quantitative information is available that relates physical cotton (Gossypium hirsutum L.) plant characteristics to lint grade for stripper harvested cultivars. In a 4‐year study, the effect of varying levels of leaf and bract pubescence and degrees of boll compactness on lint grade index of hand‐harvested seedcotton and burcotton were investigated. Leaf and bract trash, mechanically mixed in raw cotton after harvest, did not adhere to raw lint as tightly as trash incorporated by natural field weathering. Variations in growing season had more effect on lint grade index than specific plant characteristics. However, the following plant character effects were observed: (a) Increasing levels of blade trichome density (BTD) in leaves and bracts reduced lint grade index, (b) Maximum bur diameter was positively correlated with boll fluffiness index (BFI), (c) BFI was inversely related to grade index for lint obtained from burcotton. (d) Bur strength did not affect lint grade index. The results indicate that the bract attached to the bur is responsible for burcotton having lower lint grade indices than seedcotton.
Relation of Flag Smut Incidence to Spike Type in Wheat Isolines1
Authors: Allan R. E. , Pritchett J. A.
Published: July 2010

Incidence of flag smut [Urocystis agropyri (Preuss) Schroet.] was indirectly related to the club spike trait in F6 and F7 isolines of the population ‘Suwon 92’/8* ‘Omar’ (Triticum aestivum L. em Thell.). Paired comparisons between isolines showed that the club types averaged 3.0 and 12.2% more smut than lax types at two different field sites in 1971. The club sib was equal to or more heavily smutted than the lax sib in 31 of the 40 comparisons. The club lines averaged 10.5% more smut than their lax sibs in a replicated test in 1973. The relationship between the C allele and increased severity of flag smut appeared to be indirect, since no linkage or pleiotropism was detected between the two characteristics from observations on two crosses. In addition, percentage of flag smut was not significantly different between the two spike types at one site. The C allele reduces rates of seedling growth and emergence, and delayed emergence may increase the opportunity for the wheat seedling to become infected by the pathogen. Club genotypes can potentially suffer greater losses from flag smut than lax genotypes. In the development of club cultivars, breeders should especially emphasize high, stable flag smut resistance.
Effects of Emasculation on Boll Set in Three Stocks of Cultivated Gossypium1
Authors: Brown William , Lee J. A.
Published: July 2010

Flowers of two stocks of Gossypium barbadense L., AS‐2 Sea Island and Pima S‐4,' and one of G. hirsutum L., ‘Carolina Queen,’ were emasculated using two procedures: i) anthers were plucked away through a slit in the corolla, and ii) the corolla and the anthers were stripped away with an emasculating device. After hand pollination percent fruit set was recorded.

Fruit set of Carolina Queen and Pima S‐4 did not differ significantly between treatments and selfed controls. Removal of the corolla significantly reduced fruit set in AS‐2. The average number of seeds per boll did not differ among treatments for any entry.

A drop of gibberellic acid solution, 100 ppm aqueous, applied at the base of the androecium the day before anthesis increased fruit set in AS‐2 after drastic emasculation.
Ultrastructural Characterization of the Storage Organs of Zoysia and Bermudagrass1
Authors: Rogers R. A. , Dunn J. H. , Brown M. F.
Published: July 2010

Limited information exists concerning the ultrastructural characterization of storage organs of grasses including Zoysia japonica Steud and Cynodon dactylon L. The present study was undertaken to apply scanning electron microscopy in order to show differences in tissue components of rhizomes and stolons of these species which might be related to inherent low temperature tolerance. The epidermis, in all cases, contained cutinized cells which were covered by a heavily cuticularized surface layer. A sclerenchyma sheath consisting of thick‐walled, sclerified cells, five to seven cell layers thick, divided storage organs into a pith and cortex. The number of cortical cell layers separating the sheath from epidermis varied between species. A bundle sheath surrounded the vascular bundles which were located interior to the sclerenchyma sheath in both species. Cellular areas of the cortex and pith, excluding the sclerenchyma sheath, contained parenchyma cells whose main function appears to be starch storage. Cells interior to the sheath, mostly pith, stored larger quantities of starch than those exterior to the sheath. There were no major structural differences of cells between several cultivars studied or between species which would account for differences in cold hardiness. However, the heavily cuticularized epidermal surface, the thick‐walled epidermal cells, and the sclerenchyma sheath may play an important role in drought tolerance as well as thatch accumulation associated with both species.
Genetics of Vein and Stomatal Characters in Bromus inermis Leyss.1
Authors: Tan Geok‐Yong , Tan Wai‐Koon , Walton P. D.
Published: July 2010

A half‐diallel involving seven parental clones of smooth bromegrass (Bromus inermis Leyss.) was used to elucidate the genetic variation of 14 characters, including width, vein number, vein frequency, interveinal distance, stomatal length, stomatal frequency, and the product of stomatal length and frequency for both leaf and sheath, Combining ability analyses showed that general combining ability (GCA) and specific combining ability (SCA) mean square values were significant, with the exception of the GCA mean square values for leaf vein frequency and interveinal distance. The preponderance of additive gene effects was evident from the variance components for vein number on both leaf and sheath, and leaf stomatal characters. High narrow‐sense heritabilities were estimated for these characters. Phenotypic and genotypic correlation coefficients indicated no association between leaf dimension and leaf vein frequency and interveinal distance. Plants with large leaf area, wide leaves, or high specific leaf weight tended to have high vein number, large stomatal size and low stomatal frequency. Selection for high vein frequency and narrow interveinal distance may increase forage yield of both the first harvest and the regrowth. Selection for small stomata on leaf and sheath, and high stomatal frequency on sheath, should improve forage yield of the first harvest.
Genetic Control of Protein From Avena sterilis L.1
Authors: Iwig M. M. , Ohm H. W.
Published: July 2010

The purpose of this investigation was to determine the genetic control for high percent groat protein from Avena sterilis L. in agronomically acceptable lines selected from crosses of A. sativa L. ✕ A. sterilis. Six agronomically acceptable lines with the same source of high protein (CI 8320) were crossed in a diallel system (Experiment 1). Also, a high protein selection which has fair agronomic performance but is not competitive as a commercial variety, was crossed to 16 A. sativa cultivars and advanced breeding lines (Experiment 2). Genetic effects and regression coefficients for F1 and F2 cross means on their respective midparent values for seed yield and percent groat protein were estimated in both experiments. In Experiment 1, general combining ability predominated for percent groat protein in the F1 generation. Low percent groat protein was partially dominant. In Experiment 2. F1's generally produced a slightly lower percent groat protein than the midparent value and averaged 37.2% heterosis for seed yield. Heterosis for seed yield was greatly reduced in the F2, but percent groat protein was slightly higher than for F1's. High percent groat protein tended to be recessive in 15 of the 16 crosses. Regression coefficients for F1 and F2 cross means on their respective midparent values for percent groat protein in the two experiments ranged from 0.507 to 1.352. Intermating adapted, high‐yielding, homozygous lines with intermediate levels of protein for one or more cycles may be useful in concentrating alleles for high protein in commercial cultivars.
Temperatures in Early Post‐Transplant Growth: Influence on Carbohydrate and Nitrogen Utilization and Distribution in Tobacco1
Authors: Raper C. David , Weeks W. W. , Wann Mien
Published: July 2010

Tobacco plants (Nicotiana tabacum L. ‘NC 2326’) were grown in the North Carolina State Univ. phytotron unit of Southeastern Plant Environment Laboratory to examine the effects of ambient temperature on relative growth rates (RGR) of whole plants, leaves, stalks, and roots and their relative accumulation rates (RAR) soluble carbohydrates and N. RAR is calculated to be analogous to RGR and is expressed in units of weight of the component accumulated per weight if its content in the plant per day. Plants were grown under a 9‐hour photoperiod with photosynthetically active radiance of 750 einsteins‐m−2sec−1 in separate controlled‐environment rooms programmed for thermoperiods (day/night temperatures) of 18/14, 22/18, 26/22, 30/26, and 34/80 C. Plants were sampled from each thermoperiod on Mondays, Wednesdays, and Fridays, for 6 weeks after tramplanting. RGR and RAR were calculated only for the period of exponential growth which occurred within the interval from 7 to 35 days after transplanting. In general, RGR of the whole plant, leaves, stalks, and roots (RGRP, RGRL, RGRS, RGRR) were unaffected by the three intermediate thermoperiods. However, RGRP and RGRL declined at both 18/14 and 34/30 C but RGRS and RGRR declined only at 34/30 C. At all thermoperiods RGRS were greater than RGRP and RGRR were less than RGRP. RAR of N for the whole plant (RARNP) were less than RGRP but were equal to RGRR. The association of RARNP and RGRR apparently is related to RAR of soluble carbohydrates in the roots (RARSR). RARSR were equal to RGRR; thus, small (5 to 7% of dry weight) but constant pools of soluble carbohydrate were maintained in roots. Conversely, RARSP were greater than RGRP which resulted in a 40% increase in soluble carbohydrates in the whole plant during the growth period. It is proposed that both absorption of NO3‐ by roots and growth of roots are concurrently and competitively influenced by rate of flow of photosynthate to the roots.
Influence of Indeterminate Growth Habit on Yield and Irrigation Water‐use Efficiency in Upland Cotton1
Authors: Quisenberry J. E. , Roark Bruce
Published: July 2010

Based on their growth habit, 12 cultivars of upland cotton (Gossypium hirsutum L.) were placed in four groups designated as 1) High Plains‐determinate, 2) High Plains.moderately determinate, 3) High Plains‐indeterminate, and 4) non High Plains‐indeterminate. These cultivar groups were grown at three moisture levels at Lubbock, Texas, and evaluated for their degree of indeterminate growth habit, earliness of crop maturity, lint yield, and irrigation water‐use efficiency. The purpose of our study was to determine the relationships between indeterminacy, lint yield, and irrigation water‐use efficiency.

The indeterminate groups of cultivars had higher lint yields at all moisture levels than did the determinate groups. Irrigation water‐use efficiency of all cultivars was higher at the intermediate moisture level (preplant irrigation) than at the higher moisture level (full irrigation). At the intermediate moisture level, the indeterminate cu]tivars had a higher irrigation water‐use efficiency than did the determinate cultivars. The determinate cultivars had a higher irrigation water‐use efficiency than the indeterminate cultivars at the higher moisture level. Correlation analyses between individual cultivar indeterminacy values and lint yield and irrigation wateruse efficiency suggested that a cotton cultivar with a relatively inteterminate growth habit is better adapted in an environment with seasonally limited soil moisture than a cotton cultivar with a relatively determinate growth habit.
Effects of Yield Component Selection on the General Combining Ability of Maize Inbred Lines1
Authors: Geadelmann J. L , Peterson R. H.
Published: July 2010

This experiment had two objectives: 1) to evaluate changes induced in six inbred lines of maize (Zea mays L.) by backcross breeding for increased yield component expression, and 2) to determine effects of such yield component selection on general combining ability (GCA) the inbreds. Within separate programs, non‐recurrent sources of ears per plant, ear length, and kernel depth were crossed to each inbred. Two or three generations of backcrossing to the recurrent inbreds followed by four or five generations of selling were used to derive 143 modified versions of the original inbreds. The 143 modified lines were developed from the 18 inbred‐component combinations. In tests of lines per se in one environment, modified lines averaged higher in selected yield component expression than the original inbred in each of the inbred‐component combinations. GCA of the original and modified lines was evaluated by testing their topcrosses to the synthetic variety AS‐A in two environments. Average GCA for grain yield for sets of lines modified for ears per plant, ear length, and kernel depth exceeded the original inbreds by 10, 5, and 0%, respectively. Selection for yield components had little effect on ear moisture and broken stalks. Response to selection varied among the six inbreds. Inbreds with relatively low expression of a given yield component tended to show greater response to selection than did those with higher expression. Adaptation of the yield component source may have influenced results from the yield component selection programs.
Simulation of the Backcross Breeding Method. I. Effects of Heritability and Gene Number on Fixation of Desired Alleles1
Authors: Reddy Belum V. S. , Comstock Ralph E.
Published: July 2010

The potential of backcross breeding for improvement of a pure line by addition of favorable alleles from a donor line was investigated by computer simulation coupled with quantitative genetics theory. Attention was focused on the effects of heritability (among individual F2 plants) and of the number of genes of which the allele present in the donor line is more favorable than the one present in the recipient. The specific programs investigated were ones involving a large amount of effort, a minimum of 1,000 pollinations per backcross generation and selection among families in three or more generations. The criterion employed for effectiveness was the probability of fixation in the product of the program of favorable alleles derived from the donor line. Effectiveness was found to be greater when heritability is greater but the effect of increased heritability was not as great as might have been expected. Number of favorable alleles available frcm the donor line had greater impact, particularly when success was defined in terms of probability that all the available favorable alleles would be transferred from donor to recipient. Success, so defined, was limited to one allele in the case of the least laborious of the three programs studied and no more than five in the case of the most costly. On the other hand, when success was measured in terms of percent improvement in the selected trait, it appeared substantial change is possible with heritability as low as 15 percent and favorable alleles available in the range frcm 1 to 16. dditive effects and independent assortment were assumed for genes simulated.
Evidence of Inheritance of Resistance to the Mexican Bean Beetle in Soybeans1
Authors: Sisson V. A. , Miller P. A. , Campbell W. V. , Van Duyn J. W.
Published: July 2010

The inheritance of resistance to the Mexican bean beetle, (Epilachna varivestis Mulsant), in soybeans, (Glycine max L. Merr.), was evaluated using F3 populations. Four populations were obtained by crossing resistant plant introductions to susceptible commercial cultivars. Ratings of percent foliar damage were made on F3 progeny rows containing 25 plants. Progeny rows were replicated two to four times depending on seed availability. Parental lines were also grown for comparison. Population means were recorded and estimates of genotypic, environmental, and phenotypic variances computed. Broad sense heritability estimates were calculated for each population. Significant genetic variance occurred in all populations. The results suggest a quantitative inheritance of resistance in soybeans. Percent foliar damage approximated a normal distribution in the F3 populations exposed to a moderate to heavy MBB infestation. Population means of the F3 progeny were not significantly different from their mid‐parent values, alluding to a primarily additive gene action. Several F3 progeny rows with levels of resistance equal to the mean of the resistant parent were observed. Involvement of only two or three major genes is suggested from our observations, although the exact number of genes controlling resistance could not be determined. Broad sense heritabilities ranged from 44% to 81% under the conditions of this investigation.
Control and Inheritance of Prolificacy in Maize1
Authors: Harris R. E. , Moll R. H. , Stuber C. W.
Published: July 2010

The effects of various treatments (removal of first ears at intervals from silking, pollination control of first and second basipetal ear shoots, and hormone injections) on ear development were studied in prolific (two‐eared), semi‐prolific, and non‐prolific single crosses of Zea mays L. Prolificacy factors were examined in certain hybrids, their component inbred lines, and derived F2 and backcross populations using a generation means analysis. Comparisons within and among single crosses revealed that prolific plants produced significantly more grain than non‐prolific plants. Availability of only one energy sink apparently placed a ceiling on the yield of non‐prolific plants. Based on dates of silk emergence, the abortion of second ear shoots in semi‐prolific hybrids and third ear shoots in prolific hybrids appeared to be conditional upon their lack of silking synchronization with the nearest upper ear shoot. If the silking interval was long enough, the first ear shoot of semi‐prolific genotypes showed apical dominance over the second ear shoot, and the second ear shoot of prolific genotypes showed apical dominance over the third ear shoot. Genotypic responses to ear removal indicated that abortive lower silking ear shoots began to irreversibly deteriorate a few days after their successful fertilization. Prolificacy factors in F2 and backcross populations segregated in a manner predictable from the distribution of silking intervals and the penetrance and genetic segregation inferred from parental lines and single crosses. Strong prolific potential was apparently due to a recessive genetic condition. Goodness of fit tests and genotypic responses to pollination manipulation provided no evidence for rejecting a postulated model of qualitative inheritance in which the development of nonsynchronous lower ear shoots is repressed by a diffusible plant hormone that is released from the upper ear shoots before and during anthesis. Injections of the synthetic auxin IBA into the second ear shoot of prolific hybrids at silking time caused extreme kernel abortion and poor cob development in second ears.
Effects of Nitrogen Application on Yield, Plant Characters, and N Levels in Grain of Six Spring Wheat Cultivars1
Authors: Nass H. G. , MacLeod J. A. , Suzuki Michio
Published: July 2010

A 3‐year study on the effects of rate and time of N application on six cultivars of spring wheat (Triticum aestivum L.) indicated that grain yield, plant characters, and N levels in grain can be modified by N application. Maximum grain yield was achieved at 67.5 kg N/ha (67.5 N) or 90 kg N/ha (90 N). The grain yields of ‘Selkirk’, ‘Streng’, and ‘Kolibri’ increased with increasing rates of N from 45 kg N/ha (45 N) to 90 N; while the yields of the high yielding cultivars, 'Ankra' and ‘Opal’, were not significantly higher at 90 N than at 67.5 N. ‘Reward’, the lowest yielding cultivar, failed to respond to increased rates of N as measured by grain yield. Numbers of spikes/m2 increased, but kernels/spike and kernel weight did not increase with increasing rates of N. Photosynthetic area, as measured by spike extrusion, spike area, and flag leaf area and kernel N yield, increased significantly at 90 N. Compared to 90 N at seeding, there was no significant benefit in grain yield or related characters including kernel N yield when application of 90 N was split between seeding and stem elongation.
Estimates of Combining Ability and Heterosis in Converted Exotic Sorghums1
Authors: Laosuwan Paisan , Atkins R. E.
Published: July 2010

The agronomic performance and breeding behavior of 11 restorer lines (R‐lines) derived from sorghum (Sorghum bicolor L. Moench) conversion program materials were evaluated in four environments in Iowa. Data for grain yield and the primary components of yield were obtained from single crosses and three‐way hybrids involving the R‐lines as male parents.

For both types of hybrids, general combining ability (g.c.a.) effects of the R‐lines accounted for the largest portion of the variation expressed for grain yield, heads/plant, 100‐seed weight, and seeds/head. Significant tfcts for g.c.a. (females) were expressed for all characters in the single crosses, but this effect was significant only for seeds/head in the three‐way hybrids. Variation attributable to specific combining ability (s.c.a.) effects provided the smallest contribution to the inheritance of all traits in both types of hybrids.

Heterosis for grain yield was greater than that for any of the components of yield. Mean heterosis and hetcrobeltiosis for yield in the single crosses averaged 49 and 37%. In average performance with all females, the single crosses with 10 of the 11 R‐lines exceeded the mean yield of the check hybrid ‘RS 610’.
Pod Yield Component Variation and Intercorrelation in Phaseolus vulgaris L. as Affected by Planting Density1
Authors: Bennett J. P. , Adams M. W. , Burga C.
Published: July 2010

It is often observed in dry beans (Phaseolus vulgaris L.) that the number of pods per plant is the most sensitive yield component under high planting densities. Our objectives in this study were to determine the components of pod formation that are most sensitive to density and to examine the relationships among the components. Seven varieties were grown at effective densities of 17, 21, 34, and 63 plants/m2 and analyzed at maturity for branching, number of racemes, pods, and nodes. Pods per plant were partitioned into pods per raceme (P), racemes per node (R), nodes per branch (N) and branches per plant (B). Only R and B were significantly reduced by higher planting density. Although both these components are positively correlated with pods per plant, they are negatively correlated with each other. We conclude that a bean ideotype for temperate zone monoculture should have a high number of nodes per branch and three to five branches per plant.
Oviposition and Larval Survival of the Clover Head Weevil on Crimson Clover1
Authors: Smith C. M. , Knight W. E. , Frazier J. L.
Published: July 2010

Seed damage caused by the clover head weevil (Hypera meles F.) on crimson clover (Trifolium incarnatum L.) limits the utilization of this forage species. In laboratory studies weevil oviposition was greater in the second basal internode of clover stems than in any other internode. Of eight crimson clover inbred lines and five cultivars tested in the field for larval seed feeding damage, one inbred line showed decreased larval survival and decreased seed damage. An estimate of actual seed damage was obtained from five seed head samples harvested from each of 40 plants. Numbers of seeds damaged by larval calyx boring were positively correlated (P<0.05) with seed damage estimates based on numbers of pupae per seed head for the cultivars ‘Chief’ (r=0.65) and ‘Tibbee’ (r=0.61), but estimates were attained in approximately onesixth the time required to visually count bored seed. Estimating seed damage in this manner will greatly increase the amount of germplasm which can be evaluated for weevil resistance.
Germination and Growth Response of Seed Weight Genotypes of Panicum antidotale Retz.1
Authors: Wright L. Neal
Published: July 2010

Seed of blue panicgrass (Panicum antidotale Retz.) genotypes previously selected for extremes of seed weight were evaluated for growth responses. Depletion of seed food reserves, elongation of roots and shoots, and production of dry matter were measured during four phases of development: emergence; and initial, seedling, and young plant growth. Growth was sampled in three environmental procedures at varying intervals to 54 days. After initiation of growth, the germinating seedlings used most of the reserves by the sixth day, with the same pattern and rate for both heavy and light seed genotypes. Thus, the major function of seed reserves was evident during the first 6 days of germination and seedling growth. Use of remaining reserves was extended over time, and their contribution to the growth of the young plant was apparently complementary to photosynthesis. Any single measurement—weight of residual seed, weight of seedling parts, elongation of roots, or elongation of shoots—provided an accurate estimate of growth response with either nutrient solution or soil medium. Genotypes with heavy seed, having a greater quantity of endosperm and associated genetic qualities, performed better during all phases of growth from germination through reproduction than did genotypes with light seed.
Utilization of Nitrogen to Sulfur Ratio for Evaluating Sulfur‐Containing Amino Acid Concentrations in Seed of Glycine max and G. soja1
Authors: Radford R. L. , Chavengsaksongkram C. , Hymowitz T.
Published: July 2010

A screening procedure using the ratio of total N to total S (N/S) was developed for indexing methionine and cystine concentrations in seed of soybeans—Glycine max (L.) Merrill—and its putative ancestor G. soja Sieb. and Zucc. Percent N was determined by the standard micro‐Kjeldahl procedure. Total S was analyzed by reducing SO4‐S (from nitric acid‐perchloric acid digestion) to H2S and then percent S was determined by titration with HgCl2 using dithizone as an indicator.

The N/S values found in the soybean genetic type collection ranged from 24.5 to 15.4 with the mean being 18.3. The N/S values found in plant introductions of G. max that were formerly known as G. gracilis Skvortz. ranged from 20.1 to 16.3 with the mean being 18.4. The N/S values found in plant introductions of G. soja ranged from 21.5 to 12.5 with the mean being 17.5.

Results from a 2‐year investigation on the effect of growing seasons on the N/S ratios in seed revealed that the N/S ratios were quite stable from year to year in G. max and somewhat less stable in G. gracilis and G. soja. Attempts to identify the source of variation indicated that the variation in N/S values in seed of G. gracilis and G. soja largely were due to N content.

The reasonably high correlation coefficients between mg of methionine and cystine with percent S (r = 0.846) and g methionine and cystine/16 g N with N/S ratios (r = 0.787) suggest that rapid screening for N and S Glycine germplasm would be helpful in directing investigators to lines that warranted further study.
Fall Dormancy of Five F1Medicago sativa L. Populations, Two Reciprocal F1 Populations, and Respective Parents1
Authors: Knipe W. J. , Stockton L. M.
Published: July 2010

When crossing alfalfa (Medicago sativa L.) possessing different favorable agronomic traits but different fall dormancies it would be desirable to accurately predict the relative fall dormancy of the F1. This requires knowledge of inheritance of fall dormancy.

Five dormant cultivars were crossed to one of two nondormant cultivars and the seven parent populations were intracrossed. Reciprocal crosses were made in two cases. One hundred plants from each intracross and intercross were spaced planted into the field and growth of each plant was measured in late August, October, and December. Plant growth was used to estimate dormancy response.

Most F1 populations closely resembled their respective midparent values; however, some did not. When these deviations occurred, non‐dormant growth habit appeared dominant in some crosses and recessive in others. These F1 deviations from the midparent were not consistent across dates. Reciprocal effects were significant on some dates but were also not consistent.
Cottonseed Germination Related to DNA Synthesis Following Chilling Stress1
Authors: Clay Willard F. , Buxton D. R. , Katterman Frank R. H.
Published: July 2010

Identification of cotton (Gossypium spp.) seed lots that establish uniform stands has been inconsistent with the standard germination test, especially when soil temperatures are low. To aid in developing better predictive tests, critical biological processes associated with seed germination at low temperatures need to be better understood. This study was conducted to evaluate the relationship between DNA synthesis and seed performance. Pima cottonseed (G. borbadense L.) lots were evaluated during 3 years of experimentation for field emergence, germination percentage at both 15 and 25 C, and capacity to synthesize DNA during germination following a chilling stress. DNA synthesis was positively correlated with seed germination percentage at both temperatures, with the closest association occurring at 15 C when a large number of seed lots were evaluated. The DNA test was more consistently correlated with field emergence than percent germination. These results show that capacity to synthesize DNA following chilling is an important process associated with seed germination and emergence during low soil temperatures.
Effect of Ammonium and Nitrate Nitrogen upon Photosynthate Supply and Nitrogen Fixation by Soybeans1
Authors: Latimore Mark , Giddens Joel , Ashley D. A.
Published: July 2010

The N required by soybeans [Glycine max L.) Merr.] is furnished by soil and by symbiotically fixed N. The latter is associated with available photosynthate. A determinate soybean cultivar, ‘Bragg’, was grown in sand in the greenhouse in 1974 and outdoors in 1975 to further evaluate the effect of growth stages and NH4+‐N and NO3‐‐N on 14C translocation, N fixation as measured by acetylene reduction by intact nodules, and accumulation of dry matter and nitrogen.

Plants exported very little 14C to the nodules from photosynthesis of 14CO2, and acetylene reduction was very low when significant sink demand by pods became evident. Inorganic N supplied throughout the season or 10 days prior to sampling reduced 14C in nodules and acetylene reduction by nodules. NO3‐‐N generally decreased acetylene reduction more than NH4+‐N. 14C transport to plant parts other than nodules was not influenced by inorganic N. There is indication that in the determinate cultivar of soybeans used, more photosynthate was transferred to nodules during the vegetative and early reproductive stages than that reported previously for indeterminate cultivars. The data further emphasize the high demand for N at the pod‐fill stage where 333 mg N per plant (23% of total) was required during a 20‐day period, mid‐pod to late pod fill stage, and at the same time N fixation was declining.
Selection for Lower Ear Placement in Two Synthetic Populations of Maize1
Authors: Josephson L. M. , Kincer H. C.
Published: July 2010

Selection for lower ear placement in corn (Zea mays L.) was done to obtain synthetics with a high plant to ear height ratio, to maintain maturities at or near the original materials, and to obtain additional information on whether selection for lower ear placement would reduce the number and length of internodes below the ear. An early and a late flowering synthetic was selected for lower ear placement by sib‐mating over a 10‐generation period; then the 10 cycles were compared in performance trials. Ear height was reduced from 67 to 41 cm in 10 cycles of selection in the early synthetic, or an average decrease of 4.3% per cycle. In the late synthetic, the reduction was from 69 to 51 cm, or an average decrease of 2.9% per cycle. Plant heights remained fairly constant in both synthetics. Plant to ear height ratios increased from 2.7 to 4.2 in the early synthetic and from 2.7 to 3.7 in the late synthetic. In both synthetics one less leaf was produced below the ear and one leaf added above the ear, while the total number of leaves remained fairly constant. Average internode lengths below the ear were reduced from 10.1 to 7.3 cm in the early synthetic and from 9.0 to 7.7 cm in the late synthetic after 10 generations. The effect of selection for lower ears was therefore shorter internodes and the ears being borne at a lower node. There was no change in number of days to silking in the early synthetic but there was a 2‐day delay in the late synthetic. Slightly higher grain moistures were obtained in the later cycles of both synthetics. Grain yield decreased in successive cycles of selection with correlations of 0.97 and .87 (both significant at the 0.01 level) between ear height and yield in the early and late synthetics, respectively. Stalk lodging was generally reduced as ear height was lowered but correlations were not significant. Uses of the synthetics in breeding programs are discussed.