bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Testcrosses Produced from F2 and First Backcross Populations in Maize
Authors: Melchinger A. E. , Schmidt W. , Geiger H. H.
Published: July 2010

Single crosses and backcrosses from established lines are importeat parental sources for developing new inbred lines in hybrid maize (Zea mays L.) breeding. The objectives of this study were (i) compare, both theoretically and experimentally, the testcross properties of F2 vs. first backcross populations; and (ii) to outline criteria for choosing between these two types of base populations in recycling breeding programs. Two homozygous lines (P1, P2) and individual plants from their F2 and first backcross (BC1, BC2) generations were mated to an unrelated single‐cross tester. A total of 186 testcross progenies were evaluated for grain and forage traits at three and two locations, respectively. The five generations (P1, P2, F2, BC1, BC2) differed significantly (P < 0.05) in their testcross means (X̄) for grain (GY) and forage (FY) yield. A nonepistatic model accounted for 92 to 99% of the variation among testcross generation means for five of the six traits examined, yet the presence of epistasis was indicated in several instances. In accordance with theory, the ratio of BC (the pooled estimate of BC1 and BC2) to F2 genotypic variance among testcross progenies (σ2g) was close to 0.50 for all traits but one. Heterogeneous σ2g estimates in BC1 and BC2 were found for GY, FY, and grain dry matter content, suggesting the presence of epistasis. Predicted selection response for testcross performance (ΔG) was greatest in the F2. Testcross progenies of the F2, BC1, and BC2 generations displayed similar phenotypic and genotypic correlations as expected by theory. The “usefulness” criterion U = x̄ + ΔG was employed to assess the breeding prospects of each generation. With weak selection, the better backcross had superior usefulness for four traits, whereas with strong selection the F2 had highest usefulness for all traits except GY.
Forage Quality Characterization of a Chemically Induced Brown‐Midrib Mutant in Pearl Millet
Authors: Cherney J. H. , Axtell J. D. , Hassen M. M. , Anliker K. S.
Published: July 2010

Based on the negative relationship between lignin and digestibility, one of the most effective means of increasing forage digestibility is by reducing lignin content. Our objective was to chemically induce a brown‐midrib (bmr) mutation in pearl millet, Pennisetum americanum (L.) Leeke, and evaluate the resulting mutants for lignin content and similarity to existing bmr mutants in other species. Seeds from two inbred pearl millet lines derived from Tift 23D2B1/2 ✕ PI 185642 were treated with either ethyl methyl sulfonate or diethyl sulfate, planted, and selfed in 1984. In 1985 a single plant in one head row exhibited a brown‐midrib phenotype, and was selfed. The bmr pearl millet was compared to selfed normal plants from the same head row along with bmr and normal sorghum, Sorghum bicolor (L.) Moench., and maize, Zea mays L., in 1986 at two locations. Plants were harvested at anthesis and analyzed for apparent in vitro dry matter digestibility (IVDMD), permanganate lignin, alkali‐labile phenolics, and other quality parameters. Lignin concentration in bmr pearl millet was 40 g kg−1 compared to 50 g kg−1 for its normal counterpart, and IVDMD was 726 g kg−1 for the bmr genotype compared to 659 g kg−1 for the normal genotype. The differences in phenolic monomer concentrations between normal and bmr pearl millet were more like those in sorghum than maize. Based on IVDMD, lignin and phenolic monomer analyses, we concluded that bmr pearl millet was similar phenotypically to bmr mutants in sorghum. This trait has excellent potential for improving the quality of forage pearl millet.
Genetic of Fertility Restoration of ‘WA’ Type Cytoplasmic Male Sterility in Rice
Authors: Raj K. Govinda , Virmani S. S.
Published: July 2010

Information on the genetics of fertility restoration in a cytoplasmic male sterility (CMS) system facilitates breeding and/or selection of restorer lines used in hybrid breeding programs involving CMS. Inheritance of fertility restoration of ‘WA’ type CMS in rice, (Oryza saliva L.) was studied utilizing two CMS lines in combination with five restorers. Each cross was used to develop a set of materials consisting of the following generations; parent lines (A, B, and R lines); (A/R) F1; (A/F1) BC1; (F1/B) BC2; and (A/R) F2. These materials were grown in the field setwise during 1985 to 1986. Results indicated that fertility restoration in all the restorers studied (‘IR26’, ‘IR36’, ‘IR54’, ‘IR9761‐19‐1’ and ‘IR2797‐105‐2‐2‐3’) was governed by two independent and dominant genes, and one of the genes appeared to be stronger in action than the other. The mode of action of the two genes varied in different CMS/restorer combinations revealing three types of interaction: epistasis with dominance (F2 ration, 12 fertile:3 partially fertile/partially sterile:1 sterile); epistasis with recessive gene action (F2 ratio, 9:3:4); or epistasis with incomplete dominance (F2 ratio, 9:6:1). The mode of interaction of the genes of a restorer differed with the CMS line used. An allelism test involving six R lines revealed that IR26 and IR36, and IR54 and IR9761‐19‐1 possessed identical restorer genes; ‘IR42’ and IR2797‐ 105‐2‐2‐3 had different restorer genes. Four groups of restorers with different pairs of restorer genes were identified. Testcross observations involving parental lines in the pedigree of IR36 and IR42 revealed that ‘Cina’, ‘Latisail’, ‘Tadukan’, ‘TN1’, ‘TKM 6’ and (two accessions) ‘PTB 18’ and ‘SLO 17’ are the probable original sources of R genes in the two restorer lines.
Indeterminate Flowering and Reproductive Success in Birdsfoot Trefoil
Authors: Beuselinck P. R. , McGraw R. L.
Published: July 2010

Seed production of broadleaved birdsfoot trefoil, Lotus corniculatus L., is critical in southern latitudes to ensure the long‐term persistence of stands. Reproductive success of umbels produced early through late season was compared in a field test of 30 F1 genotypes grown on a Mexico silt loam (fine, montmorillonitic, mesic Udollic Ochraqualf) near Columbia, MO in 1984 and 1985. The F1 genotypes represented the progenies of three crosses among parental genotypes of PI 302921, ‘Norcen’, and ‘MO‐20’. All genotypes with 10 umbels, each with five flowers, were tagged at weekly intervals between 23 May and 5 July in 1984 and 1985, then harvested at pod maturity. Data were collected on number of pods produced per 10 umbels, number of viable seed per pod, mass of 100 seed, and number of days from tagging to pod maturity. Umbels produced at the early tagging dates produced more pods (P < 0.01), more seed per pod (P < 0.01), and had a greater 100‐seed mass (P < 0.01) than umbels produced at later dates. The responses noted appeared to be temperature related. Stand persistence is dependent on natural reseeding producing vigorous and competitive progeny. Management of stands to allow seed production from the early initiated flowers will promote better seed production and higher quality seed. The selection and development of populations with a shorter photoperiod requirement is indicated for growing areas below 40° N Lat to improve the initiation and development of flowers earlier in the season when seed production is better.
A Probability Method for Comparing Varieties against Checks
Authors: Jones T. A.
Published: July 2010

Combining results of tests conducted over a period of years is desirable when the tests are conducted at a single location or across locations known not to exhibit large nonrandom, predictable genotype ✕ location interactions. But when cumulative reports across tests are attempted, complications arise because of unbalanced structure. The objective of this work was to derive a method to compare varieties against checks using accumulated data in the usual situation, where varieties are changing over the years the accumulated tests are conducted. The resultant probability method is easy to use, easy to present in an extension publication, and easy to interpret by the extension audience. It tests the null hypothesis that a variety equals a check in performance and permits calculation of the probability that the variety equals a check in performance when the null hypothesis is rejected (type 1 error). Calculations are simplified data are coded and standardized for each test year. The method was used on an unbalanced data set yield of 23 varieties and 35 test years of alfalfa (Medicago sativa L.) grown near Ames, IA. Probability of one‐tailed Type I error anged from 0.47 to near 0.00 when data were coded on a test‐year mean basis, and from 0.86 to near 0.00 when data were coded on the basis of the mean of ‘Saranac’ and ‘Vernal’. The probability method determined that no more than seven test years were necessary to evaluate these varieties.
Influence of Phosphorus Nutrition on Phosphorus and Nitrogen Utilization Efficiencies and Associated Physiological Responses in Soybean
Authors: Israel D. W. , Rufty T. W.
Published: July 2010

Since nutrient concentrations in plant tissues are diluted by growth when the supplies in the root zone are limited, it has been difficult to evaluate the effects of nutrient stress on the efficiency of nutrient utilization in dry matter production by plants. Therefore, this study was initiated to apply the nutrient utilization efficiency concept, (whole plant biomass)/(whole plant nutrient concentration), in evaluating the effect of variable P supply on the utilization of P and N in dry matter production by soybean [Glyclne max (L) Merr.] plants and to assess physiological responses associated with changes in nutrient utilization efficiency. Soybean plants inoculated with Bradyrhizobium japonicum USDA 110 were grown in outdoor pot culture and supplied daily with either minus N or 20 mM NO−3 solutions containing 0 to 2.0 mM KH2PO4. Phosphorus utilization efficiencies and biomass accumulation for plants in both N regimes increased with increased P supply up to external concentrations of 0.25 to 0.50 raM. At the external P concentrations > 0.50 raM, P utilization efficiencies declined as P concentrations in the tissue increased without any additional growth. Maximal N utilization efficiencies in both N regimes were also attained at external P concentrations of 0.25 to 0.50 raM; however, they did not decrease at higher external P concentrations. Increases in P and N utilization efficiencies were associated with (i) increases in whole plant leaf areas and leaf area ratio, (ii) decreases in morning starch concentrations in leaves, (iii) increases in the relative proportions of dry matter, P, and N in shoot tissues, (iv) decreases in concentrations of soluble reduced‐N in tissues of NO−3‐assimilating plants, and (v) increases in concentrations of soluble reduced‐N in tissues of N2‐fixing plants.
Husk Removal and Its Effects on Maize Grain Yield
Authors: Salvador D. W. , Pearce R. Brent.
Published: July 2010

The role of husks in maize (Zea mays L.) grain development is unclear. Field experiments were conducted in 1984 and 1985 to determine the effect of husk removal on grain yield and yield components. Treatments consisted of a control, an intact ear covered with a paper bag, and ears with the husks peeled down and left down, husks removed entirely from the ear and shank, husks removed from the ear only, and husks peeled down and immediately replaced around the ear. The treatments were imposed at 15 d after pollination and all ears on which husks were manipulated were covered with paper bags for protection. All treatments involving husk manipulation resulted in decreased grain yields; the average decrease was 14.3%. Treatments in which husks remained on the ear after peeling decreased yield less (8.6%) than did those in which husks were removed entirely (17.7%). Among the husk manipulation treatments, replacing husks immediately after peeling them did not decrease kernel weight as much as did the other treatments. Kernel number per ear was reduced equally by all husk manipulation treatments. The importance of husks in the maintenance of an adequate moisture and temperature environment for the developing ear and as storage organs for remobilizable assimilate is demonstrated by the fact that husk removal reduced grain yield much more than can be accounted for by the loss of husk photosynthesis.
Use of Ethephon as a Plant Growth Regulator in Corn Production
Authors: Gaska J. M. , Oplinger E. S.
Published: July 2010

Ethephon (2‐chlorethylphosphonic acid), a plant growth regulator used widely on horticultural and agronomic crops, may reduce lodging and enhance yield in field corn (Zea mays L.). Field research was conducted in 1985 near Evansville, WI on a Seweba silt loam (fine loamy over sandy or sandy‐skeletal, mixed, mesic Typic Argiaquoll) and in 1986 at the Arlington Research Station near Arlington, WI on a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll) to determine ethephon application parameters influencing corn yield, kernel breakage, plant and ear height, lodging, and harvesting time. Four rates (0, 140, 280, and 560 g ha−1) of ethephon were applied at three application times [tassel elongation (TE), TE + 7 d, and ear elongation (EE)] to four corn hybrids each year. Pioneer Brand hybrid 3377 showed increased yields with increasing ethephon rates up to 280 g ha−1 while all others (Pioneer hybrids 3737,3732,3475, and two single crosses LH74 ✕ LH51 and LH145 ✕ LH182) showed decreased yields. A 0.77 Mg ha−1 (7.6%) yield increase using 280 g ha−1 occurred with Pioneer Brand hybrid 3377 in 1985. Early application showed less yield decrease than later timings. Grain yield per ear was increased 3% on hybrid 3377 and decreased 12% on hybrid 3737 by the high rate of ethephon. Plant and ear height were decreased up to 20% both years with the high rate of ethephon. In 1986, high rates of ethephon decreased lodging 63% and harvesting time 20% on corn harvested late in the season. Under conditions conducive to lodging, ethephon used at the high rate and early application time may preserve yields and allow for easier harvesting. If lodging is not a problem, ethephon applied to certain hybrids at high rates and late application times may reduce yields.
Soybean Seed Imbibition: Water Absorption by Seed Parts
Authors: McDonald M. B. , Vertucci C. W. , Roos E. E.
Published: July 2010

Seed imbibition is a critical stage in successful soybean [Glycine max (L.) Merr.] crop establishment. This study investigatesoybean seed imbibition with emphasis on absorption of water by the seed parts (seed coat, embryonic axis, cotyledons, and whole seed). Mter 72 h imbibition, the embryonic axis was the most hydrated portion of the seed possessing greater than 50 g kg−1 fresh weight more water than any other seed part. The embryonic axis also hydrated more than the cotyledons in a high relative humidity environment when exposed as separated parts. Using polyethylene glycol 8000 as an osmotic agent, the seed coat, cotyledons, and whole seed contained a moisture content of approximately 550 g kg−1 fresh weight and the embryonic axis 700 g kg−1 fresh weight when germination (radicle emergence but less than 1.0 cm in length) occurred. while the cotyledons and embryonic axes of accelerated aged seeds did not differ in liquid moisture uptake from nondeteriorated seeds, the axes from accelerated aged seeds absorbed less water than the unaged controls when the seed parts were hydrated at 100% relative humidity (RH). These studies show that the embryonic axis hydrates more than the cotyledons, identify the level of moisture in the embryonic axis at which soybean seed germination is observed, and indicate that deteriorated seeds hydrate in a manner similar to nondeteriorated seeds in liquid water but that differences in the axes are detectable when hydrated in a high humidity environment.
Expression and Inheritance of Resistance of ELS 6404‐160 Durum Wheat to Hessian Fly
Authors: Mass F. B. , Patterson F. L. , Foster J. E. , Ohm H. W.
Published: July 2010

ELS 6404‐160, CI17647, a durum wheat (Triticum durum Desf.) introduction from Ethiopia, was found resistant to several biotypes of Hessian fly [Mayetiola destructor (Say)]. Additional genes for resistance are needed for breeding wheat for resistance to the Hessian fly. Research was conducted on a random plant (designated as Selection 5) of ELS 6404‐160. Our objectives were to determine (i) the number of genes in ELS 6404‐160‐5 controlling resistance to biotypes B and D, (ii) if the gene(s) are different from known genes effective against biotypes B, D, and L, (iii) the pattern of resistance of ELS 6404‐160‐5 to biotypes B, C, D, and L, and (iv) the effectiveness of the resistance at three temperature regimes. Test cross progeny and F3 line analyses, conducted in greenhouses or growth chambers, indicated that ELS 6404‐160‐5 has two genes for resistance which are different from other genes known to provide resistance to biotypes D and L. Segregation of test cross progeny rows in a three segregating to one susceptible ratio following the test cross of ELS 6404‐160‐5 with susceptible D6647 indicated that resistance was governed by two genes. The occurrence of susceptible test cross progenies in test crosses following crosses of ELS 6404‐160‐ 5 with genotypes with known genes for resistance to biotype D indicated that the genes in ELS 6404‐160‐5 were different than those previously described. ELS 6404‐160‐5 is resistant to biotypes B, C, D, and L and resistance is quite stable to biotype D at three temperatures. The genes from ELS 6404‐160‐5 are designated H14 and H15. Gene H15 is closely associated with H9 on chromosome 5A; H14 may be linked to or independent of H10, which is on chromosome 5A.
Pericarp Thickness of a Shrunken‐2 Population of Maize Selected for Improved Field Emergence
Authors: Tracy W. F. , Juvik J. A.
Published: July 2010

While the pericarp of maize (Zea mays L.) protects the kernel from pathogenas, thin pericarp is desirable in imparting tenderness in sweet corn. The objective of this study was to determine the correlated response in pericarp thickness due to selection for improved field emergence and seed weight in a shrunken‐2 (sh2) population. Two experiments were performed on a population to determine this relationship. In the first experiment, pericarp thickness of 11 cycles of a sh2 population mass selected for improved field emergence and increased seed weight was examined. Thickness of excised pericarps from mature kernels was measured with a pressure micrometer. Field emergence was determined in replicated trials in Urbana, IL in 1986 and 1987. Although significant differences in pericarp thickness were found, they were not correlated with field emergence. Little of the variation in pericarp thickness was due to linear trends resulting from indirect selection (r2 = 0.15). In the second experiment the pericarp thickness was examined on kernels from 100 ears from each of Cycles 2, 5, 8, and 11 of the same sh2 population. The differences in pericarp thickness among cycles, although significant, were small and did not reflect linear trends related to cycles of selection (r2 = 0.10). Selection for improved field emergence and seed weight in this sh2 maize population did not alter pericarp thickness. Thus, field emergence of sh2 sweet corn maybe improved without increasing pericarp thickness and decreasing tenderness.
Temperature Effects on Megagametophytic Development in Meadowfoam
Authors: Franz Robert E. , Jolliff Gary D.
Published: July 2010

Seed yield of meadowfoam (Limnanthes alba Benth.), an open‐pollinated winter annual, is partially determined by the number of seeds per flower. Each flower has the potential for five seeds, but typically an average of two seeds per flower has been measured in the cultivar Mermaid. The causes of less‐than‐maximum seeds per flower are not known. Therefore, an investigation of the effects of temperature on the growth rates of the unfertilized ovule and embryo sac and on megagametophytic structure was conducted. Treatment effects at 0, 48, 96, and 144 h postanthesis (HPA) under the regimes of 15/15, 24/15, and 33/15 °C alternating day/night were measured. Growth rate for embryo sac width, ovule width, embryo sac/ovule width growth rate (ESOWGR), embryo sac length, ovule length, and embryo sac/ovule length growth rate (ESOLGR) was significantly (P < 0.01) lower at 15/15 °C than at higher temperatures. Growth rate for embryo sac width, ESOWGR, and ESOLGR was significantly (P < 0.05) higher at 24/15 than at 33/15 °C. At anthesis, the number of flowers with four or five normal appearing megagametophytes was approximately the same in all temperature regimes. However, over time, with each warmer temperature regime there were increasing numbers of abnormal embryo sacs wherein the egg apparatus pulled away from the micropyle resulting in the megagametophyte appearing to float within the embryo sac. This temperature effect may explain some of the yearly variation in seed yield and suggest the need for timely pollinator management, especially during periods of rapid bloom when temperatures are typically above 24 °C.
Evaluation of Screening Procedures for Breeding Creeping‐Rooted Alfalfa
Authors: Rodrigues G. H. S. , Smith S. E.
Published: July 2010

Introduction of the creeping‐rooted (CR) trait into nondormant alfalfa (Medicago sativa L.) populations is complicated by the time required to identify CR expression and the complex inheritance of the trait. Various procedures might be used to improve the efficiency of this breeding process. This study was conducted to examine the effects of four screening procedures on the expression of CR in transplanted and direct‐seeded plants. Comparisons were made between two methods of CR parent selection (random vs. based on field CR expression), and two harvest frequencies (nine vs. five harvests in a 44‐week period). Root morphology and CR expression were evaluated in 3508 F1 plants grown in the field at Tucson, AZ (Aqua sandy loam; coarse, mixed, thermic Typic Torriflurent). Half of the F1 population was transplanted as seedlings, the other half direct‐seeded. A higher proportion of CR plants was observed among the transplanted progenies when confirmed CR parents were used in crosses than when parents were randomly selected from CR populations. If the time required to identify CR parents is considered, then use of uncharacterized parents from CR populations appears equally as efficient. No differences were observed in CR expression between F1 progenies exposed to five or nine harvests. Use of uncharacterized CR parents, transplanting seedling progenies, and normal harvest management is an efficient strategy when breeding nondormant, CR alfalfa germplasm.
International Winter Wheat Evaluation: Relationships among Test Sites Based on Cultivar Performance
Authors: Peterson C. J. , Pfeiffer W. H.
Published: July 2010

Effective exchange of germplasm and information amonng international researchers has been hindered by lack of information concerning similarities in biotic and abiotic stresses associated with cultivar selection and performance in production areas. Seventeen years of data from the International Winter Wheat Performance Nursery were used as a basis for defining and characterizing relationships among test sites. Average correlations of cultivar yields among 56 locations 30 countries were used as a basis for principal factor analyses. Varimax rotation was used to uniquely define factors. Seven factors adequately accounted for 63% of the variation in the dependence structure. The seven regions identified were considered as mega‐environments for winter wheat (Triticum aestivum L.) production. Principal factor analysis was used to further subdivide locations within five of these mega‐environmental regions. Factor coefficients were correlated with location means for yield, heading and ripening dates, grain‐fill duration, and winter survival. The correlations provided biological interpretations of groupings in terms of general stresses associated with winter wheat production. The relationships of international winter wheat test sites documented in this study should facilitate definition and understanding of regions of cultivar adaptation.
Heritability of Resistance to Tan Spot in Durum Wheat and Its Association with Other Agronomic Traits
Authors: Elias E. , Cantrell R. G. , Hosford R. M.
Published: July 2010

Tan spot, caused by Pyrenophora tritici‐repentis (Died.) Drech. (anamorph = Drechslera tritici‐repentis [Died.] Schoem.) is considered one of the major foliar diseases of durum wheat (Triticum durum Desf.). This study was initiated in an attempt to utilize artificial inoculation techniques to estimate heritability of tan spot reaction and measure the association of disease reaction with plant height and maturity. The resistant durum wheat accession PI 184526 was crossed to the moderately susceptible ‘Calvin’ and pairs of F4 and F5 progenies were derived by single seed descent (SSD). The SSD progenies were inoculated in the greenhouse with fungal isolate PyD7 at a growth stage corresponding to 10.0 to 10.5 on the Feekes scale and tan spot ratings were recorded 9 d later. The standard unit heritability of tan spot rating based on the mean of three replications was 0.44. The SSD F4 progenies were grown and inoculated in the field at a growths tage similar to that in the greenhouse experiment. The simple correlation between greenhouse end field disease ratings ranged from r = 0.29 to r = 0.50 depending on type of disease severity rating. The correlation of days to heading and disease severity was negative (r = −0.42 to −0.58) and significant (P < 0.01). Disease severity did not appear to be associated with plant height even though the population segregated for the semidwarf character. In a separate experiment, near‐homozygous F5 progenies were derived in a hierarchical manner and were evaluated in the greenhouse to estimate additive genetic variance and additive ✕ additive epistatic variance of tan spot ratings. A significant amount of additive genetic variance was detected in the population, whereas, the additive ✕ additive genetic variance was not significant. The narrow‐sense heritability estimate was H = 0.73 indicating that selection for tan spot resistance was feasible in this population.
Cytoplasmic Effects on Photosynthetic Activities of Soybean Leaves
Authors: Diethelm R. , Shibles R. , Green D. E. , Shoemaker R. C.
Published: July 2010

Many of the thylakoid proteins involved in photosynthesis, as well as the catalytic subunit of ribulose 1,5‐bisphosphate carboxylaseoxygenase (rubisco), are encoded in the chloroplast, which is inherited maternally. Different chloroplast genomes might result in different photosynthetic rates or differential regulation of photosynthetic enzymes. Nine soybean lines [Glycine max (L.) Merr. and G. gracilis], representing four different chloroplast genomes, were reciprocally crossed to a common high‐photosynthetic parent. Reciprocal F1'S in a field experiment behaved similarly for CO2‐exchange rate (CER), photosynthetic electron transport, rubisco activity, and soluble protein content. Hence, these traits were not influenced by the different chloroplast genomes, implying that the chloroplast genomes used were not different with respect to genes involved in ratelimiting photosynthesis or any sequence changes were not expressed. Partial dominance for low CER seemed evident in the progeny of parents having large differences in CER. This effect seems to be under nuclear influence because it occurred in both F1 progeny of reciprocal crosses. This partial dominance for low CER appeared in both Glycine species and was mainly due to low protein content resulting in low rubisco activity per leaf area. The performance of the two species in photosynthesis and the related traits was similar.
Genotype‐by‐Environment Interaction in Grain Sorghum I. Effects of Temperature on Radiation Use Efficiency
Authors: Hammer G. L. , Vanderlip R. L.
Published: July 2010

Better understanding of genotype‐by‐environment interaction for radiation use efficiency could facilitate use of crop models to interface physiological research with crop improvement. We grew sorghum [Sorghum bicolor (L.) Moench] hybrids RS610 and ATx623/RTx430 at 17 and 25 °C in glasshouses, monitored dry matter by sequential harvesting, and measured intercepted photosynthetically active radiation (PAR) to determine if a genotype‐by‐temperature interaction exists. Total dry matter can be considered the product of intercepted PAR and radiation use efficiency. Above‐ground dry matter can be determined from total dry matter and partitioning between tops and roots. We used this framework to analyze treatment effects and found a significant temperature‐by‐hybrid interaction for total dry matter. The ATx623/RTx430 produced 22% more total dry matter at 25 °C than at 17 °C. Total dry matter produced by RS610 at either temperature did not differ significantly from that produced by ATx623/RTx430 at 17 °C. This interaction was caused by a similar effect on radiation use efficiency, which was 4.89 g MJ−1 for ATx623/RTx430 at 25 °C and 3.76 g MJ−1 for the other three treatments. We examined canopy structure and known effects on the photosynthesis‐respiration balance, but could not determine the physiological basis of the interaction. Hybrids differed significantly in ratio of root to total dry matter. ATx623/RTx430 partitioned more dry matter to roots (0.25) than RS610 (0.22). This effect on partitioning highlighted the potential error in comparing radiation use efficiencies among genotypes using calculations based only on above‐ground dry matter.
Western Corn Rootworm Damage in Maize: Greenhouse Technique and Plant Response
Authors: Riedell Walter E.
Published: July 2010

Corn rootworms are the most economically destructive insect pests of maize (Zea mays L.). There is little information in the literature concerning how these insects influence the physiology of their hosts. The objective of this study was to establish and validate a greenhouse technique for the investigation of the response of maize to damage caused by the western corn rootworm (Diabrotica virgifera virgifera LeConte). Plants grown in cellulose‐fiber pots for 49 d in the greenhouse were infested with second‐stage rootworm larvae. Infestation with rootworm larvae that were in relative developmental synchrony with the plant was accomplished by monitoring growing degree days (GDD). Three weeks after infestation, shoots were harvested, roots were washed free of soil, and shoots and roots were evaluated for rootworm damage. Plants infested with ISO rootworms per pot had shoot characteristics (plant height, ear shoot fresh wt., ear length and width, ear dry wt., and husk dry wt.) that were smaller than those of uninfested plants, while plants infested with 50 rootworms per pot had shoot characteristics that were larger than uninfested plants. The fourth and fifth nodes of roots were completely pruned in the 150‐rootworm treatment, while these same nodes from root systems of plants with SO rootworms per pot had only minor pruning with extensive rootworm tunneling. This tunneling damage was accompanied by extensive lateral root proliferation. Lateral roots from damaged plants were wider and of longer total length than those from uninfested plants. These rootworm damage characteristics to roots of infested plants reared in the greenhouse were very similar to those characteristics of roots damaged by rootworms under a field situation. Consequently, this greenhouse technique should be useful for rearing plants with rootworm damage for physiological studies.
Phenological Staging Schemes for Predicting Red Clover Quality
Authors: Ohlsson Christer , Wedin W. F.
Published: July 2010

No phenological schemes are available for red clover (Trifolium pratense L.) in the USA, although it is the second most important forage legume grown there. We studied red clover growth and compared three phenological schemes; one modified by us (OW) but developed earlier by Kalu and Fick for alfalfa (Medicago sativa L.), one original (HH), and one modified (HH1) byHedlund Höglund for red clover. Comparisons were based on (i) detecting differences in phenological stage among the schemes; (ii) correlation between mean stage values (MSV) and four forage quality estimates: crude protein (CP), in vitro dry matter disappearance (IVDMD), neutral detergent fiber (NDF), and acid detergent lignin (ADL); (iii) the time required to assign a MSV to a sample. ‘Arlington’ and ‘Hermes II’ red clover were sampled weekly for 8 wk in 1985 and 1986. Mean stage by weight (MSW) and mean stage by count (MSC) were calculated. The MSW method resulted in higher R2 values (range of 0.78‐0.93) than MSC (range of 0.37‐0.91) when correlated with forage quality. No observable differences in R2 values resulted between the OW and HH schemes. More time was reqaired to use the HH than the OW scheme, 20 vs. 14 s stem−1. Both schemes work well over a wide range of cultivars and are easy to use. The OW method is preferable in farm management because it requires less time than the HH scheme. The HH scheme, however, may be preferable for research because more logical stage characteristics are used.
Canopy Light and Tiller Mortality in Spring Barley
Authors: Lauer Joseph G. , Simmons Steve R.
Published: July 2010

Mortality of tillers in barley (Hordeum vulgare L.) is an important developmental event affecting spike number and yield potential of the crop. It has traditionally been thought that increased shading of young tillers by the developing canopy initiates the premature senescence of tillers. A series of field experiments were conducted in 1982, 1983, and 1984 at St. Paul, MN on a Waukegan silt loam soil (fine‐silty over sandy or sandy skeletal, mixed, Typic Hapludoll) to test this hypothesis. Degree of shading within the crop canopy was measured in relation to the position of tiller leaves during the vegetative phase of development for three genotypes. The decline in rate of leaf appearance on nonsurviving primary tillers, monitored as an early indicator of tiller senescence, was noted within 3 to 4 wk after crop emergence and before appreciable shading of tillers occurred. This indicates that tiller mortality was not initiated by lack of light. However, after main stem elongation began, tillers soon became heavily shaded suggesting the possibility that shading plays an auxiliary role in the senescence of barley tillers. We discuss the possibility that changes in light quality early in the growing season may be important for initiating the senescence of tillers.
Spring Establishment of Orchardgrass Seed Crops with Cereal Companion Crops
Authors: Chastain T. G. , Grabe D. F.
Published: July 2010

Orchardgrass (Dactylis glomerata L.) does not produce a seed crop during the first growing season. Income produced by establishing orchardgrass seed crops with cereal companion crops could offset revenue lost when a seed field is planted. This investigation was conducted to ascertain the feasibility of establishing orchardgrass seed crops with spring cereals and examine the biological and economic responses of orchardgrass to competition with cereals. ‘Hallmark’ orchardgrass was interplanted with ‘Waverly’ spring wheat (Triticum aestivum L.), ‘Steptoe’ spring barley (Hordeum vulgare L.), and ‘Cayuse’ spring oats [Avenafatua var. sativa (L.) Haussk.] in 15‐ and 30‐cm rows at right angles to grass rows. Cereals shaded orchardgrass seedlings, resulting in transitory increases in chlorophyll content. Cereals reduced soil moisture content, causing water stress in orchardgrass seedlings as indicated by greater stomatal resistance and lower transpiration rate, which reduced urchardgrass tiller and dry matter production. The negative effects on growth persisted into fall and winter, reducing fertile tiller production during the following spring. Consequently, spring cereals reduced firstyear seed yields by 40% in Trial 1 and 53% in Trial 2. Seedling growth and first‐year seed yields were similarly reduced by all cereals and row spacings. Second‐year seed yield was not influenced by cereals. Net income was increased by $212 ha−1 over a 3‐yr period in Trial 1 with wheat in 30‐cm rows. However, drier conditions in Trial 2 caused low cereal and orchurdgrass seed yield, making establishment with cereals unprofitable. This study demonstrated possible negativeffects of spring cereals on orchardgrass stand establishment; nevertheless the potential for increased profitability of orchardgrass seed crops planted with wheat companion crops was shown.
Genetics of Plant Height Reduction and Panicle Type in Oat
Authors: Federizzi L. C. , Qualset C. O.
Published: July 2010

In oat (Avena sativa L.) utilization of genes for height reduction in cultivars has been limited and development of short‐statured genotypes in material with good local adaptation is a plant breeding objective. The inheritance of plant height was examined in field studies in six crosses involving the tall genotype ‘California Red’ (CR, 150 cm), short‐statured genotypes ‘OT 207’ (OT, 110 cm) ‘Curt’ (CT, 115 cm), and the dwarf genotypes ‘NC 2469‐3’ (NC, 90cm) and ‘Palestine Dwarf’ (PD, 85 cm). The inheritance of panicle type was studied in crosses of genotypes with normal (lax) panicle type (OT and CT) with genotypes with compact panicles (NC PD). Genotypes were proposed on the basis of F2 and F3 segregation data: CR, Dw6+ Dw7+; OT Dw6 Dw7+; NC and PD Dw6+ Dw7; and CT, Dw6+ Dw7a. The Dw6, Dw7, and Dw7a alleles are dominant, partially dominant, and recessive, respectively, to the wild type Dw6+ and Dw7+ alleles in the tall parent CR. The Dw7a allele shows dominance for tallness over Dw7 dwarfing allele. Differences in panicle type were due to one additive gene (C), which was linked (0.08 ± 0.01) to Dw7. Various combinations of Dw6 and Dw7 alleles may be useful in breeding oat cultivars that have appropriate plant height for local conditions.
Pedigree Analysis of North American Oat Cultivars Released from 1951 to 1985
Authors: Souza E. , Sorrells M. E.
Published: July 2010

Pedigree analysis of large collections of cultivars is useful for evaluating effects of crop improvement and provides a basis for selection of cultivars for use as parents in breeding programs. Coefficients‐of‐parentage among 205 North American oat (Avena sativa L.) cultivars were estimated and used to: (i) measure relative changes in genetic diversity through time based on diversity of cultivars released for the two time periods: 1951–1960 and 1976–1985, (ii) measure contributions to the germplasm pool by 89 landraces and introduced cultivars (ancestral parents) of A. sativa and A. byzantina C. Koch, and (iii) identify major groupings of related cultivars through cluster analysis. The average coefficients‐of‐parentage (rp) among all cultivars released with pedigree information from 1951 to 1960 was 0.09 and for cultivars released from 1976 to 1985 rp was 0.08. The 10 most important ancestral parents in each time period, based on cumulative rp values for all surveyed cultivars, declined in their relative contribution to the germplasm pool from 79% of the parentage of cultivars in 1951 to 1960 to 54.2% for cultivars released from 1976 to 1985. The most important ancestral parent was the South American cultivar, ‘Victoria’, followed by the Swedish landrace, ‘Milton’, and the A. byzantina landrace, ‘Red Rustproof’. Cluster analysis by the unweighted pair group mean method produced seven groups of cultivars. Six of the cultivar groups corresponded to either regional germplasm pools such as the southern USA cultivars or cultivars with high degrees of relationship to specific crop introductions such as Victoria. The largest cluster contained 116 of the 205 cultivars, and most of the cultivars from the midseason growing region as well as 85% of all North American cultivars released from 1976 to 1985. Although the average relationship among cultivars has remained nearly constant, current cultivars are more broadly based due to recombination of germplasms from regional clusters with a high intracluster relationship and a low intercluster relationship to form a single large germplasm pool with a low intracluster relationship and a higher than average intercluster relationship.
Single and Multiple Vigor Tests for Predicting Seedling Emergence of Wheat
Authors: Steiner J. J. , Grabe D. F. , Tulo M.
Published: July 2010

With an estimated 40 to 50 proposed seed vigor tests available, appropriate procedures for choosing the best single test or combination of tests are necessary. The objective of this study was to compare several statistical procedures for selecting the best single and multiple predictors of seedling emergence of wheat (Triticum aestivum L.). Twenty vigor tests and a field emergence trial were performed on 49 seed lots of ‘Hyslop’ soft white winter wheat. The best single predictors of field emergence were identified by calculating simple correlation coefficients. Multiple regression models were built to determine the best combination of tests for predicting field emergence. Col linear variables were examined for usefulness in linear index models. Among the single tests, glutamic acid decarboxylase activity, seedling root length, and tetrazolium vigor were the best predictors of seedling emergence, followed by seedling dry weight and respiratory quotient. The best combination of noncollinear multiple tests was that of tetrazolium viability, adenosine triphosphate, and respiratory O2 uptake. This combination gave an increase in predictive ability over the best single model. The best overall prediction of seedling emergence was obtained by calculating the geometric mean of multiple variables that were collinear and not suitable for a multiple regression model. The most suitable combination for the geometric mean was the highly correlated seedling root length, glutamic acid decarboxylase, and seedling dry weight tests. It appears that simple seedling growth measurements can be as effective as biochemical tests as indicators of seedling emergence of wheat. When building multiple regression models, only noncollinear variables as determined by factor analysis should be included. The calculation of the geometric mean of several vigor tests is proposed as a method for utilizing multiple tests that are highly correlated.
Comparison of Selection for S2 Progeny vs. Testcross Performance for Population Improvement in Maize
Authors: Horner E. S. , Magloire E. , Morera J. A.
Published: July 2010

Several methods of population improvement in maize (Zea mays L.) are available, but more information is needed to enable breeders to make the best choice among them. This study was conducted to compare selection among S2 progenies (S2 method) with selection based on testcross performance using inbred testers (TC method) in two populations, FS8A and FS8B. For the TC method, a line from FS8A was the tester used to evaluate S2 lines from FS8B and vice versa. Four cycles of selection were completed, and the selected populations were evaluated over a 4‐yr period. Testing was done at two locations near Gainesville, FL, during both the selection and the evaluation phases. Gains in average combining ability over both populations and all tests were 4.7 and 3.0% cycle−1 for the TC and S2 methods, respectively (significantly different at P = 0.01). Linear regression based on these mean values accounted for 99% of the variation among cycles for each method. The TC method also produced higher predicted yields of populations per se (F = 0) in Cycle 4 (6.85 vs. 6.01 Mg ha−1). On the other hand, the S2 method resulted in a lower rate of yield depression in Cycle 4 for each 1% increase in inbreeding (0.04 vs. 0.06 Mg ha−) and in higher predicted yields of inbred (F = 1) populations (1.70 vs. 0.87 Mg ha−1). These results suggest that nonadditive gene action in the overdominance range is important in these populations because, in the absence of overdominance, the S2 method is expected to be the better procedure.
Sprouting Damage and Kernel Color Relationships in Durum Wheat
Authors: Soper J. F. , Cantrell R. G. , Dick J. W.
Published: July 2010

Sprout damage resulting from rainfall prior to harvest is a serious quality problem in durum wheat ( Triticum turgidum L. vat. durum). Field experiments were conducted in Fargo and Langdon, ND during 1984 and 1985 to determine if random intermating would reduce the association between red kernel color and preharvest dormancy in populations derived from the hybridization of amber‐seeded ‘Vic’ and PD44. The line PD44 possesseseed dormancy and red kernel color inherited from a Canadian experimental hard red spring wheat (T. aestivum L. em. Theli) line, RL4I37. Seed dormancy was assessed by visually rating sprouting within intact spikes in a rainsimulation chamber, and by indirectiy measuring a‐amylase activity in the sprouted grain. The simple phenotypic correlations of kernel color and dormancy parameters were significant (r = 0.28–0.67) and relatively unchanged by one or two cycles of random intermating. The genetic variability for dormancy was also similar for 0, 1, and 2 intermating cycles. The relationship between red kernel color and strong preharvest dormancy is either due to pleiotropy or extremely tight genetic linkage. Thus the use of red‐seeded germplasm as a source of dormancy for amber‐seeded durum wheat germplasm is of questionable value.
Performance of S1 Alfalfa Lines from Original and Improved Populations
Authors: El‐Nahrawy M. A. , Bingham E. T.
Published: July 2010

Inbreeding has many uses in plant breeding. Improvement of autotetraploid alfalfa (Medicago sativa L.) by selection during inbreeding was evaluated by measuring inbreeding depression on herbage yield in 60 S1 lines from original and 120 S1 lines from improved populations. Original and improved populations were produced by synthesizing both before and after selection, respectively, in ‘Vernal’, ‘Saranac’, ‘Iroquois’, ‘Honeoye’, and an experimental containing Vernal and Saranac. Selection for self‐fertility and vigor was practiced during four generations of inbreeding. Natural and directional selection during inbreeding reduced 536 S1 lines to 152 in the S2, to 75 in S3, and to 16 in the S4 generation. The 16 selected S4 inbreds were used to make single crosses, and then two sets of double crosses (DCA and DCB) that were designated improved populations. The original materials were synthesized from open‐pollinated seed of 452 of the original 536 plants (W40) and by using remnant seed of 41 lines identified as superior during the inbreeding and selection process (W41). A higher proportion of plants in the improved populations produced sufficient SI seed for field testing (49%), than did plants in the original populations (27%). The S1 lines from the improved populations showed less inbreeding depression for herbage yield (19% below S0), while those from the originalshowed more inbreeding depression (28% below S0). Higher percentages S1 entries were included in the highest three herbage yield classes from improved populations (19.7%) than from original populations (12.4%). Thus, inbreeding depression was reduced in the improved populations. Selection during inbreeding to produce the 16 S4 parents mof the improved population likely decreased the frequency of deleterious alleles and accumulated favorable alleles.