bluuebunny/crossref_metadata_2025 huggingface dataset:
Inheritance of High Glanding, an Insect Resistance Trait in Cotton
Authors: Calhoun D. S.
Published: July 2010

The high glanding (HG) trait [i.e., presence of gossypol glands the upper edge of the sepals of the upland cotton (Gossypium hirsutum L.) flower bud] confers a significant level of resistance to bollworm [Helicoverpa zea (Boddie)] and tobacco budworm [Heliothis virescens (F.)], but the inheritance of this trait is not well understood. The objective of this study was to determine the inheritance of the HG trait to aid breeders in developing improved HG cultivars. Crosses were made among HG, normal glanding (NG), and glandless genotypes, and with isolines of the HG breeding line, XG‐15, which had genotypes 2(Gl2 gl3) and 2(gl2 Gl3). The isoline, XG‐15 gl2Gl3, expressed the HG phenotype, leading to the hypothesis that HG is conferred by a special Gl3 allele derived from XG‐15. Crosses of HG × NG parents resulted in HG F1, 3 HG/1 NG ratios in the F2, and ratios of 1 HG/2 segregating/1 NG among F2:3 progeny. Crosses of XG‐15 gl2Gl3 × NG produced similar results. The cross, XG‐15 gl2Gl3 × HG, did not segregate for calyx margin glanding type. The cross, XG‐15 gl2Gl3 × glandless, resulted in glandless flower buds in the F1 and a ratio of 3 glandless (flower buds)/1 HGin the F2. The F1 HG × glandless had small sparse glands on the base of the sepals. Phenotypes of individual F2 plants did not appear to fit common segregation ratios, but data from F2:3 families supported the hypothesis that a special Gl3 allele confers the HG phenotype. This allele, derived originally from Socorro Island cotton, is tentatively designated GlS3.
Red Clover Seed Production: IV. Root Rot Resistance under Forage and Seed Production Systems
Authors: Steiner J. J. , Smith R. R. , Alderman S. C.
Published: July 2010

Red clover (Trifolium pratense L.) is an important forage legume grown in the USA, Canada, and northern and eastern Europe. The effects of root rot resistance of six improved cultivars and three regionally adapted ecotypes on forage and seed yield under typical production systems in Wisconsin and Oregon, respectively, were measured. The relationship of cultivar flowering capacity to seed yield was also measured. The objectives of this study were to: (i) determine the benefits of using improved cultivars instead of locally adapted ecotypes in Wisconsin forage production systems; (ii) determine whether selection for root rot resistance in Wisconsin benefits seed production systems in Oregon; and (iii) identify strategies to increase seed yields in cultivars with improved persistence and high forage yields. Forage and seed yields were inversely related in all improvedc ultivars except Kenland, which had lower forage yield than the other improved cultivars and the same yield as the three local Wisconsin and Oregon ecotypes. The local ecotypes produced the highest seed yield because of a greater flower producing capacity than improved cultivars following spring forage removal. Seed yield was highly associated with the number of flowers produced by late July (r = 0.87; P ≤ 0.002). Selection for root rot resistance in Wisconsin did not benefit seed production in Oregon. Improvemenitn seed yield capacity of cuitivars with high forage yield may be possible by selecting for rapid flowering after spring forage removal in the western Oregon seed production region.
The Reproductive Versatility of Eastern Gamagrass
Authors: Kindiger B. , Dewald C. L.
Published: July 2010

Eastern gamagrass [Tripsacum dactyloides (L.) L.], a native, warmseason species, is a nutritious and palatable forage for grazing livestock. The grass has potential for rangeland and pasture improvement. This field study was conducted over 10 yr and one location to determine the reproductive characteristics of the various cytotypes of Tripsacum and identify methods for breeding agronomically superior cultivars. Intra‐ and interspecific crosses were made and evaluated between several Tripsacum cytotypes. Cytological and polymerase chain reaction‐random amplified polymorphic DNA (PCR‐RAPD) techniques were used to identify methods of reproduction and types of individuals generated. Results of the study identified two methods for facilitating horizontal gene flow among sexual and apomictic cytotypes. Materials with triploid and hexaploid constitutions were essential in the movement of sexual germplasm into apomictic tetraploids and of tetraploid germplasm into sexual diploids, respectively. Triploids and hexaploids were useful materials to introgress and transfer desirable alleles across species, cytotypes, and reproductive barriers. In addition, the generation of triploid and hexaploid genotypes will continue to exert major influences on Tripsacum evolution and speciation. This study identified additional methods and systems for improving Tripsacum germplasm by utilizing its distant relative maize (Zea mays L.) in a breeding or genetic evaluation program.
Diallel Analysis of Acid‐Soil Tolerant and Intolerant Tropical Maize Populations
Authors: Salazar F. S. , Pandey S. , Narro L. , Perez J. C. , Ceballos H. , Parentoni S. N. , Filho A. F. C. Bahia
Published: July 2010

Acid soils cover approximately 30% of the global ice‐free land area. Nearly 26 million hectares of maize (Zea mays L.) is already planted on acid soils. Maize yields are low on acidic soils because of toxicities of Al. Mn, and Fe, and deficiencies of P, Ca, Mg, and K. Acid‐tolerant maize cultivars would be an environmentally friendly and relatively inexpensive method for improving maize production on acidic soils. Little information is available in the literature on the magnitude of reciprocal effects on yield and other agronomic traits when maize is grown on acidic soils. A diallel study, involving eight segregating populations and their 56 reciprocal crosses, was conducted in five acidic‐soil environments to determine relative importance of nuclear and cytoplasmic factors for yield, days to silk, ear height, ears per plant, and ear rot. Average (h) and specific (Sij) heterosis accounted for 65 and 31% of the total sum of squares for heterosis for yield. Population heterosis effects (hj) for yield were not significant, suggesting hj effects would be of little value in selecting populations for developing superior hybrids. Specific heterosis effects were negative and significant (P < 0.05) for yield and ears per plant only for the cross of CMS 36 × ETO Blanco, suggesting a minor role for nonadditive gene effects in determining yield of specific cross combinations. The absence of reciprocal differences for all traits indicated that tolerance to soil acidity was controlled by nuclear genes.
Progeny Test Selection in Two Crimson Clover Populations
Authors: Hossainzadeh A. H. , Rowe D. E. , Pratt R. G. , Windham G. L.
Published: July 2010

Two problems with breeding the forage legume crimson clover (Trifolium incarnatum L.) are how to incorporate genotype × environment effects in the evaluations and how to use destructive measurements and still cross selected genotypes. One solution is a multistep process: Produce families by inbreeding plants, produce half‐sib progenies of each inbred family and evaluate for specific characters, and use remnant seed of selections to produce plants which are intercrossed to produce an elite population for selection or a synthetic. The objectives of this research were to estimate the impact of pollen parent and level of inbreeding of families on effectiveness of this selection procedure. Selection was effected in the greenhouse for resistance to Fusarium oxysporum (Schlect.), plant regrowth, and resistance to Meloidogyne incognita (Kofoid and White) Chitwood. Moderately and highly inbred crimson clover families were evaluated as two topcrosses and one polycross haif‐sib families. For each trait, the different haif‐sib progeny tests had similar rankings for the moderately inbred families but not for the highly inbred families. Evaluations of synthetics produced from selections showed resistances to F. oxysporum and to M. incognita were improved but not the plant regrowth. A link was found between level of heterozygosity and resistance to M. incognita, and high levels of inbreeding had unpredictable effects on selection. Plant breeders need to determine the level of inbreeding of families that does not seriously bias measurement of a trait, but which minimizes sampling errors within the family selected for production of synthetics.
Growth Analysis of Spring and Summer Seeded Annual Medicago spp
Authors: Zhu Yanping , Sheaffer Craig C.
Published: July 2010

Understanding patterns of summer and fall growth and dry matter partitioning of annual medics (Medicago species) in the north central USA should be useful in developing harvest management recommendations for these legumes. Our objective was to describe changes in biomass yield and biomass partitioning to leaf, stem, and floral fractions during development of annual medics. Five Australian annual medic species and ‘Nitro’ alfalfa (M. sativa L.) were planted in spring and summer at St. Paul and Rosemount, MN. Leaf to stem dry weight ratio (L:S) of medics declined with maturation of both spring and summer seedings. Whole plant maximum DM yield averaged 5395 kg ha−1 for spring seeding and 3786 kg ha−1 for summer seeding, and these yields occurred from 10 to 14 wk after planting depending on species and environment. ‘Sapo’ (M. rugosa Desr.) and Sephi (M. truncatula Gaertn) were consistently among the highest in leaf and stem yields for spring seeding, and ‘Sava’ [M. scutellata (L.) Mill] was consistently among the highest in leaf and stem yields for the summer seeding. ‘Harbinger’ (M. littoralis Rhode), ‘Santiago’ (M. polymorpha L.), and Sava were consistently the earliest legumes to flower and the earliest to achieve maximum flower and pod yields during summer growth. They also had the highest flower and pod yields. Flowering of annual medics was not fully expressed during fall growth because of the temperature and daylength changing pattern. Varied yield responses of annual Medicago species will necessitate species‐specific harvest management practices.
Growth Dynamic Factors Controlling Soybean Yield Stability across Plant Populations
Authors: Carpenter A. C. , Board J. E.
Published: July 2010

Soybean [Glycine max (L.) Merr.] optimizes yield over a broad range of plant populations because of its ability to increase yield per plant at sparse plant populations. Greater understanding of this response would aid research efforts aimed at achieving optimal plant population (minimal plant population required for best yield). The objective of this study was to determine the growth dynamic factors responsible for yield compensation across a range of plant populations. Soybean cultivar Delta Pine 415 (Maturity Group V) was planted an optimal date during 1994 and 1995 at low (70 000 plants ha−1), medium (164 000 plants ha−l), medium/high (189 000 plants ha−1), and high (234 000 plants ha−1) plant populations on a Commerce silt loam soil (fine‐silty, mixed, nonacid, thermic Aeric, Fluvaquents) near Baton Rouge, LA. Increasing plant population by 234% from low to high treatments resulted in only a 9% yield increase. This yield stability resulted from equilibration of crop growth rate and total dry matter pers quare meter across populations by R1 and significantly greater (P < 0.05) dry matter partitioning into branch dry matter per square meter (14.8% in the low population and 9.9% in the high population). Consequently, similar branch dry matter per square meter and pod number per square meter occurred across populations. Equilibration of crop growth rate and total dry matter per square meter by R1 across populations was aided by greater light interception efficiency and net assimilation rate in the low vs. higher populations during the vegetative and early reproductive periods. In conclusion, similar yields may result as plant population declines through maintenance of crop growth rate during the early reproductive period and greater dry matter partitioning into branch dry matter per square meter.
Intercropping Legumes into Sunflower at Different Growth Stages
Authors: Kandel H. J. , Schneiter A. A. , Johnson B. L.
Published: July 2010

Sunflower (Helianthus annuus L.) residue is fragile and does not provide a lot of ground cover. Legumes intercropped in sunflower could increase soil cover, reduce soil erosion, and add nitrogen and organic matter to the soil. Field studies were designed to evaluate the effect of different sowing dates of hairy vetch (Vicia villosa Roth), yellow‐flowered sweetclover (Melilotus officinalis Lam.), alfalfa (Medicago sativa L.), snail medic [Medicago scutellata (L.) Mill.], and black lentil (Lens culinaris Medik.) intercropped in dwarf and standard‐height oilseed sunflower on agronomic traits of sunflower. Legumes were sown the same time as sunflower and at the V4 and V10 sunflower growth stages. Studies were conducted at Carrington (1992 and 1993) and Prosper (1992, 1993, and 1994), North Dakota. Sunflower oil content was not influenced by intercropped legumes. When sown at the same time as sunflower, all legumes, except black lentil, reduced sunflower seed yield. Black lentil produced 1385 kg ha−1 dry matter. Compared with the control, sunflower achenes per head, and head diameter were reduced by legumes sown at the same time as sunflower. Sunflower yield, head diameter, achenes per head, and 1000‐achene weight were not significantly lower when legumes were sown at the V4 or V10 sunflower growth stages. Hairy vetch is recommended for intercropping at V4 and V10 sunflower growth stages because it did not reduce sunflower yield and on average produced 1593 and 831 kg ha−1 dry matter. At the drier environment, Carrington 1992, biomass produced by the legumes was low when legumes were sown at the V4 or V10 sunflower growth stages, with 314 and 57 kg ha−1, respectively. Sweetclover could be sown at the V4 growth stage of sunflower to establish it as a cover crop for the subsequent season.
Chemical Characterization of a Shriveled Seed Trait in Peanut
Authors: Jakkula Lakshmi R. , O'Keefe Sean F. , Knauft David A. , Boote Kenneth J.
Published: July 2010

Seed morphology mutations affecting the major seed components in pea (Pisum sativum L.) and maize (Zea mays L.) opened specialty markets for these crops. Peanut (Arachis hypogaea L.) is an important oil and food crop of the world. Genetic alteration of seed composition may be useful in expanding markets for this crop. Some lines from the University of Florida peanut breeding program showed seed shriveling characteristic even when harvested mature. In the present study, three shriveled lines (529B, 563A, and 647A) were chemically characterized and compared with a normal‐seeded cultivar, Sunrunner. They were found to have only one third to two thirds the amount of storage lipid and double the amount of sucrose as normal peanuts. Differences were also observed for seed protein concentration, when expressed on a defatted meal basis. Higher relative proportions of phospholipid to triacylglycerol may indicate a block in the biochemical pathway for the conversion of sucrose into triacylglycerol in the shriveled seed mutants. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) patterns revealed that there were differences in the levels of various proteins between normal seed and shriveled seed phenotypes. Differences were identified in the level of accumulation of storage lipid and also in the various proteins during the development of the shriveled seed.
Carbon Isotope Discrimination, Ash, and Canopy Temperature in Three Wheatgrass Species
Authors: Frank A. B. , Ray I. M. , Berdahl J. D. , Karn J. F.
Published: July 2010

Soil water is the main factor influencing forage production in the semiarid Northern Great Plains. Developing germplasm that uses limited water more efficiently would benefit forage production for hay and livestock grazing. Development of selection criteria suited to screeniing large breeding populations for water‐use efficiency (WUE) are needed to enhance this effort. This study evaluated carbon isotope discrimination (Δ), tissue ash concentration, and canopy temperature of populations of diploid crested wheatgrass (Agropyron cristatum L.), tetrapioid crested wheatgrass [A. desertorum (Fisch. ex. Link) Schult.], and western wheatgrass [Pascopyrum smithii (Rybd.) Love] to determine the utility of using ash concentration and canopy temperaturea s alternative criteria to Δ for selecting plants with high WUE. Tissue ash concentration, canopy temperature, and Δ were measured on half‐sib families from genetically broad‐based populations of each species across two field growing seasons. Sufficient genetic variation was present for Δ and ash concentration among families within each species to suggest possible use of these traits as criteria for selecting plants with higher WUE. Differences in canopy temperature among families were present only in 1994. Correlations between ash and Δ were greatest for tetraploid crested wheatgrass and least for western wheatgrass. Correlation of canopy temperature with Δ was significant for tetraploid crested wheatgrass both years and for diploid crested wheatgrass in 1993, but neither year for western wheatgrass. Ash concentration and Δ were moderately heritable in all three grass populations, indicating that both traits are under genetic control and could likely be altered through breeding. Using ash and canopy temperature as criteria for selecting plants with greater WUE would provide a relatively low‐cost, simple approach to develop cultivars with improved WUE.
Agronomic Performance of Soybean Plant Introductions and Their Genetic Similarity to Elite Lines
Authors: Sneller C. H. , Miles J. W. , Hoyt J. M.
Published: July 2010

North American soybean [Glycine max (L.) Merr.] is derived from a narrow genetic base. Plant introductions (PI) and cultivars from the northern USA may be sources of diversity for southern U.S. cultivars. Screening diverse lines for agronomic value may identify potential parents that facilitate breeding for diversity. The objectives of this research were to evaluate the association of agronomic value and genetic diversity of selected PIs and to conduct a preliminary comparison of their value in the South with that of selected northern U.S. cultivars. Field evaluations of 31 PIs, 11 populations derived from cross of five northern cultivars × southern lines, and 15 southern lines were conducted at five environments in Arkansas. Restriction fragment length polymorphism (RFLP) data from 60 loci were collected from all PIs, parents of the populations, and 57 southern elite lines. The agronomic value of most PIs was low because of excessive shattering, lodging, and/or poor yield. Exceptions were noted. The estimated yield potential of most of the northern cultivars exceeded the mean yield of the PIs and they had less shattering than the PIs. The PIs and the northern cultivars were genetically divergent from the southern elite population and from each other. The agronomic value and relative diversity of the PIs were independent. Diverse PIs with above average agronomic value were identified. These PIs may serve as sources of genetic diversity that can be exploited through simple breeding schemes. The southern PIs and northern lines may act as complementary gene pools to provide desirable genes for diversifying southern U.S. soybean.
Somaclonal Variation and Improvement of Chilling Tolerance in Rice: Changes in Chilling‐Induced Chlorophyll Fluorescence
Authors: Bertin P. , Bouharmont J. , Kinet J. M.
Published: July 2010

Chilling is one of the major constraints for rice (Oryza sativa L.) culture at high altitude. The use of chlorophyll fluorescence to screen genotypes for chilling tolerance has been widely documented. Within a program dealing with improvement of chilling tolerance in rice, somacional variants were obtained previously and chilling tolerance was selected for during four successive generations. To evaluate the implication of the efficiency of photosystem II (PSII) photochemistry (Fv/Fm) at low temperature in the increased chilling tolerance of these somaclones, the chlorophyll fluorescence of the somaclones and their original parental cultivars was measured with a portable fluorometer (PEA Analyser, Hansatech, England). First, chilling tolerance of four rice cultivars was investigated in phytotron trials by subjecting excised leaves to at 10/5°C day/night for a 72‐h period before returning to 28/22°C. Fv/Fm was determined after 0, 3, 6, 12, 24, 36, 48, 60, 72, 75, 144, and 147 h and compared with measurements performed on control leaves maintained throughout at 28/22°C. The chilling treatment induced a marked decrease in Fv/Fm during the day, which was only partially compensated for during night. The extent of this decrease was related to cultivar chilling sensitivity. Second, leaves of somaclonal families improved for chilling tolerance and arising from three of these cultivars were chilled during 6 d under the same conditions as described above and then returned to control conditions. Large differences were found between somaclonal families and their cultivar of origin. Fv/Fm was higher in the Kirundo 3 somaclonal families, but lower in the somaclones originating front Facagro 76 and Kirundo 9. Chlorophyll fluorescence allowed detection of changes in chilling tolerance in several, but not all, somaclonal families. Different mechanisms are implicated in chilling‐tolerance improvement.
Clonal and Open‐Pollinated Progeny Testing in an Intermediate Wheatgrass Population
Authors: Berdahl J. D. , Baker R. E.
Published: July 2010

Efficient testing procedures are needed to identify superior parents for improved cultivars of cross‐pollinated forage species. The primary objective of this study was to compare clonal and open‐pollinated (OP) progeny testing in the selection of parents from an intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & Dewey] population. A second objective was to examine experimental error control from a partially‐balanced lattice design and a nearest‐neighbor analysis relative to a randomized complete block statistical design (RCBD). Parent clones were evaluated in plots that consisted of 30 closely spaced tamers, and progenies were sown in single‐row plots 6.0 m long spaced 0.6 m apart at adjacent sites near Mandan, ND. Based on 3‐yr means from one location, narrow‐sense heritability estimates from 81 parent clones and their respective open‐pollinated progenies averaged 50% for heading date, 45% for plant height, and 69% for dry matter yield. Extreme high‐ and low‐ranked entries for all three traits generally were in common for clonal and progeny tests. A lattice design and nearest‐neighbor analysis reduced experimental error but did not improve rank correlations between parent clones and their progenies or heritability estimates compared with a randomized complete block design. These results suggest that clonal and open‐pollinated progeny tests should be used to select superior parents of intermediate wheatgrass, as both test procedures have unique attributes. Clonal tests are useful in selecting for traits with relatively high heritability, while extensive progeny testing is more appropriate for complex traits such as dry‐matter yield.
Number of Seeds per Unit Area in Sunflower Correlates Well with a Photothermal Quotient
Authors: Cantagallo Julio E. , Chimenti Claudio A. , Hall Antonio J.
Published: July 2010

Potential yield in several crop species is affected by radiation and temperature when they are grown under unstressed conditions. This issue has been not explored for sunflower (Helianthus annuus L.), and the objectives of our experiments were (i) to analyze the dependence of seed number (SN, seeds m−2) on the thermal and light conditions during the period from floret initiation to the end of seed‐setting and (ii) to determine whether sensitivity of SN to radiation differs between pre‐ and post‐anthesis. Inter and intra‐annual variations in sowing dates and artificial shading were used to expose irrigated crops to different conditions of radiation (range 14–24 MJ m−2 d−1) and temperature (20–24°C) (temperature/radiation combinations = 18). Significant positive (P < 0.00001) relationships between SN (range 3499–11547 seeds m−2) and intercepted (r2 = 0.65) an incident (r2 = 0.56) short‐wave radiation during the floret initiation to seed‐setting period were found. A weaker negative association with temperature (r2 = 0.29; P < 0.05) was also found. The relationship between SN and a photothermal quotient [PQ = mean radiation/ (mean temperature‐base temperature), MJ m−2 d−1 °C−1], calculated with intercepted radiation was better than that achieved by either variable alone (SN = −436 + 9214 PQ; r2 =0.74; P < 0.000001). We conclude that PQ would be a better tool to predict SN in sunflower than the use of radiation or temperature alone. Crops subjected to shading after anthesis suffered significantly greater (P < 0.05) reductions in SN, at equivalent PQ, than those exposed to shading before anthesis.
Winter Wheat Leaf Photosynthesis, Stomatal Conductance, and Leaf Nitrogen Concentration during Reproductive Development
Authors: Frederick James R.
Published: July 2010

Leaf N concentration (LRN), stomatal conductance (gs), and grainassimilate demand each affect the leaf CO2‐exchange rate (CER) winter wheat (Triticum aestivum L.) during grain fill. Although leaf CER, gs, and LRN decrease during this time, little research has been conducted to examine whether these decreases occur simultaneously or to determine the effects of grain development on these declines. This field study was conducted (i) to monitor changes in CER, LRN, and gs during winter wheat reproductive development, (ii) to examine the relationships between the rate and duration of CER and the rate and duration of grain fill, and (iii) to determine the effects of crop N status on the decline in LRN and CER during grain fill. Two early (Andy and Gore) and two medium (Northrop King Coker 9803 Northrup King Coker 9835) maturing cultivars were grown with irrigation and two rates of spring‐applied N (56 and 112 kg N ha−1) in 1994 and 1995. Cultivar ranking was similar for the date of inflorescence emergence, the initiation and termination of grain development, and the complete loss of green leaf area and flag‐leaf photosynthetic activity. for all cuitivars, flag‐leaf CER and gs began to decrease near the beginning of grain fill, whereas LRN and leaf area index (LAI) began to decrease prior to grain fill. Rapid reductions in LRN and CER were found only after significant grain growth occurred, with the rate of decrease being relative to the cultivar ranking found for inflorescence emergence date. Averaged over cultivars and years, increasing the rate of spring‐applied N increased LAI and LRN near inflorescence emergence by 37 and 24%, respectively, but only delayed the complete loss of green leaf area by 2 to 3 d and had little effect on the duration of grain fill. Stage of grain growth had little effect on the loss of LRN and CER until the latter portion of grain fill, when rapid reductions in these variables occurred. Increasing the rate of spring‐applied N did not significantly delay these decreases or extend the duration of grain fill.
Predicting Success of Indica/Japonica Crosses in Rice, Based on a PCR Marker for the S‐5n Allele at a Hybrid‐Sterility Locus
Authors: Williams Christie E. , Yanagihara Seiji , McCouch Susan R. , Mackill David J. , Ronald Pamela C.
Published: July 2010

Exploitation of crosses between the japonica and indica subspecies of rice (Oryza sativa L.) is hindered by hybrid sterility. However, germplasm containing the S‐5n wide compatibility allele, derived from tropical japonica (javanica), can be used as an intermediate in the transfer of traits. A PCR‐based DNA marker, STS213, was used to identify the fraction of an F3 population, segregating for S‐5n and the japonica allele S‐5j, that was most likely to yield fertile progeny from crosses with indica rice. Plants carrying the STS213 allele associated with wide compatibility, had significantly higher fertility than plants containing the japonica allele. The ability to detect seedlings bearing S‐5n, the wide‐compatibility allele, will facilitate the introgression of this allele into temperate japonica cultivars while eliminating the need to test cross, self and score for ferlility a majority of the individuals during introgression.
QTL Mapping in Testcrosses of European Flint Lines of Maize: II. Comparison of Different Testers for Forage Quality Traits
Authors: Lübberstedt Thomas , Melchinger Albrecht E. , Klein Dietrich , Degenhardt Heinz , Paul Christian
Published: July 2010

Improving forage quality is a major goal in maize breeding for cooler climates. In this study, we mapped and characterized quantitative trait loci (QTL) affecting testcross (TC) performance of important forage maize quality traits and investigated their consistency across testers. Two elite flint inbred lines were crossed to generale 380 F2 individuals, 345 of which were genotyped at 89 RFLP marker loci. The 380 F3 lines produced by selfing the F2 individuals were testcrossed to two dent inbred testers. Each TC series was evaluated in field trials with two replications in five environments. The following six traits were analyzed: in vitro digestible organic matter (IVDOM), acid detergent fiber (ADF), metabolizable energy concentration (MEC), and protein concentration (CPC), all determined by near infra‐red reflectance spectroscopy (NIRS), as well as metabolizable energy yield (MEY) and protein yield (CPY). Genotypic variances (σ̂2g) mostly significant for these traits in both TC series. Heritabilities ranged from 0.24 to 0.69 and were low for IVDOM, ADF, and MEC. Genotypic correlations between testers exceeded 0.64 for each trait. Between four (CPY) and ten (CPC) QTL were detected in each TC experiment by composite interval mapping, explaining between 48.4% and 85.3% of σ̂2g in a simultaneous fit. QTL results were consistent across testers for CPC and CPY, but not for IVDOM, ADF, MEC, and MEY. Few of the detected QTL displayed significant digenic epistatic interactions. The digestibility traits IVDOM, ADF, and MEC were tightly correlated (|r̂g| > 0.88) with each other and displayed intermediate genotypic correlations (r̂g) with plant height and starch concentration, but low r̂g values with dry matter yield or dry matter concentration. In most cases, the magnitude of r̂g corresponded well with the number of common QTL regions affecting both traits.
Expression and Segregation of Genes Encoding CryIA Insecticidal Proteins in Cotton
Authors: Sachs E. S. , Benedict J. H. , Stelly D. M. , Taylor J. F. , Altman D. W. , Berberich S. A. , Davis S. K.
Published: July 2010

Epistatic and environmental effects on foreign gene expression in cotton (Gossypium hirsutum L.) could influence the breeding, stability and, in the case of pest resistance, efficacy and durability of the foreign gene. This study was undertaken to characterize the expression an segregation of two foreign cryIA genes in a range of insect‐resistant cotton lines derived in three backgrounds. The cryIA genes encoded insecticidal proteins from the bacterium Bacillus thuringiensis spp. kurstaki. The transformed cotton lines, MON 81 expressing the cryIA(b) gene and MON 249 expressing the cryIA(c) gene, were crossed to 14 cotton isolines with five different insect‐resistance traits. CryIA gene expression and variation were examined in terminal leaves of 2293 F2 progeny and subsequently in 12 F2:4 lines [cryIA(b) only] in field experiments conducted at two locations in Texas. CryIA gene expression was variable and influenced by genetic and environmental factors. Site‐of‐gene‐insertion and cotton‐background effects were significa sources of variation for the cryIA gene. Significant epistatic and/or somadonal effects increased plant‐to‐plant variation and caused cryIA gene expression to behave as a quantitative trait. Environmental effects, between and within locations and over time, decreased parent‐offspring correlations of mean cryIA gene expression between individuals from the F2 and F2:4 generations. Gene dosage at the cryIA locus influenced insecticidal protein concentration in F2 populations with the cryIA (b) gene insert—homozygotes produced 14% more CryIA(b) protein than hemizygotes. The CryIA phenotype segregated as a simple, dominant Mendelian trait. However, non‐Mendelian segregation occurred in some lines derived from MON 249. Expression of cryIA genes in cotton lines was influenced by one or more of the following: site of gene insertion, gene construct, background genotype, epistasis, somaclonal mutations, and the physical environment. These results indicate that appropriate evaluation and selection procedures should be used in a breeding program to develop new cotton lines with pest‐resistant traits conferred by foreign genes. Moreover, that a practical backcross breeding program could be used to develop cotton cultivars combining one or more pestresistant traits from foreign and native gene sources.
Changes in the Genetic Diversity of Cotton in the USA from 1970 to 1995
Authors: Van Esbroeck George A. , Bowman Daryl T. , Calhoun D. Steve , May O. Lloyd
Published: July 2010

Despite concern about genetic vulnerability, little is known about the recent changes in the genetic diversity of upland cotton (Gossypium hirsutum L.). The objectives of this study were to determine the trends in the genetic diversity of upland cotton in the USA during the last 25 yr and to investigate probable causes for these changes. Two estimates of genetic diversity, coefficient of parentage (rp) and field uniformity (ri; rp weighted by the proportion of the hectarage occupied), were made for cultivars occupying over 1% of the hectarage within a region (Southeast, South‐central, Southwest, and West) from 1970 to 1995 at 5‐yr intervals. An average of 17 (range = 8–46) cultivars accounted for 97% of the cotton hectarage within a region. Regional rp values were relatively stable at 0.12 to 0.15 from 1970 to 1990 and then sharply increased to 0.20 in 1995. Higher rp values in commonly grown cultivars than in released cultivars indicated that much of the genetic diversity in cotton remains unused by growers. Field uniformity (ri) remained at about 0.30 for all regions during the past 25 yr because increases in rp were matched with an increase in the number of cultivars grown and/or a decline in the proportion of the area planted to any single cultivar. The frequent use of several parents for the creation of new cultivars and the planting of only a small portion of the available cultivars has led to a high level of genetic uniformity.
Genotypic Differences in Dinitrogen Fixation Response to NaCl Stress in Intact and Grafted Soybean
Authors: Abd‐Alla M. H. , Vuong T. D. , Harper J. E.
Published: July 2010

Soil salinity is a major limitation to legume production. We evaluated specific soybean [Glycine max (L.) Merr.] genotypes to identify a salt‐tolerant soybean‐Bradyrhizobium system, and to determine by grafting experiments if the scion or the root was responsible for salt tolerance. The effects of three levels of salinity (0, 30, and 60 mM NaCl) on nitrogenase activity (acetylene reduction), nodule number, nodule dry matter, and growth of four soybean genotypes (Williams 82, PI 416937, DR‐1 [an Egyptian cultivar], and NOD1‐3 [a hypernodulating mutant selected from Williams]) were investigated in hydroponic cultures and growth chamber environments. Salt stress significantly inhibited nitrogenase activity, nodule number, and dry matter accumulation per plant of all four cultivars. The detrimental effects of salinity on nodulation parameters and dry matter accumulation were most pronounced for NOD1‐3 and Williams 82, intermediate for DR‐l, and less marked for PI 416937. Self‐grafted NOD1‐3 plants showed 50 to 62% inhibition in nodulation responses (activity, number, mass) while grafting of P1416937 scions to NOD1‐3 roots resulted in less than 7% inhibition by salt. Nodule number on PI 416937 roots was greater when grafted to NOD1‐3 scions (relative to self‐grafted PI 416937 plants), confirming a shoot role in autoregulation of nodule number. Conclusions are that shoot factors are of primary importance in determining salt‐tolerance of the PI 416937 genotype and that hypernodulation expression in the mutant is negatively affected by salt treatment.
Influence of Ozone Stress on Soybean Response to Carbon Dioxide Enrichment: I. Foliar Properties
Authors: Heagle A. S. , Miller J. E. , Booker F. L.
Published: July 2010

Tropospheric O3 can cause foliar injury, decreased growth, and decreased yield, whereas CO2 enrichment generally causes opposite effects. Little is known about plant response to mixtures of O3 and CO2. Open‐top field chambers were used to determine if foliar responses of soybean [Glycine max (L.) Merr.] to CO2 enrichment are affected by O3 stress and vice versa. Plants were grown in 14‐L pots and exposed to four CO2 and three O3 concentrations in 12 combinations. The CO2 treatments were ambient (366 μL−) and three treatments with CO2 added for 24 h d 1 at approximately 1.3, 1.6, and 2.0 times ambient. The O3 treatments were charcoal‐filtered air (CF), nonfiltered air (NF), and NF with O3 added for 12 h−1 ( NF+), resulting in seasonal concentrations of approximately 20, 46, and 75 nL L−1. Foliar effects of CO2 enrichment were dependent on the amount of stress caused by O3. In the CF treatment, plants were not stressed by O3, and CO2 enrichment caused chlorosis and decreased chlorophyll. In the NF and NF+ treatments, plants were stressed by 03, and CO2 enrichment suppressed chlorosis and increased chlorophyll. Ozone decreased specific leaf weight, increased foliar N and C, and decreased C/N ratios, whereas CO2 caused opposite responses for these measures. Ozone increased foliar S and B but did not affect P or K concentrations. Conversely, CO2 enrichment suppressed foliar S, B, P, and K concentrations. These interactions between O3 and CO2 emphasize a need to consider the amount of plant stress caused by O3 in studies to measure effects of CO2 enrichment.
Morphological and Growth Characteristic of Low‐ and High‐Water Use Kentucky Bluegrass Cultivars
Authors: Ebdon J. S. , Petrovic A. M.
Published: July 2010

As the competition for water increases, there is a need to conserve limited water resources applied to irrigated turfgrass sites. Consistent with this effort is the identification of water conserving Kentucky bluegrass (Poa pratensis L.) because low consumptive water use may be important in reducing irrigation requirements by enhancing drought resistance. Low evapotranspiration (ET) rates under non‐limiting soil moisture conditions have been associated with turfgrass morphology and growth characteristics that increase canopy resistance to ET and reduce leaf area components. Much of this previous research emphasized warm‐season turfgrass. A greenhouse study was conducted to determine the relationship between morphological and growth characteristics in 61 Kentucky bluegrass (KBG) cultivars and comparative water use. By means of cluster analysis, the 61 KBG cultivars were categorized as either low‐ or high‐water use cultivars based on ET rates evaluated in the growth chamber across three evaporative demand environments (1.263, 1.664, and 2.261 kPa VPD). Morphological and growth characteristics were assessed from unmowed, spaced plants and mowed turfgrass grown in fritted clay filled lysimeters. Based on single plant morphology, low‐water use cultivars had 13% more horizontal leaf orientation, 6% narrower leaf texture, 13% more lateral shoots per plant, 12% slower vertical leaf extension rate, 2% more leaves per shoot, and 7% shorter leaf blades and sheaths than the high‐water use cultivars. Based on turfgrass morphology from mowed lysimeters, the low‐water use cultivars had 17% more horizontal leaf orientation, 10% narrower leaf texture, 15% more shoots, 4% slower vertical leaf extension rate, and 4% shorter leaf sheaths than the high‐water use group. Canopy resistance to ET was not measured in this study; however, leaf angle (assumed component of canopy resistance) was the only plant characteristics evaluated under mowed conditions whose correlation with turfgrass ET exceeded 0.50 in absolute value. Differences observed among water use groups based on single plant‐ and turfgrass‐morphology was not always consistent with the high canopy resistance to ET/low leaf area hypothesis. However, characteristics were identified which may be useful in selecting for KBG with a low‐water use pattern.
Evaluating of Peanut Breeding Lines with Resistance to the Peanut Root‐Knot Nematode1
Authors: Holbrook C Corley , Noe James P. , Gorbet Daniel W. , Stephenson Michael G.
Published: July 2010

The peanut root‐knot nematode [Meloidogyne arenaria (Neai) Chitwood race 1] causes significant economic losses throughout the peanut (Arachis hypogaea L.) production areas of the southern USA. No resistant peanut cultivars are available; however, a breeding line (UF81206) has been observed to be less sensitive to M. arenaria than commercial cultivars. The objectives of this study were to evaluate the sensitivity to M. arenaria of UF81206 and related breeding lines and to determine if these responses are due to tolerance, or resistance. The yield of 10 peanut genotypes was evaluated for 2 yr in a field with high M. arenaria population densities and in a field with little or no M. arenaria. Two greenhouse tests were conducted to measure nematode reproduction. The breeding lines UF81206‐Q4, UF81206, and UF93111 yielded similarly to Florunner when grown in fields with no nematodes and significantly higher than Florunner when grown in fields with high nematode population densities. These genotypes also supported less nematodere production in greenhouse trials, indicating that these genotypes have a moderate level of resistance. P1203396is in the pedigree of these breeding lines and also exhibited a moderate level of resistance in a greenhouse trial.
Anther‐Derived Dihaploids for Lodging Improvement in Tobacco
Authors: Menchey E. K. , Aycock M. K.
Published: July 2010

Lodging due to severe weather conditions is observed in crops each year. A 2‐yr study was conducted to determine the effectiveness of anther‐derived dihaploids for improving lodging resistance, and to examine certain morphological traits which may contribute to lodging in Maryland tobacco (Nicotiana tabacum L.). Forty‐five and 35 dihaploid lines were derived from F1 plants of ‘MD 201’ ✕ ‘Catterton’ (Population 1) and MD 201 ✕ ‘NC 13’ (Population 2) crosses, respectively, using standard anther and midvein culture techniques. Mature plants were subjected to artificially produced wind, and evaluated by a severity rating based on the degree of lean from the vertical position. Significant variation amongth e dihaploid lines was observed for severity rating over the 2 yr. Heritability values for Populations 1 and 2 were 0.61 and 0.64, respectively. Based on severity ratings from the first year field study, five good and five poor dihaploid lines in Population 2 were evaluated in a 2‐yr greenhouse study for top and root fresh weights and top/root ratio (TRR). Significant variation was observed among the 10 dihaploid lines for TRR only; however, the five lines selected for good lodging performance had larger root weights and smaller TRR than the five lines selected for poor lodging performance. Results obtained from these field and greenhouse studies suggest that the development of dihaploid lines with low severity ratings, larger roots, and smaller TRRis possible, and should provide superior genetic material with a good level of lodging resistance.
Crown Node Elevation of Switchgrass and Kleingrass under Low Light
Authors: Elbersen H. W. , Ocumpaugh W. R. , Hussey M. A. , Sanderson M. A. , Tischler C. R.
Published: July 2010

Excessive crown node elevation of warm‐season grass seedlings is a major limitation to successful establishment. Crown node placement at or above the soil surface limits the opportunity for adventitious root development at the crown node. Kleingrass (Panicum coloratum L.) and switchgrass (Panicum virgatum L.) germplasm with low‐ (LC) and elevated‐ (EC) crown node placement [at 1.5 μmol m−2 s−1 photosynthetic photon flux density (PPFD)] were evaluated for crown node elevation (above soil surface) and coleoptile (or shoot) length under continuous low PPFD ranging from 0 (complete darkness) to 26.8 μmol m−2 s−1 in a growth box. The objective of this research was to characterize the differences in photomorphogenic responses of emerging seedlings of the selected and nonselected populations. In darkness, coleoptiles of LC seedlings were longer than coleoptiles of EC seedlings, while crown node elevation was higher for EC than LC. The PPFD required to prevent crown node elevation in kleingrass was about 5, 30, and >> 30 μmol m−2 s−1 (beyond our level of testing) for LC, nonselected, and EC, respectively. For switchgrass, the PPFD thresholds were lower. To prevent crown node elevation in switchgrass, about 1.6, 5, and 15 μmol m−2 s−1 PPFD were required for LC, nonselected, and EC, respectively. The LC germplasm of both species exhibits a lower PPFDth reshold for de‐etiolation, greater coleoptile length, and a decreased rate of mesocotyl elongation than EC germplasm. The populations selected for LC node placement are hypothesized to have increased establishment success, especially in conditions where low PPFD levels reach the emerging seedling.
Differential Genotypic and Root Type Penetration of Compacted Soil Layers
Authors: Bushamuka Victor N. , Zobel Richard W.
Published: July 2010

Total number of root penetrations of compacted subsoil layers have been commonly used to assess plant tolerance to subsoil compaction. Root‐type specific responses to compacted subsoil layers have not been investigated despite the documentation that plant root types are physiologically and genetically different. A set of maize (Zea mays L.) and soybean (Glycine max L. Merr.) cultivars were grown in growth chambers in containers with compacted middle layers (1.2 and 1.65 Mg m−3) of Howard soil (loamy skeletal, mixed, mesic Glossoboric Hapludalf) with 17% clay content. The containers were exposed to a neutron beam to determine the relative root lengths (RRL) of taproot (RTRL) and basal root (RBRL), the numbers of lateral roots in the compacted layer, and lengths of lateral roots above the compacted layer. The resulting neutron radiographic images revealed that maize ‘SA‐3’ and soybean ‘PI 416937’ taproots penetrated the compacted layer and maintained >90% RTRL in the subsoil, but their basal roots hardly penetrated the compacted layer. In contrast, maize ‘La Posta’ and soybean ‘Weber’ taproots were severely restricted by the compacted layer, but their basal roots penetrated the layer and had >70% RBRL in the subsoil. Maize ‘TS‐6’ taproots were also restricted by the compacted layer, but TS‐6 basal roots had a moderate penetration that produced a 38% RBRL in the subsoil. On the other hand, soybean ‘Perry’ had a moderate penetration and RRLs in the subsoil with both tap and basal roots. This variation in root type response to subsoil compaction among cultivars stresses the importance of considering different root types as distinct entities in studies on plant tolerance to compacted subsoil conditions.