bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability among Desmodium Species for Response to Root‐Knot Nematodes1
Authors: Quesenberry K. H. , Dunn R. A.
Published: July 2010

Several Desmodium spp. have shown potential for use as pasture legumes in Florida and areas of the tropics. Previous research has shown that root‐knot nematodes (Meloidogyne spp.) are a limiting factor for production of certain of these species. The objectives of this research were: (i) to evaluate the responses of germplasm introductions of six Desmodium spp. to three Meloidogyne spp., and (ii) to determine the effects of the plants on nematode reproduction. Germplasm lines were evaluated in three greenhouse experiments. Two to 3 week‐old‐seedlings were infected with 1500 Meloidogyne spp. eggs plant−1 and scored for root galling (GS) and nematode egg masses (ES) after 8 weeks. Variability in GS and ES was identified within and among species. Ten lines of D. intortum (Mill.) Urb. and three of D. uncinatum (Jacq.) DC. were highly resistant to M. arenaria race 1 (Neal) Chitwood, M. incognita race 3 (Kofoid and White) Chitwood, and M. javanica (Treub) Chitwood, but one line of D. uncinatum had an intermediate response. Desmodium barbatum (L.) Beuth., D. heterocarpon (L.) DC., D. ovalifolium Wall., and D. strigolosum Schindler all varied among lines, with GS ranging from 0.1 to 5.0. Nematode egg mass (ES) was generally highly correlated with GS. Individual lines within a species often varied in GS and ES in response to the different root‐knot species. Desmodium spp. germplasm being considered for release or use in a breeding project in areas with known root‐knot nematode infestation should be evaluated for response to the local Meloidogyne spp.
Endosperm Morphogenesis in Wheat: Transfer of Nutrients from the Antipodals to the Lower Endosperm1
Authors: Huber A. G. , Grabe D. F.
Published: July 2010

The morphogenesis of early cell formation in the endosperm of wheat (Triticum aestivum L.) was studied by light microscopy. The objective of this study was to provide a description of endosperm cell formation and corresponding changes in the surrounding diploid and haploid tissues during the first 4 days of wheat endosperm growth. Entire spikelets of large‐kerneled, soft white winter and small‐kerneled hard red winter wheat cultivars were harvested daily, embedded in paraffin, and sectioned longitudinally. The microscopic sections provided a series of photographs documenting the continuous development of the endosperm, embryo sac, and maternal tissues during their early growth. During the first 4 days of development, dense endosperm cells were formed in the lower one‐fourth of the embryo sac, immediately above the embryo. The cytoplasm that made up those cells came from endosperm vesicles formed higher in the embryo sac. These vesicles were formed in the free nuclear endosperm bordering the antipodals. As the vesicles enlarged, they became spherical, were freed, and fell to the gravitational bottom of the embryo sac. There they coalesced, in an appropriate position to be used as nourishment for the embryo. During the period of endosperm vesicle formation, there was concurrent degeneration of the antipodals. By the end of the fourth day postanthesis (PA), the antipodals had been largely consumed and vesicle formation had stopped. Also by that time, walls had grown in from the nucellus and had partitioned the mass of nucleate cytoplasm, above the embryo, into endosperm cells. By 15 days PA, these cells had been consumed entirely by the developing embryo. Cytoplasmic vesicles were found to be the developmental mechanism by which nutrients are transferred from the antipodals to the lower endosperm and ultimately to the embryo.
Endosperm Morphogenesis in Wheat: Termination of Nuclear Division1
Authors: Huber A. G. , Grabe D. F.
Published: July 2010

The morphogenesis of endosperm formation between the 5th and 15th days postanthesis (PA) was studied in wheat (Triticum aestivum L.) by light microscopy. This study was necessary because of lack of information about endosperm cell formation during the period of cellularization of the upper embryo sac. Our objective was to make a description of the changes, visible by light microscopy, in the endosperm and surrounding tissues before the time nuclear divisions end. Developing caryopses were collected daily after anthesis, fixed, embedded in paraffin, sectioned, double stained, and examined under bright‐field and phase‐contrast light. By the fifth day PA, the dense endosperm cytoplasm in the lower embryo sac and in front of the nucellar projection had been separated into cells by walls growing in from the nucellus. After that time, endosperm cells in the crease of the kernel were distinguishable as transfer cells by their greater content of cytoplasm. Between the fifth and seventh days PA, the central vacuole of the embryo sac became partitioned into a netlike reticulum by the endosperm nuclei that had previously surrounded the upper embryo sac. The nuclei were separated by material that stained as protein. The nuclei continued rapid divisions through the ninth day PA; they were associated with very little cytoplasm, compared to the endosperm cells with dense cytoplasm in the lower embryo sac. Where space was available, nuclear divisions occurred both in the peripheral layer of endosperm and throughout the upper embryo sac. The maternal inner integument and nucellar epidermis, surrounding the embryo sac, developed cuticles and stopped expanding between the 9th and 12th days PA. Endosperm nuclear divisions stopped between the 12th and 14th days PA. The reticulum of nuclei was partitioned into nondividing cells by carbohydrate‐staining walls growing inward from the maternal tissues. The aleurone layer of endosperm cells became distinguishable after nuclear divisions had ceased. Starch and protein formation was also observed only after endosperm nuclei stopped dividing. Four distinct cell types were observed during development of the wheat endosperm: (i) cells with dense cytoplasm of the lower embryo sac; (ii) transfer cells next to the crease; (iii) starch and protein storing cells formed by partitioning the upper embryo sac; and (iv) the outer layer of aleurone cells.
Structural Neutral Sugars in Legume and Grass Stems in Relation to Digestibility1
Authors: Buxton D. R. , Russell J. R. , Wedin W. F.
Published: July 2010

Composition of cell wall (CW) polysaccharides of forages can affect rate and extent of digestion by rumen microorganisms beyond the effects attributed to lignin, yet few direct comparisons of monosaccharides in CW of species and cultivars of legumes and grasses have been made. This study was conducted to determine concentration of neutral sugars in CW polysaccharides of immature and mature grass and legume stems, and to relate neutral sugar concentrations to in vitro digestibility of dry matter. In vitro true digestibility (IVTD); neutral‐detergent fiber, acid‐detergent fiber, permanganate lignin, and acid‐detergent insoluble ash (used to estimate holocellulose concentrations); and neutral sugars in ethanol‐insoluble residues were determined in 150‐mm segments of stem bases of fieldgrown cultivars of alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), smooth bromegrass (Bromus inermis Leyss.), and orchardgrass (Dactylis glomerata L.). Concentrations of total neutral sugars (TNS) and holocellulose were greater in mature than in immature stems of all species except smooth bromegrass. Glucose comprised approximately 62% of the TNS in the grasses and 67% in the legumes, whereas xylose comprised 30% in grasses and 20% in legumes. Glucose proportion of TNS increased and arabinose proportion decreased with maturity. Arabinose proportion was similar for grasses and legumes, whereas galactose, mannose, and rhamnose were present in larger amounts in TNS of legumes than in the grasses. Differences in proportions of these neutral sugars also were found among grasses and among legumes. Among grass and among legume species, IVTD concentration was closely related to lignin concentration. In spite of large differences in proportions of these neutral sugars, the only sugar associated with IVTD in dependent of lignin was mannose in grass stems.
Dryland Stand Establishment and Seed Production of Revegetation Species1
Authors: Fisher A. G. , Brick M. A. , Riley R. H. , Christensen D. K.
Published: July 2010

Seed of species used for reclamation and soil conservation in the arid western USA often is collected from native stands. There is a need to produce more seed of known genetic identity under cultivation to meet this demand. The objectives of this research were to: (i) compare stand establishment of four species on three planting dates under dryland conditions (< 360 mm annual precipitation), and (ii) evaluate stand establishment and seed production at 0.76‐ and 1.52‐ m row spacing for 11 species used for dryland revegetation. Four species were evaluated for stand establishment in southwestern Colorado when planted in April, May, and October in 1982, and April, June, and October in 1983. Eleven species were evaluated for seed production. Rocky Mountain penstemon (Penstemon strictus Benth.) and Lewis flax (Linum lewisii Pursh.) had higher stand establishment ratings when seeded in October than in the spring. Indian ricegrass [Oryzopsis hymenoides (Roem. and Schult.) Ricker] established well at all planting dates. Fourwing saltbush [Atriplex canescens (Pursh.) Nutt.] established equally well in all months tested except April. The highest seed yields were obtained from small burnet (Sanguisorba minor Scop.) and tall fescue (Festuca arundinacea Schreb.). Orchardgrass (Dactylis glomerata L.) and Indian ricegrass generally produced more seed than either western wheatgrass [Elymus smithii (Rydb.) Gould] or basin wildrye [Leymus cinereus (Scribn and Merr.) A. Löve]. The latter two species declined in seed production dramatically in the third year. Seed production in 1983 and 1985 was greater in the 0.76‐ than in the 1.52‐m row width.
Effect of Sink Level on Root and Stalk Quality in Maize
Authors: Beck D. L. , Darrah L. L. , Zuber M. S.
Published: July 2010

Grain yield and resistance to root and stalk lodging currently require major emphasis in maize (Zea mays L.) breeding programs. Selection for high expression for one of these characters is often at the expense of the others. Oar objective was to evaluate the effect of grain sink level on root and stalk strength. Fourteen entries were grown including the CO, C4, C8, and Cll of MoSQA, a white endosperm synthetic population selected for high stalk crushing strength; the CO, C4, C8, and Cll of MoSQB, a yellow endosperm synthetic population selected for high stalk crushing strength; two single crosses with high root strength; two single crosses with low root strength; B73 ✕ Mo17, a high‐yielding, widely grown single cross; and ‘US13’ a lower yielding double‐cross hybrid with poor root and stalk strength. Grain sink levels were established by allowing open pollination (100% sink level), preventing pollination (0% sink level), and by physically removing the top half of the ear 10 d after pollination (50% sink level). Root strength was measured vertical root pulling resistance and stalk strength was determined by crushing a 2.5‐cm stalk section. Results from four environments indicated that vertical root pulling resistance declined linearly as sink level increased for all entries. Stalk crushing strength declined with increased sink level for all hybrids and for most of the cycles of MoSQA and MoSQB. Exceptions were Cycle 11 of both MoSQA and MoSQB for which stalk crushing strength was similar at all sink levels.
Comparison of In Vitro Dry Matter Digestibility and Cellulase Digestion for Deriving Near Infrared Reflectance Spectroscopy Calibration Equations Using Cool‐Season Grasses
Authors: Grabrielsen B. C. , Vogel K. P. , Knudsen D.
Published: July 2010

Near infrared reflectance spectroscopy (NIRS) has recently become a potentially valuable and reliable tool for analyses of plant samples in forage‐breeding programs. The success of NIRS is dependent on identification of appropriate and reliable selection criteria and development of reliable calibration. The objectives of this study were to develop and compare NIRS analysis equations for the in vitro dry matter digestibility of cool‐season grasses based on either rumen fermentation (IVDMD) or ceilulase‐solubility (CDMD) methods and to determine if NIRS prediction equations developed from these methods would rank selected genotypes in the same order. Breeding nursery samples of smooth bromegrass (Bromus inermis Leyss.) and crested wheatgrasses [Agropyron cristatum (L.) Gaertner and Agropyron desertorum (Fisch) Schultes] were analyzed for IVDMD and CDMD to develop NIRS analysis equations. Forage samples collected at inflorescence emergence from individual genotypes in the nurseries were used to develop a rank comparison of digestibility methods. The IVDMD and CDMD laboratory values were highly correlated (r ≥0.95). Five to nine wavelengths were required to develop the NIRS analysis equations. The coefficients of determination (R2) from regression of laboratory values on NIRS spectra were 0.96 or higher for all equations. Validation procedures indicated excellent correlations between laboratory and NIRS estimates. Spearman rank order correlations of IVDMD‐ or CDMDderived NIRS digestibility values of genotypes were ≥0.77 for both grasses. At least 15 or more genotypes in the top and bottom 20 were the same with either procedure for both grasses. Near infrared reflectance spectroscopy calibrations for in vitro digestibility based on either IVDMD or CDMD procedures will adequately rank genotypes in cool‐season grass breeding programs in a similar order.
Inheritance of Fatty Acid Composition in a Soybean Mutant with Low Linolenic Acid
Authors: Graef G. L. , Fehr W. R. , Miller L. A. , Hammond E. G. , Cianzo S. R.
Published: July 2010

Linolenic acid is the unstable component of soybean [Glycine max (L.) Merr.] oil responsible for undesirable odors and flavors commonly associated with poor oil quality. The objective of this study was to determine the inheritance of fatty acid composition in A5, a soybean mutant with the lowest linolenic acid percentage of any genotype that has been evaluated for the character. Reciprocal crosses were made between A5 and two soybean cultivars, Weber and Pella. The parents were significantly different for all fatty acids, except palmitic acid in A5 and Pella. The F1 seeds, F2 seeds from F1 plants, and seeds from replicated tests of F2‐derived lines were evaluated for the percentage of palmitic, stearic, oleic, iinoleic, and linolenic acids. The F1 seeds from reciprocal crosses differed significantly for oleic, linoleic, and linolenic acids in both crosses, and for palmitic acid in the Weber cross, which indicated a maternal effect on composition for these fatty acids. Cytoplasmic inheritance of fatty acid composition was not observed, based on the lack of reciprocal cross differences for fatty acid composition in the analysis of F2 seeds from F1 plants. The composition of the F2‐derived lines exhibited a continuous distribution typical of a quantitative character for each of the fatty acids in both crosses. There were 14% of the F2‐derived lines in the Pella cross and 10% in the Weber cross that had a linolenic acid percentage as low as A5. Heritability estimates on a plot basis averaged across crosses from the analysis of F2‐derived lines were 33% for palmitic, 5% for stearic, 54% for oleic, 59% for linoleic, and 58% for linolenic acid. The results indicated that fatty acid composition should be considered a quantitative character in crosses that involve A5 as a parent.
Further Studies on Genetics of Nonnodulation in Peanut
Authors: Dutta M. , Reddy L. J.
Published: July 2010

In the peanut (Arachis hypogaea L.) nonnodulation has been reported to be controlled by both duplicate recessive genes and a single recessive gene. In the present study genetics of peanut nonnodulation was investigated in four crosses from data on F2 populations and F3 progenies from nonnodulating F2 plants. The F2 data of all the four crosses studied showed a better fit for a trigenic ratio of 61 nodulating to three nonnodulating plants compared to the previously reported duplicate digenic ratio of 15 nodulating to one nonnodulating F2, plants. Further, the segregation of F3 progenies from nonnodulating F2 plants indicated the inadequacy of the duplicate factor model. A new genetic model involving three genes in the inheritance of nonnodulation is proposed. Two genes produce nodulation while the third gene inhibits nodulation only when it is dominant and the former two genes are in recessive homozygous condition. By assuming differential heterozygosity at the three loci of the parents involved in various crosses, the duplicate factor and monogenic ratios reported by previous workers on nonnodulation could be explained by the new model. Although the occurrence or non‐occurrence of nodules is governed by a few major genes, the intensity of nodulation appears to be controlled quantitatively.
Dinitrogen Fixation Measurements in Alfalfa‐Ryegrass Swards Using Nitrogen‐15 and Influence of the Reference Crop
Authors: Hardarson G. , Zapata F. , Danso S. K. A.
Published: July 2010

The accuracy of 15N estimates of N2 fixation may be influenced by the choice of the reference crop, especially in mixed legume‐grass swards, where transfer of fixed N2 from the legume to the reference crop may occur. To investigate this, a 2‐yr field experiment was conducted in a Typic Eutrocrepts soil in Austria to measure N2 fixed in alfalfa (Medicago sativa L.) grown alone or in two seeding ratios with ryegrass (Lolium perenne L.), using pure or mixed sward ryegrass as the reference crop. Alfalfa, on the average, derived over 80% of its N from fixation over the 2‐yr period, equivalent to about 415 kg N/ha. Compared to N2 fixation in pure alfalfa sward, the % N derived from atmospheric N2 (% Ndfa) in alfalfa increased significantly in the mixed sward and even more by increasing the seeding ratio of ryegrass in the mixture. Except for the first harvest, the atom % 15N excess in mixed ryegrass was slightly lower than in the pure grass. These differences in 15SN enrichment were insignificant, suggesting that the possible release of N from alfalfa and subsequent uptake by ryegrass may have been small. The highest proportion of ryegrass N that could have been derived from the legume was estimated to be 16% in the second harvest, equivalent to only 4 kg N/ ha and <10 kg N/ha over the 2 yr. These differences in 15SN enrichments of pure and mixed ryegrass reference plants did not significantly affect the estimates of % Ndfa in alfalfa.
Relative Ability of Soybean, Fallow, and Triacontanol to Alleviate Yield Reductions Associated with Growing Corn Continously
Authors: Crookston Kent R. , Kurle James E. , Lueschen E.
Published: July 2010

Corn (Zea mays L.) usually yields more when rotated with soybean [Glycine max (L.) Merr.] than when grown continuously. The exact reason for this yield increase in unknown. One objective of this study was to determine whether the increase in rotated corn yield is due to a positive influence of the soybean or to the absence of a negative influence of continuous corn. An alternate year of fallow was compared to an alternate year of soybean to determine which was more effective in alleviating the yield reduction associated with continuous corn. A second objective was to determine if an application of triacontanol (no chemical name available) (TRIA, reported to be present in soybean residue, and to enhance the growth and yield of corn) might alleviate the yield reduction associated with growing corn continuously. Each treatment consisted of a 3‐yr cropping sequence. Corn was the crop during the first and third years. During the second or alternate year, the plots were maintained in corn, soybean, or fallow. In one series maintained in corn, the crop was treated with TRIA during the seedling stage of the third year. Corn yielded significantly better and equally well when rotated with either soybean or fallow. TRIA had no effect on corn grain yields. It appears that improved grain yields when corn is rotated with soybean are not due to the presence of TRIA or any growth promoting influence left over from the soybean. Rather, the yield increase must be due to the absence of some negative effect that otherwise persists in the soil when corn is grown continuously.
Genetic Analyses of Resistance of Durum Wheat PI 428 435 to the Hessian Fly
Authors: Obanni M. , Patterson F. L. , Foster J. E. , Ohm H. W.
Published: July 2010

Durum wheat (Triticum durum Desf.) has been a major source of resistance to the Hessian fly [Mayetiola destructor (Say)]. Plant introduction (PI) 428 435, BD1419BW28, was selected for genetic studies because of its high resistance to biotypes B, C, D, and L of the Hessian fly. Our objectives were to determine (i) the number genes in PI 428 435 that confer resistance to biotype D, and (ii) whether these genes are different from previously identified genes effective against biotype D. A plant selection out of PI 428 435 was made. Progeny from the plant selection, PI 428 435‐2‐2L, were used throughout this study, which was conducted in a growth chamber at 19 ± 2°C. The test cross data showed that a single dominant factor controls the resistance of PI 428 435 to biotype D. The data also indicated that this gene is different from all previously known factors for resistance to this biotype. This newly identified gene is designated H17. The linkage relationships with H9 and/or H10 suggest that H17 is also located on chromosome 5A. Additionally, the ‘Marquillo’ resistance is assigned gene symbol H18.
Variability and Selection for Characters Associated with Root Regeneration Capability in Alfalfa
Authors: Viands D. R.
Published: July 2010

Alfalfa (Medicago spp.) is capable of regenerating its root system to survive severe injury by biotic or a biotic stress factors. Four field experiments were conducted in Ithaca, NY to examine variability for characters associated with root regeneration capability and to determine if plant populations could be improved for root regeneration capability by phenotypic recurrent selection. Six‐week old seedlings were dug from the greenhouse and their taproots artificially pruned 3 cm below the crown. These plants were transplanted to the field, and the regenerated plants dug 8 to 13 weeks later for root observations. Alfalfa populations ranged more than two‐fold for secondary root number, secondary root size, and taproot diameter 1 cm below the crown after root regeneration. The range for fibrous root mass was 1.4‐fold. All four root characters were positively associated with each other and with topgrowth vigor. Within a genetically broad‐based population, secondary root number ranged from 3 to 23 per plant. Associations among plant characters suggested that more vigorous seedlings are better able to regenerate roots after pruning than are less vigorous seedlings. One to three cycles of phenotypic recurrent selection significantly improved regenerated secondary root number in three of five alfalfa populations. Significant increases in secondary root number ranged from 22 to 45%.
Leaf Morphology, Shoot Growth, and Gas Exchange of Multifoliolate Alfalfa Phenotypes
Authors: Etzel M. G. , Volenec J. J. , Vorst J. J.
Published: July 2010

Herbage yield of alfalfa (Medicago sativa L.) is closely associated with leaf area. The objective of this study was to examine the relationships among leaf morphology, herbage growth, gas exchange, and root carbohydrate metabolism of alfalfa genotypes having trifoliolate or multifoliolate leaves. Plants selected for consistent production of five, seven, or nine leaflets per leaf were compared with genotypes having trifoliolate leaves that were selected for slow (SSER) or rapid (RSER) shoot elongation rate. Plants were grown in a controlled environment chamber at 23°C. In Exp. 1, multifoliolate selections averaged between 4.1 and 7.3 leaflets per leaf and had up to threefold greater area per leaf than trifoliolate phenotypes. Herbage regrowth of multifoliolate phenotypes was equal to phenotype RSER and greater than that of phenotype SSER. After Day 10 of regrowth, plant leaf area development was greater for phenotypes selected for seven or nine leaflets per leaf than trifoliolate phenotypes. Dark respiration rates of recently expanded leaves of plants were similar, while net photosynthetic rates of phenotypes selected for seven or nine leaflets per leaf were slightly lower than that of phenotype RSER. In Exp. 2, removal of lateral leaflets of multifoliolate leaves during early leaf expansion, converted them to trifoliolate leaves, increased net photosynthesis and dark respiration of trimmed leaves an average of 20% over that of intact multifoliolate leaves. Yield per shoot and herbage dry weight were reduced by removal of lateral leaflets, indicating that the multifoliolate leaf morphology was an important determinant of herbage yield of these multifoliolate phenotypes. In both experiments, selection for seven or more leaflets per leaf increased plant leaf area, a factor that may enhance herbage regrowth and forage yield of alfalfa.
Canopy Development, Yield, and Market Quality in Peanut as Affected by Genotype and Planting Pattern
Authors: Jaaffar Z. , Gardner F. P.
Published: July 2010

Planting peanut (Arachis hypogaea L.) in narrow rows with greater spacing between plants in order to approach a square pattern of plant arrangement can reduce competition and increase growth, especially during juvenility. Thus, this study was designed to assess the effects of planting pattern, genotype, and their interaction on seasonal vegetative growth, fruit growth and development, pod and kernel yields, and market quality. Seven genotypes, ‘Florunner’, ‘Tamnut’, and five experimental lines were used. Planting patterns (interrow × intrarow spacing) of narrow row (0.46 × 0.15 m), row [(0.69−0.23) × 0.15 m], and conventional row (0.91 × 0.08 were each established at 15 plants m−2 (150 000 ha−1) in mid‐April of 1985 and 1986. The soil was an Arreodondo loamy sand (loamy, siliceous, hyperthermic, Grossarenic Paleudult) on The Agronomy Farm located near Gainesville, FL. Plots were 6.1 m long and three rows wide (conventional) or four rows wide (narrow and twin row). Florunner, Tamnut, and line 84‐516 from the seven genotypes were sampled biweekly for growth analysis. Plants in the narrow‐ and twin‐row planting patterns, compared to the conventional, had significantly greater ground cover, leaf area indices, canopy light interception, crop growth rates, and yields of total dry matter, pods, and kernels. Planting pattern had no significant effect (P > 0.05) on market quality. Florunner and Tamnut were superior to the experimental lines in growth and kernel yield. Planting pattern and genotype interaction effects on pod and kernel yields were not significant. We conclude that planting patterns that approach equidistant spacing or a square arrangement can produce higher pod and kernel yields than conventional (wide) rows. Furthermore, either narrow‐ or conventional‐row patterns are suitable for screening or testing genotypes of diverse growth habit and market type.
Effects of Tiller Removal on Spring Barley
Authors: Alaoui Ali Chafai El , Simmons Steve R. , Crookston R. Kent
Published: July 2010

Barley (Hordeum vulgare L.) plants normally produce tillers, many of which do not survive to bear grain. Three field experiments were conducted to test whether tillers compete with the main shoots for resources under field conditions. The specific objective was to assess whether mechanical removal of tillers influenced crop and main shoot yield, yield components, and water use under two watering regimes (rainfed only and rainfed plus supplemental irrigation). The experiments were conducted at three locations in different years. In all experiments tiller removal tended to reduce grain yield on a unit area basis. However, in two experiments the decrease in spike number resulting from tiller removal was partly offset by an increase in the grain yield of main shoots for both watering regimes. Specific main shoot yield components enhanced by detillering were kernel number per spike and mass per kernel. Main shoots also initiated more spikelet primordia per spike when tillers were removed. Tiller removal resulted in only a small reduction in the amount of water evapotranspired. These results are consistent with the hypothesis that tillers compete with the main shoot early in its development, reducing its inherent productivity. Genotypes that produce relatively few tillers may be preferred to optimize main shoot productivity and yet maintain the compensatory ability needed for successful production in most environments where barley is commercially grown.
Recurrent Selection for Tolerance to Barley Yellow Dwarf Virus in Oat
Authors: Baltenberger D. E. , Ohm H. W. , Foster J. E.
Published: July 2010

Two cycles of recurrent selection were conducted to determine the feasibility and effectiveness of this breeding strategy for improving tolerance to barley yellow dwarf virus (BYDV) in an oat (Avena sativa L.) population. The base population (C0) originated from 57 crosses between eight winter and nine spring oat lines selected for their good agronomic traits and BYDV tolerance and/or crown rust resistance (Puccinia coronata Cda.) A cycle of recurrent selection involved random intermating of the population twice followed by selection of BYDV tolerant plants to provide parents for the next cycle of random intermating. Selection for BYDV tolerance was among single S0 plants that were infected with BYDV isolate PAV and transplanted to the field for observation of BYDV symptoms. To evaluate progress for BYDV tolerance, 300 randomly selected plants from the unselected C0, C1, and C2 populations were grown to one‐leaf stage in transplanting flats and infested with viruliferous Rhopalosiphum padi L. aphids carrying the PAV isolate of BYDV. Plants were transplanted into the field in a completely randomized design with subsampling. A wooden frame cage covered with a nylon net was erected over the experimental area to exclude natural populations of aphids. Heading date and BYD sympton score were recorded for each plant. Based on the mean BYD symptom scores (0 to 9 scale) for the C0, C1, and C2 populations, progress for BYDV tolerance was made after two cycles of recurrent selection. The mean symptom score for C0 was 5.2; that for C1 was 5.0; and the mean symptom score for C2 was 4.3, significantly reduced from that of C0. Thus recurrent selection for BYDV tolerance is effective and feasible in oat.
Heterotic Patterns among Ten Corn Belt and Exotic Maize Populations
Authors: Mungoma Catherine , Pollak L. M.
Published: July 2010

Maize breeders are concerned with the narrow base of Corn Belt germplasm and the wide use of one heterotic pattern, ‘Reid’ × ‘Lancaster’, in maize (Zea mays L.). Knowledge of other heterotic patterns can contribute to a broadening of the commercial germplasm base. The study was carried out to evaluate heterotic combinations among seven yellow‐endosperm populations—‘BSSS(R)C10’,‘BSK(HI)C8 Syn 3’, ‘BS16(S)C3 Syn 2’, ‘Mexican Dent’, ‘Leaming’, ‘Midland’, among three white‐endosperm populations—‘Pride of Sameline’, ‘Johnson County White’, ‘Potchefstroom Pearl’, and among all 10 populations. In 1985, the 10 populations, their diallel crosses, and 26 checks were evaluated in a 9 × 9 partially balanced lattice with two replications in seven locations. Sources of variation for entries, populations, and general combining ability (GCA) were significant for root lodging, stalk lodging, ear height, days‐to‐pollen shed, days‐to‐silking, moisture content, and yield. Specific combining ability (SCA) mean squares were significant only for ear height. BSSS(R)C10 had the highest GCA effect for yield of all the populations tested. The BSSS(R)C10 × Mexican Dent had the highest yield of 8.77 Mg ha−1, although the four top‐yielding crosses did not differ significantly. This yield was not significantly higher than the check B73 × Mo17, but was significantly higher than BSSS(R)C10 × Lancaster, which represents the heterotic pattern Reid × Lancaster. There were no significant yield differences among the white‐endosperm population crosses. BSSS(R)C10 × Mexican Dent and Midland × BSK(HI)C8 Syn 3 should be evaluated for possible hybrid combinations.
Growth, Yield, and Yield Components of Maize as Influenced by Ethephon
Authors: Cox W. J. , Andrade H. F.
Published: July 2010

Considerable interest exists for use of plant growth regulators to control lodging in maize (Zea mays L.), thereby reducing yield losses. Field experiments were established in New York during the 1985 and 1986 growing seasons on a Honeoye silt loam (fine‐loamy, mixed, mesic Giossoboric Hapludalt) to evaluate a lodging‐susceptible and lodging‐tolerant hybrid (‘Cornell 281’ and ‘Pioneer 3901’, respectively) under recommended (64 000 plants ha−1) and high plant densities (76 000 plants ha−1) in the absence and presence of ethephon [(2‐chloroethyi) phosphonic acid], which was applied at the 15th to 16th leaf stage at 0.42 kg ha−1 a.i. Measurements of dry phytomass and leaf area were taken at 10‐d intervals and leaf area index (LAI), net assimilation rate (NAR), and crop growth rate (CGR) were calculated. In the dry 1985 season, ethephon had no effect on phytomass, NAR, and CGR, whereas in the wet 1986 season, ethephon reduced all three growth parameters. Plant density and hybrid did not influence the growth response to ethephon in this study. Although ethephon reduced lodging by 64%, it had no effect on grain yield. An interaction, however, was observed between ethephon and hybrids. Ethephon increased grain yield of Cornell 281 (7.78 to 8.24 Mg ha−1), and decreased grain yield of Pioneer 3901 (9.63 to 8.56 Mg ha−1). Ethephon also increased kernel weight of Cornell 281 (263 to 266 mg), and decreased kernel weight of Pioneer 3901 (282 to 264 mg), which probably caused the grain yield interaction. Ethephon, however, significantly decreased kernels per ear (494 to 474) in both hybrids. The data suggest that ethephon can enhance the yield of maize when lodging is a problem, but may decrease grain yield in the absence of lodging because of its potential deleterious effect on kernel number and growth.
Lignin Constituents and Cell‐Wall Digestibility of Grass and Legume Stems
Authors: Buxton D. R. , Russell J. R.
Published: July 2010

Concentration and chemical constituents of lignin are factors that may influence cell‐wall (CW) digestibility of forages. This study was conducted to determine the apparent effect of lignin concentration on extent of CW digestion in immature and mature stems of grasses and legumes and to estimate and relate monomeric products of saponification and nitrobenzene oxidation of lignin to CW digestion. The basal 150 mm of stem from cultivars of field‐grown alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), and red clover (Trifolium pratense L.) were harvested during spring growth. Laboratory evaluations included CW digestibility after 72 h of fermentation, neutral‐detergent fiber (to estimate CW concentration), permanganate lignin, alkali‐labile phenolic acids in CW, and nitrobenzene oxidation products (NBO). The apparent inhibition of CW digestion by lignin was 62% greater in grasses than in legumes. In grass stems, ferulic acid was positively correlated with arabinose [r = 0.58 (arabinose determined for another study)], whereas p‐coumaric acid was positively associated with lignin (r = 0.52). The syringaldehyde proportion in NBO increased 61% in grasses and 31% in legumes with stem maturity. The NBO as a proportion of lignin was closely related to CW digestion (r = −0.86) when both grasses and legumes were correlated. The syringaldehyde proportion in NBO was closely related to CW digestion in grass stems (r = −0.93), but not in the legumes (r = −0.23). Thus, there was close agreement between lignin concentration and CW digestibility within grass and legume stems, and the results indicate lignin chemical constituents can be important in accounting for differences in inhibition to digestion between grass and legume lignins.
Relationship of Root Tensile Strength to Vertical Root Pulling Resistance in Maize
Authors: Beck D. L. , Darrah L. L. , Zuber M. S.
Published: July 2010

Vertical root pulling resistance is used to select for improved plant standability in maize (Zea mays L.). Knowledge of the contribution of various root components will lead to better understanding of why plant standability differs among genotypes. Our objective was to study the relationships between vertical root pulling resistance, tensile strength, dry weight, volume, number of large crown roots, and lateral root density. Three hybrids were grown on Freeburg silt loam (fine‐silty, mixed, thermic, Aquic Hapludalfs). The hybrid with the greatest vertical root pulling resistance had the greatest tensile strength of thick (≥ 2.1 ram) diameter root sections, root dry weight, volume, and lateral root density. The hybrid with the lowest vertical root pulling resistance had the lowest tensile strength of medium (1.1–2.0 ram) and thick diameter root sections, root dry weight, and volume. Vertical root pulling resistance was most closely related to mass of the root system and the tensile strength of individual roots.
Differential Effects of Sodium/Calcium Ratio on Sorghum Genotypes
Authors: Grieve C. M. , Maas E. V.
Published: July 2010

Plant response to salinity is a function not only of the total salt concentration but also of the Na/Ca ratio in the root medium. Calcium transport to the shoot decreases at high external Na/Ca and, in many gramineous species, Ca concentration in the expanding blades may become deficient. This study was initiated to determine the differential susceptibility of sorghum [Sorghum bicolor (L.) Moench] genotypes ‘NK 265’, ‘NB 9040’, and ‘Hegari’ (PI 34911) to the Na/Ca ratio in solution cultures. Plants were grown in the greenhouse with six Na/Ca ratios at two salinity levels (osmotic potentials = −0.4 and −0.6 MPa.) NK 265 and NB 9040 were sensitive to high Na/Ca molar ratios at both salinity levels (Na/Ca = 34.6 at −0.4 MPa and 52 at −0.6 MPa). Shoot growth was inhibited; blade injury was typical of severe Ca deficiency. In contrast, at −0.4 MPa, Hegari grew best at high substrate Na and the seedlings had no Ca deficiency symptoms. The K:Na selectivity ratios in Hegari shoots were lower than those in either NK 265 or NB 9040 shoots. The tolerance of Hegari to high external Na was attributed to efficient Ca transport to the developing blades. At both salinity levels, low Na/Ca ratio significantly reduced dry matter yield of Hegari shoots. In all three genotypes, shoot Na decreased with decreasing Na/Ca and was preferentially accumulated in the sheaths. The diversity of the sorghum genotypes in their response to external Na/Ca may be utilized by plant breeders to develop a line that is suited to sodic soil conditions.
Pod Characteristics Influencing Calcium Concentrations in the Seed and Hull of Peanut
Authors: Kvien C. S. , Branch W. D. , Sumner M. E. , Csinos A. S.
Published: July 2010

Calcium is often a limiting factor in peanut (Arachis hypogaea L.) production. Since the peanut fruit develops underground, it will not transpire root absorbed water. Therefore, the developing fruit must absorb phloem—immobile ions such as Ca directly from the soil solution. This experiment's objective was to determine the influence of several pod characteristics on Ca accumulation and Ca concentration in peanut fruit. Eight genotypes with diverse fruit characteristics were grown for two seasons under five water stress treatments [drought 20 to 50 d after planting (DAP), 50 to 80 DAP, 80 to 110 DAP, 110 to 140 DAP, and a well‐watered control]. The 80‐ to 110‐DAP drought period had the greatest negative impact on seed Ca concentrations. Total Ca accumulation in the pod (hull + seed) was positively correlated (0.97) to pod surface area. However, five pod characteristics (days required to mature a pod, specific hull weight, pod surface area, hull thickness, and pod volume) significantly influenced seed and hull Ca concentrations. These characteristics were under genetic control, but their absolute value was modified by water stress. Supply of Ca to the seed maybe analogous to a filter system. Thin, light hulls and long pod maturity periods promote high Ca concentrations in the seed. Thick, dense hulls, short maturity periods, and small pod volumes promote high Ca concentrations the hull.
Influence of Plant Growth Stage on Cereal Aphid Reproduction
Authors: Kieckhefer R. W. , Gellner J. L.
Published: July 2010

The objective of this research was to determine the influence of the stage of growth of host plants upon the fecundity of cereal aphids. This information is useful in evaluating the potential for cereal aphid movement between, and their colonization of, a sequence of field crops in the Northern Plains and in understanding the epidemiology of plant virus diseases transmitted by cereal aphids. Aphid fecundity was tested in growth chambers on spring wheat (Triticum aestivum L.), spring barley (Hordeum vulgare L.), sorghum [Sorghum bicolor (L.) Moench], and maize (Zea mays L.) when plants were in the seedling (2—3 leaf), boot, heading, and flowering stages of growth. Aphid fecundity was also compared on vernalized and nonvernalized winter wheat. The aphids tested were the greenbug (GB) [Schizaphis graminum (Rondani)], the English grain aphid (EGA) [Macrosiphum (Sitobion) avenae (F.)], the bird‐cherry oat aphid (RP) [Rhopalosiphum padi (L.)], and the corn leaf aphid (CLA) [R. maidis (Fitch)]. The results of the tests showed that GB and RP reproduced more on headed wheat than on earlier stages of wheat growth. CLA fecundity was significantly greater on seedling barley than on later stages of growth, but there were no significant differences in GB, RP, and EGA reproduction on barley at the several stages of growth. Seedling maize was virtually immune to RP and CLA colonization; however, GB, RP, and CLA reproduction was greater on seedling sorghum than on older plants. No significant differences were detected in the fecundity of GB, RP, or EGA on vernalized versus nonvernalized winter wheat. The results are interpreted in the context of cereal aphid field biology and stage of crop development in the Northern Plains.
Yield Losses Caused by Maize Dwarf Mosaic Virus in Maize
Authors: Scott G. E. , Darrah L. L. , Wallin J. R. , West D. R. , Knoke J. K. , Louie R. , Gudauskas R. T. , Bockholt A. J. , Damsteegt V. D. , Uyemoto J. K.
Published: July 2010

Maize dwarf mosaic (MDM) is a virus disease of maize (Zea mays L.) that causes yield reductions. The objective of this study was to determine yield losses caused by maized warm fosaic virus strain A (MDMV‐A) in susceptible maize hybrids grown over a wide range of environmental conditions. Plants inoculated with MDMV‐A were compared with noninoculated plants in the years 1981 to 1984 at various locations within the USA. Inoculation levels were 100% in 1981; 33, 67, and 100% in 1982; and 50 and 100% of the plants in 1983 and 1984. The regressions of grain yields (expressed as a percentage of the noninoculated check) on MDM‐diseased plants were calculated. Linear regressions best explained the results, and deviations from linearity were not statistically significant. The b values ranged from 0.118 to 0.445 for different location and year combinations. The linear regression that best described the results over all environments and hybrids was Y = 99.7 − 0.242x where Y = predicted yield (as a percentage of the noninoculated check) and x = percentage of diseased plants. Thus, maized warm fosaic virus decreased yields by an average of 2.4% for each 10% increase in MDM‐diseased plants. This certainly emphasizes the need to grow hybrids that are resistant to this virus.
Inheritance of a 1BL/1RS Wheat‐Rye Translocated Chromosome in Wheat
Authors: Rayburn A. Lane , Mornhinweg D. W.
Published: July 2010

In the Great Plains, winter wheat (Triticum aestivum L.) lines carrying the 1BS/1RL wheat‐rye translocated chromosome are being used extensively in wheat breeding programs. This study was conducted to determine the influence of the 1BL/1RS chromosomone gametic transmission in adapted winter wheat backgrounds. Oklahoma experimental line OK83398 (‘Aurora’/2*TAM W‐101) was crossed to both ‘Arkan’ and ‘Chisholm’. The F2 plants were analyzed as to their chromosomal composition using the chromosomal N‐banding procedure. In both crosses a significant deviation of a 1 homozygous 1B:2 heterozygous:1 homozygous 1BL/1RS ratio at the P = 0.05 level was observed. The transmission of gametes containing the 1BL/1RS translocated chromosome was observed to be reduced in F1 hybrids in winter wheat backgrounds.
Evidence of Pathogen Specificity in Tolerance of Soybean Cultivars to Phytophthora Rot
Authors: Thomison P. R. , Thomas C. A. , Kenworthy W. J. , McIntosh M. S.
Published: July 2010

The recent appearance of new races of the soybean [Glycine max (L.) Merr.] pathogen Phytophthora megasperma f.sp. glycinea (Pmg) has prompted breeders to consider the use of tolerance as an alternative to race‐specific resistance. The objective of this study was to evaluate the tolerance of cultivars to different isolates and races of Pmg. The tolerance reactions of ‘Essex’, ‘Williams’, ‘York’, and ‘Ware’ to isolates of Races 1, 5, 10, and 24 were determined by transplanting 4‐d‐old seedlings into media infested with Pmg and measuring the effect on plant growth. The reactions indicate that some isolates differ only in virulence and that others differ in pathogenicity. Soybean cultivars selected for tolerance to a limited number of Pmg isolates/races may not necessarily be tolerant to others.
Heritability of Cell Wall Carbohydrates in Switchgrass
Authors: Godshalk E. B. , McClure W. F. , Burns J. C. , Timothy D. H. , Fisher D. S.
Published: July 2010

Cell wall monosaccharides are closely associated with forage digestibility in switchgrass (Panicum virgatum L.). This study was conducted to estimate the feasibility of using these monomers as selection criteria to increase in vitro dry matter disappearance (IVDMD) of switchgrass. Thirty‐three parents were selected from a population of 660 plants on the basis of forage yield, IVDMD and N concentration. The 33 parents and their half‐sib progeny were evaluated during 1985 and 1986, at Clayton, NC, in separate fields with four replicates per field. First and second harvest plant samples of the parents and their offspring were assayed for IVDMD, acid detergent fiber (ADF), neutral detergent fiber (NDF), concentrations of arabinose (ARA), galactose (GAL), glucose (GLU) and (XYL), and ratios of the monosaccharides. Narrow‐sense heritability was estimated on a family mean basis and from parent‐offspring covariances. Broad‐sense heritability was estimated from parent variance components. A relatively low family mean heritability estimate was obtained for ARA, while GAL, GLU, and XYL were moderately heritable. Only initial growth XYL in the parents and regrowth XYL in progeny significantly interacted with years. The genotypic correlation between GLU and IVDMD in regrowth was positive (rG= 0.81) and exceeded three times its standard error, while the genotypic correlation between IVDMD and XYL (rG = −0.91) was significantly negative. The digestible cell wall (DCW) fraction of NDF residues was significantly positively correlated with GLU (rG = −0.92) in regrowth and significantly negatively correlated with XYL (rG = −0.81) in initial growth. Monomeric ratios of ARA:GLU, GAL:GLU, and XYL:GLU were highly negatively correlated with IVDMD and DCW and positively correlated with ADF and NDF. Based on predicted gains from selection, correlated responses of IVDMD are expected to be greatest when using clonal selection or modified earto‐row selection for reductions in the ARA:GLU or XYL:GLU ratios.