bluuebunny/crossref_metadata_2025 huggingface dataset:
Agronomic Performance of Soybean Lipoxygenase Isolines
Authors: Pfeiffer T. W. , Hildebrand D. F. , TeKrony D. M.
Published: July 2010

Lipoxygenases (EC 1.13.11.12) are enzymes that catalyze the hydroperoxidation of polyunsaturated lipids. In soybean [Glycine max (L.) Merr.] seeds, these lipid hydroperoxides are converted to volatile compounds associated with undesirable flavors. On the other hand, lipoxygenases may be involved in plant growth and development, senescence, and pest resistance, and, while the genetic removal of soybean seed lipoxygenases might enhance soybean product quality, agronomic quality might be deleteriously affected. Mutant alleles exist for the three soybean seed lipoxygenase isozymes that genetically eliminate each lipoxygenase function. This study compared a set of 10 LxlLx1‐Lxl,Lx1 isolines for agronomic performance, and determined in ‘Century’ isolines the effect of lipoxygenase removal on pod and stem blight (Phomopsis longicolla Hobbs) fungal infection of seeds. Substituting the null allele Lx1 for the competent allele Lx1 had no deleterious effects on soybean yield in four environments. Lodging, height, seed weight, and seed oil and protein concentrations were unaffected. Maturity differed significantly, but only by I d. In 1988, only Century isoline L2−3, lacking lipoxygenase 2, had a higher level of P. longicolla seed infection than Century, and in 1989.only isoline L2L3−2−4, lacking lipoxygenases 2 and 3, had a significantly higher level. Production of soybean genotypes with reduced embryo lipoxygenase levels should not be more severely affected by pod and stem blight disease than genotypes containing all embryo lipoxygenases.
Cytological Comparison of Amplified Chromosome Segments in Four Tobacco Doubled Haploids
Authors: Reed Sandra M. , Burns Joyce A. , Wernsman E. A.
Published: July 2010

Atypical quadrivalents, which appear to be the result of pairing between amplified homologous segments in nonhomologous chromosomes, have been found in tobacco (Nicotiana tabacum L.) doubled haploid (DH) × cultivar hybrids. The purpose of this study was to determine if the same amplified chromosomes are involved in these quadrivalents in different DH lines. Chromosome pairing was studied in hybrids between four DHs, of which two were derived from ‘NC95’ and the other two from ‘C139’. Results of this study indicate that all four of the DHs contain two homologous amplified chromosomes regions. The chromosomal locations of both of these amplified segments in three of the DHs appear to be the same. One of the amplified segments in the fourth DH is located on the same and the other on a different chromosome than in the other three DHs. The difference in location of one of the amplified segments in this fourth DH could be the result of a translocation or the amplification of nontandem multigene families. That similar genetic sequences have been amplified in all four DHs studied suggests there may be some specificity to the DNA amplification that occurs as a result of anther culture in tobacco.
Nitrogen Partitioning in Maize during Ear Development
Authors: Ta C. T. , Weiland R. T.
Published: July 2010

The partitioning of N during the grain‐filling period of maize (Zea mays L.) was studied under field conditions at differing levels of fertilizer. Two hybrids with differing leaf‐canopy senescence, B73Ht × LHI05 (rapid) and B73Ht × Va35 (slow), were grown with two rates (67 and 257 kg ha−1). Separate plants were supplied with 15N the 14‐leaf stage (VI4), antbesis, or 22 d after anthesis, and the subsequent patterns of 15N partitioning were followed. Independent of time of application, hybrid, or N fertility, ⊄45% of the 15N applied was absorbed within 3 d. Three days after the V14 treatment, the stalk contained 50% of the absorbed 15N, suggesting that it acts as a major sink for N during vegetative growth. With later applications, the 15N was predominantly partitioned to the ear. Although absorption of total N from soil continued during the grain‐filling period, there was significant remobilization of N from vegetative organs (60 to 85% of the total N present at anthesis) to the ear. Leaves and stalk each contributed 45% of total N remobilized into the ear, and 10% was contributed by the roots. Loss of N from the stalk was initiated before anthesis, whereas it began around anthesis with leaves and roots. The results indicate the important role of the stalk in providing N for kernel development. Both N fertility and hybrid influenced the rate of N remobilization from vegetative tissues.
Heterogeneity of the ‘Wichita’ Wheat Monosomic Set for Grain Quality and Agronomic Traits
Authors: Stein Ira. S. , Sears Rollin G. , Gill Bikram S. , Hoseney R. C. , Cox Thomas S.
Published: July 2010

Homogeneity between the chromosome lines of an aneuploid set is necessary to avoid supplemental effects of the genetic background. The objective of this study was to determine the homogeneity of the ‘Witchita’ (WI) winter wheat (Triticum aestivum L.) monosomic set for grain quality and agronomic traits. Disomics were produced from 20 chromosome lines of the WI monosomic set and 2B disomics from ‘Cheyenne’ monosomic 2B. Three replications were planted in a field study. Disomics of 5B lines were later heading, shorter, and 2.25% higher in grain protein concentration (GPC) than the WI check. Disomics of 7B lines were shorter and had a lower 100 kernel weight. Disomics of 2B lines were similar to the WI check for GPC, height, and mixogram peak; however, they were later heading and had lower 100 kernel weight. The average GPC of disomic lines from 4B, 6D, and 7B were about 1.5 to 3.0% lower than those of 1A, SA, 5B, and 6B, while 7A dosmics were 1.5% and 2.25% lower than 5A and 5B, respectively. Mixogram peak and tolerance of the disomics were similar to the WI check; however, lines from 1A, 3B, 5B, 6A, and 6B had shorter mixing times than lines from 4D, 6D, and 7B. Significant variation for several traits measured, specifically GPC, plant height and heading date, supports the contention that homogeneity studies should accompany aneuploid studies, especially when quantitative traits are measured.
Latent‐Period Responses of Stem Rust in Tall Fescue Incubated at Four Temperatures
Authors: Welty Ronald E. , Barker Reed E.
Published: July 2010

Stem rust, caused by Puccinia graminis Pers.:Pers. subsp, graminicola Z. Urban, has recently been found on tall rescue (Festuca arundinacea L.) grown for seed in western Oregon. Development of stem rust in the field is affected, to a large extent, by environmental conditions. We conducted controlled environment studies to determine the effect of incubation temperature on development of uredinia in five tall rescue cultivars. Differences in latent period (time from inoculation to urediniospore production) were observed for stem rust development in tall rescue incubated at 10, 18, 25, and 27 °C. Maximum number of erumpent pustules occurred 15, 12, 9, and 8 d after inoculation at 10, 18, 25, and 27 °C, respectively. A latent‐period index (LPI) was developed to compare latent periods of stem rust among temperatures and cultivars. Average LPI was 17.4 at 10 °C 11.8 at 18 °C, 10.5 at 25 °C, and 10 at 27 °C. Values at 10 and 18 °C differed significantly from 25 and 27 °C, and from each other (P = 0.05, LSD 0.05 = 1.17). Average LPI was 11.9 for ‘Mesa’, 12.4 for ‘Fawn’, 12.6 for ‘Bonanza’, 12.6 for ‘Kentucky 31’, and 12.7 for ‘Adventure’. The LPI for cultivars did not differ significantly from each other (P = 0.05), and all cultivars were rated susceptible to stem rust. A significant cultivar × temperature interaction occurred, with some cultivars developing rust faster than others. For example, Fawn and Kentucky 31 had more plants developing pustules at earlier dates than did the other three cultivars. Conversely, Mesa usually had fewer plants with pustules than the other cultivars and usually required more time to develop pustules. Selection within tall rescue cultivars or sources of germplasm for resistance to stem rust should be done between 18 and 27 °C, to avoid falsely identifying plants as resistant when low temperature induces a delayed latent period. Selections for stem rust‐resistant plants can be accomplished in less time if postinoculation incubation is done at high temperature.
Variability of Malate Dehydrogenase among Cotton Cultivars with Differing Fiber Traits
Authors: Kloth Reiner H.
Published: July 2010

Little is understood about the biochemical basis of differences in quantitative traits of cotton (Gossypium hirsutum L.) fiber. Malate dehydrogenase (MDH) is implicated as an enzyme that may have effect on extension growth during the development of cotton fiber. Our objectives were, first, to determine if variability among cultivars exists for MDH, and, second, to determine if variability in MDH can be correlated with quantitative traits of fiber. Twenty‐four cultivars G. hirsutum were chosen. Polyacrylamide gel electrophoresis was used to search for MDH allozyme variation in etiolated cotyledons. Additionally, MDH activity in developing fiber was measured. All cultivars were grown in 1990 at two sites near Stoneville, MS. At 12 days post anthesis (DPA), immature bolls were harvested and the fiber separated from the ovules. An extract was prepared from the fiber and assayed for MDH activity and protein concentration. Other bolls were allowed to mature and open naturally, and from these bolls fiber was taken and tested for eight traits: elongation, maturity (ratio of wail thickness to fiber diameter), micronaire reading (fiber fineness), perimeter, 2.5 and 50% span length, strength, and wall thickness. Allozyme variation for MDH was not detected. The MDH specific activity ranged from 13.8 to 18.8 µmol NADH min−1 mg−1 protein, with a mean of 16.4 μmol NADH min−1 mg−1 protein in 12 DPA fiber. Variation among cultivars for MDH specific activity and all fiber traits was significant (P < 0.05). Though implicated in extension growth, MDH specific activity was not correlated with the length of mature cotton fiber. Only correlations between MDH specific activity and three traits of fiber walls (maturity, r = −0.476; micronaire, r −0.469; and wall thickness, r = −0.475 were significant. Cotton cultivars vary significantly for MDH activity in developing fibers and high MDH activity is indicative of low micronaire reading, thin fiber walls, and decreased maturity.
Variation in Characters Related to Leaf Photosynthesis in Wild Bean Populations
Authors: Lynch Jonathan , González Alonso , Tohme Joseph M. , García James A.
Published: July 2010

Leaf characters related to photosynthesis in wild bean (Phaseolus vulgaris L.) populations were surveyed to identify genetically useful traits. Fifty wild bean accessions collected from Mexico to Argentina were evaluated at two contrasting field locations. Canonical analysis distinguished four groups of accessions, corresponding to collection sites in Mexico, Guatemala, Peru, and Argentina. Mexican accessions had high photosynthetic rates, low soluble protein contents, and the highest instantaneous photosynthetic nitrogen‐use efficiency (PSNUE). Guatemalan accessions had low photosynthetic rates, low N content, and low PSNUE. Peruvian accessions had high photosynthetic rates, few stomates, high N, high soluble protein, high chlorophyll content, and high PSNUE. Argentinian accessions had low photosynthetic rates, few adaxial stomates, low N content, and low PSNUE. It is proposed that palisade cell size influences leaf photosynthesis by affecting specific leaf weight and therefore N content per unit leaf area. Significant variation within and between origins was observed for adaxial stomatal density. Differences in PSNUE, adaxial stomatal density, and palisade cell volume between individual accessions varied by a factor of 3, 5, and 3.5, respectively. We conclude that genetic variation for leaf photosynthetic characters exists in wild bean germplasm.
Field Screening for Rhizome Number in Tall Fescue
Authors: Bouton Joseph H. , Smith S. Ray , De Battista José P.
Published: July 2010

Rhizomes can enhance competitiveness and persistence of tall rescue, Festuca arundinacea Schreber., but reliable field screening techniques need to be developed for the rhizome trait. We investigated the effects of plant age and infection with the endophyte Acremonium coenophialum (Morgan‐Jones & W. Gams) [previously Epichloe typhina (Fries.) Tulasne] on number of rhizomes. Six, endophyte‐infected (EI) genotypes varying in ability to produce rhizomes and their endophyte‐free (EF) clones were compared in a split‐split plot design with plant age (about 3, 6, 9, and 12 mo after transplanting) as main plots, genotypes as subplots, and infection status as sub‐subplots. The experiment was planted twice and rhizomes counted on each treatment in the field at the time of digging and after washing. Number of rhizomes was highest 1 yr after transplanting. More rhizomes were counted on washed than field‐counted plants, but correlations between the two were high (r = 0.95), indicating that either would accurately rank genotypes. There was no endophyte effect on number of rhizomes, but a significant genotype × infection status interaction was found in March. Screening within a closed EI or EF population and counting rhizomes on freshly dug l‐yr‐old plants at one location is projected to be a good procedure. When this procedure was used estimate heritability for number of rhizomes within EF ‘Kentucky 31’, a broad‐sense estimate of 0.76 and narrow‐sense estimates ranging from 0.38 to 0.88 were calculated.
Relation of Rubisco to Maize Grain Yield Improvement: Effect of Water Restriction
Authors: Martínez‐Barajas E. , Villanueva‐Verduzco C. , Molina‐Galán J. , Loza‐Tavera H. , Sánchez‐de‐Jiménez E.
Published: July 2010

Yield improvement in maize (Zea mays L.) can be obtained by repeated cycles of mass stratified selection, but the biochemical mechanisms behind this method are not understood. This research focuses on testing the possible role of ribulose‐l,5‐bisphosphate carboxylase/ oxygenase (rubisco) in this process, and how water deficiency affects the enzyme during the grain‐filling period. Rubisco activity and Rubisco protein were measured in the leaf above the ear of maize plants from the original and improved population throughout the grain filling, under irrigated and water‐deficient conditions imposed during the linear part of the filling period. In fully irrigated plants, rubisco activity was higher in the selected population, but rubisco protein content was not. In water‐deficient plants, rubisco activity srongly decreased in both maize populations, but rubisco protein was less affected. Grain yeild was higher in the improved population in irrigated plants, but the advantage was lost during water deficiency. The above data suggest the the mass stratified method for grain yield improvement is selecting for plants with higher catalytic activity of rubisco, rather than greater contents of rubisco protein.
Association between Gene Lr34 for Leaf Rust Resistance and Leaf Tip Necrosis in Wheat
Authors: Singh Ravi P.
Published: July 2010

Durable resistance to leaf rust (Puceinia recondita Roberge ex Desmaz. f. sp. tritici) in bread wheat (Triticum oestivurn L.) cultivars is known to result from the interaction of Lr34 with other minor additive genes that are effective in the adult growth state. The Lr34 gene seems to be present in several CIMMYT germplasm‐derived Mexican cultivars that display temperature‐ and light‐sensitive seedling responses similar to those displayed by near‐isogenic ‘Thatcher’ lines that contain Lr34. Adult plants of these two Thatcher lines and all Mexican cultivars postulated to carry Lr34 display resistance to leaf rust and exhibit leaf tip necrosis symptoms. This study was conducted to determine whether 15‐34 and a gene or genes for leaf tip necrosis am linked. The simultaneous presence of Lr34 and leaf tip necrosis in the two Thatcher near‐isogenic lines and Mexican cultivars was confirmed by evaluating F2 plants or F3 lines obtained from various intercrosses. Lr34 and leaf tip necrosis were inherited together in a population of 117 F3 lines obtained from the cross of leaf rust resistant ‘Jupateco 73R’ (carrying Lr34 and leaf tip necrosis) with its susceptible counterpart ‘Jupateco 73s’. Linkage or pleiotropism was also evident in the crosses of six Lr34‐carrying Mexican cultivars with ‘Siete Cerros 66’ (which does not have Lr34). The gene for leaf tip necrosis, designated Lln, could be used as a marker for Lr34.
Genetic Diversity for RFLPs in European Maize Inbreds: I. Relation to Performance of Flint ✕ Dent Crosses for Forage Traits
Authors: Boppenmaier Jürgen , Melchinger Albrecht E. , Brunklaus‐Jung Elisabeth , Geiger Hartwig H. , Herrmann Reinhold G.
Published: July 2010

Restriction fragment length polymorphisms (RFLPs) have been proposed as a tool for assigning inbreds to heterotic groups and predicting heterosis and performance of single‐cross hybrids in maize (Zea mays L.). Such use was evaluated in 11 flint and 11 dent inbred lines from the European maize germplasm and in 66 F1 hybrids produced between them according to an incomplete factorial mating scheme. Inbreds and hybrids were evaluated for 12 forage yield and quality traits in three and six environments, respectively, in Germany. The RFLP assays of the 22 inbreds were performed with two restriction enzymes and 101 DNA probes distributed throughout the maize genome. Most (>97%) clone‐enzyme combinations revealed polymorphisms (⊄5.0 variants per clone‐enzyme combination). Genetic distances (GD) between lines, calculated from RFLP data, had a significantly greater mean for flint × dent (0.65) than for flint x flint (0.58) or dent × dent (0.59) line combinations. Cluster analysis based on GDs revealed associations among lines consistent with their origin from different heterotic groups and known pedigrees. The GD values pertaining to the 66 F1 hybrids were partitioned into general (GGD) and specific (SGD) genetic distances; GGD explained ⊄30% of the variation among GD values. Neither GD nor SGD was significantly correlated (|r|≤ 0.25) with F1 performance or midparent heterosis for any trait examined. Results from this study support previous investigations with U.S. maize germplasm in that RFLP data can be used for assigning inbreds into heterotic groups. However, RFLP‐based genetic distance measures are apparently not indicative of the performance of single‐cross hybrids between lines from different heterotic groups for forage traits.
Correlations and Path Analyses of Agronomic Traits in Guayule
Authors: Estilai Ali , Ehdaie Bahman , Naqvi Himayat H. , Dierig David A. , Ray Dennis T. , Thomson Anson E.
Published: July 2010

Successful breeding of guayule (Parthenium argentatum Gray) for increased rubber yield requires knowledge about the traits that influence rubber production directly and indirectly. This study was undertaken to examine the interrelationships of several agronomic traits through path‐coefficient analyses, to determine broad‐sense heritability, and to estimate genetic advance under selection. Plant height, width, dry weight, rubber content, resin content, rubber yield, and resin yield from guayule selections planted at two locations (Riverside, CA, and Maricopa, AZ) were used for analyses. The guayule selections exhibited significant differences for all traits at both locations, except for plant dry weight and plant width at Maricopa. Broad‐sense heritability estimates ranged from a low of 75.1% (for rubber content) to a high of 96.5% (for resin content) at Riverside, and from 6% (for plant width) to 93.1% (for resin content) at Maricopa. Expected netic advance ranged between 18% (for plant width) and 76% (for resin yield) at Riverside, and between 0.72% (for plant width) 41% (for resin content) at Maricopa. Rubber yield, the most critical trait for economic commercialization of guayule, showed expected genetic advance of 58% at Riverside and 37% at Maricopa. Path‐coefficient analyses indicated plant height to be less important than plant width as a component of dry weight at Riverside. Dry weight and percent rubber content had positive direct effects on rubber yield and accounted for 99% of its variation at Riverside and 85% at Maricopa.
Relationship between Chlorophyll Concentration and Iron Chlorosis in Grain Sorghum
Authors: Peterson Gary C. , Onken Arthur B.
Published: July 2010

Grain sorghum, Sorghum bicolor (L.) Moench, is susceptible to Fe chlorosis when grown on many calcareous soils. Cultivars that are high yielding and resist Fe chlorosis can be developed only after methods for identifying sources of Fe chlorosis resistance are obtained. This study was conducted to examine the relationship between leaf chlorophyll and visual scoring of Fe deficiency symptoms and to compare the effectiveness of these methods for classifying sorghum response to Fe deficiency. Sorghum cultivars and hybrids were planted in two tests at Berclair, TX, on a Weesatche fine sandy loam (fineloamy, mixed, hyperthermic Typic Argiustoll) in single‐row plots and replicated twice with each entry adjacent to the resistant and susceptible check. Chlorophyll a, b, and a + b (Chla, Chlb, and Chla+b) classified entries for resistance or susceptibility as well as visual scoring. Resistant entries identified by Chla+b included IS12684C, IS7273C, IS12682C, IS12678C, and IS7367C. Visual scoring identified IS12684C and IS7273C as being significantly superior to the resistant check and experimental entries for each measure of chlorophyll. Significant (P< 0.01) negative correlations, each greater than −0.809, existed between visual scoring and the three measures of chlorophyll. Using visual scoring and analysis of covariance resulted in a coefficient of variation of 15 for the cultivar test and 17 for the hybrid test compared with a range of 42 to 59 for the chlorophyll measurements in each test. None of the four evaluation methods was superior to another for identification of cultivars with resistance to Fe deficiency chlorosis.
Response of Alfalfa Cultivars to Salinity during Germination and Post‐Germination Growth
Authors: Al‐Niemi Thamir S. , Campbell William F. , Rumbaugh Melvin D.
Published: July 2010

During post‐germination growth, alfalfa (Medicago sativa L.) cultivars may exhibit a different salinity tolerance from that expressed during germination. To explore this possibility, 86 cultivars and experimental populations of alfalfa were exposed to nine levels of NaCl ranging from 0 to 342.2 mM during germination. Cultivars that exhibited the highest (14 cultivars) and the lowest (8 cultivars) NaCl tolerance from the germination study were exposed to 0, 88, and 132 mM after the completion of germination under 0 NaCl to determine post‐germination NaCl tolerance. There were no significant correlations between percent germination of these cultivars at 88 or 132 mM NaCl and their subsequent growth parameters. The IC30, or the NaCl concentration that inhibited germination of 50% of the viable seeds, of the cultivars was negatively correlated only with shoot‐to‐root ratio when the plants were exposed to 132 mM NaCl after germination. Post‐germination performance of cultivars that needed high NaCl concentration to inhibit 50% of their seed germination (high IC50 group) was not significantly different from the low IC^ group under 88 or 132 mM NaCl treatments. The ability of alfalfa cultivars to germinate at high NaCl concentrations was not related to their post‐germination performance under salt stress, except for the negative correlation between IC50 and shoot‐to‐root ratio at 132 mM.
Adaptation of Lentil Seed Yield to Varying Moisture Supply
Authors: Hamdi Ahmed , Erskine William , Gates Philip
Published: July 2010

Lentil (Lens culinaris Medikus) is an important component of ralnfed farming systems in West Asia and North Africa; it is also grown under irrigation in Egypt and Sudan. Our objectives were to determine the adaptation of a range of lentil genotypes to a wide spectrum of moisture regimes. Thirty‐four diverse genotypes were grown for two seasons (1984–1985 and 1985–1986) at three locations varying in water supply, in northern Syria and Lebanon. At one location (Tel Hadya, Syria), the crop was given two supplementary irrigation regimes. Variation in mean seed yield per plant was largely explained (R2 = 0.833**) by the variation in water supply. Two supplementary irrigations (50 mm each) resulted in a 20% increase in seed yield per plant. Genotypic performance was adequately summarized by genotype means and their linear responses to different levels of moisture supply, allowing selection of genotypes for either wet or dry conditions.
Root Growth, Nitrogen Uptake, and Tillering of Wheat Induced by Mixed‐Nitrogen Source
Authors: Wang Xingting , Below Fred E.
Published: July 2010

Growth and yield of wheat is enhanced when plants are provided with mixtures of NO3 and NH4, compared with either form alone. The objective of this experiment was to further evaluate the effects of N form on growth and tillering of wheat, with particular attention to tiller phenology, root morphology, and N uptake. Two species of spring wheat (Triticum durum Desf. cv. Inbar and Triticum aestivum L. cv. Len) were grown in the greenhouse with five different ratios of NO3‐N and NH4‐N (100/0, 75/25, 50/50, 25/75, 0/100). Compared with either form alone, mixtures of NO3 and NH4 increased vegetative growth of both cultivars due to enhanced development of coleoptilar and higherorder tillers. The magnitude of growth enhancement was greater (=60%) for Inbar than Len. For both cultivars, growth on N mixtures increased the number, mass, and primary branching of nodal roots, but did not affect seminal root growth. However, because nodal roots per tiller and nodal root branches per tiller were unaffected by N treatment or cultivar, changes in root morphology cannot fully explain treatment‐induced differences in tillering. Although plants of both cultivars supplied with mixed N absorbed more total N, the response was larger for Inbar because of its ability to sustain NO3 uptake when external NO3 concentrations were reduced by substitution with NH4, and to more than compensate for the decrease in NO3 uptake by additional absorption of NH4. Therefore, mixed‐N‐induced increases in tillering are also related to enhanced N uptake as well as altered root growth.
Genotypic and Cultural Effects on Condensed Tannin Concentration of Cotton Leaves
Authors: Lege Ken E. , Smith C. Wayne , Cothren J. Tom
Published: July 2010

Condensed tannins reportedly act as feeding deterrents to bollwonn [Helicoverpa zea (Boddie)], tobacco budworm [Heliothis virescens (F.)], and two spotted spider mite [Tetranychus urticae (Koch)] in cotton [Gossypium hirsutum L.]. This study was conducted to determine the effects of planting date, plant density, growth stage, and leaf age on the condensed tannin concentration of six cotton genotypes planted at College Station, TX, in 1988 and 1989. Planting commenced on 25 April in both years and consisted of three plantings at approximately 2‐wk intervals. The topmost unfolded leaf from the terminal and the fourth mainstem leaf from the terminal were sampled at five growth stages from plants spaced 8 and 30 cm, within rows spaced at 102 cm. Genotypes included two commercial checks and four high‐tannin breeding lines developed in a spider mite resistance program. Condensed tannin concentration, expressed as a percentage of fresh weight, was determined spectrophotometrically following extraction with HC1‐butanol. The younger leaf tissue had significantly higher levels of condensed tannins than the more mature leaf tissue. Condensed tannin concentration increased with plant age through the first‐bloom growth stage. The condensed tannin concentration of plants sown on Planting Dates 1, 2, and 3 did not differ in 1988, but in 1989, plants from Planting Date 2 had higher condensed tannin concentrations than those from Planting Dates 1 or 3. Plant density did not significantly affect condensed tannin concentration. Many interactions of other factors with genotypes suggest that breeding for high tannin levels would require close attention to leaf age, growth stage, and environment.
Seedling Growth, Fertilization Timing, and Establishment of Bahiagrass
Authors: Busey Philip
Published: July 2010

Bahiagrass (Paspalum notatum Flügge) makes a useful turf, but establishes slowly from seed; thus, cultivar selection and post planting practices may be important. Objectives were to compare the seedling growth, establishment, and long‐term performance of three cultivars and to evaluate the effect of fertilization timing. Seedlings of ‘Argentine’, ‘Pensacola’, and ‘RCP‐1’ bahiagrasses were harvested and weighed at weekly intervals for 10 wk after planting in a glasshouse. Cultivars did not differ in mean relative growth rate (RGR). A single 4‐wk post planting fertilization fostered equal biomass by 38 wk, compared with repetitive weekly fertilization. Bahiagrasses were planted in a nonirrigated field at 5.6 g seed m−2 Post planting fertilization (4.9 g N, 0.5 g P, and 2.0 g K m−2) was applied 0, 5, or 10 wk after planting, along with a nonfertilized control. Only Argentine and RCP‐1 achieved acceptable establishment (a visual estimate of canopy coverage, uniformity, and absence of weeds) in the second year after planting, and only when fertilized 5 wk after planting. Fertilization at 5 wk, when there were three leaves per seedling, was probably optimum because the root systems were adequate to capture nutrients that earlier might have stimulated weeds or have been leached. In another field study, Argentine maintained higher quality ratings over 4 yr and achieved higher root biomass (1870 g m−2) compared with Pensacola (1370 g m−2) and RCP‐1 (1340 g m−2), while shoot biomass did not differ. In both field and glasshouse, Argentine had greater proportion root dry weight (mean 43%) than Pensacola (39%) and RCP‐1 (38%). Superior rooting may explain the long.term competitive advantage of tetraploid (2n=40) Argentine compared with the diploid (2n=20) cultivars.
Interspecific Hybridization between Red Clover and Trifolium Alpestre Using in Vitro Embryo Rescue
Authors: Phillips Gregory C. , Grosser Jude W. , Berger Sandra , Taylor Norman L. , Collins Glenn B.
Published: July 2010

Red clover, Trifolium pratense L. (2n=2x=14), is an important forage legume worldwide that has its usefulness limited by a lack of persistence. Hybridization with related perennial species would offer the opportunity to introgress persistence and other new, useful characters into red clover. This study was aimed at the hybridization of red clover with T. alpestre L., a diploid (2n=2x=16) perennial species. An in vitro embryo rescue procedure, developed previously to obtain wide hybrids of red clover, was used in this study with minor modifications in two of the four culture media. In one experiment, immature embryos were obtained from 3% of the cross‐pollinated flowers, and a single F1 hybrid line of T. alpestre × T. pratense was successfully recovered following embryo culture. A subsequent experiment failed to yield additional hybrid plants. The hybrid resembled T. alpestre more strongly than the paternal parent, red clover. Paper chromatographic separation of nitrogenous compounds from root tip samples provided evidence that the hybrid expressed biochemical characteristics of the paternal parent. The hybrid exhibited the expected somatic chromosome number of 15, and it was functionally sterile in both male and female floral parts. This new hybrid combination may be useful for the future improvement of red clover, if the infertility barrier can be overcome.
Microspectrophotometry and Digestibility of Alkali‐Treated Walls in Bermudagrass Cell Types
Authors: Akin Danny E. , Hartley Roy D.
Published: July 2010

Phenolic compounds within plant cell walls reduce forage quality, hut information on the site and type of these compounds is needed to determine precise mechanisms influencing forage digestibility. The present study was undertaken to evaluate the loss of phenolic compounds from walls of various cell types after treatment with NaOH using microspectrophotometry and to relate this loss to digestibility by rumen microorganisms. Cell walls of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] leaf‐blade sections were untreated or treated successively with 0.1 M and 1.0 M NaOH to release phenolic acids. Sections were then digested in vitro with rumen fluid. Walls of parenchyma bundle sheath, sclerenchyma, and mestome sheath from undegraded sections were examined by ultraviolet (UV) absorption microspectrophotometry and evaluated with histochemical stains for phenolics. Walls of untreated parenchyma bundle sheaths gave UV absorption spectra similar to p‐coumaroyl or feruloyl arabinoxylotrisaccharides, and the absorption was low after 0.1 M NaOH treatment and essentially absent after 1.0 M NaOH treatment. A crude estimation of ferulic acid equivalents was calculated from Beer's Law assuming that all absorbance in parenchyma bundle sheath was due to p‐coumaroyl or feruloyl groups. Sclerenchyma and mestome sheath walls contained esterified and/or etherified p‐coumaric and/or ferulic acids and a relatively high proportion of lignin (i.e., condensed phenolic polymers). Cell walls appeared to be substantially distorted and partially degraded after 0.1 M NaOH treatment; digestion of walls treated with 1.0 M NaOH resulted in mostly unrecognizable residues. Absorption maxima were still present in undegraded mestome walls after 1.0 M NaOH treatment. Microspectrophotometry of alkali‐treated walls indicated that p‐coumaroyl and feruloyl groups appeared to be mostly responsible for limiting digestion in certain cell types (e.g., parenchyma bundle sheath), while the more refractory walls (e.g., mestome sheath) contained esterified and/or etherified p‐coumaric and ferulic acid and more recalcitrant aromatic compounds.
Self‐Incompatibility and Seed Set in Colchicine‐, Nitrous Oxide‐, and Sexually Derived Tetraploid Red Clover
Authors: Meglic Vladimir , Smith R. R.
Published: July 2010

Diploid red clover (Trifolium pratense L.) is a self‐incompatible species, but some tetraploid forms exhibit a degree of self‐compatibility, which could introduce various levels of inbreeding in the tetraploid populations. This study describes self and cross seed set of nine tetraploid populations of red clover derived either sexually (unilateral or bilateral) or chemically (N2O or colchicine). Estimates of self fertility, reported as seeds per self pollination, were determined in the greenhouse. Root tips were examined for chromosome number to ensure ploidy level. Cross seed set (grams per head) was determined on plants in the field. The hierarchical design was used to analyze the data. Bilaterally derived populations produced significantly less seed per self (0.02) than unilaterally (0.12), colchicine‐ (0.14), or N2O‐derived (0.08) populations. The unilaterally derived populations produced the greatest cross seed per head (0.09 g head‒1) and total seed per plant (4.90 g plant−1). Self seed set had a little relationship to cross seed production. The ability to set self seed seems to be a function of the number of common S alleles per plant, a high degree of self seed being observed on plants with at least two alleles in common.
Steady‐State Polypeptide Profiles of Whorl Tissue from Lepidoptera‐Resistant and Susceptible Corn Inbred Lines
Authors: Callahan Franklin E. , Davis Frank M. , Williams W. Paul
Published: July 2010

Breeding lines of corn (Zea mays L.) with resistance to the southwestern corn borer (Diatraea grandiosella Dyar) and fall armyworm [Spodoptera frugiperda (J.E. Smith)] have been developed, yet the underlying mechanisms of the resistance have not been fully elucidated. Our objective was to determine whether qualitative differences exist in polypeptide profiles of whorl tissue from leaf.feeding‐resistant inbreds (Mp708, Mp707, Mp704, and Mp496) vs. several leaf‐feeding‐susceptible inbreds (Tx601, Ab24E, GT106, and SC229). Preliminary greenhouse studies demonstrated that the validity of such comparisons required strict matching of tissue samples for overall chlorophyll content due to shading within the whorl. Two‐dimensional gel electrophoresis of total protein extracts from tissue of field‐grown plants identified two polypeptides (36 and 21 kDa) whose presence in combination was predictive of resistance. The various susceptible inbreds contained either one or the other of the polypeptides but not both. Further work, comparing the segregation of these two polypeptides with resistance levels in progeny from crosses of resistant and susceptible inbreds, will be required to determine whether they will be generally useful as markers for this source of pest resistance.
Ancestral U.S. Soybean Cultivars Characterized for Tolerance to Ultraviolet‐B Radiation
Authors: Reed Herbert E. , Teramura Alan H. , Kenworthy William J.
Published: July 2010

In an effort to characterize the U.S. soybean [Glycine max (L) Merr.] germplasm pool for variation in tolerance to ultraviolet‐B (UV‐B) radiation, 10 U.S. ancestral soybean cultivars were exposed in a greenhouse to a level of UV‐B radiation simulating a 25% O3 depletion. Two modern cultivars previously characterized for UV‐B sensitivity, Williams (tolerant) and Essex (sensitive), 10 wild annual soybean (G. soja Sieb. & Zucc.) accessions of diverse geographic origin were also included in the study. Significant variation was observed among the G. max cultivars in UV‐B radiation effects on leaf expansion, leaf area, height, aerial dry biomass, and seed yield. The cultivars CNS and Lincoln were consistently the most sensitive to UV‐B radiation, while the cultivars Williams, Arksoy, Richland, Mandarin, Manchu, and Mukden were most tolerant. The wild G. soja accessions as a group were about as sensitive to UV‐B radiation as the G. max cultivars, except that seed yield of G. soja accessions was not significantly reduced by UV‐B radiation. There was, however, UV‐B radiation treatment × genotype interaction for fewer growth traits among the wild G. soja accessions than among the G. max cultivars. Production of UV‐B–absorbing compounds and specific leaf weight were both implicated as important contributing factors to UV‐B radiation tolerance in G. max cultivars.
Rate of Development of Postanthesis Water Deficits and Grain Filling of Spring Wheat
Authors: Kobata Tohru , Palta Jairo A. , Turner Neil C.
Published: July 2010

Wheat crops (Triticum aestivum L.) often experience water deficits during grain filling, thereby reducing grain yield. We determined the effect of the rate of development of postanthesis water deficits on the grain growth of wheat. Plants were grown in a pot experiment in two temperature‐regulated glasshouses with similar temperatures, but with high and low relative humidities. Differences in the rate of increasing plant water deficits between the high and low humidity treatment became evident within 6 d after watering was stopped. During the first 19 d after anthesis, the rates were 0.10 and 0.18 MPa d−1, respectively. Grain yield at low humidity was reduced by 33%, relative to high humidity, mainly as a result of a reduction in grain size. An early cessation of grain growth after mid grain filling probably induced the reduction in grain size. We conclude that differences in grain growth in the two humidity treatments resulted from the different rates of development of water deficits in the two treatments. In the low‐humidity treatment, the size of the grain in the tillers was reduced more than the size of the grain on the mainstem. The increase in the grain dry matter of the mainstem was higher than the total increase in mainstem dry matter during the grain‐filling period. The increase in grain dry matter of Tiller 1 was also higher, but in Tiller 2 it was lower, indicating that grain growth on the mainstem was probably supported by assimilates stored in the stems, leaves, and roots and by transfer of assimilates from tillers.
Nitrogen Supply Effects on Partitioning of Dry Matter and Nitrogen to Grain of Irrigated Wheat
Authors: Cassman Kenneth G. , Bryant Dennis C. , Fulton Allan E. , Jackson Lee F.
Published: July 2010

Partitioning efficiencies of plant dry matter (harvest index, or HI) and N (NHI) to grain are determinants of economic yield and protein content of wheat (Triticum aestivum L.). Response of HI and NHI to a range of early‐ and late‐season N‐supply environments was characterized at three sites with two hard red spring wheat cultivars (Year 1), and at one site with a third cultivar (Year 2). Treatments combined preplant N rates (0–250 kg N ha−1) with additional N applied at anthesis (0∓65 kg N ha−1). The N‐supply environment had contrasting effects on the HI and NHI. Greater early‐season N supply increased both grain and vegetative yields in approximately the same proportion so that the HI was relatively constant or increased slightly over most of the response to N. Greater postanthesis N supply resulted in a small grain yield increase and a small increase in HI. In contrast, the NHI decreased linearly for all cultivars with increasing early‐season N supply. The slope and y intercepts for these regressions differed between cultivars in Year 1 due to a significant cultivar × preplant N interaction. Late‐season N addition increased or decreased the NHI depending on whether the early‐season N supply limited grain yield. Additional plant N derived from supplemental N supplied at anthesis was partitioned between grain and straw in a ratio that was predetermined by the early‐season N environment. Of the individual grain, straw, or whole‐plant parameters from which the NHI is calculated, the straw N concentration seems most useful for referencing the NHI in relation to grain N demand and plant N supply across diverse Nregime and site environments.
Planting Date and Moisture Effects on Yield, Quality, and Alkaline‐Processing Characteristics of Food‐Grade Maize
Authors: Shumway Calvin R. , Cothren J. Tom , Serna‐Saldivar Sergio O. , Rooney Lloyd W.
Published: July 2010

Grain quality specifications for maize (Zea mays L.) have been established for several processing industries. Our objective was to investigate the effects of planting date and moisture level on grain yield, physical grain quality, and alkaline‐processing characteristics of food‐grade maize. Field experiments were conducted in 1998 and 1989 at the Texas A&M University Farm, Burleson County, Texas. Seven food‐grade maize hybrids and one nonprocessing hybrid were grown with two planting dates (normal and delayed) and two moisture levels (irrigated and dryland). Delayed planting, averaged across years, decreased grain yield 15.2%, kernel weight 6.8%, kernel density 1.8%, and kernel hardness 4.4%. In 1988, the dryland treatment decreased grain yield 30.0%, kernel weight 15.2%, and kernel density 1.8%, and increased kernel protein 5%, but had no effect in 1989. Kernel hardness decreased 2.8% in 1988 with dryland treatment, but increased 4.5% in 1989. Hybrid effects varied with year for kernel weight, density, hardness, and protein. The nonprocessing hybrid (B73 × Mo17) produced high grain yield (7911 kg ha−1) and average kernel protein (109 g kg−1 but relatively low kernel weight (270 mg), density (1.06 g cm−3), and hardness (45.4%). Of the food‐quality hybrids, none consistently outperformed the others in all categories. Alkaline‐processing characteristics of the grain were affected by agronomic inputs. In general, nixtamal (i.e., cooked grain after alkaline processing) moisture increased due to delayed plantings and reduced soil water availability. Dry‐matter loss exhibited no discernible trends. Pericarp removal (qualitatively scored) was greatly affected by hybrid; RX404 consistently outperformed all other hybrids.
Relationships among Early European Maize Inbreds: I. Genetic Diversity among Flint and Dent Lines Revealed by RFLPs
Authors: Messmer Monika M. , Melchinger Albrecht E. , Boppenmaier Jürgen , Brunklaus‐Jung Elisabeth , Herrmann Reinhold G.
Published: July 2010

Restriction fragment length polymorphisms (RFLPs) have been proposed for characterizing genetic diversity of maize (Zea mays L.) germplasm. Fifty‐seven elite inbred lines representative of early‐maturing European flint and dent heterotic groups were assayed for RFLPs with 188 clone—enzyme combinations (98 genomic DNA clones, 2 restriction enzymes). Objectives of this study were to (i) investigate the amount of variation for RFLPs in these materials, (ii) determine the level of genetic diversity within and between heterotic groups, and (iii) examine the usefulness of RFLPs for assigning inbred lines to heterotic groups. All DNA clones detected polymorphism with at least one enzyme. About half of all RFLP patterns were common to the flint and dent lines, and a quarter was specific to the lines of each heterotic group. Genetic similarity (GS), calculated from RFLP data as Dice's similarity coefficient, ranged from 0.25 to 0.72 between unrelated pairs of lines. Mean GS for unrelated line combinations within the flint (0.425) and dent (0.414) heterotic groups were considerably greater than for flint × dent line combinations (0.344). All flint and dent inbreds showed a smaller mean GS to lines from the other hererotic group than to unrelated lines from the same heterotic group. For lines of mixed origin, the difference in mean GS to flint lines and to dent lines was consistent with the expected genomic proportions from each heterotic group based on pedigrees. Principal coordinate analysis of GS estimates resulted in a separate grouping of flint and dent lines. Results from this study corroborate the usefulness of RFLPs for identification of lines for assigning inbreds into heterotic groups. For the latter purpose, it seems possible to confine RFLP assays to a smaller number of clone—enzyme combinations with increased discriminatory power between lines from different heterotic groups.
Evaluation of Alternative Screening Criteria for Selecting Nitrogen‐Use Efficient Genotypes in Sorghum
Authors: Youngquist Joan B. , Bramel‐Cox Paula , Maranville Jerry W.
Published: July 2010

Development of N‐use efficient genotypes could reduce crop N fertilizer requirements; however, determining N uptake and utilization efficiencies can be costly and time consuming. The purpose of this study was to evaluate alternate screening criteria for determining relative N‐use efficiencies in sorghum [Sorghum bicolor (L.) Moench]. Different sorghum genotypes were evaluated at two soil N levels in three separate experiments on either a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudoll) or a modified Ortello fine sandy loam soil (coarse‐loamy, mixed, mesic Udic Haplustoll). Uptake efficiency was defined as total plant N per unit soil N (PN/SN), biomass utilization efficiency as total aboveground dry matter per unit PN (NE1), and grain utilization efficiency as grain dry weight per PN (NE2). For each experiment, Spearman rank correlation coefficients were calculated for relationships between N‐use efficiency traits and alternative screening criteria. Total plant dry weight (TDW), TDW/grain N (GN) and harvest index (gram dry weight/TDW) were the best predictors of genotypic performance for PN/SN, NE1 and NE2 (r = 0.89, 0.68, 0.82), respectively. The best use of the above alternative screening criteria would be as prescreening tools to eliminate the poorest genotypes. This would alleviate the need to do wholeplant analysis on a large number of samples, yet permit a fair level of confidence in making final selections.