bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional Stresses and Varietal Resistance in Rice: Effects on Whitebacked Planthopper
Authors: Salim M. , Saxena R. C.
Published: July 2010

Nutritional disorders can affect plant growth and a plant's susceptibility to pests. Our objective was to evaluate the effects of N, P, and K stresses on resistance of ‘IR2035‐117‐3’ (IR2035) and susceptibility of ‘Taichung Native 1’ (TN1) rice (Oryza sativa L.) plants to whitebacked planthopper, Sogatella furcifera (Horváth), when grown in nutrient solution in a phytotron at 29/21 °C (day/night), minimum 70% relative humidity, and natural daylight of 12 h. Nitrogen, P, or K stresses altered the chemical composition of rice plants. Deficiency of N, P, or K significantly reduced growth of rice plants. Allelochemical production decreased at low K (3 mg/kg) concentration. Insect food intake and assimilation growth, adult longevity, fecundity, and population increased significantly as N increased. In contrast, increases in K application adversely affected the biology and behavior of S. furcifera. Insect response to P‐stressed plants was not consistent. Regardless of the levels of N, P, or K, the difference between the resistance of IR2035 and susceptibility of TN1 remained distinct. Mortality of first‐instar nymphs was high on TN1 plants treated with steam‐distillate extracts of K‐stressed or unstressed IR2035 plants when compared with plants treated with acetone or TN1 extract. Resistance to S. furcifera in rice cultivars thus may be enhanced by applying moderate rates of N and high doses of K.
Response of Corn to Uneven Emergence
Authors: Nafziger Emerson D. , Carter Paul R. , Graham Edwin E.
Published: July 2010

Uneven emergence of corn (Zea mays L.) may occur when soils are dry at the time of planting. This research was conducted in seven environments in Illinois and Wisconsin during a 2‐yr period to measure the effect of uneven emergence on grain yield. Two hybrids (Pioneer Brand 3732 and 3615), chosen to represent differing responses to plant density, were hand planted in early May (E), 10 to 12 after E (M), and 21 to 27 d after E (L) to produce various patterns of among‐row and within‐row unevenness. There was no consistent interaction of hybrid with emergence patten, and responses were quite consistent among environments. Across environments, uniform E, M, and L plantings produced 11.8, 11.1, and 10.4 Mg ha−l, respectively. Uniform E rows bordered by M rows [E(M)] produced 11.4 Mg ha−l, while the other among‐row treatments E(L), M(E), L(E), and M(L) produced 12.2, 10.5, 7.9, and 11.8 Mg ha−l, respectively. The within‐row, repeating patterns of 3E:1M, 1E:1M, 3E:3M, and 1E:3M produced yields of 11.0, 10.7, 10.9, and 10.9 Mg ha−l, respectively, while the 3E:1L, 1E:1L, 3E:3L, and 1E:3L treatments produced grain yields of 10.5, 9.2, 9.4, and 9.1 Mg ha−l, respectively. Comparison of uneven within‐row patterns with incomplete stands showed that in no case did the presence of late‐emerging plants cause yield loss. While uneven emergence decreased yields, these data do not show a yield benefit to replanting in order to attain uniformity, with the possible exception of cases where one‐half or more of the plants are delayed in their emergence by at least 3 wk.
Genetic Variation in Tall Fescue Digestibility Estimated Using a Prepared Cellulase Solution
Authors: Bughrara S. S. , Sleper D. A. , Krause G. F.
Published: July 2010

Breeding tail fescue (Festuca arundinacea Schreb.) for improved digestibility in the fall is an important goal for improving animal performance. Objectives of this study were to determine the extent and nature of genetic variability for in vitro digestibility and to predict genetic gain from selection. Fifteen parents were randomly chosen from a broad‐based population, and their half‐sib (HS) families were generated using a polycross mating design. Herbage samples were incubated in a neutral detergent solution (NDS) before being subjected to degradation in a prepared ceilulase solution (PCS) obtain estimates of in vitro digestibility (NDSPCS). Neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HEM), and NDSPCS estimates were obtained for parents and their HS families for the summer and fall seasons of 2 yr. Significant (P < 0.01) variation was observed for NDSPCS estimates for HS families and parents in summer and fall, respectively. Genetic variance components for NDSPCS estimates were high among HS families and parents in the summer and fall, respectively. Narrow‐sense heritability estimates for NDSPCS were 0.65 in the summer and 0.30 for the fall. Narrow‐sense heritability estimates for crude fiber ranged from medium to high, while broad‐sense heritability estimates ranged from low to medium. Estimates of broad‐ and narrow‐sense heritabilities were similar for NDSPCS for the summer and fall harvests, because additive genetic variance appeared to be the most important component of the toal genetic variance. The narrow‐sense heritability estimated by parent‐offspring regression (h2op) for NDSPCS was higher for the fall harvest, which suggests that initiation of a breeding program to improve in vitro digestibility in the fall is possible. Predicted genetic gains per cycle of phenotypic selection were 53, 21, and 48% of the population means for the fall harvest for NDSPCS, NDF, and ADF, respectively. Phenotypic selection for improved digestibility in the fall for this population should be possible using the NDSPCS procedure.
Inheritance of Reaction to Gray Leaf Spot in a Diallel Cross of 14 Maize Inbreds
Authors: Donahue P. J. , Stromberg E. L. , Myers S. L.
Published: July 2010

Gray leaf spot of maize (Zea mays L.), caused by Cercospora zeaemaydis Tehon & Daniels, is a limiting factor in some areas where continuous minimum tillage practices are followed. The inheritance of reaction to this pathogen was studied using a diallel of 14 elite inbreds. The 91 single crosses were grown in field nurseries in Montgomery and Wythe counties, Virginia, in 1987 and 1988 using randomized complete‐block designs. Data on gray leaf spot disease ratings, plant lodging, grain yield, and grain moisture were taken during the growing season. Analyses of variance and combining ability analyses were made on these data. Resistance was found to be highly heritable and controlled by additive gene action. Many widely used inbreds (B73, Pa91, Mo17, and A632) were susceptible to gray leaf spot, explaining why many of the commercially available hybrids do not show high levels of resistance. Inbreds that provide high yielding, resistant, and agronomically acceptable hybrids were identified (B68, NC250, Pa875, Va14, Va17, and Va85), and several hybrids between these lines had high levels of resistance, high yield, and good general agronomic characters (B68 ✕ KB1250, KB1250 ✕ Pa875, and NC250 × Pa875). The data suggest that inbred lines are available to produce agronomically acceptable hybrids with high levels of resistance to gray leaf spot. These inbreds could serve as a basis for breeding programs where leaf spot resistance is emphasized.
Variation in Sodium Exclusion and Salt Tolerance in Triticum tauschii
Authors: Schachtman D. P. , Munns Ranna , Whitecross M. I.
Published: July 2010

Salt tolerance in hexaploid wheat (Triticum aestivum L.) may be determined by the D genome. Variation in salt tolerance of wild populations of Triticum tauschii (Coss.) Schmal. (donor of the D genome) was surveyed, with the aim of improving the salt tolerance of modern hexaploid wheat. A collection of 415 T. tauschii accessions was screened for Na+ concentration in the most recent fully expanded leaf, as an indicator of salt tolerance. Experiments were conducted under greenhouse conditions using gravel culture and nutrient solutions with ISO mol m−3 NaCl and 10 mol m−3 Ca2+. A subsequent growth experiment measured the relative salt tolerance of ten accessions of T. tauschii selected for high and low leaf Na+ concentrations. Salt tolerance was measured as relative biomass under saline as compared with control conditions. Two accessions were highly salt tolerant and two were highly salt sensitive. Two wheat cultivars of known salt tolerance were also tested as standards: salttolerant T. aestivum cv. Kharchia and salt‐sensitive T. turgidum L. cv. Modoc. The salt tolerance of the two most tolerant T. tauschii accessions exceeded that of the salt‐tolerant wheat standard. The salt sensitivity of the two most sensitive T. tauschii accessions equaled that of the salt‐sensitive wheat standard. Leaf Na+ concentrations in the screening and growth experiments were negatively correlated with the relative biomass in the growth experiment. This screening has identified highly salt‐tolerant T. tauschii accessions that may be useful for improving the salt tolerance of bread wheat.
Variability in Lentil Growth Habit
Authors: Erskine W. , Goodrich W. J.
Published: July 2010

The growth habit of lentil (Lens culinaris Medikus) is a key trait in the selection of cultivars for a mechanized harvest. We aimed to determine the position of pods on plants, and to assess the variation in plant architecture across seasons and genotypes. Morphological analyses were made on 25 diverse lentil genotypes sown at commercial planting density in the 1985–1986 and 1986–1987 seasons in North Syria. Biological and grain yield varied over the two seasons from 2.8 to 3.7 and 0.80 to 1.34 Mg ha−1, respectively. The low yields in the 1986–1987 season were primarily due to insufficient rainfall during reproductive growth. Over the seasons the vegetative structure of the crop was similar in stature, but the branch angle of primary branches was more acute in the dry 1986–1987 season. The relative distribution of pods among the mainstem, the primary branch system, and the secondary plus tertiary branches was 17.5, 52.4, and 30.2%, respectively. The mainstem and the lowermost two primary branches accounted for 49.5% of the seed yields. Despite large fluctuations in total pod numbers, the distribution of pods on the plant was relatively unaffected by season or genotype. The lowermost two primary branches held the six most commonly podded nodes, and podding was concentrated into fewer nodes on the primaries than on the mainstem. The study showed striking, but continuous, heritable genetic variation in growth habit, allowing the selection of types suited to mechanized harvest.
Uniformity of Plant Spacing Effect on Soybean Population Parameters
Authors: Moore S. H.
Published: July 2010

Soybean [Glycine max (L.) Merr.] plant population experiments often are conducted by thinning stands to a predetermined density in equidistant spacings. Results are used to make recommendations to producers whose stands are more irregular due to less uniform seed placement by mechanical planters and random emergence. Field experiments were conducted in central Louisiana on a Norwood silt loam soil [fine‐silty, mixed (calcareous), thermic Typic Udifluvent] in 1988 and 1989 to determine effects of equidistant and nonequidistant plant spacings on seed yield, plant height, lodging, seed size, and seed quality of ‘Hartz 5171’ soybean grown at low, medium, and high plant densities in rows spaced 97 cm apart. Yields were slightly higher both years when plants were spaced equidistantly. Yields were low due to stress in 1988 and plants in equidistant spacings produced only 157 kg ha−1 more soybean than those in nonequidistant spacings. Yields were higher in 1989 than 1988, and plants in equidistant spacings increased yield by 257 kg ha−1. There was no interaction between plant spacing and plant density on yield, which indicates that the optimum density for soybean is not dependent on plant spacings. Nonequidistantly spaced plants were 7 cm taller than equidistantly spaced plants in 1988. Less lodging occurred both years when plants were uniformly spaced. Seed size increased slightly when plants were spaced equidistantly in 1988. The results of this study indicated that although yields increased slightly under good conditions, soybean responded to plant density in the same way under either equidistant or random spacings.
Recurrent Selection for Glyphosate Tolerance in Birdsfoot Trefoil
Authors: Boerboom C. M. , Ehlke N. J. , Wyse D. L. , Somers D. A.
Published: July 2010

Glyphosate (N‐(phosphonomethyl)glycine] tolerant birdsfoot trefoil (Lotus corniculatus L.) would allow selective herbicide control of Canada thistle [Cirsium arvense (L.) Scop.] and other dicot weeds in seed production fields. The objectives of this research were to determine if recurrent selection can increase the level of glyphosate tolerance in birdsfoot trefoil and if increased glyphosate tolerance is associated with increased S‐enolpyruvylshikimate 3‐phosphate (EPSP) synthase activity. Two cycles of selection for glyphosate tolerance were made in three birdsfoot trefoil germplasms, ‘Leo’, ‘Norcen’, and ‘MU‐81’ by selecting seedlings following treatment with 0.56 kg ae/ha (kg acid equivalents per hectare) of glyphosate. To evaluate tolerance, seedings with eight leaves of the selected and parental populations were either untreated or treated with 0.56 kg ae/ha of glyphosate plus surfactant in a greenhouse. Shoot fresh weights were measured 14 days after treatment (DAT) and regrowth was measured 35 DAT. Treated shoot weights of the three C2 populations were from 44 to 85% greater than their C0 populations, indicating increased glyphosate tolerance. The evaluation of regrowth weights also showed 44 to 127% increases in the C2 populations. Tolerant plants from C2 populations had greater EPSP synthase‐specific activity (the primary site of action of glyphosate) than susceptible C0 plants. This suggested that tolerance was at least partially conferred by increased EPSP synthase activity. Genetic variance should allow continued progress from selection for increased glyphosate tolerance in birdsfoot trefoil.
Diversity among North American Spring Barley Cultivars Based on Coefficients of Parentage
Authors: Martin J. M. , Blake T. K. , Hockett E. A.
Published: July 2010

Maintenance of genetic diversity is an important safeguard against vulnerability to biotic and abiotic stresses. The coefficients of parentage, r, among cultivars computed from known pedigree information can be used as an index of genetic diversity. Because of the emphasis placed on developing barley (Hordeum vulgare L.) cultivars for the malting and brewing industry, it seemed likely that barley may have a narrower gene pool than other crop species where less emphasis has been placed on quality traits. Our objective was to examine the diversity among North American spring barley cultivars and the contribution of major ancestors to the two‐ and six‐rowed barley gene pools using the coefficient of parentage as an index of diversity. Coefficients of parentage were computed for all pairs of 167 spring barley cultivars. Mean r with major ancestors was computed for cultivars categorized by row type and era of release. A cluster analysis, performed on the coefficient of parentage matrix, produced 30 disjoint clusters. The five ancestors with highest mean r with cultivars contributed 45 and 62% of the germplasm to the early and recent two‐rowed cultivars and 52 and 44% of the germplasm pool in the six‐rowed cultivars for the two respective time periods. Mean r within the two‐ and six‐rowed cultivars was 0.11 and 0.10, respectively. Mean r within cultivars increased 180% in the two‐rowed and 36% in the six‐rowed cultivar groups from the early to recent cultivar groups. Cultivar groups formed by the cluster analysis produced mean within‐cluster r values ranging from 0.29 to 0.57. Principal coordinate analysis of the between cluster matrix showed that the two‐ and six‐rowed gene pools are essentially unrelated. Major six‐rowed malting cultivars grouped into two clusters and the major two‐rowed malting cultivars grouped into one cluster. These results show that malting barley cultivars are based on a limited sample of germplasm.
Water Relations and Productivity of Alfalfa Leaf Chlorophyll Variants
Authors: Estill K. , Delaney R. H. , Smith W. K. , Ditterline R. L.
Published: July 2010

Plant improvement to increase the water‐use efficiency of affalfa (Medicago sativa L.) has been limited. This study compared leaf color variants (pale and dark) to evaluate the effect of alfalfa leaf chlorophyll on water relations and yield of alfalfa. Leaf color populations were selected from ‘Ladak 65’ and visually selected sub‐populations evaluated under controlled‐environment and field conditions. Seven moisture regimes were established in controlled environment studies in which a commercial root medium with high water‐holding capacity was used. The field study was at Laramie, WY, on a Wyocolo soil (fine, loamy, mixed Borollic Haplargid) and consisted of irrigated and nonirrigated treatments. Traits measured for the two populations included leaf chlorophyll (Chl), leaf photo‐synthesis (as CO2 exchange rate: CER), transpiration (T), stem pressure potential (ψw), water‐use efficiency (WUE), leaf area, forage yield. Controlled. environment conditions produced pale plants that contained 15% less total Chl than dark‐leaved variants. The Chl concentration of pale variants was equal between the moisture extremes, while the dark variants decreased 20% for the low‐moisture (compared with high moisture) regime in the controlled environment. The WUE in the controlled environment of pale and dark leaf types averaged 1.47 and 1.22 g dry forage kg−1 water, respectively. This difference in WUE was attributed mostly to the greater growth of pale leaf types. The CER and CER/T ratio of the dark leaf types were more sensitive to moisture stress than the pale types. In the 2‐yr field study, the pale leaf types had a 22% lower CER than the dark leaf types across moisture regimes and 19% lower T under the irrigated regime. Even though leaf photosynthesis was lower for the pale leaf types, the forage yield was 25% higher under the irrigated regime.
Corn Seed Maturity Indicators and their Relationship to Uptake of Carbon‐14 Assimilate
Authors: Hunter J. L. , TeKrony D. M. , Miles D. F. , Egli D. B.
Published: July 2010

Various maturity rating systems have been proposed to evaluate seed development in corn (Zea mays L.). The objective of this research was to determine the relationship of seed assimilate uptake and dry weigh to three indicators of physiological maturity: moisture concentration, black layer, and milk line development. Assimilate movement into the seed was determined by exposing the leaf subtending the ear to 14CO2 at regular intervals during seed development and measuring the 14C 24 h later in F2 seed of B73 ✕ Mo17 (1984, 1985) and the stay‐green hybrids FS854 and Pioneer Brand 3358 (1985). In 1986 and 1987, plants of the same F2 hybrids and the inbreds B73 and Mo17 and their F1 cross (B73 ✕ Mo17) were defoliated at ≈20 d after pollination and seed development was compared to that of undefoliated plants. Seed dry weight, moisture concentration, and milk line and black layer development (using a five‐stage rating system) were determined at 3‐ to 5‐d intervals. Uptake of 14C‐assimilate by seed and cob tissue decreased sharply near the end of the linear phase of seed dry weight accumulation when the milk line and black layer ratings were at Stage 3 (mid‐milk line) greater. Near Stage 4 of both black layer and milk line development, 14C in the seed had fallen to the lowest levels, maximum seed weight had been reached, and the seed were physiologically mature. Both black layer and milk line followed consistent rends throughout seed development for all hybrids (including the stay‐green genotypes), defoliation treatments, and years. Seed moisture during seed development was highly correlated with both black layer and milk line, but the concentration at black layer Stage 4 was more variable (293–415 g kg−1) across genotypes and years. The data suggest that Stage 4 of both black layer and milk line development represents a useful and reliable indicator of physiological maturity.
Nuclear and Cytoplasmic Control of Anther Culture Response in Wheat: III. Common Wheat Crosses
Authors: Ekiz Hasan , Konzak C. F.
Published: July 2010

Anther culture represents a potentially important technology for production of wheat doubled haploids for plant breeding and genetics research; however, the yields of haploids from culture must be increased to achieve competitive efficiencies for the method. Genetic differences for culturability are now well known, but the relative roles of nuclear and cytoplasmic genetic factors are still unclear. The purpose of this study was to determine the significance of cytoplasm genetic variation for anther culture responses among common T. aestivum wheats. Plants were grown in a greenhouse and potato‐4 and 190‐2 media were used as callus induction and plant regeneration media, respectively. Large genotype differences in an ther culture response were observed. Among the 18 pairs of reciprocal crosses studied, 9 showed reciprocal differences for green plant regeneration, 4 showed significant differences for callus induction, and 3 were different for plant regeneration. The occurrence of reciprocal differences for all components of anther culture response, especially for green plant regeneration, indicates the the cytoplasm of microspores or maternally inherited factors interact with nuclear genes to control the response of wheat genotypes to anther culture. The results provide substantial new supporting evidence that nuclear, cytoplasm, and nuclear ✕ cytoplasm genetic interactions control the responses of common wheats to anther culture.
Reciprocal Full‐Sib Recurrent Selection in Maize: II. Contributions of Additive, Dominance, and Genetic Drift Effects
Authors: Eyherabide Guillermo H. , Hallauer Arnel R.
Published: July 2010

Reciprocal full‐sib recurrent selection emphasizes selection for additive and nonadditive genetic effects, and direct response is measured in the population crosses. Our objectives were to determine the contributions of additive and dominance effects to the response of selection and to estimate effects of genetic drift after eight cycles of reciprocal full‐sib recurrent selection (for grain yield) in maize (Zea mays L.) populations BS10 and BS11. The BS10 and BS11 populations and their crosses corresponding to Cycles 0, 2, 4, 6, and 8 were evaluated at two levels of inbreeding (F = 0 and F = 0.5) across eight environments for grain yield and moisture, stalk and root lodging, ear height, prolificacy, and days to anthesis. Population means were compared to estimate the contributions of genetic effects. The contributions of heterozygotes to the means of BS10CO and BS11CO were more important than homozygotes for grain yield, whereas the contributions of homozygotes were more important for grain moisture, prolificacy, standability, days to anthesis, and ear height. Significant heterosis was detected between BS10CO and BS11CO for grain yield. Heterosis for grain yield of the interpopulation crosses increased with selection and was caused by the accumulation of favorable alleles with additive and dominant effects from both populations and the heterozygous condition at loci for which genetic drift had caused fixation of alleles in one of the parental populations. Effects of genetic drift were significant for grain yield (BS10 and BS11), days to anthesis (BS10), and ear height (BS11). The improved grain yield of the parent populations over cycles of selection was attributed mainly to alleles with additive (BS11) and dominant effects (BS10). Means of selected BS10 and BS11 populations, adjusted for genetic drift, indicate that the difference between direct and indirect rates of response to selection for gram yield was not significant. The effects of assortative mating during progeny formation and small effective population sizes during recombination of selected progenies should be considered in longterm reciprocal full‐sib recurrent selection programs, particularly if improved performance of the parent populations is desired.
Heritability, Heterosis, and Maternal Effects of Alpha‐Amylase Activity in Barley
Authors: Kaeppler Heidi F. , Rasmusson Donald C.
Published: July 2010

Alpha‐amylase activity is an important quality factor in malting barley (Hordeum vulgare L.), yet its inheritance is not well understood. Research was undertaken to determine the inheritance and to examine maternal and heterotic effects of α‐amylase activity. The F1 and F2 seeds from reciprocal crosses among barley cultivars grown in the greenhouse were evaluated for α‐amylase activity. Heritability of α‐amylase activity was estimated by measuring activities of seed from field growouts of parents and progeny. The Ceralpha α‐amylase assay method, coupled with a modified malting procedure, was used to determine α‐amylase activity levels of all seed samples in this study. Alpha‐amylase activities of F1 seeds from reciprocal crosses were significantly different in two of three crosses. Activities of F2 seeds from reciprocal crosses did not differ, indicating that the reciprocal differences in the F1 were not cytoplasmicin origin but probably due to gene dosage. Average heterosis of α‐amylase activity of the F1's was 85% over the midparent and 47% over the high parent. In the F2 generation, average percent heterosis over the midparent was 35%. Heritability of α‐amylase activity on an F2 plant basis ranged from 0.37 to 0.65, while on an F5 line basis it ranged from 0.39 to 0.74. Average gain from selection for α‐amylase activity in the F2 and F5 generations was 5.4 and 9.1 Ug −1, respectively. Results indicate that selection for α‐amylase activity in populations of medium to wide genetic diversity should be successful in both early and advanced generations.
Inheritance of Elevated Palmitic Acid Content in Soybean Seed Oil
Authors: Fehr W. R. , Welke G. A. , Hammond E. G. , Duvick D. N. , Cianzio S. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] oil with an elevated palmitic acid content may be useful for production of some food and industrial products. Two mutant soybean lines with palmitic acid contents of > 180 g kg‐1 were developed by treatment of ‘A1937’ seeds with N‐nitroso‐N‐methylurea (NMU) and ‘Elgin’ seeds with ethyl methanesuifonate (EMS). The mutant lines, A1937NMU‐85 and EiginEMS‐421, were crossed to determine their genetic relationship for elevated paimitic acid content. The F2 and F3 generations were grown in the field and transgressive segregates with >250 g kg‐1 palmitic acid were obtained, the highest content known in soybean. The segregation ratios indicate that the two mutant lines have different alleles at two independent loci. A1937NMU‐85 was crossed to C1727, a line with the fap2 allele that controls increased palmitic acid content. The lack of transgressive segregation in the F2 generation of the cross indicate that AI937NMU‐85 and C1727 have alleles controlling high palmitic acid at the same locus or at tightly linked loci. The allele in AI937NMU‐85 was designated fap2‐b. The allele in ElginEMS‐421 was given the temporary designation of fap?(ElginEMS‐421) until its relationship to other alleles for modified palmitic acid content can be determined.
Analysis of C‐Banding Chromosome Patterns of Sorghum
Authors: Yu Hong , Liang George H. , Kofoid Kenneth D.
Published: July 2010

Chromosome banding patterns can reveal the locations of specific heterochromatin characteristics for individual chromosomes in a given species. Thus, banding patterns have been used to identify individual chromosomes, to detect chromosomal structural aberrations, and to elucidate evolutionary relationships among taxonomically related species. However, such banding patterns have not been documented for any of the species in the genus Sorghum. Since these chromosomes are small and frequently difficult to distinguish, the C‐banding technique was applied to Combine Kafir 60, a cultivar of Sorghum bicolor (L.) Moench, to determine the banding patterns of the chromosome complement. While different C‐banding treatments gave somewhat different karyotypes, all gave satisfactory results for identifying individual chromosomes. All chromosomes of Combine Kafir 60 showed intensive centromeric C‐bands. Intercalary bands were present in Chromosomes 3, 4, 5, and 9, with some variations in their positions. Telomeric C‐bands were identified in both arms of Chromosomes 1, 2, and 7, and in the short arm of Chromosome 3. Chromosomes 6, 8, and 10 had only centrometic Cbands. Some C‐bands were constant in showing their characteristics and some were facultative. All 10 chromosome pairs in Combine Kafir 60 were identified by their C‐banding patterns, along with their length and arm ratios. This banding pattern can be used as the basis for detecting intraspecific chromosomal variability and an interspecific genomic relationship.
Ergopeptine Alkaloid Production by Endophytes in a Common Tall Fescue Genotype
Authors: Hill N. S. , Parrott W. A. , Pope D. D.
Published: July 2010

The fungal endophyte, Acremonium coenophialum Morgan‐Jones & Gams, is present in many tall fescue (Festuca arundinacea Shreb.) pastures. It imparts fitness‐related traits to the tall fescue plant but produces ergopeptine alkaloids, which may be the cause of fescue toxicosis in grazing livestock. Inasmuch as the endophyte provides the plant with added vigor, development of endophyte‐infected tall fescue populations that are incapable of producing ergopeptine alkaloids may be a solution to providing a sustainable nontoxic grass base for livestock producers. Our objective was to study changes in ergopeptide alkaloid production in a common tall fescue genotype that was infected by two different endophyte isolates that express different levels of alkaloids when in their host plants. Endophytefree tall fescue Genotype PDN2 explants were cultured in vitro to obtain 28‐d‐old calli. Endophytes EDN2 and EDNll isolated from infected PDN2 and another plant genotype PDN11 were cultured and inserted into germinating somatic embryos by placing pieces of mycelium into slits at the base of the noninfected embryonic PDN2 explant. Both endophyte‐infected and ‐free plants were regenerated from callus culture. Regenerated plants with each reinfected endophyte were grown with their endophyte‐infected naturally occurring forms to compare endophyte behavior within a common plant genotype under greenhouse conditions. The PDNll plant with its naturally occurring endophyte was a high alkaloid producer while PDN2 was a low alkaloid producer. When the endophytes EDNll and EDN2 were reinfected into noninfected individuals of PDN2, the resulting plants were low alkaloid producers. These data suggest that the plant plays a major role in controlling the expression of the genetic potential of endophytes for ergopeptine alkaloid production.
Nitrogen‐Use Efficiency among Flue‐Cured Tobacco Genotypes
Authors: Sisson V. A. , Rufty T. W. , Williamson R. E.
Published: July 2010

Today's flue‐cured tobacco (Nicotiana tabacum L.) cultivars differ significantly in yield and quality from cultivars grown early in the 20th century. One major change in crop management has been an increase in fertilizer use, especially N. In view of the changing fertilization practices and the current importance of N in crop production, this study was initiated to evaluate genetic variability in N‐use efficiency in flue‐cured tobacco. Twelve popular cultivars spanning a period of development from the 1920s through the 1980s were evaluated at fertilizer N rates of 47, 68, and 89 kg ha‐1 in 1986, 1987, and 1988 at the Upper Piedmont Research Station, Reidsville, NC. Measures of cured‐leaf yield and total N concentration in leaves were used to determine N‐use efficiency and its component parts, N‐uptake efficiency and N‐utilization efficiency. Significant differences were found among cultivars and among N rates for all traits. Modern cultivars were higher yielding at all N fertility levels. Values for N‐use efficiency increased from the oldest to the newest cultivars. Variation in N‐use efficiency among the cultivars tested was due to increases in both N‐uptake efficiency and the efficiency of utilization of accumulated N in the production of dry matter. Nitrogen‐use efficiency of all cultivars examined decreased as the level of applied N increased. Nitrogen‐use efficiency was positively correlated with chemical quality of the cured leaf. Breeding for improved yield and quality of flue‐cured tobacco cultivars has indirectly led to improvements in N‐use efficiency.
Temperature Stress and Varietal Resistance in Rice: Effects on Whitebacked Planthopper
Authors: Salim M. , Saxena R. C.
Published: July 2010

Temperature greatly influences fundamental plant and pest physiological processes and interactions. This phytotron study sought to determine how optimum (29/21 °C), low (24/16 and 26/18 °C), and high (3S/27 and 36/28 °C) day/night temperature expression of regimes affect resistance of ‘IR2035‐117‐3’ (IR2035) and susceptibility of ‘Taichung Native 1’ (TN1) rice (Oryza sativa L.) cultivars to the whitebacked planthopper, Sogatella furcifera (Horváth). Both low and high temperature stresses reduced plant growth and biomass, and influenced plant chemical composition. Insect food intake, growth, longevity, fecundity, and population increased significantly when IR2035 plants were grown at low and high (vs. optimum) temperature regimes (except 36/28 °C). Insect performance on temperature‐ stressed TN1 plants was similar or superior to that on TN1 plants grown at optimum temperature, but at low temperatures, developmental period and longevity increased, while population decreased. At 36/28 °C, the insect performed poorly on both resistant and susceptible plants. In spite of temperature‐induced effects, the difference between resistance of IR2035 and susceptibility of TN1 remained distinct. Significantly more first instars died on TN1 plants painted with the steam‐distillate extract of resistant IR2035 plants (grown at all temperatures studied) than on acetone‐treated TN1 plants. Compared with unstressed plants, temperature‐stressed plants had less allelochemicals. Since temperature‐induced stresses enhance susceptibility of rice to insects, germplasm for S. furcifera resistance should be evaluated across a wide range of temperatures.
A New Greenbug Virulent to E‐Biotype Resistant Sorghum
Authors: Harvey T. L. , Kofoid K. D. , Martin T. J. , Sloderbeck P. E.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] hybrids resistant to Biotype E greenbug [Schizaphis graminum (Rondani)] had more damage than expected when heavily infested with greenbugs daring August, 1990. Greenbugs isolated from severely damaged plants of resistant sorghum in Stevens County, Kansas, were tested for virulence to Biotype‐E resistant cultivars and lines of sorghum, wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Arena sativa L.), and rye (Secale cereale L.). Greenhouse tests involving seedling plants indicated that the sorghum fines with resistance to Biotype E were susceptible to the greenbug isolate from Stevens County. The only sorghum germplasm fine that appeared resistant to this isolate was PI 266965. Small grains with resistance to Biotype‐E greenbug retained their resistance to the new isolate. Because no previously designated biotypes have shown virulence to Biotype‐E resistant sorghum, the greenbug isolate from Stevens County was designated Biotype I. If Biotype I replaces Biotype E in the field, in a similar fashion to the replacement of Biotype C by Biotype E during the 1980s, greenbug resistance now available in sorghum will be compromised and sorghum production will be vulnerable to the new biotype.
Inheritance of a New Nonnodulation Gene in Chickpea
Authors: Singh Onkar , van Rheenen H. A. , Rupela O. P.
Published: July 2010

A study was conducted to investigate the host genetic control of nonnodulation in a new nonnodulating chickpea (Cicer arietinum L.) mutant, ICC 435M, and its relationship with a previously identified mutant, PM 233. The mutant ICC 435M was crossed with its normal nodulating parent and with mutant PM 233. The nodulation of 35‐d‐old plants of the parents, F1, F2, and backcross progenies was examined in a glasshouse to study the inheritance of nonnodulation (Nod‐). Experiments indicated that nonnodulation in mutant ICC 435M is inherited as a monogenic recessive trait. Progeny tests of crosses between the two mutants showed that recessive alleles at two different loci are responsible for nonnodulation in mutants ICC 435M and PM 233. The F1 plants showed normal nodulation, indicating genetic complementation. The gene symbol m6 is proposed to be assigned to the allele controlling the Nod‐ phenotype in mutant ICC 435M.
Maize Productivity As Influenced by Mixed Nitrogen Supplied Before or After Anthesis
Authors: Below F. E. , Gentry L. E.
Published: July 2010

Maize (Zea mays L.) plants produce higher grain yields when supplied with mixtures of NO3 and NH4 than when supplied only with NO3. This study determined whether mixed N should be available before anthesis, or after it, or continuously to elicit yield increases. During vegetative development, plants of four hybrids were grown with nutrient solutions containing N as either all NO3 or a 50:50 (w/w) mixture of NO3‐N and NH4‐N. At anthesis, one‐half of the plants in each group were switched to the other N solution so that four treatment groups were obtained. Plants were harvested at physiological maturity, separated into components, and analyzed for dry matter, reduced N, P, and K. Compared with continuous NO3, mixed N supplied for at least a portion of the life cycle increased the accumulation of shoot reduced N and P, but not K compared with continuous NO3. Average increases in grain yield obtained when mixed N was available during vegetative development were 9% when plants were switched to NO3 at anthesis and 11% for continuous mixed N. In contrast, mixed N supplied only during the postanthesis period did not significantly increase yield compared with plants receiving continuous NO3. In all cases, mixed‐N‐induced yield increases were associated with increased kernel number. Regardless of timing of availability, mixed N increased the proportion of dry matter partitioned to reproductive fractions (grain, husk, shank, and cob). These results confirm that mixed N nutrition increases grain yield of maize and suggest that vegetative development is the most crucial time to supply mixed N.
Leaf Water Adjustment and Maintenance in Hard Red Winter Wheat
Authors: Gesch R. W. , Kenefick D. G. , Koepke J. A.
Published: July 2010

Tissue water content is an important determinant in freeze survival of winter wheat. Research was conducted to measure the variation in tissue water retention during drought stress of hard red winter wheat (Triticum aestivum L.) cultivars differing in potential for freeze resistance expression but without induction by cold acclimation. Tissue water status was determined on Leaf 3 of several cultivars grown in a greenhouse. The plant growth period was 20 d, followed by drought stress imposed by withholding water. Water, solute, pressure potentials, cell volumetric modulus, and osmotic adjustment evaluations were determined using the pressure volume technique. Osmotic adjustment was attributed to carbohydrate accumulation by evaluating solute potential of plants grown at varied durations of natural daylength. Greater tissue water retention was demonstrated for freeze‐susceptible compared with freeze‐resistant cultivars when subject to drought stress, in the absence of induction by cold acclimation. The significance of differential tissue water retention among these ecologically divergent cultivars could be related to an environmental sensing response, or a feature contributing directly to variance in freeze survival.
Intercropping of Maize and Winged Bean
Authors: Hikam Saiful , Poneleit C. G. , MacKown C. T. , Hildebrand D. F.
Published: July 2010

Maize (Zea mays L.) and winged bean [Psophocarpus tetragonolobus (L.) DC.] have complementary growth habits, biomass production, and protein concentrations. We evaluated yield and protein complementation between maize and winged bean to determine if intercropping can improve the quantity and quality of maize silage. An early and a late‐maturity corn hybrid were intercropped with ‘Tpt1’ winged bean at plant densities of 35 900 and 46 500 plants ha−1 in 1984 and 47 500 plants ha−1 in 1985 near Lexington, KY. In 1984, increased plant density resulted in increased maize vegetation, grain, vegetation N, and grain N yields per hectare (16, 21, 19, and 28%, respectively), while intercropping reduced maize grain yield and grain N yield per hectare by 8% each and reduced winged bean vegetation N concentration by 11% and yield per hectare by 40%. Intercropping winged bean with early maize produced 14% more biomass and 39% more N per hectare than did the reference early maize monoculture at post maize physiological maturity. In 1985, intercropping reduced maize vegetation, grain, and grain N yields per hectare (7, 14, and 14%, respectively), and reduced winged bean vegetation yield, N concentration, and N yield per hectare (58, 7, and 61%, respectively). Intercropping with early maize produced 18% more biomass and 67% more N per hectare, whereas intercropping with late maize produced 11% more biomass and 46% more N per hectare than did the respective monoculture maize. Land equivalency ratios for both dry matter and N yields per area were greater than unity for each plant density and intercropping system. Intercropping of maize with winged bean may provide greater biomass and improved protein content of silage in a temperate climate.
Assessment of Repetitive DNA Variation among Accessions of Hexaploid and Tetraploid Wheat
Authors: Talbert Luther E. , Moylan Susan L. , Hansen LeRoy J.
Published: July 2010

Genetic evidence has suggested that only a few coding genes separate varietal groups within the wheat species Triticum aestivum L. emend. Thell and T. turgidum L. emend. Morris & Sears. However, reduced chromosome pairing is often observed in wheat intraspecific hybrids. Most of the DNA in higher plants is noncoding repetitive DNA, and this type of DNA has been hypothesized to influence chromosome pairing. Our objective was to determine whether this genomic component varies among wheat accessions. Thus, we cloned representatives of six repetitive DNA families found primarily in the wheat A or B genomes. These cloned sequences were used to address the possibility of variation for either restriction fragments or sequence abundance among a diverse set of wheat germplasm. Southern blot analysis of genomic DNA from 33 accessions digested with eight restriction enzymes revealed no restriction site variation for any of the six repetitive sequences. This suggests a lack of sequence divergence for the repetitive DNA families among the accessions. However, dot blot analysis showed that one B genome sequence varied significantly (P < 0.01) in copy number among 10 diverse accessions of T. aestivum These results suggest that copy number variation for repetitive DNA families may exist among accessions of wheat, although sequences of the families as indicated by restriction fragment analysis are conserved.
Heat‐Shock Protein Gene Expression in Diploid Wheat Genotypes Differing in Thermal Tolerance
Authors: Vierling Richard A. , Nguyen Henry T.
Published: July 2010

Under high temperature stress, plants synthesize a set of proteins called heat‐shock proteins (HSPs). The objective of this research was to investigate HSP gene expression in two diploid wheat (Triticum monococcum L., 2n = 2x = 14) genotypes differing in thermal tolerance. Genotypes M3 (tolerant) and M9 (susceptible) were determined to be significantly different in acquired thermal tolerance based on the following criteria: reduction in regrowth during recovery from heat stress, reduction in chlorophyll content, and 2,3,5,‐triphenyltetrazolium chloride reduction after 12 h of heat hardening prior to a normally lethal heat treatment. Electron micrographs revealed that the cellular ultra structure of M3 was more thermally stable than that of M9 after only 2 h of heat hardening prior to a normally lethal heat treatment. Two.dimensional analysis of in vitro translated heat shock proteins revealed no observable qualitative differences in the HSP profile between the two genotypes. Northern analysis using HSP cDNAs 16.9, 26, and 70 as probes, indicated that M3 had higher steady state levels of HSP mRNA than M9 during the 2‐h heat hardening. The results suggest that acquired thermal tolerance in wheat is correlated with the level of heat‐shock gene expression during the first 2 h of heat stress.
Mapping Phytophthora Resistance Loci in Soybean with Restriction Fragment Length Polymorphism Markers
Authors: Diers B. W. , Mansur L. , Imsande J. , Shoemaker R. C.
Published: July 2010

Phytophthora root rot, caused by Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin, is one of the most serious diseases of soybean [Glycine max (L.) Merr.]. Six loci with alleles giving race‐specific resistance of soybean to phytophthora have been reported. The first objective of this study was to map the phytophthora resistance (Rps) loci using restriction fragment length polymorphism (RFLP) markers. The second objective was to map the Rj2 locus for ineffective nodulation with RFLP markers, because of the linkage of Rj2 to Rps2. The mapping was conducted using a series of ‘Williams’ near‐isogenic lines (NILs) with each having one or two phytophthora resistance alleles. The NILs were screened with 141 mapped RFLP markers. At least one polymorphism was found between each NIL and the recurrent parent. Linkage tests among the polymorphic RFLP markers, Rps loci, and the RJ2 locus were conducted using F2 populations. Linkage was found between RFLP markers and Rpsl, Kps2, Rps3, Rps4, Rps5, and RJ2. Linkage was also found between Rps2 and Rj2.
Canopy Leaf Area Development and Age‐Class Dynamics in Cotton
Authors: Wullschleger Stan D. , Oosterhuis Derrick M.
Published: July 2010

Leaf senescence contributes to reduced canopy photosynthesis when new leaf initiation cannot compensate for increased leaf aging after canopy closure. However, since leaf aging is seldom addressed in whole plant investigations, it is difficult to evaluate how age‐class composition influences crop productivity. Field studies were conducted to examine leaf area development in cotton (Gossypium hirsutum L.) and to incorporate this information into a simulation model for assessing canopy age‐class dynamics. Simulated results indicated that leaf area produced during rapid canopy expansion (60 DAP [days after planting], LAI [leaf area index] = 2.3) was largely composed of young leaves, with >35% of the LAI being < 14 d old. However, 30 d later (90 DAP, LAI = 4.5) leaf area production was no longer sufficient to offset leaf aging and the percentage LAI < 14 d old decreased to <10%, while leaves >29 d old increased to 75%. This shift in ageclass composition toward progressively older leaves altered the relative contribution of C from differing layers within the canopy. The middle portion of the canopy was the most important contributor of C early in crop growth, supplemented by roughly equal contributions from the lower and upper canopies. However, after 90 DAP the supply of assimilate from the upper canopy rapidly increased to >45% and that of the lower canopy decreased dramatically. Towards the end of the season (120 DAP), the middle and upper portions of the canopy were about equally divided in their importance to late‐season C production. These results highlight the dynamic nature of age‐related processes within the cotton canopy and the importance of leaf area development in sustaining whole‐plant C production.