bluuebunny/crossref_metadata_2025 huggingface dataset:
Tillering Relationships Between Spaced and Densely Sown Populations of Spring and Winter Wheat1
Authors: Dewey W. G. , Albrechtsen R. S.
Published: July 2010

The relationship between tillering in space‐planted early generation populations and in close‐planted commercial‐type stands of wheat (Triticum aestivum L.) was investigated over a 5‐year period. The primary objective was to determine if this relationship is strong enough to justify selection for tillering type in spaced populations. Secondary objectives were to examine tillering‐ yield relationships and possible differences in tiller survival among wheat genotypes. Four winter and two spring wheat cultivars with known tillering differences in densely‐seeded stands maintained their relative rankings when grown in spaced plantings. However, when F5 plants selected for high or low tillering in spaced populations were subsequently grown in densely‐sown F6 plant‐rows, little relationship was observed between tillering characteristics in the two planting densities. In attempting to explain the divergent results it is theorized that tillering differences among the cultivars, which had exhibited these differences over many years and environments, were largely genetic and would, therefore, likely persist regardless of planting density. Conversely, we suspect that much of the tillering variation observed among the spaced F5 plants was non genetic and would lack consistency under dense seeding. The relationship between tillering in spaced and close plantings appears to be further complicated by the differential ability of genotypes to mature spike‐bearing tillers, as a percentage of total tillers initiated. The cultivars we studied veried widely in the efficiency with which they matured fertile tillers in dense plantings. In only two of eight crosses did we observe a significant association between degree of tillering in space‐planted F5's and in their densely‐seeded F6 plant‐rows. Consequently, tillering differences in space‐planted early generation wheat populations do not appear to provide a reliable selection criterion. We observed no consistency between grain yield and degree of tillering. Other yield components largely compensated for variation in tiller number, with kernels per spike having a greater effect than kernel weight.
Heritability of Leaf Characteristics in Upland Cotton1
Authors: Keim K. R. , Quisenberry J. E. , Ray C. A.
Published: July 2010

Plants of early maturing cottons(Gossypium hirsutum L.) developed for short growing seasons generally are smaller than those plants of cultivars developed for longer growing seasons. Reduced plant size may be accompanied by altered leaf size and/or number. Information on leaf characteristics that can be genetically altered may indicate ways to enhance cotton productivity in short season environment.;. Two experiments were used to study leaf characteristics in cotton grown on the southern Great Plains. In a greenhouse experiment, three pairs of ancestral and descendant cultivars were compared for leaf traits. The descendant cultivars from two of the three pairs had significantly (P < 0.01) smaller and fewer leaves per plant. In a second experiment conducted in the field, random inbred lines from a composite cross population were used to Study the heritability of leaf size, leaves per plant, and leaf area per plant. Of the three traits studied, only leaf size displayed a significant level of genetic variability. Heritability estimates on a family mean basis for leaf size, calculated from variance components, progeny‐parent regression, and standard units were 67, 48, and 57%, respectively.
Potential for Using Leaf Turgidity to Select Drought Tolerance in Cotton1
Authors: Quisenberry J. E. , Wendt C. W. , Berlin J. D. , McMichael B. L.
Published: July 2010

Variability in leaf turgidity has been observed among cotton (Gossypium hirsutum L.) strains grown under water deficit field conditions. Two photoperiodic (long‐night) strains were identiffed as having extreme phenotypic expressions of leaf turgidity. Under water deficit conditions T25 retained turgid leaves, while T169 wilted severely. The objective of this research was to determine the potential utility of using the leaf turgidity trait to select germplasm with enhanced drought tolerance. Three types of studies were conducted on these two strains: (i) growth evaluations in wet and dry field conditions and in glass house pots, (ii) evaluations of physiological responses in wet and dry field conditions, and (iii) seed cotton yield evaluations in dry field conditions on germplasm that was introgressed with genes for the day‐neutral flowering habit. Under irrigated field conditions, shoot biomass did not differ between T25 and T169, but the interaction between tests and entries was significant. Compared under water‐deficit field conditions, the nonwilting T25 strain produced significantly more shoot biomass than did T169. In glass house studies, T25 produced more root and shoot biomass with significantly higher water‐use efficiency than did T169. Physiological evaluations showed that under irrigated field conditions, T25 maintained higher leaf water potential, lower leaf conductance, and equal gross photosynthetic rates compared to T169. Under dry (rainout shelter) conditions, T25 always had higher water potential than did T169. At 70 to 80 days after planting (DAP), T25 had higher leaf conductance and photosynthetic rates than did T169. Seed cotton yield was higher for the T25 germplasm than for the T169 germplasm in either population or selected line comparisons. Observed variability in leaf turgidity of cotton under water‐deficit field conditions may be useful in selecting germplasm with enhanced drought‐tolerance.
Effect of Exotic Cytoplasms on Seed Quality of Cotton1
Authors: Bourland F. M. , Mahill Joel F.
Published: July 2010

We evaluated seed weight, germination, and resistance to aging of eight cotton (Gossypium hirsutum L.) genotypes having cytoplasms of seven Gossypium species. After seed of the 56 populations were exposed to accelerated aging, standard germination tests were conducted on nonaged and aged seed. Resistance to aging was defined as the ratio of germination of aged seed to germination of nonaged seed, expressed as a percentage. Exotic cytoplasms were associated with increased seed weight when compared to the original G. hirsutum cytoplasm. Germination of nonaged seed averaged over G. hirsutum genotypes was not significantly affected by cytoplasms. Each exotic cytoplasm, except G. longicalyx Hutchinson and Lee and G. barbadense L., caused a decrease in resistance to aging. A significant nuclear genotype by cytoplasm interaction indicated that the tendency toward less resistance could be mitigated in specific nuclear genotype‐cytoplasm combinations.
Re‐Evaluation of the Inheritance of Urease in Soybean Seed1
Authors: Kloth R. H. , Hymowitz T.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed from reciprocal crosses of ‘Columbia’ and ‘Williams’ were used to study the inheritance of soybean seed urease. Columbia contains the homozygous electrophoretic slow variant, while Williams contains the homozygous electrophoretic fast variant. From data collected using polyacrylamide gel electrophoresis, we demonstrate that the alleles associated with the fast and slow variants are codominant. This reverses a previous report claiming that the fast form (Eu) of the seed urease is dominant over the slow form (eu). We propose that the gene symbols be changed to Eu1a for the slow variant and Eu1b for the fast variant to reflect the change in the inheritance model.
Genetic Variation for Nitrogen Assimilation and Translocation in Wheat. II. Nitrogen Assimilation in Relation to Grain Yield and Protein1
Authors: Cox Michael C. , Qualset Calvin O. , Rains D. William
Published: July 2010

An understanding of the relationship between N assimilation and grain yield and protein, and the measurement of genetic variation in preanthesis and postanthesis N assimilation in wheat (Triticum aestivum L.) are necessary to achieve additional gains in selecting for both high grain yield and high grain protein. Thus, total N assimilation in the spring wheat cultivars ‘Anza’ and ‘Cajeme 71’ and 96 F5‐lines from the cross of these cultivars was studied in field experiments. Freanthesis N assimilation was similar for the two cultivars, but by maturity Anza had assimilated 9% (P < 0.01) more N than Cajeme 71 in both high and low N fertility levels. This difference was mainly due to greater postanthesis assimilation by Anza (22% of total) than Cajeme 71 (10%). Significant genetic variation among F5 lines in N assimilation prior to anthesis occurred in two of three experiments, but no relationships were found between this trait and grain yield, grain protein concentration, or grain protein yield. Significant genetic variability in N assimilation after anthesis was detected, although estimates of heritabilities were low. Nitrogen assimilation after anthesis strongly influenced grain and grain protein yields, explaining 27 to 39% of the variation, but no relationship was found with grain protein concentration. The residuals from the regression of N assimilation after anthesis on biomass at anthesis were also strongly related to grain and grain N yield in a stagewise regression analysis, indicating variation other than random error was involved. Grain protein concentration was also positively associated with these residuals in one experiment. Possible sources of this variation, particularly with relation to roots are discussed. Total N assimilation showed broad‐sense heritabilities of 21 to 27% and was correlated (r = 0.68 to 0.86; P < 0.01) with grain and grain protein yields. Thus genetic variation in N assimilation has a role in determining grain yield and protein concentration in wheat. Further work to determine the genetic and physiological basis of factors influencing N assimilation is needed, especially with regard to roots.
Nitrate Effect on Nodulation of Soybean by Bradyrhizobium japonicum1
Authors: Gibson A. H. , Harper J. E.
Published: July 2010

It is not known whether NO−3 inhibition of nodulation is primarily due to effects on the host plant or on the bacterials train. This study was conducted to evaluate the effect of NO−3 on nodule appearance and development of nitrogenase (acetylene reduction) activity of various Glycine max (L.) Merr. cultivar ✕ Bradyrhizobiumja ponicum (Kirchner) Buchanan strain combinations. Plants were grown hydroponically in controlled environment cabinets. NO−3 was either resupplied daily (“maintained”) during the growth period or allowed to deplete with plant growth (“rundown”). Nodule development was delayed all NO−3 treatment conditions (both maintained and rundown), the delay being more severe at higher NO−3 concentrations. The external concentration of NO−3 rather than the rate of NO−3 uptake appeared to have a major effect on the initial stages of nodulation. Treatment conditions providing similar rates of NO−3 up take from different solution NO−3 concentrations( 4.0 mM rundown vs. 0.5. mM maintained) resulted in a more marked inhibition of nodule appearance at the higher level of solution NO−3. Maintaining the solution concentration of NO−3 at 1.0 mM following the appearance of nodules greatly retarded, or prevented, the development of nitrogenase activity (C2H2 reduction). Minor differences in the tolerance of nodulation to NO−3 were observed among eight B. j. uponicum strains (preselected from 46 strains). More variation existed among 12 soybean cultivars (preselected from 23 cultivars) with respect to their ability to nodulate in the presence of NO−3. The cvs. Elf and Avoyelles were notable in having good nodulation tolerance to NO−3 when infected by USDA110. This indicated that, with selection and breeding, enhanced NO−3 tolerance of nodulation between soybean and B. japonicum should be possible.
Response to Selection for Seed and Forage Traits in Smooth Bromegrass1
Authors: Jessen D. L. , Carlson I. T.
Published: July 2010

Smooth bromegrass (Bromus inermis Leyss.) is an important cool‐season forage grass in the northern half of the USA and in Canada. The objective of this study was to determine the response to selection for high and low forage yield, increased seed weight, high fertility index, and greater disease resistance in a population of smooth bromegrass selected previously for increased seed weight. Six synthetics derived from fourth‐cycle selections for increased seed weight were evaluated for seed and forage traits and compared to the third‐cycle population (SBC3) from which parent clones were selected. Selection criteria for parents of each synthetic were: SB‐1, high general combining ability (GCA) for forage yield with emphasis on regrowth after early June harvest; SB‐2, high GCA for total forage yield; SB‐3, high clonal seed weight; SB‐4, high clonal fertility index; SB‐5, high GCA for resistance to brown leaf spot [Pyrenophora bromi (Died.) Drechsl.]; andS B‐6, low GCA for forage yield. Synthetics SB‐1 and 2 were similar to SB‐C3 in total forage yield. SB‐1 was 13% greater than SB‐C3 in second‐harvest forage yield. SB‐3 was 8% heavier than SB‐C3 in 100‐seed weight. SB‐4, the only synthetic satisfactory in seed yield, was 14 percentage units higher than SB‐C3 in fertility index. SB‐5 appeared more resistant to brown leaf spot than SB‐C3 and all other synthetics. SB‐6 yielded 8% less forage than SB‐C3. Significant positive correlations were obtained between Syn 2 performance of synthetics and mean topcross progeny performance of their parental clones for total and second harvest forage yield, and for brown leaf spot reaction. Relatively intense selection pressure for fertility during selection for seed weight would be necessary to maintain seed yields at satisfactory levels. Forage yield was maintained at a high level in spite of intense selection for 100‐seed weight with relatively few plants selected in each cycle.
Grain and Plant Protein Relationships in Hard Red Spring Wheat1
Authors: Loffer C. M. , Rauch T. L. , Busch R. H.
Published: July 2010

Genetic variation for characters, related to N utilization and their relative contribution to grain protein percentage, grain protein yield, and grain yield was studied in 30 selected spring wheat (Tritieura aestivura L.) genotypes over four environments. These genotypes differed for all measured traits. Grain protein concentration was negatively correlated (P≤ 0.05) with grain yield and grain protein yield. Total plant N at maturity was not correlated with grain protein concentration. Total plant N at anthesis amounted to 93% of the total plant N at maturity. High, positive correlations were found between biomass at anthesis and total plant N at anthesis and between biological yield and total N at maturity. Plant height was not correlated with biological yield or total N at maturity. Nitrogen harvest index was negatively correlated with grain protein concentration and was positively correlated with harvest index. Stepwise regressive analyses, which included grain protein concentration, grain protein yield, and grainyield as dependent variables, indicated that harvest index was the first independent variable to be included in each of the three equations. The harvest index coefficient was negative in the case of grain protein concentration and positive in the case of grain protein yield and grain yield. Total N at maturity, with a positive coefficient, was the only variable in addition to harvest index which was determined to be important in the grain protein yield equation. Important variables, in addition to harvest index, for the grain protein concentration equation were biological yield, with a negative coefficient, and N harvest index and total N at maturity with positive coefficients. Thus, although N harvest index and grain protein concentration were negatively correlated, their relationship became positive when harvest index was taken into account first in the regression equation. Increases in N harvest index or total N at maturity may increase grain protein percentage and grain protein yield without reducing yield. However, there is a need to identify additional variability for N harvest index and total N at maturity if significant gains are to be made.
A Screening Index for Adaptation in Sorghum Cultivars1
Authors: Mann J. A. , Gbur E. E. , Miller F. R.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench], although a crop tropical origin, includes many lines adapted to temperate areas. At present, each new line in a breeding program must be checked for adaptation by growing it in a range of potential production environments, an expensive and time‐consuming procedure. Recent evidence in sorghum has indicated a relationship between the base temperature of a line measured at germination and its relative adaptation to a given set of environments. The objective of this research was to develop a new technique for determination of base temperature that is inexpensive and rapid enough to allow for the screening of many lines during each breeding cycle. A new data collection system and a new analysis procedure were used to obtain an estimate of a new screening parameter (hereafter referred to as G50). These estimates were derived from a non‐linear regression model. The procedure is illustrated with data from eight cultivars for which germination proportions for each of two 25 seed lots at each of six temperatures were available. The G50 values determined for the eight cultivars differed significantly among cultivars, and more importantly were closely related to the known adaptation types of the cultivars. Cultivars which are adapted to temperate areas showed higher G50 values than the cultivars adapted to more tropical environments. The presence of this relationship between GS0 and adaptation and the more rapid data collection method described herein can be used to screen large numbers of lines for probable adaptation without the expense and time necessary for multiple location field observations.
Protein and Oil Percentage of Temperate Soybean Genotypes Evaluated in Tropical Environments1
Authors: de Cianzio S. Rodriguez , Cavins J. F. , Fehr W. R.
Published: July 2010

Breeding for seed protein and oil content of soybean [Glycine max (L.) Merr.) genotypes adapted to temperate climates would require less time if selection could be practiced in tropical locations during the winter. The primary objective of the study was to determine the effectiveness of selection in tropical environments for seed composition of genotypes adapted to the northern United States. Twenty random F4‐derived lines from each of two crosses were evaluated in six plantings at Isabela, PR, and in one planting at Ames, IA, during each of 2 years. Protein, oil, and protein + oil percentage were determined for individual plants and for plots harvested in bulk. The genotype ✕ planting interactions were not significant for any of the traits, except for oil percentage in one cross. Phenotypic and rank correlations for performance of the genotypes in Iowa and Puerto Rico ranged from 0.75 to 0.92 and were highly significant. for each of the three traits, ranking of entries among the Puerto Rico environments was similar to the ranking between the Iowa environments. The results indicated that plantings in tropical locations can be used effectively to select for protein, oil, and protein + oil percentage among soybean lines adapted to temperate environments.
Genetic Control of Glycinebetaine Level in Barley1
Authors: Grumet R. , Isleib T. G. , Hanson A. D.
Published: July 2010

The accumulation of betaine (glycinebetaine, N,N,N‐trimethylglycine) in water‐ or salt‐stressed barley (Hordeum vulgare L.) plants may be a metabolic adaptation to stress. We investigated the inheritance of betaine level using genotypes varying in betaine content. Shoots of unstressed plants grown in growth chambers were assayed for betaine at the three‐leaf stage. Analyses of four pairs of reciprocal crosses indicated that neither maternal nor cytoplasmic effects were significant but that there may be some dominance of the low betaine trait. An incomplete diallel made with eight low‐ and five high‐betaine parents indicated that general combining ability accounted for the majority (74.6%) of genetic effects, suggesting a largely additive trait. Additive, dominance, and epistatic components of heritability were estimated by generation mean analysis of the parental, F1, F2, and backcross generations of a single high‐ × low‐betaine cross. This analysis also showed that betaine accumulation was a predominantly additive trait. Narrow‐sense heritability values for the trait were 0.53 and 0.63 from midparent‐offspring regression and generation mean analysis, respectively. The level of betaine accumulation in barley is a nuclear, predominantly additive trait of relatively high narrow‐sense heritability. Therefore, evaluation of the adaptive significance of betaine in water and salt‐stressed plants should be possible using an isopopulation approach.
Genetic Variability within U.S. Maize Germplasm. II. Widely‐Used Inbred Lines 1970 to 19791
Authors: Smith J. S. C. , Goodman M. M. , Stuber C. W.
Published: July 2010

Isozyme data for 21 loci from lines previously found to be of major importance in the production of U.S. hybrid maize (Zea mays L.) between 1970 and 1979 were analyzed by principal component analysis. The objectives were to provide an objective appraisal of the extent of genetic diversity among lines, to reveal evidence of genetic diversity in time, and to compare genetic diversity among public lines with theft found among commercial hybrids. Overall genetic variability among public lines increased gradually from 1970 to 1979. Although there was a reduction in the use of genetically diverse ‘Reid Yellow Dent’ lines, continued selections from ‘Iowa Stiff Stalk Synthetic’ produced genotypically different lines. Although there was a decline in variation among widely used ‘Lancaster Sure Crop’ lines, changes in the usage of genotypically different Lancaster Sure Crop and related lines provided genetic diversity in time. No major differences were seen in allelic frequencies between public lines and commercial hybrids. Continued use of genetically different elite lines contributes to genetic conservation by maximizing the use of currently deployed genetic res.ources. However, the longterm goal should be to increase the genetic base available to breeders and producers.
Selection for Early Flowering in Corn: 10 Late Synthetics
Authors: Troyer A. F. , Larkins J. R.
Published: July 2010

The purpose of this study was to determine if selection for earliness and better stalk quality in late synthetics would be effective. Ten corn (Zea mays L.) synthetics adapted to southern Iowa and northern Missouri were grown at high plant density in southern Minnesota near Mankato. The earliest 5% to flower were selected for 11 generations and selection for better stalk quality was also enforced, during the last six cycles. The original populations and the 11 selected cycles were then compared in performance trials at moderate plant density over 3 years. Selection effect per cycle for 11 cyclea averaged: l I Celsius heat units (about 1 day) less to pollen shed; 1.4 points less grain moisture; 23 mm less plant height; 0.3 days less silk delay; 167 kg ha∕1 (5%) more yle|d; and 0.5% more broken stalks. Comparing cycles 0 to 5 (selection for early flowering only) with cycles 6 to 11 (selection for early flowering plus better stalk quality) showed that effective selection for earlier flowering and associated less grain moisture continued in cycles 6 to 11, but at a decreased rate. Gain from selectsion against silk delay was reduced in cycles 6 to 11 because near‐optimum performance had been attained. Selection for better stalk quality was effective in cycles 6 to 11, and the number of broken stalks at harvest was stabilized. We recommend selection for early flowering with or without stalk quality selection to make. late, exotic materials earlier, thereby enhancing their potential contribution of useful genetic diversity to the U.S. Corn Bellt.
Effects of Two Introgressed Disease Resistance Factors on Agronomic Characteristics and Certain Chemical Components in Burley Tobacco1
Authors: Nielsen M. T. , Legg P. D. , Litton C. C.
Published: July 2010

Four burley tobacco (Nicotiana tabacum L.) selections differing for resistance or susceptibility to tobacco mosaic virus (TMV) and wildfire (Pseudomonas tabaci L., Wolf and Foster, Stevens) were developed in each of three genetic backgrounds and later evaluated to determine if introgression of genetic factors for disease resistance affected any of six agronomic characteristics and three chemical components. The selections were derived from crosses between burley tobacco isolines possessing the genetic factors, transferred from N. glutinosa L. and N. longiflora Cav., for resistance to TMV and wildfire, respectively. The four selections, the two isolines, and the original susceptible parent of each of the three families were grown for 2 years at Lexington, KY. Since the selections showing susceptible reactions to both mosaic and wildfire performed essentially the same as the original susceptible cultivars, we concluded that the parental genotypes were recovered and that comparisons of the resistant selections with their corresponding isolines and parental cultivars were valid. Consistent differences between the selections and the original cultivar were noted only in one family, and the majority of those differences favored the selections. The wildfire resistant isoline in one family was significantly different from the selections and the parental cultivar. The effect of the introgressed genetic factors for TMV and wildfire resistance on the traits evaluated depended on genetic background. However, the presence of both TMV and wildfire resistance in one breeding line should be considered no obstacle to the further improvement of most other traits.
Genetic Analyses of Male‐Fertility Restoration in Wheat. II. Isolation, Penetrance, and Expressivity of Rf Genes1
Authors: Maan S. S.
Published: July 2010

A previous paper reported that the Rf1 and Rf4 genes (controlling male fertility) were located on chromosomes 1A and 6B, respectively, of an alloplasmic Triticum aestivum L. R‐line (R113) with T. timopheevii Zhuk. cytoplasm. This paper reports the development of wheat lines with individual Rf genes from RI13 and the relative penetrance and expressivity of the Rf1 and Rf4 genes. Male‐sterile ‘Chris’ (mst‐Chris) monosomic 1A and monosomic 6B (with T. timopheevii cytoplasm) were crossed with R113; and cytologically identified monosomic F1's were crossed as females with euplasmic Chris pollen. The number of malefertile and sterile disomic and monosomic segregants and the mean number of seed/spike of the fertile segregants were compared between and within the two sets of F1, F2, BCF1, BCS1, BCS2, and testcross progenies; i.e., mst‐Chris ✕ BCF1, mst‐Chris ✕ BCS1 and mst‐Chris ✕ BCS2 progenies. In the BCF1 monosomic IA and monosomic 6B progenies, most disomics were fertile because they retained the Rf1 gene on 1A or Rf4 gene on 6B, respectively. In contrast, the fertile monosomic plants in BCF1 monosomic IA progeny retained the Rf4 gene on 6B; but the Rf1 gene on 1A was deleted. Similarly, fertile monosomic plants in BCF1 monosomic 6B progeny retained the Rf1 gene on 1A; but the Rf4 gene on 6B was deleted. A substantially higher proportion (indicating greater penetrance) of BCF1 fertile monosomics with Rf4 were obtained than BCF1 fertile monosomics with Rf1. Also, fertile monosomic 1A with Rf4 had a greater number of seed/spike (indicating greater expressivity) than fertile monosomic 6B with Rf1. However, the expressivity of the Rf genes was reversed in the euploid testcross progenies. Thus, the expression of Rf4 was affected to a lesser extent by the deficiency of one homologue of 1A than the expression of Rf1 was affected by the deficiency of one homologue of 6B.
Seedling Test for the Quantitative Measurement of Root Tolerances to Compacted Soil1
Authors: Asady G. H. , Smucker A. J. M. , Adams M. W.
Published: July 2010

Root responses of plant genotypes to compacted soils have not been well defined. This experiment was conducted under controlled environments using a soil core seedling test consisting of an experimentally compacted soil having air‐filled porosities of 31, 18, and 6%. Root penetration ratios were measured 14 days after planting without destroying seedling viability. Root penetration ratios and root lengths declined linearly with decreasing air‐filled porosity. Xylem accumulations of toxic anaerobic metabolites were directly correlated with soil bulk density and inversely related to oxygen diffusion rates in the soil. High correlations (r = 0.91) were observed between root penetration ratios of this rapid test and the growth and yield of field‐grown dry edible beans (Phaseolus vulgaris L.).
Relationship of Cotyledon Cell Number and Seed Respiration to Soybean Seed Growth1
Authors: Guldan Steven J. , Brun William A.
Published: July 2010

Seed Growth rate in soybean [Glycine max (L.) Merr.] is known to be important in determining final yield. Factors influencing growth rate, however, are less well understood. The objectives of this study were to investigate the relationship of cotyledonary cell number and seed component (cotyledons, seed coat, and embryonic axis) respiration to seed growth rate and final seed weight for three field‐grown soybean Plant Introduction (PI) lines with genetic differences in seed weight. They were PI 361.058 (light seeded, 92 mg seed−1), PI 317.336( medium seeded, 225 mg seed−1), and PI 416.845 (heavy seeded, 316 mg seed−1). Seed growth rate varied from 2.6 to 10.0 mg seed−1 day−1, and the number of cells in the cotyledons varied from 4.6 ✕ 106 to 10.3 ✕ 106. The three PI lines examined differed in both rates and duration of cell division in the developing seeds. Seed growth rate and final seed weight were related to number of cells in the cotyledons. However, the relationship was not linear. Growth rate per cell for the heavy seeded line was approximately 67% greater than that for the light seeded line. No relationship was observed between seed growth rate or final seed weight and respiration rates. Respiration rates among PI lines for each seed component decreased similarly during seedfill. Within each PI line, respiration rates decreased faster in cotyledon tissue than in either seed coat or embryonic axis tissue. Our results indicate that seeds having a relatively high number of cells per cotyledon have greater rates of dry matter accumulation and final dry weights, and that these growth characteristics are not associated with increased seed respiration.
Thermal Environment During Endosperm Cell Division in Maize: Effects on Number of Endosperm Cells and Starch Granules1
Authors: Jones R. J. , Roessler J. , Ouattar S.
Published: July 2010

Reductions in kernel mass are observed when corn (Zea mays L.) kernels are grown in vitro or when unfavorable temperature occurs during endosperm cell division. We investigated the possibility that a decreased number of endosperm cells or a decreased number of starch granules is responsible for the reduced kernel mass in such environments. Three‐day‐old kernels of the single cross hybrid A619 ✕ W64A were placed in culture on a denned medium at 15, 30, and 35 °C, and their growth was compared with kernels from ears developed in the field or greenhouse. Kernels cultured at 30°C attained a final mass of 164 mg compared with 274 mg for field‐grown controls. At 30°C, endosperm cell division ceased approximately 10 days earlier, and the final number of cells was reduced by 34%. Final kernel mass was reduced by 49 and 78% when kernels were cultured at 15 and 35°C, respectively, compared with those grown at 30°C. At 35°C, the rate and duration of cell division in the endosperm, and the number of endosperm cells were severely reduced. In contrast, the rate of cell division decreased in kernels cultured at 15°C, but the duration was prolonged, and the number of endosperm cells formed was not affected. However, the number of starch granules initiated at 15 and 35°C was reduced by 70 and 97%, respectively. Final kernel mass was highly correlated with the number of endosperm cells (r=0.85,p≤0.01) and starch granules formed (r=0.76, p≤0.01). These data suggest that thermal regulation of the number of endosperm cells, starch granules, or both are mechanisms by which final kernel mass may be mediated. The reduction in mass of in vitro compared with field‐ or greenhouse‐grown kernels appears to be due mainly to a decline in the number of endosperm cells formed.
The Use of Near‐Infrared Reflectance Spectroscopy to Predict Species Composition of Forage Mixtures1
Authors: Coleman S. W. , Barton F. E. , Meyer R. D.
Published: July 2010

Assessment of species composition of hay, pasture, and range samples is an important but laborious factor in forage quality evaluation. Near‐infrared reflectance spectroscopy (NIRS) was evaluated as a rapid technique for prediction of the species composition of hay and pasture forages and weeds. In Exp. 1, 97 mixtures were formed using eight species. Each species varied from 0 to 100% in each mixture. Each mixture of dried, ground material was scanned with monochromatic light from 1100 to 2500 nm at 2‐nm intervals, and the reflected energy was recorded. Percentage of each species was then regressed on the spectra using a modified stepwise regression procedure. Calibration equations with coefficients of determination (R2) from 0.94 to 0.99 and standard errors of difference (SED) from 1.9 to 6.8% were obtained using five to seven equation terms. Johnsongrass [Sorghum halepense (L.) Pers.] could not be predicted (SED = 6.8%) as precisely as the others, whereas blue panicgrass (Panicum antidotale Retz.) and sunflower (Helianthus annuus L.) were precisely predicted (SED < 2%). One to three harvest dates of seven species of hay were used in a second experiment to determine if variability within a species resulted in additional imprecision. In general, SED were higher; however, all but ‘Midland’ bermudagrass [Cynodon dactylon (L.) Pers.] gave SED of 10 or less, and the R2 of the calibration data set ranged from 0.84 to 0.98. Bermudagrass predictions were more precise if samples containing eastern gamagrass [Tripsacum dactyloides (L.) L.] cut at boot were removed from the data set. With proper calibration, NIRS could save much time normally used to separate species in hand‐clipped samples. The number of samples that can be analyzed in an experiment could be increased, and hence the accuracy of determination of species composition in a given pasture should be improved.
Root‐Knot Nematode Interaction with Berseem Clover and Other Temperate Forage Legumes1
Authors: Baltensperger D. D. , Quesenberry K. H. , Dunn R. A. , Abd‐Elgawad M. M.
Published: July 2010

Potential acreage of berseem clover has been increased by the recent release of ‘Bigbee’ berseem clover (Trifolium alexandrinum L.). Bigbee berseem clover was evaluated to determine if root‐knot nematodes (Meloidogyne arenaria, M. incognita, and M. javanica) may be a limiting factor in new berseem production areas compared with other legumes with similar geographic adaptation. Root‐knot nematode interaction with 15 other germplasm sources of berseem clover was also evaluated in at least one of three separate tests. Eight berseem germplasms were severely galled by the mixed population of Meloidogyne spp. present in the field test. All nine germplasm sources of berseem clover, including Bigbee, were severely galled by M. arenaria, M. javanica, and M. incognita race 3 in the two greenhouse experiments. Gall scores were not significantly different than for the known susceptible host ‘Amclo’ arrowleaf clover (T. vesiculosum Savi.), but were signficantly more severe than for ‘Dixie’ crimsom clover (T. incarnatum L.). ‘Florida 77’ alfalfa (Medicago sativa L.) proved to be highly resistant to all three Meloidogyne species studied. Field investigations are needed to determine if root‐knot nematodes would limit the production of Bigbee berseem clover similarly to the way they limit production of arrowleaf clover.
Inheritance of DNA Concentration, and Cellular Contents of Soluble Protein, Chlorophyll, Ribulose Bisphosphate Carboxylase, and Pyruvate,Pi Dikinase Activity in Maize Leaves1
Authors: Baer G. R. , Schrader L. E.
Published: July 2010

The inheritance of deoxyribonucleic acid (DNA) concentration, and soluble protein, chlorophyll, ribulose bisphosphate carboxylase (RuBPCase) activity and quantity, and pyruvate,Pi dikinase (PPDK) activity in maize (Zea mays L.) leaves were characterized. The amounts or enzyme activities of these cellular constituents were expressed on a DNA basis. This mode of data expression corresponds to relative cellular contents as DNA per nucleus is constant. A 6 ✕ 6 diallel revealed highly significant general combining ability effects for all traits. Although specific combining ability effects were significant for a few traits, these effects were of small magnitude, and variance associated with general combining abilities accounted for 77 to 98% of total genetic variance. Reciprocal effects were detected only for RuBPCase specific activity. Mid‐parent heterosis was found for soluble protein, chlorophyll, and RuBPCase, and the fraction of soluble protein as RuBPCase. Relative cell volume, as estimated by DNA concentration, showed little or no heterosis. Highest heterosis (up to 40%) was found for RuBPCase protein, an observation which can be accounted for by concurrent increases in the total soluble protein content and in the fraction of protein as RuBPCase in cells of these hybrids. Correlations between the degree of heterosis of paired traits indicated that hybrids heterotic for soluble protein have larger amounts of chloroplastic components per cell. The PPDK activity was determined in F1, F2, and backcross populations from a cross between two inbreds with contrasting PPDK activity. The F1 generation indicated complete dominance of the level of activity found in the high parent. Segregation in F2 and backcross generations did not fit a single dominant gene hypothesis. Calculations indicated that a minimum of one locus governs this trait, suggesting that few genes or even one gene modulated by modifiers control PPDK activity. DNA concentration (an estimate of relative cell volume) was found to be a polygenic trait (at least three loci). Variance associated with general combining abilities comprised 90% of the total genetic variance for this trait.
Responses of Kenaf to Salt Stress: Germination and Vegetative Growth1
Authors: Curtis Peter S. , Läuchli André
Published: July 2010

The response of kenaf (Hibiscus cannabinus L.), a stem‐fiber plant, to salt stress was investigated during germination and early growth in solution culture under greenhouse conditions. Kenaf has been considered for use as a summer crop in areas with warm summers and low quality water. Germination was only slightly impaired by NaCl salinity up to 200 mmol L−1. Dry weight accumulation after 6 weeks growth was reduced 20 to 40% by 75 mmol L−1 NaCl (E.C. 7.8 dS m−1) and 70 to 80% by 150 mmol L−1 (E.C. 14.0 dS m−1). Vegetative development of the three cultivars, C‐108, G‐45, and E‐71, and the breeding line 15‐2X, were similar under these salt treatments. Rate of leaf emergence and leaf relative growth rate both declined linearly with increasing salt stress. Kenaf responds to salt stress by excluding Na+ from the shoot and partitioning Na+ and Cl− away from expanding leaf tissue. It is suggested that kenaf is suitable for cultivation with irrigation water of marginal quality but not in severely salt affected areas.
Growth of C3 and C4 Grasses Under Low N Levels1
Authors: Brown R. H.
Published: July 2010

Plants with C4 photosynthesis have higher photosynthetic and growth rates per unit of plant N than C3 species. Most experiments in which nitrogen use efficiency (NUE) of C3 and C4 species have been compared have been short and conducted at high N levels. Four closely related tropical Panicum species, P. prionitis Griseb. (C4), P. laxum Sw. (C3), P. grumosum Nees (C3) and P. spathellosum Doell (C3/C4), and a common forage, ‘Coastal’ bermudagrass Cynodon dactylon (L.) Pers. (C4) were grown for 3 years in an artificial medium at low N levels in a greenhouse to determine growth and NUE. Growth rates were twice as high and the N concentration in live shoot tissue was lower for the C4 than the C3 or C3/C4 species. Concentration of N in roots at the end of the experiment was 4 g kg−1 for the C4 species compared to 6.1 to 8.3 g kg−1 for the C3 and C3/C4 species, and root weights for the C4 species were twice or more than that of the other species. Dry matter produced per unit of N absorbed was twice as high in the C4 as in the other species. It was concluded from this experiment that at very low soil N levels C4 species are likely to produce more growth and be more competitive than C3 species.
Effect of Hastened Flowering on Seed Yield and Dry Matter Partitioning in Diverse Soybean Genotypes1
Authors: Schweitzer L. E. , Harper J. E.
Published: July 2010

Optimization of relative vegetative and reproductive dry matter accumulation may provide a means of enhancing soybean [Glycine max (L.) Merr.] productivity. This 2‐year field study measured the effect of artificially hastened flowering on the accumulation of dry matter and nitrogen in the seed and stover of eight soybean cultivars. Exposure to short‐ photoperiod treatment (10‐h photoperiods from 18 June through 8 July at Urbana, IL) hastened flowering and physiological maturity by an average of 5 and 17 days, respectively. Despite this decrease in season length, short‐photoperiod treatment resulted in lower seed yield only in the relatively short‐season cultivars Wells and Corsoy in each of the 2 years, and in the early isoline of Clark (L62‐1932) in 1 year. In five later‐maturing cultivars, seed yield potential was maintained despite the abbreviation of season length in response to treatment. Dry matter harvest index was increased by treatment in six of the eight cultivars, and contributed to yield retention in all but the earlfiest cultivars. Total N accumulation was decreased by treatment in the early‐maturing cultivatars Wells, Corsoy, and L62‐1932 and unaffected in the latermaturing cultivars. Photoperiod treatment had no effect on nitrogen harvest index in any of the cultivars evaluated. Efforts to optimize the partitioning of dry matter in soybean through genetic or chemical means may be most successful if directed towards reproductive timing in late‐maturing genotypes where vegetative duration is excessive.
Tall Fescue Doubled Haploids via Tissue Culture and Plant Regeneration1
Authors: Kasperbauer M. J. , Eizenga G. C.
Published: July 2010

Genetic improvement of tall fescue (Festuca arundinacea Schreb.) by conventional breeding methodology is slow, and use of haploids and doubled haploids may accelerate the process. Androgenic haploid lines were evaluated in the field to identify differences in forage quantity and quality. Chromosome doubling to obtain fertility was attempted with some of the haploid lines. Direct regeneration of shoots from expanded (“aged”) leaf midveins, as can be done with tobacco (Nicotiana tabacum L.), was not successful for tall fescue. However, calli from tall fescue were established in vitro from the lower end of rapidly elongating (“young”) peduncles. Calli developed on such tissue explants within a few weeks on modified Linsmaier and Skoog medium with 2 mg of 2,4‐D per L and no cytokinin. After 5 weeks, the calli were removed from the explants and subcultured on the same medium formulation at 24±2°C for 15 weeks to “age” the callus tissue. The calli grew rapidly at first, but had stopped detectable growth and were beginning to senesce at 15 weeks. The “aged” calli were subdivided and placed on a plant regeneration medium (the same formulation but with only 0.25 mg of 2,4‐D per L and no cytokinin). Leafy shoots began to emerge from the calli after 3 to 4 weeks of culture under continuous illumination from cool‐white fluorescent lamps at about 15 μmol m−2s−1 in a room maintained at 23±2°C. There were numerous green shoots and a few albinos. The green shoots were excised when they were about 1 cm tall and transferred to a rooting medium (devoid of both 2,4‐D and cytokinin). The shoots developed roots within a few weeks and were transferred to sterile soil at high humidity. The humidity was decreased and light intensity increased over a several day period. After the plants were established, root tips were examined for somatic chromosome numbers. Of the normal‐appearing plants, some had 21, others had 42, and a few had 81 to 84 chromosomes. Doubled haploids were developed by this method from six different haploid lines. One of the lines also produced a few quadrupled haploids. The regeneratd doubled and quadrupled haploids are being evaluated for forage characteristics and their potential usefulness to rapidly isolate desired characteristics.
Sequential Fiber Analysis of Forage as Influenced by Sample Weight1
Authors: Cherney J. H. , Volenec J. J. , Nyquist W. E.
Published: July 2010

Situations exist where sample weight may be limiting to sequential analysis of forage fiber. The minimum sample weight that can be used to obtain reliable values for sequential fiber analysis constituents is not known. Our objective was to determine the effect of sample weight on sequential forage fiber digestion values. Sample weights of 0.05, 0.10, 0.20, 0.30, 0.40, 0.50, 1.00, and 2.00 g were evaluated for each of three species, alfalfa (Medicago sativa L.) sorghum [Sorghum bicolor (L.) Moench.], and reed canarygrass (Phalaris arundinacea L.). Five samples were measured for each sample‐weight, species combination. Sequential forage fiber analysis for neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, lignin, and insoluble ash was accomplished using glass microfiber filters and sintered glass crucibles. Although means were not greatly influenced by sample weight, variances were increased by reduced sample weight. Sample weights ranging from 0.30 to 2.0 g resulted in reasonably precise and accurate estimates of fiber constituent values.
Drying Method Effect on Leaf Chemical Constituents of Four Crop Species1
Authors: Heberer J. A. , Below F. E. , Hageman R. H.
Published: July 2010

Method of drying is known to influence chemical composition of plant tissue. The purpose of this study was to compare the effect of air‐ and oven‐drying with freeze‐drying on subsequent recovery of various chemical constituents of leaves of greenhouse grown maize (Zea mays L.), soybean (Glycine max [L.] Merr.), wheat (Triticum aestivum L.), and sunflower (Helianthus annuus L.). For all species, leaf moisture and the concentrations of reduced N, nitrate N, and P were similar following freeze‐drying, air‐drying (26°C), or oven‐drying at 60, 70 or 80°C or at 100°C for 1 h followed by 70°C (100/70°C). The total nonstructural carbohydrate (TNC) concentrations in leaves of maize and soybean were also unaffected by drying method. In contrast, TNC concentrations in leaves of wheat and sunflower were decreased by about 8 and 25%, respectively, by all non‐cryogenic procedures. For maize and soybean, only those leaves dried at 80°C or 100/70°C retained concentrations of starch and sugar similar to freeze‐dried tissue. For wheat, and especially sunflower, all non‐cryogenic procedures caused decreases in either starch or sugar concentrations in the leaves. Freeze‐drying is the preferred drying method, but for some species oven‐drying provides a valid alternative.