bluuebunny/crossref_metadata_2025 huggingface dataset:
Embryo Abortion in Three Meadowfoam Genotypes
Authors: Franz R. E. , Jolliff G. D. , Seddigh M.
Published: July 2010

Embryo abortion is believed to limit meadowfoam (Limnanthes alba Hartw.ex Benth. subsp.alba cv. Mermaid) seed yield and yield stability. The objective was to compare abortion rates in three genotypes—Mermaid, and to half‐sib lines: high‐yielding ORL85‐765 (765), and low‐yielding ORL85‐729 (729). Embryos per flower (EPF) and aborted embryos per flower (AEPF) were measured on individual flowers that were tagged at two times near peak bloom. Seeds per flower was then calculated and weight per seed (1000‐seed basis) was measured from the harvested bulk seed. Averaged across years, Mermaid and 765 produced 9 and 7% (P = 0.05) more EPF, respectively, than 729 but all three genotypes had equal AEPF. The genotype ✕ year interaction for AEPF indicated Mermaid was more variable between years. Tagging time ✕ genotype interaction further revealed that Mermaid is more vulnerable to environmental changes for EPF and AEPF. Mermaid seeds per flower varied 20% between years, compared with 7% for 765 and 0% for 729. Differences in EPF, AEPF, and seeds per flower among genotypes were reflected in heir respective seed yield in each year. Variations in weight per seed of the genotypes explained some of the seed yield differences. Mermaid was apparently more sensitive than 765 to environmental factors that cause embryo abortion, while it produced as many or more EPF as did 765. This may explain part of the large year‐to‐year variation in Mermaid seed yield. Thus, reduced sensitivities of embryos to environmental variation may be an avenue for developing consistently higher meadowfoam oil yield.
Plant Growth Regulator Effects on Foliar Discoloration, Pigment Content, and Photosynthetic Rate of Kentucky Bluegrass
Authors: Spokas L. A. , Cooper R. J.
Published: July 2010

If plant growth regulating compounds (PGRs) are to be accepted for use on moderate‐ to high‐quality turf, shoot discoloration must be reduced to an acceptable level. The first step in minimizing foliar discoloration is to attempt to understand how PGRs induce this problem. Field and greenhouse studies were undertaken to trace the developmental sequence of foliar discoloration in PGR‐treated Kentucky bluegrass (Poa pratensis L.) and to determine whether a relationship exists between PGR induced shoot discoloration and either photosynthetic rate or pigment content. The growth regulators amidochlor [N‐({acetylamino}methyl)‐2‐chloro‐N‐(2,6 diethylphenyl)acetamide] and mefluidide [N‐(2,4 dimethyl‐5‐{[(trifluoromethyl)sulfonyl]amino}phenyl)acetamide] were applied at 2.8 and 0.56 kg ha‐1, respectively, to mature Kentucky bluegrass growing on a Hadley silt loam soil (coarse‐silt}, mixed, nonacid, mesic Typic Udifluvent). Turf quality, pigment content, and apparent photosynthetic rate (APR) were determined for each treatment. Application of amidochlor caused discoloration of the turf following one of six applications, resulting in an average decline of about 1 quality point. A decrease in turf quality resulted from all mefluidide applications. Quality rating declined from 8 to 2.5 following mefluidide application at 100% turf greenup. Application of mefluidide decreases canopy APR 0.07 mg CO2 mg CO2 m‐2s‐1 compared with nontreated turf and 0.08 mg CO2 m‐2 s‐1 compared with amidochlor‐treated turf. The lag between onset of shoot discoloration and decreased APR indicates a lack of a cause and effect relationship. Thus, it does not seem likely that either reduced pigment content or APR was responsible for the foliar discoloration induced by amidochlor or mefluidide in these studies.
New Standardization and Calibration Procedures for Nirs Analytical Systems
Authors: Shenk John S. , Westerhaus Mark O.
Published: July 2010

An important objective of a near infrared spectroscopy (NIRS) analytical system is to have consistent predictions across instruments. Standardized instruments produce very similar spectra, but the standardization procedure is expensive and requires trained personnel. In addition, calibrations need to be insensitive to modest changes in sample and room temperature during routine analysis. This paper describes a simplified standardization procedure for monochromators of the same model. The procedure consisted of aligning instruments with a polystyrene standard and adjusting the baselines of spectra with a sealed sample of concentrate. Wheat Triticum aestivum L.) and hay calibration equations were used to evaluate the consistency of NIRS analyses across these standardized instruments. Bias and standard error of difference corrected for bias [SED(C)] for 29 test samples of different agricultural products were acceptable across instruments. Partial least squares was modified to incorporate a repeatability file containing spectra from different instruments and samples at different temperatures, and the equations were recalculated. The equations derived with the repeatability file showed little or no increase in the standard error of calibration. The same equations, however, showed a substantial decrease in standard error of difference across instruments on test samples with temperature varying from 19 to 29.5 °C.
Genotypic and Drought‐Induced Differences in Carbon Isotope Discrimination and Gas Exchange of Cowpea
Authors: Hall A. E. , Mutters R. G. , Farquhar G. D.
Published: July 2010

Carbon isotope composition may be useful for selection in plant breeding. Theory predicts that 13C discrimination (Δ) by leaves can be associated with the ratio of photosynthesis (as indicated by CO2 assimilation rate, A) to leaf conductance (g) to diffusion of water vapor or CO2. In earlier studies with a cowpea (Vigna unguiculata [L.] Walp.) mutant and parent, drought‐induced differences in Δ were associated with expected differences in A/g based on theory, whereas genotypic differences in Δ were not. Studies were conducted for 2 yr with a broader range of genotypes to determine whether these conclusions are generally valid. Eighteen cowpea accessions were grown under weekly irrigation or stored soil moisture in four randomized split blocks at Riverside, CA, in 1987. Twelve of these cowpea accessions were studied under similar conditions in 1988. Gas exchange measurements were made of A and leaf conductance to water vapor (gh), and leaves were sampled for Δ. Significant drought‐induced reduction in Δ of 1.6 × 10−3 was observed and an increase in A/g of 42% which is similar to the value (36%) predicted based upon the change in Δ. The drought‐induced increase in A/g was due to substantial decreases in gh, which more than compensated for a 59% reduction in A. Genotypic differences in Δ of up to 2 × 10−3 were observed which were predicted to be associated with 43% higher A/g; however, genotypic differences in A/g were small, and genotypic means of A/g and Δ were not associated as expected based on theory. Genotypic differences in Δ were more consistent than differences in A/g, A, orgh, and should be easier to select in breeding, but the physiological basis for the genotypic differences in Δ has not been elucidated for cowpea.
Breeding for Preharvest Sprouting Tolerance in White‐Seed‐Coat Spring Wheat
Authors: McCaig T. N. , DePauw R. M.
Published: July 2010

White seed‐coat is a desirable quality attribute for many uses of wheat (Triticum spp.). Unfortunately white seed coat has traditionally been associated with low tolerance to preharvest sprouting. The objective was to assess our breeding progress to improve the preharvest sprouting tolerance of white genotypes. In 1987 and 1988, two groups of white genotypes, developed in our breeding program, were compared with 20 genotypes differing in seed‐coat color (red or white), preharvest sprouting tolerance, and class of wheat. Three categories of tests were used to evaluate sprouting tolerance: (i) artificial rain (AR) treatment of intact heads, (ii) germination (G) of hand threshed heads, and (iii) field weathering (FW). The AR and G tests differentiated and ranked genotypes in agreement with previous information, while the FW test proved unsatisfactory, probably due to insufficient rainfall during the field weathering periods. The white genotypes developed from two tolerant parents (2TP) displayed higher levels of tolerance than those developed from a single tolerant parent (1TP). Only tolerant red genotypes and registered hard red spring cultivars had more tolerance than the 2TP group. The 2TP group was judged to be equal in tolerance to ‘Laura’, a hard red spring wheat with a reasonable level of sprouting tolerance, and better than eight groups comprised of 19 genotypes. The results suggest that white‐seed‐coat cultivars can be developed with high levels of preharvest sprouting tolerance. Observed differences between wheat classes probably reflect current cultivars and applied selection pressure, either direct or indirect during cultivar development, rather than inherent differences between classes.
Replacement of Replications with Additional Locations for Grain Sorghum Cultivar Evaluation
Authors: Johnson J. J. , Alldredge J. R. , Ullrich S. E. , Dangi O.
Published: July 2010

Crop failure and low yields due to insufficient rainfall have led to undernutrition and starvation in West and Central Africa in recent years. Fanners have not adopted superior cultivars recommended from research station trials, necessitating on‐farm testing of new cultivars under farmers' conditions. The number of test plots possible within a farmer‐managed on‐farm test is constrained, but the number of tests is flexible. More new cultivars could be tested in farmers' fields if replications within locations were replaced by additional locations. Improved and local cultivars of sorghum [Sorghum bicolor (L.) Moench] were tested in North Cameroon in replicated on‐farm tests in 23 locations in 1987 and 60 locations in 1988. The required number of locations necessary to replace replications was examined under different probabilities of making Type I, II, and III errors and various true differences between cultivar yields for each year. Traditionally, only Type I error risk has been considered when deriving the optimum allocation of plots among replications and locations. Type III error, leading to choice of inferior cultivars, is considered the most serious risk. Results indicated that simultaneous control of Type I and Type III errors would require two to three times the number of locations as required for control of Type I error alone. Three‐replicate tests can be replaced by 42 to 65% additional single‐replicate locations and triple the number of cultivars tested annually in farmers' fields.
Genotype and Environment Effects on Quality Characteristics of Hard Red Winter Wheat
Authors: Peterson C. J. , Graybosch R. A. , Baenziger P. S. , Grombacher A. W.
Published: July 2010

Improvement of end‐use quality in wheat (Triticum aestivum L.) depends on thorough understanding of the influences of environment, genotype, and their interaction. Our objectives were to determine relative contributions of genotype, environment, and G × E interaction to variation in quality characteristics of hard red winter wheat. Eighteen winter wheat genotypes were grown in replicated trials at six locations in Nebraska and one site in Arizona in 1988 and 1989. Harvested grain was micromilled to produce flour samples for evaluation of protein concentration, mixing characteristics, and sodium dodecylsulfate (SDS) sedimentation. Kernel hardness was determined by microscopic evaluation of individual kernels. Genotype, environment, and interaction effects were found to significantly influence variation in all quality parameters. Variances of quality characteristics associated with environmental effects were generally larger than those for genetic factors. The magnitude of G × E effects were found to be of similar magnitude to genetic factors for mixing tolerance and kernel hardness, but were smaller for flour protein concentration, mixing time, and SDS sedimentation value. Significant differences among genotype responses (b‐values) were observed in the regressions of genotype mean on location means for each quality parameter. There were few instances of significant deviations from regression. Positive correlations between genotype grand mean and genotype b‐values for flour protein, mixing time, and mixing tolerance suggest that simultaneous improvement in both mean and stability for these traits may be difficult. Based on these results, environmental influences on enduse quality attributes should be an important consideration in cultivar improvement efforts toward enhancing marketing quality of hard red winter wheat.
Gibberellic Acid and 2,4‐D Treatments for Wheat × Barley Hybridization Using Detached Spikes
Authors: Riera‐Lizarazu Oscar , Dewey Wade G. , Carman John G.
Published: July 2010

Wide hybridization is a complementary alternative for transferring desirable traits between wheat (Triticum aestivum L.) and barley (Hordeum vulgare Lo). Direct hybridization procedures have proven ineffectual because of genetic dissimilarities between diverse gene pools. Progress has been made by applying growth hormones prior to and after pollination. Using crossable lines has also contributed to successful hybridization. Detached spikes were used to evaluate the effect of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and gibberellic acid (GA3) on crossing success between ‘Fukuhokomugi’ (Fukuho) wheat and ‘Luther’ barley. Seed set was best when Fukuho was the maternal parent. More embryos were obtained by adding high concentrations of 2,4‐D to the detached‐spike culture medium (up to 225 μmol kg−l). This synthetic hormone had no effect on embryo formation when barley was used as the female parent. Gibberellic acid (8.3 to 29.8 μmol kg−1) did not affect embryo formation, regardless of the cross direction. The 2,4‐D‐induced increase in embryo set is presumably attributed to enhanced embryo survivability.
Sucrose Concentration and Its Relationship to Anther Culture in Wheat
Authors: Ball S. T. , Zhou H. , Konzak C. F.
Published: July 2010

Components of culture media influence the physical environments related to anther culture ability, as well as the nutrient balance and availability. These factors may independently affect haploid yield from anther culture. Many of these components, such as sucrose concentration, are quantitative factors and their effects should be analyzed accordingly. The objective of this study was to fit an appropriate model to data and analyze the experimental design completely, as well as determining the effects and functional relationship of sucrose concentration to haploid yield production. A two‐factor experiment in a randomized complete‐block design was used with four sucrose concentrations and six spring wheat genotypes. Natural logarithmic transformation was selected as the most effective corrective measure to stabilize variances of anther culture yield components (callus induction, plant regeneration, and green plant proportion). Highly significant (P ≤ 0.01) sucrose concentration × genotype interactions were observed for all three anther culture yield components. Large genotype differences occurred, and patterns of response to sucrose concentration varied for different genotypes. Use of the response functions to estimate sucrose concentrations at which maxima occurred implied that for some genotypes higher sucrose levels should be investigated. Because sucrose concentration greatly affects osmolality, which changes rapidly during culture due to enzyme activity, other means should be investigated for modifying osmolality along with or differentially from nutrition need. Results from this study confirm that the main aspects of the anther culture process are still under strong genetic control, but improved analyses of the functions of medium components may lead to reductions in differential responses and improved efficiency of culture methods.
Carbon and Water Economies of Well‐Watered and Water‐Deficient Cotton Plants Treated with Mepiquat Chloride
Authors: Fernández C. J. , Cothren J. T. , McInnes K. J.
Published: July 2010

The growth regulator mepiquat chloride (MC) (1,1‐dimethylpiperidinium chloride) inhibits leaf expansion, reduces leaf diffusive resistance, and reduces leaf photosynthetic rates when applied to cotton (Gossypium hirsutum L.). Whole‐plant studies in a controlled environment were conducted to evaluate the effect of MC on the C and water economies of ‘Stoneville 825’ cotton plants growing under well‐watered and water‐deficient conditions. Single, well‐irrigated plants were transferred from a nursery room into test chambers when they reached a leaf area of 0.05 m2 and were exposed to the following combinations of treatments: treated or not treated with MC and maintained well irrigated or not irrigated. MC treatment consisted of spraying 12 ± 1 mL plant−1 of a solution with a concentration of 27.3 mg a.i. L−1. Environmental conditions were typical of sunny humid days in central Texas. Carbon exchange rates and water loss rates were monitored hourly; leaf area, leaf water potential, and leaf osmotic potential were measured daily. Mepiquat chloride inhibited plant leaf area expansion, daily transpiration, daily gross C uptake, daily C loss, and daily net C gains in both water regimes; however, transpiration, gross C uptake, and net C gains of water‐stressed plants were less inhibited in MC‐treated plants than in nontreated plants toward the end of the water stress cycle. Mepiqnat chloride did not affect C‐use efficiency of cotton plants under either water regime nor the water use efficiency (WUE) of well‐watered plants, but reduced WUE of water‐stressed plants, which indicates a possible inhibition of the leaf internal photosynthetic capacity. Mepiquat chloride did not affect leaf water and osmotic potentials of well‐watered plants, but helped to maintain leaf turgor potential in water‐stressed plants. It was concluded that MC induces a water‐conservative behavior in cotton through its effect on plant leaf area and delays the onset of water stress in plants growing under water‐deficient conditions.
New Method for Supplying Substances to Cereal Inflorescences
Authors: Ma B. L. , Smith Donald L.
Published: July 2010

Study of nutritional and metabolic requirements of developing grain in cereal crops is hampered by the lack of methods for supplying substances directly to the spike during a substantial portion of the grain‐fill period. The objective of this study was to develop a system for continuous feeding of solutions containing nutrients or metabolic effectors into the peduncle of barley (Hordeum vulgare L. cv. Leger) plants and to observe their effects on the quantity and quality of the resulting grain. For each plant, one needle was inserted into the peduncle near the bottom and a second near the top. These were sealed to the peduncle with latex and attached to 20‐cm lengths of flexible plastic tubing. The tubing on the lower needle was attached to a syringe barrel. Both the syringe barrel and the open end of the upper tube were held above the spike. Solutions were placed in the syringe barrel and these flowed through the peduncle and into the upper tube. The plants were allowed to draw KNO3 or urea (30 mM‐N) solutions from this system for 20 d. The volume of solution taken up ranged from 37 to 68 mL. Supplying these N sources with the peduncle perfusion system increased N concentrations in barley grain by up to 40% and total grain N per spike by 25% relative to nonperfused or distilled water perfused controls. The amount of N removed from the perfusion system was equal to ≈50% of the total grain N per spike. Use of the perfusion system was not disruptive to normal spike development. These results show that this peduncle perfusion system is capable of delivering large quantities of substances to the developing grain of hollow‐stemmed grasses.
Reproductive Responses of Cowpea to High Temperature during Different Night Periods
Authors: Mutters R. G. , Hall A. E.
Published: July 2010

High night temperatures cause excessive floral abscission in cowpea (Vigna unguiculata (L.) Walp.), while similar or even higher temperatures during the day do not impair reproduction. The objectives of this study were to determine if high temperatures during the early part of the night have different effects on cowpea pod set than high temperatures during the late part of the night, and if distinct events of pollen development are associated with the diurnal sensitivity to heat. Two genotypes of cowpea were grown in controlled environments under a 12‐h photoperiod and subjected to high temperatures (33 °C) during the day and either the first or second 6‐h period of the night. Temperatures were optimal (24 °C) during the other 6 h of the night. All plants experienced the same heat units. Floral buds were sampled at different stages of development and the developing pollen were microscopically examined. For the two genotypes, high temperatures during the late‐night period resulted in much lower pod set (7 and 20%) and pollen viability (2 and 35%) than high temperatures during the early‐night period (51 and 76%, and 65 and 69%, respectively). No diurnal synchrony in pollen development was observed during the late‐night period when developing pollen was the most sensitive to high night temperatures. No changes in floral morphology were observed that could impede pollen transfer from the anthers to the stigma and be responsible for the low pod set. We hypothesize that the results can be explained by the existence of a physiological process that is sensitive to heat and under circadian regulation.
Time of Planting and Diurnal Soil Temperature Effects on Cotton Seedling Field Emergence and Rate of Development
Authors: Steiner J. J. , Jacobsen T. A.
Published: July 2010

Cotton (Gossypium hirsutum L.) is often planted in early spring before climatic conditions are optimum for seed germination and seedling development. The objective of this study was to determine, in the field, the effect of time of day and cool‐temperature stress from naturally varying soil temperature at a time of planting and following planting on seedling emergence (EMER) and seedling rate of development index (SRDI) for cotton. Seeds of two cultivars (GC‐510 SJ‐2) were planted at 0800 and 1600 h three days a week for 9 wks beginning 24 Feb. 1988 and ending 13 April. Emerging seedlings were counted and ranked according to their stage of development three times a week for 14 wk. Regression analysis was used to determine the time periods when EMER and SRDI were most sensitive to soil temperature. EMER was more sensitive to cool temperature stress when planted at 0800 than at 1600 h during the initial 100 h after planting. The most critical periods of stress for the two cultivars were the same (0800 and 1600 h planting times = +53 and +143 h from planting, respectively. GC‐510 EMER was more sensitive to cool soil temperatures during the initial 100 h after planting than SJ‐2. for both cultivars planted at 1600 h, EMER was similarly sensitive to cool soil temperature at 160 h after planting, a sensitive period not previously described. For neither cultivar was EMER influeced by day‐of‐planting heat units. Time of planting had no effect on SRDI values. GC‐510 SRDI was less‐tolerant of cool soil temperature than SJ‐2 during the initial 30 h from planting (most sensitive at +2 and −6h from planting for 0800 and 1600 h plantings, respectively), but then relatively unaffected by soil temperature. SJ‐2 SRDI was sensitive to cool soil temperature for nearly the entire 160‐h period from the time of planting (most sensitive to cool soil temperature at + 91 and + 138 h after planting for 0800 and 1600 h plantings, respectively). There was no relationship between EMER and SRDI. Cultivars differed in response to cool soil conditions at planting. When cool soil temperature conditions are expected, rapid and high cotton emergence in the field may be achieved by choosing a suited cultivar and by planting in the afternoon.
In Vitro Culture Responses of Alyceclover Genotypes on Four Media Systems
Authors: Wofford D. S. , Baltensperger D. D. , Quesenberry K. H.
Published: July 2010

Tissue culture protocols for regeneration are widely variable among plant species. Without known techniques for in vitro regeneration of a given species, many molecular methods cannot be applied in crop improvement programs. In this study, the in vitro response of six genotypes of alyceclover, Alysicarpus vaginalis (L.) DC., was evaluated on two organogenic systems, B5 and MS basal salts plus growth regulators, and two embryogenic systems, L2 and SH basal salts plus growth regulators. Callus growth of genotypes on the L2‐based medium was significantly greater than on the other treatments, with significantly less growth on the MS callus induction medium. Shoot bud induction, but not embryo induction, was observed for all six genotypes on one or more media treatments. Genotype FL‐1 initiated shoot buds on three of the four media treatments, B5, L2, and MS. Genotype FL‐10 produced the highest percent of call! with induced shoot buds, with 63 and 89% for the B5 and MS treatments, respectively. Plants of four genotypes were regenerated after transfer to root induction or embryo germination medium. Genotype FL‐10 produced 128 and 19 plants when cultured on the L2 and B5 systems, respectively. Genotypes FL‐1, FL‐4, and FL‐100 produced a total of 24 plants when cultured on the MS system. All regenerated plants were phcnotypically normal in appearance.
Cyclic Breeding Used to Incorporate Kernel Discoloration Resistance into Malting Barley
Authors: Gebhardt D. J. , Rasmusson D. C. , Wilcoxson R. D.
Published: July 2010

Obtaining kernel discoloration (KD) resistance in malting barley (Hordeum vulgare L.) is an important breeding objective in the midwestern USA. This study was undertaken to evaluate a cyclic breeding procedure for transferring quantitative KD resistance across a wide genetic gap, and to obtain parental germplasm or a new cultivar having KD resistance combined with good agronomic performance and malting quality. Six cycles of crossing and selection were done beginning in 1970 to incorporate KD resistance genes from ‘Chevron’ and CI 9539 into Minnesota barley lines. Chevron and CI 9539 were inferior for both agronomic and quality traits. Subsequently, 45 sixthcycle derived lines were evaluated in inoculated disease nurseries and in field trials to determine whether resistance was transferred and to assess agronomic and malting quality merit. Kernel discoloration resistance was successfully transferred using the cyclic breeding procedure, although the resistance level tended to be below that of the resistance sources. The derived lines were similar to the local cultivars Robust and Morex for agronomic and quality traits, except for kernel plumpness, and to a lesser degree malt extract. They showed marked overall improvement compared with the resistance sources, Chevron and CI 9534, and a few of the lines merit consideration as potential cultivars. Unconscious selection was hypothesized to account for the intermediate level of KD resistance observed in local germplasm. In this situation, cyclic recurrent breeding appeared to be a good choice for incorporating a quantitative disease trait into a good genetic background.
Amounts of Zeatin and Zeatin Riboside in Xylem Sap of Senscent and Nonsenescent Sorghum
Authors: Ambler J. R. , Morgan P. W. , Jordan W. R.
Published: July 2010

Xylem sap from decapitated vegetative and mature plants of nonsenescent ‘Tx2817’ and senescent ‘TxTOOO’ sorghum [Sorghum bicolor (L.) Moench] cultivars was analyzed for cytokinins to determine whether the delayed leaf senescence of nonsenescent sorghums may be associated with transport of greater quantities of cytokinins from roots. Cytokinins were assayed by high‐performance liquid chromatography (ultraviolet absorption) with l4C‐labeled zeatin (Z) as an internal standard. For field‐grown plants, the amount of Z + zeatin riboside (ZR) in xylem sap per gram shoot dry weight was 1.51 times higher for the nonsenescent sorghum. Vegetative plants were grown in solution culture for ⊄ 1 mo and then irradiance and N supply were altered for 7 or 8 d prior to collection of sap for 24 h. With high N and high light, Tx7000 and Tx2817 had nearly identical Z + ZR in the sap per gram shoot fresh weight. Treatments of 10% N supply or 50% light reduced growth only slightly. With 10% N, however, Z + ZR averaged 38% of the control for Tx7000 and 59% for Tx2817; with 50% light, Z + ZR averaged 55% of the control for Tx7000 and 136% for Tx2817. Thus, Z and ZR transport from roots to shoots of nonsenescent Tx2817 was less susceptible to reduction by low N and was actually increased by low light. High xylem sap cytokinin contents for Tx2817 with 50% light suggests that its delayed senescence and enhanced resistance to adverse conditions may be due to high cytokinin production by roots when the carbohydrate supply to the roots is reduced.
Significance of Leaf Phosphorus Remobilization in Yield Production in Soybean
Authors: Crafts‐Brandner Steven J.
Published: July 2010

The remobilization of mineral nutrients from vegetative to reproductive structures may influence plant productivity by affecting the timing and/or rate of leaf senescence. Experiments were conducted to ascertain the importance of P remobilizatlon, particularly from leaves, in seed production of soybean (Glycine max [L.] Merr. cv. McCall). For two separate greenhouse experiments, plants were grown in pots of soil that contained three levels of P fertility (PI, P2, and P3) that provided deficient, optimum, and supraoptimum P nutrition, respectively. Plants were sampled four times from growth stages R5 to RS. For both experiments, P nutrition did not influence plant ontogeny. Plant P accumulation, biomass, and yield were depressed by the P1 treatment. For the P2 and P3 treatments, however, biomass and yield production were similar, even though plant P accumulation was twoto threefold greater for the P3 treatment. Yield decreases for the P1 treatment resulted from a proportional adjustment in the number of seeds and pods per plant. Yield components were similar for the P2 and P3 treatments. Leaf P concentration was similar for the P1 and P2 treatments, even though biomass production and yield were markedly different. There was no net remobilization of P from leaf tissue for the P3 treatment during reproductive growth in either experiment. Additionally, for Exp. 1 there was no net leaf P remobilization from the P1 and P2 treatments. These results indicate that seed development in soybean may occur independently of net P remobilization from the leaves. For all P treatments, N remobilization from leaves was extensive, even though leaf N concentration was increased significantly by the P1 treatment. Thus, N remobilization from leaves was not altered by the internal P or N status of the plants.
Canopy Photosynthesis and Respiration in Winter Wheat Adapted and Unadapted to Connecticut
Authors: Gent Martin P. N. , Kiyomoto Richard K.
Published: July 2010

How is seasonal variation in photosynthesis and respiration related to adaptation of winter wheat (Triticum aestivum L.) to the climate of the U.S. Northeast? Canopy CO2 exchange rates were measured from stem elongation through grain filling for six cultivars and correlated with biomass, harvest index, and yield. Four cuitivars were bred in other climates: Avalon in England, Hart and Pike in Missouri, and Yamhil in Oregon. Houser and Ticonderoga were high‐yielding cultivars bred in New York. On average, yield was 73% greater in 1986 than in 1987, but only Hart and Houser changed rank between years. In 1986, Pike and Hart had yields similar to Houser and Ticonderoga. Yields of Avalon and Yamhil were substantially less. Over both years, high grain yield was correlated with high leaf area before heading, R = 0.8. Yield was correlated both with rapid canopy photosynthesis and rapid dark respiration per unit ground area from heading to anthesis, R = 0.7. Apparent maximum photosynthesis per unit leaf area (Po) and apparent light‐use efficiency (a) were extrapolated the irradiance response of canopy photosynthesis. The Po was greatest for Houser across all measurements, and least for Hart and Yamhil. During grain fill in 1986, α was greatest for Houser and Ticonderoga, and over both years, α was correlated with yield. Per unit ground area, canopy dark respiration was least for Yamhil; per unit shoot dry weight, respiration was greatest for Avalon. These results suggest adaptation to the climate of the U.S. Northeast was related to a high leaf area index during stem elongation, rapid canopy photosynthesis and respiration between heading and anthesis, and high photosynthetic efficiency during grain filling.
Parent‐Offspring Regression Estimates of Heritability for Salt Tolerance during Germination in Tomato
Authors: Foolad Majid R. , Jones Richard A.
Published: July 2010

Salinity impositions can markedly delay and decrease germination rates of tomato (Lycopersicon esculentum Mill.) seed. Wide phenotypic variability in plant growth and germination responses to salinity stress has been reported, but scant documentation concerning genotypic variation for salt responsiveness has restricted breeding efforts. This study evaluated the heritability of germination performance under salinity stress by parent‐offspring regression. Germination distribution data were collected for Fz and F3 seeds derived from a cross between a saltsensitive (UCT5) and a salt‐tolerant (PI 174263) cultivar under moderately high salinity levels (150 mM synthetic sea salt). Individuals germinating at different response time intervals were recovered and advanced to produce F3 and F4 progeny seeds. Progeny families were evaluated for mean times to selected germination quantiles of 25, 50, and 75% under salt stress and the family means were regressed on the individual parental values. Heritability estimates for the F2:3 regression at the selected quantiles were 0.78, 0.76, and 0.58, respectively. These results were comparable with the F3:4 regression estimates of 0.65, 0.73, and 0.58, respectively. The similarity of the estimates obtained in both parent‐offspring regressions suggests the absence of significant dominance genetic effects and when considered with the moderately high heritabilities estimated (r = 0.58‐0.78), reasonably rapid response to selection in early segregating generations would be expected for this important seed trait in tomato.
Diversity of U.S. Hybrid Maize Germplasm as Revealed by Restriction Fragment Length Polymorphisms
Authors: Smith J. Stephen C. , Smith Oscar S. , Wright Scott , Wall Steven J. , Walton Mark
Published: July 2010

One hundred six commercial hybrids of current importance in U.S. maize, Zea mays L., production were profiled for 46 restriction fragment length polymorphism (RFLP) probes. Objectives were to (i) compare diversity among hybrids with that found among public lines; (ii) reveal associations among hybrids; (iii) measure the correlation between RFLP and pedigree distances; and (iv) determine the impact on diversity from the usage of similar genotypes. Of RFLP variants found among 150 public lines 82% were found among the hybrids. Only three variants found among the hybrids were not also found among public lines. The RFLPs, therefore, showed little evidence of exotic germplasm usage. Fifty‐three hybrids fell into 10 groups within which members shared 90% of their profiles; groupings based on higher levels of similarity were also evident. Inter‐hybrid distances for RFLP vs. pedigree data for 36 hybrids with known pedigrees showed a correlation of r = 0.87. Collective use of hybrids with similar RFLP profiles had an impact on diversity at least equivalent to that of some widely used hybrids. Multivariate techniques and diversity indices failed to show a reduction of diversity due to the high intensity of individual hybrid usage because extremely disproportionate usage among maize varieties was not evident. Restriction fragment length polymorphisms could provide assessments of the amount of diversity among commercially available hybrids.
N‐ and C‐banded Karyotypes of Two Parasorghum Species, Sorghum Purpureo‐Sericeum and S. versicolor
Authors: Yu Hong , Liang George H.
Published: July 2010

Chromosome banding patterns, showing number, location, and size of heterochromatin bands, provide unique ways to identify individual chromosomes of a complement and to elucidate phylogenetic relationships among related species. However, no report is available describing banding characteristics of chromosomes for the 10‐chromosome Parasorghum spp. Therefore, the objectives of this research were to develop banding techniques suitable for the sorghum chromosomes and to depict their banding patterns. Heterochromatin banding methods (N‐ and C‐banding) were applied and the N‐ and C‐banded karyotypes were depicted for two Parasorghum species, Sorghum purpureo‐sericeum Aschers & Schweinf and S. versicolor Anderss. All chromosomes of S. purpureo‐sericeum had intensive centromeric N‐ and C‐hands on both arms, except chromosome 4, which showed a faint centromere N‐band on the long arm. Chromosomes 1, 3, and 4 showed prominent telomeric N‐ and C‐hands on short arms, in addition to the intensive intercalary N‐bands, whereas chromosomes 2 and 5 had only intensive intercalary N‐ and C‐bands on short arms. Chromosomes 3 and 4 showed faint telomeric N‐bands and intensive telomeric C‐bands on the long arm. For S. versicolor, chromosomes 1, 3, 4, and 5 showed intensive centromeric N‐ and C‐bands. Telomeric N‐ and C‐bands were faint on the long arms of chromosomes 1 and 4 and were not found on long arms of chromosomes 2, 3, and 5. Chromosome 2 had faint intercalary N‐ and C‐bands on the long arm and also a faint centromeric C‐band. For chromosomes 1, 2, and 5, N‐ and C‐banded karyotypes of the two Parasorghum species were similar, but not identical. Some variation existed between N‐ and C‐banding patterns for the same species. The N‐ and C‐banding patterns for chromosomes in S. purpureo‐sericeum and S. versicolor should be useful in identifying individual chromosomes, in detecting structural aberrations, and in evaluating their phylogenetic relationships with other Sorghum species.
Evaluation of Diverse Shoot Genotypes on selected Root Genotypes of Common Bean under Soil Water Deficits
Authors: White Jeffrey W. , Castillo Jesús A.
Published: July 2010

previous experiments using grafted plants of five genotypes of common bean (Phaseolus vulgaris L.) grown under water deficits indicated that differences in yield were determined in the root system. There was no effect of shoot genotype. To determine whether this result holds for a wider range of genotypes, genetic variation among shoots was examined by evaluating yields of 15 shoot genotypes on a rootstock of a single genotype in trials at two locations with contrasting soil types. Differences among yields of shoot genotypes were detected in three of the four screening trials. The two highest‐yielding shoot genotypes from these trials (H6 Mulatinbo and BAT 1297) were evaluated in final set of trials with two genotypes of contrasting adaptation to drought, using all possible combinations of root and shoot genotypes. Only a root genotype effect (P < 0.01) was found for yield. Shoot dry weight at maturity also showed a strong root effect. Harvest index varied with root genotype at both sites, but also varied with shoot genotype at one site. Genetic variation in shoot characteristics was also shown by a highly significant effect (P < 0.01) of shoot genotype on days maturity. Although the survey of a range of genotypes detected variation in shoot genotype, the effect of shoot genotype on growth and yield under water deficits was small compared with that of root genotype.
Genotype and Water Limitation Effects on Phenology, Growth, and Transpiration Efficiency in Grain Sorghum
Authors: Donatelli Marcello , Hammer Graeme L. , Vanderlip Richard L.
Published: July 2010

Understanding how growth and development of grain sorghum [Sorghum bicolor (L.) Moench] genotypes respond to water limitation would provide a basis to assess the value of such responses in crop production and crop improvement. We conducted a greenhouse experiment to quantify responses of six genotypes to five levels of water limitation between floral initiation and flowering achieved by daily watering to weight. At flowering, the thermal time, biomass, height, water transpired, and transpiration efficiency (biomass/water transpired) were recorded. Results for water‐limited treatments were expressed relative to the well‐watered treatment. Degree of water limitation was indexed by calculating the ratio of the amount of water transpired in water‐limited treatments to that in the well‐watered treatment. This transpiration ratio decreases from a value of one as degree of water limitation increases. Under well‐watered conditions, genotypes differed significantly in thermal time and biomass, but not in height. Differences in biomass were related to differences in both water transpired and transpiration efficiency. The least efficient genotype had a value of transpiration efficiency 25% lower than that of the most efficient. Under water‐limiting conditions, relative thermal time increased at transpiration ratios < 0.55; genotypes did not differ. Relative height decreased linearly with transpiration ratio, and genotypes did not differ. Relative biomass decreased with increasing water limitation, but genotypes differed. This was related to genotypic differences in relative transpiration efficiency for transpiration ratios < 1. Some genotypes increased transpiration efficiency 28% under water limitation. The value of expressing water limitation as transpiration ratio and possible mechanisms explaining these findings are discussed.
Soybean Resistance to Soybean Cyst Nematode Race 3 Is Conditioned by an Additional Dominant Gene
Authors: Rao‐Arelli A. P. , Anand Sam C. , Wrather Allen J.
Published: July 2010

Inheritance of resistance in soybean [Glycine max (L.) Merr.] soybean cyst nematode (SCN), Heterodera glycines Ichinohe, is complex. The objectives of this study were to determine (i) inheritance Race 3 resistance in ‘Peking’ and PI 90763 and (ii) the relationship Rhg4 and of any other genes occurring in Peking to those genes found in PI 88788 for SCN resistance. The F1, F2, and F3 plants from five different crosses among resistant (R) and susceptible (S) cultivars evaluated for SCN resistance in the greenhouse. Individual plants were categorized as resistant or susceptible based on the index of parasitism. The chi‐square test was used to determine goodness of fit between observed and expected ratios. The results indicated that SCN Race 3 resistance was conditioned by one dominant and two recessive genes in each parent. Peking and PI 90763 have all three resistance genes in common. Two genes, Rhg4 and rhgz, in both Peking and in PI 90763 were also in P1 88788. An additional dominant gene in PI 88788 and a second recessive gene in Peking and in PI 90763 provided nonallelic interaction.
Heritability and Improvement of Protein and Nitrogen Concentrations in Wilted Alfalfa Forage
Authors: Hansen Julie L. , Viands Donald R. , Steffens John C. , Sniffen Charles J.
Published: July 2010

During wilting of alfalfa (Medicago sativa L.) before preservation as silage or hay, proteinases in plant cells hydrolyze soluble protein (SP) into nonprotein N (peptides and amino acids), thus decreasing post harvest quality of alfalfa. Our objectives were to compare (i) expected gain in SP concentration remaining in wilted, iyophilized alfalfa from direct selection with expected and actual gain from indirect selection for N concentration and (ii) phenotypic selection with halfsib (HS) progeny test for gain in both SP and N concentrations in wilted, lyophilized forage. In Exp. 1, heritabilities for SP and N concentrations in wilted, lyophilized alfalfa were estimated by parent offspring regression and by HS progeny analysis. Samples of alfalfa forage from HS families and individual plants were wilted for 24 h, chopped, frozen, and lyophilized. Near‐infrared reflectance spectroscopy (NIRS) was used to predict SP and N concentrations in samples. Heritability estimates for N concentration were moderate in magnitude (0.29 to 0.76), and those for SP concentration were low (−0.03 to 0.46). The expected gain in SP concentration was higher from selection for N concentration than from direct selection. In Exp. 2, two alfalfa populations previously selected for higher N concentration and two unselected cuitivars were grown in sward plots. Unwilted forage had 25% (P≤0.01) higher SP concentration in 1987 than forage that had been wilted for 24 h and had 13% (P<0.01) higher SP in 1988. The two populations bred for higher N concentration were higher in SP concentrations, both before and after forage wilting, than the two unselected cultivars. Among the selection methods studied, pre and postwilting SP concentration in lyophilized alfalfa could be most efficiently improved indirectly by phenotypic selection for higher N concentration.
Similarities among Test Sites Based on Cultivar Performance in the Hard Red Winter Wheat Region
Authors: Peterson C. James
Published: July 2010

Maximizing crop productivity requires effective selection and targeting of cultivars for appropriate production areas. Understanding similarities in cultivar response among test sites and underlying production zones within a crop production region is important for breeders to effectively choose test sites and interpret test data. Thirty years of wheat (Triticum aestivum L.) yield data from the Southern and Northern Regional Performance Nurseries (SRPN and NRPN, respectively) were analyzed in order to determine similarities among test sites and production zones in the Great Plains hard red winter wheat growing area. Correlations of cultivar yields among locations each year were averaged and used as a basis for principal factor analysis. Six intraregional production zones were identified in the SRPN, with six factors accounting for 55% of the variability in the location correlation dependence structure. Four of the factors essentially divided the central plains region on north‐south, east‐west axes, representing the south‐central plains, north‐central plains, southern high plains, and central high plains areas. Five production zones were identified in the NRPN, with five factors accounting for 55% of the variation in the location correlation dependence structure. Factor analysis was used to further classify sites within three of the larger production zones in the SRPN and two in the NRPN. Sixteen smaller production areas were identified within these major zones. Elucidation of intraregional cultivar production zones should facilitate more precise targeting of wheat breeding and evaluation efforts.