bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Spacing and Reflected Far‐Red Light Effects on Phytochrome‐Regulated Photosynthate Allocation in Corn Seedlings
Authors: Kasperbauer M. J. , Karlen D. L.
Published: July 2010

Allocation of photosynthate among leaves, stems, and roots is critical in seedling establishment. Corn (Zea mays L.) seedlings were grown in different spacing patterns in a field and with different reflected far‐red (FR) to red (R) light ratios to test the effects of a modified FR/R ratio on photoassimilate allocation. Green leaves absorbed most of the R and reflected much of the FR. Therefore, close‐spaced plants received more reflected FR and higher FR/R ratios. Seedlings that received the higher FRJR ratios developed longer and narrower leaves, longer stems, and less massive roots. Stem elongation was an early response to increased FR/R ratio even though fight did not impinge directly on the stems, which were initially at or below the soil surface and covered by several layers of leaves. Row orientation did not significantly alter FR/R ratio or seedling morphology because corn leaves are not heliotropic and did not function as directional FR reflectors, as was observed for soybean [Glycine max (L.) Merr.] in a previous study. An increase in the FR/R ratio reflected up to seedlings from the soil surface also resulted in increased shoot size and shoot/root biomass ratio. Early morphological responses of corn seedlings to FR/R ratio in reflected light are relevant to seedling establishment and are not dependent on the cause of the altered ratio.
Evaluation of Peduncle Perfusion for In Vivo Studies of Carbon and Nitrogen Distribution in Cereal Crops
Authors: Ma B. L. , Dwyer L. M. , Smith D. L.
Published: July 2010

Peduncle perfusion, a recently developed technique for delivery of N solution into hollow‐stemmed crops, may be useful for various studies of nutrient allocation within the plant. The objectives of this study were to assess whether peduncle perfusion was suitable for in vivo studies of N and/or C distribution in cereal crops and to determine how N, growth regulator, or sucrose solutions altered C and N accumulation and partitioning in barley (Hordeum vulgare L.) and wheat (Triticum aestivum L. emend. Thell.). Ten treatments [25 and 50 mM N, 30 lμM chlormequat (2‐chioroethyl‐N,N,N‐trimethyl ammonium chloride), 15 pM ethephon [(2‐chloroethyl)phosphonic acid], chlormequat or etbephon, detillering + N, 250 mM sucrose, distilled water and non‐perfusion] were evaluated in four greenhouse experiments (two for barley, two for wheat). Treatments containing N were enriched with a 5% atom 15N. Perfusion lasted 30 d beginning 5 to 8 d after spike emergence. The total volume of solution taken up ranged from 10 to 178 mL for harley, and 8 to 129 mL for wheat. The 15N tracer showed that peduncle‐perfused N was transported and incorporated into all plant tissues. Applying N increased grain N concentration an average of 9.5 g kg−1 for barley and 18.1 g kg−1 for wheat with levels as high as 36 and 55 g kg−1, respectively. Nitrogen levels in flag leaves and non‐grain tissues of the spike were two‐ to eight‐fold higher in N perfused plants. Perfusion with sucrose or growth regulators did not affect C or N content in grain or non‐grain tissues. The data indicate that peduncle perfusion delivers substances in solution into both barley and wheat plants. Nitrogen supplied after spike emergence can substantially increase grain N accumulation without restricting C deposition.
Enhancement of Canola Seed Germination and Seedling Emergence at Low Temperature by Priming
Authors: Zheng Guo‐Hua , Wilen Ronald W. , Slinkard Alfred E. , Gusta Lawrence V.
Published: July 2010

Some seedlots of canola (Brassica napus L. and B. campestris L.) have low percentage germination and poor seedling vigor. The effect of priming canola on both seed germination and seedling emergence was investigated in controlled environment cabinets. Germination was investigated using petri dish assays, whereas emergence was studied by sowing seeds into pots containing a sandy loam soil. Seed germination and seedling emergence from soil at 10°C was enhanced for several cultivars of both species due to priming. Time to 50% germination and emergence was also reduced. A B. campestris cv. Goldrush seedlot, which showed low germination in preliminary studies, was found to be particularly responsive to priming and, therefore, was used in subsequent studies to optimize the technique. The optimal priming time varied with temperature. Excellent responses occurred with priming for 14 to 16 h at 23°C or 60 h at 10°C. Temperature during priming had little effect on percentage germination, emergence percentage, or time to 50% germination or emergence. Seeds primed for 16 h at 23°C or for 60 h at 10°C initiated seedling emergence at 10°C 4 d earlier than nonprimed seeds. Seedling emergence of primed seeds was 73% compared with 31% for the nonprimed seeds. The benefits of priming on both percentage emergence and time to 50% emergence were reduced if the seeds were primed under anaerobic conditions. In addition, the leachate from primed seeds was inhibitory to both percentage germination and time to 50% germination, particularly at 10°C. The results obtained from this study indicate that seed priming has potential for improving seed germination and subsequent seedling establishment of canola seedlots with low germination, with low vigor, or when seeds are planted in cool (<10°C) soils.
Tiller Development in Salt‐Stressed Wheat
Authors: Maas Eugene V. , Lesch Scott M. , Francois Leland E. , Grieve Catherine M.
Published: July 2010

Wheat (Triticutna estivum L. emend Thell.) grain yields are highly dependent upon the number of spike‐bearing tillers produced per plant. Salinity, drought, and other environmental stresses can greatly affect the developmeanntd v iability of tillers. Wed eterminetdh e effects of soil salinity on the occurrence and rate of tiller development and the incidence of tiller abortion in spring wheat cultivars, Anza and Yecora Rojo. Plants were grown in Pachappa fine sandy loam soil (mixed thermic, Mollic Haploxeralf)in outdoor lysimeters. Three salinity treatments were imposed by irrigating with waters containing equal weights of NaCl and CaCl2 (electrical conductivities of ≈ 1, 12, or 18 dS m−1). Salinity significantly decreased the number of primary and secondary tillers in both cultivars. Soil waters salinities ≥7.5 dS m−1 (mean electrical conductivity of the soil water in the rootzone during tiller development SW) eliminated most of the secondary tillers and greatly reduced the number of TO, T3, and T4 tillers. However, the percentage of tillers producing spikes actually increased at SW up to 8 dS m−1. Higher salinities reduced the percentage of tillers with spikes, but not as much as the reduction in tillers. Tiller and spike production per plant decreasead bout 0.13 to 0.15 organs for each unit increase in SW. Of all the potential tillers these cultivars can produce, the primary tillers on Leaves 1 and 2 (i.e., T1 and T 2) were the least susceptible to salt stress, partly because they emerged before salinity builds up during the irrigation season. Adjusting planting densities to increase the number of anticipated spike‐bearing culms per unit area could help to maintain yields on salt‐affected soils.
Genetic Diversity in Hard Red Spring Wheat Based on Sequence‐Tagged‐Site PCR Markers
Authors: Chen H. B. , Martin J. M. , Lavin M. , Talbert L. E.
Published: July 2010

Genetic variation among wheat (Triticum aestivum L.) parents is necessary to derive superior progeny from crossing and selection. However, crosses are often performed among elite lines with similar agronomic and end‐use characteristics. Thus, the potential exists for an undesirable narrowing of the germplasm base for any particular class of wheat. The relative genetic diversity within hard red spring wheat was determined in comparison to a sample of wheat accessions representing an array of types and geographic origins. Three groups of accessions were assayed for the frequencies of DNA polymorphism using a total of 38 sequence‐tagged‐site primer sets with polymerase chain reaction. Group 1 contained I0 elite hard red spring wheat cultivars under production in Montana and North Dakota, Group H included 15 hard red spring wheat cultivars and lines from the North American Great Plains, and Group HI contained 20 accessions representing a wide range of collection and morphological types. Twentyfour of 38 primer sets (63%) and 31 of 76 primer‐enzyme combinations (41%) revealed pulymorphisms. The range of genetic similarity estimated by percentage of shared restriction fragments varied from 0.65 to 0.99 among all pairwise comparisons among the 45 lines. Average genetic similarity was 0.81. Genetic similarity among the hard red spring wheats was 0.88, whereas genetic similarity among the broadly based Group HI was 0.78. Our results showed that the breeding pool for hexaploid hard red spring wheat is narrow relative to levels of diversity among and within classes in hexaploid wheat.
SAS Programs for Calculating Coefficient of Parentage
Authors: Sneller Clay H.
Published: July 2010

The coefficient of parentage between two strains is a useful estimate of genetic similarity. Many researchers have used a FORTRAN program developed by D.M. Rodgers and T.S. Cox, where the inbreeding coefficient of all strains is assumed to be unity. This note describes SAS programs, derived from their program, that (i) accommodate variation in inbreeding coefficients among strains, (ii) use a computer package that is familiar to many plant breeders and runs on mainframe or microcomputers, (iii) provide selective output, and (iv) provide summary statistics of the coefficient of parentage values of each selected strain with all other selected strains.
Genetic Diversity in Malt Quality of North American Six‐Rowed Spring Barley
Authors: Horsley R. D. , Schwarz P. B. , Hammond J. J.
Published: July 2010

Malting barley (Hordeum vulgate L.) breeders often are accused of using germplasm with a narrow genetic base for development of new cultivars. Yet, gains are being made in improving agronomic and malt quality traits. This suggests that more variability exists than otherwise can be expected by examining pedigrees. The objective of this study was to compare results from the cluster analysis based on the coefficients of parentage between 21 North American six‐rowed barley cultivars with the cluster analysis based on I0 malt quality traits oftbe same cultivars. This information may aid us in determining if further galus can be expected by intercrossing closely related genotypes, and to identify those malt quality traits in which improvement can be expected. Malt quality traits evaluated were kernel plumpness, grain protein, fine‐grind extract, coarse‐grind extract, fine‐coarse extract difference, soluble protein, soluble protein to total barley protein ratio, diastatic power, α‐amylase activity, alkaline viscosity, and total malt β‐glucan content. Data on these traits for each of the 21 cultivars were collected on malt produced from samples of grain grown at Fargo, ND, over 3 yr. Composition of the clusters based on the coefficients of parentage was different from that of the clusters based on the analysis of malt quality traits. Clusters based on the analysis of the coefficients of parentage were related to the location of development of the cultivars. Results suggesthat gains in malting quality still may be expected from inter crossing germplasm from different breeding programs and even within a program. Traits that may be improved further are kernel plumpness, diastatic power, α‐amylase activity, soluble to total protein ratio, alkaline viscosity, and total malt β‐glucan.
Genotype Variation in Kernel Cadmium Concentration in Sunflower Germplasm under Varying Soil Conditions
Authors: Li Yin‐Ming , Chaney Rufus L. , Schneiter Albert A. , Miller Jerry F.
Published: July 2010

Production of nonoilseed sunflower (Helianthus annuus L.) on certain soil series yields kernels with cadmium (Cd) concentration excess of international market Cd limits. This study was conducted to determine if genetic variability exists among sunflower germplasm for low kernel Cd accumulation, and to select genotypes under varying soil conditions for breeding low kernel Cd cultivar(s). Two‐hundred sunflower genotypes were evaluated at four different soil series in North Dakota and Minnesota. Large genetic variation in Cd content was found among genotypes. Kernel Cd concentrations showed continuous variation across the range of 0.31 to 1.34 mg/kg (average for four locations). Although Genotype × Location effect exists, genotypes were ranked similarly in Cd concentration at the four locations. Concentrations of Cd for the genotypes were highly correlated among locations, indicating genotypes performed consistently across the four environments. Results clearly show that genotypes for sunflower differ significantly in kernel Cd concentration, and it appears that this evaluation of 200 genotypes has identified sufficient low Cd germplasm for breeding low kernel Cd genotypes. Soil properties played an important role in Cd uptake and accumulation in sunflower. Data from the four soil series showed that fine textured soils from the Fargo and Grandin locations contained higher levels of diethylenetriaminepentaacetic acid (DTPA) extractable Cd and total Cd, and caused significantly higher sunflower kernel Cd across genotypes. Regressions for kernel Cd on soil measurements were all significant except for pH measures in deeper layer soil. The highly correlated relationship could be used to predict kernel Cd for some soil series which were not part of this study.
Genetic Models for Predicting Maize Single‐Cross Performance in Unbalanced Yield Trial Data
Authors: Bernardo Rex
Published: July 2010

Methods for predicting single‐cross performance would facilitate maize (Zea mays L.) hybrid development. The objective of this study was to evaluate different genetic models for best linear unbiased prediction (BLUP) of single‐cross performance in unbalanced yield data. Sixty‐seven single crosses between nine Iowa Stiff Stalk Synthetic (SSS) and 16 non‐SSS inbreds were evaluated separately in 31 different sets of multiplication yield trials from 1989 to 1993. Sets of p single crosses were chosen randomly as predictor hybrids. Yields of the remaining m = (67 — p) missing single crosses were predicted as YM = CMP C‐PP1 yp, where ym = m ✕ 1 vector of predicted yields; CMP = m × p matrix of genetic covariances between the missing and predictor hybrids; CPP = p × p phenotypic covariance matrix among the predictor hybrids; and yP = p × 1 vector of average yields of the predictor hybrids, corrected for yield trial effects. Correlations between predicted and observed single‐cross yields in the unbalanced data set ranged from 0.583 to 0.749. The correlations ranged from 0.388 to 0.493 when the missing and predictor hybrids had no parental inbreds in common, suggesting that BLUP may be useful for preliminary screening of single crosses between inbreds that have not been tested in any hybrid combination. Prediction of specific combining ability (SCA) was not effective because SCA variance was small. Genetic models that included additive × additive epistasis did not lead to better predictions of single‐cross performance compared with the model that included only testcross additive and SCA effects. THE IDENTIFICATION of pairs of inbreds with superior.
Photosynthesis and Water‐Use Efficiency of Awned and Awnletted Near‐Isogenic Lines of Hard Winter Wheat
Authors: Weyhrich Roger A. , Carver Bett F. , Martin Bjorn C.
Published: July 2010

Awned hard red winter wheat (HRWW, Triticutn aestivum L.) cultivars have prevailed in the Great Plains since the introduction of ‘Turkey’ wheat in the 1870s, but the role of awns in wheat productivity is unclear. Awns may serve a photosynthetic function during periods of drought stress, and may actually compensate for flag leaf photosynthesis reduced by drought stress. Our objectives were to determine the effect of genetic awn suppression on photosynthesis and instantaneons or season‐long measurements of water‐use efficiency (WUE), and to monitor associated changes in kernel characteristics. Plants of awned and awnletted near‐isogenic lines of three contemporary HRWW cnitivars (TAM 107, Century, and Mustang) were grown controlled‐environment chambers under well‐watered and waterdeficit conditions. Photosynthetic rates of spikes and flag leaves were measured separately at two stages of kernel development. Whole‐plant and grain WUE were measured based on actual water use. Under well‐watered conditions, net photosynthetic rates of awnletted spikes were significantly lower than awned spikes for all cnitivars at 1~1 d after anthesis (DAA) and for two cultivars at 24 DAA. Under water‐deficit conditions, rates were significantly lower for awnletted spikes of Mustang and TAM 107 at 14 DAA, while no differences were found at 24 DAA. No differences were found between isolines for flag leaf photosynthesis at either stage. Generally, differences in kernel characteristics were nonsignificant between awned and awnletted lines. Although some instantaneous photosynthetic measurements suggested higher WUE of awned spikes, this difference did not result in higher WIrE based on whole‐plant biomass or grain weight for awned isolines.
Centipedegrass—Diversity and Vulnerability
Authors: Hanna Wayne W.
Published: July 2010

The genus Eremochloa consists of eight species of which only centipedegrass [E. ophiuroides (Munro) Hack.] is cultivated for turf. In the USA, the genetic base for this species is narrow because most of the Centipedegrass grown originates from a single accession introduced as seed from China as a result of a plant exploration trip by Frank Meyer in 1916. Introduction of Centipedegrass from the area of origin, central to southern China, has been limited and sporadic. Morphological variation has been increased in this species by irradiating seed with gamma radiation and by developing a random mating population among 31 foreign introductions and 24 domestic selections. A systematic germplasm collecting expedition in the area of origin is needed for this species.
Genetic Analysis of Chlorina Mutants of Durum Wheat
Authors: Klindworth Daryl L. , Williams Norman D. , Duysen Murray E.
Published: July 2010

Chlorina mutants are useful for studies of photosynthesis and as genetic markers. Three chlorophyll‐deficient‐durum mutants (CDd1, CDd2, and CDd6) of tetraploid wheat (Triticum turgidum L.) that have the chlorina phenotype have been identified. The objectives of this study were to determine the inheritance, chromosomal location, and allelic relationships of the CDd mutants, and to determine if the mutated locus in CDd6 was allelic to the cn‐A1 locus of hexaploid wheat (T. aestivum L.). To determine the inheritance and allelic relationships of the mutant genes, the mutants were intercrossed and crossed to ‘Langdon’ durum. The CDd6 mutant was crossed to Chlorina‐1, a chlorina mutant of hexaploid wheat. Chromosomal location of the mutant genes in CDd1 and CDd6 were determined by crossing the mutants to Group 7 aneuploids of Langdon. The F2 segregation indicated monogenic inheritance of each CDd mutation. The mutations in CDd1 and CDd2 were allelic, and dosage effects indicated that CDd6 was homoeoallelic to CDd1 and CDd2. The mutation in CDd1 was located in chromosome arm 7BL, and the mutation in CDd6 was located in chromosome arm 7AL. The mutation in CDd6 was allelic or tightly linked to the cn‐A1 locus of hexaploid wheat. Because the mutations in CDd1 and CDd2 were homoeoallelic to the mutation in CDd6, CDd1, and CDd2 were probably mutations of the cn‐B1 locus.
Genetic Variation in Water‐Use Efficiency and Its Relation to Photosynthesis and Productivity in Lentil Germplasm
Authors: Johnson Richard C. , Muehlbauer Fred J. , Simon Charles J.
Published: July 2010

Lentil (Lens culinaris L.) is predominantly grown in semi‐arid regions, and improving water‐use efficiency (WUE, dry matter/transpiration) has been of longstanding interest. Our objective was to evaluate germplasm for WUE and determine how WUE was related to photosynthesis and yield. In greenhouse experiments, variation in carbon isotope discrimination (Δ), a potential estimator of WUE, was observed among 32 diverse lentil accessions. Direct determinations of the leaf net CO2 assimilation to stomatal conductance ratio (A/gCO2) and WUE showed that PI 477921 cv. Redchief, with low Δ, had higher A/gCO2 and WUE than PI 543920 cv. Crimson with high Δ. Negative correlations (n = 20) were found between A/gCO2 and Δ (r = −0.65**), WUE and Δ (r = −0.61**). Values of Δ were also correlated with root to shoot ratios (r = 0.89**), indicating that high WUE and increased dry matter partitioning to shoots were related. Nine germplasm accessions were grown in the field at Pullman, WA, in 1991 and at Central Ferry, WA, in 1992. Grain weight was positively correlated with total shoot weight (including grain) at Pullman (r = 0.94**, n = 9) and with harvest index (HI) at Central Ferry (r = 0.79**, n = 9). At Central Ferry, Δ and HI were positively correlated (r = 0.67**, n = 9), indicating an association between increased dry matter partitioning to grain and lower WUE. The results show that genetic variation for WUE is present in lentil germplasm and can be estimated by Δ; however, Δ was not correlated with grain weight at either location. Because shoot weight and HI were more closely associated with yield than Δ, these traits would apparently be more effective for improving lentil productivity than selection for WUE.
Vulnerability of Pasture and Range Legumes to Fungus Gnats
Authors: Springer T. L.
Published: July 2010

Fungus gnats, Bradysia spp., are best known as pests of greenhouse‐grown ornamentals, and some data suggests that fungus gnats may be pests of forage legumes; however, information is largely lacking about their effects on forage crops. This study was conducted to determine adult fungus gnat oviposition preference and seedling mortality for 15 legume species. Replicated free‐choice tests were conducted in the greenhouse in June 1992, and May and June 1994. Significant variation (P ≤ 0.05) in oviposition preference was attributed to differences among legume species, experiments, and experiment by species interactions. Species accounted for 44% of the total variation, experiment by species interactions (14%), and experiments (9%). Though experiment by species interactions occurred, live species were commonly preferred. These were hairy vetch, Vicia villosa Roth; cowpea, Vigna unguiculata (L.) Walp subsp. unguiculata; Illinois bundleflower, Desmanthus illinoensis (Michx.) MacM. ex Robinson & Fern.; woollypod vetch, Vicia villosa subsp. varia (Host) Corbiere; and yellow sweet‐clover, Melilotus officinalis Lam. Significant variation in seedling mortality was attributed only to legume species. All species tested were susceptible to feeding damage and seedling stand reductions of greater than 90% were caused by as few as one larva per seedling. Based on observations made in the greenhouse and the fact that fungus gnats have been reared from soil samples collected from field stands of white clover, Trifolium repeus L., fungus gnats may pose a threat during the seedling establishment phase of some forage legumes. Field studies with naturally occurring populations of fungus gnats are needed to determine the importance of these insects in reducing establishment and persistence of pasture and range legumes.
Characterization of Proteolysis in Alfalfa and Red Clover
Authors: Jones B. A. , Hatfield R. D. , Muck R. E.
Published: July 2010

The loss of protein (proteolysis) during the ensiling of forage legumes is a severe problem. Alfalfa (Medicago sativa L.) will lose 44 to 87% of its protein during ensiling, whereas red clover (Trifolium pratense L.), a legume of similar protein content, will lose only 7 to 40%. Reasons for this difference in proteolysis are unknown. Research was conducted to determine and compare the general characteristics (rates, pH and temperature effects) of proteolysis in red clover and alfalfa extracts, and secondly to evaluate different in vitro test proteins to monitor legume proteolysis. Proteolytic rates of alfalfa and red clover extracts were not significantly different when either ribulose 1,5‐bisphosphate carboxylase/oxygenase (RubisCo) or bovine serum albumin (BSA) was used as the protein substrate; however, both legumes displayed significantly higher rates for the degradation of RubisCo than BSA (P < 0.10). The pH optima were 5.5 for both legumes when RubisCo was degraded, and 5.5 and 6 for alfalfa and red clover, respectively, when BSA was the substrate. Proteolysis in the legume extracts had similar pH and temperature stabilities and temperature optimum for the degradation of RubisCo. These data suggest that alfalfa and red clover have similar inherent proteolytic activity and cannot explain the difference in extent of proteolysis in the two silages.
Heritability of Carbon Isotope Discrimination and Correlations with Earliness in Cowpea
Authors: Menéndez Cristina M. , Hall Anthony E.
Published: July 2010

Drought is a major constraint limiting rainfed crop production in semiarid regions. Selection criteria for increasing transpiration efficiency (TE) may be useful for enhancing drought adaptation. Carbon isotope discrimination (∆) has been negatively correlated with TE in cowpea [Vigna unguiculata (L.) Walp.] and several other C3 species. However, the realized heritability of ∆ is not known and ∆ has shown negative associations with days to flowering, which could limit its usefulness as a selection criterion for enhancing drought adaptation. Field studies were undertaken to estimate the heritability of ∆, estimate the genetic correlation between ∆ and earliness, and determine the response to selection for high and low ∆ and for earliness and lateness in two cowpea populations. Broad‐sense heritabilities were low to intermediate (0.27 and 0.58) for ∆ and high (0.72 and 0.80) for days to first flower (DFF). Selections were made among individual F2 plants, and selected progenies were evaluated as F3 and F4 families. Realized heritabilities were low for ∆ (0.25–0.31) but significant and high for DFF (0.89–0.96). Selecting individual F2 plants for high and low ∆ was effective in identifying F3 and F4 families with high and low ∆ only in one of the crosses. Genetic correlations between ∆ and earliness were negative and low to intermediate in magnitude (−0.14 to −0.66). Selection for earliness can be effective in the F2 generation, but it may result in some indirect selection for high ∆ and, therefore, low TE. Selection for low ∆ may be most efficient with advanced families.
Use of Wax‐Petrolatum Layers for Screening Rice Root Penetration
Authors: Yu Long‐Xi , Ray Jeffery D. , O'Toole John C. , Nguyen Henry T.
Published: July 2010

The ability of roots to penetrate compacted soils can be beneficial in avoiding drought stress. However, breeding for root penetration is hindered by the lack of an efficient, reliable screening technique. Our objectives in this study were to develop and evaluate the use of a wax‐petrolatum layer system as a reference to measure genotypic variation in root penetration ability of 11 rice (Oryza sativa L.) cultivars from dryland and wetland hydrological origins. The wax‐petrolatum layers consisted of 60% wax and 40% petrolatum white, with a penetration resistance strength of 1.4 MPa at 27° C as measured with a soil penetrometer. The wax‐petrolatum layers were placed in pots and served as a partial barrier to root growth. Rice cultivars were sown in a randomized complete block design with three replications and grown in a growth chamber. Root penetration ability was measured as the ratio of the number of roots that penetrated the wax‐petrolatum layer to the total number of roots. Consistently, rice cultivars from dryland hydrological origins had greater root penetration ability than did cultivars from wetland origins. Root penetration ability ranged from 6 to 26%. Root thickness ranged from 0.9 to 1.5 nun and was positively correlated (r = 0.81, P < 0.001) with root penetration ability. Data indicated that the use of wax‐petrolatum layers was an effective technique for measuring differences in root penetration ability.
Nitrogen Assimilation in Nitrogen‐Fixing Soybean Plants during Phosphorus Deficiency
Authors: Sa T‐M. , Israel D. W.
Published: July 2010

This study evaluated the hypothesis that P deficiency alters N assimilation in N2‐fixing soybean plants (Glycine max L. Merr.) through effects on nodule carbohydrate status. Transport of N constituents in xylem sap, concentrations and total quantities of N fractions in plant organs, and nonstructural carbohydrate status of nodules were compared in P‐sufficient (1.0 mM P) and P‐deficient (0.05 mM P) greenhouse‐grown soybean plants dependent solely on symbiotic N2 fixation. Increased ureide concentration in nodules and decreased ureide concentration in the xylem sap indicated that P deficiency restricted ureide transport from nodules to the xylem. Decreased ureide and total N concentration and flux in xylem sap, and decreased concentrations of ureide and soluble and insoluble reduced N in leaves and stems indicated that P deficiency decreased N delivery to the shoot. Phosphorus deficiency decreased the sap exudation rate per unit root mass by 75%. Thus, decreased exudation rate, as well as decreased constituent concentrations, contributed to decreased flux of N compounds in the xylem. The decreased exudation rate may have resulted from decreased hydraulic conductivity of the root system and/or decreased ion transport into the xylem. Phosphorus deficiency caused decreased hexose and sucrose concentrations and increased starch concentration in nodules, indicating impaired carbohydrate utilization. This impaired carbohydrate utilization and the resulting decrease in energy status may have contributed to the decreased movement of ureide, and other N constituents, from host cells into the xylem of nodules.
Detection of Genotypic Differences in Early Growth Response to Water Stress in Wheat using the Snow and Tingey System
Authors: Saulescu Nicolae N. , Kronstad Warren E. , Moss Dale N.
Published: July 2010

Early detection of genotypic differences in response to water stress would help in increasing selection intensity in breeding drought tolerant wheat (Triticum aestivum L.). However, detection of small differences requires adequate control of the stress level. A system was used to determine if differences among genotypes in growth response to water stress could be detected. Haun stage and shoot dry weight were determined after 20 d in 25 cultivars grown with adequate water supply or with a water deficit imposed by lowering the water table by 8 cm and by interposing a porous ceramic disk, with an air exclusion value of 0.5 MPa, in the conducting medium between the water table and the roots. Significant differences were found among cultivars in the response to the imposed water deficit. Hann stage reduction varied between 13% in the spring wheat ‘Klasic’ and 36% in ‘Apollo’, while shoot dry weight reduction was between 21% in Klasic and 67% in the club wheat ‘Moro’. The coefficient of correlation between the Haun stage and shoot dry weight response to water stress was highly significant (r = 0.78). Although no direct comparison could be made between response of early growth to water deficits and yield response in the field under drought stress, the results of the seedling growth test corresponded well with previous knowledge about the performance of the tested cultivars under water stress. Our results verified that the system could be useful for rapid evaluation of drought response in wheat breeding.
Endopolyploidization of Mesocotyls in Nebraska Maize Populations Selected for Cold Tolerance
Authors: Wilhelm Ed , Biradar D. P. , Bullock D. G. , Rayburn A. Lane
Published: July 2010

Germination and emergence in cold conditions (12–15°C) is important for obtaining improved maize (Zea mays L.) yields in low and no‐tillage production systems. The mesocotyl plays a decisive role in determining the ability of seedlings to emerge under adverse conditions such as deep planting or cold soils. The major factor involved in elongation of the mesocotyl is somatic polyploidy, referred to as endopolyploidization. Endopolyploidy of the mesocotyl tissue was determined by flow cytometry during 1992. Nuclei were isolated from mesocotyls of various maize populations grown at 23 and 15°C. Endopolyploidy of populations selected for cold tolerance was compared with endopolyploidy of their original unselected populations. The populations selected for cold tolerance had an endopolyploid distribution similar to their original unselected populations at both temperatures. Only the NA population was observed to have a different distribution of endopolyploidization in the selected population as compared with the original unselected population. The response was speculated to be the result of different mechanisms of cold tolerance in the NA vs. the NB and NS populations. Endopolyploidization was not affected by cold tolerance per se, but may be associated with freeze tolerance. A significant difference with respect to temperature was observed. At 15°C, the number of the highest ploid nuclei (8C) were reduced, while the number of 2C nuclei increased. This change reflects the slowing of cell division at cooler temperatures.
Cosegregation of Purple‐Throat Flower Color with Dihydroflavonol Reductase Polymorphism in Soybean
Authors: Fasoula Dionysia A. , Stephens Paul A. , Nickell Cecil D. , Vodkin Lila O.
Published: July 2010

Several genes act epistatically to produce flower color in soybean [Glycine max (L.) Merr.]. The genotype W1W1W3W3w4w4 produces the purple‐throat phenotype and W1Wlw3w3w4w4 gives a near‐white phenotype. Our objective was to determine whether restriction fragment length polymorphisms of several anthocyanin pathway genes are associated with flower color traits. Genomic DNA from isolines of several flower color genes in the cultivar Clark were digested with 23 different endonucleases and probed with clones representing phenylalanine ammonia lyase, chalcone synthase, or dihydroflavonal reductase (DFR). The HaeIII digest revealed a polymorphism between the isoline containing the dominant W3 allele for purple‐throat and the other isolines with the homozygous recessive w3 alleles. The DFR polymorphism cosegregated with flower color variants in an F2 population segregating for the W3 alleles. No recombinant types were found in 78 individuals, indicating either the W3 encodes DFR or is closely linked to a DFR gene.
Physical Restriction of Pod Growth Alters Development of Soybean Plants
Authors: Miceli Fabiano , Crafts‐Brandner Steven J. , Egli Dennis B.
Published: July 2010

Efforts to determine the mechanistic relationships between fruit and canopy development are complicated by difficulties in designing nondestructive treatments that modify plant‐sink development. Pod growth was physically restricted by placing plastic straws, referred to as plastic pod‐restriction devices, over 0,50, or 100% of the soybean (Glycine max L. Merr.) pods in greenhouse experiments. The objective was to determine how decreases in pod growth influenced whole‐plant growth and development. Both the rate and final accumulation of seed dry matter were decreased by restricting pod growth. Conversely, restricting pod growth increased seed number due to increased production and decreased abscission of fruits. Plant dry matter and N accumulations during the linear seed‐fill period were not affected by restricting pod growth. This resulted from proportional increases in partitioning of assimilates into stems and leaves. Thus, decreases in reproductive growth apparently did not cause feedback inhibition of photosynthesis. Although leaf abscission was delayed by restricting pod growth, dry matter and N accumulation late in development were affected only slightly. In general, restricting pod growth influenced plant development and assimilate allocation in a similar manner as physical removal of fruits. The inverse relationship between the rate of dry matter accumulation in seed and pod and seed number per plant indicated that assimilate availability (united seed number. The delay in leaf yellowing and abscission induced by physically restricting pod growth suggested that the completion of monocarpic senescence was directly affected by changes in the rate of seed dry matter accumulation per plant.
Inheritance of Soybean Susceptibility to Agrobacterium tumefaciens and Its Relationship to Transformation
Authors: Mauro A. O. , Pfeiffer T. W. , Collins G. B.
Published: July 2010

The development of genetic transformation techniques for soybean [Glycine max CL.) Merr.] has been slow, but in a few cases transgenic plants have been obtained with Agrobacterium tumefaciens as the vector. Soybean genotypes with good agronomic characteristics and susceptibility to infection with A. tumefaciens would be desirable for transformation attempts. The objectives of this study were to determine the inheritance of susceptibility to A. tumefaciens and to determine if any relationship exists between gall formation on growing plants and transformation of cotyledonary tissue in vitro. In three experiments, susceptible parent ‘Peking’, resistant parent ‘Clark’, and the F1, F2, F3, F4, BC1P1, and BC1P2 progeny were inoculated at 12 sites at the V8 growth stage with A. tumefaciens wild‐type strain A281. The distributions of galls per plant indicated quantitative inheritance of the susceptible gall formation response. However, because heritability was high (>0.50) and the number of genes controlling susceptibility was estimated as between two and three, this characteristic should be relatively easy to transfer to new genotypes. Immature zygotic cotyledons were excised from the same material, inoculated with strain A281 containing a plasmid holding the [β‐glucuronidase (GUS) reporter gene, and induced to form somatic embryos. The frequency of somatic embryos exhibiting GUS activity was greater than 50% in the first and second embryo collection periods. It was not possible to predict which genotype would be useful for transformation attempts based on the plant rating of susceptibility.
Cytogenetics of Eurasian Bluebunch Wheatgrass and Their Relationship to North American Bluebunch and Thickspike Wheatgrasses
Authors: Jensen Kevin B. , Curto Michael , Asay Kay
Published: July 2010

Bluebunch wheatgrass, Pseudoroegneria spicata (Pursh.) A. Love, is one of the most important native dryland forage bunchgrasses of the intermountain West, which often produces depleted stands under moderate to heavy grazing pressure. In recent plant collecting trips to the Altai and Tien Shan Mountains of China and Russia, a grazing tolerant bluebunch wheatgrass complex was obtained. This study was conducted to describe the cytogenetic characteristics and potential for genetic exchange between the Eurasian bluebunch wheatgrass complex [P. strigosa (M. Bieb.) A. Love, P. geniculata (Trin.) A. Love, Roegneria elytrigioides Yen and Yang, and R. glaberrima Keng et S.L. Chen] and those bluebunch thickspike wheatgrasses found in North America. Meiotic behavior of the triploid hybrids between diploid and tetraploid R. glaberrima indicated that both ploidy levels share the same genome. Almost complete pairing in hybrids P. strigosa ssp. aegilopoides (Drob.) A. Love × P. spicata, and R. glaberrima × P. spicata, demonstrated that P. strigosa ssp. aegilopoides and R. glaberrima are comprised of the basic S genome. Triploid hybrids between P. geniculata, and R. elytrigioides with either P. spicata, P. stipifolia (Czern. ex Nevski) A. Love, or P. strigosa ssp. aegilopoides exhibited trivalent frequencies consistent with the hypothesis that tetraploid R. elytrigioides is an autotetraploid (SSSS) and that P. geniculata is either a segmental autotetraploid (S1S1S2S2) or an allotetraploid (SS??). Based on the high level of chromosome pairing in the interspecific hybrids between the Eurasian and North American bluebunch wbeatgrass complex, genetic exchange is possible. Due to the close genetic and morphological similarity among individuals of P. spicata, P. strigosa, P. geniculata, R. elytrigioides, and R. glaberrima we are likely dealing with a single, polymorphic, Eurasian‐North American species complex.
Identification and Transfer of Heterotic Chromosome Blocks for Forage Yield in Short‐Day Exotic Pearl Millet Landraces
Authors: Burton G. W. , Wilson J. P.
Published: July 2010

Photoperiod sensitivity of pearl millet, Pennisetum glaucum (L.) R. Br., exotic accessions has limited their use in nontropical environmerits due to excess height and late maturity problems. Objectives of this research were (i) to describe and evaluate a modification of a direct method to screen non‐converted short‐day Burkina Faso landraces (BFL) of pearl millet for large heterosis‐creating beterotic chromosome blocks (HCBs) that can replace a small HCB in the male parent T383 of the top producing F1 hybrid Tifleaf 2 and to increase its forage yield; and (ii) to determine the variation in the size of HCBs in a single landrace. Short early T383‐1ike F2 plants in (BFL × T383) F2 populations were screened for HCBs by crossing them with T23Rp1, which carries the red marker gene, crossing those F1s on T85A {cytoplasmic male sterile (cms) green 23], growing 100 spaced plants of the cross T85 × (BFL × T383) F2, cutting and weighing 50 of the red and 50 of the green plants in each population, and analyzing the data with the SAS General Linear Model. Percent heterosis for plant forage yield in 100‐plant populations of each cross ranged from 0 to 51%. The average HCB heterosis for T383 was 4%. Sister plants within a single BFL were variable enough to make it important to cross a single BFL plant with T23Rp1 to measure HCB beterosis and with T265 (T383Rp1 to start the transfer of the top HCB to T383. The modification method requires an extra year before measuring HCBs, but requires a less variable 100‐plant screening population and should require fewer backcrosses to transfer the top HCB to T383.
The Role of Cell Wall Adjustments in Plant Resistance to Water Deficits
Authors: Neumann Peter M.
Published: July 2010

Reductions in rates of cell and tissue growth are a commonly observed response to water deficits resulting from drought or soil salinity. These can lead to reductions in plant size and yields. More severe stress can lead to accelerated death and complete loss of yields. This review deals with the final biophysical links in the chain of events underlying inhibition of growth in crop plants exposed to water deficits. It first examines and rejects the notion that a stress‐induced reduction in cellular turgor pressure is necessarily a primary cause of growth inhibition. Data supporting the involvement of an additional and often overlooked biophysical response to water deficits are then reviewed: This response involves changes in tissue extension capacity, as a result of hardening (or softening) of expanding cell walls, and is termed cell wall adjustment. Wall hardening should increase the capacity of expanding cells to maintain turgor pressure but also acts to inhibit rates of cell expansion growth. The inhibition of cell expansion can lead to reductions in leaf area that limit rates of transpirational loss of soil water reserves; in nonirrigated crops exposed to terminal drought environments, this adaptation may prolong survival and allow time for completion of reproductive development. Conversely, wall hardening responses to intermittent water deficit episodes, e.g., in irrigated crops, could be undesirable. The survival of irrigated crops is largely assured and induction of wall hardening in the intervals between irrigation could unnecessarily reduce growth and yields. Appropriate manipulation of cell wall adjustments, via selection, breeding, or genetic engineering, could prove useful for the development of more stress‐resistant crop plants suited to irrigated or nonirrigated environments.
Differential Summer Suvival of White Clover Stolons: Germplasm and Fungicide Effects
Authors: Pederson G. A. , Pratt R. G.
Published: July 2010

White clover (Trifolium repens L.) stands in the southeastern USA survive during summer drought predominantly through persistence of stolons. The decay and death of stolons during the hot, humid summer may be partially due to fungal diseases. This study determined the effect of summer fungicide applications on stolon survival of ‘Regal’ and ‘Louisiana S‐’ white clover compared with drought‐tolerant Brown Loam Syn. No. 2 germplasm (BLSyn). The three white clover entries were grown in the field on a Catalpa silty day (fine, montmorillonitic, thermic Fiuvaquentic Hapludoll) at Mississippi State, MS, in three separate 1‐yr studies. During summer stolon dormancy, plots of each entry were either untreated or sprayed biweekly with benomyl [methyl 1‐(butylcarbamoyl)‐2‐benzimidazole‐carbamate]. In 2 of 3 yr, BLSyn had 23 to 63% greater ground cover, 33 to 55% greater stolon density, and 30 to 47% greater relative live stolon length following the summer drought than Louisiana S‐1. In all 3 yr, BLSyn had greater relative live stolon length (7‐18%) following the summer drought than Regal. Plots treated with benomyl had 14 to 52% greater stolon density (in 2 of 3 yr), 14 to 40% greater stolon growing point density, and to 27% greater relative live stolon length than untreated plots. Benomyl treatment gave less of an increase in relative live stolon length of BLSyn than in the two cultivars. These results suggest that fungal pathogenesis may reduce white clover stolon survival during summer dormancy, and that greater fungal disease resistance could be part of the mechanism of improved summer survival in BLSyn white clover.
Evaluating Wheat Nitrogen Status with Canopy Reflectance Indices and Discriminant Analysis
Authors: Filella I. , Serrano L. , Serra J. , Peñuelas J.
Published: July 2010

Nitrogen deficiencies can seriously reduce yield and economic returns for farmers. Remote sensing could provide inexpensive, largearea estimates of N status and be used to monitor N status since leaf chlorophyll (Chi) A content is mainly determined by N availability. The objective was to determine if remote sensing of wheat (Triticum aestivum L.) Chi A content would provide a rapid estimation of wheat N status. We measured the reflectance of a wheat crop submitted to five different fertilization treatments throughout the growth cycle. We tested several empirical reflectance indices of pigment content: reflectance at 550 nm (R550), reflectance at 680 nm (R680), three parameters of the red edge [wavelength (λre), amplitude in the first derivative of the reflectance spectra (dRre), and sum of amplitudes between 680 and 780 nm in the first derivative of the reflectance spectra (ΣdR680–780nm)], and pigment simple ratio (PSR) and normalized pigment chlorophyll index (NPCI) (indices of carotenoid/Chl ratio). We also measured leaf Chi A and N content, and leaf area index. There were significant correlations between canopy Chi A content and R550, R680, and all the red edge parameters. The NPCI and PSR followed phenological evolution of the carotenoids/Chl A ratio and separated the different treatments. By discriminant analysis based on the pigment indices reflectance at 430 nm (R430), R550, R680, λre, dRre, and NPCI, each reflectance spectrum can be assigned to a different N status class. Thus, the use of these optical techniques offers a potential for assessing N status of wheat.