bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability in Growth Characteristics and Leafspot Resistance Parameters of Peanut Lines
Authors: Knauft D. A. , Gorbet D. W.
Published: July 2010

Peanut (Arachis hypogaea L.) genotypes have been developed with varying levels of early and late leafspot [Cercospora arachidicola Hori and Cercosporidium personatum (Berk, and Curt.) Deighton] resistance. An understanding of the changes that occur during the growing season among resistance parameters and in vegetative and pod development will be beneficial to crop scientists. In this study, 16 genotypes were grown 30 cm apart within 90‐cm rows and evaluated under disease pressure at 10‐d intervals during a 2‐yr period for disease rating, percentage leaf area necrotic, vegetative (V) stage, total vegetative weight, total pod weight, and partitioning coefficient. In both years, disease ratings differed among genotypes beginning 58 d after planting and were more effective for distinguishing among genotypes throughout the growing season than percentage leaf necrotic area. Fourteen of the 16 genotypes had similar V stages throughout the growing season. Vegetative weights of disease‐susceptible cultivars did not exceed 165 g plant‐1, while many resistant lines exceeded 250 g plant−1. Susceptible‐cultivar partitioning coefficients generally exceeded 80%, while resistant lines ranged from 20 to over 80%. Pod initiation in resistant lines lagged behind that of susceptible cultivars by 10 to 30 d, even if resistant lines had high partitioning coefficients. Use of disease rating combined with selection of high partitioning lines with early initiation of pod production may contribute to development of desirable cultivars.
Changes During Early Soybean Seed and Axes Deterioration: II. Lipids
Authors: Ferguson J. M. , TeKrony D. M. , Egli D. B.
Published: July 2010

Peroxidative changes in seed lipids are thought to be a major cause of seed deterioration during storage. This study was conducted to determine the fatty‐acid composition of soybean [Glycine max (L.) Merr.] seeds, axes, and mitochondria during the early stages of deterioration. High‐quality seed lots of ‘Union’ and ‘Desoto’ soybean were stored at 25 °C and 115 g kg‐1 seed moisture for 10 and 12 months, respectively. Seeds were sampled at frequent intervals and the fatty‐acid composition of storage and membrane lipids from seeds, axes, and mitochondria were determined. There were no detectable changes in the fatty‐acid composition of storage lipids from whole seeds or axes during the storage period for either seed lot, despite the substantial decline in seed vigor. There was a slight decrease in the percentage of unsaturated fatty acids in the membrane lipids of excised axes from Desoto seeds. The percentage of unsaturated fatty acids in the mitochondria from excised axes declined early during storage. The double‐bond index (DBI) of lipids from mitochondria of the Union axes fell from 1.76 at the beginning of storage to 1.60 after 10 months. Similar declines of 1.79 to 1.70 after 1 yr in storage were seen for the Desoto axes. Mitochondria! respiration and DBI were highly correlated for both seed lots. These data suggest that the decreases in mitochondrial respiration during storage may be associated with peroxidative changes in mitochondrial lipids and that these changes occurred prior to loss in seed vigor.
In Vitro Plant Regenation of Peanut From Seed Explants
Authors: McKently A. H. , Moore G. A. , Gardner F. P.
Published: July 2010

An efficient system of plant regeneration is critical to the success of newly developing genetic manipulation techniques as tools for crop improvement programs. This study was designed to assess the regeneration response of explants taken from the seed of peanut (Arachis hypogaea L.). Complete plants were regenerated from in vitro‐cultured embryo axes and embryonated and deembryonated cotyledons that were whole and sectioned. Multiple shoots arose on 6‐benzylaminopurine (BA) supplemented Murashige and Skoog media (0.5–60 mg L‐1), with maximum production occurring at 25 mg L‐1. Large quantities of shoots were obtained from single whole embryonated cotyledon explants cultured on BA‐supplemented medium for periods up to 238 d. Excised shoots developed roots in vitro upon transfer to medium supplemented with 1‐napthaleneacetic acid (NAA) at 1 mg L‐1 for 30 d. In vitro‐produced plantlets transferred to soil and placed in a greenhouse developed successfully, matured, and set seed. Twenty genotypes were regenerated using this tissue culture system. No phenotypic variants were observed among any of the plants produced in these experiments. Thus, this system allows for the in vitro production of morphologically normal peanut plants at high frequencies.
Condensed Tannin Concentraton in Sericea Lespedeza as Influenced by Preservation Method
Authors: Terrill T. H. , Windham W. R. , Evans J. J. , Hoveland C. S.
Published: July 2010

Accurate analysis of condensed tannins in forage is essential to characterize its effect on digestibility. The concentration of analyzable tannins are determined by the forage preservation method. The effect of forage preservation method on condensed tannins was studied in a randomized‐block field experiment with high‐tannin (HT) and low‐tannin (LT) sericea lespedeza, Lespedeza cuneata (Dumont) G. Don. Plants were harvested and fresh frozen (FF), oven dried (OD), freeze dried (FD), and sun cured (SC). Tannin concentrations were determined with a modified vanillin‐HCl procedure. To improve the vanillin‐HCl assay several parameters were examined, including (i) extraction solvents, (ii) effects of water on color reaction, and (iii) assay with purified tannin vs. catechin equivalents. A 7:3 acetone/water solution extracted the greatest amount of tannin for all drying treatments and sericea entries. Color development was greatly reduced with addition of water to the reaction solution. Use of catechin equivalents approximately doubled the estimation of tannin content compared with the purified tannin assay. Tannin concentrations were higher in HT than LT sericea for all preservation method treatments. Averaged across entries, tannin concentrations were 79, 45, 41, and 37 g kg−1 dry matter (DM) for FD, FF, SC, and OD sericea, respectively. Reduced extractability of tannins may be related to increased polymerization of tannins or complexation with other cellular constituents. Freeze drying is the most efficient method of forage preservation for tannin analysis.
Gibberellins and Heterosis in Maize: Quantitative Relationships
Authors: Rood S. B. , Buzzell R. I. , Major D. J. , Pharis R. P.
Published: July 2010

To investigate the possible relationship between gibberellins (GA) and heterosis, a diailel from four elite maize, Zea mays L., inbreds (A632, B73, CH807 [from Mo17], and CO109) was studied under controlled environment conditions. Heterosis for plant growth was substantial at 25/15 °C (day/night), as hybrid seedlings emerged more rapidly, were taller, had heavier shoots, and larger leaf areas than the parental inbreds. Gibberellic acid (GA3) at 0.1, 0.5, or 1.0 mg per plant was pipetted into the leaf whorls of 14‐d‐old seedlings. The exogenous GA3 promoted ligule and total height in all genotypes, but the inbreds were maximally influenced. Consequently, potence ratios, representing the overall degree of dominance, were reduced from an average of 7.7 to 1.7 following GA3 application, indicating decreased heterosis. In an experiment at 15 °C, imbibition of seeds in GA3 accelerated germination and seedling growth, particularly shoot elongation of the parental inbreds. Endogenous concentrations of GA1 and GA19 were determined by gas‐chromatography‐selected ion monitoring using [2H]GAs as quantitive internal standards. Highly significant regressions of height, leaf area, relative growth rate, and height increment versus the log of GA concentration were observed. These results are consistent with the theory that GA are one factor involved in the regulation of heterosis of shoot growth in maize, a theory that suggests that a partial deficiency in endogenous GA in maize inbreds limits their growth, and is a contributing cause of inbreeding depression.
Nitrogen Nutrition and Temporal Effects of Enhanced Carbon Dioxide on Soybean Growth
Authors: Vessey J. Kevin , Henry Leslie Tolley , Raper C. D.
Published: July 2010

Plants grown on porous media at elevated CO2 levels generally have low concentrations of tissue N and often appear to require increased levels of external N to maximize growth response. This study determines if soybean [Glycine max (L.) Merr. ‘Ransom’] grown hydroponically at elevated CO2 requires increases in external NO−3 concentrations beyond levels that are optimal at ambient CO2 to maintain tissue N concentrations and maximize the growth response. This study also investigates temporal influences of elevated CO2 on growth responses by soybean. Plants were grown vegetatively for 34 d in hydroponic culture at atmospheric CO2 concentrations of 400, 650, and 900 μL L−1 and during the final 18 d at NO−3 concentrations of 0.5, 1.0, 5.0 and 10.0 mM in the culture solution. At 650 and 900 μL L−1 CO2, plants had maximum increases of 31 and 45% in dry weight during the experimental period. Plant growth at 900 μL L−1 CO2 was stimulated earlier than at 650 μL L−1. During the final 18 d of the experiment, the relative growth rates (RGR) of plants grown at elevated CO2 declined. Elevated CO2 caused increases in total N and total NO−3‐N content and leaf area but not leaf number. Enhancing CO2 levels also caused a decrease in root:shoot ratios. Stomatal resistance increased by 2.1‐ and 2.8‐ fold for plants at the 650 and 900 μL L−1 CO2, respectively. Nitrate level in the culture solutions had no effect on growth or on C:N ratios of tissues, nor did increases in CO2 levels cause a decrease in N concentration of plant tissues. Hence, increases in NO−3 concentration of the hydroponic solution were not necessary to maintain the N status of the plants or to maximize the growth response to elevated CO2.
Temperature and Photoperiod Effects Mediated by the Sorghum Maturity Genes
Authors: Major D. J. , Rood S. B. , Miller F. R.
Published: July 2010

A more complete understanding of the role of photoperiod and temperature in the genetic control of flowering in sorghum (Sorghum bicolor L. Moench) will allow breeders greater flexibility in making crosses among widely differing maturity types and will also contribute to the understanding of regional adaptation requirements. The objective of this study was to characterize the photoperiodic responses of 10 sorghum lines with all known combinations of the sorghum maturity genes Ma1, Ma2, and Ma3. Twenty growth chamber trials were conducted to examine photoperiods between 11 and 15 h at 0.5‐h intervals and to examine the influence of mean daily temperature as well as the range of day/night temperature. Compared with other genotypes, the recessive maR3 allele resulted in a reduction of 3.1 leaves in the basic vegetative phase (BVP‐Ieaf number under favorable photoperiods) and also eliminated photoperiod sensitivity. There was little influence of Ma2 or Ma3 genes on BVP. The dominant Ma1 allele conferred increased photoperiod sensitivity (4.5 leaves/h) compared to homozygous ma1, condition (1.4 leaves/h). There were no significant differences detected in the Maximum Optimal Photoperiod, which was about 12 h. The Ma2 gene was implicated in a photoperiod ✕ temperature interaction, although the exact role was not clear. The dominant allele of Ma3 increased the phyllochron (leaf development rate) by about 0.2 d/leaf. Thus, the developmental response of sorghum to photoperiod and temperature involves the complementation of effects from these maturity genes.
Cellular Expression of Panicle Exsertion and Peduncle Elongation in Semidwarf Oat
Authors: Farnham M. W. , Stuthman D. D. , Biesboer D. D.
Published: July 2010

Panicle exsertion genes partially reverse the phenotypic effects of the Dw6 dwarfing gene in oat (Avena sativa L.) by elongating the peduncle. The objectives of this study were to: (i) determine the cellular basis of peduncle elongation in semidwarfs exhibiting full paniclexsertion, (ii) determine GA‐sensitivity of Dw6 semidwarfs, and (iii) attempt to mimic the action of exsertion genes with a bootstage application of gibberellic acid (GA3) to nonexserted semidwarfs. Four pairs of divergent lines, each pair consisting of a nonexserted semidwarf with a short peduncle and an exserted semidwarf with an extended peduncle, were compared in greenhouse and field experiments along with OT207, the original source of Dw6, and OT184, the nondwarf parent of OT207. Peduncle epidermal cells of all lines were measured. The GA3 was applied to field‐grown plants, and genetically nonexserted plants sprayed with GA3 were cytologically compared to exserted controls having equal length peduncles. Peduncles of OT207 had fewer and shorter cells per vertical axis than peduncles of OT184. Similar differences were observed between exserted and nonexserted lines. Thus, the Dw6 gene and the panicle exsertion genes have an effect on both cell number and cell elongation. The GA3 application elongated the peduncles by enhancing both cell number and elongation as do exsertion genes; however, GA3 application and exsertion genes did not produce peduncles with identical cellular characteristics. Effects of GA3 application on pedunclelongation were more pronounced in OT207 and nonexserted semidwarfs than in respective longer peduncle lines. Results implicate the involvement of GA metabolism in the action of Dw6 and the exsertion genes.
Diallel Analysis of Resistance to Anthracnose Stalk Rot in Maize Inbreds
Authors: Callaway M. B. , Smith M. E. , Coffman W. R.
Published: July 2010

Anthraenose stalk rot (ASR), caused by Colletotrichum graminicola (Ces.) Wils., has become an important disease of maize (Zea mays L.) in recent years. The purposes of this study were to evaluate general and specific combining ability effects for ASR resistance in a group of maize inbreds adapted to the northeastern USA, and to evaluate two commonly used ASR rating methods. Eight maize inbreds were crossed in a fixed effects diallel mating design and parents and crosses were grown at locations in New York, Delaware, and Pennsylvania. The two methods of rating for ASR resistance were: (i) total number of internodes infected, and (ii) number internodes greater than 75% infected. The inbreds LB31B, RD5264, and RD6501 had highly significant negative general combining ability effects for ASR ratings, indicating that these lines would be good choices as parents where ASR resistance is desired. The inbreds RD5215, RD5217, RD5529, B59Ht, and B37 had significant, positive general combining ability effects. Specific combining ability was important for certain combinations of lines. Results for the two rating methods were practically identical. Only one of the two rating methods need be used in a given year. The evaluation methods should be alternated at yearly intervals to minimize the possibility of preferential selection for a particular mechanism of resistance.
Aluminum Tolerance in Alfalfa as Expressed in Tissue Culture
Authors: Parrot W. A. , Bouton J. H.
Published: July 2010

Acid soils whose pH is low enough for A1 to become soluble are found throughout the world and greatly limit growth of Al‐sensitive crops like alfalfa, Medicago sativa L. Alfalfa germplasms were selected to overcome these conditions and are now available for testing. The objective of this study was to test performance of an acid‐tolerant germplasm (AT), and an acid‐sensitive check germplasm (AS), in acid, Al‐toxic cell culture conditions. Both germplasms were tested for growth as callus in normal Biaydes medium, a Blaydes medium modified by lowering pH and levels of Ca and P, and on the same modified medium but with a toxic Al level. The modified Blaydes medium depressed callas growth of both germplasms relative to their growth on normal Blaydes. This depression was equal for both germplasms of the first 6 wk of culture, but by the 8th wk, the AT germplasm outperformed the AS germplasm. The addition of Al further decreased growth of AS callus but not AT callus. This suggests that plants from the AT germplasm rapidly express Al tolerance at the tissue level. With increasing time in culture, the AT germplasm also expresses acid tolerance in culture. The differences in callus growth shown by genotypes within germplasms indicates the cell culture procedure can be used to screen genotypes for acid or Al tolerance. Significant genotypic variability for acid, Al tolerance is still present within the germplasm, suggesting that continued progress from selection should still be possible.
Haploid Pearl Millet Pollen from Near‐Tetraploid Interspecific Pennisetum Hybrids
Authors: Dujardin M. , Hanna W. W.
Published: July 2010

To determine the potential for germplasm exchange, interspecific hybrids from a cross between a pearl millet Pennisetum glaucum (L.) R. Br. ✕ Pennisetum purpureum Schum. amphiploid crossed with a P. glaucum ✕ Pennisetum squamulatum Fresen. interspecific hybrid were backcrossed four times to tetraploid pearl millet. The objective of this research was to determine the chromosomal characteristics of progeny obtained from pollinating both cytoplasmic nuclear male sterile diploid (2n = 14) and tetraploid (2n = 28) pearl millet with near‐tetraploid (2n = 26 to 32) BC4 derivatives involving P. glaucum, P. purpureum, and P. squamulatum. Forty‐five BC4 plants, 15 of which had chromosome numbers ranging from 26 to 32, were used to pollinate cytoplasmic‐nuclear male sterile diploid and tetraploid pearl millet, giving rise to 10 diploid and 70 neartetraploid BC5 progeny, respectively. The recovery of diploid progeny suggests monoploid pollen was produced by the BC4 plants. All offspring expressed phenotypic traits of the male parent. Male fertility was restored completely in two diploid hybrids and restored partially in six near‐tetraploid hybrids, probably because of the transfer of P. purpureum and/or P. squamulatum chromatin. Nine BC5 diploid offspring had 14 A and/or A' genome chromosomes, which paired as seven bivalents at metaphase I. The near tetraploid BC5 offspring had from 27 to 30 chromosomes. Chromosome numbers observed in the young microspores of the BC4 plants ranged from n = l to n = 16. These results show that monoploid pollen can be produced from tetraploid or hexaploid hybrids and used for transferring gene(s) from wild relatives into pearl millet.
Cell‐Wall Components in Divergent Germplasms of Four Perennial Forage Grass Species
Authors: Buxton D. R.
Published: July 2010

Neutral‐detergent fiber (NDF) is an estimate of total cell‐wall (CW) components, which limit digestibility in forages. This study was conducted to determine whether concentration differences exist for NDF and CW components in four perennial grasses and to what extent these can account for reported variation in digestibility. ‘Napier’ and ‘Orion’ orchardgrass (Dactylis glomerata L.), ‘Barton’ and ‘Rebound’ smooth bromegrass (Bromus inermis Leyss.), germplasm of reed canarygrass (Phalaris arundinacea L.) selected for high or low specific leaf weight, and germplasm of tall fescue (Festuca arun‐dinacea Schreb.) selected for high or low rate of leaf‐area expansion were seeded in mid‐August on a Webster silty clay loam (fine‐loamy, mixed, mesic Typic Haplaquoll). At several spring harvests in 2 yr, total herbage and plant parts were assayed for NDF and CW components. Despite large differences in tiller size, NDF concentration of herbage and plant parts did not vary consistently between germplasms within reed canarygrass or tall fescue. Thus, selecting for fast growth rate and large tillers did not affect concentrations of NDF or CW components. In orchardgrass, NDF concentration was 3% greater and CW‐lignin concentration was 24% greater in Napier than in Orion herbage. In smooth bromegrass, NDF concentration was 5% greater in herbage and stems of Barton than of Rebound; CW‐lignin concentration was 5% greater in stems of Barton than of Rebound. In orchardgrass, cultivar variation for herbage digestibility was an inverse function of CW‐lignin concentration; in smooth bromegrass, variation in NDF and CW‐lignin concentrations had equal effect.
Potential Gain from Selection in Grain Sorghum for Higher Protein Digestibility
Authors: Bramel‐Cox P. J. , Lauver M. A. , Witt M. E.
Published: July 2010

Grain sorghum [Sorghum bicolor (L.) Moench] has not been fully utilized as a feed grain because of its highly variable feeding quality, which has been related to factors such as various grain characteristics that relate to the availability and quality of the protein and starch, response to environmental conditions, and processing methods in feed preparation. The objective of this study was to evaluate the potential to genetically improve the feeding value of grain sorghum through improved protein digestibility in a random‐mated population of grain sorghum. The study consisted of a 2‐yr and 5‐location evaluation of 100 S1 families in a blocks‐in‐replication design for grain yield, protein concentration, protein digestibility, and bloom date. The phenotypic and genotypic correlations indicated there was a negative association between grain yield and maturity but a positive association between protein digestibility and maturity resulted in a dramatic undesirable shift in the population to later maturity. Selection for grain yield resulted in families with earlier maturity and reduced protein digestibility, thus, selection for any single trait did not identify high yielding high protein‐digestible families with an acceptable range of bloom date. Using a rank summation index, calculated as Rank (grain yield) + Rank (protein digestibility) — Rank (bloom date), and restricting selection to the families rated in the top 50% for yield and protein digestibility increased both traits without an undesirable change in bloom date.
Response of Peanut Genotypes with Differential Levels of Leafspot Resistance to Fungicide Treatments
Authors: Gorbet D. W. , Knauft D. A. , Shokes F. M.
Published: July 2010

Leafspot diseases, caused by Cercospora arachidicola S. Hori (early leafspot) and Cercosporidium personatum (Berk, and Curt.) Deighton (late leafspot), are worldwide production problems on peanut (Arachis hypogaea L.). The extensive use of fungicides to control these diseases on susceptible cultivars is costly to growers. Developing leafspot resistant cultivars is a primary objective in many breeding programs. ‘Southern Runner’, which was released in 1986, is the only commercially available peanut cultivar in the USA with significant leafspot resistance. Field studies were conducted in 1981 to 1983 and 1985 to 1987 on peanut breeding lines with varying levels of leafspot resistance to evaluate their disease reaction and agronomic response to three leafspot fungicide programs and to assess their potential as cultivars for use with fewer fungicide sprays. The cultivars Florunner (susceptible) and Southern Runner (moderately resistant) and three breeding lines were used in all 6 yr, with five additional lines unique to the 1981 to 1983 experiments and four additional lines unique to the 1985 to 1987 tests. All experiments were randomized‐complete block, split‐plot designs with genotypes as subplots and three fungicide spray programs as main plot treatments: (i) unsprayed, (ii) chlorothalonil (tetrachloroisophthalonitrile), 500 g L‐1 on 20‐d, and (iii) 14‐d spray schedules. Leafspot disease ratings were on a 1 to 10 scale, with 1 = no disease and 10 = dead plants, assessed prior to digging. Significant (P ≤ 0.01) genotypic differences for pod yield, percent total sound mature kernels, seed weights, and disease ratings were noted. Significant (P ≤ 0.01) differences were obtained for years, fungicide treatments, and most two‐ and three‐way interactions. Negative correlations were obtained between pod yields and disease ratings for unsprayed (r = ‐0.64) and 20‐d schedules (r = ‐0.46), but not for the 14‐d treatment. No differences in pod yield were obtained between the 14‐d (eight sprays) and the 20‐d (four sprays) fungicide treatments on the leafspot resistant genotypes. Results indicated that it is possible to develop commercially acceptable peanut cultivars with leafspot resistance that reduces the need for fungicide control of leaf‐spots.
Inheritance of Ineffective Nodulation in Cowpea
Authors: Pemberton I. J. , Smith G. R. , Miller J. C.
Published: July 2010

Nodulation is a critical step in the development of the legume‐Rhizobium symbosis. A cowpea [Vigna unguiculata (L.) Walp.] plant of the varietal mix ‘Iron & Clay’ with small, white, ineffective nodules was observed during a greenhouse experiment and designated IC‐l. Experiments were conducted to determine the genetic control of ineffective nodulation in cowpea. The IC‐1 S1 plants were ineffectively nodulated and no nitrogenase activity was detected by acetylene‐reduction assay. No segregation for symbiotic effectiveness was noted in the S2 and S3 generations of IC‐1. Crosses were made between IC‐1 S1 and normal, effectively nodulating Iron & Clay cowpea, resulting in four F2 families that segregated into effective and ineffective nodulation classes. Based on x2 analysis, ineffective nodulation in cowpea is determined by a simply inherited recessive gene, designated cpi. The interaction of cpi and eight cowpea Bradyrhizobium strains was investigated, and no strain effects were noted. Non‐strain‐specific ineffective nodulation of cowpea is conditioned by a single recessive gene pair (cpi cpi).
R‐Navajo Kernel Color Expression as a Selection Criterion in a Sugary 2; Opaque 2 Maize Synthetic
Authors: Henson A. R. , Glover D. V. , Nyquist W. E.
Published: July 2010

Grain yield increases have been reported from indirect selection for increased anthocyanin aleurone coloration by use of R‐Navajo (R‐nj) allele in early maize (Zea mays L.). This study was conducted to determine if divergent selection for high and low R‐nj kernel aleurone coloration indirectly effected correlated responses for grain yield and other agronomic traits in a sugary‐2;opaque‐2 (su2;o2) Iowa Super Stiff Stalk Synthetic (BSSSS). The normal synthetic was converted by crossing inbred B37 su2;o2 with BSSSS, then backcrossing to BSSSS for three generations followed by two generations of randomating with selection of the heterozygous su2;o2 ears. The homozygous su2;o2 kernel segregants were selected from the random mated heterozygous BSSSS population to constitute a base population on which divergent selection was initiated. Three cycles of divergent mass selection for both high and low R‐nj coloration were obtained. All cycles of selection and a check were evaluated in two‐row plots in a randomized complete‐block design with five replications at two locations in 1983 and one location in 1984. Significant differences between the regression coefficients of grain yield and kernel density on number of cycles for high and low color expression were observed, but the coefficients themselves were not significantly different from zero. Yield increased in the upward direction only 0.061 Mg ha−1 cycle−1. Cycles of selection apparently had no effect on 100‐kernel weight, 100‐kernel volume, harvest grain moisture, duration of grain fill, measured in growing‐degree‐day units (GDD), or maturity from planting to physiological maturity (GDD). This indirect selection procedure did not appear to be very effective for increasing grain yield.
Desiccation Tolerance and Its Relationship to Assimilate Partitioning in Winter Wheat
Authors: Hossain A. B. S. , Sears R. G. , Cox T. S. , Paulsen G. M.
Published: July 2010

Winter wheat (Triticum aestivum L.) is frequently subjected to stress that causes early senescence of plants and cessation of grain filling. This research evaluated chemical desiccation for selecting genotypes for tolerance to postanthesis stress and determined the relationship of chemical desiccation tolerance to carbohydrate and N partitioning. Twenty‐eight cultivars with a wide range of stress tolerance and yield potential were treated with 0 and 0.19 mol L‐1 NaCIO3 14 d after anthesis. The 2‐yr study was on a Eudora silt loam (coarse‐silty, mixed, mesic Fluventic Hapludoll); treatments were in randomized‐complete blocks with four replications. Ten cultivars representing a range of treatment responses were evaluated further at two locations on dryland and irrigated Eudora silt loam and Pratt loamy fine sand (sandy, mixed thermic Psammentic Haplustalf) in split plots with three replications. Cultivars that had high kernel weights and early release dates were generally more tolerant of chemical desiccation than cultivars with low kernel weights and recent release dates. Grain yields of chemically desiccated plants under irrigation correlated significantly with yields of untreated plants at one location but not at another location. Losses of dry matter and soluble carbohydrates, but not of N, from stems were related to grain yield response to chemical desiccation. We concluded that chemical desiccation effectively selects for postanthesis stress resistance, and that combining high carbohydrate reserves with efficient translocation to the grain should improve wheat performance in unfavorable environments.
Relative Sensitivity of Grain Yield and Biomass Accumulation to Drought in Field‐Grown Maize
Authors: Sinclair T. R. , Bennett J. M. , Muchow R. C.
Published: July 2010

Grain yields in maize (Zea mays L.) are decreased substantially by water deficits. Since the impact of drought stress on grain yield varies among growth stages, such responses are sometimes interpreted as indicators of varying drought sensitivities with crop growth stage. However, varying leaf area and biomass accumulation rate confound this interpretation because the use of water changes during the season. This research examined whether a proportional decrease in accumulated crop biomass of field‐grown maize was sufficient to account for the decrease in grain yield resulting from drought. A total of 11 field experiments were conducted at Gainesville, FL on an Arredondo fine sand (loamy, siliceous hyperthermic Grossarenic Paleudult) or a Kendrick fine sand (loamy, siliceous, hyperthermic Arenic Paleudult and Katherine, Australia on a Fenton clay loam (Oxic or Rhodic Paleustalf) in which irrigation was withheld for various periods to result in a range of severities in crop water deficits. At crop maturity, both grain yield and total accumulated biomass were measured and the relationship between these two parameters was examined. In all cases, high, linear correlations between grain yield and accumulated biomass were obtained. At moderate stresses, harvest index of the crop was stable. Under severe stress, where accumulated biomass was less than about 1100 g m‐2, grain yield was decreased to a greater extent than was accumulated biomass. Nevertheless, under a wide range of conditions, grain yield of field‐grown maize crops was closely linked to the accumulation of biomass.
Salinity Effects on Germination and Mobilization of Reserves in Jojoba Seed
Authors: Kayani Safdar A. , Naqvi Himayat H. , Ting Irwin P.
Published: July 2010

Jojoba [Simmondsia chinensis (Link) C.K. Schneid.] is a new oil (wax) seed crop for arid and semiarid environments where salinity is frequently a major problem. The objectives of this work were to study the effects of salinity on germination and mobilization of reserves in jojoba seed. Salt concentrations (NaCl:CaCl2 1:1, w/w) having electrical conductivities (EC) of 0, 5, 10, and 15 dS/m significantly reduced germination, fresh weight of seedlings, and the amount of lipid used in ‘Vista’ jojoba. Germination was reduced from 82.6% in nonsaline conditions to 42.6%, fresh weight was reduced from 314 to 98 mg, and the amount of lipid used was reduced from 136 to 83 mg in strong (EC = 15.0 dS/m) saline treatments. Higher levels of salinity also resulted in accumulation of total soluble sugars, delayed initiation of germination and lipid breakdown, and decreased C38 and C40 esters with an increase in C42. These data suggest jojoba is not salt‐tolerant during germination.
Cultivar and Cultivar ✕ Environment Effects on Relative Feed Value of Temperate Perennial Grasses
Authors: Casler M. D.
Published: July 2010

Cultivar evaluation trials for perennial forage grasses traditionally have emphasized forage yield and adaptation characteristics, such as maturity, pest resistances, and stress resistances. The objectives of this study were to evaluate cultivar effects and cultivar ✕ environmental factor interactions for relative feed value (RFV) of several grass cultivars grown in binary mixtures with alfalfa (Medicago sativa L.). Grass species were ryegrass (Lolium spp., including perennial [L. perenne L.], intermediate [L. hybridum], and festulolium [Festulolium braunii K.A.]), orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinacea L.), timothy .(Phleum pratense L.), and tall fescue (Festuca arundlnacea Schreb.). Relative feed value was computed, as an index of forage nutritive value, from neutral and acid detergent fiber (NDF and ADF). Cluster analysis revealed that environments based on similar cuttings and from the same year tended to cluster together. Only cultivars of orchardgrass, ryegrass, and timothy varied in RFV. Cultivar ✕ environment interactions were species‐specific. In orchardgrass and timothy, much of the variation was due to differences in cultivar maturity at first cutting. These maturity effects also carried over into second‐cutting RFV for timothy. For perennial ryegrass, tetraploids ranked higher in Cut‐I RFV than diploids, but did not differ in Cut‐2 RFV. Cultivars in at least three perennial forage grass species can be separated according to their RFV by replicated testing in multiple environments. Replication over at least eight environments is necessary to develop broad cultivar inferences. It was possible to discern consistent tendencies across environments only in orchardgrass and timothy, the species for which RFV was related closely to maturity.
Salinity Tolerance in F1 Hybrids of Pigeonpea and a Tolerant Wild Relative
Authors: Subbarao G. V. , Johansen C. , Rao J. V. D. K. Kumar , Jana M. K.
Published: July 2010

Salinity in soil or water presents a stress condition to crop plants that is of increasing importance in the sustainability and stability of crop production in the semiarid regions of the world. This study determined the potential for genetic introgression of salinity tolerance from a wild relative, Atylosia albicans (W. & A.) Benth., to cultivated pigeonpea, Cajanus cajan (L.) Millse. A sand culture system was used to grow the salt‐tolerant A. albicans, salt‐sensitive C. cajan, and their F1 hybrids at various precisely maintained salinity levels. The results demonstrated the feasibility of transferring salinity tolerance from A. albicans to C. cajan. The high level of salinity tolerance in A. albicans was expressed as a dominant genetic factor in both the reciprocal F1 hybrids of this species and C. cajan. The physiological attributes conferring salinity tolerance in A. albicans and the F1 hybrids include Na and Cl retention in the roots and limited translocation to the shoots, high K selectivity, and maintenance of transpiration rate under saline conditions.
Preanthesis Tiller Mortality in Spring Wheat
Authors: Davidson D. J. , Chevalier P. M.
Published: July 2010

A primary determinant of yield in wheat (Triticum aestivum L.) is the number of spike‐bearing tillers per unit area. Many tillers that emerge do not survive to produce spikes. This study was conducted to determine the point in development when tillers begin to senesce and to examine how premature senescence is affected by water deficits and plant population. Cultivars Edwall and Waverly were planted in a 2‐yr field study at two plant densities (168 and 84 kg ha−1 in 15‐ and 30‐cm rows, respectively) and with both irrigated and nonirrigated treatments. The Haun stage of leaf development was monitored weekly on five plants per plot. Tiller mortality was monitored from tiller emergence until maturity. For tillers destined to die prematurely, a reduced rate of leaf emergence and development was evident immediately after tiller emergence. The majority of tillers senesceduring main stem extension, while almost no tillers were lost during grain filling. The maximum Haun stage reached by senescing tillers was normally ≤3 for all tillers excepthe coleoptile (TO) tiller. For this tiller, the maximum Haun stage was ≤4. Premature tiller senescence occurred in both irrigated and nonirrigated plots and was greatest at the higher plant density. Water deficits increased the number of tillers that died but did not affect the stage at which senescence occurred. Tillers that emerged late during plant development were most likely to senesce prematurely.
Selection of Potato Haploid Parents for Use in Crosses with 2x (2 Endosperm Balance Number) Wild Species
Authors: Yerk G. L. , Peloquin S. J.
Published: July 2010

Haploids (2n = 2x = 24) of Solanum tuberosum L. may be used to tap the genetic diversity present in the related wild species by producing haploid ✕ species hybrids (2n = 2x = 24). The purpose of this study was to identify elite haploids for use in crosses to wild species based on percentage tuberization of their progeny, number of fruit per pollination and seeds per fruit, and their genotype for parallel spindles (ps), a meiotic mutant causing 2n pollen formation. A group of 73 haploids were selected for good flowering and cultivartype haulms. To determine their respective ps‐locus genotypes, the haploids were testcrossed as females to four plants of S. chacoense BITT. (psps). All 21 of the haploids that were successfully crossed to S. chacoense BITT. produced families with a high percent tuberization. Only one of the 39 families tested had percentage tuberization that was significantly lower than the average family performance. Eighteen of the 21 haploids were Psps, one was psps, and two gave families that deviated significantly (P < 0.05) from a 1:1 ratio. Six haploids had average seed set of greater than 40 seeds per fruit in all combinations for which twenty or more pollinations were made. Selection of elite haploids should increase the potential of the 4x ✕ 2x breeding scheme by: (i) increasing the amount species germplasm that may be selected among, (ii) making production of haploid ✕ wild species hybrids morefficient, and (iii) increasing the amount of the germplasm pool that can be transferred to the tetraploid level using 2n pollen.
Sources for Tolerance to Cold in Cicer Species
Authors: Singh K. B. , Malhotra R. S. , Saxena M. C.
Published: July 2010

Cold tolerance is an important prerequisite for successful winter sowing of chickpea (Cicer arietinum L.). In the Mediterranean region, winter sowing will increase productivity compared with the same crop sown traditionally in the spring. In the search for germplasm possessing a higher level of tolerance to cold than the cultivated species, 137 lines of eight wild annual Cicer species were evaluated during the 1987‐1988 and 1988‐1989 seasons at the International Center for Agricultural Research in the Dry Areas (ICARDA), Syria. Both seasons were effective for screening chickpea against cold, as the susceptible indicator was killed by cold spells each year. Most of the lines of C. bijugum K.H. Rech., C. echinosperum P.H. Davis, and C. reticulatum Ladiz. were tolerant to cold and had significantly higher levels of cold tolerance than the cultivated species. All lines of C. chorassanicum (Bunge) M. Popov, C. cuneatum Hochst. ex Rich., and C. yamashitae Kitamura, and all but one line of C. judaicum Boiss., were susceptible. Lines of C. pinnatifidum Jaub. & Spach showed both susceptible and tolerant reactions.
Genetics of Plant Regeneration in Immature Panicle Culture of Rice
Authors: Chu Q. R. , Croughan T. P.
Published: July 2010

The capacity to regenerate somaclones in numbers sufficient to produce adequate population sizes from which to select is an important component of utilizing somaclonal variation for cultivar improvement. This study was conducted to determine the genetics of regeneration ability in immature panicle culture. Rice (Oryza sativa L.) immature panicles derived from 10 cultivars, 12 F1 hybrids from a 4 ✕ 4 diallel, their F2 and F3 progenies, and 24 backcross hybrids were cultured in vitro. Significant genotypic differences in regeneration ability were found among the 10 cultivars. The U.S. cultivar Lemont possessed a higher regeneration ability, averaging 8.58 plants per panicle. In contrast, the indica cultivar IR36 had a low regeneration ability, averaging 0.14 plant per panicle. Generation mean analysis of regeneration ability revealed significant values for the estimates of dominance gene effects (d), and for additive ✕ additive (aa) and dominance ✕ dominance (dd) epistatic effects, but showed additive effects to be of minor importance. The heritability estimate calculated by parent‐offspring regression was 0.25. Since additive effects are of minor importance and the heritability estimate is low, improving regeneration abilities through hybridization does not appear practical. An initial screening within possible genotypes to identify those with inherently high regenerative abilities, such as Lemont or IRGA 409, appears to be a better alternative.
Elite Maize Germplasm: Reactions to Maize Dwarf Mosaic and Maize Chlorotic Dwarf Viruses
Authors: Louie R. , Knoke J. K. , Findley W. R.
Published: July 2010

Information developed on the reactions of elite maize germplasm to maize dwarf mosaic (MDMV) and maize chlorotic dwarf (MCDV) viruses should aid breeding for resistance to these pathogens. The reactions of 23 dent maize (Zea mays L.) inbreds (plus one synthetic) and 46 hybrids were evaluated in the field and greenhouse following artificial inoculation with MCDV and two strains (A and B) of MDMV. Infection, as determined by diagnostic symptoms, was higher in greenhouse than in field tests. Furthermore, most of the apparent resistance to MDMV‐A in the field was not confirmed when inoculations were made on younger, more succulent plants in the greenhouse. Inbreds B68, OhlEP, Pall, Pa405, and the synthetic, OhS2, were immune or highly resistant to MDMVA and ‐B. Inbred B64 was only resistant to MDMV‐B. No inbred was immune to MCDV, but Ga209, Oh7B, Pall, Tx601, and Oh1EP had the lowest disease incidence in the field, whereas Pall and B68 were the most resistant in the greenhouse. Most of the 32 field‐planted hybrids that were resistant to MDMV‐A had A632, A634, B64 or B68 as one parent; for MDMV‐B, only B64 or B68 germplasm conveyed effective resistance. Hybrids B64✕B68 and B68✕B64 were immune to MDMV‐A and ‐B in both field and greenhouse tests. The best and poorest hybrid reactions to MCDV in the field were B68✕Mol7 and A632✕B73, respectively. The most resistant hybrid (Mol7✕B64) in the greenhouse had =50% infected plants. Plant height and yield losses in inbreds and hybrids to MDMV were minimal, whereas MCDV usually caused significant height (34% average) and yield reductions (72% average). The reactions of these elite sources of germplasm to MDMV and MCDV suggest that evaluations for virus resistance in maize should include both field and greenhouse test environments.
Growth Responses and Mineral Nutrient Relations of Salt‐Stressed Sorghum
Authors: Boursier Patrick , Läuchli André
Published: July 2010

The production of sorghum [Sorghum bicolor (L.) Moench], a moderately salt‐tolerant crop, often occurs in areas of relatively low rainfall and on marginal soils containing excess salts. Despite the importance of sorghum to agriculture, relatively less is known about its response to these stressful environments than that of other major cereal grain crops. The purpose of this investigation was to study the effects of moderate levels of salinity on growth, assimilate partitioning, and mineral nutrient relations of a single cultivar of sorghum under both field and greenhouse conditions. Sorghum dry matter production decreased substantially in response to a moderate increase in soil electrical conductivity (2.1 to 5.9 dS m−1). Overall, total shoot and root dry weights of greenhouse‐grown plants decreased to a greater extent by moderate (−0.2 and −0.4 MPa) additions of isosmotic concentrations of NaCl than Na2SO4. However, at higher salinity levels (− 0.6 MPa), growth was more inhibited by Na2SO4. Sheath tissues of the leaves of NaCl‐stressed plants tended to accumulate chloride. Sodium concentrations in the roots of control and NaCl‐treated plants were significantly higher than in shoot tissues at all salinity levels. At higher concentrations of Na2SO4, this exclusion of Na from the shoot broke down and resulted in a dramatic increase in the Na levels of shoot tissue and concurrent decrease in K and Mg concentrations. Seminal roots contained more Ca, Mg, Cl, and Na, while adventitious roots were higher in K.
Seedling Rate of Development Index: Indicator of Vigor and Seedling Growth Response
Authors: Steiner J. J.
Published: July 2010

Seedling growth analysis has been shown to be a useful tool to supplement the results of the standard viability test when evaluating seed lots for vigor. A number of indices have been proposed to describe the vigor of a particular seed lot. Few of these indices have been rigorously tested for their response to varying hypothetical emergence distributions during initial seedling development. Seedling rate of development index (SRDI), which incorporates the concepts of completeness, rate, uniformity of germination, and morphological development during initial seedling growth, was compared with five previously published indices of seed vigor. The indices were evaluated for their response to emergence distributions, which varied by number of mode levels, degree and direction of skewness, kurtosis, and seedling mortality after initial emergence. None of the five previously published vigor indices gave satisfactory results for all of the simulated conditions. The SRDI produced acceptable results for all test conditions and was particularly good for detecting latent seedling mortality after initial emergence. Data from actual seed lots grown under controlled conditions did not dispel the conclusions based on simulations. The SRDI may be a useful supplementary tool to use in combination with standard germination percentage when evaluating seedling vigor of different seed lots or genetic stocks or when measuring seedling response to varying environmental conditions.
White Clover Response to Nematode Infestation and Plant Density
Authors: Brink G. E. , Windham G. L.
Published: July 2010

The southern root‐knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] reduces the productivity and persistence of white clover (Trifolium repens L.) throughout the southeastern USA. Our objective was to determine the response of two white clovers with differing M. incognita tolerance to nematode infection across a range of plant densities. Nematode‐susceptible ‘Regal’ and tolerant germplasm SC‐1 were established in the greenhouse at 3, 6, 12, 24, and 48 plants per fiat (0.I m−2) and root‐knot n ematode ( Race 4) eggs were applied to each fiat at 0 (control), 600 (low), or 1200 (high) eggs per 500 cm3 of soil mix. Regal exhibited no tolerance to infection, while SC‐1 exhibited tolerance (equivalent dry matter [DM] yield across initial nematode egg levels) in the first repetition of the experiment only. Total DM yield of Regal and SC‐1 increased quadratically with increasing plant density across initial nematode egg levels in the first repetition, indicating DM yield suppression was caused by factors related to intraspecific competition, rather than by nematode infection. In the second repetition, DM yield of both clovers increased linearly with increasing plant density at the low and high initial egg levels, indicating that nematode infection had a greater effect on yield than intraspecific competition. Nematode reproduction was not influenced by plant density. Stolon dry weight of both clovers was reduced a mean of 60% by nematode infection. Because total DM yield of nematode‐infected white clover increased with increasing plant density due to greater early harvest productivity immediately following nematode inoculation, increasing plant density would not be an effective means of increasing long‐term forage productivity.