bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Drought and Defoliation Stress in the Field on Soybean Seed Germination and Vigor
Authors: Vieira R. D. , TeKrony D. M. , Egli D. B.
Published: July 2010

Although drought and defoliation stress have been shown to reduce soybean [Glycine max (L.). Merr.] yield, little information has been published regarding their effects on soybean seed quality. Field experiments were conducted in 1986, 1987, and 1989 to evaluate the effect of drought and defoliation (1989 only) stress during soybean seed development on seed germination and vigor. Essex (MG [maturity group] V) and Union (MG III) were grown in 1986 and 1987, and Harper (MG III) and McCall (MG 00) in 1989. Moisture treatments were either well watered or drought stressed during seed development (R5 to R7). In 1989, a total defoliation treatment was also imposed at R6 as an additional stress factor. There were significant reductions in yield and yield components following drought stress in all 3 yr and following defoliation in 1989. Leaf conductance and transpiration also decreased in the drought stress treatments. There was no effect of drought stress on seed germination or seed vigor as measured by accelerated aging germination and the cold test across the four cultivars (determinate and indeterminate) and 3 yr. In 1989 slight changes in 3‐d germination and conductivity occurred for some drought stress treatments. Most of this response, however, was related to increased occurrence of hard seed, which does not represent an indication of a change in vigor. Seed germination and vigor were significantly reduced for small, flat, shriveled, and underdeveloped seeds that only occurred following defoliation. These seeds represented a small portion of the seed lot that would normally be removed during conditioning. The data suggest that drought stress would have no effect on seed germination or vigor, unless the stress was severe enough to produce shriveled, flat, underdeveloped seeds.
Aluminum Tolerance in Barley: Genetic Relationships among Genotypes of Diverse Origin
Authors: Minella Euclydes , Sorrells Mark E.
Published: July 2010

Aluminum toxicity is an important limitation to barley (Hordeum vulgare L.) production in many regions possessing acid soils. To determine the potential for improvement of Al tolerance using known sources of tolerance, 37 barley genotypes of diverse genetic and geographical origins were evaluated for Al tolerance, and the number of loci and allelic relationships were determined using the hematoxylin root‐staining procedure. Alleles were differentiated at different levels of Al. Segregation in populations from sensitive × tolerant, and moderately tolerant × tolerant crosses indicated a single locus. No transgressive segregation was observed in any of the populations. The most tolerant genotypes tested were CI 8411, ‘Colonial 2’, ‘Dayton’, ‘Murasski Mochi’, ‘Nakano Wase’, ‘Smooth Awn 86’, ‘Smooth Awn 203’, and ‘Sunrise’. All of these genotypes except Colonial 2, Dayton, and Sunrise are ancestral landraces or germplasms of unknown origin. Colonial 2 inherited tolerance from Nakano Wise via Sunrise, while tolerance in Dayton could come from either Nakano Wise or Smooth Awn 203. These results indicate that tolerance, as measured by the hematoxylin test, is controlled by a single locus with multiple alleles and the most tolerant ancestral genotypes have alleles conditioning similar levels of tolerance. There is little potential for improvement of Al tolerance in barley using these known sources of tolerance in cultivated germplasm. Future research should be directed toward evaluation of uncharacterized germplasm and related species.
Analysis of Main‐Spike Yield Components in Salt‐Stressed Wheat
Authors: Grieve Catherine M. , Lesch Scott M. , Francois Leland E. , Maas Eugene V.
Published: July 2010

Grain yield potential of wheat (Triticum aestivum L.) main spikes is genetically determined and depends upon the number of spikelets per spike, the number of kernels per spikelet, and the weight of individual kernels. Environmental factors may interact with the genotype to influence the expression of these components. This study was initiated to determine the effects of salinity on main‐spike yield components of two Mexican semidwarf, hard red spring wheat cultivars, Yecora Rojo and Anza. Plants were grown in greenhouse sand cultures irrigated four times daily with modified Hoagland's solution. Two saline treatments with osmotic potentials (Ψ2)of −0.65 and −0.85 MPa were imposed by adding NaCI and CaCl2 to the base nutrient solution. The electrical conductivities of the saline irrigation waters (ECiw) were 14.3 and 18.1 dS m−1, respectively. These treatments were compared to a nonsaline control treatment at −0.05 MPa (ECiw = 2.0 dS m−1). Six main‐spike yield components were measured: spike length, spikelets per spike, kernels per spike, kernels per spikelet, individual kernel weight, and total kernel weight per spike. The first three parameters decreased in response to salinity. Kernel number per Anza spikelet was unchanged by salinity. Compared with the controls, kernel number per Yecora Rojo spikelet increased at −0.65 MPa and decreased at −0.85 MPa. At −0.65 MPa, decreases in kernel numbers per spike of both cultivars were offset by increases in kernel weight, particularly in the central spikelets. As a result, grain yield per main spike was 12 to 15% higher than in the nonsaline controls. Stimulation of main‐spike yield by salinity suggests that in those salt‐affected areas where tillering capacity may be reduced, wheat production may benefit from higher planting density.
Fiber Development of Ligon Lintless‐2 Mutant of Cotton
Authors: Kohel Russell J. , Narbuth E. V. , Benedict C. R.
Published: July 2010

A new fiber mutant character in cotton (Gossypium hirsutum L.), controlled by a single completely dominant gene, produces short fibers visually similar to those produced by the Ligon lintless‐1 mutant. The new fiber mutant, Ligon lintless‐2, has normal vegetative growth, unlike the stunted and deformed vegetative morphology of Ligon lintless‐ 1 plants. A fiber developmental study of Ligon lintless‐2, Ligon lintless‐1, TM‐1, and normal segregates from crosses of Ligon lintless‐ 2 and TM‐1 was conducted utilizing a randomized complete‐block design. Mean fiber length, dry weight accumulation, and ratio of weight to length from anthesis to maturity were determined. Lines with the normal alleles were not significantly different from each other, but they were significantly different from Ligon lintless‐1 and Ligon lintless‐2 for fiber length and weight. Ligon lintless‐2 was significantly lighter than Ligon lintless‐1. The ratio of weight to length revealed no significant differences among the normal lines, but Ligon lintless‐1 (which had the highest value) was significantly different from Ligon lintless‐2. Differences in dry weight accumulation were attributed to the difference in secondary wall development between the two mutants.
Source‐Sink Manipulations and Carbohydrate Metabolism in Maize
Authors: Prioul Jean‐Louis , Schwebel‐Dugué Nicole
Published: July 2010

Grain filling is largely dependent on C export from source leaves, but little attention has been given to the use of leaf carbohydrate metabolism criteria for evaluating grain‐filling capacities. This study was conducted to test the effect of source‐sink manipulations on the relationship between starch accumulation in grain and leaf sucrose‐phosphate synthase activity for different maize genotypes. Field‐grown maize (Zea mays L.) plants were subjected to ear removal or to leaf excision at pollination, to examine the effect on regulation of C fixation and partitioning in source leaves during grain filling. At the plant level, the two treatments produced unbalanced effects: ear removal led to accumulation of dry matter in stalks, leaf sheaths, and blades and accelerated senescence of vegetative parts, whereas excision of most leaves hardly affected the remaining leaf and stalk, but drastically reduced the number of developing grains. Modifications in source leaves were estimated from leaf disks punched out in the first leaf above the ear. In this leaf, ear removal caused an increase in soluble sugars 10 days after pollination (DAP), a decrease in sucrose‐P synthase activity (20 DAP), an increase in adenosine dipbosphate glucose pyrophosphorylase activity (30 DAP), a decline of phosphoenolpyruvate (PEP) carboxylase (30 DAP) and of ribulose‐bisphosphate carboxylase (40 DAP). The onset of senescence was marked by an earlier increase in glucose and fructose, and in nonspecific phosphatases. In contrast, leaf excision did not affect senescence compared with control plants and the feedforward effect on source leaves was limited to a transient stimulation of PEP carboxylase (I0 DAP) and a doubling sucrose‐P synthase activity for 40 DAP. Leaf soluble sugars were only slightly depressed, but massive kernel abortion occurred and few grains filled normally. Aborting grains were shown to lack the usual maximum in soluble sugar at 30 DAP. Collectively, the results show that at the grain‐filling stage, sucrose‐P synthase activity more accurately reflected assimilate demand than did metabolite level or enzyme activity for C fixation.
Discrimination among 136 Tetraploid Potato Varieties by Fingerprints Using Highly Polymorphic DNA Markers
Authors: Görg Regina , Schachtschabel Undine , Ritter Enrique , Salamini Francesco , Gebhardt Christiane
Published: July 2010

The identification of a variety has an important role in the protection of plant breeders' rights and for monitoring seed production and marketing. The objective of our study was to examine whether or not a large number of registered cultivars of European potato (Solarium tuberosum subsp, tuberosum) could be distinguished using RFLPs (restriction fragment length polymorphisms) as genetic fingerprints. Genomic Southern blots with TaqI‐restricted DNA of 136 tetraploid potato varieties were hybridized to highly polymorphic potato RFLP markers. The use of four markers was sufficient to identify 130 of 136 varieties. Three pairs of varieties were identical with all markers evaluated. One marker, GP35, was the most effective: out of 134 varieties analyzed with this probe, 122 had unique RFLP patterns. The remaining 12 varieties were divided into six pairs, each showing an identical pattern. Sequence analysis showed that GP35 was not homologous to minisatellite sequences. The probability of finding a random match of RFLP patterns between two tetraploid varieties with marker GP35 was estimated to be 0.63 × 10−4. Variety identification by RFLP fingerprints is therefore feasible in potato.
Evaluation of the Afila‐Tendriled Acacia (afaf‐tactac) Pea Foliage Type under Minimal Competition
Authors: Goldman Irwin L. , Gritton Earl T.
Published: July 2010

The afila (af) and tendriled‐acacia (toe) genes condition structural modifications of the pea (Pisum sativum L.) leaf. The of gene replaces leaflets with tendrils and tac restores small leaflets to the tendrils of of plants. The agronomic performance of plants carrying tac in combination with of is unknown. Therefore, the objective of this research was to evaluate a near‐isogenic set of three foliage types: normal (AfAf‐TacTac), afila (afaf‐TocToc), and afila‐tendriled acacia (afaf‐tactac) in three genetic backgrounds. The evaluation was conducted under minimally competitive conditions on widely spaced wire trellises in order to allow for maximal foliage expression. Averaged across genetic backgrounds, tac increased the total foliage area of afaf‐tactac plants over afaf‐TacTac plants by 37%. Green pea yield did not differ significantly among the three foliage types. Dry seed yield at afaf‐tactac plants was significantly higher than afaf‐TacTac plants and equal to AfAf‐TacTac plants. Expression of the tac gene varied significantly with genetic background. The afaf‐tactac combination in the latest maturing background exhibited the largest increases in yield and yield components over its constituent foliage types.
Ear Developmental Stage Used for Timing Supplemental Nitrogen Application to Spring Wheat
Authors: Peltonen Jari
Published: July 2010

Nitrogen fertilization at sowing is not always optimal or sufficient for stable yield and quality formation of wbeat (Triticum aestivum L.). Precise timing of supplementary N application for wheat requires detailed knowledge of the physiology of the reproductive phase. Our objective was to compare developmental stages of the wheat ear, for timing supplemental N application to ensure stable wheat yield and quality. The experiments were carried out at two locations in 1989 and 1990, with four spring wheat cultivars. Soil types were sandy loam (Mollie Cryoborolls). Foliar N (20 kg ha−1) as an aqueous solution of urea (144 g L−1) was applied at f our stages of ear development. A greenhouse experiment was designed to clarify the effect of N on the formation of spikelet and floret numbers in the apex during reproductive period. Maximum effect of supplementary N was achieved at the double‐ridge stage, and at the stage when the stigmatic branches of the carpel had formed. At these developmental stages, supplementary N increased the number of grains per ear and grains per square meter. Nitrogen added at pollination mainly increased the kernel weight and bread‐making quality (rated according to protein concentration in the flour, wet gluten content, Zeleny sedimentation value, farinograph water absorption, dough stability, and Panasonic loaf volume). Timing N application to apical development may provide a useful method for the producer to stabilize wheat grain yield and protein concentration.
Genetic Base of Irrigated Rice in Latin America and the Caribbean, 1971 to 1989
Authors: Cuevas‐Pérez Federico E. , Guimarães Elcio P. , BerrÍo LuÍs , González Daniel I.
Published: July 2010

The trend to commercially exploit a reduced genetic base in most crops has raised concerns about the possibility of large yield reductions as a result of environmental disturbances. This study describes the genetic base of irrigated rice (Oryza sativa L.) from Latin America and the Caribbean. Schematic pedigrees of 143 cultivars released between 1971 and 1989 were constructed, and releases were grouped by the periods 1971 to 1975, 1976 to 1980, 1981 to 1985, and 1986 to 1989. The contribution of landraces was estimated by assuming they provided 50% of their genes in each single cross. Total contribution was calculated by summing within and across pedigrees and expressed as percentage. Genetic diversity for the 1987‖1988 crop was estimated by weighting contribution by area planted. Coefficients of parentage. (r) among cultivars and among the parents of cultivars developed the Colombian program were calculated. A total of 101 different landraces contributed to the genetic composition of the cultivars released. Number of landraces per period was proportional to the number of cultivars released. A group of 14 ancient cultivars contributed to at least one cultivar during the four periods considered, accounting for nearly 70% of the genes and contributing to an increased relationship among parents of cultivars. This group can be considered as the genetic core of irrigated rice in the region. The major landraces in the core were ‘Cina’, ‘Lati Sail’, and ‘Dee Geo Woo Gen’, mainly introduced to the region through ‘IR8’. An additional group of eight landraces was incorporated into the core after 1975, primarily to incorporate disease resistance. Mean coefficient of parentage within countries varied from r = 0.41 in Costa Rica to 0.00 in Chile. Cultivars from Argentina, Chile, Guyana, and Surinam often showed r < 0.05 with materials from other countries. Genetic variability has been broadened, combining different genes with the genetic core as needed. The identification of new genetic cores to reduce vulnerability while increasing yield potential should be considered.
Plant Regeneration and Callus Type in Barley: Effects of Genotype and Culture Medium
Authors: Bregitzer Phil
Published: July 2010

To facilitate practical application of in vitro genetic manipulation to barley (Hordeum vulgare L.), methods for the in vitro culture of barley must be improved. Fifteen genotypes of barley, primarily cultivars or elite breeding lines adapted to North America, were examined for their ability to form regenerable callus from immature embryos on modified versions of MS, B5, and CC media. Regenerable calli were obtained from all genotypes. The frequency of embryogenic callus induction, the morphology and friability of embryogenic calli, the relative growth rate of embryogenic calli, and regenerability were influenced by genotype, culture medium, and genotype × culture medium interactions. Callus cultures that were embryogenic in appearance frequently were not regenerable, or regenerated only albino plantlets. The majority of green plants grown to maturity were fertile and normal in appearance. Genotype was the most important determinant of the in vitro response. Regenerability was transient for all genotypes, with few exceptions. The best in vitro performance, based on ability to form friable, regenerable callus, was observed for ‘Golden Promise’, ‘Hector’, ‘Piroline’, and ‘Klages’.
Inheritance of Pink Flower in Soybean
Authors: Stephens Paul A. , Nickell Cecil D.
Published: July 2010

In soybean [Glycine max (L.) Merr.], there are several possible flower colors: white, near‐white, purple, purple‐throat, and magenta. We report a new flower color, described as pink, which is distinct from all previously reported flower colors. Segregation ratios for the progeny row in which the mutant was found, and subsequent selfed progeny, indicate that the pink flower color is controlled by a single recessive gene. When this pink‐flowered plant was crossed with all reported flower color genes and the F2 populations classified for flower color, results indicate that the pink flower gene is independent of known flower color genes and acts as a modifier gene to decrease pigment expression at the W1 locus. We propose the gene symbol wp to be used to describe pink flower color inheritance.
Soybean Flowering in Response to the Long‐Juvenile Trait
Authors: Sinclair Thomas R. , Hinson Kuell
Published: July 2010

A long‐juvenile trait that delays flowering has been identified in soybean [Glycine max (L.) Merr.]. This trait may be especially important in extending the range of adaptation of soybean germplasm to lower latitudes and to new management schemes with shifted sowing dates. These studies were undertaken to characterize more fully the physiological consequences of the long‐juvenile trait. Isogenic pairs were developed and subjected to three experimental tests: (i) sowing date response, (ii) extended photoperiod response, and (iii) reciprocal grafts. Analysis of the flowering response under a range of sowing dates showed that the main effect of the long‐juvenile trait was to retard the overall development of the plants toward flowering. Even though the long‐juvenile trait tended to stimulate flowering at longer photoperiods than the normal isoline, the slower development associated with the long‐juvenile trait delayed the mean flowering date by 7 to 19 d for the 15 isogenic pairs studied. Experiments under a 15‐h photoperiod confirmed that development rate towards flowering of the long‐juvenile isolines declined less than that of normal lines. The threshold illuminance for responding to the extended photoperiod was also significantly greater in the long‐juvenile isolines compared with the normal lines. Reciprocal grafts showed that the relative number of long‐juvenile leaves on a plant was associated with the delay in flowering. Since the long‐juvenile leaves altered flowering in the normal part of the grafted plant, expression of the long‐juvenile trait is apparently associated with a translocatable material.
Normal and Low Linolenic Acid Soybean Strains: Response to Planting Date
Authors: Wilcox James R. , Cavins James F.
Published: July 2010

Enzymes controlling biosynthesis of fatty acids in the oil of soybean [Glycine max (L.) Merr.] seeds are sensitive to temperature during the time of oil deposition. Soybean strains have been developed with low levels of linolenic acid (18:3) in an effort to improve oil flavor and stability. This study was conducted to determine the response of fatty acid composition in normal and low linolenic acid soybean strains to planting date, a production variable that may result in different temperatures during oil deposition. ‘Century’, C1640, and 9509 (three genotypes differing in linolenic acid due to alleles at the fan locus) were planted at four or five dates in each of 5 yr near West Lafayette, IN. Dates when 95% of the pods were mature and the fatty acid composition of the oil were determined for each plot. Fatty acid composition was not affected by planting date in either 1986 or 1990. In 1987 and 1988, levels of palmitic acid tended to decrease slightly and levels of stearic acid tended to increase slightly with successively later planting dates. From 1987 through 1989, linolenic acid was affected more than the other fatty acids by planting date. Regression of linolenic acid content on average maximum daily air temperature from 0 to 20 d prior to maturity demonstrated that 18:3 decreased 4.9 and 3.0 g kg−1 for each 1 °C increase in temperature for Century and C1640, respectively. The data demonstrate that late planting in Indiana should not result in substantially increased levels of linolenic acid in strains containing the fan allele.
Variation in Crop Radiation‐Use Efficiency with Increased Diffuse Radiation
Authors: Sinclair Thomas R. , Shiraiwa Tatsuhiko , Hammer Graeme L.
Published: July 2010

Radiation‐use efficiency (RUE; grams of biomass accumulated, divided by total solar radiation intercepted) has proven to be a useful variable for quantifying biomass accumulation by crops. Experimental results and theoretical analysis indicate that differences in RUE exist among species, but that RUE for unstressed conditions is relatively stable within a species. A departure from the general conclusion is that high values of RUE have been reported for conditions where the diffuse proportion of the total radiation is commonly large (e.g., glasshouse‐grown plants). In this paper, a simple theoretical derivation of RUE was examined to quantify potential responses in RUE to variation in the fraction of diffuse radiation. To simulate natural conditions, the absolute amount of incident diffuse radiation was held constant and the amount of the direct radiation component was varied so that both the fraction of diffuse radiation and total radiation were varied. The estimates of RUE for soybean [Glycine max (L.) Merr.] and maize (Zea mays L.) increased as the fraction of diffuse radiation increased and the total radiation decreased. These results indicate that plants grown in glasshouses or in other locations with large fractions of diffuse radiation are likely to have greater radiation‐use efficiency than observed under primarily direct radiation.
Potential Photosynthesis of Cassava as Affected by Growth Conditions
Authors: El‐Sharkawy Mabrouk A. , De Tafur Sara M. , Cadavid Luis F.
Published: July 2010

Cassava (Manihot esculenta Crantz) is a hot‐climate tropical crop that is also grow in cool areas of the highland tropics and subtropics, where yields are reduced. Because of its wide range of cultivation, there is some concern as to how growth conditions influence photosynthesis. Therefore, the purpose of this study was to evaluate potential photosynthesis of cassava as affected by growth environment. Three cultivars from contrasting habitats were grown in 40‐L pots outdoors at a high‐altitude site (cool climate) and were then allowed to acclimate and develop new leaves at a mid‐altitude site (warm climate). Leaf gas exchange was monitored by infrared gas analysis under controlled laboratory conditions. In all cultivars, photosynthesis of potted cassava was substantially reduced in cool‐climates as compared with warm‐climate leaves. The cool‐climate leaves partially recovered their photosynthetic capacity after warm‐climate acclimation for 1 wk. Broad optimum temperature from 30 to 40 °C was observed in the hot‐climate cultivars, while the cool‐climate cultivar showed an upward shift in optimum temperature from 25 °C in cool‐climate leaves to 35 to 40 °C in both the acclimated and warm‐climate leaves. Field trials using a number of cultivars were conducted under rainfed conditions at the mid‐altitude site and leaf gas exchange was monitored throughout the growing season. Maximum photosynthetic rates of 40 to 50 μmol CO2 m−2 s−1 were obtained in field‐grown cassava under wet conditions, and photosynthesis did not saturate up to an irradiance of 1800 μmol photosynthetically active radiation m−2 s−1. Cassava requires high air temperature and high solar radiation for optimal leaf development and for the expression of its photosynthetic potential.
Growth Analysis of a Tall Fescue Sward Fertilized with Different Rates of Nitrogen
Authors: Bélanger Gilles , Gastal François , Lemaire Gilles
Published: July 2010

Nitrogen fertilization increases yield of perennial grasses, but little knowledge exists on the effect of N fertilization on growth processes at the sward level. Growth of an irrigated tall fescue (Festuca arundinacea Schreber) sward fertilized with different rates of N was analyzed during two summer regrowths (1987 and 1988) and two spring regrowths (1987 and 1989). When no N was applied, cumulative shoot growth at the end of each regrowth period (summer 1987, summer 1988, spring 1987, and spring 1989) was 29, 15, 36, and 42% of that obtained with the highest N rate used in that period (160, 240, 200, and 180 kg N ha−1), respectively. Analysis of the N nutrition status of the sward based on the concept of an optimal N content indicated that N was not limiting shoot growth at the highest N rates used in any of the regrowths except during the summer of 1987. Radiation‐use efficiency at the highest N rate was 1.68 and 1.82 g DM MJ−1 in the summer regrowths of 1987 and 1988, and 1.83 and 2.16 g DM MJ−1 in the spring regrowths of 1987 and 1989. Cumulative intercepted photosynthetically active radiation (PAR) and radiation‐use efficiency both increased with an increase in N rates. The effect of the N deficiency on cumulative intercepted PAR was, for the most part, limited to situations where the relative N concentration was <0.5. Radiation‐use efficiency, however, was affected through most of the range of relative N concentrations.
Cultivar Variation in Traits Affecting Early Nodulation of Common Bean
Authors: Chaverra Martha H. , Graham Peter H.
Published: July 2010

Phaseolus vulgaris L. is inferior to other grain legumes in nodulation and N2 fixation, with early‐flowering cultivars particularly limited in the ability to satisfy their N needs through fixation. Extending the period of fixation could reduce the dependence of this crop on N‐fertilization. We sought bean accessions that were early to nodulate, and tried to identify specific traits that contributed to this ability. A root‐tip marking procedure was used to evaluate the earliness in nodulation of 40 accessions of common bean. With Rhizobium leguminosarum bv. phaseoli strain UMR1084 the accessions varied in uppermost nodule position relative to the root‐tip mark (RTM; −2.05 mm to +6.12 mm), number of nodules produced above the RTM (0.57‐3.93), and percentage of plants nodulated above this mark (37.7‐ 97.1%). Cultivars nodulated earlier with strain UMR1084 and UMR1899 than with strain UMR1242. Accessions RIZ23, RIZ108, N80068, and WI21‐58 nodulated rapidly with all strains tested, while ‘Mantequilla tropical’, RIZ21, and 0051 were slow to nodulate. selected bean accessions were then examined for inoculum dose response with UMR1084, for the percentage of infection sites giving rise to nodules, for the rate of development of nodules in the period 16 to 25 days after planting (DAP), and for plant growth and accumulation of N at 51 DAP. In these studies, ‘Puebla 152’ showed excellent nodule development and growth to the 25 DAP harvest, while the experimental line RIZ21 accumulated significantly more N and grew better in the period 25 to 51 DAP. The differences between these two accessions could be exploited in breeding programs for enhanced nodulation and N2 fixation in common bean.
Light Intensity, Row Spacing, and Photoperiod Effects on Expression of Brachytic Stem in Soybean
Authors: Huang Shurong , Ashley Doyle A. , Boerma H. Roger
Published: July 2010

Brachytic stem trait in soybean [Glycine max (L.) Merr] is characterized by a geniculate internode arrangement and markedly shortened internodes; brachytic plants are much shorter than their nonbrachytic isolines. When the brachytic trait expression is suppressed, plants have heights similar to those of their nonbrachytic isolines. A series of greenhouse and field experiments involving light intensity and photoperiod treatments were conducted to determine their effects on plant height and other stem traits in ‘Tracy‐M’ and ‘Wright’ soybean and in their brachytic near‐isolines, B.Tracy‐M and B‐Wright. The experiments demonstrated that full expression of the brachytic stem trait is a light.regulated process. Under unshaded conditions in the field, B‐Wright and B‐Tracy‐M had a plant height 48.7 and 78.9% of that of their respective nonbrachytic isolines. The most effective shading treatment (shade applied between 5 and 7 wk after emergence) produced a 46 and a 22% increase in plant height for B‐Tracy‐M and B‐Wright, respectively, by increasing internode length. The shade treatment also suppressed the geniculate expression, reducing the internodal angles by 5 to 20° for B‐Tracy‐M and 6 to 26° for B‐Wright. After shade removal, brachytic stem development resumed in subsequently formed internodes. The wide‐row (76 cm) spacing (more plants per meter of row) decreased the percentage of brachytic plants at early growth stages by 47.5% and 22.7% for B‐Tracy‐M and B‐Wright, respectively, compared with the narrow.row (25 cm) spacing. Increasing photoperiod from 14 to 16 h in the greenhouse decreased plant height and enhanced the development of brachytic stem trait. In general, B‐Tracy‐M appeared to be more sensitive than B‐Wright to the treatments imposed in these studies.
Response of Barley to Ethephon: Effects of Rate, Nitrogen, and Irrigation
Authors: Foster Kenneth R. , Taylor John S.
Published: July 2010

Lodging incidence in cereal crops depends upon both crop management and environmental conditions. Ethephon [(2‐chloro‐ethyl)phosphomic acid] controls lodging, thus preserving yield. The objective of this study was no investigate the effects of ethephon on spring barley (Hordeum vulgare L.) with different N rates, irrigation treatments, or application rates of ethephon. Ethephon was applied at Zadoks Growth Stage 43 at 0.28 kg ha‐1 in the N and irrigation studies, and at rates between 0.1 and 0.5 kg ha‐1 in the ethephon rate study. Plant height and lodging were reduced by ethephon in each study; however, ethephon did not consistently reduce lodging at Belgian indices of 7.0 and above. Differences in cultivar response were observed. In the ethiphon rate trial, 0.1 kg ha‐1 ethephon reduced lodging of ‘Harrington’, while 0.25 kg ha‐1 was required to similarly reduce lodging of ‘Leduc’. Ethephon reduced the number of kernels per spike, had variable effects on grain mass, and delayed crop maturity by up to 4 d. Whole plant protein was unaffected by ethephon. Ethephon reduced grain protein by 25% and decreased straw protein by 9% in 1986, and had no effect on grain protein in 1987. Ethephon was an effective antilodging agent only under moderate lodging pressures; it is not likely to preserve an increased yield under conditions of intense irrigation and high fertility.
Leaf Emergence, Tiller Growth, and Apical Development of Nitrogen‐Dificient Spring Wheat
Authors: Longnecker Nancy , Kirby E. J. M. , Robson Alan
Published: July 2010

Conflicting reports exist about the effect of N supply on the rate of leaf emergence. We examined effects of N deficiency on leaf and tiller emergence, tiller initiation and apical development in ‘Aroona’ and ‘Gamenya’ spring wheat (Triticum aestivum L.). Four levels of N (e.g., 50 μM N = N50) were supplied by hourly irrigation with complete nutrient solution of plants growing in sand. The control plants in Exp. 1 (N1600) had 64 g kg‐1 N intheshoots at the two‐leaf stag e, compared with 33 in N50, 50 in N300, and 58 in N800. Compared with control plants, dry matter of N50 plants was 10%, N300 50%, and N800 80%. Results in Exp. 2 were similar. The rate of leaf emergence was decreased in all N50‐treated and some N200‐treated plants, but not or N300‐treated plants. Tiller bud initiation was decreased in the treatment. The number of tiller buds was correlated with total number of leaves; if a leaf emerged, N deficiency did not affect tiller initiation. Nitrogen treatment did not alter the sequence of tiller emergence, but tiller emergence was delayed or did not occur in N50, N200, and N300 plants. Nitrogen treatment had little effect on the rate of apical development. The double‐ridge stage of development was delayed ≈2 d for both cultivars at the two lowest N treatments. Terminal spikelet production was also delayed by ≈2 d at these N treatments in Aroona, but not in Gamenya spring wheat. The rate of primordia initiation was decreased in N50 and N300 plants, resulting in fewer spikelet primordia. The level of N deficiency affected plant response to the stress.
Resistance to Six Races of Ascochyta rabiei in the World Germplasm Collection of Chickpea
Authors: Singh K. B. , Reddy M. V.
Published: July 2010

Ascochyta blight [caused by Phoma rabiei (Pass.) Khune & J.N. Kapoor; syn. Ascochyta rabiei (Pass.) Lab.] is the most important disease of chickpea (Cicer arietinum L.) in many countries. Progress in breeding blight‐resistant cultivars has been hampered by the absence of dependable sources of resistance. An effort was made to screen the world germplasm collection against races of P. rabiei with the objective of identifying resistant sources. A total of 19 343 germplasm accessions of chickpea (12 749 desi and 6594 kabuli types) were evaluated for resistance to six races of P. rabiei at Tel Hadya, Syria, between 1979 and 1991. Germplasm accessions were sown in the field during the winter season and inoculated by scattering ascochyta blightdiseased chickpea debris and spraying a spore suspension of a mixture of six races of P. rabiei prevalent in Syria and Lebanon. In greenhouse evaluations, germplasm accessions were grown in pots and inoculated by spraying the spore suspension of a composite of the six races; inoculated plants were incubated in plastic moist chambers for 1 wk. Blight severity was scored on a scale of 1 to 9, where 1 to 4 = resistant, 5 = tolerant, and 6 to 9 = susceptible. Only three desi accessions (ICC 4475, ICC 6328, and ICC 12004) and two kabuli accessions (ILC 200 and ILC 6482) were resistant in repeated field and greenhouse evaluations. Another six desi and three kabuli accessions were resistant in repeated Held tests but tolerant in greenhouse evaluations. These accessions will be used as sources of resistance in the ascochyta blight‐resistance breeding programs.
Bdv1: A Gene for Tolerance to Barley Yellow Dwarf Virus in Bread Wheats
Authors: Singh Ravi P. , Burnett Peter A. , Albarrán M. , Rajaram Sanjaya
Published: July 2010

Barley yellow dwarf (BYD) is the most economically important and widespread virus disease of small grain cereals in the world. The North American bread wheat (Triticum aestivum L. emend. Thell.) cultivar Anza and several other International Maize and Wheat Improvement Center (CIMMYT) wheats have shown tolerance to BYD. Anza and nine other tolerant wheats were studied to understand the genetic basis of tolerance. The tolerant wheats were intercrossed and crossed with the susceptible wheats ‘Bobwhite’ and/or ‘Bagula’. Parents and the F1 and F2 generations were tested during 1990 in the field near Toluca (State of Mexico) with the MAV‐Mex serotype of barley yellow dwarf virus. Seventy‐two individual F2‐plant‐derived F3 lines from each cross were classified in the field during 1991, together with the parents and F1's, with the same serotype. The intercrosses among tolerant parents failed to segregate, and the observed distribution of F3 lines in the crosses of tolerant and susceptible wheats was in accordance with a monogenic segregation ratio. We conclude that the tolerance of Anza and the other nine wheats is due to a common, partially effective and partially dominant gene, designated as Bdv1. Bdv1 could have originated in the Brazilian cultivar Frontana and should be considered a durable source, because of its deployment in numerous CIMMYT wheats worldwide.
Timing of Reproductive Abortions in Relation to Cell Division, Water Content, and Growth of Pea Seeds
Authors: Ney Bertrand , Duthion Claude , Fontaine Evelyne
Published: July 2010

Pod number is the most explicative component of the yield variability of pea (Pisum sativum L.). To understand the processes that determine pod number, the timing of reproductive abortion, seed development, and growth were studied. Cultivar Solara was grown in nonstressed conditions during three successive years, in 1988 and 1990 in a glasshouse in 7‐L pots with 4 or 5 plants per pot, and in 1989 in the field with 50 plants m−2. At all nodes, abortion occurred before ≈300 degree‐days (base temperature of 0 °C) from the date of flowering of the node; beyond this date, numbers of pods and seeds per pod remained constant at the node. During the initial 300 degree‐days, embryo cellular divisions were active and then cell number plateaued. Water content varied between 0.80 and 0.86 g g−1 of fresh weight initially, then began to decrease after 300 degree‐days. Seed lengths increased at a constant rate for the initial 300 degree‐days and then plateaued, whereas dry weight increased slowly until 300 degree‐days, but then rates increased substantially. These data indicate that seed length and water content may serve as convenient indicators to delimit the period of embryogenesis during which abortion may occur.
Emergence, Elongation, and Senescence of Maize Silks
Authors: Bassetti Paolo , Westgate Mark E.
Published: July 2010

In maize (Zea mays L.), duration of silk receptivity to pollen is limited after silks emerge from the husks. Whether this loss in receptivity reflects senescence of the entire ear or individual pistillate flowers is not known. Therefore, we examined the relationships between emergence, elongation, and senescence of silks in two hybrids varying in ear development. Plants were grown in soil in the greenhouse. For both hybrids, the first silks to emerge were from Flower Positions 6 to 15 from the base of the ear. These were followed by silks from progressively younger flowers in acropetal sequence. Silks of all flowers were exposed within 4 (Hybrid 1) to 8 (Hybrid 2) days. Silk elongation was most rapid during the first day of exposure, declined progressively with time, and ceased completely within 9 to 11 d. Silks began to senesce ≈7 to 8 d after emergence from the husk. The first silks to be exposed were also the first to senesce. Senescence was first evident as a loss of turgidity in tissues at the basal 3 mm of the silk, followed by the complete collapse of this tissue. In Hybrid 1, this process progressed from the peripheral cells towards the central tissues. In Hybrid 2, the central tissues of the silk were the first to collapse. There was no apparent effect of flower position on the interval between silk emergence and silk senescence, or on the senescence process. These results show that silks of maize undergo a well‐defined pattern of emergence, elongation, and senescence. The pattern is similar across flower positions on the ear; however, the timing and duration of these developmental events are characteristic of individual hybrids.
Water Deficit Affects Receptivity of Maize Silks
Authors: Bassetti Paolo , Westgate Mark E.
Published: July 2010

Drought during anthesis decreases seed set in maize (Zea mays L.) even if pollination occurs. To test whether low silk water potential (ψw) decreases silk receptivity, we examined silk development, pollen‐silk interaction, and kernel set in two hybrids grown in a greenhouse and exposed to a brief water deficit after silks emerged from the husks. Low silk ψw directly affected silk development. Silk elongation was inhibited as silk ψw decreased, and no growth occurred at silk ψw below −0.8 MPa. Silk senescence (collapse of basal silk tissue) was delayed, compared with controls, when silk elongation was arrested by low ψw within 3 days after the first silks appeared (DAFS). similar water deficit 5 DAFS, however, hastened silk senescence. The change in silk development had a direct effect on kernel set. Low silk ψw decreased set 20 to 40% 3 DAFS, and decreased set almost completely 5 DAFS. Pollen tubes were observed in >90% of silks pollinated at ψw between −1.0 and −1.3 MPa, although there were fewer tubes per silk. Tube growth was slow at low silk ψw, but tubes failed to reach the ovary only after silks had senesced. These results indicate that low ψw imposed <4 DAFS limited kernel set primarily by causing developmental failure within the ovary, not loss of silk function. Low ψw imposed >5 DAFS limited kernel set by hastening silk senescence. Thus, water deficits at anthesis can cause loss of silk receptivity in maize, but only when low silk ψw occurs >5 d after silks emerge from the husks.
Tall Fescue Sward Dynamics: I. Seasonal Patterns of Turf Shoot Development
Authors: Spak David R. , DiPaola Joseph M. , Anderson Charles E.
Published: July 2010

Knowledge of turfgrass sward dynamics, including shoot development and mortality, as affected by inflorescence removal during mowing may provide the insight necessary to maximize stand density through management practices. A 2‐yr field study was conducted on a mature stand of ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.) turf to determine shoot longevity and patterns of shoot development in relation to reproductive development. Mowing regimes consisted of mowing to 9.5 cm when foliar height reached 15.2 cm, and an unmowed regime that remained unclipped from April through October, when it was mowed to 9.5 cm. Twenty shoots were labeled with coded tags prior to initiation of mowing. Shoots were observed periodically and the following characteristics determined: living or dead, vegetative or reproductive, total and fully expanded green leaves, and secondary shoot development. Thirty.six percent of the shoots survived for 2 yr in mowed turf, whereas only 4% survived this period in unmowed turf. Regardless of the mowing regime, most of the shoots died in the vegetative state; only 2% of the spring shoot population became reproductive. Stand density declined from April through September by 31% for mowed turf and 63% for unmowed turf. Stand density decline was a result of continuous mortality of vegetative shoots and minimal new shoot development; only 1 to 3% of the existing shoot population developed secondary shoots. Partial, periodic removal of inflorescences and associated tissues had no effect on secondary shoot development within the sward. In this study, shoot mortality and new shoot initiation were not associated with reproductive development.
Pedigree Diversity within the Lancaster Surecrop Heterotic Group of Maize
Authors: Gerdes James T. , Tracy William F.
Published: July 2010

Maize (Zea mays L.) breeders commonly classify inbred lines into heterotic groups based on pedigree information and/or combining ability. These heterotic groups influence how germplasm is used, and have increased the efficiency of breeding programs. The most widely recognized and exploited heterotic pattern in the U.S. Corn Belt is that of Reid Yellow Dent by Lancaster Surecrop. Pedigree information was used to examine the diversity present in 37 publicly developed inbreds of the Lancaster Surecrop heterotic group, and to investigate the evolution to its present state. All of the Lancaster Surecrop germplasm in the publicly developed inbreds included in the modern Lancaster Surecrop heterotic group was derived from two inbreds, Oh40B and C103. Furthermore, the amount of true Lancaster Surecrop germplasm is 50% or less in 36 of these inbreds, with >20 non‐Lancaster Surecrop sources contributing germplasm to this heterotic group. The Lancaster Surecrop heterotic group has been modified considerably, with a reduction in Lancaster Surecrop germplasm and an increase in non‐Lancaster Surecrop germplasm including Reid Yellow Dent.
Field Performance of Abscisic Acid‐Induced Flood‐Tolerant Corn
Authors: VanToai Tara T.
Published: July 2010

Abscisic acid (ABA) applicantions can improve plant resistance to stresses such as cold, drought, and salinity. Treatment of corn (Zea mays L.) with ABA was previously shown to increase flooding survival 10‐fold. The long‐term effects of ABA treatment and flooding stress on growth and productivity have not been documented. In this study, ABA‐treated corn seedlings that survived a flooding stress in the laboratory were transplanted to the field and their growth and seed yield compared with those of nonflooded plants. While ABA treatment had no effect on nonflooded plants, ABA‐treated plants recovered from the flooding stress more quickly than plants not receiving ABA. At 4 wks after transplanting, ABA‐treated, flooded plants were as tall as nonflooded plants (56.03 ± 1.85 cm), while flooded plants that received no ABA Pretreatment were 22% shorter (43.70 ± 2.3 cm). Abscisic acid treatment and flooding did not have any long‐term effects on plant senescence. At the end of the growing season, no differences were detected in leaf chlorophyll content among the treatments. Grain yields of the surviving plants were also similar among all treatments. According to the results, ABA treatment at 100 (μM improved the flooding survival of corn seedlings 10‐fold, without any deleterious effects of subsequent growth, senescence, or productivity of corn plants. This research contributes to the understanding of the physiological mechanism by which ABA enhances the flooding tolerance in corn.
Intercepted Radiation at Flowering and Kernel Number in Maize: Shade versus Plant Density Effects
Authors: Andrade Fernando H. , Uhart Sergio A. , Frugone Mariano I.
Published: July 2010

The number of grains produced in maize (Zea mays L.) is altered by environmental conditions during growth. The response occurs primarily during flowering. The objective of this work was to study the relationship between intercepted radiation during a 31‐d period bracketing flowering and final kernel number per unit area in maize and to analyze the effect of plant density on that relationship. Shading and population density experiments were conducted at Balcarce, Argentina, under no limitations of water and nutrients. A significant and positive association between number of kernels per square meter and intercepted radiation during this 31 d was found for the shading experiments. The slope of this relationship was 5.39 kernels MJ−1 of intercepted radiation. When intercepted radiation at flowering was modified by varying plant density within suboptimal values, the response of number of kernels per unit area was larger than that observed in the shading experiments (28 vs. 5.39 kernels MJ−1; P ≤ 0.001). At supraoptimal densities, the number of kernels per unit area was significantly reduced even though the amount of radiation intercepted by the crop was not affected. This work indicates that a model developed from shading experiments and based on the amount of radiation intercepted by the crop at flowering does not predict the effect of altered plant density on kernel number. Suboptimal and supraoptimal densities produced a strong negative effect on the efficiency with which the crop or plant converts intercepted radiation into grain sink capacity.