bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Drought Stress on Productivity of Trichomeless Pearl Millet
Authors: Burton Glenn W. , Kvien Craig S. , Maw Bryan W.
Published: July 2010

The trichomeless gene, tr, has been shown to modify the cuticle of pearl millet, Pennisetum glaucum (L.) R. Br., and, thus, has the potential to affect drought resistance. Near‐isogenic lines, Tift 23D2B1 tr tr (trichomeless) and Tift 23D2B1 Tr Tr (trichomed), were compared in eight replications of a randomized complete block design on Tifton loamy sand (fine‐loamy, siliceous, thermic Plinthic Paleudult) and Norfolk sand (fine‐loamy, siliceous, thermic Typic Paleudult) in 1982, a season with good rainfall distribution. Trichomeless 23D2B1 outyielded trichomed 23D2B1 25.0% (P < 0.01) on the Norfolk sand but failed to increase forage yield on Tifton loamy sand. Near‐isogenic populations 85D2B1 trichomeless and 85D2B1 trichomed were compared under a rain shelter to create drought stress. In a 2‐yr comparison under the rain shelter, the trichomeless 85D2B1 population produced 13.6% (P < 0.01) more dry matter than the trichomed 85D2B1 population. In the 1986 Tifton loamy sand test that was naturally water stressed by only 290 mm rainfall during the 98‐d test period (74% of the 46‐yr average) the trichomeless 85D2B1 population produced 10.7% (P < 0.01) more dry matter and 23.0% (P < 0.01) more seed heads than the trichomed 85D2B1 population. Thus it appears that the recessive tr gene can be used to increase the yield of pearl millet under drought stress.
Genetic Variability for Seedling Atrazine Tolerance in Indiangrass
Authors: Kube J. G. , Vogel K. P. , Moser L. E.
Published: July 2010

Indiangrass [Sorghastrum nutans (L.) Nash] lacks sufficient seedling atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐l,3,5‐triazine‐2,4‐diamine] tolerance to permit the use of atrazine as a pre‐emergence herbicide. The principle objective of this study was to estimate the genetic variability for seedling atrazine tolerance in two indiangrass populations, ‘Nebraska 54’ and ‘Holt’, using seed harvested from replicated clones. Seedling survival in soil containing 3 mg kg−1 atrazine was determined in the greenhouse. There was significant genetic variability among half‐sib families of both populations for seedling atrazine tolerance. Heritability estimates were greater than 0.50. There was also significant genetic variability among the parent plants of both populations for atrazine tolerance as measured by the change in relative fluorescence (CRF) of leaf disks exposed to atrazinc. Atrazine blocks photosynthesis, causing differential fluorescence among plants differing in tolerance, which can be measured with a fluorometer. Correlations of CRF of the parent plants and the seedling atrazine tolerance of their progeny were low (r < 0.3) indicating that fluorescence assay would not be a usable screening procedure. Improving the seedling atrazine tolerance of indiangrass using the greenhouse soil test and conventional breeding methods is possible.
Chloroplast Genome Mapping and Plastid Ulrastructure Analysis of Chlorophyll Deficient Mutants of Alfalfa
Authors: Lee D. J. , Blake T. K. , Smith S. E. , Bingham E. T. , Carroll T. W.
Published: July 2010

Physical maps of chloroplast genomes allow comparison of genome structure and organization and can provide physical markers useful for evaluating plastid inheritance. Physical maps of the chloroplast DNA (ctDNA) from phenotypically normal alfalfa (Medicago sativa L.) genotypes and two independently isolated cytoplasmically and biparentally inherited chlorophyll‐deficient mutants were developed and compared. Both mutants were observed as somatic sectors but each had a different phenotype, one producing albino and the other yellow‐green tissue. Maps of overlapping restriction fragments were constructed using both purified chloroplast DNA and total DNA digested with the restriction endonucleases Bam HI, Xho I, and Hind III and utilizing a complete set of chloroplast probes. A total of four points of variation, two changes in restriction endonuclease recognition sites and two small addition/deletion events were observed among the genotypes studied. Combinations of these polymorphisms defined four distinct ctDNA genotypes. Only one addition/deletion polymorphism was unique to the mutant chloroplast DNA (ctDNAs) and the albino and yellow‐green chloroplast genomes were indistinguishable from each other by this analysis. Electron microscopy revealed differences in development between the two chlorophyll‐deficient mutants. Plastids from albino tissue showed envelope degradation, no internal membrane development, sparse stroma with vacuoles, and osmiophyllic globuli. Plastids from yellow‐green tissue showed limited thylakoid membrane development, no grana, relatively dense stroma with ribosome‐like particles, osmiophyllic globules, and various degrees of vacuolization. This study identified molecular markers with which to assess plastid inheritance in alfalfa and demonstrated that the dramatic arrest in plastid development found in both mutants was not paralleled by large changes in their chloroplast genomes.
Simulation Model for Studying Physiological Water Stress Responses of Whole Plants
Authors: McCree K. J. , Fernandez C. J.
Published: July 2010

Simulation models are useful tools for integrating ideas about physiological responses to soil water deficits at the whole plant level. This paper describes a model that mimics the behavior of plants exposed to a single cycle of water deficit under controlled environment conditions. The model uses linear functions to describe the following basic physiological responses to soil water: (i) rate of new leaf production, (ii) stomatal closure, (iii) rate of senescence as it affects stomatal conductance, photosynthetic and respiratory rates, and leaf area. Simulations with the model demonstrated how the assumption of a hyperbolic dependence of photosynthetic rate on internal CO2 concentration could lead to an increase in water use efficiency as stomates close. The model confirmed published data showing that stomatal closure induced by salinization increases the efficiency under water stress and leads to a greater C gain per irrigation cycle. Other simulations demonstrated how an increase in the volume of soil explored by unit mass of new roots could lead to greater amounts of water uptake and C gain per cycle. Interactions among these and other factors can be studied in a way that would not otherwise be possible.
Birdsfoot Trefoil Pod and Seed Development Affected by Temperature
Authors: Long S. J. , Barnes D. K. , McGraw R. L.
Published: July 2010

Genotype × environment interactions determine where birdsfoot trefoil (Lotus corniculatus L.) seed is produced. Temperature is an important environmental variable during seed production. The objectives of this research were to determine the effects of temperature regimes (two alternating and two constant) on development of pods and seeds in birdsfoot trefoil and to examine the effect of seed position in the pod and number of pods per umbel on seed size. Ramets of three genotypes from each of three cultivars were grown in controlled environment chambers under a ;16 h photoperiod at four temperature regimes: (i) 27/13 °C day/night; (ii) constant 20 °C; (iii) constant 26 °C; and (iv) 31/21 °C day/night. Temperature regimes (i) and (iv) simulated the temperatures during pollination and seed development in Roseau, MN, and Columbia, MO, respectively. Seed mass and number of pods per umbel were not correlated. Seed mass was linearly related to location within the pod, with the heavier seed being at the distal end. Stem length, peduncle length, umbels per plant, vegetative dry mass, pod length, and seed mass were significantly greater in regime (i) compared to regime (iv). Peduncle length, pod length, and seeds per pod were significantly greater in regime (i) compared to regime (iii). Stem length, umbels per plant, vegetative dry mass, pod length, number of seeds per pod, and seed mass were greater in regime (i) compared to regime (ii). All genotypes performed better and produced larger seed at the cooler regime (i) than at regime (iv). No temperature X genotype interactions were detected. These data support the reports that birdsfoot trefoil seed production usually is most effective in areas having cool summer temperatures.
Population Cross Diallel among High Oil Populations of Maize
Authors: Mišević D. , Marić A. , Alexander D. E. , Dumanović J. , Ratković S.
Published: July 2010

Development of commercially usable high oil maize (Zea mays L.) inbred lines is presently restricted to a single gene pool source. To improve the efficiency of high oil maize breeding programs, new pools with favorable alleles for high oil percentage, high yield, and good combining ability should be identified. The objectives of this study were to determine heterotic patterns among high oil populations and to identify superior high oil populations for use in a recurrent selection program. Six maize populations with oil percentages ranging from 5 to 18 were crossed in a diallel mating design. Parents, their crosses, and the single cross B73 ✕ Mo17 were grown in a randomized complete block design experiment in six environments in 1985 and 1986. Percent oil, grain yield, and grain moisture were recorded. Population (v1) and heterosis (hii) effects were nificant sources of variation among entries of the diallel for all three traits. However, heterosis effects accounted for less than 1.5% of the among diallel entries sum of squares for oil percentage, indicating that additive genetic effects were much more importanthan nonadditive. Percent oil and grain moisture showed negative average heterosis. High Oil Illinois Stiff Stalk Composite (RSSSC HO) had the highest and lowest vi effects for grain yield and oil percentage, respectively. Alexho Single Kernel C24 (ASKC24) had the lowest v1 effect for yield and the highest v1 effect for oil percentage. Highest and lowest specific heterosis (sii) for grain yield were found for RSSSC HO ✕ ASKC24 and RSSSC HO ✕ Yugoslavian High Oil Stiff Stalk Synthetic, respectively. Populations RSSSC HO and ASKC24 could be chosen for a reciprocal recurrent selection program because of their high hii, and sii, effects for grain yield and high population cross means for oil percentage and grain yield.
Relation of Isozyme Genotypes to Quantitative Characters in Soybean
Authors: Graef G. L. , Fehr W. R. , Cianzio S. R.
Published: July 2010

Selection based on genotypes at marker loci may increase the efficiency of plant improvement. Two interspecific crosses of soybean [Glycine max (L.) Merr ✕ G. soja Sieb. & Zucc.] were used to examine the relationships between isozyme marker loci and agronomic traits. The parents had different alleles at six isozyme loci for Cross 1 (A80‐244036 ✕ PI 326581) and eight isozyme loci for Cross 2 (A81‐157007 ✕ PI 342618A). Approximately 4000 BC2F4‐derived lines were evaluated in two replications at two locations for maturity (MAT), height (HT), lodging (LDG), plant type (PLT) and vining (VNG). Lines were identified that were homozygous for G. soja alleles at different numbers of marker loci, from 0 to 5. Within each locus class, there were a number of specific enzyme genotypes, and each enzyme genotype was represented by a number of lines from different BC2F1 families. Associations were observed for specific enzyme genotypes and every quantitative trait in both crosses, but the particular isozyme genotype/quantitative trait relationships were population specific. No complete or very tight linkages between marker loci and loci affecting quantitative traits were identified in this study, but such linkages would be useful in the identification and isolation of genes affecting the expression of quantitative traits. For every trait except MAT, an increase in the numbers of isozyme marker loci that were homozygous for alleles from G. soja resulted in a change in the phenotype toward the G. soja parent in both crosses. The relationship between numbers of homozygous marker loci and parental phenotype could increase the efficiency of an introgression program by hastening recovery of the recurrent parent phenotype while maintaining specific desired alleles from the donor parent.
Allelic Composition of Cotton at the Le1 and Le2 Loci.
Authors: Rooney William L. , Stelly David M.
Published: July 2010

Cotton (Gossypium spp.) zygotes bearing a Le2dav allelle in combination with Le1 and/or Le2 undergo a physiological reaction resulting in embryo or seedling in viability. All F1 hybrids between cultivated tetraploid cotton (G. hirsutum L. and G. barbadense L., 2n = 4x = 52) and a Le2dav homozygote are inviable. A breeding procedure being developed for mass extraction of doubled haploids of cotton relies on the “bio‐elimination” of F1 hybrids by this complementary lethal system. Success is contingent on the absence of le1le2 gametes from a prospective parent because these alleles are fully compatible with Le2dav. The primary objective of this research was to determine the frequency of le1 and le2 in a representative sample of USA‐developed G. hirsutum cultivars. A secondary objective was to determine if the timing of the incompatibility reaction was consistent across genetic backgrounds. Fifty‐two cultivars were tested by observing the frequencies of nonviable vs. viable progeny and the timing of necrosis following two types of matings: (i) cultivar ✕ le1le1Le2davLe2dav and (ii) (cultivar ✕ le1le1le2le2) ✕ le1le1Le2davLe2dav. All 52 cultivars were found to be Le1Le1Le2Le2, indicating that the frequencies of alleles le1 and le2 are zero, or nearly so, in USA‐developed G. hirsutum germplasm. Results on necrotic development indicated that the cumulative dosage of alleles Le1 and Le2 affected the onset of necrosis in the presence of Le2dav. Because alleles le1 and le2 are rare in American upland cottons, the doubled‐haploid breeding system will be applicable to these stocks.
Dwarfing Gene Effects on Coleoptile Length in Pearl Millet
Authors: Soman P. , Rai K. N. , Bidinger F. R.
Published: July 2010

Dwarfing genes have been reported to affect either or both the length of the coleoptile and mesocotyl in several cereal species, which can reduce seedling emergence. Such an effect of dwarfing genes has not been reported for pearl millet [Pennisetum glaucum (L.) R. Br.]. The objective of this study was to assess the effect of the d2 dwarfing gene in pearl millet on the length of the coleoptile, mesocotyl, and plumule in 12 pairs of isogenic tall/dwarf (d2) inbred lines and pairs of isogenic tall/dwarf hybrids. Calm lengths were measured in replicated field trials in two seasons and the lengths of coleoptiles and mesocotyls in seedlings germinated in incubators in the dark at 35 °C. Culm length differed significantly between tall and dwarf entries of both inbreds and hybrids but the length of both coleoptile and mesocotyi were similar in both height classes. There were significant differences in coleoptile and mesocotyl lengths among individual entries tested but these were due to parental line or hybrid parent effects. The d2 gene in pearl millet did not affect coleoptlle or mesocotyl length as reported for dwarfing genes in other cereals.
Screening Soybean Genotypes in the Greenhouse for Resistance to Insects
Authors: All J. N. , Boerma H. R. , Todd J. W.
Published: July 2010

Insect resistance in soybean, Glycine max (L.) Merr., cultivars would reduce the use of chemical insecticides, resulting in less risk to the environment and increased grower profits. The objectives of this research were to develop an effective greenhouse screening procedure to identify soybean genotypes with resistance to defoliating insects and provide information on the number of replications required to obtain desired levels of precision for the procedure. Neonate larvae were placed on 12‐ to 16‐d‐old potted plants. Insects had free choice among plants for 14 d within replicates, but larval movement away from a replicate was prevented by maintaining the potted plants in stainless steel pans containing 2 cm of water. Replicate blocks were separated so that leaves did not intermingle. Several hundred soybean genotypes were evaluated at one time. Defoliation of test plants by the corn earworm, Heliothis zea (Boddie), in the greenhouse screening system correlated (r = 0.60; P < 0.01) insect defoliation of soybean plants in field nurseries. The ranking of the genotypes based on defoliation by the corn earworm; tobacco budworm, H. virescens (Fabricius); soybean looper, Pseudoplusia includens (Walker); velvetbean caterpillar, Anticarsia gemmatalis Hübner; green cloverworm, Plathypena scabra (Fabricius); beet armyworm, Spodoptera exigua (Hübner); and fall armyworm, S. frugiperda (J.E. Smith), was similar in greenhouse tests. For example, feeding by all insect species was inhibited by Plant Introduction 229358 and GatIRSI‐296, genotypes with known multiple insect resistance. Of seven insect species tested, the corn earworm was the easiest to work with in the greenhouse screening program and required fewer replications than most other species to demonstrate stipulated levels of resistance. For example, a difference of 40% in the overall mean of the experiment between two genotypes required seven replicates with corn earworm and 18 replicates with soybean looper. The greenhouse procedure has been used successfully for 3 yr and is a good complement to field testing in a soybean pest resistance program.
Genotypic Variation for Hordeum bulbosum L.‐Mediated Haploid Production in Winter and Facultative Barley
Authors: Hayes P. M. , Chen F. Q.
Published: July 2010

The use of Hordeum bulbosum L.‐mediated haploid production in barley (Hordeum vulgare L.) germplasm enhancement, gene mapping, and marker‐assisted selection is limited by low efficiencies of haploid production with certain barley genotypes. The primary objective of this study was to assess genotypic variation for haploid production efficiency in an array of 10 winter and facultative barley cultivars of diverse geographic origin. Another objective was to compare in vitro floret and tiller culture as aids to haploid production by the bulbosum method. There was significant genotypic variation for haploid production efficiency (HPE), computed as the number of haploid plants regenerated/100 florets pollinated with both techniques. The highest HPE (48) was achieved with ‘Schuyler’ using floret culture, a technique in which barley florets pollinated with H. bulbosum L. are cultured on modified N6 media containing 0.5 mg L−1 kinetin and 1.2 mg 2,4‐D L−1. Mean HPEs achieved with floret and tiller culture were 35 and 15, respectively. Cultivars exhibited differential HPE response. Of the components of haploid production efficiency (seeds/100 florets, embryos/100 seeds, and plants/100 embryos), a significant genotype ✕ culture technique interaction was found only for embryos/100 seeds. The use of floret culture as an aid to H. bulbosum L.‐mediated haploid production should facilitate barley germplasm enhancement, mapping, and selection efforts requiring routine doubled haploid synthesis from genetically broadbased germplasm arrays.
Competition Thinning of Alfalfa Planted at Three Densities
Authors: Rowe D. E.
Published: July 2010

Persistence in alfalfa (Medicago sativa L.) is a critical component in long term yield but little is known of the relationships among stand density, competition, and stand thinning. This study was conducted to determine if thinning of different alfalfa populations at different densities was a simple function of competition (distance between plants). Three alfalfa were space planted in a honeycomb design in the field, an Orr loams (fine‐loamy, mixed, mesic Ardic Argixeroll), at 10, 17.7, and 30 cm on centers for high, medium, and low densities, respectively. After each of nine harvests, the dead plants in each of the replicated plots of 483 plants were mapped and classified by how many of the six surrounding equidistantly spaced plants were also dead. With random death the number of dead plants with 0,1,...,6 adjacent plants that are also dead should have binomial distribution. Significant (P < 0.05) deviations from the binomial distribution occurred for 67,37, and 88% of the test at high, medium, and low densities, respectively. For two populations, significant (P < 0.05) deviations at both low and high densities were due to an excess of larger numbers of adjacent dead plants. Disease may have been an important cause of death in these cases. The complex interactions between density and population over time indicated that increasing stand density does not simply equate to an increase in selection pressure for survival in competitive environments.
Spikelet Characteristics and Midge Predation of Hermaphroditic Genotypes of Big Bluestem
Authors: Boe A. , Robbins K. , McDaniel B.
Published: July 2010

Seed yields of big bluestem (Andropogon gerardii Vitman) can be limited by poor caryopses set. The purpose of this study was to determine if sex expression had an effect on caryopses set, caryopses weight, and mature spikelet predation by the bluestem seed midge (Contarinia wattsi Gagné). Two hermaphroditic and two andromonoecious genotypes of big bluestem from an eastern South Dakota population were evaluated for 3 yr in a space‐plant nursery at Brookings, SD. Andromonoecious genotypes exhibited 11% higher caryopses set in sessile spikelets. Sessile and pedicellate spikelet caryopses sets of hermaphroditic genotypes were 60.8% and 57.4%, respectively. Caryopses from sessile spikelets were 46% heavier than those from pedicellate spikelets of hermaphroditic genotypes. Weights of caryopses from sessile spikelets of hermaphroditic and andromonoecious genotypes were similar. Frequencies of sessile spikelets containing diapausing larvae of the bluestem seed midge were greater for hermaphroditic than andromonoecious genotypes. Mature sessile spikelets of hermaphroditic genotypes were more frequently infested by larvae than pedicellate spikelets, and no larvae were found in pedicellate spikelets of andromonoecious genotypes. The bisexual pedicellate spikelet trait increased total spikelet caryopses set in the presence of the bluestem seed midge and thus may have potential for improving seed yields.
Genotypic Interaction of Early Maturity Soybean with Row Spacings
Authors: Hugie W. V. , Orf J. H.
Published: July 2010

Previous research has demonstrated that soybean [Glycine max (L.) Merr.] seed yields in the northern USA generally increase as row spacing is reduced. However, studies examining the consequences of a genotype ✕ row spacing interaction for seed yield on selection practices used to identify superior lines for use in wide and narrow row spacings have reported conflicting results. The objectives of this study were to: (i) examine the genotype ✕ row spacing interaction in preliminary breeding material of early maturity soybean; (ii) determine whether early maturing determinate genotypes respond similarly to indeterminate genotypes for yield in wide and narrow rows; and (iii) determine if information from whole plots or from parts of samples from one row spacing could be used to predict performance of genotypes in another row spacing. Two hundred and seventy‐six indeterminate and determinate genotypes of Maturity Groups 0, I, and early II were evaluated in six yield tests at two locations over 2 yr. Genotypes were planted in 25‐ and 76‐cm row spacings. Plant samples were taken from a 0.76 m2 area of each plot to examine traits that might be useful in identifying superior genotypes for either row spacing. A genotype by row spacing interaction for seed yield was observed in four of the six tests. The determinate genotypes responded similarly to the indeterminate genotypes for yield in both row spacings. Of the traits measured, selection for mean seed yield was the most efficient characteristic in identifying superior yielding genotypes for use in either row spacing even if testing was limited to one row spacing. Generally, narrow rows were superior or equivalent to wide rows for identifying the best genotypes from preliminary yield tests for further testing in either row spacing.
Phosphorus Enhancement of Salt Tolerance of Tomato
Authors: Awad A. S. , Edwards D. G. , Campbell L. C.
Published: July 2010

Increasing plant P supply has been shown to either increase or decrease the salt tolerance of many plants. Tomato plants (Lycopersicon esculentum Mill.) were grown in a greenhouse in a continuously flowing solution culture system to investigate whether P fertilization modified the detrimental effects of NaCl at low constant P concentrations similar to those in soil solutions. Increasing P fertilization enhanced the tolerance of tomato plants to NaCl. At 0.1, 1.0, and 10 mM P, the NaCl concentrations that reduced yields of fruit by 50% were 58,72, and 130 mM, respectively. Salinity reduced foliar P concentrations. This may have been mediated partly through ionic strength effects, which decreased the activity of H2PO4−1 by about 40%. Plants grown under saline conditions had higher internal P requirements. When the NaCl concentration was increased from 10 to 50 and 100 mM, the corresponding concentrations of P in the youngest mature leaf required to obtain 50% yield were increased from 1.8 to 2.4 and 3.0 g kg−1. The change in internal P requirement was also evident by the relative severity of foliar symptoms of P deficiency in plants growing in the saline treatments at any given foliar P concentration. Adequate P nutrition was essential for effective ionic compartmentation. Under saline conditions, increasing the solution P concentration from 1.0 to 10 μM decreased Na and increased K concentrations in immature leaves but increased Na and decreased K in the mature leaves. Accumulation of ions for osmotic adjustment and restriction of Na and Cl accumulation in immature leaves appear to be involved in P enhancement of salt tolerance of tomato plants.
Herbicide Effects on Maturity of Spring Barley in Alaska
Authors: Conn J. S.
Published: July 2010

Growing season length is marginal for spring barley (Hordeum vulgare L.) production in Alaska. A study was conducted at Fairbanks, AK from 1983 through 1987 to determine whether herbicides commonly used for broadleaf weed control in barley could increase time to reach physiological maturity (PM) and time to reach kernel moisture contents (KM) of 200 g H2O kg−1 (KM20) and 140 g H2O kg−1 (KM14). The herbicides applied were: 2, 4‐D [(2,4‐dichlorophenoxy) acetic acid], MCPA [(4‐Chloro‐2‐methyl‐phenoxy) acetic acid], bromoxynil (3, 5‐Dibromo‐4‐hydroxybenzonitrile), chlorsulfuron [2‐chloro‐N‐[[(4‐methoxy‐6‐methyl‐l,3,5‐triazin‐2‐yl) amino] carbonyl] bezenesulfonamide], dicamba (2‐Methoxy 3,6‐dichloro dichcorobenzoic acid), dinoseb [2 (see‐but) l)‐4,6‐dinitrophenol], and metribuzin [4‐Amino‐6‐(l,l‐dimethylethyl)‐3‐(methyIthio)‐l,2,4‐triazin‐5 (4H)‐one]. Each herbicide was applied at 0.5,1, and 2 times the rate recommended for barley. Metribuzin was also applied at a 4✕ rate. The herbicides did not influence the amount of time required to reach PM. Metribuzin applied at 1.0 kg ha−1 increased the time to KM20 and KM14 in 1983, 1984, and 1985 by an average of 5 d. Metribuzin applied at 0.5 kg ha−1 in 1984 increased the time to reach KM20 by 7 d and to KM14 by 8 d relative to the untreated control. Dinoseb at 1.1 kg ha−1 in 1984 and 1985 increased time to KM20 by 21 and 4 d and to KM14 by 24 and 5 d, respectively. Dinoseb at 0.6 kg ha−1 delayed arrival at KM20 and KM14 by 8 d in 1984. Five of the herbicides (MCPA, 2,4‐D, bromoxynil, dicamba, and chlorsulfuron) had no effect on barley maturity in any of the five years. Dinoseb has been withdrawn from the market. Metribuzin should be applied only at recommended rates with minimal spray overlaps to avoid delays in maturity.
Selection in Red Clover for Resistance to Northern Anthracnose
Authors: Taylor N. L. , Smith R. R. , Anderson J. A.
Published: July 2010

Northern anthracnose (NA), caused by Kabatiella caulivora (Kirchn.) Karak., is a destructive disease of red clover (Trifolium pratense L.) in the northern USA. The range of adaptation of southern red clover cultivars could be broadened by addition of NA resistance. A program was initiated to enhance NA resistance in 10 parental populations related to the cultivar Kenstar, and to evaluate response to phenotypic recurrent selection in these low NA‐variation susceptible populations. These populations are resistant to powdery mildew (Erisyphe polygoni DC) and bean yellow mosaic virus strain 204‐1. The 10 populations were subjected in a greenhouse to six cycles of phenotypic recurrent selection for NA resistance. Remnant seed from each cycle of selection was used to establish an evaluation study. Northern anthracnose resistance was significantly improved. Mean disease severity index (DSI) was reduced by 36% through six cycles and was linear across cycles. However, populations were variable in their response to selection. Selection improved DSI by less than 24% through six cycles in four of the populations, while average improvement of the other six was 46%. Realized heritabilities averaged 20% per cycle and were greatest among the six populations with greatest improvement in DSI Inbreeding was minimal during the selection process, averaging 2.8% after six cycles. The resistance obtained from these low‐variation susceptible populations indicates that phenotypic recurrent selection is an effective means of uncovering latent variation for resistance to NA.
Adjusting the Phenology of Determinate Soybean Segregants Grown at High Latitude
Authors: Saindon G. , Voldeng H. D. , Beversdorf W. D.
Published: July 2010

Breeding for determinate (dt1) cnltivars has been proposed as a way of reducing lodging in soybean [Glycine max (L.) Merr.]. However, determinate lines having maturity, acceptable for high latitude areas often exhibit insufficient plant height. The possibility of obtaining early‐maturing, nondwarf determinate soybean ptaats by using a combination of alleles at loci controlling stem termination and maturity was explored. Progeny test data for the E1 maturity locus of six experimental lines indicated that the indeterminate Evans‐e3, Harosoy‐e3, X2403 (Evans‐e3e4), and X2396 (Harosoy‐e3e4) homozygous for e1, whereas the determinate PI 317334A and PI 445831 are homozygous for E1. PI 445831 and PI 317334A (both homozygous for e3 e4) wereach crossed to Evans‐e3 real Harosoy‐e3 (both homozygous for e3 E4) and to X2403 and X2396 (both homozygous for e3 e4). Days to RI and R7 stages, recorded in eight populations of F2 plants grown in the field at Ottawa (45° 25′ N, 75° 42′ W), revealed that phenotypes were generated across a large array of maturities in populations where the E1 and E4 loci jointly segregated. The El and E4 loci did not act ndditively on flowering and maturity in plants homozygous for e3. As a result of this nonadditive effect, early‐maturing determinate phenotypes adapted to the short growing season of the latitude were isolated in populations derived from PI 317334A. These genotypes were not dwarf and their putative genotype is E1E1 e3e3 e4e4 dt1dt1.
Genotypic Variation and Classification of Cowpea for Reproductive Responses to High Temperature under Long Photoperiods
Authors: Patel P. N. , Hall A. E.
Published: July 2010

Hot weather can substantially reduce pod production by cowpea [Vigna unguiculata (L.) Walp.]. The objectives were to characterize and classify cowpea based on their responses to heat during reproductive development. Diverse cowpea accessions were grown over six summers in Imperial Valley, CA under hot temperatures (mean daily max/min 41/24 °C) and long days (14 h, 51 min decreasing to 12 h, 18 min). Selected genotypes were grown at Riverside, CA, under more optimal temperatures (35/17 °C) and the same daylengths. At Imperial Valley, genotypic variation was observed for duration to first macroscopic floral bud and extent of floral bud abortion, peduncle elongation, flower production, and podding. At Riverside, similar genotypic variation occurred for days to first floral bud, but subsequent reproductive development was normal. Controlled environment studies in growth chambers showed that the detrimental effects induced in sensitive genotypes by high temperature were enhanced by long photoperiods. Based on these differing reproductive responses, the accessions were classified into eight groups. Heat‐tolerant accessions in Group I exhibited normal peduncle elongation, early flowering, and produced many flowers and pods. Accessions in Groups II and III performed similarly but set few pods (Group II) or no pods (Group III). Accessions in Groups IV through VII differed in duration to first floral bud, with Group VII being the latest and exhibiting substantial bud abortion, suppressed peduncle elongation, and no flowers. Group VIII accessions produced no visible floral buds. Cowpea developed in different regions and for specific seasons within a region fell into discrete classification groups, indicating that the system has a genetic and ecological basis. This classification system is useful for characterizing the types of heat responses present in cowpea genotypes and for selecting appropriate combinations of parents for breeding heat‐tolerant cultivars for different production zones and seasons.
Changes in Seed Germination With Time for Polycross Progenies of Cicer Milkvetch
Authors: Townsend C. E.
Published: July 2010

Relatively few seed‐longevity studies have been concerned with differences among cultivars or genotypes within a species. The purpose of this study was to evaluate the change, if any, in longevity and early seedling vigor of cicer milkvetch (Astragalus cicer L.) seed from selected populations when stored at ambient temperature in an unheated, uninsulated building and subsequently germinated at high (15/25 °C) and low (5/20 °C) alternating temperatures. Seed of polycross progenies from four populations were evaluated for rate of germination when the seed were about one year of age and after 12 yr of storage. Percentage seed germination on a daily basis through Day 14 after planting and total germination at 15/25 °C were similar for the four populations and for the 1‐ and 12‐yr‐old seeds. Progenies within populations differed significantly (P ≤ 0.05) for rate of germination except on Day 14 after planting with 1‐year‐old seed. Germinability on Day 14 ranged from 87 to 100% after 12 yr of storage. When evaluated at 5/20 °C, large differences were noted among populations and among progenies within populations for both rate of germination and total germination. This indicates that the populations and progenies within populations differed genetically for rate of germination. Genetic differences among populations were expressed at 5/20 °C, but not at 15/25 °C. The decline in early seedling vigor as measured by rate of germination at 5/20 °C suggests that care should be taken when increasing the seed supply with older seed from a synthetic cultivar of cicer milkvetch and, perhaps, with seed of other species held in a seed storage facility.
Nutritive Value and Forage Yield of Alfalfa Synthetics under Three Harvest‐Management Systems
Authors: Vaughn D. L. , Viands D. R. , Lowe C. C.
Published: July 2010

Sequential selection for agronomic vigor, high crude protein (CP) concentration, and low acid detergent fiber (ADF) concentration has been proven to increase forage quality of alfalfa (Medicago spp.) when subjected to the harvest schedule (three harvests at 6‐wk intervals, beginning late May) recommended for most of New York. No research has been reported to indicate that forage quality and yield of alfalfa populations bred for improved forage quality are also improved under other harvest systems. The objective of this research was to compare three forage quality‐improved alfalfa synthetics to ‘Saranac AR’ and ‘Oneida VR’ for nutritive value and forage yield under three harvest‐management systems typically used in the northeastern USA. Field experiments were conducted at two locations for two production years. Soil types were Rhinebeck silt loam (fine, illitic, mesic Aeric Ochraqualt) and Williamson silt loam (coarse‐silty, mixed, mesic Typic Fragiochrept). The management systems, each based on three harvests per year, varied in date of initial harvest (recommended first harvest date vs. a 10‐d delay) and in regrowth interval (5 vs. 6 wk between Harvests 1 and 2). The quality‐improved synthetics averaged 2 and 6% lower forage yield in 1985 and 1986, respectively. The synthetics developed partly from exotic germplasm had the lowest yields. Within years, locations, and harvest systems, the quality‐improved synthetics were nearly always better than the standard cultivars in all measured quality components. The improved synthetics averaged 16 and 13 g kg‐1 lower neutral detergent fiber (NDF) and ADF, respectively, compared to the standard cultivars. The improved synthetics averaged 16, 17, 12, and 3 g kg‐1 higher true digestibility (TD), cell wall digestibility (CWD), CP, and cell wall protein (CWP) concentrations, respectively. Therefore, plants selected for higher nutritive value under a recommended harvest sequence can be developed into synthetics with improved quality when grown under other typical harvest systems.
Selection for Early Flowering in Corn: Three Adapted Synthetics
Authors: Troyer A. F.
Published: July 2010

Corn (Zea mays L.) breeders strive to broaden genetic diversity within shorter‐season growing areas by selecting for early flowering in late‐maturity germplasm. This creates earlier flowering material with most of the characteristics of the late germplasm, thus broadening the diversity of germplasm grown in the shorter‐season area. The present study evaluates selection for early flowering in adapted germplasm; relative to flowering date of selection materials, not only place of selection but also place of intended use differs from the usual approach. This study measures the selection response for early flowering in three adapted synthetics. The synthetics were grown at high plant density (87 000 plants ha‐1) near Mankato, MN; the earliest 5% to flower (55 of 1100 plants) were selected for four generations, then the original populations and the four cycles for each synthetic were compared in performance trials at 48 300,62 600 and 75 500 plants ha‐1 for 5 yr. Selection response for early flowering for four cycles averaged 0.8 d less to flowering, 10 g kg‐1 less grain moisture, 4.0 cm less plant height, 2.7 cm less ear height, 0.2 d less silk delay, 0.15 Mg ha‐1 (3%) less yield, and 4% more broken stalks. The decrease in yield due to selection showed close association with decrease in plant size (r = 0.98**, significant at P = 0.01), which probably reduced photosynthetic capacity. Later‐flowering synthetics respond more to selection for early flowering than do earlier flowering synthetics. Shorter‐season growing areas with longer, cooler days at flowering favor selection for early flowering. The results indicate that selection for early flowering can help export new, diverse germplasm to shorter‐season growing areas, to broaden genetic diversity in the shorter‐season area.
Contribution of Ancestral Lines in the Development of New Cultivars of Rice
Authors: Dilday R. H.
Published: July 2010

Crop genetic uniformity is today a principal concern of plant breeders, and was the major cause of the southern leaf blight, Helminthosporium maydis Race T, epidemic on corn (Zea mays L.) in 1970. Genetic diversity can be measured, to a degree, by coefficient of parentage (r) measurements based on pedigree analysis. The objectives of this study were to construct four pedigree schematics to represent the rice (Oryza sativa L.) cultivars released in the USA, determine the relative genetic contribution of ancestral lines, and examine the genetic trends, by location, that result from using specific germplasms in cultivar development of rice. An examination of the pedigrees of 140 rice accessions demonstrated that all of the parental germplasm can be traced to 22 plant introductions in the southern Rice Belt (Arkansas, Louisiana, Mississippi, Missouri, and Texas) and 23 plant introductions in the western Rice Belt (California). The genetic base of the southern breeding programs can be traced to 13 parental accessions in Arkansas, 12 in Texas, and 16 in Louisiana. Furthermore, 10 of the 12 and 13 parental accessions in the Texas and Arkansas breeding programs, respectively, are identical and 8 of the 13 and 16 accessions in the Arkansas and Louisiana breeding programs, respectively, are identical. An examination of r showed that among the long‐grain cultivars ‘Lebonnet’ and ‘Lemont’ have more than 72% of their genes in common and almost 90% of the genes are common in the medium grain cultivars, ‘Calrose’ and ‘Caloro.’ Furthermore, the r value between locations for long grain cultivars showed that ~24 and ~19% of the genes are common in the Arkansas and Texas and the Arkansas and Louisiana cultivars, respectively. These data show how closely related the current rice cultivars are that have been released in the USA.
Behavior of an Alien Telocentric Chromosome in Callus Culture of Wheat
Authors: Whelan Ernest D. P.
Published: July 2010

Tissue culture can cause changes in chromosome number and structure. An alien telocentric addition from Elytrigia intermedia subsp. barbulata (Schur.) A. Löve that confers purple aleurone pigment and blue seed color in common wheat (Triticum aestivum L.) was used as a phenotypic marker of the telocentric chromosome to investigate the behavior of that chromosome in primary regenerants from calli of immature wheat embryos cultured for various durations. Six embryos from a plant that was a ditelocentric addition yielded 155 primary regenerants with 507 heads. Twenty‐six (5.1%) heads segregated 58.5% white to 41.5% blue seeds, indicating that the heads were monotelocentric additions and that there had been telocentric loss. Similar culture of 15 F1 hybrid embryos that were monotelocentric additions yielded 424 plants with 858 heads. Seventeen (2.0%) heads produced only white seeds, i.e., telocentric loss, and seven (0.8%) heads only blue seeds, i.e., telocentric gain. The other 834 F1 hybrid heads segregated about 74% white to 26% blue seeds, a frequency clearly different from that of the nonhybrid monotelocentric additions. The overall frequency of heads showing changes involving the telocentric chromosome was 3.7% (based on examination of seed from 1365 heads of 579 primary regenerants extracted from calli of both sets of cultured embryos). The duration of culture had no obvious relationship with the frequency with which the alien telocentric chromosome was eliminated or added.
Shikimate Dehydrogenase‐12 Allozyme as a Marker for High Seed Protein Content in Rice
Authors: Shenoy V. V. , Seshu D. V. , Sachan J. K. S.
Published: July 2010

Recent studies at the International Rice Research Institute (IRRI) on the N‐assimilating isozymes in rice (Oryza sativa L.) showed that shikimate dehydrogenase high mobility allozyme (specified by the Sdh‐12 allele) was associated with higher protein accumulation. This study was conducted to verify such association in FI and F2 progenies derived from a cross involving parents differing in Sdh‐1 alleles and seed protein content, and to examine the influence of the Sdh‐12 allele on the Osborne's solubility fractions of total seed proteins. The female parent IR36 was characterized by the Sdh‐11 allele and low seed protein content, and the male parent IR480‐5‐9‐3‐3, by the Sdh‐12 allele and high seed protein content. The results indicated that the Sdli‐1 locus assorted in a monogenic mendelian fashion expressing codominance, while the seed protein content segregated in a polygenic manner. When F2 individuals were divided into three groups based on their Sdh‐1 allozyme pattern as determined by starch gel electrophoresis of seeds and tillers, the mean protein content per seed was highest (120.3 g kg−1 brown rice, BR) for Sdh‐12 homozygotes, intermediate (106.0 g kg− BR) for Sdh‐ll/Sdh‐12 heterozygotes, and lowest (91.9 g kg‐a BR) for Sdh‐11 homozygotes. Accumulation of the oryzenin fraction in the heterozygotes and Sdh‐12 homozygotes was significantly higher than in Sdh‐P homozygotes. Since oryzenin is the major component of seed storage proteins in rice, the Sdh‐12 allozyme can be an effective marker in screening for higher seed protein content among different cultivars or segregants from hybrid progenies.
Inheritance Studies and Clonal Fingerprinting with Isoenzymes in Sugarbeet
Authors: Aicher Lauri D. , Saunders Joseph W.
Published: July 2010

Isoenzyme studies are useful in expanding knowledge and application of crop genetics with regard to linkage relationships and the distribution of variation. This study was conducted within a limited sample of Beta vulgaris L. germplasm to explore leaf isoenzyme variability for use in clonal fingerprinting in addition to inheritance and linkage relationships. Horizontal starch gel electrophoresis employing either of two buffer systems was utilized, followed by multiple enzyme‐specific staining for eight enzymes. A diverse germplasm sample consisting of 31 clones of B. vulgaris (28 sugarbeet, one chard, one mangel, and one table beet) and one of B. lomatogona Fischer & C. Meyer, was zymogrammed. Both F1 and F2 progeny from several clones were evaluated for inheritance and linkage. Five previously unreported loci were identified (Mdh2, Mdh3, Mdh4, Mdh5, and Skdh1). An additional locus (Pgi1) is proposed; it had normal F1 but skewed F2 ratios explainable by linkage to the self‐compatibility locus. Loci Pgm1, Pgi1, and Mdh1 were found to segregate independently from each other and from the B (flowering habit) and R (basic betalain factor) loci. Evidence for two further loci, Me1 and Me2, also was obtained. Pollen possessed activity for only 4 of the 10 loci studied. The ability to distinguish clones on the basis of zymograms for seven enzyme systems was demonstrated. Enough variation was found in isoenzyme mobility to be useful in future sugarbeet genetic research.
Heterotic Patterns among Mexican Races of Maize
Authors: Crossa J. , Taba S. , Wellhausen E. J.
Published: July 2010

Collection and description of the maize (Zea mays L.) germplasm complexes of Mexico began in 1943, and efforts toward the potential utilization of the 25 recognized Mexican races were initiated in 1961. This study was conducted to determine the performance of the 25 Mexican races and 300 interracial crosses evaluated in three environments identified as high (2249 m), intermediate (1800 m), and low (1300 m) elevations. Data were analyzed with the Gardner‐Eberhart model, Analysis II. At the high elevation the races Cónico, Cónico Norteño, and Chalqueño had high mean yields per se and in crosses. Cacahuacintle and Maiz Dulce had equally high yield in crosses but had lower per se yield. At the intermediate elevation, the best yielding races in crosses and per se were Comiteco, Harinoso de Ocho, Celaya, Maiz Dulce, Tabloncillo, and Tuxpeno. At the low elevation, the highest per se yields were exhibited by Harinoso de Ocho, Celaya, Pepitilla, and Tabloncillo. Across all elevations, the best general combiners were Cacahuacintle, Harinoso de Ocho, and Maiz Dulce. Results of this study could be used to (i) introgress the heterotic patterns found among races into new commercial varieties or populations, (ii) search for race collections with better agronomic type that belong to the racial heterotic pattern, (iii) improve gene pools based on racial heterotic patterns and geographical origins, (iv) establish reciprocal recurrent selection between two races that exhibited heterosis when crossed, or (v) develop hybrids based on lines derived from the collections studied in each environment.