bluuebunny/crossref_metadata_2025 huggingface dataset:
Allocation of Photoassimilate by Main Shoots and Nonsurviving Tillers in Barley
Authors: El Alaoui Ali Chafai , Simmons Steve R. , Crookston R. Kent
Published: July 2010

Field‐grown barley (Hordeum vulgare L.) plants produce many tillers that do not survive to bear grain, especially under water‐stressed conditions. Such nonsurviving tillers have traditionally been regarded as wasteful of plant resources. To test this premise, a greenhouse study was conducted to evaluate the contribution of nonsurviving tillers to the C economy of a barley plant. The study quantified the reciprocal transfer of photoassimilate between the main shoot and nonsurviving tillers during the tillering phase of development under well‐watered and water‐deficient (stressed) conditions. Main shoots and two primary tillers (T1 and T2) were labeled by exposure to 14CO2. Radiocarbon export and retention by the labeled shoots were monitored at maturity. The radioactivity partitioning data were combined with changes in the dry mass of labeled shoots over the study period to estimate dry matter exchange between shoots. For nonstressed plants, 33% of the initially fixed radioactivity was lost prior to maturity, probably due to respiration. The percentage of radioactivity lost was higher under conditions of water stress. Nonsurviving tillers retained only 18% of their initially fixed radioactivity at maturity, regardless of watering regime. Under both well‐watered and later‐imposed water stress conditions, the calculated dry matter exchange between shoots showed that nonsurviving T1 tillers returned twice as much dry matter to the main shoot as was provided to them by the main shoot. Tiller T2 also exported more than it imported but less than T1. When water stress was imposed early, tillers allocated slightly less assimilate to the main shoot than they received. We conclude that nonsurviving tillers may contribute more dry matter to surviving shoots than has previously been recognized.
Adventitious Shoot Formation from Mature Leaf Explants of Arachis Species
Authors: Dunbar Kerry B. , Pittman Roy N.
Published: July 2010

Adventitious shoot formation has important applications in genetic transformation, vegetative propagation, and germplasm storage. This investigation was conducted to evaluate the effect of light intensity, explant age, gelling agent, phytohormone, and genotype on adventitious shoot formation from mature leaf explants of Arachis species. Mature leaf explants of 13 Arachis species were cultured for 30 d on a medium with Murashige and Skoog (MS) salts, Gamborg B5 vitamins (B5), 30 g L−1 sucrose, 5 μM α‐naphthaleneacetic acid (NAA) 5 μM 6‐benzylaminopurine (BAP), and solidified with 8 g L−1 agar. After tissue from these cultures was transferred to medium with reduced auxin, shoots or shoot buds were regenerated from the cultures of A. burkartii Handro, A. lignosa nom. nud. Krap. & Greg., A. paraguariensis Chod. & Hassl., A. repens Handro, A. rigonii Krap. & Greg., A. tuberosa Benth., A. villosa Benth., and A. villosulicarpa Hoehne. Changing the gelling agent in the regeneration medium from agar to rice (Oryza sativa L.) starch produced a threefold increase in the number of shoot buds produced from leaf explants of A. villosulicarpa. Mature leaf explants of A. villosulicarpa produced an average of 50 shoots and buds after 25 d in culture at 25 °C, with a 16‐h photoperiod of 100 μmol m−2 s−1, on a medium with MS salts, B5 vitamins, 5 μM NAA and 5 μM BAP, and solidified with 120 g L−1 rice starch. The high rate of shoot regeneration observed from mature leaf explants of A. villosulicarpa may allow it to be a model to test factors affecting adventitious shoot formation from Arachis species.
Interspecific Hybrid Fiber Characteristics of Cotton Altered by Unconventional Gossypium barbadense L. Fiber Genotypes
Authors: Percy Richard G. , Turcotte Edgar L.
Published: July 2010

Although fiber traits of interspecific hybrids of cotton (Gossypium hirsutum L. × G. barbadense L.) have been manipulated through choice of parent cultivar, the potential range of fiber trait expression in hybrids remains unclear due to limited trait variation in improved G. barbadense germplasm. This study was conducted to determine the effects of unconventional G. barbadense fiber genotypes on hybrid fiber. A second goal was to alter the fiber of interspecific hybrids from a fiber resembling an extra‐long staple (35 mm) cotton to a fiber possessing long staple (30 mm), Acala‐type parameters. Four G. barbadense strains bred for extremely short, coarse fiber and the cultivar Pima S‐6 were crossed to four G. hirsutum cultivars to produce 20 hybrid populations. In four tests of parent and hybrid populations conducted at three locations, parent contribution to hybrid fiber length, uniformity, strength, elongation, micronaire reading, and yarn strength were apparent. Linear regressions of hybrid on G. barbadense parent fiber traits produced an R2 of 0.95 for 2.5% span length and an R2 of 0.52 for micronaire reading. A 0.3‐mm change in hybrid length was estimated for every increase or decrease of 1 mm in the parental fiber. Estimated change in hybrid micronaire was 0.03 units for every 0.1 unit of change in parent micronaire. Heterotic effects in hybrids exceeded responses due to parent contribution and opposed the direction of selection practiced within the G. barbadense parents. Hybrid fiber resulting from the use of short, coarse‐fibered G. barbadense genotypes was unique, fitting neither the long staple or extra‐long staple classifications.
Selection for Barley Yellow Dwarf Virus Tolerance in F2 Oat Populations in the Greenhouse
Authors: Gourmet Catherine , Kolb Frederic L. , Hewings Adrianna D. , Brown Charles M.
Published: July 2010

Barley yellow dwarf (BYD) is an important viral disease that reduces grain yield in small grains. Breeders usually do not screen for barley yellow dwarf virus (BYDV) tolerance prior to selection of homozygous lines from segregating populations. If early generations of segregating populations could be screened in the greenhouse to increase the frequency of BYDV‐tolerant genotypes, the overall efficiency of selection would be improved. The objective was to determine if selection for BYDV tolerance in four F2 populations of spring oat (Avena sativa L.), which resulted from crosses of tolerant × tolerant parents and sensitive × tolerant parents, is effective in increasing the frequency of tolerant genotypes in the F4. F2 populations grown in the greenhouse were infested with viruliferous oat‐bird cherry aphids (Rhopalosiphum padi L.) that had been reared on plants infected with the BYDV PAV‐IL isolate. Response to selection was evaluated in the F4 in the field using the same PAV‐IL isolate. Selection in the F2 generation was moderately effective in increasing the frequency of tolerant genotypes in the sensitive × tolerant crosses, but was not effective in changing the mean BYDV tolerance in tolerant × tolerant populations. Heritability estimates calculated in 1990 and 1991 were high (0.5–0.8 and 0.8–0.9, respectively) and confirm that selection based on inoculated hills in the field should be effective in eliminating sensitive genotypes.
Selection Among S1 Families Vs. Selfed Half‐Sib or Full‐Sib Families in Autogamous Crops
Authors: Burton Joe W. , Carver Brett F.
Published: July 2010

In autogamous craps, half‐ and full‐sib families are rautinely generated in various systems of intermating. Usually, these families have not been used as units of selection, due to low expected gains relative to other selection units (e.g., S1 families). The use of selfed half‐ (SHS) or full‐sib (SFS) families, and differences in phenotypic variance between these and S1 families, might reduce the difference in expected gains between the selection methods. Our primary objective was to predict the expected gain fram selection on each family unit, based on a genetic model with additive and homozygous dominance effects. A second objective was to empirically estimate phenotypic variances among SHS, SFS, and S1 families derived fram random‐mating populations of wheat (Triticum aestirum L.) and soybean [Glycine max (L.) Merr.], and use those estimates to compare expected gains. Estimates of phenotypic variance for yield of SFS wheat families (O2SFS) were small compared with estimates for S1 families (O2S1) due to smaller error variances. Phenotypic variances of SHS soybean families (O2SHS) tended to be smaller than those of S1 families for seed yield and size but not for seed pratein and oil concentrations. As with the wheat populations, error variances tended to be smaller for SHS families. The expected relative efficiencies of S1 family selection vs. SFS or SHS family selection are 1.14 (σSFS/σS1) in wheat and 2.29 (σSHS/σS1) soybean. Substituting phenotypic standard deviations into each formula resulted in no consistent advantage to using S1 family selection with the exception of seed pratein and oil in soybean. In conclusion, election among SHS or SFS families should be of greatest benefit for productivity traits that require larger seed quantifies for testing. These selection units allow larger plot sizes and/or increased replications, thereby impraving the precision of entry‐mcan estimates and reducing phenotypic variance.
Selection for Yield and Stability among Oat Lines
Authors: Helms Theodore C.
Published: July 2010

Methods to simultaneously select for yield and stability need to be compared to determine which index is the best choice to identify high‐yielding, stable genotypes. A comparison of the repeatability of different measures of stability would be useful because stability statistics with high repeatability should be superior to identify stable genotypes. Stability measures were evaluated for 116 oat (Avena sativa L.) lines in 36 Iowa environments. The objectives were (i) to evaluate the mean selection differential when selection was for yield, stability statistics, or simultaneous selection for both yield and stability, using different indices; (ii) to compare repeatability of the stability regression (b1) stability variance component (σ21), and deviation from regression mean square (sd21) across random subsets of 18 environments; and (iii) estimate rank correlations between stability statistics and mean grain yield, in all environments. Simultaneous selection for yield and stability, based on three indices, identified high‐yielding, stable genotypes. Selection solely for yield identified genotypes with high mean yield that on average were not stable. Selection solely for each stability measure identified genotypes with low yield that were stable. The repeatability of b1 was 0.61, and the index that used this measure of stability combined with selection for yield identified 12 genotypes that yielded 3% less than the average of the highest yielding 12 genotypes. Repeatability of σ21 was 0.28 and repeatability of σ21 was 0.17. The correlation between yield and b1 was 0.73, between yield and σ21 was 0.21, and between yield and σ21 was 0.28.
Genetic Variability for Nutritional Composition and Cooking Time of Improved Cowpea Lines
Authors: Nielsen S. Suzanne , Brandt Wendy E. , Singh Bir B.
Published: July 2010

Cowpea, Vigna unguiculata (L.) Walp., is a major source of dietary protein in sub‐Sahara Africa, Asia, and Latin America. Current breeding objectives are disease and insect resistance and high yield potential, but efforts are being made to initiate a selection program to improve protein content and cooking quality. This study was undertaken to estimate variability for protein content and cooking quality in 100 improved cowpea breeding lines grown in the field at Ibadan, Nigeria in 1986. Moisture, protein, fat, and ash content were determined by standard methods. Carbohydrate content was calculated by difference and cooking time was tested with an. automated Mattson‐type bean cooker. Genetic variability was observed for all traits. The values, on a dry weight basis, ranged from 22.9 to 32.5% for protein, 2.9 to 3.9% for ash, 1.4 to 2.7% for fat, 59.7 to 71.6% for carbohydrate, and 21.1 to 61.9 minutes for 50% cooking time. The breeding line IT83S‐872 had the highest protein content, 1T85F‐2805 and IT8SF‐ 1380 had the highest fat content, IT84S‐2085 and IT86D‐466 had the highest ash content, IT86D‐463‐1 had the lowest carbohydrate, and IT85F‐2805 had the shortest cooking time. Protein content was positively correlated with ash content, but negatively correlated with fat and carbohydrate contents. Carbohydrate content was negatively correlated with ash content. Small seed size and rough seed coat were associated with shorter cooking time. Results indicated significant genetic variability for protein content and cooking time, which can be exploited in a breeding program to develop nutritionally superior and acceptable cowpea cultivars.
Senescence Parameters of Organs Constituting the Panicle, First Internode, and Flag Leaf in Rice
Authors: Sasahara Takeo , Satoh Suguru , Odaka Katsunori , Abe Toshinori
Published: July 2010

Long‐lived rice (Oryza sativa L.) panicles with high physiological activities are important for maintaining translocation of assimilates and nutrients. We studied senescence parameters, N concentration, and rate of N loss from panicles, first internodes, and flag leaves from flowering until maturity. In 1988, 76 rice cultivars were started indoors in pots and grown outdoors in paddies under standard fertilization (94.5 kg N ha−1). In 1989, six cultivars were grown under 94.5, 154.5, and 214.5 kg N ha−1. The rate of Kjeldahl N loss from organs was estimated from Y = ABx, where Y is N concentration at ✕ d after flowering, and A is N concentration at flowering. The regression coefficient B (fraction of N retained after unit time) was significantly different from zero in all cultivars and organs in both years. The N concentration at flowering was highest in flag leaves, intermediate in rachis and rachis branches, and lowest in hulls; among cultivars, it varied largely in the first internodes. Conversely, the rate of N loss, calculated as A (1 − B), was lowest in flag leaves, intermediate in rachis and rachis branches, and highest in hulls. Fertilizer application increased N concentration at flowering, but showed little effect on the rate of N loss. The rate of N loss exhibits cultivar specificity. It seems likely that fertilizer application can change the N level of panicles and organs only at initiation of grain filling. Although there are positive correlations between the two parameters in hulls, rachis, and rachis branches, cultivars with panicles exhibiting high initial N concentration in combination with a cultivar‐specific low rate of N loss may be developed through breeding.
Evaluation of Leaf Rust Resistance from Wheat Chromosomal Translocation Lines
Authors: Dyck P. L. , Friebe B.
Published: July 2010

The genetic pool of effective sources of rust resistance used in wheat (Triticum aestivum L.) breeding includes related species. As part of a search for new sources of resistance, a group of radiation‐induced rust‐resistant wheat Agropyron intermedium [(Host) P.B.] derivatives originally developed by A. Wienhues were investigated. Resistance to leaf rust [Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Eriks. & E. Henn) D.M. Henderson] was transferred to the spring wheat cultivar Thatcher. The inheritance of leaf‐rust resistance was studied in F3 lines developed from the fifth backcross to Thatcher. A number of backcross lines with different types of resistance were selected and evaluated for rust reaction in greenhouse and field tests. RL6097 had gene Lr38 present in wheat A. intermedium T6DS‐6DL‐7Ai#2L chromosome translocation (where a 4.19‐μm segment of the long arm of A. intermedium chromosome 7Ai#2 replaced a 1.45‐μm segment of the long arm of wheat chromosome 6D) derived from translocation line T7 as identified by C‐banding. The male transmission rate of this translocation was reduced. Although this line was highly resistant to leaf rust, its grain yield was low. None of the other backcross lines had A. intermedium chromatin. RL6093 had an unidentified gene for leaf rust resistance from addition line T2. Two genes, Lr3bg (RL6094) and Lr16 (RL6096), were obtained from T6. Adult‐plant resistance to leaf rust was also transferred from several of the translocation lines. This resistance may be different from that previously reported, and may have originated from the translocation lines' donor parent ‘Heine FV’. Of the genes found, Lr38 may not be useful in wheat breeding because of the reduced yield of RL6097; however, the gene for seedling resistance in RL6093 and the adult‐plant resistance in RL6095 should be useful.
Effect of Years and Planting Dates on Fatty Acid Composition of Soybean Genotypes
Authors: Schnebly S. R. , Fehr W. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] genotypes with modified fatty acid composition in the seed oil are being considered for commercial production. The stability of fatty acid composition across a range of environmental conditions will be an important factor for end users of the new soybean oils. The objective of this study was to evaluate the influence of years and planting dates on the fatty acid composition of soybean genotypes with elevated palmitic acid, elevated stearic acid, or reduced linolenic acid. Ten soybean lines with modified fatty acid composition and two common cultivars were grown in 1988, 1989, and 1990 at the Iowa State University Agricultural Engineering and Agronomy Research Center near Ames. Planting dates were 2 May, 16 May, 30 May, and 13 June. For the genotype with elevated palmitic acid, A21, there were significant differences among years, but the maximum difference was only 10 g kg−1. Effects of planting dates were not significantly different for the palmitic acid content of A21. For the genotype with elevated stearic acid, A6, differences among years, planting dates within individual years, and years × planting dates interaction were significant, but the effect of planting dates averaged across years was not significant. Differences among years were significant for the linolenic acid content of most genotypes; however, the maximum difference among years was only 3 g kg−1 for genotypes with an average of <25 g kg−1 linolenic acid. Early planting dates favored lower linolenic acid content, but the maximum difference between 2 May and 13 June for any genotype with <25 g kg−1 linolenic acid was only 4 g kg−1. Average daily high temperature during the seed‐filling period did not consistently explain the differences in fatty acid content among planting dates or years. Our data indicated that different planting dates could not be used as a substitute for years in determining environmental stability of fatty acid composition.
Selection for Gluten Strength in Three.Durum Wheat Crosses
Authors: Clarke J. M. , Howes N. K. , McLeod J. G. , DePauw R. M.
Published: July 2010

Strong gluten in durum (Triticum turgidum L. var durum) semolina is desirable for manufacture of pasta, so estimates of gluten strength are used as selection criteria in breeding programs. Gliadin band 45 (gli 45) is associated with high gluten strength, while band 42 (gli 42) is associated with weaker gluten. Our objective was to compare prediction Of gluten strength in early generations by means of the sodium dodecyl sulphate (SDS) sedimentation test with the method using giladin electrophoresis banding pattern. The methods assist in elimination of undesirable lines, thereby reducing the cost of testing for yield and other traits. Three single crosses were made among four parents, one of which (‘Wascana’) carries the allele for gli 42, while the others carry the g!i 45 allele. Spaced F2 plants were grown in the field in !990, and F2‐derived F4 lines were grown in 1991 on an Aridic HapIoborall soil. Gluten strength was predicted by SDS sedimentation, and gliadin bands were identified by a monoclonal antibody (MAb) on seed from single F2 plants. The SDS sedimentation test was repeated on seed harvested from F4 lines, and efficacy of the two methods was compared. Heritability of SDS sedimentation ranged from 0.57 to 0.68 for the three crosses. Elimination of F2 lines carrying gli 42 reduced the population size by up to 44%, and increased (P < 0.01) mean sedimentation of the F4 by 0.3 to 0.6 cm compared with the unselected populations. Retention of lines homozygous for glie 45 further increased (P < 0.01) F4 sedimentation, and was not different from selection for F2 sedimentation at an intensity of 20%. The MAb test is faster and less costly than the SDS‐sedimentation test. We recommend the MAb test for initial screening, followed by the SDSsedimentation test on selected F2 plants.
Comparison of Components of Resistance in Peanut to Late Leafspot in Different Environments
Authors: Chiyembekeza A. J. , Knauft D. A. , Gorbet D. W.
Published: July 2010

Little is known about the consistency of the resistance reaction of peanut (Arachis hypogaea L.) genotypes to late leafspot (Mycosphaerella berkeleyi Jenk.) in varied environments. This study was conducted to determine resistance reactions of peanut genotypes in two disparate environments. Four peanut lines with known levels of resistance to late leafspot in Florida were used to create 12 cross combinations. Parents and segregating generations from these crosses were grown at Gainesville, FL, and Kasinthula and Chitala, Malawi and inoculated with late leafspot. Latent period (LP), lesion diameter (LD), and amount of spomlation (SP) were evaluated. Measurements of the components at Gainesville were significantly correlated with those at Malawi. The correlations between locations for each component were LP, r = 0.52; LD, r = 0.64; and SP, r = 0.64. In both locations LP was negatively correlated with LD ( r = ‐0.55) and SP ( r = ×0.63); LD and SP were positively correlated ( r = 0.44). Narrow‐sense heritability estimates were similar at Gainesville and Malawi. Based on parent‐offspring regression, heritabilities averaged 0.62 for LP, 0.55 for LD, and 0.42 for SP. Realized heritability estimates in Malawi were 0.69 for LP, 0.63 for LD, and 0.51 for SP.
Germination Inhibition of Alfalfa by Two‐Component Salt Mixtures
Authors: Rumbaugh M. D. , Johnson D. A. , Pendery B. M.
Published: July 2010

Soil and water salinity can severely constrain agricultural production by reducing plant stands and growth. Breeders have used germination in saline (NaCI) media to screen plant germplasm for salt tolerance. However, salt tolerance during germination in NaCI may not adequately describe the ability of seeds to germinate in mixtures of salts. Naturally occurring combinations of salts may be more or less inhibitory than the individual salts alone. The objective of this research was to quantify the effects of individual as well as two‐component mixtures of various salts and ions on the seed germination of alfalfa (Medicago saliva L.). Seeds of the alfalfa cultivars Condor and Rambler were germinated in petri plates in a darkened growth chamber maintained at 25 °C and exposed to biologically equivalent concentrations of one‐ and two‐salt solutions of NaCI, Na2SO4, KCI, K2SO4, MgCl2, and MgSO4. Specific interaction effects of the salts in two‐salt combinations were detected; however, as indicated by simple correlations, germination was affected more by concentration of Na+ than any other single variable. When all independent variables were considered, concentrations of Cl− and Mg2+ were more important than Na+ and the other ions, choice of cultivar, or the osmotic tension and pH of the solutions. While maximum genetic gain in salt tolerance during germination of alfalfa seeds may only be achieved by selection in solutions containing more than one salt, selection in NaCI solutions may account for most of the potential gain.
Growth of White Clover Clones in Monoculture and Contrasting Bermudagrass Swards
Authors: Brink G. E. , Rowe D. E.
Published: July 2010

Spaced‐plant arrangements provide a means of evaluating white clover (Trifolium repens L.) germplasm for a range of characteristics. Growth of spaced white clover plants in monoculture, however, may not be related to growth with grasses. Our objective was to determine the relationships among various growth parameters of white clover grown as spaced plants in monoculture and with contrasting grass swards. Vegetative clones of 47 plants of Southern Regional Virus Resistant white clover germplasm were planted on 1‐m centers in previously established common or hybrid (‘Tifton 44’) bermudagrass (Cynodon dactylon (L). Pers.) swards, in monoculture in a Catalpa silty clay soil (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) in the fall of 1988. Growth of each clone was measured in the spring and fall of 1989, and in the spring of 1990 and 1991. At each sampling, clover dry matter (DM) yield, plant spread, and stolon branching were lower for clones grown with common bermudagrass than with hybrid bermudagrass or in monoculture. Growth of clones with hybrid bermudagrass was intermediate to growth with common bermudagrass and in monoculture, presumably because of the density of aboveground competition from hybrid compared to common bermudagrass (260 vs. 470 g DM m−l2; 5‐cm stubble). Correlations between clover yield and stolon branching, and clover yield and plant spread were greatest for clones grown with common bermudagrass (0.42 and 0.85, respectively). Stolon branching of clones in monoculture was not correlated with stolon branching in either bermudagrass. The influence of the grass on stolon branching and the relationship of branching to persistence suggest the necessity of evaluating white dover germplasm in association with grasses.
Relationship to Maize Seedling Responsee to Lysine‐Plus‐Threonine Medium and Whole Kernel Amino Acid Profile
Authors: Muenchrath D. A. , Phillips R. L.
Published: July 2010

Maize (Zea mays L.) kernels are nutritionally deficient in the amino acids lysine, tryptophan, and methionine. Exogenous lysine‐plus‐threonine (LT) synergistically inhibits root growth of geminating kernels. We tested the hypothesis that the relative growth of seedlings grown on LT‐supplemented and unsupplemented media (LT response) is a function of the relative concentrations of kernel methionine and lysine. Thirty‐three genotypes were evaluated for LT response and amino acid composition. The correlation between LT response and the methionine to lysine ratio (M/L) was highly significant (r = 0.59). The root‐growth bioassay effectively detects kernels with altered amino acid concentrations.
Interrelationship of Plant Architecture and Yield Components in the Pinto Bean Ideotype
Authors: Brothers M. E. , Kelley J. D.
Published: July 2010

Ideotype breeding in common bean (Phaseolus vulgaris L.) has emphasized the selection of modified morphological traits that include upright, Type II (indeterminate) growth habit. Progress in the medium‐seeded (⊄40 g/100 seed) pinto bean appeared to have been limited by negative linkages between small seed size (⊄20 g/100 seed) and desired architectural traits. The objectives of this study were to determine the inheritance of seed weight and plant architecture, evaluate the genetic relationships among both traits, and to define a pinto bean ideotype for the humid midwestern USA. The genetic associations among three specific architectural traits, seed weight, and upright plant architecture were investigated in F2 and F2:3 generations at E. Lansing, MI, in 1990 and 1991, respectively. Upright plant architecture was estimated to be moderately heritable with narrow‐sense estimates ranging from HNS = 0.42 to 0.62. F2 data from 1206 individuals indicated that plant architecture and seed weight are not linked (r = 0.05, P = 0.08). Directional selection for high (>30 g/100 seed) or low (<24 g/100 seed) seed weight resulted in significant differences in the average number of seeds per pod and the average number of seeds per plant. These directional selection results provide evidence that a pinto bean ideotype will differ from the small‐seeded navy bean ideotype by having fewer pods per plant and fewer seeds per pod. Selection for medium‐seeded, upright (Type II) genotypes in other commercial classes would be greatly facilitated through the use of the pinto bean ideotype as a genetic bridge.
Highland Maize from Central Mexico—Its Origin, Characteristics, and Use in Breeding Programs
Authors: Eagles H. A. , Lothrop J. E.
Published: July 2010

The races of maize (Zea mays L.) which are cultivated in the highlands of central Mexico at altitudes above 2000 m include Palomero Toluqueño, Cónico, Arrocillo Amarillo, Chalqueño, and Cacahuacintle. This complex of races is of ancient origin and has a distinct plant morphology, karyotype, and isozyme frequency compared to other types of maize except, possibly, some races from the highlands of Guatemala. It is adapted to cool areas with mean growing season temperatures between about 12.5 and 17.0 °C and is superior to maize from temperate, mid‐altitude tropical, and lowland tropical regions for seedling emergence, photosynthetically‐based growth, and ability to continue grain filling at low temperatures. It also has better frost and hail tolerance, but is poorly adapted to high temperatures. It can emerge from sowing as deep as 0.25 m, and is resistant to rust caused by Puccinia sorghi Schw. With the support of the Mexican government, hybrids and improved open‐pollinated cultivars have been derived from these races. CIMMYT is conducting a breeding program based on these races for tropical highlands worldwide, but with the inclusion of other germplasm to improve grain yield and agronomic traits, especially resistance to lodging. These programs have shown excellent prospects for improving grain yield and agronomic traits in highland tropical environments. Research from New Zealand suggests that this germplasm resource has potential for raising grain yields in cool, temperate environments.
Yield, Yield Components, and Fiber Properties of Insect‐Resistant Cotton Lines Containing a Bacillus thuringiensis Toxin Gene
Authors: Wilson F. Douglas , Flint Hollis M. , Deaton W. Randy , Buehler Robert E.
Published: July 2010

Crop yield and quality could be affected in transgenic crop plants carrying foreign genes which confer resistance to plant pests. Scientists at Monsanto Company produced nine transgenic cotton (Gossypium hirsutum L.) lines, each containing one of the two Bacillus thuringiensis var. kurstaki (Berliner) constructs, cryIA(b) or cryIA(c), that encode a protein toxic to lepidopteran insects. We undertook this study to determine whether these transgenic lines exhibit any undesirable agronomic or fiber properties. At Maricopa, AZ, we grew five, four, and three transgenic lines in field plots in 1990, 1991, and 1992, respectively; the parental ‘Coker 312’ and the locally adapted, nectariless, high fiber‐strength ‘Md 51 ne’ were included each year. Somaclonal variation, insertion of the insect‐control protein genes, and the expression of the insecticidal protein caused no general reduction in lint yield, primary or secondary yield components, or fiber properties. The transgenic lines varied significantly in every trait measured. Mean lint yields over the 3 yr were as follows: transgenic lines, 135.4 ± 4.5 g m−2; Coker 312, 115.1 ± 7.7 g m−2, MD 51 ne, 141.2 ± 11.4 g m−2. Six of the nine transgenic lines yielded significantly more lint (13–30%) than did Coker 312. Lint yields of the same six lines (10% less to 7% more) were not significantly different than that of MD 51 ne. Compared with Coker 312, four of nine transgenic lines had longer fiber, eight had stronger fiber, two had higher fiber elongation, and two did not differ significantly in micronaire. Compared with MD 51 ne, five of the nine transgenic lines did not differ significantly in fiber length, two did not differ in strength, three did not differ in elongation, and six did not differ in micronaire. These transgenic lines are valuable sources of germplasm, not only for insect resistance but also for agronomic and fiber properties.
Analysis of Cytoplasmic Diversity in an Outcrossing Population of Soybean
Authors: Lee Donald J. , Caha Carol A. , Specht James E. , Graef George L.
Published: July 2010

The maintenance of genetic variation is a critical consideration in the derivation of plant populations for use in recurrent selection or cultivar development. This study~was conducted to determine the number of distinct cytoplasmic genotypes contributed by female parents of a soybean [Glycine max, (L.) Merr.] population and the effect of continuous cycles of forced outcrossing on the maintenance of this cytoplasmic variability. This population was derived by crossing 39 female lines with four male‐sterile (Ms2ms2) maintainer lines and advancing each generation by selecting only outcrossed seed borne on male‐sterile plants. Restriction fragment length polymorphisms (RFLPs) were used to assess chloroplast DNA (cpDNA) and mitochondrial DNA (mtDNA) variation. The 39 female lines were classified into six cytoplasmic groups based on cpDNA and mtDNA RFLPs. The combinations of cpDNA and mtDNA polymorphisms observed in these lines suggest a possible maternal lineage of G. max. Analysis of randomly sampled individuals from the population after one, three, five, and seven cycles of outcrossing revealed a gradual loss of cytoplasmic diversity in the population. Four of the six cytoplasmic groups were observed among 199 individuals sampled from the population after one outcrossing cycle, while only two of these cytoplasmic groups remained among the 135 individuals sampled from Cycle 7. The lack of reproductive success among plants with four of the six cytoplasmic genotypes has consequently reduced the cytoplasmic variability in this outcrossing population.
Alleviation of Salinity Stress in Kentucky Bluegrass by Plant Growth Regulators and Iron
Authors: Nabati D. A. , Schmidt R. E. , Parrish D. J.
Published: July 2010

In many areas, nonpotable water is relegated for turfgrass irrigation. This research is conducted to determine if exogenous applications of selected substances to turfgrass could reduce the effects of saline irrigation. Field and greenhouse experiments investigated the effect of seaweed extracts, triazole fungicides, and Fe on Kentucky bluegrass (Poa pratensis L. cv. Plush) grown under various levels of salinity. In Exp. 1, Kentucky bluegrass was treated with a proprietary seaweed extract (SE) at 38 L ha−1, propiconazole [1‐{2‐(2,4‐dichlorophenyl)‐4‐propyl‐1,3‐dioxolan‐2yl}methyl ‐1‐H‐1,2,4‐triazole] (PPC) at 1.8 L active ingredient (a.i.) ha−1, and chelated Fe (Na‐diethylene‐triamine‐pentaacetate‐chelated Fe) at 4.7 kg a.i. ha−1. In Exp. 2, treatments included SE at 56 L ha−1, and chelated Fe at 2.2 kg a.i. ha−1. Two weeks after treatment in both experiments, plugs taken from field plots were transplanted into 4‐L metal containers. The transplanted plugs were watered with 0, 0.15, or 0.3 S m−1 NaCl solutions for 7 wk. As salinity increased, leaf water stress increased, and clipping dry weight and rooting decreased. All treatments, except Fe, enhanced growth under 0.15 S m−1 salinity water. Under the higher salinity, PPC enhanced foliage weight, and all treatments, except Fe, stimulated rooting. Propiconazole‐treated plants had the strongest root system under the higher salinity. In Exp. 2, CPC was the most active chemical in enhancing rooting. Result indicate that selected materials have potential use for Kentucky bluegrass production in saline environments.
A Comparison of Two Genes for Sulfonylurea Herbicide Resistance in Transgenic Tobacco Seedlings
Authors: Brandle J. E. , Morrison M. J. , Hattori J. , Miki B. L.
Published: July 2010

Previous work in tobacco (Nicotiana tabacum L.) showed the csr1‐1 gene for sulfonylurea resistance was inadequate for use in conjunction with a new, low residual sulfonylurea herbicide, DPX‐R9674 {a mixture of (methyl 2[[[[N‐4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)methylamino]‐carbonyl]amino]sulfonyl) benzoate) and (methyl 1‐3‐[[[[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)amino] carbonyl]amino]sulfonyl]‐2‐thiophenecarboxylate}. This study compared a new sulfonylurea resistance gene, ahas3r, with csr1‐1 in order to determine if ahas3r confers superior resistance to DPX‐R9674. The genetic material used in the study consisted of transgenic tobacco seedlings carrying either one of the two genes alone or both genes together. These genotypes were compared with each other and untransformed controls using acetohydroxyacid synthase (AHAS) assays and contrast comparisons of absolute growth rates of tobacco seedlings 10 and 20 d following herbicide application. Both the AHAS assays and the growth analyses of tobacco seedlings showed the genes to confer similar levels of resistance to chlorsulfuron {2‐chloro‐N‐[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐yl)aminocarbonyl] benzenesulfonamide}. However, the ahas3r gene clearly conferred a greater degree of resistance to DPX‐R9674 than the csr1‐1 gene and may therefore be a good candidate for use with this herbicide.
Genetic Diversity of Tall Fescue Germplasm Based on RFLPs
Authors: Xu W. W. , Sleper David A. , Krause Gary F.
Published: July 2010

The amount of genetic variation among and within tall fescue (Festuca arundinacea Schreb.) cultivars is an interest of geneticists and breeders. However, limited information is available on this. The objective of this study was to investigate the genetic diversity of tall fescue germplasm based on RFLP data. Twenty‐four probes from a tall fescue PstI‐genomic library were hybridized to EcoRI‐ or HindIII‐digested genomic DNA from nine turf and seven forage cultivars. Twenty plants per cultivar were individually analyzed. Results showed variation within cultivars was high, varied among cultivars and probes, and increased with the number of parental clones (PN) up to 10 and then plateaued, indicating additional genetic variation could not be detected in cultivars with more than 10 parents. The number of bands was significantly different among cultivars and related to the within‐cultivar genetic diversity, but not to the PN. Probes not hybridizing to the P genome detected less variation. Genetic distances calculated from 4,8,12,16, and 20 plants were similar within cultivars, implying full random mating in tall fescue cultivar development. The between‐cultivar genetic distances, however, decreased in larger sample sizes and became consistent when sample size reached 16 plants. Results suggested 16 randomly chosen plants was the minimum number to maintain adequate genetic diversity in these tall fescue cultivars. The associations of the 16 cultivars from cluster analysis agreed with available pedigree information. Turf cultivars tended to be clustered while forage cultivars were more divergent.
Evaluation of Cateto Maize Accessions for Grain Yield and Physical Grain Quality Traits
Authors: Hameed Abdul , Pollak Linda M. , Hinz Paul N.
Published: July 2010

Because many exotic corn (Zea mays L.) races have different evolutionary histories from those of U.S. races, they may possess unique, favorable alleles for physical grain quality traits. This study explored the effectiveness of using exotic inbreds from Uruguay, Argentina, South Africa, and Taiwan (representing ‘Cateto’‐type, intermediate, and non‐Cateto races) to improve physical grain quality of U.S. Corn Belt hybrids. Eighteen exotic inbreds were crossed to two Corn Belt inbreds, Mo17 and B73, which represent the ‘Lancaster Sure Crop’ and the ‘Iowa Stiff Stalk Synthetic’ backgrounds, respectively. A randomized complete block design was used to evaluate testcrosses (F1s), their F2 and backcross (to the Corn Belt inbreds) generations, and four checks grown at two locations in Iowa and at one location in Missouri. The experiment showed significant differences among races for 1000‐kernel weight, test weight, grain yield, and harvest moisture content. Testcrosses and generations were significantly different for kernel weight, test weight, breakage susceptibility, grain yield, and harvest moisture content. Significant differences were also found between testers for all traits except moisture. Entry × tester interaction, however, was significant only for breakage susceptibility and yield, whereas entry × generation interaction was significant for all the traits except breakage susceptibility. This study showed that Catetotype inbreds have the potential to improve test weight of Corn Belt hybrids. The Cateto race inbreds also contributed favorable alleles for lowering harvest moisture content, which may indirectly help reduce breakage losses.
Susceptibility of Hard Red Spring Wheats to Common Root Rot
Authors: Stack Robert W.
Published: July 2010

Common root rot caused by Cochliobolus sativus (Ito et Kurib) Drechs. ex Dastur causes substantial loss in spring wheat (Triticum aestivum L.) in the northern USA and Canada. This study was done to test hard red spring wheat cultivars and lines for susceptibility to common root rot. Spring wheat genotypes were planted in Fargo, ND, in eight field experiments from 1977 to 1990 on a Fargo silty clay (Vertic Haplaquoll). Genotypes exhibited a continuous range of response from susceptible to moderately resistant but none were entirely free from disease. Eight genotypes equalled or exceeded the level of resistance of ‘Thatcher’, long considered the standard for a high level of resistance to this disease.
Relationship of Wheat Seed Sprouting Severity, Planting Depth, and Seed Treatment to Emergence and Yield
Authors: Chastain T. G. , Klepper B. L. , Wilkins D. E.
Published: July 2010

Negative effects of preharvest sprouting on wheat (Triticum aestivum L.) baking quality are well known, but limited information is available on field performance of sprouted seed and plants grown from sprouted seed. Field trials were seeded with ‘Stephens’ soft white winter wheat in 1989 and 1990 near Pendleton, OR, to determine the effects of sprouting severity (Trials 1 and 2), and seeding depth, and fungicide seed treatment (Trials 3 and 4) on emergence, growth, development, and yield of plants from sprouted seed. A sprouting‐severity score was developed as follows: A = no visible sprouting, B = partial embryo exposure, C = full embryo exposure, and D = physically damaged embryo. Emergence and early crop growth were not affected when sprouting was not visible (A), but were significantly reduced when embryos were fully exposed (C) or damaged (D). Emergence and early seedling growth were reduced in proportion to sprouting severity of the seed. Carboxin + thiram [5,6‐dihydro‐2‐methyl‐N‐phenyl‐ l,4‐oxathiin‐carboxamide + bis(dimethylthiocarbamoyl)di‐sulfide] seed treatment had negative effects on stands produced from sprouted seed with fully exposed embryos, but these results were not consistent from year to year. Grain yield of plants grown from sprouted seed was not different from that of normal seed except when embryos were damaged (D). In seeding depth and seed treatment experiments, sprouted seed produced poorer stands and early growth than normal seed only in Trial 3. Treating sprouted seed with carboxin + thiram further reduced stands and growth in Trial 3. Sprouting did not affect seedling emergence and vigor in Trial 4 probably because the seed was less severely sprouted. Grain yield of plants produced from sprouted seed was not influenced by seed treatment in Trials 3 and 4. Shallow seedings produced better stands and yield than deep seedings, regardless of seed quality. The sprouting‐severity score has potential in evaluating sprouted seed lots for use as seed wheat.
Cytogenetically Monitored Transfer of Powdery Mildew Resistance from Rye into Wheat
Authors: Friebe B. , Heun M. , Tuleen N. , Zeller F. J. , Gill B. S.
Published: July 2010

Powdery mildew, caused by the fungus Erysiphe graminis DC. ex Merat f. sp. tritici Em. Marchal, is a serious disease of cultivated bread wheat, Triticum aestivum L. em Thell. About 20 powdery mildew resistance genes are known in wheat and most of them are used in cultivar improvement. however, many of these genes were overcome by th funus and are no longer effective and therefre, new sources of resistance are continuously being sought. recently, we reported a new source of powdery mildew resistance, preliminarily desinated MIP6L, that was derived from the long arm of chromosome 6R of secale cereale L. cv. Prolific. the aim of this study was to transfer MIP6L to a cytologically stable wheat‐rye chromosome translocation. Here we report the transfer of MIP6L from a monosomic 6RL (6D) chromosome substitution line by homologous recomination to a cytologically stable T6BS‐6RL weat‐rye chromosome translocation. The powdery mildew resistance gene was desinated Pm20. The powdery mildew resistance gene was designated Pm20. C‐banding analysis was used to physically map Pm20 in the distal third of the recombined translocation chromosome T6BS 6RLrec.. The succesful transfer of the resistance gene was veriied by artificial inoculation with the powdery mildew funus. Furthermore, a strategy for transferring additional useful genes from alien species to wheat is discussed.
Foliar Nutrient Concentrations of Insect Susceptible and Resistant Soybean Germplasm
Authors: Elden T. C. , Kenworthy W. J.
Published: July 2010

Differences in host plant quality to insect herbivores may be explained by variations in secondary plant compounds and plant nutrients. Soybean [Glycine max (L.) Merr.] germplasm resistant to foliar feeding insect pests have been identified and developed. Investigations into the chemical basis of this resistance have met with limited success. The objectives of this study were to determine the foliar concentrations of 12 nutrients in 18 field‐grown soybean lines with known quantitative levels of resistance or susceptibility to the Mexican bean beetle (MBB) (Epilachna varivestis Mulsant) and to determine if a relationship exists between nutrient concentrations and resistance. Eighteen soybean genotypes were evaluated. The six MBB‐resistant lines of Group 1 included PI 171451 or lines derived therefrom. The six MBB‐resistant lines of Group 2 included PI 229358 or lines derived therefrom. The six Group 3 lines were MBB‐susceptible commercial cultivars. The MBB feeding damage and foliar concentrations of P, Ca, and Fe in resistant Groups 1 and 2 were significantly less (P < 0.01) than in susceptible Group 3. Significant positive linear contrasts indicated that as damage increased, foliar concentrations of P, Ca, and Fe increased. Results indicate that none of the foliar nutrients analyzed in this study have a direct cause‐effect relationship with MBB resistance. However, the foliar concentrations of three nutrients (P, Ca, and Fe) are significantly lower in MBB‐resistant soybean genotypes using PI 171451 or PI 229358 as the resistant parent, which suggests that these nutrients are associated or linked to the true cause of resistance.