bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Materials Registered by Crop Science Incorporated into the National Plant Germplasm System
Authors: White G. A. , Eberhart S. A. , Miller P. A. , Mowder J. D.
Published: July 2010

The Crop Science Society of America (CSSA) provides a voluntary registration program for crop cultivars, parental lines, elite germplasm, and genetic stocks. Since January 1987, plant materials registered by Crop Science have been incorporated into the U.S. National Plant Germplasm System. Seed samples are deposited in the National Seed Storage Laboratory and in appropriate working collections. These materials are available from the working collections in small quantities for research purposes. Information about the plant material, referred to as passport data, is documented by the Plant Introduction Office and Plant Introduction numbers are assigned. These data and evaluation data added later are in easily retrievable form in the national database—the Germplasm Resources Information Network. The type of information to be documented, the procedure and quantity of seed needed for the National Seed Storage Laboratory and the working collections, the description of genetic stocks, and the provision for handling the import of foreign materials for registration are discussed.
Modeling the Effects of Light, Carbon Dioxide, and Temperature on the Growth of Potato
Authors: Yandell Brian S. , Najar Amina , Wheeler Raymond , Tibbitts Theodore W.
Published: July 2010

This study examined the effects of light, temperature and carbon dioxide on the growth of potato (Solanum tuberosum L.) in a controlled environment in order to ascertain the best growing conditions for potato in life support systems in space. ‘Norland’ and ‘Russet Burbank’ were grown in 6‐L pots of peat‐vermiculite for 56 d in growth chambers at the University of Wisconsin Biotron. Environmental factor levels included continuous light (24‐h photoperiod) at 250, 400, and 550 μmol m−2 s−1 PPF; constant temperature at 16, 20, and 24 °C; and CO2 at approximately 400, 1000 and 1600 μL L−1. Separate effects analysis and ridge analysis provided a means to examine the effects of individual environmental factors and to determine combinations of factors that are expected to give the best increases in yields over the central design point. The response surface of Norland indicated that tuber yields were highest with moderately low temperature (18.7 °C), low CO2 (400 μL L−1) and high light (550 μmol m−2 s−1 PPF). These conditions also favored shorter stem growth. Russet Burbank tuber yields were highest at moderately low temperature (17.5 °C), high CO, (1600 μL L−1) and medium light (455 μmol m−2 s−1 PPF). Models generated from these analyses will be used to project the most efficient conditions for growth of potatoes in closed ecological life support systems (CELSS) in space colonies.
Proposed Schemes for Mass‐Extraction of Doubled Haploids of Cotton
Authors: Stelly David M. , Lee Joshua A. , Rooney William L.
Published: July 2010

We propose (i) synthesis of hybrid‐eliminating, haploid‐inducing (HEHP) lines and populations homozygous for the Le2 dav hybrid lethality allele and the Se allele for semigamous reproduction, (ii) cross pollination of HEHP plants with pollen of normal cotton (Gossypium hirsutum and G. barbadense) to form inviable true hybrids, but viable haploids, and (iii) bulk treatment of all seed or young viable seedlings with colchicine to recover doubled haploids en masse. Doubled paternal haploid plants and sectors will be phenotypically unique, as distinguished by fertility, size of plant parts, and expression of genetic marker(s). Inclusion of male sterility in segregating HEHP populations will facilitate manual or natural cross pollination, allowing large‐scale usage. To convert cytoplasms of HEHP materials, available semigamous lines with the desired cytoplasm can be crossed with a HEHP pollen parent to obtain paternal haploid progeny that can be colchicine‐doubled. The HEHP materials should facilitate all types of cytogenetic manipulations involving extraction of doubled (paternal) haploids. The basic concepts and methods proposed might be extrapolatable to other crops.
Photosynthate Partitioning in Alfalfa Before Harvest and During Regrowth
Authors: Cralle H. T. , Heichel G. H.
Published: July 2010

During the harvest regrowth cycle of alfalfa (Medicago sativa L.) plants, factors such as source to sink distance, sink size, and interorgan competition continually change. However, consequent changes in the pattern of photosynthate partitioning from leaves to other organs are poorly understood. Our objective was to examine photosynthate partitioning from upper and lower alfalfa leaves at intervals before herbage harvest and during regrowth after harvest. The uppermost or lowest fully expanded leaf on the longest or dominant stem was labeled with 14CO2. After a 24‐h translocation period, the plants were divided into various organs to determine distribution of the radiocarbon. Partitioning from upper and lower source leaves was similar before harvest and during the first 9 d of vegetative regrowth after harvest. During regrowth, photosynthate partitioning to the rapidly growing meristematic regions of the dominant stem progressively increased by three to fivefold at the expense of the crown shoots, crown, root, and nodules. At Day 21 following harvest, differences in the distribution of photosynthate from the leaf positions were pronounced. At that time, the upper leaf preferentially partitioned photosynthate to the shoot apex, unexpanded leaves and axillary shoots of the dominant shoot, whereas the lower leaf preferentially distributed photosynthate to the crown shoots, crown, root, and nodules. Expressions of 14C partitioning were affected differently by organ mass. While the smallest organs such as nodules and unexpanded leaves always ranked higher for 14C based on relative specific activity, the largest organs such as roots and crown shoots accumulated the largest percentage of total plant recovered radioactivity. The results illustrate the importance of growth stage and leaf position in photosynthate partitioning in alfalfa and the dominance of herbage meristems for current photosynthate during regrowth.
Factors Influencing Somatic Embryo Induction from Orchardgrass Anther Cultures
Authors: Songstad D. D. , Conger B. V.
Published: July 2010

Somatic embryos from orchardgrass (Ductylis glomerata L.) anther explants have been initiated in our lab but further research is needed to optimize this response. The objectives of this research were to: (i) determine the role of anther density/orientation and various medium supplements on embryogenesis; and (ii) examine chromosomes and nucleoli from regenerated plants to determine a gametic or somatic cell origin. Anthers were pretreated for 0, 3, or 6 wk at 4°C before planting on Schenk and Hildebrandt (SH) medium containing various levels of dicamba, sucrose, or the cytokinins, 6‐ furfurylaminopurine (kinetin) or benzylaminopurine (BAP). Incubation was in the dark at 25 °C. No differences in response were obtained from a flat vs. an on edge orientation but a density of 10 anthers/mL resulted in a higher frequency of embryogenesis than 100 anthers/mL. Optimum responses were obtained with 30 pmol L−1 dicamba and 263 μmol L−1 sucrose. Both cytokinins had a significant inhibitory effect at all concentrations tested. Somatic embryos were formed directly from somatic tissue of anthers receiving a 0‐ or 3‐wk cold pretreatment whereas those receiving a 6‐wk cold pretreatment initiated embryogenic calli. One of six plants regenerated from anthers exposed to the 6‐wk cold pretreatment was a mixoploid containing cells with 14, 28,56, and more than 100 chromosomes and 1 to 8 nucleoli per nucleus. This work suggests that cytokinins hinder whereas sucrose, dicamba, and a cold pretreatment promote embryogenesis from orchardgrass anthers.
Inheritance of Double Nulls for Protein Components of Soybean Seed
Authors: Prischmann J. A. , Hymowitz T.
Published: July 2010

The objective of this study was to determine whether it was possible to develop in soybean [G. max (L.) Merr.] seeds double null genotypes for the Kunitz trypsin inhibitor (ti) null in reciprocal combinations with genotypes lacking lectin (le), lipoxygenase‐1 (/xl), μ‐amylase (sp1), and urease (Eul‐sun). Homozygous double recessive soybean lines were obtained for all eight combinations. From F2 data collected using colorimetric, immunological, and electrophoretic tests, we demonstrated that the Kunitz trypsin inhibitor locus segregated independently of the lectin, lipoxygenase‐1, urease and α‐amylase loci.
Genetic Analysis of a White Mutant in Cotton
Authors: Kohel R. J.
Published: July 2010

A cotton, Gossypium hirsutum L., mutant with a new phenotype was discovered in the developmental breeding nursery at College Station, TX in which newly formed leaves turned white and subsequently the seedlings died. Seedlings with white leaves were grown under conditions of low light and a seedling greened and developed into a mature plant that provided the basis for further study. Genetic analysis revealed that the expression was controlled by duplicate recessive genes. The aberrant type was called white mutant and assigned the gene symbols wht1,wht2,. Linkage analysis revealed no detectable associations with the 14 genetic markers of multiple markers T582 and T586.
Inheritance of a Second Virescent Mutant in American PIMA Cotton
Authors: Turcotte E. L. , Percy R. G.
Published: July 2010

Eighteen virescent mutants have been described in allotetraploid cotton (Gossypium sp.); however, only one originated in G. barbadense L. These mutants are useful as seedling and mature plant markers for studies of genetic systems and photosynthesis. A second virescent mutant was found in a G. barbdense (Pima) breeding nursery at Maricopa, AZ in 1984. Experiments indicated that it was under genetic control and was a new phenotype in Pima cotton. The objectives of the present study were to determine the inheritance of this new virescent trait and its linkage and allelic relationships with other Gossypium mutants. The genetic studies showed that the virescent trait is inherited as a monogenic recessive, and that it is not linked with 22 Gossypium mutant genes or allelic with v7 in G. barbdense of v1 and v2 in G. hirsutum L. The name virescent‐21 and the gene symbol v21, are assigned to the new Pima plant color trait.
Cytology of Bilaterally Derived Tetraploid Red Clover
Authors: Tofte J. E. , Smith R. R.
Published: July 2010

An interest in increasing heterozygosity in tetraploid (2n = 4x = 28) red clover (Trifolium pratense L.) has led to the use of 2x‐2x (bilateral) crosses for tetraploid production. This study cytologically examined F2 bilaterally derived tetraploid red clover plants (Bi4x) for aneuploid frequency and meiotic chromosome pairing. Cytological results on Bi4x were compared to colchicine derived, N2O derived, and 2x‐4x (unilateral) derived tetraploid populations. In addition, dry pollen morphology of 90 Bi4x plants was examined. The frequency of aneuploids in Bi4x was 23%, with chromosome numbers of 25, 26, 27, and 30. Hypoploids (2n < 28; frequency = 90.48%) were more frequent than hyperploids (2n > 28; frequency = 9.52%). Chromosome associations in euploid pollen mother cells averaged 0.35 univalents, 5.96 bivalents, 0.14 trivalents, and 3.80 quadrivalents. The difference between euploid chromosome associations and aneuploids was nonsignificant (x2 = 2.36; P > 0.50). Observations on dry pollen morphology indicated 78.6% of the Bi4x population produced more than 80% tetrahedron shaped pollen (typical of n = 2x = 14 pollen). The frequency of cylindrical shaped pollen (typical of n = x = 7 pollen) ranged from 1% to 90%. The Bi4* plants with a high frequency of cylindrical pollen were crossed to diploid and tetraploid plants. The 2x ✕ Bi4x crosses produced no seed, whereas, the 4x ✕ Bi4x crosses produced seed (18.13% fertility) suggesting cylindrically shaped pollen in the Bi4x population reverted to morphology typical of pollen from diploid plants (n = 2x = 14). Fiftyfour Bi4x plants were selfed and seven seeds were obtained from 6177 hand pollinations indicating a high level of self incompatability.
Inheritance of Tolerance to, and Agronomic Effects of, Difenzoquat Herbicide in Spring Wheat
Authors: Busch R. , Behrens R. , Ageez A. , Elakkad M.
Published: July 2010

The herbicide difenzoquat (1,2‐dimethyl‐3,5‐diphenyl‐1 H‐pyrazolium) has been widely used to control wild oat (Arena fatua L.) growth in wheat (Triticum aestivum L.). Different wheat genotypes have been found that are susceptible and tolerant to difenzoquat. Our objectives were to determine the inheritance of tolerance, and the effect of difenzoquat on agronomic traits in spring wheat. Two tolerant (T) and two susceptible (S) spring wheat cultivars crossed in all combinations (reciprocals bulked) to produce six populations. Four hundred sixty‐two F2 derived F4 lines were evaluated for herbicide injury when treated at 2✕ (twice) the recommended rate. Three classes of injury level (tolerant, intermediate, and susceptible) were recognized. From one of the four T ✕ S populations, 10 lines for each class were selected. These lines and their parents were exposed to 0, 1✕, and 2✕ rates of difenzoquat for 2 yr, and agronomic traits and herbicide injury were measured. In the genetic study, lines from each of the T ✕ S populations exhibitedifferential herbicide reactions, while the lines within the T ✕ T and S ✕ S populations did not differ. All T ✕ S populations, individually and combined, fit a 3:1 ratio suggesting a single dominant gene for tolerance. However, lines with intermediate tolerance were found, indicating that other genes may modify the expression of tolerance. In the agronomic study, when untreated, the tolerant, intermediate, and susceptible lines did not differ for yield, plant height, or days to head. The 1✕ and 2✕ rates had no apparent effect on agronomic traits of lines in the tolerant class. The intermediate lines yielded 92 and 80% of their untreated check at the 1✕ and 2✕ rates, respectively, while the susceptible lines yielded 69 and 51% as much grain as their untreated check in these treatments. Since no deleterious effects of tolerance were found, its incorporation into susceptible genotypes should pose few problems.
Sheep Preference for Perennial Glandular‐haired and Eglandular Medicago Populations
Authors: Lenssen A. W. , Sorensen E. L. , Posler G. L. , Harbers L. H.
Published: July 2010

Erect glandular‐haired Medicago species and hybrid populations have been developed that possess a high degree of resistance to the alfalfa weevil [Hypera postica (Gyllenhal)] and potato leafhopper [Empoasca fabae (Harris)]. Trials were conducted at the North Agronomy Farm, Manhattan, KS, in June and August 1986 to determine if erect glandular hairs on diverse perennial Medicago populations affect forage preference of sheep (Ovis aries). Glandular‐haired (+) and eglandular (−) populations were selected from each of the following: diploids M. prostrata Jacq. and M. glandulosa David (KS94) and tetraploids M. glutinosa Bieb. (KS108), M. sativa L. ✕ M. prostrata (KS159), and M. sativa ✕ M. glutinosa (KS160). Eglandular M. sativa ‘Riley’ (2n = 4x = 32) and M. sativa spp. caerulea (Less, ex Ledeb.) Schmal. (2n = 2x = 16) (MS2x) were included as controls. Four pairs of Suffolk wethers were allocated randomly among four replicates of Medicago populations in a cafeteria grazing trial. Sheep bites were counted 1 of every 5 min that grazing occurred. Pre‐ and postgrazing plant heights were measured. Populations differing by (+) or (−) showed significant differences for five of the 10 comparisons for the two grazing periods. The KS108(+), KS159(+), and KS160(+) entries were preferred to their corresponding eglandular populations in the June period. The KS108(+) and KS159(−) entries were preferred to their corresponding (−) and (+) entries, respectively, in the August period. Riley was significantly preferred over MS2x in the August period. Tetraploid entries had significantly higher initial plant height and were generally more preferred than diploid entries for both periods. For these populations, the presence of glandular hairs and their exudates did not negatively affect forage preference by sheep.
Selection for Iron Efficiency of Soybean in Nutrient‐Solution and Field Tests
Authors: Diers B. W. , Fehr W. R.
Published: July 2010

A nutrient‐solution system has been developed that may be useful for selection of iron (Fe) efficiency among soybean [Glycine max (L.) Merr.) plants in a greenhouse throughout the year. The objective of our research was to determine the effectiveness of the nutrient‐solution system for single‐plant selection of Fe efficiency compared with single‐plant selection among plants grown on calcareous soil in the field. Selection for Fe efficiency was practiced among F3 plants from six single‐cross populations in the field on calcareous Harps soil (fine‐loamy, mesic Typic Calciaquoll) during 1985 and 1986 and in nutrient solution during 1985. The progenies of the F3 plants were evaluated for Fe efficiency in the field on calcareous soil in replicated tests during 1986 and 1987. The heritability of Fe efficiency on a single‐plant basis as determined by parent‐offspring regression averaged 16% for selection in the field during 1986 and 14% for selection in nutrient solution. Heritability of Fe efficiency based on variance component estimates of random lines evaluated in the field during 1986 and 1987, was 17% on a plot basis and 55% on an entry‐mean basis. The results suggest that single‐plant selection in populations derived from crosses between parents with moderate Fe efficiency is of limited value with either field or nutrient‐solution evaluation. With such populations, selection among lines in replicated tests would be most appropriate.
Assimilation and Distribution of Photosynthate in Winter Wheat Cultivars Differing in Harvest Index
Authors: Gent Martin P. N. , Kiyomoto Richard K.
Published: July 2010

Yield differences among New York winter wheat (Triticum aestivum L.) are related to harvest index. This study was conducted to see how four cultivars, which differed in harvest index and plant height, differed in partitioning of photosynthate before and during grain filling. Experiments were conducted in field plots grown at Hamden, CT in 1985 and 1986 in Cheshire fine sandy loam (coarse‐loamy, mixed, mesic Typic Dystrochrept). The assimilation, distribution, and retention of radioactivity from 14CO2‐derived photosynthate was measured. In each year, the canopy was labeled at heading and early and late in grain filling. Harvest index was inversely related to stem height. The fractional distribution of the 14C remaining at maturity varied with labeling date and cultivar. The amount in the spike was 0.35 to 0.5 when labeled at heading, with less than 0.15 in the grain. When labeled during grain filling, a greater fraction of 14C was distributed to the spike in the semidwarf than in the tall cultivars, 0.9 and 0.8, respectively, and most of the 14C in the spike was in the grain. Almost half of the radioactivity initially assimilated was lost from the plants by maturity. Tall semi‐dwarf ‘Purcell’ retained a greater fraction of radioactivity initially assimilated than did tall ‘Honor’, 0.56 and 0.51, respectively. Thus, differences in harvest index were related to differences in distribution of photosynthate and to differences in retention of photosynthate to maturity.
Feasibility of Selection for Quantitative Traits among Haploid Tobacco Sporophytes
Authors: Witherspoon W. D. , Wernsman E. A.
Published: July 2010

The ability to produce large haploid populations, a significant correlation of performance between haploids and doubled haploids (DH) of the same genotypes, and the capacity to double the chromosomes of selected individuals are basic requirements for mass selection among haploid sporophytes. Nine hurley tobacco (Nicotiana tabacum L.) genotypes were pollinated with N. africana Merxm. and Buttler pollen; resulting seeds were sown in the greenhouse and at two seeding dates in the field. Number of haploid plants recovered per 1000 seed from field and greenhouse seedings were not different, but higher numbers of aneuploid hybrids were produced in the greenhouse. An estimated mean of 0.75 haploid plants per capsule seeded was obtained from the field plant beds. Haploid and diploid plants of nine genotypes were grown in six replications of a split‐plot design in two environments. The performance of the nine genotypes for green and cured leaf yields, total alkaloid and reducing sugar concentrations, plant height, and leaf number per plant was highly correlated between the two ploidy levels. Environmental effects on the haploid plants, and genotype ✕ environment interactions did not mask variability among genotypes in the haploid condition. The highest yielding and the lowest yielding genotypes occupied similar positions of rank in the two ploidy conditions. Mass selection for quantitative traits among tobacco haploids followed by chromosome doubling of selected individuals should be a means of developing DH populations whose mean performance would be superior to that of a random DH population.
Adventitious Root Initiation in Kleingrass in Relation to Seedling Size and Age
Authors: Tischler C. R. , Voigt P. W. , Holt E. C.
Published: July 2010

Successful establishment of grasses depends on initiation and growth of adventitious roots. This study was undertaken to determine the minimum size and/or age requirement for adventitious root development in kleingrass (Panicum coloratum L.) seedlings, and also to determine which of these two factors is more important in controlling or regulating adventitious root development. Shoot mass was modified in dependently of age through use of populations having different seed mass. These were ‘Selection 75’ (low seed mass), ‘Verde’ (intermediate seed mass), and 79‐35 (greatest seed mass). Seeds were planted in soil in plastic cones and were germinated and grown in a growth chamber. Resulting plants were sampled at 5, 6, 8, 10, 12, and 14 d after emergence. Shoot masses of the three entries (at all sampling dates) were in the same relative order as seed masses of the entries, and Selection 75 initiated adventitious roots at the lowest shoot mass. Seedling age at first adventitious root development was not related to seed weight differences. However, Verde and 79‐35 were superior to Selection 75 in primary root length, number of adventitious roots, and length of longest adventitious root (data averaged over all sampling days). Because seedling age in kleingrass is apparently more important than seedling mass in influencing adventitious root initiation, selecting for rapid seedling growth will not necessarily shorten the interval between planting and development of the first adventitious root. However, selection for rapid seedling growth may concomitantly improve other root characteristics.
Forage Source and Maturity Effects on Enzymatic Digestion Rate of Isolated Cellulose
Authors: Fairbrother T. E. , Brink G. E.
Published: July 2010

This study was conducted to determine the rate of enzymatic hydrolysis of isolated cellulose from grass and legume forages important to the southeastern USA, and to compare the difference in hydrolysis rate between grasses and legumes at two stages of maturity. Cellulose from six grass and nine legume species harvested at two stages of maturity were isolated using an acid chlorite delignification procedure followed by hemicellulose extraction with 0.12 M NaOH solution. Residual dry matter from isolated cellulose samples was determined to contain between 901 and 958 g kg− glucose. Cellulose samples were incubated at 40°C in a solution of commercially obtained cellulose enzyme for 8 h. Solutions were sampled at hourly intervals and analyzed for glucose concentration. Results indicated that glucose production was linear during the sampling period for all cellulose samples. The rate of enzymatic hydrolysis was greater (P < 0.01) for cellulose isolated from grass samples than from legume samples (8.06 and 6.94 mg kg 1 s 1, respectively). Stage of maturity also affected enzymatic digestion rate (P < 0.01). Rates for enzymatic digestion of cellulose from immature and mature forage were 8.61 and 8.06 mg kg 1 s 1, respectively. Even though enzymatic digestion rates between grasses and legumes were significantly different, the differences were small. Correlation between cellulose digestion rate and in vitro dry matter digestion of forage was not significant, indicating that cellulose digestion rate was not important in determining digestibility of whole plant tissue.
A Comparison of Two Methods of Establishing Bahiagrass Test Plots
Authors: Burton Glenn W.
Published: July 2010

The objective of this study was to determine how well a 12‐plant‐plot establishment method that saves at least 1 yr and supplies other useful information in a field‐yield trial could evaluate 10 bahiagrass entries (Paspalum notatum Flugge), established by the conventional seeded‐plot method. The 12‐plant‐plot‐test can indicate if a selection is apomictic (uniform) or sexual (variable) in its mode of reproduction, suggest the extent to which it will “breed true” and produce seed the first year—not supplied by the seeded‐plot method. The 10 bahiagrass entries included the apomictic tetraploid, Tifton 54 and nine sexual Pensacola diploids. The 12‐plant‐plots were established with plants from seed planted in the greenhouse in December and transplanted to 5‐cm clay pots in early February. Twelve such potted plants were set 30 cm apart in a single row in the center of 1.3‐ by 4.3‐m plots 30 Apr. 1980. On the same day, the 10 entries were seeded at a rate of 22 kg/ha in the same sized plots arranged so that the two establishment methods of each entry were side‐by‐side. At the end of the first year, the plants in the 12‐plant‐plots had established a solid strip of grass about 60 cm wide. Respective correlation coefficients comparing the 1980, 1981, 1982, and 3‐yr averages for seeded vs. 12‐plant plot were 0.67, 0.73, 0.83, and 0.94 for dry matter yield; 0.82, 0.83, 0.89, and 0.95 for dry matter percentage; and 0.45, 0.33, 0.87, and 0.78 for in vitro dry matter digestibility (IVDMD). Thus the 12‐plant plot test that requires only a few seeds, saves at least 1 yr in a field‐yield trial and supplies other useful information, can adequately evaluate bahiagrass selections and replace the seeded‐plot test when circumstances deem it desirable.
Reactions of Eleven Tetraploid and Hexaploid Wheat Introductions to Hessian Fly
Authors: Obanni M. , Ohm H. W. , Foster J. E. , Patterson F. L.
Published: July 2010

The expression of resistance of wheat (Triticum spp.) to the Hessian fly (Mayetiola destructor Say) is affected by cultivar, biotype, and temperature. The objectives of this study were to: (i) evaluate the resistance of seven durum wheat (T. durum desf.) and four common wheat (T. aestivum L.) introductions, and three wheat checks to biotypes B, D, and L of Hessian fly, and (ii) examine their expressions of resistance to biotype D at three temperatures. Tests against the three biotypes were conducted in a greenhouse at 19 ± 2 °C; temperature experiments were conducted in controlled environment chambers at 19, 23, and 26 ± 2 °C. In all experiments, 30 seeds of each wheat line were planted in a row in a 54 ✕ 36 ✕ 8 cm wooden flat filled with a greenhouse soil mixture. Twenty‐one days after infestation, the seedlings were classified as resistant or susceptible. The 11 wheat introductions were resistant to biotypes B, D, and L under greenhouse conditions. Nearly all seedlings of the durum lines Portugal 2536, Portugal 2852, Rebeiro, BD 3431 and IN 8464(H5H5) were resistant at 19, 23, and 26 °C. Fewer seedlings of the durum lines BD 3414, BD 3885, and PI 422297; and of the common wheat lines PI 86202, PI 117499, PI 134867, PI 321644, and ‘Abe’(H5H5) were resistant at temperatures > 19 °C. Resistance conferred by the H5 gene was expressed in a greater percentage of seedlings of IN 8464 than Abe, especially at temperatures > 19 °C. These results are of practical importance to wheat breeders in tropical or subtropical regions of the world where Hessian fly is a serious pest of wheat.
Testcross Evaluation of Exotic Soybean Germplasm of Different Origins
Authors: Sweeney P. M. , St. Martin S. K.
Published: July 2010

Two separate testcross experiments were used to determine whether germplasm strains differing in geographic origin also differed in their potential to increase yield and genetic diversity in soybean [Glycine max (L.) Merr.] breeding programs. Plant introduction strains (PI) were selected on the basis of maturity and yield per se to represent four origin groups: Modern North China (introduced since 1958), Old North China (introduced before 1933), Europe, and Korea. Twenty four strains per origin group were crossed to the male‐sterile tester line L74‐01H, and F2 bulks were tested at three locations in 1985. Eight strains per origin group were crossed to ‘Zane’, and 20 random F2‐derived lines per cross were evaluated in microplots in 1985. The best four lines per cross, selected on the basis of an index incorporating yield and maturity, were tested at two locations in 1986 and 1987. No differences in yield were associated with origin groups in the L74‐01H testcrosses. In the test of random lines from the Zane testcross, lines derived from the Old North China and Europe groups outyielded those from Modern North China and Korea by 6 to 9%. Crosses derived from Korean strains had, on average, greater genetic variances for yield than those from other groups. In the test of selected lines, there were no yield differences among origin groups. Our results suggest that, where germplasm strains have been selected for performance per se, geographic origin may be of some help in predicting the magnitude of genetic variability in exotic ✕ adapted populations.
Characterization of Inhibitory Substances of Tall Fescue on Birdsfoot Trefoil
Authors: Luu K. T. , Matches A. G. , Nelson C. J. , Peters E. J. , Garner G. B.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) is known to inhibit the growth of birdsfoot trefoil (Lotus corniculatus L.) seedlings, but the inhibitors have not been identified. Our objectives were to characterize and identify these inhibitory substances. Water extracts of tall fescue herbage were fractionated into anion, cation, and neutral fractions. Paper and gas‐liquid chromatography were used to identify possible inhibitory substances. Birdsfoot trefoil germination and seedling development were inhibited mainly by the anion fraction. At pH 7.0, the anion fraction suppressed root growth by two‐thirds and hypocotyl growth by one‐halL Dilution of the total extract or its anion fraction to one‐third of its original concentration eliminated inhibition of germination, but not of hypocotyl and root growth. Root growth was inhibited more by the inhibitory substance(s) than either germination or hypocotyl growth. Concentration of extracts and low pH of the anion fraction were partial contributory factors to inhibition. Lactic, succinic, malic, citric, shikimic, glyceric, fumaric, and quinic acids plus several unknowns were identified as possible inhibitory substances. Lactic and succinic acids appeared as the major inhibitors.
Nutritive Quality of Foliar Disease Resistant and Susceptible Strains of Intermediate Wheatgrass
Authors: Karn J. F. , Krupinsky J. M. , Berdhal J. D.
Published: July 2010

Intermediate wheatgrass [Elytrigia intermedia (Host) Nevski] including the pubescent subspecies [E. intermedia subsp, barbulatum (Schur) A. Löve], is an important introduced cool‐season grass the plains of northern USA and southern Canada. It is susceptible, however, to foliar diseases, primarily those caused by Cochliobolus sativus, Pyrenophora tritici‐repentis, and Leptosphaeria nodorum. The primary objective of this study was to evaluate the effect of naturally occurring foliar diseases on the nutritive quality of a diverse group of intermediate wheatgrass germplasm selected for resistance or susceptibility to these diseases. A secondary objective was to examine the effect of plant height on nutritive quality and the development of foliar diseases. Herbage samples were collected from resistant and susceptible plants selected from 12 cultivars or strains on 29 July 1983 and 2 July 1985. Susceptible plants infected with foliar diseases (2‐yr means) were lower in N, and higher in neutral‐detergent fiber (NDF) (P < 0.05) than resistant plants. In 1985, susceptible plants had higher concentrations of acid‐detergent fiber (ADF), but there was no significant (P > 0.05) difference between resistant and susceptible plants with respect to cellulose and hemicellulose expressed on an NDF basis, indicating the affect of foliar diseases was on the cell contents, not on the cell walls. Correlation coefficients between disease ratings and in vitro digestible organic matter, N, and NDF were r = −0.27, −0.71, and 0.76, respectively, in 1983. Correlation coefficients involving these entities were lower in 1985. Plant height did not not affect the plants' resistance or susceptibility to foliar diseases. Results from this study demonstrate over a representative germplasm base that nutritive quality of intermediate wheatgrass is diminished by leaf spot diseases, and that leaf spot resistant plants maintain a higher nutritive quality in the presence of disease.
Breeding Potential in the USA and Argentina of Corn Populations Containing Different Proportions of Flint and Dent Germplasm
Authors: Brun Eduardo L. , Dudley J. W.
Published: July 2010

Recent yield increases of flint corn (Zea mays L.) hybrids in Argentina are probably due to introgression of elite dent germplasm from the USA into breeding materials being used to develop flint hybrids adapted to the Argentine Corn Belt. The present study was conducted to evaluate the breeding potential of four corn populations with different proportions of flint and dent germplasm for grain yield and other agronomic traits in the USA and Argentina. Each population was crossed to an Argentine flint and a USA dent inbred tester. The population testcrosses were evaluated in 1984 in the USA. In addition, 50 S2s from each population were crossed to both testers. The testcross families were evaluated under 0 and 280 kg N ha−1 at Champaign, IL and under 20 and 300 kg N ha−1 at Havana, IL during 1985 and under 0 and 200 kg N ha−1 at three locations in Argentina during 1986. In both countries, yields increased significantly as the proportion of dent germplasm in the population increased. The increased yields could be explained by heavier ears, higher ear kernel row number, and heavier and deeper kernels. Conversely, when tested in the USA, kernel protein and oil concentration decreased as proportion of dent germplasm in the population increased. Crosses to the dent tester had lower concentrations of protein and oil than crosses to the flint tester. Within a country, populations did not differ significantly for family variance component or heritability estimates for any trait. Pooled across populations, prolificacy showed the highest positive genetic correlation with grain yield in both countries. The use of prolificacy as a secondary trait could improve the efficiency of index selection of these populations with the flint tester in the USA by approximately 3%. The population with 25% flint germplasm seems to be the most suitable for developing high‐yielding hybrids with good standability.
Testcross Evaluation of F2 Populations from Maize Inbreds selected for Unique Favorable Alleles
Authors: Zanoni Urs , Dudley J. W.
Published: July 2010

A method has been developed to identify donor inbreds with favorable alleles not present in an elite hybrid. Evaluation of the method requires comparison of performance of progenies from lines identified as having high numbers of favorable alleles with those from lines having a low number. The objective of this study was to compare testcrosses of F2 plants from crosses of an elite line with donor lines selected for high estimates with those of F2 plants from crosses of an elite line with donor lines having low estimates of favorable dominant alleles not present in the elite hybrid. For the improvement of maize (Zea mays L.) hybrids B73 ✕ Mo17 and B73 ✕ B77 donor lines derived from Stiff Stalk Synthetic, Lancaster, and other sources with low and high estimates of the relative number of favorable dominant alleles for grain yield not present in the elite hybrids were selected. Testcrosses of randomly chosen F2 plants from the cross between selected donor inbreds and parental lines were evaluated at two locations in 1986. The F2 testcross populations developed from inbreds with large estimated number of favorable alleles had on the average more testcrosses genetically superior to the check mean than those from inbreds with low estimates. Changes of the F2 population mean compared to the check mean and the expected variability among testcrosses could be predicted. These predictions were reliable for traits where favorable alleles were either dominant or recessive. Methods were developed to estimate the total number of loci segregating (n) in the testcrosses and the average difference between homozygotes (μ).
Genetics of Resistance to Ascochyta Blight in Four Chickpea Lines
Authors: Singh K. B. , Reddy M. V.
Published: July 2010

Inheritance of resistance to race 3 of Ascochyta blight (Ascochyta rabiei (Pass.) Lab.), an important disease in chickpea (Cicer arietinum L.), was studied in four resistant lines at ICARDA in Syria from 1983 to 1986. The parents, F1, and F2 populations were evaluated for Ascochyta blight resistance under artificial epiphytotic conditions in the greenhouse during the 1983 to 1984 season. The F3 progenies from selected F2 resistant plants for each of the four crosses involving resistant and susceptible lines were evaluated for segregation of blight resistance and susceptibility in. the greenhouse during the 1985 to 1986 season. Results suggested that a single dominant gene conditioned resistance to race 3 in the four parents, ILC 72, ILC 202, ILC 2956, and ILC 3279. Allelic tests indicated that the resistance gene present in these four resistant lines was the same. When these resistant parents were evaluated against six races of A. rabiei, each was resistant to races 1 and 3 and to at least two other races, but no two lines showed the same resistance pattern. Furthermore, the disease reaction of these resistant lines differed when tested in 13 countries. The variation in reaction of four resistant lines to six races and in different countries appears to be due to the presence of some other resistant genes in addition to a common gene.
Inheritance of Genes for Resistance to Soybean Cyst Nematode Populations
Authors: Luedders V. D.
Published: July 2010

The arbitrary division of continuous distributions of phenotypes on F2 plants into ratios of resistant:susceptible categories may not accurately reflect the number and dominance of genes for resistance to pests. Resistance of soybean, Glycine max L. Merr., lines to soybean cyst nematode (CN), Heterodera glycines Ichinohe, populations has been variously defined, representing relatively few cysts per plant phenotypes. This review considers the genetic principles that are relevant to genetic studies involving CN and soybean. The distribution of a phenotype, such as number of cysts per F2 plant, is determined by the number and dominance of soybean genes for resistance segregating and the frequencies of CN genes for avirulence with which they interact in a gene‐for‐gene manner. An assumption seems to have been that only one soybean genotype conferred resistance, which implied heterogeneous CN populations. The resistant: susceptible ratios commonly used were deduced to be 3d:4N‐3d, with dominant (d) and recessive (r) genes for resistance at N independent loci. An A_ or aa genotype (of d and r genes) at any one locus may condition F2 plant resistance to homozygous (for avirulence) CN (and parasite clones). Then only one genotype or 3r gives susceptibility as 4N−3r:3r ratios. Some of the resistant:susceptible ratios were not greatly different, and might be the same with the effects of linkage. Heterogeneous and homozygous CN populations may not be distinctly different, rather the differences are in the distributions of phenotypes they effect with F2 plants: continuous with heterogeneous but discrete phenotypes, similar to the parental ranges, with homozygous populations. The materials and methods for definitive genetic studies, including allelism and linkage, were discussed.
Genetic Analysis of Brown Stem Rot Resistance in Soybean
Authors: Willmot David B. , Nickell C. D.
Published: July 2010

Genetic resistance of soybean [Glycine max (L.) Merr.] to Phialophora gregata (Allington and Chamberlain) W. Gains, the cause of brown stem rot (BSR), can reduce yield losses in northern USA and Canadian production regions. Although two major dominant genes have been identified, additional sources of resistance may provide higher levels of resistance and/or more stable resistance over environments. The objectives of this study were to: (i) determine the pattern of inheritance of the BSR resistance found in PI 437970 and (ii) study allelic relationships of resistance genes in PI 437970 with Rbs 1, and Rbs 2. Evaluations were conducted using a root dip inoculation method in the field and greenhouse. The F2 and F3 plants were classified as resistant or susceptible based on mean parental reactions. Segregating generations of the cross PI 437970 ✕ ‘Pioneer Variety P9271’ revealed a single dominant gene conditioning BSR resistance. Crosses of PI 437970 with L78‐4094 ( Rbs 1 and PI 437833 ( Rbs 2) each demonstrated duplicate dominant epistasis indicating a third distinct gene designated Rbs3.
Reproductive Advantage in Soybean Associated with Resistance to Soybean Cyst Nematode: Effects of Tolerance and Nematode Density
Authors: Waller R. W. , Boerma H. R. , Hussey R. S.
Published: July 2010

Natural selection is used by plant breeders to increase the frequency of desirable genotypes in a population. When soybean [Glycine max (L.) Merr.] populations segregating for resistance to soybean cyst nematode (SCN) (Heterodera glycines Ichinohe) are grown on SCN‐infested soil, resistant genotypes produce more seed than susceptible genotypes. In a bulk‐harvested population this differential reproduction results in an increased frequency of resistant genotypes in the population. This research was conducted to determine the effects of tolerance to SCN and the frequency of resistant genotypes in the population on the effectiveness of natural selection for resistance to SCN. A second objective was to relate initial SCN population densities and parental pure‐stand yield ratios to the effectiveness of natural selection. Four 1:1 viable seed mixtures of resistant (R) and susceptible (S) genotypes were evaluated in four SCN‐infested fields for 2 yr. Two of the S genotypes were moderately tolerant and two were intolerant to SCN. The R genotypes in mixtures with moderately tolerant, S genotypes had an average reproductive advantage (ratio of R/S seed number) of 2.2 compared to 4.2 for R genotypes in mixtures with intolerant, S genotypes. In a second experiment, five ratios, 1:9, 3:7, 1:1, 7:3, and 9:1, of R to S genotypes were compared for two of the genotypic mixtures (‘Gordon’/‘ Bragg’ and Gordon/‘Wright’). The effectiveness of natural selection was not related to the frequency of the R genotype in the mixture. On an individual‐plot basis across the four mixtures the linear regression of the pure‐stand R/S yield ratios predicted 47% of the variation in reproductive advantage of R genotypes compared to 22% for log10 of initial density of SCN eggs. Effectiveness of natural selection for SCN resistance was dependent on the initial population density of SCN, the specific environmental conditions, and the tolerance level of the genotypes in the soybean population.
Expression and Inheritance of a Shriveled‐Seed Mutant in Soybean1
Authors: Honeycutt R. J. , Burton J. W. , Shoemaker R. C. , Palmer R. G.
Published: July 2010

The problem of shriveled or shrunken seed in soybean [Glycine max (L.) Merr.] has needed genetic definition and characterization. Shriveled or shrunken seed that occur in other crops are known to be due to alterations in genetic information. Genetic information can interact with environmental conditions to produce differing severities of shriveled or shrunken seed. Studies were undertaken to characterize a new shriveled‐seed mutant in soybean. Initial experiments revealed incomplete expressivity and penetrance for the mutant gene. Phytotron studies were conducted to determine the effect of day/night temperatures on the expression of the shriveled‐seed phenotype. The results showed that genotype ✕ environment interaction, particularly the night temperature ✕ genotype interaction, strongly influenced the phenotypic expression. Field studies conducted with F1, F2, and F3 plants of reciprocal crosses between the shriveled mutant and ‘Minsoy’ established that the trait is inherited as a single recessive allele. This mutant has been assigned the gene symbol shr by the Soybean Genetics Committee. Linkage tests indicate that the gene is not linked to the W1, Pb, or T loci.
Response of Wheat Genotypes to Temperature and Photoperiod in Natural Conditions
Authors: Masle Josette , Doussinault G. , Sun B.
Published: July 2010

Floral initiation in wheat (Triticum aestivum L.) depends on complex interactions between temperature and photoperiod. The aim of this study was to analyze genetic variation in the response to combined variations of changing and often suboptimal photoperiods and temperatures as they occur in natural environments. Twelve genotypes were analyzed in the field, using vernalized and nonvernalized seeds, for times of floral initiation, anthesis, and beginning of stem elongation. Climate was varied by changing sowing date, year, and site. This resulted in large variations in the date of achievement of all stages. However, these variations could be expressed by a unique curve for each genotype when dates were characterized by the combination of the thermal time from seedling emergence (K) and of the daylength (P) on the date considered. The curve was specific to a stage and to a genotype. The curves obtained for the different genotypes were variants of the same general curve, which allowed definition and quantitative assessment of three characteristics for describing the developmental response of a genotype to climate: vernalization requirements, photothermal sensitivity, and intrinsic earliness. These three components, which are confounded in the common notion of earliness, showed large variations among genotypes, especially at the lemma stage. They were largely independent. Our results also show that, compared to differences in the sensitivity to photoperiod and temperature, differences in vernalization requirements are of secondary importance in choosing a genotype in temperate areas, even for a very late spring sowing.