bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypernodulation of Soybean, Mung Bean, and Hyacinth Bean Is Controlled by a Common Shoot Signal
Authors: Harper J. E. , Corrigan K. A. , Barbera A. C. , Abd‐Alla M. H.
Published: July 2010

Identification of commonality of nodulation control among legumes will facilitate progress in improving symbiotic N2 fixation in agricultural systems. Interspecies grafts between soybean [Glycine max (L.) Merr] and mung bean (Vigna radiata L.), or soybean and hyacinth bean (Lablab purpureus L.), were made to evaluate whether a common translocatable signal controls expression of hypernodulation among legume species. Grafting of a ‘NOD1‐3’ (hypernodulating soybean) shoot to roots of mung bean or hyacinth bean resulted in hypernodulation, a 4.1‐fold increase in nodule number for mung bean, and a 2.7‐ to 5.5‐fold increase (depending on bacterial strain) in nodule number for hyacinth bean, relative to self‐grafted mung bean or hyacinth bean, respectively. ‘Williams 82’ shoots doubled nodule number when grafted to mung bean roots, but had no effect on nodulation when grafted to hyacinth bean roots. Symbiotic Nz fixation (as measured by nitrogen accumulation in the plant) by nodulated mung bean roots was enhanced by 67% when grafted to Williams 82 and by 78% when grafted to NOD1‐3 soybean shoots, compared with self‐grafted mung bean plants. Grafting soybean shoots to hyacinth bean roots positively affected symbiotic N2 fixation (9–40% depending on bacterial strain), but the magnitude was less than observed when mung bean roots were grafted to soybean shoots. It was concluded that control of hypernodulation expression by a shoot‐transmissible factor is common among soybean, mung bean, and hyacinth bean. Seed were obtained from reciprocal grafts between soybean and mung bean to test for bacterial specificity for infection and nodule development. Seedling progeny from the reciprocal mung bean‐soybean grafts were not altered in terms of bacterial specificity for nodulatiou.
Effects of Chemical Drying Agents on the Fine Structure of Alfalfa Cuticles and Epicuticular Waxes
Authors: Panciera M. T. , Krause C. R.
Published: July 2010

Chemical drying agents reduce the curing time of alfalfa (Medicago sativa L.), but mechanisms have not been defined to explain this reduction. This study was conducted to define the physical effects of drying agents on alfalfa stem surfaces and to determine the distribution of applied cations on the stems. Field‐grown alfalfa was treated with water and nine solutions consisting of all possible combinations of three cations (Na+, K+, Cs+) and three anions (C2H3O−2, CO2−3, OH−). Following treatment application, plants were air‐dried under ambient conditions, stem samples excised and prepared for scanning electron microscopy (SEM) and energy dispersive x‐ray microanalysis (EDXA). Epicuticular waxes were removed with chloroform on one set of samples to allow observation of the cuticle. All nine treatments reduced drying time relative to the control Based on SEM observations, treatment with C2H3O−2 ompoundrse sulted in large cracks in epicuticular waxes and the cuticle, while CO2−3 and OH− treatments altered wax texture and caused pitting of the cuticle. Cesium was detected on the Cs‐treated samples with EDXA and its distribution was uniform over the stem surface. Drying agents affected the physical structure of alfalfa epicuticular waxes and cuticles, but treatments that produced the most subtle physical changes caused the greatest reductions in drying times. These observations do not support extensive wax removal, wax platelet reorientation, or inhibition of stomatal closure as mechanisms of increased drying rates.
Molecular Marker Analysis of the Approach to Homozygosity by Selfing in Diploid Alfalfa
Authors: Brouwer D. J. , Osborn T. C.
Published: July 2010

Although inbreeding is used extensively in alfalfa breeding and genetics, the actual approach to homozygosity during inbreeding is unknown and may differ from that predicted by the inbreeding coefficient (F) because of the need to select for vigor and fertility when inbreeding. Observed and expected values of heterozygosity were compared by means of 40 co‐dominant RFLP loci for two inbred series each consisting of four independent lines derived by selfing two diploid alfalfa genotypes. Selfing was continued with selection for fertility until self‐sterility was reached at the S2, S3, or S4 generation. Additional S1 progenies were also evaluated to identify the heterozygons RFLP loci. The observed percentage heterozygosity, calculated as the percentage of the 40 RFLP loci still heterozygous in each plant, declined less than expected based on the inbreeding coefficient in each inbred series. The lowest observed percentage heterozygosity was 30% in one inbred series and 40% in the other inbred series despite expectations as low as 6%. Tests of genotype and allele ratios indicated that the deviations may be due to selection favoring hetcrozygotes. Our results show that inbreeding in diploid alfalfa proceeds more slowly than expected, based on F, and that inbreeding depression may limit the level of homozygosity obtainable.
Stand Regeneration of Alysicarpus and Desmodium Germplasm in Louisiana
Authors: Pitman W. D. , Hafley J. L. , Cuomo G. J. , Kretschmer A. E.
Published: July 2010

Alysicarpus Necker ex Desv. and Desmodium Desv. have potential for increased use as pasture legumes in warm‐temperate and subtropical environments. Seven accessions of D. heterocarpon (L.) DC. and 40 accessions of Alysicarpus, primarily A. vaginalis (L.) DC., were evaluated in Louisiana in 1995 and 1996. Single‐row plantings with three replications in randomized complete block designs were established at the Iberia, Rosepine, and Southeast Research Stations. Data collected were visual stand ratings during the 1995 and 1996 growing seasons. An uncharacteristic period of 96 h with only two brief afternoon periods above freezing in February 1996 at Rosepine provided an opportunity to discriminate among entries for winter hardiness and to identify individual plants from each D. heterocarpon entry possessing winter hardiness. Alysicarpus plants did not survive the winter, but several accessions produced reseeded stands in 1996. Performance of the Alysicarpus germplasm was substantially better at the Southeast Station than at other locations, while more Desmodium entries survived at Rosepine than at the other locations despite lower winter temperatures at Rosepine. The surviving D. heterocarpon plants provide a potential source of winter hardiness for development of a perennial warm‐season pasture legume for the lower gulf coast region.
The Nonselective Nature of a Modified Single‐Seed Descent Breeding Procedure
Authors: Gourmet C. , Kolb F. L. , Brown C. M. , Smyth C. A. , Biradar D. P. , Rayburn A. L.
Published: July 2010

The objectives of this study were to determine (i) if selection for barley yellow dwarf virus (BYDV) tolerance occurred under a modified single‐seed descent (MSSD) procedure when used in conjunction with BYDV inoculation, and (ii) if changes in nuclear DNA content occurred during MSSD. Plants from four intraspecific spring oat (Avena sativa L.) crosses were grown in the greenhouse under a MSSD procedure and were infected with BYDV by inoculation with viruliferous aphids. These populations were compared with populations grown without exposure to BYDV. BYDV tolerance was evaluated in the field in the F4:5 and F4:6 generations. Inoculation with BYDV under the MSSD method did not selectively eliminate BYDV susceptible genotypes. To determine if the MSSD procedure induced selection for a particular nucleotype, seeds harvested from the parents (grown under the MSSD procedure) were tested for nuclear DNA content. No difference in DNA content was observed among progeny grown from seeds of stressed plants compared with progeny grown from seeds of nonstressed plants. These results suggest that even the most BYDV susceptible plants produced seeds during MSSD, and the MSSD method does not seem to induce directed changes in nuclear DNA content.
A Soil‐on‐Agar Method to Evaluate Acid‐Soil Resistance in White Clover
Authors: Voigt P. W. , Morris D. R. , Godwin H. W.
Published: July 2010

White clover (Trifolium repens L.) is adapted to the Appalachian region but is rarely found on strongly acid soils. To select for improved acid‐soil resistance we needed an effective and efficient soil‐based procedure. Our objective was to develop a simple, rapid, nondestructive technique that could be used to evaluate acid‐soil resistance of clover accessions. Our technique uses a thin layer of acid, Al‐toxic soil on top of solidified water agar. Germinated white clover seed, selected for uniform radical length of about 1 mm, are transplanted into the soil. Root emergence from the soil into the agar is visually observed. We evaluated the technique using non‐limed (pH 4.2, Al saturation 70%) and limed (pH 5.0, Al saturation 14%) Porters soil (coarse loamy, mixed, mesic Umbric Dystrochrept) and four white clovers, two larger‐leafed (ladino) clovers developed in the USA, and two smaller‐leafed cultivars from New Zealand. Root emergence was observed daily for 10 d. Root emergence from the limed and nonlimed soil began on day one and on day four, respectively. This delay in emergence indicates that the clover seedlings were responding to toxic factors in the acid soil that were alleviated by liming. The larger‐leafed cultivars emerged more slowly than the smaller‐leafed cultivars in the non‐limed soil but were similar to them in the limed soil. The soil‐on‐agar technique allows easy collection of root growth data, is rapid, nondestructive, and can be used with large populations. The technique should be useful for characterization of acid‐soil resistance of white clover and other small‐seeded species. We suggest that seedlings whose roots emerge more quickly from acid soil are more resistant than those whose roots emerge later and that the technique has promise for selecting resistant and susceptible populations.
Inheritance of Somatic Embryogenesis in Orchardgrass
Authors: Tar'an B. , Bowley S. R.
Published: July 2010

The ability for plant tissue to regenerate following in vitro culture is highly dependent on the genotype. The inheritance of somatic embryogenesis in orchardgrass (Dactylis glomerata L.; 2n = 4x = 28) was studied using one embryogenic genotype (Embryogen‐P) random plants from two nonembryogenic populations, Jay and OSG‐ 13. Individual plants from F1 (Embryogen‐P × Jay), F2, BC1, and test cross (F1 × OSG‐13) matings were evaluated for somatic embryogenesis. Leaf bases were cultured in the dark on SH medium containing 30 ttM dicamba (3,6‐dichloro‐o‐anisic acid) at 25°C for 4 wk. Qualitative differences of callus quality ranging from undesirable watery and gelatinous to desirable compact, firm, and friable were observed in all segregating populations. The percentage of plants initiating a firm and friable callus was significantly (P < 0.05) correlated to the frequency of embryogenic plants. The segregation ratios observed across all matings indicated that the ability to form somatic embryos from cultures derived from leaf base explants of orchardgrass was conditioned by two independent dominant genes with complementary effects. The genotype of Embryogen‐P was simplex/simplex. The simple model of inheritance and the dominance of the character simplifies development of cultivars with improved in vitro response that would facilitate the application of biotechnological techniques in this species.
Application of Recurrent Selection for Low Grain Moisture Content at Harvest in Tropical Maize
Authors: Hawbaker M. S. , Hill W. H. , Goodman M. M.
Published: July 2010

Late maturity and high grain moisture content at harvest have been major limitations to the use of tropical maize (Zea mays L.) germplasm in temperate regions. The objective of this study was to determine if selection for reduced grain moisture content at harvest in a tropical maize population indirectly influenced grain yield potential. Two hundred sixteen temperately‐adapted S4 lines were derived in 1991 at Raleigh, NC, from Cycle 9 of recurrent phenotypic selection for reduced grain moisture at harvest in the tropical maize population TROPHY, and these were testcrossed in 1992 at Raleigh, NC, to the temperate hybrid B73Ht × Mo17Ht. Selected subsets of these testcrosses were evaluated for their agronomic potential in seven environments over two years, and their performance was compared with that of Cycle 0 S0 testcrosses as well as three public and three commercial F1 hybrids. Selected Cycle 9 S4 testcrosses had higher mean grain yield (7.14 Mg ha‒1) and lower mean grain moisture at harvest (184 g kg−1) than the Cycle 0 So testcrosses (6.77 Mg ha−1, and 189 g kg−1 respectively). The highest yielding Cycle 9 S4 testcrosses were comparable to the commercial hybrid LH132 × LH51. This study supported the conclusion that ergonomically competitive inbred lines with acceptable grain moisture content at harvest can be derived from 100% tropical germplasm.
Changes in Temperature Sensitivity of Development from Sowing to Flowering in Rice
Authors: Yin Xinyou , Kropff Martin J. , Goudriaan Jan
Published: July 2010

To accurately predict the time of flowering, it is essential to determine the effects of environmental factors on crop development at different stages. The objective of this study was to examine the variation in flowering responses to day temperature (TD) and night temperature (TN) during the preflowering period (PFP) in rice (Oryza sativa L.). Three controlled‐environment experiments were conducted in which plants of three contrasting cultivars, CO36, Shan You 63, and Nipponbare, were transferred at different times after sowing between two constant temperatures (26 and 21°C), between two with the same TD (TD/TN: 26/26 and 26/16°C), or between two TD with the same TN (28/19 and 19/19°C). In all experiments, the relationship between the time to flowering and the time of transfer was defined by separate linear phases, indicating that the sensitivity of flowering responses to both Tn and TN varies during PFP. The entire PFP can be divided into three consecutive phases. Temperature sensitivity during the second phase was greater than that during the first and third phases, which did not differ significantly. The length of the second phase varied greatly, depending on both temperature and cultivar. For all cultivars, the second phase was shorter at HT (5.4–17.0 d) than at LT (20.7 to more than 78.7 d). The duration of the first phase ranged from about 20 d in the japonica cv. Nipponbare to 32.4 to 64.2 d in the two indica cultivars. The length of the third phase also varied among cultivars, but to a lesser extent, from 16.4 to 38.1 d. Any significant effects of temperature on main‐stem leaf number occurred in the second phase. For accurate modeling of rice flowering dates, functions describing the effects of both TD and TN in the second phase have to be different from those in the first and third phases.
Bahiagrass Response to a Plant Growth Regulator as Affected by Mowing Interval
Authors: Goatley J. M. , Maddox V. L. , Watkins R. M.
Published: July 2010

Bahiagrass (Paspalum notatum Fluegge) is a widely used grass for low maintenance turf areas such as highway rights‐of‐ways in the southeastern USA. Although well adapted to poor soils, low fertility, and low rainfall conditions, bahiagrass requires frequent mowing to maintain turf uniformity because of rapid and prolific seedhead production. This study was conducted in June and August of both 1995 and 1996 to determine the effects of various mowing timings either before or after application of the plant growth regulator AC 263,222 [(AC) (±)‐2‐ [4,5‐dihydro‐4‐methyl‐4‐(1‐methylethyl)‐5‐oxo‐lH‐imidazol‐ 2‐yl]‐5‐methyl‐3‐pyridinecarboxylic acid]. Unimproved bahiagrass turf was clipped to a 7.5‐cm height at times corresponding with the following mowing treatments: mow 3 or 7 d before treatment (DBT) with AC 263,222 (0.07 kg ha−1 for all treatments), 1 h before treatment (HBT), 1 after treatment (HAT), 3 or 7 d after treatment (DAT), and control that had been mowed 2 wk earlier. Evaluations of bahiagrass color, seedhead count and height, and vegetative canopy height were made biweekly through 6 wk after AC treatment. Mowing at 3 or 7 DBT with AC resulted in color ratings that were always equal to or above the minimal acceptable rating and also provided at least 90% seedhead suppression through 6 WATin all trials. Mowing bahiagrass at 3 or 7 DAT consistently resulted in color ratings less than the minimal acceptable rating of 5 through 2 WAT, but bahiagrass growth regulation was excellent through 6 WAT in all trials. The mowing treatments of 1 HBT or 1 HAT both resulted in excellent growth regulation characteristics, but color ratings for turf mowed 1 HAT were consistently higher than those for plots mowed 1 HBT. These data indicate acceptable color and plant growth regulation can be obtained by timing mowing events at least 1 h before or after spraying AC 263,222 in low maintenance bahiagrass turf.
Breeding Potential of Maize Accessions from Argentina, Chile, USA, and Uruguay
Authors: Salhuana W. , Pollak L. M. , Ferrer M. , Paratori O. , Vivo G.
Published: July 2010

The Latin American Maize Project (LAMP) evaluated nearly 12 000 maize (Zea mays L.) accessions in 12 countries to select germplasm that can be used in breeding programs to improve commercial materials. In Argentina, Chile, Uruguay, and the USA, 1692 and 988 native accessions were evaluated in the first and second period, respectively. Sixty‐nine selected accessions were evaluated in all countries in the third stage. Accessions per se showed silk delay, indicating a lack of adaptation. The 69 selected accessions topcrossed with B73 × B14A, Oh43 × MolT, and SR76 were evaluated in the four countries to (i) identify temperate accessions from Latin America and the USA that could enhance yield, tassel and silk synchronization, lodging resistance, and maturity; and (ii) identify the U.S. heterotic group to which the accessions belong. The topcross results identified germplasm equal or superior to the performance of the checks in all countries, indicating that selected germplasm could be used to increase yield. Even though topcrosses showed significant improvement for silk delay and stalk lodging across the accessions, additional improvement is needed to facilitate wider use of the material. The Argentinean accessions had the best mean per se and topcross performance. Some accessions performed well in most countries and should be included in cooperative enhancement efforts.
Plant Survival and Root and Bud Composition of Alfalfa Populations Selected for Contrasting Fall Dormancy
Authors: Cunningham S. M. , Volenec J. J. , Teuber L. R.
Published: July 2010

Fall dormancy is correlated with improved winter survival in alfalfa (Medicago sativa L.), but the physiological basis for this association is not understood. Our objectives were to determine how selection for contrasting fall dormancy influenced (i) fall height and winter survival, (it) crown bud development, and (iii) sugar, starch, protein concentration and composition of roots and crown buds. Three cycles of selection for contrasting fall dormancy were conducted in Davis, CA using ‘Norseman’, ‘Lahontan’, ‘CUF 101’, and ‘Wadi Qurayat’ as parental sources. Seed of parental cultivars and seed of progeny from the third cycle of selection were planted in rows in the field (Starks‐Fincastle, fine‐silty, mixed, mesic Aerie Ochraqualf) West Lafayette, IN, in May 1993 and 1994, and roots and crown buds were sampled at approximately monthly intervals between September and December. Plant survival was determined in March of the year following seeding. Parental cultivar differences in fall dormancy and winter survival were associated with changes in crown bud development, elevated total nonstructural carbohydrate and sugar concentrations in buds, and sugar and protein accumulation in roots. Cultivar differences in fall dormancy also influenced polypeptide composition of green buds and roots. Selection for greater fall dormancy reduced the height of CUF 101 and markedly improved its winter survival. Concentrations of sugars and proteins in buds and roots of the dormant selection of CUF 101 increased to values similar to those observed for the fall‐dormant, winter‐hardy Norseman. Selection solely for contrasting fall dormancy can alter cold acclimation in buds and roots and winter survival of alfalfa.
Yield and Risk Utilizing Short‐Season Soybean Production in the Mid‐Southern USA
Authors: Boquet Donald J.
Published: July 2010

Maturity Group (MG) V and VI soybean [Glycine max (L.) Merr.] grown in the mid‐southern USA often produce low yield. The objective of this study was to determine if yields could be increased and risk of production reduced by utilizing early‐maturing cultivars at early planting dates (short‐season system). Field experiments were conducted from 1992 through 1994 on Sharkey clay (very‐fine, montmorillonitic, non‐acid, thermic Vertic Haplaquept) to evaluate mid‐ April through early‐June planting dates (PD), row spacings of 75 and 100 cm, and irrigated vs non‐irrigated treatments for selected MG III, IV, V, and VI cultivars. The cultivars were MG III, ‘Williams (W) 82’; MG IV, ‘Asgrow (A) 4715’, ‘Northrup King Ringaround (RA) 452’, and ‘Riverside (RVS) 499’; MG V, ‘Deltapine (DP) 105’ and MG VI, ‘Davis’. Maturity Group and PD had large effects on soybean growth and yield, whereas row spacing and irrigation had small effects and were not important factors in yield determination at most PD. The optimal PD for MG III through V cultivars centered around early May. Yields of MG IV at early‐ to mid‐May PD were equal to or greater than their yields at April PD. In April plantings, MG IV, RA 452, and RVS 499, usually yielded higher than MG V and sometimes yielded higher than MG VI. Adaptation to early PD was related to length of growing season and plant size. Attaining harvest maturity in fewer than 120 d at an April PD or fewer than 108 d at a May PD reduced both plant height and yield. The risk for short‐season production was less than for plantings of MG V or VI cultivars because the short‐season system produced higher yields and there was no difference between the two systems in yield variation across years.
Core Set of Primers to Evaluate Genetic Diversity in Soybean
Authors: Thompson Jeffrey A. , Nelson Randall L.
Published: July 2010

A large number of random primers are available to generate random amplified polymorphic DNA (RAPD) markers; however, not all primers are equally informative. The focus of this research was to identify a small set of RAPD primers that can adequately describe the relationships among major North American soybean [Glycine max (L.) Merr.l ancestors and selected plant introductions (Pls). Two hundred eighty‐one polymorphic RAPD fragments evaluated on 35 ancestors and Pls were screened for reproducibility and levels of diversity. Principal‐components analysis (PCA) was employed identify RAPD fragments associated with the largest sources of variation. Hierarchical and nonhierarchical cluster analyses were used to depict the relationships among the 35 genotypes. One hundred twenty RAPD fragments from 64 random primers were highly reproducible and had polymorphism information content (PIC) scores ≥0.30. Principal‐ components analysis revealed that eight components explained 60% of the total variation. Stepwise removal of fragments from individual primers revealed that fragments from only 35 primers were critical to the analysis. The product‐moment correlation of pairwise distances estimated from the complete RAPD fragment data set and this core data set was 0.86 (P < 0.0001). Results from cluster analysis confirmed that this set of 35 primers provides an accurate measurement of the relationships among the 35 genotypes. These primers will be useful for estimating relationships between exotic accessions and the current North American genetic base.
Evaluation of Carribean Maize Accessions to Develop a Core Subset
Authors: Taba Suketoshi , Diaz Jaime , Franco Jorge , Crossa José
Published: July 2010

Core subsets of germplasm collections facilitate their evaluation and use. Field evaluations were conducted to develop a core subset of Caribbean maize (Zea mays L.) accessions from the CIMMYT maize germplasm bank. Most accessions were from the West Indies and others were from Central and South America. The accessions were divided into two trials of 249 accessions and seven common checks that were evaluated in a 16 by 16 α‐lattice design with two replications. The trials were planted in two seasons at two sites in Mexico during 1992 through 1994. Data were taken on agronomic and morphological traits and the combined analysis was performed by a mixed linear model. The adjusted means of plant height, ear height, senescence, ear diameter, ear length, days to silk, days to anthesis, moisture (%), rating on ease of shelling, and number kernel rows were used to cluster accessions into homogeneous groups. Twelve non‐overlapping clusters were formed and patterns of phenotypic diversity among and within clusters were determined using canonical discriminant analysis. A selection index based on yield (Mg ha−1), ear rot (%), erect plants (%), and moisture (%) was calculated for each accession. The upper 20% of the accessions (100 in total) which represent the phenotypic diversity of the clusters and have superior selection indexes were used to form a core subset of the Caribbean maize collection.
Pollen Control During Transgenic Hybrid Maize Development in Mexico
Authors: Garcia M. C. , Figueroa J. M. , Gomez R. L. , Townsend R. , Schoper J.
Published: July 2010

Pollen containment may be necessary to prevent the dissemination of novel genes from transgenic crops into sexually compatible land races or wild relatives in locations where these are grown or occur naturally in the same vicinity. Routine maize (Zea mays L.) breeding activities employ controlled pollinations and are sometimes done in areas where land races or wild relatives are known to occur. The ability of researchers to control pollen movement and to thereby control the potential flow of novel genes from transgenic maize to land races or wild relatives was investigated. Using white‐ and yellow‐seeded inbreds, pollen control was measured in two mating designs. The ability to control pollen was assessed by observing seed color in pollinations on adjacent plantings intended to trap uncontrolled pollen. In one experiment, the yellow‐seeded maize contained a transgene. In this experiment contaminant seeds observed in the white maize were analyzed for the presence of recombinant DNA and the gene expression product. The results from these experiments indicated that routine plant breeding activities can be conducted with completely effective pollen containment if the transgenic line is detasseled and serves as the female for pollination with a nontransgenic male inbred. However, precautions in addition to those used in these experiments are necessary to provide complete control of pollen dissemination if a transgenie male is used to make crosses and ≈0.1% outcrossing to adjacent rows is deemed unacceptable.
Genetic Variation within among White Clover Populations from Managed Permanent Patures of the Northeastern USA
Authors: Gustine David L. , Huff David R.
Published: July 2010

White clover (Trifolium repens L.) population dynamics and genetic variation were characterized in populations under continuous grazing management. RAPD (random amplified polymorphic DNA) profiles were developed for individuals sampled from managed permanent pastures on 18 farms in Pennsylvania (PA), New York (NY), and Vermont (VT). Genomic DNA from individual white clover plants (48) sampled over two transects at each location during fall, 1996, was amplified by the PCR (polymerase chain reaction). RAPD profiles of 54 RAPD markers were used to compute genetic distances between pairs of individuals. The data set for each location was evaluated by AMOVA (Analysis of Molecular Variance), which apportioned total variation among individuals within populations, among populations within states (PA, NY, VT), and among state populations (PA, NY, VT). An interpopulation distance matrix of 18 fall‐sampled populations was used to calculate a dendrogram. Two groups of 6 and 10 populations were evident, with two populations as single branches. VT populations were in the larger population group, and the PA and NY populations were in both groups. White clover genetic variability in the swards was higher than expected, all populations were significantly different (P < 0.001) from each other, and the PA, NY, and VT populations were indistinguishable from each other. Populations from four PA locations also sampled in summer changed significantly two months later in the fall. Rapidly changing white clover diversity may be due to rapid, differential growth of individuals best adapted to seasonal changes in the microenvironment, or to unexpectedly high levels of seedling recruitment.
Intellectual Property Rights, Access to Plant Germplasm, and Crop Production Scenarios in 2020
Authors: Evenson R. E.
Published: July 2010

The scope of intellectual property rights (IPRs) has been expanded in recent years to cover plant varieties. Plant breeders' rights (PBRs) provide weak protection to private plant breeders in many countries. The United States and a few other developed countries provide patent protection to plant varieties as well as to some genetic resources. In principle, the strengthening of IPRs for plants should encourage more plant breeding and more variety options for farmers. However, developing countries often lack the institutional setting to enable them to realize these options. A second type of IPR providing for “farmers' rights” has been prepared in the Convention on Biodiversity. Negotiating a payment framework for farmers' rights may result in a period of limited international exchange of genetic resources. Policy simulations based on an international economic model confirm that developing countries will be harmed by weak IPRs while developed countries will not be affected. They also confirm that both developing and developed countries will be harmed by reduced exchange of genetic resources associated with protracted negotiations over farmers' rights.
Maize Genotypes Show Striking Differences for Induction and Regeneration of Haploid Wheat Embryos in the Wheat × Maize System
Authors: Verma Vinesh , Bains N. S. , Mangat G. S. , Nanda G. S. , Gosal S. S. , Singh Kuldeep
Published: July 2010

A number of maize (Zea mays L.) genotypes were tested for their influence on induction and regeneration of haploid wheat (Triticum aestivum L.) embryos to improve further the efficiency of the wheat × maize system of haploid production. Fifteen maize genotypes were crossed to five diverse wheat F1 hybrids in a line × tester fashion in three replications. Two efficiency parameters, caryopses formation frequency (CFF—number of caryopses/100 pollinated florets) and embryo formation frequency (EFF—number of embryo‐carrying caryopses/100 pollinated florets), were estimated. Analysis of variance revealed that lines (wheat genotypes), testers (maize genotypes), and their interaction showed significant effects on both efficiency parameters, but the effect of maize genotypes was greater than that of wheat genotypes. The EFF of individual maize genotypes ranged from 1.1 to 23.4% and the EFF of individual wheat genotypes ranged from 8.4 to 10.2%. Maize genotypes also showed significant differences for general combining ability estimates. In addition to EFF, maize genotypes had a striking effect on haploid embryo regeneration as analyzed using one of the wheat genotypes. The values ranged from 0.0 to 87.8%. For maize genotypes producing the highest EFFs, the regeneration frequency was not necessarily higher. Hence, we suggest a new index, haploid formation efficiency (HFE—number of haploid plants formed /100 pollinated florets), be used for identification of efficient pollinators. The HFE ranged from 0.0 to 9.9%. In this study, a pop corn cultivar, Pearl Pop Corn, was identified as the best pollinator with an average EFF of 15.1% across five wheat genotypes and an HFE of 9.9% with the one wheat genotype tested.
Economic Efficiency of One Cycle of Marker‐Assisted Selection
Authors: Moreau L. , Lemarié S. , Charcosset A. , Gallais A.
Published: July 2010

The efficiency of molecular markers to improve genetic prediction has been proved by many studies. Nevertheless, the additional cost due to marker genotyping is seldom considered in the comparison between marker‐assisted selection (MAS) and phenotypic selection. In the context of plant breeding, the relative cost efficiency of MAS in the first cycle of selection is evaluated through an analytical approach taking into account the effect of the experimental design (population size, number of trials, and replications per trial) on quantitative trait loci (QTL) detection. The same global cost is assumed for both methods. In a first step, the optimal allocation of the experimental resources is studied for each method before comparing them at their optimum. For traits sensitive to genotype × environment interactions, unreplicated trials are optimal for both methods but the optimal number of trials is different. It increases with the investment for phenotypic selection while it becomes nearly equal to one for MAS. The loss of efficiency due to non‐optimal designs is evaluated. The expected economic return of MAS compared with phenotypic selection decreases with the cost of genotyping. When this cost is high, MAS interest is limited to traits with a low heritability, provided that the investment is high enough to evaluate a large population size, which is the necessary condition to explain with markers a large part of genetic variation. The maximal genotyping cost that is acceptable for MAS to be efficient is given for different values of investment and trait heritability.
Genetic and Agronomic Evaluation of wp‐m in Soybean
Authors: Hegstad J. M. , Vodkin L. O. , Nickell C. D.
Published: July 2010

Transposable element systems have been proposed to explain instability in floral pigmentation of several plant species, including soybean [Glycine max (L.) Merr.]. Soybean lines with chimeric (purple and pink sectored) flowers are hypothesized to contain wp‐m, an active transposable element that is able to excise from the wp locus during morphological development. The objectives of this research were (i) to determine the inheritance of the chimeric flower phenotype when crossed to stable pink or purple flowered revertant lines and (ii) to determine the effect of wp on agronomic traits in stable flowered lines derived from wp‐m Chimeric flowers crossed to pink flowered revertant (wp*) lines produced four F2 populations with unusual segregation ratios of 52 pink, three purple, and two chimeric flowered plants. Crossing chimeric flowers to revertant purple flowered (Wp*) lines resulted in F2 populations that did not have the chimeric flower phenotype evident. In the agronomic evaluations, stable wp* lines were later in maturity and averaged 4 g kg−1 higher in protein content and 3 g kg−1 lower in oil content than Wp* lines. The data suggest wp acts in a pleiotropic manner to influence protein synthesis, as purple flowered revertant lines from a pink flower source had lower protein content than sister lines with wp*. Pink flowered lines derived from a purple flower source had higher levels of protein than sister lines with Wp*. The influence of wp on the anthocyanin pathway, plant morphology, and protein accumulation is a unique phenomenon that has not been reported in other plant species.
Birdsfoot Trefoil Seed Production: II. Plant‐Water Status on Reproductive Development and Seed Yield
Authors: Garcia‐Diaz C. A. , Steiner J. J.
Published: July 2010

Forage legume seed crop responses to water stress differ for each species, so a single optimal water management strategy is not applicable. The objectives of this study were to determine the effects of irrigation timing and replenishment amount on birdsfoot trefoil (Lotus corniculatus L.) reproduction and seed yield in the Willamette Valley of western Oregon, USA. Six treatments varying in water depletion percentage and replenishment amount were applied in 1994 and 1995 on a Woodburn silt loam soil (fine‐silty, mixed, mesic Aquultic Argixeroll) near Corvallis. In 1996, only a low stress (LS) that met the weekly crop evapotranspirative demand and a non‐irrigated control (C) treatment were investigated. In the first year of production, maintaining plants under low‐stress conditions sustained flowering longer than with limited or no irrigation. Flowering was not affected by irrigation in the subsequent two production years. Total above‐ground phytomass was correlated with the amount of irrigation water (r = 0.92). The C and all single application treatments had greater seed yields (SY) than the LS treatment in 1994. In 1995, all single application treatments had greater SY than the LS treatment. There was no difference between LS and C in 1995 and 1996. Umbel density and the number of seeds per pod were the primary determinants of total seed yield (r = 0.77 and 0.92, respectively). Optimal total seed production was achieved without supplemental irrigation under the humid temperate marine climatic conditions found in western Oregon.
Genetic Relationships between Loci Controlling the High Stearic and the High Oleic Acid Traits in Sunflower
Authors: Pérez‐Vich Bego n ˜ a , Garcés Rafael , Fernández‐Mart í nez Jose Mar í a
Published: July 2010

Sunflower (Helianthus annuus L.) lines with seed oils containing either high oleic (C18:1) or high stearic (C18:0) acid have been obtained through induced mutagenesis. The combination of the seed oil phenotypes of these lines would result in a novel oil quality of great value for the food industry. The objectives of this study were (i) to determine the genetic relationships between the high C18:0 and the high C18:1 traits, and (ii) to combine both characters. The sunflower lines HAOL‐9 (high C18:1), carrying the high C18:1 Ol alleles, and CAS‐3 (high C18:0), with the high C18:0 alleles es1 and es2, were reciprocally crossed. The fatty acid content of the F1, F2, BC1F1 to both parents, and F3 seeds was analyzed by gas–liquid chromatography (GLC). The segregation patterns for C18:0 (F2 ratio of 15:1) and C18:1 (F2 ratio of 1:3 or 7:9) in the F2 and BC1F1 to both parents fit those previously reported when each fatty acid was studied independently. However, a distortion was observed in their combined segregation, indicating that neither character was independently inherited. Furthermore, the analysis of the F3 generation revealed that F2 half seeds with the highest C18:0 concentration in a high C18:1 background were still heterozygous for either the C18:0 or the C18:1 levels, suggesting a genetic linkage between the alleles Es2 and Ol These alleles determine a lower C18:0 and a higher C18:1 content, respectively. No F2 recombination between them was achieved, resulting in the absence of high C18:0/high C18:1 phenotypes. However, some intermediate C18:0/high C18:1 F2 seeds led to stable F3 seeds with this phenotype (130 g kg−1 C18:0/790 g kg−1 C18:1).
Nitrogen Dynamics and the Physiological Basis of Stay‐Green in Sorghum
Authors: Borrell Andrew K. , Hammer Graeme L.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] hybrids containing the stay‐green trait retain more photosynthetically active leaves under drought than do hybrids that do not contain this trait. Since the longevity and photosynthetic capacity of a leaf are related to its N status, it is important to clarify the role of N in extending leaf greenness in stay‐green hybrids. Field studies were conducted in northeastern Australia to examine the effect of three water regimes and nine hybrids on N uptake and partitioning among organs. Nine hybrids varying in the B35 and KS19 sources of stay‐green were grown under a fully irrigated control, post‐flowering water deficit, and terminal water deficit. For hybrids grown under terminal water deficit, stay‐green was viewed as a consequence of the balance between N demand by the grain and N supply during grain filling. On the demand side, grain numbers were 16% higher in the four stay‐green than in the five senescent hybrids. On the supply side, age‐related senescence provided an average of 34 and 42 kg N ha−1 for stay‐green and senescent hybrids, respectively. In addition, N uptake during grain filling averaged 116 and 82 kg ha−1 in stay‐green and senescent hybrids. Matching the N supply from these two sources with grain N demand found that the shortfall in N supply for grain filling in the stay‐green and senescent hybrids averaged 32 and 41 kg N ha−1, resulting in more accelerated leaf senescence in the senescent hybrids. Genotypic differences in delayed onset and reduced rate of leaf senescence were explained by differences in specific leaf nitrogen and N uptake during grain filling. Leaf nitrogen concentration at anthesis was correlated with onset and rate of leaf senescence under terminal water deficit.
Trypsin inhibitory activity measurement: Simplifications of the standard procedure used for pea seed
Authors: Page D. , Quillien L. , Duc G.
Published: July 2010

A major breeding criterion for pea (Pisum sativum L.) is a low seed trypsin inhibitor activity (TIA), but the high cost of measurement limits the screening of new experimental lines. Our objectives were to devise two simplified procedures for screening for TIA using micro titration plates. In the first procedure, the inhibition induced by one single extract is measured. It allows for a rapid ranking of genotypes, but not calculation of seed TIA. Conversely, the second procedure is a titration procedure, where results are expressed in conventional trypsin inhibitor units (TIU). The time required for the measurements is reduced compared with that required with the standard procedures. The different methods were performed on cultivars ranging from low to high seed TIA. The results using the screening procedure showed very low standard deviations and allowed the ranking of the cultivars into three classes according to their seed TIA. The ranking was consistent with results obtained using the standard procedures. Results of the titration procedure were not significantly different from results obtained with the standard procedures on pea lines ranging from 2 to 10 TIU mg−1 dry weight.
Tetcyclacis and Abscisic Acid Differentially Affect Growth of Wheat (Triticum aestivum L.) Seedlings Isogenic for Reduced‐Height Genes
Authors: Klein Joshua D. , Hebbe Yonit
Published: July 2010

Wheat (Triticum aestivum L.) varieties with the dwarfing Rht (reduced height) alleles have reduced sensitivity to endogenous or exogenous gibberellin (GA). The Rht isolines are also less sensitive to the effects of chlormequat and other compounds which cause dwarfing by depressing GA synthesis. Abscisic acid (ABA) inhibits cereal seed germination and is in dynamic tension with GA, which enhances germination. Tetcyclacis is a cytochrome P450 mono‐oxygenase inhibitor of GA synthesis. It also inhibits ABA hydroxylase, thus extending ABA activity. In preliminary experiments, wheat varieties differing in Rht complement responded differently to ABA and/or tetcyclacis. We therefore investigated the effect of seed applications of ABA (100 μM), with or without tetcyclacis (25 μM), on germination and initial growth of Rht wheat isolines Rht‐B1b, Rht‐B1a (dwarf); Rht‐B1b,Rht‐D1b (dwarf); Rht‐B1b + Rht‐D1b (double‐dwarf); and Rht‐B1a, Rht‐D1a (tall) to determine a possible genetic basis for the observed varietal differences. Treating seeds with ABA, tetcyclacis, or both, delayed emergence by 1, 1.8, or 3.7 d, respectively, compared with controls. ABA had little or no effect on final emergence, shoot height, or fresh weight, but led to a slight reduction in dry weight of Rht‐D1b and Rht‐B1b+D1b Tetcyclacis reduced growth rate (mm/d), shoot height, fresh weight, and percentage dry weight in proportion to Rht dosage, as is typical of GA synthesis inhibitors. Synergistic effects of ABA and tetcyclacis were not detected for any parameter measured, except for rate of emergence. ABA did not exert a profound effect on seedling germination or initial growth of the Rht wheat isolines examined in this study.
Agronomic and End‐Use Qualities of Wheat streak mosaic virus Resistant Spring Wheat
Authors: Baley G. J. , Talbert L. E. , Martin J. M. , Young M. J. , Habernicht D. K. , Kushnak G. D. , Berg J. E. , Lanning S. P. , Bruckner P. L.
Published: July 2010

Development of wheat (Triticum aestivum L.) cultivars resistant to Wheat streak mosaic virus (WSMV) that remain productive in the absence of the disease would benefit wheat growers. A wheat germplasm (KS93WGRC27) carrying a Thinopyrum intermedium (Host) Barkworth and Dewey chromosome 4Js translocation conferring WSMV resistance was used to develop spring wheat populations segregating for WSMV resistance. Four populations, consisting of a total of 22 translocation‐positive (WSMV‐resistant), 36 translocation‐negative (WSMV‐susceptible), and eight parental lines, were grown as a randomized complete block with three replications at Bozeman and Conrad, MT, in 1998 and 1999. Treatments were arranged as a split plot with populations as main plots and progeny and parents as subplots. The agronomic performance of resistant and susceptible lines was compared under inoculated and noninoculated conditions to assess the effectiveness of the WSMV resistance gene and to determine the effects of the Thinopyrum translocation in the absence of disease. A small but significant decrease in yield was observed for noninoculated resistant lines in contrast to susceptible lines. However, the yield range of resistant entries suggests that the recovery of parental yield was possible. The resistance source was highly effective in limiting virus accumulation and yield losses to WSMV, resulting in only a 5% yield reduction in resistant lines under inoculated conditions compared with 32% for susceptible lines. In all instances where WSMV was introduced to field trials, the Thinopyrum translocation provided a significant benefit for resistant lines when compared with susceptible lines. The T. intermedium translocation present in resistant lines had no detrimental effects on end‐use quality or other agronomic traits.
Distribution of Buffalograss Polyploid Variation in the Southern Great Plains
Authors: Johnson Paul G. , Kenworthy Kevin E. , Auld Dick L. , Riordan Terrance P.
Published: July 2010

Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is indigenous to the short‐grass prairies of North America and is a polyploid series of diploid, tetraploid, and hexaploid individuals. It has a base chromosome number of x = 10. The distribution pattern of these ploidy levels is not well‐defined, especially in the southern Great Plains. We predicted the ploidy levels of 273 buffalograsses from the southern Great Plains of North America using flow cytometry to measure cellular DNA content. The buffalograss accessions were grouped into four distinct ploidy level groups. Very few diploid accessions were collected (2.6% of the collection), and all were found in northwest Texas and eastern New Mexico. Tetraploid accessions (23% of the collection) were found exclusively in the western regions of the southern Great Plains. Hexaploids were the most prevalent ploidy level, representing 73% of the collection and found throughout the collection area. Pentaploid accessions were also found in field sites (1.8% of the collection). No clear pattern of adaptation for ploidy levels is apparent from these data. In other collections, cold hardiness appears associated with higher ploidy levels, but this pattern is not apparent in the southern Great Plains.