bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified Procedure for Estimating Tissue Affinity for Bound Water in Durum Wheat
Authors: Rascio A. , Ruscio M. , Di Fonzo N.
Published: July 2010

Bound water has been studied intensively in relation to abiotic stress tolerance, but investigations of its role as a component of drought resistance in crop plants have been hampered by lack of rapid, inexpensive, and reliable methods capable of processing large populations in a short time. We investigated the possibility of estimating thermodynamic properties of strongly bound water in wheat leaves (Triticum durum Desf.) using a simplified analysis of water sorption, which made use of 39 paired isotherm curves constructed at 5 and 20°C, and thermodynamic parameters derived from them. Tissue affinity for strongly bound water (expressed as average differential enthalpy = ΔH̄) was compared with measurements of the difference in water sorbed (DWS) by the leaves at 5 and 20°C at relative humidities of 7, 11, 33, and 43%. Measurement of DWS at 33% relative humidity gave the best estimate of Δ̄, and therefore constituted a reliable, inexpensive, simplified method for the evaluation of tissue affinity for strongly bound water.
Quantification of Ergovaline in Tall Fescue by Near Infrared Reflectance Spectroscopy
Authors: Roberts C. A. , Joost R. E. , Rottinghaus G. E.
Published: July 2010

Near infrared (NIR) reflectance spectroscopy was examined as a possible alternative to high performance liquid chromatography (HPLC) analysis for ergovaline in tall fescue (Festuca arundinacea Schreber). Tall fescue samples were collected from field plots in Missouri and analyzed by NIR spectroscopy and HPLC. Spectral prediction equations produced coefficients of determination for calibration and cross validation of 0.93 and 0.88, respectively. The mean was 225 μg kg−1 dry matter (DM), and the standard errors for calibration and cross validation were 35 and 44 μg kg−1 DM, respectively. A close examination of NIR spectra revealed several wavelengths consistently correlated with ergovaline concentration in tall fescue.
Molecular Genetic Diversity after Reciprocal Recurrent Selection in BSSS and BSCB1 Maize Populations
Authors: Labate Joanne A. , Lamkey Kendall R. , Lee Michael , Woodman Wendy L.
Published: July 2010

Iowa Stiff Stalk Synthetic (BSSS) and Iowa Corn Borer Synthetic #1 (BSCB1) are undergoing reciprocal recurrent selection as part of Iowa's Federal‐State maize (Zea mays L.) breeding program. This study focused on molecular genetic variation in BSSS(R) and BSCB1(R) cycle 0 (CO) and cycle 12 (C12) populations, as well as the inbred progenitor lines (P) used to synthesize BSSS and BSCB1. The objectives were to quantify amounts of genetic variation within populations, to estimate what proportion remained after selection, and to compare genetic diversities between BSSS and BSCB1 populations. Genotypic data for 82 restriction fragment length polymorphism (RFLP) loci were collected from 100 randomly sampled individuals from each CO and C12 population, 16 BSSS(R) progenitors, and 12 BSCB1(R) progenitors. Progenitor lines were highly homozygous as expected. No single progenitor made excessive genetic contributions to CO or C12. The BSSS and BSCB1 progenitor populations were initially genetically similar (Nei's genetic distance = 0.07). After 12 cycles of selection, they substantially diverged (Nei's distance = 0.66). Gene diversity (expected heterozygosity under random mating) across progenitor populations was very broad (mean gene diversity = 0.6) and remained at that level to C12. Within both populations, the polymorphism level decreased from about 99 to 75%, and gene diversity decreased from about 0.6 to 0.3 between P and C12. The mean number of alleles per locus dropped from about four to less than three. Assuming an effective population size as the mean number of selected S1 lines over 12 cycles, the observed loss of variation was consistent with theoretical expectations resulting from genetic drift of neutral alleles.
Maturity and Pubescence Color Are Associated in Short‐Season Soybean
Authors: Cober E. R. , Voldeng H. D. , Morrison M. J.
Published: July 2010

Soybean [Glycine max (L.) Merr.] pubescence characteristics may affect maturity in short‐season germplasm. The objective of this study was to investigate the association of pubescence color and density with maturity in short‐season soybean germplasm. In Exp. 1, 106 F2‐derived quadruplets differing in pubescence color and density were developed from crosses between a F3:4 progeny row, with dense pubescence and segregating for pubescence color, and four grey‐ and four tawny‐pubescent lines with normal pubescence density. These 424 lines were evaluated for maturity for 4 yr at Ottawa, ON. Grey‐pubescent lines matured an average of 8.6 d later than tawny‐pubescent lines. Dense‐pubescent lines matured an average of 2.6 d later than lines with normal pubescence density. In Exp. 2, crosses were made between five grey‐ and five tawny‐pubescent parents and the maturity of 1397 homozygous grey‐ or tawny‐pubescent F3 progeny rows was observed. Grey‐pubescent progeny rows matured an average of 8.6 d later than tawny‐pubescent progeny rows. One tawny‐pubescent parent produced progeny in which maturity was not associated with pubescence color. In short‐season (e1e1) soybean germplasm, tawny pubescence is associated with early maturity. Since the E1 maturity locus is linked to the T pubescence color locus, there may be a third allele at the E1 locus or alternatively there may be a second maturity locus linked to pubescence color.
Kernel Set and Flower Synchrony within the Ear of Maize : I. Sowing Date Effects
Authors: Otegui María E. , Melón Soledad
Published: July 2010

Maize (Zea mays L.) grain yield depends on the number of kernels per plant that reach maturity. In this work, associations between floral development within the ear and final grain number of maize hybrids differing in prolificacy were studied under nonstress conditions in Argentina. In one experiment at Rojas (34°08′S), four hybrids were sown on four dates, at 8 plants m−2, during 2 yr. Ears were observed at silking to determine the variation in the number of spikelets per ear. In the second experiment at Saito (34°33′S), a nonproliflc (DK638) and a prolific (DK 3S41) hybrid were sown at 7 plants m−2 on three dates. Ears were examined between the three‐leaf stage and silking + 12 d to determine floral differentiation. No sowing date effect was evident for the number of spikelets per ear, the number of rows per ear, or the number of spikelets per row, but hybrids differed for thesecharacters (P < 0.05). During active spikelet initiation, spikelet number in apical ears increased at a rate of 0.13 (DK 638) or 0.17 (DK 3S41) spikelets per row per °Cd. At silking, almost nil spikelets along a row in the apical ear had completed floral development in both hybrids, but the prolific type showed less spikelet abortion in the apical ear and a more synchronous development between ears. Kernel number per ear was independent of floral development stage at siiking, but was related to the rate of ear growth (in length) around silking. These results suggest that assimilate partitioning to the ear during this period is critical for kernel set.
Film Coating Impairs Leaching of Germination Inhibitors in Sugar Beet Seed
Authors: Duan Xianming , Burris Joseph S.
Published: July 2010

Polymer film coating has been applied to commercial sugar beet (Beta vulgaris L.) seeds in the USA as an effective delivery system for agrochemicals. This research was conducted to study the impact of polymer film coating on sugar beet seed germination. Twelve seed lots, representing nine monogerm cultivars, had standard germination of 89 to 95%. After film coating (20 g of polyvinyl polymer per kilogram seed), the germination percentage varied from 68 to 94%. Six seed lots, including three lots of cultivar HH55, exhibited significant germination reductions after coating. Besides significant cultivar differences, seed lots within the same cultivar (HH55) also showed different responses to coating. After removal of the pericarp, the true seed of sensitive cultivar HH55 did not show germination reductions after coating. This indicates that the interaction between film coating and pericarp factors accounted for the germination reduction in film‐coated seeds. Sensitivity to film coating was alleviated by presoaking or peroxide treatments. A high negative correlation was found between absorbance at 265 am (A265 nm) of seed steep solution and coated seed germination percentage (r = −0.96***). The A265 nm of steeping solution could reduced to near zero by filtering the solution through the phenolic absorbent polyvinylpyrrolidone. Polymer film coating induced germination reductions in sensitive cnitivars were likely related to restricted oxygen supply to the enclosed embryo and to the retention of water soluble germination inhibitors, which would normally be leached into the germination medium and/or oxidized and deactivated.
Germination of Immature Soybean Seeds to Shorten Reproductive Cycle Duration
Authors: Roumet Pierre , Morin Frédérique
Published: July 2010

The soybean [Glycine max (L.) Merrill] reproductive cycle represents more than 50% of the length of the total growth cycle. Immature embryo culture could be used to shorten this cycle. This study was conducted to develop an efficient technique to shorten the soybean reproductive cycle and to make it possible to develop recombinant lines from populations more rapidly. The importance of a pod pretreatment before embryo extraction, the effects of embryo age on germination rate, embryo position in the pod, and the composition of the germination medium (supplemented with sucrose or not) were analyzed to define an optimal technique. Plant recovery rate and genotype effects on germination were evaluated with 22 genotypes representing a broad genetic background. It was necessary to pretreat immature seed by exposing pods to 26°C for 4 d to induce germination. Best results (up to 100% germination) were obtained from embryos sampled at the end of lag phase of seed development (approximately 18 d after flowering). For three‐seeded pods, the central embryos generally had a higher germination rate than distal and proximal embryos (25 and 44 percentage points, respectively). Whatever the embryo position in the pod, adding sucrose significantly increased the germination of embryos sampled 14 to 18 d after flowering. Plantlets were obtained from 73% of the germinated embryos and the length of cycle was reduced from 130 to 140 d to 65 to 70 d. Average germination of the 22 genotypes was 80%; thus, this technique, paired with the single seed descent method, provides soybean breeders with a tool to develop lines quickly.
Regions of the Genome That Affect Grain and Malt Quality in a North American Two‐Row Barley Cross
Authors: Mather D. E. , Tinker N. A. , LaBerge D. E. , Edney M. , Jones B. L. , Rossnagel B. G. , Legge W. G. , Briggs K. G. , Irvine R. G. , Falk D. E. , Kasha K. J.
Published: July 2010

Malting is an important end use of barley (Hordeum vulgare L.). The suitability of barley for malting depends on numerous quality characteristics, all of which are affected by genetic and environmental variation and many of which are inter‐related. Here, our objective was to use genome mapping to improve knowledge about the genetic basis for variation and covariation in grain and malt quality characteristics. Kernel plumpness, kernel weight, grain protein, fine‐grind extract, fine‐coarse difference, soluble protein, extract β‐glucan, extract viscosity, diastatic power, and a‐amylase activity were measured on grain produced in six field environments, from parents and doubledhaploid progeny of a two‐row barley cross, ‘Harrington’/‘TR306’. Quantitative trait loci and QTL × environment interactions were detected by means of 127 mapped markers and two methods of QTL analysis: simple interval mapping (SIM) and simplified composite interval mapping (sCIM). Each trait was affected by two to four primary QTL (those detected using both SIM and sCIM) and similar numbers of secondary QTL (those detected by only one of SIM or sCIM). Together, these QTL explained 21 to 67% of the phenotypic variance per trait. The numbers, effects, and relative positions of these QTL were in concordance with the quantitative trait distributions and with correlations among traits. All chromosomes, except chromosome 2, contained regions with at least one important QTL. Several genomic regions affected multiple traits. Most QTL interacted with environment, but many showed effects consistent enough that they might serve as targets for marker‐assisted selection. There was little similarity in the QTL positions detected here and those detected previously for the same traits in crosses representing other germplasm groups.
Agronomic Evaluation of Medicago ruthenica Collected in Inner Mongolia
Authors: Campbell T. A. , Bao G. , Xia Z. L.
Published: July 2010

Medicago ruthenica (L.) Ledebour has long been recognized as a potential new forage crop, which may also have potential as a source of genes for improving abiotic stress tolerance in cultivated alfalfa (M. sativa L.). This study was designed to assess the genetic variation among 50 M. ruthenica accessions, collected in Inner Mongolia in 1991 from 15 environments ranging from sand dunes to lush grassland, and to assess the agronomic potential of the species in the humid eastern USA. Accessions were evaluated in the field at Beltsville, MD, in 1993 and 1994 on an luka sandy loam (coarse‐loamy, siliceous, acid, thermic, Aquic Udigluvent; pH 6.4) in boron and potassium deficient soil. Stand retention was only 47% (compared with 94% for M. sativa checks) after the winter of 1993, indicating that the species is not well adapted to the humid eastern USA. Significant variation was noted for reaction to environmental stress (possibly boron deficiency), days from seeding to tillering, dry matter yield, growth habit, leaf shape, and plant height and width. No disease symptoms were noted; however, a detailed pathological examination was not conducted. A positive relationship was noted between plant width and yield, and between uprightness and narrow leaves. The more procurebent plants with broader leaves may have been less susceptible to winter damage under Beltsville conditions. Some of the most agronomicaily desirable accessions could have resulted from genetic shifts due to selection. Analyses indicate that M. ruthenica may have the potential to become a new forage crop, perhaps for low input systems, and that semi‐erect (for hay production) or procumbent (grazing tolerant) populations with improved seedling vigor and yield could be developed. Considering the antiquity and isolation of M. ruthenica, its harsh native environment, and the stress tolerance and yield of elite accessions under low‐input conditions, M. ruthenica may provide genes that could be of considerable value to cultivated alfalfa.
Meiotic Anomalies in Hybrids between Wheat and Apomictic Elymus rectisetus (Nees in Lehm.) A. Löve & Connor
Authors: Peel Michael D. , Carman John G. , Liu Zhi Wu , Wang Richard R. ‐C.
Published: July 2010

Four B111 hybrids (2n = 9x = 63, ABDStStYYWW) were obtained between wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) and a diplosporic and 2n‐pollen‐producing Elymus rectisetus (2n = 6x 42, StStYYWW) accession. We determined whether apomeiosis and 2n pollen formation, which occur in the male parent, also occur in the Bill hybrids. Pistils were cleared for UV microscopy of callose and recleared for cytological observations using interference contrast microscopy. Callose fluorescence from most megaspore mother cells (MMCs) was typical of sexual species. These were classified as sexual. Abnormally elongated MMCs with walls devoid of callose were observed in 4.7% of pistils collected at meiotic prophase. These traits are typical of many apomeiotic MMCs in E. rectisetus. Asynapsis followed by mitosis in pollen mother cells (PMCs) consistently preceded unreduced pollen formation in E. rectisetus. This was not observed in the B11l hybrids, though the following meiotic anomalies were observed: (i) asynapsis, aggregation of chromosomes to several poles, and multiple divisions to form four to eight unbalanced microspores, and (ii) incomplete synapsis, formation of anaphase I laggards, and a second division resulting in four unbalanced microspores with micronuclei. The wheat haplome enforced PMC meiotic pairing (albeit abnormal) among homologous E. rectisetus chromosomes and generally inhibited apomeiosis, also by enforcing meiosis. Diplospory may be caused by the expression of embryo sac signals from one genome precociously expressed with megasporogenesis signals from another. If this is correct, the successful induction of apomixis in wheat may require the transfer of alien gene cassettes that confer appropriate degrees of reproductive asynchrony.
Stomatal Closure of Maize Hybrids in Response to Drying Soil
Authors: Ray Jeffery D. , Sinclair Thomas R.
Published: July 2010

In studying differences among genotypes in physiological response to drying soil, it is important that the genotypes be compared at equivalent soil water contents. Unless the comparisons are made at the same soil water content, genotypic difference may only he a consequence of differences in soil water status. In this study, the objective was to compare stomatal closure among eight maize (Zea mays L.) hybrids in response to soil drying. Three greenhouse experiments were conducted in which daily transpiration and soil water content were measured by weighing each pot. Daily transpiration of stressed plants was normalized relative to that of control plants to minimize variation due to environmental effects. This daily transpiration ratio also was normalized relative to the well‐watered condition to minimize variation among plants and was recorded as normalized transpiration ratio (NTR). Daily soil water content was expressed as the fraction of transpirable soil water (FTSW). Among the eight hybrids examined, there were statistical differences in the FTSW at which the stomata began to close. In all experiments, Hybrid 3165 was consistently among the hybrids that began to close their stomata at small FTSW values; whereas, Hybrid 3737 began to close its stomata at large FTSW values. While we surveyed a small genetic base, our results indicated genotypic differences exist for stomatal responses to a drying soil.
Base Temperature and Growing‐Degree‐Hour Requirements for the Emergence of Canola
Authors: Vigil Merle F. , Anderson R. L. , Beard W. E.
Published: July 2010

Spring canola (Brassica napus L. and B. rapa L.) is sometimes planted when soil temperatures are below the optimum, causing farmers to have stand losses because of seed rotting in cold soil. Knowledge of the growing‐degree hours (GDH) required for emergence of canola from different planting depths could help producers decide when and how deep to plant this crop. Our objectives were to quantify the base temperature (the minimum temperature required) for emergence, the number of GDH required for initial emergence of five cultivars of spring and winter canola, and to evaluate temperature × planting depth Interactions of spring canola. ‘Alto’, ‘Global’, ‘Tobin’, ‘Crystal’, and ‘Glacier’ cultivars were planted 1 cm deep into pots of Weld silt loam (fine, montmorillonitic, mesic aridic Paleustolls). Pots were incubated at 0, 2, 4, and 16°C. Seedlings emerged were counted daily for all temperatures and twice daily during rapid emergence at 16°C. Simple‐linear and segmented‐nonlinear‐regression were used to determine base temperatures and GDH requirements for initial emergence. Calculated base temperatures were between 0.4 and 1.2°C. Regardless of the constant temperature regime, emergence began between 1560 and 1940 GDH for the spring canola. Winter canola emerged at 1600 to 2800 GDH. Two cultivars (Tobin and Global) were also planted at 1‐, 2‐, 2.5‐, 3‐, and 4‐cm depths and incubated at 4, 8, 12, and 16°C to investigate planting depth × temperature interactions. A reduction in emergence, as a function of an interaction between temperature and planting depth, was found for Global but not Tobin at the temperatures and planting depths used in this study. A match between the accumulated heat units in early spring for a location and the GDH required for initial emergence of the spring cultivars tested can be used to determine early spring canola planting dates. This analysis indicates that severe reductions in stand are possible when canola is planted at soil temperatures that are sustained much below 8°C. The heat unit approach used allows for the transfer of the relationships developed in this study to other locations.
Leaf Appearance Rate and Final Leaf Number of Switchgrass Cultivars
Authors: Van Esbroeck G. A. , Hussey M. A. , Sanderson M. A.
Published: July 2010

In switchgrass (Panicum virgatum L.), maximum yields occur with late flowering genotypes that have an extended duration of vegetative growth. However, little is known about the developmental basis for a long vegetative growth phase in perennial grasses. Studies were carried out on the leaf development of five switchgrass cultivars with varying flowering times (Cave‐in‐Rock, Caddo, Kanlow, NC2, and Alamo) to provide inputs for crop simulation models and to determine if a long duration of vegetative growth was associated with a reduced rate of leaf appearance or a high final leaf number. The studies were carried out in the field at College Station, TX, (30°38'N, 96°20'W), during 1994 and 1995. Thirty tillers emerging in spring were tagged and visible leaves were recorded weekly until panicles emerged. Final leaf numbers were recorded on the flowering tillers which had emerged in spring and after a June defoliation. Tillers of all cultivars emerged in March and panicles emerged during a 2‐too period from May to July. Final leaf number of spring‐emerging tillers of all cultivars ranged from nine to 11, whereas summer‐emerging tillers flowered after seven leaves had appeared. The phyllochron [growing degree days (GDD) between the appearance of two successive leaves] for all cultivars increased with advancing leaf number. High average phyllochron values (GDD base 10°C) were associated with late panicle emergence and a long duration of vegetative growth. Cave‐in‐Rock, the earliest flowering cultivar, averaged 79 GDD per leaf and required 634 GDD to attain panicle emergence, while Alamo, the latest to flower, averaged 152 GDD per leaf and required 1777 GDD to attain panicle emergence. A slow rate of leaf appearance was identified as the primary developmental trait associated with a long duration of vegetative growth in switchgrass.
Branch Yield Components Controlling Soybean Yield Stability across Plant Populations
Authors: Carpenter A. C. , Board J. E.
Published: July 2010

Soybean [Glycine max (L.) Merr.] optimizes yield over a broad range of plant populations, but mechanisms responsible for compensation have not been fully elucidated. Identification of these factors would help in selecting cultivars‐genotypes having low optimal plant populations (minimal plant population required for best yield) and provide agronomists and farmers with indicators of optimal plant population. Our objective was to determine the mechanism for plant yield compensation across a range of plant populations. Soybean cultivar DeltaPine 415 (Maturity Group V) was planted at an optimal date at low (70 000 plants ha−l), medium (164 000 plants ha−l), medium‐high (189 000 plants ha−l), and high (234 000 plants ha−l) plant populations on a Commerce silt loam (fine‐silty, mixed, nonacid, thermic Aeric, Fluvaquent Haplaquepts) near Baton Rouge, LA(30°N Lat.). A 58% population decrease from 164 000 plants ha−l resulted in a yield decrease of only 12%, while a 43% increase resulted in no significant yield change. Yield per plant was primarily regulated by changes in branch dry matter per plant, which averaged 14.0, 5.3, and 3.6 g per plant for the low, medium, and high populations, respectively. Greater branch dry matter per plant created more branch nodes, branch reproductive nodes, and branch pods. Pod per reproductive branch node also affected yield in some cases. High correlation between branch dry matter per plant and yield (r2 = 0.95; P ≤ 0.001) demonstrated the usefullness of this yield component for identifying cultivars or genotypes with low optimal plant populations.
Apospory‐Linked Molecular Markers in Buffelgrass
Authors: Gustine D. L. , Sherwood R. T. , Huff D. R.
Published: July 2010

Isolation of a gene controlling apomixis would be useful to plant breeders for fixing hybrid vigor. A single gene encodes for aposporous apomixis in buffelgrass (Pennisetum ciliare L. Link), which is inherited in a autotetraploid fashion. Only two molecular markers linked to the gene are known: C04‐600, a RAPD (random amplified polymorphic DNA) and UGT197‐144, an STS (sequence‐tagged site). The objective of this study was to identify new RAPD markers linked to the apospory locus in butfelgrass and to prepare a linkage map. Sexual clone B‐2s was crossed to aposporous butfelgrass cultivar Higgins and to aposporous clone B‐12‐9. Progeny of each cross were screened for RAPD markers by bulked segregant analysis. Seven preparations of bulked genomic DNA (equal amounts DNA from each of 10 individuals) from sexual or aposporons progeny were examined for RAPD markers. Using 500 decanucleotide primers, we found five new markers potentially linked to the apospory gene. Analysis by MAPMAKER/EXP 3.01 indicated markers J16‐800 and M02‐680 were linked to the apospory gene, as was previously established marker UGT197‐144, and the three were placed on the map. Marker A20‐730 was loosely linked in both crosses, marker B14‐550 was unlinked in the Higgins cross, and marker N15‐370 was unlinked in both crosses, and they were not placed on the map. These data provide the first map for the bulfelgrass chromosome bearing the apospory gene.
Genetic Analysis of Plant Regeneration from Seed‐Derived Calli in Rice (Oryza sativa L.)
Authors: Takeuchi Yoshinobu , Abe Toshinori , Sasahara Takeo
Published: July 2010

The ability of rice (Oryza sativa L.) to regenerate plantlets from calli differs among different cultivars. The present experiments were~ implemented to examine genetic characteristics of plant regeneration from calli in different rice cultivars. The rate of plant regeneration from mature seed‐derived calli was higher in Tadukan (indica) than in Norin 1 (japonica). The inheritance mode of plant regeneration ability was analyzed in populations of the F2 generation from Norin 1 × Tadukan and in those of the back‐crossed generation (FIBCI) from Norin 1 × F1 plants (Norin 1 × Tadukan). A Chi‐square test in the F2 generation showed a 3 (dominant) : (recessive) segregation ratio for the higher and the lower plant regeneration abilities, respectively. A Chi‐square test in the F1BC1 generation showed a 1 (dominant):l (recessive) segregation ratio for the higher and the lower plant regeneration abilities, respectively. Thus, the higher plant regeneration characteristics of Tadukan appear to be regulated by a single dominant gene.
Classifying Mexican Maize Accessions Using Hierarchical and Density Search Methods
Authors: Franco Jorge , Crossa José , Villaseñor José , Taba S. , Eberhart Steve A.
Published: July 2010

Cluster analysis is commonly used for studying genetic diversity. Problems with hierarchical cluster analysis include how to combine different types of variables (discrete and continuous), choosing distance measurements, applying an appropriate clustering strategy, designating the optimal number of clusters, and identifying variables with significant discriminatory power. Hierarchical clustering methods are only descriptive and do not represent probabilities for classifying individuals into groups. The objectives of this study were to: (i) examine the performance of different cluster strategies based on several criteria, (ii) propose a classification method for germplasm accessions with statistical properties, and (iii) examine how the results of the proposed classification classification method can be applied to form core subsets. Morphologic and agronomic attributes collected for 115 Mexican maize (Zea mays L.) accessions, grouped in five races, from the Latin America Maize Project (LAMP) were subjected to the hierarchical cluster algorithms UPGMA (arithmetic mean method), Centroid, Median, and the Ward method. Two other techniques were studied, Density and the Normix (Nor) density search methods, which were both restricted continuous variables. The Nor method was applied to groups formed “a priori” by means of the hierarchical methods UPGMA, Centroid, Median, and Ward and resulted in subgroups denoted as NorU, NorC, NorM, and NorW, respectively. The NorW method formed five well defined groups of accessions and was an appropriate strategy for grouping accessions into relatively homogeneous groups. Strategies UPGMA, NorU, Centroid, NorC, Median, NorM, and Density were not very effective for classifying accessions into homogeneous groups. Different subsets can be formed based on the characteristics of the five homogeneous groups formed by NorW.
Hybrid Seed Production of Pearl Millet × Napiergrass Triploid Hybrids
Authors: Osgood R. V. , Hanna W. W. , Tew T. L.
Published: July 2010

Pearl millet (PM), Pennisetum glaucum (L) R. Br., × napiergrass (NG), P. purpureum Schum., interspecific hybrids (PMN) have the potential to extend production of high quality forage into the late summer and fall in the USA. The objective of this study was to determine if interspecific hybrid seed could be produced on a commercial scale at Kunia, HI, and to identify production problems. Although one block yielded 1145 kg ha−1 PMN seed in 1986, seed yields in most years averaged 300 to 600 kg ha−1 if birds were controlled. Rain storms during November and December, when seed was maturing, reduced both seed yields and seed quality. Observations in this study indicated that PMN seed may be more successfully produced if flowering of plants is manipulated to mature seed in March in Hawaii or if produced in a tropical climate with a dry winter season.
Comparison of Seed‐Derived Lines from ‘Florigraze’ Rhizoma Perennial Peanut
Authors: Venuto B. C. , Elkins W. M. , Hintz R. W. , Reed R. L.
Published: July 2010

Rhizoma perennial peanut (RPP—Arachis glabrata Benth.) is a high quality, vegetatively propagated, forage legume introduced into southern USA from South America. Information on the performance of seed‐derived lines from this germplasm is lacking. This information is needed to help determine the feasibility of establishing a recurrent selection breeding program to improve the performance of this germplasm. The objectives of this study were to evaluate the variation within Florigraze seedling progeny for reproductive and morphological traits, and to identify lines with superior agronomic characteristics. Three hundred naturally occurring seedlings of Florigraze were identified in the field and characterized for traits including floral initiation, growth habit, leaf morphology, main stem height, lateral growth, and plant density. Seven lines were vegetatively increased for forage evaluation. These lines were evaluated for 2 yr at two locations, for dry matter forage yield, forage quality, plant height, lateral growth, and stand density. None of the Florigraze lines flowered earlier than Florigraze and 22% failed to flower in 3 yr of observation. Means of lines for all morphological traits were consistently below the mean of Florigraze plants. None of the seven replicated lines outperformed Florigraze for all forage traits. Some lines were superior for forage yield or crude protein, but not across locations. If the poor performance of seed‐derived lines from Florigraze is representative of RPP, then future selection and advancement of this germplasm may be seriously limited.
Interaction of Virescent Genes in Upland Cotton (Gossypium hirsutum L.): Chlorophyll Content
Authors: Zhang Tian Zhen , Pan Jia Ju , Xiao Song Hua , Kohel R. J.
Published: July 2010

The interactions between the virescent genes v2 and v14 of cotton (Gossypium hirsutum L.) were determined and compared with other virescent genes. Single crosses were made among various virescent lines, and the progenies were tested from 1991 to 1994. Allelic tests established that v2 and v14 were nonallelic, but their F1 hybrid plants were virescent, with phenotypic expression and chlorophyll content intermediate between the parents. In the F2 population, plants segregated into classes with various degrees of virescent expression — from green, parental virescents, deep yellow, to chlorotic types with extremely low vigor. The chlorophyll content of functional leaves on the deep‐yellow type (0.54–0.56) was less than one‐half that of the parental virescent types (1.13–1.43). The interaction effect between v2 and v14 was prominently reflected in the reduced content of Cb and the high Ca/b ratio of the deep‐yellow type. This complementary function can be due to the nondiploidized function of homoeologous loci of the G. hirsutum allotetrapioid.
Combining Ability of Response to Photoperiod in Peanut
Authors: Nigam S. N. , Dwivedi S. L. , Ramraj V. M. , Chandra S.
Published: July 2010

Photoperiod insensitivity plays an important role in the adaptation of peanut (Arachis hypogaea L.) genotypes across environments. However, little is known of its genetic control. The objective of this study was to determine the combining ability of response to photoperiod in peanut. The F1 progenies from a six‐parent diallel cross excluding reciprocals were studied together with their parents for response to photoperiod under short and long day conditions in the field for three seasons. The experiment was conducted in a split plot design with photoperiod as main plots and genotype as subplots. The response to photoperiod (DSL) was computed as the difference in harvest index (adjusted pod weight/adjusted biomass) between short and long day treatments. The mean square for response to photoperiod was highly significant for parents and their crosses. Season by cross interaction was the only significant interaction effect. The response to photoperiod was mainly associated with general combining ability variance. ICG 2405 and ICGV 86031 were good general combiners for insensitivity to photoperiod. All crosses of sensitive × sensitive and sensitive × insensitive parents were sensitive to photoperiod. However, in several cases, this response was not consistent across seasons and resulted in a significant season × cross interaction. The F1 between insensitive parents was insensitive to photoperiod in the three seasons tested. A comparison of F1 response with parents and midparent value of crosses between photoperiod sensitive and insensitive parents suggested additive gene action in some crosses and partial dominance to dominance in others.
Wheat Breeding Nurseries, Target Environments, and Indirect Selection for Grain Yield
Authors: Cooper M. , Stucker R. E. , DeLacy I. H. , Harch B. D.
Published: July 2010

Use of appropriate nursery environments will maximize gain from selection for yield of wheat (Triticum aestivum L.) in the target population of environments of a breeding program. The objective of this study was to investigate how, well‐irrigated (low‐stress) nursery environments predict yield of lines in target environments that varied in degree of water limitation. Fifteen lines were sampled from the preliminary yield evaluation stage of the Queensland wheat breeding program and tested in 26 trials under on‐farm conditions (Target Environments) across nine years (1985 to 1993) and also in 27 trials conducted at three research stations (Nursery Environments) in three years (1987 to 1989). The nursery environments were structured impose different levels of water and nitrogen (N) limitation, whereas the target environments represented a random sample of on‐farm conditions from the target population of environments. Indirect selection and pattern analysis methods were used to investigate selection for yield in the nursery environments and gain from selection in the target environments. Yield under low‐stress nursery conditions was an effective predictor of yield under similar low‐stress target environments (r = 0.89, P < 0.01). However, the value of the low‐stress nursery as a predictor of yield in the water‐limited target environments decreased with increasing water stress (moderate stress r = 0.53, P < 0.05, to r = 0.38, P > 0.05; severe stress r = −0.08, P > 0.05). Yield in the stress nurseries was a poor predictor of yield in the target environments. Until there is a clear understanding of the physiological‐genetic basis of variation for adaptation of wheat to the waterlimited environments in Queensland, yield improvement can best be achieved by selection for a combination of yield potential in an irrigated low‐stress nursery and yield in on‐farm trials that sample the range of water‐limited environments of the target population of environments.
Root Protein and Vegetative Storage Protein Are Key Organic Nutrients for Alfalfa Shoot Regrowth
Authors: Avice J. C. , Ourry A. , Lemaire G. , Volenec J. J. , Boucaud J.
Published: July 2010

Organic reserves in below‐ground storage organs are generally recognized as indicators of regrowth and persistence potential of forages. The objective of this experiment was to examine the causal relationships between regrowth potential of alfalfa (Medicago sativa L.) and root organic reserves, i.e., nonstructural carbohydrates or N reserves as N, soluble protein, and vegetative storage protein (VSP). Variations in reserve level induced by cultivar differences (cv. Lodi or Europe), length of the previous regrowth period (30 or 45 d), or by competitive position for light within a dense canopy were studied during 35 d of regrowth. Field grown plants were harvested at weekly intervals, and separated as dominant, intermediate, and suppressed plants. Taproot starch and N contents were influenced by the length of the previous regrowth period, but not by the position of the plant within the canopy. In contrast, soluble protein and VSP concentrations increased when the previous regrowth lengthened from 30 to 45 d and were greater in dominant plants within the canopy. Starch, N, soluble protein, and VSP contents were greater in taproots of Lodi plants. Shoot regrowth was linearly related to taproot soluble protein and VSP contents on the day of defoliation, whereas no relationships was detected between shoot regrowth and initial starch or N contents. These results suggest that root protein and VSP are key organic nutrient for alfalfa shoot regrowth after harvest.
Forage Quality Variation in the U.S. Alfalfa Core Collection
Authors: Jung H. G. , Sheaffer C. C. , Barnes D. K. , Halgerson J. L.
Published: July 2010

Alfalfa (Medicago sp.) is the most important perennial forage crop in the USA. The cultivars currently grown commercially are based on a limited and intermixed set of germplasm. Our objective was to survey the genetic variation in leaf and stem quality in the crop by analyzing the core collection of the U.S. alfalfa plant introductions. The 200 plant introductions of the core were planted at Rosemount, MN, in 1991 and 190 entries were sampled at flowering in 1992. Sixtyone entries were re‐sampled in 1993. Leaf and stem tissues were analyzed separately for crude protein, neutral and acid detergent fiber (NDF and ADF, respectively), acid detergent lignin, in vitro dry matter disappearance (IVDMD), and ficin degradable CP (FDCP). Additionally, stems were analyzed for cellulose concentration and enzymatic degradability, 24‐ and 96‐h in vitro NDF digestibility (IVNDFD),and lignin composition. For all forage quality traits, significant variation was found among the plant introductions. Concentration of NDF varied widely for leaves among entries, but relatively little variation occurred in stem NDF. The opposite trend occurred for IVDMD which varied more in stem material than leaves. This result was attributed to the high degree of variation in stem IVNDFD among the plant introductions. Stem FDCP was among the more variable traits measured. Quality traits of four contemporary check cultivars included in the trial were never as high or low as the extremes observed among the plant introductions. Significant sampling year effects were observed for most quality traits, but year × entry interactions were minimal. Concentration of NDF and IVDMD had significant negative correlations between leaf and stem values. In general, if leaf or stem quality was high, then the quality of the other plant part was low although this correlation was not large. Significant variation in forage quality traits exists in the U.S. alfalfa germplasm collection that could be used to improve the quality of commercial cultivars.
Transgenic Corn Expressing a Cry9C Insecticidal Protein from Bacillus thuringiensis Protected from European Corn Borer Damage
Authors: Jansens Stefan , van Vliet Adri , Dickburt Catherine , Buysse Linda , Piens Carla , Saey Bernadette , De Wulf Ann , Gosselé Veronique , Paez Alix , Göbel Elke , Peferoen Marnix
Published: July 2010

The European corn borer, Ostrinia nubilalis (Hübner), is devastating insect pest in the corn (Zea mays L.) growing regions of North America and Europe. Field evaluations in the USA and Belgium showed that transgenic corn events expressing Cry9C, an insecticidal crystal protein from Bacillus thuringiensis subsp, tolworthi, very effectively control both generations of the European corn borer. Second to fourth instar larvae fed with leaf material of event CBH351 expressing the Cry9C protein all died within 4 d. Cry9C events, expressing high levels of the insecticidal protein, showed minimal stalk tunneling after heavy artificial infestations. Event CBH351 tested in plots containing only Cry9C transgenic plants had 0.14‐ and 0.09‐cm tunneling per stalk compared with more than 30‐ and 23‐cm tunneling per stalk for the negative controls, in the Belgium and Iowa field trial, respectively. In plots containing 30% non‐transgenic plants the event CBH351, showed only 1.45‐cm tunneling per stalk. Leaf, tassel, and pith tissue contained 39.0, 17.4, and 84.8 μg Cry9C protein mg−1 soluble protein, respectively, in analyses conducted at harvest of the Belgium trial. The implications of Cry9C use for resistance management strategies are discussed.
Recombination between a Crown Rust Resistance Locus and an Interchange Breakpoint in Hexaploid Oat
Authors: Wilson W. F. , McMullen M. S.
Published: July 2010

The oat (Avena sativa L.) cultivars, Steele and Dumont, differ by a chromosomein terchange. Twot ightly linked or allelic crown rust resistance genes (Pc‐63 and Pc‐38) are located on one of the segments involved in the interchange. Recombinant chromosomes can result from crossing‐over in the region between the crown rust resistance locus and the interchange breakpoint. Our objectives were to use a diallelic duplicate locus to (i) identify recombinant BC1F1 genotypes with Pc‐63 in the interchanged position, (it) estimate the linkage relationship between the crown rust resistance locus and the interchange breakpoint, and (iii) recover duplication genotypes that possess four copies of Pc‐63. Segregation of BC1F2 families was used to detect recombination within an interchanged chromosome segment in F1 interchange heterozygotes. Only 3/7 of the single crossover recombinant gametes could be recognized by duplicate dominant segregation in BC1F2 families. After inoculation of 145 BC1F2 families with a crown rust (Puccinia coronata Corda var. avenae W.P. Fraser & Ledingham) isolate avirulent on Pc‐63 and virulent on Pc‐38, we identified 11 recombinant families segregating 15R:1S. A 15:1 segregation ratio indicated Pc‐63 recombined to an interchanged position as a result of crossing‐over between the crown rust resistance locus and the interchange breakpoint. Our data indicated Pc‐63 was linked in repulsion and distal to the interchange breakpoint with 17.7% recombination observed between the crown rust resistance locus and the breakpoint. Testcross segregation ratios confirmed that recombination occurred and allowed identification of a true breeding duplication genotype that possessed four copies of Pc‐63. Increasing the dosage of Pc‐63 did not alter the expected infection type conferred by a one or two copies of Pc‐63.
Chromosome Location of Leaf Rust Resistance Gene Lr43 from Aegilops tauschii in Common Wheat
Authors: Hussien Temam , Bowden R. L. , Gill B. S. , Cox T. S.
Published: July 2010

Wheat leaf rust resistance gene Lr43 was recently transferred from Aegilops tauschii Coss. to common wheat (Triticum aestivum L.) to produce hard red winter wheat germplasm line KS92WGRC16. Monosomic and telocentric analyses were used to determine the chromosomal and chromosome arm location of Lr43. KS92WGRC16 was crossed with each of the seven D‐genome monosomic lines. The F2 families were inoculated with race PBJL of the leaf rust fungus, Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Eriks. & E. Henn.) D.M. Henderson. The number of resistant to susceptible seedlings did not deviate significantly from a 3:1 ratio in crosses involving 1D, 2D, 3D, 4D, 5D, or 6D monosomic lines. However, the 7D monosomic‐derived F2 deviated significantly from a 3:1 ratio (x2 = 32.2, P < 0.001) indicating that Lr43 is located on this chromosome. Twenty resistant F2 plants from the critical cross were progeny tested, and results confirmed the location of Lr43 on chromosome 7D. Telocentric analysis showed that Lr43 is on the short arm of chromosome 7D (7DS) and it is unlinked to the centromere. This information may facilitate development of molecular markers and result in more efficient breeding for resistant cultivars.
Residue Management Strategies for Kentucky Bluegrass Seed Production
Authors: Chastain T. G. , Kiemnec G. L. , Cook G. H. , Garbacik C. J. , Quebbeman B. M. , Crowe F. J.
Published: July 2010

Open‐field burning provides effective, economical post‐harvest residue management in Kentucky bluegrass (Poa pratensis L.) seed crops, but public concern over air quality necessitates the identification of nonthermal management strategies. On‐farm trials were conducted in Oregon's Grande Ronde Valley to investigate the effect of nonthermal management in two cultivars of Kentucky bluegrass on crop regrowth, seed yield, and seed quality. Residue treatments imposed after the first, second, and third seed harvests included (i) removal of straw by baling (Bale), (ii) baling, flailing with a rotary scythe, followed by residue removal with a needle‐nose rake (Rake), (iii) baling, followed by removal of the residue by vacuum‐sweeper (Vacuum), (iv) flail‐chopping residue three times with no removal (Flail 3X), and (v) open‐field burning (Burn). Tillers were etiolated at the cessation of fall regrowth in Flail 3X (stubble height reduced, no straw removal) and Bale (no stubble height reduction, 75% straw removal) treatments. Fertile tiller number was lower in the following spring with Flail 3X and Bale treatments compared with Burn. Seed yield averaged across the 3‐yr period was reduced 38% when managed with Flail 3X and 10% when managed with Bale compared with Burn. Crop regrowth, fertile tiller production, and seed yield resulting from Rake and Vacuum treatments were equivalent to the Burn treatment. Rake and Vacuum treatments reduced stubble height and removed at least 90% of the straw. High seed yield and seed quality can be maintained in Kentucky bluegrass without open‐field burning when straw removal is thorough and stubble height is reduced prior to crop regrowth.