bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Variation within Maize Breeding Populations
Authors: Fountain M. O. , Hallauer A. R.
Published: July 2010

Proper choice of germplasm determines the ultimate success of selection for genetic improvement. Germplasm included in maize (Zea mays L.) breeding has evolved from the original landrace cultivars to F2 populations of elite line crosses. Objectives of our study were to determine the mean and genetic variability (σ2G) of yield and other traits within three F2 populations (B73 × B84, B90 × Mo17, and B73 × Mo17), within three genetically narrow‐base synthetics (NBS) [BS14, Mol7‐Syn., and H73‐Syn.], and within three genetically broadbase synthetics (BBS) [BSll(FR)C9, BSCBI(R)C9, and BSSS(R)C9]. Fifty S1 progenies for each of the nine populations were evaluated at three locations for 2 yr. Differences among S1 progenies within each population were significant for most traits. Estimates of σ2G were determined from the S1 component of variance, and average estimates of σ2G for grain yield were similar for F2 and BBS populations, whereas the average estimate of σ2G for NBS populations was 40% smaller. Within population types, the related line cross (B73 × B84)F2 had 50% less σ2G for grain yield than the other two F2 populations. BS14, H73‐Syn., and BSCBI(R)C9 had smaller estimates of σ2G for grain yield than the other synthetic populations. Estimates of σ2G suggest selected F2 and BBS populations have greater potential for improved gains than the NBS populations. The related line (B73 × B84)F2 had 50% less 62G than either (B90 × Mo17)F2 or (B73 × Mo17)F2. (B90× Mo17)F2 and (B73 × Mo17)F2 had similar estimates of σ2G, although B90 and Mo17 are in the same heterotic group, whereas B73 and Mo17 are in different heterotic groups [Reid Yellow Dent (B73) and Lancaster Sure Crop (Mo17)]. Selection for improvement of yield would be more effective within the (B90 × Mo17)F2 than within (B73 × B84)F2 and more useful than within (B73 × Mo17)F2.
Relationship between Heterosis and Genetic Distance Based on Restriction Fragment Length Polymorphism Markers in Oilseed Rape (Brassica napus L.)
Authors: Diers B. W. , McVetty P. B. E. , Osborn T. C.
Published: July 2010

Significant heterosis for seed yield in oilseed rape (Brassica napus L.) has created interest in the development of hybrid cultivars. The objective of this study was to determine the value of restriction fragment length polymorphism (RFLP) markers in predicting hybrid performance. The hybrids and parents of two sets of diallel crosses were evaluated at three environments for seed yield and other agronomic traits. The parents of the first diallel were seven oilseed rape cultivars and the parents of the second diallel were seven unselected S6 lines derived from the cultivars. Genetic distances (GD) between the parents crossed in the diallels were estimated by RFLP data from 43 DNA clones. Both general combining ability (GCA) and GD estimates were significantly (P < 0.05) correlated with hybrid seed yield in both diallels, although GCA was more greatly correlated than GD. Genetic distance was significantly correlated with heterosis for seed yield only in the inbred diallei whereas GCA was significantly correlated with heterosis only in the cultivar diallel. Midparent yield was significantly correlated only with heterosis for the cultivar diallel. A multiple linear regression model that included both the GD and GCA of the parents was more greatly correlated with hybrid seed yield than any variable alone. The GCA values were significantly correlated with hybrid plant height, and seed oil and protein concentration in both diallels whereas GD was significantly correlated only with hybrid plant height. These results suggest that GD estimates alone do not identify high yielding hybrid combinations with the consistency to be useful in breeding programs.
Yield of Selected and Unselected Bahiagrass Populations at Two Cutting Heights
Authors: Pedreira C. G. S. , Brown R. H.
Published: July 2010

Yields of bahiagrass (Paspalum notatum Flugge) have been increased over that of ‘Pensacola’ through several cycles of selection. To determine factors contributing to the increased yields, a field experiment was conducted for 3 yr to examine yields, biomass, and, leaf area index of three populations representing Cycles 0 (Pensacola, original population), 9 (‘Tifton 9’) and 14 (T14). Plots were mowed every 2 wk at 3.5‐ and 10‐cm heights and quadrat samples were taken to estimate dry weights of stubble after mowing plus rhizomes. In the first harvest year, T14 yielded more than the other two populations when mowed at 3.5 cm, but less when mowed at 10 cm. Yields averaged across the second and third years and across cutting heights were 20 and 25% higher for Tifton 9 and T14, respectively, than for Pensacola. Total biomass (excluding roots) was higher in July of the first year for Pensacola than for Tifton 9 and T14, and for the latter two, harvested yield made up a larger percentage of the total. However, in July of the third year neither biomass nor percentage of the biomass harvested differed among the populations. Stubble plus rhizome weights increased throughout the 3‐yr period and were higher for Pensacola than Tifton 9 and T14 because of its more prostrate growth habit. If the annual increase in weight of stubble plus rhizomes were added to harvested yields, then biomass production by Tiflon 9 and T14 was 12.4 and 12.9 t ha‐1 yr‐1, respectively, compared with 10.4 t ha‐1 yr‐1 for Pensacola. Thus, it appears that selection for increased yield has resulted in increased allocation of dry matter to harvestable foliage and possibly a greater production of non‐root biomass.
Evaluation of Selected Nonlinear Regression Models in Quantifying Seedling Emergence Rate of Spring Wheat
Authors: Gan Yantai , Stobbe Elmer H. , Njue Catherine
Published: July 2010

Fast and uniform seedling emergence increases yield potential of spring wheat (Triticum aestivum L.) in short‐season areas. An accurate method of quantifying rate of seedling emergence is needed. In this study, we compared the relative effectiveness of the Gompertz, Logistic, and Weibull models in quantifying emergence rate of spring wheat. ‘Roblin’ wheat was grown in a growth room under five soil water potential: − 0.002, − 0.165, − 0.41, − 1.00, and − 1.45 MPa. Daily‐recorded emergence data were fitted to each of the models. The analyses of stability and accuracy functions, residual sum of squares, and variance showed that the Weibull model was not appropriate in quantifying rate of emergence.The Gompertaz and Logistic models functioned in a similar way with great stability and accuracy in most cases. The Gompertz predictions most closely fitted the observed set of responses with residual points scattered around zero. For lognormally distributed emergence patterns common under field conditions, the Gompertz model provided the most appropriate characterization of emergence.
Seed Gossypol Variation within Gossypium barbadense L. Cotton
Authors: Percy R. G. , Calhoun M. C. , Kim H. L.
Published: July 2010

Gossypol, a triterpenoid aldehyde found in all species of the genus Gossypium, possesses insecticidal, antimicrobial, antifertility, and antitumor properties. Gossypol content in cotton seed varies among cultivated species and among cultivars within species. This investigation was conducted at the Texas Agricultural Research Center in San Angelo, TX, in 1993 to determine the regional and geographic variability for seed gossypol content and isomer form in G. barbadense L. A set of 57 accessions (collected during 50 yr from 21 countries) representing five regions, and 26 cultivars were analyzed. Species′ variation for gossypol and isomer content exceeded previous reports. Total gossypol content in seed ranged from 3.0 to 34.0 g kg‐1 kernel weight. The more biologically active negative isomer ranged from 249 to 689 g kg‐1 total seed gossypol. Cotton accessions collected west of the Andes mountains in South America displayed the greatest variation in seed gossypol and gossypol isomer contents. Accessions from Central Americaa nd Argentina displayed the least variation. Subsets of accessions, possessing unique levels of seed gossypol or gossypol isomer, were identified within regional groups or cultivars. A low (r = 0.02) phenotypic correlation between gossypol content and isomer ratio suggested that simultaneous selection for the two traits is feasible.
Natural Outcrossing In Chickpea (Cicer Arietinum L.)
Authors: Tayyar Rana , Federici Claire V. , Waines Giles J.
Published: July 2010

The rate of natural outcrossing in the cultivated chickpea (Cicerarietinum L.) was estimated with five lines grown over three planting dates in the 1988–1989 season, and four other lines grown in one planting date in 1989, and over two planting dates in 1991. At each planting date, a randomized complete block design with six replications was employed. The location of the study was at the University of California, South Coast Research and Extension Center, Irvine, CA, where high outcrossing rates have been previously observed in different genotypes of the common bean (Phaseolus vulgaris L.). Compound leaf, controlled by a single dominant gene (Silv/silv), was used as a morphological marker. Unifoliate genotypes were used as female parents and were interplanted in the middle row of every plot with genotypes with compound leaves designated as male parents. Although many bumble bees (Bombus spp.) and honey bees (Apis mellifera L.) visited open chickpea flowers, progeny tests revealed that the average rate of natural outcrossing in the lines under investigation was less than 1%.
Evaluation of Lines Derived from Wild Emmer Chromosome Substitutions: II. Agronomic Traits
Authors: Elias E. M. , Steiger D. K. , Cantrell R. G.
Published: July 2010

Improving yield and other agronomic traits in durum wheat(Triticum turgidum L. var. durum) depends on adequate genetic diversity. Genetic diversity in durum wheat is limited. An accession of wild emmer (Triticum turgidum L. var. dicoccoides) with high protein concentration was used to develop a complete set of ‘Langdon’ (T. dicoccoides) [LDN(DIC)] substitution lines. This study was conducted evaluate the potential of using these substitution lines as parents for deriving lines with acceptable agronomic traits. Each of the 14 substitution lines and Langdon were crossed to a common male parent, ‘Vic’. Parents, F2:4, and F2:5 lines were grown in replicated trials at two locations in North Dakota in 1989 and 1991, respectively. Days to heading, plant height, grain yield, and kernel weight were measured. Population means and genetic variances were compared to those of the Langdon/Vic population to identify substitution lines that conferred favorable agronomic characteristics to derived lines. Heritabilities were estimated based on parent‐offspring regression and variance components. All substitution populations except these with LDN(DIC) 4B and 5B were earlier in heading date than the Langdon/Vic population. Langdon dicoccoides substitution populations 1A, 2A, 4A, 6A, 7A, 1B, 4B, 5B, and 6B were significantly shorter than the Langdon/Vic population. Langdon dicoccoides substitution population 4B had higher yield than the Langdon/Vic population. Langdon dicoccoides substitution populations 2A, 3A, and 5B had a mean kernel weight greater than the Langdon/Vic population. Our data suggests that there is a possibility of deriving lines with high grain yield and good agronomic traits from LDN(DIC) 4B.
Inheritance and Allelic Relationships among Russian Wheat Aphid Resistance Genes in Winter Wheat
Authors: Saidi A. , Quick J. S.
Published: July 2010

The Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), has caused extensive economic damage to wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the western Great Plains and intermountain area of North America during 1986–1994. Genetic information is necessary to efficiently develop adapted resistant cultivars. Genetic studies were conducted to determine the mode of inheritance and allelic relationships among four resistant winter wheat accessions, PI 372129, PI 243781, PI 262605, and PI 294994. To determine the mode of inheritance, the resistant lines were crossed to the susceptible winter wheat cultivar Carson, and F1, F2, and BC1F1 seedlings were screened for RWA reaction. To determine allelism, the resistant lines were intercrossed and crossed to two other known RWA‐resistant wheat accessions, PI 137739 (Dn1) and PI 262660 (Dn2), and the F2 seedlings were evaluated. Resistance in PI 262605 and PI 294994 was controlled by one and two dominant genes, respectively, and the resistance gene in PI 262605 was allelic to Dn1 and Dn2. In contrast to an earlier report, Dn1 and Dn2 are probably allelic since no segregation was observed among F2 seedlings from this cross, and progeny of crosses with four other accessions gave similar ratios. Resistance in PI 372129 and PI 243781 is conditioned by single dominant genes that are independently inherited. The gene symbols Dn4 and Dn6 are recommendedfo r the resistance genes in PI 372129 and PI 243781, respectively.
Kernel Sink Capacity in Maize: Genotypic and Maternal Regulation
Authors: Jones Robert J. , Schreiber Beth M. N. , Roessler Jeffery A.
Published: July 2010

Previous research has shown that kernel sink capacity, the potential of maize ( Zea mays L.) kernels to achieve maximal mass, is established during the early stages of kernel development and is a function of the number of endosperm cells and starch granules formed. In this study, the genetic regulation of endosperm cell and starch granule number was investigated. Kernel growth was characterized in four disparate inbred lines (which differed in relative maturity and kernel size) and their reciprocal crosses. Relative maturity affected the pattern of kernel development (i.e., when endosperm cell division and starch granule formation was initiated) but not the maximum number of endosperm or starch granules formed nor the mature kernel mass obtained. Kernel growth rate and mature kernel mass of the large kernel inbreds were nearly twofold higher than that of the small kernel inbreds, regardless of relative maturity. Comparison of F~ kernels from reciprocal crosses revealed a strong maternal influence on mature kernel mass. However, in reciprocal crosses between A619 (large kernel) and W64A (small kernel), the maternal effects on mature kernel mass were due to changes in the number of endosperm cells formed, whereas in reciprocal crosses between Mo17 (large kernel) and B73 (small kernel), it was due to modulation of the number of starch granules. The results confirm that the number of endosperm cells and/or starch granules are good indicators of kernel sink capacity in maize. Moreover, the data show a strong maternal influence on kernel sink capacity and mature kernel mass. However, whether the number of endosperm cells or the number of starch granules is the more important determinant of mature kernel mass is genotype dependent.
Water‐Deficit Effects on Cell‐Wall Composition and In Vitro Degradability of Structural Polysaccharides from Alfalfa Stems
Authors: Deetz D. A. , Jung H. G. , Buxton D. R.
Published: July 2010

Forage crops from drought years are often reported to be of higher quality than normal. Maturity through its effects on plant composition is recognized as a major determinant of forage quality. Our objective was to determine the effects of water deficit and maturity on cell‐wall composition and structural polysaccharide degradability in alfalfa (Medicago sativa L.). Plants were grown under a mobile weather shelter and irrigated to 65, 88, and 112% of field capacity. Basal stems were harvested after 21, 35 and 49 d of regrowth. Components of the cell wall were determined (neutral sugars, uronic acids, Klason lignin, and ester‐ and ether‐linked p‐coumaric and ferulic acids). In vitro 12‐ and 72‐h degradabilities were determined for cell‐wall polysaccharide components. As maturity advanced, cell‐wall and Klason‐lignin concentrations increased (4.8 and 2.9%, respectively), while uronic acids declined (10.7%). Cell‐wall signification was not affected by water status. Stems from plants most severely restricted in water supply were lowest in cell‐wall and neutral sugars concentration, and contained progressively less glucose. Concentrations of esterified and etherified phenolic acids were low and not consistently related to maturity or irrigation level. Degradability (12 h) of both glucose and uronic acids decreased (8.9 and 4.8%, respectively) as plants matured, but only the 72‐h degradability of uronic acids was decreased (6.5%) during maturation. Water status had no influence on cell‐wall component degradability except for an increase (3.0%) in 12‐h uronic acid degradation with increasing water‐stress. Principal component analysis indicated that Kiason‐lignin concentration was negatively related to both 12‐ and 72‐h cell‐wall polysaccharide degradation, p‐Coumaric and ferulic acids affected 72‐h polysaccharide degradation because of both their concentration and whether the phenolic acids were ester‐ or ether‐linked to the wall. Improvement in alfalfa forage quality during periods of water deficit was not generally attributable to improved cell‐wall degradability, but was likely the result of delayed maturity and decreased cell‐wall concentration.
Phenotypic Evaluation of Root Traits in Soybean and Applicability to Plant Breeding
Authors: Pantalone V. R. , Rebetzke G. J. , Burton J. W. , Carter T. E.
Published: July 2010

The southeastern USA is vulnerable to drought during critical times in the development of soybean [Glycine max (L.) Merr.]. A Japanese plant introduction, PI 416937, exhibits drought tolerance and may be an important breeding line for the region. PI 416937 has an extensive fibrous root system that confers drought tolerance. The objective of this study was to relate visual root scores to other measurable root characteristics in order to provide breeders with a means for rapid phenotypic evaluation of soybean roots. Root score, root surface, and root dry weight were measured for ‘Lee 74’ and PI 416937 at three soybean stages of development in 1992 and 1993. Nodule number and nodule dry weight were also measured during the second year. PI 416937 had higher root score, root surface, nodule number, and nodule dry weight than Lee 74. Root score was positively correlated with root surface, nodule number, and nodule dry weight (r = 0.74, 0.83, and 0.80, respectively). Phenotypic root scores could be utilized effectively in selection programs to rapidly evaluate large numbers of progeny in order to identify those with extensive fibrous root systems.
A Rapid Seedling Screening Method for Determination of Fungal Endophyte Viability
Authors: Belanger Faith C.
Published: July 2010

Infection of turf and forage grasses with Acremonium Link:Fr. and Epichloe (Fr.) Tul. & C. Tul. fungal endophytes is often desirable because it confers enhanced insect tolerance to these plants. Determination of the viability of the endophytes in seed lots is important for commercial producers and consumers of seed. A current method of determining viability relies on staining leaf sheath epidermal peels for the presence of endophyte hyphae. It is difficult to obtain an epidermal peel from a young seedling, so plants must often be grown for several months before checking for viability. The objective of this study was to develop a method of screening very young seedlings for endophyte viability. Here it is reported that endophyte viability could be determined within 2 to 3 wk of germination by staining intact leaf sheath tissue with an alkaline rose bengal stain. This method of endophyte detection allows a more rapid assessment of percentage of viable endophyte in a seed lot.
Genetic Analysis of Primitive Cotton Germplasm Accessions
Authors: McCarty J. C. , Jenkins J. N. , Tang B. , Watson C. E.
Published: July 2010

The recent conversion of primitive cotton (Gossypium hirsutum L.) stocks to the day‐neutral flowering habit has effectively made these accessions readily available for direct use in plant breeding programs. Genetic analysis of these accessions would be useful in ascertaining parental material for improvement of specific traits. The objective of this study was to estimate genetic variances for 13 yield, fiber, and other agronomic traits in 79 accessions and 11 cultivars. A minimum norm quadratic unbiased estimation (MINQUE) method was used for estimating genetic variance components and an adjusted unbiased prediction method for predicting genetic effects. Additive × environment interaction variances were significant for lint yield and node of first fruiting branch. The additive variance components made relatively high contributions to the phenotypic variances for lint percentage and boll size. Additive variances were relatively low for other traits. Narrow‐sense heritabilities ranged from 8 to 50% for the traits studied. The proportion of accessions displaying significant, positive effects ranged from 12.7% for 50% span length to 30.4% for lint percentage and 2.5 span length. Positive additive effects for yield, lint percentage, and fiber traits except micronaire and negative effects for N1FB, NOMS, and plant height could be considered favorable effects. Although 16 of the primitive accessions showed significant positive additive effects for lint yield, only MDN‐74 and MDN‐101 could be predicted to produce stronger fiber, as well as higher lint yield and lint percentage. Results indicate that many primitive accessions may be used in crosses with commercial cultivars without serious loss of agronomic potential in the progeny.
Soybean Photoperiod‐Sensitivity Loci Respond Differentially to Light Quality
Authors: Cober E. R. , Tanner J. W. , Voldeng H. D.
Published: July 2010

Soybean [Glycine max (L.) Merr.] genotypes have been identified that show differential sensitivity to light quality. The use of different lamp types emitting light of different quality changed flowering responses to long days. The objective of this study was to investigate the flowering response of three photoperiod‐sensitivity loci to long days of various light qualities. ‘Harosoy’ near‐isogenic lines were grown under 20‐h‐long days of different light qualities, as measured by the bichromatic ratio of red to far‐red quanta (R:FR), and under light quality gradients. Generally, the photoperiodic response was greater, i.e., later flowering, with decreased R:FR. The El allele was most sensitive to light quality and required an R:FR approximating that of natural daylight for response to long days. The E3 allele was the least sensitive, and the E4 allele showed intermediate sensitivity to light quality. The earliest‐flowering near‐isogenic line (e1 e3 e4), previously found to be insensitive to long day length, showed sensitivity to long days of low R:FR light. Long days of high R:FR light were not effective in delaying flowering for some genotypes. Sensing the R:FR ratio is the function of phytochrome in light‐grown plants. The three loci studied in this work responded differentially to changes in R:FR, suggesting either a close relationship between soybean E alleles and phytochrome or the possibility that some photoperiod‐sensitivity loci are part of the phytochrome family of genes.
Soybean Petiole Ureide Response to Water Deficits and Decreased Transpiration
Authors: de Silva Manjula , Purcell Larry C. , King C. Andy
Published: July 2010

The sensitivity of N2 fixation to drought is greater than many other physiological processes in soybean [Glycine max L. (Merr.)], and, therefore, maintaining N2 fixation may he a key process for improving soybean drought tolerance. The ureides, allantoin and allantoate, are the final products of N2 fixation in soybean, and ureide concentration in petioles has been correlated with nitrogen accumulation in well‐watered plants. Petiole ureide concentration may, therefore, be used as a screening tool provided that it is closely associated with N2 fixation during drought. The objectives of this study were to determine the relationship between petiole ureides and nodule activity during drought, and to determine the relationship between transpiration rate and petiole ureide concentration in well‐watered plants. Soybean was grown in the greenhouse until the V6 growth stage when water was withheld for either 0, 4, 5, or 7 d to create several stress levels on the day of harvest. Plants were harvested at 0700, 1400, and 1900 h. In general, petiole ureide concentration increased with stress severity, and was negatively associated with nitrogenase activity at 1400 h (r = − 0.62**) and 1900 h (r = −0.49**) but not at 0700 h (r = −0.34). In well‐watered plants, treatments that decreased transpiration also resulted in increased petiole ureides. The increase in petiole ureide concentration during drought was concluded to be due partially to low transpiration. Petiole ureide concentration holds promise as an indicator of N2 fixation during drought, but the consistency of the relationship between petiole ureide concentration and N2 fixation across genotypes must be evaluated.
Seasonal Changes in Nonstructural Carbohydrates, Protein, and Macronutrients in Roots of Alfalfa, Red Clover, Sweetclover, and Birdsfoot Trefoil
Authors: Li Rong , Volenec J. J. , Joern B. C. , Cunningham S. M.
Published: July 2010

Root total nonstructural carbohydrate (TNC) has been studied, but little is known about seasonal trends in proteins and other macronutrients in legume roots. Our objectives were to determine how winter hardening and resumption of growth in spring influence (i) concentrations of sugars and starch, and activities of amylases; and (ii) protein concentration and composition, and abundance of N, P, and K. Alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.), and biennial sweetclover (Melilotus officinalis L.) were seeded in rows in the field in May and roots were sampled at approximately monthly intervals in autumn and biweekly in spring. All species accumulated high root TNC and starch concentrations in autumn. Starch and TNC concentrations declined throughout winter, but increased in roots of alfalfa and red clover in May. Starch accumulation and degradation patterns in spring were correlated with root endoamylase activity. Root sugar concentrations increased threefold from October to November. Root N and soluble protein concentrations increased 50% between September and December, and declined between March and May. Specific proteins accumulated to high concentrations in alfalfa roots during autumn. Root P increased 50% between October and April and was associated with an increase in root phytate. Proteins, N, P, and phytate accumulated during winter hardening in autumn in roots of these forage legume species that, in conjuction with TNC, may supply nutrients to regrowing shoots in spring.
Day and Night Temperature Effects during Grain‐Filling in Oat
Authors: Hellewell K. B. , Stuthman D. D. , Markhart A. H. , Erwin J. E.
Published: July 2010

Temperature has a large effect on oat (Avena sativa L.) growth and development. The objective of this study was to determine the effects of day temperature (DT), night temperature (NT), the day‐night temperature differential (DIF) during grain filling on oat grain yield and other agronomic traits and to determine if these traits exhibit a thermoperiodic response. Three genotypes of varying maturity (early‐, mid‐, and late‐season) were grown in controlled environment chambers with varying planting dates to synchronize heading date among the cultivars. At heading, plants of each cultivar were divided into nine treatments of all possible DT‐NT combinations of 31, 23, and 15°C. The temperature treatments were imposed until the plants were fully mature. Grain yield was 87%, kernel weight 51%, grain‐filling period 27%, and grain‐filling rate 45% greater at 15°C DT than at 31°C DT with a NT of 15°C. For NT, grain yield was 24%; kernel weight 12%, and grain‐filling period 27% greater at 15°C NT than at 31°C NT with a DT of 15°C. NT had no effect on grain‐filling rate. DIF had no effect on any of the traits. No evidence was found for a thermoperiodic response for any of the traits; however, optimal conditions for grain yield, kernel weight, and grain‐filling period was at the lowest temperature treatment and the possibility of a thermoperiodic response for these traits cannot be dismissed. All cultivars responded similarly to increased temperatures. Under a 16‐h photoperiod, the effect of DT was much larger than the effect of NT.
Mainstem Leaf Stage and Its Relation to Single Plant Grain Yield in Spring Wheat
Authors: Gan Yantai , Stobbe Elmer H.
Published: July 2010

Mainstem leaf stage (MLS), determined with the Haun scale, has been used to indicate plant development in small grain crops, but it is not clear whether MLS can be used to predict final grain yield. A field study was conducted on a Neuhorst clay loam (fine‐loamy, frigid, Aquic Haploboroll) at Portage la Prairie, MB, Canada, in 1990 and 1991, to determine the relationship between MLS and single plant grain yields within a canopy of spring wheat (Triticum aestivum L.). Plants were grown with small (2.2–2.4 mm wide), large (3.0–3.2 nun wide), and mixed (>2.2 but >3.2 mm wide) seed sizes. The MLS was determined 2, 3, 4, and 5 wk after initial seedling emergence (the date of the first seedling emergence in a plot), and grain yields were determined at maturity, on a single plant basis. Seed size had a significant effect on MLS only during the early seedling stages; plants grown from large seeds had greater MLS and lower plant‐to‐plant variation in MLS than those from small or mixed seed sizes. Within a canopy, early‐emerging plants had greater MLS and were more uniform than late‐emerging plants. Plant grain yields linearly responded to the MLS determined 2, 3, and 4 wk after seedling emergence. The MLS determined 230 degree‐days from planting most accurately reflected final grain yield. With the Haun scale, MLS measured 2 to 4 wk after seedling emergence can be used to predict single plant grain yield in hard red spring wheat.
Induced Micronutrient Toxicity in ‘Touchdown’ Kentucky Bluegrass
Authors: Lee Chiwon W. , Jackson Marcus B. , Duysen Murray E. , Freeman Thomas P. , Self James R.
Published: July 2010

The growth of turfgrass may be affected by excess levels of micronutrients. The objectives of this study were to determine changes in growth responses, leaf pigmentation, and chloroplast structure of Kentucky bluegrass (Poa pratensis L. cv. Touchdown) as affected by elevated levels of micronutrients. Plants were established in peat‐lite mix in 11‐cm pots using a standard nutrient solution and were thereafter constantly fertilized with nutrient solutions supplemented with individual treatments of 0.5, 1, 2, 4, 6, 8, or 12 mM of boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn) for 7 wk. The control solution had (in μM) 20 B, 0.5 Cu, 40 Fe, 10 Mn, 0.5 Mo, and 4 Zn. The lowest micronutrient concentrations that showed visual toxicity symptoms were 0.5 mM B, 12 mM Cl, 1 mM Cu, 4 mM Fe, 0.5 mM Mo, or 4 mM Zn. A reduction in dry matter yield was evident when the nutrient solution contained 2 mM B, 4 mM Cu, 2 mM Mo, or 4 mM Zn. Elevated levels of Cl, Fe, or Mn did not alter the biomass yield. Chlorophyll‐a (Chl‐a), chlorophyll‐b (Chl‐b), and carotenoid contents decreased as B concentration increased. Chlorophyll (Chl) content, particularly that of Chl‐b, increased with elevated levels of Fe. The altered Chl‐b levels induced by Fe correlated with increased levels of light harvesting chlorophyll (LHC) apoproteins and granai membrane accumulations. The loss of Chl in the B and Mo treatments correlated with decreased stroma membrane level and smaller chloroplast size, respectively. A linear relationship between the tissue and nutrient‐solution concentration existed for each micronutrient, suggesting a passive uptake by the plants. Findings of this study may be used in identifying altered growth and physiological characteristics of Kentucky bluegrass caused by supraoptimal levels of micronutrients.
Molecular Markers Associated with Soybean Plant Height, Lodging, and Maturity across Locations
Authors: Lee S. H. , Bailey M. A. , Mian M. A. R. , Carter T. E. , Ashley D. A. , Hussey R. S. , Parrott W. A. , Boerma H. R.
Published: July 2010

The identification of quantitative trait loci (QTL) has the potential to improve the efficiency of selection for polygenic traits in a plant breeding program. In this study a soybean, Glycine max (L.) Merr., population derived from the cross of ‘Young’ and PI 416937 was evaluated with restriction fragment length polymorphism (RFLP) markers to identifiy QTL related to plant height, lodging, and maturity. One hundred‐twenty F4‐derived lines were evaluated for segregation at 155 RFLP loci. Field data were obtained in four different locations in 1994 (Athens and Plains, GA, and Windblow and Plymouth, NC). The genetic map consisted of 137 RFLP loci which converged into 31 linkage groups and covered more than 1600 centimorgan (cM). means of single‐factor analysis of variance, 11 independent markers associated with plant height and the eight with lodging explained most of the genetic variability for these traits in combined analysis over locations. Of the 11 RFLP markers associated with plant height and the eight with lodging, only two markers for plant height (Blt043 and A063a) and one for lodging (A169) were detected in all locations, indicating either the inconsistency of these molecular markers across locations or the inability to detect putative QTL with the population size of 120 lines. However, good agreement of QTL across locations was found for maturity. Five markers were identified that explained variation in mean maturity over three locations, four of which were associated with maturity in all three locations. Results from this research indicate the level of consistency of QTL across environments is trait specific.
Identification of Agronomicaily Superior Latin American Maize Accessions via Multi‐Stage Evaluations
Authors: Holland J. B. , Goodman M. M. , Castillo‐Gonzalez F.
Published: July 2010

Few data exist regarding the agronomic utility of tens of thousands of available tropical maize (Zea mays L.) racial accessions. A long‐term, multi‐stage evaluation project has been developed at North Carolina State University to evaluate the breeding potentials in the temperate USA of typical Latin American maize germplasm collections. Agronomic evaluations of accessions per se were performed in daylength neutral environments. Superior accessions were crossed to a temperate‐adapted inbred line and converted to photoperiod‐insensitive 50%‐exotic and 75%‐exotic populations by selection during 1986 to 1990. These semi‐exotic populations were evaluated as testcrosses to Corn Belt testers in North Carolina during 1993 and 1994. Testcrosses of many 75%‐exotic families were higher‐yielding than the hybrid tester, B73Ht × Mo17Ht, providing evidence that agronomically superior Latin American maize accessions possess favorable genes for yield that apparently are absent from Corn Belt germplasm. Yields of accessions evaluated as 100%‐exotic and 50%‐exotic populations were significantly correlated (r = 0.62, P = 0.005) with each other, but not with yields of 75%‐exotic populations. Some accessions exhibited extreme ranking changes across different testing stages. Multi‐stage evaluations of maize racial accessions successfully identified superior germplasm for use by U.S. breeders, but there is no guarantee that all of the most valuable accessions were advanced to later testing stages. Evaluations in many environments and minimal culling levels at each stage could be used to improve the probabilities of successfully identifying useful accessions in future multi‐stage evaluation procedures.
Yield and Yield Components of Early Maturing Soybean Genotypes in the Mid‐South
Authors: Akhter M. , Sneller C. H.
Published: July 2010

Maturity group (MG) IV soybean [Glycine max (L.) Merr.] cultivars are planted in April through June in the mid‐south. April plantings are used to avoid mid‐season droughts, though seed quality from April plantings of MG IV cultivars is often poor. Thus, a late June planted seed quality nursery is required for breeding material. This range of planting dates for MG IV lines may affect yield, plant morphology, and produce genotype × planting date interactions that affect cultivar selection. Our objectives were to study yield, yield components, and the relationships between traits in MG IV genotypes planted in April and June in the mid‐south. Twenty‐seven indeterminate and nine determinate genotypes were planted in mid‐April and late June in 1992 and 1993 in Arkansas. Data were collected on yield, yield components, height, and days to R2 and R8. Neither planting date nor stem termination affected yield. Genotype × date interactions were significant for many traits in indeterminate but not in determinate lines. Plant height was reduced in April plantings for both types, yet for indeterminate types, main stem node number increased. Number of branches, pods per branch, and percentage of total yield derived from branches were greater in April than in June plantings. These trends were more pronounced in indeterminate than in determinate lines. Few strong associations between yield and its components were noted for determinate lines or June‐planted indeterminate lines. For the April‐planted indeterminate lines, yield was strongly associated with a complex of components that was dominated by number of main stem nodes. Number of main stem nodes and plant height may be useful selection criteria for improving seed yield of MG IV cultivars.
Linkage of RFLP Markers to an Aluminum Tolerance Gene in Wheat
Authors: Riede C. R. , Anderson J. A.
Published: July 2010

More than 20% of the world’s agricultural land may contain acid soil. Aluminum toxicity becomes a serious growth limiting factor in many plant species when the soil pH is lower than 5.5. Wheat (Triticum aestivum L.) genotypes differ widely in tolerance to excess Al, and breeding of more tolerant genotypes is a priority in many affected regions. Our objectives were to confirm the number of genes for Al tolerance and determine their chromosomal arm location in the Brazilian wheat cv. BH 1146 and to identify DNA markers linked to Al tolerance gene(s). A population of recombinant inbred lines, developed by single‐seed descent from the cross of BH 1146 × ‘Anahuac’, was screened for Al tolerance with two methods in hydroponic nutrient solution. Both methods showed a bimodal distribution for Al tolerance, consistent with single gene inheritance. Eighty‐three low‐copy DNA clones were used to screen for polymorphism between the parents. Clone bed1230 detected a restriction fragment that is located 1.1 centiMorgans from this gene on Chromosome 4DL and explained 85% of the phenotypic variation in Al tolerance. We propose the symbol AltBH to designate the major gene for Al tolerance located on 4DL. This RFLP marker can aid the transfer of this gene into sensitive germplasms.
Degree‐Days for Predicting Smooth Crabgrass Emergence in Cool‐Season Turfgrasses
Authors: Fidanza M. A. , Dernoeden P. H. , Zhang M.
Published: July 2010

Successful smooth crabgrass [Digitaria ischaemum (Schreber) Schreber ex Muhlenb.] management in turfgrass with herbicides depends on accurate application timing. Little information exists, however, regarding smooth crabgrass seed germination, and there are no reliable methods for predicting crabgrass emergence. The objective of this study was to utilize degree‐day (DD) accumulation as a means of predicting smooth crabgrass seedling emergence in cool‐season turfgrasses. Smooth crabgrass seedlings were counted and removed from field plot grids on a weekly basis from 1 Apr. to 31 Aug. 1992 to 1994 in turf maintained at two mowing height treatments (i.e., 3.7 or 6.4 cm). Air and soil temperatures at the thatch surface and 2.5 and 5.0 cm below the soil surface were monitored. Soil temperature at the 2.5‐cm depth provided the highest correlation with emergence and was used to quantify DD accumulation with a base temperature of 12°C. The mean soil temperatures during the 7‐d period prior to seedling emergence were 15.6, 13.9, and 17.5°C in 1992, 1993, and 1994, respectively. Minimum soil temperatures during the same periods of each year ranged from 10.4 to 12.5°C. A mean soil temperature >22.8°C was required for the emergence of large numbers of seedlings. Smooth crabgrass first emerged between 42 and 78 DD; however, the major emergence period corresponded to a range of 140 to 230 DD. A cumulative percentage emergence model was developed based on DD accumulation, which was accurately described by a Gompertz distribution (r2 = 0.96).
Basal Growth Temperatures and Growth Rate Constants of Warm‐Season Turfgrass Species
Authors: Unruh J. B. , Gaussoin R. E. , Wiest S. C.
Published: July 2010

Degree‐day modeling applications in turfgrass management have recently seen increased interest. The predictive capacity of any degree day model is dependent on an accurate determination of the basal growth temperatures for the species under consideration. The objective of this study was to determine basal growth temperatures and growth rate constants for eight warm season turfgrasses (five species). Sprigs from bermudagrass [Cynodon dactylon (L.) Pers. cv. Arizona Common and C. dactylon lc C. transvaalensis Burtt Davey cv. Midiron], buffalograss [Buchloë dactyloides (Nutt.) Engelm. cv. Kansas Common and Texoka], zoysiagrass (Zoysia japonica Steudel cv. Meyer), St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze cv. Raleigh and Floratam], and centipedegrass [Eremochloa ophiuroides (Munro) Hackel, cv. Common] were grown at temperatures ranging from 5 to 30°C in a controlled environment chamber under 14‐h photoperiods. Chamber temperature was decreased in a step‐wise fashion to the next temperature after two leaves were fully expanded. Leaf growth rates at each temperature were calculated and expressed as millimeters per day. Base temperature and growth rate constants for each turfgrass were calculated with segmented nonlinear regression analysis. Base temperatures for the eight tested cultivars ranged from 0 to 13°C. Interspecific and intraspecific differences for basal growth temperature were found, indicating that degree‐day model application accuracy is dependent on proper determination of target species and cultivar basal growth temperature.
Spikelet and Floret Naming Scheme for Grasses with a Spike Inflorescence
Authors: Wilhelm W. W. , McMaster Gregory S.
Published: July 2010

Effective schemes to name uniquely and define parts of grass plants allow researchers to communicate results of their experiments accurately and precisely. Naming schemes for vegetative parts of grass plants have been developed; however, no system exists to name uniquely parts of the inflorescence. In this report, we present a method to extend existing systems to name parts of grass spikes. Spikelet positions are denoted by the letter S and numbered acropetally along the rachis. For example, the third spikelet position from the base of the rachis is named S3. Likewise, floret positions along the rachilla are named F (or C after fertilization) and numbered acropetally from the base to tip. The second caryopsis (floret) in the spikelet at the third spikelet position on a spike would be named S3C2. This simple scheme, when combined with the system for naming tiller, leaves, and roots, will allow all plant parts to be named uniquely. If the caryopsis in the previous example was produced on the tiller formed in the axil of the first leaf on the main stem, the complete description of the caryopsis is T1S3C2. Using this system, researchers and practitioners can communicate precisely findings on development, growth, and functional characteristics of plants and plant parts.
Best Linear Unbiased Prediction of the Performance of Crosses between Untested Maize Inbreds
Authors: Bernardo Rex
Published: July 2010

In some situations, maize (Zea mays L.) inbreds may not have testcross data available for best linear unbiased prediction (BLUP) single‐cross performance. The objective of this study was to evaluate the effectiveness of BLUP when the parents of a single cross have not been tested in hybrid combination within a given heterotic pattern. Yield, moisture, stalk lodging, and root lodging data were obtained for 4099 single crosses evaluated by Limagrain Genetics in multilocation trials in 1990 to 1994. For each of 16 heterotic patterns, the performance of an i × j single cross was predicted as follows: (i) with all available testcross data for both i and j and their relatives; (ii) disregarding all testcross data for i; (iii) disregarding all testcross data for j; and (iv) disregarding all testcross data for both i and j. Correlations between predicted and observed performance, obtained with a cross‐validation procedure, were highest when testcross data for both parents of a single cross were utilized. Except for moisture, these correlations were severely reduced to <0.50 when both i and j were assumed untested. Prediction of performance of the cross between two untested inbreds seems unwarranted, but this situation is rare because new inbreds are usually crossed to extensively tested inbreds. The performance of the cross between an untested inbred and a tested inbred was predicted effectively when the number of tested single crosses in the heterotic pattern was large. In this situation, the highest correlations were ≈ 90% of the corresponding correlations obtained when data were available for both parents of the single cross.
Nutritionally Induced Changes in Endosperm of shrunken‐1 and brittle‐2 Maize Kernels Grown In Vitro
Authors: Faleiros R. R. S. , Seebauer J. R. , Below F. E.
Published: July 2010

Although mineral nutrition affects maize (Zea mays L.) yield by controlling starch deposition in kernels, the mechanisms involved are largely unknown. Our objectives were to examine this relationship by nutritionally and genetically altering starch production in the endosperm. Kernels of W64A and two starch‐deficient mutants, shrunken‐1 and brittle‐2, were grown in vitro with varying supplies of N (0–50 mM) or P (0–6 mM) to produce different degrees of endosperm starch production, and the levels of enzyme activities and metabolites associated with carbohydrate and N metabolism were examined. In vitro grown kernels exhibited the expected starch phenotypes, and a minimum level of media N (25 mM) and P (2 mM) was required optimal growth. However, increasing the availability of N or P could not overcome the genetically induced decrease in starch deposition of the mutants. Nitrogen deficiency enhanced sugar accumulation, but decreased amino acid levels, soluble protein, enzyme activity, starch synthesis, and endosperm dry weight. Phosphorous deficiency also decreased starch production and endosperm dry weight, but with only a minimal effect on the activities of ADP‐glucose pyrophosphorylase and alanine transaminase. Genotypic differences in endosperm starch, and the increases induced by N and P supply, were closely associated with the level of endosperm N, but not endosperm P. Thus, while both N and P are crucial for optimal yield of maize grain, they appear to act by different means, and with different importance in governing starch deposition in the endosperm.