bluuebunny/crossref_metadata_2025 huggingface dataset:
Forage Quality Variation among Maize Inbreds: In Vitro Digestibility and Cell‐Wall Components
Authors: Lundvall J. P. , Buxton D. R. , Hallauer A. R. , George J. R.
Published: July 2010

Forage maize (Zea mays L.) hybrids with improved feeding value might be produced if breeders had better information about inbred variation in maize for stover quality. This study was conducted to determine variation for in vitro digestible dry matter (IVDDM) and cell‐wail componenct oncentrations amonge lite maize inbred lines and to determine the relationship between IVDDM and cell‐wail components. Leaf blades and elongated basal stem internodes of 45 maize inbred lines grown near Ames, IA, were sampled at an early harvest near silking, and stem internodes were sampled again at a late harvest near physiological maturity. Significant variation existed among the inbreds for IVDDM and cell‐wall components. Variation was greatest in late‐harvest stems and least in leaf blades. The IVDDM ranged from 262 to 650 g kg−1 dry matter (DM) in late‐harvest stems, from 465 to 727 g kg−1 DM in early‐harvest stems, and from 580 to 676 g kg−1 DM in leaf blades. Stem IVDDM was most closely associated with stem neutral detergent fiber concentration both at the early harvest (r = −0.74) and at the late harvest (r = −0.82), whereas leaf IVDDM was most closely associated with leaf lignin concentration (r = −0.61). Early‐harvest stem IVDDM was not closely associated with leaf IVDDM (r = 0.31) or late‐harvest stem IVDDM (r = 0.40). Hence, effective selection for improved IVDDM of maize stover may require total stover sampling near physiological maturity.
Phyllochron Differences in Wheat, Barley, and Forage Grasses
Authors: Frank A. B. , Bauer A.
Published: July 2010

The phyllochron is a measure of rate of development of plant leaves. Knowledge of the phyllochron for crop species is useful in formulating simulation models and for tracking plant development to determine when to apply management practices that depend on crop development stage. Our objectives were to determine the phyllochron and genetic effects among cultivars of hard red spring wheat (Triticum aestivum L.), durum wheat (T. durum Desf.), and spring barley (Hordeum vulgare L.) and among and within species of crested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes], western wheatgrass [Elymus smithii (Rybd.) Gould], intermediate wheatgrass [Elytrigia intermedia (Host) Nevski:Syn:A. intermedium (Host) Beauv.], and reed canarygrass (Phalaris arundinacea L.). Phyllochrons for all cultivars of hard red spring wheat, durum wheat, and spring barley averaged 76.9,79.6, and 77.2 growing degree days (GDD) per leaf, respectively. The range in phyllochron among cultivars of hard red spring wheat, durum wheat, and spring barley was 11.2, 5.1, and 9.8 GDD, respectively. Among forage grasses, the phyllochron was 90, 99, 119, and 139 GDD for reed canarygrass, crested wheatgrass, intermediate wheatgrass, and western wheatgrass, respectively. Phyllochron differences among clones within crested wheatgrass cultivar Summit was 21 GDD and within cultivar Nordan was 17 GDD. Specific genetic factors influencing the phyllochron of the species studied were not identified. However, variation among cultivars within species and variation among clones within heterogeneous cultivars suggest that genetic expression should be considered in evaluating the phyllochron for each species.
Accuracy of Equations Predicting the Phyllochron of Wheat
Authors: McMaster Gregory S. , Wilhelm W. W.
Published: July 2010

Predicting the rate of leaf appearance, or phyllochron, aids in understanding and modeling grass development and growth. Nine equations predicting the phyllochron of wheat (Triticum aestivum L.) were evaluated using field data from a variety of locations, cultivars, and management practices. Each equation is referred to by the last name of the first author; if there is more than one equation by the first author, additional descriptors were included. The BAKER and KIRBY equations predict the phyllochron based on changes in daylength following seedling emergence; CAO‐TEMP and CAO‐DAY use a curvilinear relationship with temperature and daylength, respectively; CAO‐T&D uses the ratio of temperature to daylength; VOLK mathematically refines CAO‐T&D; MIGLIETTA uses an ontogenetic decline in the rate of leaf appearance; and MIGLIETTA‐DAY adds photoperiod effects to MIGLIETTA. No equation adequately predicted the phyllochron. The r2 values between predicted and measured phyllochron for winter wheat and spring wheat cultivars, respectively, were BAKER (0.001, 0.486), KIRBY (0.002, 0.487), CAO‐DAY (0.000, 0.174), MIGLIETTA‐DAY (0.013, 0.008), MIGLIETTA (0.002, 0.405), CAO‐TEMP (0.100, 0.190), CAO‐FIELD (0.078, 0.036), T&D (0.066, 0.030), and VOLK (0.119, 0.043). All equations predicted the phyllochron for spring wheat cultivars better than winter wheat cultivars. BAKER and MIGLIETTA showed no bias towards either over or underestimating the phyllochron; KIRBY tended to overestimate the phyllochron; and the remaining equations were biased towards underestimating the phyllochron. Equations developed from field data had the greatest range of predicted phyllochrons. Based on multiple criteria, the BAKER equation best predicted the phyllochron for the experimental data set. Other factors must be added to the equations to improve predictions. Much opportunity exists to improve our ability to predict the phyllochron.
Hybrid Performance in Wheat as Related to Parental Diversity
Authors: Martin J. M. , Talbert L. E. , Lanning S. P. , Blake N. K.
Published: July 2010

The probability of recovering a superior individual from the cross of two inbred parents is greater if both parents are similar in performance as opposed to one parent being inferior. Heterosis, coefficients of parentage, and molecular markers have been advocated to assess genetic diversity directly between parents. This study was done to determine the extent of DNA polymorphisms among a set of seven hard red spring wheats and the relationship between genetic diversity based on these molecular markers and coefficients of parentage, and to examine the relationship between diversity and hybrid performance in a diallel cross of these parents. Parents plus the F1 hybrids were grown in three environments. Grain yield, kernel weight, and protein concentration were measured. Coefficients of parentage, r, were computed for all pairwise combinations of parents. Parents were assayed with 63 sequence tagged site (STS) polymerase chain reaction (PCR) primer sets. Genetic similarities, GS, were computed using 27 STS PCR primer sets that showed polymorphisms. Rank correlations were computed between the 1 ‐ r and 1 ‐ GS measures of genetic diversity and F1 performance, mid‐parent beterosis, and SCA effects. The only significant associations between diversity and hybrid performance were those between 1 ‐ r and kernel weight SCA effects and beterosis, and protein concentration heterosis. Genetic diversity was inversely related to heterosis and SCA effects for protein concentration. Correlations between the 1 ‐ r and 1 ‐ GS measures of diversity and hybrid performance traits were of the same sign and about equal in magnitude. Coefficient of parentage and GS were significantly correlated, and cluster analysis based on the 1 ‐ r and 1 ‐ GS measures of diversity grouped the genotypes similarly. Neither diversity measure showed promise for predicting F1 performance, but both measures provided similar information for grouping and differentiating genotypes.
Inheritance of Elevated Palmitic Acid in Flax and Its Relationship to the Low Linolenic Acid
Authors: Ntiamoah Charles , Rowland Gordon G. , Taylor David C.
Published: July 2010

Palmitic acid, a 16‐C saturated fatty acid, is important in the production of margarine, shortening, and other fat products. This study was conducted to determine the inheritance of ethyl methanesulfonate‐ induced high palmitic acid (278 g kg− 1) in a tlax (Linum usitatissimum L.) mutant (E67) and to determine the feasibility of combining this elevated palmitic acid trait with a reduced linolenic acid trait of another mutant (E1747), both derived from ‘McGregor’ flax. The E67 mutant also possessed elevated levels of palmitoleic acid (48 g kg− 1). Reciprocal crosses of E67 × McGregor and E67 × E1747 were made. Gas chromatography analyses of fatty acids from seed oil of F1, F2 and backcross populations indicated that the control of the high palmitic and palmitoleic acid character in E67 was the result of the pleiotropic effect of a single additive gene. The study confirmed that the control of the deficient linolenic acid trait in E1747 was by two independent recessive genes. Neither gene was linked to the high palmitic acid locus. Combination of the mutant traits in E67 and E1747 was therefore possible. Quantitative 1H‐nuclear magnetic resonance analysis revealed that the mutant allele in E67 had no effect on oil content, whereas in E1747, an increase of ⊄ 100 g kg− 1 was observed under phytotron conditions.
Two Measures of Grain Filling in Spring Wheat
Authors: Darroch B. A. , Baker R. J.
Published: July 2010

Grain weight is a component of grain yield and duration of grain filling is a component of maturity. Both are important traits in applied plant breeding and both depend upon the grain filling process. Grain filling has been described by multi‐point and two‐point curves. Multipoint curves, based on repeated measurements of grain weight during the grain filling period, are much more demanding of labor and laboratory resources than curves based on records of anthesis, maturity, and final grain weight. To evaluate these two methods of measuring grain filling characteristics, we grew II spring wheat cultivars in irrigated and dryland field trials at Saskatoon, SK, Canada in 1989 and 1990. Final grain weight, time to 50% filled, and relative grain growth rate were estimated from logistic curves fitted to grain weights measured twice weekly from anthesis to maturity. Duration of grain filling and average filling rate (harvest grain weight/duration) were estimated from records of anthesis and maturity. Relative grain growth rate was not related to average filling rate (r = −0.01), and was less closely related than average filling rate to harvest grain weight (r 0.08 compared with r = 0.93, P = 0.01). Estimated time to 50% filled was moderately correlated with observed duration (r = 0.66, P = 0.05) and, compared with observed duration, differences among cultivars were more consistent and less sensistive to environmental influence. Compared with two‐point curves, logistic curves provided better estimates of inherent differences in rate and duration of grain filling. However, this advantage does not justify routine use of multi‐point curves in plant breeding except where late season stress masks inherent differences in maturity.
Phenological Plasticity as an Adaptation by Common Bean to Rainfed Environments
Authors: Acosta‐Gallegos Jeorge A. , White Jeffrey W.
Published: July 2010

Under rainfed conditions in the semi‐arid highlands of Mexico, time to first flower and to maturity of some cultivars of common bean (Phaseolus vulgaris L.) is strongly reduced with late plantings. Consideration of rainfall patterns in the region suggested that this response might be an adaptation to growing seasons of variable length, where length is determined by tune of onset of summer rains and by risk of water deficit or low temperatures at the end of the season. Analysis of weather patterns at two sites in the highlands suggested that when rains commenced in early June, there was a high probability of adequate precipitation during the season. When rains commenced in mid‐ to late‐July, total precipitation was lower. For a third site, total precipitation showed no relation with date of onset of rains. Evaluations of 20 bean genotypes planted at five dates each in 2 yr at Pabellon, Aguascalientes, (20° 11′ N latitude, elevation 1910 m) demonstrated large differences in plasticity of the pre‐flowering and reproductive periods. Cultivars Garbancillo Zarco and Tlaxcala‐475 were late to flower and mature under early plantings, but were similar to other genotypes in late plantings. Other genotypes of highland origin showed little or no plasticity, suggesting that this trait is not universal among cultivars currently grown there. Furthermore, cultivars and breeding lines from other regions showed no plasticity. Marked phenological plasticity occurred only in genotypes from the highlands which were highly photoperiod sensitive, but several highly sensitive genotypes showed no or little plasticity. Similar patterns were noted in a survey of 81 genotypes that included a wider range of highland germplasm.
Cell Wall Accessibility and Cell Structure Limitations to Microbial Digestion of Forage
Authors: Wilson J. R. , Mertens D. R.
Published: July 2010

Discussion of limits to ruminant digestion of plant cell walls largely focuses on the lignification and chemical nature of these walls. We examined the anatomical limitations to digestion of thick‐walled fiber particles in grasses. Estimates were made of wall surface area to cell wall volume ratio (SA/CWV), rate of bacterial digestion, and accessibility to bacteria for different types of cell walls. The analysis reveals the following: (i) Bacterial digestion of fiber cells can progress only from the interior (lumen) surface because their middle lamella‐primary wall region is consistently found to be indigestible. (ii) Because of secondary walll thickness (c. 1‐5 μm), we calculate that at best only 0.45 to 0.60 μm of wall thickness (as little as 20% of the wall in some cells) would be digested within the average residence time of fiber particles in the rumen assuming digestion of wall at the fast rate of 0.02 μm h‐1. (iii) This potential rate of wall digestion overestimates that of typical fiber particles in the rumen because these particles are comprised of many hundreds of cells and relatively few will be disrupted by chewing to give bacteria immediate access to cell lumens. (iv) Digestion of thick‐walled cells by bacteria is surface‐based and sclerenchyma cells have a particularly low SA/CWV ratio. Calculated ratios for single cells are sclerenchyma (1:5) < stem parenchyma (1.0:1) < mesophyll (6.7 to 13.3:1). (v) During digestion of secondary walls, an accumulation of toxic levels of phenolic monomers in cell lumens and at the digesting surface is unlikely, but more slowly diffusing phenolic‐carbohydrate complexes could reach concentrations toxic to bacteria. The structural limitations described are discussed in relation to future research directions.
Agrobacterium tumefaciens Transformation of Monocotyledons
Authors: Smith Roberta H. , Hood Elizabeth E.
Published: July 2010

Agrobacterium tumefaciens (Smith and Townsend, 1907) has been an extremely useful vector to transfer foreign genes into dicotyledonous plants. Monocotyledonous plants, particularly the cereals, have been considered outside the host range for A. tumefaciens, which has necessitated the development of other transformation systems such as naked DNA delivery to protoplasts and, most recently, microprojectile bombardment delivery of DNA to cells and tissues. Both systems have worked, but there are still many difficulties encountered in routine transformation of any monocotyledon. Recently, there has been renewed interest in using the A. tumefaciens system to transform economically important grasses and other monocotyledons. This paper examines the literature and steps involved in transformation of monocotyledons by A. tumefaciens. The many recent advances in understanding the biology of the infection process (meristematic target cell, vir gene inducing compounds, and wide host range strains of A. tumefaciens), and availability of more monocotyledon gene promoters and improved selectable markers greatly improve the opportunities of developing monocotyledon transformation systems with A. tumefaciens.
In Situ Conservation of Landraces in Centers of Crop Diversity
Authors: Brush Stephen B.
Published: July 2010

The importance of crop germplasm found in landraces is well established, and a comprehensive international program exists to conserve this resource ex situ in gene banks and botanical gardens. Landraces are still cultivated in regions of crop domestication and diversity. In situ maintenance has been neglected by genetic resource conservation programs in part because of misconceptions about farming systems that produce landraces. This paper presents three cases of on‐going maintenance of landraces by farmers who have also adopted high‐input technology, including high yielding crop cultivars. These cases are potatoes (Solanum spp.) in the Andes of Peru, maize (Zea mays L.) in southern Mexico, and wheat (Triticum spp.) in western Turkey. These cases suggest that on‐farm conservation of landraces can be decoupled from traditional farming practices. Factors that promote in situ conservation are the fragmentation of land holdings, marginal agricultural conditions associated with hill lands and heterogeneous soils, economic isolation, and cultural values and preference for diversity. Landraces are likely to persist in patches and islands of farming systems in regions of crop domestication and diversity, and these patches provide potential sites for conservation programs. In situ conservation may be a valuable complement to ex situ methods because it can preserve the biological and social processes of crop evolution. Research is needed on the biogeography and conservation biology of remaining landrace populations in order to plan in situ conservation.
Combining Ability Analysis of Root‐Knot Nematode Resistance in Cotton
Authors: McPherson G. Randall , Jenkins Johnie N. , McCarty Jack C. , Watson Clarence E.
Published: July 2010

The southern root‐knot nematode (RKN), Meloidogyne incognita (Kofoid and White) Chitwood, is a serious pest of cotton (Gossypium hirsutum L.). This study determined the combining abilities of eight cotton lines for RKN resistance. The 28 possible single crosses among the susceptible M8, the adapted resistant M‐315 RNR, and the day‐neutral converted primitive resistant lines M19‐RNR, M25‐RNR, M75‐RNR, M78‐RNR, M188‐RNR, and M487‐RNR were evaluated for resistance in two greenhouse environments. Number of eggs per plant was determined on the basis of a five‐pot row 40 d after planting one seed per 250‐cm−3 pot 7 d after each pot was inoculated with 10 000 Race 3 RKN eggs. Since the relative plant resistance to RKN is inversely proportional to RKN reproduction, negative combining ability effects indicated resistance. The general combining ability (GCA) effects were highest for M‐315 RNR. Specific combining ability (SCA) effects of six hybrids were significant in both environments. The SCA effects for M8 crossed with M‐315 RNR or M75‐RNR were negative, while the SCA effect of M‐315 RNR with M75‐RNR was positive. Although M‐315 RNR and M75‐RNR had the highest GCA, the two lines combined poorly together suggesting that they may have the same resistance genes. The SCA effects for MS crossed with M78‐RNR and M188‐RNR were positive, while the SCA effect of M78‐RNR with M188‐RNR was negative. This suggests that M78‐RNR and M188‐RNR may have different resistance genes that combined to produce progeny more resistant than predicted from the GCA effects.
Freeze‐Induced Changes in Carbohydrates Associated with Hardiness of Barley and Rye
Authors: Olien C. R. , Clark J. L.
Published: July 2010

Deficiencies in winter hardiness of barley (Hordeum vulgare L.) with respect to osmotic and adhesive components of freeze stress might be improved by genetic transfer of specific traits from rye (Secale cereale L.). These protective traits may include the hydrolysis of fructan for accumulation and secretion of sugars. The objectives of this research were (i) to measure total and intercellular water soluble carbohydrates (CLIO), sucrose, glucose, fructose, and fructan, in ‘Hudson’ barley and ‘Rosen’ rye by ethanol/water extraction of plants and by perfusion of crowns; and (ii) to estimate relief of freeze stress caused by adhesive and osmotic energies. Carbohydrates were detected and quantified by refractometry after high pressure liquid chromatography (HPLC). Freezing (−3°C, 4 d) caused a greater change the molar concentration of CHOs in rye than in barley extracts (26 vs. 16% increase, respectively), which would proportionally decrease freeze dehydration. The sugars perfused from frozen plants consisted of a higher proportion of monosaccharides in rye than barley, which would result in a greater potential for relief of adhesion. These mechanisms involve increase of sugar content in locations which relieve critical freeze stress.
Field Evaluation of European Corn Borer Control in Progeny of 173 Transgenic Corn Events Expressing an Insecticidal Protein from Bacillus thuringiensis
Authors: Armstrong Charles L. , Parker Gregory B. , Pershing Jay C. , Brown Sherri M. , Sanders Patricia R. , Duncan David R. , Stone Terry , Dean Duff A. , DeBoer David L. , Hart Jesse , Howe Arlene R. , Morrish Fionnuala M. , Pajeau Mark E. , Petersen William L. , Reich Barbara J. , Rodriguez Reymundo , Santino Colleen G. , Sato Shirley J. , Schuler William , Sims Steven R. , Stehling Sam , Tarochione Lance J. , Fromm Michael E.
Published: July 2010

The European corn borer [ECB; Ostrinia nubilalis (Hübner)] is an economically significant pest of corn (Zea mays L.). The ability to routinely transform corn has broadened the control options available to include the introduction of resistance genes from sexually incompatible species. In this study, microprojectile bombardment was used to introduce synthetic versions of cryIA insecticidal protein genes from Bacillus thuringiensis subsp, kurstaki (Btk) into embryogenitcis sue of the Hi‐II] (A188/B73 derivative) genotype of corn. Of 715 independent transgenic calli produced, 314 (44%) had insecticidal activity against tobacco hornworm (Manduca sexta L.) larvae. Plants were regenerated, self‐pollinated when possible, and crossed to B73. First‐generation progeny of 173 independent Btk‐protein expressing calli were evaluated under field conditions with artificial ECB infestations in 1992 or 1993. Approximately half (89/173) segregated in single‐gene manner for resistance to first‐generation ECB leaf‐feeding damage. All of the 89 lines evaluated in 1992 or 1993 for resistance to second‐generation ECB exhibited less stalk tunneling damage than the non‐transgenic controls. In 1993, 44% (34177) of the lines tested had ≤2.5 cm of tunneling, compared to severe damage (mean = 45.7 cm) in the B73 × Hi‐II controls. Experiments are in progress to evaluate the effect of the introduced genes on yield and other agronomic properties.
Use of RFLP Markers for Genetic Linkage Analysis of Oil Percentage in Sunflower Seed
Authors: Leon A. J. , Lee M. , Rufener G. K. , Berry S. T. , Mowers R. P.
Published: July 2010

Increased seed oil percentage is an important objective when breeding for high oil yield in sunflower (Helianthus annuus L.). Although some researchers have investigated the genetics and heritability of sunflower oil percentage, most analyses were conducted on the oil percentage in the whole seed through conventional breeding and biometric procedures. The primary objective of this research was to identify restriction fragment length polymorphisms (RFLPs) linked to quantitative trait loci affecting seed oil percentage, kernel oil percentage, and kernel percentage. An F2 population consisting of 289 individuals was produced by crossing two inbred lines that differ for the traits. The RFLP and trait data were obtained directly from self‐pollinated F2 plants. The RFLP markers (identifying 201 codominant loci) located six regions representing 57% of the genetic variation of seed oil percentage. Two of these regions were associated with kernel oil percentage, two with kernel percentage, and two with both components. Additive gene action was predominant for seed oil percentage and its components.
Genotypic Variability and Genotype × Environment Interactions among Switchgrass Accessions from the Midwestern USA
Authors: Hopkins Andrew A. , Vogel K. P. , Moore K. J. , Johnson K. D. , Carlson I. T.
Published: July 2010

Genetic variation for economically important traits in switchgrass (Panicum virgatum L.) is needed to develop improved populations. Objectives of this research were to determine the genotypic variability, and the magnitude of genotype × environment (G × E) interaction for agronomic, forage quality, and biofuel feedstock traits among switchgrass accessions collected from remnant midwestern prairies. A total of 23 accessions and five check strains were evaluated in space planted nurseries at Mead, NE; Ames, IA; and West Lafayette, IN, during 1991 and 1992. Forage quality traits were measured at a vegetative growth stage and at heading. Disease ratings were taken just prior to forage harvest at heading. Forage composition was determined by near infrared reflectance spectroscopy. Across locations and years, significant variation among accessions was observed for forage yield at heading, vegetative in vitro dry matter digestibility (IVDMD), and heading date. Some accessions, such as IA34, were comparable in forage yield at heading to check strains and should be useful genetic sources of variation for this trait. Except for disease rating, G × E interactions were important for all traits. Selection among accessions for forage yield at heading followed by selection for IVDMD within such accessions should be an effective approach in utilizing genetic variation in switchgrasses from remnant prairie sites.
Rapid Screening Procedure for Methionine Levels in Maize and Soybean
Authors: Wright Allen , Orman Bruce
Published: July 2010

Methionine is an essential amino acid critical to human, livestock, and poultry nutrition. A microbiological method has been tested for use as a rapid, inexpensive, and reliable means of screening maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] seed for methionine concentration. Maize and soybean meal samples with various methionine contents were defatted before enzymatic proteolysis. An aliquot of each hydrolyzate was added to liquid media free of methionine, autoclaved, and inoculated with a bacteria auxotrophic for methionine. After incubation for 20 h, the turbidity of the cultures was measured and methionine concentration was calculated from standard curve data. Significant positive correlation (r = 0.74 maize; r = 0.88 soybean) was found between the microbiological and chemical determinations. These results demonstrate that the less expensive microbiological procedure would have great utility in a methionine enhancement plant breeding program.
Variation in Salt Tolerance and Ion Accumulation among Subterranean Clover Cultivars
Authors: Shannon M. C. , Noble C. L.
Published: July 2010

Increased productivity of forage crops under saline conditions is a desired characteristic in irrigated areas in both the USA and Australia. Clover (Trifolium) species are often used in single or mixed stands. Studies were conducted to determine physiological mechanisms and the extent of variability for salt tolerance among cultivars of subterranean clover. Six cultivars of subterranean clover (T. subterraneum L.) belonging to three different subspecies, brachycalycinum (cv. Clare and Wenijup), subterraneum (cv. Bacchus Marsh and Tallarook), and yanninicum (cv. Meteora and Trikkala), were tested for salt tolerance during germination and emergence and at the vegetative stage of growth in sand cultures salinized with 20 to 80 mM NaCl. Cultivars differed in final emergence, growth rates, salt tolerance, and ion accumulation. When salinity was applied at the time of seeding, the cultivars Clare and Tallarook were the most tolerant. When plants were salinized after the three‐ to four‐trifoliate leaf stage, Clare had the highest relative salt tolerance as defined by shoot dry weight yield reduction as a percent of the unsalinized controls. Relative salt tolerance followed the order Clare > Bacchus Marsh = Trikkala = Tallarook > Meteora = Wenijup. Meteora had the highest productivity as defined by total dry weight production under high NaCl treatment. Productivity of clover under saline conditions requires high growth potential and low reduction in yield with increasing salinity. High productivity under salinity stress was positively correlated with restricted Na+ uptake in the shoot and the maintenance of high K+/Na+ ratios.
Relationship of Nitrogen Utilization Patterns with Soybean Yield and Seed‐Fill Period
Authors: Vasilas B. L. , Nelson R. L. , Fuhrmann J. J. , Evans T. A.
Published: July 2010

A positive relationship generally exists between duration of seed‐fill period (SFP) and seed yield in soybean [Glycine max (L.) Merr.], but exceptions have been reported. The objective of this research was to determine if differences in N2 fixation, N accumulation, or N remobilization could explain inconsistent relationships between duration of SFP and seed yield in soybean. Eight experimental soybean lines were selected, on the basis of differences in SFP and seed yield in previous experiments, to provide lines differing in (i) SFP and seed yield, (ii) SFP but not seed yield, and (iii) seed yield but not SFP. Field experiments were conducted at two locations in Delaware on a Matapeake silt loam (fine‐silty, mixed, mesic, typic Hapluduit) and on a Rumford loamy sand (coarse‐loamy, siliceous, thermic, typic Hapludult). Plant samples were taken at the beginning and at the end of SFP. Nitrogen fixation was determined by isotope dilution. Seed yields ranged from 229 to 290 g m−2; SFP ranged from 35 to 45 d. Nitrogen derived from N2 fixation ranged from 51 to 82%. Lines with short SFP remobilized more N and dry matter than lines with long SFP. Seed yields were not consistently associated with seed N concentration, N remobilized, total N2 fixed, vegetative biomass, dry matter remobilized, or N2 fixed prior to SFP. Yield was positively associated with dry matter production and N2 fixation rates during SFP. The duration of SFP is an important factor in defining yield potential, but the duration and rates of accumulation of N and C during this period determine how much of that potential will be realized.
Change of Sucrose Synthase Activity in Developing Endosperm of Rice Cultivars
Authors: Kato Tsuneo
Published: July 2010

Sucrose synthase (SS, EC 2.4.1.13) in rice (Oryza sativa L.) endosperm acts as the first step in the sucrose‐starch conversion pathway and is thought to have some relation to photosynthate accumulation and grain development. This study investigated genotypic differences in the change of SS activity in developing endosperm using four rice cultivars with different grain sizes and grain‐filling rates. The difference in SS activity between grain positions within a panicle was also examined. In addition to SS activity, activities of acid invertase (AI, EC 3.2.1.26) and UDP‐glucose pyrophosphorylase (UDPGP, 2.7.7.9) were observed in the same samples used for SS activity assay. In every cultivar and grain position, SS activity showed a maximum value at the middle of the linearly increasing period of grain dry weight, and decreased thereafter. Mean SS activity per gram fresh weight across sampling times and grain positions was not significantly different among cultivars. A significant difference among cultivars was detected in SS activity per grain. As for the difference between grain positions, the activities both per gram fresh weight and per grain were significantly higher in grains on primary branches showing a higher grain‐filling rate. The changes of AI and UDPGP activities did not correspond with the change of grain dry weight. These results suggest that SS activity in developing rice endosperm plays a role in the regulatory system of grain development, but does not have any relation to genetic variations in grain size and grain‐filling rate.
Altering Source‐Sink Relationships in Prolific Maize Hybrids: Consequences for Nitrogen Uptake and Remobilization
Authors: Pan W. L. , Camberato J. J. , Moll R. H. , Kamprath E. J. , Jackson W. A.
Published: July 2010

Competition between grain and roots for photoassimilates may reduce post‐anthesis N uptake (Na), thereby limiting grain production of prolific maize (Zea mays L.). Field experiments were conducted to determine if this competition was minimized during the selection for new high‐yielding prolific lines, providing a plausible physiological explanation for the improved grain yields. The dry matter (DM) and N accumulation and partitioning of two high‐yielding and three low‐yielding prolifics were compared under full pollination, limited pollination of the apical ear, or no pollination. The following year, one high‐yielding and one low‐yielding hybrid were grown at 34 000 and 45 000 plants ha−1. Fully pollinated, high‐yielding hybrids averaged 74% more grain weight (Gw) than low‐yielding hybrids. A highyielding hybrid produced 71% more Gw under full pollination than with apical ears only pollinated, while limiting pollination had little effect on low‐yielding hybrids. Greater contributions of subapical ears in new prolifics were attributed to greater kernel weight and number, which were positively correlated with post‐anthesis DM accumulation (Twa). The DM partitioning to vegetative tissue [Twa − Gw] is indicator of photosynthate availability for plant functions during grain‐filling. Greater [Twa − Gw] occurred at the low plant density and with limited pollination, and this was positively related to Na while inversely related to Nr. The high‐yielding hybrids maintained Ta and Na during multiple ear development. These results suggest Na is regulated by the ear sink size relative to photosynthate supply.
Assimilatory Capacity Effects on Soybean Yield Components and Pod Number
Authors: Board J. E. , Tan Qiang
Published: July 2010

Soybean [Glycine max (L.) Merr.] yield is more restricted by assimilatory capacity (source strength) during the reproductive (R1 to R7) compared with vegetative period (emergence to R1). Although pod number (per unit ground area) is recognized as an important factor affecting yield, the period in which this yield component is source restricted has not been clearly identified. Therefore, the objective of this study was to determine this period by identifying yield components through which source strength affects pod number and finding when these yield components are determined. Field studies were conducted during 1991 and 1992 with ‘Centennial’ soybean at Baton Rouge, LA, on a Mhoon silty clay soil (fine‐silty, mixed, nonacid, thermic Typic Fluvaquent). Treatments were partial defoliations designed to create light interception differences during R1 to R7. Yield was reduced 23% by defoliation. Harvest index, which was 0.59 for the control, ranged from 0.56 to 0.60 for the defoliation treatments. Source strength influenced pod number (per unit ground area) through branch dry matter, branch number, branch node number, and pods per reproductive node on the whole plant. Pods per reproductive node were regulated by pod initiation (pods at least 0.5 cm long) and/or abortion initiated pods. Determination of final pod number occurred at 10 to 12 d after R5. In conclusion, pod number was source restricted from R1 to 10 to 12 d after R5. Stresses that restrict source strength during this period should be avoided to optimize pod number and yield.
Correlation among Yield Stability Parameters in Common Bean
Authors: Duarte João Batista , Zimmermann Maria José de O.
Published: July 2010

Phenotypic yield stability is a trait of special interest for plant breeders. Many statistical procedures are available for stability analysis, each of them allowing for different interpretations. The objective of the present study was to determine the degree of correlation among the 13 statistical parameters that can be used for the analysis of phenotypic stability. Such correlations could be used to assess the extent to which these 13 parameters identify unique genetic effects. Yield data were obtained from 12 yield trials involving 76 common bean (Phaseolus vulgaris L.) genotypes and 12 location‐year production environments in Brazil. The stability statistics were divided in four groups according to the structure from which they were derived. On the basis of rank correlation, it was concluded that (i) there were highly significant correlations between many of the stability statistics (among and within groups) indicating that several of the statistics probably measure similar aspects of phenotypic stability; (ii) mean yields were positively correlated with many of the stability statistics; (iii) there was an association between the Group A statistics (variances and ranges) and the Group C statistics (regression and determination coefficients), and a similar association between the Group B (ecovalence) and Group D (variance of deviations from regression) statistics; (iv) the segmented linear regression coefficient (b1i) was overall the most independent parameter, indicating that the other stability statistics do not satisfactorily reflect genotypic responses in poor environments; (v) the strong correlation between the regression coefficients and the coefficients of determination indicates that the latter are not needed to measure the predictability of the estimated genotypic response; and (vi) the variance of the deviations from regression can provide assessment of the relative contribution of the genotype to the genotype × environment interaction as well as its biological stability.
Diversity among African Pearl Millet Landrace Populations
Authors: Ouendeba Botorou , Ejeta Gebisa , Hanna Wayne W. , Kumar Anand K.
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] is widely grown in arid to semi‐arid regions of Africa. The crop is particularly adapted to Sahelian West Africa where landraces have evolved in different ecological niches. These landraces have accumulated interpopulation diversity that has not been characterized. Evaluation of genetic diversity is a prerequisite for successful germplasm exploitation through breeding. The objective of this study was to characterize morphological and agronomic variability among African landrace populations of pearl millet. Ten pearl millet landrace populations widely grown in several African countries and two experimental F1 hybrids were evaluated at two locations in Niger during the 1989 rainy season. Thirteen characters (downy mildew [Sclerospora graminicola (Sacc.) Schroet] incidence, days to flowering, primary spike length, peduncle exsertion, spike girth, flag leaf width, stem diameter, spike number per plant, non‐productive tillers per plant, plant height, spike yield per plot, grain yield per plot, and 1000‐seed weight) were measured on six replicates of each landrace populations. In the pooled analysis, all landrace populations were significantly different for one or more of the characters evaluated. The Niger landrace populations showed much less variation than the other African landrace populations for most characters investigated. Ward's cluster and principal component analyses were used to investigate the nature and degree of divergence in the landrace populations. The cluster analyses revealed similarities between Niger and Senegal and between Niger and Nigerian landrace populations. Four principal components were found to explain 92% of the total variation. Days to flowering, plant height, stem diameter, primary spike length, and grain and spike yield per plot were the major sources of diversity among the landrace populations. These results could be useful in choosing potentially heterotic pearl millet populations for intercrossing to develop improved cultivars, synthetics, and hybrids for use in Africa.
Septoria tritici Resistance and Associations with Agronomic Traits in a Wheat Cross
Authors: Camacho‐Casas M. A. , Kronstad W. E. , Scharen A. L.
Published: July 2010

Septoria leaf blotch of wheat (Triticum aestivum L. em Thell) caused by the pathogen Septoria tritici Rob. in Desm. [telemorph Mycosphaerella graminicola (Fuckel) J. Schroeter in Cohn] is a major disease reaching epidemic proportions in many parts of the world. Concerns have been expressed that widespread distribution of early maturing semidwarf cultivars and changes in cultural practices have contributed to its increased incidence. This study was undertaken to determine the mode of inheritance of Septoria leaf blotch resistance and possible associations between specific traits in a cross of two parents representing extremes in their reaction to Septoria leaf blotch. Parents, F1, F2, F3, and backcrosses were evaluated under field conditions over a 3‐yr period. Both natural and artificial inoculations were used. Generation mean analyses were employed to study gene effects for resistance to the disease. Phenotypic correlations and path coefficient analyses were calculated to determine associations among heading date, plant height, disease severity, and grain yield. Differences for all measured traits were observed in all generations. Frequency distribution of the F2 population for disease reaction was continuous. Both additive and nonadditive gene action contributed to the expression of disease resistance with dominance and epistasis effects being the most important. Negative associations were observed for both plant height and heading date on disease severity with heading date having the largest direct effect. When the associations were examined in relation to grain yield, a negative association was observed between heading date and yield, whereas a positive association was noted between plant height and yield. A large negative, direct effect of disease severity on grain yield was measured from path coefficient analyses. Because no resistant progeny were observed that were as early and short as the susceptible parent, a compromise may have to be reached for these traits to achieve acceptable levels of disease resistance in this cross.
Improvement in Two‐Allele Autotetraploid Populations of Alfalfa Explained by Accumulation of Favorable Alleles
Authors: Woodfield D. R. , Bingham E. T.
Published: July 2010

Accumulation of favorable alleles in linkage blocks (linkats) is important for population improvement and increased heterosis in autotetraploid alfalfa (Medicago sativa L.). Original generation (OG) genotypes, produced by chromosome‐doubling heterozygous diploid plants, are partially inbred (F = 0.33), and have a maximum of two alleles and therefore only one allelic interaction per locus. Inbreeding these OG genotypes by selfing and up to six generations of sib‐mating reduces both heterozygosity (F = 0.50–0.59) and allelic interactions in these advanced generation (AG) two‐allele autotetraploid populations (TAPs). Single crosses (SCs) between AG TAPs also have fewer allelic interactions than SCs between then‐ respective OG genotypes, and the relative performance of these SCs provides an unambiguous test of the importance of accumulating favorable alleles. The forage yield of a series of OG and AG SCs was compared from 1990 to 1992 in three replicated Wisconsin field experiments, whereas differences in fertility were determined in greenhouse studies. The mean forage yield of the AG (F1 and F2) SCs was 7 to 23% higher than their comparative OG SCs; however, there was no significant difference between OG and AG (S1) SC performance. The AG SCs also had significantly higher fertility levels. The improvements in AG SC forage yield and fertility provided strong evidence that inbreeding and selection in TAPs resulted in accumulation of favorable alleles with additive to completely dominant effects.
Genetic Control of a Long‐Juvenile Trait in Soybean
Authors: Ray Jeffery D. , Hinson Kuell , Mankono J. Emmanuel Bidja , Malo Maria F.
Published: July 2010

The long‐juvenile (LJ) trait in soybean [Glycine max (L.) Merr.] has been defined as delayed flowering under short‐day conditions. The genetic control of this trait remains ambiguous in the literature, and this study was undertaken to determine the genetic control of the LJ trait. Three field experiments were conducted between 1984 and 1991. In the first experiment, segregation patterns of the LJ trait were examined in six F2 populations from crosses between conventional‐juvenile (CJ) lines and P1 159925 (source of the LJ trait). Results indicated that the LJ trait is controlled by a single recessive gene influenced by the genetic background in which it occurs. In the second experiment, the confounding effect of other genes segregating for flowering was eliminated by studying F2 populations from crosses between members of four pairs of near isogenic lines primarily differing in the presence of the LJ trait. A total of 1954 F2 plants were observed from eight crosses. Within all F2 populations, the segregation patterns for the LJ trait had a good fit to a 3:1 ratio of CJ/LJ expected for a single recessive gene. The dominance relationship of the alleles was examined in the third experiment using F5 and F6 families developed from seven different crosses. Results indicated that the J allele, which conditions the CJ phenotype, is nearly completely dominant. Our results indicated that the LJ trait is controlled by a single recessive gene and the symbol J/j has been assigned for the alleles conditioning the flowering response (J‐, CJ, and jj, LJ).
Combining Ability and Heterosis Estimates for Kernel Cadmium Level in Sunflower
Authors: Li Yin‐Ming , Chaney Rufus L. , Schneiter Albert A. , Miller Jerry F.
Published: July 2010

On certain soil series, nonoilseed sunflower (Helianthus annuus L.) yields kernels with a cadmium (Cd) concentration in excess of some international Cd limits. The purpose of this study was to determine the relative importance of general combining ability (GCA), specific combining ability (SCA), and heterosis estimates needed to develop low Cd hybrid cultivars of nonoilseed sunflower. The kernel Cd accumulation of 36 sunflower F1 hybrids, obtained by crossing six inbred cytoplasmic male‐sterile lines to six inbred male‐fertile lines in a factorial mating design, was evaluated from field tests conducted at four locations with different soil types. Although the genotype × location interaction was statistically significant, the correlations for Cd among locations were significant over F1 hybrids and parental lines, indicating that inbred parental lines and hybrids performed consistently across the four locations. GCA was significant and accounted for 80% of the hybrid sums of squares. The interaction between males and females also was significant. These results indicate that additive genetic effects predominantly influence the expression of kernel Cd accumulation in hybrids. The regression of actual hybrid kernel Cd on expected hybrid kernel Cd, based on parental GCA values, was highly significant. Although the regression of actual hybrid kernel Cd on midparent also was statistically significant, the R2 value was only 0.21. These results indicated that GCA was more effective than midparent for describing hybrid performance. The levels of heterosis varied widely among crosses, ranging from −50 to 50%. Twenty‐seven of the 36 crosses registered double‐digit negative heterosis, indicating breeding for low kernel Cd in sunflower hybrids should be feasible.