bluuebunny/crossref_metadata_2025 huggingface dataset:
Path Analyses Identify Indirect Selection Criteria for Yield of Late‐Planted Soybean
Authors: Board J. E. , Kang M. S. , Harville B. G.
Published: July 2010

Research aimed at increasing yields of late‐planted soybean [Glycine max (L.) Merr.] in the southeastern USA would be facilitated by identification of yield components that indicate plot yield (combine‐harvested yield). Such yield components could be used as criteria in environmental and genetic research where plot yield cannot be obtained. Thus, our objective was to apply path analysis to previous studies to evaluate yield components for potential use as selection criteria (yield indicators) for future late‐planted studies. Path analysis was applied to plot yield (response variable) and various yield components (predictor variables) for five late‐planted studies conducted across 1987 to 1993 near Baton Rouge, LA (30°N Lat). Studies were grouped into four data sets based on treatment factors: row spacing‐plant population; row spacing; partial defoliation treatments during the reproductive period; and row spacing‐cultivar. All studies involving row spacing, plant population, and partial defoliation showed that seed number was the best indirect selection criterion for predicting plot yield. However, in a study involving 12 cultivars, genotypic path analysis indicated pod per reproductive node as the best indirect selection criterion. Because of the greater inferential base of this study and the positive influence of pod per reproductive node at both phenotypic (path coefficient = 1.61) and genotypic levels (path coefficient = 4.31), greater attention should be given to this yield component for genetic improvement of soybean at late plantings.
Rooting and Drought Avoidance of Warm‐Season Turfgrasses and Tall Fescue in Kansas
Authors: Qian Y. L. , Fry J. D. , Upham W. S.
Published: July 2010

Rooting characteristics of ‘Midlawn’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt‐Davy], ‘Prairie’ buffalograss [Buchloe dactyloides (Nutt.) Engelm.], ‘Meyer’ zoysiagrass (Zoysia japonica Steud.), and ‘Mustang’ tall rescue (Festuca arundinacea Schreb.) are not well documented, but likely contribute to drought avoidance. Experiments were conducted between 1993 and 1995 to determine (i) vertical rooting patterns in the greenhouse and field and (ii) relationships among rooting parameters, soil water depletion (SWD), and turfgrass wilting in the field. Tall fescue was mowed once weekly at 6.5 cm, whereas warm‐season grasses were mowed twice weekly at 4.5 cm. In the greenhouse, total root length (TRL) of tall fescue between 0 and 120 cm was 180 to 270% greater, and its maximum root extension (MRE) was 33 to 60% deeper than warm‐season grasses. Tall fescue also had a shoot/root ratio (SRR) 29 to 63% lower than ratios of warm‐season grasses. When sampled to a 90‐cm depth in a silt loam soil (fine, montmorillonitic, mesic Aquic Arquidolls) in the field, tall fescue exhibited 39 and 140% greater TRL than warm‐season grasses in 1993 and 1994, respectively. Zoysiagrass had the lowest root length density (RLD) at 30 to 60 and 60 to 90 cm of any grass studied in the field. Soil water depletion during five 7‐ or 12‐d precipitation‐free periods in the field indicated that tall fescue extracted over 50% more water than bermudagrass and zoysiagrass at 90 cm. Buffalograss extracted 66% more water than zoysiagrass at 90 cm during one of these periods. Wilting of warm‐season grasses at the end of dry down in the field was correlated with RLD at 30 to 60 (r = 0.74) and 60 to 90 cm (r = 0.66). Deep and extensive rooting of Mustang tall fescue and intermediate rooting of Prairie buffalograss and Midlawn bermudagrass were important components of leaf wilt resistance during drought. Shallow rooting resulted in poor drought avoidance in Meyer zoysiagrass.
Association of Loci Underlying Field Resistance to Soybean Sudden Death Syndrome (SDS) and Cyst Nematode (SCN) Race 3
Authors: Chang S. J. C. , Doubler T. W. , Kilo V. Y. , Abu‐Thredeih J. , Prabhu R. , Freire V. , Suttner R. , Klein J. , Schmidt M. E. , Gibson P. T. , Lightfoot D. A.
Published: July 2010

Coinheritance of field resistance of soybean [Glycine max (L.) Merr.] to sudden death syndrome (SDS) [caused by the fungus Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burk.) Snyd. & Hans.] and soybean cyst nematode (SCN) race 3 (caused by Heterodera glycines Ichinohe) sometimes occurs in crosses among adapted cultivars. Our objective was to characterize the loci underlying this coinheritance. One hundred thirty DNA markers were compared with SDS disease response and SCN score among 100 recombinant inbred lines (RILs) derived from a cross between SDS and SCN resistant ‘Forrest’ and SDS and SCN susceptible ‘Essex’. SDS disease incidence (DI) was determined in replicated sites during 4 yr encompassing five locations. The SCN score was determined in the greenhouse from naturally infested field soil samples. Two separate genomic regions identified by random amplified polymorphic DNA (RAPD) markers OI03450 and OW15400 were associated with mean SCN score (P = 0.0001) and jointly accounted for about 47% of variability in SCN score. OI03450 identified a QTL for resistance to SCN (R2 = 14%) within a genomic region that was strongly associated with SDS DI (R2 = 20%), partly explaining the coinheritance of the two traits. This locus could be assigned to the region of linkage group G already known to encompass the major SCN resistance locus.
Convergent‐Divergent Selection for Seed Production and Forage Traits in Orchardgrass: II. Seed Yield Response in Oregon
Authors: Barker R. E. , Casler M. D. , Carlson I. T. , Berg C. C. , Sleper D. A. , Young W. C.
Published: July 2010

More than 90% of U.S. production of orchardgrass (Dactylis glomerata L.) seed occurs in the U.S. Pacific Northwest. However, breeders in forage‐producing regions are unable to effectively select for Pacific Northwest seed yield by direct selection in their environment. This study was undertaken to determine if selection for broad adaptation for seed yield within forage‐producing regions could maintain commercially adequate seed production when grown in the U.S. Pacific Northwest. Two cycles of convergent‐divergent (C/D) selection were conducted and the resulting populations were evaluated for 2 yr in Oregon. The experiment was a randomized complete block design with three replicates grown in the field on a Woodburn silt loam (fine silty, mixed, mesic Aquultic Argixeroll, on 0–3% slopes) soil. Panicle seed weight (PSW) was the selection criterion for seed production. Except for the WO11 population, PSW remained unchanged when the selected and original populations were grown in Oregon. Both C/D and local selection methods resulted in decreased PSW in WO11. However, total seed yield (TSY) increased 163 and 111 kg ha−1 cycle−1 for the MO2 and WO11 populations, respectively, from C/D selection. Populational buffering for TSY appeared to be present in these two populations because single‐location selection at each of four sites was ineffective in increasing TSY as measured in Oregon. Total seed yield of 179DT and PLS4 was not changed by either C/D or local selection. A shift toward later maturity occurred in three of the four populations as a result of either C/D or local selection. A population selected from WO11 was both as late maturing and as high yielding as the latest‐maturing and highest‐yielding cultivars tested. Multiple‐location selection, such as C/D selection, can effectively accumulate genes for broad adaptation making it possible to achieve high seed yields concomitantly with later maturity.
Variation in Grain Functional Quality for Soft Winter Wheat
Authors: Hazen S. P. , Ng P. K. W. , Ward R. W.
Published: July 2010

Soft wheat (Triticum aestivum L.) is an ingredient in a broad range of end‐use products. The purpose of this research was to study variation in soft wheat flour yield, protein content, mixograph, and wire‐cut formulation cookie diameter and height. Five soft winter wheat cultivars were grown in replicated trials in nine environments in Michigan. Analysis of variance revealed that cultivar, environment, and cultivar × environment effects were significant for flour yield, protein content, cookie diameter, and mixograph peak height. Only cultivar significantly (P < 0.05) affected cookie height. Mixograph peak time was significantly (P < 0.01) affected by cultivar and environment, but not cultivar × environment interaction. Hühn's nonparametric stability statistic showed differences in rank stability for flour yield only. Principal component analysis of the cultivar × environment interaction effects showed no consistent patterns of behavior for similar cultivars, locations, or seasons. A reasonable degree of accuracy can be obtained by evaluating bulked replications from a few locations per year. When purchasing grain, knowledge of the cultivar is useful in predicting quality relative to other cultivars. Knowledge of local environments is of little use when attempting to predict grain quality. The mixograph and wire‐cut cookie tests employed here appear to be useful indicators of quality in soft wheat.
Efficiency of Secondary Traits for Improving Maize for Low‐Nitrogen Target Environments
Authors: Bänziger M. , Lafitte H. R.
Published: July 2010

Consideration of secondary traits could improve selection efficiency under stress conditions. This study assesses the value of secondary traits for improving lowland tropical maize (Zea mays L.) for low‐N target environments. Nineteen experiments grown with no N applied at CIMMYT, México, between 1986 and 1995 were analyzed for grain yield, anthesis‐silking intervai (ASI), number of ears per plant, leaf chlorophyll concentration, and an estimate of leaf senescence. Broad‐sense heritabilities of traits, genetic correlations between secondary traits and grain yield, and predicted response of grain yield to selection for single or multiple traits were calculated. Multiple traits were combined using an unrestricted selection index (Smith‐Hazel index). Broad‐sense heritabilities averaged 0.46 for grain yield, 0.52 for ASI, 0.44 for ears per plant, 0.35 for leaf chlorophyll concentration, and 0.60 for leaf senescence. Genetic correlations of secondary traits with grain yield averaged −0.47 for ASI, 0.78 for ears per plant, 0.24 for leaf chlorophyll concentration, and 0.42 for leaf senescence. Direct selection for grain yield was superior to selection for single secondary traits in most experiments. When information on all traits was combined in a Smith‐Hazel index, selection efficiency improved by 14% on average over selection for grain yield alone. Among secondary traits, ears per plant and leaf senescence discriminated high‐yielding genotypes the best. Leaf chlorophyll concentration, and in some instances ASI, provided information on environmental variation within experiments. We conclude that secondary traits can increase the efficiency of selection for grain yield in maize breeding programs targeting low‐N environments.
Combining Ability for Within‐Boll Yield Components in Cotton, Gossypium hirsutum L
Authors: Coyle Gwen G. , Smith C. Wayne
Published: July 2010

Lint yield and fiber quality in upland cotton, Gossypium hirsutum L., are interrelated through a series of individual components that include bolls/unit land area, mean fiber length and weight/unit length, and a series of within‐boll components. Numerous studies have investigated the relationships among various components of lint yield and yield per unit land area, but none have reported on the relationships among the most basic within‐boll yield components and fiber quality. The objective of this study was to evaluate the combining ability for within‐boll lint yield components among a group of cotton genotypes that varied by date of release, type of release, originating program, and their fiber quality parameters, especially fiber bundle strength. Four cultivars, one each released in 1905, 1943, 1979, and 1981, and two modern germplasm lines were crossed in a half diallel. Parents and F1s were grown at College Station, TX, in 1989 and 1992. Twenty‐five and 100 normal bolls were hand harvested from each plot of a randomized complete block design in 1989 and 1992, respectively. Fiber quality parameters were determined by high volume instrumentation. Within‐boll yield components were determined by direct measurement or through calculations. Genotypes having good general combining ability (GCA) estimates for fiber quality exhibited negative GCA estimates for the most basic within‐boll yield components. Among these genotypes, three‐way crosses, modified backcross, or recurrent selection procedures would be required to select for improved fiber quality and simultaneously increase the number of harvestable fibers per unit of seed surface area.
Water Stress during Reproductive Stages Affects Seed Quality and Yield of Pea (Pisum sativum L.)
Authors: Fougereux Jean‐Albert , Doré Thierry , Ladonne Fabienne , Fleury André
Published: July 2010

Physiological quality of pea (Pisum sativum L.) seed depends on various factors affecting the plant, including water supply, the effect of which has not been fully characterized. The effects of different periods of water stress during reproductive stages on the seed yield and seed physiological quality were investigated in field studies for 3 yr (1991, 1992, and 1993) at Brain‐sur‐ľAuthion, France, on a Mollisol, Rendoll, eutrochreptic soil. Irrigation during seed filling (IDSF) and irrigation during the period from the start of flowering to the start of seed filling were compared with a non‐irrigated (NI) and season‐long, irrigated‐as‐needed (WI) treatment. The physiological quality of pea seeds was assessed by germination percentage and the conductivity and cold tests. The germination percentage averaged 98% and was not modified by water stress. In 1993, rainfall during the reproductive stages was high, and there were no differences in seed yield or quality between treatments. In 1991 and 1992, the rainfall was much lower, and the NI treatment showed the lowest seed yield and quality as far as the conductivity test and cold test were concerned. The WI treatment showed the best yields. Water stress during the flowering period did not reduce seed quality more than WI, and reduced seed yield only slightly. Water stress during seed filling decreased seed yield but the effect on seed quality was not significant. Individual seed weight was higher and less variable in IDSF treatments than in WI treatments. Changing irrigation strategies for pea seed production by irrigating during seed filling may improve the physiological quality of the seedlots without decreasing the seed yield.
Management Practices to Reduce Gray Leaf Spot of Maize
Authors: Ward J. M. J. , Laing M. D. , Cairns A. L. P.
Published: July 2010

The beneficial effects of stubble tillage on soil and water conservation are widely recognized, but surface stubble also increases the potential for crop damage by fungal pathogens that overwinter in the previous season's debris. In recent years, gray leaf spot (GLS) has become a major yield‐limiting disease, resulting in grain yield losses as high as 60% in high yield potential maize (Zea mays L.) production areas. A study was launched to investigate strategies that could be adopted to facilitate the continuation of conservation tillage practices without exposing maize to unnecessarily high risk from GLS. The aim of the study was to investigate the interactive effects of four tillage practices leaving varying amounts of surface residues and fungicide treatments for the control of stubble‐associated pathogens. In the hot, dry season, unfavorable for GLS, the onset of disease was 23 d earlier in no‐till with higher disease than conventional tillage. The benefits of conserved soil moisture under stubble tillage with concomitant higher grain yields than conventional tillage offset the detrimental effects of higher disease. Results from the study indicate that tillage practices are unlikely to have a major impact in managing GLS; since the mean yield of conventional tillage with minimal stubble (3% residue), during four seasons, was between 28 and 209 kg ha−1 lower than tillage treatments leaving 82 and 26% stubble on the soil surface, respectively. During the four seasons of the study, grain yield responses to fungicide treatment ranged from 477 kg ha− in unfavorable seasons to 3830 kg ha− in seasons favorable for GLS. The judicious application of fungicides will reduce the risk of financial loss from GLS and will allow the continuation of the desirable stubble tillage practice in sustainable farming systems.
Intercropping Effects on Mustard Aphid (Lipaphis erysimi Kaltenback) Populations
Authors: Singh D. , Kothari S. K.
Published: July 2010

Aphids (Lipaphis erysimi Kaltenback) often reduce mustard (Brassica juncea L.) yield in India. This study was conducted to determine if intercropping with aromatic plant species could provide an environmentally safe method for aphid control. Aphid infestation on monocrop mustard (‘Rohini’) was compared with intercrop treatments of artemisia (Artemisia annua L.), coriander (Coriandrum sativum L.), chamomile (Matricaria chamomilla L.), fennel (Foeniculum vulgare Mill.), and dill (Anethum sowa Kurz). Intercropping with fennel resulted in a significantly lower aphid infestation. These preliminary results warrant additional studies to determine control processes and if the practice is effective in commercial mustard fields.
Combining Ability Analysis of In Vitro Callus Formation and Plant Regeneration in Red Clover
Authors: Poerba Y. S. , Quesenberry K. H. , Wofford D. S. , Pfahler P. L.
Published: July 2010

Red clover (Trifolium pratense L.) is an important forage species grown in temperate climates around the world. Most genetic transformation methods require regeneration of whole plants from single undifferentiated cells, but one of the major problems encountered in red clover tissue culture is low frequency of plant regeneration. Nine genotypes of red clover, with a range in the level of callus formation and plant regeneration [low (01L, 04L, 30L), intermediate (231, 641, 741), and high (34H, 54H, 71H)] on a B5 basal salts medium protocol, were used in a combining ability study of in vitro callus formation and plant regeneration. Hypocotyl sections from 40 progeny from each of 36 F1 crosses were evaluated on a B5 medium protocol for callus formation at 4 wk of culture and plant regeneration at 12 wk of culture. Analysis of variance showed significant effects of crosses, general combining ability (GCA), and specific combining ability (SCA). Results obtained from diallel analysis (Griffing's Method 4, Model I) showed that crosses with 34H, 54H, or 71H as one parent were among the combinations showing the highest callus diameter and regeneration capacity. Those crosses with OIL, 04L, or 30L as one parent were among the lowest in callus diameter and regeneration response. A highly significant positive relationship (r = 0.91, df = 34) was found to exist between callus diameter and regeneration capacity. Although both general and specific combining ability (SCA) were significant sources of variation for callus diameter and plant regeneration, SCA effects were significant for only a few crosses. The results are in agreement with our previous research showing that red clover regeneration from tissue culture can be improved using recurrent selection methods which exploit additive genetic effects. Initial selection for large callus size should result in improved regeneration capacity.
QTLs and Epistasis Associated with Vernalization Responses in Oat
Authors: Holland J. B. , Moser H. S. , O'Donoughue L. S. , Lee M.
Published: July 2010

Oat (Avena sativa L.) genotypes differ in their patterns of growth and development in response to vernalization (cold temperatures applied to germinating seeds). Genomic regions controlling vernalization response in heading date, plant height, and tiller number were mapped in a recombinant inbred (RI) population derived from the cross of oat cultivars ‘Kanota’ (vernalization‐responsive) and ‘Ogle’ (vernalization‐insensitive).Seventy‐one F6‐derived RI lines were subjected to vernalization and no‐vernalization treatments, and then grown in growth chambers. A genetic linkage map of 561 (primarily RFLP) loci was used to identify quantitativet rait loci (QTLs) affecting the traits in vernalized and non‐vernalized plants. Nine to 16 linkage groups and unlinked loci were associated with each trait assessed herein. Individual loci explained up to 37% of the phenotypic variation. Three to five significant loci were included in multiple locus linear models which explained up to 66% of phenotypic variation for each trait. One to 14 interactions between loci were found for each trait. The interactions explained up to 30% of the phenotypic variation not accounted for by the main effects of loci involved in the interactions. Inclusion of epistatic interactions tended to improve the fit of multiple locus models. As much as 83% of phenotypic variation was explained by multiple locus models including epistasis. Numerous epistatic interactions involving at least one locus with no significant main effect were detected.
Apomixis and Sexuality in Some Paspalum Species
Authors: Burson Byron L.
Published: July 2010

Paspalum is a large genus that contains several important forage and turf grasses. Little or no information is available concerning the cytology and reproductive behavior of many of these species. The objectives of this study were to determine the cytology, method of reproduction, and fertility of accessions of eight different Paspalum species. Paspalum modestum Mez., P. monostachyum Vasey, P. repens Bergius, and one P. alcalinum Mez. accession were sexual dipioids with 2n = 2x = 20 chromosomes. Meiosis was regular with primarily bivalent pairing. Even though P. modestum was sexual, the female gametophyte deteriorated in 43% of the ovules. Two P. alcalinum, one P. falcatum Nees, two P. paucifolium Swallen, three P. polyphyllum Nees, and one P. unispicatum (Scribn. et Merr.) Nash accessions were tetraploids with 2n = 4x = 40 chromosomes. During meiosis their chromosomeass sociated primarily as bivalents, quadrivalents, and univalents. Regardless of the species, all tetraploids were facultative aposporous apomicts. One P. alcalinum accession was a pentaploid with 50 chromosomes. Meiosis was irregular with the chromosomeass sociating as univalents, bivalents, trivalents, and quadrivalents. This accession reproduced as an obligate aposporous apomict. Seed set in P. modestum and P. monostachyum was very low but was high enough in the other species that they could be propagated by seed. These findings demonstrate the cytological and reproductive diversity within this large complex genus.
Heterosis in Soybean and Its Prediction by Genetic Similarity Measures
Authors: Manjarrez‐Sandoval P. , Carter Thomas E. , Webb D. M. , Burton J. W.
Published: July 2010

Coefficient of parentage (CP) and restriction fragment length polymorphism‐based genetic similarity estimates (RFLP‐GS) have been proposed as measures of genetic distance in crop species. If these measures are to have application in practical breeding, it is important to validate their utility in predicting genetic traits of interest such as heterosis. The objectives of this paper were to (i) estimate heterosis for yield in soybean [Glycine max (L.) Merr.] adapted to the southern USA, and (ii) predict heterosis by means of CP and RFLP‐GS as genetic distance measures. Twenty‐four F2 populations were developed by crossing three testers (‘Young’, ‘Centennial’, and ‘Tracy’) eight contrasting parents, representing a wide range of CP and RFLPGS. The experimental material was divided into three sets representing the testers above, and was evaluated in eight replications at Clayton and Plymouth, NC, in 1994. Midparent heterosis for yield was 7.9, 4.5, and 7.9% for Sets 1, 2, and 3, respectively. Heterosis was 3.5, 1.6, and 3.0% for 100‐seed weight, and 4.1, 5.4, and 13.2% for plant height. The CP and RFLP‐GS were highly correlated (r = 0.80, 0.92 and 0.95 for Sets 1, 2, and 3, respectively, P = 0.01), but neither predicted heterosis well for yield averaged across locations because of a large genotype × environment (G × E) interaction. In contrast, CP and RFLP‐GS predicted heterosis well for 100‐seed weight and plant height in two of the three sets averaged over locations. Our estimates of high parent heterosis for yield (as high as 11% over locations), may justify soybean hybrids as a breeding objective. However, the limited predictive value of CP and RFLP‐GS in our study indicates that the identification of favorable heterotic combinations may require extensive field testing.
Selection Responses for the Characters Related to Yield Sink Capacity of Rice
Authors: Kato Tsuneo
Published: July 2010

Yield sink capacity, the maximum size of sink organs to be harvested, is an important target in breeding for high‐yielding cultivars. Using two sets of F2 and F2:3 populations of rice (Oryza sativa L.), this study carried out disruptive selection in each F2 population for every characterelated to yield sink capacity, evaluated the direct and correlated selection responses in their F2:3 progenies, and estimated genetic correlations and realized heritabilities. Among the components of the number of spikelets per panide, the number of primary branches (PB) per panicle resulted in the highest realized heritability which exceeded the heritability for the number of spikelets per panide. The genetic correlations indicated that the number of PB per panide was positively and strongly associated with the number of spikelets per panicle in both populations. Thus, in one population, indirect selection on the number of spikelets per panicle via selection on the number of PB per panicle was slightly more effective than direct selection on the number of spikelets per panicle. The number of PB per panicle was not positively correlated with the number of spikelets on SB (secondary branches) per SB, and also was not positively correlated with the number of SB per PB. Since rice spikelets on PB generally produce fully filled grains, in contrast to spikelets on SB, we should be able to construct genetically a rice panicle type which has a sufficient number of spikelets with high filled‐grain percentage by increasing the number of PB and by suppressing the number of spikelets on SB.
Breeding Potential of European Flint and Earliness‐Selected U.S. Corn Belt Dent Maize Populations
Authors: Moreno‐Gonzalez J. , Ramos‐Gourcy F. , Losada E.
Published: July 2010

Flint × dent maize (Zea mays L.) hybrids are commonly planted in the early corn growing regions of Europe (northern and the Atlantic Coast of Europe). Evaluation of the early maize germplasm is important for the development of new commercial hybrids adapted to cooler summer regions. Our objectives were to assess the potential of flint and earliness‐selected dent germplasm as base populations for developing early grain maize hybrids and to determine the performance and heterosis of this germplasm. Eight populations formed the base material of this study. Four populations were U.S. Corn Belt dent populations that had undergone several cycles of selection for earliness. The other four were European early flint populations. The eight populations, their diallel crosses, and topcrosses to inbreds A632 and EC18 were evaluated at five environments in northwestern Spain in 1991 and 1992. Dent populations outyielded Hint populations by 220 g kg−1 at the per se level, by 100 g kg−1 when crossed to flint and dent inbred testers, and by 50 g kg−1 in the population diallel crosses. The yield heterosis of population crosses was 26% of the population yield mean. The dent germplasm exhibited less stalk and root lodging than flint germplasm. When yield and other agronomic traits are globally considered, the earliness‐selected dent populations seem best for the development of hybrids to be grown in mild summer environments. Because specific dent germplasm is being developed for early areas, it seems that dent × dent commercial hybrids should progressively replace flint × dent hybrids in the early maize growing regions of Europe.
Genetic Variances of Agronomic and Morphological Traits of Diploid Crested Wheatgrass
Authors: Ray Ian M. , Frank Albert B. , Berdahl John D.
Published: July 2010

Crested wheatgrass breeding efforts in the USA have focused on tetraploid germplasm, resulting in little genetic information available for diploid germplasm. This study was conducted to estimate progenymean heritability (h2) of eight traits of diploid crested wheatgrass (Agropyron cristatum L.) grown under seeded competitive conditions in the northern Great Plains. Thirty half‐sib families were randomly selected from a genetically broad‐based population, and evaluated at one location over 2 yr, in single‐row 1.5‐m plots, spaced 38 cm apart, and seeded at 90 seed m−1. Heritabilities based on the progeny meansof 30 families were determined for forage dry matter yield (h2 = 52%), filler height (h2 = 63%), first‐cut vigor (h2 = 15%), regrowth vigor (h2 = 68%), proline content (h2 = 49%), spikelets per spike (h2 = 59%), anthocyanin pigmentation of stem nodes (h2 = 36%), and flag leaf pubescence (h2 = 70%). Heritability of forage yield, tiller height, regrowth vigor, number of spikelets per spike, and flag leaf pubescence were estimated with the greatest precision. Firstcut vigor, proline content, and node color were estimated with less precision. Proline accumulation was not associated with either dry matter yield or regrowth vigor under water stress. Regrowth vigor was not associated with first‐cut yield (P ≥ 0.24), indicating that improvement in first‐cut yield would have little effect on forage regrowth potential. A moderately high heritability estimate for regrowth vigor indicated that selection for this trait could extend the grazing season of crested wheatgrass. Genetic variance components for all traits except first‐cut vigor exceeded their standard errors. Significant family × year effects were detected only for node color. The results indicate that evaluation over multiple years would not be needed for most traits studied.
An Encoding Process for Morphological Analysis of Soybean Fruit Distribution
Authors: Keisling Terry C. , Counce Paul A.
Published: July 2010

Numerical analysis and summarization of soybean [Glycine max (L.) Merr.] morphological data has been complicated by the amount of data and the use of stick diagrams to illustrate plant growth. This note explains how to encode morphological data by mapping fruit locations with a tree directory. Encoded data are easily entered into computers for analysis by commercial statistical and graphical software. Three examples are given to illustrate the power and versatility of using numerical analysis to explore critical facts and tendencies of soybean morphology. This encoding procedure can be adapted to other branching plants or branching plant parts.
Usefulness of Marker‐QTAL ssociations in Early Generation Selection
Authors: Eathington S. R. , Dudley J. W. , Rufener G. K.
Published: July 2010

Early generation testing allows the discarding of lines with poor combining ability early in the inbreeding process; however, maintaining a high probability of retaining superior performing lines at homozygosity requires a low selection intensity in early generations. This study was conducted to determine the usefulness of marker associated effects estimated from early generation testcross data for predicting later generation testcross performance. From the maize (Zea mays L.) cross BS11(FR)C7×FRMo17, 190 random families represented in the S1 and S4:5 generations were testcrossed to an elite B73 type inbred. Families were genotyped at 157 marker loci in both generations. Models using S1 testcross data, net molecular scores, and indices combining phenotypic and molecular information were evaluated for their ability to predict S4:5 testcross performance. for both grain yield and percent stalk lodging, an index including both phenotypic and marker information predicted S4:5 testcross performance better than either phenotypic or marker information alone. For grain yield, combining marker information with phenotypic information allowed a reduction of 40% in the number of lines tested in the S4:5. Because of the high heritabilities in this study, phenotypic informationp redicted the top S4:5 testcrosses better than markerin formation alone. Because of the high heritability for grain moisture, combining marker information with phenotypic information did not improve predictability. Adding marker information to phenotypic information also improved prediction of S4:5 testcross performance for an index of multiple traits. Markemr odels for S1 testcross grain yield developed for a set of high yielding environments contained different marker loci than models developed for a set of low yielding environments. For models developed from the high yielding environments, marker information was able to improve selection of the top S4:5 families over selection based on phenotypic data.
Weighted Means Are Unnecessary in Cultivar Performance Trials
Authors: Hühn Manfred
Published: July 2010

The mean performance of a particular cultivar across environments is commonly estimated by the arithmetic (unweighted) mean. However, if variances are heterogeneous across environments, weighted means may be better estimators. The yield of the ith cultivar in the jth environments is χij = μ + αi + βj + τij where μ = overall mean; αj = effect of the ith cultivar; βj = effect of the jth environment; and τij = residual effect. The correlation (r) between weighted and unweighted average cultivar performances depends on κ = [V(κj)/V(Zi)]1/2 and ρ = correlation between αj and Ζi, where Ζi = Cov(τij, gj) and gj = weight of Location j. For any predetermined numerical magnitude (r0) of r, r ≥ r0 for κ ≥ (1 − r20)−1/2 with any arbitrary value of ρ. For r0 = 0.90, for example, this condition reduces to r ≥ 0.90 if κ ≥ 2.29. In practice, the validity of κ ≥ 2.29 and its consequence r ≥ 0.90 will be realized in almost all relevant situations. This result was clearly demonstrated by analyses of extensive data sets from the official German registration trials for several agronomic crops. The theoretical investigations, therefore, lead to the recommendation to use the arithmetic mean in estimating average cultivar performance, even if error and cultivar × environment interaction variances are heterogeneous.
Heritability of Seed Shape and Seed Size in Soybean
Authors: Cober E. R. , Voldeng H. D. , Frégeau‐Reid J. A.
Published: July 2010

Round seeds are desirable for food‐type soybean [Glycine max (L.) Merr.] cultivars and an understanding of the heritability of seed shape would benefit the development of these cultivars. The objectives of this study were to estimate heritability of seed shape and seed size by parent‐offspring regression, parent‐offspring correlation, and realized heritability, and to determine the correlation between seed size and seed shape in germplasm ranging in seed size. From parents differing in seed shape, four populations (three oilseed‐type and one small‐seeded natto‐type) were generated. A total of 694 random F2 plants, grown in 1994 at Ottawa, ON, and their resulting F2:3 progeny, grown in unreplicated rows in 1995 at Ottawa, were used for analysis. Seed shape was quantified by two aspect ratios (the ratio of minimum to maximum seed diameter), each calculated from a different seed orientation with digital image analysis. Seed size (cross‐sectional area) was measured in the same two orientations. Estimates of heritability for seed shape varied across the four populations; parent‐offspring regression coefficients ranged from 0.55 to 0.75, parent‐offspring correlation coefficients ranged from 0.49 to 0.76, and realized heritability estimates ranged from 0.59 to 0.79. Estimates of heritability for seed size ranged from 0.19 to 0.56 across populations. There were significant positive correlations between the aspect ratios calculated from the two different orientations; therefore, selection for round shape in one orientation would result in indirect selection for round shape in the other orientation. There was no consistent association between seed shape and seed size. In the natto population, <5% of the F3 lines were smaller or rounder than the smallest‐ roundest‐seeded parent. Heritability estimates indicate that plant breeders can select for round seed shape, on a single plant basis, in early generations of populations ranging in seed size.
Effects of Coating on Seed Imbibition: I. Model Estimates of Water Transport Coefficient
Authors: Schneider Anne , Renault Pierre
Published: July 2010

Seed coatings are used to facilitate local applications of products, including systemic chemicals. However, they may slow imbibition, the rate of which will probably further decrease with multi‐layer coatings. In this paper, we propose a method based on the use of a simplified model for estimating of the hydraulic conductivity and vapor diffusion coefficient of seed coatings as a function of seed water content. This method results from theoretical calculations established for spherical systems having only an external resistance to water transport. Extension of these calculations to systems in which the internal resistance to water transport may not be neglected was checked with a onedimensional spherical mechanistic model of seed imbibition. Using a numerical method, we simulated imbibition for seeds in liquid water with the mechanistic model. These simulation results were analyzed, thereafter, by the simplified model. Whatever the ‘seed‐coating’ system of interest, it was always possible to simulate imbibition with the simple model without introducing a bias larger than 3% of the average seed water content. When seed resistance was negligible compared with coating resistance, the estimate of the coating hydraulic conductivity as a function of the water content was nearly equal to the theoretical conductivity. If the seed resistance was large, relative to the coating resistance, estimates of this relationship were possible if imbibltion data were available for different levels of seed coating. In the studied situations, the method led to a bias contained within a 1 to 25% range for the conductivity of the coating.
Drought‐Resistance Mechanisms of Seven Warm‐Season Turfgrasses under Surface Soil Drying: I. Shoot Response
Authors: Huang B. , Duncan R. R. , Carrow R. N.
Published: July 2010

Knowledge of drought response differences in turfgrasses would accelerate the effectiveness in developing water‐use‐efficient species. The study was designed to evaluate shoot morphological and physiological traits in relation to drought resistance for seven warm‐season turfgrasses: bermudagrass [Cynodon dactylon (L.) Pets. ‘Common’], centipedegrass [Eremochloa ophiuroides (Munro) Hackel ‘TifBlair’], seashore paspalum (Paspalum vaginatum Swartz, four ecotypes), and zoysiagrass (Zoysia japonica Steudel × Z. tenuifolia Steudel ‘Emerald’) under surface soil drying and rewatering conditions. Plants were grown in a greenhouse during 1995 and 1996 in sectioned PVC tubes under four soil moisture treatments. Drought resistance among the turfgrasses was assessed using canopy temperature, leaf chlorophyll content, relative water content, and shoot dry matter production in response to drying of 0‐ to 20‐ and 0‐ to 40‐cm soil layers. The rank in drought resistance in the 0‐ to 40‐cm drying regime was: Paspalum PI 509018 = TifBlair centipedegrass > AP14 = PI 299042 > Adalayd > Common bermudagrass = Emerald zoysiagrass. Shoot dry matter production recovered fully after rewatering for TifBlair centipedegrass and paspalums except Adalayd, but only partially for Common bermudagrass and Emerald zoysiagrass. The differences in shoot responses to drought stress and rewatering among the seven grasses were presumably related to variations (plasticity) in rooting characteristics as demonstrated in root responses.
Mitotic and Ultrastructural Changes in Root Meristems of Grass Seedlings Treated with Alaninyl‐Alanine
Authors: Unruh J. B. , Christians N. E. , Horner H. T.
Published: July 2010

Alaninyl‐alanine (Ala‐Ala), is a biologically active dipeptide that inhibits the rooting of germinating seeds. Previous research revealed that cells of root tips treated with Ala‐Ala were void of cellular components, specifically discernible nuclei and mitotic structures, as well as an overall loss of cytoplasmic integrity. Treated root tips had extensive cell wall abnormalities, including uneven thickening and shattering. Many commonly used herbicides, such as the dinitroanilines, the carbamates, and dithiopyr [S,S ‐dimethyl 2‐(difluoromethyl)‐4‐(2‐methylpropyl)‐6‐(trifluoromethyl)‐3,5‐pyridinedicarbothioate], produce effects similar to Ala‐Ala in root meristems. The objectives of these investigations were to use time‐course studies to observe the mitotic activity of perennial ryegrass (Lolium perenne L.) seedling roots grown in petri dishes containing Ala‐Ala, to describe Ala‐Alainduced changes in cellular ultrastructure in an effort to elucidate the mode of action of this biologically active dipeptide through the use of light and transmission electron microscopy, and to compare the results of these studies with reported modes of action of other commonly used herbicides. Results showed that Ala‐Ala exhibited activity on mitosis in root meristems within 4 h of exposure, and by 6 h, reduction in the number of mitotic figures was nearly 100%, resulting in only interphase cells. Microscopic analysis revealed profound treatment effects. By 12 h, dense droplets, presumably membrane lipids, were visible in vacuoles and intercellular spaces. After 48 h of exposure, epidermal and cortical cells in the treated roots appeared compressed with a disruption in cell polarity. Root lateral branching, similar to effects of preemergence herbicides, was also noted after a 48‐h exposure time. Root tips showed no gross external abnormalities until after a 96‐h exposure to Ala‐Ala.
Identifying Subsets of Maize Accessions by Three‐Mode Principal Component Analysis
Authors: Rincon Froylan , Johnson Blaine , Crossa José , Taba Sukethosi
Published: July 2010

Gencbank accessions are a potential source of genetic variability for maize (Zea mays L.) breeding programs. Identification of useful individual entries is commonly based on the expression of one or more attributes in different sites or environments. This study was motivated by the need to identify a subset of Caribbean accessions for introgression in to elite germplasm of the western Corn Belt. Thus the objective was to identify potentially useful Caribbean accessions, based on (i) simultaneous consideration of six agronomic attributes deemed economically important for the western Corn Belt, and (ii) response patterns observed across four sharply contrasting environments. Both (i) and (ii) were addressed by means of three‐mode principal component analysis (PCA) of data on six agronomic and morphological attributes for 184 Caribbean maize accessions evaluated at four environments. Three‐way data were analyzed by three‐mode PCA and based on (i) and (ii), two joint plots were generated. From the PCA and joint plots, two subsets of accessions were identified. First, a subset of 14 accessions having body yield, intermediate plant height, and average days to anthesis was identified. Secondly, a subset of 10 accessions having average performance over all environments was identified. Two accessions were common to both subsets. Jointly, the two approaches produced a combined subset of 22 accessions, representing 12% of the total evaluated, and including representatives of 11 maize races. Three‐mode PCA integrated information on accessions, attributes, and environments, and provided a means of simultaneously visualizing these three types of information. Three‐mode PCA can complement standard methodologies used by plant breeders for identification of potentially useful accessions in introgression programs.
Genetic Relationships among Soybean Plant Introductions with Resistance to Soybean Cyst Nematodes
Authors: Diers B. W. , Skorupska H. T. , Rao‐Arelli A. P. , Cianzio S. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] cultivars in the USA, which are resistant to soybean cyst nematode (SCN) (Heteroderag lycines Ichinohe), have resistance derived from only a few plant introductions (PIs). Many other SCN resistant PIs have been identified which could be used as sources for broadening the diversity of resistance genes in cultivars. The objectives of this research were to study the relationship among PIs with SCN resistance using restriction fragment length polymorphism (RFLP) markers and to assess their resistance response to five races of H. glycines. Thirty‐eight PIs previously reported as being resistant to one or more SCN races were evaluated for resistance to H. glycines Races 1, 2, 3, 5, and 14 in a greenhouse and were tested with 201 genomic DNA clones. PI 437654 and PI 438489B were resistant to all five SCN races. Four PIs were resistant to four SCN races, nine resistant to three races, four resistant to two races, four resistant to one race and the remainder had only moderate resistance or moderate susceptibility to one or more races. The PIs were polymorphic for 138 clones which revealed 301 polymorphic DNA fragments. The groupings of the PIs for both cluster analysis and principal component analysis (PCA) were associated with resistance responses to races of H. glycines. One major group of PIs was distant from all previously used sources of resistance. These PIs had only moderate resistance to Race 3 but could potentially provide new genes for resistance to this race. The other PIs were in groups that included Pls with resistance sources previously used by breeders. This information on the relationship of the PIs should help researchers developing resistant soybean cultivars to identify sources of SCN resistance which are not closely related to previously used sources.
Stem‐Tip Inoculation of Alfalfa with Sclerotinia trifoliorum: II. Performance of S1 and F1 Progenies from Resistant and Susceptible Selections
Authors: Halimi E. S. , Rowe D. E.
Published: July 2010

Two types of resistance responses have been identified on alfalfa (Medicago sativa L.) for Sclerotinia crown and stem rot caused by Sclerotinia trifoliorum (Eriks) following st em‐tip in oculation. A plant with the Type 1 resistance stops the lengthening of necrotic region on the stem about eight days after inoculation, but a plant with the Type 2 resistance continues slow expansion of necrotic region for the duration of the 14 d test. This research determined the levels of resistance in progenies from crosses of selections with same and different types of resistance to Sclerotinia, from crosses of resistant and susceptible selections, and from self‐fertilization of selections. The daily development of disease was measured from four to 14 d after inoculation on progenies from a diallel of six resistant selections and from a factorial cross of four resistant and four susceptible selections. The crosses among selections with Type I resistance produced progenies only with Type 1 resistance. Crosses of selections with Type 1 and Type 2 resistance produced four progenies with Type I resistance and four progenies with Type 2 resistance. Selfing the four selections with Type 1 resistance resulted in three progenies with Type 1 resistance and one with Type 2 resistance. Crosses of susceptible plants and those with Type 1 resistance resulted in low levels of Type 2 resistance. Selfing generally decreased the level of resistance in the resistant selections. For development of synthetic varieties, parents should be selected with high levels of Type 1 resistance and for self‐sterility.