bluuebunny/crossref_metadata_2025 huggingface dataset:
Drought‐Resistance Mechanisms of Seven Warm‐Season Turfgrasses under Surface Soil Drying: II. Root Aspects
Authors: Huang B. , Duncan R. R. , Carrow R. N.
Published: July 2010

Knowledge of drought‐resistance mechanisms in turfgrasses would improve management strategies and facilitate turfgrass breeding for drought resistance. The experiment investigated root morphological and physiological characteristics in response to surface soil drying and rewatering for bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’], centipedegrass [Eremochloa ophiuroides (Munro) Hack ‘Tif‐Blair’], seashore paspalum (Paspalum vaginatum Swartz, four ecotypes), and zoysiagrass (Zoysia japonica Steudel × Z. tenuifolia Steudel ‘Emerald’). Plants were grown in sectioned PVC tubes with four soil moisture regimes in a greenhouse during 1995 and 1996. Root growth was reduced when the upper 20‐ and 40‐cm soil layers dried for Emerald zoysiagrass, Common bermudagrass, and Adalayd paspalum, but only with upper 40‐cm soil drying for PI 299042, AP14, and PI 509018 paspalums, and TifBlair centipedegrass. Root dry weight recovered fully to control levels after rewatering for TifBlair centipedegrass and the three paspalum accession, but only partially for Adalayd paspalum, Common bermudagrass, and Emerald zoysiagrass. Superior drought resistance to surface soil drying for PI 509018 paspalum and TifBlair centipedegrass was associated with enhanced root growth and rapid root water uptake at deeper soil layers, maintenance of root viability at the surface drying soil, and rapid root regeneration after rewatering. Differences in these drought avoidance characteristics among turfgrasses could serve as selection criteria for improving turf drought resistance.
Ruminal In Vitro Degradation of Protein in Tannin‐Free and Tannin‐Containing Forage Legume Species
Authors: Broderick Glen A. , Albrecht Kenneth A.
Published: July 2010

Protein in forages often is poorly utilized by ruminants because of extensive degradation in the rumen. Our objectives were to assess the variation in ruminal protein degradability among forage legumes and to determine whether degradability was reduced by tannins. Legumes representing a range of species adapted to temperate regions were harvested on 29 Aug. 1989 and 31 Aug. 1990 from triplicate plots, then lyophilized, ground, and analyzed for tannins by radial diffusion. Ruminal protein degradation rates and escapes, estimated assuming a passage rate of 0.06 h−1, were determined both years by an in vitro limited substrate inhibitor procedure, and on samples from 1990 by a Michaelis‐Menten method. Protein degradation rates and escapes (limited substrate method) in 1989 ranged from 0.27 h−1 and 18% for white clover (Trifolium repens L.) to 0.001 h−1 and 96 and 97% for two cultivars of sericea lespedeza [Lespedeza cuneata (Dum.‐Cours.) G. Don]. In 1990, rates and escapes ranged from 0.21 h−1 and 21% for alfalfa (Medicago sativa L.) to virtually 0 and 93 to 97% for two cultivars of sainfoin (Onobrychis viciifolia Scop.) and three of sericea lespedeza. More rapid degradation rates were obtained with the Michaelis‐Menten approach for the most slowly degraded entries. Differences in degradation rate and ruminal escape were proportional to tannin concentration. However, red clover (Trifolium pratense L.), which does not contain tannins, had a protein degradability comparable with forages with low levels of tannin. These data suggest that differences in ruminal protein degradation among forage legumes are only partly explained by the presence of tannins.
Forage Yield, Quality, and Fertility of Sorghum × Sudan Grass Hybrids in A1 and A3 Cytoplasm
Authors: Pedersen J. F. , Toy J. J.
Published: July 2010

Currently, no information is available comparing the agronomic performance of A1 and A3 cytoplasms in sorghum × sudangrass [Sorghum bicolor (L.) Moench] hybrids. The objectives of this study were to compare the effects of A1 and A3 cytoplasm on the maturity, fertility, height, forage yield, and forage quality of sorghum × sudangrass hybrids. In 1989, pollen from a bulk of eight sudangrass populations was used to pollinate four sorghum lines that had been male‐sterilized in both A1 and A3 cytoplasm. Hybrids were grown at the Univ. of Nebraska Field Laboratory, Ithaca, NE, in 1990 and 1991, in a split‐plot design with inbreds (females) treated as whole plots and cytoplasms treated as subplots. The soil was a Sharpsburg silty clay loam (fine montmorillonitic, mesic Typic Agriudoll). Cytoplasm had no effect on days to 50% anthesis, height, forage yield, in vitro dry matter disappearance (IVDMD), or crude protein. Seed set under selfing bags (fertility restoration) in A3 hybrids was observed, with interaction among A3 cytoplasm sources and lines.
Transgressive Segregation of Tiller Angle in Rice Caused by Complementary Gene Action
Authors: Xu Yunbi , McCouch Susan R. , Shen Zongtan
Published: July 2010

Transgressive segregation is often observed for quantitative traits in the offspring of both intraspecific and interspecific hybrids. Understanding its genetic base is important for the improvement of these characters. In this research, we began with four indica cultivars, 5002, Zhu‐Fei 10, HA79317‐7, and Zhen‐Long 13, all having similar tiller angles. F2 populations were derived from the crosses 5002/Zhu‐Fei 10 and HA79317‐7/Zhen‐Long13, and divergent selection for tiller angle was practiced in each F2 population. As a result of selection, two types of true‐breeding phenotypic extremes were obtained, one with larger tiller angle and the other with smaller tiller angle. for loci contributing to variation in tiller angle, the alleles of similar effect were proved to be dispersed in the original parents and associated in the extreme selections. Crossing two extreme strains derived from different original crosses revealed new transgressive segregation in the F2, demonstrating that different loci controlled tiller angle in the two cross combinations examined in this study. When the extreme phenotypes were crossed with each other, strains with the largest tiller angle represented recombinants containing all increasing alleles from the four original parents. Four quantitative trait loci (QTLs) were inferred to be responsible for the transgressive segregation in the two original crosses. The intervarietal transgression could be explained by complementary action of additive genes that had been dispersed among the original parents. To test for allelism of the QTLs for large tiller angle and a previously identified major‐gene mutant, lazy (la), one of the extreme strains from the second cycle of selection having the largest tiller angle was crossed with the lazy growth mutant, H‐79. Results indicated that la was not allelic to any of the QTLs. Breeding experiments demonstrated that multiple crossing followed by one cycle of selection could be used to accumulate into one strain the genes that were dispersed in the parents.
Epistasis for Vegetative and Reproductive Traits in Peanut
Authors: Upadhyaya Hari D. , Nigam Shyam
Published: July 2010

Most genetic models assume absence of epistasis while estimating components of genetic variation. However, epistasis when present introduces bias. These biased estimates affect the progress in a breeding program since they influence the choice of breeding methodology. The objectives of this study were to determine the significance of epistasis in the inheritance of pod yield and related traits in 15 peanut (Arachis hypogaea L.) cultigens, and to estimate the additive and dominance variances for the traits not influenced by epistasis. Two cultigens and their F1 hybrid were each crossed to 15 cultigens from 13 countries, representing three botanical groups. The experiment was conducted in the 1992‐1993 post‐rainy and 1993 rainy environments at the ICRISAT Asia Center, Patancheru, India. The deviations were analyzed to detect epistasis of 11 traits. Epistasis affected the expression of eight traits in both environments. Environments interacted more strongly with epistatic gene actions than with additive or dominance gene actions. Expression of epistasis was influenced by genotypes and environments, indicating the need for more genotypes and environments for effective detection of epistasis. Evidence for additive genetic variance and lower levels of partial dominance for canopy breadth and additive and dominance variances and complete dominance for shelling outturn was obtained in the post‐rainy environment.
Identifying Resistance to Phytophthora sojae in Selected Soybean Accessions Using RFLP Techniques
Authors: Hegstad J. M. , Nickell C. D. , Vodkin L. O.
Published: July 2010

Phytophthora sojae (Kauffmann and Gerdemann) is the causal agent of phytophthora root and stem rot of soybean [Glycine max (L.) Merr.]. disease outbreak infavorable environmental conditions has the potential to inflict 100% yield loss. Soybean accessions fromcentral China offer unique genetic variability and are potential sources for novel genes conferring phytophthora resistance. Approximately 500 accessions have been classified for reaction to races 1, 3, and 7 of P. sojae. Eighteen accessions were selected that were resistant to races 1 and 3 and susceptible to race 7. RFLP markers linked to resistance alleles were used to compare the accessions to isolines with known Rps alleles. Restriction fragment length polymorphism (RFLP) results were supported with greenhouse hypocotyl inoculations with zoospores of races 1, 3, 5, 8, 12, 13, and 25. One plant introduction (PI) was found likely to possess Rps1a, five possibly possessed Rps2, seven could carry Rps3, and four were found possibly to possess Rps4. Evidence of multigene combinations were detected in eight accessions. Unique RFLP bands and hypocotyi inoculation reactions were discovered in PIs 567343, 567530, 567572A, 567574A, 567583A, 567764, and 567766, implying possible presence of novel Rps alleles. Knowledge of which Rps allele combinations are present in these accessions will allow for integration of the novel resistance into modern cultivars.
Growth and Final Weight of Central and Lateral Barley Grains under Mediterranean Conditions as Influenced by Sink Strength
Authors: Voltas J. , Romagosa I. , Araus J. L.
Published: July 2010

Grain weight largely determines the end‐use quality of barley (Hordeum vulgare L.). In six‐rowed types, central spikelets commonly bear heavier grains than lateral spikelets. However, the extent to which such differences in weight are influenced by source availability remains unclear. Field experiments were carried out in nine rainfed trials of northeastern Spain and showed large variability in grain weight. Three six‐rowed genotypes were used: Barberousse, Orria, and Plaisant. Sink strength of mainstems was decreased by half at anthesis by sterilizing 50% of fertile central and lateral florets. Variation among spikelets in grain growth parameters [maximum grain filling rate (GFR) and grain filling duration (GFD)] and in final grain weight was evaluated in control and sink‐reduced spikes. Central grains outweighed lateral ones in control spikes from 7.3 to 14.8 mg across trials. Absolute differences in weight increased progressively in those trials favoring larger grains, although lateral to central grain weight ratios (L/C) remained fairly constant, with an average value of 0.77. This advantage of central grains was mostly caused by higher GFR values. A 50%‐reduced sink increased grain weight of both central and lateral spikelets similarly and did not diminish the absolute differences in weight found in control spikes. This result suggests that central grains have a greater intrinsic potential weight. While grain yield was partially source limited in all environments, lateral grains exhibited on average a major degree of source limitation (24.2%) than central grains (19.1%). Sink reduction increased grain weight of both central and lateral grains by stimulating GFR in all trials, and also by lengthening GFD in poor rainfed environments.
Relationship between Carbon Isotope Discrimination, Water Use Efficiency, and Evapotranspiration in Kentucky Bluegrass
Authors: Ebdon J. S. , Petrovic A. M. , Dawson T. E.
Published: July 2010

Carbon isotope discrimination (Δ) is negatively correlated with water use efficiency (WUE) in several C3 grass species and was proposed as a selection criterion for improving WUE. Our objectives were to determine the relationship between Δ and WUE in cultivars of Kentucky bluegrass (Poa pratensis L., KBG) maintained as turf, and to determine the relationship between cultivar Δ and evapotranspiration (ET) rate measured under non‐limiting soil moisture conditions. We view Δ as a potential index of ET and an alternative to weighing lysimeters in selecting C3 turfgrass for reduced ET. WUE of 11 cultivars was evaluated in 25‐cm‐diam., fritted clay filled lysimeters, over two 4‐d harvest periods. Clipping dry weight accumulated above a 50‐inm base mowing height for each 4‐d period was used as the productivity component in calculating WUE. Gravimetric water loss determined by the water balanced method was used as the transpirational component. Cultivars differed significantly (P ≤ 0.05) in WUE, Δ, and ET, depending on the harvest period. Also, the reliability of Δ in predicting WUE and ET was dependent on the harvest period. During the first harvest period, Δ was inversely related with WUE (r = −0.55**, significant at P ≤ 0.01) and cultivar ET varied significantly with Δ (r = 0.64*, significant at P ≤ 0.05). During the second harvest period, no significant relationship (P > 0.05) developed between Δ and WUE (r = −0.21), or between Δ and cultivar ET (r = 0.32). Observations for the first and second harvest periods varied considerably in canopy temperature, with temperature ranging from 20.5 to 22.0 ± 1.3°C, and 27.3 to 36.0 ± 3.4°C, respectively. Theory predicts under the assumption of equal leaf temperature, Δ and WUE are correlated. It was likely that leaf temperature differences during the second harvest contributed significantly to the breakdown of the relationship between Δ and WUE. This assumption was likely met during the first harvest period only, therefore Δ and WUE (and ET) were related. Selecting for low Δ appears to have potential for identifying cool season turfgrass for reduced ET. However, further research is needed to determine the reliability of Δ in predicting ET under non‐limiting and water limiting conditions.
Changes in Polar Lipid Fatty Acid Composition during Cold Acclimation in ‘Midiron’ and ‘U3’ Bermudagrass
Authors: Samala Suresh , Yan Jiyu , Baird Wm. Vance
Published: July 2010

‘Midiron’ and ‘U3’ bermudagrass were exposed to conditions known to induce cold acclimation [e.g., 8/4°C (day/night) temperature, 10‐h photoperiod, 250 μmol m−2 s−1 photosynthetic photon flux density (PPFD)]. Tissues (leaves, crowns, and roots) were harvested stored frozen until processed. Polar membrane ids were isolated by thin layer chromatography, and fatty acids (FA) were separated and quantified by gas chromatography. Different organs from the same plant responded differentially to low temperature. Crowns showed the most dramatic changes in total FA content and composition and were the focus of this study. Overall, greater than 95% of the total FA content was accounted for by four FA species: palmitic acid (16:0), stearic acid (18:0), linoleic acid (18:2), and linolenic (18:3). Midiron (relatively cold‐tolerant) responded more rapidly to a greater extent than did U3 (relatively cold‐sensitive) as illustrated by the nearly four‐fold increase of unsaturated FA:saturated FA ratio for Midiron vs. U3, and by the significant difference between the double bond index of the two genotypes. These data suggest that specific desaturase enzymes (e.g., ω‐3 and ω‐6) are of fundamental importance in controlling membrane lipid/fatty acid composition in response to low temperature and ultimately in avoiding the winter damage suffered by bermudagrass along its northern boundary of adaptation.
Segregation at Microsatellite Loci in Haploid and Diploid Gametes of Musa
Authors: Crouch Hutokshi K. , Crouch Jonathan H. , Jarret Robert L. , Cregan Perry B. , Ortiz Rodomiro
Published: July 2010

The triploid genome of plantain (Musa spp., AA group) has been considered intractable to genetic improvement because of the production of putatively homogeneous 2n (= 3x) gametes. Plantain breeding schemes have been based on the hybridization of 2n megaspores from the triploid plantain and haploid microspores from a wild diploid banana. The resultant fuli‐sib populations of tetraploid hybrids exhibited extreme variation in phenotypic characteristics. This study was conducted to analyze the genetic constitution of tetraploid hybrids in order to characterize the nature of the gametes from which they were derived. Parental genotypes were screened with 31 primer pairs specific to different Musa microsatellite loci. Primers which detected polymorphisms between the parental genotypes were used to screen a population of 14 full‐sib tetraploid hybrids. A subset of primers was also used to screen a population generated by self‐pollination of the parental diploid banana. During analysis of the tetraploid hybrid population, 75% of the alleles donated by the maternal genotype (Obino l'Ewai) were observed to segregate. These data demonstrate the occurrence of recombination during the formation of 2n megaspores in triploid plantain. Analysis of the paternal diploid banana accession (Calcutta 4) and its selfed progeny suggests that this accession is highly heterozygous. These data demonstrate the importance of genetic characterization to Musa breeding, and also indicate that microsatellite markers are well suited for marker‐assisted selection systems in Musa.
Transformation of Oat Using Mature Embryo‐Derived Tissue Cultures
Authors: Torbert K. A. , Rines H. W. , Somers D. A.
Published: July 2010

Mature embryos of oat (Avena sativa L.) have been used to establish regenerable tissue cultures with potential use for transformation. The objective of this study was to investigate tissue cultures established from mature embryos of oat as an alternative source of totipotent target cells for microprojectile bombardment‐mediated transformation. Mature embryos of a specific genotype, GAF/Park‐1, were incubated on a tissue culture induction medium for 1, 4, 8, or 9 wk before either being directly bombarded after 1 and 4 wk, or bombarded as tissue cultures initiated after 8 and 9 wk incubation. The 8‐ and 9‐ wk‐old tissue cultures yielded the greatest numbers of transgenic tissue cultures (3.2 transgenic tissue cultures per microprojectile bombardment treatment). Three additional transformation experiments were conducted with mature embryo‐derived 8‐ to 9‐wk‐old tissue cultures to determine the regeneration capacity and production of fertile transgenic plants. Overall, fertile plants were regenerated from 35 of 85 independently derived transgenic tissue cultures. Identification of mature embryo‐derived tissue cultures as a source of transformable totipotent cells should reduce the expense and labor involved in oat transformation. Moreover, the uniformity and convenience of this explant likely will stimulate further investigations in oat transformation efficiency.
Embryogenic Competence of Immature Wheat Embryos: Genotype, Donor Plant Environment, and Endogenous Hormone Levels
Authors: Hess J. Richard , Carman John G.
Published: July 2010

The genotype and the environment in which donor plants grow influence embryogenic competence of immature wheat (Tritium Estevan L.) embryos and levels of endogenous hormones in kernels. We studied relationships between embryonic competence and hormone levels in kernels and Calli of PC YT 10 (highly competent) and Yaqui 50 (nearly incompetent) wheat grown at 15 and 25°C. Endogenous levels of abscissa acid (ABA), in dole‐3‐acetic acid (AA), and stockings were determined for kernels at 0, 4, 8, and 12 d past an thesis (DOPA). Immature embryos were cultured at 12 DOPA and hormone content of Calli was determined at 7, 14, 21, and 28 d past culture initiation (DP|). Somatic embryos were counted at 28 DIP. Embryonic competence was associated with low AA and ABA levels in kernels from 0 to 12 DOPA, high seating to AA ratios in kernels at 4 DOPA, and high stoking to auxin ratios in Calli. Incompetence in Yaqui 50 may be due to low stoking to auxin ratios in kernels at 4 DOPA and sharp increases in kernel AA and/or ABA levels prior to embryo excision (12 DOPA). Low temperatures during donor plant growth delayed the rise in AA and ABA in Yaqui 50 kernels and significantly increased the embryogenic response from both Yaqui 50 and PCYT 10 embryos. It may be possible to increase competence of nearly nonembryogenic wheat lines by growing donor plants in cool conditions, which appear to delay the accumulation of IAA and ABA in kernels.
Smut Resistance and Grain Yield of Pearl Millet Hybrids Near Isogenic at the Tr Locus
Authors: Wilson J. P. , Hanna W. W.
Published: July 2010

Trichomeless pearl millet [Pennisetum glaucum (L.) R. Br.], homozygous for the tr allele, expresses resistance to smut caused by Moesziomyces penicillariae (Bref.) Vanky. These studies examined the hypotheses that smut resistance is the result of the tr allele rather than a closely linked gene, and that the tr allele has no effect on grain yield in the absence of smut. Trichomed inbreds Tilt 90DBE and Tift 8677 and trichomeless derivatives were crossed to produce eight hybrids differing for female parent and genotype at the tr locus. Hybrids were assessed for smut resistance and grain yield. Smut severity of inoculated panicles was reduced by about 13% when a Tift 90DBE genotype was used as the female parent, compared with hybrids produced with a Tift 8677 genotype as the female parent. Smut severity was reduced by about 50% in the trichomeless phenotype compared with the trichomed phenotypes. Homozygous and heterozygous trichomed hybrids did not differ in smut severity. The recessive smut resistance is most likely a pleiotropic effect of the tr allele and not the result of another closely linked gene. Although trichomelessness can be used as a marker to select for smut resistance, both parental inbreds must be trichomeless to produce smut‐resistant hybrids. Trichomeless hybrids tended to yield more than trichomed hybrids, but yield was primarily reduced in heterozygous trichomed hybrids compared to the homozygous TrTr genotype. From these results, we conclude that the tr allele can be incorporated into smut‐resistant hybrids with no detrimental effect on grain yield.
Inheritance of Tolerance to Chilling Stress in Rice during Germination and Plumule Greening
Authors: Sthapit B. R. , Witcombe J. R.
Published: July 2010

Rice cultivars (Oryza sativa L.) that are adapted to high altitude areas of the sub‐tropics, such as Nepal, have to germinate and rapidly synthesize chlorophyll in the emerging plumule at chilling temperatures. This study was conducted to determine, at the chilling temperature of 17°C, the heritabilities of four traits: germination, the rate of germination (RG) index, plumule greening, and plumule vigor. Estimates were made in the F3 generation of two crosses between two Nepalese chilling‐tolerant cultivars and a chilling‐susceptible Nepalese cultivar. Most traits were significantly heritable. Heritability estimates ranged from 0.7 to 0.9 for germination and the rate of germination, and was 0.7 for plumule vigor and for plumule greening at chilling temperature. Four methods of estimating germination rate were examined. Of these, an index that took into account final percentage germination, unlike the index usually used for rate of germination at optimal temperatures, gave the highest heritability. Predicted genetic advances due to selection were highest for germination rate and greening ability. All of the traits were significantly correlated (P ≤ 0.05) with early seedling vigor in the field. We conclude that it would be useful in a breeding program for improved chilling tolerance to screen for germination rate with an index and to select for plumule greening ability because these traits are highly heritable, easily measured, and correlate well with field performance at high altitudes.
Gamete Selection for Upright Carioca Bean with Resistance to Five Diseases and a Leafhopper
Authors: Singh Shree P. , Cardona César , Morales Francisco J. , Pastor‐Corrales Marcial A. , Voysest Oswaldo
Published: July 2010

Growing cultivars that possess multiple disease‐and‐pest resistance minimizes crop losses, reduces the need for pesticides, and lowers production costs. Our objective was to use gamete selection (i.e., selection based on F1‐derived families that come from crosses that are multiple‐parent, heterogeneous, and heterogametic) to develop upright carioca‐type beans (Phaseolus vulgaris L.) with resistance to angular leaf spot (ALS), anthracnose (ANT), bean common mosaic (BCM), bean golden mosaic (BGM), common bacterial blight (CBB), and leafhopper (LHP). Two multiple‐parent, interracial crosses (BZ 9780 and GX 9792) were made, using plant‐to‐plant pollinations, in 1990‐1991. The F1‐derived F2 (F1.2) families were evaluated for ALS and CBB, and F1.3 families for ANT and LHP. In F4, carioca‐type seeds from promising families were saved. The F1.4 families were then evaluated for BGM. All 127 F1.2 families from BZ 9780 were discarded by F4 because none segregated for six resistances and possessed carioca‐type seeds. Of the GX 9792 population, 260 F5‐derived F9 (F5.9) lines, originating from only 12 of 460 F1.2 families, were evaluated for ALS, ANT, BCM, BGM, CBB, and LHP. Six parents, eight checks, and 86 F5.9 lines resistant to at least ANT, BCM, and CBB were tested for yield in seven environments in 1995–1996, using a partially balanced lattice design with three replicates. Only eight lines, originating from four of the 460 F1.2 families, possessed resistance to all five diseases and LHP. Of these lines, one outyielded the check cultivar Carioca, and that line with one other outyielded the two carioca‐type parents (A 769 and EMP 250) used in the GX 9792 populations. Thus, the use of gamete selection and early generation testing was effective in developing high‐ yielding upright lines with resistance to multiple biotic stresses.
Brachytic Stem Trait, Row Spacing, and Plant Population Effects on Soybean Yield
Authors: Adams Pamela D. , Weaver David B.
Published: July 2010

Brachytic stem (sb1sb1sb2sb2) of soybean [Glycine max (L.) Merr.] is characterized by shortened internodes, resulting in shorter, sturdier plants than normal stem types. Although studies have shown yield of brachytics to be less than normal types, this trait may have potential for higher yield in some environments. Little information is available on response of brachytics to planting pattern, particularly for duration of development stages or yield components. A field study was conducted to determine brachytic trait effects on yield, agronomic traits and yield components of four near‐isoline pairs, each consisting of one normal and one brachytic near‐isoline tested at plant populations of 51 and 26 plants m−2 and row spacings of 76 and 28 cm in four environments. Soil types were a Cahaba fine sandy loam (fine‐loamy, siliceous, thermic Typic Hapludults) and a Norfolk fine sandy loam (fine‐loamy, siliceous, thermic Typic Kandiudults). Normal types yielded more and responded to narrow rows; brachytics did not. Row spacing and plant population did not affect most other traits. Brachytics flowered later and had shorter reproductive period than normal types. Brachytic soybean produced more branch and mainstem nodes and greater seed mass and harvest index than normal types, but this was not enough to effect yield advantages over normal soybean. We concluded that plant growth and yield performance of the brachytic trait is influenced more by genetic background than other factors; however, under suitable conditions, brachytic soybean's production of larger seeds and more nodes indicates its potential for higher yields.
Tillage Management for Doublecropped Soybean Grown in Narrow and Wide Row Width Culture
Authors: Frederick James R. , Bauer Philip J. , Busscher Warren J. , McCutcheon Gloria S.
Published: July 2010

Leaving residues on the soil surface and deep tillage may reduce the severity of yield‐reducing, plant water stress on the southeastern Coastal Plain. For narrow (<75 cm) row width culture, little is known about the seed‐yield response of doublecropped soybean [Glycine max (L.) Merr.] to surface tillage or deep tillage. We conducted a 2‐yr field study on a Goldsboro sandy loam soil to (i) determine the seed‐yield response of doublecropped soybean to surface tillage and deep tillage when grown using 19‐ and 76‐cm‐row widths and (ii) determine the effects of surface tillage and deep tillage on branch and mainstem yield components. Doublecropped soybean was grown following winter wheat (Triticum aestivum L.) harvest using all combinations of surface tillage (disked or no surface tillage), spring deep tillage (deep tilled or no deep tillage before soybean planting), row width culture (production practices for row widths of 19 or 76 cm), and fall deep tillage (no deep tillage or deep tilled before wheat planting) treatments. Averaged across years and all other treatments, the soybean grown with the 19‐cm‐row width had a 53 and 83% greater seed yield than the soybean grown with the 76‐cm‐row width in the disked and no‐surface‐tillage plots, respectively. When deep tilled, soybean yields were consistently higher with no surface tillage, compared with disking, only when the 19‐cm‐row width was used. Seed‐yield increases due to deep tillage were greatest when plots were deep tilled before planting both crops and when no surface tillage and the narrow row width culture were used. Across all treatments and years, seed yield was highly correlated with seed number per square meter (r = 0.93), but less so with individual seed weight (r = 0.52). Results indicate that seed‐yield increases due to deep tillage and no surface tillage are greater when doublecropped soybean is planted using production practices established for narrow row width culture.
Late‐Planted Soybean Yield Response to Reproductive Source/Sink Stress
Authors: Board J. E. , Harville B. G.
Published: July 2010

Research approaches for increasing soybean [Glycine max (L.) Merr.] yield at late planting dates would be better focused if knowledge of source/sink restrictions for yield during the growing season were better understood. Although soybean yield is known to have greater source restriction during the reproductive vs. vegetative period, little is known about differences in source restriction during the early (R1 to shortly after R5) compared with late (effective filling period) reproductive periods, or about potential sink restriction during the late reproductive period. Using crop growth rate as an indicator of source strength and seed number as an indicator of sink strength, our objectives were to: (i) Determine if yield of late‐planted determinate soybean had the same degree of source restriction during the early and late reproductive periods; and (ii) Determine the potential for sink restriction of yield during the late reproductive period under field conditions. Field studies in a randomized complete block with four replications were conducted during 1993 and 1994 with ‘Centennial’ soybean (Maturity Group VI) at Baton Rouge, LA, on a Commerce silt loam soil. Crop growth rate and source/sink ratio (crop growth rate/seed number) were altered by partial defoliation and pod removal treatments. Reduced crop growth rate during the early reproductive period had 147% (in 1993) and 63% (in 1994) greater effect on yield compared with depressed crop growth rate during the late reproductive period, indicating source restriction was greater during the early vs. late reproductive period. In conclusion, soybean yield is most affected by stresses which reduce crop growth rate, when those stresses occur during the early reproductive period.
White Clover Response to a Water‐Application Gradient
Authors: Brink G. E. , Pederson G. A.
Published: July 2010

Periods of drought, common during the summer and fall in the southeastern USA, can be detrimental to growth of the shallowrooted, temperate forage legume, white clover (Trifolium repens L.). Our objective was to determine the growth response (lateral spread, morphology) of white clover to a water‐application gradient during the summer and fall on a Marietta fine sandy loam (fine‐loamy, siliceous, thermic Fluvaquentic Eutrochrept). From May to October, a linesource irrigation system produced regimes of high, medium, low, and zero water‐application across parallel 1.0‐m rows of three cultivars and three germplasms transplanted (10 plants row−1) into a common bermudagrass (Cynodon dactylon (L.) Pers, var. dactylon) sod the previous fall. Plots were continuously‐stocked (5‐cm stubble) with cattle (Bos taurus L.). Each month, differences in lateral plant spread among entries were similar regardless of water‐application regime. Within each regime, spread declined sharply after June and remained near a minimum (<0.20 m2 row−1) from August until October. Yield and morphology differences among entries in July were similar in each of the water‐application regimes as well. By October, however, there were differences in herbage yield, stolon length, and number of stolon apices among entries at the high water‐application regime, but not at the medium, low, and zero regimes. The results suggest that either there is no difference in drought tolerance among these cultivars and germplasms, or that white clover drought tolerance does not impact growth in the presence of stresses such as grazing and associated grasses.
Genetic Analysis of Resistance to Soybean Mosaic Virus in Four Soybean Cultivars from China
Authors: Wang Y , Nelson R. L. , Hu Y.
Published: July 2010

Soybean mosaic virus (SMV) is one of the most common soybean viruses and can cause economic losses. The objective of this research was to determine the inheritance of resistance to SMV‐G1 1n four soybean [Glycine max (L.) Merr.] cultivars from China. Each cultivar was crossed to the susceptible cultivar Williams and to lines with known sources of resistance genes to test for allelism. The crosses were evaluated in the F2 and F3 generations in the field and in the greenhouse for reaction to inoculation with SMV‐G1. Results showed that each of the Chinese cultivars has a single dominant gene for resistance to SMV‐G1. The resistance gene carried by ‘Feng shou huang’ (PI 458507) is at the Rsv1 locus. The resistance gene in ‘Ke feng No. 1’ (PI 556949) is at the non‐Rsv1 locus in PI 486355. The resistance gene carried by ‘Da bai ma’ (PI 556948) is not at the Rsv1 locus. The resistance gene in ‘Xu dou No. 1’ (PI 556950) is at neither the Rsv1 locus nor the non‐Rsv1 locus in PI 486355.
Inheritance of Common Bunt Resistance in Androgenetically Derived Doubled Haploid and Random Inbred Populations of Wheat
Authors: Knox R. E. , Fernandez M. R. , Brûlé A. L. , DePauw R. M.
Published: July 2010

Random inbred lines, derived from random head‐to‐rows, and doubled haploids, derived androgenetically, represent two types of progeny populations valuable in genetic studies. This study was undertaken to estimate inheritance in wheat (Triticum aestivum L.) of resistance to common bunt [Tilletia tritici (Bjerk.) Wint. in Rabenh.; syn. Tilletia caries (DC.) Tul. & C. Tul.] in random inbred and doubled haploid populations with common parentage. The bunt susceptible experimental line HY377 was crossed with the bunt resistant lines SC8021V2 and L8474D1. The populations formed were DH‐HY377/ 8021 and DH‐HY377/8474 (androgenetically derived doubled haploid) and R‐HY377/8021 and R‐HY377/8474 (random inbred). Trials grown both in the growth chamber and the field were inoculated with common bunt of wheat race T19. The F1 plants from both crosses expressed resistance intermediate between the parents indicating incomplete dominance of gene expression. Resistance segregating from progenies of the cross L8474D1 by HY377 fit a one and not a two gene expected ratio in both the DH‐HY377/8474 and R‐HY377/8474 populations. The results indicate the segregation of a single major gene for resistance in L8474D1. Segregation of resistance from SC8021V2 in the R‐HY377/8021 population fit the expected ratio for one and not two major genes. Comparison of variances of the resistant progeny class and resistant parent indicate at least one minor gene segregating in addition to the one major gene. The size of the DH‐HY377/8021 population was too small to make conclusions about gene segregation. Where population size was not limiting, conclusions regarding modes of inheritance were similar from both doubled haploid and random inbred line populations. Lines tested in the growth chamber could be classified for resistance more readily than lines tested in the field.
Path Analyses of Yield and Yield‐Related Traits of Fifteen Diverse Rice Genotypes
Authors: PB. Samonte S. O. , Wilson L. T. , McClung A. M.
Published: July 2010

Literature on the path analyses of grain yield and at least 14 yield related traits in a path diagram that is organized with at least second order variables has been lacking. The objectives of this study were to obtain and interpret information on the nature of interrelationships between first‐, second‐, and third‐order yield‐related traits and rice (Oryza sativa L.) grain yield. Fifteen rice genotypes were used in this study to represent the combinations of low and high levels of four traits that were identified as important yield determinants — maximum number of tillers, grain size, panicle node number, and panicle size. ‘Lemont’ and ‘Teqing’ were two of these genotypes. The remaining genotypes were F9 lines from a Lemont × Teqing cross. Field experiments were conducted during the 1994 and 1995 cropping seasons at the Texas A&M University Agricultural Research and Extension Center near Beaumont, TX. The 1994 path coefficient (p) of panicle weight on grain yield (p = 0.72; r2 = 0.93) was used to predict the 1995 grain yield (r2 = 0.90). Based on a path analysis of the combined 1994 and 1995 data, the following traits had positive path coefficients on grain yield: panicle weight (p = 0.84), number of filled grains per panicle (p = 0.67), panicle density (p = 0.52), maximum filler density (p = 0.34), number of spikelets per panicle (p = 0.34), and 100‐grain weight (p = 0.23). The panicle node number has a negative path coefficient on grain yield (p = −0.23). These results may be useful to rice breeders for the indirect selection of grain yield during the early segregating generations when yield tests are not yet being conducted.
Grain Yield Increase in Recent Argentine Wheat Cultivars
Authors: Abbate P. E. , Andrade F. H. , Lázaro L. , Bariffi J. H. , Berardocco H. G. , Inza V. H. , Marturano F.
Published: July 2010

This study analyzes differences in potential yield among six semidwarf awned spring bread wheat (Trilicum aestivum L.) cultivars recently selected in Argentina. Yield was considered as the product of number of grain per square meter (NG) and weight per grain. The NG was analyzed in terms of (i) duration of the inflorescence growth period (excluding grains), (ii) crop growth rate during that period, (iii) partitioning of crop dry matter to spikes during the same period, and (iv) grain/spike weight ratio (i.e., number of grains per gram of spike). The data were obtained from two field experiments in the Province of Buenos Aires. Grain yield (range: 453–689 g m−2) was related more to NG (range: 13.3–21.3 ✕ 103 grain m−2) than to weight per grain. Duration of spike growth period was the same (27 d) for all cultivars. During this period, intercepted photosynthetically active radiation, radiation‐use efficiency (mean: 2.7 ± 0.28 g MJ−1), and crop growth rate (mean: 26 ± 2.5 g m−2 d−1) were similar for all the cultivars examined. Differences among cultivars in partitioning to spikes (ranges: 28–34%) were significant. The NG, however, was not related to partitioning to the spike. There were clear differences among cultivars in the grain/spike weight ratio (range: 61–106 grain g−1); NG was more closely related to this ratio (r = 0.96, P < 0.01) than to dry weight of spikes at the end of their growth period (r = −0.30). Increments in potential yield by means of high grain/spike weight ratio were not previously reported and may be a path to future potential yield improvements.
Date of Planting Effects on Seeded Turf‐Type Buffalograss
Authors: Frank Kevin W. , Gaussoin Roch E. , Riordan Terrance P. , Miltner Eric D.
Published: July 2010

Establishing seeded buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is often difficult because improper timing can result in weed interference or stand failure. Research was conducted to determine optimal buffalograss seeding dates and growing degree day (GDD) requirements for ‘Cody’ and ‘Texoka’ buffalograss establishment. Both cultivars were seeded monthly at 10 g burs m−2 from April through October in 1995 at the John Seaton Anderson Turfgrass Research Facility near Mead, NE, and at the Greenville Research Farm at Logan, UT. The soil types at the Nebraska and Utah sites were Sharpsburg silty clay loam (fine, montmorillonitic, messic Typic Argiudoll) and Millville silt loam (coarse‐silty, carbonatic, mesic Typic Rendoll), respectively. The percentages of buffalograss and weed cover were rated visually on a 0 to 100% scale. Buffalograss density was determined by tossing either a 0.1‐ or 0.2‐m2 quadrat into the plot and counting the number of plants in the quadrat. The experimental design was a randomized incomplete block design with three replications. Location, buffalograss cultivar, and planting date were treatment factors. The optimal seeding time for buffalograss at the Nebraska site was late April through June and at the Utah site, late April through July. August, September, and October planting dates at both sites did not result in successful stands. The negative relationship between the percentage of weed cover and the percentage of buffa‐Iograss cover implicated weed interference as a factor limiting establishment. Our results indicate that to ensure survival and establishment of buffalograss in regions where soils freeze during the winter, at least 1000 postplanting GDD are required before cessation of growth in the fall.
Seasonal Variation in Morphology of Continuously Stocked White Clover
Authors: Brink G. E. , Fairbrother T. E. , Rowe D. E.
Published: July 2010

Efforts to improve persistence of white clover (Trifolium repens L.) in the southeast USA would benefit from knowledge of annual growth patterns and associated periods of environmental stress. Our objective was to determine seasonal changes in morphological traits that contribute to plant growth and persistence among adapted cultivars and germplasm. ‘Louisiana S‐l’, ‘Osceola’, Brown Loam Synthetic No. 2 germplasm, and Southern Regional Virus Resistant germplasm were sown in common bermudagrass [Cynodon dactylon (L.) Pers.] pastures in September 1993 at Mississippi State and Newton, MS, and continuously stocked with cattle to maintain a 5‐ to 10‐cm sward height. Stolon length, viability of axillary buds, and seedling numbers were measured monthly for the next 2 to 3 yr. Stolon length of all entries increased to a maximum by June before declining to a minimum in October. Peak stolon production in the first, second, and third year after seeding at Mississippi State was 42, 123, and 59 m m−2, respectively. There were no monthly differences among the four entries for proportion of stolon nodes having elongated, viable, or nonviable axillary buds at either location. The proportion of nodes with elongated buds increased from 10 to 20% in October to 45% in March before declining during the spring. An increase in elongated buds during early summer preceded the fall decline. Number of volunteer seedlings ranged from 10 to 1870 m−2 during the year, but any positive influence on stand persistence was not apparent. The cyclical trends for axillary bud viability indicate continued potential for vegetative persistence, particularly in the winter and spring, but the longterm decline in stolon length of all entries suggests that selection for different characters was not associated with improved persistence.
β‐l,3‐Glucanase and Resistance to Aspergillus flavus Infection in Maize
Authors: Lozovaya Vera V. , Waranyuwat Aree , Widholm Jack M.
Published: July 2010

Studies of the activity levels of the fungal cell wall degradative enzyme, β‐l,3‐glucanase, were carried out with Zea mays L. embryogenie callus cultures and kernels of genotypes with different abilities to resist aflatoxin formation on the ears. Dual‐culture experiments of the aflatoxin forming fungus, Aspergillus flavus Link: Fr. with maize callus, demonstrated that the growth of A. flavus on plates was inhibited more by callus of a resistant genotype (Tex 6 ✕ Mol7 denoted T✕M) than by a sensitive genotype (Pa91). The inhibition correlated with the activity levels of β‐1,3‐glucanase in the callus and in the culture medium. The presence of the fungus caused an increase in enzyme activity in T✕M but not in Pa91 callus. Direct treatment of callus of both genotypes with A. flavus spores caused the amount of callose to increase within 30 min. An elevated β‐l,3‐glucanase activity in maize kernels was also correlated with lower A. flavus infection observed in the resistant genotype (Tex 6) compared with a susceptible one (B73). Fungal inoculation of the ears increased the enzyme activities both in kernels in contact with and not in contact with the fungus. These studies indicate that β‐l,3‐glucanase activity may have a role in the inhibition of growth of the A. flavus fungus, that maize embryogenic callus and kernels do respond to the presence of this nonpathogenic fungus, and that these systems might be useful in further plant‐fungal interaction studies.
Population Improvement in Alfalfa: Fertility and S1 Forage Yield Performance in Original and Improved Populations
Authors: Kimbeng C. A. , Bingham E. T.
Published: July 2010

Inbreeding in alfalfa (Medicago sativa L.) may reduce heterozygosity and permit population improvement through selection of favorable alleles and elimination of deleterious ones. Two‐allele autotetraploid populations (TAPs) are suitable for studying the effectiveness of selection because they are derived from chromosome doubling of heterozygous diploid plants and therefore have a maximum of two alleles and a single allelic interaction per locus. The effectiveness of inbreeding and selection was tested by comparing TAPs that had undergone inbreeding and selection with their original counterparts. The original (designated OGDC) and improved (designated AGDC) populations were produced by intercrossing two single‐cross lines from the original and improved TAPs, respectively. Self fertility, female cross fertility, and S1 forage yield performance were compared in original and improved populations. Self fertility increased by 57% in the AGDC compared with the OGDC, whereas female cross fertility was reduced by 12% in this population. A higher proportion of plants in the AGDC population produced sufficient $1 seeds (82%) for field evaluation than did plants in the OGDC population (57%). The mean forage yield of the AGDC S1 families was significantly higher (13.3%) than their comparative OGDC S1 families. Improvement in self fertility and S1 forage yield by inbreeding and selection was consistent with population improvement due to elimination of deleterious alleles and a corresponding increase in the frequency of favorable ones. However, the concurrent decrease in female cross fertility was inconsistent with this hypothesis. Therefore, selection for cross fertility may be necessary during inbreeding in alfalfa.