bluuebunny/crossref_metadata_2025 huggingface dataset:
Modified Early Generation Testing Procedure for Yield Selection in Soybean
Authors: Cooper Richard L.
Published: July 2010

An early generation testing program to identify crosses with superior yield potential and F2 plants within these crosses which receive a superior complement of yield genes would be useful in soybean [Glycine max (L.) Merr.] breeding. Early generation testing is effective in identifying superior yielding pure lines, but requires extra yield testing. This paper describes a modified early generation testing procedure where the number of yield test plots required per cross has been reduced from 1860 to 175 plots, allowing a 10‐fold increase in the number of crosses that are evaluated per year. This was accomplished by reducing the number of F2‐derived lines per cross from 300 to 30 and by using single location, single replication data as a basis for selection in F2.3 through F2.4.6. This modified early generation testing procedure has been used in a soybean breeding program since 1972, resulting in the release of eight high‐yielding soybean cultivars.
Selecting Oat Lines for Yield in Low‐Productivity Environments
Authors: Atlin G. N. , Frey K. J.
Published: July 2010

Cultivars for use in low‐productivity environments (LPE) can be selected directly, in LPE, or indirectly, in medium‐ or high‐productivity environments (MPE or HPE, respectively). These contrasting strategies were compared by means of predictions and an empirical selection experiment in which random populations of oat (Avena sativa L.) lines were selected for grain yield in LPE, MPE, or HPE; selected lines were then evaluated at each productivity level. The influence of replication (across environments) of the selection unit on the relative effectiveness of direct and indirect selection for yield in LPE was also examined. At low levels of replication, the greatest predicted and realized response in LPE resulted from selection in MPE. However, when replication was increased, direct selection resulted in the greatest predicted and realized yield gains in LPE. A positive correlation between degree of replication and the relative effectiveness of direct selection in LPE is expected when: (i) heritability (h2) is greater in HPE than in LPE and (ii) when the genetic correlation (rg) between yield in HPE and in LPE is less than one. These conditions were shown to exist in the present case, and may occur often in plant breeding programs. The results indicate that separate breeding programs may result in the greatest yield gains for some low‐productivity cropping systems. Estimates of h2 in HPE and LPE, and rg between yields in HPE and LPE, can be used to predict such situations.
Pollen Load, Seed Position, and Agronomic Performance in Alfalfa
Authors: Smith S. E. , Conta D. M. , Bechert U.
Published: July 2010

Competition among male gametophytes for a limited number of ovules has been related to improved performance in some sporophytic traits. However, gametophytic competition has not been widely exploited in plant breeding. In alfalfa (Medicago sativa L.), we examined two factors associated with gametophytic competition in other species: (i) amount of pollen on the stigma (pollen load), and (ii) seed position in the pod (a measure of stigma‐ovule distance). Relationships were evaluated between these two factors and survival and forage yield of transplanted seedlings for 10 harvests at Tucson, AZ. Emergence and weight of seedlings were determined in a greenhouse test. Progenies derived from both one and two generations of hand pollination with heavy or light pollen loads were compared. Alcohol emasculation procedures were used to reduce pollen loads since this process reduces pollen adhesion to the stigma in alfalfa. This followed vacuum emasculation treatment to remove maternal anthers that could obstruct pollen application to the stigma. Normal hand‐pollination procedures with vacuum emasculation to remove maternal anthers were used to produce heavy pollen loads. Heavy pollen loads resulted in more than 27 times more pollen tubes per ovary than light pollen loads. Analysis of seed set and the number of pollen tubes per ovary indicated that the potential for differential gametophyte competition existed in the two types of pollination. No differences were observed between progeny from heavy and light pollen loads for any of the traits evaluated. Seed position in the pod was also not related to forage yield or survival. Our data suggest that increasing pollen loads or selecting seeds from the pedicellar end of pods may have little impact in alfalfa breeding.
Gene Transfer in Apomictic Buffelgrass through Fertilization of an Unreduced Egg
Authors: Bashaw E. C. , Hignight K. W.
Published: July 2010

Opportunities for gene manipulation are often limited in apomictic species, and conventional breeding methods may be totally ineffective. Lack of good sexual germplasm led us to investigate improvement of apomictic buffelgrass (Cenchrus ciliaris L.) through fertilization of an unreduced egg (2n+n), using an apomict as the female parent. The primary objective of this research was to determine the potential for gene transfer in buffelgrass through 2n+n hybridization. When an apomictic pentaploid accession with an alien genome (2n=5x=45) was crossed with tetraploid apomictic birdwoodgrass (C. setigerus Vahl, 2n=4x=36), 1.3% of 950 progeny resulted from the fertilization of an unreduced egg (BIII hybrids) and had 2n = 7x=63 chromosomes. Origin of these hybrids from the union of 2n and n gametes was confirmed by the presence of the alien genome from the female parent and diagnostic morphological characteristics of the male parent. Hybrids were all obligate apomicts and most were relatively high in seed set compared to the parents. The results demonstrated an effective method for gene transfer in some apomictic species. Complete emasculation was considered essential for maximum hybridization.
Seed Yield Characteristics of Alfalfa Populations Selected for Receptacle Diameter and Nectar Volume
Authors: Teuber L. R. , Rincker C. M. , Barnes D. K.
Published: July 2010

Honey bees (Apis mellifera L.) and alfalfa leafcutting bees (Megachile rotundata F.) collect nectar when pollinating alfalfa (Medicago sativa L.). The objectives of this study were to: (i) determine the expression of receptacle diameter (RD) and nectar volume (NE) in the field for subpopulations selected in the greenhouse, and (ii) determine if differences in either RD or NE were associated with seed yield. Bidirectional selection was practiced for RD and for NE in three cultivars. Cycle‐2 subpopulations from each source were evaluated at Five Points, CA, and at Prosser, WA for RD, NE, number of seeds/pod, 100 seed weight, number of pods/raceme, and seed yield. Large and small RD subpopulations differed (P ≤ 0.05) at both Five Points (score = 1.9 and 1.1, respectively) and Prosser (score = 3.1 and 1.3, respectively). Small RD subpopulations produced higher seed yields than large RD subpopulations. CUF 101 subpopulations selected for high and low NE differed in NE at both Five Points (15.7 vs. 6.0 μL/100 florets, P ≤ 0.05) and Prosser (62.1 vs. 44.8 μL/100 florets, P ≤ 0.10). Team and Vernal subpopulations selected for high and low NE differed (P ≤ 0.05) for the trait only at Prosser (70.1 vs. 39.8 and 68.7 vs. 32.9 μL/100 florets, respectively). The high NE subpopulation derived from CUF 101 produced more seed (P ≤ 0.05) than the corresponding low NE subpopulation (653 vs. 472 kg/ha, respectively). Greenhouse selection for RD and NE altered these traits under field conditions. Increased NE in alfalfa has the potential for increasing seed production.
Effects of ‘Cheyenne’ Chromosomes on Milling and Baking Quality in ‘Chinese Spring’ Wheat in Relation to Glutenin and Gliadin Storage Proteins
Authors: Mansur Levi M. , Qualset Calvin O. , Kasarda Donald D. , Morris Rosalind
Published: July 2010

The ‘Cheyenne’ (Cnn) chromosome substitution lines (SL) in ‘Chinese Spring’ (CS) wheat (Triticum aestivum L.) were used to determine the effect of individual Cnn chromosomes on various chemical and physical grain‐quality characteristics. All SLs except SL2B, which was not available, were assayed electrophoretically for high‐molecular‐weight glutenin (HMW‐glu) and gliadin seed storage proteins. Sixteen SLs had electrophoretic patterns as expected based on the proteins present in the parental cultivars. Three contained the designated substituted Cnn chromosome and an additional recombinant Cnn/CS chromosome as indicated in parentheses: SL4B (6B rec.), SL4D (1B rec.), and SL6A (ID rec.). The SL7A was a mixture of plants having several HMW‐glu and gliadin variants. The Cnn, CS, and SLs were evaluated for milling and breadbaking in one field experiment in 1986 and two in 1987. Improved milling quality was associated with Cnn chromosomes ID, 2A, 2D, 3B, 4A, 5D, and 7B, while 3D and 6B reduced milling quality. Good breadbaking properties were associated with Cnn HMW‐glu alleles of Group 1 chromosomes as previously shown by others. The SL4D (1B rec.) showed improved bread loaf volume to the same extent as SL1B. It had the Cnn Glu‐Blc HMW‐glu allele located on the long arm of 1B; however SL4D (1B rec.) was dissimilar to SL1B for bake water absorption, flour protein, and SDS sedimentation, implying that genes affecting these traits are on the opposite arm of Cnn 1B. Loaf volume was improved significantly by Cnn chromosomes 3A, 3B, and 7B, showing that not only Group 1 chromosomes have genes that contribute to good baking quality. The Cnn Group 6 chromosomes, with gliadin loci, had no beneficial or negative effects on quality, but showed a tendency for reduced flour protein content. Nonadditivity of Cnn chromosome effects on quality was detected, which may have a bearing on the difficulty of recovering Cnn‐equivalent quality in breeding programs.
Optimization of Surface Sterilization for Legume Seed
Authors: Caetano‐Anollés G. , Favelukes G. , Bauer W. D.
Published: July 2010

Roots of alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), and soybean [Glycine max (L.) Merr.j seedlings are frequently contaminated with bacteria even after surface sterilization of the seeds and germination under aseptic conditions. Several seedsterilization procedures were compared for their ability to minimize or eliminate such contamination without damaging the plant. Mercuric chloride proved the best seed disinfectant for alfalfa and white clover. Calcium hypochlorite was the best for soybean. For alfalfa seeds, treatment with 95% ethanol (v/v) for 60 min followed by 0.2% HgCl2 (v/v) for IS min prior to rinsing and imbibition resulted in a low frequency (<5%) of seed and root contamination. This treatment resulted in no measurable damage to alfalfa seedlings with respect to root growth, nodulation efficiency, or rate of nodule emergence following inoculation with Rhizobium meliloti. Longer exposures to HgCl2 further reduced bacterial contamination, but also caused modest reductions in seed germination. None of the surface‐sterilization techniques tested completely eliminated bacterial contaminants. It appears that these sterilization‐resistant contaminants are borne within the seed and proliferate on plant surfaces after germination, with possible effects on plant health.
Laboratory Vigor Tests Used to Predict Pepper Seedling Field Emergence Performance
Authors: Trawatha Susan E. , Steiner Jeffrey J. , Bradford Kent J.
Published: July 2010

Few investigations have sought to determine the usefulness and repeatability of laboratory vigor tests as predictors of field seedling emergence for multiple locations and years for vegetable crops. The objective of this study was to evaluate a number of previously reported laboratory measures of seed viability and vigor tests that could be used alone, or in combination to reliably predict pepper (Capsicum anuuum L. var. annuum) seedling field emergence. Several indices of seed vigor also were used. The results of these tests were correlated with final field emergence percentages obtained from Davis and Fresno, CA in 1986 and 1987. Either 30 or 32 seed lots were used for each location and year. Measures of seedling growth were the best indicators of field performance and the cool‐temperature (15 °C) percent germination at 14 d was the best overall average single‐test predictor of field emergence for all locations and years. Improved predictions could be made by combining selected vigor tests in multiple regression modes, but these were location and year dependent. An index consisting of the geometric mean of cooltemperature percent germination (Day 14) and seedling dry weight was the best overall average predictor of seedling emergence, accounting for an average of 36% of the total variation in emergence. Simulation trials indicated that a ranking of field performance among seed lots could be done with good success using the geometric mean index.
Salinity Tolerance in Sorghum. II. Cell Culture Response to Sodium Chloride in S. bicolor and S. halepense
Authors: Yang Y. W. , Newton R. J. , Miller F. R.
Published: July 2010

Grain sorghum (Sorghum bicolor (L.) Moench], is reported to be less tolerant to salt than the noxious weed and potential biomass energy crop, johnsongrass [S. halepense (L.) Pers.). The objective was to compare callus growth and osmotic responses to salinity of these two sorghum species. Callus was grown for 2 wk in a liquid Murashige and Skoog medium to which NaCl was added to final concentrations of 0.05,0.1, and 0.15 M. Relative fresh weight growth of callus in response to increased salinity in the culture medium was greater in S. halepense than in S. bicolor. After 2 wk of NaCl treatment, brown coloration and apparent necrosis were observed on callus of S. bicolor but not on that of S. halepense. The Na/K ratios were lower in callus of S. halepense than that of S. bicolor at all NaCl concentrations. Total amino acids in salinized callus did not change, but proline increased; this increase was greater in S. halepense callus than in that of S. bicolor. Levels of Na and Cl were larger in S. halepense callus treated with 0.1S mM NaCl and these were associated with a ψp of 0.40 MPa, whereas a ψp of 0.26 MPa was observed in callus of S. bicolor. Accumulation of NaCl accounted for three‐fourths of the solutes involved in osmotic adjustment in the callus of both species. Growth and Na/K ratios in salinized callus in this study were correlated with whole plant responses determined in another study. Callus growth and Na/K ratios could therefore be used as indicators of whole plant salt tolerance in Sorghum.
Endosperm Modified by Cross‐Pollinating Maize to Induce Changes in Dry Matter and Nitrogen Accumulation
Authors: Tsai C. L. , Tsai C. Y.
Published: July 2010

The question of whether the vegetative source or kernel sink represents the major constraint for grain yield of maize (Zea mays L.) has not been satisfactorily answered. In a field experiment, the sink of two hybrids, Pioneer brand 3732 (P3732) and B73 ✕ Mol7 was modified through cross‐pollination to study effects of sink alteration on dry matter and N accumulation. The two hybrids were grown with 268 kg N ha−1 spring‐applied in a randomized split‐plot design with four replications. Sib‐pollination and reciprocal crosses were made by controlling the pollen source. Dry weight and N content in plant parts as well as black layer development in kernels were analyzed at various stages during kernel maturation. Modification of the P3732 endosperm genotype by cross‐pollination with B73 X Mol7 pollen significantly increased kernel weight, kernel protein content and protein concentration, and grain yield. These increases were the result of increased assimilate production in vegetative tissues rather than improved partitioning efficiency. The P3732 crossed kernels delayed black layer development for about 10 d. Increases in protein concentration were primarily in the form of zein. In contrast, modification of the B73 ✕ Mo 17 endosperm by crosspollination with P3732 pollen had no effect on these traits. The effects of sink alteration on total plant dry matter and N accumulation were also different between P3732 and B73 ✕ Mol7 in that sink alteration of P3732 increased the accumulation of these two traits in vegetative tissues during the period of grain‐fill. These observations confirm that sink determination of grain yield is hybridspecific.
Pollen Deposition Rate Effects on Seed Set in Meadowfoam
Authors: Jahns Thomas R. , Jolliff Gary D.
Published: July 2010

Meadowfoam (Limnanthes alba Hartweg ex Benth. cv. Mermaid) is an entomophilous, winter‐annuai oilseed crop that typically produces an average of only two out of five potential seeds per flower. This study was conducted to determine whether improved pollination enhances seed set of this new crop. In the field, 1, 6, and 11 honey bee (Apis mellifera L.) visits per flower resulted in 1.6, 2.3, and 3.3 seeds per flower, respectively. In later pollen deposition studies, one and six honey bee visits per flower deposited an average of 15 and 43 pollen grains per five stigmatic papillae (FSP) per flower, respectively, in 1988, and 22 and 47 pollen grains per FSP, respectively, in 1989. Hand‐applied pollen deposition treatments were studied in a greenhouse to investigate the cause of these flowervisitation responses. Seeds per flower increased linearly (b = 0.086) in the range of 5 to 25 pollen grains deposited per receptive FSP. Seed set was 4.1 seeds (out of five potential seeds per flower) with 25 pollen grains per FSP. Although the greenhouse results cannot be directly extrapolated to the field, these data suggest that multiple honey bee visits to meadowfoam flowers are required for maximum pollination and seed set to occur.
Yield Testing of Early Generation Populations of Common Bean
Authors: Singh Shree P. , Lépiz Rogelio , Gutiérrez J. Ariel , Urrea C. , Molina A. , Terán H.
Published: July 2010

Identification of superior yielding populations in early generations of common bean (Phaseolus mlgaris L.) would help eliminate poor populations, permit adequate sampling of promising populations, and save resources. Our objective was to determine the value of yield testing early generation bulks. Three checks and 33 populations were yield tested in a randomized complete‐block design with two replications at three locations in Colombia during three seasons. Each plot consisted of 4 rows; 3, 4, and 5‐m long in the F2, F3, and F4 generations, respectively. Data were taken on yield, seed weight, maturity, anthracnose, angular leaf spot, and common bacterial blight. Populations and locations were considered random and generations fixed effects. Differences were observed among populations for all traits. Effects of locations were significant (P < 0.01) for yield, seed weight, and maturity. Positive correlations (r) were found for yield between the F2 and F3, F2 and F4, and F3 and F4 at Popayán; and all r values except between the F2 and F4 were positive and significant (P < 0.05) at Palmira. No associations were found at Quilichao. When data were pooled over any two or all three locations, all but one r value were positive and significant (P < 0.05). Heritability estimates obtained by the regression of the F3 on F2 were 0.29 for yield, 0.61 for seed weight, and 0.47 for maturity. Predicted gain from selection (20% selection intensity) for yield in the F2 was 6.1% and actual gains in the F3 and F4 were 5.6 and 5.1%, respectively. Values for seed weight were >15% and for maturity <3%.
Fertility Restoration in Male Sterille ✕ Maintainer Hybrids of Pearl Millet
Authors: Rai K. N. , Hash C. T.
Published: July 2010

Effects of environment and parental nuclear genotype may cause considerable difficulties in the identification of maintainer lines (Blines) and in the classification of different sources of cytoplasmic male‐sterility (cms) in pearl millet [Pennisetum glaucum (L.) R. Br.]. We studied the pollen shedding pattern as a measure of fertility restoration in A ✕ B hybrids of pearl millet by crossing seven cytoplasmic male‐sterile lines (A‐lines) with the B‐lines of each of the A‐lines at the ICRISAT Center in the dry and rainy seasons for 2 yr. Five of the A, system A‐lines (i.e. A ✕ B parental crosses) were stable for male‐sterility, whereas one was sterile in the dry season but produced a low frequency of pollen shedders in the rainy season. The non‐Al system A‐line (PT 732A) produced a low frequency of pollen shedders in both dry and rainy seasons. In comparison, almost all the non parental A ✕ B hybrids were uniformly or predominantly fertile across all the tests. The seed set data under selfing were generally supportive of the pollen fertility pattern. These results indicate that isonuclear lines or hybrids should be used for the reliable classification of cms sources in pearl millet. Fertility restoration pattern of hybrids in our study does not provide adequate evidence for differentiating the cytoplasm of PT 732A from that of Tift 23A1. A higher proportion of B‐lines produced sterile hybrids on 81A than on other A‐lines, indicating that 81A is a more efficient tester than other A‐lines used in this study for identifying B‐line sources.
Inheritance of Resistance to Goss's Wilt in Maize
Authors: Treat C. L. , Tracy W. F. , Drolsom P. N. , Coors J. G.
Published: July 2010

Resistant genotypes are the best means of control for Goss's wilt (Corynebacterium micMganense ssp. nebraskense Schuster, Hoff, Mandel, and Lazar) of maize (Zea mays L.). The purpose of this study was to identify susceptible and resistant genotypes and to determine the inheritance of resistance to Goss's wilt using generation means analysis and diallel experiments. Thirty‐nine inbred lines were screened for resistance to Goss's wilt. Sixteen were susceptible, 15 intermediate, and 8 resistant. Four experiments, two generation mean analyses (GMA), and two diallels were used to investigate the inheritance of Goss's wilt. One GMA experiment consisted of the resistant inbred Mol7Ht, the susceptible inbred A634Ht, the F1, F2, and the F1 backcrossed to both parents. A second GMA experiment involved resistant MolTHt, susceptible CM105, the F1, F2, and the F1 backcrossed to both parents. One diallel had five parents and one six. Additive gene action was important in the generation mean analyses for resistance to Goss's wilt. Year effects and the generations × years interaction were highly significant. In the diallel experiments, general combining ability was highly significant for both, demonstrating the importance of additive gene effects. General combining ability and specific combining ability sums of squares accounted for 97.7 and 2.3% of the variation among crosses, respectively, in the first diallel, and for 91.0 and 9.0% in the secondiallel. The results suggest that recurrent selection should be effective among the maize lines tested for resistance to Goss's wilt in maize.
Assigning Isocitrate Dehydrogenase to Linkage Group 11 in Soybean
Authors: Hedges B. R. , Sellner J. M. , Devine T. E. , Palmer R. G.
Published: July 2010

Linkage Group 11 (LG 11) in soybean [Glycine max (L.) Merr.] contains the fasciation locus (F), affecting stem development, and a locus (Rjl) regulating nodulation. The objective of this study was to add additional genetic markers to LG 11. All loci except Idhl (isocitrate dehydrogenase) tested for linkage with F and Rjl were inherited independently of these two loci. Linkage estimates between F and Idhl and between Idhl and Rjl were homogeneous and pooled linkage estimates were calculated. The recombination values for F‐Idhl from three F2 populations were 22.2 ± 3.1, 22.3 ± 2.9, and 30.5 ± 3.7%. The combined recombination value for the two loci was 24.7 ± 1.9%. Three F2 populations segregating for Idhl‐Rj1 had recombination values of 24.6 ± 3.3, 25.0 ± 3.1, and 30.9 ± 3.4%. The pooled linkage estimate for these two loci was 26.9 ± 1.9%. The gene order on LG 11 was F‐Idhl‐Rjl. The F locus was inherited independently of Aco4, Ap (LG 9), Dial, Idh2 (LG 17), Pgml, Pb (LG 14), and Y12 (LG 1). The Rj1 locus was inherited independently of Aco4, Dial, Idhl, Pgml, and Y12.
Linolenic Acid Content of Soybean Seed Estimated with 2‐Thiobarbituric Acid Test
Authors: Bubeck D. M. , Duvick D. N. , Fehr W. R. , Hammond E. G.
Published: July 2010

The linolenic acid content in soybean [Glycine max (L.) Merr.] seed oil generally is determined by gas chromatography (GC). A more rapid method of comparing the linolenic acid content of soybean seed samples would be useful for screening a large number of lines in a soybean breeding program. The objective of this study was to determine if the 2‐thiobarbituric acid (TBA) reaction could be used as a rapid method for determining the relative differences in linolenic acid content of soybean seed samples. Sixty‐eight random F2 plants from each of two populations were used to compare TBA scores with linolenic acid content as measured by GC. The correlations between TBA score and linolenic acid percentages were 0.71 for Cross 1 and 0.60 for Cross 2. The results indicated that the TBA test cannot be used as a substitute for GC analysis in evaluating soybean samples. However, the TBA test may be a useful method to rapidly eliminate genotypes with excessively high linolenic acid before GC analysis.
Diazonium Compounds Localize Grass Cell Wall Phenolics: Relation to Wall Digestibility
Authors: Akin D. E. , Hartley R. D. , Morrison W. H. , Himmelsbach D. S.
Published: July 2010

Phenolic compounds in plant cell walls limit forage digestibility. The objective of this work was to compare three diazonium salts with more widely used lignin stains for their ability to stain phenolic compounds in grass cell walls and to relate the results to cell wall digestibility. Acid phloroglucinol, chlorine‐sulfite, azure B, diazotized sulfanilic acid, diazotized p‐nitroaniline, or p‐nitrobezenediazonium tetrafluoroborate was reacted with a series of low molecular weight phenolic compounds (acids, aldehydes, and esters), lignin extracts, and intact plant cell walls in leaf blades and stems of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.]. In vitro digestibility of individual plant cell walls was assessed by microscopy of sections incubated with rumen fluid. Diazonium salts were more effective than acid phloroglucinol, chlorine‐sulfite, or azure B in forming colored compounds with phenolic acids, aldehydes, and esters. Lignin preparations from grasses gave positive reactions with all stains, and differences in color reactions occurred with some plants. Polysaccharides did not have positive histochemical reactions with the exception of larchwood xylan, which apparently contained phenolics that reacted with all stains except acid phloroglucinol and azure B. The diazonium salts and chlorine‐sulfite tended to give positive reactions with the same cell wall types, but the salts gave more stable colors and no false negatives. Treatment of a series of warm‐and cool‐season grass leaf blades with diazotized sulfanilic acid indicated positive reactions with indigestible tissues of both grass types and with the slowly or partially digested cell walls of warm‐season grasses. Diazonium compounds offer an improved method to characterize histochemically the phenolics of plant cell walls.
Relationship of Tissue Digestion to Textural Strength in Bermudagrass and Alfalfa Stems
Authors: Akin D. E. , Rigsby L. L. , Lyon C. E. , Windham W. R.
Published: July 2010

Forage quality is determined to a large extent by the physical degradation of fiber and by exit of the digesta from the rumen. The effect of plant structure and prior microbial activity on the ease of physical breakdown, which occurs during chewing, is poorly defined. The objectives of this work were to identify structural characteristics primarily responsible for providing textural strength in stems and to relate this strength to tissue digestion by whole rumen fluid, by bacteria, or by fungi. The textural strength of stem residues was determined by applying force perpendicularly to the longitudinal axis of l‐cm stem sections. Three‐millimeters stem sections from the fourth and fifth internode of ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] stems and from midway of stems of ‘120’ alfalfa (Medicago sativa L.) plants were incubated with the microbial groups or in control media for 72 h and compared for percentage area of tissue lost in cross sections or for the cross‐sectional width of tissues remaining in stems. Rumen fluid and bacteria degraded substantial amounts of the stem parenchyma, but rumen fungi degraded significantly (P ≤ 0.05) lower amounts. None of the microbial groups removed the lignified ring tissues in either forage, and loss of other tissues within plants was similar for the microbial groups. Stems incubated with fungi were reduced the most in textural strength. Results indicated that the presence and integrity of the lignified ring was the primary structure responsible for strength in stem residues and that removal of parenchyma from stems under the conditions of this study was not a major factor affecting textural strength of stem residues.
Genetic Analysis of Crosses among Maize Populations Representing Different Heterotic Patterns
Authors: Mišsević Dragan
Published: July 2010

Maize (Zea mays L.) breeders are concerned with the narrowing germplasm base and the wide‐spread usage of a single heterotic pattern. The primary objective of this study was to estimate genetic parameters for a set of seven elite maize populations from the USA, Yugoslavia, and Latin America for selection of base populations in recurrent selection programs. Populations per se, population crosses, populations per se selfed, crosses selfed, and hybrid check B73 ✕ Mo17 were grown in a randomized complete‐block design experiment with four replications at three locations in 1987 and 1988. Contributions of homozygous (ak) and heterozygous, (dk) loci to population means, mean of random homozygous inbred lines (µ), and heterosis effect (hkj) with its subdivisions (average heterosis, population heterosis, and specific heterosis) were estimated. Contributions of heterozygous and homozygous loci to population means accounted for the largest and smallest portions of variation among diallel entries, respectively, for both grain yield and plant height. Heterosis accounted for 11.3 and 8.7% of the total among diallel entries sum of squares for grain yield and plant height, respectively. BS11(FR)C7 had the highest populations per se yield due to its large contribution of both homozygous and heterozygous loci, and the highest estimate of inbreeding depression for grain yield. BSSS(R)C7 had the highest estimate of heterosis effect, but lowest per se yield due to low ak and dk estimates. The highest yield and the highest specific heterosis estimates were found for crosses BS11(FR)C7 ✕ BS16(S2)C3 and BSSS(R)C7 ✕ ZPEP. BSSS(R)C7 ✕ had the highest overall heterosis effect.
Tolerance to Barley Yellow Dwarf Virus in Triticale
Authors: Collin J. , Comeau A. , St‐Pierre C.A.
Published: July 2010

There is considerable genetic variability for tolerance to barley yellow dwarf virus (BYDV) in triticale (✕ Triticosecale rimpani Wittm.); however, nothing has been published previously about the nature of this genetic tolerance. The objective of this study was to determine the genetic basis for tolerance to BYDV in three crosses of the spring parental triticale lines Z‐9, tolerant (T); 'Beagle', moderately tolerant; and ‘Mapache’, sensitive (S); and in three crosses of the winter lines ‘OAC Wintri’ (T), GWT‐112 (T), and GWT‐133 (S). For each cross, six generations (P1, P2, F1, F2, F1, ✕ P1, and F1 ✕ P2) were evaluated in two environments in the presence and absence of artificial inoculation of Cloutier isolate (PAY type) of BYDV carried by Rhopalosiphum padi. The spring triticale lines were evaluated at two different sites, and the winter lines were evaluated in an unheated tunnel‐shaped commercial greenhouse structure and in the field. The studies showed that tolerance to BYDV in triticale is heritable. Generation means analysis for visual symptoms, and for biomass yield, height, and number of tillers expressed as percentage of control showed that genetic effects differed according to the cross and to the character studied. Important additive effects were found in the Z‐9 ✕ Beagle and Wintri ✕ GWT‐133 crosses, but no significant genetic effect could be detected in the Wintri ✕ GWT‐112 cross. The lack of fit of the additive‐dominance model (including environment interactions) indicated the presence of more complex epistatic genetic effects, and possibly epistatic ✕ environment interaction effects in the other crosses.
Yield and Fiber‐Quality Potential for Second‐Generation Cotton Hybrids
Authors: Meredith William R.
Published: July 2010

Due primarily to the difficulty of producing F1, seed, use of heterosis in cotton (Gossypium hirsutum L.) has been limited. The objective of this study was to evaluate the potential of using F2 hybrids by comparing them with parents and F1's for yield, fiber quality, and interaction with environments. The genetic design was a half‐diallel consisting of seven mid‐South parents, 21 F1's, and 21 F2's. The 49 genotypes were grown in 1987 and 1988 at three sites near Stoneville, MS. At each site, April and May planting was made, resulting in a total of 12 environments. Yield, yield components, and fiber length, strength, and micronaire reading were determined from four replications. Yarn tenacity was determined from two 1987 tests, and short‐fiber content from three 1987 tests. Average first‐harvest yield was 594, 688, and 643 kg ha−1 for the parents, F1's and F2's, respectively; total yield was 953, 1065, and 1025 kg ha−1, respectively. Average yarn tenacity was 130, 134, and 132 kN m kg−1 for the parents, F1, and F2 hybrids, respectively. Both F1 and F2 hybrids had significantly fewer short fibers than the parents. The highest‐yielding parent was ‘DES 119’, which averaged 1031 kg ha−1, while ‘Deltapine 50’, the most commonly grown cultivar in the USA, averaged 959 kg ha−1. The highest‐yielding F1 hybrids DES 119 ✕ ‘Delcot 344’ and DES 119 ✕ ‘Coker 81–613’ averaged 1145 and 1143 kg ha−1, respectively, ~15% higher than the average of DES 119 and Deltapine 50; their F2 hybrids averaged 8% higher. No differences in adaptive ability between parents, F1's, and F2's were detected. The results indicate that F2 hybrids have the genetic potential for increasing cotton yields and fiber quality.
Lignification and Physiological Factors of Yield in Maize
Authors: Larroque C. M. , Planchon C. L.
Published: July 2010

The digestibility of forage maize (Zea mays L.) may be improved by reducing plant lignification. This study was aimed at determining the variation in plant lignin concentration among inbred lines and their F1 hybrids and its relationship with some physiological traits of canopy photosynthesis. Lignification was characterized by the lignin concentration of the first internode of the plant and by the amount of lignified tissues of the leaf. The effects of a decrease in plant lignification were analyzed for association with various traits influencing biological yield: leaf angle, net photosynthesis under high light, chlorophyll fluorescence index (representative of the photosynthetic functioning under low light). The variation of the various parameters was investigated under controlled and field conditions with water not limited. The large variation in stem lignin concentration was more closely correlated with degree of lignification of the vascular bundles than with their number. A high lignification of stems and leaves induced an erect orientation of the leaves, but had no influence on the net photosynthesis per unit leaf area, which has been associated with the number of vascular bundles in leaves and stems, and with leaf area. Low lignin genotypes displayed the highest fluorescence index, indicating the potential of an increased use of low light in canopies with horizontal leaves. The best compromise between digestibility and crop productivity may be obtained by selecting for genotypes with a high photosynthetic efficiency under low light.
Soil Temperature Simulator for Seed Germination Studies
Authors: Cabrera E. R. , Boyd A. H. , Welch G. B.
Published: July 2010

Conventional laboratory equipment used in seed germination research provides only constant and alternating temperature. The temperature of the soil in the seed bed is hardly ever constant or alternating in the same manner, but fluctuates constantly. In order to simulate the fluctuation of soil temperature that occurs in the field, a soil temperature simulator (STS) was designed, built, and evaluated. Plastic crispers containing soil in which seed are to be planted can be partially submerged in a rectangular tank into which water can be placed to a depth of 10 cm. Temperature of the water can be adjusted by heating and refrigeration systems under the control of a variable input programmer system. Maximum capabilities of the STS are: (i) maximum temperature drop 4 °C/h, (ii) maximum temperature rise 7.5 °C/h, and (iii) maximum temperature gradient within the unit 1.0 °C. The STS is capable of simulating fluctuations in soil temperature within a range of 4 to 40 °C and is particularly suited for the study of seed imbibitional chilling injury.
Addition Series Approach to Assessing Competition in a Small Grain‐Alfalfa Companion Crop Community
Authors: Nickel S. E. , Simmons S. R. , Sheaffer C. C. , Radosevich S. R.
Published: July 2010

Assessment of competitive interactions within plant communities is a goal for many crop ecologists and agronomists. In the addition series approach, multivariate response models quantify intraspecific and interspecific competition in plant communities. Our objective was to test this approach in a small grain‐alfalfa (Medicago sativa L.) companion intercrop, a common forage‐establishment system in North America. Experiments were conducted on a Waukegan silt loam soil, with two oat (Avena sativa L.) and two barley (Hordeum vulgare L.) genotypes as companion crops for alfalfa establishment. Alfalfa and small‐grain herbage was harvested at boot and soft‐dough stages of small‐grain development. Multiple regression of log dry mass per plant against plant densities indicated a large competitive influence of the small grain on itself and on the alfalfa. Competition from alfalfa was negligible. Oat plants were less competitive than barley, and dwarf‐statured genotypes were less competitive than conventional genotypes. The addition series is well suited to research applications involving agronomic systems.
Inheritance of Early Maturity of Indeterminate Dry Bean
Authors: Cerna J. , Beaver J. S.
Published: July 2010

Knowledge of the heritability and genetic relationships among traits associated with harvest maturity should facilitate selection of bean (Phaseolus vulgaris L.) genotypes having earlier harvest maturity. The objectives of this study were to estimate the narrow sense heritabilities of days to first flower (DFF), days to physiological maturity (DPM), and length of the reproductive period (HP) and to measure the genetic correlations among these traits. Progeny derived from three different crosses between early and later maturity indeterminate genotypes were evaluated for two planting dates at Isabela, PR. Narrowsense heritability estimates for DFF were generally large (0.29 to 0.75), which suggests that early generation selection for DFF in these populations would be successful. Narrow‐sense heritability estimates for DPM were intermediate to large (0.31‐0.63); however, magnitude of estimates varied between planting dates. Narrow‐sense heritability estimates for RP of the three crosses were generally intermediate to low, indicating that selection for the RP trait would be most effectively conducted in replicated nurseries in advanced generations. F3 lines with RP = 10 d longer than the parental genotypes were identified in all three crosses. Genetic correlation coefficients between DFF and DPM were positive and significant, ranging from r = 0.43 to r = 0.85. Genetic correlation coefficients between DFF and RP were generally negative and significant, suggesting that selection for a greater RP would likely be related to a reduced DFF. Genetic correlation coefficients between DPM and RP varied among crosses and between years.
Inheritance of Leaf Rust Resistance in Durum Wheat
Authors: Zhang Hongtao , Knott D. R.
Published: July 2010

The inheritance of resistance to leaf rust (Puccinia recondita L. sp. tritici) in durum wheat (Triticum turgidum L.) is poorly understood. Eight leaf rust‐resistant durum cultivars of diverse origin were crossed and backcrossed to a susceptible line, RL6089, to determine the inheritance of resistance and to provide useful information for durum wheat breeders. Seedlings of the F2, F2, and BCF2 generations were tested with Race 15 in the greenhouse. Lines carrying single genes for resistance were developed from the backcrosses and tested with six races of leaf rust: 1, 15, 58, 100, 104, and 161. Diallel crosses among the resistant parents were made and F2 seedlings tested with Race 15 to determine if any of the parents carry genes for resistance in common. The data showed that ‘Stewart 63’ and ‘Medora’ each carry one dominant and one recessive gene, ‘Quilafen’ carries one dominant gene, and ‘Wakooma’, ‘Lloyd’, ‘Pelissier’, and ‘Golden Ball’ each carry a single recessive gene. ‘Vie’ carries a dominant gene and possibly a recessive gene. All of the diallel crosses segregated susceptible plants, indicating that the parents carry different genes for resistance. A comparison of the reaction to the six races of the derived single‐gene lines and near‐isogenic lines of ‘Thatcher’ carrying specific Lr genes revealed that the dominant gene carried by Stewart 63 may be Lr16 and the dominant gene in Quilafen may be Lr17. The seven other genes have probably not been previously identified. Most of the genes should be of value in durum wheat breeding.
Nitrogen Fertilization of Direct‐Seeded Flooded vs. Transplanted Rice: I. Nitrogen Uptake, Photosynthesis, Growth, and Yield
Authors: Schnier H. F. , Dingkuhn M. , De Datta S. K. , Mengel K. , Faronilo J. E.
Published: July 2010

Direct‐seeded flooded rice (Oryza sativa L.) culture is becoming an increasingly popular alternative to transplanting in some regions of Asia. Two field studies were therefore conducted to compare the growth patterns of wet‐row‐seeded and transplanted ‘IR64’ rice as affected by rate of N fertilizer application (0 and 90 kg N ha−1 in 1987 and 0, 30, 60, 90, 120, and 150 kg N ha−1 in 1988). Row‐seeded rice exhibited faster crop establishment and a more productive vegetative growth phase, because transplanting shock was absent and tiller number greater. Leaf area index was greater in row‐seeded than in transplanted rice. During the reproductive and ripening stages, lower foliar N concentration depressed canopy CO2 assimilation and crop growth rate of row‐seeded rice. Lower foliar N concentration was caused by dilution and not by reduced uptake. Greatest grain yield was 9.0 Mg ha−1 with 120 kg N ha−1 applied in transplanted rice and 150 kg N ha−1 in row‐seeded rice. Yield response to applied N was significant up to 60 and 90 kg N ha−1 in transplanted and row‐seeded rice, respectively. The harvest index was lower in row‐seeded than in transplanted rice at all N rates. Row‐seeded rice had a higher N demand and an inferior ability to convert high biomass production into grain yield as compared with transplanted rice. Alternative genotypes with reduced tillering ability and limited leaf area production during the reproductive stages may improve the performance of tropical wet direct‐seeded rice.
Nitrogen Fertilization of Direct‐Seeded Flooded vs. Transplanted Rice: II. Interactions among Canopy Properties
Authors: Dingkuhn M. , Schnier H. F. , De Datta S. K. , Dörffling K. , Javellana C. , Pamplona R.
Published: July 2010

Growth analyses of transplanted and row‐seeded ‘IR64’ rice (Oryza sativa L.) grown in the Philippines at six levels of applied N indicated that growth and CO2 assimilation rates were low during reproductive growth in row‐seeded as compared with transplanted rice. This study sought to quantify the effect on growth of various canopy properties, and to develop a concept for improving yield of direct‐seeded tropical rice. Mathematical relationships among growth parameters were established based on empirical patterns of leaf area index (LAI), foliage N concentration, canopy CO2 exchange rate (CER), and dry matter accumulation. Patterns of tissue death were used to estimate senescence. Relative foliage expansion rates were calculated from LAI patterns. Across all treatments and most developmental stages, uniform response patterns of foliage expansion, tissue death, and CER to LAI and foliage N concentration were observed. With increasing LAI, the minimum foliage N concentration for foliage expansion and tissue maintenance increased. Cessation of foliage expansion and onset of tissue death depended similarly on foliar N status and LAI. Canopy CO2 exchange rate was positively correlated to LAI up to a certian LAI optimum, which depended on foliage N concentration (LAI 3‐6 at 10‐40 g N kg−1). Further increases in LAI reduced CER. Leaf area limited biomass accumulation during the vegetative growth phase, whereas foliage N concentration became limiting thereafter, in all treatments. Overexpansion of foliage was particularly marked in row‐seeded rice, due to the absence of transplanting shock and the high plant density, leading to an unfavorable respiration/photosynthesis ratio. Simulation suggested higher yield for direct‐seeded lowland rice in a modified plant type with lower LAI and higher foliar N concentration during the reproductive growth phase, lower tillering ability, and higher assimilate storage capacity in the stems.
Degradation of Switchgrass Anatomical Tissue by Rumen Microorganisms
Authors: Twidwell E. K. , Johnson K. D. , Patterson J. A. , Cherney J. H. , Bracker C. E.
Published: July 2010

Factors that influence rumen microbial degradation of switchgrass (Panicum virgatum L.) tissues are not well understood. Our objective was to measure and compare the anatomical degradation of leaf blades, leaf sheaths, and stems by tureen microorganisms. Two field‐grown switchgrass cultivars were harvested when three‐fourths of the inflorescence had emerged. Three‐millimeter portions of blade, sheath, and stem tissue were incubated in buffered rumen fluid for 0, 24, and 48 h, then removed and processed for light microscopy. Tissue composition and microbial degradation within each morphological component were measured with a computer‐based optical image analyzer. No differences in degradation were apparent between cultivars. The largest portion (35.7%) of blade cross‐sectional area was occupied by the mesophyll. After 48 h of incubation in rumen fluid, 32% of this tissue was partially degraded and 68% completely degraded. In contrast, leaf sheath parenchyma tissue was more resistant to complete degradation than that of the blade. In the sheath, 17.2% of tissues in the cross‐sectional area were at least 80% intact after 48 h of incubation; only 4.3% of the cross‐sectional area of the blade was this resistant to degradation. These differences in degradation resulted in lower (101 g kg−1) in vitro dry matter disappearance (IVDMD) in the sheath compared with the blade. Tissues (cortex, xylem, and bundle sheath) in which at least 80% of their area was intact after 48 h of incubation occupied 25.8% of the stem's cross‐sectional area. It is these resistant tissues that appear to cause the stem to have the lowest IVDMD of the three major morphological components of switchgrass. A detailed understanding of differences in degradation of anatomical tissues will result in the development of more digestible cultivars and morefficient forage utilization by livestock.