bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining Ability and Heterosis in U.S. Southern Long‐Grain Rice
Authors: Gravois Kenneth A. , McNew Ronald W.
Published: July 2010

Combining ability and heterosis estimates are excellent statistics to help discern breeding program goals and direction. Currently, combining ability and heterosis estimates for U.S. southern long‐grain rice (Oryza sativa L.) are lacking, and, thus, our objectives were to estimate these parameters for rice yield, plant height, panicle number, panicle length, panicle weight, and primary branch number. In 1989, two 4 × 4 crossing factorials were completed, and the 32 F1 hybrids and their 16 parents were evaluated in 1990 at two Arkansas locations: the Rice Research and Extension Center near Stuttgart and the Cotton Branch Experiment Station near Marianna. The 16 parents constituted a representative sample of elite U.S. southern long‐grain rice germplasm available to rice breeders. Hill plots consisting of single plants were planted 61 cm apart in a square grid pattern. General combining ability (GCA) was more important than specific combining ability (SCA), accounting for 70% of the variation for yield, 89% for plant height, 84% for panicle number, 60% for panicle length, 69% for panicle weight, and 85% for primary branches. Specific combining ability was significant for all traits except panicle number, indicating that nonadditive gene action was important as well. When crossing combinations are being decided, the sole use of midparent means would not adequately predict progeny mean performance. High parent beterosis for yield ranged from ‐ 16 to 68%. Heterosis for yield was due primarily to beterosis for panicle weight rather than panicle number. U.S. southern long‐grain rice yields could be improved through the use of hybrid rice varieties.
Planting Date and Preplant Tillage Effects on Emergence and Survival of Rhizoma Perennial Peanut
Authors: Williams M. J.
Published: July 2010

Poor stand establishment has limited use of rhizoma perennial peanut, Arachis glabrata Benth. The effect of preplant tillage (plowedbottom plowed and disked, disked‐disked only, and sod‐planted directly into grass sod) and planting date (winter, 17 Feb. 1988 and Jan. 1989; summer, 22 July 1988 and 21 July 1989) on rhizoma peanut sprout emergence and survival was determined in a Florida study. Total number of sprouts per square meter, time to first and last sprout emergence, time to first and last sprout death, percent of sprouts that died, and number of live sprouts per square meter were evaluated for 2 yr. Additionally, spread of rhizoma peanut from original rows was determined for all plots 8 mo after the second summer planting. Time to first sprout emergence ranged from 2 to 5 wk post planting with winter plantings (5.1 wk) emerging slower (P = 0.0001) than summer (3.1 wk). Time to first sprout emergence was shorter (P = 0.0003) for plowed (3.7 wk) than disked (4.4 wk) or sod (4.3 wk) treatments. Sprouting had declined to essentially zero by 6 to 7 wk after firstsprout emergence, regardless of preplant tillage, planting date, or year. General ranking for total emergence was plowed > disked = sod (P = 0.0001) and winter > summer (P = 0.04). Death losses emerged sprouts ranged between 21.4 and 93.3% and were not affected (P > 0.05) by preplant tillage. Summer plantings (43.1%) lower (P = 0.007) death losses than winter plantings (58.8%), this better survival did not compensate for lower number of sprouts emerging in summer plantings. Differences in initial sprout population were reflected in spread differences (P = 0.002) even as long as 2 post planting. This study indicates that the recommendation for establishing rhizoma peanut stands in well‐prepared fields during the winter should be continued.
Rice Ratoon Crop Yield Linked to Main Crop Stem Carbohydrates
Authors: Turner Fred T. , Fund Michael F.
Published: July 2010

Ratooning of rice (Oryza satira L.) may be agronomically possible in climates where the crop season is to short too produce two rice crops, but factors influencing ratoon rice yields are not well understood. The influence of main crop total nonstructural carbohydrate (TNC) and main crop N topdfessing on ratoon crop yield of four contrasting field‐grown riee cultivars were evaluated in Texas during 1988 and 1989. Allowing panicles to develop normally or removing the upper two‐thirds of each main crop panicle 10 d after initial main crop heading created a range in TNC of the culm and leaves during later stages of main crop development for determining TNC effects on ratooning. Nitrogen applied 10 d after initial main crop heading corrected, any possible N deficiency, but did not increase main crop yield, TNC, or ratoon crop yield, indicating no benefits to N applied immediately after main crop heading. During main crop grain filling, culm and leaf TNC levels of plants with normal panicles decreased to low levels (0‐90 g kg‐1), then gradually increased and ranged from 40 to 170 g kg‐1 at harvest. In contrast, TNC in culms and leaves of plants with incomplete panicles gradually increased during main crop grain filling reaching 140 to 310 g kg‐1 at main crop harvest. Main crop plants with elevated TNC levels produced ratoon yields up to 5.3 Mg ha‐1, averaging 48 and 33% higher than plants with low TNC at main crop harvest in 1988 and 1989, respectively. These data illustrate a moderate positive correlation (R2 = 0.66) between ratoon yields and TNC in cuim and leaves at main crop harvest for effects due to years, panicle removal, and cultivars.
Gas Exchange Characteristics of Wheat Stands Grown in a Closed, Controlled Environment
Authors: Wheeler Raymond M. , Corey Kenneth A. , Sager John C. , Knott William M.
Published: July 2010

Information on gas exchange of crop stands grown in controlled environments is limited, but is vital for assessing the use of crops for human life‐support in closed habitats envisioned for space. To studies were conducted to measure gas exchange of wheat stands (Triticum aestivum L. cv. Yecora Rojo) grown from planting to maturity in a large (20 m2 canopy area), closed growth chamber. Daily rates of dark‐period respiration and net photosynthesis of the stand subsequent CO2 drawdown in the light (i.e., a closed‐system approach). Lighting was provided as a 20‐h photoperiod by high‐pressure sodium lamps, with canopy‐level photosynthetic photon flux density (PPFD) ranging from 500 to 800 μmol m‐2 s‐1 as canopy height increased. Net Photosynthesis rates peaked near 27 μmol CO2 m‐2 s‐1 at 25 d and then gradually declined with age. Responses to short‐term changes in irradiance after canopy closure indicated the stand light compensation point for photyosynthesis to be near 200 μmol m‐2 s‐1 PPFD. Tests in which CO2 concentration was raised to ≈2000 μmol mol‐1 and then allowed to draw down to a compensation point showed that net photosynthesis rates dropped sharply with decreasing CO2. The CO2 compensation point for photosynthesis occurred near 50 μmol mol‐1 Short‐term (24 h) temperature tests showed net photosynthesis at 20 °C ≥ 16 °C > 24 °C, while dark‐period respiration at 24 °C > 20 °C > 16 °C. Rates of stand evapotranspiration peaked near Day 25 and remained relatively constant until about Day 75, after which rates declined slowly. Results from these tests will be used to model the use of plants for CO2 removal, 02 production, and water evaporation for controlled ecological life support systems propsed for extraterrestrial environments.
Genetic Relationships among and Selection for Rice Yield and Yield Components
Authors: Gravois Kenneth A. , McNew Ronald W.
Published: July 2010

Genetic correlations provide useful information to plant breeders for developing selection schemes. Genetic correlations among yield and yield components (panicle number, panicle weight, panicle length, primary branches, and plant height) for U.S. southern long‐grain rice (Oryza sativa L.) have not been reported. The objectives of this work were to estimate and use genetic correlations in developing selection methodologies in rice breeding programs. In 1989, two 4 × 4 crossing factorials (Design II) were completed, and the 32 F1 hybrids and the 16 parents were evaluated in 1990 at two Arkansas locations (Stuttgart and Marianna). Additive genetic and broad‐sense genetic correlations were estimated. At both the additive and broad‐sense genetic levels, yield was positively correlated with panicle weight. Yield was negatively correlated with panicle number, but the effect was diminished at the broad‐sense genetic level. Panicle weight was negatively correlated with panicle number. Path analysis, however, revealed positive direct effects for both panicle number and panicle weight on rice yield at both the additive genetic and broad‐sense genetic levels, with panicle weight exhibiting larger direct effects on yield than panicle number. Selection indices were developed from the additive genetic and phenotypic variances and covariances. The selection indices indicated that selecting for increased yield via selection for either panicle weight or panicle number alone would be ineffective. A selection index that included selection for both increased panicle weight and panicle number to increase yield was estimated to be 91% as effective as selecting for yield directly.
Barley Semidwarf and Standard Isotype Yield and Malting Quality Response to Nitrogen
Authors: Nedel Jorge L. , Ullrich Steven E. , Clancy Janet A. , Pan William L.
Published: July 2010

Introduction of certain semidwarf genes into wheat (Triticum spp.) has improved N‐use efficiency, particularly at high N supply. This study was conducted to determine whether yield and grain quality differ between standard height (STD) and mutant semidwarf (SD) malting barley (Hordeum vulgare L.) isotypes with varying levels of N supply. Isotype pairs (‘Morex’, ‘Hazen’, ‘Norbert’, and ‘Andre’) and check cultivars (Steptoe, Klages) were grown with 30, 60, 90, and 120 kg N ha−1 in 1987 and 1989. Yield, grain characteristics, and malting quality parameters were evaluated. The STD isotypes had higher yield (6781 vs. 5642 and 5202 vs. 4504 kg ha−1 in 1987 and 1989, respectively) and generally higher values for yield components and harvest index, as well as better grain quality than their respective SD isotypes; however, two‐row SD isotypes had better malting quality than their STD isotypes. The generally superior performance of STD isotypes in part may be due to the SD isotypes being raw induced mutants that had not been improved by crossing. Malting quality parameters, such as total malt protein and malt extract, were affected negatively by N >60 kg ha−1, when the preceding crop was pea (Pisum sativum L.; high N); however, for yield and some malt quality parameters such as diastatic power, all genotypes responded significantly and positively to N fertilization when the preceding crop was barley (low N). In general, the response to N was similar for both barley types. As SD malting barley cultivars are developed to control lodging, they may not utilize more N or yield more than STD types.
Root Growth of Wheat Genotypes in Hydroponic Culture and in the Greenhouse under Different Soil Moisture Regimes
Authors: Mian M.A.R. , Nafziger Emerson D. , Kolb Frederic L. , Teyker Robert H.
Published: July 2010

Root characteristics of wheat (Triticum aestivum L.) genotypes are believed to be important in tolerance to drought and flooding, yet neither the extent of differences in root size among modern soft red wheat cultivars nor the degree of association between root size and drought or flooding tolerance is known. This study was conducted to see whether genotypes differ in root size, and to see if root size is associated with tolerance to flooded soil and to drought during early vegetative growth. We found differences in root fresh weight (RFW), shoot fresh weight (SFW), number of roots longer than 40 cm (NR), longest root length (LRL) and total root length (TRL) of 40 winter wheat genotypes grown in hydroponic culture for 4 wk. Each of these parameters was positively correlated with all others. Twelve genotypes with different root sizes selected from these 40 were grown in a greenhouse soil experiment for 3 wk, after which soil moisture treatments of control, flooding, and drought were imposed for a period of 21 d. Flooding did not affect SFW and number of tillers (NT), but decreased RFW. Drought drastically decreased all three parameters. The genotype × moisture treatment interactions for SFW, RFW, and NT were significant. Root and shoot growth of these genotypes in hydroponic culture were correlated to their root and shoot growth under both control and flooded conditions, but not under drought. Thus, it appears that the expression of genotypic root growth potential may be influenced by the availability of soil moisture, and that selection of wheat seedlings for vigorous growth in hydroponic culture will select for vigorous early growth in soil with adequate or excess moisture, but not under severe drought.
Comparison of Reporting Methods for Root Growth Data from Transparent‐Interface Measurements
Authors: Glinski Darryl S. , Karnok Keith J. , Carrow Robert N.
Published: July 2010

Transparent viewing planes provide a useful and popular means of observing and quantifying root growth. This study was conducted to compare root growth quantification by soil depth and distribution using three tracing methods of reporting root growth: (i) traced root intensity (traced RI), (ii) traced root‐length density (traced RLD), and (iii) traced root‐length area (traced RLA). These three root‐tracing methods were compared with actual RLD and actual RLA determinations made from the bulk soil volume at the termination of the study. Creeping bentgrass (Agrostis stolonifera L.; syn A. palustris Huds.) sod was planted in clear, flexible polyethylene containers slanted at a 20° angle. During a period of ≈2 mo, root growth by depth was monitored by tracing roots onto clear polyester sheets. None of the reporting methods for traced roots generated root growth measurements equivalent to actual rooting. Traced RLD yielded the best estimates of root quantity at each soil depth, yet, generated poor root distribution estimates. Traced RLA yielded the most accurate estimate of root distribution compared with actual root distribution when data were transformed to a percent basis. Flexible, transparent polyethylene containers used for viewing‐plane measurements of root growth quantification and distribution can, when reported by these three methods, differ substantially from actual bulk soil RLD or RLA. Thus, this transparent viewing‐plane procedure exhibits the same problems inherent in root measurements from rhizotrons and minirhizotrons.
Selection of Cultured Wheat Cells for Tolerance to High Temperature Stress
Authors: Wang Wen Chung , Shang Xiao Min , Yücel Meral , Nguyen Henry T.
Published: July 2010

In vitro culture offers approaches to study cellular responses and to obtain cells tolerant to high temperature stress. The objectives of this study were to select wheat cells that tolerate high temperature stress, study cell line stability and cytogenetic characteristics, and compare protein synthesis in selected and control cell lines after exposure to heat stress. Three of 600 colonies plated were recovered after cells had been exposed to 48 °C. Forty‐five percent of the cells of the tolerant cell line, M48, survived when they were returned to a normal temperature (22 °C) for mo and rechallenged with a 48 °C treatment. The control cell line exhibited 0.8% survival under this treatment. Chromosomal elimination and genomic rearrangements were observed extensively for the cell lines before and after heat selection. Heat selection did enhance the occurrence of polytene chromosomes and the frequency of extrachromosomal DNA. When cell viability was evaluated in cell suspension cultures, M48 had a higher percentage of viable cells than the control cell line. Analysis of 35S‐methionine in vivo labeled proteins showed that the selected M48 cell line maintained the synthesis of most normal proteins under a heat shock of 40 °C for 4 h, with synthesis of several unique low molecular weight heat‐shock proteins (HSPs). quantitative in crease in high molecular weight HSPs was also observed in this cell line. This study demonstrated that a heat‐tolerant cell line of wheat can be obtained from in vitro selection, and that this phenomenon was associated with the synthesis of specific proteins under heat stress.
Agronomic Performance of Fasciated Soybean Genotypes and Their Isogenic Lines
Authors: Leffel Robert C. , Bernard Richard L. , Yocum John O.
Published: July 2010

The fasciated soybean [Glycine max (L.) Merr.] is a morphological type caused by the recessive gene f. The original sources of the gene exhibit a broadened and flattened stem, with most of the pods at the stem tip. Fasciation has been suggested as a new gene for soybean improvement. These studies were conducted to determine (i) the agronomic performance of improved fasciated lines and (ii) the average effects of the fasciation ff genes in soybean via isogenic line comparisons. Second‐cycle improved fasciated genotypes were developed from each of six crosses of first‐cycle improved fasciated lines × ‘Hobbit’ and evaluated in local and regional field tests. Five pairs of F9 isogenic lines, ff vs. FF, were developed from each of the six crosses by maintenance of heterozygosity at the fasciation locus. Selection for seed yield among fasciated lines apparently decreased penetrance and expressivity of ff genes. Second‐cycle fasciated lines were developed that were comparable to current cultivars in seed yields in loweryielding but not in higber‐yielding environments. Seed yields of fasciated lines were not increased at higher plant densities in narrower rows. Fasciated lines were generally taller, more susceptible to lodging, and exhibited poorer quality seed as compared with commercial cultivars. The average effect of ff gene in 30 pairs of F9 isogenic lines was +3 d plant maturity, +9 cm plant height, +2.3 plant lodging score, +14 mg seed−1 seed weight, +0.1 seed quality score, and −441 kg ha−1 seed yield. Most of the detrimental effects of the fasciated gene are probably attributable to its increased plant lodging.
Soybean Maturity Effect on Expression of Resistance to Lepidopterous Insects
Authors: Rowan Gina B. , Boerma H. Roger , All John N. , Todd James W.
Published: July 2010

The development of soybean [Glycine max (L.) Merrill] cultivars with resistance to defoliating insects requires characterization of genotypes for the degree of defoliation by natural insect populations in several field environments. Combined analysis of variance over environments for insect defoliation often shows genotype × environment interactions. This research documents the importance of plant maturity and insect seasonality on this interaction. Fourteen (seven resistant and seven susceptible) soybean genotypes, ranging across Maturity Group(s) (MG)V to VIII, were evaluated in four field environments [three with populations of velvetbean caterpillar (VBC), Anticarsia gemmatalis (Hübner) or mixed populations of VBC and soybean looper (SBL), Pseudoplusia includes (Walker), occurring late in the growing season, and one with a mid‐season population of beet armyworm (BAW), Spodoptera exigua (Hübner)], four greenhouse experiments [14‐d‐old plants artificially infested with either VBC, BAW, corn earworm (CEW), Helicoverpa zea (Boddie), or SBL], and two field‐cage experiments [45‐d‐old plants artificially infested with CEW]. In the vegetative and early reproductive stages of development, soybean maturity was unrelated to insect defoliation (r = −0.21 to 0.35). In three field experiments with late season VBC or mixed VBC and SBL populations, the early maturing genotypes had greater defoliation than late maturing genotypes (r = −0.74 to −0.90). This negative association of maturity and defoliation resulted in greater defoliation of resistant MG V genotypes than susceptible MG VII and VIII genotypes.
Genetic Linkage of the Rps1 and L2 Loci in Soybean
Authors: Kilen Thomas C. , Tyler Jeff M.
Published: July 2010

Genome mapping of important genes in soybean, Glycine max (L.) Merr., is rather limited compared with that of other major crops. Such genetic information is needed by those involved in soybean genetic improvement. In this study, genetic linkage of the Rpsl locus controlling reaction to Phytophthora megasperma Drechs. f. sp. glycinea T. Kuan & D.C. Erwin, and the L2 locus controlling pod wall color was tested. Populations segregating for both genes were derived from the cross Bedford × D78‐3173. At maturity the pod wall color of F2 plants was recorded. The F3 seedlings derived from those plants were evaluated in a greenhouse for reaction to race 1 of P. megasperma using the hypocotyl puncture inoculation method. The chi‐square test for linkage was significant (P < 0.0005). Recombination was calculated by the ratio of products method (27 ± 4.3%) and maximum likelihood method (28 ± 4.1%), indicating that these genes are on the same chromosome.
Inheritance of Septoria Glume Blotch Resistance in Wheat
Authors: Bostwick Dwight E. , Ohm Herbert W. , Shaner Gregory
Published: July 2010

Incorporation of resistance to septoria glume blotch, caused by Stagonospora nodorum (Berk.) Castellani & E.G. Germano, into wheat (Triticum aestivum L.) is complex because resistance is quantitatively inherited. The Brazilian wheat ‘Cotipora’ expresses a high level of resistance to this pathogen. Crosses were made between Cotipora and the susceptible Purdue line, P831791A1‐1‐6. Populations of parents, F1, F2, BCF1, and BCF2 were inoculated with a conidial suspension of the pathogen containing 2.5 × l06 spores mL−1 and given a moist period of 52 h. Percentage of diseased tissue was estimated on the spikes and flag leaves four times over a 20‐d period, and an area under disease progress curve (AUDPC) was calculated. Correlations between AUDPCs of spike and flag leaf in the F2 and BCF1 populations were 0.312 and 0.283, respectively, indicating that resistance is at least partially controlled by different genes in these two plant organs. Resistance was partially dominant in the F1 generation in both the spike and flag leaf. In the F2, BCF1, and BCF2 generations, however, dominant gene action was not evident. The gene number estimate for the spike reaction was 3.16. Broad sense heritability estimates were 0.51 and 0.34 for the spike and flag leaf reactions to S. nodorum, respectively. Cotipora is a valuable source of S. nodorum resistance because of its high level of resistance expressed in the spike and flag leaves.
Inheritance of Improved Leaf Rust Resistance in Somaclones of Wheat
Authors: Oberthur Laura E. , Harrison Stephen A. , Croughan Timothy P. , Long David L.
Published: July 2010

Leaf rust of wheat (Triticum aestivum L.) caused by Puccinia recondita Roberge ex Desmaz. f. sp. tritici (Prt) has been controlled through incorporation of genetic resistance into host genotypes. Somaclonal variation may provide additional sources of resistance genes. This study was conducted to determine the gene source and inheritance of improved resistance to leaf rust found in somaclones of ‘Coker 916’. Two wheat somaclones, regenerated from immature embryo‐derived calli of Coker 916, had increased field resistance to leaf rust and were screened with 36 Prt isolates to identify Lr genes. Screening results indicate Coker 916 contains Lr3, 10, and possibly Lrl4a, 15, 20, and either 27 or 31. The pedigree of Coker 916 includes known sources of Lrl, 3, 10, 11, 14a, and 27 seedling‐resistance genes. The two somaclones, LTC 122 and LTC 140, contain Lr3, Lr10, and additional resistance genes not found in Coker 916, possibly Lr genes 1, 3ka, 9, 14a, 15, 18, 20, 23, 27, 30, 31, 32, and/or 33. Four Rl‐derived R2 LTC 122 lines reacted identically to leaf rust isolates; thus the altered resistance may have been monogenic in the R0 plant. Crosses were made between Coker 916 and the somaclones. The F2 progeny of LTC 122 × Coker 916 contained both Lr3 and LR10 and segregated for two additional independent, dominant resistance genes in a 15 (low disease reaction): 1 (high disease reaction) ratio. Somaclonal variants should be useful sources of additional resistance to foliar pathogens.
Near Infrared Reflectance Analysis with Single and Multiproduct Calibrations
Authors: Shenk John S. , Westerhaus Mark O.
Published: July 2010

Single‐product calibrations for near infrared (NIR) spectrophotometers are normally developed for each type of material to achieve a high level of prediction accuracy. Developing multiproduct calibrations with thousands of samples was not practical with personal computers until recently. Advancements in software now make it possible to include thousands of samples into multiproduct calibrations. This study was conducted to evaluate the accuracy of a multiproduct calibration consisting of forage samples. Large single‐product files of hay and fresh forage, haylage, and small grain silage spectra were available for this study. Every sixth sample from each file was reserved to test calibration accuracy. Single‐product calibrations were developed for each product and a multiproduct calibration was developed for all four products. There was very little difference between the accuracy of the multiproduct calibration containing all samples and the single‐product calibrations. In a second study, a multiproduct calibration developed from 756 haylage and small grain silage samples was used to predict the quality of 100 hay samples. The prediction error was found to be unsatisfactory, so 50, 100, 166, and 500 hay samples were added to the multiproduct calibration file to see if the hay prediction errors could be improved. The expanded multiproduct calibration was more accurate than a custom single‐product hay calibration when <150 hay samples were available to develop a custom calibration or expand the multiproduct calibration. This suggests that if only a few samples are available, it may be more cost‐effective to expand a similar product library and recalibrate than to gather a large number of samples for a new calibration.
Isozyme Diversity in the Cowpea Species Complex
Authors: Vaillancourt René E. , Weeden Norman F. , Barnard John
Published: July 2010

The cowpea [Vigna unguiculata (L.) Walp] is an important crop in many countries of tropical Africa, Asia and South America. Compared with other leguminous crops, little is known about the population structure of the cowpea and the partitioning of genetic diversity between cultivated and wild cowpea. One hundred and twelve accessions of cultivated cowpea (V. unguiculata ssp. unguiculata) and 43 of wild cowpea (V. unguiculata ssp. dekindtiana) were evaluated for genetic diversity at 26 isozyme loci. Cultivated accessions were characterized by very low genetic diversity (Ht = 0.029), with only six polymorphic loci. Four of these polymorphic loci displayed one very common allele and one rare allele. Accessions possessing these rare alleles were dispersed throughout Africa and a geographical center of isozyme diversity was not evident. Cultivated groups biflora (the catjang) and sesquipedalis (the yard‐long bean) could not be differentiated from the cowpea. Wild cowpea, on the other hand, were highly diverse (Ht = 0.168), with 19 out of 26 loci polymorphic. Our data indicate introgression from wild to cultivated must be very rare. Six wild accessions displayed high identity with the cultivated cowpea. Wild cowpea may, therefore, be the progenitor of the cultivated cowpea. Because these wild accessions were dispersed throughout equatorial Africa, there is no isozyme evidence for a narrowly defined center of domestication.
Genetic Diversity in North American Soybean: I. Multivariate Analysis of Founding Stock and Relation to Coefficient of Parentage
Authors: Gizlice Ziya , Carter Thomas E. , Burton Joseph W.
Published: July 2010

Pedigree analysis provides information helpful in the preservation of genetic diversity in soybean [Glycine max (L.) Merr.]. An often‐used, but untested assumption in pedigree analysis of soybean is that the pedigree relationship between ancestors of unknown origin is zero. We investigated genotypic relationships among 14 ancestors that constitute ≈ 70% of the genetic base for North American public soybean cultivars. The experiment was conducted at the Southeastern Plant Environmental Laboratories phytotron under controlled light and temperature conditions. The ancestral strains of soybean exhibited a wide range of genetic diversity for 10 metric traits; more than that predicted by a previous study employing molecular markers. Multivariate analysis collapsed the 10 traits into four principal components that explained 80% of the total genotypic variation among the strains, Similarity estimates (s) for all pairs of the ancestral types were derived from the four components. Subsequently, coefficient of parentage (r) estimates (derived from pedigree analysis) were calculated for 258 modern soybean cultivars. A first pedigree analysis employed the standard assumption given above and a second analysis substituted s values in place of zero as estimates of genetic relatedness in the founding stock. The similarity estimates did not have a large effect on estimates of r for cultivars released after 1980. Thus, the assumption of zero relation among founding stock should not influence soybean breeders' approaches to the use or preservation of genetic diversity. The small impact of s on the estimation of r is theorized to result from the infrequent occurrence of extremely high or low s values between the nine ancestors that are major contributors to modern soybean. A small r was observed between the modern southern and northern cultivars, indicating that these two gene pools remain distinct and offer the best available reservoirs of quantitative gentic diversity for practical breeding.
Genetic Diversity in North American Soybean: II. Prediction of Heterosis in F2 Populations of Southern Founding Stock Using Genetic Similarity Measures
Authors: Gizlice Ziya , Carter Thomas E. , Burton Joseph W.
Published: July 2010

Genetic distance measures are typically derived from multivariate statistical analysis of morphological, isozymic, or RFLP data but not agronomic data. Rational application of genetic distance measures to plant breeding requires some evidence that these measures are associated with agronomic traits such as seed yield. No such proof is available in soybean. The objectives of this study were to (i) evaluate agronomic diversity among five of the founding stock of Southern U.S. soybean employing F2 heterosis for seed yield, and (ii) investigate the association of agronomic genetic diversity with three genetic similarity (GS) estimates. Two estimates, GS1 and GS2, were constructed from multivariate analysis of biochemical and morphological traits in the founding stock grown in a phytrotron facility. The third, variance for 100‐seed weight (GS3) in the F2 progeny of the founding stock, was chosen because 100‐seed weight was the trait most heavily weighted in the statistical construction of GS1and GS2. The five ancestral strains and their ten F2 progeny bulks were evaluated for seed yield and 100‐seed weight at two locations in North Carolina in 1989 and 1990. Half of the 10 F2 progeny populations exhibited significant (P < 0.05) midparent heterosis for seed yield. Mean heterosis was 9.3% with a range of −1 to 19%. One F2 progeny bulk, that of Tokyo × Roanoke, produced only slightly less seed yield than two modern cultivars derived from 40 yr of soybean breeding. The F2 heterosis for yield was predicted by GS2 and GS3 but not GS1. GS2 and GS3 more clearly distinguished the differences among the strains than did GS1 because these estimates were based soley upon the genotypes under study while GS1 was developed to maximize discrimination among a much broader base of ancestral strains. We conclude that the application of genetic distance measures as predictors of agronomic genetic diversity should be made with caution. Their utility may be population dependent. The F2 heterosis we observed was not associated with previously published similarity indices developed from isozymic and RFLP data.
Two Photoperiodic‐Reactions in Photoperiod‐Sensitive Genic Male‐Sterile Rice
Authors: Yuan Sheng‐Chao , Zhang Zi‐Guo , He Hao‐Hua , Zen Han‐Lai , Lu Kai‐Yang , Lian Jian‐Hong , Wang Ben‐Xian
Published: July 2010

Plant photoperiodism is an important principle explaining the growth and developmental processes of many plants, including rice (Oryza sativa L.). Most researchers currently believe that the effect of photoperiodism in rice plants is restricted to accelerating or delaying heading and flowering. This paper discusses a second effect of photoperiodism on certain lines of rice, the effect of inducing pollen sterility. It summarizes nearly 10 yr of study on photoperiod‐sensitive genic male‐sterile (PGMS) rice. There are two photoperiodic reactions existing simultaneously in the growth and development of PGMS rice. The first photoperiodic reaction (FPR) accelerates or delays both panicle differentiation and heading and is common to all rice lines. The second photoperiodic reaction (SPR) is novel and determines whether pollen will be sterile or fertile. Results show that FPR can be affected by broad changes in photoperiod, light intensity, and temperature and is controlled by one to two pairs of genes. On the other hand, the SPR requires a more critically timed photoperiod, higher light intensity, and higher temperature than does FPR. The SPR is also controlled by one or two pairs of genes and is inherited independently of the genes that modify the FPR. Several lines of PGMS rice have been produced with Nongken58S as a donor parent. Five growth and development phases comprise the life cycle of PGMS rice. The effects of environment on PGMS rice described in this review may guide the practice of breeding and use of PGMS rice in a newly‐developed two‐line production system for hybrid rice.
Molecular Markers in Plant Improvement: Manipulation of Genes Affecting Quantitative Traits
Authors: Dudley J. W.
Published: July 2010

The use of molecular markers to enhance plant breeding efforts is being widely studied. A major area of research is the use of molecular markers to identify and manipulate chromosome segments QTL (quantitative trait locus or loci depending on context) controlling quantitative traits. The objective of this paper is to review the theory and results associated with the use of molecular markers to manipulate QTL in plant breeding programs. First, methods of identifying marker‐ QTL associations are considered. The various statistical methods used for this purpose are reviewed along with a discussion of appropriate probability levels to use in declaring associations real. The effects of genotype × environment interaction and repeatability between populations are then considered. Following the section on identification of associations, the use of marker‐QTL associations in breeding procedures is reviewed. A review of procedures useful for small numbers of QTL is followed by a review of procedures appropriate when large numbers of QTL are found. The use of marker‐QTL associations for multiple trait selection is considered. Throughout the review, appropriate theory is considered and results which have been obtained are presented.
Genotype‐by‐Environment Interactions of Barley in the Mediterranean Region
Authors: van Oosterom E. J. , Kleijn D. , Ceccarelli S. , Nachit M. M.
Published: July 2010

In the Mediterranean region, progress in selection for yield in harsh environments is hampered by large environmental variation between seasons and locations. This study analyzes the genotype‐by‐environment (GE) interaction of 36 two‐rowed genotypes of barley (Hordeum vulgare L.), grown in 14 environments in Syria and North Africa. It assesses the effect of growth type (winter or spring type) and heading date on the GE interaction and determines whether or not high‐yielding (HY) environments are representative of low‐yielding (LY) ones. Average grain yield per environment ranged from 7 to 513 g m−2. Genotypes and environments were classified by a cluster analysis and the interaction was analyzed with an additive main effects and multiplicative interaction model. Genotypes were classified into four clusters, related to their growth type and earliness of heading. Environments were clustered in a HY and LY group; this classification was related to seasonal rainfall and temperature. Medium‐early heading winter types had a positive interaction with LY environments and a negative interaction with HY environments, whereas late heading genotypes (spring and winter types) had the opposite interaction pattern. Early heading spring types had above‐average mean yields; the highest‐yielding among them tended to have a low interaction with environments. High‐yielding environments did not discriminate well between genotypes with high or low yields in LY environments, and may thus have limited value for yield selection for LY environments. For a breeding program aimed at improving yield in environments where favorable conditions are rare, selection for yield should be done in representative less‐favorable environments.
Inheritance of a Lipoxygenase‐1 Allozyme in Soybean
Authors: Pfeiffer T. W. , Hildebrand D. F. , Orf J. H.
Published: July 2010

Three soybean [Glycine max (L) Merr.] seed lipoxygenase isozymes, involved in generating products which contribute to undesirable flavors in processed protein products, have been characterized genetically. The objective of this study was to determine the inheritance of an alternate lipoxygenase‐1 allozyme, which has a more acidic isoelectric point than the normal allozyme (pI 5.79 vs. pI 5.85 for the normal allozyme). This alternate allozyme was originally seen in soybean strains L2‐3 and PI 86023, which are null for lipoxygenase‐2, genotype lx2 lx2. A similar alternate allozyme was subsequently seen in ‘McCall’. The 1:2:1 F2 segregation ratios from several crosses of “normal” allozyme × alternate allozyme parents indicated codominant inheritance of the two allozymes. The gene symbol Lxb1 is assigned to the allozyme with pI 5.79, and the gene symbol for the allozyme with pI 5.85 becomes Lxa1 This gives an allelic series at the lipoxygenase‐1 locus Lxa1, Lxb1, and lx1. The lx1 and lx2 loci are very tightly linked. Crosses between Lxa1 Lxa1 Lx2Lx2 and Lxb1 Lxb1 lx2lx2 genotypes would be designed to incorporate the lx2lx2 genotype into cultivars with improved protein flavor attributes for soyfood products. while phenotypes of Lx2Lx2 and lx2lx2 genotypes are indistinguishable in terms of lipoxygenase‐2, the presence of two electrophoretic bands for lipoxygenase‐1 (Lxa1 Lxb1) when the lipoxygenase‐2 locus is also heterozygous makes it possible to identify individuals with the recessive lx2 allele. The selection of heterozygotes can reduce the time needed to backcross the lx2 allele.
Inheritance of Adult Plant Resistance to Leaf Rust in Six Durum Wheat Cultivars
Authors: Zhang Hongtao , Knott D. R.
Published: July 2010

Leaf rust [Puccinia recondita Rob. ex Desm. f. Sp. tritici D.M. Henderson] was widespread in Canada and the USA in 1986 and some Canadian cultivars were less resistant than expected. Studies on the inheritance of leaf rust resistance were begun to provide information of use to durum wheat breeders. The inheritance of adult plant resistance to race 15 of leaf rust was investigated in six durum wheat (Triticum turgidum L. var. durum) cultivars, Lloyd, Medora, Pelissier, Quilafen, Stewart 63, and Wakooma, which had been previously shown to carry genes for seedling resistance. Each cultivar had been crossed and backcrossed to a susceptible line, RL6089. Four of the F2 populations and 29 or 30 F2 families from each of the six backcrosses were tested with race 15 in a field nursery. The results were compared with those for the same material tested at the seedling stage in a greenhouse. The combined data showed that each of the genes for seedling resistance was effective at the adult plant stage in the field. The segregation of the BC1F2 progenies indicated that Lloyd carries a dominant gene and Pelissier a recessive gene, that are effective only in adult plants. Thus, all of the seedling resistance genes are of potential value to durum wheat breeders and Lloyd and Pelissier carry additional genes for adult plant resistance that should also be useful.
Repeatability of Stability Estimators for Grain Yield in Wheat
Authors: Jalaluddin Md. , Harrison S. A.
Published: July 2010

Stability statistics that are used to explain genotypic response to environments are not useful to plant breeders unless they are repeatable across sets of environments. The purpose of this study was to examine the repeatability of the stability estimators: regression coefficient (b1), regression coefficient away from mean regression (|b1 − 1|), mean squares for deviation from regression (Sd2i), Shukla's stability variance (σ2i), variance of genotypic means (S2i), and genotypic coefficient of variation (CVi), in addition to coefficient of determination (r2i) and mean yield (X̄i). These statistics were calculated from three sets of yield data of the Louisiana Agricultural Experiment Station winter wheat (Triticum aestivum L.) performance trials grown in 36 environments. Repeatability was estimated by Spearman's rank‐correlation coefficient and Kendall's coefficient of concordance. The |bi — 1|, σ2i, and Sd2i were not repeatable between any two subsets of environments, and repeatability of S2i and r2i s were low. Among the stability estimators, only bi and CVi were repeatable across subsets of environments. The CVi was not a reliable statistic to describe genotypic stability because the rank order of CVi was induced by the rank order of X̄.i Mean yield was the most repeatable genotypic character. Gain in selection for yield stability can be expected from the combined use of bi and X̄i. If data do not fit the linear regression model, then low values of S2i (Type 1) or Type‐4‐variance (variance of genotypic means across unpredictable environments averaged across predictable environments) may be used as an alternative criterion for yield stability.
Inheritance of Resistance to Hessian Fly in Rye and in Wheat‐Rye Translocation Lines
Authors: Hatchett J. H. , Sears R. G. , Cox T. S.
Published: July 2010

Rye, Secale cereale L., is an important genetic resource for resistance to Hessian fly, Mayetiola destructor (Say). Resistance genes have been transferred from ‘Chaupon’ rye chromosome arm 2RL and ‘Balbo’ rye chromosome arm 6RL to common wheat (Triticum aestivum L.) via wheat‐rye chromosomal translocations. Our objectives were to determine (i) the number of resistance genes in Chaupon and Balbo and their allelic relationships, and (ii) the mode of inheritance of resistance in the wheat‐rye translocation lines. Several crosses were tested in a greenhouse for reaction to Biotype L of Hessian fly. Analyses of F2 populations showed that Chaupon and Balbo each segregated for two independent dominant genes exhibiting duplicate epistasis. All genes conditioned antibiosis to first‐instar larvae. One of the genes in Chaupon expressed a chlorotic lesion reaction in response to larval feeding and was different from the genes in Balbo. When this gene occurred together with genes that did not cause expression of chlorotic lesions, F2 plants segregated in modified ratios of 12 resistant plants without lesions: 3 resistant plants with lesions: 1 susceptible plant. Crosses of T2BS.2RL translocation line with susceptible wheat ‘Karl’ showed that resistance from Chaupon chromosome arm 2RL was inherited as a single dominant factor and that 2RL carries the gene that expresses chlorotic lesions. Crosses of Ti4AS‐4AL‐6RL‐4AL translocation lines with susceptible wheat ‘TAM106’ showed that resistance from the Balbo 6RL segment was inherited as a single dominant factor. These results demonstrate that the wheat‐rye translocations can be utilized efficiently for incorporating Hessian fly resistance into wheat.
Recurrent Selection for Test Weight and Grain Yield of Oat
Authors: Klein S. J. , Smith M. A. , Frey K. J.
Published: July 2010

Continued advances in oat (Avena sativa L.) breeding rely in part on the improvement of test weight and grain yield while maintaining genetic variability. The objective of this study was to determine the efficacy of three cycles of recurrent selection for high test weight (HT population) or Smith‐Hazel index of test weight and grain yield (HTG population) in oat. The recurrent selection procedure consisted of intermating selected S0:1 lines, growing the S0 seeds to produce S0:1 lines, and field evaluating the S0:1 lines. Each cycle took 1 yr to complete and about 300 lines were evaluated in each population of each cycle. Twenty S0:1 lines were selected from each population to initiate the next cycle. Response to selection in a population was evaluated by testing 95 S0:1 lines randomly chosen from among Cycles 0, 1, and 2, the complete Cycle 3 population, parents from all cycles, and a set of check cultivars. There were significant (P < 0.05) increases in mean test weight of 17.8 ± 3.5 kg m−3 and 6.9 ± 1.5 kg m−3 per cycle in the HT and HTG populations, respectively. For grain yield, there was a significant decrease of 0.11 ± 0.03 Mg ha−1 per cycle in HT populations, and an increase of 0.12 ± 0.07 Mg ha−1 per cycle in HTG populations. Broad‐sense heritabilities and genotypic variances remained high in all cycles of each population. The results of this study show that recurrent selection in oat is an effective breeding procedure for improving test weight and grain yield without significant reductions in genetic variability.
Soybean Yield Component Responses to a Light Interception Gradient during the Reproductive Period
Authors: Board J. E. , Harville B. G.
Published: July 2010

The yield‐enhancing effect of increased light interception (LI) narrow row/late‐planted soybean [Glycine max (L.) Merr.] culture could be better understood if LI effects on the reproductive period [first flower (R1) through physiological maturity (R7)] were clarified. The primary objective was to determine yield and yield component responses to a LI gradient during R1 to R7. Field studies were conducted during 1989 and 1990 at a late planting with ‘Centennial’ determinate soybean using 50‐cm row spacing. The test was conducted at Baton Rouge, LA, on a Mhoon silty clay soil (fine.silty, mixed, nonacid, thermic Typic Fluvaquent). Treatments were a control (no defoliation) and four partial defoliation treatments that consisted of keeping the area 12.5 cm to both sides of the interrow midline (i.e., 50% of the interrow area) free of leaf blade material until pod initiation (R3), pod elongation (R4), start of seed filling (R5), or mid‐seed filling (R6.5). These treatments resulted in a LI gradient during R1 to R7, without affecting node production or leaf area index (LAI) and total dry matter (TDM) by R1. In response to reduced LI, pods per reproductive node and pod number (both formed during R3‐R5) declined. Similar source/sink ratios [crop growth rate (CGR) at R5 ÷ pod number] at seed initiation were maintained across all treatments. Thus seed per pod and seed size (formed during R5–R7) were unaffected. In conclusion, in cases such as narrow rows where LI is increased throughout the reproductive period, the determining effect on yield occurs during R1 through R5. Results also indicated that the relationship between seed number and LI (during R1–R7) occurs through adjustments in pod number.