bluuebunny/crossref_metadata_2025 huggingface dataset:
New Sources of Resistance to Greenbug, Biotype I, in Sorghum
Authors: Andrews David J. , Bramel‐Cox Paula J. , Wilde Gerald E.
Published: July 2010

The greenbug [Schizaphis graminum (Rondani)] has been a major pest of sorghum [Sorghum bicolor (L.) Moench] since 1968, and several biotypes have evolved. Except for PI 266965 [S. halapense (L.) Pets., a tetraploid] and Cargill hybrid 607E, all previously reported sources of resistance to the widespread Biotype E are susceptible to Biotype I, a new biotype first reported in Kansas in 1990. Greenbug is a serious pest in Russia. To determine whether Russian sorghum contains resistance to Biotype I, 110 germplasm accessions obtained from Krasnodar Province in the fall of 1991 were assessed for their reaction to Biotype I greenbug. In two replicated growth chamber tests using individually caged plants, 10 accessions (3 grain sorghum and 7 sudangrass types) showed significantly higher (P = 0.05) levels of resistance than did the susceptible check when rated 13 to 14 d after infestation. The accession showing greatest resistance, PI 550610, a durra grain type originally from Syria, showed a level of resistance equal to that of the resistant hybrid check.
Variation in Water‐Use Efficiency and Its Components in Wheat: I. Well‐Watered Pot Experiment
Authors: Ehdaie Bahman , Waines J. Giles
Published: July 2010

Genetic variation exists for season‐long water‐use efficiency (WUE) among bread wheat (Triticum aestivum L.) cultivars. To facilitate the study of such variation, we define WUE and its components so that the contribution of each component trait to variation in WUE can be evaluated. Seven diverse bread wheat cultivars were grown in replicated glasshouse pot experiments under well‐watered conditions. Significant genotypic variation was observed for WUE (ratio of grain yield to water used), evapotranspiration efficiency (ETE, ratio of total dry matter to water used), and harvest index (HI, ratio of grain yield to total dry matter). Old tall cultivars, on average, had relatively higher ETE (3.95 vs. 2.67 g kg−1), but much lower HI (0.35 vs. 0.53) than modern semidwarf and dwarf cultivars. Cultivars with similar WUE showed different patterns of component traits. Evapotranspiration efficiency, and HI accounted for 59%, and 41%, respectively, of the genotypic variation in WUE. A path coefficient analysis revealed that ETE had a higher direct effect on WUE than did HI. However, their positive direct effects were counterbalanced by negative indirect effects via each other, because ETE and HI were negatively correlated. Carbon isotope discrimination showed a negative correlation with WUE (−0.62) and ETE (−0.84), but a positive correlation with HI (0.43). Days from planting to maturity, plant height, root dry matter, and shoot dry matter each had a positive correlation coefficient with ETE, but a negative correlation with HI.
Simplified Sample Preparation for HPLC Analysis of Ergovaline in Tall Fescue
Authors: Hill Nicholas S. , Rottinghaus George E. , Agee Christopher S. , Schultz Linda M.
Published: July 2010

Increased interest in the endophytic fungus, Acremonium coenophialum Morgan‐Jones & Gams, and its symbiotic inhabitance of tall fescue, Festuca arundinacea Schreb., has created the need for rapid and reliable ergovaline analysis in research and in extension service (for diagnosis). A simplified sample preparation method provides faster and more reproducible results for ergovaline quanitation in tall fescue. The method involves extraction with alkaline chloroform, purification with a silica gel solid‐phase chromatography column, and direct ergovaline analysis of methanol eluants by high performance liquid chromatography (HPLC) with fluorescence detection. When compared with a previous method specific for tall fescue vegetative tissue, the simplified method reduced variability and increased recoveries of internal standard from 83 to 94% and of ergovaline from 82 to 93%. This method when used with automated HPLC equipment, permits analysis of 60 to 80 samples per day. Twenty tall fescue samples were analyzed by two separate laboratories using the simplified method; ergovaline results from each were regressed against the other. Ninety‐seven percent of the variability from one laboratory could be accounted for by analysis of the samples by the other, suggesting that the simplified method is highly reproducible.
Generation of Haploids in Maize: A Modification of the Indeterminate Gametophyte (ig) System
Authors: Kindiger Bryan , Hamann S.
Published: July 2010

Haploids in maize, Zea mays L., are relatively infrequent, but have continually been considered potential tools for the development of fixed inbred lines or as vehicles of cytoplasmic transfer. This study was undertaken to develop an efficient method for the production of androgenetic haploids in maize. A novel modification of the indeterminate gametophyte (ig) system was developed and the resulting frequency of androgenetic haploids investigated. The method combines the traditional genetic behavior of the ig allele with a tertiary trisomic (3 3 B‐‐3Ld) stock in modified W23 background. Maintenance and generation of ig homozygotes are greatly simplified. The frequency of haploid generation has been elevated to as high as 8% utilizing inbreds of Lancaster heritage. The C, S, SD, Vg, ME, MY, CA, L, and Q cytoplasmic male‐sterile stocks, homozygous for ig and of similar background to the tertiary trisomic stock, are also discussed. Development of a 3(ig) 3(ig) B‐3Ld(Ig) tertiary trisomic stock in an improved modified W23 background should simplify the production of androgenetic haploids and facilitate the exchange of male‐sterile cytoplasm into inbred lines of maize. This stock has potential use in experiments involving wide hybridizations between maize, teosinte [Zea mays subsp, mexicana (Schrader) Iltis], and eastern gamagrass [Tripsacum dactyloides (L.) L.]
Distribution and Analysis of Isozyme Polymorphism in North American Cultivated Oat Germplasm
Authors: Phillips Timothy D. , Murphy J. Paul
Published: July 2010

This study was conducted to analyze the extent and distribution of isozymic variation among 405 accessions of fall‐ and spring‐sown North American oat (Avena sativa L. and A. byzantina K. Koch) cultivars, introductions, and germplasm releases. Each accession was screened for variation at 29 enzyme zones. An initial classification of cultivars was based upon date of introduction or release, and by fall vs. spring season of production. Spring and fall germplasm pools were separated on the basis of frequency differences for isozyme genotypes present in both germplasms rather than genotypes unique to either pool. Fall germplasm appeared more genetically diverse due to its greater numbers and percentage of genotypes present at intermediate frequencies. A second analysis based upon Jaccard's distances between all pairwise combinations of the 405 accessions revealed 16 clusters containing nine or more accessions. Nine clusters were predominantly spring germplasm, four were predominantly fall germplasm, and three were comprised of a mixture of both. Thus, a continuum in cluster composition was observed when no a priori categorization of cultivars by season of production was imposed. Nine spring, fall, and mixed germplasm clusters containing many spring and fall introductions and cultivars of the pre‐1940 era grouped in the center of a three‐dimensional principal component plot. Post‐1940 spring accessions formed two clusters on either side of this older germplasm. Based upon isozymic diversity, the fall‐ and spring‐sown North American germplasm pools probably represent different ecotypes of a single species.
Cotton Boll Retention and Its Relationship to Lint Yield
Authors: Heitholt James J.
Published: July 2010

Fruit retention helps determine cotton (Gossypium hirsutum L.) yield. Study objectives were to (i) characterize genotypic variation in whole‐plant boll retention percentage, (ii) determine the relationship between retention and lint yield, and (iii) characterize timing, stage, and frequency of fruiting‐form abscission over two seasons in eight field‐grown genotypes: normal‐, sub okra., okra‐, and super okra‐leaf isolines of MD 65‐11 and four commonly grown higher‐yielding cultivars. Flower production was higher in okra‐ (238 m−2) and super okra‐leaf (323 m−2) than in normal (160 m−2) and sub okra.leaf (164 m−2) isolines, but boll retention was lower in okra‐ (29%) and super okra‐leaf (21%) than in the normal‐ (42%) and sub okra‐leaf (45%), so lint yields did not differ significantly among isolines. The cultivars averaged 16% more flowers, 33% more bolls, and 37% higher lint yield than normal‐leaf MD 65‐11, but lint yield correlated with boll retention (r = 0.84*; P < 0.05) when super okra‐ and okra‐leaf types were excluded. Genotypes differed slightly in distribution of mature bolls on mainstem nodes and on sympodial branch positions. Deltapine 90 produced fewer bolls (73%) on lower mainstem nodes (8–20) than the other genotypes (86–92%), reflecting its full‐season fruiting habit. Distribution of open bolls on sympodial fruiting positions differed between normal‐leaf (98% at Positions 1 and 2) and super okra‐leaf MD 65‐11 (88%). The other genotypes produced 94 to 96% of their bolls at Positions 1 and 2, which differs significantly from both extremes. When seven of these genotypes and three others were grown in the greenhouse and observed for development of squares and bolls, the normal‐leaf types shed more small squares (bract width >2 cm) but fewer bolls than did the okra‐ and super okra‐leaf types.
Maize Productivity as Influenced by Form and Availability of Nitrogen
Authors: Gentry Lowell E. , Below Fred E.
Published: July 2010

Although N, especially mixtures of NO3 and NH4, can increase the productivity of maize (Zea mays L.), it is unclear when this N needs to be available for maximum benefit. This study was conducted to determine the importance of preanthesis N form and the need for available postanthesis N on the productivity of maize. Four single‐cross hybrids (B73 × LH51, LH74 × LH51, LH74 × LH82, and LHE136 × LH82) were grown in field‐hydroponics and supplied N as either all NO3 or an equal mixture of NO3 and NH4 (mixed N nutrition) until anthesis, whereupon N was withdrawn from one‐half of the plants. At physiological maturity, whole shoots were harvested, separated into component fractions, weighed, and analyzed for yield, yield components, and macronutrient composition. Compared with all NO3, mixed N nutrition increased grain yield of all hybrids whether the N was available full season (average of 11%) or only during vegetative growth (average of 10%). In contrast, regardless of the N form, N deprivation during grain fill decreased grain yield for three of the four hybrids (range of 6 to 19%) but increased yield (5%) for LHE136 × LH82. Changes in sink‐source partitioning, kernel number, and plant N accumulation were closely related to both yield enhancement associated with mixed N nutrition, and yield reduction due to N removal. Therefore, these data show that N form, timing of N availability and genotype are all factors that interact to influence N use and productivity of maize.
Host‐Specific Pathogens Do Not Account for the Corn‐Soybean Rotation Effect
Authors: Whiting Kelly R. , Crookston R. Kent
Published: July 2010

Soybean [Glycine max (L.) Merr.] generally yields more when rotated with another crop rather than grown continuously. The specific reasons for this yield response are unknown. The objective of this study was to investigate the extent to which a soybean‐corn (Zea mays L.) rotation limited the buildup of host‐specific pathogens of soybean, and to evaluate whether plant diseases were involved in the rotation effect. Incidence and severity of seven diseases and seed yield were recorded at two locations in the field in 1987 and 1988 for soybean maintained in four cropping sequences ranging from annual alternation with corn to 1,2, or 5 yr of continuous cropping. Brown stem rot (BSR) caused by the fungus Phialophora gregata (Allington & D.W. Chamberlain) W. Gains was found to be the most prevalent disease during both years and at both locations. Rhizoctonia root rot (Rhizoctonia solani Kühn) and stem canker (Diaporthe phaseolorum Cooke. & Ellis Sacc. var. Cavlivora Athow & Caldwell) were noted in 1987 at both locations among <5% of all plants monitored. The BSR‐prevalence ratings were relatively high (mean 60%) for Hodgson 78, a susceptible cultivar, and relatively low (mean 22%) for BSR101, a resistant cultivar. Seed yield data from the various cropping sequences for the two cultivars indicated no clear relationship between BSR severity and seed yield. In 1987, rotation with corn resulted in a yield benefit to both cultivars. In 1988, both yield and development of BSR were adversely affected by drought. A comparison of the seed yield of severely infected and uninfected plants within cropping sequence indicated that BSR had a minimal effect on soybean yield in 1988. Therefore, within the conditions of this study, the yield benefit to soybean from rotation with corn did not appear to be due to the reduced incidence of plant diseases.
Using Near Infrared Reflectance Product Library Files to Improve Prediction Accuracy and Reduce Calibration Costs
Authors: Shenk John S. , Fales Steven L. , Westerhaus Mark O.
Published: July 2010

Deriving a near infrared reflectance spectroscopy (MRS) calibration for new samples is an expensive and time‐consuming process. Often a laboratory analyzing samples with NIRS will receive new samples that are spectrally different from the library samples for that product. This study was performed to develop a method to: (i) identify previously analyzed samples in a product library that best match the spectra of the new samples for a local calibration, (ii) compare the prediction accuracy of the broad product library calibration to the local calibration, and (iii) if necessary, expand the local calibrations with a few of the new samples when greater prediction accuracy is required. Three groups of new samples were obtained for the study. They were 68 hay samples, 106 grass samples, and 110 whole‐plant corn (Zea mays L.) samples. Every third sample was reserved for validation. A product library file of 2176 hay, haylage, and fresh forage spectra supplied the product calibration and similar spectra for the hay and grass samples, and a corn silage product library file of 309 spectra supplied the product calibration and similar spectra for the whole‐plant corn samples. The spectra in the library most similar to the new samples were identified and selected with a new program, MATCH. Local calibrations were developed from these selected samples. Calibration accuracy was tested with the new samples reserved for validation using equations developed from the product library. In 7 of the 12 comparisons, the local calibrations were more accurate than the broad‐product library calibrations, but only two of these calibrations were acceptable. By expanding the local calibrations with 10 samples of each new group and recalibrating, accuracy of the expanded calibrations was similar to the accuracy of custom calibrations derived from the new samples not reserved for validation. Only 30 samples out of 284 needed new reference values to obtain acceptable prediction accuracy. This would have resulted in a cost reduction of 89% in reference value analysis. Guidelines for using this procedure are presented.
Recurrent Selection for Plant Regeneration from Red Clover Tissue Culture
Authors: Quesenberry Kenneth H. , Smith Richard R.
Published: July 2010

Methods for plant genetic transformation generally require that single transformed cells can be regenerated in to whole plants. Plant development from callus tissue culture has been shown to be under genetic control in various species. This study was conducted to determine the variability for this trait and to select for increased frequency of regeneration in red clover (Trifolium pratense L.). Five cycles of recurrent phenotypic selection (one cycle per year) for increased plant regeneration via somatic embryogenesis from callus tissue culture were carried out beginning with a base population from the cultivar Arlington. Progeny were evaluated on a half‐sib family basis for estimation of narrow sense heritability. A three‐step tissue culture protocol (callus induction, embryo induction, and plant development) based on Gamborg's B5 basal salts, NAA and 2,4‐D (2,4‐dichlorophenoxyacetic acid) as auxins, and kinetin and adenine as cytokinins was utilized. Explant source was petiole sections. Percentage regenerating plants in the base population, recurrent phenotypic selection cycle 1 (RPS1), RPS2, RPS3, RPS4, and RPS5 was 4, 9, 16, 20, 41, and 72%. A cycle of genotypic selection (progeny testing) was more efficient increasing regeneration frequency on a per cycle basis but less efficient on a per year basis since 2 yrs were required to complete a cycle of genotypic selection. Number of regenerating plants per petiole explant was >200 for selected RPS5 individuals compared with <10 in base population individuals. Narrow sense heritability estimates ranged from 40 to 50%. These results show that plant regeneration from callus tissue of red clover is a highly heritable trait. The population developed in this research should be immediately useful for genetic transformation of red clover.
Linkage between the Rpg1 Gene for Stem Rust Resistance and the f5 Locus on Barley Chromosome 1
Authors: Jin Yue , Steffenson Brian J. , Franckowiak Jerome D.
Published: July 2010

Linkage studies can expedite the transfer of agronomically important genes in breeding programs. A study was conducted to determine the linkage relationship between loci segregating for stem rust (Puccinia graminis Pers.:Pers. f. sp. tritici Eriks. & E. Henn.) resistance (Rpg1) and a chlorina mutant (f5), and to confirm the linkage among Rpg1, br1 (brachytic) and fc (chlorina seedling). ‘Bowman’ barley (Hordeum vulgare L.) was crossed to genetic stocks possessing br1, fc, and f5, respectively. Estimates of linkage distances were 9.6 ± 1.4% between Rpg1 and br1, 13.6 ± 1.8% between Rpg1 and fc, and 25.9 ± 2.6% between Rpg1 and f5. The linkage between Rpg1 and f5 was established.
Quantification of Tannis in Birdsfoot Trefoil Germplasm
Authors: Roberts C. A. , Beuselinck P. R. , Ellersieck M. R. , Davis D. K. , McGraw R. L.
Published: July 2010

Condensed tannins in birdsfoot trefoil (Lotus corniculatus L.) have been detected, but not quantified extensively. The objective of this study was quantitative analysis of tannins in birdsfoot trefoil germplasm. Diverse accessions were evaluated at two locations and on three harvest dates, and their tissues were analyzed by near infrared reflectance spectroscopy (NIRS), an accurate and efficient procedure increasingly used in quantitative germplasm evaluation. Ninety‐seven diverse accessions of L. corniculatus were obtained from the USDA Northeast Regional Plant Introduction Station at Geneva, N.Y. Seedlings were transplanted to fields near Columbia and Mt. Vernon, MO. Herbage regrowth was harvested three times at 30‐d intervals, lyophilized, and analyzed for total condensed tannins. Treatments were arranged in a split‐plot design at two locations with accessions as main plots and harvest dates as sub‐plots. Treatment combinations were replicated three times. Accessions were clustered according to the single variable, tannin concentration, by the Scott‐Knott non‐overlapping means separation technique. Performance mean and standard error of NIRS equations were 51.0 and 11.0 g catechin equivalents (CE) kg−1 dry matter (DM), respectively; NIRS squared correlation coefficients exceeded 0.90. Condensed tannins different (P < 0.01) among accessions and harvest dates, and an accession × harvest date interaction occurred P < 0.01). concentrations ranged from 0 to 132 g CE kg−1 DM, but 75% of the accessions contained less than 40 g CE kg−1 DM. For accessions appearing in the highest clusters, tannins decreased 40% at Columbia and 27% at Mt. Vernon from July to September. Accessions from Ethiopia contained an average of 100 g CE kg−1 DM and usually appeared in the highest clusters.
Heterosis and Combining Ability among African Pearl Millet Landraces
Authors: Ouendeba B. , Ejeta G. , Nyquist W. E. , Hanna W. W. , Kumar A.
Published: July 2010

Breeding procedures used in pearl millet [Pennisetum glaucum (L.) R. Br.] improvement in India and the USA are aimed at exploitation of hybrid vigor for both grain and forage yields. Selection efforts in Africa have been limited to intrapopulation improvement for grain yield. Knowledge of heterotic patterns and combining ability of the widely cultivated African landraces would be useful in the development of a sound breeding program in Africa. The objectives of this study were to evaluate the combining ability and heterosis among African pearl millet populations and to explore the utility of inter‐population improvement for the development of high yielding varieties and hybrids. Five populations and their 10 interpopulation crosses were evaluated in a randomized complete‐block design with six replications at two locations in Niger during the 1989 and 1990 rainy seasons. Plant height, flowering time, natural incidence of downy mildew, spike length, grain yield, and 1000‐seed weight were measured in different populations. Significant differences among entries for most of the traits were observed. Better‐parent heterosis for grain yield ranged from 25 (Iniari × Ugandi) to 81% (Mansori × Ex.Bornu). Six of the crosses showed significant heterosis and gave 36 to 81% more grain yield than their better parent. All crosses except one were significantly more tolerant to downy mildew than their better parent. Mean squares for general combining ability were significant (P < 0.05) for most traits indicating the importance of additive gene effects for these traits. The large heterotic effects and the magnitude of the additive effects observed in the experiment should be useful in choosing pearl millet landraces for intercrossing in the development of cultivars with improved grain yield.
Drought Stress and Irrigation Effects on Germination of Harvested Soybean Seed
Authors: Heatherly Larry G.
Published: July 2010

Drought stress consistently reduces soybean [Glycine max (L.) Merr.] yield, while irrigation increases yields above nonirrigated levels in the southern USA in most years. Little information is available regarding drought stress and irrigation effects on quality of harvested soybean seed in this region, however. Field experiments using Maturity Group (MG) IV, V, and VI soybean cultivars were conducted in 1990 and 1991 at Stoneville, MS, to evaluate effects of drought and irrigation during reproductive development on subsequent germination of harvested seed. Treatments included a nonirrigated (NI) control and furrow irrigation (I) applied at various times during the reproductive period (R1–R6) in four different experiments. All experiments were grown on Sharkey clay (very‐fine, montmorillonitic, nonacid, thermic Vertic Haplaquept), a major soil in the alluvial plain of the lower Mississippi River Valley. Irrigation significantly increased seed yield and number of seed from all cultivars in all experiments. Effect of irrigation on weight per seed was none or small relative to effects on seed yield and number of seed. Drought stress resulted in significantly inferior quality (standard germination < 80%) seed from all cultivars in all experiments. Irrigation initiated during flowering and continued into the seed‐fill period significantly increased standard germination of seed from all experiments. Irrigation during the full reproductive period was required to realize both maximum seed yield and maximum germination of harvested seed. The results show that drought stress can result in reduced germination of harvested soybean seed, and that irrigation can be used to overcome this effect.
Soybean Radiation‐Use Efficiency as Influenced by Nonuniform Specific Leaf Nitrogen Distribution and Diffuse Radiation
Authors: Sinclair Thomas R. , Shiraiwa Tatsuhiko
Published: July 2010

Radiation‐use efficiency (RUE) has proven to be an effective expression of the biomass accumulation capacity of crop canopies. Two factors that may influence RUE, however, are the N distribution among leaves in the canopy and the fraction of the diffuse component in the incident radiation. Radiation‐use efficiency was measured for soybean [Glycine max (L.) Merr.] grown at Gainesville, FL, and Shiga, Japan, to examine the potential influence of these two factors on RUE. Radiation‐use efficiency was found to be substantially greater for soybean grown in Japan as compared with Florida. It was hypothesized that a greater fraction of incident diffuse radiation in Japan could explain much of the difference in RUE between the locations. In addition, a nonuniform specific leaf N distribution (SLN, g N m−2) was shown theoretically to enhance RUE. A comparison is presented between the experimental observations of RUE, and the RUE obtained by accounting for the nonuniform SLN distribution in soybean canopies and for hypothetical differences between locations in the diffuse radiation component.
Use of Radiation to Transfer Alien Chromosome Segments to Wheat
Authors: Sears E. R. , Gustafson J. P.
Published: July 2010

Ionizing radiation can accomplish the transfer of genetic information from species so distantly related to wheat (Triticum aestivum L. em Thell.) that their chromosomes pair very little, if at all, with those of wheat, even in the absence of the homoeologous‐pairing suppressor Ph1. In a successful transfer, the alien segment must almost always replace a homoeologous wheat segment, but radiation induces translocations largely at random; therefore automatic selection in favor of desirable translocations must be provided if the size of the project is to be kept within reasonable limits. Pollen selection will occur if seeds or plants monosomic for both an alien chromosome and one of its wheat homoeologues are irradiated. Making the plants also deficient for Ph1 may increase the number of suitable transfers. High‐frequency occurrence of the desired alien character in M2 head‐rows from plants grown from irradiated seed can identify favorable transfers with little cytological work. Irradiation of plants shortly before meiosis, using them to pollinate ditelosomics or double ditelosomics for the wheat arm or chromosome concerned, and cytologically examining offspring which have the alien character can not only identify the desirable transfers, but also reveal the lengths of the alien segments involved.
An International Initiative in Biotechnology: Priorities, Values, and Implementation of an A.I.D. Project
Authors: Cohen Joel I.
Published: July 2010

Biotechnology is a recent addition to international crop improvement. for its contribution to be effective, it must be fully integrated with conventional agricultural research. Based on recommendations contained in a National Research Council (NRC) report, the Agency for International Development (A.I.D.), in collaboration with the International Agricultural Research Centers (lARCs) and National Agricultural Research Systems (NARS), prioritized biotechnology research relevant to agricultural problems of the developing world and identified those suitable for mutually beneficial research. A new plant biotechnology project was designed, awarded, and implemented to address these priorities while complementing other international programs. The Agricultural Biotechnology for Sustainable Productivity (ABSP) project supports separate public and commercially oriented research efforts by providing multiple routes for the development and release of germplasm. These efforts are implemented through collaborative research agreements which include support for regulatory review, field testing, and legal/contractual agreements for protection of intellectual property rights (IPR). Efforts to determine the research priorities, innovative modalities for collaborative agreements, and value decisions on which these are based are reviewed as an example of ongoing international biotechnology initiatives.
Response to Selection for Tolerance to Acid Soils in a Tropical Maize Population
Authors: Cranados G. , Pandey S. , Ceballos H.
Published: July 2010

Soil acidity reduces maize (Zea mays L.) yields on about eight million hectares in developing countries. We report on response to selection for tolerance to soil acidity, using an altered version of modified ear‐to‐row (MER) and full‐sib (FS) selection. In the MER selection, 120 half‐sib (HS) families were evaluated under 45 and 80% AI saturation. One to three ears from each of the best 30% of the families were selected each cycle. After 16 cycles of MER selection, FS selection was initiated. Two hundred and fifty FS families were evaluated at five to six acid (ASEs) and one normal soil environments (NSE) the best 25% were selected each cycle. Cycles 2, 4, 6, 8, 10, 12, and 14 of MER and 0, 1, and 2 of FS selection were evaluated in three to nine replications at six ASEs and five NSEs during 1990–1991. Across the 11 environments, gain from selection in yield averaged 40 kg ha−1 cycle−1 (1.49**%) with MER and 250 kg ha−1 cycle−1v (8.10*%) with FS selection. Across the six ASEs, yield improvements of 40 kg ha−1 cycle−1 (1.99**%) with MER and 310 kg ha−1 cycle−1 (13.96**%) with FS selection were obtained. Yield also improved across the five NSEs by 50 kg ha−1 cycle−1 (1.10**%) with MER and 150 kg ha−1 cycle−1 (3.31%) with FS selection. Results indicate that tolerance to soil acidity can be improved with recurrent selection and that the progress will be higher with a system more efficient at reducing the experimental error and genotype ✕ environment interaction.
Rootworm Feeding Tolerance in Single‐Cross Maize Hybrids from Different Eras
Authors: Riedell Walter E. , Evenson Paul D.
Published: July 2010

Insect‐tolerant plants provide farmers with alternatives to insecticide use for limiting crop losses. This study was conducted to evaluate western corn rootworm (Diabrotica virgifera virgifera LeConte) larval feeding tolerance of single‐cross maize (Zea mays L.) hybrids representing three successive 10‐yr eras. A 2‐yr study was conducted as a split‐split plot with plant density (37, 50, or 74 thousand kernels ha−1) as main plot treatments, rootworm infestation level (0, 2200, or 6600 eggs m−1 of row) as subplot treatments, and plant genotype (11 genotypes from the 1980, 1970, and 1960 eras) as sub‐subplot treatments. There was no significant interaction between genotype and infestation level for root damage ratings, suggesting that genotypes used in our study did not exhibit antibiosis to rootworm larvae. Vertical root pull resistance values for 1980‐ and 1970‐era genotypes were significantly greater than those seen for 1960‐era genotypes. At the low plant density, the lodging percentage of all genotypes gradually became greater in response to increased rootworm infestation level. At higher plant densities, however, the 1960‐era genotypes suffered significantly more lodging than the 1970‐ and 1980‐era genotypes in the presence of moderate rootworm damage. Our results suggest that large root system size and decreased plant lodging are the rootwormtolerance traits present in 1980 maize genotypes. Even with this level of tolerance in 1980‐era hybrids, however, substantial grain yield loss occurred when plants sustained moderate to heavy rootworm larval damage when these genotypes were grown at low and moderate plant densities.
Reaction of Twenty Cultivars of Tall Fescue to Stem Rust in Controlled and Field Environments
Authors: Welty R. E. , Barker R. E.
Published: July 2010

Stem rust, caused by Puccinia graminis Pers.:Pers. subsp, graminicola Z. Urban, is a serious disease of tall rescue (Festuca arundinacea Schreb.). Reliance on field evaluation of resistance ran be unreliable when climatic factors do not favor disease development. The objective of this study was to develop an effective controlled‐environment screening procedure for stem rust resistance and to compare response to disease in controlled environments with disease responses in the field. Twenty cultivars of tall rescue were used to evaluate the infection responses to stem rust in 5‐ and 10‐wk‐old seedlings in controlled conditions and disease severity on the same plants grown in the field during three consecutive years. Although there was a significant difference (P = 0.001) among cultivars for both 5‐ and 10‐wk‐old plants for stem rust infection types, all cultivars were rated susceptible. Some cultivars (e.g., Mesa, KY31‐F, and Arid) had smaller average infection types (AIT) and more stem rust resistant plants within a cultivar. Stem rust severity differed significantly among cultivars on each date of assessment in 1990, 1991, and 1992. Conditions were favorable for stem rust development in 1990 and 1992. In 1991, stem rust was slow to develop with 74% of the plants remaining rust free. When individual plant responses were compared at 5‐wk, 10‐wk, and on the final assessment date in the field (29 May 1992), 81.1% retained the same rating for resistant or susceptible as young plants and field plants, 15.8% were rated susceptible as young plants and resistant in the field, and 3.1% had mixed responses for resistance or susceptibility. A reliable glasshouse/field screening program was developed enabling rapid progress in producing stem rust resistant cultivars of tall rescue.
Heterosis among Insect‐Resistant Maize Populations
Authors: Widstrom N. W. , Bondari K. , McMillian W. W.
Published: July 2010

Information on heterosis is critical to assimilation of desirable traits into usable maize, Zea mays L., germplasm. Our objective was to identify maize populations with heterosis for desirable traits. Twelve southern‐adapted maize populations with resistance to damage by ear and leaf‐feeding insects and all 66 possible population crosses were evaluated in a randomized complete‐block design in three environments. Population effects, heterosis, and specific combining ability (SCA) effects were estimated for seven plant traits. Population effects were significant (P ≤ 0.01) for all traits except yield, heterosis effects were significant for all traits, and SCA effects were significant for all traits except insect damage. Population and average heterosis effects were less important amongenetic effects than SCA, which accounted for more than one‐half the heterosis sums of squares for all traits. Population performance as a predictor of relative crossbred performance was least effective for grain yield and quality. Average heterosis, relative to midparent values, varied from 2.2% for lodging to 22.$% for yield. Crosses existed with SCA effects for resistance to one or more insects for all traits. Genotype × environment interactions were significant for all traits except insect damage. Heterosis interactions with environment accounted for more variation than population × environment interactions. Among beterosis interactions with environments, those due to average heterosis and SCA effects were of greatest significance. The information will be useful in the development of germplasm with resistance to insects and improved agronomic performance.
Genes for Resistance to Russian Wheat Aphid in PI294994 Wheat
Authors: Elsidaig Ahmed A. , Zwer Pamela K.
Published: July 2010

Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is major economic pest of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in several western U.S. states. Genetic resistance is an effective strategy for protecting the wheat crop from RWA while minimizing the use of pesticides. The study was conducted to determine the number of genes conferring resistance in the seedling and adult growth stages in the wheat line PI294994 and to establish whether greenhouse and field resistances were related. The resistant line PI294994 was crossed with the club wheat cultivars Morn and Hyak. F2 and F3 seedlings and F2 adult plants from the two crosses were artificially infested with RWA and evaluated for their reactions in the greenhouse and field, respectively. Seedling and adult plant reactions indicated that the resistance in the line PI294994 is controlled by two genes. Resistance is conferred by a dominant allele at one locus and by a homozygous recessive allele at the second locus. PI294994 is an effective source of genetic resistance in the field to RWA in the Pacific Northwest.
Indirect Selection for Grain Yield of Barley in Harsh Mediterranean Environments
Authors: van Oosterom E. J. , Ceccarelli S.
Published: July 2010

Selection for yield of barley (Hordeum vulgare L.) in unfavorable Mediterranean environments will be more efficient if plant traits can be identified that are related to yield under stress. The aim of this study was to assess whether, in fall‐sown barley, plant traits measuredin favorable environments can be used as criteria for indirect selection for grain yield in unfavorable environments. Thirty‐six two‐row barley genotypes were grown in 15 Mediterranean environments. The plant traits measured were plant ideotype in winter (WPI, a principal component of winter growth habit, winter plant color, and cold tolerance) and heading date. Values were averaged across three favorable environments. Winter type barley had high values for WPI; spring type barley had low values. Grain yield under favorable and unfavorable conditions was represented by average standardized yields in six high‐yielding (HY) and five low‐yielding (LY) environments, respectively. In LY environments, a high value for WPI and early heading had a significantly positive effect on yield. A high value for WPI tended to result in late heading, however. In HY environments, a high value for WPI had a weakly negative effect on yield; heading date had no effect. Both WPI and heading date had a significant effect on yield response. Selection in HY environments for WPI and heading date together can be an efficient method of selection for yield of barley under stress, especially in early generations, when yield trials are difficult to conduct.
Cause of Tall Off‐Types in a Semidwarf Spring Wheat
Authors: Storlie E. W. , Talbert L. E.
Published: July 2010

Tall off‐types that occur in semidwarf wheat, Triticum aestivum L., cultivars may reduce grower acceptance and present problems in seed certification programs. Tall off‐types occur in ‘Hi‐Line’ spring wheat at a frequency of 0.20%. Segregation analysis for height indicates Hi‐ Line contained the Rht1Rht1rhl2rht2 genotype. Cytological analysis of selfed progeny of the tall off‐types showed a high proportion of monosomic chromosome numbers, indicating that aneuploidy may be associated with the tall off‐types. Further investigation involved the use of PCR (polymerase chain reaction) with primers designed from clones detecting restriction fragment length polymorphism (RFLP) at loci on homoeologous Group 4, which contained height‐reducing loci Rht, and Rht2. Three sets of primers were used to screen progeny of tall off‐types from Hi‐Line. The results of this screening indicate 20% of the offspring were nullisomic for chromosome 4B. Analysis of progeny using morphological and PCR based screening indicate that offspring of tall off‐types were 72% monosomic 46:8% disomic: 20% nullisomic 4B. Thus, cytological and molecular analysis reveal that Hi‐Line tall off‐types result from a monosomic 4B condition, which causes hemizygosity for Rht1. Due to the random occurrence of monosomic 4B progeny from disomic semidwarf wheat, our results suggest that tall off‐types may be an inherent and unavoidable feature of semidwarf wheats with the genotype Rht1,Rht1,rht2rht2.
Restriction Fragment Length Polymorphism in Soybean Germplasm of the Southern USA
Authors: Skorupska H. T. , Shoemaker R. C. , Warner A. , Shipe E. R. , Bridges W. C.
Published: July 2010

A soybean restriction fragment length polymorphism (RFLP) map (ISU/USDA‐ARS‐FCR, Ames, IA) was derived from an interspecific cross of Glycine max (L.) Merr. × G. soja Siebold & Zucc. using early maturity group genotypes. We characterized the feasibility of the application of this map to physiologically distant soybean genotypes mainly maturity group (MG) V to IX. A total of 108 genotypes of G. max were surveyed. Germplasm represented ancestral genotypes, breeding lines and elite cultivars. The RFLP markers (83 probes) used in this research spanned fifteen major linkage groups at an average distance of 26 centimorgans (cM). Fifty‐four percent of the probes were non informative. Thirty‐five percent had a probability of detecting polymorphism between any two random genotypes with a frequency above 0.3. The RFLP probes detecting polymorphism with high frequency were identified. Restriction fragment length polymorphism was associated with cultivar pedigree and relation to ancestral genotypes. The majority of genotypes showed molecular similarities to ‘Ralsoy’, ‘Dorman’, ‘Dunfield’, and ‘Ogden’ germplasms; a smaller group of genotypes showed molecular similarities to S‐100. Genotypic similarities were observed among most genotypes. However, genotypes of MG VI and VII retained potentially valuable levels of genetic diversity. Soybean cyst nematode and bacterial pustule resistance were present in many different genetic backgrounds and no association with donor genotypes was observed in principal components analysis. The set of identified RFLP probes with high frequency of polymorphism detection should serve as a core of molecular markers for initiating mapping of agronomic traits and detection of gene linkages across a wide range of maturity groups of cultivated soybean. Genomic diversity described by the principal components analysis may be useful in germplasm selection to develop populations for genome mapping in soybean.
Statistical Tests and Retention of Terms in the Additive Main Effects and Multiplicative Interaction Model for Cultivar Trials
Authors: Cornelius P. L.
Published: July 2010

The additive main effects and multiplicative interaction (AMMI) model has been recommended for cultivar trials repeated across locations and/or years. Previous studies, using approximate F‐tests introduced by Gollob, have declared more AMMI interaction principal components (PCs) significant than cross validation could show to predictively useful. This study used Monte Carlo simulation to investigate whether such a result in an international maize (Zea Mays L.) yield trial of nine cultivars in 20 environments could be wholly or partially explained by liberality of the Gollob tests and also to compare properties of Gollob tests and several more conservative procedures. Gollob tests were found extremely liberal (Type I error rate as high as 66% when the first interaction PC in a 9 by 20 table is null) and AMMI users are warned not to rely on them. Tests known as FGHI and FGH2 were essentially equivalent and effectively controlled Type I error rates at or below the intended level, but were conservative for any component for which the previous component was small. Simulation tests and iterated simulation tests with greater power than FGHI and FGH2, but apparently with adequate control of Type I error rates, were developed. Simulation results suggest that Fant or FGH1 could usually be used to choose a predictive model with only a small loss in accuracy, and sometimes a gain, as compared to the expected model choice by cross validation with half of the data used for modeling and the other half for validation. In some cases cross validation is likely to choose a model with fewer PCs than the optimal truncated model obtainable from the full data set. If cross validation is used to choose a model, it is recommended that all but one replication should be used for modeling and only one for validation.
Combining Ability for Yield and Protein Quality among Modified Endosperm opaque‐2 Tropical Maize Inbreds
Authors: Pixley K. V. , Bjarnason M. S.
Published: July 2010

The opaque‐2 mutation has been used in maize (Zea mays L.) breeding to develop cultivars with increased concentrations of lysine and tryptophan. Very little information is available, however, about combining ability for protein quality traits for modified/vitreous‐endosperm opaque‐2 maize (quality protein maize, or QPM), although such information is essential for planning an effective hybrid development program. This research assessed the relative importance of general and specific combining ability effects (GCA and SCA) for grain yield, protein concentration in grain, tryptophan concentration in grain, and tryptophan concentration in protein for various tropical, late maturity, white grained QPM lines. Four diallel trials, involving a total of 28 lines from five populations, were evaluated from 1988 to 1990, each at two to five locations during 1 yr. The best QPM hybrid in each trial exceeded the best normal‐endosperm maize check by an average of 14% for grain yield, 48% for tryptophan concentration in grain, and 60~ for tryptophan concentration in protein. Mean squares for GCA effects in across‐location analyses were significant (P < 0.05) for grain yield, protein concentration in grain, and tryptophan concentration in protein for three of the four trials, and for tryptophan concentration in grain in two trials. Mean squares for SCA effects were not significant except for grain yield in one diallel. Location × GCA interaction was generally significant for all traits except tryptophan concentration in protein. Our results suggest that QPM hybrids with the highest values for protein quality traits will be crosses between lines with the highest GCA values. Concurrent improvement of yield and protein quality should be possible for this germplasm because phenotypic correlation coefficients were not significant for grain yield with concentration of protein in grain, concentration of tryptophan in grain, and concentration of tryptophan in protein.
Selection Index Based on Genetic Correlations Among Environments
Authors: Van Sanford D. A. , Pfeiffer T. W. , Cornelius P. L.
Published: July 2010

Plant breeders often conduct preliminary tests of genotypes at one or two primary locations due to limited seed supply and/or limited resources. The location of these tests may be somewhat arbitrary, and in general, it is not known how performance at these locations relates to performance in a much broader target environment. The objective of this study was to develop a method for weighting performance at primary locations, based on the genetic correlations between these locations and the target environment, that would lead to greater predictive value of the primary locations. Using data from wheat (Triticum aestivum L. em. Thell) and soybean (Glycine max L.) cultivar trials in Kentucky from 1987 to 1991, we developed a selection index based on the genetic correlations of cultivar performance in the primary locations, Lexington (LEX) and Princeton (PR), and the target environment, represented by as many as seven locations from the cultivar trials (Ȳ). As expected from theory, predicted response to index selection exceeded predicted response to selection at either LEX or PR, and it was superior to predicted response of selection based on the unweighted mean of LEX and PR. In all years, a lower number of statistically significant wheat genotype rank changes occurred when ranks across the primary locations were based on the index than when ranks were based on the unweighted means. For soybean, this was true in 4 of 5 years. Although the use of cultivar trial data for parameter estimation violates some of the usual assumptions of traditional quantitative genetic investigations, we suggest the potential benefits to breeding programs outweigh these concerns.