bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetics of Tolerance to White Clover Mosaic Virus in Red Clover
Authors: Martin Pierre H. , Coulman Bruce E. , Peterson Jean F.
Published: July 2010

Virus diseases are known to reduce the yield and longevity of red clover (Trifolium pratense L.) stands. White clover mosaic virus (WCMV) is a commonly occurring virus in red and white clover (Trifolium repens L.). Tolerance to WCMV, as defined by a lack of symptom expression, has been detected in red clover. The objective of this study was to determine the inheritance of this tolerance. Progenies of red clover were screened for tolerance (T) to WCMV means of mechanical inoculations, and selection based on visual symptoms and ELISA (enzyme‐linked immnnosorbent assay). Average rates of tolerance to WCMV in progenies increased in two successive generations from 24.5% in T ✕ T to 34.2% in (T ✕ T) ✕ (T ✕ T), but in progenies of crosses involving susceptible (S) plants it remained almost constant: 8.4 and 9.7% in T ✕ S and (T ✕ S) ✕ (T ✕ S), respectively. Tolerance to WCMV behaved as it were controlled by polygenes. Percent tolerant progenies increased linearly through the two cycles of recurrent selection. It was concluded that a recurrent selection program would be effective in producing populations of red clover with high percentages of tolerant plants.
Spatial Dependence of Growth Attributes and Local Control in Wheat and Oat Breeding Experiments
Authors: Samra J. S. , Anlauf R. , Weber W. E.
Published: July 2010

Adjustment for microenvironmental heterogeneity in inadequately replicated field experiments is desirable for maximizing genetigains through selection. Moving means, empirically weighted means, and a model‐based optimal predictor (kriging) have been used to estimate an index of the local heterogeneity of 276 wheat (Triticum aestivum L.) and 336 oat (Avena sativa L.) plots. The adjustments of the data based on this index have been compared. The wheat experiment was unreplicated and that on oat had two replications. Trend variation along rows and columns was about 25% of the variance in wheat and 9 to 18% in the oat trial. Depending on the trait, 39 to 54% of the remaining variability of wheat and 7 to 20% of oat was stochastically isotropically spatially structured. Kriging reduced the coefficient of variation (CV) in all the traits, including yield, and never made overcorrections for the local variation, whereas adjustments based on moving means and empirically weighted means frequently increased the CV. Local control simulated only from check plots was less practical in wheat as compared to oat. Wheat selections from the unadjusted data were paired or clustered in localized parts of the field. These selections became randomly distributed across the entire field after the microenvironmental variation was removed by the kriging method.
Morphological and Growth Characteristics of Low‐ and High‐Maintenance Kentucky Bluegrass Cultivars
Authors: Burt M. G. , Christians N. E.
Published: July 2010

Kentucky bluegrass (Poa pratensis L.) cultivars differ greatly in performance when grown under low‐maintenance regimes. This greenhouse study was conducted to determine if certain growth and morphological characteristics are common five cultivars that have consistently performed well and to five cultivars that have consistently performed poorly when grown in a low‐fertility, nonirrigated field trial in Iowa. The low‐maintenance cultivars were K3‐162, Kenblue, Vantage, S‐21, and South Dakota Common; the high‐maintenance cultivars were Bonnieblue, Lovegreen, Columbia, I‐13, and A20. Clear, polyethylene tubes, 60 cm long and 3.2 cm o.d., were filled with fritted clay and supported by polyvinyl chloride(PVC) pipe along a research greenhouse bench. Single seedlings of each cultivar were transplanted into each tube and replicated four times. Data collected during the 10‐wk experiments included weekly rooting depths and clipping yields. Plant morphological measurements, root dry weights from three equal sections of the root tubes, shoot fresh and dry weights, and lateral branch numbers were recorded at harvest. The experiment was conducted three times. Low‐maintenance cultivars were found to root 12% deeper, produce 56% more total root weight, maintain a lower shoot‐to‐root ratio, and contain proportionally less moisture in their shoot tissue. They also had narrower leaf blades, more leaf folding, 27% longer sheaths, a greater leaf angle from horizontal, and 13% fewer leaves per shoot. The identification of growth and morphological characteristics common to low‐maintenance grasses appear to be important in the selection and development of new cultivars for minimal‐maintenanced conditions.
Heat Tolerance in Winter Wheat: II. Membrane Thermostability and Field Performance
Authors: Saadalla M. M. , Quick J. S. , Shanahan J. F.
Published: July 2010

High‐temperature stress during the grain‐fill period of wheat is one of the major constraints to increased production. The objective of this work was to determine the relationship between membrane thermostability (MT) and other agronomic traits of winter wheat (Triticum aestivum L.). Hardened seedlings of 137 F5 genotypes (derived from crosses of heat‐tolerant and sensitive parents) and seven cultivars were evaluated for MT and the results expresseds relative injury (RI). The same 144 genotypes were grown at three field sites in eastern Colorado and evaluated for maturity (days to anthesis), grain yield, grain volume weight, and yield components. Relative injury varied significantly (P ≤ 0.01) among the 144 genotypes, with arange of 31 to 78%. Based on RI values, the genotypes were separated in to three groups: heat‐tolerant (HT), intermediate (I), and heat‐sensitive (HS). Accordingly, 27 genotypes were classified as HT, 71 as I, and 46 as HS. There were no differences in maturity among the three groups, indicating no association between maturity and RI. At one site, the HT group produced 9 and 19% more yield than the I and HS groups, respectively, and the trend in yield among the three groups was similar at the other two sites. Additionally, grain volume weight and kernel weight were greater for the HT vs. I or HS group at all three sites. Thus, heat tolerance, as evaluated by the MT test, was associated with grain yield and quality. These results suggest that the MT test would be a suitable procedure for selecting heat‐tolerant winter wheat genotype in a breeding program.
Influence of Bradyrhizobium japonicum Strain and Far‐Red/Red Canopy Light Ratios on Nodulation of Soybean
Authors: Hunt P. G. , Kasperbauer M. J. , Matheny T. A.
Published: July 2010

Dinitrogen fixation, an important aspect of soybean [Glycine max (L.) Merr.] production, is affected by many environmental factors. Nodulation can be altered, for example, by changes in the ratio of far‐red to red (FR/R) canopy light. The influence of canopy light spectral balance on the nodulation of ‘Coker 368’ soybean when inoculated with different strains of Bradyrhizobium japonicum was evaluated in field and growth chamber studies. Soybean seedlings were inoculated with USDA 110 (110) or Brazil 587 (587) and grown in 10‐cm diameter pipes that were filled with vermiculite and inserted at 1.0‐m intervals in seedling soybean rows that were oriented north‐south (N/S) or east‐west (E/W) on a Norfolk loamy (fine‐loamy, siliceous, thermic Typic Kandiudult). The FR/R ratios of canopy light (relative to the ratio in incoming sunlight, which was assigned a value of 1.00), were 1.38 for N/S‐ and 1.26 for E/Woriented rows. Row orientation significantly affected nodulation when 110 was the inoculum but not when 587 was the inoculum. Nodule biomass of ll0‐inoculated seedlings was 48% higher with E/W than with N/S row orientation. In the growth chamber study, soybean seedlings were inoculated with 110 or 587, and their shoots received high or low FR/R ratios at the end of each day. Nodulation was significantly affected by the FR/R ratio of canopy light when the inoculant was 110 but not when the inoculant was 587. Soybean seedlings that received the low FR/R ratio and were inoculated with 110 had 53% greater nodulation; the FR/R effects on nodulation were not statistically significant when the seedlings were inoculated with 587. These results show that even small changes in the FR/R ratio of canopy light can affect soybean nodulation in both field and controlled environments. They also show that this effect can be enhanced or diminished by B. japonicum strain.
Developmental Periods in Soybean: Photoperiod‐Sensitive ✕ Insensitive Crosses Evaluated at Diverse Latitudes
Authors: de Cianzio S. Rodriguez , Green D. E. , Chang C. ‐S. , Shibles R. M.
Published: July 2010

Selection for long duration of seed‐filling period (SFP) in segregating soybean [Glycine max (L.) Merr.J populations may be a way to increase seed yield. Tbe objective of tbe study was to assess the relative effectiveness of selecting for SFP from tropical environments to develop lines for temperate locations in crosses of photoperiod insensitive ✕ sensitive genotypes. A second objective was to determine if selection for longer SFP is possible without delaying date of physiological maturity (R7). Three populations were developed by crossing a photoperiod‐insensitive genotype of Maturity Group (MG) HI to photoperiod‐sensitive genotypes of MG I, II, And III. Random F4‐derived lines were evaluated at Ames, IA, at Isabela, PR (under both natural and lighted environments), and at Hualien, Taiwan, for days from emergence to beginning flowering (Rl), rapid seed‐filling (R5), R7, SFP, and reproductive period (RP). Significant (P < 0.05) differences among lines, environments, and environment ✕ genotype were observed. Phenotypic and rank correlations of Stages Rl, R5, and R7 between environments ranged from 0.22 to 0.83. The range in correlation coefficients for SFP and RP was from 0.06 to 0.62. It is possible to select lines for duration of SFP at PR environments in plantings under natural daylength or under lights. Selections in PR included genotypes ranked in the top 33% at the IA location, and generally included at least one of the five topranked lines. Lines may also be selected with a desired combination of duration of SFP and number of days to reach Stage R7.
Performance and Genetic Variance among S1 Lines and Testcrosses of Iowa Stiff Stalk Synthetic Maize
Authors: Walters S. P. , Russell W. A. , Lamkey K. R.
Published: July 2010

Iowa Stiff Stalk Synthetic (BSSSC0) maize (Zea mays L.) population has been used in two long‐term recurrent selection programs: reciprocal recurrent selection (R) and half‐sib followed by S2‐progeny (S) recurrent selection. Advanced populations after nine cycles of reciprocals recurrent selection [BSSS(R)C9] and seven cycles of half‐sib and three cycels of S2 progeny selection [BS13(S)C3] were evaluated. Objectives of this study were to compare performance and amount of genetic variation present among S1 lines from BSSSC0, BSSS(R)C9, BS13(S)C3, and BSSS(R)C9 ✕ BS13(S)C3(C3 ✕ C9) and, also, to compare performance and genetic variation among testcrosses of the S1 lines by using two testers of different heterotic background, B73 and Mo17. The S1 lines from BSSS(S)C9 and BS13(S)C3 showed significant increases in grain yield compared with S1 lines from BSSSC0. The C3 ✕ C9 S1 lines showed high‐parent heterosis for grain yield. Genetic variance component estimates of S1 lines were significant in all four populations, and C3 ✕ C9 reflected midparent estimates between the estimates for C3 and C9. Mean grain yield for Mo17 testcrosses was significantly greater than for B73 testcrosses within each of the four populations. Testcrosses involving C3 and a related inbred, B73, showed a nonsignificant grain yield variance estimate. The average yield for the testcrosses of S1 lines from C3 ✕ C9 for both testers was intermediate between the testcrosses of S1 lines from C3 and C9; thus, the high‐parent heterosis observed for C3 ✕ C9 S1 lines was not observed for the testcross means.
Photoperiod Sensitivity in Tropical Maize Accessions, Early Inbreds, and Their Crosses
Authors: Mungoma C. , Pollak L. M.
Published: July 2010

One factor causing lack of adaptation of tropical and subtropical maize (Zea mays L.) to the U.S. Corn Belt is its photoperiod sensitivity. Six tropical maize populations (‘Caingang‐BOV 78’, ‘Negro de Tierra Caliente‐GUA146’, ‘Lenha‐RGS XX’, ‘Negro de Tierra Caliente‐GUA159’, ‘Negrito’, and ‘Costeño‐VEN 453’) and five testers (‘Zapalote Chico’ PI 217413, ‘BI4A’, ‘Oh43’, ‘CM105’, and ‘A654HT’) were used to determine which tester most effectively reduced time to flowering when crossed with tropical populations and to determine whether there was a population ✕ tester interaction for genes controlling photoperiod sensitivity. Evaluations were carried out in 1987 and 1988 under decreasing photoperiod (18‐9 h of light) in the growth chamber for the populations, testers, and testcrosses and also in the field for the testcrosses. Three field environments, two in Iowa and one in Puerto Rico, were utilized. In the growth chamber, days to tassel emergence differed among populations and testers per se and among testcrosses. Tassel emergence for populations and testers occurred from the 12‐h to the 9‐h photoperiod. The tropical population least sensitive to photoperiod was Negro de Tierra Caliente‐GUA146, while CM105 was the least sensitive tester. There were significant differences among testcrosses in the combined analysis for days to pollen shed for the field environments. Two testers, CM105 and A654HT, produced the earliest testcrosses over all environments. There were significant differences in the contribution testers made toward earliness in tropical population testcrosses in temperate environments.
Cotton Emergence Force as Affected by Soil Temperature, Moisture, and Compression
Authors: Chu Y. N. , Coble C. G. , Jordan W. R.
Published: July 2010

Emergence force of a seedling is a major factor influencing the ability of the seedling to emerge through a surface soil crust. This study was conducted to evaluate effects of soil physical conditions on the maximum emergence force of cotton [Gossypium hirsutum L.]. Effects of soil temperature and moisture on the emergence force were studied when the seedling was supported laterally to prevent buckling. The effect of compression of the top soil was investigated using a plate on the soil surface to simulate a crust. Measured emergence forces when the seedlings were laterally supported were greater than previously reported for cotton. Maximum emergence force varied quadratically with increases in soil temperature and moisture. The highest force was 11.4 N for a temperature of 28.5 °C and a soil water potential of −10 J kg−1. Maximum emergence force increased linearly with the hypocotyl cross‐sectional area, while calculated turgor potentials of hypocotyl cells were 768, 756, and 518 J kg−1 at soil water potentials of −10, −30, and −300 J kg−1, respectively. The emergence force was greatly reduced when lateral support was not provided. A compression pressure of 13.8 kPa on the top soil increased emergence force from 0.9 N at zero compression to 2.2 N, only ≈20% of the maximum force observed with adequate lateral support.
Rank Comparisons of Unadapted Maize Populations by Testers and Per Se Evaluation
Authors: Abel B. C. , Pollak L. M.
Published: July 2010

Evaluation of the many unadapted maize (Zea mays L.) accessions in the world's gene banks is a monumental task. This study compared rankings of unadapted accessions testcrossed to eight testers with their per se performance as sources of favorable genes that enhance grain yield and other traits. Testers included the populations BS13 and BS26, the single crosses B14 ✕ B37 and Oh43 ✕ Mo17, and the inbreds B37, B14, Oh43, and Mo17. The accessions were a diverse array of 34 populations collected from Yugoslavia. The 272 testcrosses and the 34 accessions per se were evaluated in a series of randomized complete‐block designs, with each block containing a set of either testcrosses within each tester or the accessions per se. Field experiments were conducted at three Iowa locations for 3 yr (1985–1987). Significant variation among testcrosses or accessions occurred within sets for grain yield, grain moisture, root lodging, stalk lodging, days to anthesis, plant height, and ear height. Testcrosses with B14 ✕ B37, B14, Oh43, and Mo17 did not interact with environments for grain yield. Testcrosses with B14 and Mo17 had the least root lodging, and those with B14 ✕ B37 and B14 had the least stalk lodging. Testers ranked some accessions somewhat similarly for grain yield, but extreme differences in ranking by different testers also occurred. The most extreme differences occurred comparing Oh43 with Mo17 and B14 ✕ B37 with Oh43 ✕ Mo17. Ranking of accessions per se for grain yield was different from ranking via testers. Rankings of accessions for other traits were similar for testers and per se evaluation. Due to differential ranking among testers and per se evaluation for grain yield, it is suggested that more than one tester be used to screen unadapted maize accessions. That tester should also exhibit a high frequency of favorable alleles for traits such as root and stalk lodging, to allow easier data collection.
Cytology and Fertility of the Interspecific Hybrid Trifolium ambiguum ✕ T. repens and Backcross Populations
Authors: Anderson J. A. , Taylor N. L. , Williams E. G.
Published: July 2010

Interspecific hybridizations of white clover (Trifolium repens L.), a widely grown forage legume, with kura clover (T. ambiguum M. Bieb.) have been made to facilitate transfer of genes conferring virus resistance and longevity from kura clover to white clover. Additionally, kara clover may be improved by the seedling and aftermath vigor of white clover. The objectives of this study were to backcross both tetrapioid and octoploid interspecific hybrids of kura clover (2n = 4x = 32) and white clover (2n = 4x = 32) to both parents, and to estimate the possibility of successful introgression of genes between the two species. Cytology and pollen stainability of the parents, resulting progeny, and additional backcross plants previously obtained were examined. Eighteen plants were obtained from backcrosses of one 4x interspecific hybrid (Hybrid 435) to white clover. Ten of the backcross progeny had 48 (6x) somatic chromosomes, five had 32; three others were aneuploid. The higher than expected ploidy level may have resulted from union of 2n gametes contributed by the Hybrid 435 female parent with n gametes of white clover. Backcrosses to kura clover produced no progeny. Backcross progeny (2n = 32) of Hybrid 435 to white clover averaged 77.9% pollen stainability. Meiotic chromosomes of plants from backcrosses of 4x Hybrid 435 to white clover associatetl predominantly as bivalents, indicating the presence of allosyndetic pairing. The high frequencies of allosyndetic pairing that occur in first backcross progenies of 4x interspecific hybrids to white clover, and theoretically in second backcross progeny of 8x interspecific hybrids to kura clover, should allow recombination of genes from kura clover and white clover.
Genetic Nomenclature in Clovers and Special‐Purpose Legumes: III. Lotus, Lespedeza, Kummerowia, and Vicia spp
Authors: Beuselinck P. R. , Mosjidis J. A.
Published: July 2010

A compilation and revision of gene symbols for four forage legume genera, Lotus, Kummerowia, Lespedeza, and Vicia are presented. These genera include annual and perennial species utilized for their high‐quality herbage. The objective was to provide geneticists working with these legumes a single, uniform source of genetic nomenclature, including the assigned symbols for the identified genes of these genera.
Symptomatology and Enzyme‐Linked Immunosorbent Assay Used to Facilitate Breeding for Resistance to Wheat Soilborne Mossaic
Authors: Hunger R. M. , Sherwood J. L. , Smith E. L. , Armitage C. R.
Published: July 2010

Wheat soilborne mosaic (WSBM) can significantly reduce wheat (Triticum aestivum L.) yields. The only feasible method for controlling this disease is to plant resistant cultivars; however, development of WSBM‐resistant wheat can be difficult, because soil fertility, soil moisture, or other viruses cause symptoms that mimic or mask symptoms induced by the WSBM virus. Thus, the objective of this research was to develop a system that effectively identifies resistance to WSBM. Reactions to WSBM were determined for advanced breeder lines, single plants from advanced lines, and headrow progeny from advanced lines, using symptomatology and the enzyme‐linked immunosorbent assay (ELISA) in growth chamber test and in the field. Results indicate that large numbers of plants or lines can be screened using the growth chamber test to eliminate susceptible entries. In addition to confirming results from the growth chamber test, the field test also detected lines segregating for disease reaction. Individual plants resistant to WSBM were identified from these segregating lines, using a combination of the growth chamber and field tests. Use of this system in breeding for resistance to WSBM reduces the possibility of misidentifying the reaction of wheat lines or plants to WSBM and facilitates the development of wheat resistant to this disease.
Inheritance of Nonnodulating Mutants of Sweetclover
Authors: Miller J. E. , Viands D. R. , LaRue T. A.
Published: July 2010

Legume mutants defective in nodule formation are useful for understanding interactions between host and bacterium. Nonallelic nodulation mutants have been relmrted within only a few legume species. Inheritance of nonnodulation in 10 sweetclover (Melilotus alba Desr.) mutants was determined from F1, F2, and F3 generations derived from crosses between each mutant and the nodulating accession U389. Nonnodulation in each mutant was conditioned by a single recessive gene. Complementation analysis was performed on F1 and F2 seedlings derived from diallel crosses among the mutants. Five of the mutants were nonallelic, indicating that at least five different genes are involved in nodule formation in M. alba. The following symbols are proposed for the genes controlling nonnodulation of these sweetclover mutants: sym‐1, sym‐2, sym‐3, sym‐4, and sym‐5.
Inbreeding Effects for Selected Agronomic Characters in Eastern Gamagrass
Authors: Kenna M. P. , Taliaferro C. M. , McNew R. W.
Published: July 2010

Information on the consequences of inbreeding in naturally crosspollinated plants is useful in determining strategies for genetic manipulation. Research was conducted in 1982 and 1983 to determine the effects of inbreeding in eastern gamagrass [Tripsacum dactyloides (L.) L.) on plant height (PH), plant weight (PW), 100‐spikelet weight (SW), and fertility measured by the percent of spikelets containing pure live seed (PLS). Plant materials consisted of 20 randomly chosen parents from a diploid (2n = 2x = 36) panmictic population and S1 and S2 progeny derivatives. Twenty ramets of each parent, 822 S1 seedlings, and 593 S2 seedlings were field grown using a completely randomized design. Parental plants had higher mean PH, PW, and SW than S1 or S2 progeny populations (P < 0.01). No consistent differences for these traits were detected between the S1 and S2 generations. More than two‐thirds of the parents had significantly higher PH and PW than their S, or S2 progenies. In 1982. SW did not differ between generations; in 1983, however, 80% of the parents had significantly greater SW than their respective S1 or S2 generation progenies. Inbreeding had little detrimental effect on PLS. Less than one‐half of the parents had a greater percentage of spikelets containing PLS than their corresponding S1 and S2 generation progenies in 1982, and even fewer differences were found in 1983. Plants with reduced vigor but normal color, yellow and albino plants, and plants with altered floral morphology were found in selfed progeny populations. Inbreeding eastern gamagrass should have value in exposing recessive alleles existing at low frequencies and in the development of inbred lines.
Near Infrared Reflectance Spectroscopy for Analysis of Sugarcane from Clonal Evaluation Trials: II. Expressed Juice
Authors: Berding Nils , Brotherton G. A. , le Brocq D. G. , Skinner J. C.
Published: July 2010

The analysis of fibrated sugarcane (Sacclmrum spp. hybrids) with near infrared reflectance spectroscopy (NIR) offers the possibility of replacing standard laboratory analyses for quality components, including sugar and fiber content. Analysis of expressed juice by NIR spectroscopy does not provide an estimate of fiber content, but has the advantage of using a more uniform sample. This approach has potential application in early selection stages, and also offers considerable promise for process control in manufacturing. This research aimed to assess NIR spectroscopy for analysis of quality components of juice. Two replicated trials provided samples of cane from which juice was expressed. Quality components were analyzed by routine laboratory methods. Samples of juice were scanned in a transflectance cell of a Technicon 450R NIR spectrophotometer to provide transflectance data (log I/TF). Independent calibration and prediction experiments were conducted. Correlation coefficients from the tests of prediction were: Brix (0.97), CCS (0.97), conductivity (0.47), impurity (0.63), polarimetry (pol) reading (0.98), and (0.58). Skew for prediction regressions was significant for all components except CCS. Bias was significant for CCS. The NIR and routine lab analyses differed significantly for all components except Brix. The bias and skew resulted from problems associated with fouling of the transflectance cell by particulate matter. Acceptable calibrations were obtained from data from a closed population in one experiment. Sampling analyses of spectrophotometer readings (log I/TF) indicate duplicate determinations were unnecessary. The standard of determination of quality components of juice by NIR spectroscopy approaches that required for clonal evaluation.
Bacterial Interference with in Vitro Assays of Tall Fescue Seeds for Acremonium Coenophialum
Authors: Gwinn K. D. , Trigiano R. N. , Gavin A. M. , Conger B. V.
Published: July 2010

In vitro embryo‐derived callus culture is an efficient and useful technique for determining viable fungal endophyte (Acremonium coenophialum Morgan‐Jones & Gams) levels in tall fescue (Festuca arundinacea Schreb.) seed lots; however, the presence of a yellow‐pigmented bacterium occasionally interferes with detection of the fungus. The objectives of this study were to control and identify this bacterium. Excised embryos from 26 seed lots were plated on Schenk and Hildebrandt medium amended with 20 μM dicamba (2‐methoxy‐3,6‐dichlorobenzoic acid); bacteria‐infested seeds were found in 22 lots. Infestation levels ranged from 1 to 100%. Medium supplemented with 50 mg L−1 streptomycin eliminated bacterial growth without interfering with the growth of A. coenophialum. Based on microscopy, biochemical tests, and fatty acid analyses, the bacterium was identified as an Erwinia species with characteristics of the herbicola group.
Soybean Plant Introductions Selected for Seed for Seed Filling Period or Yield: Performance as Parents
Authors: Pfeiffer T. W. , Suryati D. , Egli D. B.
Published: July 2010

Soybean [Glyclae max (L.) Merr.] plant introductions (PI) been investigated as sources of unique favorable alleles for yield improvement, even though most PIs are inferior to the best adapted coltivars for yield. A physiological character that is a component of yield might be useful for identifying Pls that might contribute unique favorable alleles for yield. The objective of this study was to compare, in terms of progeny yield, the value as a parent of a PI selected for yield (P1423897) with a PI selected for length of the seed‐filling period (stage RS‐RT) (PI 398401). Each PI parent contributed of the germplasm to separate BCI populations produced with the breeding lines or cultivar A80‐345005, LN80‐9359, and Ripley. Furty random BC1F3‐derived lines from each of the six populations were compared at Lexington, KY, in 1986 and 1987. The progeny groups from the two PIs did not differ for yield or seed‐filling period. The to,yielding 20% of each population were compared at the two Kentucky locations in 1988. The PI 423897 progeny were 8% higher yielding than the PI 398401 progeny, with no significant difference in the length of the seed‐filling period. Seven of the top 10 progeny lines for yield bad PI 423897 as the PI parent. Selection of a PI based on a seed‐filling period longer than the adapted cultivars was not su0erior to selection of a PI based on yield, even though the adapted coltivars were higher yielding than the PI selected for yield.
Tray System for Measuring Drought Tolerance of Forage Grasses
Authors: Tischler C. R. , Voight P. W. , Young B. A.
Published: July 2010

A soil‐tray system used in conjunction with a growth chamber was evaluated and used to determine drought tolerance of hybrids of Eragrostis curvula var. confera Nees (boer lovegrass, 57‐4‐69) ✕ E. curvula (Schrad.) Nees (common weeping lovegrass) and Plant Introductions (PIs) of kleingrass (Panicum coloratum L.). The stress endpoint was based on a predetermined threshold gravimetric water loss. Results with the tray system agreed with field performance of genotypes with known drought tolerance. Plant 57‐4‐69 was as drought tolerant as ‘Catalina’ beer lovegrass (selected for seedling drought tolerance). Hybrids between 57‐4‐69 and common (not especially drought tolerant) exhibited a broad range of drought tolerance, whereas kleingrass PIs showed less variability in drought tolerance than the lovegrass. This system successfully identifies drought‐tolerant germplasm in lovegrass.
Reconciling Water‐Use Efficiencies of Cotton in Field and Laboratory
Authors: Radin John W.
Published: July 2010

Stomatal behavior of cotton (Gossypium hirsutum L.) differs between controlled environments and the field. Two important differences are the much greater stomatal conductance maintained in the field in the absence of water stress, and the reduced response of stomata to water stress in the field. This review paper describes and supports the hypothesis that the differences in stomatal behavior result from effects of temperature upon abscisic acid (ABA) metabolism. The reasoning is based on the following points: (i) controlled‐environment experiments are frequently run at unrealistically low temperatures near the optimum for plant growth (≈ 30 °C); (ii) higher temperatures in controlled environments change stomatal behaviors to resemble those seen in the field, and they promote the metabolic loss of ABA from leaf tissue; (iii) in the field, ABA concentrations leaves are very low at high temperatures, and stomatal responsiveness to CO2 (an indicator of a role for ABA in mediating stomatal movements is poor; (iv) stomata at high temperatures in the field retain the ability to respond to exogenous ABA; (v) in the field late in the season, when temperatures resemble those of controlled environments, ABA concentrations of leaves and stomatal properties shift to resemble those seen in controlled environments; and finally, (vi) these shifts are unrelated to photosynthetic properties of the mesophyll. Evidence indicates that stomatal behavior in the field may be related to heat tolerance of the crop, with the very high conductances at high temperatures permitting substantial evaporative cooling of the foliage. Both plant physiology and agronomy need controlled environments, because these permit studies of stomatal responses to environmental factors in the absence of confounding variables. Such experiments must use realistic temperatures that simulate the field environment, however, to obtain results relevant to field performance.
Anatomical Location and Inheritance of Variegated Red Seed Coat Color in Hexaploid Wheat
Authors: Hare R. A.
Published: July 2010

Inherited somatic variegations in seed coat in a number of species, including maize (Zea mays L.), have been the subject of considerable study and have led to an expanded understanding of gene expression and control; however, there are no reports of such studies in hexaploid wheat (Triticum aestivum L. emend. Thell.). The anatomical location and inheritance of variegated red seed coat color in a hexaploid wheat line, 10859, was investigated. Line 10859 was crossed to ‘Sundor’ (white kernel), ‘Selkirk’ (three‐gene red kernel) and a purple pericarp line, 42502 (complementary two‐gene purple kernel). Color variegation or sectoring was located in the seed coat tissue of the pericarp by microscopic dissection. Kernel color and seed coat color variegation were scored on kernels from F2 plants from the above crosses. The data indicated that recessive alleles at the variegation locus regulate the expression of red seed coat pigment, which is controlled by dominant alleles at one of three R loci. The identity of this R locus is unknown. Data suggests that the variegation and R loci are not linked. This system, although rare in wheat, provides some interesting and potentially valuable avenues for cell and genetic research.
Response of Hard Red Spring Wheat Genotypes to Management Systems
Authors: Khan Aslam , Spilde LeRoy A.
Published: July 2010

Average yields of hard red spring wheat (HRSW) (Triticum aestivum L.) are low compared with the intensively managed winter wheat of western Europe. Information on intensive cereal management (ICM) of HRSW is limited in the USA. This study was conducted to investigate the agronomic response of 12 HRSW genotypes to ICM inputs. A randomized complete‐block design in a split‐plot arrangement was used with genotypes as main plots and management systems as subplots. Genotypic selection was based on year of selection from 1911 through 1986. The ICM treatment consisted of imazalil (1‐[2‐(2,4‐dichlorophenyl)‐2(2‐propenyloxy)ethyl]‐H‐imidazole), seed treatment, foliar N application applied at 55 kg ha−1 in three growth stags and foliar application of ethephon [(2‐chloroethyl)phosphonic acid], and propiconazole [1‐[2‐(2,4‐dichlorophenyl)4‐propyl‐1,3‐dioxolan‐2‐ylmethyl]‐1H‐1,2,4‐triazole], at growth stage 10 to control lodging and foliar diseases, respectively. The control treatment did not include any ICM inputs. Genotypes responded similarly to management systems regardless of selection year. The ICM treatment decreased (P < 0.05) plant height, lodging, grain yield, protein yield, test weight, kernel weight, foliar diseases, common root rot disease severity and incidence, and delayed heading and maturity when averaged across environments and genotypes. Protein concentration increased, but the increase was too small to positively influence economic value. Grain yield of five genotypes was significantly reduced by ICM inputs. Results from this study indicated that these inputs were not a viable option when employed as a complete package in our northern U.S. environment.
Molecular Marker Information and Selection of Parents in Corn Breeding Programs
Authors: Dudley J. W. , Maroof M. A. Saghai , Rufener G. K.
Published: July 2010

Selection of donor lines to improve parents of single crosses and the relationship between inbred per se and hybrid performance are major concerns of corn (Zea mays L.) breeders. We attempted to use molecular marker technology to address these concerns. Our specific objectives were to evaluate methods of using molecular marker data to (i) identify parents useful for improving single cross hybrid and (ii) compare marker genotypic means measured at the inbred level to those measured at the hybrid level. Performance data from a diallel cross among 14 corn inbreds were used. Molecular marker data were obtained on the 14 inbreds for 14 allozyme and 52 restriction fragment length polymorphism loci. Number of unique marker alleles in a donor inbred was not a good measure of the value of the donor for improving a single cross. A donor value calculated using genotypic means for loci that showed significant associations with grain yield was highly correlated with μG, a measure of the value of a donor. Means of homozygous marker genotypes measured at the inbred level were significantly correlated with means measured at the hybrid level. These correlations (0.71 for yield, 0.75 for plant height, 0.51 for ear height, and 0.82 for flowering date) were generally higher than those between midparent and F1 means, but not high enough to accurately predict hybrid performance if selection were based on inbred genotypic means.
Wheat Protein Concentration after Two Cycles of Divergent Selection for Seed Density
Authors: Griffey C. A. , Peterson C. J. , Mattern P. J.
Published: July 2010

Improvement of seed protein concentrations in wheat (Triticum aestivum L.) has been hindered by lack of effective selection methods applicable to early‐generation segregating populations. The objective of this study was to evaluate selection for imbibed seed density as a method to increase or decrease seed protein concentrations of bulk winter wheat populations. Twelve populations, each in F3, F4, F5, and F6 generations derived from crossing exotic and adapted cultivars (each cross possessing at least one high‐pl~protein parent), were used in two cycles of selection without recombination. Low‐ and high seed density fractions were selected visually after low‐temperature seed imhibition using sucrose‐NaCl solutions with densities of ⊄ 1.24 and 1.25 Mg m−3, respectively. Six of the 12 Cycle 1 selected populations had significant protein increases with low seed‐density selection, and four populations were reduced in seed protein concentration with high density selection. Protein changes achieved, using a selection intensity of ⊄ I0%, ranged from 2 to 4 g kg−1 for density selected vs. unselected populations. After two cycles of selection, protein concentrations were significantly increased in 9 of 12 low density selected populations, ranging from 3 to 7 g kg−1. High‐density selection was less effective, with significant protein decreases in 6 of 12 populations, ranging from 3 to 5 g kg−1 less than unselected bulks. Selflng within populations did not influence selection efficiency. Change in kernel weights of selected bulks was small. A negative association between protein concentration and grain yield was noted. Lack of relationship between initial protein differences after separation and results in field trials suggests that non genetic variation in protein concentrations of individual seed may limit effectiveness of the technique.
Cytoplasmic‐Nuclear Gene Interaction for Plant Vigor in Helianthus Species
Authors: Jan C. C.
Published: July 2010

Genetic diversity provided by of wild sunflower (Helianthus spp.) has not been exploited. This field and greenhouse study determined the inheritance and characterized a unique type of cytoplasmic‐nuclear interaction involving major genes affecting plant vigor. Reduced vigor (RV) plants with pale‐green leaves and stunted growth were obtained when back crossing inbred line HA 89 into cytoplasms of five perennial Helianthus species: H. mollis Lam., H. maximiliani Schrader, H. grosseserratus Martens, H. divaricates L., and H. angustifolius L. Reduced‐vigor plants produced only RV progenies, either through back crossing or self‐pollination. Crossing normal backcross (BC) progenies with HA 89 resulted in a segregation ratio of one normal to one RV, suggesting that each of the five species has a single dominant nuclear gene capable of restoring normal plant vigor. Progeny of diallel crosses among normal plants in advanced BC generations in the five cytoplasms segregated three normal to one RV plants, indicating similarities among these perennial cytoplasms and among their restoration genes. Compared with normal plants, the RV plants had significantly reduced plant height, head diameter, seed weight, percent seed set, net photosynthesis, total leaf chlorophyll, and delayed flowering. Effects of H, maximiliani cytoplasm were less extreme. These perennial species may have shared a common evolutionary origin, and their utilization as sources of genetic variability for sunflower improvement should not be affected by the described cytoplasmic‐nuclear interaction.
Weighted vs. Unweighted Mean Performance of Varieties across Environments
Authors: Bernardo Rex
Published: July 2010

If within‐environment error and variety × environment interaction variances are heterogeneous across environments, weighted means may provide more precise estimates of varietal mean performance than the arithmetic (unweighted) mean. The objective of this study was to compare the arithmetic mean (YA) and two types of weighted means (YR and YE) as estimators of varietal performance. Weights were inversely proportional to Shukla's residual variance estimates in YR and to withinenvironment error mean squares in YE. Fifty‐threenvironments used in a corn (Zea mays L.) yield trial were repeatedly partitioned into model data and validation data. Compared with YR and YE, YA had slightly higher correlations with validation data means. Least significant differences of YA were 2 and 11% smaller than those of YR and YE, respectively. The failure of YR to be superior over YA was attributed to sampling error in the estimates of residual variances. The continued use of the arithmetic mean in estimating average varietal performance is suggested, even if error and variety × environment interaction variances are heterogeneous.
Fertile Transgenic Rice Plants Generated via Protoplasts from the U.S. Cultivar Labelle
Authors: Li Zhijian , Xie Qingjin , Rush Milton C. , Murai Norimoto
Published: July 2010

Toward a long‐term goal of applying gene transfer technology to enhance rice (Oryza sativa L.) breeding programs in the USA, we initiated a concerted effort to establish a transformation system for the long‐grain commercial cultivar Labelle. Embryogenic protoplasts were isolated from immature panicle‐derived suspension cultures. A hygromycin resistance gene was introduced into protoplasts by treatment with polyethylene glycol. Up to 6% of the colonies showed hygromycin resistance after 3 wk selection in the presence of 190 µM hygromycin B. Plantlets were regenerated from ≈30% of the resistant calli. All six transgenic Labelle plants that were grown to maturity set viable seeds. Southern blot hybridization and progeny segregation analysis demonstrated that hygromycin resistance genes were integrated into the rice genome and inherited as a single locus or closely‐linked loci. We now have a successful procedure to introduce important agronomic traits from other organisms into U.S. long‐grain rice cultivars.
Retention of Genetically Superior Lines during Early‐Generation Testcrossing of Maize
Authors: Bernardo Rex
Published: July 2010

Selection of partially inbred maize (Zea mays L.) lines, based on early‐generation testcross performance, involve some risk of losing lines that would eventually perform well in testcrosses at homozygosity. The objectives of this study were to calculate the probabilities of retainingenetically superior lines during early testing and examine selection intensities appropriate for differentesting generations and levels of heritability. Expected genetic and phenotypic correlations among testcrosses at different selfing generations were used to calculate the conditional probabilities that (i) the testcross genetic value of a homozygous (SI) line is in the upper aI of the distribution, given that the testcross phenotypic value of its ancestral Sn line is in the upper an of the distribution; and (ii) the testcross phenotypic value an Sn line is in the upper an of the distribution, given that the testcross genetic value of its descendant SI line is in the upper aI of the distribution. Low heritability values severely decrease the effectiveness of early testing. If heritability is low, selfing for two or three generations prior to test crossing may be desirable to increase the likelihood of retaining lines that would perform well at homozygosity. Larger proportions of lines need to be retained at earlier than at later selfing generations to prevent excessive loss of genetically superior lines. The conditional probabilities given in this paper may help breeders choose a combination of stage of test crossing and selection intensity that would allow a balance between number of lines retained for further testing and risk of losing genetically superior lines.
Pod Removal Effects on Cowpea Genotypes Contrasting in Monocarpic Senescence Traits
Authors: Gwathmey C. Owen , Hall Anthony E. , Madore Monica A.
Published: July 2010

In grain legumes, the extent of leaf senescence during podding varies among genotypes and may also be modified by sink reductinu, but few studies have compared these phenomena. In this study of delayed leaf senescence (DLS) in cowpoa [Vigna unguiculata (L.) Walp.] field grown populations of normally senescent (CB5 and 1411) and DL (7964 and 8517) genotypes were subjected to two treatments: remova of pods reaching color‐break, and a nonpicked control. Picking increased leaf area duration more in normally senescent genotypos than in DLS genotypes during the reproductive phase. Pod removal change the reproductive pattern of senescent genotypes from a monomod to a bimodal distribution similar to that of nonpicked DLS genotypes Picking had little influence on the number of pods produced during the first podset. Removing pods from CB5 progressively increased the ratio of photosynthetic source size to reproductive sink size during the first podset, relative to nonpicked CBS. During the same time, soluble sugar concentrations were maintained and starch accumulated in stems of picked CB5 and of nonpicked DLS genotypes, while these carbohydrates were depleted from stems of nonpicked CBS. Maintenance of stem carbohydrate concentrations was associated with greater plant survival of the first podset, which led to greater pod production during the second podset. Second‐set pod production of picked CB5 and 1411 approached that of nonpicked DLS genotypos. We hypothesize that pod removal altered photo assimilate partitioning in normally senescent genotypes such that they phenotypically resembled nonpicked DLS genotypes.
Recurrent Selection for Resistance to Leaf Feeding by Fall Armyworm on Maize
Authors: Widstrom Neil W. , Williams W. Paul , Wiseman Billy R. , Davis Frank M.
Published: July 2010

Populations and inbreds of maize, Zea mays L., with effective levels of resistance to damage by fall armyworm, Spodoptera frugiperda (J.E. Smith), are needed to transfer resistance to commercial hybrids for the U.S. Southeast. Recurrent S1 selection for resistance to leaf feeding by larvae of fall armyworm was conducted with an exotic maize synthetic, FAW‐CC. Our objectives were to estimate genetic variances, heritabilities, and genetic gain and to evaluate effectiveness of selection by comparing predicted and realized progress after five cycles of selection. Variance components and heritabilities were estimated from the S1 progeny performance tests for each cycle of selection, and progress was determined from a replicated evaluation of populations per se that were generated by recombinations from each selection cycle. Estimates of genetic variance for resistance to leaf feeding, evaluated on a rating scale of 0 to 9 (0 = no damage, 9 = all leaves destroyed), were significant for all but the S1 progenies in the Cl generation. Significant genotype × location interactions also occurred among S1 progenies. Heritability estimates were significant (range = 0.45–0.77) for all but the Cl cycle S1s, and selection gains were about two‐thirds as large as predicted from estimated parameters. The regression of leaf‐damage rating on selection cycles gave a significant b value of −0.31 units per cycle of selection. Advanced cycles of FAW‐CC should be good sources of inbreds with intermediate to high levels of resistance to leaf feeding by larvae of the fall armyworm.