bluuebunny/crossref_metadata_2025 huggingface dataset:
Crop Effects on Broad‐Sense Heritabilities and Genetic Variances of Sugarcane Yield Components
Authors: Milligan S. B. , Gravois K. A. , Bischoff K. P. , Martin F. A.
Published: July 2010

Estimates of genetic variances and derived statistics of pertinent traits are essential for efficient plant breeding programs. For clonal sugarcane (Saccharum spp.) populations in Louisiana, such estimates (and unconfoanded estimates of genotype by environment [GE] and genotype by crop [GC] variances) were lacking. The objectives of this study were to estimate broad‐sense genetic and GE variance components for a clonal sugarcane population representative of initial stages of replicated testing and to determine the relative importance of years, locations, and crops. Thirty‐seven genotypes were planted in 1983 and replanted in 1984 in replicated tests at five locations. Data from two 3‐yr. crop cycles were used. Genetic advance (GA) indicated considerable improvement potential in sucrose yield, cane yield, and stalk number and weight. Genotypic variance was generally secondary to error variance in determining phenotypic variance; GE variances were tertiary to genotypic and error variances. Within a crop, genotype by location (GL) variances tended to be larger than genotype by year (GY). Estimates of potential of plant cane sucrose yields over years and locations implied testing across locations could substitute for years, effectively reducing the time to identify elite clones. Analysis across crops showed GC, GL and GYL interaction variances were usually larger than GY. Estimates of GA showed no difference in potential gain from replicating across years vs. crops. For several traits, the most potential for improvement is in older crop performance, and selection is best practiced with regard to crop.
Inheritance of Resistance to Gray Leaf Spot of Corn
Authors: Elwinger G. F. , Johnson M. W. , Hill R. R. , Ayers J. E.
Published: July 2010

Host plant resistance can play an important role in reducing the severity of gray leaf spot (caused by Cercospora zeae‐maydis Tehon & Daniels) on corn (Zea mays L.). Inheritance of resistance was studied using four generations (inbred, single cross, F2, and backcross) produced from inbred lines PA875, VA59, B68Ht, H93, PA887P, and PA76‐22. Four weekly estimates of percent leaf area affected were made on experiments planted at Shenandoah County, Virginia, and Franklin County, Pennsylvania. Disease progress curves were estimated for each genotype using orthogonal polynomial regression. There were significant differences (P < 0.05) among genotypes for the mean, linear, and quadratic regression response effects within the inbred, single cross, and backcross generations and for the mean response effect within the F2 generation. No differences were detected among cubic effects in any of the generations. General combining ability (GCA) and specific combining ability (SCA) mean squares were significant (P < 0.01) for and linear response effects in diallel analyses of single crosses; GCA sums of squares were from 1.8 to 11.5 times larger than SCA sums of squares for these effects. Prediction of single cross performance using information from per se evaluation of inbreds resulted in r2 values of 0.55 to 0.67 for mean response effects and 0.33 to 0.45 for linear responseffects. Prediction of backcross performance using information from diallel analyses resulted in r2 values of 0.81 to 0.90 for mean response effects and 0.61 to 0.89 for linear response effects. Regression of area under the disease progress carve data onto two models based on complete dominance indicated that dominance was important. For the genotypestudied, a model more complex than simple additivity was required to fully explain inheritance of resistance to gray leaf spot; however, screening of inbreds prior to testing them for combining ability should be effective in eliminating those that are most susceptible.
Intra‐ and Interspecific Hybridization between Dallisgrass and Vaseygrass
Authors: Caponio I. , Quarín C. L.
Published: July 2010

Two sexual tetraploid (2n = 4x = 40) biotypes of dallisgrass (Paspalum dilatatum Poir.) were crossed with vaseygrass (P. urvillei Steud.) (2n = 4x = 40) to investigate their genomic relations and determine the feasibility of gene exchange between these forage grasses. There are some morphological differences between the dallisgrass biotypes. They are referred to as P. dilatatum (F) and P. dilatatum (V) in this study. These biotypes also were crossed to investigate their relations. Cytologically, P. dilatatum (F), P. dilatatum (V), and P. urvillei behaved as allotetraploids, averaging 19.94, 19.97, and 20 bivalents per metaphase I cell, respectively. Crossability between P. dilatatum (F) and P. dilatatum (V) was 19.2%. The intraspecific hybrids had regular meiotic chromosome pairing, averaging 19.94 bivalents per cell. Thus P. dilatatum (V) apparently has the same genomes (II JJ) as the P. dilatatum (F) biotype. Crossability between P. dilatatum (F) and P. urvillei was low (1.2%). Chromosome pairing in the hybrids was regular averaging 19.96 bivalents per cell, indicating that P. dilatatum (F) and P. urvillei share the same genome formula (II JJ). Seed set in the hybrids was low ranging from 1.4 to 2.1%. Crossability between P. dilatatum (V) and P. urvillei was 19.3%. The hybrids exhibited similar meiotic behavior as the previous hybrids averaging 19.88 bivalents per cell. Fertility was investigated for six P. dilatatum (V) ✕ P. urvillei F1 hybrids and seed set ranged from 0.3 to 18.8% among them. Seed set increased in the F2 and backcross progenies. Some backcross plants exhibited similar seed set as the parental species. Findings from this study strongly implies that gene exchange between tetraploid P. dilatatum biotypes and P. urvillei is possible.
Additive Main Effects and Multiplicative Interaction Analysis of Two International Maize Cultivar Trials
Authors: Crossa J. , Gauch H. G. , Zobel R. W.
Published: July 2010

The methodology used by the International Maize and Wheat Improvement Center (CIMMYT) to develop and improve its maize (Zea mays L.) germplasm involves evaluation of families or experimental varieties in extensive international testing trials. The genotype‐environmental interaction is produced by differential genotypic responses to varied environmental conditions. Its effect is to limit the accuracy of yield estimates and complicate the identification of specific genotypes for specific environments. The objective of this study was to use the Additive Main effects and Multiplicative Interaction (AMMI) method, with additive effects for genotypes and environments and multiplicative terms for genotype‐environment interaction, for analyzing data from two international maize cultivar trials. Results from the first trial were: (i) predictive assessment selected AMMI with one principal component axis, (ii) AMMI increased the precision of yield estimates equivalent to increasing the number of replications by a factor of 4.30, (iii) AMMI provided much insight into genotype‐environment interactions, and (iv) AMMI selected a different highest‐yielding genotype than did treatment means in 72% of the environments. Results for the second trial were that predictive assessment selects the AMMI with none of the principal component axes, which increased precision equivalent to increase the number of replications by a factor of 2.59.
Gene Frequency Changes in Soybean Bulk Populations Exposed to Phytophthora Rot
Authors: Kilen T. C. , Keeling B. L.
Published: July 2010

Phytophthora rot (caused by Phytophthora megasperma Drechs. f. sp. glycinea Kuan & Erwin) frequently causes severe injury to soybean [Glycine max (L.) Merr.]. Screening populations for resistance genes in cultivar improvement programs is labor intensive, and alternative systems would be desirable. The objective of this study was to determine the shift in frequencies of two genes controlling resistance to phytophthora rot when segregating soybean populations were advanced on fields naturally infested with the pathogen. ‘Tracy’ (having resistance genes Rpsl‐b and Rps3) was crossed with ‘Forrest’ and a highly susceptible breeding line, D55‐1492. Forrest has no known genes for resistance to phytophthora rot, but shows minimal injury from the disease in field plantings where D55‐1492 shows stand loss or is severely stunted. Populations were advanced on clay soil known to be predominantly infested with Race 1 of the pathogen. To identify individual genes, 200 randomly selected plants from each population were harvested individually and their progeny inoculated with Races 2 and 7. A shift to a higher frequency of the Rpsl‐b allele, but not Rps3, was observed after 5 yr of advance in the Tracy ✕ DSS‐1492 cross. No shift to a higher frequency occurred in the Tracy ✕ Forrest cross, suggesting that the field resistance of Forrest was competitive with genetic resistance. The results indicate that the frequency of phytophthora‐resistance genes can be effectively increased under natural disease pressure if the population segregates for highly susceptible plants (or if disease pressure is much greater than in the environments sampled).
Rootworm and Mechanical Damage Effects on Root Morphology and Water Relations in Maize
Authors: Riedell Walter E.
Published: July 2010

There is little information in the literature concerning the effect of corn rootworm larval feeding on the physiology of maize (Zea mays L.). This study was conducted to determine if root damage caused by western corn rootworms (Diabrotica virgifera virgifera LeConte) affects relative water content, leaf water potential, or stomatal conductance in leaves of the host plants. The effect of mechanical root‐cutting treatments was also evaluated. The experiment was conducted under controlled‐environment conditions in a greenhouse. Plants were damaged at the V9 stage of leaf development by prior infestation with 50 or 150 larvae per plant or by cutting 25 or 75% of the root system from the plant. Root systems and plant water relations were evaluated at this stage of development and again at tassel. Larval root damage was confined to the axes of the fourth and fifth nodes of roots. There were no differences in relative water content, leaf water potential, or stomatal conductance between infested plants or controls at V9; at tassel, however, leaf water potential was significantly higher and stomatal conductance was significantly less in infested plants (P < 0.05). Mechanical cutting of roots caused significant differences (P < 0.05) in relative water content and stomatal conductance at both sampling dates. These results indicate that mechanical root damage reduced the ability of root systems to provide adequate water to the shoots to a much greater extent than did corn‐rootworm damage.
Leaf Orientation of Soybean Seedlings. I. Effect of Water Potential and Photosynthetic Photon Flux Density on Paraheliotropism
Authors: Berg Virginia Seymour , Heuchelin Scott
Published: July 2010

Paraheliotropic (light avoiding) leaf movements can reduce transpirational water loss by lowering light interception by the leaf through action of the pulvinus. We investigated effects of plant water potential (ψw) and photosynthetic photon flux density (PPFD) on paraheliotropism in young seedlings of soybean [Glycine max (L.) Merr. cv. Northrup King S1346], The effect of paraheliotropism on leaf temperature, ψw, and stomatal conductance (ge) was determined. The angles of unifoliolate and lower trifoliolate leaves were measured for plants at a range of ψw values under different sources of illumination (sun, metal halide lamp, and fluorescent light bank) at PPFD ranging from 500 to 1600 μmol m‐2 s‐1. Leaf temperatures and gc were measured for selected plants, including those with'leaves restrained in a horizontal position. The angle between unifoliolate leaves, measured at the base of the leaves, was highly correlated with ψw. Both unifoliolate leaves and the terminal leaflets of trifoliolate leaves exhibited less paraheliotropism at a given ψw when PPFD was reduced. Paraheliotropism was associated with improved plant water status and lower leaf temperatures, but gc did not differ between paraheliotropic leaves and those restrained in a horizontal position. Paraheliotropic leaf movement and stomatal closure acted in parallel, commencing at approximately −0.4 MPa. Paraheliotropic leaf movements in soybean seedlings provide a mechanism that, with stomatal closure, can reduce transpiration under conditions of low ψw and high PPFD.
Potassium Nutrition Effects on Lint Yield and Fiber Quality of Acala Cotton
Authors: Cassman K. G. , Kerby T. A. , Roberts B. A. , Bryant D. C. , Higashi S. L.
Published: July 2010

Although results from in vitro ovule culture studies have demonstrated a specific K requirement for fiber growth, a direct association between the K status of the cotton (Gossypium hirsutum L.) plant and fiber quality has not been established under field conditions. To evaluate this relationship, a single cultivar (1985) and two cultivars (1986 and 1987) were grown with 0, 120, 240, or 480 kg K ha‐1 in 10 blocked replicates of each K level on an irrigated, vermiculitic soil. There was a significant seed‐cotton yield response to applied K in each year. Lint yield, however, increased relatively more than seed yield, resulting in a greater lint percentage as plant K supply increased. The greater lint percentage reflected increased fiber length and secondary wall thickness (measured as a micronaire index) obtained from plants that received fertilizer K. For both cultivars, the fiber length, micronaire index, fiber strength and percent elongation, and fiber length uniformity ratio (dependent variables) were each positively related to (i) fiber K concentration at maturity, (ii) leaf K concentration at early bloom, and (iii) an index of soil K availability as independent variables in regression analyses. Comparison of cultivar regressions, however, indicated that fiber quality of ‘Acala GC510’ was higher than that of ‘Acala SJ2’ at low fiber, leaf, or soil K levels. We conclude that K supply to cotton fruit is an important determinant of fiber quality under field conditions, and that the K requirement for producing high lint yield with acceptable quality may differ among genotypes.
Evaluation of Northern USA Soybean Cultivars for Maturity in Chile
Authors: Bryon D.F. , Orf J.H.
Published: July 2010

Selection for maturity of soybean [Glycine max (L.) Merr.] genotypes in winter nurseries may increase the efficiency of soybean breeding programs. The objective was to determine if soybean adapted to Minnesota and Wisconsin would mature similarly in the USA and Chile. Six cultivars of Maturity Groups 00, 0, and I were evaluated for maturity differences at Prescott, WI and Rosemount, MN in the summers of 1984 and 1985 and at Santiago and Buin, Chile during the northern hemisphere winters of 1984–1985 and 1985–1986. Cultivar ✕ location interactions were not significant (P ≥ 0.10) within countries. When maturity differences among cultivars were compared between the two countries, the cultivar ✕ country and cultivar ✕ years/countries interactions were significant (P < 0.01), but the interactions were due to differences in magnitude rather than differences in rank. Selection for maturity can be done effectively in Chile for soybeans of Maturity Groups 00, 0, and I.
Plant Height vs. Mesocotyl and Celeoptile Elongation in Rice: Linkage or Pleitropism?
Authors: Dilday R. H. , Mgonja M. A. , Amonsilpa S. A. , Collins F. C. , Wells B. R.
Published: July 2010

Semidwarf cultivars of rice (Oryza sativa L.) produce shorter mesocotyls and coleoptiles than normal‐height rice. Short mesocotyl and coleoptilelongation can cause poor emergence and inadequate stand establishment. The hypothesis has been that, in rice, plant height and mesocotyl and coleoptile elongation are pleiotropic (i.e., one gene controls more than one plant characteristic). Laboratory, greenhouse, and field experiments were conducted to evaluate the relationship of mesocotyl and coleoptile elongation to stand establishment, seedling vigor, and plant height in rice. The potential length of the mesocotyl and coleoptile of semidwarf and standard cultivars was evaluated in the laboratory. The germplasm lines exhibited inherent differences in mesocotyl and coleoptile elongation. The semidwarf germplasm (‘MI01’ and RU7703008) described this study ranged from 75 to 90 cm in height and showed reduced mesocotyl, coleoptile, and total lengths (mesocotyl + coleoptile), whereas the tall plant types (‘L201’ and ‘Labelle’) had comparatively longer mesocotyl, coleoptile, and total lengths. Significant differences were detected among seeding depths and cultivars in the greenhousexperiment for emergence percentage. The field experiment, which was conducted on a Crowley silt‐loam soil (fine, montmorillonitic, thermic Typic Albaqualt), verified that poor stand establishment at deep planting depths of the semidwarf cultivars was associated with short mesocotyls and coleoptiles. Semidwarf germplasm was developed that can produce a long mesocotyi and coleoptile, which demonstrates that plant height and mesocotyi and coleoptile elongation in rice is not due to pleiotropism but to linkage.
Adequacy of Interval Estimates of Yield Responses to Ozone Estimated from NCLAN Data
Authors: Somerville M. C. , Dassel K. A. , Rawlings J. O.
Published: July 2010

Relative yield losses from O3 have been estimated by the National Crop Loss Assessment Network (NCLAN) using a nonlinear Weibull response model. The estimated losses were presented in terms of confidence interval estimates based on first‐order linear approximations of variances and normality of estimates. Such interval estimates (Wald estimates) from nonlinear models can be inadequate. Nine Weibull response equations estimated from NCLAN studies were used to assess the adequacy of Wald confidence interval estimates by comparison with interval estimates based on the likelihood ratio test. Three response equations from individual studies were used for illustration of second‐order adjustments to the Wald estimates and the use of measures of parameter‐effects curvature as flags for cases where linear approximations may be inadequate. The Wald interval estimates were clearly inadequate in two of the three individual studies, which had been chosen to represent cases most likely to show inadequacy because of limited coverage of the response curve and/or high variability. In the third study, which had good coverage of the response curve and relatively low variability, the Wald confidence intervals were nearly identical to the likelihood ratio intervals. Measures of parameter effects curvature identified the two cases where the linear approximation was inadequate and showed whether the second‐order adjustments would result in acceptable confidence intervals. Comparisons suggested that Wald confidence interval estimates provided satisfactory approximations for NCLAN response curves that had been computed from data involving more than one experiment, and even for individual experiments where there was adequate coverage of the response curve and moderate variability.
Fruiting Efficiency in Cotton: Boll Size and Boll Set Percentage
Authors: Jenkins Johnie N. , McCarty J. C. , Parrott W. L.
Published: July 2010

Cotton plants, Gossypium hirsutum L., initiate more fruiting buds than are matured. This research quantified the boll set percentage and boll size by fruiting site in a population of cotton plants. The fruiting sites of harvestable bolls were recorded for 2 yr in eight cultivars: Stoneville 213 (ST 213), Stoneville 506 (ST 506), Stoneville 825 (ST 825), Tamcot CAMD‐E (CAMD‐E), Deltapine 50 (DPL 50), McNair 235 (MC 235), DES 119, and Deltapine 20 (DPL 20). Plants were thinned to ~95 000 plants ha−1 in rows spaced 1 m apart. All cultivars behaved similarly; however, in the newer, early‐season cultivars (DPL 50, DPL 20, and DES 119), more plants retained a boll at Nodes 6 through 8 than in the older cultivar ST 213. Percentage of plants with a harvestable boll at Position 1 on a sympodial branch increased from 9.6% at Node 6 to 48.7% at Node 12, declining thereafter, and varied from 0.2 to 21.2% at Position 2. Fewer than 5% of the plants matured a boll at Position 3. Percentage of plants with a harvestable boll peaked at Nodes 11, 9, and 8 for Positions 1, 2, and 3, respectively. Assuming a 3‐d vertical flowering interval, boll size and boll set percentage began decreasing 15 to 18 d after first bloom. In 1988, fewer plants matured a harvestable boll at Nodes 9 through 12 than in 1987. This was attributed to reduced solar radiation, lower temperatures, and more daytime rainfall events during July. Bolls at Position 1 were 14 and 21% larger than those at Positions 2 and 3, respectively. Boll size followed a pattern similar to percent of plants with a harvestable boll. Partitioning of photosynthate to older bolls resulted in fewer mature bolls at Positions 2 and 3 for all nodes. Smaller bolls had fewer and smaller seed. This information on plant fruiting by positions and nodes can guide breeders in selection for earlier‐ and higher‐yielding cultivars.
High‐ vs. Low‐Stress Yield Test Environments for Selecting Superior Soybean Lines
Authors: Whitehead W. F. , Allen F. L.
Published: July 2010

An important factor in cultivar development is the choice of yield testing sites that permit the best discrimination among breeding lines. The objectives of this study were to test the hypotheses that: (i) there are genotypes that have superior yield potential in both low‐ and high‐stress edaphic conditions, and (ii) yield tests conducted exclusively in low‐stress environments can be used effectively for selecting such genotypes. Forty‐eight random F4‐derived soybean [Glyciue max (L). Merr.] lines were evaluated for yield over 4 yr on a low soil acidity, high fertility site (low‐stress) and on a high soil acidity, low‐medium fertility site (high‐stress) at each of two locations (Crossville and Milan, TN). In addition, low‐stress yield tests were conducted at five other locations during each of the last 2 yr. The grand mean of low‐stress tests was 2.25 Mg ha−1 compared to 0.62 Mg ha−1 for high‐stress tests. The 16 lines (33% selection intensity), which had overall mean yields above the grand means of combined high‐ and combined low‐stress tests were designated as the superior lines. Simulated selections revealed that 32 to 54% of the superior lines would have been selected using either type of nursery at either the Crossville or Milan location each year. At least one of the top three lines would have been chosen in every case, regardless of type(s) of nursery environment, location(s), or year(s) used. These results indicate that the low‐stress environments commonly used in soybean breeding programs should provide high probabilities for selecting genotypes that have superior yield potential in both low‐ and high‐stress edaphic conditions. Regression coefficients for line mean yield regressed on site mean were generally highest for the superior lines (b ≥ 1.0), but the deviations from regression were similar to the non superiors. The ranges for maturity and plant height were similar for both groups indicating that selection for superior lines would not have led to extremes for either trait.
Prodiamine Effects on Quality and Rooting of Kentucky Bluegrass Turf
Authors: Hummel Norman W. , Fowler Melissa Craven , Neal Joseph C.
Published: July 2010

As new herbicides are investigated for use on turf, it is important to study the effects continued use of these materials have on desirable grass species. A field investigation was conducted to determine the influence of prodiamine [2,4‐dinitro‐N3,N3‐dipropyl‐6‐(trifluoromethyl)‐1.3‐benzenediamine] application rate and frequency on Kentucky bluegrass (Poa pratensis L.) turf over a 4‐yr period. Root mass and turfgrass density decreased following prodiamine treatment. Turfgrass quality ratings decreased as prodiamine rate increased, but remained acceptable at rates below 1.1 kg ha−1 a.i. The projected use rate for prodiamine in the northeastern USA is 0.56 kg ha−1 a.i. Quality was reduced and necrotic ring spot (Leptosphaeria korrae Walker and Smith) disease more severe when prodiamine was applied annually vs. biennially. Percent turf area damaged by necrotic ring spot also increased as prodiamine rate increased, but was most severe at rates greater than 2.2 kg ha−1 a.i. The quality, density, and disease data indicated that annual applications of prodiamine can be detrimental to Kentucky bluegrass turf. These results suggest that it may be advantageous to avoid prodiamine applications in successive years or to alternate it with less phytotoxic preemergence herbicides.
Turkish Alfalfa Cultivars Screened for Alfalfa Weevil Resistance
Authors: Ratcliffe Roger H. , Elgin James H.
Published: July 2010

Alfalfa (Medicago sativa L.) cultivars have been developed with tolerance to the alfalfa weevil [Hypera postica( Gyllenhal)], but not antibiosis or nonpreference. This study evaluated 28 Turkish alfalfa cultivars as sources of resistance expressed as antibiosis or feeding nonpreference. One hundred plants of each cultivar were tested in the laboratory to characterize resistance. Resistance was evaluated by caging 10 neonate alfalfa weevil larvae on plants for 8 d. Mean larval survival and weight after 8 d feeding was compared with that on the susceptible cultivar Ranger. Plants selected for resistance were vegetatively propagated and re‐evaluated in replicated tests. Larval survival and development on Turkish cultivars did no differ from that on Ranger although larval survival was lower on three selected clones in one experiment. These clones did not demonstrate resistance when retested approximately 2 mo later. None of the Turkish cultivars appeared to be promising sources of antibiosis or nonpreference.
Reaction of 578 Spring Spelt Wheat Accessions to 35 Races of Wheat Stem Rust
Authors: McVey D. V.
Published: July 2010

A survey of spelt wheat accessions (Triticum aestivum ssp. spelta L.) was made to characterize their reactions to stem rust (Puccinia graminis Rob. ex Desm. f. sp. tritici). Spelt wheat genotypes cross readily with bread wheat (Triticum aestivum L.) and could be used as donor parents in bread wheat breeding programs. Because of the paucity of information on their reaction to stem rust in the literature, the objectives of this study were to: (i) screen spelt accessions for possible new sources of resistance to wheat stem rust, and (ii) postulate and confirm the presence of known genes for resistance to stem rust. Infection‐type data from seedlings artificially infected with stem rust were used to postulate Sr genes present in 578 spring spelt accessions from the USDA National Small Grain Collection. Conventional genetic studies were used to confirm the hypothetical resistance genotypes derived from infection‐type data. Genetic studies confirmed the presence of postulated genes for resistance Sr9e, Sr9f, Sr18, SrLC, and SrMcN; Sr9g was absent. Other genes for resistance postulated to be present included Sr9a, Sr9d, Srl0, Sr15, Sr17, Srl9, and Sr20. Infection‐type data proved the absence of Sr5, Sr6, Sr8a, Sr9b, Sr11, Sr13, Sr14, Sr16, Sr24, Sr25, Sr26, Sr29, Sr36, and SrTmp in these spelt accessions. Several unidentified genes that were postulated to be present may provide useful levels of resistance when transferred in combinations to bread wheat.
Brachytic Stem and Narrow Leaflet Effects on Soybean Seed Composition and Yield
Authors: Kilen T. C.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seed protein and oil concentrations and their interrelationships with seed yield are important considerations in a soybean breeding program. Brachytic stem and narrow leaflet traits were transferred to a ‘Tracy‐M’ background to evaluate their effect on seed yield and concentration of seed protein and oil. Data were collected oil eight brachytic stem (sb) lines, eight narrow leaflet (In)lines, seven lines with the combination (sb, In) of traits, and the recurrent parent, Tracy‐M, from 1986 through 1988 at Stoneville, MS, on a Sharkey clay soil (very‐fine, montmorillonitic, nonacid, thermic Vertic Haplaquept). Seed protein and oil concentrations were determined by near infrared reflectance. Combined over years, Tracy‐M had a seed yield of 2612 kg ha−1. Seed yields of the sb, sb In, and In groups were 2352, 2213, and 2361 kg ha−1, respectively, and were significantly (P ≤ 0.01) lower than that of Tracy‐M. Seed protein concentration of the sb, sb In, and In groups were 441, 444, and 426 g kg−1, respectively, and were all significantly (P ≤ 0.01) different from the 432 g kg−1 protein concentration of Tracy‐M. Only the sb In group had an oil concentration that was significantly (P ≤ 0.01) different from that of Tracy‐M. The reason for the significantly higher seed protein concentration of brachytic lines over that of the recurrent parent Tracy‐M is unknown. None of the ancestors used in the development of the experimental lines has a seed protein concentration as high as that of Tracy‐M.
Cytogenetics and Reproductive Behavior of 48‐Chromosome Pearl Millet ✕ Pennisetum squamulatum Derivatives
Authors: Dujardin Michel , Hanna W. W.
Published: July 2010

Pennisetum squamulatum Fresen is a perennial, hexaploid (2n = 6x = 54) species belonging to the tertiary gene pool of cultivated pearl millet [P. glaucum (L.) R. Br.]. Pennisetum squamulatum is a source of genes controlling apomixis, and useful genetic variability can be released in hybrids between sexual pearl millet and apomictic species. New genome combinations were produced between tetraploid pearl millet (2n = 4x = 28) and P. squamulatum by pollinating a sexual interspecific F1 hybrid (2n = 41) with an apomictic 56‐chromosome derivative from another F1 interspecific hybrid (2n = 41). Fifteen hybrids with 2n = 47 or 48 chromosomes resulted from the crosses. All were perennial and morphologically similar to or taller than their parents, showed irregular metaphase I chromosome behavior, and were partially male and female fertile. Nine plants reproduced sexually, two by facultative apomixis, and four by obligate apomixis. This cross allowed the increase of the pearl millet genome in the new hybrids while introducing apomictic reproduction into several genotypes.
Genetic Diversity for Restriction Fragment Length Polymorphisms: Relation to Estimated Genetic Effects in Maize Inbreds
Authors: Melchinger A. E. , Lee M. , Lamkey K. R. , Woodman W. L.
Published: July 2010

Restriction fragment length polymorphisms (RFLPs) have been proposed for investigating relationships among inbred lines and predicting heterosis and performance of single‐cross hybrids in maize (Zea mays L.). Such use was evaluated in 20 maize inbreds classified as first‐cycle, second‐cycle, good, and poor lines, and in diallel crosses within types. Eight generations (parents, F1, F2, F3, backcrosses, and backcrosses selfed) from 67 crosses were evaluated for grain yield in five Iowa environments. Genetic effects were estimated from generation means by ordinary diallel analyses and the Eberhart‐Gardner genetic model. Poor inbreds showed significantly greater average heterosis than did good lines. Estimates of additive ✕ additive epistatic effects were negative and highly significant in all except first‐cycle lines. Using two restriction enzymes and 82 genomic) DNA probes distributed throughout the maize genome, all but one probe revealed polymorphisms with at least one enzyme (~4.5 variants per RFLP locus). Genetic distances between lines within types were estimated as Rogers' distances (RD). Within diallel sets, RD values were partitioned into general (GRD)and specific (SRD). All four types of lines showed similar means and substantial variation for RD; GRD explained ~40% of the variation among RD values. Cluster analyses revealed associations among lines generally consistent with expectations based on known pedigrees. Correlations of RD and SRD with F1 yield heterosis, specific heterosis, and specific combining ability were positive but small (r = ≤ 0.50) when combined for all crosses. Results indicated that RFLPs can be used to investigate pedigree relationships among maize inbreds, but also suggest that RFLP‐based genetic distance measures are of limited use in predicting heterotic performance of single crosses between unrelated lines.
Aluminum Tolerance in Soybean: I. Genotypic Correlation and Repeatability of Solution Culture and Greenhouse Screening Methods
Authors: Campbell K. A. Garland , Carter T. E.
Published: July 2010

Breeding for Al tolerance in soybean [Glycine max (L.) Merr.], has been hindered by confusion regarding screening methodology. This study was undertaken to determine the relationship between greenhouse and solution culture screening methods, using 12 diverse soybean genotypes. Greenhouse media consisted of a Goldsboro sandy loam (fine‐loamy, siliceous, thermic Aquic Paledult) at 19% Al saturation and the same soil amended with Al2(SO4)3 to 55% Al saturation. Solution‐culture media consisted of 0 or 11 μM Al2(SO4)3 added to 200 μM CaSO4 solutions. Traits measured were shoot dry weight in greenhouse pots and radical elongation rate in solution culture. Aluminum tolerance was detected with both screening methods; however, unlike previous studies, agreement between methods was good (rG = 0.81), indicating that the solution‐culture screen does have some utility in plant breeding. The solution‐culture screen had a higher repeatability (0.78, based on six replications, compared with 0.54 for the greenhouse), further substantiating its utility. Two factors were critical in establishing the relationship between the two screens: (i) expression of Al tolerance as a percentage of the control and (ii) abundant replication in the greenhouse. Reliance on growth in Al alone as a measure of tolerance led to poor agreement between methods in our study and is not recommended for breeding purposes, except where the genetic population is very uniform morphologically. Earlier published studies of Al tolerance in the greenhouse may have suffered from inadequate replication.
Diallel Analysis of Resistance in Sorghum to Greenbug Biotype E: Antibiosis and Tolerance
Authors: Dixon A. G. Olonju , Bramel‐Cox P.J. , Harvey T. L.
Published: July 2010

The greenbug [Schizaphis graminum (Rondani)] has been recognized as a major insect pest of sorghum [Sorghum bicolor (L.) Moench] in the Great Plains of the USA since 1968. Biotype E has been prominent since 1980 and twelve sources of resistance within the Sorghum genus have been identified. The objective of this study was to investigate the inheritance of resistance in sorghum among seven sources of resistance and three susceptible lines for antibiosis and tolerance involving Biotype E. A complete diallel mating, including reciprocals, of the ten resistant and susceptible lines of sorghum was evaluated in the growth chamber to estimate heterosis, general combining ability (GCA), specific combining ability (SCA), maternal and specific reciprocal effects for seedling antibiosis, and tolerance to greenbug Biotype E. The majority of crosses between the resistant sources and susceptible lines showed intermediate reactions and various degrees of partial dominance for both antibiosis and tolerance, suggesting polygenic inheritance. Combining ability analyses revealed that GCA, SCA, maternal, and specific reciprocal effects were significant for both seedling antibiosis and tolerance, but GCA was clearly more important in determining tolerance. The most antibiotic parent, IS2388, had the largest GCA effect for antibiosis while the most tolerant parent PI 229828, had the largest GCA effect for tolerance. The significant maternal and specific reciprocal differences found among parents and crosses, respectively, suggested that the variation observed in this experiment was due not only to direct genetic effects, but also to maternal and/or cytoplasmic inheritance and specific interactions of cytoplasmic and genetic factors.
Assimilation, Partitioning, and Nonstructural Carbohydrates in Sweet Compared with Grain Sorghum
Authors: Vietor D. M. , Miller F. R.
Published: July 2010

Nonstructural carbohydrate concentrations in stems are greater for sweet than grain sorghums [Sorghum bicolor (L.) Moench). Knowledge of plant characteristics associated with high nonstructural carbohydrates in sweet sorghum will aid efforts to increase nonstructural carbohydrates in grain sorghum stems. This study tested the hypothesis that variation of CO2 assimilation rate, leaf area, branching at upper nodes, and partitioning of 14C‐labeled assimilate to main stems are associated with variation of stem nonstructural carbohydrates. A sweet (Atlas ✕ Rio) and a grain (ATx623 ✕ RTx5388) hybrid, stages near and after physiological maturity, and defoliation and gibberellic acid (GA3) treatments provided sources of variation for study. Concentrations of nonstructural carbohydrates in lower and upper stems of the sweet hybrid were 1.4 and 2.7 times higher, respectively, than for the grain hybrid, after physiological maturity. Variation in branching, including 14C‐assimilate partitioning to branches, was not consistently associated with hybrid differences in stem nonstructural carbohydrates. Increased recovery (twofold) of 14C‐assimilate in roots and labeled leaves corresponded with lower percentages of 14C‐assimilate and lower concentrations of nonstructural carbohydrates in stems of the grain hybrid. Leaf areas and leaf CO2 exchange rate were twice as great for the sweet hybrid. Although defoliation of the sweet hybrid minimized leaf area differences between hybrids, the sweet hybrid accumulated twice as much nonstructural carbohydrates in branches after physiological maturity. Greater potentials for CO2 assimilation and for 14C‐assimilate accumulation in mature stem tissue were associated with higher levels of stem nonstructural carbohydrates in the sweet compared with the grain hybrid.
Seasonal Dry Matter, Nitrogen, and Dinitrogen Fixation Patterns of Crimson and Subterranean Clovers
Authors: Brink G. E.
Published: July 2010

Annual legumes are potential N sources in forage‐livestock systems, but information on the quantity and distribution of N2 fixed is lacking. Field experiments were conducted to determine the quantity and seasonal distribution of N2 fixed by two annual clovers, ‘Tibbee’ crimson clover (Trifolium incarnatum L.) and ‘Mt. Barker’ subterranean clover (T. subterraneum L.), having diverse annual dry matter (DM) production patterns. Plots were established on a Catalpa silty clay soil (fine, montmorillonitic, thermic Fluvaquentic Hapludoll) in each of 2 yr. Dinitrogen fixation was estimated by the I5N isotope dilution method with ‘Marshall’ annual ryegrass [Lolium multiflorum (L.) Lam.] as the non‐N2‐fixing control. A mean of 77% of the annual herbage yield provided by crimson clover was obtained by early April compared to 39% for subterranean clover. Subterranean clover produced greater annual herbage yield than crimson clover the first year (7.6 vs. 6.4 Mg DM ha−1), while yields under drought conditions were similar the second year (mean of 4.8 Mg DM ha−1). The clovers fixed an average of 196 and 114 kg N ha−1 in the first and second years, respectively. Depending on the harvest date, fixed N2 comprised 32 to 91% of total N in crimson clover and 75 to 91% of total N in subterranean clover. The average seasonal proportion of N derived from symbiosis by both clovers was equivalent in the first and second year (mean of 81 and 75%, respectively). Seasonal need for herbage production, rather than N2 fixation capability, may govern the value of crimson vs. subterranean clover in forage‐livestock systems.
Heat Tolerance in Winter Wheat: I. Hardening and Genetic Effects on Membrane Thermostability
Authors: Saadalla M. M. , Shanahan J. F. , Quick J. S.
Published: July 2010

Identification of heat‐tolerant winter wheat (Triticum aestivum L.) genotypes for the central and southern Great Plains of the USA as well as other areas of the world is desirable. In this study, the suitability of using the membrane thermostability (MT) test for ascertaining heat tolerance of winter wheat was determined. The MT test was conducted on seven cultivars using seedlings exposed to 0, 6, 12,18, 24, and 48 h of hardening (34 °C) and flag leaf material from the same cultivars grown to anthesis and exposed to 0, 48, and 120 h of hardening (34 °C), with the results expressed as relative injury (RI). Additionally, the MT test was conducted on 90 F5 genotypes derived from two crosses (45 genotypes per cross) involving one heattolerant and two heat‐sensitive parents (parents were a subset of seven previous cultivars). Plant material for the MT test was sampled at seedling (hardened for 48 h at 34 °C) and anthesis (hardened for 120 h at 34 °C) stages of growth. Large differences in RI were observed among the seven cultivars at both growth stages, ranging from 37 to 80% RI for seedlings and 31 to 69% RI at anthesis. The treatment protocols involving hardening for 48 and 120 h at seedling and anthesis stages, respectively, provided the greatest sensitivity in detecting genotypic differences in RI. The correlation of RI assessment for seedlings vs. that at anthesis for the 90 F5 genotypes was 0.79 (P ≤ 0.01), indicating that RI determined at the two developmental stages was highly associated.
Photosynthetic Carbon Production and Use by Developing Cotton Leaves and Bolls
Authors: Wullschleger S. D. , Oosterhuis D. M.
Published: July 2010

Understanding the photosynthetic C contribution of leaves to vegetative and reproductive processes is important in defining yield productivity. However, the morphological complexity of the cotton (Gossypium hirsutum L.) canopy has proven a significant barrier to establishing specific yield relationships. Therefore, a 2‐yr study examined the developmental sequences of C production and utilization by leaves and bolls within the crop canopy. Photosynthesis of sympodial leaves reached a maximum just prior to anthesis of the subtended flower and thereafter declined throughout the boll‐filling period. Carbon budgets for individual sympodial leaves and their subtended bolls at mainstem Nodes 8, 10, and 12 indicated that C production was seldom synchronized with C utilization. Carbon import requirements for the first three fruiting positions at mainstem Node 10 were 50,37, and 21%, respectively. Bolls at mainstem Node 8 collectively required >60% import of C to sustain growth during the season. Only at mainstem Node 12 were leaves capable of supplying the total C needs of their subtended bolls. Carbon deficiencies at mainstem Nodes 8 and 10 suggested that substantial translocation of photosynthate from adjacent leaves and leaves outside the mainstem node was necessary. This was confirmed through short‐term studies of l4C‐assimilate movement from leaves to developing cotton bolls. Breeding goals for improved C production by leaves were simulated to evaluate avenues for increased yields through crop genetics. These simulations indicated an advantage of increased leaf longevity in the maintenance of C production.
Cowpea Yield Response to Light Reflected from Different Colored Mulches
Authors: Hunt P. G. , Matheny T. A. , Kasperbauer M. J.
Published: July 2010

The spectral balance (quality) of canopy light, which influences plant growth and development, may be altered by colored mulches. Field studies were conducted to evaluate the influence of mulch surface color on spectral composition of canopy light and the effect of these changes on pod yield of ‘Colossus’ and ‘Mississippi Silver’ cowpea [Vigna unguiculata (L.) Walp.]. Cowpea was grown on a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult) and mulched with red, white, and black surface‐colored mulches for four site‐years. The far‐red (FR) to red (R) photo ratios of reflected light were expressed relative to the FR/R ratio in incoming sunlight, which was assigned a value of 1.00 at the time of measurement. The FR/R ratios of light reflected from the various colored surfaces were stable relative to sunlight during the study periods; light reflected from black and white mulch surfaces had mean FR/R ratios of 1.05 ± 0.05. Red mulches reflected light with mean FR/R ratios of 1.25 ± 0.05. White, red, and black surfaces reflected = 35, 12, and 3% of the incoming photosynthetic photon flux density (PPFD), respectively. Mean daily soil temperatures at 20 mm varied <1 °C among treatments. The cultivar and the color ✕ cultivar treatment effects were not significant. Cowpea grown over red, white, and black mulches had 4‐site‐yr means of 6.74, 6.32, and 6.02 Mg ha−1, respectively; the red treatment mean was significantly higher (P = 0.08). It was concluded that the FR/R ratio in light reflected from mulch surfaces can influence yield of cowpea.
Expression of Maturation‐Specific Genes in Soybean Seeds
Authors: Hsing Yue‐ie C. , Rinne Robert W. , Hepburn Angus G. , Zielinski Raymond E.
Published: July 2010

This laboratory, has previously shown (Rosenberg and Rinne, 1988, Plant Physiol. 87:474‐478) that several polypeptides are synthesized de novo during natural and precocious soybean [Glycine max (L.) Merr.] seed maturation. The present study was undertaken to investigate soybean seed maturation at the molecular level. The objective of this investigation was to see if changes could be observed at the molecular level that support our previous physiological and biochemical studies. A cDNA library was prepared from poly A* RNA from precociously dried soybean seeds and screened by differential hybridization with probes made from poly A* RNAs isolated from fresh and pod‐dried seeds to isolate dehydration‐related cDNA clones. Hybrid‐selected translation, cross‐hybridization, and DNA sequencing experiments using five clones with the strongest hybridization signals revealed that each appears to encode a 31‐kD polypeptide and represent the same mRNA sequence. The mRNA encoding this protein is expressed exclusively in maturing seeds from =55 d after flowering through maturity. Expression of the 31‐ kD polypeptide mRNA increases about 200‐fold during soybean seed maturation in situ, and it can be induced to a comparable level of expression by precociously maturing 35 d after flowering seeds. Expression of this mRNA occurs predominantly after expression of the genes encoding the major storage proteins, and it coincides temporall with seed desiccation.
Multiple Embryo Sacs in Sexual Buffelgrass Treated with Ammonium Sulfate
Authors: Gounaris I. , Gustine D. L. , Sherwood R. T.
Published: July 2010

Ovules of sexual genotypes of buffelgrass, Cenchrus ciliaris L., form a single meiotically reduced embryo sac of the polygonum type. In contrast, apomictic lines develop one to several unreduced aposporic sacs which lack antipodals. Seeking chemical means to manipulate embryo sac formation, we watered sexual plants, bearing premeiotic inflorescences, with 1 M (NH4)2SO4 solution every 2nd d for 1 to 2 wk. Among 493 pistils sampled from treated plants, (i) 190 pistils showed protrusion of the embryo sac through the micropyle, (ii) many protruding and eight nonprotruding sacs lacked antipodals, (iii) 72 pistils were sterile, and (iv) 27 pistils formed two or three embryo sacs, sometimes without antipodals. Normal polygonum‐type embryo sacs formed in 145 treated pistils and in untreated controls.