bluuebunny/crossref_metadata_2025 huggingface dataset:
Probability of Wheat Quality Traits Falling within Acceptable Limits
Authors: Eskridge K. M. , Peterson C. J. , Grombacher A. W.
Published: July 2010

Improving consistency of wheat (Triticum aestivum L.) end‐use quality requires simultaneous consideration of a large number of quality traits evaluated in multiple growing environments. Stability analyses have inherent limitations that make analyses of large numbers of intercorrelated variables, or non‐normally distributed values, difficult. Univariate and multivariate approaches were used to measure genotypic consistency of wheat quality traits based on the probability of traits falling within acceptable limits. Eighteen wheat genotypes were evaluated across 14 environments for flour protein concentration, mixograph mixing time and tolerance, sodium dodecylsulfate sedimentation volume, and kernel hardness. Acceptability of traits was defined by (i) values falling within chosen upper and lower limits of acceptability across environments, and (ii) values exceeding those for check genotype at each location. Multivariate probabilities of all five traits falling within upper and lower limits of acceptability ranged from 0.0 to 0.45 among genotypes. Univariate probabilities of acceptance were calculated for each trait. They ranged from 0.03 to 1.00 for genotype trait combinations and indicated the relative contributions of individual quality traits to the multivariate probability value. Several genotypes had low multivariate probabilities as the result of only one or two traits with low univariate probabilities. The probability based approach provides a simple and flexible decision‐making tool to identify genotypes with high probability of providing acceptable quality when grown across multiple environments.
Genetic Relationships among Plant Introductions for Resistance to Soybean Cyst Nematode Race 5
Authors: Young Lawrence D. , Kilen Thomas C.
Published: July 2010

Three soybean [Glycine max (L.) Merr.] plant introductions (PI) 399061, PI 424595, and PI 438342 were recently identified as resistant to Race 5 of the soybean cyst nematode (SCN) Heterodera glycines Ichinohe. Plant breeders need to know if these plant introductions have the same or different genes for resistance than those in previously identified resistant plant introductions. Crosses were made between the Race 5 resistant plant introductions and progenies were tested for segregation for resistance to the nematode. Crosses between the three plant introductions and susceptible ‘Tracy‐M’ soybean were made to estimate the number of genes involved in resistance to SCN Race 5. There was no segregation in F3 progenies in crosses among resistant PI 424595, PI 438342, ‘Peking’, PI 90763, and PI 437654. A few susceptible progenies were found from crosses of resistant genotypes ‘Cordell’ or PI 399061 with the other resistant genotypes. All the resistant genotypes appear to have the same genes for SCN Race 5 resistance at most loci, but P1 399061 probably differs in resistance genes from other resistant genotypes at one or more loci. Data from crosses of Tracy‐M with P1399061, P1424595, and P1438342 indicate resistance is controlled by three or more genes.
Selection for Agronomically Acceptable Inbred Lines in Adapted × Exotic Sorghum Backcross Populations
Authors: Menkir Abebe , Bramel‐Cox P. J. , Witt M. D.
Published: July 2010

The correlation between yield and other undesirable agronomic traits in sorghum (Sorghum bicolor (L.) Moench) may limit the isolation of suitable inbred lines from adapted × exotic backcrosses. The objective of this study was to compare use of a rank summation index with independent culling when trying to select agronomically acceptable lines from progeny of matings between three exotic accessions and two adapted parents, an inbred line, and a broad‐based population. Phenotypic correlations among yield, plant height, days to flowering, and seed weight were generally low (r < ±0.50). Selection for yield alone resulted in lines with increased height and days to flowering. The number of agronomically acceptable lines derived from two of the three matings of the adapted population (KP9B) by using independent culling levels was greater than the number derived from the corresponding matings of the adapted inbred line (CK60). Also, with the use of rank summation index scores, KP9B matings gave a higher number of acceptable lines than did corresponding CK60 matings. Mean yields and seed weights of the top‐scoring 10 lines selected by using the rank summation index were either comparable with or better than the means of their respective adapted parent. In most instances, selections were earlier flowering and slightly taller than then' adapted parent. Overall, backcrossing to an adapted population enhanced the utilization of exotic accessions more than backcrossing to an adapted inbred line. Selection for agronomic acceptability within introgressed populations was effective by using rank summation index and independent culling.
Immunological Identification of Seed Lipoxygenase Genotypes in Soybean
Authors: Evans D. E. , Nyquist W. E. , Santini J. B. , Bretting Peter , Nielsen N. C.
Published: July 2010

Elimination of lipoxygenases from soybean reduces the undesirable beany off‐flavor associated with soy products. Breeding programs, as well as quality control procedures, that utilize lipoxygenase null‐alleles to improve soybean flavor are dependent upon an accurate and efficient means to identify those lines that lack these enzymes. The use of an enzyme‐linked immunosorbent assay is one approach to this problem. Monocional antibodies specific to each of the three predominant soybean [Glycine max. (L.) Merr] seed lipoxygenases are described. The antibodies can be used to quantitate the amount of each isozyme in seed extracts. The antibodies are useful for the identification of specific lipoxygenase genotypes in progeny from crosses among lines bearing lipoxygenase null‐alleles. Statistical methodology is described that permits a determination of the percentage of contamination of L2L3‐1ess seeds by normal seeds that contain lipoxygenases in seed lots derived from commercial operations. Statistical approaches to sampling such as this may have wider application to quality assurance in other identity preserved crops.
Application of Embryo Rescue in Recovering Rice (Oryza sativa L.) Germplasm
Authors: Dilday R. H. , Yan Wengui , Lee F. N. , Helms R. S. , Huang F. H.
Published: July 2010

Conservation of existing germplasm is essential because of the constant erosion of gene pools and native germplasm throughout the world. Conservation of rice (Oryza sativa L.) germplasm, especially accessions in the rice portion of the USDA‐ARSSm all Grains Collection, is essential because rice is not native to the United States. This study was conducted to determine if rice accessions that did not emerge when seeded in the field could be rejuvenated in the laboratory. Six‐thousand rice accessions were seeded at the Rice Research and Extension Center, University of Arkansas, Stuttgart, AR, in 1991. Two‐hundred‐and‐eleven of the accessions, originally introduced from 21 countries, failed to emerge in the field. The viability of these accessions was tested in the growth chamber, on agar medium, and by an embryo culture method. Germination in the growth chamber recovered 27 lines that had been stored for an average of 10.6 yr at Beltsville, MD, and Aberdeen, ID. Fifty‐eight additional lines with an average storage age of 15.2 yr were rejuvenated by culturing the grain on agar medium. Embryo culture was used to test the remaining 126 lines, and 76 lines with an average storage time of 19.1 yr survived and produced seeds. All three laboratory techniques recovered rice germplasm that did not emerge in the field. However, embryo culture was superior to grain culture and both of these methods were more effective in rejuvenating rice germplasm than the growth chamber method.
Isozyme Variation and Phylogenetic Relationhips among Open‐Pollinated Sweet Corn Cultivars
Authors: Revilla P. , Tracy W. F.
Published: July 2010

Sweet corn (Zea mays L.) is one of the most important vegetables in the USA. But, little is known regarding the phylogeny and diversity among open‐pollinated sweet corn cultivars. To determine the relationship and diversity among sweet corn cultivars, isozyme variability among 60 North American cultivars and four Mexican and two Peruvian sugary1 (sul) populations were compared by principal components analysis (PCA) and cluster analysis (CA). Four major groups were identified: yellow‐kernel sweet corn (‘Golden Bantam’ type), whitekernel sweet corn, Mexican and Amerindian sweet corns, and Peruvian populations. Two cultivars ‘Early June’ and ‘Country Gentleman’ did not fall into any group. The first two groups originated in the northeastern USA. To determine the relationship among sweet corn germplasm and the major North American races of corn, PCA and CA were performed on the isozyme data from the 66 cultivars and populations and mean allele frequencies of the races ‘Northern Flint’ (NF), ‘Southern Dent’ (SD) and ‘Corn Belt Dent’ (CBD). The mean frequencies from NF, SD, and CBD were obtained from previously published data. Northern Flint was grouped with the white and yellow kernel sweet corns, while SD and CBD were grouped with the Mexican and Amerindian cultivars. Fifty‐three of the 60 North American sweet corn cultivars were grouped closely together and could be considered a discrete race, Northeastern Sweets. But, due to the commercial importance of Country Gentleman and the introgression of non‐sweet germplasm into modern sweet corn, we believe that sweet corn should be defined based on its use as a vegetable and on the presence of one or more genes that increase sugar levels in the endosperm.
Inheritance of Vegetative Growth Index and Related Traits in Pearl Millet
Authors: Lynch P. J. , Rattunde E. W. , Frey K. J.
Published: July 2010

Growth index (GI) is a measure of plant dry weight produced per unit of land area per day (grams per square meter per day). The objective of this study was to elucidate the inheritance pattern of GI for pearl millet [Pennisetum glaucum (L.) R. Br.]. A generation means analysis was conducted to determine the relative importance of additive, dominance, heterotic, and additive × additive epistatic genetic effects for GI. Two elite open‐pollinated and three landrace varieties of pearl millet were mated, and the parents, parent selfed, F1s, F1s selfed, and F1s randomated were evaluated in 1990 and 1991 at the International Crops Research Institute for the Semi‐Arid Tropics, near Hyderabad, India. Traits measured were GI at 10 d after bloom date (GI1) and at maturity (GI2), bloom date, biomass, harvest index, and plant height. The fully fitted genetic model for the generation means explained from 88 to 95% of the variation among the generations sum of squares for the various traits. Additive effects accounted for the largest proportion of the variation among generation means for all traits except GI2 and biomass, where additive × additive epistatic effects were of greatest importance. Even though inheritance patterns for GI1 and GI2 were dissimilar, a breeding method that emphasizes selection for additive genetic effects should be suitable for improving them.
Response of Digitaria decumbens Leaf Carbohydrate Levels and Glucan Degrading Enzymes to Chilling Night Temperature
Authors: Shatters Robert G. , West S. H.
Published: July 2010

Experiments were performed to analyze how chilling temperatures present during the night period affect leaf carbohydrate metabolism in pangolagrass (Digitaria decumbens Stent.), a warm‐season forage grass. Plants were exposed to three consecutive 14‐h night periods of either 25 or 10°C. Control plants (25°C nights) displayed an average 75% decline in leaf glucose levels during the night. This decline was more than 50% smaller in chilled plants (10°C nights) during all three nights. In control plants, leaf sucrose levels declined 78% during the night period. In chilled plants, this decline was inhibited to less than 2% of the available sucrose during the first night, and 47 and 44%, respectively, during two subsequent chilling nights. Greater than 90% of leaf starch was mobilized in control plants during the night, whereas 52, 46, and 16% of leaf starch was mobilized during three consecutive chilling nights, respectively. Chilling did not cause observable alterations in the ex planta activity of specific amylase enzymes; however, two diurnally regulated extrachloroplastic amylolytic enzymes were identified. Total leaf α‐1,4‐glucan phosphorylase (GP) activity was diurnally regulated with highest activity at the end of the night period, and activity increased in chilled plants after two consecutive chilling nights. Therefore, during three consecutive chilling nights the diurnal fluctuations in neither leaf carbohydrate levels nor GP activity remained constant. This dynamic response indicates that previous chilling night exposure influenced subsequent night‐period carbohydrate metabolism despite each night period being separated with a warm (25–33°C) 10‐h d period.
Field Population Dynamics of Soybean Cyst Nematode on Resistant and Susceptible Soybeans and Their Blends
Authors: Wallace M. K. , Orf J. H. , Stienstra W. C.
Published: July 2010

Soybean cyst nematode (Heterodera glycines Ichinohe) (SCN) become an increasing problem in the upper midwest. In order to develop appropriate practices to manage SCN populations it is important to understand the population dynamics of SCN under field conditions. Soybean cyst nematode population dynamics were determined in naturally infested commercial soybean [Glycine max (L.) Merr.] fields in southern Minnesota on a monthly basis during 1991 and 1992 for an adapted susceptible (S) and a SCN Race 3 resistant (R) cultivar and three blends (25% R:75% S; 50% R:50% S; 75% R: 25% S). Population dynamics differed between sites and years. In 1991, fields with similar initial cyst densities were compared. Densities of second‐stage juveniles (J2) peaked in August at one site and gradually declined throughout the growing season at the other. Total cyst production was lower at the site where J2 densities declined. In 1992, fields with high and low initial egg densities were compared. SCN population densities increased when initial densities of J2 and eggs were low and decreased when initial J2 and egg densities were high. Physiological race of the nematode influenced population dynamics on resistant plants. The cyst index under field conditions for the resistant cultivar was 10 (moderately resistant) against Race and 32 (moderately susceptible) against Race 1. The blends generally lowered SCN population densities, but not significantly. Final egg density and cyst production for the resistant cultivar were significantly lower than the susceptible cultivar at each site. The use of SCN resistant cultivars alone or in a 75:25% mixture with a susceptible cultivar (25%) is recommended as a SCN population management strategy to delay shifts from one race to another thus prolonging the effectiveness of resistant cultivars.
Stress Tolerance in Tropical Maize is Linked to Constitutive Changes in Ear Growth Characteristics
Authors: Lafitte H. R. , Edmeades G. O.
Published: July 2010

The tolerance of maize (Zea mays L.) grain yields to abiotic stresses is largely determined by events that occur at or shortly after flowering. Our objective was to evaluate ear growth after silking under unstressed conditions or low N environments in two late lowland tropical maize populations, previously selected for tolerance to drought or to low N. Selection under low N or drought reduced florets per ear by 12 and 11 per cycle when evaluated under unstressed conditions. The lag period between pollination and the onset of linear grain growth increased by 1.7 d cycle−1 in the low N tolerant population grown under unstressed conditions and by 0.6 d cycle−1 in the drought tolerant population under low N. Selection for tolerance to low N increased biomass per kernel at the end of the lag and linear grain filling periods by 40 and 7% per cycle and by 10 and 4% per cycle in the drought tolerant population, across N environments. The duration of linear grain filling declined with selection in the low N tolerant population when grown under unstressed conditions. Selection for tolerance to either stress did not significantly increase grain yield under unstressed conditions, though improvement for drought tolerance increased yield by 7.5% per cycle (P < 0.05) under low N. Selection for tolerance to both stresses increased kernels per plant across environments. Apparently, selection for tolerance to low N or drought results in more kernels achieving the minimum biomass needed to prevent kernel abortion at the onset of the linear growth phase, resulting in greater grain sink strength under stressed and unstressed environments.
The Effect of Carbon Dioxide on Maize Seed Recovery after Flooding
Authors: Cerwick S. F. , Martin B. A. , Reding L. D.
Published: July 2010

Flooding of recently planted fields of maize (Zea mays L.) in the spring results in poor emergence of some germplasm. Previous studies have shown genetic variation for flooding tolerance of maize inbreds and hybrids. This study was conducted to identify a biochemical basis of reduced germination after flooding and determine differences between tolerant and sensitive inbreds. Seeds soaked in nonaerated water accumulated CO2. Reduction of germination after soaking was partially reversed by venting the seed with ambient air after soaking and prior to planting. Respiration was measured immediately after soaking and after venting. Respiration rates of flood tolerant inbreds increased faster and to a higher level after flooding and venting than those of sensitive inbreds. The apparent Michaelis constants for succinate oxidation by isolated intact mitochondria of flood sensitive inbreds were higher than those of tolerant inbreds. Succinate oxidation was competitively inhibited by bicarbonate. As the apparent quantitation of inhibition (Ki) bicarbonate increased, flooding sensitivity decreased. Genetic differences in flooding tolerance of maize inbred seed germination were at least in part influenced by sensitivity of respiration to CO2.
Genetic Base of U.S. Mainland Sugarcane
Authors: Deren C. W.
Published: July 2010

Evaluations of the genetic diversity of many crop breeding populations have been conducted in response to concern over their genetic vulnerability to diseases and insects. The purpose of this study was to evaluate the genetic diversity of U.S. mainland sugarcane (Saccharum L. spp.) cultivars. Eighty‐eight cultivars from Florida, Louisiana, and Texas were traced back to seventeen original ancestors. Coefficients of parentage (r × 100) were calculated among cultivars and ancestors. Cytoplasmic genetic sources were also traced. Ten ancestors contributed germplasm to 90% or more of Florida cultivars, whereas only two ancestors contributed germplasm to 90% or more of Louisiana cultivars. Mean coefficients of parentage for current commercial cultivars in Florida ranged from 8.2 to 18.6. For Louisiana commercial clones, coefficients of parentage ranged from 16.3 to 25.8. Cytoplasmic sources traced to three S. officinarum L. clones. The ancestor Black Cheribon (S. officinarum) contributed the greatest amount of nuclear and cytoplasmic germplasm. In comparison with many crops, sugarcane is probably relatively well buffered genetically.
Integration of Simple Sequence Repeat DNA Markers into a Soybean Linkage Map
Authors: Akkaya Mahinur S. , Shoemaker Randy C. , Specht James E. , Bhagwat Arvind A. , Cregan Perry B.
Published: July 2010

A total of 40 simple sequence repeat (SSR) or microsatellite DNA markers were mapped in a soybean [Glycine max (L.) Merrill] mapping population that consisted of 60 F2 plants from a cross between near isogenic lines of the cultivars Clark and Harosoy. The first objective of study was to determine the map location of SSR loci in relation to 13 classical loci controlling pigmentation and morphological traits, seven isozyme loci, and a total of 118 RFLP and RAPD markers. The second objective was to determine if the microsatellite loci were randomly distributed in the soybean genome. Linkage analysis with MAPMAKER 3.0b yielded 29 linkage groups with a total map length of 1486 centimorgans (cM). This compares with a map length of 1056 cM if the SSR markers were removed from the data set. Thirty‐four of the microsatellite loci were placed in linkage groups. SSR loci were linked to loci controlling nine of the 13 classical traits, and two of seven isozyme loci. Eighteen of the 29 linkage groups contained at least one SSR locus. While this result suggested that the microsateilite loci were randomly distributed throughout the soybean genome, two clusters of five and four SSR loci, spanning 23.4 and 33.6 cM, respectively, were detected. These results indicated a relatively limited amount of clustering of soybean SSR loci, and demonstrated that microsatellite genetic markers should provide an excellent complement to RFLP and RAPD markers for use in soybean molecular biology, genetics, and breeding research. Because SSR markers detect only single genetic loci and are highly polymorphic, they can be extremely informative in pedigree tracing studies, in the analysis of progeny from multiparent matings, in a wide range of mapping applications, and in genotype identification.
Three‐Mode Analyses of Maize Using Morphological and Agronomic Attributes Measured in Multilocational Trials
Authors: Crossa José , Basford Kaye , Taba Suketoshi , DeLacy Ian , Silva Edison
Published: July 2010

This study provides examples of the application of three‐mode methods to agronomic and morphological data from multiattribute and multilocational trials of accessions from two Mexican maize (Zea mays L.) races, Cónico and Tuxpeño. Initially, Cónico accessions from the state of México were classified into five subgroups, whereas Tuxpeño accessions were classified into three subgroups based on the ecogeographical region of origin. A three‐mode classification method reassigned accessions to form more homogeneous subgroups. The new Cónico groups were called C1, C2, C3, C4, and C5 and the new Tuxpeño groups were named T1, T2, and T3. Intra‐racial genetic diversity was investigated by three‐mode principal component analysis. Most Cónico Group C3 accessions had low grain yield, early maturity, short plants, and short ears. Group C2 accessions had the tallest plants, the shortest kernels, and the narrowest ears; whereas, Group C4 accessions had the longest kernels and the widest ears. Accessions in Groups C1 and C5 were the highest yielders and had the longest ears. A core subset would include accessions from all five subgroups with an approximate average response for all attributes, pins some accessions with extreme responses. Tuxpeño Group T2 accessions were earlier and had shorter plants than the accessions from Group T1. Group T3 accessions had higher grain yield and longer kernel length. A core subset of Tuxpeño accessions could be formed as suggested for Cónico. If a Tuxpeño core subset with high grain yield and shorter plant type is desired, more accessions from Groups T2 and T3 should be included.
Inheritance of Tillering in a Winter Wheat Population
Authors: Van Sanford David A. , Utomo Herry
Published: July 2010

Tillers are an important component of wheat (Triticum aestivum L. emend. Thell.) grain yield, yet there is uncertainty in the literature about improving yield by selecting for tiller number. The objectives of this study were to estimate the heritability of tiller number, to quantify genotype × environment (G × E) interaction, and to assess tiller number as an indirect selection criterion. We measured tiller number at five growth stages, grain yield, and kernel size in 92 soft red winter wheat F4 lines in 1987 and in their bulk F5 progeny at two planting dates in 1988. Heritability (h2) of tiller number at Feekes growth stages 2, 4, 7, 10.1, and 11.2 in a single environment ranged from 0.05 to 0.60. When G × E interaction was accounted for in a combined analysis, however, heritability estimates were much lower, ranging from −0.14 to 0.19. Genotype rank changes were common among pairs of environments, though in certain cases, scale differences predominated. Tiller number at growth stage 10.1 was highly correlated with yield (r = 0.58, P < 0.01) and had higher heritability (h2 = 0.19) than yield (h2 = 0.05), and thus, we predict a higher response (36%) to indirect selection than to direct selection for yield itself. Indirect selection for tiller number with visual keys would be most appropriate in early generations when direct yield assessment is difficult, followed by direct selection for yield in later generations.
Gene Action for Resistance in Sorghum to Midge, Contarinia sorghicola
Authors: Sharma H. C. , Abraham C. V. , Vidyasagar P. , Stenhouse J. W.
Published: July 2010

Gene action for resistance to sorghum midge (Contarinia sorghicola Coq.) was studied in a diverse array of midge‐resistant and midge‐susceptible females and males under natural infestation and under uniform infestation with a no‐choice headcage technique. Gene action for glume and grain characteristics associated with resistance to sorghum midge was also studied to understand their role in expression of resistance to this insect. Gene action for resistance to midge is largely governed by additive gene action. Genotype × environment interaction was significant for midge damage rating under natural infestation but nonsignificant under no‐choice headcage screening. The GCA effects of midge‐resistant cytoplasmic male‐sterile (CMS) females (PM 7061 A and PM 7068 A) were significant and negative, and such effects for the midge‐susceptible CMS females ICSA 42 and 296 A were positive. Similar results were observed for the males (except for CS 3541 and MR 750 for midge damage in one out of two seasons). Dominance (mid‐parent heterosis) was also important for midge resistance in some cross combinations. For genotypic nonpreference by the midge females, the SCA effects were greater than the GCA effects. The SCA effects for genotypic nonpreference were negative for PM 7061 A. The GCA effects were significant and negative for glume length in PM 7061 B, glume hardness for 296 B, and glume hairiness for PM 7061 B. The GCA effects were significant and positive for glume length, glume hairiness, and glume hardness of ICSB 42. Resistance is needed in both the parents to produce midge‐resistant hybrids.
Acremonium coenophialum‐Mediated Short‐ and Long‐Term Drought Acclimation in Tall Fescue
Authors: Hill N. S. , Pachon J. G. , Bacon C. W.
Published: July 2010

The mutualistic association between Acremonium coenophialum Morgan‐Jones and Gams and its tall fescue (Festuca arundinacea Shreb.) host provides plant scientists with unique opportunities to create superior turf and forage cultivars. The objectives of this research were to determine endophyte‐mediated drought acclimation in tissue‐cultured regenerants of tall fescue containing one of three A. coenophialum isolates during short‐ and long‐term drought stress. Two experiments were conducted by growing vegetative propagules of plants with endemic or introduced endophytes in 120‐L tubs containing fritted clay: one experiment examined water relations during a 15‐d drought period and the other during a 70‐d water stress period. Leaf water potential and turgor pressure responses to soil water content differed among infected and non‐infected plants, among endophytes inserted within a plant genotype, and among plant genotypes containing a common endophyte during 15 d of stress. Among endophytes, only EDN11 induced acclimation to 70 d of stress when inserted into plant genotype PDN2. Leaf water potential and turgor pressure were approximately 0.50–0.75 MPa greater when PDN2 was infected with EDN11 compared to other endophytes during the 70 d of stress. Endophyte had no effect on leaf osmotic potential and minimal effect on plant water soluble mineral and sugar concentrations, and endophyte‐mediated adaptation to drought stress was an avoidance mechanism. Because enhanced drought tolerance is a result of specific interactions between plant genotypes and endophyte isolates, selection of endophytes specifically for enhancing drought tolerance in tall fescue is not likely to have a general effect on the plant population.
Genotypic Classification of Cowpea Based on Responses to Heat and Photoperiod
Authors: Ehlers J. D. , Hall A. E.
Published: July 2010

Heat and photoperiod influence reproductive development and yield of crop plants. In cowpea (Vigna unguiculata [L.] Walp.), genetic variation is present for heat tolerance and responses to photoperiod during different stages of reproductive development. A genotypic classification system had been developed based on responses to high temperature under long days. Further studies were needed under short and long days and hot and moderate temperatures to characterize genotypic variation for juvenility and photoperiod response and interactions with temperature. Forty‐four contrasting cowpea genotypes were sown in the field with moderate (31.5/16.5°C day/night) and hot (38/22.5°C day/night) temperature long day environments and in glasshouses in hot (35/26°C day/night) or moderate (32/18°C day/night) temperatures under short (11 h 20 min at planting to 12 h 20 min after 30 d) and long (14 h 50 min at planting to 14 h 16 rain after 30 d) days, and these genotypes were evaluated for juvenility and photoperiod and temperature responses. The genotypes were classified into II groups based on photoperiod response (change in position of the first reproductive node or period to appearance of floral buds in long compared with short days), juvenility (minimum period for appearance of floral buds when grown under short days), and suppression of floral bud development and pod set under hot long days. This classification system will aid breeders and agronomists in their understanding of the genetic variation for these characteristics and in choosing genotypes with appropriate juvenility, photoperiod response, and heat tolerance for breeding and agronomy programs serving tropical and subtropical production environments.
Selective Control of Common Bermudagrass in St. Augustinegrass
Authors: McCarty Lambert B.
Published: July 2010

Common bermudagrass [Cynodon dactylon (L.) Pens.] is the most troublesome weed in commercially produced St. Augustinegrass (Stenotaphrum secundatum (Walter) Kuntze] sod due to inadequate selective control methods. Currently available herbicides are nonselective and require multiple applications, which delays replanting, and cause significant St. Augustinegrass injury. Research was conducted to evaluate several herbicides for selective control of common bermudagrass in ‘Floratam’ St. Augustinegrass. Herbicides included ethofumesate [(±)2‐ethoxy‐2,3‐dinydro‐3,3‐diinethyl‐5‐benzofuranyl methanesulfonate] and ethofumesate plus either flurprimidol [αa‐(1‐methylethyl)‐α‐[4‐trifluourmethoxyy)phenyl]‐5‐pyrimidinemethanol], atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], or siduron [N‐(2‐methylcyclohexyl)‐N‐phenylurea]. Excellent (>95%) common bermudagrass control followed sequential applications of ethofumesate plus atrazine applied in March, April, and May. Good control (80–89%) was observed with ethofumesate alone applied the same months. Inconsistent and/or poor control (<70%) of common bermudagrass was obtained with ethofumesate plus either flurprimidol or siduron. Additional treatments made in February and/or in November of the previous year did not increase control. St. Augustinegrass turf quality was unaffected by ethofumesate plus atrazine. Turf quality was reduced 4 to 8 wk after repeat applications of ethofumesate plus siduron. Ethofumesate plus flurprimidol combinations reduced turf quality for 8 to 12 wk. Properly timed ethofumesate plus atrazine applications is the first reported means of selectively controlling common bermudagrass in St. Augustinegrass turf.
Testcross Selection Prior to Further Inbreeding in Maize: Mean Performance and Realized Genetic Variance
Authors: Bernardo Rex
Published: July 2010

Testcross evaluation of maize (Zea mays L.) families is usually done after, but not prior to, several generations of selfing. The objectives of this study were to (i) evaluate the usefulness of one cycle of testcross selection and recombination of F3 families prior to further selfing and (ii) develop a method for estimating realized genetic variance. In each of two biparental maize populations (POP1 and POP2), five Cycle F3 families that had the highest yields when testcrossed to B73 were recombined to form Cycle 1. Testcrosses of Cycle 1, Cycle 0, and the five selected Cycle 0 F3 families were evaluated at five locations in 1993. Selection differentials (S) for yield were 7 to 8% of the corresponding Cycle 0 means. Observed response to selection (R) expressed as a proportion of the Cycle 0 mean was 7% in POP1 and 5% in POP2. In each population, the five highest‐yielding Cycle 1 testcrosses outyielded the five highest‐yielding Cycle 0 testcrosses by 8 to 9%. Testcross selection would have added 2 yr to the time required for inbred development, but average gains per year for yield were 0.9% larger with than without selection and recombination of the best five F3 families in Cycle 0. Realized genetic variance was estimated as Rσ̂2G = SR/i2, where i was the standardized selection differential with truncation selection. There was no evidence that genetic variance decreased after one cycle of testcross selection. In experiments that compare several cycles of selection, realized genetic variance can be estimated with bulks of all families and bulks of the selected families instead of estimating genetic variance with large numbers of individual families in each cycle.
Late Season Water Stress in Cotton: I. Plant Growth, Water Use, and Yield
Authors: Gerik T. J. , Faver K. L. , Thaxton P. M. , El‐Zik K. M.
Published: July 2010

The behavior of water stressed cotton (Gossypium hirsutum L.) is well documented but our knowledge of traits which can be genetically manipulated to improve drought tolerance is incomplete. This study was conducted to determine which morphological and physiological factors lessen the effects of water stress on the yield of two short‐season cultivars [i.e., TAMCOT HQ95 (HQ95)and (G&P 74+ (GP74)] with a common parent in ancestry. Plants were grown in a rain shelter‐ lysimeter facility containing a Pedernales fine sandy loam soil (fine, mixed, thermic Udic Paleustalf)in 1990 and 1991 at Temple, TX. Water stress was imposed by replenishing a fraction of the water lost to evapotranspiration, beginning about 78 d after emergence. HQ95 and GP74 did not differ in leaf area index( LAI) or in the rate of leaf area development before water stress was imposed. The rate of LAI decline and average LAI were similar between cultivas when water stress was imposed. HQ95 used more water and used it at a faster rate than GP74 when water stressed. HQ95 produced more bolls and had higher yield under both well‐watered and water stressed conditions than GP74 in each of the 2 yr. The largest difference in boll load between cultivars occurred on sympodia branches in the lower canopy, where HQ95 had 37, 60, and 182% more bolls than GP74 when plants received 0, 50 or 75, and 100% of the depleted soil water. Whether well watered or water stressed, individual boll weight did not differ between the two cultivars. However, the harvest index and the production efficiency of bolls (i.e., bossl pr unit leaf area)of HQ95 was consistently higher than GP74 for all water regimes. On average, HQ95 located 21% more dry matter to yield and produced 32% more bolls per square meter than GP74. While differences in yield between the cultivars mirror harvest index, large differences in boll production efficiency suggested that the intrinsic photosynthetic capacity of HQ95 may be greater than GP74.
Responses to S1 Selection in Flint and Dent Synthetic Maize Populations
Authors: Garay G. , Igartua E. , Alvarez A.
Published: July 2010

Flint × dent is a common heterotic pattern exploited in maize (Zea mays L.) breeding programs across Europe. Two maize synthetics, EZS1, a mixture of Spanish open‐pollinated flint varieties, and EZS2, crosses among North American dent‐improved populations, were produced in Zaragoza, Spain. The synthetics showed heterotic behavior and were subjected to two cycles of S1‐progeny intrapopulation selection for grain yield and lodging resistance before starting reciprocal recurrent selection. Our objectives were to partition the response to selection into additive and dominance effects after two cycles of intrapopulation selection, with generation mean analysis and diversity analysis. The entries resulting from a diallel mating design, without reciprocals, among the original and first two cycles for each population, were tested in five environments. The results showed that both populations were responsive to selection for improved grain yield, but only EZS2 was improved by selection against lodging. Diversity analysis was less conservative than the generation means model in detecting significant genetic effects. Genetic effects associated with selection for grain yield and lodging were mostly additive, but a significant dominance effect was detected in EZS2 for lodging. The improvement of the population cross did not match that of the populations per se, especially for EZS2. A loss of heterosis for the cross was detected, which might become unrecoverable if S1 selection is continued. It was concluded that S1 selection should be discontinued and that reciprocal recurrent selection should be initiated.
Inheritance of Homozygous Somaclonal Variation in Rice
Authors: Xie Q. J. , Rush M. C. , Linscombe S. D.
Published: July 2010

Homozygous mutations are common phenomena in rice (Oryza sativa L.) somaclones. Previous reports indicated that inheritance of the variants from these mutations were stable only in the homozygous condition resulting from selfing. To better understand the inheritance of homozygous somaclonal variation in rice, five variants, two from the U.S. long‐grain cultivar Labelle (short and light tawny apiculus) and three from the U.S. long‐grain cultivar Lemont (tall, purple apiculi, and dwarf), were used in this study. Reciprocal crosses between the original cultivars and the somaclones with mutations were made in 1987 and the F1 plants were grown in the greenhouse to produce seeds. The F2 populations and F3 families were grown in the field at the Louisianna State University Rice Research Station in Crowley, LA, during 1988 to 1990 and evaluated for segregation of the variants. The light tawny apiculus character was controlled by a single recessive gene. The purple apiculus character was controlled by a dominant gene. The tall character was controlled by two complementary dominant genes. No disappearance of these three characteristics in the segregating generation was observed. The dwarf character was controlled by one or two recessive genes, which were not stable in the heterozygous condition due to gene conversion. The short character was controlled by quantitative genes, but the single mode distributions observed in the F2 populations may be another case of aberrant segregation. Stability of useful homozygous somaclonal variation in rice should be determined prior to its use in breeding programs.
Genetic Mapping of a Locus (hyp) Affecting Seed Hypodermis Color in Sunflower
Authors: Leon A.J. , Lee M. , Rufener G. K. , Berry S. T. , Mowers R. P.
Published: July 2010

Sunflower (Helianthus annuus L.) seed color is determined by pigmentation of three layers of the pericarp (hull): epidermis, hypodermis, and phytomelanin layer. A gene with major effects on hypodermis color was reported previously. However, genetic factors that determine the presence or absence of pigment in the hypodermis have not been reported. We identified RFLP markers linked to factor(s) affecting hypodermis pigmentation and assessed the relationship between this trait and oil percentage in sunflower seed. An F2 single‐cross population was produced from homozygous and homogeneous inbred parents ZENB8 and HA89, with pigmented and unpigmented hypodermis, respectively. Two hundred sixty‐seven F2 plants and their F3 families were evaluated. A dominant factor (Hyp) determining the presence of white pigments in the hypodermis was located to linkage group ‘G’. Seeds with white hypodermis had lower oil percentage than those with unpigmented hypodermis. The Hyp factor was located in the same map interval as one QTL with major effects on seed oil percentage in this population. Knowledge of genetic linkage among DNA markers, hypodermis pigmentation, and oil percentage should enhance breeding programs.
Identification of Tall Fescue Cultivars by Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis of Seed Proteins
Authors: Krishnan Hari B. , Sleper David A.
Published: July 2010

Tall fescue (Festuca arundinaceae Schreb.) is a cool‐season grass used widely for turf and forage. There is a steady increase in the number of new cultivars of tall fescue that are released through the effort of plant breeders. Most of these cultivars are closely related in pedigree and are similar phenotypically. As a result, identification of tall fescue cultivars has become increasingly cumbersome. The purpose of this study was to develop an electrophoretic procedure which will aid in routine identification of different cultivars of tall fescue. We isolated salt‐soluble globulins and alcohol‐soluble prolamines from nine tall fescue cultivars and resolved them by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Salt soluble globulins were very similar in their polypeptide profiles and hence offered little promise in cultivar identification. However, SDS‐PAGE analysis of seed prolamines effectively differentiated the tall fescue cultivars on the basis of presence and absence of unique polypeptides. Subtle differences in the banding patterns of prolamines of closely related cultivars were enhanced by computer assisted densitometer scans. The results of this study indicate that SDS‐PAGE analysis of alcohol‐soluble prolamines can be used as a rapid and reliable method for identification of tall fescue cultivars.
Response of Native Eastern North American Trifolium spp. to Root‐Knot Nematodes
Authors: Quesenberry K. H. , Call N. M. , Moon D. E. , Dunn R. A.
Published: July 2010

The true clovers (Trifolium spp.) are important pasture plants, but most of the cultivated species have low resistance to root‐knot nematodes (RKN) (Meloidogyne spp.). Plant introductions of seven Trifolium spp. native to eastern North America (T. bejariense Moric., T. calcaricum Collins & Weiboidt; T. carolinianum Michx., T. polymorphum Poir. ex Lam. & Poir.; T. reflexum L., T. stoloniferum Muhlenberg, and T. virginicum Small ex Small & Vail.) were evaluated in two greenhouse experiments, conducted in spring 1992 and 1993, for response to four RKN species, Meloidogyne arenaria (Neal) Chitwood race 1, M. hapla Chitwood, M. incognita (Kofoid and White) Chitwood race 3, and M. javanica (Treub) Chitwood. Additionally, T. riograndense Burkhart and one accession each of T. ambiguum M.B. and T. repens L. were evaluated. Responses determined were numbers of galls or egg masses 8‐wk after inoculation rated on a 0 to 5 scale where 0 is no galling or egg masses per plant and 5 is greater than 100. Among the annual species, T. carolinianum and T. bejariense were the most resistant annual species. Among the perennials, T. calcaricum and T. stoloniferum were highly resistant (ratings < 1.0) except that T. stoloniferum had an intermediate response to M. hapla (ratings of 2.5–3.5). Ttifolium polymorphum was variable in response among RKN. The kura and white clover lines and T. riograndense were highly susceptible to RKN (ratings > 4.5). The federally endangereds pecies, T. stoloniferum, rated less than 1.0 in response to M. arenaria, M. incognita, and M. javanica. The recently described rare species, T. calcaricum, had the most resistant response of any species evaluated. These native eastern North American clovers may contain valuable genes for RKN resistance, but due to sexual incompatibility with the cultivated clover species, exploitation of such genes will require molecular methods of gene transfer.
RAPD Based Assessment of Genetic Diversity in Cultivated Races of Sorghum
Authors: Menkir Abebe , Goldsbrough Peter , Ejeta Gebisa
Published: July 2010

Analysis of the extent and distribution of genetic diversity in crop plants is essential for optimizing sampling and breeding strategies. We used random amplified polymorphic DNA (RAPD) markers to assess genetic diversity and taxonomic relationships in 190 accessions sampled to represent the cultivated races of sorghum [Sorghum bicolor (L.) Moench], A high level of variation was detected among cultivated genotypes. Partitioning the genetic variation in cultivated sorghum with Shannon's diversity index revealed that 86% of the total genetic variation occurred among accessions and 14% among races. We also examined the degree of association of accessions with their geographic areas of origin by using Shannon's diversity index. The results indicated that only 13% of the total genetic variation was attributable to divergence among regions. Further tests using principal component analysis also failed to show separation of accessions into discrete racial or geographic groups. Despite such limited differentiation among races or regions, RAPD markers successfully identified races and regions with maximum genetic diversity. For example, accessions within races bicolor and guinea had greater genetic diversity than accessions from race kafir. Accessions from southern Africa had a lower level of genetic diversity than accessions from Far and Middle East, Central and Eastern Africa, and Western Africa. Thus, use of RAPD markers may optimize sampling of genetically divergent accessions for introgression into breeding pools.
Genetic Analysis of High Molecular Weight Proteins in Rice (Oryza sativa L.) Endosperm
Authors: Sadimantara Gusti Ray , Abe Toshinori , Sasahara Takeo
Published: July 2010

Genetic and physiological characteristics of the main rice (Oryza sativa L.) storage proteins, glutelin and prolamin, have been extensively studied. In contrast, information on high molecular weight proteins is limited. Experiments were undertaken to identify the genes that control the synthesis of high molecular weight proteins (40–90 kDa) in rice endosperm. Total endosperm proteins of japonica and indica cultivars, and their F2 progeny, were analyzed by two‐dimensional polyacrylamide gel electrophoresis (2D‐PAGE). Nine high molecular weight proteins were detected in three cross combinations between japonica and indica cultivars. Segregation of these endosperm proteins in the F2 progeny fits with a ratio of 1:1:1:1 (HpxHpxHpx:HpxHpxhpx:Hpxhpxhpx:hpxhpxhpx), resulting from double fertilization. Three protein subunits (D, E, and M) were found only in the cross combination of Taichung 65 × BlueBelle, but other six protein subunits (F, G, H, I, K, and L) were commonly in three cross combinations. The dominant genes appeared to regulate expression of the high molecular weight protein subunits, anda dose effect of dominangt enes was detected.