bluuebunny/crossref_metadata_2025 huggingface dataset:
Progress from Selection in Eight Tropical Maize Populations Using International Testing1
Authors: Pandey Shivaji , Diallo A. O. , Islam T. M. T. , Deutsch J.
Published: July 2010

Eight full‐season tropical maize (Zea mays L.) populations were improved by the International Maize and Wheat Improvement Center (CIMMYT) using full‐sib (FS) selection and international testing. Cycles CO, C2, and the latest (fourth or fifth) cycle of selection were evaluated at six locations to measure the progress from FS selection. Gains per cycle, averaged over the eight populations for yield, days to silk, plant height, ear height, ear rating, and ears per plant were 1.31, −0.59, −1,06, −1.77, −1.15, and 0.87%, respectively. The ranges in improvement for the same traits were, −0.04 to 1.90, −0.93 to 0.27, −1.89 to 0.75, −3.38 to 0.36, −3.41 to 0.71, and 0 to 1.92%, respectively. In all environments, the latest cycles of selection yielded higher than CO. Our results suggest that FS selection is an effective method for improving maize populations and that the progress per cycle would vary with the selection intensity, quality of data, type of FS selection, and the heritability of the trait. Improved CIMMYT maize populations as such, experimental cultivars developed by recombining among their superior families, as well as their superior FS families are being used by national programs as cultivars, in hybrid combinations, and for extraction of inbred lines.
Selection for Seedling Cold Tolerance in Grain Sorghum1
Authors: Bacon R. K. , Cantrell R. P. , Axtell J. D.
Published: July 2010

Improvement in cold tolerance for sorghum (Sorghum bicolor (L.) Moench] would allow expansion of this crop into cooler regions than the current production areas, as well as lessen stand reductions in cool soils currently in production. Experiments were conducted in 1981 and 1982 to evaluate effectiveness of selection for cold tolerance in sorghum. A genetically broad‐based, random‐mating grain sorghum population, Purdue Population 9 (PP9), was used as the source population for increasing seedling cold tolerance. Purdue Population 9 Cold Tolerant (PP9CT) was developed through a phenotypic recurrent selection procedure utilizing natural selection in early spring plantings. Progress from selection was evaluated in early spring plantings in 1981 and 1982. In 1981, the C0 to C3 generations of PP9CT and two check genotypes were evaluated in plots planted with 100 seeds in a randomized complete block design. In 1982, the C4 generation was also included. Results from the first year indicated that a 10.6% increase in cold emergence had been accomplished after three cycles of selection. Data from 1982 indicated a 14.9% increase in cold emergence after four cycles of selection. Regression analysis on the combined tests showed a linear increase of 2.8% cycle−1. Plant height, days to half bloom, seed color, and grain yield were evaluated in trials planted at normal planting dates to determine the correlated responses in PP9CT following selection for seedling cold tolerance. Plant height showed an irregular response, days to half bloom decreased by 0.55 days cycle−1, seed color increased by 0.13 color units cycle−1, and grain yield increased by 197.7 kg ha−1 cycle−1.
Comparative Temperature Response of Corn Belt Dent and Corn Belt Dent ✕ Pool 5 Maize Hybrids1
Authors: Hardacre A. K. , Eagles H. A.
Published: July 2010

Low temperatures occurring during the growth of maize (Zea mays L.) have been shown to reduce growth and yield in cooler maize growing areas of New Zealand, Europe, and North America. As part of a program to breed cool tolerant maize cultivars, the vegetative growth and development of four hybrids of maize were compared in five temperature environments in controlled environment rooms. The hybrids were A665 ✕ W153R, A665 ✕ H99, A665 ✕ NZlA, and H99 ✕ 5‐514. The inbred lines A665, W153R and H99 are of Corn Belt Dent origin, while NZlA and 5‐514 are derived from CIMMYT (International Maize and Wheat Improvement Center) Pool 5. The temperature environments were 16/6°C day/night, or constant day/night temperatures of 16, 20, 24, and 28°C. Harvests were made of entire plants at comparable stages of development defined by the number of mature leaves. Above 16°C, differences among the hybrids were small. In the 16/6°C environment, plant dry weights, leaf areas, net assimilation rates, shoot:root ratios, and chlorophyll concentrations were markedly greater for A665 ✕ NZlA and H99 ✕ 5‐514 than for A665 ✕ W153R and A665 ✕ H99, but the number of mature leaves were almost identical. It is concluded that hybrids containing NZlA and 5‐514 can tolerate temperatures below 16°C substantially better than Corn Belt Dent hybrids. Furthermore, their vegetative growth is at least equal to pure Corn Belt Dent hybrids in warmer environments up to 28°C.
Chemical and in Vitro Digestible Dry Matter Composition of Maize Stalks after Selection for Stalk Strength and Stalk‐Rot Resistance1
Authors: Albrecht K. A. , Martin M. J. , Russel W. A. , Wedin W. F. , Buxton D. R.
Published: July 2010

Although maize (Zea mays L.) is a major forage crop, little attention has been given to possible alteration of forage quality associated with breeding for increased resistance to stalk lodging. This study was designed to evaluate changes in stalk composition and digestibility resulting from three cycles of recurrent selection each for improved stalk strength (BSlMS) and stalk‐rot [Diplodia maydis (Berk.) Sacc.] resistance (BSlSR). The second elongated internmode plus half of each adjacent internode from plants of the original population (BSlCO) and from C1 to C3 for the BSlMS and BSlSR populations were sampled approximately 35 days after midsilking for chemical and in vitro digestible dry matter (IVDDM) evaluation. Major composition changes from the BSlCO to BSlMSC3 and BSlSRC3 populations, respectively, were: concentration of cell wall constituents, 616 to 520 and 542 g kg−1; concentration of acid detergent fiber, 422 to 353 and 373 g kg−1; concentration of lignin, 57 to 42 and 47 g kg−1; concentration of total nonstructural carbohydrates (TNC), 184 to 258 and 244 g kg−1; and concentration of IVDDM, 514 to 621 and 594 g kg−1. Both selection regimes increased TNC concentration, which diluted stalk fiber concentration and resulted in a net increase in IVDDM. Recurrent selection for traits associated with improved stalk lodging resistance did not have negative effects on the forage quality of maize stalks in late reproductive stages.
Response to Environmental Variation of Soybean Lines selected for Altered Unsaturated Fatty Acid Composition1
Authors: Carver Brett F. , Burton Joseph W. , Carter Thomas E. , Wilson Richard F.
Published: July 2010

Stability of performance across environments is considered essential to the release of soybean genotypes with improved oil quality. Recent advances in the development of soybean genotypes with higher oleic acid and lower linoleic and linolenic acid percentages may be accompanied by changes in genotype ✕ environmental (GE) interaction of the selected material. The purpose of this study was to evaluate stability of unsaturated fatty acid composition in lines derived from the original unselected population and from the third and sixth cycles of recurrent selection for high oleic acid. Lines were classified in two maturity groups and measured for seed fatty acid composition across eight environments in North Carolina, Mississippi, and Puerto Rico. Stability analysis was applied to the data using two environmental variables. The regression analyses showed that GE interactions for each unsaturated fatty acid could be attributed to differences among genotypes in their linear responses to change in environment mean. Further partitioning of these components between maturity groups indicated that stability analysis of genotypes within maturity groups may be more appropriate. This analysis revealed a higher proportion of selected lines sensitive in oleic and linoleic acid percentages to environmental variation compared with the unselected lines. However, the opposite trend was noted for linolenic acid percentage. Low linolenic acid lines tended to show lower‐than‐average linear responses to change in environment mean. Furthermore, differences among genotypes in their linear response to change in environment mean could be attributed to their differential sensitivities to change in growth temperature. Because lines lower in linolenic acid percentage tended to be less sensitive in that trait to environmental variation (compared to the oleic acid trait), direct selection for low linolenic acid is suggested when testing genotypes in very few environments.
Control of Dry Matter Accumulation in Soybean Seeds1
Authors: Hanson W. D.
Published: July 2010

Seed development was characterized for greenhouse‐grown soybean genotypes [Glycine max (L.) Merr.] representing 12 selections differing in petiole diameters and 12 selections differing in seed size. The objective was to evaluate regulation of dry matter accumulation by seeds. Sucrose release rates per square meter (SRRA) and per seed coat (SRRT) from opened seed coats into 0.2 M sorbitol, adjusted for sucrose exudate from cut pod walls, and dry matter accumulation rates per seed (DMAR) were selected to characterize seed development. Six measures, selected as ✕ variables, were grouped into two sets of closely correlated variables: Group 1 (petiole area and leaf area) and Group 2 (area of seed‐coat cup, seed‐coat area, weight per seed, and seed number). Highly significant differences were found among genotypes for SRRA, SRRT, and DMAR. The DMAR variability among genotypes was explained by the regression of DMAR on the six ✕ variables with Group 2 variables being of primary importance. The DMAR per unit seed‐coat area or per plant were similar among groups of genotypes differing in seed size. The SRR measures were associated with Group 1 variables with petiole area being most important. The SRRA measure was also associated with leaf area. The SRR measures and DMAR were not associated. The SRR measures reflected (presumed) transport capacity with no tie to the control of DMAR. No evidence was found using this technique, for a control operating at the seed‐coat level that affected SRR and DMAR. Dry matter accumulation rates per plant reflected primarily a genetically controlled balance operating at a level other than the seed.
Methods of Estimating Developmental Periods in Soybean1
Authors: Agudelo Orlando , Green D. E. , Shibles Richard
Published: July 2010

Three methods of characterizing the duration of developmental stages in two soybean [Glycine max (L.) Merr.) populations were evaluated in the field in 1982. The major objective was to compare the three methods for estimates of the duration of developmental periods, especially days to beginning seed‐filling and the seed‐filling period. Methods used were the Fehr and Caviness method, a first‐flowering‐ node method, and a similar‐node method. In the first‐flowering‐ node method, all notes were taken on the first node to begin flowering. In the similar‐node method, notes were taken on nodes of plants of lines from each stem‐termination group that began flowering on the same day. The lines evaluated were from two crosses between ‘Harosoy‐63’, a daylength‐sensitive and previously widely used cultivar, and two daylength‐insensitive plant introductions, ‘Shinsei’ (PI317.336) and a selection from ‘Kitami Shiro’ (PI317.334B). A comparison of lines in two stem termination types, determinate and indeterminate, was made for days to certain stages of development by using the three methods of characterization. The three methods were equal in differentiating among lines within a given stem‐termination type for stages Rl, R5, and R7 and for duration of the flowering, seed‐filling, and reproductive periods. The Fehr and Caviness method estimated the determinate lines to be earlier in reaching the beginning seed‐filling stage and, thus, to have a longer seed‐filling period than the first‐flowering‐node and similar‐node methods. The best method of characterizing developmental stages of the soybean lines would depend on the genetic material being studied and the information desired. The first‐flowering‐node and similar‐node methods may be best if lines with different stem‐termination types are being compared because they are based on the reproductive development at one node.
Graft‐Transmissible Influence on Fatty Acid Composition of Soybean Seed1
Authors: Carver Brett F. , Burton Joseph W. , Wilson Richard F.
Published: July 2010

Studies involving reciprocal matings in soybean [Glycine max (L.) Merr.] show that the genotype of the maternal plant usually governs phenotypic expression of fatty acid traits in the seed, and that the maternal influence is not inherited through cytoplasmic genes. The objective of this research was to determine whether the maternal influence on fatty acid composition of soybean seed is graft‐transmissible. Autografts and reciprocal heterografts were made prior to flowering in two field environments (early and late plantings) using two genotypes (N78‐2245 and ‘Essex’), which were similar in phenological development but differed in fatty acid composition. By comparing heterografted scions with autografted scions for a given rootstock genotype, the rootstock genotype significantly influenced the seed fatty acid composition of heterografted scions. The magnitude of the influence was greater when heterografted scions were defoliated throughout seed development. It was concluded that the genotype of the maternal plant may control phenotypic expression of fatty acid percentages in the seed via translocated factors. These factors presumably originated in leaf tissue instead of the roots.
Genetic and Environmental Effects on Dry Matter Content of Cassava Root1
Authors: Kawano Kazuo , Fukuda Wania Maria Goncalves , Cenpukdee Uthai
Published: July 2010

Genetic and environmental variabilities of root dry matter content (RDMC) of cassava (Manihot esculenta Crantz) clones (accessions and breeding lines) were estimated at different harvest months (8 12 months), seasons (wet and dry), and locations (three altitudes). To assess the possibility of obtaining higher dry matter yield through selection for RDMC, genetic studies based on F1 variability and parents‐offspring regressions also were conducted. Age of plant, season, and location significantly affected root dry matter content. Temperature appeared to be an important factor related to the effect of location. The highest RDMC was obtained with 8 month‐old plants harvested at the beginning of the dry season in the high altitude location, while the lowest occurred with 12‐month‐old plants harvested at the beginning of the wet season at the low altitude location. The clone effect was highly significant and a broad‐sense heritability of 0.87 was obtained. Clone ✕ location interaction was also significant, but the magnitude of this effect was much smaller than that of the clone effect. Genetic analyses suggested that inheritance of RDMC was controlled mainly by polygenic additive factors. Narrow‐sense heritabilities ranging from 0.51 to 0.67 were obtained. There was no indication of negative response in root dry matter content after intensive mass selection for root fresh yield. The data indicate that RDMC can be increased by simple breeding techniques such as phenotypic mass selection. Selection of clones at one location was largely valid for other locations; however, final selection should be made at each specific location for maximum potential gain.
Photosynthate Partitioning in Plants of Alfalfa Population Selected for High and Low Nodule Mass1
Authors: Cralle Harry T. , Heichel G. H. , Barnes D. K.
Published: July 2010

Alfalfa (Medicago sativa L.) N2 fixation can be improved by recurrent selection for associated characters, especially nodule mass. Because of the interdependence of nodule metabolism and shoot CO2 assimilation, selection for nodule mass might have correlated effects on photosynthate partitioning to dry matter. This possibility was examined by investigating leaf CO2 assimilation, dry matter distribution among organs, and photosynthate partitioning in alfalfa plants from experimental populations developed for high and low nodule mass. Experimental populations with low (LNM), intermediate (INM), and high (HNM) nodule mass/plant were developed by crossing two subpopulations produced from two different germplasm sources. The subpopulations had been developed for high and low nodule mass by two cycles of divergent recurrent selection. Glasshouse grown plants at two stages of ontogeny were radiolabeled with 14CO2 and analyzed for allocation of radiolabel. Selection for HNM yielded plants with larger organs than those of the INM control, and selection for LNM yielded plants with smaller organs. Compared to the LNM population, plants from the HNM population had 40% greater nodule mass, 29% greater leaf mass, 34% greater mass of crown shoots, 35% greater crown mass, 41% greater root mass, and 35% greater phytomass. Despite the direct response of nodule mass and the correlated responses of other organs to selection for nodule mass, the relative distribution of whole‐plant dry matter among organs was unaffected by selection. Furthermore, selection for nodule mass did not materially change the partitioning of photosynthate to dry matter among organs of the experimental populations, leaf CO2 assimilation, or export of photosynthate by labeled leaves. The results indicate that photosynthate partitioning was unaltered by selection of experimental populations differing by 40% in nodule mass. The results also indicate that selection of alfalfa for greater N2‐fixation capability by selection for nodule mass may maintain or increase yields without changes in C allocation.
Identification of Chromosomes that Condition Dhurrin Content in Sorghum Seedlings1
Authors: Gorz H. J. , Haskins F. A. , Morris R. , Johnson B. E.
Published: July 2010

Young plants of sorghum and sudangrass [Sorghum bicolor (L.) Moench] may be toxic to livestock because of the presence of the cyanogenic glucoside, dhurrin [p‐hydroxy‐(S)‐mandelonitrile‐β‐Dglucoside], in the forage. In the present study a set of 11 chromosomal reciprocal translocations in ‘Combine 7078’ grain sorghum, involving each of the 10 chromosome pairs of sorghum in at least two of the translocations, was used to determine which chromosomes carried genes conditioning dhurrin content of sorghum seedlings. Each translocation stock was crossed and backcrossed once to a low‐dhurrin line of sudangrass. Backcross progenies and parental plants were started in the greenhouse, and 100 plants of each backcross and 50 of each parental stock were transplanted to a field nursery in a randomized complete block design with five replications. Individual backcross plants were classified as semisterile or fertile on the basis of seed set. They were also classified for high or low dhurrin content based on a spectrophotometric assay of first leaves of 1‐week‐old seedlings grown from selfed or open‐pollinated seed that had been harvested from the backcross plants. Results suggested the presence of one or more genes conditioning dharrin content on at least 5 of the 10 chromosome pairs.
Inheritance of Resistance to Two Races of Fusarium Wilt in Three Cowpea Cultivars1
Authors: Rigert K. S. , Foster K. W.
Published: July 2010

Fusarium wilt [caused by Fusarium oxysporum f. sp. tracheiphilum (E.F. Sm.) Snyder and Hansen] is a serious disease of cowpea [Vigna unguiculata (L.) Walp.] in California. The objectives of this study were to determine the inheritance of resistance to F. oxysporum f. sp. tracheiphilum races 2 and 3 in ‘California Blackeye Number Five’ (CB5), ‘California Blackeye Number Three’ (CB3), and line 7964, and to determine if the genes for resistance to each race were independent of each other. Cultivar CB5 is susceptible and CB3 and 7964 are resistant to races 2 and 3. The F1, BC1, F2, F3, and F5 progenies were evaluated for resistance to each race using a seedling root dip inoculation procedure. Some F1 and F2 progenies were also evaluated for resistance using a tray inoculation procedure. A single dominant race 3 resistance gene was identified in CB3 and a single dominant race 2 resistance gene was identified in 7964. The F3 family reaction to both races suggested that the race 3 gene in CB3 also conferred incompletely dominant resistance to race 2, and the race 2 gene in 7964 also conferred incompletely dominant resistance to race 3. The reaction of F5 lines to both races did not support this hypothesis. It was concluded that CB3 also possessed a single incompletely dominant gene for race 2 resistance and that 7964 also possessed a single incompletely dominant gene for race 3 resistance.
Inheritance of a Second Source of Greenbug Resistance in Barley1
Authors: Merkle O. G. , Webster J. A. , Morgan G. H.
Published: July 2010

Genetic studies were conducted to determine the inheritance of resistance to biotype E greenbug, Schizaphis graminum (Rondani), in PI 426756, a barley (Hordeum vulgare L.) line previously identified as resistant to this pest. An additional objective was to determine whether the genes governing resistance in PI 426756 and ‘Post’ are allelic or nonallelic. Results from greenbug‐infested F2 and F3 seedlings in the greenhouse indicated that the resistance in each line is governed by a single dominant gene, and that these two genes are nonallelic and independent. The discovery of another gene for greenbug resistance is important because greenbug resistance in all current U.S. commercial barley cultivars appears to trace back to the same single dominant gene present in Post. The gene symbol Rsg2b was assigned to this gene; whereas, the gene symbol formerly designated Grb was modified to Rsg1a.
Relationship between High Molecular Weight Glutenin Subunits and Loaf Volume in Wheat as Measured by the Sodium Dodecyl Sulphate Sedimentation Test1
Authors: Lorenzo A. , Kronstad W. E. , Vieira L. G. E.
Published: July 2010

The objective of this investigation was to evaluate the contribution of different high molecular weight (HMW) glutenin protein subunits in wheat (Triticum aestivum L.) to loaf volume as measured by the sodium dodecyl sulphate sedimentation test. Two segregating populations were developed from parental lines differing in their HMW glutenin subunits. ‘Buck Pucara,’ a hard red spring cultivar developed by Criadero Buck in Argentina, was crossed to two spring wheat hexapioids, lines 13 and 14, developed at the Volcani Institute in Israel and derived from wild emmet (Triticum turgidum L. var. Dicoccoides Korn Bowden). Parents, F2 individual plants, and F2‐derived F4 segregating lines were evaluated. Combined effects of the good quality glutenin subunits from each of the alleles tested were not additive as previously reported. Bands 5 and 10 in a homozygous state always were associated with higher loaf volumes than bands 3 and 12 or the heterozygous state bands 5 and 10 + 3 and 12, contributed by the D genome. The importance of individual subunits in the A and B genome depended on the interaction with other glutenin proteins. There was evidence for intra‐allelic interactions among HMW glutenin subunits in a heterozygous state. Hybrid wheat breeders may find it difficult to predict loaf volume based on the banding pattern of the corresponding parental combinations.
Effect of Incubator Aging on Soybean Seeds during the Ripening Period of Seed Development1
Authors: Yaklich R. W. , Kulik M. M.
Published: July 2010

The effect of incubator aging of soybean [Glycine max (L.) Merr.] pods on soybean seed quality was determined during the ripening period of seed development. Soybean pods of four cultivars were picked at 3‐ or 4‐day intervals from two replicates of field‐grown plants when green beans attained full size (growth stage R6) and aged for 1 week in an incubator set at 30°C and 100% relative humidity. Aged pods were then dried at 22°C or in an unheated attic. One‐hundred seeds from each replicate were subjected to the accelerated aging vigor test and 50 seeds were evaluated for Phomopsis phaseoli infection. Inner and outer soybean pod surfaces and soybean seeds were observed by scanning electron microscopy to determine points of entry of P. phaseoli hyphae. Incubator aging of soybean seeds in the pod lowered subsequent accelerated aging test scores for seeds and increased P. phaseoli infection. The drying treatments did not affect the results of the incubator aging treatment. Cultivars with impermeable seed coats had significantly less P. phaseoli infection. One of the impermeable seed coat cultivars (Sooty) had a black seed coat and significantly less P. phaseoli infection. Stomates on the outer surface of soybean pods were points of entry for hyphae of P. phaseoli. Hyphae were observed on the inner surface of the soybean pod and on the surface of the seed coat and hilum. Hyphae were observed entering the hilar fissure, micropyle, and pores on the seed coat surface. These results demonstrate that there can be a decrease in soybean seed quality in the absence of a significant increase in P. phaseoli infection. Further, they also demonstrate that there is resistance to infection.
Incompatibility Mechanism in Interspecific Peanut Hybrids1
Authors: Halward T. M. , Stalker H. T.
Published: July 2010

Mechanisms of incompatibility among interspecific peanut(Arachis spp.) hybrids were investigated in an attempt to determine efficient methods for the introgression of germplasm from diploid Arachis species (2n = 20) into A. hypogaea L. (2n = 40). Hexaploid interspecific hybrids (2n = 60) with restored fertility were used in a backcross program, in reciprocal, with diploid Arachis species in an attempt to rapidly reduce the chromosome number from 2n = 60 to 2n = 40. All attempts to cross hexaploids and diploids failed to produce viable hybrids. The proposed mechanisms for such failure are: (i) lack of pollen germination on the stigma or restricted pollen tube growth (in crosses using diploid A. cardenasii as the female parent), and (ii) endosperm degeneration and/ore mbryo abortion( in all other crosses examined). When A. cardenasii Krap. et Greg. nom. nud. (coll. GKP 10017) (2n = 20) was used as a female parent, no pegs (the basal portion of the gynoecium that grows by the activity of an intercalary meristem and carries the fertilized ovule into the soil) werep roduced. When A. duranensis Krap. et Greg. nom. nud. (coll. K 7988) (2n = 20) or batizocol Krap. et Greg. (col l. K 9484 (2n = 20) was used as a female, very few pegs were produced and the hybride mbryosa bortedw ithin 10 days after pollination. When either of the two hexaploidh ybrids(A. hypogaea ✕ A. batizocoi or A. hypogaea ✕ A. cardenasii was used as a female, peg development was more frequent,b ut all developed pods contained tiny, shrivelled, black seeds. Embryo rescue techniques were applied as a means for overcoming embryo abortion. The seeds were successfully germinated in culture and shoots and roots were initiated.
Natural Selection in a Doubled‐Haploid Mixture and a Composite Cross of Barley1
Authors: Patel J. D. , Reinbergs E. , Mather D. E. , Choo T. M. , Sterling J. D. E.
Published: July 2010

Natural selection can modify cereal breeding populations that are advanced in bulk. Its effects may vary among populations and environments. We examined changes in two barley (Hordeum vulgare L.) populations of similar ancestry: an F3 composite cross and a mixture of doubled‐haploid (DH) lines. Bulk plots of these populations were grown in Ontario, in Prince Edward Island, and with alternation between Ontario and Prince Edward Island. After 5 yr, the grain yields, heading dates, and plant heights of 50 random lines from each of eight resulting populations were evaluated at two locations in Ontario. On the average, these lines were higher yielding, later heading, and taller than the original DH lines. Composite‐cross populations, which would have had potential for segregation, recombination, and heterosis during the natural selection period, had higher mean yields and later mean heading dates than did DH mixtures. Alternated populations were lower yielding and taller, and retained greater variability for plant height, than nonalternated populations. Populations grown or initiated in Ontario were higher yielding than those grown or initiated in Prince Edward Island. Genotype by testing location interactions were not important. Correlations among traits were affected by natural selection, but not in any consistent direction. It was concluded that natural selection can favorably affect grain yield, but may unfavorably affect maturity, plant height, and relationships among traits. Natural selection was less effective when material was advanced outside its intended region of adaptation, or was alternated between locations.
Divergent Selection for Stalk Quality and Grain Yield in an Adapted ✕ Exotic Maize Population Cross1
Authors: Albrecht Bruno , Dudley J. W.
Published: July 2010

The choice of breeding materials, evaluation techniques, and breeding methodologies crucial in improving lodging resistance of maize (Zea mays L.). The present study was conducted to evaluate progress from selection for different stalk quality traits and for grain yield in the F2 of Illinois Stiff Stalk Synthetic Composite (RSSSC) ✕ South African Photoperiod Insensitive Composite II (PIC2), population that has good potential for stalk quality and yield improvement. One cycle of divergent S1 family selection was practiced for the following traits:(i) grainy ield, (ii) lodging resistance (iii) rind puncture resistance using penetrometer measurement (iv), stalk crushing strength, and (v) a desired gain selection index based the first three traits. In addition, one cycle of divergent mass selection for rind puncture resistance was completed. Evaluation of progress from selection was based on Cycle 1 populations, testcrosses to FRMo17 an d Oh43,a ndo n random Cycle 1 S1 families grown in 1984 and/or 1985. When valuated as C1 populations, response to S1 selection was significant for all five traits. Selection for higher grain yield resulted in a deterioration of stalk quality. Index selection was effective in increasing rain yield while maintaining acceptable lodging resistance. For improving stalk lodging resistance, selection for lodging resistance, per se, was most effective, followed by selection for high rind puncture resistance and high stalk crushing strength. In testcrosses, the selections for high rind puncture resistance showed greatest gains in stalk lodging resistance. Based on Cycle 1 S1 families, the direct response to positives election for grain yield, index, and rind puncture resistance were 1.2, 0.9, and 1.1 phenotypic standard deviations respectively. Significant genetic variance was present, indicating further progress from selection is possible. Mass selection for rind puncture resistance was as effective as S1 selection and resulted in fewer undesirable correlated changes for simultaneous talk quality andg rain yield improvement, S1, index selection, including rind puncture resistance and yield, appears promising.
Comparison of Half‐Sib and S1 Recurrent Selection in the Krug Yellow Dent Maize Populations1
Authors: Tanner A. H. , Smith O. S.
Published: July 2010

Eight cycles of half‐sib family [BSK(HI)] and S1 progeny [BSK(S)I recurrent selection have been completed in cv. Krug Hi I Syn.3 (BSK), a strain of the open‐pollinated maize (Zea mays L.) cv. Krug Yellow Dent. Experiments were conducted to evaluate and compare the changes in grain yield, grain moisture, and lodging in BSK(S), BSK(HI), and in crosses with testers used in the BSK(HI) program. The genetic gains per cycle for grain yield in the populations per se for Cycles 0 to 4, adjusted for the effects of finite population size, were significantly larger for BSK(S) than for the BSK(HI). Cycles 4 to 8, genetic gains (adjusted for drift) in BSK(S) were lower (not significantly) and higher for BSK(HI), compared with their respective rates in Cycles 0 to 4. This resulted in a nonsignificant difference between methods for Cycles 4 to 8. In the populations selfed and in crosses with testers used in the BSK(HI) program (averaged over three testers), genetic gains paralleled gains in the populations per se, except for Cycles 4 to 8 in BSK(HI). The effects of finite population size (genetic drift) were significant for grain yield for both methods and confounded the observed response to selection, especially in Cycles 4 to 8. The effects of drift were larger in BSK(S). Genetic gains, adjusted for drift, were smaller than predicted gains for both methods.
Effect of Rotating 'Forrest' and 'Bedford' Soybean on Yield and Soybean Cyst Nematode Population Dynamics1
Authors: Francl L. J. , Wrather J. A.
Published: July 2010

The soybean cyst nematode (Heterodera glycines Ichinohe) is a serious pest that might be managed by the judicious use of resistant cultivars. Soybean [Glycine max (L.) Merr. ‘Bedford’] was rotated with ‘Forrest’ for 5 yr on a Tiptonville silt loam (Typic Arguidolls) to determine the effect of selection pressure on the reproductive ability of H. glycines and the effect of rotations on seed yield. At the end of the field experiment in 1984, nematode populations were tested in the greenhouse for compatibility with five soybean lines having genes for resistance to H.glycines. Population levels of H. glycines at harvest when Forrest and Bedford were monocultured were not significantly different after the second year. A 2‐yr rotation of Forrest and Bedford reduced cyst populations levels on Bedford at harvest relative to Bedford monoculture, but no rotation scheme reduced nematode population density after growing Forrest. Yields were higher for Bedford than for Forrest in the first 2 yr of the study, but thereafter no rotation was consistently superior. Cyst reproduction in the greenhouse was highest on Forrest and lowest on PI90763. Bedford best differentiated the field‐selected nematode populations in the greenhouse experiment. Reproduction on Bedford was lower if Forrest was grown in the last year of the field experiment than if Bedford was grown, indicating that the frequency of virulence gene(s) was not maintained in the nematode population in the absence of selection pressure.
Effects of Nitrogen Fertilizer Rate, Seeding Rate, and Row Spacing on Semidwarf and Conventional Height Spring Oat1
Authors: Marshall H. G. , Kolb F. L. , Roth G. W.
Published: July 2010

Lodging may cause serious grain losses when conventional height oat (Avena sativa L.) plants are grown at high levels of soil fertility in humid regions. The use of semi dwarf cultivars could alleviate this problem, but because none have been available, little is known about their potential value. Our objective was to compare conventional height ‘Ogle’ to semi dwarf ‘Pennlo’ oats when grown at different management levels. In 1982 and 1983, the two cultivars were grown near University Park, PA, in a factorial experiment with row spacings of 13 and 18 cm, seeding rates of 67, I01, and 134 kg ha‐1, and N rates of 67, I01, and 134 kg ha‐1. Overall, Ogle yielded 18% more grain and 29% more straw than Pennlo in 1982 and 13% more grain and 33% more straw in 1983. The semidwarf was 27% shorter than Ogle and did not lodge. Ogle lodged severely in some treatments, but this occurred too late to limit yield. Grain yield increases in response to reduced row spacing were similar for Ogle and Pennlo (6.2 and 9.6% for the 2 yr). With the exception of Pennlo in 1982, grain yield of both cultivars was increased by using a seeding rate of I01 kg ha‐1. A high seeding rate increased the test weight of both cultlvars and the lodging of Ogle. Increasing N rate from 67 to 134 kg ha‐1 increased grain yield of both cultivars. Considering all management levels over the 2 yr, there were no major response differences between the conventional height and the semi dwarf cultivars.
Regeneration of Bermudagrass Cultivars and Evidence of Somatic Embryogenesis1
Authors: Ahn B. J. , Huang F. H. , King J. W.
Published: July 2010

Plant regeneration via somatic embryogenesis is a prerequisite to utilizing in vitro culture techniques for improving bermudagrasses. This study was conducted (i) to apply the culture methods, previously developed for common bermudagrass [Cynodon dactylon (L.) Pers.], for plantlet regenerations from a genotypic array of bermudagrasses, (ii) to determine a mode of the regeneration, and (iii) to establish and characterize cell suspension cultures. Embryogenic calli (EC) were produced from immature inflorescences of ‘Tifton 44’, ‘74 ✕ 12‐6’, and ‘Tifway’ bermudagrass on N6 agar medium supplemented with 1 mg L‐1 2,4‐D (2,4‐dichlorophenoxy acetic acid). The EC were maintained for over 30 weeks (140 weeks in common bermudagrass) without loss of embryogenic competence by subculturing to fresh medium. Plantlets were regenerated 2 weeks after the EC were transferred to auxin‐free N6 medium. Histological observation of regenerating EC confirmed plant regeneration through somatic embryogenesis in common bermudagrass. Suspension cultures of common bermudagrass were composed of mostly vacuolated, tubular, single cells or cell aggregates that formed only nonembryogenic calli when cultured in N6 agar medium (0.5 mg L‐1 2,4‐D, 8 g L‐1 agar). Small, cytoplasmically rich embryogenic cells were found mostly in compact cell clumps that developed globular embryoids in suspension with 0.25 mg L‐l 2,4‐D. The clumps produced numerous plantlets upon transfer to regeneration medium. These cultural methods can be useful to genetically improve forage and turf‐type bermudagrass species for desirable agronomic traits.
A Recessive Gene for a Zero Cyst Phenotype in Soybean1
Authors: Luedders V. D.
Published: July 2010

The identification of specific genes for resistance is essential for efficient control of parasites. The number of cysts per plant is one phenotype of the soybean cyst nematode‐soybean association [Heterodera glycines lchinohe‐Glycine max (L.) Merr.] and is determined by genes of both organisms. The continuous distribution of the phenotypes is used to arbitrarily assign soybean lines into resistant or susceptible categories. Genetic studies have not been definitive using heterogeneous nematodes and soybean with many genes for resistance. The objective of the current study was to show that single gene resistance was possible. One nematode population was selected and inbred to produce zero cysts on the “susceptible” PI88287. Results with F2 plants and their progeny showed discrete phenotypes as a result of one recessive gene for resistance in PI88287. Apparently, one gene can condition the zero cyst phenotype (“resistance”) when the frequency of the corresponding nematode gene for avirulence is high.
Relationship of Tissue Water Relations to Asparagine Uptake in Developing Soybean Seeds1
Authors: Guldan Steven J. , Brun William A.
Published: July 2010

Amino acids play an important role in the N nutrition of developing soybean [Glycine max (L.) Merr.] seeds. Factors affecting cotyledonary amino acid uptake within those seeds are not well understood. The objectives of this study were to investigate the effects of altered soybean cotyledon water relations on in vitro asparagine uptake by those cotyledons. Two experimental plant introduction (PI) lines with genotypic differences in seed growth rate and final seed weight were grown in the field. They were PI 416.845 (heavy seeded), and PI 361.058 (light seeded). Cotyledons were sampled at 32 days after anthesis for the light seeded line, and 32 and 45 days after anthesis for the heavy seeded line. Cultivar Evans was used for the studies involving plants grown in the growth chamber. Cotyledons were incubated in uptake buffer solutions containing 10 mmol kg‐1 14C‐asparagine and adjusted to various water potential levels with mannitol (a slowly penetrating osmoticum) or ethylene glycol (a rapidly penetrating osmoticum). Solution water potential levels were approximately 0, −0.5, −1.0, −1.5, and −2.0 MPa. The rate of asparagine uptake for the heavy seeded genotype was greater than that for the light seeded genotype. Uptake was greater at −0.5 and −1.0 MPa than at 0 and −2.0 MPa in the experiments using plants grown in the growth chamber. In the study using field‐grown plants, asparagine uptake was similar in mannitol solutions of 0, −0.5, and −1.0 MPa, but declined in mannitol solutions of −1.5 and −2.0 MPa. Results for ethylene glycol as osmoticum were similar at 32 days after anthesis although reductions of uptake at −1.5 and −2.0 MPa were not as great. Our results indicate that asparagine uptake by excised cotyledons is influenced by the water potential components of their cells, specifically the cell turgor.
Evaluation of Sweet Sorghum for Fermentable Sugar Production Potential1
Authors: Smith G. A. , Bagby M. O. , Lewellan R. T. , Doney D. L. , Moore P. H. , Hills F. J. , Campbell L. G. , Hogaboam G. J. , Coe G. E. , Freeman K.
Published: July 2010

This study was prompted by the special interest in sugar crops, at a time of high petroleum prices and fuel shortages, as potential renewable resources which would supplement non‐renewable fossil resources. Four to six sweet sorghum [Sorghum bicolor (L.) Moench] cultivars were evaluated 4 yr for fermentable sugar production potential at eight locations in the continental USA and at one location in Hawaii. Latitudes represented ranged from 21 to 47° N with the average number of frost‐free days ranging from 120 to more than 350. Data were collected for biomass yield, percent lignin, percent cellulose, stalk sugar yields, and other agronomic characters. Total sugar yield for the continental USA ranged from 4 Mg ha‐1 to 10.7 Mg ha‐1 during 3 yr of the study and up to 12 Mg ha‐1 at the Hawaiian location. Accordingly, theoretical ethanol production in the continental USA ranged from 2129 L ha‐1 to 5696 L ha‐1. Results of the study demonstrated that sweet sorghum is far more widely adapted than was anticipated for a plant of tropical origin and certainly has the potential for providing a good source of fermentable carbohydrates across a wide geographic area.
Genotypic Differences in Tolerance of Ice Encasement, Low Temperature Flooding, and Freezing in Winter Wheat1
Authors: McKersie B. D. , Hunt L. A.
Published: July 2010

A key to improved winter survival of cereals in eastern Canada and northeastern USA appears to be resistance to a combination of winter stresses. Three traits associated with winterhardiness in winter wheat (Triticum aestivum L. emend Thell.) were measured on 34 genotypes in late fall and early spring in 2 successive yr, to determine whether the environmental controls of icing and flooding tolerances are more or less complex than those for freezing tolerance. Significant genotypic differences were observed for all three traits, and significant genotype ✕ environment (year and sampling) interactions were noted for icing and freezing tolerances. The environmental controls for the expression of icing and freezing tolerances thus appear relatively complex, whereas the control of low temperature flooding tolerances appears somewhat simpler. Genotypes with high freezing tolerances tended to exhibit high tolerance of both ice encasement and low temperature flooding, but there were some exceptions. ‘Norstar’ and ‘Roughrider’, which exhibit good winterhardiness in western North America, did not express the same relative stress tolerance in this study.
Inheritance and Linkage Studies with Five Isozyme Loci in Soybean1
Authors: Griffin Jeffrey , Palmer Reid G.
Published: July 2010

Horizontal starch gel electrophoresis, followed by enzyme‐specific staining, allows us to separate and visualize several soybean [Glycine max [L.] Merr.] isozymes. Using extracts prepared from the cotyledons of seeds germinated 3 to 4 days, we detect five bands (zones) of aconitase [aconitate hydratase, enzyme commission (EC) 4.2.1.3] activity and one band of endopeptidase activity. We have observed mobility variants of all of these isozymes. An understanding of the genetic basis of the variants would facilitate their use as markers in soybean genetics or breeding studies. One objective of this research was to investigate the inheritance of mobility variants for four of the five aconitase isozymes, as well as a mobility variant for the endopeptidase band. Segregation data (either individual F2 zymotypes or F2 genotypes determined by progeny testing) were collected on F2 populations derived from F1 individuals whose parents had different zymotypes. Mobility variants of the four aconitase isozymes are conditioned by four independent loci with codominant alleles. The aconitase loci and alleles are: Aco1 (a, b), Aco2 (a, b), Aco3 (a, b), and Aco4 (a, b, c). The endopeptidase mobility variants are conditioned by the codominant alleles Enp‐a and Enp‐b. A second objective was to determine if these five isozyme loci are linked to one another, or to other known loci. Data were collected on F2 populations segregating for several loci conditioning isozyme and morpholigical traits. Deviations from independent assortment were determined by Χ2 analysis. Locus Aco3 is linked to the Spl locus; the frequency of recombination varied from 4.6 ± 0.9% in the cross ‘A1937’ ✕ PI 342662A (G. soja Sieb. et Zucc.) to 30.6 ± 3.0% in the cross PI 437728 (G. max) ✕ ‘Evans’. Locus Aco3 also is linked to the T locus, with a recombination frequency of 28.8 ± 4.3%, as determined in the cross ‘Amsoy 71’ ✕ PI 342622A. Both Sp1 and T are on linkage group 1. The present data allow us to assign Aco3 to linkage group 1, but do not allow us to unambiguously establish its position relative to other markers. The other four loci also were tested for linkage with several loci; Aco1 (11 loci), Aco2 (10 loci), Aco4 (13 loci) and Enp (8 loci) segregated independent of all loci tested. These five loci conditioning isozyme mobility variants can be useful tools in soybean genetic research.
Potential Ethanol Production from Sugar Beet and Fodder Beet1
Authors: Theurer J. C. , Doney D. L. , Smith G. A. , Lewellen R. T. , Hogaboam G. J. , Bugbee W. M. , Gallian J. J.
Published: July 2010

Fodder beet and sugar beet (Beta vulgaris L.) cultivars were evaluated in field trials at six locations to assess the potential ethanol fuel production from beet crops in the USA. This research was stimulated by the potential world petroleum fuel shortages in the 1970s and a need to assay the merit of sugar and starch crops for potential alcohol fuel production. Fodder beet cultivars had greater root weight and less sucrose content than sugar beet. Fodder beets contained more glucose and fructose than sugar beet but these sugars amounted to < 1% of the total sugar content. Average potential ethanol production for all locations was 5.34 and 6.38 kL ha−1 in 1980 and 1981, respectively, for fodder beet, compared to 5.36 and 6.68 kL ha−1 for sugar beet cultivars. Salinas, CA, with a long growing season, had a potential alcohol yield from beets of 8.64 kL ha−1, while potential ethanol yields at Fargo, ND, where the growing season is short, were <5.00 kL ha−1. Adapted sugar beet hybrids show better promise than fodder beet as a fuel crop in the USA, since sugar beet produces an equal or greater quantity of fermentable sugar, has less bulk to transport, more extractable sugar per unit mass, and resistance to prevalent sugar beet diseases.