bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of Genetic Variation for Oil Properties and Agronomic Characteristics of Soybean1
Authors: Brossman G. D. , Wilcox J. R.
Published: July 2010

The effects of ethyl methanesulfonate (EMS) for inducing significant useful genetic variation in fatty acid composition of oil from mature seeds and in agronomic characteristics of soybean [Glycine max (L.) Merr.] were determined. Seeds of ‘Century’ were soaked for 24 h in a 0.018 mol L−1 solution of EMS. Fieldgrown M1 plants were harvested individually and 20 seeds per plant were sown the following year in M2 plant rows. At maturity three M2 plants (lines) were randomly selected from 100 M1 families. The lines were evaluated in hill plots, 5 plants per hill, during 1981 and 1982 for agronomic characteristics, and harvested seeds were evaluated for fatty acid composition of the oil. The EMS induced significant genetic variation in fatty acid composition and in agronomic characteristics. The distributions of fatty acids were skewed toward high levels of oleic acid and low levels of linoleic acid. Agronomic characteristics were skewed toward low yielding, late maturing lines. The mean of each characteristic for the EMS treated lines did not differ significantly from Century. Broad‐sense heritability estimates for agronomic characteristics of the EMS treated lines were similar to estimates based on populations derived from hybridization. Genetic correlations indicated that very few significant interrelations existed between agronomic characteristics and fatty acid composition of the oil.
Further Analysis of the Mating System in Two Mass Selected Populations of Maize1
Authors: Pollak L. M. , Gardner C. O. , Kahler A. L. , Thomas‐Compton M.
Published: July 2010

In order to determine whether main stalks (MS) and tillers (T) outcross at different rates, estimates of the amount of outcrossing (t) vs. self‐fertilization (s = 1 − t) were made at nine enzyme loci in MS and T fractions of two maize (Zea mays L.) populations that had been mass selected for prolificacy [NHG(M)P‐17] and grain yield [NHG(M)C‐22]. The weighted mean single‐locus estimates of t were 0.96 for P‐17MS, 0.92 for P‐17T, 0.82 for C‐22MS, and 0.95 for C‐22T. The multilocus outcrossing values were 1.00, 0.93, 0.83, and 0.93. The results show that outcrossing was the predominant form of mating in all population fractions, but a substantial amount of selfing (9%) also occurred. The P‐17 population selected for prolificacy selfed at a lower rate (4%) than the C‐22 population selected for increased grain yield (12%). The rate of selfing was similar in T fractions of both populations (7%), but MS selfed at a higher rate (17%) in C‐22 than in P‐17 (0%). This suggests a possible advantage to using MS samples when selecting for increased prolificacy in ‘Hays Golden’ germplasm. The results also suggest that for the C‐22 population greater progress from mass selection for high grain yield would occur if progeny from T ears (t = 0.93) were used to form the successive generation rather than progeny from MS ears (t = 0.83).
Inheritance of Mature Plant Resistance to Helminthosporium maydis Race 0 in Maize1
Authors: Thompson D. L. , Bergquist R. R.
Published: July 2010

Inheritance of resistance of inbred NC250 of maize (Zea mays L.) to southern corn leaf blight incited by Helminthosporium maydis Nisik. & Miy. race 0 was investigated using seedlings and mature plants. Reactions of seedlings artificially inoculated in greenhouse tests indicated resistance was recessive and ratings of three parents were B73 susceptible, B73rhm resistant, and NC250 segregating. Mature plant ratings by contrast were B73 and B73rhm susceptible and NC250 resistant. Most mature plant evaluations were made under severe natural epiphytotics in south Florida where 25 to 50% of the foliage of susceptible cultivars was usually destroyed by flowering time. Parents, F1, F2, F3, and backcross generations were rated on a scale of 1 (resistant) to 5 (susceptible) in increments of 1.0 or 0.5. Generation mean and diallel analyses indicated mainly additive effects for reaction to H. maydis race 0. Resistance conditioned by rhm‐gene was generally satisfactory to about flowering and then declined in effectiveness; however, rhm‐gene influenced mature plant resistance as demonstrated by comparisons between 200 F3 families in each of two populations: F3's from B73rhm ✕ NC250 and B73 ✕ NC250 averaged 2.2 and 3.3 for leaf blight ratings and 48.5 and 10.0 for the percentage of families in the three most resistant classes, respectively. These comparisons demonstrated enhancement of mature plant resistance by a gene for resistance in the seedling stage. Segregation ratios for F2 plants and F3 families indicated two recessive complementary loci for resistance while quantitative analyses estimates suggested this interpretation was an over simplification. The mature plant resistance of NC250, which persisted through the reproductive stage to near physiological maturity, was largely independent of reaction in the seedling stage, was not complex, and maybe transferred by backcrossing.
Selection for Kernel Weight in Two Four‐Rowed Spike Populations of Durum Wheat1
Authors: Haugerud N. G. , Cantrell R. G.
Published: July 2010

Selection experiments were conducted on two four‐rowed spike (FRS) or tetrastichon populations of durum wheat (Triticum turgidum L. var. durum) to determine if grain yield could be improved by selection for kernel weight. Populations 1 and 2 were derived from crosses involving two FRS genotypes with known sources of high kernel weight plus fecundity, and high kernel weight, respectively. We selected 28 FRS F3 families from Population 1 and 37 FRS F3 families from population 2 for high kernel weight. Equal numbers of families also were randomly chosen from both populations. Selected and random F2 derived F4 lines from each population were grown with parents and checks in separate experiments at Langdon, ND in 1981, and spike characters were evaluated. From each population, 15 F4 families with the highest kernel weight and 15 random families were selected in 1981 and grown in separate experiments at Prosper and Langdon, ND, in 1982. Spike characters, grain yield, and test weight were measured on each plot. Significant gains in kernel weight were obtained in both populations. The improvements in kernel weight were associated with a decline in number of kernels per spike. Selection for kernel weight improved spike productivity and grain yield relative to the FRS parent, but the yields of the selected FRS lines were not significantly higher than the durum cultivars now grown in North Dakota.
Comparative Growth of Obsolete and Modern Cotton Cultivars. I. Vegetative Dry Matter Partitioning1
Authors: Wells Randy , Meredith William R.
Published: July 2010

Lint yields of cotton (Gossypium hirsutum L.) cultivars have increased consistently in this century due to breeding selection for lint production. Little is known concerning what differences in vegetative growth and development have occurred as a result. The objective of this study was to ascertain what differences in vegetative growth have occurred as a result of selection for increased yield. Twelve cultivars, six from the Stoneville, and six from the Deltapine lineage, were planted on 26 Apr. or 12 May 1982. Growth was monitored at various times during the season via leaf dry weights (LDW), stem dry weights (SDW), specific leaf weights (SLW), and leaf area indexes (LAI). In addition, light interception characteristics of the canopies were determined at 59 and 78 days after planting (DAP). Planting date did not affect the relationships found among the cultivars. Old cultivars (released before 1920) partitioned more dry matter into stems while displaying similar peak quantities of LDW. Leaf area index and light interception values indicate that many of the cultivars produced more leaf area than that required for complete light capture. Net assimilation rates (NAR) were not higher in the newer cultivars, indicating the absence of increased assimilatory capacity per unit leaf area. Negative correlations of vegetative parameters beyond 96 DAP to year of cultivar release suggest that modern cultivars make an earlier transition from vegetative to reproductive growth and may have a better coordination of assimilatory capacity with reproductive sink activity.
Comparative Growth of Obsolete and Modern Cotton Cultivars. III. Relationship of Yield to Observed Growth Characteristics1
Authors: Wells Randy , Meredith William R.
Published: July 2010

Yield differences among cotton (Gossypium hirsutum L.) lines have been used as the measure of cultivar suitability in this century. The result has been a steady increase in yields as progressively newer cultivars have been developed, while little or no information pertaining to the alterations in growth responsible for the enhanced performance has been collected. To assess the association of growth response to lint yield, 12 cotton cultivars representing release years since 1900 were examined for yield, yield components, and their relationship to seasonal vegetative and reproductive growth patterns resulting from two planting dates during 1982. The observed yield of lint exhibited a linear increase in association with the increased year of cultivar release. The largest contributor to yield variation was the number of bolls produced. The modern cultivars (since 1950) produced a greater proportion of their total lint and boll number before 135 days after planting. The early lint production of these cultivars is associated with smaller vegetative plant canopies and an earlier transition to reproductive growth. The modern cultivars exhibited smaller boll weights and a greater lint percentage. Fiber quality, with the exception of micronaire, showed little improvement due to plant breeding. Micronaire tended to increase in the newer cultivars. The data indicate that breeding efforts have altered the number of harvestable bolls to a greater extent than any other characteristic.
Winter Wheat Production on the North Central Canadian Prairies: Potential Quality Classes1
Authors: Fowler D. B. , de la Roche I. A.
Published: July 2010

Southwestern Alberta has been the traditional winter wheat (Triticum aestivum L.) production area in western Canada. In recent years, direct seeding of winter wheat into standing stubble has resulted in an extension of this production area to include most of the western Canadian prairies. This study was undertaken to assess the potential quality of winter wheat grown in one section of the expanded production area, namely, the north‐central part of the agricultural area of Saskatchewan. Three grain quality measurements—kernel hardness, mixograph peak time, and protein concentration—were utilized to evaluate the quality of nine winter wheat cultivars grown in 15 trials and of five winter and four spring wheat cultivars grown in six trials. The cultivars represented a wide range of winter and spring wheat quality classes. Cultivar differences and the cultivar by environment interactions were significant for all three measurements of quality. Environmental effects were also significant for all quality measurements except mixograph peak time. However, for kernel hardness and mixograph peak time, the variability due to those sources was usually small when compared to that due to cultivars, Variability due to sources other than cultivars was much greater for protein concentration and yield. Higher grain yield of winter wheat, together with apparent environmental limitations to protein production plus possible genetic differences, resulted in lower protein percentages for hard red winter as compared to hard red spring wheat cultivars. On the basis of these observations, no genetic or environmental restrictions are apparent for the production of winter wheat cultivars suitable for all except the highest protein, common wheat quality classes.
Relative Stalk Sugar Yields among Maize Populations, Cultivars, and Hybrids1
Authors: Widstrom N. W. , Bagby M. O. , Palmer D. M. , Black L. T. , Carr M. E.
Published: July 2010

Recent emphasis on alternate energy sources has prompted research on several crops as carbohydrate sources for conversion to fuel energy. We have been assessing maize (Zea mays L.) stalks as a potential sugar source for conversion to alcohol fuel. Two methods of determining sugar yields and their relationships with plant height and maturity were also evaluated. Fifteen openpollinated maize cultivars or populations and 19 hybrids were evaluated for fermentable stalk sugar yields in replicated randomized complete block experiments in 1980 and 1981. The range of average sugar yields for the populations and cultivars was 23 to 55 g plant−1 when determinations were made on the basis of percent soluble solids by water content and 24 to 64 g plant−1 when determinations were based on high performance liquid chromatography analysis for fermentable sugars in the stalks. Comparable ranges for the hybrids were 25 to 50 g plant−1 and 17 to 52 g plant−1 by the respective methods. Hybrid means determined by the two methods were significantly correlated, while the methods for population and cultivar means were not significantly correlated because of the greater genetic heterogeneity within cultivars and populations compared to hybrids. Hybrid and cultivar or population 1980 means were highly correlated with those of 1981. The average sugar yields of cultivars and populations on a per plant basis were comparable to the hybrids, and large differences within both groups suggested that selection progress for improved yield is a reasonable expectation. The better performing entries of each group would be expected to produce sugar yields in excess of 3.5 Mg ha−1 at populations of 60 000 to 70 000 plants ha−1.
Variation in Phenotype and Chromosome Number in Alfalfa Protoclones Regenerated from Nonmutagenized Calli1
Authors: Johnson Lowell B. , Stuteville D. L. , Schlarbaum S. E. , Skinner D. Z.
Published: July 2010

Two populations of alfalfa (Medicago sativa L.) regenerated from nonmutagenized mesophyll protoplasts were compared to their parent clones (RS‐K1 and RS‐K2) for changes in phenotype and in chromosome complement. Thirty and 45% of RS‐K1 and RS‐K2 protoclones, respectively, had 32 chromosomes (2n = 4x = 32). Chromosomal changes observed included increased ploidy, aneuploidy, and translocations. Some protoclones were more susceptible to winter damage than were their parents, and various other phenotypic changes were observed. Dry weight forage yields for four harvests were obtained from ramets in replicated field plots the year after transplanting. Protoclones significantly superior, equal, and inferior (P = 0.05) to their respective parents were obtained, with the latter two classes greatly predominating. Between the third and fourth cuttings, a crown rot killed 60% of the protoclones. Fusarium solani and/or F. roseum and Rhizoctonia solani were isolated from these plants. One RS‐K2 protoclone appeared to exhibit resistance under this naturally‐occurring epidemic.
In Vitro and in Vivo Analyses of Hays of Switchgrass Strains Selected for High and Low in Vitro Dry Matter Digestibility1
Authors: Vogel K. P. , Britton R. , Gorz H. J. , Haskins F. A.
Published: July 2010

In a previous report the progress made in altering the in vitro dry matter digestibility (IVDMD) of switchgrass (Panicum virgatum L.) in one cycle of divergent selection was described. In this study, the detergent system of analyses was used in an attempt to determine what plant constituents had been altered by the selection for IVDMD. Hays from five switchgrass strains differing in IVDMD harvested over a 3‐year period were analyzed for protein content, neutral detergent fiber (NDF), acid detergent fiber (ADF), ash, and lignin. Although there were differences (p ≤ 0.05) among strains for IVDMD as determined by two different procedures (with and without additional N), there were no differences among strains for ADF, ash, lignin, and protein. The strains ranked the same with the two IVDMD procedures but the IVDMD‐N (with additional N) test averaged 6.7 percentage points higher in digestibility. There were small differences (p ≤ 0.1) among strains for NDF in 2 of the 3 years. The strain with the highest IVDMD had the lowest NDF, suggesting that, in part, the improved IVDMD was due to a decrease in the cell wall component of the harvested forage. Hays of three of these strains, high‐IVDMD PC, low‐IVDMD PC, and ‘Pathfinder’ from the 1980 harvest were ground and fed to sheep to compare in vivo and in vitro digestibilities. After grinding, the hays had IVDMD‐N values of 49.9,45.5, and 46.7%, respectively. There were no differences among strains in the sheep feeding trial for in vivo digestibility, dry matter intake, and fiber digestibility. The in vivo digestibilities for these strains were: high‐ IVDMD PC 50.4%, low‐IVDMD PC 49.0%, and Pathfinder 50.8%. In contrast to a previous report in the literature, the IVDMD‐N values were generally similar to in vivo digestibilities for switchgrass hays. Parameters of the conventional detergent system of analyses, while useful in identifying factors responsible for changes in digestibility of switchgrass hays, would probably be of little value as selection criteria in a breeding program. Because of the large number of animals required to obtain statistical significance in in vivo digestibility studies, the IVDMD procedure would be preferable in studies in which breeding material is being evaluated and small differences in digestibility are expected.
Developmental Changes in Acyl‐Composition of Soybean Seed Selected for High Oleic Acid Concentration1
Authors: Carver Brett F. , Wilson Richard F. , Burton Joseph W.
Published: July 2010

Recurrent selection methodology has been utilized in the development of a soybean [Glycine max (L.) Merr.] genotype, designated as N78‐2245, that contains a high concentration of oleic acid (18:1) and lower concentrations of linoleic (18:2) and linolenic (18:3) acids compared to seed from typical soybean cultivars. The nature of fatty acid metabolism and deposition during the ontogeny of soybean seed with the high‐18:l trait has not been shown previously. The objective of this study was to determine how expression of the high‐18:l trait affected lipid composition during seed development. To achieve that objective fatty acid synthesis and composition were evaluated in seed of N78‐2245 and ‘Dare’, a typical soybean cultivar, at 15‐day intervals during reproductive growth. In N78‐2245 seed the greatest amount of 18:1 accumulateduring the period from 30 to 45 days after flowering. The amount of 18:1 deposited in that period was three‐times greater than that deposited in Dare. In the intervals after 45 days after flowering, 18:1 deposition declined in N78‐2245 seed with a concommitant increase in 18:2 and 18:3. The abrupt shift in net accumulation of 18:1 and 18:2 plus 18:3 during N78‐2245 seed ontogeny was attributed to developmental rather than environmental causes. These data have shown that late developmental increases in 18:2 and 18:3 deposition significantly affected the total unsaturated fatty acid composition of mature N78‐2245 seed.
Comparisons of Effects of Intrapopulation vs. Interpopulation Selection in Maize1
Authors: Moll R. H. , Hanson W. D.
Published: July 2010

The responses of two populations of maize(Zea maysL.), ‘Jarvis’ and ‘Indian Chief’, after 10 cycles of full‐sib family( F) selection and 10 cycles of reciprocal recurrent (R) selection are reported. Average F selection responses per cycle were 3.5 and 1.4% for the two population and 2.0% for the population cross. Average R selection responses per cycle were 2.4 and ‐0.3% for the two populations and 2.7% for the population cross. A change in response to selection following the 8th selection cycle was observed for both selection procedures. the nature of genetic changes within populations following selection wase valuated using a divergence measure obtained from diallel information. Total divergence was resolved into additive‐associated and dominance‐associated gene effects. A two‐fold greater divergence was obtained within Jarvis than within Indian Chief. for F selection, divergence resulted from a dditive‐associated effects for the first 8 cycles whereas for R selection, divergence resulted from additive‐associated effects in Jarvis and dominance‐associated effects primarily in Indian Chief. Ear number increased consistently with increased grain yield during 8 cycles of selection. With continued selection, ear number changed in some, but not all, populations and dominance played an increasingly more important role in both selection programs. Cumulative inbreeding depression and increased complexity of the genetic effects under selection were explanations for observed changes in response to continued selection. Maximum divergence occurred with R selection; however, the highest yielding cross was Jarvis (R) C10 X Indian Chief (F) C10.
Cuticle and Cell Wall Thickness: Relation to Mechanical Strength of Whole Leaves and Isolated Cells from Some Forage Legumes1
Authors: Lees G. L.
Published: July 2010

Leaflets from seven legumes were examined by electron microscopy to determine the thickness of the cuticle, outer tangential epidermal cell wall, and mesophyll cell wall. Sainfoin (Onobrychis viciifolia Scop.), cicer milkvetch (Astragalus cicer L.), and birdsfoot trefoil (Lotus corniculatus L.) have a high resistance to leaf and cell rupture while alfalfa (Medicago sativa L.), arrowleaf clover (Trifolium vesiculosum Savi), red clover (T. pratense), and white clover (T. repens L.) are more susceptible. The cuticle and the epidermal cell wall and the mesophyll cell wall were thicker in sainfoin, cicer milkvetch, and birdsfoot trefoil. Correlation coefficients show a strong relationship between a thick cuticle, epidermal, or mesophyll cell wall and a greater resistance to certain types of mechanical damage in whole leaflets or isolated cells. Among the species, cuticle thickness measurements provided a larger coefficient of variation than thickness measurements for epidermal cell wall plus cuticle or cell wall alone. Those legumes which had thicker cuticles and cell walls are considered bloat‐safe. Epidermal cell wall and cuticle and mesophyll cell wall thickness are probably leaf morphological characters which contribute to the non‐bloating nature of some forage legumes.
Selection for Linoleic Acid Concentration Among Progeny of a High ✕ Low Linoleic Acid Oat Cross1
Authors: Karow R. S. , Forsberg R. A.
Published: July 2010

The objective of this investigation was to study the effect of early generation selection on linoleic acid concentration in oats (Avena sativa L.) using F6 families from a cross of oat lines with high and with low levels of linoleic acid. The F6 families were derived by single‐seed descent from nine F2 plants representing the range of linoleic acid concentrations measured in a 64‐plant F2 population from a ‘Sauk’ ✕ ‘Dal’ cross. In the F6, each selected F2 was represented by six lines. Differences among families and among lines within families were highly significant. The F2 linoleic acid concentrations accounted for 94% of the variation observed for linoleic acid among F6 families. The Castle‐Wright prediction of gene number for linoleic acid concentration was 1.5. These data indicate that in this cross, linoleic acid concentration was simply inherited with some genotypes fixed in the F2 generation. While oleic acid concentration was not used as a selection criterion, the strong negative relationship between linoleic and oleic acids made it possible to predict oleic concentration means of F6 families from F2 values. Single gene, multiple allele control of oleic‐linoleic acid concentrations has been found in safflower (Carthamus tinctorius L.) and in maize (Zea mays L.) and such a system may also exist in oat.
Clonal Interactions with Harvests and Years for Quality Components in Intermediate Wheatgrass1
Authors: Rice J. S. , Brown R. B.
Published: July 2010

Genotypic response to environments is important in forage breeding programs. Twenty intermediate wheatgrass [Agropyron intermedium (Host) Beauv.] clone:; were evaluated for content of nitrogen (N), acid detergent filler (ADF), neutral detergent fiber (NDF), hemicellulose, K, Mg, Ca, P, and S for four harvest periods in each of 2 years. Analyses of variance revealed significant differences among clones and among harvests and years for all traits. Clone ✕ harvest interactions were significant for N, ADF, and Ca. Clone ✕ year interactions were significant for all traits except K and S. Clone ✕ year ✕ harvest interactions were significant for N, ADF, and S. Harvest (linear) ✕ clone interactions were detected for N in both years, ADF in 1982, and Ca in 1981. Harvest (quadratic) ✕ clone interactions were detected for ADF in 1982 and Ca in 1981. These results help describe the nature of the clone ✕ harvest ✕ year interactions. The bulk of interactions involving genotypes was due to differences in variability within years and to linear responses to harvests.Examination of linear contrast effects of harvests for each clone revealed that the interactions could be explained on the basis of differences in degree of response of clones to harvests. Significant effects of clone on linear effects suggested that clones could be selected for minimum deterioration in quality over the spring growth period. Interactions of clones with harvests and years could complicate selection for these traits but the effect is not overwhelming. These interactions appear less severe for NDF, hemicellulose, K, and P. Examination of the harvest (linear) ✕ clone interactions provided a more complete understanding of the nature of the interactions.
Inheritance of Cell‐Division Rate in Roots of Sugarbeet1
Authors: Doney Devon L. , Theurer J. Clair
Published: July 2010

Differentiation in sugarbeet (Beta vulgaris L.) roots is completed in the first 4 to 5 weeks of growth. From then on, growth is by simultaneous cell division and cell expansion. Selection for root yield may exert selection pressure on either cell‐division rate or cell expansion or both. The degree of selection pressure applied to either of these two cellular parameters depends on their respective inheritance behavior and the breeding and selection methods used. This study was initiated to determine the inheritance of cell‐division rate (cell number). Cell‐division rate was based on the number of cells across the radius of a cross section of 20‐ to 28‐day‐old plants. Heterosis was determined in progeny of six males crossed to line L29, two‐by‐five females ✕ males crosses and a five‐parent diallel. Genotypic variance estimates were made in a three‐by‐three female ✕ males cross and the five‐parent diallel. Cell number showed significant heterosis in all but two hybrids tested. Both general and specific combining ability effects were significant for cell number, with specific combining ability showing the greatest significance. Estimates of nonadditive genetic variance accounted for between 75 and 95% of the total genetic variance. It is concluded that cell‐division rate (cell number) is conditioned largely by nonadditive type genes and that beet root heterosis is due primarily to increases in cell number rather than cell size. Breeding and selection methods that capitalize on nonadditive genetic variation will, therefore, increase sugarbeet root yield by increasing cell‐division rate.
Morphological Characteristics and Genetics of Two Mutations for Early Maturity in Pearl White1
Authors: Hanna W. W. , Burton G. W.
Published: July 2010

Mutations for early maturity can help cultivars escape adverse environmental conditions and fit into double cropping systems. The purpose of this research was to compare and describe the morphological characteristics and genetics of two mutations for early maturity which occurred in ‘Tift 23’ pearl millet, Pennisetum americanum (L.) Leeke, treated with either ethyl methane sulfonate or thermal neutrons. Each of the two mutations is controlled by a single recessive locus. The new mutations are assigned the gene symbols e1 and e2. Plants with the e1e1 genotype or the e1e2 genotype flowered in 49 and 38 days, respectively, after planting on 12 June compared to 76 days for Tift 23, the normal maturing counterpart. Both mutants had significantly (P<0.01) shorter plant height, shorter heads, and thinner stems than Tift 23. Significant differences between Tift 23 and the e1 and e2 mutants were also observed for flag leaf length, peduncle length, internode lengths, and internode number. Data showed that Tift 23 with the e1 genes till has the good combining ability of Tift 23. The e1 gene was associated with no detectable undesirable characteristics and could be readily used to develop new early maturing cultivars. Linkage tests showed the e1 locus to be independent of the d2 (dwarf) locus.
Inoculation of Seedling Cuttings for Screening the Soybean Against Races of Phytophthora megasperma f. sp. glycinea1
Authors: Nguyen Mung V. , Rode Marvin W. , Payne Donald W.
Published: July 2010

Young soybean [Glycine max (L.) Merr.] seedlings grown sand were cut at the base of their hypocotyls, and mycelia of Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Ervin (Pmg) were smeared onto the cut surfaces. The cuttings were then transferred to water. The cuttings were classified as “resistant” if they continued to grow and had produced roots on the hypocotyls 7 days after inoculation; they were classified as “susceptible” if the hypocotyls decayed and collapsed with no root initiation. Similar results were obtained with cuttings vs. hypocotyl in oculations when soybean cultivars differing in their reactions to races 1 and 5 were tested. The method described herein is compared to several other currently used techniques, and their respective advantages and disadvantages are discussed. In general, inoculating soybean seedling cuttings for Phytophthora screening is efficient, reliable, and inexpensive. Compared to other methods, it is simple and requires very little equipment and working space in the laboratory, but requires more inoculum.
Rate and Duration of Spikelet Initiation in 10 Winter Wheat Cultivars1
Authors: Peterman C. J. , Sears R. G. , Kanemasu E. T.
Published: July 2010

Number of splkelets per spike and florets per spikelet are determined early in the life cycle of winter wheat (Triticum aestivum L.). Rate and duration of spikelet formation developmentally precedes and thus directly influences spikelets per spike and fertile florets/spikelet. To study differences among cultivars for rate and duration of spikelet initiation, 10 cultivars varying in phenotype were planted at two dates with four replications each. Plants were sampled and dissected two or three times weekly in the spring to determine the stage of development of the spike. Duration of spikelet initiation was defined as the number of days from double ridge formation to terminal spikelet formation. At harvest, total spikelets per spike were counted. Rate of spikelet initiation was computed as total spikelet number divided by duration of spikelet initiation. Comparisons of interest included differences among benchmark cultivars, between semidwarf and standard height wheats, and between semidwarf pure lines and hybrids. Differences among cultivars for duration of spikelet initiation were significant. Values ranged from 15.3 days for the hybrid ‘DKI04A’ to 21.5 days for ‘Turkey’. Rate of spikelet initiation was also significantly different among cultivars and ranged from 1.4 spikelets/day in DK104A to 0.82 spikelets/day in Turkey. With yield improvements, benchmark cultivars have progressed towards a shorter duration and a faster rate of spikelet initiation. Semidwarf wheats had a longer duration than the standard height wheats but maintained a high rate. Hybrids had a short duration and a fast rate of spikelet initiation. These results suggest the possibility of improving wheat spike types and yield through manipulation of the spikelet initiation stage.
Variability for Yield and Yield Components in IAP1R Grain Sorghum Random‐Mating Population. I. Means, Variance Components, and Heritabilities1
Authors: Lothrop J. E. , Atkins R. E. , Smith O. S.
Published: July 2010

Genetic variability of the random‐mating sorghum [Sorghum bicolor (L.) Moench] population IAP1R was evaluated in seven environments. Three cycles of gridded mass selection for grain yield of individual plants had been completed in the population. One‐hundred‐twenty half‐sib and 120 S1 families chosen randomly from the C3 were included in Exp. I at Ames (central Iowa), and another sample of 120 S1 families was grown in Exp. II at Ames and Castana (western Iowa). Estimates of inbreeding depression at 100% homozygosity were −13.6% for grain yield, −6.3% for seeds/panicle, and −4.9% for 100‐seed weight; indicating that heterotic effects were relatively important in the expression of yield, of moderate impact on seed numbers, and small for seed size. Genotype‐environment variances for yield were low for half‐sib and S1 families in the Ames 1978 through 1980 environments (Exp. I), and progeny mean estimates of broad‐sense heritability were high (0.84, 0.85). Heritabilities these environments also were moderate to high for the components of yield; 0.76, 0.79 for seeds per panicle, 0.74, 0.82 for 100‐seed weight, and 0.63, 0.66 for panicles per plant. S1 families at Ames and Castana 1981‐1982 (Exp. II) displayed large genotype‐ environment variance for yield, and its heritability was 0.74. Heritabilities in Exp. II were 0.80 for seeds per panicle, 0.78 for 100‐seed weight, and 0.77 for panicles per plant. Individual plant estimates of heritability in the two experiments were low for grain yield (0.13, 0.06) and seeds per panicle (0.20, 0.23). Heritability estimates of 0.41 and 0.43 for 100‐seed weight, however, suggested that improvements in seed size should be possible by using gridded mass selection.
Water Use Efficiency of Cassava. III. Influence of Air Humidity and Water Stress on Gas Exchange of Field Grown Cassava1
Authors: Cock James H. , Porto Mario C. M. , El‐Sharkawy Mabrouk A.
Published: July 2010

Field measurements of gas exchange were made to study the response of field grown cassava (Manihot esculenta Crantz) to changes in air humidity under well‐watered and unirrigated conditions. ‘M Col 1684’ was used as testing material at Palmira and Santander de Quilichao, CIAT, Colombia, South America. The infrared gas exchange technique was modified to allow for field sampling of leaf CO2 exchange rates using the syringe injection method at locations far from the laboratory. There was a remarkable decrease in the leaf photosynthetic rate with decreasing air humidity in both well‐watered and unirrigated plants. Leaf photosynthetic rate was significantly correlated with VPD and leaf conductance but was not correlated with leaf water potential at midday and early afternoon. The midday leaf water potential of the plants without irrigation was slightly higher than that of the well‐watered plants. Photosynthetic rate of the plants without irrigation was always lower than the well‐watered ones. Transpiration initially increased with increased leaf to air vapor pressure difference (VPD) and then sharply declined with further increases in VPD. Leaf water use efficiency (WUE) decreased in curvilinear pattern with VPD. The results agree with previous reports on laboratory controlled experiments. Dry root yield and total biomass production of cassava was increased by increasing the relative humidity in the crop canopy by artificial misting. There was 91,15, and 27% increase in dry root, top and total dry matter, respectively, after 40 days of misting as compared with the control. These differences in biomass production were neither associated with changes in soil water nor with changes in leaf area indices but rather with enhanced photosynthetic rate per unit leaf area of the misted plants. The leaf photosynthetic rate of cassava decreased with leaf age with a maximum rate of 26 /ümol CO2 m‐2 s‐1 for young leaves as compared with 13 ümol CO2 m‐2s‐1 for old leaves lower in the canopy. Photosynthetic saturation irradiance was around 1500 and 800 ümol m‐2s‐1 for young and old leaves, respectively. The modified syringe injection method proved reliable and suitable for handling a large number of field samples in a short time. Photosynthetic rates of several C3 and C4 crop species were similar to reported values obtained with the conventional infrared gas exchange technique.
Morphological Development and Water Use in Clonal Lines of Four Forage Grasses1
Authors: Frank A. B. , Berdahl J. D. , Barker R. E.
Published: July 2010

A need exists for information on the morphogenesis and water use by forage species to use as a basis to improve management and grazing practices, varietal improvement, and for development of plant growth simulation models. Our objectives were to evaluate morphological development and water use in clonal lines of crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schult.], western wheatgrass [Pascopyrum smithii (Rhdb.) Löve Syn: A. smithii Rydb.], intermediate wheatgrass [Elytrigia intermedia (Host) Nevsk: Syn: A. intermedium (Host) Beauv.], and reed canarygrass (Pharlaris arundinacea L.). We also defined the relationship between morphological development, water use, and air temperature expressed as growing‐degree days (GDD) with a base temperature of O°C. The study was conducted during 1981 and 1982 in the field on a Parshall sandy loam soil (coarse‐loamy, mixed Pachic Haploboroll) with two clones of each of two cultivars per species. Number of leaves developed in the spring and GDD per phyllochron varied among species and among clones within a species. Reproductive (spike forming) tillers of clonal lines of crested wheatgrass and western wheatgrass developed six leaves with 557 and 778 GDD, respectively; intermediate wheatgrass, seven leaves with 780 GDD; reed canarygrass, eight leaves with 706 GDD. Number of GDD required to develop a single leaf was 84 for reed canarygrass, 104 for crested wheatgrass, 125 for intermediate wheatgrass, and 147 for western wheatgrass. Western wheatgrass extracted soil water from a deeper soil depth and to a lower content than the other species. Dry matter yields were highest in intermediate wheat‐grass and lowest in western wheatgrass. Water‐use‐efficiency (WUE) was highest in crested wheatgrass and lowest in western wheatgrass. There were no difference in total water used among clones within any species. Among the three wheatgrasses, earlier morphological development corresponded to higher WUE. Differences were observed for yield and WUE among crested and western wheatgrass clones.
Transpiration Rate and Water Use Effeciency of Soybean Leaves Adapted to Different CO2 Environments1
Authors: Valle Raul , Mishoe J. W. , Jones J. W. , Allen L. H.
Published: July 2010

Gas exchange rates were measured during podfill on leaflets of soybean [Glycine max (L.) Merr. ‘Bragg’] plants grown in 330 (ambient) and 660 (high) μmol CO2−1 environments in outdoor growth chambers and rooted in a reconstituted profile of Arredondo fine sand (loamy, siliceous, hyperthermic Grossarenic Plaleudult). Carbon exchange rates (CER), transpiration rates (TR), leaf resistance (rL) and leaf temperature (TL) measured to investigate their diurnal changes. These parameters were also measured during midday periods at various CO2 concentrations (90‐990 μmol CO2 mol−1) to study the effects of adaptation to ambient and high CO2, environments on the subsequent response to CO2 levels. The primary objective was to determine CO2 effects on leaf water use and water‐use efficiency, an important question as global CO2 continues to rise. Diurnal TR of leaflets grown and measured at high CO2 levels was not different from TR of leaflets grown and measured at ambient CO2. Leaf temperature was approximately 1.5°C higher for the leaflets at the high CO2 concentration; also, rL was higher throughout the day on these leaflets than rL of those at ambient CO2 levels. Water use efficiency (WUE = CER/TRf) or leaflets at high CO2 was about twice the WUE of leaflets grown and measured at ambient CO2. Transpiration rates of leaflets adapted to ambient or high CO2 concentrations were not significantly affected by short‐term CO2 changes. However, regardless of CO2 level of adaptation, TL and rL increased as CO2 increased. It was concluded that: (i) TR of the high CO2 leaflets was similar that of ambient CO2 leaflets because the increases in rL caused by high CO2 were partially offset by increases in vapor pressure gradient between leaf‐to‐air caused by increased TL; (ii) Leaves adapted to high CO2 had higher WUE than leaves adapted to ambient CO2, mainly because of a two‐fold increase in CER.
Inheritance of Resistance to Two Races of Leaf Rust in Dry Edible Bean1
Authors: Grafton K. F. , Weiser G. C. , Littlefield L. J. , Stavely J. R.
Published: July 2010

A study was conducted to determine the inheritance of resistance to races 44 and 52 of leaf rust (causal organism Uromyces appendiculatus (Pers. ex Pers.) linger var. appendiculatus) in the dry edible bean (Phaseolus vulgaris L.) cultivars ‘T‐39,’ ‘Aurora,’ and ‘Olathe.’ T‐39 and Aurora each express hypersensitive resistance to race 52 but are susceptible to race 44. Olathe is hypersensitive resistant to race 44 and susceptible to race 52. Crosses were made between these cultivars and with ‘UI‐114,’ a pinto bean cultivar susceptible to both races. Resistance of Ft progeny and segregation ratios within F2 populations and among F3 progeny from individual F2 plants of crosses with UI‐114 indicated that resistance to each race was controlled by a single, dominant gene. Segregation ratios of the F2 population and F5 progeny from individual Fj plants of the cross Olathe ✕ T‐39, inoculated with race 44 only, indicated that complementary dominant genes controlled resistance to race 44. Segregation ratios of genes for resistance to races 44 and 52 in progenies of Olathe ✕ Aurora indicated independent assortment without epistasis. The following tentative genotypes for rust reaction of the cultivars studied are proposed: Olathe ‐ UraUraUrcUrcthe cultivars studied are proposed: Olathe ‐ UraUraUrcUrcthe cultivars studied are proposed: Olathe ‐ UraUraUrcUrcurburb; T‐39 ‐ urauraurcurcUrbUrb; Aurora ‐ urauraUrcUrcUrbUrb; UI‐114 ‐ urauraUrcUrcurburb.
Genetic Variability Within U.S. Maize Germplasm. I. Historically Important Lines1
Authors: Smith J. S. C. , Goodman M. M. , Stuber C. W.
Published: July 2010

Isozyme data for 21 loci from 72 historically important U.S. Corn Belt and southern lines of maize (Zea mays L.) were analyzed by principal component analysis. The objectives were to compare relationships with those to be expected from known pedigrees and to discuss the information revealed by isozyme data with regard to the utilization of elite germplasm. Considerable genetic diversity was found, especially among ‘Reid Yellow Dent’ and ‘Iowa’ Stiff Stalk Synthetic' lines. Several isozyme differences were apparent between Corn Belt and southern lines. Isozyme data tended to group lines of similar background together although tight clustering of related lines was not found. Iowa Stiff Stalk Synthetic lines showed little or no relationship to ‘Lancaster Sure Crop’, ‘Minnesota 13’, or ‘Midland’ lines, but they did appear to be a blend of Reid Yellow Dent and non‐Reid Yellow Dent germplasm. The germplasm base of U.S. maize appeared broader than would have been expected solely on the basis of the numbers of races involved in its origins. The most successful sources of elite germplasm each encompassed a broad range of genetic diversity.
Variability Among Alfalfa Clones in Seed Production. I. Effective Population Size1
Authors: Rowe D. E.
Published: July 2010

The plant‐to‐plant variation in gamete production of alfalfa (Medicago sativa L.) plants was shown to increase the levels of inbreeding and probability of significant random change in gene frequencies of six alfalfa populations grown for seed at Reno, NV. The inbreeding effective population sizes [Ne(i)] and variance effective population sizes [Ne(v)] were estimated by assuming that gamete production was proportional to number of racemes on a plant. The Ne(i) averaged 45% of N, the population size, and the Ne(v) were 59 to 144% of N. Both effective population sizes were far below ideal values which occurs only with equal gametic contributions by each plant to the next generation. Three of the populations were in their 2nd year of seed production while the others were in their 1st year of production. Those transplants in 2nd year of production were much more productive than those in their 1st year but also had a proportionally greater plant‐to‐plant variation in gamete production. The result was nearly constant effective population sizes over years of production. The effect of limiting the number of seeds collected from each plant effectively reduced between plant variation in female gamete production but had no effect on variation in male gamete production. The increases in effective population sizes were 17 to 35% for Ne(i) and 47 to 75% for Ne(v). The maximum increases of effective population sizes occurred with seed collection limits at 60 to 80% of the mean plant seed yields for a population. The common practice of collecting the same small amount of seed from each plant appeared to be an unsatisfactory procedure for controlling inbreeding or random change in gene frequency.
Structure of the Keel‐Locking Mechanism in Insect‐Pollinated and Self‐Pollinated Alfalfa Species1
Authors: Kreitner G. L. , Sorensen E. L.
Published: July 2010

Keel petals of the papilionaceous legume Medicago were studied by scanning and transmission electron microscopy to further elucidate the flower‐tripping mechanism. The structures responsible for closure of keel petals in untripped flowers were compared for insect‐pollinated, perennial alfalfa (M. sativa L.), and self‐pollinated, annual M. scutellata (L.) Mill. In both species, the surfaces where the keel petals are locked together are characterized by parallel ridges and grooves. In the closed condition, the ridges on one petal are sunken into the grooves of the opposing petal. The large cell‐wall ridges of M. sativa intermesh in a tongue and groove arrangement and in microscopic sections resemble interlocked jigsaw puzzle pieces. Keel petal ridges of M. scutellata are small parallel folds of the epidermal cuticle, so that strength of attachment between keel petals is weak. The tongue and groove closu?e of the M. sativa keel is consistent with the view that moisture tension facilitates tripping of alfalfa flowers by pollinators. We speculate that intermeshed cell‐wall ridges partially collapse with a loss of turgidity and are more easily disengaged by pollinator activity.
Transfer of Powdery Mildew Resistance from Helianthus debilis Nutt. to Cultivated Sunflower1
Authors: Jan C. C. , Chandler J. M.
Published: July 2010

Powdery mildew (Erysiphe cichoracearum) of sunflower is a disease which can have a serious economic impact when the crop is grown in warmer regions. An accession of H. debilis ssp. debilis Nutt. (2n=34) found to be highly resistant to sunflower powdery mildew at Davis, CA was used in a program to transfer resistance to the cultivated sunflower, Helianthus annuus L. (2n=34). Plants of the wild accession were pollinated by the susceptible H. annuus cv. Peredovik and line P21. The F1 plants were backcrossed once with P21 and the BC1F1 plants were selfpollinated, sib‐pollinated, or further backcrossed with P21. Disease evaluations on all tested plants were conducted in a greenhouse under cool temperature and high humidity using previously infected, susceptible plants as the source of inoculum. Infection was measured as the percent of leaf surface covered by mildew. The mean infection percentages of P21, the F1 and H. debilis were 100, 15, and 0, respectively. Resistance was incompletely dominant in the F1 and backcross progenies. This source of disease resistance may enable the production of resistant hybrid cultivars suitable for warmer regions.