bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrogen Assimilation in an Improved Alfalfa Population1
Authors: Phillips Donald A. , Cunningham Scott D. , Bedmar Eulogio J. , Sweeney T. Colleen , Teuber Larry R.
Published: July 2010

Alfalfa (Medicago sativa L.), which is capable of fixing N2 in symbiosis with Rhizobium meliloti, normally is grown in soils with varying amounts of available N. We have demonstrated previously that population selected from ‘African’ and ‘Hairy Peruvian’ for increased dry matter and N assimilation under both N2‐ and NH4NO3‐dependent conditions outperformed the original parental materials when grown with the extremes of N nutrition, i.e., totally dependent on N2 or completely sustained by mineral N. The objective of this study was to compare i) growth and N assimilation of the original Hairy Peruvian (HP) and the improved Hairy Peruvian 32 (HP32) with various strains of R. meliloti and no nitrate and ii) one strain of R. meliloti and different levels of nitrate. Tests showed that, although only one strain of Rhizobium had been present during selection, HP32 grown in the absence of combined N increased N2 fixation in three other strains of R. meliloti by 22 to 53% relative to the same strains in HP. When HP and HP32 were tested with 0, 1, 2, or 8 mM nitrate in symbiosis with the Rhizobium strain used during the selection process, HP32 assimilated an average of 32% more total N than HP under all N regimes. Estimates of N2 fixation using the 15N‐dilution method under those conditions showed that HP32 fixed an average of 38% more N2 than HP under all nitrate treatments. The inhibition of N2 fixation by nitrate, however, was proportionately similar in HP and HP32. The fact that HP32 increased N2 fixation by all strains of R. meliloti tested suggests that HP32 has some general physiological trait which might be used to improve the symbiotic performance of the mediocre indigenous Rhizobium strains that nodulate alfalfa in many soils.
Inheritance of Three Chlorophyll‐Deficient Mutants of Common Wheat1
Authors: Williams N. D. , Joppa L. R. , Duysen M. E. , Freeman T. P.
Published: July 2010

Simply inherited chlorophyll‐deficient mutants are useful in genetic and cytogenetic experiments as markers for specific chromosomes or chromosome sites and in studies of photosynthesis. Three chlorophyll‐deficient mutant lines, CD2, CDS, and CD4, were obtained in the hexaploid wheat (Triticum aestivum L.) line ND496‐25 by treating seed with ethyl methanesulfonate. Inheritance of mutant phenotype was studied in the F2 and F3 of crosses of the mutant lines with ND496‐25. Allelism and linkage were studied in the F1, F2, and F3 of a diallel cross of the three mutant lines. Each of the mutant phenotypes appeared to be conditioned by a single recessive nuclear gene. Mutant genes of the three lines appeared to segregate independently. The CDS chlorina mutant was well expressed and easily classified from seedling emergence through maturity. The mottling phenotype of the CD2 and CD4 mutants could be classified only after heading. The CD4 mutant was poorly expressed in the greenhouse. The CDS mutant should be an excellent genetic marker and useful for studying photosynthesis. The CD2 and CD4 mutants should have limited usefulness as genetic markers.
Comparisons Among Effective Filling Period, Reproductive Period Duration,and R5 to R7 in Determinate Soybeans1
Authors: Salado‐Navarro Luis R. , Sinclair Thomas R. , Hinson Kuell
Published: July 2010

Visual estimates of seed filling duration are important tools in soybean [Glycine max (L.) Merr.] research. Yet little information exists on the correspondence between visual estimates of seed filling duration and direct measurements of seed mass accumulation. The objectives of our study were a) to compare visual estimates of seed filling duration with those obtained from seed growth data to determine if they could be used interchangeably and b) to determine their comparative stability across environments, to assess which estimates of seed filling duration would be a better selection criterion.Five field experiments were conducted in 2 years at Gainesville, FL. Crop growth analyses were performed on 88 random F7 lines from two crosses and their parents in 1982, and on 20 selected lines combined from both crosses in 1983. Genotypes used had determinate growth habit and were in Maturity Groups VII and VIII. The period R5 to R7 was determined additionally on 56 random genotypes in 1983. Effective filling period (EFP) was determined as the time required to achieve final mature plant seed mass using the calculated linear seed growth rate. Reproductive period duration (RPD), defined as the period of linear harvest index (HI) crease, was estimated disregarding fallen leaves.The beginning of EFP and RPD occurred simultaneously while stage R5 occurred 9 to 17 days earlier. The period R5 to R7 was 8 to 13 days longer than EFP, and 1 to 7 days longer than RPD. Associations among EFP, RPD, and R5 to R7 were always positive, but not consistently significant. Therefore, EFP, RPD, and R5 to R7 estimated different periods in the reproductive ontogeny of determinate soybeans. The usefulness of EFP, RPD, and R5 to R7 as selection criteria appears to be limited by the existence of highly significant genotype by environment interactions that were primarily due to changes in the ranking of genotypes across environments. Low broad sense heritability estimates for R5 to R7 were observed.
Soybean Genotypes with Resistance to Races of Soybean Cyst Nematode1
Authors: Anand S. C. , Wrather J. A. , Shumway C. R.
Published: July 2010

Resistance to soybean cyst nematode (SCN) Heterodera glycines Ichinohe has been derived from only a few soybean (Glycine max L., Merr.) lines resulting in a narrow genetic base for SCN resistance in the commercial cultivars. Screening of the soybean germplasm has resulted in the detection of additional sources of resistance. Ten soybean plant introductions (PI lines) were evaluated for reaction to races 3, 4, and 5 of SCN. The screening was done in the greenhouse by inoculating with 1000 eggs of SCN and counting the white females (cysts) on the roots after 30 days. Of the 10 lines, seven were resistant to race 3, two were resistant to race 4, and four were resistant to race 5. One line, PI 437654 was resistant to all three races. This PI line is a possible source of resistance to races 3, 4, and 5 of SCN, and may be genetically different from other sources of resistance previously reported.
Screening Trifolium spp. for Response to Meloidogyne spp.1
Authors: Quesenberry K. H. , Baltensperger D. D. , Dunn R. A.
Published: July 2010

Lack of a rapid, reliable screening procedure has hampered the identification and development of clover (Trifolium spp.) germplasm with tolerance to Meloidogyne spp. The objectives of this research were: (i) to evaluate a previously developed Meloidogyne screening technique for use on Trifolium spp., (ii) to evaluate the effects of growth container sizes and nematode inoculum rates on gall scores, and (iii) to compare the relative levels of susceptibility of several Trifolium spp. to Meloidogyne spp. In Exp. 1, one line each of crimson (Trifolium incarnatum L.), red (T. pratense L.), white (T. repens L.), and arrowleaf (T. vesiculosum Savi.) clover was grown in either 50 or 150 cm3 Conetainers®, infested with either 0, 1, 3, or 9 eggs cm−3 soil of one of three Meloidogyne spp. and scored for severity of galling 10 weeks after infestation. In Exp. 2 and 3, germplasm lines of white and crimson clover, T. mutabile Portenschl., and 'Fresa' strawberry clover (T. fragiferum L.) were evaluated for response to infestation with 9 or 10 Meloidogyne spp. eggs cm−3 soil when grown in 150 cm31 Cone‐tainers. The 150 cm3 Cone‐tainers provided a less dense plant spacing and were easier to maintain at uniform soil moisture among cones than the 50 cm3. Gall scores were usually lower on plants grown in 50 cm3 Cone‐tainers than in the 150 cm3 size, thus only the 150 cm3 size was used in later experiments. In the 150 cm3 Cone‐tainers, the 9 eggs cm −3 soil infestation rate gave higher (P < 0.001) gall scores than the lower rates for all legumes except arrowleaf clover. Overall tolerance to Meloidogyne spp. was crimson, > red = white > arrowleaf clover. Only one white clover clone, which traces to SCI germplasm, had a high level of tolerance to M. incognita (Kofoid and White, 1919) Chitwood, 1949. Fresa strawberry clover and one introduction of T. mutabile were highly susceptible to the three Meloidogyne spp. Variation in gall scores among 31 lines of crimson clover was significant and lines were identified with lower gall scores than ‘Dixie’.
A New Semidwarf Mutant in a Long‐Grain Rice Cultivar1
Authors: McKenzie K. S. , Rutger J. N.
Published: July 2010

The inheritance of an induced short stature mutant, Short Labelle, recovered from the rice (Oryza sativa L.) cultivar Labelle was investigated. In crosses with Labelle and ‘Lebonnet’, the F1 plants were tall, and the short stature characteristic segregated as a single recessive factor in the F2 generation. Progeny tests in a cross with ED7 indicated Short Labelle carried semidwarfing gene nonallelic to the sd1> gene in ED7. F1 sterility and F2 segregation for sterility was observed in the Labelle and Lebonnet crosses. Pleiotropic effects on grain and mesocotyl lengths were noted. In 2 yrs of multiple location testing the agronomic characteristics of Short Labelle were similar to Labelle, although Short Labelle yields were generally lower. However, because it has a semidwarfing gene nonallelic to the sd1 source, Short Labelle may be a useful germplasm source for rice improvement.
Performance of Cottons when Infested with Tobacco Budworm1
Authors: Jenkins Johnie N. , Parrott W. L. , McCarty J. C. , Dearing Lee
Published: July 2010

Thirteen germplasm lines of cotton, Gossypium hirsutum L., including seven cultivars were grown for 3 years with and without tobacco budworm, Heliothis virescens F. There is a paucity of information available on the performance of cotton germplasm when grown under tobacco budworm infestation. Development of insecticide resistance in this insect or a loss of effective insecticides from the market would pose substantial problems for the cotton industry. Objectives of this study were i) to determine the performance of 13 diverse germplasm lines when grown under controlled, uniform levels of tobacco budworm infestation, ii) to identify germplasm useful to breedersf or use in developing cultivars resistant to tobacco budworm, iii) to identify germplasm lines with different levels of resistance useful for studies on how or why cotton germplasm resist tobacco budworm and iv) to develop information useful for improving breeding practices in cotton. Plots were grown on a Leeper silty clay loam, fine montmorilloritic, non‐acid, thermic, chromondertic, Haplaquept, 0 to 2%s lope. Infested plots were inoculated with first instar tobacco budwormla rvae five to six times at weekly intervals beginning about the second week of squaring as determinedi n ‘Stoneville 213’. Worm‐free plots were sprayed weekly with fenvalerate [cyano(3‐phenoxyphenyl)methy4‐chloroalpha‐(l‐methylethyl)benzeneacetate]. Resistance was measured as the ability to resist yield loss when continually infested with tobacco budworm larvae for 5 to 6 weeks. Resistance was identified in ‘Stoneville 506’ and confirmed in PEE DEE 875, PEE DEE 8619 and ‘Tamcot CAMD‐E’. Because two are cultivars and are presently being grown, information on them can immediately be put to use. Each of the four germplasms should be useful to breeders as parental lines to increase resistance to tobacco budworm. Regression analyses on one year's data suggest that about 65% of the resistance is associated with early, rapid fruiting. However, additional unidentified factors are also involved.
Sugar Accumulation in Shrunken‐2 Sweet Corn Kernels1
Authors: Michaels T. E. , Andrew R. H.
Published: July 2010

Sweet corn (Zea mays L.) quality is judged in part by the sugar concentration of its kernels at fresh harvest. Genotypes promoting high kernel sugar throughout the fresh harvest period may improve sweet corn quality and consumer acceptance. This study was undertaken to determine the influence of environment, harvest date, and inbred parent on kernel sugars of shrunken‐2 (SuSu sh2sh2) sweet corn hybrids. Ten hybrids from a diallel cross of five shrunken‐2 sweet corn inbreds were assayed for reducing sugar, sucrose, and total sugar as proportion of kernel dry weight. Kernels were sampled at three fresh harvest dates in 3 yrs. Warmer seasons resulted in lower reducing sugar and higher sucrose at Harvests 1 and 2 (200 and 245 thermal units after pollination, base 10 °C), while cooler seasons were associated with higher reducing sugar and lower sucrose. At Harvest 3 (290 thermal units after pollination), reducing sugar was near 45 g kg−1, and sucrose was near 325 g kg−1 in all years. Compensation by these two carbohydrates at Harvests 1 and 2 led to uniformity in total sugar among years. Total sugar was near 430 g kg−1 at Harvest 1, 415 g kg−1 at Harvest 2, and decreased to near 370 g kg−1 at Harvest 3. Hybrid differences were detected for sucrose and total sugar, but not for reducing sugar. The predominance of specific combining ability (SCA) and SCA ✕ harvest effects on sucrose indicate that the concentration and pattern of sucrose accumulation in each hybrid depended upon the combination of inbreds involved in the cross. In addition to SCA and SCA ✕ harvest effects, total sugar was also influenced by general combining ability (GCA) effects; hybrids sharing a common inbred had similar levels of total sugar accumulation. Kernel sugar was high in these shrunken‐2 sweet corn hybrids relative to standard sugary (susu Sh2Sh2) sweet corn hybrids. Sugar concentration at any one harvest was not as useful for selection among these hybrids as stability of sugar concentration throughout the fresh harvest period. Two hybrids were found not to change significantly in total sugar during the harvest period. One inbred generally promoted stability in kernel sugar across harvests in its crosses.
Photosynthetic Rate Control in Sorghum: Stomatal and Nonstomatal Factors1
Authors: Krieg D. R. , Hutmacher R. B.
Published: July 2010

The purpose of this series of experiments was to determine the cause of photosynthetic rate responses to environmental effectors in one grain sorghumh ybrid [Sorghum bicolor (L.) Moench cv. ATX623 ✕ TX430]. Field experiments were conducted over a 4‐year period (1980–1983) at two locations using a range irrigation levels, to provide different degrees of plant waters tress. One site had a fine loamy sand soil (fine loamy, mixed, thermic family of Aridic Paleustaifs) with the second site having a clay loam (fine mixed, thermic family of Torrertic Paleustolls). Gas exchange rates of individual leaves were monitored on both a diurnal and seasonal basis. The results indicated that the primary cause of the photosynthetic rate changes due to leaf age, water stress, and photon flux density effects was related to mesophyll problems rather than due to stomatal conductance limitations. Increasing leaf age and environmental stress affected the photosynthetic processes by reducing the CO2 saturated rate (Amax) and the assimilation rate at all intercellular CO2 concentrations evaluated. The assimilation rate per unit photon flux density was also reduced in water‐stressed plants. Stomatal conductance responded to photosynthetic rate changes to maintain a relatively constant intercellular CO2 concentration at ambient CO2 levels. The primary control of photosynthetic carbon fixation in sorghum appears to be related to chloroplast activity rather than to CO2 supply due to stomatal conductance.
Defoliation Responses of Determinate and Indeterminate Late‐Planted Soybeans1
Authors: Goli Ankon , Weaver D. B.
Published: July 2010

Late‐planting (later than 15 June) in double‐cropping systems is a common practice among soybean [Glycine max L. (Merr.)] growers in the southeastern USA. Many experiments have been conducted to evaluate the effects of insect or hail‐simulated defoliation on yield and agronomic characteristics of full‐season soybeans, but information on defoliation response of late‐planted soybeans is lacking. Field experiments were conducted to determine effects of complete defoliation of late‐planted soybeans at stages of development R4, R5, and R6. Yield and yield components of determinate cultivars ‘Braxton’ and ‘Foster’ were compared to those of indeterminate ‘Duocrop’. Defoliated plants generally matured earlier, lodged less, and had smaller seeds and fewer pods per plant than undefoliated controls. Defoliation had no effect on plant height except in Duocrop, which was shorter when defoliated at the R4 stage. Average yield losses for the determinate cultivars were 72, 81, and 40% and 67, 87, and 44% for the indeterminate cultivar following defoliation at the R4, R5, and R6 stages, respectively. Yield loss was primarily attributed to a reduction in number of pods per plant. Indeterminate Duocrop had no advantage over determinate Braxton and Foster for defoliation recovery when planted late.
Germination of Grass Seeds After 8 Years of Weekly Removal from Subfreezing Storage1
Authors: Rincker Clarence M.
Published: July 2010

The use of subfreezing storage temperatures has increased in recent years for many kinds of seeds. However, the literature contains no information on the effect on seed viability when grass seeds are frequently removed from subfreezing storage for sampling purposes. Seeds of six grass cultivars produced at Prosser, WA, in 1976 were divided into five sublots for a long‐term storage study. The study included two cultivars each of orchardgrass (Dactylis glomerata L.) and red fescue (Festuca ruba L.) and one each of chewings fescue (Festuca ruba var. commutata Gaud.) and Kentucky bluegrass (Poo pratensis L.) The storage conditions were (A) cotton bags in an unheated warehouse, (B) vacuum‐sealed cans stored in an unheated warehouse, (C) continuous frozen storage (D) frozen storage but thawed one day each month, (E) frozen storage but thawed 1 day each week. Seed moisture content before storage was 8% ± 0.4%. Germination tests were conducted prior to storage and once each year thereafter. A freezer set at −10°C and near 60% relative humidity was used for the subfreezing storage. The original and 8th year germination results of sublots from storage treatment (E) were ‘Latar’ orchardgrass, 90 and 84%; ‘Pennlate’ orchardgrass, 91 and 87%; ‘Dawson’ red fescue, 83 and 83%; ‘Erika’ red fescue,87 and 86%; ‘Barfalla’ chewings fescue, 80 and 76%; and ‘Baron’ bluegrass, 93 and 88%, respectively. Germination losses for sublots from storage treatment (A) ranged from 19 to 53%. Results indicate germination percentages of grasses can be maintained at, or near original levels for at least 8 years when seed is either continuously frozen or frozen and thawed weekly for 24 h and returned to subfreezing storage but declines significantly when stored in an unheated warehouse.
Cotton Resistance to the Root Knot‐Fusarium Wilt Complex. I. Relation to Fusarium Wilt Resistance and its Implications on Breeding for Resistance1
Authors: Shepherd Raymond L. , Kappelman Albert J.
Published: July 2010

Fusarium wilt disease (FW) caused by Fusarium oxysporum Schlect f. vasinfectum [(Atk.)Synd. & Hans.] and root‐knot nematodes (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] cause a major disease complex affecting cotton (Gossypium hirsutum L.). The purpose of this study was to determine the efficacy of using resistance to FW in the vascular system of plants grown in a greenhouse as a criterion for selecting cotton plants that are resistant to FW in the RKN‐FW complex as it occurs in the field. Eighteen cotton cultivars and breeding lines were inoculated in a greenhouse by injecting spores of the FW fungus directly into stems. Incidence of FW ranged from 29 to 82%. The FW percentages of the 18 cotton cultivars and lines in a field infested with both the fungus and RKN ranged from 3 to 99%. Results indicated that stem vascular resistance to FW was probably independent of any mechanism of resistance that might have prevented fungal invasion of the vascular system and that differences in vascular resistance were probably genetically controlled. Vascular resistance observed in the greenhouse failed to discriminate between differences in FW resistance among several cottons when grown in the field. This and other evidence presented indicated that a low probability of success would be expected for developing cotton cultivars with high field resistance to FW in the RKN‐FW complex by either selecting for vascular resistance expressed in plants grown in a greenhouse or through field selection by present techniques. Field selection for many decades had resulted in development of moderately resistant cultivars but had not been successful in developing highly FW‐resistant cultivars. Further progress by the field selection method may be possible in the future, if genes for higher resistance, such as in breeding line Auburn 623 RNR, are used and more precise screening techniques can be developed.
Selection with Partial Selfing. II. Family Selection1
Authors: Wright A. J. , Cockerham C. Clark
Published: July 2010

The expected immediate and permanent responses to various types of family or individual selection on the basis of progeny tests were formulated for a population whose members have a common fixed probability of self‐fertilization(s). These results were derived using covariances of relatives and their component quadratic genetic functions for a model with arbitrary additive and dominance effects. The families considered were outcrossed full‐ and half‐sibs(F and H), progenies from self‐pollination (S), and those from natural pollination (M), and pair matings without exclusion of natural selfing (C). Methods for the prediction of both immediate and permanent selection responses are given. Numerical analysis of various models with two alleles at each of a number of loci showed the proportion of the immediately observable response that is permanent gain retained by the distant descendants of the selections to be greater for progeny testing than for family selection. Both were greater than that for mass selections studied earlier(Wright and Cockerham 1985). The range of heritability values in which family selection gives greater permanent gains than mass selection following reproduction is greatest whens is low. However, the comparison of progeny testing to mass selection prior to reproduction is less dependent on s. The S families were the preferred type for all models and s values, and the values of M and C familiese exceeded that of their counterparts under strict outcrossing (H and F), particularly for high s values and when environmental variation was large.
Dinitrogen Fixation of Rice‐Klebsiella Associations1
Authors: Yoo I. D. , Fujii T. , Sano Y. , Komagata K. , Yoneyama T. , Iyama S. , Hirota Y.
Published: July 2010

We report N2 fixation by Klebsiella oxytoca strain NG13, isolated from the rhizosphere of a rice (Oryza sativa L.) plant, in association with Indica type rice strain, C5444. The C2H2‐reducation assays, biomass measurements, N content determinations, and 15N isotopic dilution assays indicated that inoculation of C5444 with NG13 resulted in a 6% increase of total plant+soil N content, and a 19% 15N isotopic dilution of plant N after 120 days of cultivation. Our results demonstrated significant levels of N2 fixation by K. oxytoca when associated with rice. By optimizing such rice plant‐bacterial N2 fixation capacity, the N uptake by rice could be enhance.
Rate of Synthesis of Cell Wall Components in Sorghum Leaf Blades1
Authors: Volanec J. J. , Cherney J. H. , Moore K. J.
Published: July 2010

Cell wall structure is an important characteristic influencing intake and digestibility of forages. Our objective was to examine changes in cell wall composition that occur during leaf development and estimate rates of synthesis of cell wall components in elongating leaf blades of greenhouse‐grown sorghum [Sorghum bicolor (L.) Moench]. The leaf intercalary meristem and segments of the eighth elongating leaf blade, each representing the average daily growth increment of the leaf, were analyzed for neutral detergent fiber (NDF) and lignin, and hemicellulose and cellulose concentrations were calculated. Concentrations of cell wall components on a dry weight basis generally increased acropetally from the leaf intercalary meristem. When expressed on an NDF basis, concentrations of hemicellulose and cellulose decreased and increased, respectively, from the intercalary meristem to the leaf tip. Lignin concentrations on an NDF basis were highest in 1‐day‐old segments and decreased thereafter. Concentrations of arabinose, galactose, and uronic acids were highest in cell walls of leaf intercalary meristems, and decreased acropetally while xylose concentrations in the cell wall increased. Rates of hemicellulose and cellulose synthesis averaged 0.46 and 0.38 mg segment−1 day−1, respectively for 1‐ to 5‐day‐old segments, while lignin synthesis averaged 25 µg segment−1 day−1 in 1‐ to 4‐day‐old segments. The large relative changes in cell wall composition between the intercalary meristem and 2‐day‐old segments of the elongating leaf indicate that the major changes in fiber composition of leaves occurs early during leaf development.
Winter Wheat Grain Yield Responses to Soil Oxygen Diffusion Rates1
Authors: Box James E.
Published: July 2010

Aeration status of a Southern Piedmont Cecil sandy loam soil (Typic hapludult) during the reproductive phase of winter wheat (Triticum aestivum L. cv. Stacy) growth affects grain yields. This study characterized gaseous soil oxygen diffusion rates (ODR) and concentration during the reproductive phase of winter wheat growth in 1983 and 1984. Soil oxygen diffusion rates at 0.10, 0.20, 0.30 and 0.45 m depths; and O2 concentrations at 0.20 and 0.50 m depths were measured in drained and undrained plots planted to wheat. The ODR in 1983 were all less than 33 µg−2S−1, and between Days 115 and 152 of 1984 the 0.10, 0.20, and 0.30 m depths were approximately 50 µg m−2S−1. Soil O2 concentration was not affected by drainage treatment in 1983, and in 1984 was lower at the 0.50 m depth in the drained plots. Air temperatures were predominately higher after Day 100 (flag leaf just visible) in 1983 than 1984. Poor rainfall distribution in May and June 1984 made them dry months. Grain yields averaged 240 and 393 g m−2 in 1983 and 1984, respectively; the 2‐yr averages for drained and undrained plots were 323 and 309 g m−2. Grain yields were significantly different for years but not for drainage treatment. Selecting soft red winter wheat cultivars that adapt to low ODR (wet soils) by development of aerenchyma tissue, which arises by cell separation (schzogenously) or by partial breakdown of the cortex (lysigenously), giving rise to continuous gas‐filled lacunae may be the only practical solution to obtaining consistently high soft red winter wheat yields in waterlogged Southern Piedmont soils.
Evaluation of Polycross Progenies of Cicer Milkvetch for Palatability by Sheep1
Authors: Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.), a nonbloat‐inducing forage legume, has many traits that make it a potentially desirable species. Relatively little information, however, is available on animal acceptance of cicer milkvetch forage. The objective of this study was to determine if the component polycross progenies of ‘Monarch’ differed in palatability as measured by grazing sheep (Ovis aries) offered a choice of progenies. The progenies were evaluated in a spaceplanted, irrigated nursery during three grazing cycles in 1980 and two grazing cycles in 1981. Progenies differed significantly (P ≦ 0.05) for grazing score (palatability) during four of the five cycles. Several progenies ranked consistently high for palatability, while other progenies ranked consistently low. None of the Monarch progenies, however, were significantly more palatable than ‘Lutana’. All sheep remained healthy and suffered no observable side effects during the course of the study. Plant height, vigor, and flowering score were not related to palatability of progenies. The results suggest that it may be possible to improve the palatability of cicer milkvetch by breeding and selection.
Cytogenetics of Pennisetum schweinfurthii Pilger and its Hybrids with Pearl Millet1
Authors: Hanna W. W. , Dujardin M.
Published: July 2010

A better understanding of the cytogenetics of wild species aids in the utilization of exotic germplasm to improve cultivated species. The objectives of this research were to describe the cytogenetics and fertility of Pennisetum schweinfurthii Pilger and the interspecific hybrids between pearl millet [Pennisetum americanum (L.) Leeke] and P. schweinfurthii. Pennisetum schweinfurthii is a sexual diploid (2n = 14 chromosomes) annual species. Pennisetum schweinfurthii is the only other Pennisetum Rich. species, other than pearl millet, reported to have 2n = 14 chromosomes and an annual growth habit. Its chromosomes are similar in size but nonhomologous to those of pearl millet. Chromosomes paired as seven bivalents at meiosis. Selfand open‐pollinated seed set ranged from 40 to 56% and 40 to 91%, respectively, indicating the presence of a partial self‐incompatibility mechanism in this species. Interspecific hybrids between P. schweinfurthii and pearl millet were male sterile, partially female sterile, and morphologically intermediate to both species. Chromosomes of the interspecific hybrids remained mainly as 14 univalents, but five hybrids averaged 0.48 to 1.97 bivalents per microsporocyte.
Sugar and Starch Redistribution in Maize in Response to Shade and Ear Temperature Treatment1
Authors: Setter Tim L. , Flannigan Brian A.
Published: July 2010

Based on previous studies, it has been suggested that sugars stored in the maize (Zea mays L.) stem can be exported to growing kernels, and thus contribute to kernel dry matter. The objective of the current study was to determine to what extent sugar and starch depletion from maize (cv. Cornell 175) stem responds to shade and ear temperature treatments. Stem sugar concentrations in pith and vascular bundle tissues of stem remained at stable levels throughout a diurnal time course and after 3 days of canopy shading. In contrast, free space sugar concentrations were lower at 0600 h than at 1800 h (EST). When ear temperatures were controlled at 6, 16, 25, and 32°C from 18 to 27 days after pollination (DAP), plants had similar glucose, sucrose, and starch cooncentrations in leaf blades and sheaths at all ear temperatures; however, sucrose concentrations in a composite sample of cobs, shanks, and husks (CSHs), and in stems were higher in plants with the 6°C ear temperature than in plants with the 25°C ear temperature treatment. When plants were shaded to exclude 85% of light flux and ear temperatures were controlled during the period from 34 to 44 DAP, sugar and starch concentrations in leaf blades and sheaths were not affected. Glucose, sucrose, and starch concentrations in certain stem fractions were higher in plants with 6°C treatments than in corresponding stem fractions of plants with higher ear temperature. The differences between total sugar content in stems of the 6°C treatment and the contents in stems of the 16, 25, and 32°C treatments were 3.6, 4.1, and 4.1 g/plant, respectively. These differences were not attributed to respiratory loss because, at the end of the treatment period, stem and ear respiration rates among plants with various ear temperatures were not discernibly different. It appears that temperature‐induced increases in kernel sink strength at the middle and late kernel‐fill stages increase the extent of carbohydrate redistribution from vegetative plant parts to kernels.
Effect of Latitude on Genotype ✕ Environment Interactions for Seed Yield in Birdsfoot Trefoil1
Authors: McGraw R. L. , Beuselinck P. R. , Smith R. R.
Published: July 2010

Columbia, MO and Madison, WI are sites of plant breeding projects for the improvement of birdsfoot trefoil (Lotus coruiculatas L.). Northern Minnesota is presently a primary area of commercial seed production. Our objective was to ascertain if seed yield potential as measured at the plant breeding locations would predict actual seed yield in the area of commercial seed production. Forty genotypes were randomly chosen from each of ‘Leo’, ‘Norcen’, and ‘MO‐20’ birdsfoot trefoil cultivars. In 1981, ramets from each genotype were transplanted in similar field layouts using similar cultural practices at Columbia, MO; Arlington, WI; and Roseau, MN. Roseau is located in the major commercial seed production area for birdsfoot trefoil. Plants were individually harvested at each location in 1981 and 1982. Seed yield, vegetative yield, and seed yield components were measured. Simple correlations for seed yield measured in Missouri or Wisconsin vs. seed yield in Minnesota were not statistically significant either year. Multiple regression models composed of all possible combinations of seed yield or seed yield components predicted seed yield in Minnesota poorly. The best model used all traits measured at Wisconsin in 1982 to predict seed yield in Minnesota in 1982 (r=0.65). These data suggest a high genotype ✕ environment interaction among the three locations. Testing for seed production potential of breeding material of birdsfoot trefoil will need to be done in the environment where the seed will be produced commercially.
Early Season Cold Tolerance in Soybean1
Authors: Unander D. W. , Orf J. H. , Lambert J. W.
Published: July 2010

Early planted soybean [Glycine max (L.) Merr.) frequently encounters cold soil conditions. Several reports indicate soybean genotypes differ in rates of germination in the growth chamber at low temperatures and in early field plantings. However, in each experiment only one seed source was used. The objectives of our experiments were: i) to examine the effect of seed source environment on cold germination ratings in the growth chamber and on field performance at early plantings; ii) to compare genotypes from the Midwest and foreign countries for cold germination tolerance; iii) to determine if oil or protein concentration, seed size, or date of harvest were correlated with cold germination data; and iv) to compare growth chamber cold germination measurements with field performance at early plantings. Twenty diverse genotypes were grown at five locations in each of 2 yrs. Seed samples from these plantings were tested for rate of germination at 10°C in the growth chamber in a randomized complete block design. Analysis of germination indexes showed highly significant genotype and genotype ✕ location effects each year. The subset of foreign accessions were more consistent in germination cold tolerance ratings than the subset of North American genotypes. Only oil concentration showed a small significant positive correlation with cold germination. The same 20 genotypes were planted in the field in a randomized complete block as early as possible in 1982 and 1983. Significant genotypic differences were observed both years in field performance. Growth chamber germination ratings and field data means were rarely correlated. Our data suggest that selection against poor emergence or vigor under cold conditions seems more practical in most cases than selection for good emergence or vigor. Several seed sources should be used when evaluating genotypes for early season cold tolerance.
Selection for Spikelet Fertility in a Semidwarf Durum Wheat Population1
Authors: Cantrell R. G. , Haro‐Arias E. S.
Published: July 2010

Genetic variability for spikelet fertility is present in durum wheat (Triticum turgidum L. var. durum). Divergent selection for spikelet fertility was practiced in a semidwarf durum population derived from a single cross of parents that differ for number of kernels/spikelet to determine the effect of indirect selection for this yield component on grain yield. The group selected for high spikelet fertility exhibited significantly higher numbers of kernels/spikelet and kernels/spike than the random group and the groups selected for low fertility. Selection for spikelet fertility did not result in a significant change in grain yield, but test weight and kernel weight were significantly lower in the groups of families selected for high spikelet fertility. This association of yield components was evident in the phenotypic correlations on the random group of F4 and F5 families where kernels/ spikelet and kernels/spike were negatively associated with kernel weight (r = −0.52 to r = −0.86). Variation for tiller number was limited in the random group of F4s in 1983 and the F5s in 1984. Tiller number was negatively correlated with spikelets/spike in both 1983 (r = −0.45) and 1984 (r = −0.59) but was not associated with yield or other yield components. The lack of yield response from early generation selection for spikelet fertility indicates that the full yield potential of increased sink size via this yield component is difficult to obtain in these North Dakota environments. A selection program should therefore involve some type of simultaneous selection for several yield components or yield per se.
Agronomic Comparisons among Wheat Lines Nearly Isogenic for Three Reduced‐Height Genes1
Authors: Allan R. E.
Published: July 2010

The two most commonly used reduced‐height genes of wheat (Triticum aestivum L.) are Rht1, and Rht2. The Rht3, gene is known to be a potent height‐reducing gene. Information is limited as to the comparative effects of these three genes on agronomic traits, especially when placed in a common genetic background. This study made multiple site‐year comparisons in Washington for grain yield, plant height, volume weight, kernel weight, and tiller number among five reduced‐height, near‐isogenic lines and their recurrent parent, ‘Burt’. One line had the Rht3, gene. One line each had the Rht1, and Rht2, genes combined from ‘Norin 10’ and from ‘Suwon 92’. One line each had either the Rht1 or Rht2, gene separately from these two sources. Plant heights of lines with either Rht1, or Rht2, alone, Rht1, and Rht2, combined, and with Rht3, were reduced 24, 52, and 64%, respectively. The Rht3, line had the lowest (P<0.05) across‐test mean yield of 3360 kg ha−1. The two lines with both Rht1, and Rht2, exceeded (P<0.05) the yield of the Rht3, line with means of 3660 and 3840 kg ha−1; these values were less (P<0.05) than the Burt mean yield of 4440 kg ha−1 as well as the yields (4300 and 4900 kg ha−1) of lines with either Rht1 or Rht2. The Suwon 92 derived line with either Rht1 or Rht2, exceeded (P<0.05) the mean yields of other lines and Burt by 10 to 46%. The Rht3 line had significantly lower (P<0.05) mean volume weight, kernel weight, and tiller number than the other lines and Burt. Reductions in these traits of the Rht3 line compared to Burt were 11, 31, and 11% respectively. Lines with one or both Rht1 and Rht2, genes had lower (P<0.05) kernel weights than Burt. All Rht genes reduced volume weight. Although Rht3, is an effective height‐reducing gene, it caused negative effects on yield, volume weight, kernel weight, and tiller number. Single dosages of Rht1, or Rht2, caused neutral or positive effects on yield and tiller number, and warrant use in breeding.
Evaluation of Chlorophyll Fluorescence Parameters for an Intact‐Plant Herbicide Bioassay1
Authors: Shaw D. R. , Peeper T. F. , Nofziger D. L.
Published: July 2010

The correlations between various chlorophyll fluorescence induction curve parameters and metribuzin [4‐Amino‐6‐(1,1‐dimethyl‐ethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4/H)‐one], diuron [3‐(3,4‐Dichlorophenyl)‐1,1‐dimethylurea], and atrazine (2‐chloro‐4‐ethylamino‐6‐ isopropylamino‐S‐triazine) concentrations were compared in laboratory studies. The ratio of the initial inflection point (I) to the initial peak (P) was the most precise indicator of photosynthetic inhibition over time intervals of 4 to 48 h after an oat (Avena sativa L. ‘Chilocco’) plant was transplanted into herbicide‐treated soil. The height of the initial inflection point (I), the peak level (P), and the fluorescence level 30 s after the onset of illumination (T) were also useful at 4 and 8 h after transplanting, but correlated poorly with herbicide concentration at later time intervals. Other variables examined included the slopes from I to P and P to S, the percent decay from P to T, and the complementary area. These parameters did not correlate to herbicide concentration as well, and had a much higher degree of variability associated with them.
Effects of Ethephon and its Decomposition Products on Germination of Rice and Watergrass1
Authors: Southwick K. L. , Lamb N. , Storey R. , Mansfield D. H.
Published: July 2010

This study aimed to determine whether ethephon, 2‐chloroethyl phosphonic acid, differentially influences the germination and seedling development of rice (Oryza sativa L.) and one of its major weeds, watergrass (Echinochloa crus‐galli (L.) Beauv. var. oryzicola). Seeds were germinated at pH 7.0 at 30°C in flasks under N2. Ethephon at 10 000 mg L−1 inhibited germination indices by 91 and 29% in watergrass and rice, respectively. Ethephon at 2000 mg L−1 significantly reduced coleoptile growth in both species. Ethylene at 1 and 100 μL−1 stimulated watergrass germination but did not affect rice germination and enhanced coleoptile growth of both species. Potassium or sodium salts of phosphate and chloride, when administered in a manner simulating the anions' release from ethephon, inhibited germination of watergrass and coleoptile growth of both species. Watergrass germination was inhibited completely with 100 mM mannitol or PEG 8000 (−0.42 MPa) and by 68% with 100 mM potassium phosphate. Rice germination was also inhibited by these osmotica but to a lesser extent than watergrass. Thus, at comparable experimental concentrations, ethephon, phosphate, and chloride inhibited while ethylene promoted or did not influence seed germination or coleoptile growth of both species. We conclude that in both species, the inhibition of germination and coleoptile growth by ethephon is attributed to the effects of ethephon decomposition products other than ethylene. This effect should be considered in studies using high ethephon concentrations or when using tissues highly sensitive to osmotic stress.
Roots of Sorghum Exude Hydrophobic Droplets Containing Biologically Active Components1
Authors: Netzly David H. , Butler Larry G.
Published: July 2010

Roots of Sorghum are known to exude materials that exhibit allelochemical activity, but the compounds identified do not completely account for the observed species‐specific allelochemical activities. The purpose of this investigation was to characterize both water‐soluble and water‐insoluble exudates from roots of sorghum [Sorghum bicolor (L.) Moench] seedlings grown in petri dishes. Hydrophilic exudates included phenols, protein, and 3‐deoxyanthocyanidin derivatives. Hydrophobic droplets, exuded from root hairs, tested positively for phenols and lipids. These hydrophobic exudates strongly inhibit (85%) root elongation in lettuce (Lactuca sativa cv. Great Lakes) seedlings, but do not affect that of corn (Zea mays L. cv. B73Ht), nor the germination of either of these plants. Associated with these hydrophobic droplets are novel quinones, yet unidentified. The results indicate that these hydrophobic exudate droplets contain components that may have species‐specific biological activities.
Economical, Automated Data Collection, Storage, and Transfer1
Authors: Cook A. F. , Alexander W. L. , King R. G.
Published: July 2010

Though interfacing measuring devices to microcomputers increases efficiency of data collection and reduces numbers of transcription errors, the economics of implementation have been a deterrent to many potential users. Weighing is one of the most frequent measurements employed in evaluating biological entities. A low cost system was developed employing a portable microcomputer interfaced to an electronic balance. Software was written for the microcomputer to facilitate data collection from the balance and independently for field‐note recording. Procedures were developed to upload data from the portable microcomputer to a larger system for processing. Considerable time savings in recording data and in data entry for analysis is realized. Additionally, virtual avoidance of transcription errors and flexibility (i.e., word processing, high‐level language programmable, telecommunication, and terminal emulation) in lab and remote field situations makes this system an asset to researchers. Programs were written to convert data files and merge them with other data or field book files. These programs are available from the senior author upon request.
Inbred Lines as Testers for General Combining Ability in Maize1
Authors: Zambezi B. T. , Horner E. S. , Martin F. G.
Published: July 2010

Inbred testers have been used successfully for the improvement of general combining ability (GCA) in maize (Zea mays L.), but they are not generally accepted as being equal to testers with a broad genetic base for this purpose. The objective of this study was to compare estimates of GCA obtained by use of the two tester types. Ten parents (nine S2 lines and the original population) from one population were crossed in a factorial design with a like set of parents from another population, and the resulting 100 crosses (10 involving each parent) were. tested at two locations. Significant estimates of GCA effects were obtained in both populations for grain yield, ear height, husk rating, and percentage erect plants at harvest. Specific combining ability (SCA) effect estimates were significant, but much smaller than those for GCA. Crossbred performance values for parents (testers) were compared by correlation analyses with predicted values based on GCA estimates for both parents. Correlation coefficients for the 18 inbred parents were similar to those for the two broad‐base populations, which suggests that the former were in general as effective as the latter for ranking parents for GCA. These results provide further evidence that inbred testers can be used successfully for improving GCA as well as SCA in maize.
Effect of Temperature during Seed Maturation on the Oil Composition of Low‐Linolenic Genotypes of Flax1
Authors: Green A. G.
Published: July 2010

The flax (Linum usitatissimum L.) cultivar Glenelg, two low‐linolenic genotypes derived from it by induced mutation (M1589, M1722), and a very low‐linolenic genotype (“Zero”), obtained by recombination of the M1589 and M1722 mutations, were grown under six post‐flowering temperature regimes ranging from 15/10°C (day/night) to 30/25°C. The effect of temperature on seed weight, oil concentration, and fatty acid composition was studied. High temperatures resulted in significantly decreased seed weight in all four genotypes, and decreased oil concentration in Glenelg and Zero. Oil concentration in M1589 and M1722 was below that in Glenelg and Zero at all temperatures and was less sensitive to temperature. In all four genotypes, increased temperature had pronounced effects on the relative proportions of the unsaturated fatty acids; linoleic and linolenic acids were considerably decreased and there was an equivalent increase in oleic acid percentage. The percentages of the saturated fatty acids, palmitic and stearic, increased slightly but significantly with increased temperatures. The alteration in fatty acid composition was due to the marked sensitivity of the oleic acid desaturation step to increased temperature, the subsequent desaturation of linoleic acid being highly temperature stable. In the 15/10°C and 18/13°C treatments, the percentage of linoleic acid in the Zero genotype was > 62% of the total fatty acids, a level that is suitable for manufacturing polyunsaturated margarines and oils.