bluuebunny/crossref_metadata_2025 huggingface dataset:
Sampling Error for Leaf Water Potential Measurements in Wheat1
Authors: Johnson R. C. , Nguyen H. T. , McNew R. W. , Ferris D. M.
Published: July 2010

Leaf cutter psychrometers are a rapid method of obtaining samples for leaf water potential measurements. There is, however, concern that the relatively small cut disc (0.24 cm2) may lead to evaporative losses associated with a high cut surface area to sample volume ratio, and thus result in measurement errors. Experiments in growth chambers with wheat (Triticum aestivum L.) plants at different stress levels showed that leaf water potential values obtained with lamina averaging 7 cm2 (with a very low cut surface to volume ratio) compared quite closely with those from 0.24 cm2 cut discs. The relatively good agreement between techniques may be related to the rapid sealing of the disc in the psychrometer chamber, usually within 3 s after cutting. Using leaf cutter psychrometers, flag leaf water potential was measured, and sampling and experimental statistical errors determined on wheat under control vs. stress conditions. This was done to estimate sample and replication numbers needed to attain a given level of statistical precision in water potential measurements. Stress was induced in greenhouse plants by withholding water from pots, and in the field by severing roots by approximately 5 cm below the soil surface. The experiments were randomized in complete blocks with four replications and 10 water potential samples per replication. With water potential means ranging from −0.82 to −5.23 MPa, sampling error was generally large compared with experimental error. Total error (experimental + sampling) was significantly larger (P<0.05) for stress than for control treatments. This heterogeneity of error associated with water potential measurements was only partly stabilized by a natural log transformation. Using the mean total error from stress treatments only, a combination of replications and/or samples per replication of about 12 per treatment was required to obtain a 95% confidence interval on a treatment mean of ± 0.50 MPa.
Genetic Variability of Mineral Concentrations in Tall Fescue Grown under Controlled Conditions1
Authors: Reeder L. R. , Nguyen H. T. , Sleper D. A. , Brown J. R.
Published: July 2010

Altering mineral concentrations of herbage by breeding has been suggested as a means of reducing the grass tetany potential of coolseason forage grasses. Objectives of this research were to: i) determine the genetic variation, heritability, and interrelationships of yield, Mg, Ca, and K concentrations, and the K/(Ca+Mg) ratio in tall fescue (Festuca arundinacea Schreb.) herbage grown under two controlled temperature regimes and two soil Mg levels in growth chambers, and ii) to determine if any genotype ✕ environment interactions existed under these conditions. Fifteen parental plants of tall fescue were randomly chosen from a genetically broad‐based population for use in a polycross mating design. Half‐sib families were evaluated for herbage yield, herbage concentrations of Mg, Ca, and K, and the K/(Ca+Mg) ratio for two harvests. Additive genetic variance was significant for all traits. Most genotype ✕ environment interactions were significant, which indicated that plants should be evaluated under different temperatures and levels of soil Mg. Narrow‐sense heritability estimates, on a family mean basis, were 77, 75, 79, 89, and 77% for yield, Mg, Ca, and K concentrations, and K/(Ca+Mg) ratio, respectively. Predicted gains from one cycle of phenotypic family selection were 12, 13, 14, 19, and 16% of the base population mean for yield, Mg, Ca, and K concentration, and the K/(Ca+Mg) ratio, respectively. Correlations between Mg and the K/(Ca+Mg) ratio showed that selection for a high Mg concentration would also reduce the ratio, which would be desirable in producing improved populations with reduced grass tetany potential.
Correlated Changes in Agronomic Traits from S1‐line Recurrent Selection for Cold Tolerance in Two Maize Populations1
Authors: Hoard K. G. , Crosbie T. M.
Published: July 2010

Cold tolerance is an aggregate trait important to dependable stand establishment in many environments. Selection for improved cold tolerant maize (Zea mays L.) germplasm, however, must not deter improvement of traits that are important later in the growing season. Correlated changes in agronomic traits due to five cycles of S1‐line recurrent selection for cold tolerance were evaluated in two maize populations. Correlated changes in means were expressed in terms of changes in allelic frequency due to pleiotropy or linkage and drift. Selection was associated with correlated genetic changes (2Δpα) grain yield [0.22 Mg ha‐1 cycle‐1 when averaged over both BS13(SCT) and BSSS2(SCT)], grain moisture (‐0.3% cycle‐1), early stand count (0.7 plants plot‐1 cycle‐1), and final stand (387.4 plants ha‐1 cycle‐1). Root lodging resistance was increased 2.5% cycle‐1 in BS13(SCT) and decreased 2.0% cycle‐1 in BSSS2(SCT). Stalk lodging resistance decreased 0.40% cycle‐1 in BS13(SCT). The increased frequencies of pleiotropic or linked genes controlling grain yield and grain moisture were expressed at both early and normal planting dates. The correlated genetic changes in early stand count, final stand, and root and stalk lodging resistance were influenced by date of planting. Genetic drift (2Δp2d) was significant for grain yield (‐0.23 Mg ha‐1 cycle‐1). Genetic drift overwhelmed the increase in allelic frequency due to selection for grain yield; hence, the populations per se were unchanged. The data suggesthat selection for cold tolerance with larger effective population sizes may result in correlated improvements in yield of the populations per se.
Dry Matter Accumulation and Carbohydrate Concentration Patterns of Field‐Grown and in Vitro Cultured Maize Kernels from the Tip and Middle Ear Positions1
Authors: Hanft J. M. , Jones R. J. , Stumme A. B.
Published: July 2010

Tip and middle position kernels from field‐grown ears and in vitro cultured maize (Zea mays L.) were compared for dry matter accumulation and pedicel and endosperm carbohydrate concentration patterns. The experiment was designed to determine whether the growth of tip kernels is limited by their inherent potential to accumulate dry matter or by the supply of assimilate entering the kernel. Tip kernels from field‐grown ears had the lowest linear dry matter accumulation rate, the shortest duration of kernel growth, and therefore, the lowest maximum mass. The mass of tip kernels cultured in vitro was three times greater than tip kernels from field‐grown ears, which indicated that tip kernels on field‐grown ears fail to attain maximum potential mass. The mass of tip kernels cultured in vitro was lower than the mass of middle kernels cultured in vitro or from field‐grown ears. Tip kernels that developed on field‐grown ears had a much lower pedicel fructose, glucose, and sucrose concentration throughout kernel growth than did tip kernels cultured in vitro and middle kernels of both field grown and in vitro culture. Tip kernels from the field also had a reduced maximum endosperm sucrose concentration as compared to tip and middle kernels cultured in vitro and middle kernels from field‐grown ears. The relative endosperm starch accumulation of field‐grown tip kernels was comparable to that of tip kernels cultured in vitro. Starch synthesis in the endosperm of tip kernels from the field was initiated 4 days later than in tip and middle kernels cultured in vitro and middle kernels from field‐grown ears. The low sugar concentrations in the pedicel and the decreased endosperm sucrose concentration in tip kernels from field‐grown ears indicate that an inadequate assimilate supply reaching these kernels may be limiting their growth more than their inherent potential to accumulate dry matter.
Selection for Tolerance to Low Temperature‐Induced Spikelet Sterility at Anthesis in Rice1
Authors: Khan D. R. , Mackill D. J. , Vergara B. S.
Published: July 2010

Low temperature stress is a major constraint to adoption of modern rice (Oryza sativa L.) cultivars in many temperate and tropical rice growing areas. Spikelet sterility induced at the reproductive stage is the most damaging effect of low temperature. The inheritance of tolerance for low temperature at anthesis was studied in four indica (tropical) rice cultivars. The F1, F2, and F2‐derived F3 families of crosses between cold tolerant and cold susceptible parents were used. Individual plants were grown in small pots in the glasshouse room of the phytotron at the International Rice Research Institute, Los Baños, Philippines. Cold tolerance was measured as percent spikelet fertility of plants subjected to low day/night temperatures (20/20°C or 21/21°C) for 5 days at anthesis in the phytotron. Cold tolerance was usually associated with a higher number of pollen grains shed on the stigma. A continuous, unimodal distribution for the F2 populations suggested polygenic inheritance. The realized heritability based on response to selection ranged from 0.35 to 0.45. The results showed that it should not be difficult to recover cold tolerant progeny in crosses between tolerant and susceptible indica rices. Selection based on spikelet fertility in the F2 generation should give a marked response.
Physiological Changes Associated with Three Cycles of Recurrent Selection for Grain Yield Improvement in Oats1
Authors: Payne T. S. , Stuthman D. D. , McGraw R. L. , Bregitzer P. P.
Published: July 2010

Recurrent selection has been successful in cross‐pollinated crops for some time, but only recently has it been utilized in self‐pollinated crops. The original parents and the third cycle parental selections of a recurrent selection program for grain yield in spring oat (Avena sativa L.) were compared in a field study. Possible yield‐related traits were also measured to assess correlated responses. The latter included a growth analysis of the genotypes to enable a post facto assessment of changes in plant growth in response to selection for grain yield. Grain yield was increased 12% during the three cycles of selection, with increases in kernel number (8%) and kernel weight (3%) being the most noteworthy yield component responses. Heading and maturity were delayed about 2 days, but the grain‐filling period duration remained constant. The rate of grain filling increased 12%, whereas vegetative growth rate during the linear, preanthesis phase did not increase significantly in response to selection for grain yield. The ratio of grain to vegetative growth rates was higher for cycle 3 genotypes, suggesting that a greater proportion of assimilate was distributed to reproductive growth by the advanced cycle selections. Harvest index values did not change. These results suggest that increasing biomass may be necessary to achieve future grain yield increases, and that more attention should be given to grain‐filling rates than to vegetative growth rates.
Genetic Variation for Nitrogen Assimilation and Translocation in Wheat. III. Nitrogen Translocation in Relation to Grain Yield and Protein1
Authors: Cox Michael C. , Qualset Calvin O. , Rains D. William
Published: July 2010

Translocation and assimilation of N during grain filling are involved in determining grain protein content in wheat (Trificum aestivum L.). Considerable controversy on the physiological basis for high grain protein concentration exists. These aspects of N movement within the plant were studied in field experiments with the spring wheat cultivars Anza and Cajeme 71 and 96 F5 lines from the cross of these cultivars. Cajeme 71 had higher grain protein concentration, higher translocation, translocation efficiency, and a higher proportion of N in the grain than Anza, but no relationship between any of these three parameters and grain protein concentnation was found in the F5 lines. The ratio of N harvest index to grain harvest index, which gives a rough estimate of the relative proportioning of N and carbohydrate in the grain, was positively related to grain protein concentration (r=0.39 to 0.45, P < 0.01), emphasizing the need to consider both N and carbohydrate partitioning while studying the genetic basis of high grain protein concentration. A relatively simple genetic basis was postulated for the observed variation. A two‐gene additive model fit the F5 frequency distribution observed in both low and high N experiments. The F5 lines that assimilated more N after anthesis than required for their yield level, identitied by regression of N assimilation after anthesis on grain yield (Le., high positive residuals), and that had high N translocation were found to be high in grain protein concentration. Excess assimilated N, the sum of translocation and these residuals (positive or negative), was closely related to grain protein concentration (r=0.8 to 0.9, P < 0.01). Further, these data for excess N conform closely to theoretical calculations of the additional N requirement for a 1% increase in grain protein concentration.
Seedling Development as a Component of Increased Yield in an Improved Alfalfa Population1
Authors: Kapulnik Yoram , Teuber Larry R. , Phillips Donald A.
Published: July 2010

Hairy Peruvian 32 (HP32), an alfalfa (Medicago saliva L.) population developed from ‘Hairy Peruvian’ (HP) by two cycles of phenotypic recurrent selection for high dry weight and high N concentration under both N2‐ and NH4NO3‐dependent growth conditions, was studied to determine the bases of its superior C and N assimilation characteristics. Analyses during seedling development and two subsequent regrowth cycles in the presence of 0,1, 2, or 8 mM nitrate under glasshouse conditions showed that absolute rates of dry matter and N assimilation were consistently higher in HP32 than in HP. Detailed studies of seedling growth under N2‐dependent conditions demonstrated that more prolific root nodulation at the earliest stages and an increased number of stems per plant were associated with 35% more dry matter and 55% more total N in HP32 than in HP. The number of stems in HP32 continued to be significantly greater than HP during the first and second regrowth periods and may have contributed to the yield advantages measured for HP32 in those harvests. During seedling development there were no significant differences between HP32 and HP in relative growth rate, relative N assimilation rate, or 14CO2 partitioning patterns. These results do not imply that selection for prolific early nodulation and an increase in stem number in HP would result in more forage production, but they do indicate that a more vigorous seedling development is one result of the complex selection protocol used to produce HP32.
Manipulating Panicle Transpiration Resistance to Increase Rice Spikelet Fertility during Flowering Stage Water Stress1
Authors: Garrity D. P. , Vidal E. T. , O'Toole J. C.
Published: July 2010

Rice (Oryza sativa L.) is much more sensitive than other cereal crops to drought stress during the flowering period. Anthesis is reduced when the panicle water potential decreases, resulting in largescale spikelet sterility. Improvement of the crop's capacity to flower successfully during water stress will require the improvement of mechanisms to exploit stored soil water or conserve water by reducing transpiration losses from the panicle. Rice panicles typically have very low resistance to water loss even under severe desiccation. This study explored the effects of increased resistance to panicle transpiration as a tactic to maintain high spikelet fertility when anthesis occurs during a drought period. Cultivar IR36 was grown in each of two environments in a phytotron: 1) a glasshouse room with 85% relative humidity (RH), 29/21°C day/night temperatures, and natural light conditions; and 2) Koitotron cabinets (Tokyo, Japan) with 50% RH, 29/21°C day/night temperatures, and natural light conditions. Three water stress treatments were imposed at flowering in each environment by irrigating at a fraction of potential evapotranspiration. Four treatments were applied for 6 days to emerging panicles: Glassine caps open at both ends (GO), or closed at both ends (GC), aluminum foil caps closed at both ends (AC), or no treatment (C). The panicle treatments reduced panicle transpiration rates from 18 to 78% compared to the control. Spikelet temperatures were increased by 1.0 to 2.5°C by the panicle treatments. In the absence of water stress, spikelet fertility was the same for the C, GO, and GC treatments. Under moderate and severe stress in the glasshouse, GO had slightly but not significantly higher spikelet fertility than C. In the Koitotron, all panicle treatments had lower fertility than C when the flowering plants were drought stressed. The panicle treatments decreased transpiration and increased panicle resistance over a substantial range but did not enhance spikelet fertility in the drought stressed treatments. The results indicate that an attempt to improve flowering‐stage drought resistance by breeding morphological changes that increase panicle resistance may not be fruitful.
Evaluation of Indirect Ploidy Indicators in Dactylis L. subspecies1
Authors: van Santen Edzard , Casler M. D.
Published: July 2010

The importance of maximizing heterozygosity in tetrasomic tetraploids, such as orchardgrass (Dactylis glomerata L. ssp. glomerata Hayek), has been demonstrated. Germplasm transfer from 2x Dactylis ssp. utilizing diploid clones that produce 2n gametes (meiotic mutants), enhances heterozygosity. Because most meiotic mutants produce n as well as 2n gametes, depending on environmental conditions, the ploidy level of progeny from interploidy crosses will not be uniform. Ploidy determinations are therefore necessary. Several indirect ploidy indicators (yield, vigor, leaf blade dimensions, leaf blade area, and stomatal guard cell length) were evaluated for their usefulness in identifying tetraploid hybrid progeny reliably and with minimal effort. Cultivated 4r clones, 2x germplasm, and their selfed and hybrid progeny were utilized in this study. Dry matter and vigor data were obtained during four successive growth periods in the greenhouse. The remaining traits were evaluated once at the beginning of the first growth period (10 Jan. 1984) and a second time immediately before the last harvest (1 May 1984). Dry matter yield was shown to be unsuitable as an indirect ploidy indicator because of a large overlap in clonal mean ranges from different ploidy levels. Stomatal guard cell length can be a reliable ploidy indicator only if tetraploid inbred clones and triploid hybrid clones are not expected among the progeny, as may be the case in 2x–4x crosses. Visual vigor rating was effective but required extensive experimental replication to achieve the necessary precision. Among the leaf blade dimensions, area gave the most dependable separation of tetraploid hybrids. Nongenetic causes were found to contribute less than 20% to the total observed variance for leaf blade area. Because aneuploidy influences fertility in Dactylis, final ploidy determination should always be made cytologically.
Agronomic Features of Two Maize Synthetics Selected for High and Low Stalk‐Crushing Strengh1
Authors: Berzonsky W. A. , Hawk J. A.
Published: July 2010

Maize (Zea mays L.) stalk lodging remains a major production‐limiting problem despite progress in improving standability. Efforts to improve stalk quality may result in the production of maize with undesirable agronomic features. Two Missouri maize stalk‐quality synthetics (MoSQA and MoSQB), were grown at Newark and Georgetown, DE, to determine if any changes in agronomic characteristics were associated with selection for high and low stalkcrushing strength in an environment other than Missouri. Plants from three levels of selection (C6 low = 6th cycle of selection for low crushing strength, C6 high = 6th cycle of selection for high crushing strength, and CIO high = 10th cycle of selection for high crushing strength) and the original population (C0) were evaluated for each synthetic. Plants were grown at 37 064 and 74 129 plants ha−1 at both locations. Both synthetics responded significantly to selection for high crushing strength. Rind puncture pressure values (kg) of MoSQA taken 3 weeks after midsilking were 12.4 (C6 low), 17.0 (C0), 19.1 (C6 high), and 22.2 (C10 high). The corresponding values for MoSQB were 10.5, 15.0, 17.1, and 18.1. A significantly higher percentage of soft and lodged stalks was associated with low crushing strength selections compared with high crushing strength selections. The percentage of soft stalks decreased by 2.8% per cycle for MoSQA and 3.5% per cycle for MoSQB from C0 to C10 high. Stalk lodging was not increased at the high plant density for either synthetic due to the improved stalk quality following selection for high crushing strength. A significant increase in kernel yield for MoSQA with selection for high stalk‐crushing strength was associated with increased plant height. An undesired significant increase in ear height, plant height, and a delay in maturity occurred for MoSQB. The MoSQA kernel yield increased 8.6% from C0 to C10 high with no consistent changes in ear height or maturity. However, a nonsignificant 3.1% kernel yield increase for MoSQB from C0, to C10, high was accompanied by a kernel moisture increase of 44.9%. Plant height, ear height, plant maturity, and yield should be carefully monitored when selecting for improved stalk quality in maize.
Effects of Environment upon Ovule Abortion in Interspecific F1 Hybrids and Single Species Cultivars of Cotton1
Authors: Percy R. G.
Published: July 2010

High ovule abortion rates (mote production) observed in Gossypium hirsutum L. ✕ G. barbadense L. interspecific F1 hybrids (ISH) have generally been attributed to the presence of genetic incompatibilities between the two parent species. Other causes of mote production within G. hirsutum and G. barbadense cottons are adverse environmental factors. This study was conducted to determine to what degree environment contributes to the large mote numbers observed in ISH, to determine if ovule abortion in ISH is more reactive to environment than in single species cultivars, and to determine if parental combinations might influence hybrid sensitivity to mote production. Data were collected from four ISH and their four parent strains under normal and reduced irrigation regimes at two locations in 1983 and under normal and reduced irrigation regimes on three dates at one location in 1984. The soil at the Maricopa, AZ, location used in both years was a Mohall clay loam, a member of the fineloamy, mixed, hyperthermic Typic Haplargids. The Safford, AZ, location used in 1983 possessed a fine loamy, mixed, thermic Typic Torrifluvent soil type. Measurements made included: potential seed number (determined to be the number of seed plus motes per locule), ovule abortion rate (expressed as the percent of the potential seed number per locule which were motes), and locule weight (grams seed cotton per locule). Significant generation and species differences were noted for all traits measured in both years. Significant generation ✕ environment interactions were obtained for ovule abortion rates in 1983 and for ovule abortion rates, potential seed number, and locule weight in 1984. Interspecific F1 populations were more reactive to the environment than their parent lines. There appeared to be a species contribution to the hybrids' environmental responses, but little evidence of a cultivar‐within‐species contribution. Little or no environmental response variation was observed among the ISH populations for the traits measured. An environmental sensitivity for ovule abortion within ISH cottons which appears to be independent of parental contribution was documented.
Selection for in Vitro Dry Matter Disappearance in Switchgrass Regrowth1
Authors: Godshalk E. B. , Burns J. C. , Timothy D. H.
Published: July 2010

The potential for genetic progress from selection for in vitro dry matter disappearance (IVDMD) of switchgrass (Panicum virgahm L.) regrowth forage has not been determined by breeders. Improved regrowth quality is needed to increase average daily gain of ruminants in mid‐ to late‐summer. In this study, 33 half‐sib families of switchgrass were evaluated over 2 yr for initial growth dry weight, IVDMD, and N concentration, and for regrowth IVDMD. The regrowth IVDMD was measured from plant samples taken in July (IVDMDl) and August (IVDMD2). Genetic variance estimates were obtained to predict direct selection responses and correlated responses using the modified ear‐to‐row procedure. Selection indices were also constructed to predict responses to multiple‐trait selection. Expected gains from direct selection for dry weight (1.19 kg plant−1), IVDMDl (666 g kg−1), and IVDMD2 (498 g kg−1) were 0.24 kg plant−1, and 50 and 35 g kg−1, respectively, while maximum gains from correlated responses were 0.02 kg plant−1, and 40 and 36 g kg−1, for the respective traits. An estimated index consisting of initial growth dry weight, IVDMD, N, and regrowth IVDMD2 provided simultaneous expected gains of 0.04 kg plant−1 for dry weight and 42 g kg−1 for IVDMD2. Switchgrass regrowth IVDMD may be improved without greatly altering dry matter yield per plant and should receive greater priority in cultivar development.
Yield and Reproductive Growth of Simulated and Field‐Grown Soybean I. Seed‐Filling Duration1
Authors: Salado‐Navarro Luis R. , Sinclair Thomas R. , Hinson Kuell
Published: July 2010

The existence of close associations between yield and seed‐filling duration in soybean [Glycine max (L.) Merr.] populations may make indirect selection for yield feasible. However, reported positive associations have not been consistently strong. A dual approach was taken to examine the association between yield and seed‐filling duration estimates in soybean. First, 45 simulated soybean genotypes were generated with a simulation model of soybean reproductive growth. The hypothesis that a positive association exists between yield and seed‐filling duration was formulated using the simulated genotypes. Plant traits associated with the dependence of yield on seed‐filling duration were examined. Second, this hypothesis was tested in four field experiments using 88 random and 16 to 18 selected F7 determinate (MG VI1 and VIII) genotypes from two populations and their parents. Data on 11 additional field experiments were also used to compare visual seed‐filling duration estimates, as predictors of yield across environments, with predictions based on yield itself. Simulations predicted linear yield increases (r2 = 0.46**, significant at the 0.01 probability level) with longer effective filling periods (EFP) and reproductive period duration (RPD), (r2 = 0.48**). In field experiments among selected genotypes, usually small portions of the variation in yield were explained by EFP (r2=0.01 to 0.34) and RPD (r2=0.12). Associations of yield with R5 to R7 increased to r2=0.39** and 0.42**. Among random genotypes, associations of yield were either nonsignificant or positive with RPD (r2= 0.05 to 0.16**) and R5 to R7 (r2=0.08 to 0.23**). Simulations indicate that weak positive relationships of yield with seed‐filling duration can be expected due to differential associations of yield with other plant traits. Generally, nonsignificant and inconsistent correlations were observed between yield and seed‐filling duration estimates (EFP, RPD, R5 to R7) across field environments. Yield in any single year was a better predictor of yield than seed‐filling duration. Simulation analyses and field studies showed that while higher yielding soybean usually had longer seed‐filling duration, selection for this trait would not necessarily result in selection for higher yields.
Water Relations of Field‐Grown Soybean under Drought1
Authors: Cortes P. M. , Sinclair T. R.
Published: July 2010

Two strategies for decreasing plant vulnerability to drought are increased access to the stored soil water and increased amount of osmotic adjustment in tissue to preserve turgor. Two indeterminate soybean [Glycine max (L.) Merr.] cultivars that had been identified in preliminary studies as having differing responses to drought were studied to aid in the evaluation of these strategies. Drought stress was imposed on the cultivars during 2 yr at differing ontogenetic stages of growth. Soil water extraction was determined with Bouyoucos gypsum blocks. Stress during vegetative growth was associated with a failure of the drought‐susceptible cultivar to extract water from the deeper soil depths. Components of leaf water potential were determined from pressure‐volume curves obtained with a pressure chamber. These data showed that drought stress resulted in a decrease in leaf osmotic potential of 0.4 to 0.5 MPa in both cultivars. Since, as compared to the more drought‐tolerant cultivar, the total leaf water potential was as much as 0.9 MPa lower in the droughtsusceptible line, comparable osmotic adjustment did not prevent it from experiencing less turgor. Therefore, relatively higher drought tolerance was not associated with greater osmotic adjustment. It appears from the comparison of these two cultivars that maintaining the water supply to the plant tissue was of much greater benefit than tissue osmotic adjustment.
Rate and Extent of Digestion of Cell Wall Components of Brown‐Midrib Sorghum Species1
Authors: Cherney J. H. , Moore K. J. , Volenec J. J. , Axtell J. D.
Published: July 2010

Cell wall composition and structure are important factors influencing utilization of forages in diets of ruminant animals. Our objective was to compare the cell wall composition and rate and extent of digestion of cell walls of normal and brown‐midrib (bmr) genotypes of sorghum [Sorghum bicolor (L.) Moench.) species. Brown‐midrib ‘Greenleaf’ sudangrass [Sorghum bicolor (L.) Moench.], and ‘Redlan’ ✕ ‘Greenleaf’ and Redlan ✕ ‘Piper’ sorghum ✕ sudangrass hybrids were planted in the field in a Zanesville silt loam soil (finesilty, mixed, mesic Typic Fragiudalf) along with corresponding normal genotypes. Stover was harvested and analyzed sequentially for fiber components, total nonstructural carbohydrates, and neutral sugar and phenolic acid composition of cell walls. Samples were incubated in buffered rumen fluid for 0, 6, 9, 14, 21, 48, and 72 h and rate constants were determined for neutral detergent fiber (NDF), cellulose, and hemicellulose digestion. The NDF, cellulose, and lignin concentrations of bmr genotypes were lower than the corresponding normal genotypes. This resulted in 7% higher in vitro dry matter digestibility of bmr tissues over the normal genotype. Rate constants for digestion of NDF, cellulose, and hemicellulose differed, averaging −0.083, −0.088, and −0.079 h−1 for the bmr genotypes, compared to −0.064, −0.068, and −0.066 h−1 for the normal genotypes, respectively. The bmr genotypes had a higher extent of NDF, cellulose, and hemicellulose digestion when compared to the normal genotypes. The lignin concentration in the cell wall of bmr genotypes was initially lower than normal genotypes, but as digestion progressed the lignin concentrations of both genotypes merged at 138 g kg−1 NDF. This indicates that the proportion of lignin in the cell wall may be a limiting factor for extent of cell wall digestion. A portion of the lignin initially present was apparently digested, with extent of lignin digestion at 111 g kg−1 for the bmr genotypes compared to 186 g kg−1 for its normal counterpart. Ferulic acid (FA) concentration on a NDF basis was higher and p‐coumaric acid (PCA) concentration lower in the bmr genotype, indicating considerable differences in linkages may exist between core lignin and structural carbohydrates. The FA/PCA ratio was 0.75 and 0.34 for the bmr and normal genotypes, respectively. This agrees with the suggested positive relationship between cell wall digestion and the FA/PCA ratio.
Relationship between Resistance to Hessian Fly and Powdery Mildew in Soft White Spring Wheat PI 4689601
Authors: Sunderman D. W. , Hatchett J. H.
Published: July 2010

Tests of F2 and F3 progenies from crosses of near‐isogenic spring wheat (Triticum aestivum L.) lines of PI 468960 segregating for reaction to powdery mildew (Erysiphe graminis DC. f. sp. tritici Em. Marchal) and Hessian fly [Mayetiola destructor (Say)] suggested that the Pm3a and H3 genes previously identified as located on chromosomes 1A and 5A, respectively, were linked in repulsion. Crossover values were calculated as 10.5 and 14.3%, by the maximum likelihood and product methods, respectively. Microsporocytes from F1 plants of PI 468960/susceptible showed that a ring of four chromosomes caused the linkage. PI 468960 will be a useful parent in breeding programs where screening for resistance is limited to one pest.
Performance of High ✕ High, High ✕ Low, and Low ✕ Low Crosses of Lines from the BSSS Maize Synthetic1
Authors: Lamkey Kendall R. , Hallauer Arnel R.
Published: July 2010

Twenty‐four high‐ and 24 low‐yielding lines per se selected from 247 random inbred lines of the ‘Iowa Stiff Stalk Synthetic‘ (BSSS) maize (Zea mays L.) population were used to produce 48 high ✕ high (HH), 96 high ✕ low (HL), and 48 low ✕ low (LL) single‐cross hybrids. The objectives of the study were to determine how crosses of lines selected for yield per se perform, and to examine the relationship of per se and hybrid performance. The 192 hybrids were evaluated in two replications at each of six Iowa environments. There were significant differences among HH, HL, and LL hybrid group means for grain yield and they were ranked (HH > HL > LL) as expected under a model assuming partial to complete dominance. The data suggests that on the average overdominance was not important for yield in BSSS. Correlations of inbred line traits with the same traits of the hybrids were larger than correlations of inbred line traits with hybrid yield. The correlations of inbred traits with hybrid yield were too small to be of predictive value. The data suggested that selection among lines per se for yield could be used to separate a population into a group of high and low combining lines based on their per se performance. However, per se performance within groups was not related to either specific or general combining ability. After selection for per se performance the smaller group of selected lines could be crossed to a series of testers to identify lines with the greatest hybrid potential.
Divergent Selection for In Vitro Dry Matter Digestibility in Smooth Bromegrass1
Authors: Ehlke N. J. , Casler M. D. , Drolsom P. N. , Shenk J. S.
Published: July 2010

Improving the nutritive value of smooth bromegrass (Bromus inermis Leyss.) is dependent on successfully selecting for traits that influence digestibility and intake. The objectives of this research were to evaluate the effects of divergent selection for in vitro dry matter digestibility (IVDMD) and to determine correlated responses to selection for cell wall constituents. Divergent selection for IVDMD was practiced in the Wisconsin experimental smooth bromegrass synthetic B8, resulting in two nine‐clone first cycle synthetics, B8HD and B8LD. The B8, B8HD, and B8LD synthetics were seeded in May 1981 at Arlington, WI, in seven randomized complete blocks. In 1982 and 1983, forage samples were harvested at six spring and eight summer growth stages for the prediction of IVDMD, crude protein, and cell wall constituents using near‐infrared reflectance spectrophotometry. In vitro dry matter digestibility decreased in the spring from 878 to 660 g kg−1 and in the summer from 804 to 658 g kg−1. Divergent selection responses were significant for IVDMD for all growth stages from late May through late August. Correlated divergent responses for acid detergent lignin (ADL) were significant for the same growth stages as IVDMD. Correlated selection responses for crude protein and all other cell wall constituents were never significant for more than three growth stages. Population ✕ year interactions tended to be nonsignificant. Selection responses indicated that ADL was the most limiting factor to IVDMD in B8. The nearly season‐long improvement in IVDMD was indicative of nutritive value improvements to smooth bromegrass for hay or pasture.
Comparisons of Agronomic Characteristics in C0 and C4 of IAP3BR(M) Random‐Mating Grain Sorghum Population1
Authors: Kwolek T. F. , Atkins R. E. , Smith O. S.
Published: July 2010

Agronomic performance and genetic variability of the random‐mating sorghum [Sorghum bicolor (L.) Moench] population IAP3BR(M) were evaluated after four cycles of mass selection for large seed (g/100 seed). Sixty S1 families chosen at random from both the initial cycle (C0) and the fourth cycle (C4) of the population were grown in 2 yr in central, southern, and northwestern Iowa. Estimates of genotypic variance (σ2g) among S1 families were not significantly different to C0 and C4 for g/l00 seed, seeds/panicle, and plant height. Estimates differed significantly, and they were larger in C4, for grain yield, panicles/plant, and days to midbloom. Heritability estimates for C0 and C4 for each character most often were of similar magnitude. The highest heritabilities were for g/l00 seed, followed by seeds/panicle, grain yield, and panicles/plant. Mass selection was effective for increasing seed size in IAPJBR. Undesirable changes in the means for grain yield, seeds/panicle, and panicles/plant indicated that mass selection for seed size was not effective in improving the overall merit of this population. Means and components of variance, together with estimates of response to selection and correlated response among characters, indicated that SI family testing for grain yield may serve better than mass selection for 100‐seed weight for overall improvement of the population beyond the fourth cycle.
Greenbug Nonpreference for Bloomless Sorghum1
Authors: Weibel D. E. , Starks K. J.
Published: July 2010

Greenbugs [Schizaphis graminum (Rondani)] attack sorghum plants [Sorghum bicolor (L.) Moench] every year, causing damage and reduced yields. Bloomless sorghum (lack of white, waxy exudate on leaf sheath) is a nonpreferred host to greenbug biotype C. The purpose of this research was to determine the age at which bloomless and sparse‐bloom sorghum plants become nonpreferred hosts to greenbug biotype C. Greenbugs were counted on near‐isogenic pairs of lines over a period of several weeks. Data from 2 yr indicated that bloomless plants 4 weeks old were nonpreferred hosts by the greenbug. It was concluded that bloomless plants 4 weeks of age could protect themselves and reduce the need for chemical control. Sparse‐bloom plants 4 weeks old were less preferred hosts than normal bloom sorghum plants, and probably could not protect themselves as well as bloomless plants.
Alleviation of Imbibitional Chilling Injury by Use of Lanolin1
Authors: Priestley David A. , Leopold A. Carl
Published: July 2010

Imbibitional chilling of seeds is generally associated with rapid entry of water in the cold. A means of alleviating chilling injury would be to retard the entry of water in the cold. Attempts to slow the rate of imbibition of soybean [Glycine max (L.) Merr.], corn (Zea mays L.) and cotton (Gossypium hirsutum L.) seeds through the application of a thin coat of lanolin (20 to 30 g kg−1 seed) provided alleviation of chilling injury in the chilling susceptible soybean and cotton.
Heritability of Resistance to Leaf Spot Diseases in Intermediate Wheatgrass1
Authors: Berdahl J. D. , Krupinsky J. M.
Published: July 2010

Intermediate wheatgrass [Thinopyrum intermedium (Host.) Barkworth & Dewey] is susceptible to leaf spot diseases caused by Cochliobolus sativus Ito & Kurib., Pyrenophora tritici‐repentis (Died.) Drechs., and Leptosphaeria nodorum E. Müller. These diseases, particularly C. sativus, have potential to reduce forage yield and quality. Development of cultivars with genetic resistance to leaf spot diseases is likely the only economically feasible control measure. Forty intermediate wheatgrass parents and their respective half‐sib families were used to estimate narrow‐sense heritabilities of resistance to leaf spot diseases. Parents and progeny were inoculated with C. sativus and rated for percent necrosis, lesion number, and lesion size in a greenhouse environment. Disease reaction resulting from natural infection by leaf spot pathogens, primarily C. sativus, was rated for 4 yr on parents and 2 yr on progeny in the field. In greenhouse evaluations, lesion size had a narrow‐sense heritability estimate of 36%, while heritability estimates for percent necrosis and lesion number did not exceed 10%. Narrow‐sense heritability for disease scores of parents and progeny that had been established in the field for at least 1 yr ranged from 38 to 97%. Heritability ranged from 6 to 15% for disease scores measured on parents in the establishment year and progeny that had been established for more than 1 yr. Greenhouse measurements of disease reaction were not significantly correlated with field measurements. Thus, selection for resistance to leaf spot diseases in intermediate wheatgrass would be effective only with field plots that had been established for at least 1 yr.
Performance and Potential of Intergeneric Wheatgrass Hybrids in the Central Great Plains1
Authors: Vogel K. P. , Jung H. G. , Reece P. E.
Published: July 2010

Three studies were conducted to evaluate intergeneric wheatgrass hybrids for their potential as range and pasture grasses in the Central Great Plains. Quackgrass [Elytriga‐repens (L.) Nevski] ✕ bluebunch wheatgrass [Psueodoroegneria spicata (Pursh) A. Love] F5 hybrid lines (RS lines) developed by D.R. Dewey were grown in a space transplanted nursery at Lincoln, NE, to estimate genetic variability for forage yield and quality as measured by in vitro dry matter digestibility (IVDMD) and protein in the RS population. There was significant variability among the RS lines for all traits (broad‐sense heritability H > 0.5) except for first harvest IVDMD (H = 0.26). The highest yielding RS lines yielded only about half as much forage as ‘Slate’ intermediate wheatgrass [Thinopyron intermedium (Host) Barkworth and D.R. Dewey subsp. intermedium], which was included as a check. Slate intermediate wheatgrass, ‘Ruff’ crested wheatgrass [Agropyron cristatum (L.) Gaertner], ‘Nordan’ crested wheatgrass [A. desertorum (Fisch.) Schultes], RS‐1 and RS‐2 (quackgrass ✕ bluebunch wheatgrass germplasm), and a quackgrass ✕ A. desertorum hybrid designated as RD were then evaluated in sward nurseries in two environments (Mead and Alliance, NE) that differ widely in climate. Intermediate wheatgrass was clearly superior in forage yield and quality as measured by IVDMD in the eastern part (Mead) of the Central Great Plains. In the western part of this area (Alliance) intermediate and the crested wheatgrasses were equal or superior to the RS hybrids in forage yield and intermediate wheatgrass had higher IVDMD. The RD hybrid had lower yields than the other strains at both locations. Yields of the intergeneric wheatgrass hybrids could be improved by breeding to make them more competitive with intermediate and crested wheatgrasses. The same breeding effort could be used to improve these pure species for which substantial genetic variability for both yield and IVDMD has been previously documented and would probably result in greater overall progress. Forages from grasses grown at Mead in swards were analyzed using the detergent system of analyses and there was considerable variation among the grasses in fiber composition and digestibility of the fiber components even though the grasses were very similar in physiological maturity when harvested. The results suggest that there are genetic differences among these wheatgrasses in forage fiber composition and the digestibility of the fiber components.
Selection for Increased Phosphorus in Alfalfa and Effects on Other Characteristics1
Authors: Miller David , Waissman Naomi , Melton Bill , Currier Cliff , McCaslin Bob
Published: July 2010

Phosphorus is an essential element in both plant and animal nutrition. However, in some alkaline soils alfalfa (Medicago sativa L.) does not always respond to P fertilization despite deficient or low P concentrations in the tissues. Objectives of this study were to determine the feasibility of selection for increased P concentration in alfalfa grown in alkaline soils and effects on nontarget forage yield and quality characteristics. Ten diverse unselected alfalfa populations, and first and second cycle selected populations were evaluated for P and Ca concentration, Ca:P ratio, and forage yield. selected populations were also evaluated for forage yield, nontarget minerals, and forage quality characteristics. Unselected populations differed in P concentration, but variability among individual plants was considerably greater than among populations. Selection on the basis of P concentration of individual plants was effective with 7 to 12% increases over the check in Cycle 1 and an additional gain of 6% with a second cycle of selection. Realized heritabilities with individual plant phenotypic selection were 0.17 and 0.36 in the first and second cycles of selection, respectively. Selection for increased P concentration did not affect Ca concentration, but reduced the Ca:P ratio and increased Zn concentration. No detrimental effects of selection for increased P concentration were found for nontarget minerals, components of forage quality, or yield. Selected populations did not differ from the check population in response to P fertilization. Selection among individual alfalfa plants from any genetic source based on P concentration in forage from the first harvest would be the most efficient breeding procedure to increase P concentration.
Resistance to Fusarium Wilt in selected Inbred Lines of Crimson Clover1
Authors: Pratt R. G. , Knight W. E.
Published: July 2010

A Fusarium wilt disease (caused by Fusarium oxysporum Schlect.) occurs on crimson clover (Trifolium incarnatum L.) in Mississippi. Infection can result in death of plants of all ages, and existing cultivars are not resistant. The objectives of this study were to indentify resistance to Fusarium wilt in crimson clover and to develop nonsegregating resistant inbred lines. Cultivars and derived inbred lines were screened for resistance to Fusarium wilt during five spring seasons in the greenhouse. Inbred lines were developed by selfing individual plants with few or no disease symptoms. The S3 lines were compared with parent cultivars and with each other in 1984, and S4 lines were compared in 1985. Of 44 S3 lines, 28 had significantly (P < 0.05) lower mean disease scores than parent cultivars and were considered to manifest resistance, 14 did not differ from parent cultivars, and two were more susceptible. Possible reasons for a lack of resistance in some lines are discussed. Resistance was observed in S3 lines from cultivars ‘Auburn’, ‘Autauga’, and ‘Tibbee’, but not from ‘Chief’, ‘Dixie’ or ‘Talladega’. Disease scores of $3 lines considered resistant, in comparison to parent cultivars, represented a broad range with numerous significant differences between them. Segregation for resistance within S1, S2, and S3 lines was indicated by differences in disease scores of derived S3 and S4 lines. An absence of segregation within S3 lines with high resistance, as indicated by similar low disease scores of S4 progeny, suggests that these lines may be true‐breeding and suitable for use in germplasm improvement programs.