bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate and Extent of Cell Wall Digestion of Total Forage and Morphological Components of Oats and Barley1
Authors: Cherney J. H. , Marten G. C. , Goodrich R. D.
Published: July 2010

Rate of cell wall (CW) digestion in forages has been proposed an indicator of intake potential by ruminant animals. Extent of CW digestion determines the nutritive value potential of the nonsoluhle (fibrous) part of forage dry matter. The objectives of this study were to compare the rate and extent of CW digestion of the total forage and the morphological components of oats (Avena sativa L.) and barley (Hordeum vulgare L.) and to ascertain the effect of maturity on CW digestion. Oats (cv. ‘Lyon’) and barley (cv. ‘Manker’) were grown at each of two locations and harvested at each of six maturity stages. Rates of CW digestion in barley total forage (10.34 to 7.35%/hour) were significantly greater than those of oats (7.88 to 3.88%/hour) all maturity stages. Extent of CW digestion was also significantly greater for barley (72.4 to 49.3%) than for oats (69.2 to 41.2%). The decline in both rate and extent of CW digestion with increasing maturity was statlsticaHy linear. Rate of CW digestion was most highly correlated with in vitro digestible dry matter (r = 0.83, P<0.01). Extent of digestion was most highly correlated with acid detergent lignin (ADL; r = −0.92; P<0.01) and ADL/cell wall constituents (r = −0.93, P<0.01). Of the morphological components, the leaf blade had the fastest rate of CW digestion (10.67%/hour), whereas rates of CW digestion for stem (7.53%/hour) and leaf sheath (7.91%/hour) were similar. We conclude that forage quality assessment in grasses involving leaf/ stem ratios does not necessarl]y require the tedious task of separation of sheaths from stems in that the best leaf/stem ratio relationship to forage quality of barley and oats occurred when the stem and sheath were grouped as one morphological entity. Because rate of CW digestion declined slowly with maturation until stage 3 and then declined sharply as grain filling initiated (between stages 3 and 4), we conclude that oats and barley should be harvested by stage 3 in animal feeding systems that require high intake (high rate of digestion) such as systems for milk production or rapid animal growth. These results substantiate our earlier report that if the cultivars of barley and oats used in this and previous studies are representative of adapted cultivars generally, barley provides a superior quality forage.
Germination of Forage Crop Seeds After 20 Years of Subfreezing Storage1
Authors: Rincker Clarence M.
Published: July 2010

There is little literature on the effect of long‐term subfreezing storage of forage crop seeds. Furthermore, most seed storage studies include only one or two samples of a given kind of seed. In this study germination percentages for 260 forage crop seed lots were determined after 20 years of subfreezing storage. The study included alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), white clover (T. repens L.), alsike clover (T. hybridum L.), birdsfoot trefoil (Lotus corniculatus L.), smooth bromegrass (Bromus inermis Leyss.), orchardgrass (Dactylis glomerata L.), timothy (Phleum pratense L.), and perennial ryegrass (Lolium perenne L.) Seed from 26 cultivars of nine species produced at three locations (Prosser, Wash., Shafter and Tehachapi, Calif.) in 1961, was placed in cotton bags in a freezer at −15 C and 60% relative humidity soon after cleaning in the year of harvest. Each seed lot was tested for germination in 1961 and retested in 1981. Red clover, bromegrass, orchardgrass, and timothy retained germinability for 20 years in this study in sharp contrast to the significant losses in a previous study. Continuous subfreezing storage conditions in this study, as opposed to most seed lots in the earlier study being stored 1 to 2 years at 5 C before being placed in subfreezing storage, may account for these differences. Location of seed production was not important except for significant losses in germination of alfalfa seed produced at the two California locations. This was responsible for a significant loss in alfalfa seed germination when values from all three locations were pooled. There was evidence that the California alfalfa seed had been thresher‐damaged which could account for this loss in germination. The 1981 germination values for timothy were significantly higher than in 1961 but this probably was due to testing procedures used in 1961. Excluding the timothy seed lots, the mean germination for the remaining 231 seed lots declined less than 2% after 20 years of subfreezing storage. High quality bromegrass seed is not limited to 12 years of subfreezing storage as earlier concluded.
Increased Soybean Productivity with a Rhizobium japonicum Mutant1
Authors: Williams Larry E. , Phillips Donald A.
Published: July 2010

A mutant of Rhizobium japonicum strain USDA 110 with approximately 100% greater C2H2‐reduction capacity in free‐living culture than the wild‐type strain was analyzed on soybean [Glycine max (L.) Merr., ‘Clark’] under controlled environmental and field conditions. The mutant strain, C33, which also was deficient in nitrate reductase activity, increased dry weight and N content approximately 40% (P ≤ 0.05) relative to the wild type 110 after 45 days in plants grown under a photosynthetic photon flux density (PPFD) of 1,500 (µmol/m2 sec with 2mM KNO3. Similar trends, but fewer significant bacterial effects, were measured in plants grown under a PPFD of 700 µmol/m2 sec with 2 mM KNO3. In field trials, strain C33 increased the 2‐year mean of seed yield and seed N content significantly (P ≤ 0.05) compared with the wild‐type strain 110. The promotive effects on seed yields and seed N content were about 12%, but 9 to 10% increases in above‐ground biomass and N content at the R5 growth stage associated with strain C33 were not significant. A greater promotive effect of strain C33 on seed yield and seed N content during the second year in the field was associated with low soil N availability. Estimates of seasonal N2 fixation, based on both the 15N‐dilution assay and a difference in total N relative to a non‐nodulating control, showed that both Rhizobium strains fixed more N2 in the second year. During both years more than 80% of the bacterial isolates from root nodules of plants inoculated with strain C33 were identified as C33 on the basis of bacteriophage sensitivity and resistance to chlorate. The results indicated that, although it was possible to select a symbiotically superior mutant of Rhizobium japonicum in free‐living culture, the beneficial effects produced in the plant under controlled environments were variable, and promotive effects in the field could be measured only under conditions of low soil N availability.
Yield, Water Relations, Gas Exchange, and Surface Reflectances of Near‐Isogenic Wheat Lines Differing in Glaucousness1
Authors: Johnson Douglas A. , Richards Richard A. , Turner Neil C.
Published: July 2010

Near‐isogenic lines that contrast in the presence or absence of glaucousness were developed in durum wheat (Triticum turgidum L. durum group) and common wheat (T. aestivum L.) and grown in plots in three field environments varying in soil water availability. The glaucous selections yielded significantly more grain and dry matter than non‐glaucous selections in the two higher yielding environments but not in the very dry environment where average yield was 66 gm‐2. No differences within or between lines were found in soil water extraction patterns. Furthermore, leaf water potentials determined at predawn and midday exhibited no consistent differences between glaucous and non‐glaucous selections. Lines selected for glaucousness varied in wax content of the different plant parts. Although differing in glaucousness, the glaucous selections did not necessarily exhibit greater amounts of epicuticular wax. Field gas exchange measurements for flag leaves and sheaths also indicated no beneficial or detrimental effects of glaucousness at saturating light and optimum temperature for photosynthesis. Surface reflectances in the 400 to 700 nm wavelengths were the same for the adaxial surface of the flag leaf, but were 8 to 15% higher in the glaucous than nonglaucous selections of one line for the ear, sheath, and abaxial flag leaf surface. Reflectances increased linearly with amount of epicuticular wax and were greater in the driest environment. The greater yield of the glaucous over the non‐glaucous lines is discussed in relation to differences in reflectance and the possible influence of glaucousness on tissue temperature, leaf area duration, and other factors.
Tolerance of Weeping Lovegrass Cultivars to Herbicides1
Authors: Bovey R. W. , Voigt P. W.
Published: July 2010

Weeping lovegrass [Eragrostis curvula (Schrad.) Nees] is relatively easy to establish if weed infestations arc not serious. The purpose of our research was to evaluate the response of ‘Morpa’ and ‘Rennet’ weeping lovegrass to 27 pro‐ and post‐emergence herbicides. Weeping lovegrass was grown in a 1:1:1 Blelberville day (Udlc pellnstcrt): sand:peat moss mixture in small pots. Five to 10 plants were grown in each pot with five replications (pots) per treatment. All herbicides were sprayed in water at a spray volume of 93.5 liter/ha. All herbicides were sprayed at rates of 0.6, 1.1, and 2.2 kg/ha. Herbicide and/or dead plants per pot 14 days after treatment. Morpa and Rennet were tolerant to preoemergence applications of propazinc [2‐ddoro‐4, 6‐bis(isopeopylamino)‐s‐trlazine] and butylate (S‐ethyl isobutylthlocarbamate). Morpa also showed little phytotoxiclty to 0.6 and 1.1 kg/ha of atrazlne [2‐chloro‐4‐(ethylamino)‐6‐(isopropylamino)‐ s‐trlazlne] and p~razon [5‐amino‐4‐chloro‐2‐phenyl‐3(2H)‐pyrldazlnone] and 0.6 kg/ha of dinron [3‐(3,4‐dlchlorophenyl)‐l, 1‐dlmethylurea]. Rennet tolerated the pre‐emergence applications of atrazlne, dluron, and propachlor (2‐chloro‐N‐isopropylacetanilidc) 0.6 kg/ha. Acltluorfen 15‐[2‐chloro‐4‐(trittuorometh~l) phenoxyl]‐2‐ nltrobenzolc acldl and atrazine (pre‐emergence) were much more phytotoxlc to Rennet than Morpa. Post‐emergence herbicides showing the least injury to both cultivars were barban (4‐chloro‐2‐but~nyl m‐chlorocarbanilate] and bromoxynil [3,5‐dlbromo‐4‐hydroxybenzonitrile]. Other herbicides warranting further study as post‐emergence sprays included asulam (methyl sulfanilylcarbamate), atrazine, blfenox [methyl 5‐(2,4‐dichlorophenoxy)‐2‐nitrobenzoate], and pyrazon. For both pre‐ and post‐emergence herbicides, Renner was generally more susceptible to herbicide damage than Morpa.
Frequency of Pigment Glands and Capitate and Covering Trichomes in Nascent Leaves of selected Cottons1
Authors: Bryson Charles T. , McCarty Jack C. , Jenkins Johnie N. , Parrott W. L.
Published: July 2010

Twenty‐nine cotton strains, Gossypium hirsutura L., were evaluated to assess potential physical and chemical barriers confronting Heliothis ovipnsltion and feeding in relationship to the frequency of pigment glands and covering and capitate trichomes on the laminae of nascent terminal leaves. Significant differences were found among strains for each of the structures, with a two‐fold difference in the number of pigment glands among glanded strains, a two‐fold difference in capitate trlchomes, and a range of 0 to >1500 covering trichomes per cm2. Frequencies of covering trlchomes between adaxial and abaxial surfaces were significantly different among strains. The frequencies of glands and of the two types of trlchomes seemed to be independent of each other. Of the structures studied, only the density of glands had any influence on Heliothis larval growth. The number of pigment glands per cm2 of leaf tissue was negatively correlated with larval weight after five days of feeding.
Quantitative Inheritance and Correlations among Forage Yield and Quality Components in Timothy1
Authors: Berg Clyde C. , Hill R. R.
Published: July 2010

Forage yield and quality can be improved by breeding only if genetic variance exists within the population. This study was conducted to determine the genetic variability within a population of plants selected at random from a seed lot of ‘Cllmax’ timothy (Phleum pratense L.), to predict the possibility of improving several traits, and to investigate associations among traits. Progeny from diallel crosses of seven sets of six clones each were used to establish field plots. Forage yields were recorded and forage quality characteristics determined for forage from each plot. Significant general combining ability variances were observed for most traits, while specific combining ability variances were significant only for Ca/P ratio and percentage dry matter and Ca. Year ✕ general combining ability variances were significant for some traits, but year ✕ specific combining ability variances were of little or no importance. Narrow sense heritabilities ranged from 0.08 (Pb) to 0.85 (Ca). The genotypicorrelation between forage yield and percentage dry matter was significant and positive. Genotypic correlations between forage yield (and percentage dry matter) and IVDMD, protein, P, and K were negative. The genotypic correlations among IVDMD, protein, P, and K were positive. Most of the other genotypic correlations studied were near zero. Calculated compositions of mixtures of timothy and alfalfa forages are shown graphically. Moderately producing dairy cattle require higher concentrations of most minerals than those contained in timothy forage. Breeding programs making use of general combining ability, such as polycross progeny test, should be used when attempting to improve forage yield and quality of timothy; however, breeding programs should start with a broader based population than found in Climax.
Gas Exchange and Water Relations of ‘Olaf’ Spring Wheat1
Authors: Morgan Jack A. , Willis W. O.
Published: July 2010

Experiments have been performed previously in which one or a small number of microclimate and water relations factors were investigated in relation to their effect on apparent photosynthesis in wheat, but little progress has been made attempting to monitor several of these factors in a single field study of canopy apparent photosynthesis (AP). In the present study, several microclimate and plant variables of field grown wheat plants, subjected to two irrigation regimes, were monitored to observe their combined effect on chamber measurements of AP. Dirunal AP and evapotranspiration (ET) measurements were taken on ‘Olaf’ spring wheat (Triticum aestivum L.) on 5 days from heading through late milk growth stages. Plants were irrigated either weekly (W) or biweekly (BW). A sequential analysis of covariance of the total data set showed AP was significantly associated with flag leaf stomatal resistance and water potential, canopy air temperature, leaf area index (LAI), irradiance, date, and time day. The consistently higher AP rates of treatment W were attributed mostly to higher values of LAI and water potential, and lower stomatal resistances, compared to treatment BW. Although reductions in leaf area and increases in stomatal resistance resulted in less ET for treatment BW, AP was reduced proportionately more by the effects of biweekly irrigation. Thus, water use efficiency was always greater for treatment W. Maximum AP rates alway occurred in the morning and earlier than maximum rates of ET. This observation was attributed partly to warmer afternoon temperatures, which increased ET and, in combination with lowered leaf water potentials, decreased AP. As a result, photosynthetic capacity was always greater in the morning than the afternoon. However, time of day still affected AP significantly after accounting for all of the variability associated with these and other measured variables which were known to affect AP. Based on measurements taken for both treatments, stomata appeared to be generally more open after than before anthesis. On the final day of measurements, stomata of treatment BW were closing, apparently in response to leaf aging.
Productivity and Survival of Alfalfa Hybrid and Inbred Plants Under Competitive Conditions1
Authors: Veronesi F. , Lorenzetti F.
Published: July 2010

A study was conducted at Perugla, Italy in 1981 to evaluate the importance of intra‐specific competition in alfalfa (Medicago sativa L.) and to investigate the consequence of different percentages of inbred seeds on forage yield. Three seed mixtures having ratios of inbred seed to hybrid seed (S1/F1) of 1/9, 3/7, 1/1 were sown, seed by seed, in micro‐plots (50 ✕ 30 cm) at a seeding rate of 1600 seeds/m2. Data were collected on establishment, green matter yield per plant of inbred or hybrid origin, dry matter yield per plot at first, second, and third cut, height and number of stems per plant at the third cut, and number of plants alive in the fall season. The results are summarized as follows: 1) yield of S1 plants was much lower than that of F1 in each of the three mixtures; the inbreeding effect was higher than that usually shown in spaced plant trials; 2) since no differences were observed in dry matter yield per plot among mixtures, differences in S1 seed percentage would not seem important to productivity of alfalfa in the 1st year; and 3) no differences were observed in establishment between S1 and F1 seedlings but fall survival percentages of S1 plants were significantly lower than those of F1 in all mixtures. This confirms that selective elimination of S1 plants begins during the seeding year. The selection against S1 plants increases over time and suggests that 1 year after seeding few S1 plants will survive irrespective of their percentage in the initial seed lot.
Historical and Current Taxonomic Perspectives of Agropyron, Elymus, and Related Genera1
Authors: Dewey Douglas R.
Published: July 2010

The taxonomy of the perennial grasses of the Triticeae tribe (Agropyron, Elymus, et al.) has been in an unsettled state for many years, with Eurasian and North American authorities often using different systems of classification and applying different names to the same species. North Americans have generally relied on the treatment given in A.S. Hitchcock's 1951 Manual of the Grasses of the United States, while realizing that it was seriously outdated. Publication of treatments of the Triticeae in Poaceae URSS by N.N. Tzvelev in 1976 and in Flora Europaea by A. Melderis et al. in 1980 has made it advisable for North Americans to reevaluate their taxonomic traditions with respect to these grasses. Tzvelev's treatment is compatible with biological relationships as determined by chromosome pairing in interspecific and intergeneric hybrids. The perennial genera of the Triticeae recognized by Tzvelev include: 1) Agropyron (restricted to A. cristatum and other crested wheatgrasses), 2) Elymus (self‐fertilizing and caespitose species previously in Elymus and Agropyron) 3) Leymus (usually cross‐pollinating and often rhizomatous species previously in Elymus), 4) Elytrigia (usually cross‐pollinating and rhizomatous or caespitose species previously included in Agropyron, with the exception of the crested wheatgrasses), 5) Psathyrostachys (crosspollinating species with brittle rachises and multiple spikelets, including Russian wildrye), and 6) Hordeum (treated in its traditional sense). With a few exceptions, I endorse Tzvelev's treatment because it closely reflects biological and phylogenetic relationships.
Genetic and Phenotypic Path Analyses and Heritability in Sugarcane1
Authors: Kang M. S. , Miller J. D. , Tai P. Y. P.
Published: July 2010

This study was undertaken to determine phenotypic and genetic correlation coefficients among several agronomic traits in sugarcane (Saccharum spp.) and to analyze their interrelationships through path‐coefficient analyses. Other objectives were to determine broad‐sense heritability and genetic advance under selection for the traits studied. Random selections from two biparental crosses (‘CP 59‐50’ ✕ ‘CP 57‐603’ and ‘CP 62‐374’ ✕ ‘CP 57‐614’) were evaluated in the field for several attributes in plant cane, and first‐ and second‐ratoon crops. Genetic path‐coefficient analyses indicated plant height to be less important than stalk diameter and stalk number as a component of cane yield; but at the phenotypic level, all three components were of equal importance. Sucrose (%) had a large direct positive effect on sugar per ton of cane (S/T) whereas Brix (percent soluble solids) had a small negative direct influence on S/T. The S/T component exerted a greater direct effect on tons per hectare of sugar (THS) than did tons per hectare of cane (THC). Broad‐sense heritability estimates based plot means for various traits ranged from a low of 77% for THS to a high of 94% for stalk diameter. Expected genetic advance for various traits was reasonably high under selection intensities of 2 to 30%. THC estimated from the weight of a 10‐stalk sample per plot was genetically and phenotypically correlated with THC determined by weighing the entire plot (rg = 0.92, rp = 0.64) which suggested that a 10‐stalk sample per plot would be adequate to determine THC.
Alfalfa Response to Soil Water Deficits. II. Plant Water Potential, Leaf Conductance, and Canopy Temperature Relationships1
Authors: Carter P. R. , Sheaffer C. C.
Published: July 2010

Information is needed on the regulation of water vapor loss and on the plant water status of alfalfa (Medicago sativa L.) subjected to soil water deficits. Our objective was to characterize diurnal and seasonal plant water potential (ψp), leaf conductance (G1), and canopy temperature (Tc) relationships for field‐grown alfalfa. Measurements of ψp, G1, and Tc were made hourly from sunrise to sunset on 13 clear days from 10 July to 2 October on alfalfa subjected to a range of soil water levels during vegetative, bud, and bloom growth stages. Plant water potentials of well‐watered plants were −0.1 to −0.4 MPa at sunrise and declined to −0.8 to −1.2 MPa at midday. With soil water depletions, ψp declined rapidly (0.08 to 0.4 MPa/day) and diurnal ψp cycling continued. Under severe plant water stress, ψp were below −2.0 and −4.5 MPa at sunrise and midday, respectively. The G1 under high moisture conditions reached a peak of up to 0.033 m/s at midmorning and decreased gradually until sunset. At moderate plant water deficits, G1 was greatest during low transpirational demand periods (early morning and late afternoon) and depressed at midday. Under extreme plant water stress, G1 remained at low levels (0.001 to 0.003 m/s) the entire day. Stomatal closure at midday resulted in Tc up to 8.5°C higher for water‐stressed vs. well‐watered alfalfa. Leaf conductance declined linearly with decreasing ψp until ψp reached −2.5 MPa. Below a ψp of −2.5 MPa, G1 stabilized at low levels. Regression coefficients (slopes) of the G1 vs. ψp (<−2.5 MPa) linear regression equations were greatest when daily maximum air temperature (MAT) was high and decreased as MAT declined. Under nonlimiting soil moisture conditions, G1 declined linearly as Tc was reduced. Growth stage and daily pan evaporation did not influence the G1 ‐ ψp relationship.
Spike Differentiation and Floret Survival in Semidwarf Spring Wheat as Affected by Water Stress and Photoperiod1
Authors: Oosterhuis D. M. , Cartwright P. M.
Published: July 2010

Previous work on the effects of water stress on wheat spike morphogenesis and floret survival has been conducted mainly on standard height (nondwarf) cultivars. Effects of water stress on the spike were therefore studied using a semidwarf spring wheat (Triticum aestivum L.). Plants were raised in the glasshouse under 8 h and 16 h photoperiods, and 7‐day periods of water stress were imposed during different development phases up to spike‐emergence. Water stress at critical times generally caused floret and sometimes whole spikelet death at the terminal ends of the spike. Water stress during the late vegetative phase just before spike initiation adversely affected the final number of fertile florets per spike, the reduction in fertile florets being accounted for by fewer spikelet primordia being formed. Water stress during late internode elongation prior to spike emergence resulted in death of florets and whole spikelets at the terminal and basal ends of the spike. The spike initial had minimum sensitivity to water stress during the period immediately following the initiation of the terminal spikelet. Stress effects in semidwarf wheat particularly during internode elongation, appeared to be similar to those reported for conventional standard height spring wheats. Greater spikelet number per spike was obtained in the short days (8 h) than in the long days (16 h). This was mainly due to photoperiod and possibly also because water stress of the same duration and similar intensity may have been relatively less severe in the prolonged development phases in the short days.
Responses of Tall Fescue Leaf Meristems to N Fertilization and Harvest Frequency1
Authors: Volenec J. J. , Nelson C. J.
Published: July 2010

Leaf elongation rate (LER) of tall rescue (Festuca arundinacea Schreb.) and other forage grasses is known to be modified by management practices. Our objectives were to estimate the influence of harvest frequency and N fertilization on cell division, cell elongation, and other associated cellular changes that collectively result in the modified LER of tall rescue. In two experiments, LER was estimated, then length of epidermal cells was measured at 2 mm intervals from the base of the elongating leaf throughout the leaf intercalary meristem. Using mature epidermal cell lengths and number of epidermal cells in the intercalary meristem, several calculations were made to assess the relative cellular responses influencing LER. In Exp. I, field plots of two genotypes selected for low (LYT, slow LER) or high yield per tiller (HYT, rapid LER), were clipped at 2‐ or 6‐week intervals. The 30% higher LER of plots cut at 6‐week intervals relative to plots cut at 2‐week intervals could be attributed to a 17% greater increase in mature epidermal cell length and a 14% increase in the number of cells matured per day per cell column. In Exp. II the same genotypes were grown in controlled‐environment chambers with two rates of N. The 89% greater LER of plants receiving the equivalent of 336 kg ha−1 N could be accounted for by a 90% increase in the number of epidermal cells matured per day per cell column when compared to plants receiving 22 kg ha−1 N. Cells within the intercalary meristem of plants receiving high‐N also elongated 22% faster than those receiving low N. Lengths of leaf intercalary meristems removed from plants harvested at 2‐week intervals or receiving 22 kg ha−1 N tended to be shorter than those removed from plants harvested at 6‐week intervals or receiving 336 kg ha−1 N. Averaged over treatments within each study, LER of the HYT genotype exceeded that of the LYT genotype by about 50%. This genotypic difference in LER could be attributed to a 28% greater increase in epidermal cell length and a 22% increase in number of epidermal cells matured per day per cell column of the HYT genotype when compared to the LYT genotype. Increased LER due to genetic selection or infrequent cutting was associated with increased rate of cell production and increased cell length, whereas increase due to N‐fertilization was due only to increased cell production.
Impact of Plant Breeding on the Grain Yield and Genetic Diversity of Spring Oats1
Authors: Rodgers D. M. , Murphy J. P. , Frey K. J.
Published: July 2010

The genetic relationships among, and grain yields of spring oat (Avena sativa L.) cultivars released in the north central and northeastern USA between 1941 and 1980 were investigated using coefficients of parentage (r) and least squares means (LSM). These parameters were evaluated in two data sets, Early and Midseason, which were based on uniform regional nursery trials conducted between 1944 and 1980. The mean coefficient of parentage (r̄) among oat cultivars released within the same 5‐year period has oscillated between approximately 0.1 and 0.3 since the mid‐1940's in each data set with no apparent long‐term positive or negative trend. The level of r̄ during 1976–1980 was 0.22 and 0.13 in the Early and Midseason data sets, respectively. The LSM's were used to estimate genotypic value for grain yield of each cultivar tested for 3 or more years. The LSM's of cultivars released within the same 5‐year period were averaged (x̄LSM) and compared with the LSM of ‘Gopher’ (LSMG), a selection from the 19th century cultivar ‘Kherson’. Increases in x̄LSM were relatively modest from 1941 to 1975. In the 1971–1975 period, the x̄LSM's were 116 and 111% of LSMG for the Early and Midseason data sets, respectively. However, in the 1976–1980 period, a substantial increase in x̄LSM to 134% of LSMG was observed in the Early data set indicating a genetic gain during this 5‐year period which equaled that of the entire 35‐year period prior to 1976. A breakthrough in yield was also suggested in the Midseason data set because two recently released cultivars, ‘Ogle’ and ‘Porter’, had LSM's ≥130% of LSMG. The recent large increases in oat grain yield were obtained over a broad base of germplasm. Coefficients of parentage among the five cultivars having LSM's ≥130% of LSMG indicated that a minimum of three distinct sources of germplasm with high yield potential was involved.
Diallel Analyses of Winterhardiness in Peas1
Authors: Auld D. L. , Adams K. J. , Swensen J. B. , Murray G. A.
Published: July 2010

The parental lines and 36 F2 populations obtained from a nonreciprocal diallel cross among nine lines of peas [Pisum sativum L. and P. sativum subsp. arvense (L.) Poir] were evaluated for winterhardiness in the field at Moscow, Idaho and for freezing tolerance in a programmable freezer at −3 and −6 C. Combining ability analyses indicated that general combining ability (GCA) played a significant role in conditioning survival under both field and laboratory conditions. The ratio of sum of squares for GCA and GCA plus specific combining ability (SCA) ranged from 0.59 to 0.87, indicating there was sufficient GCA in these populations to allow successful selection for winterhardiness. Under field conditions the lines ‘Melrose’ and ID 2 exhibited high levels of winterhardiness, had high mean parental effects and large estimated GCA effects which indicate these lines were good parents for winterhardiness. Although the three spring lines did not differ in winterhardiness in the field, the mean parental effects and estimated GCA effects of ‘Tracer’ indicated this line was a better parent to use in crosses with winter‐hardy parents than the other two spring lines. Although differential survival was measured in laboratory evaluations of freezing tolerance, the results were not as distinct as in the field evaluation. Correlation coefficients of only 0.55** and 0.59** (Significant at the 0.01 level.) were measured between percent survival in the field and percent survival at −3 and −6 C, respectively. Because survival in the field is dependent on factors other than freezing tolerance, such as soil drainage, snow cover, and disease infection, these relatively low correlation coefficients were expected. Final selection for winter survival should be made under field conditions.
Genotype by Cropping System Interactions in Maize Grown in a Short Season Environment1
Authors: Brakke J. P. , Francis C. A. , Nelson L. A. , Gardner C. O.
Published: July 2010

Broad adaptation for maize (Zea mays L.) hybrids is a goal of many plant breeders, but limited information is available on genotype by cropping system interactions. We studied the magnitude of this interaction in the western Panhandle region of Nebraska in a short‐season, dry environment where at present there is no location specific improvement program. Maize topcrosses were planted in two contrasting cropping systems with two locations per cropping system in 1980. Normal land preparation and irrigation was compared to ecofallow, a zero‐tillage cropping system used in the region to minimize water loss due to tillage, reduce production costs, and conserve soil resources. Significant effects of cropping system, location within cropping system, maize genotype, and genotype by cropping system were observed for days to flower, yield, and harvest moisture. The genotype by cropping system interactions in the topcrosses may have been due to differential effects of water level, soil temperature during the early part of the growth cycle, or some combination of these factors. Results suggest that maximum maize yields can be achieved in Nebraska by development of specific cultivars for each cropping system in distinct environments.
Use of Tropical Environments in Breeding for Oil Composition of Soybean Genotypes Adapted to Temperate Climates1
Authors: Hawkins S. E. , Fehr W. R. , Hammond E. G. , Rodriguez de Cianzio S.
Published: July 2010

The objective of this study was to determine the influence of genotype ✕ environment interaction on selection for fatty acid composition among soybean [Glycine max (L.) Merr.] lines adapted to the northern United States when grown in tropical environments. Twenty lines of maturity groups I to III were grown in three environments in Iowa and four environments in Puerto Rico. Seeds from two replications in each environment were analyzed for the percentages of palmitic, stearic, oleic, linoleic, and linolenic acids. The line ✕ environment interactions were significant for all fatty acids; however, the phenotypic and rank correlation coefficients for the average performance of lines between Iowa and Puerto Rico were all highly significant. The lines with the lowest average percentage of palmitic, stearic, linoleic, or linolenic acid were the same at both locations. The lines with the highest percentages of the fatty acids in Iowa were ranked within the three highest lines in Puerto Rico. The results indicate that selection for fatty acid composition in tropical environments should be effective for genetic improvement of lines adapted to the northern United States.
Relative Genetic Contributions Among Ancestral Lines to North American Soybean Cultivars1
Authors: Delannay X. , Rodgers D. M. , Palmer R. G.
Published: July 2010

An examination of the pedigrees for 158 USA and Canadian soybean [Glycine max (L.) Merr.] cultivars of hybrid origin indicated that the North American soybean gene pool could be traced to only 50 plant introductions. Evaluations were made of the relative genetic contributions of those introductions to the cultivars released in the northern and southern gene pools of North America over four time periods, i.e., before 1951, 1951–1960, 1961–1970, and 1971–1981. Although more introductions have been used in recent times, a few constitute an increasingly greater proportion of the genetic base for our modern cultivars. Ten introductions contributed, collectively, more than 80% of the northern gene pool, while only seven contributed the same share to the southern gene pool. Furthermore, many of the predominant introductions originated from the same geographic area. These data confirm previous estimates of the narrowness of the genetic base for present‐day soybean cultivars. Examples, however, are provided describing the recent use of new introductions in the development of soybean cultivars.
Biochemical Basis of Resistance in Corn to the Corn Leaf Aphid1
Authors: Beck D. L. , Dunn G. M. , Routley D. G. , Bowman J. S.
Published: July 2010

Field experiments were conducted to determine the relationship between hydroxamic acid, total phenol, and orthodihydroxyphenol concentrations in corn (Zea mays L.) tassels and resistance to the corn leaf aphid [Rhopalosiphum maidis (Fitch)]. Eleven corn inbreds were evaluated for aphid resistance soon after tassel emergence using a visual rating scale and index system. The corn tassels were harvested and analyzed for hydroxamic acid, total phenol, and orthodihydroxyphenol content. A highly significant negative correlation (r = −0.63) was obtained between aphid infestation and hydroxamic acid concentration. Poor correlations were found between aphid infestation and both the total phenol and orthodihydroxyphenol concentrations. Seven corn inbred lines were further evaluated for corn leaf aphid resistance by artificial infestation in the greenhouse. A highly significant correlation (r = 0.90) was found between the greenhouse and field results.
Embryo Culture of Helianthus Hybrids1
Authors: Chandler John M. , Beard Benjamin H.
Published: July 2010

An embryo culture system using two modification of Gamborg's B5 medium was used to produce interspecific Helianthus hybrids. Embryos initially developed on a solid medium containing inorganic components, vitamins, amino acids, and 120g/L sucrose. For embryo germination and seedling growth the cultured embryos were transferred to a liquid medium containing only the inorganic components and 10g/L sucrose. Embryos were successfully excised and cultured 3 to 7 days after pollination. Fifty‐three combinations of species have been successfully hybridized using this system, including 21 which have not been reported using conventional methods. Embryo culture techniques avoid embryo abortion and seed dormancy. The decrease in generation time using embryo culture can be useful in breeding schemes where small numbers of plants are needed per generation.
Reproductive Responses of Cowpea to Heat Stress: Genotypic Differences in Tolerance to Heat at Flowering1
Authors: Warrag M. O. A. , Hall A. E.
Published: July 2010

The effect of high temperature on ability of cowpea [Vigna unguiculata (L.) Walp.] to set pods was investigated under field conditions and in controlled environments. During hot weather in the Imperial Valley, Calif., the cowpea strains TVu 4552, PI 204647, and ‘Prima’ produced substantial numbers of pods, while 55 other strains produced no or few pods, even though they produced numerous open flowers. Studies in growth chambers demonstrated that TVu 4552 has greater tolerance to high night and high day temperatures at flowering than the California cultivar, ‘California Blackeye No. 5’ (CBS), whereas Prima is intermediate. Susceptibility to high temperatures was associated with low pollen viability and indehischent anthers for CB5 and with anther indehiscence for Prima. Artificial pollination demonstrated that pistil viability of all three genotypes was not significantly affected by high temperature. Thus, the flower abscission observed with CB5 and Prima at high temperatures was mainly caused by male sterility. In addition, substantial levels of embryo abortion were observed with CB5 and Prima at high day temperatures. Apparently, Imperial Valley provides a suitable field environment during the summer for screening cowpeas for heat tolerance. This environment is presently being used to screen the segregating populations from crosses designed to incorporate the heat tolerance of TVu 4552 and Prima into genetic backgrounds suitable for the tropics and subtropics.
Carbon Balance as a function of Plant Size in Sorghum Plants1
Authors: McCree K. J.
Published: July 2010

In young plants, the daily respiratory loss rate is expected to be almost proportional to the daily photosynthetic input, since photosynthate is being converted to new biomass with constant efficiency and maintenance losses are small. As plants increase in size, the maintenance requirement is thought to increase in proportion to the biomass, while the photosynthetic input also increases, but at a slower rate due to mutual shading of leaves. Thus, the maintenance requirement plays an increasingly greater role and may dominate the daily carbon balances of large plants. The photosynthetic input, conversion efficiency and maintenance requirement of vegetative sorghum plants [Sorghum bicolor (L.) Moench ‘RS 610’] were determined as a function plant size in plants growing under constant conditions (28°C and 1000 μmol s−1 m−2 of photosynthetically active radiation for 12 h). Although the sorghum plants grew much faster than field‐grown plants of the same cultivar, the morphology and growth characteristics were shown to be very similar when compared at the same size of plant. The maintenance requirement per unit biomass decreased with increasing plant size, from 26 mgC gC−1 day−1 for the smallest plants to 20 mgC gC−1 day−1 for plants with a biomass of 19 gC (50g dry weight). The protein content decreased in about the same proportion (from 29 to 20% protein). The average maintenance requirement per gram of protein was 39 mgC g protein−1 day,−1 which is considerably less than that of white clover (Trifolium repens L.) growing under the same conditions (60 mgC g protein−1 day−1). It is suggested that a smaller fraction of the protein is degradable in the sorghum than in the clover. The ontogenetic changes in maintenance requirement found in this experiment were relatively small, considering the wide range of plant sizes studied. Very little error would be introduced by extrapolating from data taken on moderately‐ sized plants. However, these data should be taken over a range of different growth conditions, since it has already been shown that the maintenance requirement per unit biomass is a function of the growth rate, as it is affected by environmental conditions such as temperature, light and soil moisture.
Covariances of Relatives from Self‐Fertilization1
Authors: Cockerham C. Clark
Published: July 2010

Covariances of relatives stemming from self‐fertilization of initially noninbred parents are formulated for a quantitative model with any number of alleles and loci with additive and dominance effects (no epistasis). The results are phrased in terms of five quadratic genetic components whose coefficients are given by descent measures. To estimate the components with any reliability or to test for adequacy of various models, relatives in the first few generations of selfing must be utilized. With more than four generations of selfing, the variances and Covariances are essentially a function of a single composite which represents the variance among homozygous individuals. If this is actually the variance desired, then five or more generations of selfing are sufficient.
Cotton Allelochemics and Growth of Tobacco Budworm Larvae1
Authors: Jenkins Johnie N. , Hedin P. A. , Parrott W. L. , McCarty J. C. , White W. H.
Published: July 2010

Eight alleged allelochemics that naturally occur in cotton, Gossypium hirsutum L., or as a constituent part, were added to a commercial wheat‐germ diet at various concentrations. Neonate larvae of tobacco budworm [Heliothis virescens (F.)] were allowed to feed for 5 days and then weighed to determine the effects of allelochemics on larval growth. Regression equations were fitted to the data. A linear regression in the form Y = a + bX described the relationship for cyanidin, delphinidin, and gossypol up to 0.20% in the diet. A curvilinear regression equation in the general form of Y = aXb described the relationships for catechin, condensed tannin, chrysanthemin (cyanidin ‐3‐β‐glucoside), isoquercitrin, and quercetin. These were fed at higher levels (up to 1%) than the three allelochemics fitted with the linear regression equation. The level of each allelochemic in cotton required to reduce larval weight 90% is within the range of the amounts found in various cotton strains and primitive accessions. All except gossypol are found in several plant families and may thus be useful in developing plant resistance to tobacco budworm in several plant families. Several species of Heliothis are pests of economic importance worldwide.
Genetic Analyses of Male‐Fertility Restoration in Wheat. I. Chromosomal Location of Rf Genes1
Authors: Maan S. S. , Luchen K. A. , Bravo J. M.
Published: July 2010

A monosomic set of Triticum aestivum L. ‘Chris’ was used to determine the chromosomal location of male‐fertility restorer (Rf) genes in R113, a T. aestivum R‐line with T. timopheevii Zhuk. cytoplasm. Cytologically identified monosomic F1s (Chris monosomic × RII3) were crossed as males to cytoplasmic malesterile Chris with T. timopheevii cytoplasm. The testcross F1 progenies were grown in the greenhouse in 1981 and 1982. Seed set data obtained from bagged spikes of plants within each of the 21 segregating populations were used to identify progenies with Rf genes. Rl13 had Rf genes on chromosomes 1A and 6B. The gene on 6B had higher penetrance than the gene on 1A, and the gene on 1A had higher expressivity than the gene on 6B. Also, Rf genes of low penetrance or modifier genes were located on chromosomes 1B, 4B, and 4D, and inhibitors of male fertility were located on 5A, 6A, and 5B; their expression was influenced by environment. In gelaeral, the effect of Rf genes on 1A and 6B was not large enough to influence mean seed sets of fertile plants within their respective families relative to the mean seed sets of fertile plants within the non‐critical families. Results from testcross F1‐derived F2 progenies further indicated that genes on chromosomes 7B, 1D, 4D, 5D, and 7D apparently had a positive effect on fertility restoration when they were homozygous but not when they were heterozygous. Therefore, the high fertility restoration potential of hybrids involving Rl13 may result from the balanced, cumulative effects of the Rf genes and their modifiers located on several chromosomes of the A, B, and D‐genomes of wheat.
Simulation of Potato Crop Growth and Development1
Authors: Ingram K. T. , McCloud D. E.
Published: July 2010

Potato (Solanum tuberosum L.) crop yield is the result of net crop dry matter assimilation (NDMA) and fraction of NDMA partitioned to tubers (α) integrated from the day of tuber initiation onset (TIO) through the day of tuber growth cessation (M). These four physiological yield parameters respond to environment and crop development by complex and poorly understood relationships. A crop growth and development model was constructed to determine the integrated temperature sensitivity of the four yield parameters and to test the hypothesis that temperature effects on α may be explained by growth temperature responses of different potato crop components. The crop was divided into three components, canopy, roots, and tubers. Model inputs were daily mean air temperature, soil temperature at 10 cm, solar radiation, and initialization parameters. Simulation began at emergence and continued through three developmental phases, canopy growth, tuber initiation, and tuber growth, which were demarked by four events, emergence, TIO, tuber initiation end, and M. Simulated TIO wau a function of temperature, whereas tuber initiation end and M were indirectly related to both temperature and radiation. Net crop dry matter assimilation was a direct function of incident solar radiation, canopy light interception, and tuber growth rate. Temperature affected NDMA indirectly through effects on canopy light interception and tuber growth rate. Assimilate partitioning was modeled as a function of available assimilates and empirically derived functions of the relationship between potential growth and temperature for each crop component. Potential growth of root and canopy had a 22 to 24°C optimum, whereas potential tuber growth had a 14 to 16°C optimum. Simulated leaf duration decreased as temperature increased. The model appropriately responded to temperature and solar radiation inputs to simulate cultivar Sebago growth in North Florida. In simulations, the most temperature sensitive yield parameter was TIO, with cool temperatures generally causing earlier TIO. Both M and NDMA were relatively insensitive to temperature with α having intermediate temperature sensitivity. Maximum simulated yield was at 15°C which corresponded with earliest TIO and maximum α. We conclude that temperatureffects on assimilate partitioning may be explained by differential temperature growth responses of potato crop components.