bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection in Alfalfa for Forage Yield with Three Moisture Levels in Drought Boxes1
Authors: Salter RoseMary , Melton Bill , Wilson Marvin , Currier Cliff
Published: July 2010

Although soil moisture availability is the most limiting factor in crop production in many areas of the United States, little progress has been made in developing cultivars tolerant to moisture stress. The objective of our study was to evaluate a drought box screening procedure for use in alfalfa (Medicago sativa L.) breeding to improve performance under less than optimum moisture conditions. Seven diverse alfalfa cultivars and three germplasm sources were evaluated for forage yield and root characteristics under three moisture treatments in drought boxes in a shadehouse. Divergent selection for forage yield was practiced in the low and intermediate moisture treatments, and for high forage yield in the high moisture treatment. Selected plants were intercrossed within groups and progenies were evaluated under similar conditions. Average forage yield was reduced 30 and 55% in the intermediate and low moisture treatments, respectively, when compared to the high moisture treatment. Entries did not differ for yield in the low moisture treatment, but they varied in their yield response to increasing rates of irrigation. Variability among plants for forage yield was not reduced by moisture treatments. Root weight decreased and root fibrousness increased as moisture stress increased. Entries differed for all root characteristics measured. Forage yield was correlated with all root characteristics, but we concluded that the added information did not justify the time, labor, and expense of root excavation. Selection and evaluation in the intermediate moisture treatment resulted in the greatest progress and differentiation among populations.
Indications of Yearly Variation of Acremonium Coenuphialum in Seed from a Permanent Tall Fescue Sward1
Authors: Pedersen J. F. , Williams M. J. , Clark E. M. , Backman P. A.
Published: July 2010

The fungal endophyte Acremonium coenophialum of tall fescue (Festuca arundinacae Schreb.) is not thought to spread by means other than through infected seed. The objective of this paper is to report a case in which an apparent increase in percent infection of a permanent tall fescue sward occurred. The breeder seed field of ‘AU Triumph’ tall fescue, originally thought to be endophyte free, produced essentially clean seed for 4 years (1978–1981). However, breeder seed were 31% infected in 1982. The breeder seed field was found to have been established from seed 59% infected, producing plants that were 57% infected in 1982. Acremonium levels may have increased by some means of inoculum spread or yearly environmental differences may have influenced the level of infected seed produced.
Measurement Errors in Field Calibration of in Situ Leaf Psychrometers1
Authors: Savage M. J. , Cass A.
Published: July 2010

Development of techniques for in situ field measurement of leaf water potential using thermocouple psychrometers highlight the need for an accurate analysis of the errors associated with such measurements. The major sources of error arise from random calibration errors, the temperature dependence of the calibration relationship, temperature differences between the leaf and the psychrometer sensing junction and the error in reading the psychrometer output voltage. In an analysis of such errors, using insulated field‐calibrated psychrometers, the major source of error was found to be in the calibration relationship, particularly as temperature decreased and approached the value of the calibration intercept. This resulted in total relative error values of 8 to 10% of the measured water potential at 0°C, whereas the error was less than 4% for temperatures greater than 20°C (for a potential of —1250 kPa).
Variation in Seed Total Phosphorus, Phytic Acid, Zinc, Calcium, Magnesium, and Protein among Lines of Glycine max and G. soja1
Authors: Raboy V. , Dickinson D. B. , Below F. E.
Published: July 2010

Analysis of 163 soybean [Glycine max (L.) Merr.] lines was conducted to identify lines that had either a high or low concentration of phytic acid (PA). Several of these lines, along with additional soybean lines of interest, and 20 G. soja (Sieb. & Zucc.) lines, were evaluated in the field in 1982. Extensive variation in seed mineral accumulation was observed among the soybean lines (ranges were approximately 50% of the species means), and among the G. soja lines (ranges were approximately 35% of the species means). Among soybean lines, PA and seed total P were highly correlated (r=0.94), as were total P and PA with protein (r=0.74 for both relationships), and total P and PA with (r=0.63 and r=0.58, respectively). In some instances soybean lines with similar levels of total P had significantly different levels of PA. The concentration of PA, total P, Zn, and Ca was approximately 30% greater in seeds of G. soja lines than in soybean seeds. For soybean lines grown in the field trial, mean PA, seed total P, Zn, Ca, and protein were 17.6 g kg−1, 6.9 g kg−1, 52 mg kg−1, 2.7 g kg−1, and 408 g kg−1 respectively, and for the G. soja lines mean values were 22.9 g kg−1, 9.4 g kg−1, 69 mg kg−1, 3.4 g kg−1, and 474 g kg−1 respectively. Seed Mg averaged 2.7 g kg−1 among all Glycine lines, with little observed variation. Soybean lines high in an individual mineral tended to be high in most minerals studied. Among G. soja lines, only two relationships, seed total P:PA and PA:protein, were statistically significant.
Recurrent Selection for Tolerance to Phytophthora Rot in Soybean1
Authors: Walker A. K. , Schmitthenner A. F.
Published: July 2010

Evidence suggests that tolerance to phytophthora rot caused by Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin is a quantitative character of soybean [Glycine max (L.) Merr.]. Recurrent selection can be an effective method of improving soybean populations for quantitative characters. The objective of our study was to evaluate the use of recurrent selection by S1‐line evaluation for the development of a soybean population with improved tolerance to phytophthora rot. An intermated population, designated PMGT, was developed from 10 high‐yielding lines and cultivars from Maturity Groups I to IIl with moderate or better tolerance levels. Each cycle of selection of 1 year included the growing of S0 plants in Puerto Rico during the winter to obtain S1 lines, evaluation of the S1‐lines for tolerance in the greenhouse and in a field nursery, selection of the most tolerant lines before flowering, and recombination of selected lines. Progress from selection was evaluated by comparing the mean performance of the parents for the cycle 0, 1, 2, and 3 populations in the greenhouse using the myceliuminoculum‐layer method and in a field nursery using visually rated hill plots. There was a significant linear improvement in mean tolerance score from cycle 0 to 3. Total realized gain was 21% when evaluated in the greenhouse and 10% when evaluated in the field. Genetic improvement in the population indicated that recurrent selection by S1‐line evaluation is an effective method for improving populations for tolerance to phytophthora rot. The success of selection by S1‐line evaluation indicated that early‐generation testing can be effective for determining the level of tolerance to phytophthora rot.
Growth Analysis of Spring Wheat Cultivars of Varying Drought Resistance1
Authors: Clarke John M. , Townley‐Smith Fred , McCaig Thomas N. , Green David G.
Published: July 2010

Field studies were undertaken to relate dry matter accumulation and loss patterns to drought resistance and yield performance of wheat. A total of 23 hexaploid (Triticum aestivum L.) and tetraploid (T. turgidura var. durum L.) wheat genotypes were grown under rainfed field conditions at Swift Current, Saskatchewan from 1975to 1978, and under both rainfed and irrigated conditions in 1979 and 1980. Weekly dry matter samples were taken in the 1975 to 1979 trials, starting before anthesis and continuing to maturity. Growth parameters were then related to apparent drought resistance, which was characterized by comparing rainfed and irrigated yields. The genotypes were divided into drought susceptible and drought resistant groups on the basis of a drought susceptibility index. In contrast to results in some other studies, Pitic 62 appeared to be somewhat drought susceptible, perhaps because of late flowering. Mean head yield:biological yield ratios (approximation of harvest index) ranged from 0.52 to 0.60 over the 5 years, and tended to be higher under moist or irrigated conditions than under dry conditions. Significant differences in preanthesis growth rates occurred in only I of the 5 years, and did not appear to be related to drought resistance or yield. There were consistent cultivar differences in stem dry weight reduction prior to maturity, but there was no obvious relationship between this trait and drought resistance. Leaf duration after anthesis was not correlated with yield or drought susceptibility index. Growth analysis is a labor intensive procedure that is unlikely to identify traits which are strongly related to drought resistance.
Inbreeding Depression, Inbred and Hybrid Grain Yields, and Other Traits of Maize Genotypes Representing Three Eras1
Authors: Meghji M. R. , Dudley J. W. , Lambert R. J. , Sprague G. F.
Published: July 2010

Improvement in the genetic worth of maize (Zea mays L.) hybrids over the years can be a consequence of increased heterosis and/or improved inbred parents. The objectives of this study were to determine the nature of the genetic improvement of maize hybrids over a period of about 40 years using a representative series of hybrids and to determine any associated changes in morphological and yield component traits. Non parental single crosses of double crosses from the 1930's and the 1950's and single crosses of the 1970's, their inbred parents, and their F, generations were grown at 31 500 and 58 800 plants/ha. The study was conducted at Urbana and Shabbona, 111. However, the inbreds were grown at Urbana only and, because of poor germination of the inbreds of the earlier decades, were grown at 31 500 and 48 800 plants/ha. The majority of the improvement in inbred and hybrid yielding ability occurred between the 1950's and the 1970's. Recent inbreds and hybrids stand better, stay green longer, and have smaller tassels than their earlier counterparts. Grain yield inbreeding depression (and heterosis) increased from the 1950's to the 1970's and a part of it is manifest at loci that condition the responsiveness of the hybrids of the 1970's to increased plant densities. Plant and ear height inbreeding depression seem to have decreased from the 1950's to the 1970's.
Phototropic Leaflet Reorientation in Alfalfa in Response to Vectorial Light1
Authors: Reed R. , Travis R. L.
Published: July 2010

The phototropic reorientation of alfalfa (Medicago sativa L.) leaflets in response to vectorial light involves a complex series of movements in which the elevational angle of the leaflets either increases or decreases, the compass direction of the leaflet midrib changes and the leaflet rotates about its midrib axis. The exact combination of movements depends upon the leaflet position on the plant and the azimuth and elevational angle of the vectorial light source. The photoreceptor for leaflet reorientation is sensitive to blue light, insensitive to red and far red light and is located in the pulvinule. The time required for leaflet reorientation was dependent upon the vectorial photosynthetic photon flux density (PPFD). At high PPFD (850 to 1600 μmol m‐2 s‐1) reorientation proceeded rapidly with the full response requiring 45 to 60 min. As the PPFD was decreased the rate of reorientation also decreased. At the lowest PPFD tested (100 μmol m‐2 s‐I) the response only occurred after a 2 h lag period but then proceeded at a rapid rate with the leaflet attaining its final position in 30 rain. Upon completion of the reorientation response the adaxial surface of the leaflet was nearly perpendicular to the light source. The final position was independent of PPFD.
Using the Kernel Milk Line to Visually Monitor Grain Maturity in Maize1
Authors: Afuakwa Joe J. , Crookston R. Kent
Published: July 2010

Maize (Zea mays L.) growers use a variety of methods to estimate the maturity status of the grain. The objective of this study was to evaluate the usefulness of the kernel milk line as a visual means of monitoring grain maturity in maize. Five hybrids were field grown at St. Paul, Minn. in 1980 and 1981. Movement of the kernel milk line was followed in these hybrids and compared to moisture loss, dry weight accumulation, and black layer development in the kernels. Four of the hybrids were also defoliated at various stages of kernel development so that kernel milk‐line movement could be characterized under conditions of prematurity stress. The milk line was always a readily‐identifiable feature of maturing kernels. Under normal conditions, disappearance of kernel milk was coincident with blacklayer development and the cessation of kernel dry weight increase (physiological maturity). However, it was easier to determine the day on which milk was no longer present in kernels than to determine when the placental region was black. Movement of the milk line was useful in “timing” the maturity process. At the half‐milk stage, (milk line positioned half‐way between the tip and the base of the kernel) kernels had achieved about 90% of their final dry weight, contained approximately 40% moisture, and were 2 to 3 weeks from the optimal date to begin harvest. When plants were completely defoliated at the half‐milk stage, the kernels accumulated 95% of normal dry weight. We recommend using both development of the black layer and milk disappearance as indicators of maturity in maize. Development of the black layer was the more reliable indicator of physiological maturity. The milk line was more useful in monitoring grain maturation prior to physiological maturity.
Inheritance of Subcrown Internode Length in a Winter Barley Cross1
Authors: Dofing S. M. , Schmidt J. W.
Published: July 2010

The inheritance of subcrown internode length was studied in a controlled environment in a winter barley (Hordeum vulgare L.) cross between the cultivars NE62203 (C.I. 15542), with a short subcrown internode, and MO B2632 (MO B475/‘Tschermak’), with a long subcrown internode. Cultivars with short subcrown internodes and, therefore, deep crowns have been observed to show less winter injury than those with shallow crowns. Segregation patterns of the F2, F3, B1s, and B2s generations were discontinuous. In each generation, a distinct group of progeny occurred in the 0.0 to 0.5 cm class, suggesting that short subcrown internode length is determined primarily by a gene(s) with major effect. An analysis among generation means detected relatively large dominant gene effects in the direction of long subcrown internode length. Neither a 3:1 monogenic ratio nor a 15:1 digenic ratio were able to sufficiently explain the observed segregation pattern. Apparently, genes with smaller effects also influence the expression of subcrown internode length. A heritability (narrow sense) estimate of 86.9% for subcrown internode length was obtained. Realized genetic advance for short subcrown internode length at 10% intensity of selection was 2.7 cm, or 77.1% of the F3 population mean. Because of the high heritability and presence of a gene(s) with major effect determining short subcrown internode length, F2 selection for short subcrown internode length should be effective.
Effect of Growth Habit of Beans on Tolerance to Competition from Maize When Intercropped1
Authors: Davis J. H. C. , van Beuningen L. , Ortiz M. V. , Pino C.
Published: July 2010

Three trials were planted at CIAT, Colombia, with selected lines of red seeded beans (Phaseolus vulgaris L.), representing the best that has emerged from breeding of each growth habit, in order to study the relationship between growth habit and competitive ability with maize (Zea mays L.) when intercropped. Treatments included sole cropping without stakes, and with stakes that varied in height from 1 m to 2 m, and intercropping with short and tall maize cultivars. Highly significant interactions of bean lines by cropping systems were found. Correlations between yields of bean lines in sole cropping without stakes and intercropped were negative or zero, whereas correlations between sole cropping with stakes and intercropping were significant and positive. Internode length increased with growth habit, from bush to climbing types, and indeterminate types were stimulated to develop more main stem nodes either by the presence of a stake or a maize plant. Climbing types (Type IV) tended be later to flowering and maturity and were more competitive with the maize than bush types. Harvest index was reduced less in the Type IV lines when intercropped with maize than in the bush lines (Types I, II, and III). In a breeding program, selection in crosses among growth habits will tend towards bush types of beans when selected in sole cropping, and climbing types in intercropping.
Mass Selection and Inbreeding Depression in Three Autotetraploid Maize Synthetics1
Authors: Lamkey K. R. , Dudley J. W.
Published: July 2010

Three autotetraploid maize (Zea mays L.) synthetics (B, CD, and OP) were evaluated to determine the effectiveness of mass selection for improved seed set and agronomic type, and to study inbreeding depression from one generation of self‐pollination. S0 populations of B(M)C0, B(M)C5, B(M)C11, B(M)C17, B(M)C21, CD(M)C0, CD(M)C3, CD(M)C7, CD(M)C11, CD(M)C14, OP(M)C0, OP(M)C4, OP(M)C8, OP(M)C12, and OP(M)C17 were evaluated in 1979 and1 980. S0 and S1 populations of B(M)C0, B(M)C11, B(M)C22, CD(M)C0, CD(M)C7, CD(M)C15, OP(M)C0, OP(M)C8, and OP(M)C18 were evaluated in 1981 and 1982. Visual mass selection improved seed set in B and OP, although a plateau appears to have been reached in the later cycles of selection. Significant increases in yield and ear height were found in B and OP, while days to flower and plant height increased in all synthetics. Inbreeding depression for seed set was small, suggesting seed set may not be the limiting factor in maintaining autotetraploid maize inbred lines that it is in other autotetraploid species. Inbreeding depression for yield corresponded to that expected based on the coefficient of inbreeding assuming the completely inbred generation has a mean of zero. Rates of inbreeding depression were similar to rates from other studies of autotetraploid maize. However, the rates of inbreeding depression for yield (g plant−1) and ear length appear to be higher in autotetraploids than in diploids. No significant differences in rate of inbreeding depression between early and late cycles of selection were found.
Radiation Levels in Growth Chambers Fitted with High Intensity Discharge Lamps, with or without Thermal Barriers1
Authors: McCree K. J.
Published: July 2010

Levels of photosynthetically active radiation that approach full sunlight can be achieved in growth chambers fitted with high intensity discharge lamps, but the high levels of photosynthetic radiation may be accompanied by abnormally high levels of nonphotosynthetic radiation. Downward irradiances of photosynthetic radiation (400 to 700 nm) shortwave radiation (280 to 2800 nm), thermal radiation, and total radiation (shortwave plus thermal), were measured in growth chambers fitted with metal halide, high pressure sodium, and low pressure sodium lamps, some with glass or plastic barriers, and some without. Ratios of photosynthetic to shortwave radiation were generally at or above those found in natural sunlight (about 0.5), but ratios of photosynthetic to total radiation were less than half of this value, in a chamber fitted with metal halide lamps and no barrier. This was due to the large flux of thermal radiation from the bulbs and fixtures. Leaf temperatures were as much as 16°C above air temperature. A plate glass barrier removed 75% of the thermal radiation, while transmitting 81% of the photosynthetic radiation and 74% of the shortwave radiation. With the barrier, leaf temperatures were close to air temperature. It is concluded that barriers are essential in chambers fitted with metal halide or high pressure sodium lamps. The low pressure sodium lamps operated at a lower bulb temperature, causing thermal radiation fluxes to be lower and leaf temperatures to be closer to air temperature, without the use of a barrier.
In Vitro Regenerative Potential of Alfalfa Germplasm Sources1
Authors: Mitten D. H. , Sato S. J. , Skokut T. A.
Published: July 2010

Regeneration capacity of 35 tetraploid alfalfa (Medicago sativa L.) cultivars representing all of the nine germplasm sources of U.S. alfalfa is reported. Approximately 20 genotypes from each cultivar were tested for regeneration using hypocotyl derived callus on a standard media sequence. ‘Ladak’, ‘Norseman’, ‘Turkistan’, and ‘Nomad’ were clearly superior sources of regenerating genotypes; however, a wide spectrum of varieties possessed genotypes that would regenerate. This information should predict sources of potential regenerators among modern alfalfa cultivars.
Osmotic Adjustment and Solute Accumulation in Two Wheat Genotypes Differing in Drought Resistance1
Authors: Johnson R. C. , Nguyen H. T. , Croy L. I.
Published: July 2010

Field observations have indicated that the winter wheat (Triticum aestivum L.) cv. TAM W‐101 is relatively drought resistant compared with the cv. Sturdy. In a growth chamber experiment, osmotic adjustment and various solutes potentially involved in osmotic adjustment were measured in leaves of TAM W‐101 and Sturdy. Plants were grown in sand culture for 28 days at 20°C with 16 h light per day (=600 μmol m‐2 s‐1). Stress treatments were then imposed by limiting water in pots for 14 days, after which water relations were determined with pressure‐volume curves on leaves of stressed plants following overnight hydration (prestressed), and on hydrated unstresssed plant leaves. Leaf solutes measured were total amino acids, proline, free sugars, and K. Prestressed leaves of both cultivars had significantly lower solute potential at full turgor (Ψfs) and zero turgor (Ψos) than unstressed leaves, indicating osmotic adjustment. But prestressed TAM W‐101 apparently adjusted more, with significantly lower values for Ψfs (−1.61 MPa) and Ψos (−2.44 MPa) compared to prestressed Sturdy (−1.40 and −1.98 MPa, respectively). The relative reduction of dry matter produced in prestressed TAM W‐101 plants did not, however, differ from prestressed Sturdy plants. Water use efficiency (WUE, mg total dry matter/g H2O lost per pot) was significantly lower in TAM W‐101 (2.27) than in Sturdy (2.55) and in prestressed (1.81) than unstressed (2.40) leaves. Tissue elasticity was also lower in TAM W‐101 than Sturdy and lower in prestressed than unstressed leaves. Nonreducing sugars increased from 15 g/kg dry wt in unstressed to 39 g/kg dry wt in prestressed (1.4%) leaves, but reducing sugars did not differ among treatments. Only amino acids, including proline, were greater in prestressed TAM W‐101 than Sturdy leaves. But calculated as ideal osmotica, amino acid concentrations were too low to explain the difference in Ψfs between prestressed cultivars. As the adaptive significance of the cultivar differences in osmotic adjustment, WUE, and tissue elasticity are clarified, selection for these factors to improve wheat drought resistance may be possible.
Variation among Sorghum Mutants Resistant to Periconia circinata (Mang.) Sacc.1
Authors: Schertz K. F.
Published: July 2010

Mutations at certain loci in sorghum [Sorghum bicolor (L.) Moench] are known to occur at high frequencies. Although mutation frequencies have been recorded and lines have been established from the mutants resistant to Periconia circinata (Mang.) Sacc., the cause of milo disease, little is known about the nature of these mutations. This study was conducted to determine if mutants with resistance to P. circinata differed from the susceptible source, ‘Colby’, in characteristics other than resistance. Field studies of 16 lines, 15 of which were from naturally occurring resistant mutants, were conducted in 2 years at College Station, TX to determine height, days to anthesis, and kernel weight characteristics. In addition to being resistant, two mutant lines were consistently different from their susceptible source in other characteristics. They were shorter, required more days from planting to anthesis, and had smaller kernels than Colby. Other resistant mutant lines differed from their source in fewer characteristics, and all except one line differed from the source in some observed characteristic. One of the two most diverse lines had yellow stripes in leaf blades and sterility. Possible explanations for these differences that occurred concurrently with mutations in disease response include pleiotropic effects of different mutant alleles and mutations at loci other than the one controlling reaction to P. circinata. These alternative hypotheses have not been tested.
Partitioning of Photoassimilates by Four Potato Clones1
Authors: Gawronska H. , Dwelle R. B. , Pavek J. J. , Rowe P.
Published: July 2010

The partitioning of photoassimilates was compared for four field‐grown potato clones. Russet Burbank was used as a standard for comparison, and the other three clones were selected because they generally produce higher yields and have higher photosynthetic rates than Russet Burbank. In this study we examined whether the patterns of assimilate partitioning change with the stage of plant development and with the time after labelling and also whether these partitioning patterns vary for different clones. The most recently‐expanded leaf on each plant was labelled with 14CO2 at three different growth stages: the beginning of tuberization, 3 and 5‐weeks later; and representative plants from each treatment were harvested at three time intervals: 2 h after labelling, 7 days after labelling, and the end of the growing season. The total quantity of 14C‐1abel exported from the exposed leaf increased beth with age of the plant and with time after labelling. The exported assimilates were partitioned in varying quantities to all plant organs, including trace amounts to the mother tubers (seed pieces). Some of the assimilates produced after tuber set and originally partitioned to other organs may have been remobilized to the tubers near the end of the season. At later growth stages, some clones delivered assimilates to the tubers more rapidly than others. The potential exists for plant breeders to combine late season maintenance of photosynthesis with rapid and/or greater delivery of assimilates to the tubers as an approach for increasing tuber yield.
Callus Initiation, Plant Regeneration, and Evidence of Somatic Embryogenesis in Red Fescue1
Authors: Torello W. A. , Symington A. G. , Rufner R.
Published: July 2010

The effects of auxin type and concentration on callus growth of two cultivars of red fescue (Festuca rubra L. var commutata Gaud. ‘Jamestown’ and F. rubra L. var trichophylla Gaud. ‘Dawson’) were evaluated and the potential for plant regeneration over extended culture periods was determined. Mature caryopses of each cultivar were dehusked, surface sterilized, and cultured for 8 weeks on one‐half strength Murashigea nd Skoog (M + S) mediumco ntaining either 2,4‐D [(2,4‐dichlorophenoxy) acetic acid], 2,4,5‐T [(2,4,5‐trichlorophenoxya)c etic acid], or NAA (a naphthaleneacetic acid) at concentrations of 10, 20, 30, or 40μM. Maximum callus induction and growth were promoted by 20 μM 2,4‐D for both Jamestown and Dawson with 2,4,5‐T being as effective as 2,4‐D for Dawson. All concentrations of NAA tested were ineffective for both cultivars. Calli of both cultivars were initiated with 20 μM 2,4‐D and were subcultured at 8‐week intervals for 24 weeks. At both 16 and 24 weeks calli were transferred to regeneration medium consisting of one‐half strength M + S media with 0.1 mg/L BA [6‐(benzylamino purine]. Plant regeneration was extremely high at both 16 and 24 weeks from Dawson callus compared to Jamestown. The majority of Dawson calli were shown to be embryogenic and were white to yellow and compact compared to the translucent, friable nonembryogenic Jamestown callus. The increased frequency and duration for plant regeneration from Dawsonca llus was attributed to somatic embryogenesis associated with embryogenic callus.
Random Intermating Before Selection in Spring Wheat1
Authors: Altman D. W. , Busch R. H.
Published: July 2010

Random intermating before selection for quantitative traits in self‐pollinated crops has been proposed to increase genetic recombination. Three populations of spring wheat (Triticum aestivum L.) from adapted single crosses were intermated (I) three cycles (I2 to I4). Thirty random lines from each cycle and from two samples of the base single cross (I0 and I1 for each population were analyzed as three separate line experiments. Bulks were composited with 75 lines from each I level for each population and included with the parents in an additional test. Correlations between traits suggested that certain shifts over I levels may have occurred. The I3 mean for grain yield based on percent of check cultivars exceeded the other I levels in one population and plant height and lodging decreased in all populations for the I3 and I4. However, the highest yielding lines from advanced intermating cycles were only similar in yield to the best lines derived from the single crosses in all populations. Comparisons of individual elite lines did not indicate multiple trait improvement, and outlier frequency for yield components did not generally change over levels of intermating. Few unidirectional changes in genetic variance estimates occurred, and no trends over I levels were detected. Hence, we conclude that random intermating within single cross populations resulted in insufficient useful recombination to justify its use as a primary breeding procedure prior to selection.
Selection for High and Low Grain Protein in Six Winter Wheat Crosses1
Authors: Guthrie D. A. , Smith E. L. , McNew R. W.
Published: July 2010

There has been a tendency for the more recent higher yielding cultivars of hard red winter wheat (Triticum aestivum L. em. Thell.) to have lower grain protein content. As a result of this, plant breeders are striving to maintain or increase grain protein levels. Six winter wheat populations involving three high‐protein (HP) and one “normal”‐protein (NP) genotypes were studied to determine the effectiveness of early generation selection for higher grain protein. The HP parents used were ‘Atlas 66’, ‘Flex’, and ‘Danne/Nap Hal’. The NP parent was KS73114. Three HP ✕ HP and three HP ✕ NP crosses were studied. Random spikes from the six F2 populations were grown as F3 head rows. Each cross was divided into four equal sized grids to reduce environmental bias on selection and 25 rows were selected from each grid to obtain 100 rows per cross. Each row was selected on the basis of acceptable agronomic characteristics and harvested. Percent grain protein was then determined by the Kjeldahl procedure. The five highest protein and five lowest protein lines per grid were then identified for a total of 20 high‐protein and 20 low‐protein lines per cross. The high‐low selections were grown as F4's in replicated tests at Stillwater, OK in 1979–1980. All crosses differed significantly for grain protein percentage between high‐protein and low‐protein selection groups, with differences ranging from 0.5 to 1.0% protein. No significant differences for grain yield between high‐protein and low‐protein groups were observed for three crosses. In two other crosses the low‐protein groups were significantly higher yielding than the high‐protein groups while the reverse was found in the remaining cross. Realized heritability estimates for grain protein ranged from 0.39 to 0.61. Phenotypic correlation coefficients of grain protein and grain yield were negative for all crosses and statistically significant, ranging from −0.32 to −0.60. The use of grids in this study resulted in an average 9.2% increase in efficiency of selection for grain protein.
CO2‐Enrichment Effects on Soybean Physiology. I. Effects of Long‐Term CO2 Exposure1
Authors: Havelka U. D. , Ackerson R. C. , Boyle M. G. , Wittenbach V. A.
Published: July 2010

Soybeans [Glycine max (L.) Merr. ‘Kent’ and ‘Ware’], grown under field conditions, were exposed to a CO2‐enriched atmosphere (1232 μL L−1) from 22 days after planting to maturity. Seed yield increased 81% in Kent and 56% in Ware in response to CO2 enrichment. Plants grown at high CO2 concentrations maintained higher rates of apparent photosynthesis and lower leaf conductances throughout ontogeny than those grown at low CO2 concentrations. Carbon dioxide‐enriched plants accumulated larger pools of soluble sugars and starch in the leaves compared with control plants. Rapid depletion of the stored carbohydrates was evident at the time flower buds were developing and flowering commenced. Carbon dioxide‐enriched plants also maintained large pools of starch and sucrose in the leaves during the grain‐filling periods, suggesting that these were not utilized for seed development. In contrast, control plants were virtually devoid of sucrose and starch at plant maturity. Examination of leaf chlorophyll, protein and proteolytic enzyme activity revealed that CO2 enrichment did not delay senescence in soybeans.
Prevalence of Phytomelanin in Pericarps of Sunflower Parental Lines and Wild Species1
Authors: Seiler G. J. , Stafford R. E. , Rogers C. E.
Published: July 2010

American sunflower breeders have not actively selected for the phytomelanin layer in breeding programs. Phytomelanin in the pericarp of sunflower (Helianthus annuus L.) achenes can be an effective mechanism for reducing yield losses due to achene injury by larvae of the sunflower moth, Homoeosoma electellum (Hulst). The objectives of the present study were to screen achenes of publicly released parental breeding lines and wild species (Helianthus spp.) for presence of phytomelanin in the pericarps and to evaluate and compare a rapid, inexpensive mechanical (scraping) test to a more time consuming, expensive chemical (potassium dichromate‐sulfuric acid) test, which served as the standard in this study. One hundred one parental breeding lines and 50 species of wild sunflower were grown during 1980–1982 at Bushland, TX. Five 20‐achene subsamples were examined from each line or wild species. Phytomelanin was present in 90% of the cms HA and HA lines, 37% of the RHA lines, and 100% of the wild species as determined by the chemical test. The mechanical (scrape) test agreed with the chemical test 92% of the cms HA and HA and 100% of the RHA and wild species cases when phytomelanin was present. There was not a significant difference between the two techniques for detecting the presence or absence of the phytomelanin layer in cms HA and HA lines as determined by Chi‐square analyses.
Inheritance of a Narrow‐Leaf Trait in Crimson Clover1
Authors: Friesner D. L. , Knight W. E.
Published: July 2010

A narrow‐leaf trait found in crimson clover (Trifolium incarnatum L.) is characterized by oblanceolate, serrate leaflets. Crosses made between narrow‐leaf and normal‐leaf plants produced normal‐leaf F1 plants. In the F2 population, an acceptable fit was found to a ratio of three normal plants to one narrow‐leaf plant. The normal F2 genotypes fit a 2:1 (segregating: nonsegregating) ratio. The heterozygous F2 plants produced normal‐leaf to narrow‐leaf plants in a ratio of 3:1. These data indicate that narrow‐leaf is controlled by a single recessive gene. The genetic symbol, nl, is proposed to designate this recessive leaf character. This characteristic would make an excellent genetic marker since it can be identified in the seedling stage.
Effects of Clipping on Growth and Physiology of ‘Merion’ Kentucky Bluegrass1
Authors: Krans J. V. , Beard J. B.
Published: July 2010

Reduced growth and vigor caused by close and frequent clipping is a common problem in turfgrass culture. The objectives of this study were to evaluate the effects of clipping on the growth and physiology of ‘Merion’ Kentucky bluegrass (Poa pratensis L.). Using a controlled environment (23°C day and 16°C night), uniculm seedlings were grown from seed in pots for an 8‐week establishment period. These plants were then cut at 2.5 and 6.2 cm at a frequency of semiweekly (3 to 4 days), weekly, and biweekly, and compared with a control that was not clipped. Plant responses to clipping were measured at 0 to 2, 2 to 4, and 4 to 6 week intervals after the first clipping. Dry weight of roots and regrowth of shoots following clipping were greater in plants frequently cut at 2.5 cm than in plants infrequently cut at 6.2 cm. Lateral stem formation (tillers plus rhizomes) was greater or similar in plants cut biweekly than semiweekly at both cutting heights. Root:shoot (sheath plus blade tissue) ratios were generally greater in plants cut semiweekly than weekly or biweekly at both cutting heights. Plants clipped frequently had in most cases greater 14C‐photoassimilate accumulation in the root and sheath fractions and less accumulation in the blade fraction than plants clipped infrequently. Rat~s of apparent photosynthesis and dark respiration per unit leaf area were generally higher in plants cut semiweekly than biweekly; whereas, these same parameters based on a total leaf area were lower in plants cut semiweekly than biweekly. Reduced growth and vigor associated with close and frequent clipping in Merion Kentucky bluegrass is attributed to loss of leaf area. Based on these findings, altering clipping frequency may be a mo:re effective means of reducing the detrimental effects of clipping in Merion Kentucky bluegrass than adjustments in cutting height.
Cytology and Reproduction of Reciprocal Backcrosses Between Pearl Millet and Sexual and Apomictic Hybrids of Pearl Millet ✕ Pennisetum squamulatum1
Authors: Dujardin Michel , Hanna Wayne
Published: July 2010

Interspecific hybrids (2n = 41) between pearl millet, Pennisetum americanum L. Leeke (2n = 4x = 28), and P. squamulatum Fresen (2n = 6x = 54) were used ~s pollen and maternal parents and backcrossed (BC) to pearl mi}let to determine the potential for germplasm exchange and for transfer of apomixis to pearl millet. Backcrosses to diploid pearl millet (2n = 14) resulted in 12 28‐ or 27‐chromosome male and female‐sterile plants from more than 600 pollinated inttorescences. Backcrosses to tetraploid pearl millet (2n = 4x = 28) resulted in 2830 BC1 progenies (crossability 91%). These BC1 progenies had somatic chromosome numbers ranging from 2n = 32 to 2n = 39 with a mode of 2n = 35 chromosomes. They were perennial and more closely resembled pearl millet in morphological characteristics than did the original interspecific hybrids. Meiosis was irregular with a mean of 4.88 bivalents. Univalents, trivalents, quadrivalents, and other multivalents were present in all microsporocytes. Eightyfour percent of these plants did not shed pollen and the remaining 16% were semi‐sterile with pollen stainability ranging up to 6.6%. Among 177 semi‐sterile BC1 plants resulting from crosses with highly apomictic F1 hybrids as pollen parents, 55 progenies showed only apomictic t:mbryo sac development. Seed set ranged from 0 to 14 seed per head under open‐pollination. Similar chromosome behavior and fertility as above were observed in progeny from reciprocal backcrosses between the sexual interspecific hybrids and diploid or tetraploid pearl millet. The production of partially male‐fertile apomictic BC1 plants should make it possible to continete gene transfer from P. squamulatum to pearl millet in succeeding generations.
Response of Tropical and Temperate Soybean Genotypes to Temperature During Early Reproductive Growth1
Authors: Lawn R. J. , Hume D. J.
Published: July 2010

Twelve soybean [Glycine max (L.) Merr.] lines of tropical and temperate origin were grown to anthesis and then subjected to a range of thermal regimes, using growth cabinets, to test their sensitivity to low temperature during early reproductive growth. Plants were grown under an 11‐h photoperiod with 30/20°C day/night, 12‐h thermoperiods prior to flowering, then during and after flowering, with all eight combinations of 20°C and 30°C day and 8, 12, 16, and 20°C night thermoperiods. There were large differential responses among lines in the sensitivity of podset to low night temperature. As a group, lines of tropical adaptation were more sensitive than temperate lines but there was variation among lines in both groups. The most sensitive (tropical) line, No. 29, failed to set pods in 8 and 12°C night temperatures while the least sensitive (temperate) line, Fiskeby V, set pods in all thermal regimes. Failure of lines to set pods in the lowest night temperatures was associated with pollen abnormalities. With the exception of Fiskeby V, there was little evidence that high day temperature compensated for the effect of low night temperature on podset. The greater sensitivity of the tropical lines to low temperature was consistent with field experience in northern Australia and it is suggested that breeding strategies for the dry (winter) season of the low latitude tropics, particularly for inland and for elevated areas, must seek to develop lines with less sensitivity to low temperature.
Mode of Inheritance and Chromosomal Allocation of Stunting Genes in Common Wheat1
Authors: Christopher D. A. , Atsmon D. , Feldman M.
Published: July 2010

Long day low temperatures (LDLT) and Ethrel (an ethylene‐releasing compound) were combined for inducing maximal expression of long‐term stunting in line 492 of common wheat (Triticum aestivum L.) and in its F1 and F2 hybrids with several normal cultivars and lines (‘Chinese Spring’, ‘Barkaee’, R.N. 228, ‘Alpha’, ‘Hazera 18’, and ‘Lakhish’). The above‐mentioned treatment was found to be most effective in inducing maximum phenotypic expression of the stunting genotypes. Most F1 hybrids were intermediately stunted in response to the treatment; hybrids with Barkaee or Chinese Spring had a normal phenotype. Analysis of F2 segregating populations indicated a difference of one dominant or incompletely dominant gene between most cultivars and line 492. A difference of two recessive stunting genes existed between the relatively late spring cv. Chinese Spring and line 492. The degree of earliness appeared to be related to the number of stunting genes. Monosomic analysis of F2 populations derived from crosses between all the monosomic lines of Chinese Spring and line 492, under the stunting inducing conditions, (i.e., LDLT with Ethrel), revealed that chromosomes 4B and 5B of 492 possessed major genes for stunting. These genes appeared to work in an additive manner, with the stronger gene on 4B. Modifiers suppressing stunting expression appeared to be located on chromosome 2A and 2B of Chinese Spring. A reduction in stunting expression was observed in the F2 populations of Chinese Spring monosomics 3A ✕ 492 and 3D ✕ 492, indicating that chromosomes 3A and 3D of Chinese Spring carried weak stunting promoters.
Calibration Transfer Between near Infrared Reflectance Spectrophotometers1
Authors: Shenk J. S. , Westerhaus M. O. , Templeton W. C.
Published: July 2010

The utilization of Near Infrared Reflectance (NIR) spectroscopy by the forage and feed industry has been limited by the requirement that each instrument be individually calibrated. One possible solution to the problem is the transfer of NIR calibrations by computer from one instrument to another. Computer programs have been developed by our laboratory to accomplish this objective. We conducted research to test this software with seven NIR scanning monochromators. Sixty sealed samples were used in the transfer process. One monochromator was chosen to be the master instrument. Calibration equations developed on it were transferred to six slave instruments. The standard errors of difference including bias (SED) among instruments for crude protein, acid detergent fiber, neutral detergent fiber, lignin, and in vitro dry matter disappearance were less than SED among laboratories for chemical analysis. Satisfactory transfer was accomplished with as few as 10 samples. Computerized transfer of equations promises to be a satisfactory alternative to individual instrument calibration.
Genotype Assay and Method of Moments Analyses of Five Quantitative Traits in a Spring Wheat Cross1
Authors: Mulitze D. K. , Baker R. J.
Published: July 2010

The purpose of this study was to evaluate the genotype assay procedure for estimating the number of genes governing quantitative traits. For comparison, numbers of genes were also estimated by applying the method of moments procedure to the same material. The genotype assay and method of moments procedures were used to estimate the number of genes controlling differences in spikelets/spike, kernels/spike, kernel weight, grinding time, and culm length between the spring wheat (Triticum aestivum L.) cultivar Cook and line NB125. A modified split‐plot field experiment with 176 F5‐derived families was conducted in each of 2 years at one location. Genotype assay analysis gave estimates of numbers of genes of 3 to 24+, 2 to 8, 2 to 8, 1 to 6, and 3 to 17 controlling spikelets/spike, kernels/spike, kernel weight, grinding time, and culm length, respectively. The method of moments gave estimates of 2 to 7, 4 to 7, 3 to 8, 2 to 9, and 6 to 10 for the same traits. Genotype‐environment interaction contributed to variation in estimates from both methods. Genotype assay was sensitive to the level of Type I error used to test for variation among grandprogeny lines while the method of moments analysis was sensitive to the method used for estimating genotypic range. A general equation for estimating gene number by the method of moments from any generation within a cross of two inbred lines was developed. The advantages of using the method of moments in later generations was discussed. The method of moments applied to later generations may often be superior to genotype assay for estimating the number of genes affecting a quantitative trait.