bluuebunny/crossref_metadata_2025 huggingface dataset:
Divergent Mass Selection for Ear Length in Maize1
Authors: Cortez‐Mendoza Hernan , Hallauer A. R.
Published: July 2010

Mass selection for increased and decreased ear length was conducted in ‘Iowa Long Ear Synthetic’ of maize (Zea mays L.) for 10 generations. Evaluation trials of the selected populations were conducted in five environments, and measurements were made for ear length and eight other plant and ear traits. The objectives of the study were to determine the direct and correlated responses for 10 cycles of divergent mass selection for ear length in Iowa Long Ear Synthetic.

Direct response to 10 cycles of divergent mass selection for ear length was asymmetrical. The predicted and realized responses for increased ear length were nearly the same. Realized response for decreased ear length, however, was twice as great as for increased ear length. It seemed that unequal gene frequencies and directional dominance of genes affecting ear length were responsible for the asymmetry observed for ear length.

The correlated responses of grain yield per plant, ear diameter, kernel depth, ear height, and days to silking also were asymmetrical. Selection response for increased ear length was not accompanied by a correlated response in grain yield per plant. Selection response for decreased ear length, however, was accompanied by a significant response for decreased grain yield per plant. A significant decrease in kernel depth with selection for increased ear length caused the lack of yield response with selection for increased ear length. Other correlated responses to selection for increased ear length were taller plants, later silking, and decreased diameter. Selection for decreased ear length resulted in shorter plants, but there was no change in days to flower, ear diameter, and kernel depth. Selection for increased ear length was not effective for increasing yield.
Relative Efficiencies of Population Improvement Methods in Corn: A Simulation Study1
Authors: Choo T. M. , Kannenberg L. W.
Published: July 2010

The relative selection gains per year of three breeding methods (mass, modified ear‐to‐row, and S1 selection) for corn (Zea mays L.) population improvement were simulated for additive and complete dominance genetic models. The character was assumed to be controlled by 20 major (genotypic value of A = 2) and 20 minor (A = 1) genes with half of the genes of each type at an initial frequency of 0.5 and half at a frequency of 0.1. Genes were independently assorted. Selection intensities of 0.05 and 0.25 (or equivalent), and heritabilities of 0.2 and 0.6 were used~ The population size was 400. The half‐sib families in modified ear‐to‐row selection were evaluated in a four‐replication trial, and the S1 progenies were tested in a 10‐plant plot with four‐replications.

Our studies indicated that S1 selection would be more efficient than the other two methods, provided that a winter nursery is used to shorten the cycle to 2 years. At the high heritability (0.6), mass selection was more effective than modified ear‐to‐row selection, but the latter was more effective under the low heritability. Genotypic variances decreased in all cases as selection proceeded, but the decrease was most rapid under S1 selection. About 14 cycles of S1 selection exhausted the genotypic variance at the high heritability and high selection intensity. The results also suggested that an S1 progeny evaluation trial with 10‐plant plots and four replications is adequate for improving population performance.
Cold Tolerance of Maize Inbred Lines Adapted to Various Latitudes in North America1
Authors: Mock J. J. , McNeill M. J.
Published: July 2010

We evaluated cold‐tolerance responses [measured by percentage emergence (30 days after planting), emergence index (an estimate of emergence rate), and seedling dry weight (sampled 42 days after planting)] of 34 maize (Zea may L.) inbred lines adapted to various latitudes in North America. Evaluations were performed in field experiments planted in early April at Ames and Algona, Iowa, in 1974 and 1976. Objectives of our study were: i) to assess genetic variability and breeding potential for improvement of cold tolerance within maize germplasm adapted to North America, ii) to study associations of cold‐tolerance traits with other plant traits (including grain yield), and iii) to examine relationships between geographical locations of origin and cold‐tolerance responses of inbred lines adapted to North America.

We observed large amounts of variability for each of the three cold‐tolerance traits. Means ranged from 27.5 to 82.9% for percentage emergence, 20.0 to 24.0 days for emergence index, and 0.33 to 1.16 dg for seedling dry weight; respective heritability estimates were 0.85 ± 0.06, 0.72± 0.06, and 0.80 ± 0.06. Genotypic correlations among the three traits were high, suggesting selection for improved cold tolerance (as an aggregate of the three traits) should be possible. Environments and genotype ✗ environments mean squares were highly significant; therefore, evaluations of cold tolerance of maize inbred lines should be conducted in more than one environment.

Correlations of all three traits with juvenile plant height and leaf number (measured in early July), 50% silk emergence, mature plant height, and grain yield usually were low. Thus, seedling cold tolerance was not associated with vegetative vigor of juvenile plants, flowering date, or mature plant height. Seedling dry weight, however, was significantly correlated with grain yield (r = 0.48**), indicating good seedling vigor was related to high grain yield.

Cold‐tolerance response generally was not related to geographical location of adaptation; however, 9 of the 10 best inbred lines were adapted to the central latitudes of the U.S. Corn Belt. Inbreds from the northern and southern regions ranked average or lower for cold tolerance. The three best cold‐tolerant inbreds were B73, (V3 x B14)‐2‐1 (both from Iowa), and Mo 17 (from Missouri). Breeding populations developed from the best inbreds in our study should contain gene complexes for good cold tolerance, plus variable flowering dates, plant heights, and grain yields.
Inhibition of Chlorophyll Synthesis by Pseudomonas glycinea1
Authors: Gulya T. , Dunleavy J. M.
Published: July 2010

Soybean (Glycine max L.) cotyledons treated with toxin extracted from culture filtrates of Pseudomonas glycinea formed significantly less chlorophyll and aminolevulinic acid (ALA), a precursor of chlorophyll, than control cotyledons. The toxin induced a comparable reduction in the percentage of ALA and chlorophyll, which suggests that chlorosis produced by P. glycinea toxin results from an inhibition of some step at, or prior to, ALA synthesis.

Toxemia‐affected trifoliate leaves of infected soybean plants were chlorotic and smaller than similar leaves of control plants. The toxin‐affected leaves did not differ significantly from control leaves in percentage of pheophytin, a chlorophyll degradation product, nor in the chlorophyll a:b ratio. Thus, chlorosis in toxemia‐affected leaves appears to be due to an inhibition of chlorophyll synthesis rather than an accelerated rate of chlorophyll degradation.
Effects of POD Removal Upon Seeds of Nodulating and Nonnodulating Soybean Line1
Authors: Openshaw S. J. , Hadley H. H. , Brokoski C. E.
Published: July 2010

Previous studies have shown that removal of developing pods from soybean (Glycine max (L.) Merr.) plants can result in prolonged nodule activity and in increased percent protein content of the remaining seeds. In order to investigate the hypothesis that the increase in percent seed protein is associated with the lengthened period of N fixation, we initiated this study in which we compared the responses of nodulating and nonnodulating lines to pod removal. Depodding increased average seed weight and percent protein and, in most cases, decreased percent oil in both nodulating and nonnodulating lines. Apparently, increases in seed size and percent protein following pod removal result from reduction of competition from other pods rather than from prolonged N fixation during pod filling.
Response to Mass Selection for Flowering Time in Meadowfoam1
Authors: Jain S. K.
Published: July 2010

A population of meadowfoam (Limnanthes alba Hartw.) was subiected to mass selection for early and late flowering time for two generations. Selected plant bulks were grown in C1 and C2 generations along with the original population (C0). The responses to selection were significant in both generations. Heritability estimates assuming random mating, ranged from 0.24 to 0.73. Flowering time involved phenotypic assortative mating, which was discussed for its effects on the herltability estimates and population structure of outbreeding species. Early flowering cultivars of meadowfoam would be desirable in a double‐cropping scheme
Effects of Powdery Mildew on Yield and Quality of Isogenic Lines of ‘Chancellor’ Wheat1
Authors: Johnson J. W. , Baenziger P. S. , Yamazaki W. T. , Smith R. T.
Published: July 2010

The effect of powdery mildew (Erysiphe graminis DC. f. sp. tritici E. Marchal) infection on yield, and milling and baking quality was determined under natural field conditions. Near‐isogenic lines of ‘Chancellor’ wheat (Triticum aestivum L.), involving at least seven independent genes for resistance to powdery mildew, were grown at College Park and Queenstown, Md. in 1974 and 1975. A regression equation was determined to predict the effects of disease severity on yield.

The severity of powdery mildew infection varied among years and locations. Chancellor yielded 34% less than the average yield of the resistant lines. Yield was negatively correlated with percent powdery mildew on the whole plant and on the flag leaf (r = ‐0.78** and −0.80**, respecively). The regression equation of yield in q/ha (Ŷ) on percent powdery mildew on the flag leaf was Y = 33.4 − 0.18 X, r2 = 0.65**. The gene in ‘Michigan Amber’ and the three Pm 3 genes were highly effective in reducing infection.

The isolines differed significantly for percent flour protein, cookie diameter, and adjusted cookie diameter when grown under severe powdery mildew infection. The lines with the highest disease rating also had the lowest flour protein content. Percent flour protein was negatively correlated with percent powdery mildew on the whole leaf and the flag leaf (r = −0.77** and −0.80**, respectively). However, severe powdery mildew infection did not adversely affect the over‐all baking quality. Milling quality (flour yield and flour ash percent) was not affected by the severity of powdery mildew infection.
Inheritance of Stem‐Nematode Resistance in Alfalfa1
Authors: Elgin J. H.
Published: July 2010

Inheritance of resistance to stem nematode [Ditylenchus dipsaci (Kühn) Filipjev] in alfalfa (Medicago sativa L.) was investigated by selfing and testcrossing 25 resistant and three susceptible clones. Progeny were inoculated with stem nematodes and resistant:susceptible segregation ratios were determined. Segregation ratios could be explained under the hypothesis that resistance was conditioned by two complementary, dominant, tetrasomically inherited genes, Sn and Sn1. In addition, segregations from earlier reports proposing possible disomic multiple‐gene inheritance schemes were reevaluated and were found to fit tetrasomic inheritance schemes.
Photosynthesis of Grass Species Differing in CO2 Fixation Pathways. I. Water‐use Efficiency1
Authors: Brown R. H. , Simmons R. E.
Published: July 2010

Panicum milioides Nees ex. Trin. and P. schenckii Hack, have lower photorespiration rates than the C3 grass, tall fescue (Festuca arundinacea Schreb.), and some anatomical characteristics similar to those of C4 grasses. Since C4 grass leaves have little detectable photorespiration, but greater apparent photosynthesis (AP) and greater water use efficiency (apparent photosynthesis/ transpiration; AP/T), comparisons were made of the photosynthetic responses to water stress in the C4 grass, guineagrass (Panicum maximum Jacq.), tall fescue, P. milioides, and P. schenckii. The latter two species have similar leaf anatomical, photosynthetic, and photorespiratory characteristics. Decreases in AP under water stress were associated with decreases in stomatal plus boundary layer conductance (k1) and mesophyll conductance (km) in all four species. In P. maximum (C4), km was greater than k1, contributing to the greater water use efficiency for this species than was the case for tall fescue in which k1 was greater than km. P. schenckii appeared to have higher AP/T than tall fescue, but lower than P. maximum. P. milioides had AP/T values between those for P, schenckii and tall fescue at near atmospheric CO2 concentrations. At low CO2, both P. milioides and P. schenckii had AP/T values higher than tall fescue and lower than P. maximum. Thus it appears that the reduced photorespiration in P. milioides and P. schenckii causes them to have water use efficiencies intermediate between C3 and C4 species.
Root and Shoot Formation from Callus Cultures of Tall Fescue1
Authors: Lowe Karen W. , Conger B. V.
Published: July 2010

The objectives of this study were to: i) initiate and maintain callus cultures of tall rescue (Festuca arundinacea Schreb. cv. Ky 31); ii) determine the frequency of root and shoot formation after different periods of subculture, iii) establish actively growing plants from these cultures. Calli were initiated from mature embryos on a modified Murashlge and Skoog (MS) medium containing 9 mg/liter of 2,4 dichlocophenoxyacetic acid (2,4‐D). After 28 days, the calli were transferred to a fresh MS medium containing 5 mg/liter of 2,4‐D and incubated for another 28 days before subculturing and testing for root and shoot formation. At this time, each callus was divided and one piece maintained on MS medium with 5 mg/liter of 2,4‐D and another piece placed on a medium with 0.5 mg/liter of 2,4‐D to test for root and shoot formation. This procedure was repeated for two additional subcultures at 28‐day intervals.

Results based on more than 800 calli showed that the frequency of calli forming roots was about 45% regardless of number of subcultures. The frequency of calli forming shoots, however, decreased with increasing number of subcultures from 9.6% for the first subculture to 3.1% for the third subculture. A similar decrease was also noted for caili exhibiting both shoot and root formation. The identity of each callus was maintained throughout the entire period from initial plating of the embryo to the final subculture. Of 150 individual calli forming shoots, only 14 did so during more than one subculture period. Only one callus source exhibited shoot formation on all three subcultures. Plantlets and actively growing plants were easily established from calli with shoot formation.
Genetic Variation in Root and Shoot Growth of Sorghum in Hydroponics1
Authors: Jordan W. R. , Miller F. R. , Morris D. E.
Published: July 2010

Thirty sorghum (Sorghum bicolor L. Moench) genotypes were grown in hydroponics and characteristics of their shoot and root growth compared to determine if genetic variability exists in the balance of growth between shoots and roots and within the crown root system. A demonstration that such variability exists is a necessary first step in systematic improvement of root systems.

All genotypes were compared relative to RTx2536, a standard common to all experiments. Comparisons were based on the ratios of leaf area (LA) to crown root length (RL) and shoot dry weight (S) to root dry weight (R), which reflect overall shoot to root balance, and on the ratio of RL to total root volume (RV) which describes the balance between crown root axes and lateral root branches. Standard breeding lines RTx7078, BTx3197, BTx378 and RTx7000 were similar to RTx2536 in all three ratio comparisons. This similarity may reflect the narrow genetic base available to breeders when these lines were developed, or similar environments during selection.

Recent breeding efforts have yielded lines which differ from standard lines as measured by the three ratios. Eight of the 30 entries had LA/RL ratios which differed from RTx2536; seven ratios were higher while only one was lower. Of the seven entries with higher LA/RL ratios, six also had higher S/R ratios. Seven entries had RL/RV ratios different from RTx2536, four entries had higher ratios, and three had lower ratios. Genotypes with low RL/RV ratios did not have more or fewer crown roots and the frequency of lateral roots was not different from RTx2536, but growth and branching of lateral roots was more extensive. We conclude that sufficient variability exists in shoot and root growth characteristics to warrant further study on the problem of systematic improvement of sorghum root systems which may allow superior crop performance in specific environments.
Heterosis and Ploidy Effects on the Growth of Alfalfa Callus1
Authors: Keyes G. J. , Bingham E. T.
Published: July 2010

The influence of heterosis and ploidy level on callus fresh weight production in alfalfa (Medicago sativa L.) was studied using diploids (2x), their isogenic tetraploid (4xCD) counterparts derived by chromosome doubling, hybrids at 2x and 4x levels, and 4x and isogenlc 8xCD materials Chromosome doubling has an inbreeding fect equivalento sewing (2 to 3 generations in 4x), thus 4xCD and 8xCD materials were partial inbreds. Both the 4xCD and 8xCD materials produced less callus than their non‐inbred 2x and 4x counterparts, respectively. A set of 4x partial inbreds obtained by two generations of conventional self‐pollination (S2) also produced less callus than the non‐inbred (S0). Among hybrids evaluated, there was no heterosis for callus production among 2x hybrids which were derived from non‐inbred parents, but there was appreciable heterosis among most 4x hybrids which were derived from partially inbred 4xCD parents. Midparent heterosis for callus production was highly significant (p = 0.01) in three of four hybrids on one medium and in fottr of six 4x hybrids on the other medium. Ploidy effects which were not confounded with the inbreeding associated with chromosome doubling were evaluated using three sets of equivalent 2x and 4x hybrids. Two of the three 4x hybrids produced several fold more callus than equivalent 2x ybrids and the differences were highly significant (p = 0.01). Heterosis and ploidy effects were found to be more pronounced on one of two media used in several experiments. The potential use of heterosis as a selective mechanism in tissue culture experiments was discussed.
Glandular Secretory System of Alfalfa Species1
Authors: Kreitner Gerald L. , Sorensen E. L.
Published: July 2010

We studied the functional secretory activity of glandular trichomes on annuals (diploid Medicago disciformis DC, tetraploid M. scutellata (L) Mill.) and perennials (diploid M. prostrata Jacq., tetraploids M. sativa L. subsp. sativa and praefalcata) to help explain plant defense against alfalfa weevils [Hypera postica (Gyllenhal)]. Light and electron microscopy were used to documenthe secretory function of erect and procumbent glands. Glands matured and secretion initiated on unelongated parts within the plant terminal. Pressure exerted by the secretion caused the cuticle to separate from the underlying cell wall, creating a subcuticular space. In erect glands, uplifting of the cuticle from the cell wall was initiated most often along common walls of adjacent secretory cells of the gland head. Procumbent glands formed a single subcuticular space in the gland apex. Photomicrographs suggested that the secretion was released by teanng or splitting of the cuticle. Only the two terminal cells of procumbent gland heads participated in the release of secretion.

The sudan stain for Hpids reacted positively with the gland exudate. Dense patches of sudanophilic material appeared on heads and stalks of glands after staining. The affinity for stain was less in procumbenthan in erect gland secretions.
Diffusion and Adoption of Semidwarf Rice Cultivars as Parents in Asian Rice Breeding Programs1
Authors: Hargrove Thomas R.
Published: July 2010

The first widely grown semidwarf cultivars of rice (Oryza sativa L.) were ‘Taichung Native 1’ (TN1), released in 1956, and ‘IR8’, in 1967. To determine the impact of new semidwarf cultivars on the genetic diversity of the world's rice crop, the International Rice Research Institute (IRRI) traced the diffusion and adoption of improved rice cultivars as parents among national breeding programs at 14 agricultural research centers in seven Asian nations from 1965 to 1975.

Sixty‐one percent of the 1965–67 crosses and 84% of the 1974–75 crosses involved at least one semidwarf parent. Crosses that involved a tall cultivar decreased. In 1965–67, 28% of the total gene pool was semidwarf and 40% tall. Ten years later, the percentage of semidwarfs almost doubled and that of talls dropped sharply. Apparently, breeders were increasingly crossing semidwarf parents to other semidwarfs.

TN1 and IR8 were the most popular gene sources in 1965–67; each was used in about 20% of the crosses. Use of TN1 and IR8 dropped to only 1 to 3% by 1974–75, while use of other IRRI semidwarfs increased significantly. But the strongest trend was the growing use of locally developed semidwarfs — from 2% of the 1965–67 crosses to 49% in 1974–75. The genetic makeup of those local semidwarf parents was traced back two generations; 76% were progeny of IR8 or other IRRI rices.

Breeders in India adopted TN1 and IR8 earlier, and more extensively, than breeders in the six other countries. By 1974–75, 75% of Indian crosses involved a local semidwarf. In the six other countries, IRRI remained the major source of semidwarf breeding material but breeders increasingly used local semidwarfs. The semidwarf indica rices largely replaced japonica, ponlai, and other races in the breeding programs.
Breeding Cicer Milkvetch for Improved Seedling Emergence1
Authors: Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.) has not been grown extensively because of its relatively poor seedling emergence. Therefore, selection for rapid seedling growth at two temperature treatments in environmental chambers and selection for rapid seedling emergence in the greenhouse were evaluated as methods for improving seedling emergence under field conditions. In the environmental chambers with a 15‐hour photoperiod, one cycle of recurrent selection was more effective at the 20 C day/15 C night than at the 25 C day/20 C night regime. Percentages of progeny in which seedling emergence was significantly higher than that of the reference were 44 and 15 for the 20/15C and 25/20C regimes, respectively. Because of concern for inbreeding depression, intercross progenies were evaluated for seedling emergence prior to the second cycle of recurrent selection. Of the intercross progenies selected, seedling emergence was significantly improved in 53% from the 20/15 C and in 17% from the 25/20 C regime.

Selection for rapid seedling emergence from a 3.8‐cm depth of planting hi the greenhouse was not an effective method for improving seedling emergence in the field. Only 8% of the selected polycross progenies were significantly better than the reference progeny. Seedling emergence was poor in polycross progenies of other populations not selected for rapid seedling growth at 20/15 C. Only about 2% of such progenies were significantly better than the reference progeny. Selection of seedlings for rapid growth in a 20/15 C environment was an effective method of improving seedling emergence of cicer milkvetch under field conditions
Senescence in Field‐grown Wheat1
Authors: Patterson Thomas G. , Moss Dale N.
Published: July 2010

We examined the senescence pattern of hard red spring wheat (Triticum aestivum L. em Thell) grown in a field environment. The upper five leaf blades and sheaths of the canopy were analyzed for chlorophyll, chlorophyll a/b ratio, protein, and free amino acids. An estimation of the photosynthetic activity of these organs was made by measuring the uptake of 14CO2. The photosynthetic activity of the canopy reached a maximum after anthesis, then declined rapidly thereafter. Lamina chlorophyll content reached a maximum at the time of full expansion and declined continuously thereafter. Sheath chloropyll followed a different pattern of accumulation and degradation than that of the lamina and declined more slowly than the lamina chlorophyll content. Chlorophyll a/b ratio of the leaf blades was found to vary with the position in the canopy, with lower blades having a declining a/b ratio and the upper leaves a constant ratio. The sheaths had a constant a/b ratio. Protein content of the leaf blades was highest at full expansion and decreased with age. Sheath protein was essentially constant over the season. Free amino acids content of both the lamina and sheaths showed a dramatic increase prior to anthesis, then declined thereafter. None of the components measured correlated well with the photosynthetic activity of the canopy. For this reason they were judged to be unacceptable as screening techniques for leaf senescence.
Genotypic Evaluation for Iron Deficiency Chlorosis in Soybeans by Visual Scores and Chlorophyll Concentration1
Authors: Rodriguez de Cianzio S. , Fehr W. R. , Anderson I. C.
Published: July 2010

A comparison was made of the effectiveness of visual scores (Vs) and concentrations of chlorophyll a (Ca), chlorophyll b (Cb), and total chlorophyll (Cab) for evaluating the response of soybean [Glycine max (L.) Merr.] genotypes to Fe deficiency chlorosis. A total of 400 entries, including breeding lines, parents, and check cultivars, were evaluated in replicated tests on calcareous soils at two locations in Iowa. Visual scores and chlorophyll concentration were determined on the first trifoliolate leaf when it was fully developed. Visual scores ranged from I, no yellowing, to 5, severe yellowing, and chlorophyll concentration in mg dm‐2 leaf area was determined by acetone extraction.

There were significant differences among entries for the four characters. Highly significant correlations from 0.97 to 0.99 were observed among Ca, Cb, and Cab. Vs had highly significant negative correlations from −0.89 to ∓0.90 with the chlorophyll concentrations on an entry mean basis. The four characters were equally effective in selecting lines with superior chlorosis resistance on the basis of simulated selection experiments. Vs would be the most efficient procedure for direct comparison of genotypes because it requires considerably less labor than chlorophyll determination. Chlorophyll determination may be preferred, however, for research studies in which an objective measure of chlorosis is needed, particularly if different environments and persons are involved.
Influence of Five Gossypium Species Cytoplasms on Yield, Yield Components, Fiber Properties, and Insect Resistance in Upland Cotton1
Authors: Meredith W. R. , Meyer Vesta , Hanny B. W. , Bailey J. C.
Published: July 2010

The influence of five exotic cotton (Gossypium spp.) cytoplasms on yield, yield components, fiber properties, and insect populations was determined at Stoneville, Miss. The five cytoplasms were G. herbaceum L., G. arboreum L., G. anomalum Wawra ex Wawra & Peyr., G. barbadense L., and G. tomentosum Nutt. ex Seem. The five cytoplasms were combined by repeated backcrossing into the following upland cotton (G. hirsutum L.) cultivars: ‘B3080’, ‘Coker 201’, ‘Delcot 277’, ‘Deltapine 16’, and ‘Stoneville 213’. The average number of backcrosses into G. hirsutum was 10.1 and into the specific cultivars, 6.5.

The characteristic most influenced by exotic cytoplasms was yield. Cytoplasm from G. arboreum decreased yield I8%, averaged for all cultivars. Exotic cytoplasms in general decreased yields, but this trend was not consistent for all cultivars. The average 1977 decrease in yield was 80, 61, 41, 17, and −5 kg/ha for Deltapine 16, Coker 201, Stoneville 213, B3080 and Delcot 277, respectively. The foreign cytoplasms had no strong deleterious effects on yield components and fiber properties.

No evidence of variations in tolerance to tarnished plant bugs (Lygus lineolaris Palisot de Beauvois) was detected in the 1977 study. In 1978 no differences due to cytoplasms were detected in numbers of tarnished plant bugs and white flies (Trialeurodes abutilonea Haldeman). However, the AD3 (G. tomentosum) cytoplasm resulted in a 70% increase in numbers of leafhoppers (primarily Empoasca spp.) and a 35% decrease in weights of 7‐day old larvae of tobacco budworm (Heliothis virescens F.).

The interaction of some nuclear genes and exotic cytoplasms was compatible for yield and significant for some pest damage. This result suggests that a back‐up cytoplasmic system could be developed to help reduce the danger of major ephiphytoties or damage by insects.
Characterization of Internal Water Relations of Rice by a Pressure‐Volume Method1
Authors: Cutler J. M. , Shahan K. W. , Steponkus P. L.
Published: July 2010

A pressure‐volume technique using a pressure chamber for measurement of water potential and its components of rice (Oryza sativa L.) leaves is described. Procedures for estimating bound water content and the volumetric moduli of elasticity and for the construction of Hofler diagrams and the relations between turgot potential and total water potential for single leaves are given. The ease of the procedure and the large number of important parameters and relations which are readily inferred recommend the technique for many applications.
Effect of Nitrogen Supply on Photosynthate Partitioning, Root Carbohydrate Accumulation, and Acetylene Reduction in Birdsfoot Trefoil1
Authors: Barta A. L.
Published: July 2010

Birdsfoot trefoil (Lotus corniculatus L.) has both low rates of N2 fixation and low levels of root total nonstructural carbohydrate (TNC) during midsummer regrowth. These observations suggest that reduced assimilate transport to roots may limit N2 fixation and consequently total plant growth. The objective of this study was to determine how rate of growth, as influenced by N supply, affected the distribution and accumulation of photosynthate during regrowth of trefoil. Nutrient solution supplied to well‐nodulated plants grown in sand was either 0 or 1 mM N (NH4NO3). Two and 4 weeks after cutting and the start of N treatments, plants were harvested and analyzed. Supplemental N caused a sharp decrease in acetylene reduction rate and a two‐fold increase in shoot dry weight 4 weeks after cutting. However, neither root dry weight nor TNC were significantly affected by supplemental N. Distribution of 14C showed reduced amounts of photosynthate accumulated in N supplemented roots at both 2 and 4 weeks after cutting. These data suggest that shoot growth of trefoil is a dominant sink for photosynthate and that photosynthate accumulation is not readily altered by N source or amount supplied. Numerous significant differences in distribution of 14C among classes of metabolites were evident only at the 2‐week harvest. More rapid metabolism of labeled sugars into other growth intermediates in N‐supplemented plants at this stage indicates that available soil N may be very important for rapid regrowth after cutting. Four weeks after cutting, when N2 fixation rates had increased several fold, distribution of 14C among various metabolites was not influenced by N source indicating little effect of N source on rate of assimilate metabolism in the plant.
Screening Soybeans for Drought Resistance. II. Drought Box Procedure1
Authors: Sammons D. J. , Peters D. B. , Hymowitz T.
Published: July 2010

The effects of progressively increasing soil moisture stress on soybean (Glycine max (L.) Merr.) plant growth rate (PGR) and leaf lamina expansion rate (LER) were studied in a greenhouse experiment. Twenty cultivars were observed through a 30‐day drought period in an effort to identify differences in drought response. Cultivars were classified as drought resistant, intermediate, or drought susceptible for each variable based on their individual response to soil moisture stress relative to the average response measured for all the cultivars in the study. Analysis of the pooled data indicated that PGR and LER were dramatically decreased under the severe soil moisture stress encountered late in the droughting period. An overall estimate of cultivar performance under drought based on this procedure suggested that one cultivar (‘Grant’) is drought resistant and two (‘Manitoba Brown’ and ‘Pagoda’) are drought susceptible. Although the results supported the hypothesis that soybean cultivars in this study differ in vegetative response to the imposed drought period, the procedure appeared to be more conservative than others cited in measuring cultivar performance under soil moisture stress since most cultivars fell into an intermediate group. Comparison of the results of this study to those of two independent studies suggests the desirability of further testing of the material in the field to fully characterize individual cultivar differences in drought resistance.
Selection for Winterhardiness in Wheat. II. Variation within Field Trials1
Authors: Fowler D. B.
Published: July 2010

Differential winterkill is a prerequisite to effective selection among winter wheat (Triticum aestivum L.) strains in field survival trials. However, when differential winterkill does occur it is usually irregular, with the result that experimental error is high. To determine the magnitude of the variability in winter stress levels experienced in field trials and to investigate methods of controlling this source of experimental error, 26 winter wheat cultivars were grown in field trials in 1973 to 1974 and 1974 to 1975 in Saskatchewan, Canada. The wide range of winter survival ability of these cultivars allowed for detection of differences in winter stress levels experienced in each trial. Based on these differences, field stress contour maps were developed. These maps demonstrated that large, rapid changes took place in the levels of winter stress experienced and emphasized the irregular pattern of these changes. The primary cause of this response was attributed to variable snow cover on the test sites. The implications of these observations in selection for winter survival potential under field conditions are discussed.
Evaluation of Vigor Tests in Soybean Seeds: Relationship of ATP, Conductivity, and Radioactive Tracer Multiple Criteria Laboratory Tests to Field Performance1
Authors: Yaklich Robert W. , Kulik Martin M. , Anderson James D.
Published: July 2010

Laboratory tests for ATP content, conductivity of seed steep water, and the multiple criteria were performed on soybean seeds [Glycine max (L.) Merr.] in 1975 and 1976. Results of laboratory tests were compared with emergence and stand data obtained from the same seed lots on two sites (sandy and heavy soil types) and three dates of planting (early, pre‐optimum, and optimum) each year. Yield data were obtained for the heavy soil type, optimum planting date.

Conductivity, leachate, and protein synthesis were laboratory test measurements that were significantly correlated with emergence for the various sites and dates of planting each year. The magnitude of the correlations was conductivity > leachate > protein synthesis. The soluble radioactive fraction from the multiple criteria test was correlated with emergence in 1975 and ATP content and water uptake were correlated with emergence in 1976. Conductivity/gram seed wt. gave the highest correlations both years (r ≥ 0.670).

Correlations of the laboratory tests by cultivar with field emergence showed differences both years. For the conductivity test, ‘Essex’ in 1975 and 1976 and ‘York’ and ‘Adelphia’ in 1976 gave non‐significant correlations. Leached radioactivity from the multiple criteria gave similar results with ‘Beeson’ and ‘Wayne’ being the only two cultivars giving significant results both years. Overall correlations between conductivity and leachate showed significance in 1975 but not in 1976. Correlations by cultivar demonstrated significance in 1975 but not in 1976 with Essex showing no significance either year. Resuits are discussed in reference to possible genetic dif. ferences, sample size, and year to year variation.
Genetic Variability for Seedling Root Numbers in Wild and Domesticated Wheats1
Authors: Robertson B. M. , Waines J. G. , Gill B. S.
Published: July 2010

Genetic variability for seedling root number within the genus Triticum was characterized to determine if this trait could be used in wheat breeding. Average seedling root numbers were determined in the laboratory for 143 accessions of wheat including the diploid species Triticum boeoticum Boiss., T. monococcum L., and T. urartu Tum.; the tetraploid species T. araraticum Jakubz., T. dicoccoides Körn., T. turgidum L. var. dicoccon Schrank and var. durum Desf., and T. timopheevi Zhuk.; the hexaploid species T. aestivum L. var. aestivum, vat. compactum, var. macha, var. spelta, var. sphaerococcum. and var. vavilovii, and T. zhukovskyi Men. & Er. Significantly differently mean root numbers were found within each ploidy level and, in most cases, within each species or variety. The highest mean root number, 6.45, was found in an accession of T. turgidum var. durum, the lowest, 2.50, in accession of T. araraticum. Seed weight was positively correlated with mean root number (r = 0.71) but within each ploidy level accessions having similar seed weights and significantly different mean root numbers were found. Progeny tests of 15 diploid and seven tetraploid accessions showed that seedling root number was stable from one generation to the next. A test of 33 of these accessions and progeny in a greenhouse experiment showed this trait was stable (r = 0.91) across the two environments tested.

Embryos sectioned by hand showed that all accessions tested had about five seminal root primordia present. In general, greater seedling root number may be selected for by selecting for higher seed weight, but exceptions to this rule were observed.
Effect of Increasing Foliage Reflectance on Yield, Growth, and Physiological Behavior of a Dryland Cotton Crop1
Authors: Moreshet S. , Cohen Y. , Fuchs M.
Published: July 2010

The effect of kaolin reflectant sprays on the yield, physiological activity, and growth of ‘Acala SJ‐2’ dryland cotton (Gossypium hirsutum L.) was studied during 2 successive years in separate field experiments. In the first experiment the treatment increased yield by 12.6%. In the second experiment a significant increase in the number of flowers resulted from the kaolin spray, but subsequent high rates of abscission prevented this spray from producing a significant increase in yield.

The reflectant sprays decreased the rate of 14CO2 uptake due to a reduction in light absorption. A reduction in epidermal conductance due to partial physical blockage of the stomata was believed to cause the slower decrease in xylem leaf water potential which followed reflectant treatment. Plant growth, characterized by the stand's height, leaf area index, and dry weight, was not significantly affected.
Natural Resistance to Thrips Injury in Cotton as Measured by Differential Leaf Area Reduction1
Authors: Quisenberry J. E. , Rummel D. R.
Published: July 2010

Ten entries of cotton (Gossypium hirsutum L.) were evaluated for 2 years to measure their relative resistance to injury from thrips (Thripidae). Resistance was measured as the percentage of leaf area reduction associated with thrips damage. Leaf area was determined three times at weekly intervals during each year.

Pilose (H2) was associated with a high level of resistance to thrips. Other morphological traits such as Okra‐leaf shape (L°), Red plant color (R1), glandless (gl2, gl3), nectariless (ne1, ne2), or smooth leaf (Sm1, Sm2) did not provide the plant with resistance. Significantly less leaf area damage occurred on the pubescent ‘Tamcot SP‐37’ cultivar than on the glabrous ‘Tamcot SP‐21’ cultivar.
Collection and Evaluation of Avena Fatua for Use in Oat Improvement1
Authors: Rines H. W. , Stuthman D. D. , Briggle L. W. , Youngs V. L. , Jedlinski H. , Smith D. H. , Webster J. A. , Rothman P. G.
Published: July 2010

More than 2,200 samples of the wild oat (Avena fatua L.) were collected from western North Central U.S. as part of a program to preserve natural variant populations of this species and to further evaluate its potential as a germplasm source for the improvement of cultivated oats (A. sativa L.). This report summarizes the results of screening these samples for tolerance to barley yellow dwarf virus (BYDV), resistance to cereal leaf beetle (Oulema melanopus L.), and resistance to oat stem rust (Puccinia graminis Pers. f. sp. avenae Eriks. and E. Henn.), plus analyses of groat protein and amino acid composition.

High level tolerance to BYDV was identified in 34 of 483 samples tested. Tolerance appeared to be more frequent among samples collected in areas with a higher incidence of disease. Low level resistance to cereal leaf beetle was observed in 20 of 400 samples. The occurrence of resistance was unrelated to the incidence of the beetle. No resistance to the highly virulent race 94 of oat stem rust was identified in more than 1,600 samples tested. Groat protein levels ranging from 16.7 to 27.1% were observed among 723 A. fatua samples analyzed, whereas amino acid profiles of 70 A. fatua samples tested were similar to those reported for cultivated oats. The A. fatua collection described in this report not only provides potential new sources of BYDV tolerance and high groat protein percentage but also constitutes a valuable germplasm reservoir.
Variability in Flower‐Bud Gossypol Content and Agronomic and Fiber Properties within the Primitive Race Collection of Cotton1
Authors: Dilday R. H. , Shaver T. N.
Published: July 2010

Forty‐one accessions from the “race” (Texas race stock) collection of cotton, Gossypium hirsutum L., were grown in Tuxpan, Veracruz, Mexico and analyzed for flowerbud gossypol content and agronomic and fiber properties. The selected accessions are from diverse points of origin and represented four distinct growth types (“races”). Flower buds were harvested seven times from November 1974 to March 1975 and seedcotton was harvested in April 1975. Terpenoid aldehyde percentages (including gossypol) from flower buds harvested on the fourth date were significantly higher than from those harvested at other dates. The highest mean terpenoid aldehyde percentages were shown by Texas 766 (T‐766; 1.33%), T‐197 (1.29%), T‐663 (1.27%), T‐805 (1.23%), T‐1150 (1.20%), and T‐216 (1.15%). Nineteen accessions produced significantly higher percentages (≥ 0.88%) than the check, Stoneville 213 (0.74%), and 12 accessions showed levels above 1.0%. Seven accessions showed significantly lower levels (≤ 0.60%) than the check. Correlation coefficients between terpenoid aldehyde percentages and both boll size and seed index were negative and significant, but correlations between terpenoid aldehyde percentages and seed/locule, lint index, lint percentage, and micronaire were not significant. However, two of the six accessions (T‐197 and T‐216) that produced the greatest terpenoid aldehyde contents from flower buds had significantly larger bolls, more seed/locule, and higher seed index than the others. These two accessions and T‐805 had a higher lint index, and T‐216 and T‐805 had a significantly higher lint percentage than the other high terpenoid entries in the test. Thus, we selected good combinations of terpenoid aldehyde percentages and agronomic and fiber properties in spite of certain negative correlations.
Haploid Plants by Anther‐Panicle Culture of Tall Fescue1
Authors: Kasperbauer M. J. , Buckner R. C. , Springer W. D.
Published: July 2010

Haploid plants were cultured from ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.). Field‐grown plants were cut at the soil surface when the panicles showed about 3 cm above the flag leaf. The plants were kept in a flask of tap water and preconditioned in darkness at 5 C before cultures were made. Florets attached to about 2.5 cm of panicle tissue were cultured on modified Murashige and Skoog medium containing 2 mg of 2,4‐dichlorophenoxyacetic acid (2,4‐D)/liter. The panicle segments served as nurse tissue. Loose proliferations of cells emerged from several anthers after about 5 weeks. Some plantlets became apparent at about 7 weeks. More than 30 green plantlets formed. There were no albino plantlets. Examination of metaphase cells in root and shoot tips showed that 22 of the 23 plants examined had the haploid chromosome number, n = 21. The plants grew vigorously after transfer to pots in a plant growth chamber.
Response of Oats to Atrazine1
Authors: Brinkman M. A. , Langer D. K. , Harvey R. G. , Hardie A. R.
Published: July 2010

The popularity of atrazine [2‐chloro‐4‐(ethylamino)‐6‐ (isopropylamino)‐s‐triazine], a persistent corn (Zea mays L.) herbicide, has caused problems for oats (Avena sativa L.) grown in rotation with corn. Despite frequent inquiries about the response of oats to atrazine, very little testing for cultivar differences to atrazine has been conducted. Therefoxe, the objective of this study was to evaluate the response of current oat genotypes to atrazine.

Twenty oat genotypes were evaluated for response to atrazine for 2 years. Five atrazine treatments, 0, 1.12, 2.24, 3.36, and 4.48 kg/ha, were applied postemergence to corn land during each of the years prior to growing the oats. Atrazine damage to oats grown in 1976 was light because of wet conditions during the last half of 1975, while damage to oats grown in 1977 was more severe because of dry conditions during the last half of 1976.

Grain and straw yield responses of the genotypes were evaluated on the combined data from the 2 years of testing with a regression procedure. Tolerant genotypes were expected to have a high mean and a regression coefficient less negative than −1.0, while intolerant genotypes were expected to have a low mean and a regression coefficient more negative than −1.0. There was significant genetic variability for grain yield response to atrazine. Froker, Lang, Mackinaw, X2078‐1, and X1839‐1 were more tolerant of atrazine than Dal, Lyon, Otee, and Allen. There also was significant variability for straw yield response to atrazine, but grain and straw yield responses (regression coefficients) were not significantly correlated. Straw yield response to atrazine was closely associated with plant height.

The influence of atrazine on kernel quality was evaluated in a subset of eight genotypes. Groat protein percentage was increased by higher levels of residual atrazine, but groat protein yields were reduced because of the grain yield reductions. Groat percentage and 100‐seed weight were not reduced in 1976 when atrazine damage was light, but both were reduced in 1977 when damage was severe.

Although there was significant genetic variability for response to atrazine among the 20 genotypes tested, the variability probably is not sufficient to warrant intercrossing them in an effort to develop genotypes with improved tolerance. A thorough search of the World Oat Collection for more tolerant genotypes is recommended.