bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Genetic Transfers from Aegilops squarrosa L. to Hexaploid Wheat1
Authors: Gill Bikram S. , Raupp W. J.
Published: July 2010

Methodology of direct genetic transfer from diploid Aegilops squarrosa L. (2n = 14) to cultivated wheat (Triticum aestivum L.) (2n = 42) was explored as a possible applied plant breeding technique for rapid introgression of useful traits. One or more plants of 31 accessions of A. squarrosa (selected for resistance to certain pests of cultivated wheat) were crossed with ‘Wichita’ or ‘Newton’. A total of 219 hybrid embryos were cultured on a synthetic medium to overcome interploidy hybrid embryo‐endosperm incompatibility. Of the 219 embryos, 114 from crosses involving 17 accessions did not grow and were lost. However, one or more hybrids were obtained from crosses involving the 14 other accessions, and 24 F, hybrids were grown to maturity. The F,s were male sterile, but backcross (BC) progenies included fully fertile and meiotically stable 42‐chromosome plants. The partially fertile BC1 plants had a chromosome number range of 40 to 50; 50% with 2n = 40 to 42 and another 50% with 2n = 49 to 50; the latter arose from the functioning of restitution gametes. The probability of transfer of A. squarrosa genes from an F1hybrid to a single BC1 plant is 0.75. The BC1 and BC2 progenies segregated for several phenotypic traits and several lines with resistance to Hessian fly (Mayetiola destructor Say) biotype D, greenbug (Schizaphis graminum Rond.) biotype E, and leaf rust (Puccinia recondita Rob. ex Desm. f. sp. tritici) culture PRTUS6 were selected. Thus, the use of the embryo rescue method facilitated direct genetic transfers from A. squarrosa to hexaploid wheat, and thereby averted the need of using bridging species or prior synthesis of T. turgidum/A. squarrosa amphiploids to overcome interspecific cross‐incompatibilities.
Effect of Root System Genotype and Nitrogen Fertility on Physiological Differences between Burley and Flue‐Cured Tobacco. I. Single Leaf Measurements1
Authors: Crafts‐Brandner S. J. , Leggett J. E. , Sutton T. G. , Sims J. L.
Published: July 2010

Burley and flue‐cured tobacco (Nicotiana tabacum L.) cultivars differ in several phenotypic and chemical characteristics. This study was conducted to characterize differences between representative burley and flue‐cured cultivars and to determine the root system influence on shoot physiology. Control and reciprocally grafted plants of burley ‘Ky 14’ and flue‐cared ‘Speight G 28’ were grown in the greenhouse at two levels of N fertilization. Leaves were sampled from 10 days before to 30 days after topping (DAT). At both N levels, the genotype of the root system did not influence any of several parameters measured. This result was clearly indicated by total shoot dry weights that, at the final sampling, were higher at both N levels for G 28 shoots regardless of the genotype of the root system. Chlorophyll concentration was consistently higher for G 28 compared to Ky 14 at both N levels. At high N, CO2 exchange rates were similar and declined over time for both tobacco types. At low N, however, higher CO2 exchange rates were maintained for G 28 compared to Ky 14 until 20 DAT and this result appeared to be due in part to a differential decline in Rnbisco concentration. Leaf expansion and dry weight accumulation were decreased, and specific leaf weight increased by the low‐N treatment. For Ky 14, but not G 28, low N resulted in cessation of leaf expansion and dry weight accumulation after 20 DAT. For the high‐N treatment, G 28 accumulated leaf dry weight to a greater extent than Ky 14, and at both N levels G 28 had significantly greater specific leaf weight than Ky 14. The results indicated that the burley cultivar was more sensitive to Iow‐N fertility than the flue‐cured cnltivar, and the root system was not a factor in the expression of physiological differences observed in the shoot.
Harvest Date and Sucker Control Method on Maryland Tobacco1
Authors: Bruns H. A.
Published: July 2010

Adverse weather and other factors can sometimes delay the harvest of Maryland tobacco (Nicotiana tabacum L.). A study was conducted in 1984 and 1985 to evaluate the combined effects of five sucker control methods and delayed harvest. The sucker control methods used were: (i) topped‐hand suckered (THS); (ii) Royal 30 (KMH) (K salt of 1‐2‐dihydro‐3,6‐pyridazinedione‐maleic hydrazide); (iii) Prime + (P+), (2‐chloro‐N‐12,6‐dinitro‐4‐(trifluoromethyl) phenyl]‐N‐ethyl‐6 flurobenzenemethanamine); (iv) Bud (BN) (isopropyl N‐(3 chorophenyl) carbamate); and (v) Off Shoot T‐85 (OST‐85) (l‐decanol plus 1‐octanol mixture). Harvest dates were 2, 3, 4, and 5 weeks after topping. Chemical sucker control treatments produced higher yields and value per hectare than handsuckered treatments. The OST‐85 and P+ treatments were highest in yield and value at 5 weeks, apparently due to more growth of the upper leaves. Differences were noted for leaf chemical and physical properties and for effectiveness of sucker control among sucker control methods. No significant differences among harvest dates were noted for yield, value, and total N. Year × harvest date interactions occurred for burn duration and filling capacity. A significant increase in total alkaloids occurred with delayed harvest.
Effects of Monocropping Resistant and Suspectible Soybean Cultivars on Cyst Nematode Infested Soil1
Authors: Hartwig E. E. , Young L. D. , Buehring N.
Published: July 2010

Studies of soybean [Glycine max (L.) Merr.] cultivar sequence and use of nematicides were conducted on a soil uniformly infested with the soybean cyst nematode (SCN), Heterodera glycines Ichinohe. Assumption that new races of SCN would develop rapidly if only SCN resistant cultivars were grown had led to specific recommendations that SCN resistant cultivars not be grown > 2 yr without rotating with a SCN susceptible cultivar or a nonhost crop. No field data were available to support the recommendation. This study was initiated in 1976 to more critically evaluate the effects of SCN on soybean productivity in a long‐term monocropping program. Resistant to SCN race 3, ‘Centennial’, and one that is susceptible, ‘Tracy’, were grown continuously with and without a nematicide. The nematicide treatment was dropped after 6 yr. The two cultivars were also grown in a sequence of 2 yr of Centennial and 1 yr of Tracy and in a blend of 80% Centennial with 20% Tracy. A breeding line resistant to SCN races 3 and 4 constitutedhn additional treatment. Sorghum [Sorghum bicolor (L.) Moench.] replaced the nematicide treatment in the seventh or seventh and eighth years to be followed by Tracy. Nematicide treatment did not enhance seed yield for either the susceptible or the resistant cultivar. No treatment was superior to growing the SCN race 3 resistant cultivar Centennial continuously over the 10‐yr period. No advantages were determined for including a SCN susceptible cultivar in the program. Beginning with the third year of this study and seventh year of continuous soybean production, the SCN population appears to have stabilized at a low level.
Response to Full‐Sib Selection in Four Medium Maturity Maize Populations1
Authors: Pandey Shivaji , Diallo A. O. , Islam T. M. T. , Deutsch J.
Published: July 2010

The International Maize and Wheat Improvement Center uses full‐sib (FS) family selection based on internationally replicated trials to improve several tropical maize (Zea mays L.) populations. Improvements made in four medium maturity tropical maize populations are reported here. Selection from CO to C1 in ‘ETO Blanco’ (EB) and ‘Antigua‐Republica Dominicana’ (ARD), and from C0 C2 in ‘Blanco Cristalino‐l’ (BC) and ‘Mezcla Amarilla’ (MA), involved formation of 250 FS families in one season, and their evaluation in three to six environments in the second season in a 16 ✕ 16 simple lattice design using 40% selection intensity. Additional cycles of selection involved selection among and within FS families using a 2‐yr four‐season system; evaluation and selection of families were done as above, superior S1 plants of the selected FS families were bulk‐sibbed, and the resulting half‐sib families used to develop FS families for subsequent cycles of selection. The C0, C2, and C5 of BC and MA, and CO, C1, and C4 of EB and ARD were evaluated in seven environments to measure progress from selection. Gains per cycle (%) averaged over populations and environments for yield, days to silk, plant height, ear height, ear rating, and ears per plant were 2.11** (significant at the 0.01 probability level), −0.31**, −0.26**, −0.47**, −1.35**, and 1.05**, respectively. The regressions of entries on environmental means generally did not differ significantly from 1.0, indicating stability in the performance of the materials for yield, days to silk, and plant height. Our results indicate that FS selection is an effective method to improve tropical maize populations for the six traits studied.
Measuring Seed Yield in Soybean Populations Segregating for Male Sterility1
Authors: Nelson Randall L.
Published: July 2010

Using genetic male sterility to facilitate intermating in a recurrent selection scheme requires that either the male‐sterile allele be removed from the population before yield testing or that the effects of male‐sterile plants be known and considered in evaluating seed yield. This study was conducted to determine the effect of male‐sterile plants on seed yield and to test methods of estimating the yield of fully fertile plots from data collected on plots segregating for male sterility in soybean [Glycine max (L.) Merr.] populations. Nine F2 populations were grown in both hill and row plots. Each population was tested with and without segregation for genetic male sterility. Plots were established, in a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudolls) in 1981 and a Drummer silty clay loam (fine‐silty, mixed, mesic Typic Haplaquolls) in 1982. Data were collected on maturity, seed yield, and number of fertile and sterile plants. The yield of plots segregating for male sterility was adjusted by four procedures: (i) mean yield of fertile plants ✕ total number of plants, (ii) plot yield divided by 0.75, (iii) least square means (LSM) calculated using total number of fertile plants as a covariate, and (iv) LSM calculated using total number of fertile plants and total number of plants as covariates. Seed set was very low on male‐sterile plants and the presence of male sterility significantly reduced yield. Methods of adjusting the yield of plots with male‐sterile plants were more successful with hill plots than with row plots. The presence of male sterility is a complicating factor in measuring seed yield and the statistical procedures tested did not successfully remove the detrimental effect of barren or near‐barren plants.
A Comparison of Rhizobial Strain Compatibilities of Glycine max and its Progenitor Species Glycine soja1
Authors: Devine T. E.
Published: July 2010

Glycine soja Seib. and Zucc. is considered the wild progenitor species from which the domesticated soybean [G. max (L.) Merr.] was developed. Glycine soja hybridizes readily with G. max and is a source of agronomically valuable genes for introgressing into G. max. Such introgression could result in concomitant introgression of genes controlling rhizobial symbiosis. Because little is known of the nodulation response of G. soja with U.S. rhizobial strains, we tested Asiatic G. soja plant introductions for nodulation response with bradyrhizobial strains USDA 7 and USDA 61 isolated from the USA. For comparison, Asian plant introductions of G. max were also tested. Seed of 537 lines of G. soja and 691 lines of G. max originating from China, Japan, Korea, and USSR in Maturity Groups OO thru ✕ were evaluated for nodulation response. Five seeds of each line were decontaminated in 50% ethyl alcohol, planted in vermiculite in growth trays, inoculated with 4‐ to 7‐day‐old broth cultures of rhizobia, and grown in the greenhouse for 4 to 5 weeks. then, roots were extracted and nodulation response was determined by visual examination. Both G. soja and G. max were polymorphic for effective vs. ineffective nodulation with both strains of bradyrhizobia. This suggests that polymorphism existed in G. soja prior to domestication of G. max and that G. max was domesticated from a polymorphic population of G. soja. The frequency of ineffective nodulation in G. soja with both strain USDA 7 (10.9%) and USDA 61 (63.4%) was higher than in G. max (2.4%, 26.4%, respectively). Therefore, use of G. soja in breeding programs could increase the probability of ineffective nodulation with these bacteria in derived lines. The marked difference in the nodulation incompatibilities between G. soja and G. max from Korea suggest that the G. max introductions were not domesticated from the G. soja lines from Korea and that there has not been a substantial introgression of genes controlling nodulation from Korean G. soja into Korean G. max.
Inheritance of an Ethyl Methanesulfonate‐Induced Dwarf in Soybean and Analysis of Leaf Cell Size1
Authors: Werner B. K. , Wilcox J. R. , Housley T. L.
Published: July 2010

A dwarf soybean [Glycine max (L.) Merr.] mutant designated MS2060 was found after treatment of seeds of C1421, a backcross‐derived strain of ‘Adelphia’, with ethyl methanesulfonate (EMS). Dwarf plants were much smaller than C1421 plants in all measured characteristics and the leaves were somewhat lighter green in color. The MS2060 line was crossed with C1421 and the resulting F1 plants were intermediate in height between the parents, indicating that the controlling gene showed no dominance. The gene in MS2060 was shown to be nonallelic to the ‘Lincoln’ dwarf (df2), ‘Adams’ dwarf (df3), ‘Hark’ dwarf (df4), and T263 (df5) genes, and was independently inherited with respect to each. The designation, dr6, is assigned to this gene. The gene is maintained as line T286 in the USDA Soybean Genetic Type Collection at Urbana, IL. Mean leaf area of both MS2060 and C1421 plants was compared as was the mean area of leaf epidermal cells from the lower surfaces of these leaves. Cells of MS2060 were 76% smaller than C1421 cells, while MS2060 leaves were 80% smaller than C1421 leaves. The number of epidermal cells per leaf was not significantly different for the two strains, indicating that the difference in leaf size was primarily due to a difference in cell size.
Yield and Quality of Forage from Orchardgrass selected for Resistance to Purple Leaf Spot1
Authors: Oberheim Robert L. , Berg Clyde C. , Sherwood R. T. , Zeiders K. E.
Published: July 2010

The development of forage species with resistance to leaf diseases appears to be the only feasible method of limiting yield and quality losses. Our goal in this study was to determine if forage yield and quality were inadvertently changed during three cycles of recurrent phenotypic selection in orchardgrass (Dactylis glomerata L.) for resistance to purple leaf spot (caused by Stagonospora arenaria Sacc.), and to determine if variability existed within the third cycle for yield and quality traits. Twelve disease resistant half‐sib families from Cycle 3 were compared with a composite of the original entries (Cycle 0), with a composite of Cycle 3, and with two commercial cultivars in broadcast seeded plots harvested three times in 1982 and twice in 1983. Very little purple leaf spot occurred in the plots. Averaged over 2 yr, Cycle 3 was later in maturity than Cycle 0 (P<0.01), and Cycle 3 had slightly lower protein content (P<0.05) at first harvest than Cycle 0. Although ranges were usually small, significant differences were found among half‐sib families for crude protein (CP), in vitro dry matter disappearance (IVDMD), acid detergent fiber (ADF) at first and second harvests, and neutral detergent fiber (NDF) at first harvest (averaged over years). Significant differences were found among half‐sib families at the third harvest in 1983 for CP, IVDMD, ADF, and NDF. Half‐sib families varied in dry matter yield only for the first harvest. When entries differed significantly, the yield, CP, or IVDMD of one to several resistant half‐sib families equalled or exceeded that of Cycle 0, Cycle 3, or the cultivars. Breeding for resistance to purple leaf spot did not result in appreciable changes in the traits measured. However, the selected population contained some genetic variability for each quality trait.
Gene Locations for Flour Quality in Winter Wheat Using Reciprocal Chromosome Substitutions1
Authors: Zemetra R. S. , Morris R. , Mattern P. J. , Seip L.
Published: July 2010

Superior flour quality is one of the prime objectives in the development of hard red winter wheat (Triticum aestivum L.) cuitivars. Therefore, information on the cytogenetic control of this trait would benefit plant breeding and genetic programs in wheat. Reciprocal sets of chromosome substitution lines in duplicate between the cultivars Wichita and Cheyenne were used to identify chromosomes carrying genes for glutenin protein, and flour mixing time and mixing tolerance. The duplicate 2B lines and one 3B line of Cheyenne in Wichita were not included in this study due to insufficient backcrosses. Seeds from nonrandomized plantings of the lines at Yuma, AZ were analyzed for glutenin banding patterns using sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE). The only lines showing significant differences from the recipient cultivar were those involving group 1 chromosome substitutions and one duplicate of Wichita 6B in Cheyenne. Cheyenne group 1 substitutions in Wichita had glutenin bands at 41 kilodaltons (kd)(1A), 62 (1B), and 32 kd (1D). The corresponding bands for Wichita group 1 substitutions in Cheyenne were 40 kd (1A), 59 kd (1B), and 33 (1D). In addition, Wichita chromosome 1B in Cheyenne carried pair of bands at 47 kd that had no apparent corresponding bands for the Cheyenne 1B in Wichita line. One of the duplicates of Wichita 6B in Cheyenne had banding patterns for both Cheyenne 1B and Wichita lB. The same reciprocal substitution lines and recipient cultivars were planted in the field at Lincoln, NE, using a randomized comlete block design. Seeds from two replications were milled and flour mixing time was determined by mixograms. Flour mixing tolerance was evaluated from a standard set of curves developed at the University of Nebraska. There were no significant differences in grain protein percent between Cheyenne and Wichita, but Cheyenne had a longer flour mixing time and a greater flour mixing tolerance. The number of Cheyenne substitutions in Wichita having significant effects on flour mixing time and mixing tolerance was over four times the number of the reciprocal set. Reciprocal differences in mixing time occurred with chromosome lB. Both duplicates of Cheyenne 1B and 7B substitutions into Wichita gave significant increases in mixing tolerance over Wichita. It appeared that chromosome 1B carried major genes for quality differences between the two cultivars. The difference in glutenin banding patterns for this chromosome may be useful as a tool to screen for improved flour quality.
Reciprocal Differences in Bee‐Pollinated Alfalfa Strain Crosses as an Indicator of Crossing Patterns and Aids to Selection1
Authors: Rummey Jeff , Kimmell Jeff , Melton Bill , Currier Cliff
Published: July 2010

Strain crosses have shown potential as a method of incorporating multiple‐pest resistance into alfalfa (Medicago sativa L.) cultivars. Another application of strain crossing is to produce populations for further selection. Bee‐pollinated strain crosses increase the complexity of pollination patterns and decrease predictability as compared with hand‐pollinated strain crosses. This study was conducted to evaluate differences between reciprocal strain crosses as an indicator of percent crossing and to compare levels of resistance in reciprocal strain crosses with parental sources as an aid to selection. The parental sources and reciprocal strain crosses were evaluated for resistance to two diseases, one insect, forage yield, and fall dormancy. Approximately 90% of the reciprocals of strain crosses were significantly different for pest resistance and fall dormancy. This was attributed to crossing within parental sources. Level of pest resistance in reciprocals was approximately halfway between the midparent value and the parental source that would be expected if crossing between parental sources was 50%. This level of crossing between parental sources would significantly reduce the size of the required population for selection. Forage yields of reciprocal strain crosses were similar.
Population Development for the Selection of High‐Yielding Soybean Cultivars with Resistance to Iron‐Deficiency Chlorosis1
Authors: Hintz R. W. , Fehr W. R. , Cianzio S. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] genotypes with an exceptionally high level of resistance to iron‐deficiency chlorosis on calcareous soil have been developed by recurrent selection. The objective of this study was to compare alternative strategies for the use of the highly resistant genotypes as parents in developing populations from which high‐yielding cultivars with chlorosis resistance could be selected. Single‐cross populations were developed by mating two highly resistant genotypes with three high‐yielding, chlorosis‐susceptible lines. The F2‐derived lines from each single cross were evaluated for chlorosis resistance on calcareous soil in the field, and the superior ones from each population were backcrossed to the high‐yielding parent. The F4‐derived lines from the single‐cross populations and BC1F3‐derived lines from the backcross populations were evaluated for seed yield on noncalcareous soils and for chlorosis resistance on calcareous soil. The backcross populations had a higher mean yield and a lower level of chlorosis resistance than did the single‐cross populations. Seven percent of the lines in the single‐cross populations and 1% of the lines in the backcross populations were equal to the highly resistant parents for chlorosis resistance. An average of 36% of the lines in the single‐cross populations and 43% of the lines in the backcross populations had a seed yield not significantly different from the recurrent parent and chlorosis resistance not significantly less than a check cultivar with acceptable resistance. Phenotypic correlations between the yield of lines on noncalcareous soil and their chlorosis resistance on calcareous soil were not significant in half of the populations and were negatively associated (p<0.01) in the other populations. The negative correlations indicated either that there was no physiological association between the traits or that the association was favorable for the selection of high‐yielding lines with chlorosis resistance.
Influence of Grind and Gravimetric Technique on Dry Matter Determination of Forages Intended for Analysis by near Infrared Reflectance Spectroscopy1
Authors: Windham W. R.
Published: July 2010

Accurate chemical analysis of calibration samples is critical for successful analysis of forage by near infrared reflectance spectroscopy (NIRS). An important component of accurate chemical analysis is dry matter (DM) determination. Variability in DM determination will produce inaccuratestimates of not only DM, but all chemical components when expressed on a DM basis. An additional factor that may influence the accuracy of DM determination of forages intended for analysis by NIRS is Udy cyclone grinding. The objectives of this study were to determine the difference in DM values and precision of the estimate due to hot weighing without desiccation or cool weighing with Drierite (Hammond Drierite Co., Xenia, OH) desiccation, and the effect of regrinding Wiley milled samples through the cyclone mill on DM estimates during sample preparation for NIRS analysis. Fifty forage samples that had been preserved by either oven drying, freeze drying, or sun‐caring were used in the study. The samples were Wiley milled (1 mm) and Udy cyclone milled (1 mm), and analyzed for DM by drying at 105°C for 24 There was no difference (P > 0.05) in DM values due to the hot vs. desiccator method. However, milling method caused variation in DM values (P < 0.001) and was dependent on the Wiley mill DM prior to cyclone regrinding (i.e., Wiley mill DM < cyclone regrind (P 0.001)). The DM values from cyclone regrinding were 9.0, 4.1, and 0.75% greater than the Wiley milled material in the 750 to 800, 800 to 900, and 900 to 950 g kg‐1 range, respectively. The choice of gravimetric techniques in DM determinations is dependent on preference and suitability to laboratory protocol. Analysis of DM by NIRS on cyclone milled material and validation with Wiley milled DM laboratory values resulted in large negative bias and poor standard error of analysis.
Somaclonal Variation in Soybean Plants Regenerated from the Cotyledonary Node Tissue Culture System1
Authors: Graybosch R. A. , Edge M. E. , Delannay X.
Published: July 2010

The cotyledonary node tissue culture system stimulates the genesis of shoots from newly formed and pre‐existing meristematic regions of nodal tissue cultured on media containing benzyladenine (BA). The intent of this study was to determine whether soybean (Glycine max L. Merr.) cultivars differ in their response to this system, and to test for the presence of tissue culture derived genetic variants. The response of three soybean cultivars (Calland, Funman, and Wayne) to this system was analyzed. Slight, but statistically significant, differences were observed in shoots per seed, plants per seed, and regeneration time. The number of shoots derived from a given seed after 6 weeks in culture was not correlated with the number of plants ultimately derived from the same seed. Field analysis of progeny of regenerated plants demonstrated no variability for lodging and maturity among seven families. Variability for yield was observed in 2 of 19 families compared to control cultivars. One of 22 families exceeded the control in height, and variability for height was increased among regenerated families. Recessive mutations for putative sterility characters were observed in 2 of 89 families, but mutations in six marker genes were not apparent.
Establishment of Cicer Milkvetch with Four Cool‐Season Grasses1
Authors: Kenno H. , Brick M. A. , Townsend C. E.
Published: July 2010

Cicer milkvetch (Astragalus cicer L.), a promising, nonbloat inducing legume, has relatively poor seedling vigor and is more difficult to establish than most species of forage legumes. The objectives of this study were to compare three methods of seeding cicer milkvetch with four cool‐season grasses to determine establishment success and forage yield in the seedling year under irrigated conditions. The three planting methods were: (i) legume and grass as a mixture in the same rows, (ii) legume and grass seeded alone in alternate rows, and (iii) legume and grass seeded alone in rows perpendicular to each other. The four grass species were smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (B. biebersteinii Roem. and Schult.), orchardgrass (Dactylis glomerata L.), and intermediate wheatgrass [Elytrigia intermedia (Host) Nevski]. Total forage yield, legume content, and height of the legume were measured. Forage yields were not affected by seeding methods during the establishment year. Alternate‐seeded rows produced forage with a greater proportion of cicer milkvetch than mixed‐ or cross‐seeded rows. Height of the legume at harvest also was greatest in alternate‐seeded rows. The smooth bromegrass‐cicer milkvetch mixture produced more forage than other mixtures. Cicer milkvetch‐grass mixtures should be seeded in alternate rows with smooth bromegrass, meadow bromegrass, orchardgrass, or intermediate wheatgrass. Establishment of the legume component in the alternate planting arrangement was enhanced because there was less competition from the grass species.
Recurrent Selection in Blue Grama. I. Seedling Water Uptake and Shoot Weight1
Authors: Nason Debora A. , Cuany Robin L. , Wilson A. M.
Published: July 2010

The interval between emergence and production of adventitious roots is critical in the survival of blue grama [Bouteloua gracilis (Willd. ex Kunth) Lag. ex Griffiths] seedlings, because the threadlike seminal root and subcoleoptile internode provide the only water for the developing shoot. The objectives of this study were to evaluate plant characteristics related to water uptake and determine potential for genetic gain by selection. Six‐week‐old seedlings that had reached a ceiling in their capacity for 24‐h water uptake were tested in a greenhouse study. Seedlings were prevented from forming adventitious roots by a dry soil layer, and pots were sealed to allow water loss only through seminal root uptake and transpiration. Shoot weights as well as water uptake values were criteria for recurrent selection of approximately the top 10% of the population over three cycles. Shoot weights of the polycross progenies from the three cycles were compared in a combined experiment. There was about a two‐fold difference (P < 0.01) in water uptake and shoot weight between the lowest and highest progeny in each generation, with broad‐sense heritabilities of 62 and 69% on a family mean basis indicating useful genetic variance in those traits. Results indicated a 21% increase in shoot weight for two cycles of simple recurrent selection, and narrowsense heritability by parent‐progeny regression was 48% and 42% for the second and third cycles. Shoot weight was significantly (P ≤ 0.01) associated with water uptake (r = 0.81) and with caryopsis weight (r = 0.40). Selection for high shoot weight in seedlings (from high caryopsis weight parents) supported by the seminal root, rather than selection for water uptake, should result in more efficient progress because a larger number of seedlings could be evaluated. Genetic gain with use of this approach should increase survival and establishment of blue grama seedlings.
Plant Pubescence, Genetic Background, and Seasonal Effects on Agronomic and Fiber Properties of Upland Cotton1
Authors: Wilson F. D. , Shepherd R. L.
Published: July 2010

Smooth‐leaved lines of cotton (Gossypium hirsutum L.), although showing resistance to certain insects, have frequently been deficient in some agronomic and fiber properties. In this study, we compared lint yield, yield components, and other agronomic and fiber properties in smoothleaf and hirsute cotton in eight genetic backgrounds in 1981 and 1982, and in two backgrounds in 1983. Plots were grown at Tempe, AZ; soil type was a Contine clay loam (a fine, mixed, hyperthermic Typic Haplargid). The objective of this study was to determine whether certain deficiencies were associated consistently with the smoothleaf phenotype. The 1981 and 1982 results showed that no agronomic or fiber‐property deficiencies were associated consistently with smoothleaf. In 1983, however, the smoothleaf line that had been selected for high lint yield in 1981 and 1982 yielded 36% less lint per plant than the hirsute sibling cultivar, and the smoothleaf line that had been selected for low insect damage yielded 30% less lint per plant than the hirsute cultivar. Lower lint yields in both smoothleaf lines mainly were attributable to fewer bolls per plant. These lower yields and interactions of years with level of pubescence reinforced our earlier decision, based mainly on equivocal results from insect‐resistance studies, to discontinue smoothleaf lines in our breeding program except for those carrying the delta smooth (more properly, semismooth) allele, t3
Inheritance of Resistance to Aphid in Cowpea1
Authors: Bata H. D. , Singh B. B. , Singh S. R. , Ladeinde T. A. O.
Published: July 2010

Aphid (Aphis craccivora Koch) is a major pest of cowpea [Vigna unguiculata (L.) Walp.] particularly in the drier regions of the tropics. It causes direct damage by feeding on the plants and also transmits viruses. Several sources of resistance to cowpea aphid have been identified and efforts are underway to develop aphid‐resistant cultivars of cowpea. This study was undertaken to elucidate the inheritance of resistance to aphid in cowpea. Three resistant lines were used in the study. Parental, F1, F2, F3, and backcross populations involving resistant ✕ susceptible and resistant ✕ resistant lines were evaluated in the greenhouse using artificial infestation with aphids. The F1 plants in all the crosses were resistant and the F2 populations derived from all the crosses involving resistant and susceptible parents segregated into 3 resistant:1 susceptible ratio. The backcross populations involving susceptible parents segregated into 1 resistant:1 susceptible ratio, whereas the backcross populations involving resistant parents were completely resistant. The F3 progenies derived from resistant F2 plants showed a ratio of 1/3 true breeding resistant:2/3 segregating like F2's. These data indicated monogenic dominant inheritance of aphid resistance. The gene symbol Rac (resistance to Aphis craccivora) is being assigned for this trait.
Relationship between Ear‐Removal‐Induced Leaf Senescence and Green Score in Maize1
Authors: Willman M. R. , Below F. E. , Hageman R. H. , Lambert R. J.
Published: July 2010

Ear removal (or pollination prevention) in maize (Zea mays L.) accelerates leaf senescence in certain hybrids and may be a useful means of identifying genotypes with extended leaf‐area duration independent of grain development. The present study was undertaken to clarify the relationship between ear‐removal‐induced leaf senescence and leaf stay‐green when ears are present, and to determine the effect of hybrid pedigree, relative maturity, and environment on the expression of these two traits. A sample of 130 and 101 commercial and precommercial maize hybrids were evaluated in 1984 and 1985, respectively. The hybrids, representative of seven relative maturity groups, were evaluated as separate groups in separate randomized complete block designs at one of two locations. Four of the seven groups were evaluated in both 1984 and 1985. Plants were visually assessed for the rate of ear‐removal‐induced leaf senescence and for the percent green leaf tissue on eared plants at physiological maturity. In each maturity group, significant variation among hybrids was observed for both traits. Although seven of the eight yearby‐genotype interactions were significant, the proportion of the total sums of squares accounted for by this interaction was minor (6‒15%). Simple correlations and comparisons among hybrid pedigrees indicated that the relationship between ear‐removal‐induced and normal leaf senescence is complex and is influenced by hybrid genotype. The results suggest that ear‐removal‐induced senescence represents a phenomenon independent of grain development and raise the possibility that this trait may be beneficial as an additional means of identifying hybrids with late‐season plant health.
Effect of Selecting for Downy Mildew Resistance in Alfalfa on Saponin Content1
Authors: Stuteville D. L. , Skinner D. Z.
Published: July 2010

Alfalfa (Medicago sativa L.) saponin is toxic to several plant disease organisms, including some Oomycetes closely related to Personospora trifoliorum d By., the alfalfa downy mildew fungus. Resistance in alfalfa to downy mildew has been changed significantly during selection to alter the forage saponin content. The primary objective of this research was to determine the effects of selecting for downy mildew resistance in alfalfa on forage saponin levels. Alfalfa ‘CUF 101’ and germplasms UC 123 and UC 143 derived from it by one and two cycles, respectively, of recurrent phenotypic selection for resistance to P. trifoliorum were evaluated for forage saponin content. The percent of plants resistant (symptomless) to P. trifoliorum isolates I–7 and I–8, respectively, were 28 and 3 for CUF 101; 62 and 3 for UC 123; and 62 and 72 for UC 143. Saponin indices (higher index = lower saponin content) were CUF 101, 101; UC 123, 92; UC 143, 100; ‘Lahotan’ (low‐saponin check), 98; and ‘Uinta’ (high‐saponin check), 35. Alfalfa germplasms KS80, KS145, KS167, and K78‐10, all higly resistant to P. trifoliorum and several other fungi and insects, had saponin indices about midway between those of Lahonton and Uinta. Saponin apparently played no role in the resistance of UC 143 to P. trifoliorum since UC 143 was derived from the very low‐saponin CUF 101 cultivar without affecting the saponin index.
Evaluating Genetic Changes Associated with Selection Utilizing Information from Diallel Mating Designs1
Authors: Hanson W. D.
Published: July 2010

This study compares the generation mean analysis and the diversity analysis as analytical tools and evaluates changes resulting from a selection program. Genotypic values for diallel matings between base populations and selections from these base populations were expressed in terms of parameters containing both additive and nonadditive gene effects. These parameters directly translated to those based on the assumption of additive effects among loci. The mean analysis provides information on the variability associated with realized gains. The diversity analysis provides information on the nature of divergence due to selection. Published results from reciprocal recurrent (RRS) and half‐sib (HSS) selection in maize (Zea mays L.) were reevaluated using the diversity analysis. The mean analysis had yielded estimates for direct and indirect responses to selection. Both selection schemes effectively increased grain yield in maize. Divergence from the base populations occurred for genes having additive‐associated and dominance‐associated gene effects under both RRS and HSS. The basis for divergence was not associated with the selection scheme. Divergence of the two selected populations from their base populations under RRS was parallel‐like, supporting the conclusion that grain yield depended primarily on genes having partial to complete dominance effects. Selection based on top‐cross performance (HSS) emphasized a set of dominance‐associated gene effects different from RSS. Distances obtained from the diversity analysis correlated (+0.89) with distances reflecting inbreeding depressions obtained when corresponding gene pools were combined.
Evaluation of Soybean Genotypes for Iron‐Deficiency Chlorosis in Potted Calcareous Soil1
Authors: Fairbanks D. J. , Orf J. H. , Inskeep W. P. , Bloom P. R.
Published: July 2010

Iron‐deficiency chlorosis in soybean [Glycine max (L.) Merr.] is a problem on some calcareous soils in the upper Midwest. Past attempts to screen soybean genotypes using potted calcareous soil from the field have not been successful. The objective of this research was to evaluate methods for screening soybean genotypes for Fedeficiency chlorosis in potted calcareous soil. Twelve soybean genotypes representing a range of resistance to Fe chlorosis were evaluated in potted calcareous soils taken from five locations in Minnesota and Iowa. Each soil was sieved and thoroughly mixed. Pots were prepared by packing soil evenly to a bulk density of 1.1 Mg m−1. Soil water content was maintained constant by daily watering of undrained pots (bottom holes absent) to a specific weight, or by flooding greenhouse benches until the water level was 0.1 m below the soil surface in drained pots (bottom holes present). Second trifoliolate leaves were given chlorosis scores. The soil water content at which the most intense chlorosis occurred, differed for each soil. However, when gravimetric soil water content values were converted to matric potential values, the most intense chlorosis occurred within the range of ‒3 to ‒1 kPa, values slightly below saturation. Chlorosis scores of soybean genotypes when grown in pots were significantly correlated with field results in three out of four comparisons in the growth chamber and in one out of four comparisons in the greenhouse. Some soils that produce chlorosis in the field apparently do not produce chlorosis in pots. Significant differences in chlorosis scores and in some ranks were observed in the different soils. This is similar to what is observed in different field sites, however, the general classification of genotypes in the pots was the same as in the field.
Nodule Development in a Split‐Root System in Reponse to Red and Far‐Red Light Treatment of Soybean Shoots1
Authors: Hunt P. G. , Kasperbauer M. J. , Matheny T. A.
Published: July 2010

A split‐root (sides A and B) study with soybean [Glycine max (L.) Merr. (‘Lee’)] and USDA strain 3I1b110 Bradyrhizobium japonicum was conducted to assess the effect of red and far‐red light treatments of shoots on the timing of B. japonicum‐induced suppression of root nodulation. Plants were grown at 25°C in a growth‐chamber with 12‐h daily photosynthetic periods that ended with 5‐min exposures to red or far‐red light. Day 0 for inoculation was 7 days after planting at which time roots had extended into both sides of the split‐root system. When side B was inoculated 2 to 4 days or longer after side A, nodulation and nodule mass on side B were significantly less than on side A. The number of nodules formed on roots of either side A or B were lower when shoots were treated with far‐red than with red light. Therefore, total suppression of nodulation on side B occurred more rapidly with far‐red than red light treatment. When far‐red treatment was followed immediately by red treatment, plants responded similarly to the red treatment for nodule weight as well as nodule number. These data show that the timing of suppression of secondary nodulation on the roots can be affected by spectral balance of light received by the shoots, and the reversible nature of the effects of far‐red light with red light strongly indicates phytochrome involvement. This interaction could have significant effects on nodulation patterns of soybean grown in different populations, row widths, and row orientations because these treatments alter the far‐red/red ratio of light received in soybean canopies. It may also be important in the interpretation of greenhouse and growth‐chamber studies of phenomena such as soybean nodulation and B. japonicum strain preference by different soybean cultivars.
Water Relations and Osmotic Adjustment of Leaves and Roots of Lupins in Response to Water Deficits1
Authors: Turner Neil C. , Stern Walter R. , Evans Pedro
Published: July 2010

Increasingly, lupins (Lupinus spp.) are being grown as a dryland crop in marginal rainfall areas, yet their water relations characteristics and adaptation to water deficits are largely undescribed. The present study was initiated to determine the waterelations and degree of osmotic adjustment in leaves and roots of lupins in the greenhouse and in the field. Four experiments were conducted. In the first two, the leaf water relations of Lupinus angustifolius and L. cosentinii were compared. The results showed the L. angustifolius leaves were morelastic and had a higher osmotic pressure under adequately watered conditions, but the degree of osmotic adjustment to a slowly imposed water deficit was negligible in L. angustifolius and about 0.2 MPa in L. cosentlnii. In the third experiment, the waterelations and osmotic adjustment of leaves and roots of five lupin species/cultivars were compared at a predawn leaf water potential of ‒ 1.6 MPa. Leaf elasticity in general was not influenced by water deficits. In the leaves, osmotic adjustment varied among species; L. pilosus and L. atlanticus had the greatest degree of osmotic adjustment (0.4–0.5 MPa) and L. augustifolius the least (0.1 MPa). The increases in osmotic pressure arising from a water deficit were paralleled by decreases in the turgid weight/dry weight ratio. In this greenhouse experiment, no osmotic adjustment was observed in the roots of any of the species. In the fourth experiment, conducted in the field, the leaves of L. angustifolius adjusted osmotically by 0.2 to 0.3 MPa and roots by about 0.4 MPa. The osmotic adjustment in both leaves and roots was accompanied by a decrease in the turgid weight/dry weight ratio. The data suggest that changes in turgid weight/dry weight ratio may provide a simple screening method for osmotic adjustment in Lupinus.
Dependence of Stomatal Conductance on leaf Water Potential, Turgor Potential, and Relative Water Content in Field‐Grown Soybean and Maize1
Authors: Bennett J. M. , Sinclair T. R. , Muchow R. C. , Costello S. R.
Published: July 2010

Soybean [Glycine max. (L.) Merr.] and maize (Zea mays L.) were grown in field plots on an Arredondo fine sand (loamy, siliceous hyperthermic Grossarenic Paleudult) and subjected to either five or four water management treatments in 1985 and 1986, respectively. Treatments included daily irrigation, irrigation at either 4‐ or 8‐day intervals, irrigation to maintain a slight reduction in stomatal conductance, and no irrigation. The objective of the study was to investigate the hypothesis that stomatal conductance (gs) is more closely related to leaf relative water content (RWC) than to either bulk leaf water (ψL) and xylem potential (ψx) or leaf turgor potential (ψp), of which have been frequently used to describe leaf water status. An important feature of this study was an attempt to characterize the waterelations and stomatal conductance of field‐grown crops subjected only to mild water deficits. A comparison of the coefficients of variation among the parameters used to evaluate leaf water status showed the greatest value for ψp, followed by ψL, with RWC having the smallest. When mild plant water deficits were imposed, gs was significantly decreased without decreases in either ψL, ψp, or RWC. There were no significant relationships between gs and any of the measures of leaf water status when data from only the daily irrigated and mildly stressed treatments were pooled. However, linear regressions of gs vs. ψL, ψp, ψx, and RWC were often statistically significant when data from the nonirrigated, severely stressed treatment were included in the analyses. We conclude that bulk leaf measurements of ψL, ψp, ψx, and RWC cannot be used to describe accurately the response of gs to soil dehydrations that result in only mild plant water stress in field‐grown soybean and maize.
Root‐Knot Nematode Effect on Nine Cotton Cultivars in Mississippi1
Authors: Minton Earl B. , Meredith William R.
Published: July 2010

Lint yields of cotton (Gossypium hirsutum L.) in the USA have decreased since the mid‐1960s even though new cultivars developed during this period are more productive than the cultivars they replaced. Nematodes have been suspected of being a factor in declining yields. This field study was designed to compare the performance of nine cotton cultivars when grown in fumigated and nonfumigated soils (Typic Dystrochrepts). The target nematode species was the root‐knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, and the fumigant was 92% 1,3‐dichloropropene (Telone II3). Seedling survival and plant height were not affected significantly by soil fumigation. Numbers of second stage root‐knot nematode juveniles in soil samples and root‐gall indices of cotton cultivars were reduced by fumigation with Telone II. The greatest reduction in root galling occurred on nematode‐susceptible cultivars. Telone II reduced lint yield of ‘Delcot 311’, ‘Auburn 56’, and LA 434 RKR from 1 to 4%. The latter two are the most tolerant to root‐knot nematode of the cottons tested. Lint yields of the more susceptible cultivars were increased from 2 to 6% by Telone II. Regression analysis of the yield differences between nonfumigated and fumigated treatments on the root‐knot indices of the cultivars grown in the nonfumigated plots showed that M. incognita reduced lint yields 35.7 kg ha−1 for each unit increase in root‐gall index.