bluuebunny/crossref_metadata_2025 huggingface dataset:
Genotype and Genotype ✕ Environment Interaction Effects for Forage Yield and Quality of Intermediate Wheatgrass1
Authors: Vogel K. P. , Reece P. E. , Lamb J. F. S.
Published: July 2010

Intermediate wheatgrass [Thinopyrum intermedia (Host) Barkworth and D.R. Dewey] is grown over a vast geographical area in North America, but information on the genetic variability for agronomic traits and the stability of these traits over environments is limited. Genotype and genotype ✕ environment interaction effects for forage yield and quality of intermediate wheatgrass were studied using 36 strains (plant introductions, experimental strains, and a released cultivar). They were grown in two central Great Plains environments, Lincoln and Alliance, NE, that differ markedly in climate. Forage yield and forage quality, measured by in vitro dry matter digestibility (IVDMD) and percent protein, were determined in both locations in 1980 and 1981 in spaced‐plant nurseries. In the combined analyses over years and locations, there were significant differences among strains or genotypes (G) for first‐cut yield and IVDMD, but not for protein. Strain ✕ location (GL) and strain ✕ year (CY) interaction effects were significant for first‐cut forage yield but not for IVDMD, a trait that appears to be relatively stable over environments. For forage yield, the variance component for strains (σ2g) was 300% larger than those for GL (σ2gl) and GY (σ2gy). These variance components results plus rank correlations of the strains in the two environments of 0.77 for both first‐cut IVDMD and yield indicate that the strains ranked similarly for both traits in both environments. Existing genetic variability for forage yield and quality as measured by IVDMD should permit the development of improved intermediate wheatgrass populations. At least in the initial stages of a breeding program, selection for these traits could be done in a single environment. Concurrent selection for both first‐cut yield and IVDMD is feasible since the phenotypic correlation coefficients between these traits were positive and significant for both locations.
Improvement in the Yield Potential of Bread Wheat Adapted to Northwest Mexico1
Authors: Waddington S. R. , Ransom J. K. , Osmanzai M. , Saunders D. A.
Published: July 2010

Two trials were conducted at the Mexican National Institute of Agricultural Research (INIA) experimental station, Yaqui Valley, Sonora, Mexico, to determine the genetic yield potential of bread wheat (Triticum aestivum L.) cultivars released in northwest Mexico over the period from 1950 to 1982, with emphasis on progress since 1970. Nonlimiting levels of fertility and moisture, a preventative pest and disease program, and netting to prevent lodging were used. Grain yield, yield components, and rates of phytomass production and grain filling were determined. Yield data on selected genotypes grown in 4 yrs of the International Spring Wheat Yield Nursery (ISWYN) at the same station were also examined. The grain yield potential of cultivars, successively released since 1950, has risen at an estimated (from a regression slope) average of 59 kg/ha/yr of release, or about 1.1%/yr. Although yield potential may have plateaued in the early 1970s, cultivars released since 1979, i.e., modern genotypes (e.g., ‘Ciano 79’, ‘Genaro 81’, ‘Glennson 81’, and ‘Seri 82’) have improved yield potential at an estimated rate similar to that prior to 1970. Improvements in grain yield were associated with increases in grain number per unit area (r = 0.74, P < 0.01), which has risen by about 34% in modern genotypes compared to pre‐1970 cultivars, and grain number per spike (r = 0.51, P<0.05). The 1000‐grain weight, was reduced slightly in the modern high grain number cultivars (r = −0.76, P<0.01). Harvest indices for modern genotypes were lower than those of the landmark cultivar ‘Yecora 70’, but the modern genotypes had, on average, 16% greater phytomass than pre‐1970 cultivars. However, only 43% of the variation in grain yield was attributable to phytomass. The improvements in yield potential are mainly the result of empirical selection for grain yield. Indications were that rates of grain filling and phytomass production in modern genotypes were similar to those in Yecora 70. The higher grain yield and phytomass in modern genotypes compared to Yecora 70 was probably due to the formation and survival of a larger grain sink (more grains/m2) and greater C assimilation during a longer preanthesis phase.
Genome Analysis of the Tetraploid Pseudoroegneri tauri1
Authors: Wang Richard R‐C. , Dewey D. R. , Hsiao C.
Published: July 2010

The alloploid nature of some tetraploid accessions of Pseudoroegneria tauri (Boiss. & Bal.) A. Löve and P. spicata (Pursh) A. Löve was investigated by conducting meiotic analyses of the following hybrids: P. tauri (2n=28) ✕ P. libanotica (Hackel) D.R. Dewey (2n=14, genomes SS); P. tauri ✕ P. spicata (2n=14, genomes SS); P. tauri ✕ P. spicata (allo‐4x, 2n=28, genomes SSXX); P. tauri ✕ Agropyron cristatum (L.) Gaertn. (2n=14, genomes PP); and P. tauri ✕ A. cristatum (2n=28, genomes PPPP). Meiotic data of these hybrids showed that P. tauri possessed both the S and P genomes, and it had only the S genome in common with the allotetraploid P. spicata. Mitotic cells showed 14 short and 14 long chromosomes in P. tauri; 14 short and 7 long chromosomes in P. tauri ✕ P. libanotica; and 14 long and 7 short chromosomes in P. tauri ✕ A. cristatum. It is concluded that two tetraploid accessions of P. tauri from Iran used in this study have the PPSS genome formula in which the long chromosomes are those of the P genome and the short ones are those of the S genome. An unknown (X) genome present in allotetraploid P. spicata differs from both the S and the P genomes, and possibly is an H genome. This study revealed that the alloploid nature of P. tauri, and possibly some tetraploid P. spicata accessions, is not due to the presence of a Ph‐like genetic system because of the high frequencies of nonhomologous pairing or incomplete preferentiality observed in these triploid and tetraploid hybrids. In view of these findings, forage grass breeders should not use these amphiploids in crosses with autotetraploid species in the genus Pseudoroegneria. Taxonomists must find a way to classify the natural amphiploid species with PPSS genomes.
Multidirectional Selection for Fiber Strength in Upland Cotton1
Authors: McCall Lloyd L. , Verhalea Laval M. , McNew Ronald W.
Published: July 2010

Selection experiments are usually conducted in one or two directions, whereas studies involving multidirectional selection are rare. This multidirectional selection experiment for T1 fiber strength was conducted through five cycles within a genetically variable population of upland cotton (Gossypium hirsutum L.) to investigate the direct and correlated responses to selection for that trait. The original population was a mixture comprised of equal amounts of mature F2 seed from 45 crosses. The stronger‐fibered 10% of the plants, as well as the weaker‐fibered 10%, were selected within each population in each cycle. Selfed seed from selected plants were used to form new populations for testing and further selection. Analyses of variance detected significant differences among populations for all traits in selection cycles 3, 4, and 5, except for fiber fineness in cycle 4. No genotype ✕ environment interactions were detected for T1 fiber strength. Selection for fiber strength was effective. After four cycles of selection under enforced self‐pollination, half the populations still possessed sufficient genetic variability to show a significant selection response in the fifth selection cycle. One generation of reverse selection for fiber strength was often followed by dramatic increases in variability and in subsequent selection response; however, two or more low‐strength selections had a detrimental effect on later selections for high fiber strength. Selection for stronger fiber tended to result in lower picked and pulled lint percents; increased 2.5 and 50% span lengths, uniformity index, T0 fiber strength, and earliness; and variable response for lint yield and fiber fineness.
Diploid‐Tetraploid Comparisons in Rye. III. Temperature Effects on Seedling Development1
Authors: Sullivan B. P. , Pfahler P. L.
Published: July 2010

The late fall planting season for rye in the southeastern USA is typically characterized by an extreme range of temperature conditions. The potential for selection of diploid and tetraploid rye (Secale cereale L.) populations possessing superior seedling growth characters over a broad range of temperatures was assessed by examining the effect of genetic background on various seeding growth characters at three temperatures (12, 20, 28°C). Diploid populations, and their colchicine‐derived tetraploid counterparts from five genetic backgrounds (‘Elbon’, ‘Explorer’, ‘Florida Black’, ‘Gator’, ‘Wrens Abruzzi’) were compared. The seedling characters included shoot and primary root growth day−1, root cross‐sectional area at the meristematic region, and primary root bluntness ratio (distance from the plane of maximum root diameter at the meristematic region to the root tip divided by the maximum root diameter at the meristematic region). Highly significant ploidy level (PL), genetic background (GB), and temperature (T) main effects were obtained for both shoot and primary root growth day−1. A highly significant T✕GB✕PL interaction was found for shoot growth day−1, but this effect was not significant for root growth day−1. The T ✕ PL interaction was significant for primary root growth day−1 at the 0.05 level. Highly significant ploidy level (PL) and temperature (T) main effects were obtained for root cross‐sectional area. A highly significant ploidy level (PL) main effect was found for the bluntness ratio. The lower ratios obtained for the tetraploid populations indicated that the tetraploid root tips were blunter than those of diploids, which may be a factor in soil penetration and root proliferation. The results indicated that substantial genetic variation for seedling growth characters was present among genetic backgrounds as well as within populations at both ploidy levels over a wide temperature range. It was concluded that selection for diploid as well as tetraploid rye populations possessing superior seedling growth characters over a broad range of temperatures would be successful.
A New Technique for Crossing Mungbeans1
Authors: Cupka T. B. , Edwards L. H.
Published: July 2010

Improved crossing techniques are needed to exploit the genetic potential of mungbean [Vigna radiata (L.) Wilczek]. In our technique, only the tip of the bud is opened to expose the stigma and style. After the anthers are gently removed with forceps, the emasculated bud is then ready to be crossed. When pollination is completed, cellophane tape is placed over the opening to seal the bud and the process is complete. An experienced technician can complete an emasculation and pollination in 1 min. The success rate using this technique averaged 60% with an average of six seeds per pod per successful cross. This technique differs from those presently being used in other legume crops because most other crossing techniques open the entire dorsal edge of the bud in order to make an emasculation and pollination. This technique appears to reduce moisture and temperature fluctuations within the bud and reduces bud abortion subsequent to artificial pollination.
Cumulative Response to Various Recurrent Selection Schemes in Soybean: Oil Quality and Correlated Agronomic Traits1
Authors: Carver Brett F. , Burton Joseph W. , Wilson Richard F. , Carter Thomas E.
Published: July 2010

practiced in a soybean [Glycine max (L.) Merr.] population to indirectly decrease linolenic acid percentage in the seed oil. Three selection schemes were employed during specific stages of the program: Individual or mass (Cycles 1 to 3), mass plus within half‐sib family (Cycles 4 to 7), and S1‐progeny selection (Cycle 8). In addition, reverse selection for low oleic acid (LO) was initiated in Cycle 6 and continued simultaneously with HO selection. Objectives of this study were to evaluate cumulative selection response for fatty acid traits and other correlated traits, and to evaluate the potential for further selection progress. To achieve those objectives, selected lines from each cycle were composited in bulk populations and tested in eight environments. Regression analysis showed that the average rate of change in oleic acid percentage increased from 1.15 f 0.17% per cycle (HO mass selection) to 2.64 ± 0.24% per cycle (HO mass plus within half‐sib family selection). The difference in observed genetic gains was consistent with theoretical expectation. Rate of change in linolenic acid percentage, however, did not increase in magnitude, averaging −0.34 ± 0.03% (HO mass selection) and −0.24 ± 0.05% per cycle (HO mass plus within half‐sib family selection). Divergent responses to HO and LO selection for oleic and linolenic acid percentages indicated that genes governing those traits were not fixed after six cycles. Seed weight and days to maturity were correlated with selection for oleic acid, but no consistent trends throughout the selection program were noted for seed yield or oil and protein percentages. Although further progress from HO selection can be expected, a change in selection criterion to low linolenic acid percentage may be justified to minimize bias caused by genotype ✕ environment interaction.
Grain Yield Reduction Caused by Second Generation European Corn Borer in BS9 Corn Synthetic1
Authors: Klenke J. R. , Russell W. A. , Guthrie W. D.
Published: July 2010

Damage to the corn (Zea mays L.) plant caused by the European corn borer (ECB) [Ostrinia nubilalis (Hübner)] can cause substantial grain yield reduction. The ECB damage results in both physiological reduction, caused by decreases in plant productivity, and harvest loss, caused by weakening of the stalk and shank from tunneling by the fifth instar larvae (borers). Yield reductions caused by ECB can be decreased with the use of resistant hybrids. Iowa normally has two generations of ECB per year, and resistance to the two generations is expressed by separate genetic mechanisms. A corn synthetic, designated BS9, was specifically developed and selected for resistance throughout the life of the plant. This study used hand and machine‐harvested plots of a control treatment and a treatment of a high infestation of second generation ECB to estimate the magnitude of physiological reduction and harvest loss contributing to a decrease in total grain yield. Corn cultivars used were the original and fourth cycle populations of BS9 [BSSCO and BS9(CB)C4], the two populations crossed with four inbred line testers, and two check single‐cross hybrids. Physiological reduction and harvest loss were estimated to be 25.9 and 2.8%, respectively. Harvest loss had little effect on total yield reduction, and contributions by other genetic factors seemed more important than ECB damage on harvest loss. Ear drop page under high insect pressure was determined more by the inherent properties of the hybrids for ear retention than as resistance to ECB. Whereas ear droppage before harvest had little effect, stalk lodging was significantly correlated with harvest loss.
Inheritance of Scent in American Long Grain Rice1
Authors: Berner D. K. , Hoff B. J.
Published: July 2010

Scented or aromatic rice (Oryza sativa L.) is highly valued in many areas of the world, but the development of high yielding scented cultivars has been limited by a lack of information on the inheritance of scent. Reciprocal crosses were made between the scented cultivar ‘Della’ and the nonscented cultivar ‘Dawn’ to study the inheritanceof scent in rice. Leaf tissue and seed samples from plants of the parental cultivars and of F1 and F2 progeny were placed in 0.3 mol L−1 KOH solution and rated for strength of aroma. The results indicated that the F1 plants were nonscented and the F2 populations segregated in a 3:1( nonscented:scented)r atio. Individual seeds from F1 plants were chewed and rated as scented or nonscented and the results showed that, due to xenia, the seeds from the heterozygous F1 plants also segregated in a 31 (nonscented:scented) ratio. Of 992 F2 seeds individually rated for scent, 748 were nonscented and 244 were scented. Chewing and rating individual F3 seeds of F2 plants confirmed the monogenic recessive inheritance of the scent character. It was found that scent could be detected in half of a single seed by chewing the distal portion while saving the portion of the seed with the embryo. Normal germination, with approximately 80% plant survival in the field, was observed when the embryo portions were planted. The scent character may be transferred into improved cultivars by several methods using the demonstrated ability to identify scented genotypes by chewing individual seeds.
Fast‐Growing Rhizobium fredii are Poor Nitrogen‐Fixing Symbionts of Soybean1
Authors: DuTeau N. M. , Palmer R. G. , Atherly A. G.
Published: July 2010

Soybean‐Rhizobium genotype combinations with high rates of N2 fixation are useful in soybean (Glycine max L. Merr.) breeding programs. Nitrogen fixation was examined in 13 soybean cultivars and wild soybean (G. soja Sieb. & Zucc.) plant introductions inoculated with Bradyrhizobium japonicum strain 61A76 and four fast‐growing strains of Rhizobium fredii. Five‐week‐old plants were assessed for nodule morphology, acetylene reduction rate, nodule number, nodule fresh weight, and plant‐top dry weight. All fast‐growing strains formed effective nodules on cultivars ‘Peking’, ‘Virginia’, ‘Hardee’, and the G. soja plant introductions. In contrast, three of the fast‐growing strains formed ineffective nodules on the other cultivars. One strain, USDA191, formed effective nodules on all cultivars. No nodules were formed by the fast‐growing R. fredii on ‘Harosoy rj1 rj1’. Rhizobium fredii strain USDA191 fixed N, as well as the slow‐growing control with cultivars Peking, Virginia, ‘Harosoy 63’, and ‘Rampage’, and G. soja plant introductions PI 342622A and PI 101404B, but fixed less NJ than the slow‐growing control with cultivars ‘Evans’, ‘Williams’, Hardee, ‘Hill’, and G. soja PI 407217 and PI 81762.
Host Restriction of Nodulation by Bradyrhizobium japonicum Strain USDA 123 in Soybean1
Authors: Cregan P. B. , Keyser H. H.
Published: July 2010

The displacement of indigenous Brudyrhizobium juponicum serogroup USDA 123 in soybean [Glycine mar (L.) Merr.] nodules in favor of a more effective inoculant strain(s) has been suggested as an approach to enhance soybean productivity in the midwestern USA. Our objective was to determine if the host plant could serve as a vehicle to restrict nodulation by an indigenous serogroup thereby allowing nodulation by a more effective rhizobial strain. A total of 1278 soybean plant introductions and cultivars were screened in the greenhouse with B. juponicum strain USDA 123. Thirteen genotypes demonstrated restricted nodulation with USDA 123 when compared to five standard cultivars. Two of these genotypes, PI 371607 and PI 377578, were planted along with the cultivar ‘Williams’ in a soil free of B. juponicum and inoculated with USDA 123 and either USDA 110,122, or 138. In each competition treatment, greater than 75% of the nodules of Williams were occupied by USDA 123 whereas, in all cases, less than 10% of the nodules of the PI genotypes contained USDA 123. The PI genotypes excluded strain USDA 123 in favor of the inoculant strain. In another experiment, the two PI genotypes and Williams were inoculated with either USDA 123 or 110. With USDA 123, nodulation and N accumulation was significantly less in the PI genotypes than in Williams. In contrast, with USDA 110, nodulation and N accumulation of the PI genotypes was similar to Williams. Thus, while the PI genotypes nodulated and fixed N2 poorly with USDA 123, nodulation and fixation with an efficient strain such as USDA 110 was normal. Our results suggest that the trait identified in the PI genotypes could positively impact soybean productivity by excluding all or part of the indigenous serogroup 123 population in favor of more effective strains of B. japonicum.
Yield Manipulation from Selection on Allozyme Genotypes in a Composite of Elite Corn Lines1
Authors: Frei O. M. , Stuber C. W. , Goodman M. M.
Published: July 2010

The possibility that alleles at allozyme loci are markers of quantitative trait loci and that they may serve as selection criteria in population improvement programs was studied in a composite population. Thirty inbred corn (Zea mays L.) lines were intercrossed to generate the base population, which was expected to have strong linkage disequilibria, a primary prerequisite for effectively utilizing allozyme marker loci in selection. Prior to this study, one cycle of intensive topcross selection (with B73 as tester) among S2, lines from this population was conducted that provided yield data and seed from the C1 cycle to identify yield‐responsive allozyme alleles. Allozymes at 23 loci were assayed and 8 of them showed markedly higher frequencies in the high performing S, lines. These eight were defined as yield‐associated allozymes. Divergent selection for high (+) and low (−) multilocus frequencies of these yield‐associated allozyme alleles showed an upward trend for yield in the positive allozyme selections when evaluated at seven locations as B73 topcrosses, but a downward trend when evaluated as populations per se. Checks that were selected by a topcross procedure with B73 as tester showed the same yield trends, indicating that allozyme selection as well as phenotypic selection increased specific combining ability with B73 but decreased the population performance per se. Five allelic contrasts also were generated in which favorable allozymes at individual loci were fixed in the (+) populations and unfavorable allozymes were fixed in the (−) populations. Yields of these contrasting populations showed consistent trends with increases in the (+) groups and decreases in the (−) groups. Differences for yield (and plant height) were significant, however, only when all contrasts were subjected to a combined analysis. It was concluded that allozyme associations with yield existed, but the magnitudes of their effects on yield in the allozyme selection experiment were small in the specific population used for the study.
Physiological Responses of Barely Leaves to Foliar Applied Urea‐Ammonium Nitrate1
Authors: Turley Robert H. , Ching Te May
Published: July 2010

Foliar applied supplemental N could be a convenient and rapid method to enhance plant growth and increase seed yield and protein content. The magnitude and duration of physiological responses in greenhouse‐grown barley (Hordeum vulgare L., ‘Scio’) leaves to foliar applied urea‐ammonium nitrate (UAN) were examined by determining changes in leaf content of urea, ammonium, sugars, amino acids, soluble protein, and chlorophyll, and activities of nitrate reductase (NR), urease, glutamine synthetase (GS), and glutamate synthase (GOGAT). Within 4 h of spraying 30 g (N) kg−1 fresh weight, seedling leaves contained 44‐ and 8‐fold more urea and ammonia, respectively, than the control with a consistent increase of 17‐ and 28‐fold in the in vivo activity of urease and NR. The increases declined to control levels within 4 days. Leaf amino acid, soluble protein, and chlorophyll content were significantly increased, and the activity of GS and GOGAT was stimulated by the UAN spray. Three weekly UAN applications to 12‐week‐old plants resulted in greater total plant weight, leaf area, and leaf chlorophyll content. Leaves of mature greenhouse‐grown plants responded similarly. An additional UAN‐spray one week after anthesis significantly increased seed protein to 11% greater than that of controls. Experimental results indicated that applied UAN provided substrates for the synthesis of amino acids, chlorophyll, and soluble protein by increased enzyme activity. Induction of enzyme synthesis by substrates was indicated but not verified.
Physiological Response of Salt‐Tolerant and Nontolerant Alfalfa to Salinity during Germination1
Authors: Allen S. G. , Dobrenz A. K. , Bartels P. G.
Published: July 2010

Identification of the physiological processes involved in salt tolerance is required to develop appropriate selection criteria for breeding salt‐tolerant crops. For this purpose selected physiological characteristics were evaluated in five alfalfa (Medicago sativa L.) populations selected for NaCl tolerance during seed germination and the source population, 'Mesa‐Sirsa'. Seed of the populations (Syn‐1) was germinated in distilled water and solutions of NaCl, NaNO3, KC1, KNO3, and mannitol ranging from −1.0 to −1.6 MPa osmotic potential. The mean difference in percent germination between Mesa‐ Sirsa and ‘AZST1982’, the most salt‐tolerant population, was greater in the NaCl solutions than the other salt solutions (P < 0.01). Seed from AZST 1982 also had higher percent germination than Mesa‐Sirsa in mannitol solutions (90.6 and 2.8%, respectively, at −1.6 MPa osmotic potential). Mesa‐Sirsa had higher (P < 0.01) average seed respiration rate than AZST 1982 between 3 and 24 h of germination in NaCl solutions of −0.6 to −3.0 MPa osmotic potential. There was no significant difference between Mesa‐Sirsa and AZST 1982 for Na+ or Cl− accumulation after 48 h of germination in NaCl solutions of −0.6 to −1.8 MPa osmotic potential, or absorption of tritiated water after 6 and 12 h of germination in NaCl solutions of −1.3 and −2.0 MPa osmotic potential. Selection for NaCl tolerance in germinating alfalfa seed results in two separate types of tolerance: tolerance of an inhibitory effect specific to NaCl and tolerance of lowered water potential. Selection for NaCl tolerance of alfalfa during germination does not appear to influence ion accumulation or the rate of imbibitional water uptake.
Isogenic Heading Data Effects on Yield Component Development in ‘Titan’ Barley1
Authors: Smail V. W. , Eslick R. F. , Hockett E. A.
Published: July 2010

Crop adaptation in the Rocky Mountain northwest is strongly dependent on proper heading date. A series of six isogenic lines of ‘Titan’ barley (Hordeum vulgare L.) were developed by backcross techniques to determine the specific effect of genetically controlled heading date differences on barley yield and yield component responses. The isotypes were grown in 15 Montana environments using commercial planting rates, and in one space‐planted environment. Strong mean yield component compensation and nonsignificant yield differences among the isotypes over the drill‐planted environments were revealed by correlation analysis. Increases in all yield components and yields with later heading isotypes were found in the low‐stress, space‐planted environment. Correlations among yield and the yield components over the drill‐planted environments (stress matrix) revealed significant correlations of the yield components to heading dates, but not to yield. Correlation matrices in each environment revealed that late heading isotypes consistently developed more kernels per spike and had lower kernel weights than the early heading isotypes in most environments. Stability analysis of each isotype against the mean of each environment revealed consistent significant isotype ✕ environment interactions for spikes per square meter, few significant interactions for kernel weight, and no interactions for kernels per spike or yield among the six isotopes. This study detailed the effect of genetic maturity on yield component development over a large number of environments. The consistent kernels per spike response among the isotypes implies that yield improvements in early lines may be gained by positive selection for this character.
Soybean Cultivar Mixtures in a Narrow‐Row, Noncultivatable Production System1
Authors: Schweitzer L. E. , Nyquist W. E. , Santini J. B. , Kimes T. M.
Published: July 2010

A yield advantage of some cultivar mixtures has been observed in soybean (Glycine max (L.) Merr.] in that their yield has exceeded the weighted mean of the component cultivars grown in pure stands. However, no previous work has evaluated the performance of mixtures of soybean cultivars differing in both height and relative maturity and grown in a noncultivatable, narrow‐row production system. The objective of this 2‐yr field study was to evaluate the performance of mixtures of short‐determinate (early ‘Gnome’ or late ‘Elf’) and tall‐indeterminate (early ‘Century’ or late ‘Williams’) cultivars grown in 0.13‐m row widths. Ratios of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100 were used for the components in each two‐cultivar mixture. A significant (a = 0.05) quadratic component was observed in regression analysis of yield of Elf‐Century mixtures, indicating overcompensation. The predicted mean yield for the highest yielding ratio, 54 Elf/46 Century, was 11% greater than the pure stand yield observed for its higher yielding component, Elf, and 12% greater than the weighted mean yield of 54 Elf/46 Century based on purestand performance. The quadratic component was significant at a = 0.10 for Gnome‐Century mixtures, indicating undercompensation as compared with the pure‐stand performance of Gnome and Century. Elf‐Williams and Gnome‐Williams mixtures showed no significant regression components. Diversity in relative maturity, as well as height, may have contributed to overcompensation by Elf and Century grown in mixtures in this narrow‐row environment. This combination of the short‐late Elf with the tall‐early Century was the most diverse of the cultivar pairs evaluated in mixture.
Pink Bollworm Resistance, Lint Yield, and Lint Yield Components of Okra‐Leaf Cotton in Different Genetic Backgrounds1
Authors: Wilson F. Douglas
Published: July 2010

The two leaf (L) types, Okra leaf [2(L02)] and normal leaf, from seven genetic backgrounds (G) of cotton, Gossypium hirsutum L., were subjected over two seasons (Y) to natural populations of pink bollworm (PBW), Pectinophora gossypiella (Saunders), at Tempe, AZ. In other experiments, one of the seven Okra‐leaf strains and an Okra‐leaf cultivar, ‘Gumbo 500’, were compared with ‘Stoneville 213’, a normal‐leaf cultivar, for one to three seasons. Objectives of this study were to determine whether (i) L interacted with G or Y for seed damage caused by PBW, for lint yield, or for earliness; and (ii) yield of Okra‐leaf strains could be increased by selecting for improved yield components. An important goal is to determine whether PBW‐resistant, Okra‐leaf cottons will yield as much lint as normal‐leaf cottons in stressful environments. In the leaf shape‐genetic background experiments, significant L ✕ G and Y ✕ G interactions were detected for seed damage by PBW, but not for lint yield or earliness. Mean yield per plant and percent seed damage for the seven normal‐leaf cultivars were significantly higher than those of the Okra‐leaf strains, 36.0 vs. 30.7 g/plant, and 17 vs 14%, respectively. Okra‐leaf strains were not significantly earlier than normal‐leaf cultivars. Examination of lint yield components suggested that selection for lint per seed, a highly heritable trait, should increase lint yields of some Okra‐leaf cottons. However, bolls per plant, expected to have low heritability, was the main yield component that limited tint yield of most of those cottons. The Okra‐leaf strains and cultivar, when compared to Stoneville 213, generally had less seed damage and yielded less lint. An exception was in 1985, when Gumbo 500 did not yield significantly less lint than Stoneville 213. In a preliminary experiment in 1985, two Okra‐leaf advanced breeding stocks outyielded the normal‐leaf counterparts by 23 and 18%, respectively.

Results thus show that Okra‐leaf breeding stocks in certain genetic backgrounds have a modest level of resistance to PBW and also may yield as much or more lint than do normal‐leaf cultivars. However, the inconsistent response of some Okra‐leaf cottons emphasizes the importance of comparing those cottons with normal‐leaf cultivars over a range of environments.
Midparent Values as Indicators of Performance of Alfalfa Strain Crosses1
Authors: Miller Don , Melton Bill , Currier Cliff
Published: July 2010

Alfalfa (Medicago sativa L.) breeders strive to incorporate an increasing number of pest resistance factors into cultivars in a minimal time period. Strain crossing appears to be a desirable procedure that also minimizes the effects of inbreeding. Objectives of this study were to determine pest resistance, forage yield, and fall dormancy of strain crosses originated by bee pollinations of diverse parental sources and to determine the effectiveness of the midparent value as an indicator of performance. Twenty‐three two‐parent strain crosses were produced from 24 germplasm sources in field isolation cages and pollinated by honeybees (Apis mellifera L.). Parental sources were planted within crossing blocks in a checkerboard pattern with four to six replications. Seed of each parent was harvested and processed separately. Strain crosses were formulated by mixing equal quantifies of seed from each parent. Strain crosses were evaluated for resistance to four insects and four diseases, forage yield, and fall dormancy. Pest resistance evaluations used standardized testing procedures. Forage yield was measured for a 2‐yr period in field plots. Fall dormancy was based on natural plant height measurements taken in the forage production plots 3 weeks after the last fall harvest. Performances of the strain crosses were near the midparent values in 84% of the evaluations. Deviations from midparent values were most frequent for resistance to the spotted alfalfa aphid and for fall dormancy. Deviations from midparent values for one trait were not indicative of expected results for other traits in specific crosses. It was concluded that bee‐pollinated strain crosses of widely divergent parental sources offers an effective method of incorporating multiple‐pest resistance into alfalfa cultivars while avoiding some inbreeding effects associated with a narrow genetic base.
Genetic Variability and Heritability for Resistance to Early Leafspot in Four Crosses of Virginia‐Type Peanut1
Authors: Green C. C. , Wynne J. C.
Published: July 2010

The potential for the development of large‐seeded, high‐yielding cultivars in peanut (Arachis hypogaea L.) with improved resistance to early leafspot (Cercospora arachidicola Hori) was determined in four crosses. A large‐seeded, high‐yielding cultivar (✕NC 6✕) was crossed to four small‐seeded, low‐yielding genotypes (PI 109839, PI 270806, PI 269685, and ‘Kanyoma’) with reported resistance to early leafspot. Estimates of additive and additive ✕ additive genetic variance for lesion count were determined for each cross and used to estimate narrow‐sense heritabilities. Realized heritabilities were determined after one generation of selection among F5 lines for high and low lesion count. Additive genetic variance was greater than the additive ✕ additive genetic variance in the crosses NC 6 ✕ PI 109839, NC 6 ✕ PI 270806, and NC 6 ✕ PI 269685, whereas only additive ✕ additive genetic variance was found in the cross NC 6 ✕ Kanyoma. The variance‐component heritability estimates were moderate to high for resistance to early leafspot, ranging from 0.41 to 0.78. Estimates of realized heritability, which ranged from 0.45 to 0.57, were similar to the variance‐component estimates.
Expression and Inheritance of Resistance of ‘Marquillo’ Wheat to Hessian Fly Biotype D1
Authors: Mass F. B. , Patterson F. L. , Foster J. E. , Hatchett J. H.
Published: July 2010

Resistance of ‘Marquillo’ wheat (Triticum aestivum L.) to the Hessian fly [Mayetiola destructor (Say)] has been used effectively wheat cultivars for more than 30 yrs. Previous analyses of the genetic basis for resistance have been inconclusive. Our objectives were to determine the optimum temperature for expression of the Marquillo resistance in seedlings, to determine the number of genes controlling resistance to biotype D of Hessian fly, and to determine the relation of the Marquillo gene to other genes for resistance. We used biotype D of Hessian fly and standard methods of analysis of resistance of seedling progenies. The Marquillo resistance was expressed most consistently at 16°C. One partially dominant gene controlled resistance at this. temperature in crosses of Marquillo by susceptible cultivars. The Marquillo resistance appeared to be inherited independently from the H12 resistance in the F2 plant progenies of Marquillo/ Luso crosses. Known dominance and genomic relationships imply that the Marquillo gene is distinct from all other known genes for resistance to biotype D of the Hessian fly.
Variable Reaction within Corn Inbreds to Maize Dwarf Mosaic Virus not Genetically Controlled1
Authors: Scott Gene E. , Rosenkranz Eugen
Published: July 2010

Some plants of corn (Zea mays L.) inbreds resistant to maize dwarf mosaic virus (MDMV) develop symptoms when mechanically inoculated with the virus in the field. The objective of this study was to determine if variability for occurrence of maize dwarf mosaic (MDM) symptoms among plants of resistant inbreds could be attributed to genetic variability within that inbred. Eight plants with and eight without MDM symptoms in each of three inbreds (Tx601, Mo18W, and T220A) were self‐pollinated and the progenies from symptomless plants were compared with progenies from diseased plants for their reaction to inoculation with MDMV. Comparisons were made in three field tests and one greenhouse test. In the four environments, the average incidences of plants with MDM symptoms were 5, 12, 2, and 68% for the progenies from symptomless plants and 5, 12, 3, and 71% for progenies from diseased plants. Thus, whether plants of these three resistant inbreds develop symptoms or remain symptomless is not conditioned by genetic variability within the inbred.
Variation in Regrowth and Its Implications for Multiple Harvest of Guayule1
Authors: Estilai A. , Waines J. G.
Published: July 2010

To distribute the high cost of stand establishment across several years of production, guayule (Parthenium argentatum A. Gray) is harvested after a minimum of 4 yr by digging entire plants. An alternative is multiple harvest of the shrub, cut at ground level, at an optimal interval as long as an economic yield is obtainable. for this, guayule cultivars with nearly 100% survival after each harvest are required. The objectives of this study were to compare guayule cultivars and selections in the filed for their regrowth ability after harvest, and to determine the relative contributions of under‐ and aboveground parts to the overall rubber yield of the plant. In a completely randomized design with three replications, 84‐week‐old dormant, 96‐week‐old actively growing, and 132‐week‐old dormant plants of 11 cultivars and selections were cut at ground level in February and May 1985, and February 1986. Harvest date was found to be a critical factor: an average of 49% of the plants harvested in February regrew, while only 1.4% of those harvested in May regrew. Marked differences between lines were observed in the February harvests. Approximately 97% of selection C2501 plants produced vigorous regrowth, but only 5.5% of C2551 plants regrew. Regrowth of the other entries lay within these extremes. Five of the entries were compared for the contributions of the under‐ and aboveground parts to the overall yield. The underground part produced 6.0 to 13.5% of the total rubber yield. If plants were harvested at 5 and 10 cm above the soil surface, 3.4 to 8.9% and 9.4 to 22.5%, respectively, of the aboveground yield was not recovered. This study identified selections that meet the demands of multiple harvest.
Stability of Harvest Index and Grain Yield in Winter Wheat1
Authors: Sharma R. C. , Smith E. L. , McNew R. W.
Published: July 2010

Cereal breeders seeking yield improvement have considered that selection for harvest index (HI) might be more effective than selection for yield per se. However, no information is available on the stability of HI across diverse environments. This study was conducted to determine the stability of HI and grain yield and to study the correlation between the 2 in 10 adapted winter wheat (Triticum aestivum L.) genotypes. The genotypes were grown in replicated tests at six locations in Oklahoma in each of 2 yr. Two stability parameters were obtained as linear regression coefficient (b) of an entry mean on the average of all entries in each environment and deviations from regression (s2d), and stability was tested with the hypotheses b = 1.0 and s2d = 0. Genotypes differed significantly for HI and grain yield, and significant genotype ✕ environment interactions occurred for both traits. Regression coefficients ranged from 0.65 to 1.46 and 0.75 to 1.17 for HI and grain yield, respectively. Deviations from regression were significant for most genotypes for both traits. On the basis of the estimates of stability parameters, all genotypes were unstable for both traits. Correlation coefficients between HI and grain yield were inconsistent in good and poor environments. This study suggested that both HI and grain yield are significantly affected by environmental changes. Consequently, selection for yield per se might be as effective as selection for HI for improving wheat grain yields in the diverse environments in the Southern Great Plains.
Digestible and Indigestible Cell Wall Carbohydrates of Flaccidgrass, Tall Fescue, and Coastal Bermudagrass1
Authors: de Ruiter J. M. , Burns J. C.
Published: July 2010

Structural carbohydrates of forage plants are possible indicators of differing ruminal fermentation characteristics. The objectives of this study were to assess the use of trifluoroacetic acid (TFA) hydrolysis in characterizing the cell wall of an immature (IM) and mature (MA) subtropical perennial grass, flaccidgrass (Pennisetum flaccidum Griseb.), and to make comparisons with a midseason's growth of IM Coastal bermudagrass (Cynodon dactylon L. Pers.) and MA Kentucky 31 tall fescue (Festuca arundinacea Schreb.). In vitro digestion for 20 and 72 h was followed by neutral detergent fiber (NDF) or acid detergent fiber (ADF) determination to estimate the disappearance of these detergent in soluble fractions. Hemicellulose (HC) was determined by difference (NDF minus ADF). vitro disappearance (IVD) of NDF, ADF, and HC (determined component sugar differences before and after 72‐h fermentation) from IM flaccidgrass averaged 58% greater than MA flaccidgrass, In vitro disappearance of the fiber fractions was similar for both tall fescue and bermudagrass, and intermediate between the IM and MA flaccidgrass. The TFA hydrolysis of NDF yielded xylose, glucose, arabinose, and galactose compared with xylose, glucose, and only traces of arabinose from ADF. Xylose and glucose constituted the greatest proportion of monosaccharides hydrolyzed from all forage fiber residues. Of the individual monomers hydrolyzed from flaccidgrass NDF, xylose showed the least disappearance (652 g kg−1 for IM and 380 g kg−1 for MA) and glucose the most (943 g kg−1 for IM and 853 g kg−1 for MA). Xylose IVD was most influenced by plant maturity. Monosaccharides hydrolyzed from NDF and HC of IM flaccidgrass had greater IVD than MA tall fescue and IM bermudagrass. Mature flaccidgrass composition and IVD of the insoluble residues were similar to IM bermudagrass, indicating that flaccidgrass would be of higher quality than bermudagrass at similar maturity. Flaccidgrass maturity effects were significant (P ≤ 0.05) for xylose, glucose, and total hydrolyzed monosaccharides.
Effect of Semidwarf Stature, Head Number, and Kernel Number on Grain Yield in Barley in Morocco1
Authors: Zahour Ahmed , Rasmusson Donald C. , Gallagher Lynn W.
Published: July 2010

The purpose of this research was to obtain information on the contribution of semidwarf stature, high head number, and high kernel number to increasing grain yield in barley (Hordeum vulgare L.) in Morocco. The three traits were selected because of their potential to enhance grain yield. Six populations, two for each character, were developed by crossing the Moroccan cultivar ‘Arig 8’ to six Minnesota lines and then backcrossing the F1's to Arig 8. This was followed by selection in the BC1F3 generation in St. Paul, MN, and in the BC1F4 generation in Morocco. Data were collected in Morocco from yield trials conducted in four field environments in 1981–1982 and 1982–1983. The procedure of introducing yield‐related traits via backcrossing to an adapted cultivar gave progenies that were superior to the relatively high‐yielding local cultivar, Arig 8. Eleven lines from the head number populations and eleven from the kernel number populations produced significantly higher grain yields than Arig 8. Two semidwarf lines were superior in yield to Arig 8. Semidwarf selections had increased lodging resistance and harvest indices, but were relatively taller in Morocco than in Minnesota. Generally, the highest yielding lines had modestly higher head number (differences not significant) or higher kernel number than Arig coupled with high kernel weight. Kernel weight was higher or near the high level of Arig 8 in most of the highest yielding lines. We could not determine whether the transgressive segregation for grain yield resulted from breeding for the three characters in question or from the reassortment of other genes from Arig 8 and the Minnesota parents. In this breeding effort the major limiting factor appeared to be an inability to consistently obtain uniform yield trials, and not available germplasm.
Reactions of Oat, Barley, and Wheat to Infection with Barley Yellow Dwarf Virus Isolates1
Authors: Baltenberger D. E. , Ohm H. W. , Foster J. E.
Published: July 2010

Two isolates of barley yellow dwarf virus (BYDV) were used determine if oat (Avena sativa L.), barley (Hordeum vulgare L.), and wheat (Triticum aestivum L. em. Thell.) cultivars with diverse sources of BYDV tolerance reacted differently when infected with either of the two isolates. Seedlings were infested in the one‐leaf stage with viruliferous oat‐bird cherry aphids (Rhopalosiphum padi L.) carrying either isolate RPV or PAV. Infested and noninfested (control) seedlings were transplanted to the field in a split‐plot design with three replications. Cultivars were assigned at random to whole plots. The RPV and PAV isolates and control were assigned to subplots. Analyses of six different plant and agronomic characters showed that ‘Ogle’ oat and ‘CM’ barley were more susceptible to the PAV isolate than to the RPV isolate. ‘Porter’ and Accession 1575 oat and the wheat ‘Elmo’ and ‘Caldwell’ were tolerant to both isolates, while ‘Clintland 64’ oat and ‘Abe’ wheat were susceptible to both isolates. Therefore, some cultivars react differently when infected with the RPV or PAV isolates of BYDV. Infection with single BYDV isolates in all cultivars had little effect on harvest index; however, BYDV had significant effects on plant height, number of tillers per plant, and grain yield. Infection by both RPV and PAV caused a significant increase in BYDV severity in all cultivars compared to infection by PAV or RPV singly.