bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Erect Leaf Angle on Grain Yield in Barley1
Authors: Tungland Lee , Chapko Louis B. , Wiersma John V. , Rasmusson Donald C.
Published: July 2010

Breeding for erect leaf angle has been suggested as a method for increasing grain yield in cereal crops. This study was designed to investigate the effect of erect leaf angle on grain yield in barley (Hordeum vulgare L.). Five cycles of crossing and selection were used to incorporate the erect leaf of C16146 into adapted Minnesota barleys. Subsequently, erect leaf lines from five populations were evaluated in yield trials. In addition, the yield response of erect leaf lines was compared to check cultivars at planting rates of 56, 94, and 132 kg ha−1. No significant difference was found for grain yield between erect leaf lines and check cultivars in three populations. Comparisons of erect and horizontal leaf progeny in two other populations showed no difference in one population; however, the horizontal leaf group was higher yielding in the second. The yield responses of erect and horizontal leaf‐types to the three planting rates were similar, although significant interaction was observed for kernel number and weight, suggesting that canopy type may influence these components. Erect leaf lines had less culm flex, more erect spikes, lower head number, later maturity, and greater lodging resistance than horizontal leaf lines. These associations with the erect leaf trait, which likely resulted from pleiotropy, were confounded with the effect of erect leaves and likely reduced the chances of finding a positive grain yield response. Although the potential of increased lodging resistance and the leaf‐type density interaction for kernel number and weight offer some encouragement for continuing research, results from our study provide little or no evidence that erect leaf angle enhances grain yield in barley.
Sub Okra Leaf Influence on Cotton Yield1
Authors: Meredith William R. , Wells Randy
Published: July 2010

A study in three diverse environments in 1985 near Stoneville, MS compared the yield of eight BC4F3‐derived sub okra leaf (Lu2) and normal leaf (I2) cotton plants (Gossypium hirsutum L.). Sub okra leaf cotton averaged significantly higher yields (3%) than normal leaf cotton. Also, a significant (P = 0.03) leaf type ✕ cultivar background interaction was detected. For the cultivar backgrounds of ‘Stoneville 825’, ‘Deltapine 26’, ‘Deltapine 5540’, DES 2–10, and ‘Tamcot CAMD‐E’, the average yield of sub okra and normal‐derived populations was 968 and 971 kg/ha, respectively. For the backgrounds of ‘DES 422’, ‘SC‐’, and MD 65‐11 the average yield was 972 and 894 kg/ha, respectively. No major differences between sub okra and normal leaf populations for earliness, yield components, or fiber properties were detected. The results from these backcross‐derived populations indicate that previous evaluation studies using F3 hybrid populations that were genetically similar except for one simple inherited trait, leaf type, were an acceptable method for measuring approximate yield potential of the new trait. This study indicates that for some genetic backgrounds and environments that the use of sub okra to replace normal leaf offers a potential yield increase of 3 to 5%.
Genetic Analyses of Nonfluorescent Root Mutants Induced by Mutagenesis in Soybean1
Authors: Sawada Souhei , Palmer Reid G.
Published: July 2010

Nonfluorescent root mutants in soybean [Glycine max (L.) Merr.] are useful as markers in genetic studies and in tissue culture research. Our objective was to obtain mutagen‐induced nonfluorescent root mutants and to conduct genetic studies with them. Thirteen nonfluorescent mutants were detected among 154 016 seedlings derived from soybean lines treated with six mutagens. One of these mutants, derived from ‘Williams’ treated with 20 kR gamma rays, did not correspond to any of the known (standard) nonfluorescent spontaneous mutants. This is the first mutagen‐induced nonfluorescent root mutant in soybean. It was assigned Genetic Type Collection no. T285 and the gene symbol fr5 fr5. The fr5 allele was not located on trisomics A, B, or C and was not linked to five chlorophyll‐deficient mutants (y9, y11, y12, y13, and y20‐k2) or flower color mutant w1. The remaining nonfluorescent root mutants were at the same loci as known spontaneous mutants; i.e., four had the fr1 allele, five had the fr2 allele, and three had the fr4 allele.
Inducing Male Fertility in Crosses Between Pearl Millet and Pennisetum orientale Rich.1
Authors: Dujardin Michel , Hanna Wayne
Published: July 2010

Male sterility in interspecific crosses between cultivated and wild species often interferes with the transfer of exotic germplasm. Our research objective was to investigate various pathways of inducing male fertility in interspecific hybrids of pearl millet (Pennisetum americanum L. Leeke) (2n = 14) ✕ Pennisetum orientale Rich. (2n = 36) and their derivatives. The F1 interspecific hybrids between pearl millet (A chromosomes) and P. orientate (O chromosomes), 2n = 25 (7A + 18O), were partially female fertile and male sterile regardless of whether they received male‐sterility‐inducing or male‐fertility‐inducing cytoplasm from pearl millet. The BC1 F1 hybrids from backcrosses to diploid pearl millet as males included 23‐chromosome (14A + 9O) and 27‐chromosome (7A + 20O) derivatives that were male and female sterile, and 32‐chromosome (14A + 18O) plants were partially female and male fertile, provided they received fertility‐inducing cytoplasm. Male‐fertile 32‐chromosome plants also were produced by pollinating male‐fertile tetraploid 2n = 4x = 28 pearl millet with P. orientate pollen. The 32‐chromosome plants ranged in pollen stainability from 30 to 50%, were highly self‐incompatible with only sparse, selfed seed set, and showed 2 to 4% aposporous embryo sac development. Tetraploid pearl millet ✕ 32‐chromosome plant crosses produced BC derivatives, with 28 to 30 chromosomes but were male and female sterile. Crosses of 23‐chromosome (14A + 9O) derivatives ✕ pearl millet produced 14‐chromosome pearl millet progeny by elimination of the P. orientate genome. The 14‐chromosome progeny lacked P. orientate characteristics. Because they are partially fertile, the 2n = 32 chromosome plants provided a valuable bridge for germplasm transfer between pearl millet and P. orientate. Germplasm transfer between genomes of the two species probably will require nonconventional methods such as use of radiation to produce small translocations or other genetic engineering methods such as vectors and transposable elements.
Diallel Analysis of Maize Resistance to Sorghum Downy Mildew1
Authors: Borges Orángel L. F.
Published: July 2010

A diallel cross, including reciprocals, of six maize (Zea mays L.) inbred lines was analyzed for reaction to sorghum downy mildew [Peronosclerospora sorghi (Weston and Uppal) C.G. Shaw]. The crosses between the resistant lines and the susceptible ‘48‐S‐28’ showed intermediate disease reaction, suggesting a polygenic system for resistance to sorghum downy mildew in maize. The combining ability analysis revealed that both additive and nonadditive gene effects were present. However, additivity was clearly more important in determining disease reaction. Significant maternal differences were found, indicating that maternal and/or cytoplasmic inheritance is involved in the reaction to P. sorghi. Recurrent selection would be appropriate for accumulating genes for resistance to sorghum downy mildew in maize.
Development of Nitrogen‐Efficient Prolific Hybrids of Maize1
Authors: Moll R. H. , Kamprath E. J. , Jackson W. A.
Published: July 2010

Selection was conducted to develop single‐cross hybrids of maize (Zea mays L.) with high grain yield, high levels of prolificacy, and high values for the components of N‐use efficiency. Hybrid and S1 progenies were developed from reciprocal crosses and self‐pollinations of paired plants of the improved ‘Jarvis’ and ‘Indian Chief’ populations, JR10 and IRI0. Selection among hybrid S0 ✕ S0 progenies for high yield at high N and selection for two ears per plant in the parental lines was effective in increasing the number of ears per plant and N uptake, but it resulted in no increase in yield over the population hybrid, JR10 ✕ IR10. Subsequently, selection carried out among remaining hybrid S1 ✕ S1 progenies for five criteria (N‐use efficiency averaged over two levels of N supply, three components of N‐use efficiency, and ears per plant) was effective in improving yield at high N supply as well as N‐use efficiency, N‐uptake efficiency, and efficiency of utilization of accumulated N. Nitrogen‐use efficiency averaged over levels of N supply was the most effective selection criterion. In the selected prolific hybrids, both major components of yield (ears per plant and weight per ear) were highly correlated with grain yield. Of the six superior hybrids, five showed significant positive correlations between ears per plant and weight per ear.
Combining Ability Effects for Mineral Elements in Forage Sorghum Hybrids1
Authors: Gorz H. J. , Haskins F. A. , Pedersen J. F. , Ross W. M.
Published: July 2010

The concentrations of minerals in forages are important in satisfying animal requirements, but little attention has been given to determining these concentrations in forage sorghum [Sorghum bicolor (L.) Moench.] breeding programs. In this 2‐yr study, the objectives were to determine the contents, genetic variability, combining ability effects, and correlations for 12 mineral elements in 49 experimental hybrids of forage sorghum. Mineral elements studied were N, Mg, Si, P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn. General combining ability (GCA) effects exceeded specific combining ability (SCA) effects for all elements except P, Cl, and Fe in females, and S and Cl in males. The GCA and SCA effects in females were low for both Fe and Cu. Genetic ratios, resembling heritability, were higher for GCA than SCA except for Cl and Fe in females, and S and Cl in males. Thirty phenotypic correlations among the 12 elements were statistically significant. Some of the highest values were from the relationships of N with P, S, Cu, and Zn; Mg with Si and Cu; Si with Ca; P with Cu and Zn; S with K; and Cu with Zn. Some of the highest phenotypic correlations calculated among the mineral elements and 12 agronomic and quality traits were the positive association of protein with P, and the negative relationship of height with N and P, Brix of stem juice with K, and neutral detergent fiber with P. Data obtained in these studies show the feasibility of altering the mineral content of forage sorghum by breeding.
Resistance to Three Species of Root‐Knot Nematode in Soybean1
Authors: Luzzi B. M. , Boerma H. R. , Hussey R. S.
Published: July 2010

Root‐knot nematodes (Meloidogyne spp.) significantly reduce yield of soybean [Glycine max (L.) Merr.] in the southeastern USA. Cultivars with higher levels of resistance than currently available will reduce yield loss in nematode‐infested fields and may eliminate the need for expensive nematicides. Soybean genotypes (2370) in the Southern Germplasm Collection (Maturity Group V, VI, VII, and VIII) were sequentially screened in a greenhouse to identify the highest levels of resistance to M. incognita (Mi), M. arenaria (Ma), and M. javanica (Mj) based on root galling and nematode reproduction. After three levels of screening using an inoculum density of 2000 nematodeggs per plant, 61, 56, and 61 genotypes were identified as resistant to Mi, Ma, and Mj, respectively. In the next two screening levels, two or three inoculum densities were used to differentiate the levels of resistance among these genotypes. The screening for Mi identified ‘Amredo’, PI96354, PI408088, and PI417444 with lower gall indices, fewer eggs per root system, and eggs per gram of root than ‘Forrest’, the resistant check. In the Ma screening PI200538 and PI230977 had lower gall indices and fewer eggs per root system than ‘Jackson’, the resistant check. The Mj screening identified PI230977 with a lower gall index than ‘Gordon’, the resistant check. These new sources of resistance will be useful to soybean breeders in developing cultivars with higher levels of resistance to root‐knot nematodes than currently available in commercial cultivars.
Precision of Genetic Variance and Heritability Estimates from Sorghum Populations1
Authors: Knapp S. J. , Ross W. M. , Stroup W. W.
Published: July 2010

The emphasis of variance component and heritability estimation experiments has been on point estimation. Minimal attention has been given to confidence interval estimation. Our research was motivated by the limited use of confidence intervals and the importance of interval estimation to the statistical inference process. Our objectives were to evaluate variance component and heritability estimate precision from confidence interval estimate data and to describe the effects of experiment size and point estimate magnitude on interval estimate width. Point and interval estimates (1 ‐ α = 0.90) for the family variance component and heritability on a family mean basis were obtained from half‐sib, full‐sib, or S1 family selection experiments in four sorghum [Sorghum bicolor (L.) Moench.] populations. Agronomic traits were measured on 200 families per population grown on a Typic Argiudoll soil at Mead, NE, in 1981 and 1982 in a replications‐in‐incomplete blocks experimental design. Confidence interval estimate widths (widths) were functions of F =(family mean square)/(family ✕ year mean square) Mf/Mfy and tabled F‐values determined by degrees of freedom for Mf (dff) and Mfy (dffy) and the confidence coefficient (1 ‐ α). Ratios of widths point estimates (ratios) decreased at a decreasing rate as F increased for fixed F‐values. Widths and ratios decreased at a decreasing rate as dff and dffy increased for fixed F. Ratios for drf= dfy = 190 for variance components were 0.32 for F = 10.0 and 4.27 for F = 1.11, and for heritability were 0.05 for F = 10.0 and 4.05 for F = 1.11. Our data demonstrated the problems of wide interval estimates for large experiments and variation in precision among point estimates for experiments of fixed size.
Drought/Greebug Interactions: Photosynthesis of Greenbug Resistant and Susceptible Wheat1
Authors: Ryan James D. , Johnson R. C. , Eikenbary R. D. , Dorschner K. W.
Published: July 2010

The greenbug [Schizaphis graminum (Rondani)] is a severe pest of wheat (Triticum aestivum L.) in the Great Plains that can cause leaf chlorosis and tissue death. The simultaneous presence of drought and greenbug stress in a wheat crop has frequently resulted in very heavy grain yield losses. Our objective was to quantify the effect of greenbug stress on photosynthetic characteristics of susceptible and resistant growth chamber grown plants both with and without drought stress. Data collected from single infested leaves of susceptible plants (cv. Sturdy) showed greenbug (biotype C) induced decreases in the C assimilation rate (A), transpiration (E), stomatal conductance to water vapor (gs), and total chlorophyll (CHL). No significant effects were noted for water use efficiency (WUE), intercellular CO2 concentration (Ci), or specific photosynthetic activity of chlorophyll (A/ CHL). Infestations on a resistant plant (OK 80268) caused a significant drop in E and gs only. Although greenbug damage decreased gs, A vs. Ci response curves for infested and noninfested susceptible plants showed that there was no increased stomatal limitation to A associated with greenbug damage. Carbon dioxide saturated photosynthesis was lowered by about one‐third, indicating a loss of photosynthetic capacity in the mesophyll associated with chlorosis. When greenbug infestations were applied to drounght‐stressed, susceptible plants, sharp drops in WUE and A/CHL were observed in addition to an increase in Ci. The results show that greenbug induced decreases in A were caused by decreased photosynthetic capacity in the mesophyll rather than decreased gs and that drought stress in combination with greenbugs caused damage to the mesophyll capacity for photosynthesis beyond that explained by chlorosis alone.
Yield Accumulation, Leaf Area Index, and Light Interception of Smooth Bromegrass1
Authors: Engel R. K. , Moser L. E. , Stubbendieck J. , Lowry S. R
Published: July 2010

Smooth bromegrass (Bromus inermis Leyss.) is a cool‐season grass used extensively in the midwestern USA for spring and fall grazing. Smooth bromegrass has limited production in this region during the summer. This study was conducted to document the growth characteristics and yield accumulation of smooth bromegrass under various levels of N fertilizer. Live yield (dry matter yield of living herbage), leaf area index (LAI), light interception (LI), and crop growth rate (CGR) were determined on an established stand of ‘Lincoln’ smooth bromegrass grown on a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls) in eastern Nebraska. Zero, medium, and high N levels were maintained at each growth period. Irrigated spring, summer, and fall growths of smooth bromegrass were sampled at 1‐ or 2‐week intervals in 1981 and 1982 depending on growth rate. Live yield, LAI, and CGR were all highest in the spring. Live yield reached a maximum of 10.3 Mg ha−1, CGR reached a maximum of 190 kg ha−1 day−1, and LAI reached a maximum of 6.8, which intercepted up to 99% of the incoming photosynthetic photon flux density during the spring growth period. Summer values for maximum live yield, LAI, and LI were 3.2 Mg ha−1, 4.1, and 73%, respectively. Maximum values of live yield, LAI, and LI for the fall growth period were 2.8 Mg ha−1, 5.2, and 97%, respectively. Smooth bromegrass has different growth and canopy characteristics at different seasons of the year. Growth models should consider seasonal differences in canopy characteristics as well as environmental parameters.
Yield Components, Plant Morphology, and Forage Quality of Alfalfa as Influenced by Plant Population1
Authors: Volenec J. J. , Cherney J. H. , Johnson K. D.
Published: July 2010

Understanding differences in herbage yield of alfalfa (Medicago sativa L.) can be simplified by using yield components: plants per area; shoots per plant; and yield per shoot (YPS). Our objective was to examine the influence of plant population on yield components, plant morphology, and forage quality of ‘Vernal’, ‘Hi‐Phy’, and Beltsville International Composite 5‐WH alfalfa. Ten‐week‐old seedlings were transplanted in 0.9‐m2 plots at populations of 11, 22, 43,97, and 172 plants m−2 in early May 1984 and 1985. Plants were clipped in late June of both years, and plants were harvested at first flower, twice in 1984, and three times in 1985. Yield per area increased with plant population up to 172 plants m−2, while yield per plant, shoots per plant, and YPS decreased with increasing plant populations. Path coefficient analysis indicated that YPS was always an important component of yield per plant, but especially so at high plant populations. Stem diameter and nodes per stem decreased as plant population increased. Stems from plants grown at 172 plant m−2 populations contained 10 g kg−1 less lignin and were 30 g kg−1 more digestible than were stems from plants grown at 11 plant m−2 populations. Vernal produced more and finer stems per plant, and these stems were lower in lignin and higher in digestibility when compared to the other cultivars. Selection of genotypes with high YPS may be an effective means of increasing yield, but may result in larger diameter, less digestible stems.
An Improved Technique for Measuring Resistance to Root Pulling in Maize1
Authors: Beck D. L. , Darrah L. L. , Zuber M. S.
Published: July 2010

Root‐pulling resistance is one method for selecting maize (Zea mays L.) genotypes with superior resistance to root lodging. We compared a mechanical and a manual technique for speed, efficiency, and accuracy. The manual procedure for root pulling included a clamp and scale mounted onto a bipod and lever. The mechanical procedure consisted of a similar scale and clamp mounted to the boom of a small, maneuverable, skid‐steer loader. Three maize hybrids with a range of resistance to root pulling were used. Competitive plants were pulled at 20 days after flowering. The mechanical technique was considerably faster and required far less labor than the manual method. Mean root‐pulling values, measured as load‐kilograms per plant were significantly higher for the mechanical technique (182) than for the manual technique (154). The accuracy of the techniques was similar based on a homogeneity of variance test and comparisons of coefficients of variation from separate analyses of variance for each hybrid.
Chromosomal Arm Location and Gene‐Centromere Distance of a Dominant Gene for Male Sterility in Wheat1
Authors: Maan S. S. , Carlson K. M. , Williams N. D. , Yang T.
Published: July 2010

To establish the chromosomal location and gene‐centromere distance of a dominant gene (Ms3) for male sterility in wheat (Triticum aestivum L.), male‐sterile euploid ‘Chris’ plants were crossed with a set of nullisomic‐tetrasomics of ‘Chinese Spring’ wheat, and the resulting male‐sterile trisomic‐monosomic (2n = 42;19″ + 1″ + 1′) F1s were testcrossed to their respective ditelosomics (20″ + t″) and/or double ditelosomics (20″ + 21″). The testcross progenies were cytologically examined for meiotic chromosome number and pairing in the pollen mother cells (PMCs). In the testcross progeny of trisomic SD‐monosomic 5A, all male‐fertile plants (except two) had PMCs in which paternal telocentric(s) remained unpaired at meiosis, and all male‐sterile plants (except three) had PMCs in which paternal telocentric(s) were paired with their maternal monosome 5A. Of the five cytologically exceptional plants, three male‐sterile plants received a short‐arm telocentric and their PMCs had 20″ + t″(5AS) + t″(5AL); two male fertile plants received a long‐arm telocentric or isocentric produced by the misdivision of the maternal chromosome 5A. In the remaining 20 testcross progenies, the sterility or fertility of the segregants was not related to the presence or absence of the maternal monosome. These results indicated that the Ms3 gene was located on the short‐arm of chromosome 5A. Data from additional crosses including (i) exceptional male‐sterile plants [20″ + t″(5AS) + (SAL)] ✕ 20″ + t″(SAL), and (ii) male‐sterile plants with 20″ + ttl″ (SAL + 5AS + 5A) − euploid Chris confirmed that the Ms3 gene was located close to the centromere (c.o. = 0.03) on the short‐arm of chromosome 5A.
Designations for Genes in Wheat Germplasm Conferring Greenbug Resistance1
Authors: Tyler J. M. , Webster J. A. , Merkle O. G.
Published: July 2010

The greenbug [Schizaphis graminum (Rondani)], is a pest of wheat (Triticum aestivum L.). Only two sources of greenbug‐resistant wheat germplasm were documented prior to 1980. In the last 5 yr, three additional sources have been identified. Since there are now five distinct sources of resistance, it is appropriate to assign numerical designations to these genes, as this will aid in communications among breeders and geneticists. Our objective was to show that greenbug resistance in the wheat germplasms “Dickinson” Selection 28A (DS 28A), ‘Amigo’, ‘Largo’, CI 17959, and CI 17882 is conditioned by five different genes. Two criteria were used to distinguish genes: differing reactions to a greenbug biotype and nonallelism. Original data and a review of literature were combined to show that the five genes are different. The numerical designations Gbl, Gb2, Gb3, Gb4, and Gb5 were suggested for the genes in DS 28A, Amigo, Largo, CI 17959, and CI 17882, respectively.
Enhanced Regeneration from Wheat Callus Cultures Using Dicamba and Kinetin1
Authors: Papenfuss J. M. , Carman J. G.
Published: July 2010

The purpose of this study was to compare the effects of 2,4‐D (2,4‐dichlorophenoxyacetic acid) and dicamba (3,6‐dichloro‐o‐anisic acid) on cultured immature wheat (Triticum aestivum L.) embryos from a responsive (‘PCYT 10’) and a less responsive (‘Fremont’) cultivar by evaluating precocious germination, callus growth, and shoot formation. Dicamba (2 mg/L) reduced precocious germination of cultured 14‐ and 21‐day‐old embryos of both cultivars to a greater extent than 2,4‐D (2 mg/L). Dicamba also induced formation of call! with significantly greater mass and numbers of shoots, especially when embryos were cultured in the dark on modified Murashige and Skoog medium (MSM). The addition of 0.1 mg/L kinetin (6‐furfurylaminopurine) improved the shoot‐forming ability of cultures on medium containing 2,4‐D or dicamba. The positive effects of dicamba on callus growth and shoot formation in the dark were significantly reduced when calli were exposed to a 16‐h photoperiod (4 W/m2). This photoperiod did not alter the effect of dicamba on precocious germination, nor did it affect growth or shoot formation of cultures incubated on medium that contained 2,4‐D. Overall, PCYT 10 was superior to Fremont in tissue culture with > 50 shoots per explant appearing within 6 weeks on many of the cultures. However, significant cultivar ✕ medium interactions were found, which emphasize the importance of evaluating the differential effects of culture variables when testing cultivars for tissue culture responsiveness.
Effect of Growth Retardants on Seed Yield of Birdsfoot Trefoil1
Authors: White S. K. , McGraw R. L. , Russelle M. P.
Published: July 2010

The difficulty of obtaining reliable seed yields from birdsfoot trefoil (Lotus corniculatus L.) has limited its use as a forage. Several growth retardants reported to increase seed production in other species were evaluated on birdsfoot trefoil in the greenhouse. Four field experiments were conducted during 1984 and 1985 to evaluate the effects of the two most promising growth retardants, daminozide [butanedioic acid mono (2,2‐dimethylhydrazide)] and mepiquat chloride (l,l‐dimethyl‐piperidinium chloride), on reproductive characteristics of two genotypes and two cultivurs of birdsfoot trefoil. These growth retardants affected neither the yield ratio of reproductive to total dry matter production nor seed yield in any of the four experiments.
Molecular Marker‐Facilitated Investigations of Quantitative Trait Loci in Maize. II. Factors Influencing Yield and its Component Traits1
Authors: Stuber C. W. , Edwards M. D. , Wendel J. F.
Published: July 2010

Because traits such as grain yield are polygenically inherited and strongly influenced by environment, determination of genotypic values from phenotypic expression is not precise and improvement strategies are frequently based on low heritabilities. Increased knowledge of the genetic factors involved in the expression of yield should enhance the improvement of this trait. The objectives of this study were to identify and locate genetic factors (i.e., quantitative trait loci, QTL's) associated with grain yield and 24 yield‐related traits in two F2 populations of maize (Zea mays L.) using isozyme marker loci. (The populations were generated by selfing the F1, hybrids CO159 ✕ Tx303 and T232 ✕ CM37.) In addition, assessments of the types and magnitudes of gene effects expressed by these QTL's were made. About two‐thirds of the associations among 17 to 20 marker loci and the 25 quantitative traits were significant with a large proportion of these at P < 0.001. Proportions of variation accounted for by genetic factors associated with individual marker loci varied from less than 1% to more than 11%. Although individual marker loci accounted for relatively small proportions of the phenotypic variation for these yield‐related traits, differences between mean phenotypic values of the two homozygous classes at certain loci were occasionally more than 16% of the population mean. Also, different genomic regions contributed to yield through different subsets of the yield‐related traits. Predominant types of gene action varied among loci and among the 25 quantitative traits. For plant grain yield, top ear grain weight, and ear length, the gene action was primarily dominant or overdominant. However, mainly additive gene action was implicated for ear number, kernel row number, and second ear grain weight. Results from these studies should prove to be useful for manipulating QTL's in marker‐facilitated selection programs.
Effect of Endosperm Type on Pericarp Thickness in Sweet Corn Inbreds1
Authors: Tracy W. F. , Schmidt D. H.
Published: July 2010

Sweet corn (Zea mays L.) quality is adversely affected by thick pericarp. Most cultivars of sweet corn in the USA have had sugary (su) endosperm. Recently, other endosperm mutants have become important in sweet corn improvement. Given the close relationship between endosperm and pericarp, it would be useful to determine if endosperm type has any affect on pericarp thickness. The objective of this research was to determine the effects of 10 combinations of endosperm mutants on pericarp thickness in seven sweet corn inbred backgrounds. Endosperm types that may be useful in sweet corn improvement were included. Pericarp thickness of seven sets of near‐isogenic lines that differed in endosperm composition was measured using a pressure micrometer. The endosperm mutants studied were sugary (su), dull (du), waxy (wx), sugary‐2 (su2), and shrunken‐2 (sh2). Pericarp thickness was significantly affected by inbreds, endosperm types, endosperm by inbred interactions, ear, and position of measurement on the kernel. Pericarp thickness of inbreds averaged across endosperm types ranged from 53.3 üm to 33.9 üm. Averaged across inbreds, the endosperm combination Su su2 had significantly thicker pericarp, 48 üm, than all other endosperm types. Endosperm combination su su2 had the thinnest pericarp, 38.5 üm, but was not significantly different from Su sh2 (38.7 üm), su (39.1 üm), or three of the other endosperm combinations. The thicker pericarp associated with Su su2 could adversely affect tenderness. However, the average pericarp thickness of the most widely used new endosperm type, sh2, was not significantly different than the pericarp thickness of standard (su) types, and thus would not be expected to alter pericarp tenderness of converted inbreds.
Seed Coat Anatomy and the Scarification of Cicer Milkvetch Seed1
Authors: Miklas P. N. , Townsend C. E. , Ladd S. L.
Published: July 2010

The impermeable seed coat of cicer milkvetch (Astragalus cicer L.) restricts water imbibition and results in poor seed germination and subsequent stand establishment. Our objectives were to study the seed coat anatomy, areas of initial water imbibition, scarification effects on the seed coat, and the relationships between seed characters and percentage hardseed. Seed from 10 polycross progenies with a wide range of hardseededness (12 to 77% after scarification) were used. Scanning electron microscopy showed the following: the cuticle had a distinct faveolate pattern at the strophiole at magnifications of ✕ 125 and higher; the malpighian cells became longer and thinner as they neared the strophiole in comparison to the rest of the seed coat; the osteosclereids were shorter and wider at the seed tip in comparison to other sites on the seed coat; and the osteosclereids were not present at the hilum or the strophiole. In general, the seed coat anatomy was similar to that of small‐seeded legume species belonging to the subfamily Papilionoideae. The strophiole and seed tip accounted for 98% of the area of imbibition following mechanical scarification. The effect of mechanical scarification on the seed coat varied from no effect to small scrapes and indentations, large cracks, and complete removal. The strophiole accounted for 75% of the area of imbibition following H2SO4 (18.0 m0l H2SO4 L‐1) scarification. The effect of H2SO4 to the seed coat occurred in a distinctive pattern at the strophiole. The cuticle and exterior portions of the malpighian cells were dissolved, forming a circular cavity that had a large groove at its base. Percentage hardseed following mechanical scarification was correlated (P = 0.05) with seed length, width, volume, and weight (r = −0.91, −0.66, −0.88, and −0.82, respectively). Density was the only seed character that was significantly correlated (r = 0.70) with percentage hardseed following H2SO4 scarification. None of the seed characters were significantly correlated with natural permeability. Although the progenies did not differ for seed coat anatomy, it appears that selection can be made for increased permeability following mechanical scarification. Of the seed characters measured, weight would be the easiest to use when selecting for increased permeability.
Restriction Fragment Length Polymorphism Analysis of Loci Associated with Insect Resistance in Tomato1
Authors: Nienhuis James , Helentjaris Tim , Slocum Mary , Ruggero Bill , Schaefer Alison
Published: July 2010

Selection is often difficult for quantitatively inherited traits that have low heritabilities. The use of indirect selection for a genetically correlated trait, which is either easier to evaluate or has a higher heritability than the desired trait, may result in increased efficiency in selection. Restriction fragment length polymorphisms (RFLPs) are DNA markers which have a heritability of 1.0, i.e., the genotype = phenotype, and could be used as indirect selection criteria for traits with low heritabilities. The objective of this study was to identify RFLP loci associated with the quantitative trait loci (QTL) affecting expression of insect resistance in a wild tomato species. Lycopersicon hirsutum f. glabratum C.M. Mill (hirsutum). The principal toxic factor involved in the insect resistance of hirsutum is a methyl ketone compound, 2‐tridecanone (2TD), which is localized in the tips of the glandular (type VI) trichomes which cover the foliage. An population, consisting of 900 individuals derived from a cross between a hirsutum accession and an adapted tomato, L. esculentum L., cultivar, Manapal, was assayed colorimetrically for 2TD, and 74 individuals were selected which represented the widest range of expression for colorimetric absorbance. The DNA was extracted from each of the 74 selected individuals, and the genotype at from 36 to 99 RFLP loci determined. The RFLP loci on three different linkage groups were found to be correlated with expression of colorimetric absorbance. In a second study, 96 F2 plants, visually selected to represent a wide range of colorimetric absorbance, were grown under controlled environment conditions and assayed for 2TD production. The genotype at three pairs of RFLP loci from each of the previously identified linkage groups was determined. The gene effects of each of the RFLP loci was estimated, and a multiple regression model, using the three genotypic classes at each of four RFLP loci as independent variables, was developed which accounted for 38% of the phenotypic variance for colorimetric absorbance. The results suggested that direct selection for RFLP marker loci would result in a correlated response increasing the frequency of favorable alleles associated with expression of 2TD‐mediated insect resistance.
A Soybean Genotype Resistant to Phomopsis Seed Decay1
Authors: Brown E. A. , Minor H. C. , Calvert O. H.
Published: July 2010

Phomopsis seed decay (PSD) reduces soybean [Glyclne max (L.) Merr.] seed quality and seedling establishment. Experiments were conducted in Columbia, MO, and Isabela, PR, over a 3‐yr period to identify a source(s) of resistance to PSD in soybean. All genotypes evaluated were field grown under conditions favorable for infection by Phomopsis spp. Percentage infection was determined by counting colonies of Phomopsis spp. growing from surface‐sterilized seeds plated on acidified potato (Solanum spp.) dextrose agar. Plant introduction (PI) 417479 was free of Phomopsis spp. seed infection at Columbia in 1984 and Isabela in 1985, and had 3% infection at Columbia in 1985. A phenotypically indistinguishable genotype, PI 360841, had levels of infection that did not differ statistically from those observed for PI 417479 and may be a duplicate in the germplasm collection. In the same environments, the widely grown ‘Williams 82’ showed from 25 to 59% infection. The PI 417479 exhibited less infection than the reported P. sojae Lehman resistant genotypes PI 80837 and ‘Delmar’ in all but one test. Maturity dates of PI 417479 were near the average of all genotypes tested. The PI 417479 appears to have been exposed to average, or above average, disease pressure. Thus, the level of resistance to PSD measured cannot be attributed to maturation during periods of favorable environmental conditions. Also, antagonism of Phomopsis spp. seed infection by Cercospora kikuchii (T. Matsu. & Tomoyasu) Gardner did not appear to influence the conclusions relative to PI 417479. Detectable seed infection of PI 417479 by C. kikuchii was 2% or less in all experiments.
Selection for Late‐Planted Soybean Yield in Full‐Season and Late‐Planted Environments1
Authors: Pfeiffer T. W.
Published: July 2010

As the hectarage in double‐cropped soybean [Glycine max (L.) Merr.) production has increased, the necessity of breeding soybean specifically adapted to double cropping (planting soybean after a small grain crop is harvested) has been suggested. The objectives of this research were to compare random genotypes in full‐season and late plantings for genotype ✕ cropping system interaction and to evaluate different selection criteria for the identification of genotypes with superior yield performance in delayed plantings. Full‐season (0.76‐m row width, average planting date 21 May) and late‐planted (0.38‐m row width, average planting date 3 July) tests were grown at three sites [soil types Maury silt loam (Typic Paleudalfs), Lanton silt loam (Cumulic Haplaquolls), and Crider silt loam (Typic Paleudalfs)] with 28 genotypes in each of three maturity classifications. There were no significant maturity class ✕ cropping system or genotype within maturity class ✕ cropping system interactions. Lateplanted tests were grown at two other sites (Melvin silt loam (Typic Fluvaquents) and Newark silt loam (Aerie Fluvaquents)] to provide additional evaluation environments. Full‐season yield (Yfs), lateplanted yield (Y1p), mean productivity (MP) = (Yfs + Y1p)/2 and tolerance = Ylp − Yfs were used as criteria to select the top 10% of the genotypes at each of the three sites having two planting dates. Four other late‐planted tests were used as evaluation environments, and progress from selection was measured by comparing the yield of selected genotypes with the mean yield of all genotypes in the evaluation environments. Average progress was 6.9, 5.1, 4.0, and 1.2% based on MP, Yfs Y1p and tolerance, respectively. There is no indication that a separate breeding program will be necessary to select superior genotypes for use in double‐cropping systems.
Effects of Shading on Winter Wheat Yield, Spike Characteristics, and Carbohydrate Allocation1
Authors: McMaster Gregory S. , Morgan Jack A. , Willis Wayne O.
Published: July 2010

Light intensity has variable effects on plant morphology, carbohydrate allocation, and yield. This study tested whether shading ‘Vona’ winter wheat (Triticum aestivum L.) altered allocation and spike characteristics that contribute to final grain yield under field conditions (Nunn clay loam, Aridic Argiustolls). The shaded treatment consisted of 50% ambient light reduction from 1 week before booting through the first week of grain fill (6 weeks total). Plants harvested were partitioned into stem, leaf blades by position on culm, and spike components. At maturity, spikes were divided into individual spikelets by position on the rachis. Carbon‐14‐labeled tracer was applied 24 h prior to each harvest. Shading significantly decreased spike weights for the later samplings, but had little effect on leaf or stem weights. Despite high spike sink activity and increasing spike size, when carbohydrates were limiting, photosynthate partitioning to spikes was not increased. Greater tiller mortality resulted in fewer culms per plant (and fewer spikes per plant) in shaded treatments. Shading altered spike morphology by decreasing the number and weight of kernels per spikelet and, therefore, total spikelet and spike weight; the number of grain‐bearing spikelets was unaffected. Spikelets were decreased most at the lower central portion of the spike, contrasting with other studies that found decreases in the upper half or basal portion of the spike. The combined effects of shading resulted in 32% lower yield, due mostly to lower spike density, but also to decreased kernel number and size.
Partitioning Yield Reduction from Early Cotton Planting1
Authors: Kittock D. L. , Taylor B. B. , Hofmann W. C.
Published: July 2010

Delayed cotton (Gossypium spp.) planting generally reduces lint yield because it reduces the length of the growing season. Planting cotton too early also can reduce lint yield. Most growers believe that reduced yield with early planting is caused by reduced stand. Previous research suggested that low temperature during germination and early seedling growth may reduce lint yield regardless of stand. This study attempts to clarify low temperature effects on lint yield by partitioning cotton lint yield reduction from early planting into the effects from reduced stand and other factors. Soils were Typic Torrifluvents. Thermic Torrilluvents, and Anthropic Torrifluvents. Upland cotton (Gossypium hirsutum L.) had significantly (P < 0.05) reduced lint yield from early planting in five tests. American pima cotton (G. barbadense L.) grown in four of the tests had smaller, nonsignificant lint yield decreases from early planting in three of the tests and higher lint yield from early planting in the fourth test. Early planted cotton generally was shorter. A comparison of upland cotton lint yields, using adjustment by regression analyses with plant population, indicated that something other than plant population, presumably low temperature, caused approximately 100, 94, 66, 22, and 0 % of the lint reduction from early planting in five analyses. Thus physiological and morphological effects of low temperatures early in the cotton planting season often may contribute as much to reduced lint yield as does reduced stand.
Evaluation of a Greenhouse Screening Technique for Iron‐Deficiency Chlorosis of Sorghum1
Authors: Bowen C. Roger , Rodgers D. M.
Published: July 2010

Iron‐deficiency chlorosis can reduce sorghum [Sorghum bicolor (L.) Moench] yields in certain soils of the Great Plains. The purpose of this study was to determine if Fe efficiency and/or biomass of field‐grown sorghum plants can be predicted by evaluating greenhouse seedlings grown in Ulysses silt loam soil (fine‐silty, mixed, mesic Aridic Haplustolls) known to induce Fe‐deficiency chlorosis. Seedlings were grown in a soil/sand mixture high in pH and Ca, and low in organic matter and available Fe. Progeny of randomly selected lines from KMP1Fe, a population that has undergone recurrent phenotypic selection for Fe efficiency, were evaluated. Three height classes were established to reduce inter‐plot interaction between genotypes of different height in field studies. A control treatment consisted of plants grown in a soil/sand mixture with Fe added as FeEDDHA (ethylenediaminedi(O‐hydroxyphenylacetate)). Seedlings were evaluated for chlorosis symptoms, vigor, shoot length, and dry weight. Entry mean squares for chlorosis score were significant for the short and tall groups, but not for the medium. Greenhouse results were compared to results from a field experiment. Final greenhouse chlorosis scores for entries grown in the unamended soil mixture were significantly correlated with field chlorosis score and biomass. Regression analysis on the short height group grown in the unamended soil mixture indicated that field chlorosis score could be predicted by greenhouse chlorosis score (r2 = 0.80). Similar results were noted for field chlorosis score for the other height groups.
Association of Alleles for High Stearic Acid with Agronomic Characters of Soybean1
Authors: Lundeen P. O. , Fehr W. R. , Hammond E. G. , Cianzio S. R.
Published: July 2010

Alleles that control four to sevenfold increases in the content of stearic acid in soybean [Glycine max (L.) Merr.] oil have been obtained by artificial mutagenesis. The objective of this study was to evaluate the association of three alleles for high stearic acid with agronomic and chemical characters of soybean. Three mutant lines, A6 with 282 g kg−1 stearic acid, A9 with 163 g kg−1 stearic acid, and A10 with 146 g kg−1 stearic acid, each with a different allele at a single locus controlling stearic acid content in the seed oil, were crossed to one of three high‐yielding genotypes with stearic acid content of about 40 g kg−1. The F1 plants of each mating were backcrossed without selection to the high‐yielding parent. Pairs of highand low‐stearic‐acid lines were selected from BC1F2‐derived lines segregating for a high‐stearic‐acid allele. The pairs of lines were evaluated in a replicated test at three Iowa locations. There were no significant differences in the average yield of the high‐ and the low‐stearic‐acid lines from the A9 and A10 crosses. In the A6 cross, the low‐stearic‐acid lines had significantly greater seed yield than high‐stearic‐acid lines by an average of 7.7%. For the other characters measured, the maximum differences between the mean performance of high‐ and low‐stearic‐acid lines for any of the three crosses were 2.9 days for time of maturity, 4 cm for plant height, 0.3 units for lodging score, 8 mg seed−1 for seed weight, 13 g kg−1 for seed protein, and 1 g kg−1 for seed oil. The stearic acid contents of the BC1F3‐derived lines generally were less than those of their donor parent, which indicated that modifying genes may influence this character.
Twenty Cycles of Divergent Mass Selection for Seed Size in Corn1
Authors: Odhiambo M. O. , Compton W. A.
Published: July 2010

Twenty cycles of divergent mass selection for seed size have been completed in the corn (Zea mays L.) cv. Krug yellow dent. A 2‐yr field study was conducted to evaluate direct and indirect responses to seed‐size selection and to observe whether significant changes in yield occur with selection for seed size. A third objective was to investigate the immediate effect of male gametes (pollen) on seed size and to observe whether such effects exhibit heterosis. The study was conducted in the breeding nursery in Lincoln, NE, where the soil type is Kennebec silt loam (Cumulic Hapludolls). Selection was highly effective for both large and small seed size. Selection for small seeds resulted in a decrease in kernel weight of 7.21 g/1000 kernels per cycle while selection for large seeds resulted in an increase in kernel weight of 4.68 g/1000 kernels per cycle. The effect of male gametes on seed size was found to be dependent on the source of the pollen. After 20 cycles, pollen from the large seed‐size population (L) increased seed size by 0.12 g/kernel when used to pollinate plants from the small seed‐size population (S). Pollen from the S population reduced seed size by 0.15 g/kernel when used on plants in the L population. Such large effects were not expected although some effects had been previously demonstrated in dent corn. Even though selection for small seeds resulted in a significant increase in the number of seed harvested per square meter, yield was significantly reduced. Selection for large seeds had no significant effect on yield.