Genetic diversity at electrophoretic loci in the house fly,Musca domestica L.

Vertical polyacrylamide gel electrophoresis was used to separate enzyme proteins at 73 putative loci in natural house fly populations sampled in central Iowa. Thirty-nine of the loci were polymorphic (53%). The mean effective number of alleles per polymorphic locus was 1.93 and 1.47 alleles among 68 scored loci. Observed and expected heterozygosities at 34 house fly loci were 0.1628 and 0.1834, respectively. No statistically significant differentiation was detected among nine central Iowa fly populations in 1989 or among nine Iowa and three Minnesota populations in 1990. Journal Paper No. J-14125 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 2949.     

Temporal and spatial trends in allozyme frequencies in house fly populations,Musca domestica L.

Summary Allelic and genotypic frequencies were sampled from a single age class of the common house fly, Musca domestica L., at five farms on six dates from July 6 to October 12, 1982. Allozymes at six loci were resolved with vertical polyacrylamide gel electrophoresis. No consistent departures from random mating were detected. No consistent linkage disequilibrium was observed. Allele frequencies at the farms changed in independent and unpredictable ways. Gene frequencies at the five farms were initially divergent, converged in midsummer, and then progressively diverged. The divergence occured in mid-August when fly populations were large. Variation in gene frequencies at adjacent farms accounted for a large proportion of the variance in allele frequencies among all farms. These observations are consistent with the hypothesis that allele frequencies in young adult flies reflected the habitat in which they matured as larvae.Journal Paper No. 11718 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 2411     

Effect of environmental alcohol on in Vivo properties of Drosophila alcohol dehydrogenase

The effects of environmental 2-propanol on the in vivo properties of Drosophila alcohol dehydrogenase (E.C. 1.1.1.1.) are presented. Exposed flies were found to exhibit a significant decrease in ADH specific activity with a concomitant increase in the enzyme's relative in vivo stability and concentration. The possible adaptive significance of the observed responses is discussed.This work was supported by NSF grant #DEB 7815466 to J.M. Journal Paper No. J-9979 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2272.     

A method for determining the in vivo stability of Drosophila alcohol dehydrogenase (E.C.1.1.1.1.)

A rapid and accurate method of measuring the relative in vivo stability of Drosophila alcohol dehydrogenase is presented. The potential of this technique for examining posttranslational control of in vivo enzyme concentrations is discussed.This work was supported by NSF grant #DEB 7815466 to J.M.Journal Paper No. J-9977 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2272.     

Identification of genomic regions affecting plant height in sorghum and maize

The objective of this study was to use restriction fragment length polymorphisms (RFLPs) to determine the genetic location and effects of genomic regions controlling plant height in sorghum. F₂ plants (152) from the cross CK60 x PI229828 were used. Genomic and cDNA clones (106) identified 111 loci distributed among ten linkage groups covering 1299 cM. Interval mapping identified four regions, each in a separate linkage group. These regions may correspond to loci (dw) previously identified by alleles with qualitative effects. Also, these regions identified in sorghum may be orthologous to those previously reported for plant height in maize. Gene effects and gene action varied among genomic regions. In each region, PI229828 alleles resulted in increased plant height. Each region accounted for 9.2–28.7% of the phenotypic variation. Positive, additive effects ranged from 15 to 32cm. Tallness was dominant or overdominant and conferred by alleles from PI229828 for three quantitative trait loci (QTL). At the fourth QTL, PI229828 contributed to increased plant height, but short stature was partially dominant. One digenic interaction was significant. The presence of a PI229828 allele at one region diminished the effects of the other region. A multiple model indicated that these four regions collectively accounted for 63.4% of the total phenotypic variation. The utility of this information for germplasm conversion through backcross breeding is discussed.Journal Paper No. J. 15649 of the Iowa Agriculture and Home Economic Experiment Station, Ames, Iowa. Project No. 3134     

An analysis of precursors accumulated by several chlorophyll biosynthetic mutants of maize

Summary Several mutants of maize defective in chlorophyll synthesis are analysed. By feeding shoots of dark-grown seedlings -aminolevulinic acid, the regulatory step in chlorophyll biosynthesis is bypassed and chlorophyll precursors accumulate. In normal plants this results in a buildup of protoporphyrin IX and protochlorophyllide, while mutants accumulate precursors, depending on the site of the mutant-induced lesion. Mutants at three loci, l ^*-Blandy4, 113, and oy, are defective in conversion of protoporphyrin IX to Mg-protoporphyrin. Mutants at the oro and oro2 loci are defective in conversion of Mg-protoporphyrin monomethyl ester to protochlorophyllide. A dominant modifier gene, Orom, which allows oro seedlings to bypass their lesion is also described.Journal Paper No J-9076 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa Project No. 2035     

Variation in polychlorinated biphenyl levels in common carp from a primarily agricultural drainage

Concentrations of polychlorinated biphenyls (PCBs) in common carp, Cyprinus carpio, from the Des Moines River, Iowa, were assessed for variability related to sampling location, sampling period, fish age, and fat content. Concentrations were highest at a location near the City of Des Moines; they were substantially lower in 1981 than in 1980. Age and fat content had little influence on PCB concentrations in carp. Overall concentrations were some of the lowest recorded in the United States and Canada in recent times.The Unit is jointly supported by Iowa State University, the Iowa State Conservation Commission, and the U.S. Fish and Wildlife Service.Journal Paper No. 10754 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2465. Financed by a grant from the U.S. Department of Defense Army Corps of Engineers and made available through the Engineering Research Institute, Iowa State University.     

Laelius utilis [Hym.: Bethylidae], a parasitoid ofAnthrenus fuscus [Col.: Dermestidae] in Iowa

Larvae ofAnthrenus fuscus Olivier, an Old World dermestid beetle, are established in Ames, Iowa, and are parasitized locally by the native bethylid wasp,Laelius utilis Cockerell; this is a new state record. Life history and new host information forL. utilis is presented, as well as morphological and biological means for differentiating it fromL. pedatus Say of similar appearance. Journal Paper N^o 10661 of the Iowa Agriculture and Home Economics Experiment Station, Ames. IA 50011. Project N^o 2259.     

Unusual genetic phenomena associated with Tn5 mutagenesis in Alcaligenes eutrophus strain H1

Tn5 was introduced into Alcaligenes eutrophus strain H1 by a suicide vector pSUP1011. Physical characterization of mutants obtained after Tn5 mutagenesis revealed a relatively high frequency of plasmid curing, or deletion of a 50 kb plasmid DNA segment. Results of Southern hybridization and chromosomal walking indicate that the same continuous stretch of plasmid DNA (designated as D region of plasmid) is deleted in four independent isolates. Moreover, the same deletion of plasmid DNA is also observed in a mitomycin C-generated mutant strain H1-4.Journal Paper No. J-12095 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2607, supported in part by a grant from the Iowa High Technology Council     

Vegetative growth and sporulation ofBipolaris sorokiniana on sequentially older infected leaves ofPoa pratensis exposed to postemergence herbicides

Poa pratensis was exposed to the postemergence herbicides 2,4-D, MCPP, and dicamba at concentrations of 10^–6 M applied to the soil surface. Sequentially older leaf blades were inoculated withBipolaris sorokiniana and detached to determine the effect of the herbicides on saprophytic hyphal growth and sporulation on the tissue of each older leaf. 2,4-D and dicamba stimulated hyphal growth in vitro from leaf tissue of all ages; MCPP had no effect on hyphal growth. All herbicides increased sporulation byB. sorokiniana on leaf tissue of all ages. Both hyphal growth and sporulation increased progressively on tissue from sequentially older leaves ofP. pratensis exposed to dicamba.Journal Paper No. J-14985 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, USA, Project No. 2616.     

Molecular-marker-facilitated investigation of host-plant response to Exserohilum turcicum in maize (Zea mays L.): components of resistance

RFLPs were used to investigate components of host-plant response to Exserohilum turcicum in 150 unselected F₂₃ lines of a B52/Mo17 maize population. Following inoculation with spore suspensions of the pathogen (race 0), components of disease development were measured and then quantitative trait mapping was performed to identify the location and effects of quantitative trait loci (QTLs) determining host-plant response. Components of interest were the average number of lesions per leaf, the average percent leaf tissue diseased (severity) and the average size of lesions (cm²). Based on a LOD threshold of 2.31 (P<0.05), the number of lesions appears to be associated with QTLs on chromosomes 1S, 3L, 5S. Severity was associated with analogous regions and, in addition, QTLs on chromosomes 7L and 8L. Most QTLs, for either of these two components, involve additive gene action and partial dominance or overdominance. In contrast, lesion size was associated with QTLs on chromosomes 7L and 5L; recessive gene action may be involved at 7L.Journal Paper No. J-15178 of the Iowa Agriculture and Home Economic Experiment Station, Ames, Iowa. Project No. 3134     

Tagging of a maize gene involved in kernel development by an activated Uq transposable element

Summary A quiescent Uq transposable element has been activated in a maize plant treated with 5-aza-2-deoxycyti-dine. This activated Uq cosegregates with a heritable dominant miniature (Mn) kernel phenotype, indicating its physical association with a maize miniature locus (Mn:: Uq). The Mn:: Uq mutant is dominant in producing a miniature seed phenotype of variable size and in reducing seedling vigor in the early growth stage. Genetic experiments indicate that the Mn:: Uq mutant also affects the activity of the male gametophyte, whereby pollen germination is inhibited, thus lacking pollen tube growth resulting in the male nontransmissibility of this mutant. Proof for the Uq element in this mutant is derived by its ability to transactivate the standard a-ruq reporter allele to yield spotted aleurone tissue. However, the Mn:: Uq mutant does not transactivate a normally Uq-responsive c-ruq allele, suggesting a structural difference between the two ruq receptors at the A1 and C1 loci. It is anticipated that cloning of the Uq transposable element would facilitate the molecular cloning and characterization of the maize miniature gene.Journal Paper No. J-13425 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011, USA, Project No. 2850     

Chromosome labeling with transposable elements in maize

Transposable elements randomly insert into a targeted locus at a frequency of 10^-6 to 10^-5. The En element has been shown in previous studies to transpose more frequently into closely linked sites. Thus, it is appropriate to place an En element onto each of the 20 chromosome arms in maize to maximize tagging efficiency. This is called chromosome labeling for tagging purposes with transposons. After a chromosome arm has been labeled with a transposon, genes residing in that arm will have a greater chance to be tagged by the transposon. To date, all of the maize chromosome arms have been labeled with at least one of five Encontaining alleles. The elements were linked to the arms using reciprocal translocations. The usage of these arm-labeled lines is discussed in the context of gene tagging.Journal Paper No. 15224 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa; Project No. 3176     

Studies of chloroplast development in four maize mutants defective in chlorophyll biosynthesis

Four mutants of maize (Zea mays L.) defective in chlorophyll biosynthesis have been analyzed with regard to the sites of their lesions and their effects on chloroplast development. Two yellow mutants, which accumulate no detectable porphyrin precursors when grown in darkness, are defective in the conversion of protoporphyrin IX to magnesium protoporphyrin. Etioplasts of these mutants may develop elaborate lamellar membrane systems, but prolamellar bodies are never observed. Two mutants, which are necrotic when grown under illumination, develop normal (non-necrotic) leaf tissue in the dark and accumulate a small amount of magnesium protoporphyrin monomethyl ester, corresponding approximately to the amount of protochlorophyllide accumulated by normal plants. The etioplasts of these mutants contain noncrystalline bodies. The implications of these observations with respect to chloroplast development are discussed.Journal Paper No. J-9136 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa Project No. 2035     

Quantitative and qualitative trait loci affecting host-plant response to Exserohilum turcicum in maize (Zea mays L.)

Molecular markers at 103 loci were used to identify the location of quantitative sources of resistance to Exserohilum turcicum in 150 F₂₃ lines of a B52/Mo17 maize population. Host-plant response was measured in terms of the average number of lesions per leaf, the average percent leaf tissue diseased (severity), and the average size of lesions. The location of quantitative trait loci were compared with three loci having known qualitative effects, namely Ht1, Ht2 and bx1. Chromosomal regions containing the Ht1 and Ht2 loci showed a small contribution in determining lesion size, even though alleles with dominant, qualitative effects at these loci have never been reported in either inbred parent. Similar effects were not observed for the number of lesions or for disease severity. Likewise, some contribution was observed for chromosomal regions encompassing the bx1 locus in determining lesion size but not the number of lesions or disease severity. Overall the contribution of loci in the vicinity of Ht1, Ht2 and bx1 was small relative to variation attributable to loci with quantitative effects identified in this study. Molecular-marker-facilitated mapping concurred with previous reciprocal translocation mapping studies on the importance of chromosomes 3, 5 and 7, despite the fact that these studies utilized diverse sources of resistant germplasm.Journal Paper No. J-15177 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 3134     

Genetics of tassel branch number in maize and its implications for a selection program for small tassel size

Summary Tassel branch numbers of six crosses of maize (Zea mays L.) were analyzed to determine inheritance of this trait. Generation mean analyses were used to estimate genetic effects, and additive and nonadditive components of variance were calculated and evaluated for bias due to linkage. Both narrow-sense and broad-sense heritabilities were estimated. Additive genetic variance estimates were significant in five of the six crosses, whereas estimates of variance due to nonadditive components were significant in only three crosses. Additionally, estimates of additive variance components usually were larger than corresponding nonadditive components. There was no evidence for linkage bias in these estimates. Estimates of additive genetic effects were significant in four of six crosses, but significant dominance, additive × additive and additive × dominance effects also were detected. Additive, dominance, and epistatic gene action, therefore, all influenced the inheritance of tassel branch number, but additive gene action was most important. Both narrow-sense and broadsense heritability estimates were larger than those reported for other physiological traits of maize and corroborated conclusions concerning the importance of additive gene action inferred from analyses of genetic effects and variances. We concluded that selection for smalltasseled inbreds could be accomplished most easily through a mass-selection and/or pedigree-selection system. Production of a small-tasseled hybrid would require crossing of two small-tasseled inbreds. We proposed two genetic models to explain unexpected results obtained for two crosses. One model involved five interacting loci and the other employed two loci displaying only additive and additive × additive gene action.Journal Paper No. J-9231 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011. Project No. 2152     

Basis for the diversity of states of controlling elements in maize

Summary In maize the insertion of a controlling element such as the regulatory element, En, (Enhancer) at a locus generates diverse derivatives. These derivatives include stable phenotypes that range from colorless to full color. Distinguishable patterns are determined by timing and frequency of mutation events. It has been hypothesized that diverse expressions are based either on position of the controlling element at the locus or composition differences among controlling elements. — Experiments with two target loci, A2 and C, indicate that the previous pattern of a controlling element does not influence the pattern generated at a new site. This finding supports the hypothesis that these diverse trans-effects of En are not caused by a change in the genetic information of En itself but rather by its position; diverse expressions are a manifestation of the effect of an element at a specific locus site. — Controlling elements are discussed in relation to chromosome structure, gene activation, gene programming and possible parallels in prokaryotes.Journal Paper No. J-8416 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50011. Project No. 1884. Support from NSF GB38328     

Statistical techniques for detection of major genes in animal breeding data

Summary Statistical techniques for detection of major loci and for making inferences about major locus parameters such as genotypic frequencies, effects and gene action from field-collected data are presented. In field data, major genotypic effects are likely to be masked by a large number of environmental differences in addition to additive and nonadditive polygenic effects. A graphical technique and a procedure for discriminating among genetic hypotheses based on a mixed model accounting for all these factors are proposed. The methods are illustrated by using simulated data.Journal Paper No. J-12733 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1901     

Differential activity of the maize mutator Mu at different loci and in different cell lineages

Summary Mutator activity of the maize mutator (Mu) system varies for different loci. Mutation frequencies as high as 7.54x10^–5 and as low as 4.0x10^–6 are observed for 5 loci (i.e., y ₁,yg2, bz1, sh2, and wx). For the waxy locus, a higher mutation frequency is observed in Mu plants crossed as males than when Mu plants function as females. The frequency of unselected mutations also is found to be higher in Mu plants crossed as males than in the first-generation Mu plants crossed as females. The mutation frequency of the y1 locus, however, does not differ in the male or female crosses. Mu-induced mutation frequencies vary with respect to loci and, for some loci, may depend on other factors such as the sex of the Mu parent or the previous crossing history of the Mu parent. More limited data have been obtained for 4 additional loci(su1, c1, c2 and o2).Journal Paper No. J-11487 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2623     

The synthesis of compound bands in Drosophila melanogaster salivary gland chromosomes

Small chromosome aberrations were utilized to construct compound bands in the 3C region of Drosophila melanogaster salivary gland chromosomes. The results imply that one should expect to find multiple functions associated with single bands, especially heavy bands. It is suggested that the natural occurrence of compound bands needs to be recognized and that exceptions to the one gene: one band correspondence are expected to occur.Journal Paper No. J-9459 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No. 1985