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Iowa State University

Plant Sciences

Plant breeding and cytogenetics

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Inbreeding Depression Rates For Six Synthetic Populations Of Maize , David Lee Benson Jan 1991

Inbreeding Depression Rates For Six Synthetic Populations Of Maize , David Lee Benson

Retrospective Theses and Dissertations

The objective of inbreeding in maize (Zea mays L.) is to develop pure lines that are used to repeatedly produce an elite hybrid. Inbreeding in maize is accompanied by a reduction in the mean phenotypic value for most traits. The reduction in the mean is caused by an increased number of loci in an individual becoming identical by descent from a common ancestor. This genetic phenomena is known as inbreeding depression;Limited empirical information was available to determine how inbreeding depression rates have changed by recurrent selection in maize populations. The population per se and seven bulked inbred subpopulations (S ...


Comparison Of Three Recurrent Selection Regimes For Increasing Groat-Oil Content Of Oat , Harm Schipper Jan 1991

Comparison Of Three Recurrent Selection Regimes For Increasing Groat-Oil Content Of Oat , Harm Schipper

Retrospective Theses and Dissertations

Recurrent selection has been conducted in various ways. In this study, three recurrent selection regimes for increasing groat-oil content of oat (Avena sativa L.) were compared. In regimes 1 and 2 selection was based on field- and greenhouse-grown S[subscript]0 plants, respectively, whereas in regime 3 selection was practiced among field-grown S[subscript]0 plants followed by selection among and within greenhouse-grown S[subscript]0:1 progenies. In a replicated experiment conducted over two years in the field and greenhouse, 48 oat lines were evaluated for groat-oil content. The results indicated that gain in groat-oil content from selection in ...


Restriction Fragment Length Polymorphism Mapping Of Quantitative And Qualitative Traits In Soybean , Brian William Diers Jan 1991

Restriction Fragment Length Polymorphism Mapping Of Quantitative And Qualitative Traits In Soybean , Brian William Diers

Retrospective Theses and Dissertations

The purpose of this thesis was to map traits of interest to soybean (Glycine max (L.) Merr.) breeders and geneticists with RFLP markers. The thesis consists of three separate studies;In the first study, quantitative trait loci (QTL) for seed size, protein and oil content and for the content of the fatty acids palmitate, stearate, oleate, linoleate and linolenate were mapped. The traits were measured on seed harvested from a replicated trial of 60 F[subscript]2-derived lines from a cross between the G. max experimental line A81-356022 and the G. soja Plant Introduction 468916. Each F[subscript]2 was ...


Comparative Testcross And Per Se Performance Of Heterogeneous Maize Lines With Their Homozygous Derivatives , Kermit B. Bohning Jan 1991

Comparative Testcross And Per Se Performance Of Heterogeneous Maize Lines With Their Homozygous Derivatives , Kermit B. Bohning

Retrospective Theses and Dissertations

The objectives of this study were to compare the testcrosses of S[subscript]2 lines from BS13(S2)C1 with two S[subscript]2 lines from Lancaster Composite with their S[subscript]8 x S[subscript]8 counterparts, to compare S[subscript]2 per se performance with their S[subscript]8 derivatives, to compare S[subscript]2 per se performance with their S[subscript]8 testcross performance, and to evaluate the performance of S[subscript]2 x S[subscript]2 hybrids. Twenty-seven S[subscript]2 lines and their S[subscript]8 derivatives from BS13(S2)C1 were crossed to two ...


The Rss System Of Unidirectional Cross-Incompatibility In Maize: Control By The Interaction Of Non-Allelic Male And Female Genes , Abdul Rashid Jan 1991

The Rss System Of Unidirectional Cross-Incompatibility In Maize: Control By The Interaction Of Non-Allelic Male And Female Genes , Abdul Rashid

Retrospective Theses and Dissertations

Self-incompatibility has never been reported in maize but some cases of unidirectional cross-incompatibility have been reported in the literature. One such case of unidirectional cross-incompatibility was noticed in the maize cytogenetics nursery Ames, Iowa during 1975. In this case, the crosses between the derivatives of a particular line am(pa-pu)/a1 sh2 and a specific male parent al et/al et resulted in reduced seed setting (<25 seeds/ear). The reciprocal crosses between the same parents gave normal seed setting (NSS). It was also observed that this unidirectional cross-incompatibility was heritable and the factors controlling this incompatibility were different from the known unidirectional cross-incompatibility locus ga1.;The present investigations were made to study the genetics of this unidirectional cross-incompatibility and the mechanism involved in the rejection of the incompatible pollen. It was found that this cross-incompatibility system is not controlled by cytoplasmic factors but nuclear genes are involved in the incompatibility reaction. The results showed that this system is controlled by three recessive loci. One locus named cif (cross-incompatible female) controls the incompatibility reaction in the female parent (called RSS female) and the other two, cim1 and cim2 (cross-incompatible male), are controlling the incompatibility reaction in the male parent (called RSS male). The cross will be incompatible only when the female parent has the cif locus in homozygous recessive form and the male parent has the cim1 as well as cim2 locus also in homozygous recessive form. The reciprocal cross between the same parents will be compatible.;The cytological studies on the in vivo pollen germination and pollen tube growth showed that there was no difference between the compatible and the incompatible pollen tube growth during first 6 hours of pollination. The incompatibility reaction occurs between 6 and 12 hours of pollination as the tips of the pollen tubes in the incompatible pollinations appeared swollen to a considerable extent compared with the tips of the pollen tubes in the compatible crosses. It was also observed that sometime between 18 and 24 hours of pollination, the swollen tips of the pollen tubes burst and the pollen tube growth is stopped.


Introgression Of Genes For Small Seed Size From Glycine Soja Into Glycine Max , Allen Rubin Leroy Iii Jan 1990

Introgression Of Genes For Small Seed Size From Glycine Soja Into Glycine Max , Allen Rubin Leroy Iii

Retrospective Theses and Dissertations

Soybean (Glycine max(L.) Merr.) cultivars with a seed weight of less than 100 mg sd[superscript]-1 are preferred for some food products. The wild species Glycine soja Sieb. & Zucc. has a seed weight of less than 30 mg sd[superscript]-1, but its undesirable agronomic characteristics prevent its direct use in commercial production. The objective of the first study was to evaluate the transfer of genes for low seed weight from G. soja into high-yielding cultivars of G. max through backcrossing. For three G. max x G. soja crosses, selection between backcross generations for low seed weight was compared with no selection during backcrossing. For each cross, 40 F2-derived lines from each backcross generation from the BC0 to BC3 were evaluated in two replications at two locations for seed weight, seed coat color, lodging, petiole retention, and maturity. Selection resulted in backcross progeny with smaller seed weights than those obtained from backcrossing without selection. There were 37% of the BC3F2-derived lines that had seed weights of 100 mg sd[superscript]-1 or less in the populations obtained by selection compared with 18% of those obtained without selection. From each cross, BC3F2-derived lines were evaluated for yield. A significantly lower yield was exhibited by the selected population in only one of the three crosses. Among lines with seed weights of 100 mg sd[superscript]-1 or less, higher yielding lines were recovered from the selected populations of each cross. Up to 89% of the yield of the recurrent parent was exhibited by lines with seed weights of 100 mg sd[superscript]-1 or less;The objective of the second study was to determine the effectiveness of direct and indirect selection for small seed in three interspecific G. max x G. soja crosses based on seed weight and pod width measurements. Forty random BC2F2-derived lines from each of three crosses were evaluated for seed weight and pod width at two environments in Iowa and two environments in Puerto Rico. For each of the three crosses ...


Comparison Of Methods Utilizing Generation Variances For Estimation Of Heritability And Minimum Number Of Genes Affecting Eight Traits In Maize , Daria Helene Schmidt Jan 1990

Comparison Of Methods Utilizing Generation Variances For Estimation Of Heritability And Minimum Number Of Genes Affecting Eight Traits In Maize , Daria Helene Schmidt

Retrospective Theses and Dissertations

The use of single-plant selection via marker-assisted selection (HAS) has recently been discussed in the literature (Lande and Thompson, 1990). For this reason, six methods of heritability estimation and number of effective factors responsible for a trait (n) were computed and compared for 30 crosses using generation variances. The crosses were created in two six-parent diallels, one containing older inbreds (pre-1960), the other containing newer inbreds (post-1970). Five generations of each cross were evaluated on a single-plant basis in three replications in four environments;Methods of estimating heritability and n differed in some instances, depending on the trait and specific ...


Evaluation Of 11 Cycles Of Reciprocal Recurrent Selection In Bsss And Bscb1 Maize Populations , Vichien Keeratinijakal Jan 1990

Evaluation Of 11 Cycles Of Reciprocal Recurrent Selection In Bsss And Bscb1 Maize Populations , Vichien Keeratinijakal

Retrospective Theses and Dissertations

Eleven cycles of reciprocal recurrent selection (RRS) were conducted in two maize (Zea mays L.) populations, BSSS(R) and BSCB1(R). The objectives were to evaluate the direct and indirect response to selection, combining ability of populations with related and unrelated inbred testers, and effects due to selection and genetic drift on response to selection.;The direct response for grain yield observed in the population crosses was greater than indirect responses observed in the populations per se. The observed rate of response for grain yield was significant in BSSS(R) x BSCB1(R) and BSCB1(R) but a significant response ...


Response To Selection By Yield And Prolificacy At Different Environments In A Tropical Maize Population , José Ever Vargas-Sánchez Jan 1990

Response To Selection By Yield And Prolificacy At Different Environments In A Tropical Maize Population , José Ever Vargas-Sánchez

Retrospective Theses and Dissertations

Mass selection for yield and prolificacy, using independent culling levels, was made in a Colombian maize (Zea mays L.) population, MB 21, which corresponds to an advanced crossing of ETO x USA 342 (West Indian Composite). The research was conducted in Palmira, Colombia for 10 years, using three environmental situations: selection at the A semester, the less favorable cropping season, selection at the B semester, the more favorable cropping season, and selection at both the A and B semesters;Changes in the three populations developed (MB 21 A, MB 21 B, and MB 21 AB), respect to the original population ...


Inheritance Of Test Weight And Associated Traits Of Oat (Avena Sativa L.) , Kevin Vail Pixley Jan 1990

Inheritance Of Test Weight And Associated Traits Of Oat (Avena Sativa L.) , Kevin Vail Pixley

Retrospective Theses and Dissertations

Test weight is a measure of grain quality for oat (Avena sativa L.) and is a selection criterion in most oat breeding programs in the USA. This study investigated the genetic variability and inheritance for test weight, as well as the associations between test weight and other agronomic traits, for matings among elite inbred oat lines. Populations or segregates, each consisting of 50 random F 2:3 lines, were developed from 13 biparental matings for experiment I (Exp. I). For experiment II (Exp. II), a Design II mating plan with six sets was utilized to intermate 24 inbred oat lines ...


The Use Of Morphological, Developmental, And Plant Nitrogen Traits In A Selection Scheme In Soybean , Hassan Zeinali-Khanghah Jan 1990

The Use Of Morphological, Developmental, And Plant Nitrogen Traits In A Selection Scheme In Soybean , Hassan Zeinali-Khanghah

Retrospective Theses and Dissertations

A three year study was conducted in which the objective was to determine the response in seed yield from a tandem selection scheme in which the first step was to select desirable lines from each of two single cross populations for morphological and developmental traits, using independent culling. The second step was to select for high plant nitrogen (N) content at the R5 developmental stage. The genetic material was 213 F6 derived indeterminate lines from three maturity groups (79 early, 93 medium, and 41 late lines) from a single cross population (IX139) and 102 lines from three different stem termination ...


Direct And Correlated Response To Selection For Earliness In A Tropical Maize Population , Luis Alberto Narro Jan 1990

Direct And Correlated Response To Selection For Earliness In A Tropical Maize Population , Luis Alberto Narro

Retrospective Theses and Dissertations

Earliness is a highly heritable trait and selection is an efficient method to decrease days to flowering in maize (Zea mays L.). In many tropical environments, earliness is important for a brief rainy season or for a specific cropping sequence. The evaluation of 15 cycles of selection at 13 environments has been performed in the present study to measure the direct effect of selection for earliness and the correlated response in other agronomic traits in the Compuesto Seleccion Precoz population;Direct response to selection resulted in a decrease in time to flowering of 0.5 days per cycle of selection ...


The Effects Of Hordeum Spontaneum C. Koch. Germplasm On Barley Production , Daniel R. Currier Jan 1990

The Effects Of Hordeum Spontaneum C. Koch. Germplasm On Barley Production , Daniel R. Currier

Retrospective Theses and Dissertations

Several studies have shown that Hordeum spontaneum contains potentially useful genes for improving agronomic traits of cultivated barley. In this study, the value of seven accessions of H. spontaneum C. Koch as donors of both cytoplasmic and nuclear genes affecting agronomic traits of barley were investigated;Favorable effects of H. spontaneum cytoplasm were found for straw yield, unit straw weight, and vegetative growth index. These favorable effects were actually attributed to nuclear-cytoplasmic interactions as indicated by the presence of cytoplasm-mating interactions and absence of cytoplasmic-generation interactions. Thus, H. spontaneum cytoplasmic genome must have interacted with H. vulgare nuclear genome. H ...


Comparison Of Testers Used To Evaluate Unadapted Maize Populations , Bryce Carl Abel Jan 1989

Comparison Of Testers Used To Evaluate Unadapted Maize Populations , Bryce Carl Abel

Retrospective Theses and Dissertations

Numerous open-pollinated maize (Zea mays L.) accessions are maintained in the world's gene banks. These accessions need to be evaluated, particularly for quantitative traits, but they tend to be adapted only to specific environments. Temperate maize accessions may contain new alleles that can be used for maize improvement in the U.S. Corn Belt. Testcrossing unadapted populations to a series of testers has been proposed as an evaluation method. This study compared the ranking of temperate unadapted populations via testcrosses with eight testers consisting of broad-based populations, single crosses, and inbred lines. Also, the accessions were evaluated per se ...


Hybridization And Growth Studies In The Grain Amaranths (Amaranthus Hybridus L.) , James Wayne Lehmann Jan 1989

Hybridization And Growth Studies In The Grain Amaranths (Amaranthus Hybridus L.) , James Wayne Lehmann

Retrospective Theses and Dissertations

Thirty-two amaranth accessions from the world's collection were hybridized to produce eighty-seven Fls which were evaluated for heterosis and combining ability in three factorial mating designs. On average, interspecific matings of Amaranthus cruentus L. and A. hypochondriacus L. produced significant (P = 0.01) biomass increases over their parents. With A. cruentus African vegetable accessions as females, male parents of both species showed significant (P = 0.05) general combining ability (GCA). Midparent heterosis for biomass ranged from -13% to 88%. Late flowering of interspecific matings strongly influenced the larger biomass yields. Intraspecific matings of Asian A. hypochondriacus accessions exhibited highly ...


Estimates Of Quantitave Genetic Parameters In Iap2b Random-Mating Sorghum Population , Anthony J. Maves Jan 1989

Estimates Of Quantitave Genetic Parameters In Iap2b Random-Mating Sorghum Population , Anthony J. Maves

Retrospective Theses and Dissertations

Seed composition from S[subscript]1 families of C0, C2, C3, C4, and half-sib families of C1, C2, C3, and C4, together with 60 individual S[subscript]1 families chosen randomly from C0 and C4 of sorghum (Sorghum bicolor (L.) Moench) population IAP2B were evaluated in five Iowa environments;Four cycles of gridded mass selection of individual-panicle grain weight shifted the mean for grain yield favorably, and the range among S[subscript]1 families was extended. Increased values in C4 also were observed for seeds/panicle, 100-seed weight, days to midbloom, and plant height, but panicles/plant decreased. Genotypic variance ...


Comparative Performance Of Two Reciprocal Recurrent Selection Procedures In Maize , Donald John Blackburn Jr. Jan 1989

Comparative Performance Of Two Reciprocal Recurrent Selection Procedures In Maize , Donald John Blackburn Jr.

Retrospective Theses and Dissertations

Reciprocal recurrent selection (RRS) and a modified reciprocal recurrent selection procedure (RRSI), conducted in BS21 and BS22 maize (Zea mays L.) synthetics, were evaluated for changes in agronomic traits after three cycles of selection. BS21(R)CN and BS22(R)CN were used reciprocally as testers for each other in RRS. In RRSI, A632, an inbred line related to BS22, was used to test S[subscript]0 plants of BS21(A632HI)CN, while the tester for S[subscript]0 plants of BS22(H99HI)CN was H99, an inbred line related to BS21;BS21(R)CN x BS22(R)CN had ...


Comparison Of Mass Selection And S1-Testing Recurrent Selection Methods In Sorghum , Ronald Earl Secrist Jan 1989

Comparison Of Mass Selection And S1-Testing Recurrent Selection Methods In Sorghum , Ronald Earl Secrist

Retrospective Theses and Dissertations

The effectiveness of two selection methods for the improvement of grain sorghum (Sorghum bicolor (L.) Moench) populations was compared in two experiments. IAP1R(M) was developed by using mass selection for individual-panicle grain weight, while IAP4R(S1) was developed from the same base population by using replicated yield tests of S1 families;Results from Experiment I indicated that the selection methods significantly (P 0.05) between selection schemes for the improvement of grain yield of the C2 and C3 populations. Gain per cycle was estimated at 0.117 Mg/ha (2.06%/cycle) for mass selection and 0.170 Mg ...


Characterization Of Genetic Variability As Affected By Selection In Iowa Stiff Stalk Synthetic , David Scott Stucker Jan 1989

Characterization Of Genetic Variability As Affected By Selection In Iowa Stiff Stalk Synthetic , David Scott Stucker

Retrospective Theses and Dissertations

A cross-classification (North Carolina Design II) mating design was used to produce half-sib and full-sib progenies within each of three groups of Iowa Stiff Stalk Synthetic (BSSS) maize (Zea mays L.) lines. The groups of lines represented the resynthesized BSSS population, the current BSSS population maintained at Iowa State University; and the BS13(S)C1 population that has undergone seven cycles of half-sib and one cycle of S1-S2 recurrent selection for improved grain yield. Progenies were evaluated in experiments at three central Iowa locations in 1986 and 1987. Data were collected for grain yield, grain moisture, ear length, ear diameter ...


Estimates Of Combining Ability Of S2 Families Derived From The Random-Mating Sorghum Population Iap1r , Keith Richard Ess Jan 1989

Estimates Of Combining Ability Of S2 Families Derived From The Random-Mating Sorghum Population Iap1r , Keith Richard Ess

Retrospective Theses and Dissertations

IAP1R sorghum (Sorghum bicolor (L.) Moench) random-mating population was constituted by using 80% adapted U.S germplasm and 20% converted exotic sorghums. After three cycles of mass selection for individual-panicle grain weight, forty S[subscript]2 families were selected from the population and crossed to three male-sterile inbreds ( A[subscript]1 Combine Kafir 60, A[subscript]1 Redbine 58, and A[subscript]1 Martin) to produce 120 single-cross hybrids. The experimental hybrids along with three commercial sorghum hybrids were grown in two years at two locations in Iowa. Measurements from the four environments for grain yield, seeds/panicle, 100-seed weight ...


Response To Eight Cycles Of Full-Sib Reciprocal Recurrent Selection For Grain Yield And Standability In Bs10 And Bs11 Maize Populations , Guillermo Hugo Eyherabide Jan 1989

Response To Eight Cycles Of Full-Sib Reciprocal Recurrent Selection For Grain Yield And Standability In Bs10 And Bs11 Maize Populations , Guillermo Hugo Eyherabide

Retrospective Theses and Dissertations

The full-sib reciprocal recurrent selection (FSRRS) is designed to improve the performance and the heterosis exhibited by the cross between two populations. FSRRS can be integrated with maize (Zea mays L.) breeding programs whose ultimate goal is to obtain of hybrid cultivars. A comprehensive evaluation of a medium- to long-term selection program of FSRRS in maize populations BS10 and BS11 was conducted to determine direct and indirect response to selection in BS10, BS11, and the cross of BS10 and BS11;FSRRS was effective in improving the performance of the population cross and the populations themselves for grain yield and moisture ...


The Application Of Primary Trisomics And Transposon-Induced Mutations In Genetic Studies Of Soybean (Glycine Max (L.) Merr) , Bradley Robert Hedges Jan 1989

The Application Of Primary Trisomics And Transposon-Induced Mutations In Genetic Studies Of Soybean (Glycine Max (L.) Merr) , Bradley Robert Hedges

Retrospective Theses and Dissertations

The development of a soybean (Glycine max (L.) Merrill) genetic map is an ongoing process. Formulae to calculate expected critical genotypic and phenotypic F[subscript]2 ratios were developed to facilitate the mapping of codominant markers by using primary trisomics. A method is given for calculating the minimum family size required to distinguish between a critical and noncritical segregation ratio when three phenotypic classes are present;The five known soybean primary trisomics A, B, C, D, and S were tested for linkage with 10 isozyme loci. Only one locus was assigned to a chromosome. The Dial (diaphorase) locus was located ...


Bidirectional Selection For Dry-Matter Digestibility In Orchardgrass , Mohammad Jurial Rind Baloch Jan 1989

Bidirectional Selection For Dry-Matter Digestibility In Orchardgrass , Mohammad Jurial Rind Baloch

Retrospective Theses and Dissertations

Studies by many researchers have shown that orchardgrass has lower dry-matter digestibility than other cool-season perennial grasses at comparable growth stages. Selection for higher digestibility could be done in the greenhouse under more controlled conditions than in the field. The main purpose of this research was to determine direct and correlated field responses to individual plant selection in the greenhouse for high and low in vitro dry-matter digestibility (IVDMD). Three hundred and twenty-five individual plants from a broad-based germplasm source were evaluated for IVDMD in the greenhouse. Twenty-two plants selected for high and 22 for low IVDMD were evaluated clonally ...


Association Between Isozyme Genotypes And Quantitative Traits In Soybean , Juan Carlos Suárez Jan 1989

Association Between Isozyme Genotypes And Quantitative Traits In Soybean , Juan Carlos Suárez

Retrospective Theses and Dissertations

Glycine soja Sieb. & Zucc. is the wild progenitor of the cultivated soybean, Glycine max (L.) Merr. Although G. soja is agronomically undesirable, it is a potential source of new germplasm for breeding programs. Marker loci may be useful in an introgression program to enhance the recovery of desirable traits of the cultivated species by decreasing the number of segregants that must be evaluated in the field. Isozyme loci have a number of characteristics that make them desirable as markers. Before developing marker-based selection schemes, it is necessary to understand the relationships that exist between isozyme loci and genes involved in ...


The Molecular Analysis Of C1-P And C1-M1, Two Recessive Alleles Of C1: A Regulatory Locus Of The Anthocyanin Pathway In The Aleurone Tissue Of Zea Mays L. , Brian Eric Scheffler Jan 1989

The Molecular Analysis Of C1-P And C1-M1, Two Recessive Alleles Of C1: A Regulatory Locus Of The Anthocyanin Pathway In The Aleurone Tissue Of Zea Mays L. , Brian Eric Scheffler

Retrospective Theses and Dissertations

C1 is a regulatory locus of the anthocyanin pathway in Zea mays L. The locus is specifically expressed in the aleurone and scutellum tissue of maize kernels. The C1 protein sequence has homology to myb proto-oncogene products and the protein might act as a transcriptional activator;The research presented here involves the analysis of two recessive C1 alleles: c1-p and c1-m1. In homozygous c1-p maturing kernels there is no anthocyanin production, but those kernels produce anthocyanin when germinated in the presence of light. The DNA sequence analysis of the c1-p genomic clone is presented. The sequence revealed minor alterations in ...


Evaluation Of Selection Indices In A Recurrent Selection Program In Corn (Zea Mays L.) , Julio Hernando Milla Jan 1989

Evaluation Of Selection Indices In A Recurrent Selection Program In Corn (Zea Mays L.) , Julio Hernando Milla

Retrospective Theses and Dissertations

Index selection is a procedure used for selecting more than one trait at a time in a breeding program. Several types of selection indices have been proposed. The first one formally introduced and probably the most widely known is the Smith-Hazel index which requires estimates of phenotypic and genotypic parameters for its calculation. These estimates are subject to sampling errors that affect the performance of the index. In this study, several selection indices were compared, and the effectiveness of pooling parameter estimates over several cycles of selection on the estimation of the Smith-Hazel index was evaluated for the simultaneous improvement ...


Comparisons Of Performance And Genetic Variance Among S1 Lines And Their Testcrosses From The Original Iowa Stiff Stalk Synthetic And Three Improved Stiff Stalk Populations Of Maize , Sean Patrick Walters Jan 1989

Comparisons Of Performance And Genetic Variance Among S1 Lines And Their Testcrosses From The Original Iowa Stiff Stalk Synthetic And Three Improved Stiff Stalk Populations Of Maize , Sean Patrick Walters

Retrospective Theses and Dissertations

Iowa Stiff Stalk Synthetic (BSSS) was developed in the mid-1930s by intermating 16 inbred lines that were above average for stalk quality. BSSS has been involved in two long-term recurrent selection programs: reciprocal recurrent selection and half-sib followed by S2-progeny recurrent selection. Advanced populations from these programs are BSSS(R)C9 and BS13(S)C3, respectively;Objectives of this study were: (1) to compare the amount of genetic variation present among S1 lines from BSSSC0 (C0), two improved BSSS populations, BS13(S)C3 (C3) and BSSS(R)C9 (C9), and BS13(S)C3 x BSSS(R)C9 (C3 x C9 ...


Efficiency Of S2 Recurrent Selection For Improvement Of Exotic And Semi-Exotic Populations In Maize (Zea Mays L.) , Carlos Ariel Iglesias Jan 1989

Efficiency Of S2 Recurrent Selection For Improvement Of Exotic And Semi-Exotic Populations In Maize (Zea Mays L.) , Carlos Ariel Iglesias

Retrospective Theses and Dissertations

An experiment was conducted to evaluate the progress from use of S2 recurrent selection in BS16, BS2, and BSTL maize populations representing 100, 50, and 25% exotic germplasm. The objectives were to evaluate the response to selection, its genetic basis, the heterotic pattern among populations, and the changes in combining ability with cycles of selection. The study was conducted at eight environments and included the following entries: the original populations, an intermediate, and on advanced cycle of selection evaluated per se and selfed; a complete diallel among populations; testcrosses of the populations with four elite inbred testers (B73, B84, Mo17 ...


Mass-Selection Strategies For Pearl Millet Improvement , Henry Fredrick Rattunde Jan 1988

Mass-Selection Strategies For Pearl Millet Improvement , Henry Fredrick Rattunde

Retrospective Theses and Dissertations

Mass selection is frequently used for genetically improving pearl millet (Pennisetum glaucum R. Br.). To ascertain the ability of mass selection to modify traits of agronomic importance to pearl millet, this study determined (a) the heritability and interrelationships of those traits and (b) the realized gains obtained from selection. S[subscript]0 and S[subscript]1 populations of three pearl millet composites were evaluated for an array of agronomic and developmental traits. Parent-offspring heritability values ranged from 0.46 to 0.64 for panicle size and seed traits, from 0.27 to 0.58 for productivity traits, and from 0 ...


Estimates Of Genetic Homeostasis In Maize , Roberto Valdivia-Bernal Jan 1988

Estimates Of Genetic Homeostasis In Maize , Roberto Valdivia-Bernal

Retrospective Theses and Dissertations

Genetic homeostasis was studied in different maize (Zea mays L.) genotypes and populations to determine whether selection has affected homeostasis and to determine whether homeostasis is heritable. The maize materials included one group of six inbred lines released before the 1960s (older lines), and another group of six inbred lines released after the 1970s (newer lines). Within each group, single cross, F2, and backcross generations were developed. The experiments were conducted at two Iowa locations in 1985 and 1986. Individual plant measurements were taken for eight maize traits: yield, ear length, ear diameter, kernel-row number, kernel depth, plant and ear ...