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THE EFFECT OF ACCESSORY CHROMOSOMES ON THE RESISTANCE OF MAIZE TO VIRAL INFECTIONMcGirr, Scott Craig, 1950- January 1977 (has links)
No description available.
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Physiological studies of a genetic mutant of Zea mays L.Homan, Mac Delano, 1933- January 1959 (has links)
No description available.
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Physiological genetics of dwarf (4963) of Zea mays L.O'Donald, William Arthur, 1934- January 1959 (has links)
No description available.
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THE INFLUENCE OF B CHROMOSOMES ON THE SUSCEPTIBILITY OF MAIZE TO GAMMA IRRADIATION INDUCED DNA DAMAGE (RECOMBINATION).STAUB, RICK WALTER. January 1984 (has links)
Tests were conducted to ascertain whether B chromosomes influence the susceptibility of maize (Zea mays L.) plants to gamma-radiation-induced DNA damage. Isogenic stocks of Black Mexican sweet corn with and without B chromosomes were premeiotically irradiated and DNA damage was assayed by measuring pollen viability. Higher pollen viabilities relative to non-irradiated control plants were consistently obtained in irradiated plants with B chromosomes when compared to irradiated plants without B's. Furthermore, among plants irradiated with 1250R those with one B chromosome produced the greatest proportion of viable pollen and plants with increasing numbers of B's produced progressively less viable pollen. An exophenotypic trait elicited by B chromosomes is also reported. Plants with 5 or more B chromosomes often display an aberrant phenotype characterized by longitudinal white leaf stripes and/or narrow leaves. This phenotype intensifies with increasing numbers of B chromosomes and is the first case of a qualitative exophenotypic trait attributable to B chromosomes reported in maize.
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AFLP and PCR markers for the Ht1, Ht2, Ht3 and Htn1 resistance genes in maizeVan Staden, Derick 12 1900 (has links)
Thesis (PhDAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Maize is undoubtedly South Africa's most important field crop. The identification of
markers and genes for traits of interest is important to sustain the improvement of
maize cultivation. Northern corn leaf blight (NClB) is a disease that occurs worldwide
and can dramatically reduce yield. A number of single dominant resistance
genes have been identified for NClB and some have been mapped. Currently there
are no simple PCR markers for any of these resistance genes, making markerassisted
selection (MAS) difficult.
The aim of this study was to develop PCR markers for the NClB resistance genes
Ht1, Ht2, Ht3 and Htn1 in maize. To accomplish this, the AFlP (amplified fragment
length polymorphism) technique was first optimised. The results indicated that the
Mlul/Msel restriction enzyme combination produces a higher percentage of
polymorph isms when compared to the PstllMsel enzyme combination. It was also
shown that the enzyme combination plays an important role in the percentage of
polymorphic fragments observed, whereas the number of restriction enzymes used in
AFlP analysis only significantly affects the total number of fragments scored.
Populations segregating for the different resistance genes were not available for this
study. Nearly-isogenic lines (Nils) were used in combination with AFlP technology
to identify markers that map close to the genes. AFlP markers common in at least
two resistant or susceptible lines were cloned and converted to PCR markers. Two
commercially available recombinant inbred line (Ril) populations were then used to
map the identified markers.
For Htn1 fifteen polymorphic fragments were present in both resistant lines. They
were selected for sequence specific marker conversion. Seven of the fifteen
sequence characterized amplified region (SCAR) markers were polymorphic on the
Nil pairs and five mapped to one region of maize chromosome 8.05/06. Twenty-one
AFlP markers were identified for Ht1 and four SCAR markers were polymorphic In
the Ht1 Nils. Three of these were mapped to chromosome 2.07. Three AFlP
markers were identified for Ht2 of which two were converted to SCAR markers. Both
SCAR markers were polymorphic on the Ht2 Nils and mapped to chromosome 8.05/06. On the Ht3 NILs, four AFLP markers were identified and two converted
SCAR markers and one microsatellite marker (bnlg1666) were polymorphic. One of
the SCAR markers and the microsatellite marker were mapped to chromosome 7.04
using a RIL population. This reports the first tentative mapping position for the Ht3
locus.
The next step was to determine if a set of marker alleles could be used in a number
of Htn 1 resistance lines to identify a common donor region selected by the breeders.
Nine markers consisting of five SCAR markers, three converted RFLP markers and
one microsatellite marker were used on 16 Htn1 resistant lines. The marker allele of
us3 was in 12 of the 16 lines in coupling with Htn1 resistance. Second was the
marker us5 in 11 of the 16 lines. Using this data 14 of the 16 lines shared a common
introgressed region between the markers us3 and us5. A further common
introgressed region between 11 of the inbred lines was found between the markers
us14 and asg17.
The last aim of this study was to propose a new marker technique that might be more
successful than the AFLP technique in the identification of markers closely linked to
genes. A new marker approach was identified where a MITE (Hbr) primer was used
as an anchor primer in combination with resistance gene analog primers. This was
found to be a highly polymorphic marker technique that could be used to identify
markers and possibly candidate genes. It is a robust technique, which is affordable
since amplifications occur from undigested genomic DNA and the primers mainly
amplify fragments from genic regions. / AFRIKAANSE OPSOMMING: Mielies (Zea mays) is ongetwyfeld Suid Afrika se belangrikste lanbou gewas. Vir
volgehoue opbrengs verbetering is die identifisering van merkers en gene vir
belangrike eienskappe noodsaaklik. Noordelike blaarskroei (NBS) kan opbrengs
wesenlik kan beïnvloed. Tans is daar reeds "n aantal enkel weerstandsgene
geïdentifiseer, maar geen PKR-merkers is beskikbaar vir merker gebaseerde
seleksie nie.
Die doelwit van hierdie studie was om PKR-merkers te ontwikkel vir vier enkel
weerstands gene (Ht1, Ht2, Ht3 en Htn1) teen NBS in mielies. Om die doelstelling te
bereik is die AFLP-tegniek eers geoptimiseer. Op grond van waargenome aantal
polimorfismes, was Mlul/Mse/"n beter restriksie ensiem kombinasie as Pstl/Msel. In
die studie is ook bewys dat die aantal (meer as twee) restriksie ensieme wat gebruik
word slegs die aantal fragmente, en nie die persentasie polimorfismes, wesenlik
beïnvloed nie.
Geen segregerende populasie was vir die verskillende gene beskikbaar nie. Naby
isogeniese lyne (NILe) is daarom in kombinasie met die AFLP-tegniek gebruik om
merkers te identifiseer wat naby die gene karteer. Alleenlik polimorfiese merkers wat
in ten minste twee weerstand biedende of vatbare lyne voorgekom het, is gekloneer
en omgeskakel na PKR-merkers. Daarna is twee kommersiële rekombinante
ingeteelde lyn populasies gebruik om die gene te karteer.
Vyftien fragmente is gevind wat gekoppel was met die Htn1 weerstand. Sewe van
hierdie merkers is omgeskakel in polimorfiese SCAR-merkers waarvan vyf gekarteer
is in een gebied op chromosoom 8.05/06. Een-en-twintig AFLP-merkers is
geïndentifiseer vir Ht1 en vier is omgeskakel na polimorfiese SCAR-merkers. Drie
hiervan is gekarteer op chromosoom 2.07. Drie AFLP-merkers is geïndetifiseer vir
Ht2 waarvan 2 omgeskakel is na polimorfiese SCAR-merkers. Altwee hierdie
merkers is gekarteer op chromosoom 8.05/06. Op die Ht3 lyne is vier AFLP-merkers
geïdentifiseer waarvan twee omgeskakel is na polimorfiese SCAR-merkers. Een
mikrosatelliet merker (bnlg1666) is ook gevind wat die selfde polimorfiese patroon
wys op die Ht3 lyne. Die mikrosateliet en een van die SCAR-merkers het gekarteer op chromosomale posisie 7.04. Hierdie is die eerste tentatiewe posisie vir die Ht3
lokus.
Die volgende stap was om te bepaal of "n stel polimorfiese merker-allele gebruik kan
word om die donor DNA-segment te identifiseer wat die plantteiers geselekteer het.
Nege PKR-merkers wat bestaan het uit vyf SCAR-merkers, 3 omgeskakelde RFLP
merkers en een mikrosateliet is gebruik op 16 Hnt1 weerstandslyne. Us3 was die
merker alleel wat in die meeste gevalle gekoppel was met die Htn1 weerstandslyne
(12/16). Tweede was die merker us5 (in 11 van die 16 lyne). Uit die data blyk dit dat
14 van die 16 lyne "n donor segment het wat beide merkers us3 en us5 bevat.
Merkers us14 en asg17 het in 11 van die 16 bestande lyne saam voorgekom.
Die laaste doelstelling van hierdie studie was om "n nuwe tegniek te ontwikkel wat
dalk meer suksesvol as AFLPs kan wees om merkers te identifiseer nabyaan gene.
"n Nuwe tegniek word voorgestel waar "n MITE (Hbr) inleier gebruik kan word in
kombinasie met weerstandgeen-analoog inleiers. Dit is gevind dat hierdie
kombinasie van inleiers "n hoogs polimorfiese band patroon gee en dat die merkers
ook dalk kandidaat-gene kan wees. Die tegniek is maklik uitvoerbaar, relatief
goedkoop en maak gebruik van onverteerde genomiese DNA. Die fragmente wat
geamplifiseer word is hoofsaaklik vanaf geenryke areas.
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Isolation and characterization of abscisic acid-responsive, embryo specific genes from Zea maysWilliams, Bruce January 1993 (has links)
No description available.
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A role for maize ROP2 GTPase in the male gametophyteCarroll, Kirstin Arthur 26 October 2004 (has links)
ROP GTPases are crucial regulators of pollen tube growth. The Rop GTPase family in maize consists
of nine known rop genes, ropl-rop9. A subset of these genes (rop2, rop8, and rop9) are expressed in
pollen. The rop2 and rop9 genes are a highly conserved duplicate gene pair of ancient origin. The
rop2/rop9 duplicate gene pair displays differential expression in mature and germinated pollen,
suggesting different roles for the genes in the process of male gametophyte development. To explore
ROP2 function in maize, five Mutator transposon insertions in the rop2 gene were isolated (rop2::Mu
alleles). I showed that three of the rop2::Mu alleles displayed reduced transmission through the male
and were associated with reduced levels of ROP2-mRNA. Interestingly, the rop2::Mu male-specific
transmission defect was apparent only when wild-type pollen was also present, an indication that the
mutation reduces the competitive ability of the rop2 gametophytes. Dual pollination and pollen
mixing experiments indicated that this competitive disadvantage is expressed by the majority of the
mutant gametophytes, and that expression of the phenotype is associated with a delay in the ability to
accomplish fertilization. Using the waxy phenotypic marker (linked to rop2 via a reciprocal
translocation) to distinguish between rop2::Mu and wild-type pollen derived from heterozygous plants,
I demonstrated that the delay is associated with a defect in early progamic development (i.e,
germination and early pollen tube growth). The defect was detectable in vivo as early as 15 minutes
after pollination. However, quantitative measurements provided no indication that the rop2 mutation
affects pollen tube growth in the style. Finally, investigations focusing on the final stages of pollen
function raise the possibility that a defect in the very last stages (i.e. either pollen tube guidance
through the micropyle to the egg sac, or fertilization of the egg sac) may also contribute to the rop2
mutant delay. This work provides direct in vivo evidence confirming a role for Rop in male
gametophyte development, and is the first study to demonstrate a role for Rop in the early stages of
post-pollination gametophytic function. / Graduation date: 2005
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Isolation and characterization of abscisic acid-responsive, embryo specific genes from Zea maysWilliams, Bruce January 1993 (has links)
Embryogenesis in plants, as in animals, requires the regulated expression of sets of genes involved in developmental processes. To gain insight into the processes regulating gene expression during embryogenesis differential screening was used to identify embryo-specific sequences in a cDNA library constructed from Zea mays embryo RNA. Four embryo-specific sequences and one constitutive sequence were characterized further by RNA blot hybridization and DNA sequence determination. The constitutive sequence and two of the embryo-specific sequences were found to encode parts of the previously-reported chloroplast 23S rRNA, Oleosin KD-18, and RAB-17 genes. Two sequences, named Emb5 and Emb564, were found to encode novel maize homologs of a gene expressed during late embryogenesis in a wide range of seed plants. These 5 genes exhibited differential temporal and spatial accumulation during development. Moreover, analysis of RNA from cultured embryos suggested that 4 of these genes were regulated by abscisic acid. The ABA-responsive genes could be divided into 3 classes, based on their developmental expression, tissue-specificity, and sensitivity to ABA. Antibodies raised against a $ beta$-galactosidase:EMB564 fusion protein were used to analyze the accumulation of the EMB564 and/or EMB5 proteins. These polyclonal antibodies detected one or several polypeptides with a molecular weight less than 14 kD which exhibited patterns of developmental accumulation and regulation similar to Emb5 and Emb564 transcripts.
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Agronomic evaluation of short season quality protein maizeSpaner, Dean Michael January 1992 (has links)
The introduction of Quality Protein Maize (QPM), hard endosperm opaque-2 maize, into northern temperate maize growing areas is a desirable breeding objective. In topcrosses with opaque-2 testers, in diallel combination, as inbreds per se, and in inbred disease screening nurseries, some QPM lines performed better than or equal to the best local checks. In general, while agronomic potential is high for some lines and gains from selection are statistically possible, longer days to flowering intervals and higher levels of moisture at harvest than check hybrids indicated a need to improve adaptation for the locations studied. Methodology experiments indicated that detasselling of check hybrids is a suitable experimental method to facilitate the inclusion of normal endosperm local checks into QPM performance tests. The screening for Fusarium graminearum resistance in the seedling stage has not been proven to be a viable alternative to field scale ear inoculation screening procedures. (Abstract shortened by UMI.)
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Quantitative genetic analysis of recombinant inbred lines (RIL) from tropical maize singlecrossesMoon, Hyeon Gui January 1995 (has links)
Thesis (Ph. D.)--University of Hawaii at Manoa, 1995. / Includes bibliographical references (leaves 228-240). / Microfiche. / xx, 240 leaves, bound ill. (some col.) 29 cm
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