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Doctorat
États-Unis
2017
A joint genetic linkage mapping and genome-wide association study of drought and salinity tolerance and verticillium wilt and thrips resistance in cotton
Titre : A joint genetic linkage mapping and genome-wide association study of drought and salinity tolerance and verticillium wilt and thrips resistance in cotton
Auteur : Abdelraheem, Abdelraheem R.T..
Etablissement de soutenance : New Mexico State University,
Grade : Doctor of Philosophy (PhD) 2017
Résumé partiel
Cotton (Gossypium spp.) is grown in arid and semi-arid regions including the
southwest and west U.S., where abiotic and biotic stresses such as drought, salt,
erticillium wilt (Verticillium dahliae) and thrips (Frankliniella occidentalis) are
prevalent. Resistances or tolerances to these stresses are interconnected and have
much in common ; however, the genetic basis of the resitances is not fully understood
due to complexity of the stress resistance and difficulties in phenotyping. Although
developing and using resistance germplasm is the most effective method to manange
these stresses, most cotton cultivars and breeding lines have been developed under
non-stress conditions. Therefore, genes for resistance to different stresses are
randomly fixed in breeding lines that can be identified in breeding, genetic and
genomic studies.
The aims of this study were to measure the extent of genetic variation for the
abiotic and bioticstress resistance in tetraploid cotton and to identify quantitative trait
loci (QTL) responsible for drought and salt tolerance related morphological and
physiological traits, and yield and its components as well as fiber quality under both
stress and non-stress conditions, and for Verticillium wilt and thrips resistance.Two
genomic approacheswith five independent studies were taken including genetic
linkage mapping usingthree bi-parental permanent populations and a genome-wide
association study (GWAS) using a diversity panel of 376 Upland cotton germplasm
lines.
In the first study, seedlings of 142 backcross inbred lines (BILs) derived from
Upland cotton ‘Sure-Grow 747’ (G. hirsutum) * ‘Pima S-7’ (G. barbadense) were
evaluated in two replicated tests for plant height, fresh shoot weight and root weight under two treatments [5% polyethylene glycol (PEG) and water-control conditions]
using a hydroponic system in the greenhouse. The experiment in each test was a
randomized complete block design with three replications. The analysis of variance
for the two tests detected significant genotypic variation in PEG-induced stress
tolerance within the BIL population and between the parents. Heritabilities were
moderate to high and were higher under the control conditions than under the PEG
treatment, and the three traits were also significantly and positively correlated. Based
on a linkage map with 292 DNA markers, six QTL were detected including two for
plant height, and two each for fresh shoot weight and root weight. This study
represents the first report in using a permanent mapping population in genetic and
linkage analysis of water stress tolerance in cotton
Page publiée le 18 septembre 2017, mise à jour le 21 décembre 2019