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University of São Paulo USP (2014)

Diversidade genética e mapeamento associativo de caracteres associados à tolerância do arroz ao déficit hídrico

Savio, Filipe Luís

Titre : Diversidade genética e mapeamento associativo de caracteres associados à tolerância do arroz ao déficit hídrico

Genetic diversity and association mapping for drought tolerance characters in rice

Auteur : Savio, Filipe Luís

Université de soutenance : Escola Superior de Agricultura Luiz de Queiroz (University of São Paulo USP)

Grade : Doctorat 2014

Résumé
Germplasm characterization and the knowledge of its diversity and population structure are important to effective utilization of genetic resources in breeding programs specially drought breeding program. In this work 192 landraces from all over Japan were evaluate for their morphological and productive characteristics, using field trials and high throughput screening methods. The screening using herbicide barrier approach at 30 cm depth was able to detect genetic diversity between the landraces for root length and clearly distinguish between deep root landraces and shallow root landraces. With this approach was possible to select 20 landraces with deep root system as possible donor of drought tolerance genes. Aiming characterize the landraces to agromorphological characteristics field trials were carried in 4 different locations exposing the landraces for a diversity environment effect. Using 13 traits phenotypically data generate a total of 15 groups during cluster analysis. The average result for drought sensitive index was 0.99, however this results presents a huge variability having landraces with scores about 0.6 to landraces with score up to 1.12. Drought effect was huge and statistically significant affecting directly yield and panicle size. The landraces presented genetic variability for drought tolerance and some landraces presenting yield and panicle size reductions due to drought comparable with drought-tolerant controls were detected. A total of 73728 alleles were detected by the SNP markers, indicated a high percentage of A (40,8%) and G (34,6%) alleles compared to C(15,6%) and T (3.6%). Heterozygocity of A/G was highest (0,54%) and lowest in A/T (0.04%). Of 3 chromosomes of rice, chromosome 8 produced highest percentage of heterozygocity compared to other chromosomes. Accessions were classified as 98.4% belonging to japônica subspecies. Association between markers and phenotypes was performed using a mixed linear approach (MLM), which incorporates information regarding population structure and kinship. Among the 384 markers used, 10 were responsible for significant associations with drought sensibility index, based on different criteria to correct for multiple tests.These associations were selected to determine the allelic effects over the traits, in order to generate preliminary data for marker assisted selections (MAS). Estimated size of haplotype blocks were 100 kb (r <0.05) and 75 kb (r <0.1). Future studies should confirm marker trait associations here found using different populations.

Mots clés : Oryza sativa Desequilíbrio de ligação Diversidade genética ISS Mapeamento associativo SNP Tolerância a estresse hídrico Oryza sativa Association mapping Drought tolerance Genetic diversity Linkage desequilibrium SNP

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