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Showing 3 results for Linkage Disequilibrium
Association analysis using SSR markers for resistance to Sclerotinia basal stem rot disease in oily sunflower (Helianthus annuus L.) under filed conditions
R. Paknia, R. Darvishzadeh , F. Shahriari , S. Malekzadeh,
Volume 9, Issue 3 (9-2018)
Abstract
Aims: Sunflower (Helianthus annuus L.) is mainly cultivated for the extraction of edible oil, and Sclerotinia sclerotiorum is a pathogen in sunflower fields. The aim of this study was to indetify markers associated with resistance to Sclerotnia Scleritiorum diseases in sunflower, using association analysis.
Materials and Methods: In the present experimental research, a population including 100 lines of oily sunflower was cultivated. Traits such as contamination progress after 4, 8, and 12 days, 100 seeds weight of contaminated and non-contaminated plants, contaminated and non-contaminated plant yield, 100 seeds weight loss, and yield loss were studied. The molecular profiles of germplasm were prepred with 30 microsatellite primer pairs. Genetic structure analysis of population was performed based on Bayesian model.
Findings: The highest coefficient of variation was related to the yield loss (86.41%) and weight loss (78.48%), and the lowest was contamination progression after 8 and 12 days (26.47% and 20.44%), respectively. Based on the mixed linear model (MLM), 6 microsatellite markers related to traits were identified at the level of p≤0.01. The highest number of markers was associated with contamination progression after 8 days. The P733, P807, and P1256 markers were simultaneously associated with 3 traits.
Conclusion: Four lines including RHA274, H100A-83HR4, B45-03, and Iranian line with code 28 were identified with different genetic origins and high resistance levels. According to the general linear model (GLM) and MLM, 24 and 15 SSR markers are related to the traits, respectively. The P733, P807, and P1256 markers are simultaneously associated with 3 traits.

Genetic Variability, Structure Analysis, and Association Mapping of Resistance to Broomrape (Orobanche aegyptiaca Pers.) in Tobacco

Volume 18, Issue 5 (9-2016)
Abstract
Broomrape is a debilitating holoparasiting weed in tobacco (Nicotiana tabacum L.) fields with devastating effects on its production. In this study, the reaction of 89 tobacco genotypes was evaluated against broomrape (Orobanche aegyptiaca) in randomized complete block design with three replications during two years. In each year, genotypes were planted in both non-inoculated and inoculated conditions where the soil of pots was mixed with 0.06 g of broomrape seed. Considering the average data of two years, studied genotypes did not show infection to broomrape at non-inoculated condition, whereas in inoculated condition, the majority of genotypes showed infection to broomrape. Two genotypes including ‘TB 22’ and ‘Kramograd NHH 659’ did not show any infection to broomrape in inoculated condition. In a molecular experiment, the fingerprint of tobacco genotypes was prepared with 26 SSR loci. Using model-based Bayesian approach, the studied association panel was divided into three subgroups. The D¢ was used to test the LD between pairs of SSR loci using the software package TASSEL. 7.08% of possible SSR locus pairs showed significant level of linkage disequilibrium (P<0.01). By using mixed linear model, 5 SSR loci from linkage groups 2, 10, 11 and 18 of tobacco reference map were identified as DNA markers to be linked to gene(s) controlling broomrape resistance in tobacco.
Genome-Wide Association Mapping Revealed SNP Alleles Associated with Resistance to Cereal Cyst Nematode (Heterodera filipjevi) in Wheat

Volume 26, Issue 4 (7-2024)
Abstract
Resistance traits are economically important in crops in terms of accessibility to promising resistant germplasm. This study was conducted to evaluate SNP marker-trait association for Cereal Cyst Nematode (CCN), Heterodera filipjevi, in a large number of natural bread wheat populations. Phenotypic data analyzed using GLM (Generalized Linear Model) indicated significant differences among the landrace accessions for resistance to H. filipjevi. The genotyping was performed by 152K SNP chip on 188 accessions. After filtering, 10,471 polymorphic SNPs were employed for Genome Wide Association Study (GWAS). Population structure among the wheat genotypes were investigated using 840 well distinct SNP markers. Two sub-populations were revealed by structure software, and eleven markers were found to be significantly (P-value< 0.001) associated with resistance to H. filipjevi on chromosomes 2A, 3B, 4A, 4B, 5A, 5B, 5D, and 6B. The linkage disequilibrium analysis for all significantly associated SNPs showed that markers on chromosomes 4A and 4B were in high intra-chromosomal linkage disequilibrium, and, consequently, eight markers were recommended as strongly associated with resistance to H. filipjevi. The present study demonstrated valuable sources of resistance in the studied wheat genotypes against a widespread and important species of CCNs. The associated markers could be used in molecular breeding programs of bread wheat.

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