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dc.contributor.authorHa, Bo Keun
dc.description.abstractThis study was conducted to enhance marker-assisted selection for southern root-knot nematode [Meloidogyne incognita (Kofoid and White) Chitwood] (Mi) and reniform nematode (Rotylenchulus reniformis Linford and Oliveira) in soybean [Glycine max (L.) Merr.]. The objective of the first study was to determine the frequency of elite Mi-resistant cultivars that inherited the major resistance QTL (Rmi1) on LG-O and identify the ancestral source of the Mi-resistance allele at this locus in elite U.S. soybean cultivars. Forty-eight soybean genotypes, including ancestral, Mi-susceptible, and Mi-resistant genotypes, were evaluated for Mi-gall formation in a greenhouse in a randomized complete block experimental design with six replications. These genotypes were genotyped at six SSR loci (Satt358, Sat_132, Satt487, Satt500, Satt492, and Satt445) that flank the major Mi QTL on LG-O. Codescent analysis of markers and phenotypes across six cycles of breeding showed that Mi-resistant cultivars inherited a 200-bp band at Satt358 and a 238-bp band at Sat_132 from ‘Palmetto’. The objective of the second study was to identify SNPs linked to the Mi resistant QTL on LG-O and LG-G and to optimize SNP genotyping conditions using Luminex 100 flow cytometer. We discovered four SNPs in Satt358 allele sequences located near a major Mi-resistant QTL on LG-O and 4 SNPs in Satt199 allele sequences located near a minor Mi-resistant QTL on LG-G between PI 96354 (Mi resistant) and Bossier (Mi susceptible). Using a direct hybridization assay, the genotypes of the SNP358 marker that targets two SNPs in Satt358 allele sequences were identical to the genotypes of the SSR marker Satt358 among 94 F2:3 lines of PI 96354 ´ Bossier. The genotypes of SNP199 marker which targets a SNP in Satt199 allele sequences also showed 100% congruence with the genotypes of the SSR marker Satt199. The objective of the third study was to map soybean QTL conferring resistance to reniform nematode in a population of 228 recombinant-inbred lines (RILs) derived from a cross between susceptible ‘BSR101’ and resistant PI 437654 . A major resistance QTL 2(R=21%) conditioning reniform reproductive index was found on LG-L flanked by Sat_184 and Satt513. Two other QTL were identified. One was located in the interval 22from Satt359 to Satt484 on LG-B1 (R=16%) and the other on LG-G (R=8%) linked to Sat_168. By screening the ‘Prichard’ ´ S94-1956 RILs, we confirmed that QTL on LG-G and -B1 would enhance reniform nematode resistance.
dc.subjectGlycine max
dc.subjectMeloidogyne incognita
dc.subjectSouthern root-knot nematode
dc.subjectRotylenchulus reniformis
dc.subjectReniform nematode
dc.subjectNematode resistance
dc.subjectDirect hybridization
dc.titleMolecular approaches to facilitate marker-assisted selection for the southern root-knot nematode and reniform nematode in soybean
dc.description.departmentCrop and Soil Sciences
dc.description.advisorH. Roger Boerma
dc.description.committeeH. Roger Boerma
dc.description.committeeSteve Knapp
dc.description.committeeDaniel Phillips
dc.description.committeeJoe Bouton
dc.description.committeeRichard Hussey

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