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Reference Report for RTN20170502.5
Title:Molecular characterization of Als1, an acetohydroxyacid synthase mutation conferring resistance to sulfonylurea herbicides in soybean
Authors:Ghio, C., Ramos, M.L., Altieri, E., Bulos, M., Sala, C.A.
Source:Theor. Appl. Genet. 2013, 126:2957-2968
Abstract:Sulfonylurea (SU) resistance in soybean is con- trolled by Als1, a semi-dominant allele obtained by EMS mutagenesis over the cultivar Williams 82. The overall objective of this research was to map Als1 in the soybean genome and to determine the nucleotidic changes confer- ring resistance to SU. Four nucleotide sequences (GmA- has1Ð4) showing high homology with the Arabidopsis thal- iana acetohydroxyacid synthase (AHAS, EC 4.1.3.18) gene sequence were identified by in silico analysis, PCR-ampli- fied from the SU-resistant line BTK323STS and sequenced. Expression analysis showed that GmAhas1, located on chromosome 4 by in silico analysis, is the most expressed sequence in true leaves. F2:3 families derived from the cross between susceptible and resistant lines were evaluated for SU resistance. Mapping results indicate that the locus als1 is located on chromosome 4. Sequence comparison of GmAhas1 between BTK323STS and Williams 82 showed a single nucleotide change from cytosine to thymine at posi- tion 532. This transversion generates an amino acid change from proline to serine at position 197 (A. thaliana nomen- clature) of the AHAS catalytic subunit. An allele-specific marker developed for the GmAhas1 mutant sequence cosegregated with SU resistance in the F2 population. Taking together, the mapping, expression and sequencing results indicate that the GmAhas1 sequence corresponds to the Als1 gene sequence controlling SU resistance in soy- bean. The molecular breeding tools described herein create the basis to speed up the identification of new mutations in soybean AHAS leading to enhanced levels of resistance to SU or to other families of AHAS inhibitor herbicides.






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