Acetohydroxyacid synthase (AHAS) inhibiting herbicides have played a significant role in effective weed control in the cultivation of sunflower since their discovery. The development of sunflower lines and hybrids resistant to these herbicides made their post-emergence application possible. In this study, wildHelianthusspecies were screened phenotypically for imidazolinone (IMI) and sulfonylurea (SU) resistance by herbicide spray and for allelic variations atAhasl1(Ahas1 large subunit) locus using simple sequence repeat and single nucleotide polymorphism markers.Helianthus praecoxaccession 1823 plants showed promising resistance to three classes of SU-based herbicides andHelianthus nuttalliiaccession NUT05 plants remained green for a longer time after imazethapyr spray. A total of 50 accessions belonging to 21 wildHelianthusspecies of different ploidy levels were analysed for allelic variation along with some parents of commercial sunflower hybrids. None of the wild species showed the resistant allele (Ahasl1-1) similar to SCG101 (IMI-resistant line), although it is present in some of the parental lines of hybrids. However, the parental lines havingAhasl1-1-type allele failed to survive the field dose of imazethapyr spray. Inter-species and inter-accessional allelic variation could be observed among the species. PRA1823 and NUT05 showed repeat length variations atAhasl1locus. Sequencing of full lengthAhasl1gene from both these accessions did not reveal any resistance mutations in the protein sequences. The molecular basis of the phenotypes identified in this study could be explored further and utilized in breeding programmes for imparting herbicide resistance in cultivated hybrids across sunflower growing regions of the world.

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