Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower

Abstract

Wild biotypes of cultivated sunflower ( Helianthus annuus L.) are weeds in corn ( Zea mays L.), soybean ( Glycine max L.), and other crops in North America, and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides. Biotypes resistant to two classes of AHAS-inhibiting herbicides-imidazolinones (IMIs) or sulfonylureas (SUs)-have been discovered in wild sunflower populations (ANN-PUR and ANN-KAN) treated with imazethapyr or chlorsulfuron, respectively. The goals of the present study were to isolate AHAS genes from sunflower, identify mutations in AHAS genes conferring herbicide resistance in ANN-PUR and ANN-KAN, and develop tools for marker-assisted selection (MAS) of herbicide resistance genes in sunflower. Three AHAS genes ( AHAS1, AHAS2, and AHAS3) were identified, cloned, and sequenced from herbicide-resistant (mutant) and -susceptible (wild type) genotypes. We identified 48 single-nucleotide polymorphisms (SNPs) in AHAS1, a single six-base pair insertion-deletion in AHAS2, and a single SNP in AHAS3. No DNA polymorphisms were found in AHAS2 among elite inbred lines. AHAS1 from imazethapyr-resistant inbreds harbored a C-to-T mutation in codon 205 ( Arabidopsis thaliana codon nomenclature), conferring resistance to IMI herbicides, whereas AHAS1 from chlorsulfuron-resistant inbreds harbored a C-to-T mutation in codon 197, conferring resistance to SU herbicides. SNP and single-strand conformational polymorphism markers for AHAS1, AHAS2, and AHAS3 were developed and genetically mapped. AHAS1, AHAS2, and AHAS3 mapped to linkage groups 2 ( AHAS3), 6 ( AHAS2), and 9 ( AHAS1). The C/T SNP in codon 205 of AHAS1 cosegregated with a partially dominant gene for resistance to IMI herbicides in two mutant x wild-type populations. The molecular breeding tools described herein create the basis for rapidly identifying new mutations in AHAS and performing MAS for herbicide resistance genes in sunflower.

Variation in chickpea germplasm for tolerance to imazethapyr and imazamox herbicides

“…The existence of tolerance to imazethapyr/imazamox is not unique to chickpea, as natural genetic variation in tolerance to IMI herbicides has been observed in field pea with postemergence application of the herbicide (Hanson and Thill 2001). The mode of inheritance of tolerance to ALS-inhibiting herbicides has been reported to be relatively simple with a single, dominant nuclear-gene in some species (Lee and Owen 2000;Van Eerd et al 2004), or a single, partially dominant gene in others (Boutsalis and Powles 1995;Kolkman et al 2004). Exploitation of chickpea germplasm that carries herbicide-tolerance is seen as an attractive approach for the development of an integrated weed management in chickpea.…”

Differences in sensitivity of F1 and F2 generations of herbicide tolerant sunflower volunteers to selected acetolactate synthase inhibiting herbicides

“…Nevertheless, high differences were observed among experimental years (Tables 4 and 5). Low sensitivity of ExpressSun to imazamox was very surprising because mutation of ALS gene in position 197 results usually in no or low tolerance to imidazolinone herbicides (Kolkman et al 2004). However, Park et al (2012) tested the level of resistance of thifensulfuron resistant Sonchus asper population to some other ALS inhibiting herbicides and the lowest level of resistance was recorded for imazamox.…”

“…Two lines (IMISUN-1 and IMISUN-2) were developed with resistance to imidazolinone herbicides . Pro197Leu mutation in ALS gene was shown to confer resistance to sulfonylurea herbicides in the wild biotype of sunflower (Kolkman et al 2004). Two lines were developed with resistance to sulfonylurea herbicides by introgression of mutations from wild isolates ANN-KAN and ANN-PUR, respectively, into elite breeding lines SURES-1 and SURES-2 (Miller and Al-Khatib 2004).…”

History of the race structure of Orobanche cumana and the breeding of sunflower for resistance to this parasitic weed: A review

“…Several authors have reviewed known mutations of the AHAS genes that confer resistance to AHAS-inhibiting herbicides in weeds and crops (Preston & Mallory-Smith, 2001;Tranel & Wright, 2002;Tan et al, 2005). Based on molecular studies, Kolkman et al (2004) identified and characterized three genes coding for the AHAS catalytic subunits in sunflower (Ahasl1, Ahasl2 and Ahasl3). Ahasl1 is a multilallelic locus and the only member of this small family in which all the induced and natural mutations for herbicide resistance have been described thus far in sunflower.…”

“…Ahasl1 is a multilallelic locus and the only member of this small family in which all the induced and natural mutations for herbicide resistance have been described thus far in sunflower. Ahasl1-1, also known as Imr1 (Bruniard & Miller, 2001) or Ar pur (Kolkman et al, 2004), harbours a C-to-T mutation in codon 205 (Arabidopsis thaliana nomenclature), which confers a moderate resistance to imidazolinone (IMI). Ahasl1-2 (also known as Ar kan ) shows a C-to-T mutation in codon 197 conferring high levels of sulfonylurea (SU)-resistance (Kolkman et al, 2004).…”