Acetohydroxyacid synthase mutations conferring resistance to imidazolinone or sulfonylurea herbicides in sunflower.
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.
Kolkman
Judith M
JM
Department of Crop and Soil Science, Oregon State University, Corvallis, OR 97331, USA.
Slabaugh
Mary B
MB
Bruniard
Jose M
JM
Berry
Simon
S
Bushman
B Shaun
BS
Olungu
Christine
C
Maes
Nele
N
Abratti
Gustavo
G
Zambelli
Andres
A
Miller
Jerry F
JF
Leon
Alberto
A
Knapp
Steven J
SJ
D000095:Acetolactate Synthase / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D017343:Genes, Plant; D005819:Genetic Markers; D006368:Helianthus / Q000187:drug effects / Q000235:genetics*; D006540:Herbicides / Q000633:toxicity*; D048288:Imidazolines / Q000633:toxicity*; D007113:Immunity, Innate / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013453:Sulfonylurea Compounds / Q000633:toxicity*
D018744:DNA, Plant; D005819:Genetic Markers; D006540:Herbicides; D048288:Imidazolines; D013453:Sulfonylurea Compounds; D000095:Acetolactate Synthase