A standardized, accurate, and easy system is needed to describe sunflower (Helianthus annuus L.) plant development. The objective of this study was to develop and describe stages of sunflower plant development in a manner which is simple but accurate.Plants were divided into either Vegetative (V) or Reproductive (R) stages of plant development. Vegetative development is divided into two phases, emergence and true leaf development. The latter stages are determined by the number of true leaves in excess of 4 cm in length. The number of vegetative stages is dependent upon the number of true leaves formed by the plant, making the method flexible but accurate. The reproductive development was divided into nine stages based on the development of the inflorescence from its initial appearance through anthesis to physiological maturity of the seed. This method of describing the stages of development in sunflower is rapid, accurate, greatly simplifies current methods, and can be used to determine plant development for either single or branched inflorescence 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.

Sunflower (Helianthm animus L.) oil high in oleic fatty acid composition is less susceptible to oxidative changes during refining, storage, and frying; therefore, quality is retained longer than sunflower oil high in linoleic fatty acid in both processed oil and the seed. Objectives of this study were to: (i) determine if oleic content of sunflower oil was maternally influenced, (ii) determine the genetic control of oleic acid content, and (iii) identify any modifying factors influencing high oleic acid content. High oleic lines of sunflower derived from 'Pervenets' were crossed with the low oleic inbred line, HA 89. The F, seed was intermediate in oleic acid content with reciprocal crosses showing maternal effects. This maternal effect on oleic acid is important in determining isolation of both hybrid seed production and general field production of high oleic acid and high linoleic acid sunflower. Oleic acid content was controlled by a major gene with partially dominant gene action, Ol, and a second gene, designated ml. When the recessive gene, ml, is present in homozygous condition, and combined with the gene Ol, oleic levels in seed were elevated to 820 g kg" 1 of oil or higher. The linear correlation coefficient between linoleic and oleic acid content for seed analyzed was-0.84, indicating that linoleic and oleic were the fatty acids primarily affected. For expression of very high oleic content in a sunflower hybrid grown in the north central states of the USA, a dominant allele of the Ol gene and the recessive alleles, mlml, of the Ml gene will be necessary.

Wildtype sunflower (Helianthus annuus L.) seeds are a rich source of alpha-tocopherol (vitamin E). The g = Tph(2) mutation disrupts the synthesis of alpha-tocopherol, enhances the synthesis of gamma-tocopherol, and was predicted to knock out a gamma-tocopherol methyltransferase (gamma-TMT) necessary for the synthesis of alpha-tocopherol in sunflower seeds--wildtype (g(+) g(+)) lines accumulated > 90% alpha-tocopherol, whereas mutant (g g) lines accumulated > 90% gamma-tocopherol. We identified and isolated two gamma-TMT paralogs (gamma-TMT-1 and gamma-TMT-2). Both mapped to linkage group 8, cosegregated with the g locus, and were transcribed in developing seeds of wildtype lines. The g mutation greatly decreased gamma-TMT-1 transcription, caused alternative splicing of gamma-TMT-1, disrupted gamma-TMT-2 transcription, and knocked out one of two transcription initiation sites identified in the wildtype; gamma-TMT transcription was 36 to 51-fold greater in developing seeds of wildtype (g(+) g(+)) than mutant (g g) lines. F(2) populations (B109 x LG24 and R112 x LG24) developed for mapping the g locus segregated for a previously unidentified locus (d). B109, R112, and LG24 were homozygous for a null mutation (m = Tph(1)) in MT-1, one of two 2-methyl-6-phytyl-1,4-benzoquinone/2-methyl-6-solanyl-1,4-benzoquinone methyltransferase (MPBQ/MSBQ-MT) paralogs identified in sunflower. The d mutations segregating in B109 x LG24 and R112 x LG24 were allelic to a cryptic mutation identified in the other MPBQ/MSBQ-MT paralog (MT-2) and disrupted the synthesis of alpha- and gamma-tocopherol in F(2) progeny carrying m or g mutations--m m g(+) g(+) d d homozygotes accumulated 41.5% alpha- and 58.5% beta-T, whereas m m g g d d homozygotes accumulated 58.1% gamma- and 41.9% delta-T. MT-2 cosegregated with d and mapped to linkage group 4. Hence, novel tocopherol profiles are produced in sunflower seed oil by three non-allelic epistatically interacting methyltransferase mutations.

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