| Abstrakt: |
Response of sunflower (Helianthus annuusL.) to in vitro culture has been shown to depend on medium, genotype and explant tissue. The objective of the present study was to evaluate the potential for shoot organogenesis from callus, of globular‐ to torpedo‐stage embryos (0.2–1.2 mm long), of 59 sunflower genotypes. Embryos were cultured on four modified Murashige and Skoog media (MS) varying in concentrations of NAA (naphthalene acetic acid) and BA (6‐benzylaminopurine). The MSO contained 1 mg/L NAA and 0.1 mg/L BA; MSI contained 2 mg/L NAA and 1 mg/L BA; MS2 contained 0.5 mg/L each NAA and BA; and MS3 contained 0.1 mg/L NAA and 1 mg/L BA. Frequency of embryo‐derived callus forming shoots was used to measure potential for plant regeneration. Five genotypes produced no callus or shoots from callus on any media, and both callus and shoot formation occurred on 5% or less of the plated embryos of eight genotypes. Three genotypes showed 80% or more callus formation with little or no shoot organogenesis; whereas, for four genotypes, more than 70% of the plated embryos developed shoots from callus on one or more media. One‐half of the genotypes showed 20% or more shoot‐forming callus. Effect of the medium varied in importance. All media were equivalent for callus formation, but MS3 had the most genotypes with a high frequency of shoot formation from callus. MS2 was second in promoting shoot organogenesis from callus. Because of a strong genotype ✕ medium interaction, the use of two MS media with different hormonal compositions is recommended to increase the frequency of sunflower genotypes regenerating shoots from callus derived from globular‐ to torpedo‐shaped embryos. |
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