EXPERIMENTAL STUDIES ON SEVERAL FACTORS AFFECTING UNFERTILIZED OVULE CULTURE IN SUNFLOWER

In sunflower ovule culture, there are two kinds of products; the gynogenetic embryoid, somatic proliferation including endothelial embryoid and the integumental callus. It is very important to regulate the balancne between them in favor of the former. We have carried out a large-scale design of experiments. The factors studied included: donor cultivars, basic media, kind of explents, embryo sac stage, culture on solid or liquid medium, shallow culture and ovule-density culture, and illumination condition, etc. Each factor could influence each kind of the derivatives differently. By regulation of various factors we were able to enhance induction-frequency of gynogenesis and meanwhile eliminate somatic derivatives. A suitable procedure in sunflower ovule culture concluded in this paper is to choose high-responsive cultivars; pretreat the inflorescence at 4℃ for 24—48 hours; pick out ovules from the florets 1—3 days before anthesis and inoculate them on N6 medium(solid or liquid) supplemented with 12% sucrose, 100mg/l inositot, but free of exogenous hormone, keep the culture in approx.27℃ and darkness for about 30 days; dissect the enlarged ovules and take out, if any induced, the gynogenetic embryoids; transfer the embryoids onto adequate medium for regeneration.