Relationship between endogenous hormone levels of grapevine callus cultures and their morphogenetic behaviour

Dark callus cultures from leaves and anthers of three grapevine genotypes ( Seyval blanc, Riesling and Trollinger) were propagated in vitro for almost two years on medium deprived of growth regulators. Three different callus l ines originated from these initial callus cultures: A dark non-embryogenic one, another composed by clusters of somatic embryos and a friable, whitish callus line that can produce somatic embryos under appropriate circumstanc es, Endogenous hormone levels viz, indole-3-acetic acid (IAA), abscisic aci d (ABA), gibberellins A(1), A(3) and A(20), zeatin/zeatin riboside and N-6( Delta (2)-isopentenyl) adenine/ N-6(Delta (2)-isopentenyl) adenosine, were analysed in the different callus types. Only higher ABA levels correlated w ith the morphogenetic capacity of the cultures. When endogenous hormone lev els were analysed in the line constituted by conglomerates of somatic embry os at different dates during the whole culture period, higher levels of IAA and ABA were found during the winter months even if the cultures were main tained permanently under constant temperature and photoperiod conditions. A 4-week chilling period led to a reduction of the endogenous ABA level.