RELATIONSHIP BETWEEN ENDOGENOUS AUXIN (INDOLE-3-ACETIC ACID) AND ADVENTITIOUS ROOTING IN DALBERGIA SPECIES OF DIFFERENT ROOTING ABILITY

A vegetative multiplication trial was conducted in two commercially important timber species with different rooting abilities from the genus Dalbergia. Dalbergia latifolia, globally known as ‘Indian rosewood’, is a premium-quality high priced Indian timber species. It is vulnerable in the forest and bears the constraint of poor adventitious rooting through branch cuttings, hence classified as a difficult-to-root (DR) species. On the other hand, D. sissoo is a multipurpose timber species of North India known for its guaranteed rooting, hence classified as an easy-to-root (ER) species. Among the commercially synthesised auxins viz. indole-3-acetic acid (IAA), indole-3-butyric acid (IBA) and 1-naphthalene acetic acid (NAA), and rooting synergists, thiamine and piperazine, 5.0 mM IAA resulted in the highest rooting percentage (12%) in the branch cuttings of the DR species. High genetic variation was observed among the accessions of the DR species on rooting ability. No significant correlation was obtained between the endogenous auxin (IAA) level and rooting ability in both DR and ER species. The results indicated that the adventitious rooting potential varies from tree to tree within a species and is significantly not dependent on their endogenous IAA level. The findings did not support the concept that endogenous auxins directly affect root formation. However, a more refined extraction procedure and assay, with advanced instrumentation, at different stages, can validate the possible role of IAA in adventitious rhizogenesis.