Abstract

Little leaf disease was observed in some nurseries and plantations of Eucalytus tereticornis and E. grandis in Kerala. Attempts to transmit the disease to eucalyptus seedlings through grafts and dodder were not successful. Anatomical studies showed excessive formation of phloem tissues and phloem necrosis in diseased tissue. Dienes'stain gave positive reaction with distinct blue areas under bright field. Aniline blue, a callose binding fluorochrome, showed bright yellow green fluorescent spots in the phloem tissue of little leaf diseased eucalyptus. However, Hoechst 33258, a DNA binding fluorochrome gave negative reaction. TEM studies revealed the presence of pleomorphic MLO in the sieve elements in low concentration. Infusion of aqueous solution of tetracycline-HCI into diseased trees gave temporary remission of disease symptoms. The light macroscopic and TEM studies and remission of disease symptom by tetracycline-HCI infusion confirm the association of MLO with the