Study on morphology and anatomy of witches'broom infected longan (Dimocarpus longan Lour. cv. Eedor)
1997
Pracha Suppawattanabodee
Studies on witches'broom disease of Longan cv. Eedor showed significantly distinct symtoms of offshoot like witches'broom with short internodes. The leaves are curly, small in size, yellowish brown colour and fragile. Midribs and veins were unusually enlarged. Inflorescences had numerous hermaphrodite flowers. The quantity of both female and male flowers was less than normal. The number of fruits per inflorescence decreased. Anatomical study revealed that the epidermis of primary growth stems, mature leaves, sepals and petals were increasingly changed into hair cells. Phloem of secondary growth roots and stems, mature leaves, sepals, petals, filaments and styles had accumulated significantly in some substances. Vessels of leaves from infected plants were significantly smaller than those from normal plants. In young leaves, there are two large vascular strands while a normal plant has only one strand. The mature leaves have no cutin covering the adaxial epidermis. Stomata cannot be found either on the adaxial nor the abaxial side. The ultrastructure of infected secondary growth stem, midrib and petiolule exhibited some mycoplasma-like organisms with eliptic and global shape, 300-500 nanometer in size, in sieve tube and companion cells.
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