Molecular and Electron Microscope Evidence for an Association of Phytoplasma with Sesame Phyllody in Egypt

Document Type : Original Article

Authors

1 Plant Pathol. Dept., Fac. Agric., Cairo Univ., Egypt

2 Plant Pathol. Res. Inst., A.R.C., Giza, Egypt

3 Plant Production. Dept., Fac. Agric., Ibb Univ., Yemen.

Abstract

Phyllody is a serious disease of sesame worldwide. In the present study investigations were carried out on the symptomatology, etiology, and transmission of this disease. Floral virescence, phyllody, witches-broom and proliferation are the most observed symptoms on naturally infected plants. In some cases, these symptoms are accompanied by yellowing, cracking of seed capsules, germination of seeds in capsules, and formation of dark exudates on the foliage.
Shoot apex fasciation has also been occasionally observed. The plant samples were collected from several fields located in Abou-Rowash County, Giza Governorate. The phytoplasma under investigation was transmitted from diseased plants to healthy ones by grafting with percentage of 100% and by dodder (Cuscuta compestris) 20% but not by sap or seeds. Pleomorphic bodies typical to phytoplasma structures were observed in phloem sieve elements in ultra-thin sections of
infected plants inspected using transmission electron microscope (TEM). Amplification of a fragment (1250-bp) of 16S rDNA characteristic to phytoplasma using the primer pairs R16F2n/ R16R2 confirmed that sesame was infected by a phytoplasma, Using the primer pair SR1/ SR2 a fragment of 325bp was amplified through nested PCR indicating that the phytoplasma under investigation belongs to witches broom group. 

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