Ultrastructural changes in tomato plant induced by phytoplasma infection and attempts for its elimination using tissue culture techniques
Ultrastructural changes in tomato plant induced by phytoplasma infection and attempts for its elimination using tissue culture techniques
Eman A. Ahmed1, Osama Y. shalaby2, Emad F. Dwidar2, Samah A. Mokbel1 and Ahmed K. El-Attar1
ABSTRACT
Light microscopy was used to compare the anatomical characteristics of stem, flower petiole and leaves of infected tomato with phytoplasma with healthy ones in order to reveal anatomical modifications caused by the infection process. The results obtained showed that infection of tomato plants with phytoplasma led to an increase in stem diameter by 10.23% as well as greatly increase in measurements of the other stem components while the diameter of pith was decreased by 38.46%. This infection was led to an increase in the diameter of petiole by 109.2% and also the other components of flower petiole. At the same time, tomato leaves were greatly affected as a result of the infection with phytoplasma. The thickness of leaf blade was remarkably increased by 200% as well as thickness of either palisade or spongy tissues by 212.5% or 275%, and significant malformation in leaflet midvein was observed which consequently led to increase in both length and width of midvein by 15.19% and 5%. Electron microscopy was used to recognize the internal changes in cell organelles due to phytoplasma infection. The results obtained showed that, general disorganization of phloem tissue and thickness of cell wall resulted from high concentration of phytoplasma units; necrosis starts in companion cells; severe damage in chloroplasts with abnormal membrane and thylakoid system was absent. The xylem vesicles were characterized by deforming the secondary walls. Three methods were done towards the production of phytoplasma-free tomato plantlets through tissue culture using antibiotic compound (tetracycline hydrochloride in three concentrations 25mgL-1, 50mgL-1 and 75mgL-1), irradiation by three doses (3, 5 and 10 Gy) of gamma ray and natural compound (1ml of garlic juice). All treatments proven to be a very useful effect against phytoplasma, except concentration 25 mgL-1 of tetracycline hydrochloride. The findings of this study have proven treatment at lower dose of gamma rays (3 Gy) of efficient methods on growth promotion.
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