Samah Mokbel:Effectiveness of radiation processing in elimination of phytoplasma from in vitro plantlets

Effect of Gamma Irradiation on Production of Phytoplasma-Free Hibiscus Plantlets

Samah A. Mokbel

Department of Virus and Phytoplasma Research, Plant Pathology Research Institute, Agricultural Research Center., Egypt. Dr.SamahMokbel@gmail.com

ABSTRACT:

Controlling phytoplasma-causing disease through combination of tissue culture technique and radiation treatment represented a short method for high level management. To investigate the effect of gamma rays to produce healthy plantlets, the hibiscus witches' broom phytoplasma was transmitted by grafting into healthy hibiscus plants, the in vitro-infected hibiscus explants were exposed to gamma radiation at different doses - 5 gray  (Gy), 10Gy, 15Gy, 20Gy and 25 Gy- emitted from cobalt 60 (⁶⁰Co) for 30 minute. All applied doses resulted in phytoplasma-free hibiscus plantlets with different survival activity. The presence of phytoplasma 16Sr DNA was examined using PCR detection before and after treatments. The different treatments of radiation resulted in different survival rates and phytotoxic effects including leaf yellowing and lack of growth. The 5Gy dose was proved to be best effective dose for controlling the phytoplasma without affecting the in vitro growth and survival rate, while the higher doses leaded to strongly reducing the survived hibiscus explants with increasing the inability to re-shoot.

Keywords: Hibiscus, phytoplasma, gamma irradiation, in vitro, PCR, graft transmission, tissue culture.

How to cite this article:

Mokbel, A.S. and El-Attar, A.K.  (2014). Effect of Gamma Irradiation on Production of Phytoplasma-Free Hibiscus Plantlets. Egyptian J. of Virology, 11(2): 35-45.

Samah Mokbel:First Record of a Witches'-Broom Phytoplasma Infecting Tomato in Egypt

Occurrence, Etiology and Molecular Characterization of phytoplasma diseases on Solanum lycopersicum crop in Egypt

Samah A. Mokbel

Department of Virus and Phytoplasma Research, Plant Pathology Research Institute, Agricultural Research Center., Egypt. Dr.SamahMokbel@gmail.com

ABSTRACT: Surveys were carried over the course of the 2012 and 2013 in different areas of tomato-growing fields in Egypt (Giza, Ismailia, Bani-Sweif, Fayoum and Qena) in order to determine the occurrence and distribution of phytoplasma associated with diseased tomato plants (Solanum lycopersycum L.), and to identify and classify the phytoplasma involved. A detection survey of infected tomato plants, which showed symptoms of big bud, witches'-broom and phyllody, in all regions of the screened governorates, reacted positively when assayed by nested polymerase chain reactions (PCR) using universal phytoplasma-specific primer pair P1/P7 and R16F2n/R16R2. Similar assays were used to detect phytoplasma interactions with experimentally host plant. Dienes’ stain was also used for detection of natural infection of phytoplasma. The phloem of infected tissues showed scattered area stained bright blue. Different techniques for transmission of phytoplasma to healthy tomatoes and periwinkles in an insect-proof greenhouse were tested, including mechanical inoculation, wedge grafting, parasitic plant dodder (Cuscuta campestris), insects in the family Cicadellidae (leafhopper, Empoasca decipiens) and in germinated seeds within the fruit, suggesting mechanical inoculation and seed-transmissible were not feasible while the positive results were obtained by the other three techniques for host plants with numerous symptoms obtained later. Application of transmission electron microscopy (TEM) technique for detection of experimentally inoculated samples, revealed phytoplasma in the phloem of most of tested samples. Phytoplasma were observed as rounded bodies, ranging in size from 200 to 600 nm. The molecular characterization was performed for three different samples representing the different symptoms of phytoplasma through cloning and direct sequencing. The DNA sequencing, phylogenetic analysis and the multiple alignments for the sequences of the Egyptian clones with each other and with the other sequences of phytoplasma strains on GenBank suggested that we may have three different phytoplasma isolates (witches’ broom, phyllody and big bud) infecting tomato plants in Egypt and listed under accession numbers KT225548, KT230865 and KT225545, respectively.

Key words: Phytoplasma, PCR, Sequencing, Dienes’stain, TEM, graft, dodder and insect transmission.

How to cite this article:

Ahmed, A.E., Shalaby, O.Y., Dwidar, E.F., Mokbel, A.S. and El-Attar, A.K. (2014). Occurrence, Etiology and Molecular Characterization of phytoplasma diseases on Solanum lycopersicum crop in Egypt. Egyptian J. of Virology, 11(2): 244-261.