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Phytopathogenic Mollicutes
Year : 2015, Volume : 5, Issue : 2
First page : ( 100) Last page : ( 106)
Print ISSN : 2249-4669. Online ISSN : 2249-4677.
Article DOI : 10.5958/2249-4677.2015.00068.7

Molecular characterization of 16SrII phytoplasma group and associated down-regulation of ABA and IAA in Opuntia caracasana

Dewir Yaser Hassan1,2,*, El-Mahrouk Mohamed El-Sayed2, Omar Ayman Faisal3

1Plant Production Department, College of Food and Agriculture Science, King Saud University, Riyadh-11451, Saudi Arabia

2Horticulture Department, Faculty of Agriculture, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt

3Agricultural Botany Department, Plant Pathology and Biotechnology Laboratory, Faculty of Agriculture, Kafrelsheikh University, 33516, Kafrelsheikh, Egypt

*Corresponding author e-mail: Yaser Hassan Dewir, ydewir@hotmail.com

Online published on 13 January, 2016.

Abstract

A phytoplasma was detected in Opuntia cacti plants (Opuntia caracasana) with symptoms including stunted growth and dense clusters of highly proliferating cladodes. The symptomatic samples were tested with universal phytoplasma primers in direct and nested assays. The 880 kb sequence obtained in the 16S rRNA gene was compared to those of 28 phytoplasmas belonging to different 16Sr groups and subgroups. The sequence analyses indicated that the phytoplasma, which given name Opuntia caracasana proliferation phytoplasma (OcPP), is clustering with members of 16SrII phytplasma group. Analyzing different part of the infected plants, the phytohormone level of indole-3-acetic acid and abscisic acid (ABA) was significantly decreased in phytoplasma infected cladode as compared with symptomless cladode. This indicates thatABA was not associated in stress defense mechanism in infected tissues, but it was rather involved in the release of axillary buds representing an overgrowth effect due to loss of apical dominance. The cladode proliferation symptoms in O. caracasana induced by phytoplasma presence is therefore effective to produce young, green and meristematic vegetative tissues to attract their insect vectors.

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Keywords

Abscisic acid, apical dominance, cactus, fasciation, phytoplasma.

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