Rhizoctonia solani affecting micropropagated Garnem ( Prunus amygdalus x Prunus persica ) rootstock - characterization a
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ORIGINAL ARTICLE
Rhizoctonia solani affecting micropropagated Garnem (Prunus amygdalus x Prunus persica) rootstock - characterization and biocontrol with Rhizobia Noura Jemai 1 & Samia Gargouri 2 & Imen Hemissi 2 & Kaouther Ben Mahmoud 2 & Med Fakhri Ksouri 1 & Ahmed Jemmali 2 Received: 19 March 2020 / Accepted: 20 November 2020 # Società Italiana di Patologia Vegetale (S.I.Pa.V.) 2020
Abstract The objective of this study was to (1) identify the causal agent of damping-off observed on Garnem (Prunus amygdalus x Prunus persica) rootstock micropropagated plants during acclimatization phase; and (2) test the potential antagonism of Rhizobia against this dangerous fungus. In addition to the previously published results (KY964496, KY964499), further isolates have been collected and characterized. Morphological traits of these isolates and sequencing of their rDNA ITS gene showed that they also belong to Rhizoctonia solani anastomosis group 1-IC (AG-1-IC). Two supplementary sequences were deposited in GenBank as KY964497 and KY964498. Pathogenicity testing confirmed the direct implication of this pathogen in wilting, crown and root rot symptoms that may lead to plant damping-off. The possibility to control R. solani by using Rhizobia as a potential antagonist has been further investigated. In vitro dual culture of R. solani and 40 Rhizobium strains resulted in different mycelium inhibition (I) rates. The significantly highest I rates were observed with strains from pea (PP6, PPOUEDP292, PP29), chickpea (Pch Kass) and bean (HaD4002). In vivo test showed that HaD4002 (T4) conferred the highest survival rate (21%). Keywords Garnem rootstock . Micropropagation . Acclimatization . Rhizoctonia solani . Rhizobium . Antagonism
Introduction Tissue culture conditions promote growth and multiplication of shoots at the heterotrophic mode of nutrition. They often result in the formation of plants with abnormal leaf morphology and anatomy characterized by poor photosynthetic activity and defective mechanism of transpiration that make them vulnerable to dehydration during transfer to acclimatization (Ziv 1986; MarÃn et al. 1988; Preece and Sutter 1991; Desjardins 1995). Thus, their survival is especially conditioned by high relative humidity during the first days of acclimatization. High humidity is favorable to fungi proliferation and their involvement in plant mortality has been suspected
* Kaouther Ben Mahmoud [email protected] 1
National Agronomic Institute of Tunisia, University of Carthage, Tunis, Tunisia
2
National Institute of Agronomic Research of Tunisia, University of Carthage, 1004, Elmenzah, Tunis, Tunisia
(Ghorbel et al. 1994), but paradoxically not much data has been reported on the identity of the causal agents, especially in the case of micropropagated rootstocks. More recently, our team succeeded to isolate four fungi species from stone fruit rootstock plants during acclimatization phase. Among these species (Rhizoctonia solani, Fusarium oxysporum, Botrytis cinerea and Pythium sp.), R. solani was th
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