Potential of selected tobacco endophytic fungi against Sclerotinia sclerotiorum, the causal agent of tobacco collar rot disease

Mohammad Reza Safari Motlagh, Samar Alavi Rad, Marwa T. Mohesien, Monga I. Mossa, Alireza Seidavi, Soumya Ghosh, Donia H. Sheir, Kavya Dashora & Ahmed M. Abdel-Azeem

Sydowia 75: 221-232

Published online on February 7th, 2023

Tobacco collar rot (TCR) disease is caused by the fungus Sclerotinia sclerotiorum, which is able to infect over 300 different types of plants, including common weeds. S. sclerotiorum is one of the most important pathogens of tobacco reported from all tobacco cultivating regions of the world. Controlling this disease by chemical and cultural methods seems highly difficult and using resistant cultivars has not been sufficient. Endophytic taxa hosted by Nicotiana tabacum were evaluated against pathogenic S. sclerotiorum isolates in vitro and in greenhouse. Based on phenotypic identification, five endophytic taxa were identified as Trichoderma harzianum, T. virens, Curvularia australiensis, Aureobasidium pullulans and Geotrichum candidum respectively. These isolates exhibiting inhibitory effects against S. sclerotiorum were cultivated in vitro on PDA plates and the percent of inhibition was calculated. T. harzianum came first by showing the highest percentage of inhibition against S. sclerotiorum followed by T. virens, C. australiensis, A. pullulans and G. candidum. In growth chamber experiments, all taxa were able to reduce TCR disease rating. C. australiensis was deemed the most effective for reducing disease rating up to 2.6 (23.75 %) followed by A. pullulans, G. candidum, T. virens and T. harzianum respectively. In greenhouse studies, T. virens increased the height, fresh and dry weight of the plant shoots in the presence of TCR which reflects the stimulating properties of T. virens in the growth of shoot organs of tobacco plants. Microscopic examination showed that all endophytic taxa have a positive tropism and anastomosis toward S. sclerotiorum. Overall, the antagonistic endophytic fungus C. australiensis is recommended as an effective biocontrol agent for S. sclerotiorum wilt management in tobacco plants. We recommend further research on this taxon in order to develop an industrial eco-green biostimulant against TCR disease.

Keywords: Bioprospecting, biotechnological potential, fungi, Nicotiana tabacum, Sclerotinia spp

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