Abstract
This study aimed to evaluate the efficiency of Enterobacter cloacae PS14 and Trichoderma asperellum T34 in the control of potato wilt, caused by Ralstonia solanacearum (Smith), under greenhouse and field conditions. In vitro, the endophyte E. cloacae PS14 caused the highest reduction of the pathogen growth among 7 screened bacteria. It produced an inhibition zone as 16.9 mm compared to a specific antibiotic (20.0 mm). E. cloacae PS14 was selected as an effective antagonistic bacterium to be compared to T. asperellum strain T34 for reduction of the disease as well as increasing the crop yield of potato plants. Both E. cloacae and T. asperellum reduced the disease severity up to 10.7–26.5%, respectively, under greenhouse and up to 26.6–36.6%, respectively, under field conditions. The results approved that both E. cloacae and T. asperellum increased the yield of the crop by 20.44–40.96%, respectively. Their mode of action was indicated by suppression of the pathogen as well as induction of plant systemic resistance. The induction of systemic resistance was confirmed by increasing the total phenol and salicylic acid contents as well as increasing the activities of peroxidase, lipoxygenase, and polyphenol oxidase in potato plants than the healthy or only infected plants. Production of siderophore, indole-3-acetic acid (0.577–0.884 μM), hydrogen cyanide (2.34–3.61 μg/ml), and salicylic acid (0.436–1.488 μg/ml) was confirmed by E. cloacae PS14 and T. asperellum T34, respectively, in vitro. The study recommends the new strain E. cloacae PS14, as new endophytic effective bacteria, in the control of R. solanacearum causing the potato wilt disease.
Highlights
Bacterial wilt disease caused by Ralstonia solanacearum (Smith) is one of the serious plant diseases worldwide (Peeters et al 2013)
The results indicated that the highest inhibitory effect against the PHYRS3 was attributed to the bacterial strain no. 7, which caused production of inhibition zone as 16.9 mm compared with 20.0 mm because of specific antibiotic streptomycin
The potent antagonistic bacterium was identified by 16S rRNA gene and their sequences were compared to data available in the GenBank using BLAST search
Summary
Bacterial wilt disease caused by Ralstonia solanacearum (Smith) is one of the serious plant diseases worldwide (Peeters et al 2013). In Egypt, as well as in many countries, it has become a severe problem for the production of potato plant (Abo-Elyousr and Bagy 2018). Traditional control methods such as short rotation, resistant cultivars, and soil fumigation have been suggested. Such methods are not always enough effective since R. solanacearum can remain with the infested plant debris in the soil for a long time. The research focuses on some alternative methods to control the disease that are characterized by being environmentally safe, long lasting and effectiveness (AboElyousr and Bagy 2018).
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