Streptomyces Strains Induce Resistance to Fusarium oxysporum f. sp. lycopersici Race 3 in Tomato Through Different Molecular Mechanisms

Abstract

Plant growth promoting rhizobacteria (PGPR) are potential natural alternatives to chemical fungicides in greenhouse production via inducing plant immune system against biotic stresses. In this research, 126 Streptomyces isolates were recovered from rhizosphere soils of 13 different commercial vegetable greenhouses in Iran. Streptomyces isolates were screened for in vitro Plant growth promoting (PGP) traits and ability to antagonize Fusarium oxysporum f. sp. lycopersici race 3 ( FOL ), the causal agent of Fusarium wilt of tomato (FWT). Six isolates with the highest antagonistic activity and at least three PGP traits were selected and compared with chemical fungicide Carbendazim ® in a greenhouse experiment. All bacterial treatments mitigated FWT disease symptoms like chlorosis, stunting and wilting at the same level or better than Carbendazim ® . Strains IC10 and Y28 increased shoot length and shoot fresh and dry weight compared to not inoculated control plants. Phenotypic characterization and 16S rRNA gene sequencing showed, strains IC10 and Y28 were closely related to S. enissocaesilis and S. rochei , respectively. The ability of the superior biocontrol strains to induce antioxidant enzymes activity and systemic resistance (ISR) was investigated. Increased activity of catalase (CAT) in plant treated with both strains as well as an increase in peroxidase (POX) activity in plants treated with Y28 pointed to a strain specific-induced systemic resistance (ss-ISR) in tomato against FOL . The differential induced expression of WRKY70 and ERF1 (two transcription factors involved in plant defense) and LOX and TPX by the analyzed Streptomyces strains, especially after inoculation with FOL , suggests that ss-ISR is triggered at the molecular level.

Isolation and Screening of Soil Chitinolytic Actinobacteria as the Anti-Fungal Producer of Plant Pathogens

“…The mean inhibition zone of KK-15 chitinolytic actinobacteria isolates on the ninth day after testing had a higher percentage of 46 % with an inhibition zone radius of 14 mm compared to KK-05, KK-06, KK-07, KK-08, and KK-16 isolates. The results of this study are in line with research conducted by Rashad et al (2017), which succeeded in isolating the bacterium Streptomyces griseorubens E44G from agricultural land from Saudi Arabia, which was able to inhibit the fungus Fusarium oxysforum with an inhibition zone diameter of 24 mm.…”

Identification of antagonistic Streptomyces strains isolated from Algerian Saharan soils and their plant growth promoting properties

“…Decimal dilutions (from 10 -1 to 10 -7 ) were spread on isolation medium ISP2 (International Streptomyces Project-2) amended by cycloheximide (100 µg mL -1 ), then incubated for 21 days at 28°C (Khamna et al 2010). Typical actinobacteria colonies were picked, purified, and maintained in glycerol (20% v/v) (Ser et al 2018;Abbasi et al 2019).…”

Tissue-specific synergistic bio-priming of pepper by two Streptomyces species against Phytophthora capsici

“…The phosphate solubilizing Streptomyces species might be as ISR triggered PGPRs suggested by Walters. Siderophore-producing Streptomyces strains SS14 and IT20 were positive for cellulase activity [7]. As seen from the previous study [36], growth inhibition failure of Oomycete pathogen was correlated to the inability of Streptomyces strains in producing cellulase.…”

“…It is noteworthy that these bacterial strains were screened based on hydrolytic enzyme activities and antifungal ability against some soil-borne fungal pathogens. According to our previous investigations, these strains were able to grow on nitrogen-free medium and produce siderophore [7]. Eight of these strains produced cellulase (the greatest halo zone/colony diameter ratio for cellulase activity).…”

“…as a biocontrol agent was investigated against some soil-borne fungal pathogens such as Rhizoctonia solani [6] and Fusarium oxysporum f. sp. lycopersici [7]. There is a growing interest in using PGPRs a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 capable of solubilizing inorganic phosphorus (P) [8].…”