Biological Control Using Streptomyces sp. Kp109810 and Different Genotypes of Pepper (Capsicum annuum L.) on Root Rot Diseases

This study was carried out through two experiments in laboratory and greenhouse at the Agricultural botany department and Biological Control Center, Faculty of Agriculture, Suez Canal University. The isolated fungi, which caused root-rot of pepper plants, were identified as Rhizoctonia solani (R) and Macrophomina phaseolina (Mc) from infected pepper samples. The pathogenic fungi showed deformation, shrinkage, and collapse when observed by scanning electron microscopy (SEM) and Streptomyces sp < em>. KP109810 (S) showed the presence of PKSII and NRPS genes by polymerase chain reaction (PCR) amplification. The extract was analyzed for chemical profiling by Thin-layer chromatography (TLC), and a unique pattern of secondary metabolites was observed. The strain was positive production for protease and chitinase while it was negative for cellulase. Antagonistic Streptomyces sp < em>. KP109810 was subjected to a comprehensive in vitro screening for various plant growth promoting (PGP) traits. Streptomyces sp < em>. KP109810 (S) showed strong antagonism against test fungi (R and Mc) which showed 84.6% and 78.7% maximum inhibition respectively, in dual culture plat assays as a result of diffusible compounds produced by (S), the inhibitory effect of volatile compounds was recorded up to 78.2% against (R) and 66.3% against (Mc) and multiple plant growth promoting attributes such as Indole Acetic Acid (IAA), phosphate solubilization activity, siderophore, NH₃ and HCN production. Five genotypes of pepper planted in greenhouse and treated with six treatments: control, (S), (R), (Mc), (S+R) and (S+Mc). Through mean performance analysis, results showed Saidah and SUPER MARD genotypes have tolerant ability to root rot diseases over rest studied genotypes, although there is a significant decrease in growth and yield under (R) and (Mc) treatments for all genotypes. Streptomyces sp treatment acts as biocontrol to these fungi by reducing the percentages of damping-off and root rot severity. There is a positive significant correlation between fruits weight/plant and all studied traits except root length under control and biotic stress conditions. Fruits weight / plant, fresh weight of root and shoot traits used as a good indicator to select root rot resistance genotypes of pepper as they have high values of heritability (h2) and high values of genetic advance as a percent of mean (GAM).