Studies on endophytic microorganisms isolated from some plants and their biocontrol potential against some fungal pathogens of wheat plant

Abstract

All kinds of microorganisms like fungi, bacteria and actinomycetes can survive inside plants as endophytes and protect their host from adverse conditions and infectious agents by several mechanisms. With the aim of studying the biodiversity and antagonistic potential of endophytes against some wheat pathogenic fungi to control some wheat diseases and improve its growth, endophytes were isolated from 15 healthy different plants (medicinal plants ''basil, green onion, green pepper, mint, roselle, tagetes, watercress and white radish'' and common plants ''corn, cotton, jew's mallow, marrow, okra, wheat and tomato'') collected from El-Qalyubia ''El-Qanatir El-Khairiya'' and El-Fayoum governorates. All the studied plants found to be resided with endophytic fungi in their different organs tissues but endophytic bacteria and endophytic actinomycetes reported only in 6 and 2 of the studied plants, respectively. Sixty-two endophytic fungal species belonging to 18 genera and 3 morphospecies of mycelia sterilia group were identified according to morphological methods, while 7 endophytic bacterial species belonging to 6 genera and 2 endophytic actinomycetes species belonging to 2 genera were identified by molecular methods. Out of all the identified endophytic fungi, Aspergillus, Fusarium, Penicillium, Alternaria, Acremonium and mycelia sterilia were with a predominance during the isolation and Aspergillus had the highest relative frequency in all the studied plants but not found in green pepper. Nine wheat pathogenic fungi were obtained from naturally infected wheat plants grown in El-Qalyubia (El-Qanatir El-Khairiya) governorates and were identified as Alternaria alternata, Alternaria cichorii, Alternaria dianthi, Alternaria sonchi, Aspergillus petrakii, Curvularia penniseti, Fusarium oxysporum, Fusarium semitectum and Fusarium solani. Screening of all the identified endophytic species for in vitro antagonistic activity against nine wheat pathogenic fungi was carried out using dual culture methods. From this experiment results, seven endophytic antagonists were selected with respect to their potent activity against 4 of wheat pathogenic fungi. The inhibition percentages were as the following: Aspergillus melleus gave 70 % with Alternaria dianthi, Penicillium chrysogenum and dark septate sterile mycelium isolate gave 69.57 % and 56.52 %, respectively with Aspergillus petrakii; while, Aspergillus unguis and Cladosporium cladosporioides gave 74.29 % and 60 %, respectively with Fusarium oxysporum. Fusarium subglutinans and Streptomyces rochei showed percentages of 72.97 % and 51.35 %, respectively with Fusarium semitectium. The identification of the six selected endophytic antagonistic fungi were confirmed by the molecular methods based on their ITS-rDNA sequences. Enzymatic index of six tested enzymes by the selected seven species revealed that only cellulase was produced by all the selected species which associated with the colonization processes. The role of the selected endophytic antagonists to control root rot and leaves diseases development and to stimulate growth of wheat plants under greenhouse conditions was studied. Root rot disease caused by Aspergillus petrakii, Fusarium oxysporum and Fusarium semitectium were reduced by seeds coating method by different selected endophytes. The lowest root rot severity percentage was observed with dark septate sterile mycelium isolate (15.56 %), Cladosporium cladosporioides (6.67 %) and Fusarium subglutinans & Streptomyces rochei (20 %) in soil infested with Aspergillus petrakii, Fusarium oxysporum and Fusarium semitectium, respectively.