ENDOPHYTIC BACTERIA AS BIOCONTROL AGENTS AGAINST ROOT PATHOGENS IN MARSHMALLOW

Abstract

Marshmallow (Althaea officinalis) is an important medicinal plant known for its therapeutic
properties, but it is increasingly threatened by root diseases caused by soil-borne pathogens. These
diseases lead to significant reductions in plant health, yield, and overall productivity. Traditionally,
chemical treatments have been used to manage these diseases, but their detrimental effects on the
environment and human health have prompted the search for alternative, sustainable control
methods. One promising approach is the use of endophytic bacteria, microorganisms that live
within plant tissues without causing harm. This study explores the potential of endophytic bacteria
as biocontrol agents to manage root diseases in marshmallow plants. In this research, several
endophytic bacterial strains were isolated from healthy marshmallow plants and evaluated for their
antagonistic effects against common root pathogens, including Fusarium spp. and Rhizoctonia
solani. The isolated bacteria were screened for their ability to produce antimicrobial compounds,
compete for nutrients, and inhibit pathogen growth in vitro. Among the strains tested, several
exhibited significant antagonistic activity, with some demonstrating strong inhibitory effects on
pathogen growth. To assess their efficacy under natural conditions, greenhouse experiments were
conducted, where marshmallow plants were inoculated with both pathogenic fungi and selected
endophytic bacteria. Results revealed that plants treated with the biocontrol strains had
significantly healthier root systems, with reduced disease symptoms and improved growth
parameters compared to untreated controls. Furthermore, the biocontrol bacteria induced systemic
resistance in the plants, evidenced by higher levels of defensive enzymes such as peroxidases and
phenylalanine ammonia lyase. The findings suggest that endophytic bacteria can effectively
suppress root diseases in marshmallow plants through a combination of direct antagonism and the
induction of plant defense mechanisms. These results provide a promising alternative to chemical
pesticides, supporting the use of endophytic bacteria as part of integrated disease management
strategies for marshmallow cultivation. This study contributes to the growing body of knowledge
on plant-associated microbes and their potential in sustainable agriculture, highlighting the
benefits of using natural, eco-friendly solutions to protect valuable medicinal crops.