Survival and Spread of Agrobacterium tumefaciens in Soil Under Different Organic Matter and pH Conditions

Abstract

Agrobacterium tumefaciens is a soil-borne bacterial pathogen responsible for crown gall disease in a wide range of horticultural and woody crops, leading to significant economic losses. The present study investigated the survival and spread of A. tumefaciens in soil under varying organic matter content and pH conditions. Controlled soil microcosm experiments were conducted to evaluate bacterial persistence, population dynamics, and dissemination potential under different physicochemical environments. Bacterial survival was quantified periodically using selective media, while spatial spread was assessed through soil sampling at defined distances from the inoculation point. The results demonstrated that both soil pH and organic matter content significantly influenced the survival and distribution of A. tumefaciens. Higher organic matter levels supported prolonged bacterial survival by providing enhanced nutrient availability and favorable microhabitats, while low organic matter conditions reduced persistence over time. Soil pH played a critical role in bacterial activity, with near-neutral to slightly alkaline conditions favoring higher survival and spread compared to acidic soils, which suppressed bacterial growth and longevity. The combined effect of high organic matter and optimal pH conditions resulted in increased bacterial population density and wider spatial distribution in soil profiles. Conversely, unfavorable pH and low organic content restricted bacterial survival and limited its spread. These findings highlight the importance of soil physicochemical properties in regulating the epidemiology of crown gall disease. The study provides valuable insights into environmental factors affecting A. tumefaciens persistence and supports the development of soil management strategies aimed at reducing pathogen survival and disease incidence in agricultural systems.