DEVELOPING A RHIZOSPHERE BIOMARKER PANEL TO BREAK THE NITROGEN-SHEATH BLIGHT LOOP IN INTENSIVELY IRRIGATED PADDY

Abstract

The rhizosphere is the narrow but biologically active zone of soil influenced by living roots. It is not simply a reservoir of nutrients; rather, it functions as a dynamic biochemical interface where roots release sugars, amino acids, organic acids, phenolics, enzymes and other compounds that regulate microbial communities and nutrient transformations. The development of a reliable biomarker panel requires substantial validation across rice growing environments. The experiment was designed to determine whether a rhizosphere biomarker panel can identify and predict the development of sheath blight under different nitrogen and irrigation regimes and, subsequently, be used to optimize nitrogen management and reduce disease severity without compromising rice yield. The experimental framework demonstrated that the nitrogen–sheath blight relationship in intensively irrigated paddy should be interpreted as a combined soil, rhizosphere, plant and pathogen phenomenon rather than as an isolated disease problem. The biomarker panel provided a multidimensional approach for assessing nitrogen availability, biological nitrogen cycling, pathogen pressure, beneficial microbial activity and the disease suppressive capacity of the rhizosphere. This approach is particularly relevant to irrigated rice because nitrogen use efficiency is generally low, with the biomarker document indicating that only about 30–40% of applied nitrogen is typically recovered by the crop, while the remainder may be lost through nitrification–denitrification and volatilization. A rhizosphere biomarker panel offers such an approach by providing measurable biological and biochemical indicators of nitrogen availability, microbial activity, plant nutritional status, pathogen pressure and disease-suppressive capacity before visible symptoms become severe. Biomarker monitoring can therefore help distinguish beneficial biological activation from uncontrolled nutrient release. An important advantage of the biomarker approach is its potential for precision nutrient and disease management.