Nutrient imbalance indices are closely related with susceptibility of pomegranate to bacterial blight disease

- High concentration of N, K and S in leaves make plant susceptible to blight disease.
- Calcium, Cu, Fe, Mn and Mg are important for imparting resistance to blight disease.
- Nutrient imbalance indices closely relate with blight disease severity in pomegranate.
- Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis(CND) approaches are suitable to diagnose nutrient imbalances in relation to disease severity.

Bacterial blight disease caused by Xanthomonas axonopodis pv. punicae is a major threat to pomegranate cultivation causing heavy losses. An attempt was made to establish nutrient sufficiency range for imparting moderate disease resistance and diagnosing nutrient imbalance causing disease development. Two approaches i.e. Diagnosis and Recommendation Integrated System (DRIS) and Compositional Nutrient Diagnosis (CND) were considered to evaluate the nutrient balance status in pomegranate. Nutritional survey revealed that concentration of Ca, Mg, Mn and Cu in leaves were significantly high in moderately resistant germplasms, while N, K and S concentration were observed to be high in susceptible ones. Deficiency of Ca was observed as the cause of disease in 80% of the susceptible germplasms studied. The next important nutrient deficiencies in the susceptible germplasm were Cu (77.14%), Fe (77.14%), Mn (68.57%) and Mg (65.71%). Nutrient imbalance indices of susceptible germplasm diagnosed through DRIS and CND had linear relationship (R2 = 0.93 and R2 = 0.82) with bacterial blight disease severity however, DRIS approach is superior for diagnosis of nutrient imbalances. As per DRIS analysis, leaf nutrient status of N 1.56-2.05%, P 0.11-0.28%, K 0.83-1.20%, Ca 1.60-2.16%, Mg 0.38-0.82%, S 0.09-0.16% and micronutrients viz. Fe 132.50-187.00 mg kg−1, Mn 31.60-58.40 mg kg−1, Zn 13.20-27.40 mg kg−1 and Cu 26.00-47.80 mg kg−1 could result in imparting moderate resistance to bacterial blight disease. The nutrient norms were validated and found to have linear relation between nutrient imbalance indices and bacterial blight disease severity.