A Case Study on the macronutrient Differences Between Healthy and Insidious Fruit Rot–Infected Harumanis Mango Leaves in West Malaysia

Abstract

Insidious fruit rot (IFR) is a major problem in mango cultivation. It can reduce fruit quality without any visible symptoms except when the fruit is cut in half. This problem is an increasing concern among Harumanis growers, one of the premium mango varieties in Malaysia, due to its high cost and maintenance requirements. A previous study found a highly significant difference in soil nutrient content between Harumanis orchards with and without IFR. However, no information on plant nutrient content was provided. The objectives of this study were to measure and compare the macronutrient contents between mango trees with and without IFR incidence and to evaluate the nutrient relationships at each study site. A total of 22 leaf samples were collected from 10 and 12 mango trees with and without IFR incidence, respectively. Approximately 20 leaves were collected from each mango tree, specifically from the third or fourth leaf of the current flush, and processed before analysis. Total nitrogen (N) was determined by combustion, while phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) were determined by dry ashing. The N/Ca and K/Ca ratios were manually calculated. The results demonstrated significantly higher N, P, K, Mg, N/Ca ratio, and K/Ca ratio in trees with IFR incidence at 0.57%, 0.05%, 0.15%, 0.27%, 1.50, and 0.37, respectively, while Ca was significantly lower at 2.05%. A highly negative correlation was observed between Ca and the N/Ca ratio. These findings indicate that nutrient imbalance in plants was associated with this problem.