Evaluation of Postharvest Stem-End Rot on Coconut Fruits

Abstract

The stem-end rot on coconut fruits is the main postharvest crop disease, causing heavy losses especially when the product is sold fresh. The efficient and practical control of this plant disease has been difficult to date, such as the damage evaluation, which has been done exclusively by the incidence of the disease. However, the incidence parameter alone does not provide a satisfactory understanding of the lesion area and the intensity it can achieve during the storage period, and about the environmental conditions in which the fruits are subjected to the aggressiveness of Lasiodiplodiatheobromae, when it is confirmed as the causal agent of the disease, and the control measures applied. Thus, in this study we propose to evaluate the basal rot development in coconut fruits during postharvest and to prepare and validate a diagrammatic scale to enable the estimation of disease severity. Fruits were inoculated and the external and internal symptoms of disease developments were photographed to measure the damaged area, which were grouped into eight disease levels. Sixty images were assessed by 30 evaluators for three consecutive times at intervals of 7 days and data were subjected to linear regression analysis. Hence, it was possible to create and validate a diagrammatic scale to evaluate the disease severity on coconut fruits with an accurate, precise and reproducible manner. Furthermore, the proposed scale allowed us to distinguish the aggressiveness of different isolates of the fungus through the symptoms of internal fruit rot.