Effect of pre-harvest Potassium Treatment on Stem-end Rot Disease Development of Mango (Mangifera indica L.)cv. TomEJC during Fruit Ripening

Abstract

Mango (Mangifera indica L.) cv. TomEJC has utmost potential in export market due to its unique quality. Post-harvest disease of mango such as stem-end rot can cause considerable losses of fruits and could therefore be considered as a great threat to local and export market. This disease is controlled by application of fungicides from the time of flowering in cultivations where this disease is severe. However, the use of fungicides could lead to hazardous effects such as oncogenic risks on the consumers. Therefore, search for alternative measures for the management of stem-end rot disease is essential. In this study, an attempt was made to find out the effect of preharvest application of KCl on controlling stem-end rot disease development of ripe fruit. KCl at concentrations of 1 gl-1, 2 gl-1 and 4 gl-1 were sprayed on fruit when fruits were immature. All fruits were bagged with paper bags and fruits were harvested at the correct maturity stage. Then all fruits were inoculated with Botryodiplodia theobromae mycelial plug and allowed for natural ripening. A significant difference was observed in fruit length, fruit width and fruit volume in KCl- treated fruits when compared to controls. Highest fruit volume was observed in 1 gl-1 KCl- treated fruits and the lowest amount of total soluble solids was observed in 2 gl-1 KCl- treated fruits. An increase in lightness and yellowness of peel color in KCl- treated fruits when compared to control II (non-inoculated, non-treated) was evident, indicated by increasing L*, b* and chroma values. However, no significant difference in hue values of peel color was observed among treatments. Flesh color showed a different response to treatments and no difference in chroma value was observed among treatments. The highest L* value and hue value was observed in 2 gl-1 KCl- treated fruits. Incidence and severity of stem-end rot was significantly decreased by 2 gl-1 KCl treatment without drastically affecting the physico-chemical properties of fruits. Vast research has shown that potassium and chloride fertility have been effective in reducing crop injury from diseases. Different mechanisms such as nutritional effects, changes of the Sabaragamuwa University Journal Volume 14 Number 2; December 2015, pp 119-132 ISSN 1391-3166; eISSN 2386-2041 DOI : http://dx.doi.org/10.4038/suslj.v14i2.7700 120 host-pathogen environment and production of disease inhibitory compounds could be some possible ways of action of both K and Cl in modifying disease resistance or susceptibility. Since 2 gl-1 KCl was able to suppress stem-end rot disease development in inoculated fruits, this concentration can be recommended as a field application to control this disease in mango variety tested after repeating the same experiment at different locations.