Physiological responses of nine mango cultivars seedlings inoculated with Ceratocystis fimbriata

Mango (Mangifera indica L.) is facing increased biotic and abiotic stresses that lead to reduced number of trees and total fruit production in many producing countries, including Oman. Mango sudden wilt (MSW), caused by Ceratocystis fimbriata (syn. C. manginecans), is a major fungal disease that spread over the past decades causing loss of up to 60% of mango trees in Oman. The aim of this study was to determine the physiological responses of nine mango cultivars commercially grown in Oman that included 'Zafaran', 'Batikah', 'Disheheri', 'Ishbiah', 'Baramasi', 'Banishan', 'Piri', 'Rose' and 'Langra' inoculated by C. fimbriata. Measured parameters included (net carbon assimilation rate (A), transpiration rate (E), stomatal conductance to water vapor (gs), water use efficiency (WUE), sub-stomatal cavity (internal) CO2 concentration (Ci) and chlorophyll content (SPAD) and florescence (Fv/Fm). Physiological responses of the inoculated and non-inoculated cultivars varied significantly among cultivars and their interaction with the inoculum. This indicated that under controlled (glasshouse) and non-stressful conditions, physiological processes of different cultivars did not equally respond to fungal infection as compared to non-inoculated seedlings. However, correlation among various conductance (gs) was considered as the independent variable. All cultivars showed a strong correlation between stomatal conductance (gs) and transpiration (E) (r2 ∼0.99) but this value varied with the gs relationship with assimilation (A). The correlation between A and gs was highest for 'Zafaran', 'Batikah', 'Disheheri' and 'Baramasi', while the other cultivars showed moderate to low correlation like 'Banishan', 'Piri', 'Rose' and 'Langra'. Nonetheless, the correlation between stomatal conductance (gs) and other physiological parameters affected by stomatal aperture (primarily A and E) indicated the sensitivity of various cultivars to infection by C. fimbriata. However, inference about cultivar sensitivity to the disease can be obtained from the relationship of assimilation and transpiration with stomatal conductance.