INFECTION AND QUIESCENCE OF MANGO STEM-END ROT PATHOGENS
Sequential sampling of stem, inflorescence and peduncle tissue between flowering and harvest revealed that SER fungi occurred endophytically in mature stem tissue, and colonised the fruit peduncle tissue by endophytic outgrowth of hyphae within the inflorescence, several weeks prior to harvest. Hyphae of the fungi remained quiescent in the peduncle until after harvest, and SER developed during ripening. Infection of mangoes by L. theobromae also occured following soil contamination of the cut end of the peduncle during desapping procedures. SER developed earlier in fruit that were infected by soilborne inoculum of L. theobromae. Exposure of harvested, desapped mangoes to the atmosphere beneath a mango tree for 6 h did not increase the occurrence of SER, indicating that airborne inoculum was not a significant source of inoculum for SER in these in these investigations.
The postharvest quiescent period for SER pathogens was influenced by the storage temperature, the pathogen involved, and the mode of infection, ranging from 4 to 5 d at 22°C, to 14 d at 13°C, in fruit that were naturally infected with Dothiorella spp. and C. gloeosporioides, or inoculated with D. dominicana at the stem-end, and from 8 to 13 d at 23°C, depending upon whether the primary inoculum was soilborne (L.theobromae) or endophytic (Dothiorella spp.) respectively.
Control of SER could involve the prevention of invasion.by, or the eradication of, the endophytic inoculum in the peduncle, the avoidance of soil contamination of the cut peduncle during harvest and, the selection of postharvest storage conditions which slow symptom expression.