Evaluation of inoculum density of different postharvest pathogens on infection of tomato fruit

Tomato at its postharvest stage is affected by plethora of pathogens of which Aspergillus niger, Rhizopus stol onifer and Fusarium spp are most important. The initial inoculm density on host surface is critical to successful infection leading to wastage of product and may require culling within the package resulting considerable economic loss. The critical role of inoculum density of these three postharvest pathogens under in vitro condition has been determined. Critical threshold limits are linked to incubation period, generally at higher density, incubation period is reduced. While no visible symptom is discernible before 48 hours of incubation for Aspergillus niger and Fusrium oxysporum but becomes evident with Rhizopus stolonifer at 24 hours of incubation. The critical threshold limit determined for Aspergillus niger was 10¹ after 72 hours but higher inoculum density of 10⁴ for 48 hours of incubation. Similarly, for Fusrium oxysporum the value is peggedat 10³ during 48 hours which is not reduced at higher inoculums. In case of Rhizopus stolonifer, a fast growing fungus requires only 24 hours time for the inoculums density of 10⁴. Faster rate of rotting was noticed at conc. of 108 for Aspergillus niger, 10⁸ for Fusrium oxysporum and 10² for Rhizopus stolonifer.