ABSTRACT
Histopathology of infected categorized seeds of different crops by pathogens ranging from well-known necrotrophs to biotrophs has shown that the extent and amount of fungal inoculum in seed tissues are directly correlated with the severity of seed infection. Developmental histopathological studies suggest that there is a primary site of colonization by the fungal mycelium in seed, depending on the course of penetration and the availability of space or soft tissue. Seeds usually do not have unifungal infection, but information on histopathology of seeds infected with more than one fungus is limited. The location of pathogens in seed affects seed viability as well as control of seed-borne infection. Hyphae and pycnidia of Phoma lycopersici, which causes stem rot in tomato, are located in spaces left by the absorption of the parenchymatous cells of the middle zone of the seed coat. In mixed fungal infections of seeds, hyphae of different fungi compete for colonization, showing antagonistic or synergistic behavior.
