Disease reactions of 11 apple genotypes (Braeburn, Empire, Gala, Granny Smith, Golden Delicious, Jonathan, Jonagold, MacIntosh, Red Delicious, Red Rome and Spartan) to 3 genetically distinct bitter rot pathogens (Colletotrichum gloeosporioides [teleomorph (T) and nonteleomorph (NT)] and C. acutatum) were examined. Fruit were surface sterilized, and then inoculated either by placing a 100 ul spore suspension (2×104 spores/ml) into wounds or spraying the inoculum onto unwounded fruit. Inoculated fruit were incubated at 26C and 100% RH. Disease reactions were quantified by measuring lesion diameter and depth in wounded fruit, or counting the number of lesions on unwounded fruit. There was a significant interaction between apple genotypes and all 3 pathogenic isolates. The T isolate was the most virulent on all genotypes. In general, cultivars with the smallest lesions in the wound test had the fewest lesions in the unwounded test. Lesion number and size were significantly lower on Granny Smith, Jonagold, Jonathan, Red Delicious and Red Rome. Of the genotypes tested, Braeburn, Gala and MacIntosh apparently were the most susceptible.
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