Identification and characterization of isolates of Botrytis obtained from blossom blight and fruits with calyx-end rot in apples in Chile

Calyx-end rot, caused by Botrytis cinerea, reduces the production and quality of apples. In this study, isolates of Botrytis obtained from blighted blossoms and fruits with calyx-end rot, were cultured and then morphologically and molecularly characterized. Twenty isolates were classified based on the morphology of their colonies on three culture media (PDA, PAM, and KMB). The morphological parameters evaluated included the shape and size of conidia and conidiophores on PDA. The same isolates were molecularly characterized by DNA amplification and sequencing of glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) genes. Pathogenicity tests were carried out on ‘Cripps Pink’, ‘Fuji’, ‘Gala Premium’, and ‘Granny Smith’ apples. All the isolates corresponded to Botrytis based on their morphological characterization. The molecular analysis also confirmed that all the isolates were grouped with the reference isolates of B. cinerea One isolate, however, was grouped between B. caroliniana and B. fabiopsis clusters, and was named as Botrytis sp1. Pathogenicity tests were positive in all the apple varieties evaluated, with apparent differences in virulence between the isolates of B. cinerea. This research is the first attempt to characterize isolates of B. cinerea obtained from blossom blighted and calyx-end rot in apples in the Maule Region, Chile. Other isolates of Botrytis may group with Botrytis sp. 1. and their frequency and importance must be studied.