Endophytic and pathogenic fungi of developing cranberry ovaries from flower to mature fruit: diversity and succession

Culturable fungal population diversity and succession was investigated in developing cranberry ovaries of fruit rot-resistant and rot-susceptible cranberry selections, from flower through mature fruit. Fungi were recovered in culture from 1185 of 1338 ovary tissues collected from June to September, yielding 2255 isolates that represented 42 morphotaxa. During the season, species richness varied from 2 to 17 and 2 to 18 in rot-resistant and rot-susceptible selections, respectively, increasing from wk1 to wk10 and then gradually declining to wk14. Shannon-Wiener diversity index varied from 0.27 to 2.32 in rot-resistant and 0.18 to 2.38 in rot-susceptible, and Pielou's evenness index varied from 0.11 to 0.63 and 0.06 to 0.64 in rot-resistant and rot-susceptible selections, respectively, confirming that diversity of fungi in developing ovaries was similar among rot-resistant and rot-susceptible selections, but varied among sampling time points. Principal component analysis grouped samples collected at the same sampling time point together regardless of rot susceptibility of the selections, and detected the predominant fungal species associated with each stage of development. Successional changes were observed in populations of endophytic, pathogenic and saprophytic fungi throughout the season as ovaries matured.