Endophytic Yeasts in Apple Fruits of Cultivated and Wild Growth Forms: Total Diversity and Occurrence of Opportunistic Species

Abstract

Background: Apples are widely distributed in different geographical zones and are an important part of human diet. They are a popular subject for research and development of new technologies for biological protection of fruits against phytopathogens. Among yeasts, true phytopathogens are practically unknown. But among them there is a group of clinically significant species of the genus Candida. The development of these species in fruits can affect human health. Primarily, this concerns people with a weakened immune system and a genetic predisposition to mycogenic allergies. The presence of opportunistic yeasts is particularly likely in natural substrates under anthropogenic impact. This study is devoted to the comparison of endophytic yeasts of apples grown industrially and growing wild in urban areas. Results: Endophytic yeasts were detected in 80% of samples. The average yeast abundance depended (F=24.26; p < 0.01) on the sugar concentration in tissues. At a content of 7-12 °Bx, the average yeast abundance was 4.96±1.07 × 10³ CFU/g; at 12-18 °Bx, 9.61±1.09 × 10³ CFU/g. A total of 33 yeast species were isolated from apples. The greatest number of endophytes was observed in wild apples. Detection the opportunistic yeast Candida parapsilosis distinguished yeast complexes of wild apples from commercial industrial products. The relative abundance of C. parapsilosis in apples collected in the urban area exceeded 30%. Conclusion: The data on the high abundance of C. parapsilosis in endophytic yeast communities of apples collected in urban areas allow us to make a preliminary suggestion to avoid the consumption of such fruits.