A Comparative Study on Fungal Diversity in Organic and Conventionally Cultivated Lemons During Accelerated Storage

There has been a growing interest in organic farming as a countermeasure to the environmental burden caused by chemical pesticides. We analyzed and compared the fungal diversity of lemon fruits from organic and conventional cultivation by automated rRNA intergenic spacer analysis (ARISA), accompanied by isolation of cultured colonies and metagenomic analysis. Lemon peels were cut out and subjected to the analyses at purchase and after accelerated storage at 28 °C. The organic lemons did not decay even after 14 weeks, while most of the conventional lemons did decay. The fungal colony counts were not significantly different, although the number of fungal species together with the Shannon index, considering the abundance of each species, clearly showed more diversity in organic lemons than in conventional lemons (p = 0.011). Fusarium sp. (putative F. solani) accounted for as much as 90% of the relative abundance in the decayed conventional lemons. Metagenomic analysis also supported the lack of fungal diversity in conventional lemons. These results may suggest that organic cultivation maintains the diversity of native fungal flora in lemon fruit and could contribute to preventing decay during ambient storage.