Bacterial diversity of cantaloupes and soil from Arizona and California commercial fields at the point of harvest

Authors: GOFORTH, MADISON - University Of Arizona; OBERGH, VICTORIA - University Of Arizona; PARK, RICHARD - University Of Arizona; PORCHAS, MARTIN - University Of Arizona; BRIERLEY, PAUL - University Of Arizona; TURINI, THOMAS - University Of California Agriculture And Natural Resources (UCANR); PATIL, BHIMANAGOUDA - Texas A&M University; RAVISHANKAR, SADHANA - University Of Arizona; Huynh, Steven; Parker, Craig; COOPER, KERRY - University Of Arizona

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/5/2024
Publication Date: 9/26/2024
Citation: Goforth, M., Obergh, V., Park, R., Porchas, M., Brierley, P., Turini, T.A., Patil, B.S., Ravishankar, S., Huynh, S., Parker, C.T., Cooper, K.K. 2024. Bacterial diversity of cantaloupes and soil from Arizona and California commercial fields at the point of harvest. PLOS ONE. 19(9). Article e0307477. https://doi.org/10.1371/journal.pone.0307477.
DOI: https://doi.org/10.1371/journal.pone.0307477

Interpretive Summary: Across the United States, melons are a high demand crop reaching a net production of 2.7 million tons in 2020 with an economic value of $915 million dollars. Specifically, cantaloupe is major melon variety produced and consumed within the United States. In fact, the North American cantaloupe variety has been adapted to California and Arizona climates to have two growing periods in each state to provide a year-round supply. The goal of this study was to characterize the bacterial diversity of cantaloupe rinds and soil from commercial melon fields at the point of harvest from these two major production regions, Arizona and California. Cantaloupes and composite soil samples were collected from three different commercial production fields, including Imperial Valley, CA, Central Valley, CA, and Yuma Valley, AZ, at the point of harvest over a three-month period. The 16S rRNA gene amplicon sequencing was used to assess bacterial diversity and community taxonomic constitutions of the cantaloupe rinds and soil. Our data showed higher diversity of bacteria among soil samples compared to the cantaloupe rind samples regardless of the sampling location. Regional diversity of soil differed significantly, whereas there was no difference in diversity on cantaloupe surfaces. Bray-Curtis Principal Coordinate Analysis (PCoA) dissimilarity distance matrix found the samples clustered by soil and melon individually, and then clustered tighter by region for the soil samples compared to the cantaloupe samples. Taxonomic analysis found total bacterial families among the regions to be 48 for the soil samples and 11 among cantaloupes from all three locations, but composition and abundance did vary between the three locations. Core microbiome analysis had three taxa shared among soil and cantaloupe which were Bacillaceae, Micrococcaceae, and Planococcaceae. This study lays the foundation for characterizing the cantaloupe microbiome at the point of harvest that provides the cantaloupe industry with those bacterial families that are potentially present entering post-harvest processing, which could assist in improving cantaloupe safety, shelf-life, cantaloupe quality and other critical aspects of cantaloupe post-harvest practices.

Technical Abstract: Across the United States, melons are a high demand crop reaching a net production of 2.7 million tons in 2020 with an economic value of $915 million dollars. The goal of this study was to characterize the bacterial diversity of cantaloupe rinds and soil from commercial melon fields at the point of harvest from two major production regions, Arizona, and California. Cantaloupes and composite soil samples were collected from three different commercial production fields, including Imperial Valley, CA, Central Valley, CA, and Yuma Valley, AZ, at the point of harvest over a three-month period, and 16S rRNA gene amplicon sequencing was used to assess bacterial diversity and community taxonomic constitutions. The Shannon evenness index showed higher diversity among soil compared to the cantaloupe rind regardless of the sampling location. Regional diversity of soil differed significantly, whereas there was no difference in diversity on cantaloupe surfaces. Bray-Curtis Principal Coordinate Analysis (PCoA) dissimilarity distance matrix found the samples clustered by soil and melon individually, and then clustered tighter by region for the soil samples compared to the cantaloupe samples. Taxonomic analysis found total families among the regions to be 48 for the soil samples and 11 among cantaloupes from all three locations, but composition and abundance did vary between the three locations. Core microbiome analysis had three taxa shared among soil and cantaloupe which were Bacillaceae, Micrococcaceae, and Planococcaceae. This study lays the foundation for characterizing the cantaloupe microbiome at the point of harvest that provides the cantaloupe industry with those bacterial families that are potentially present entering post-harvest processing, which could assist in improving cantaloupe safety, shelf-life, cantaloupe quality and other critical aspects of cantaloupe post-harvest practices.