Prevalence of postharvest diseases of mandarin fruit in California

Authors: Saito, Seiya; Xiao, Chang-Lin

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/29/2017
Publication Date: 11/2/2017
Citation: Saito, S., Xiao, C. 2017. Prevalence of postharvest diseases of mandarin fruit in California. Plant Health Progress. 18(4):204-210. https://doi.org/10.1094/PHP-08-17-0048-RS.
DOI: https://doi.org/10.1094/PHP-08-17-0048-RS

Interpretive Summary: In recent years, storing mandarin fruit in cold facilities has become a common practice to retain fruit quality and expand the marketing window. However, postharvest diseases can limit the storage of the fruit and cause significant economic losses if left uncontrolled. Understanding which postharvest diseases affect mandarin fruit during storage would help identify the targets for disease control and thus could develop relevant control measures to reduce losses resulting from these postharvest diseases. We conducted a survey to determine the prevalence of postharvest diseases affecting stored mandarins. Decayed fruit were collected from various grower lots either at pre-sorting or after cold storage in 2015 and 2016. Fungal isolation and identification were attempted for all decayed fruit. We found that Alternaria rot caused by Alternaria spp. was most prevalent on the non-stored fruit that were collected at pre-sorting, accounting for 53.5% and 83.1% in 2015 and 2016, respectively. On the stored fruit that were collected after cold storage, green mold caused by Penicillium digitatum (36.3%) was most prevalent followed by Mucor rot caused by Mucor piriformis (27.7%) and blue mold caused by P. italicum (23.3%) in 2015, while gray mold caused by Botrytis cinerea (29.7%) was most prevalent followed by Mucor rot (27.1%) and sour rot caused by Geotrichum citri-aurantii (18.7%) in 2016. Our results indicate that gray mold and Mucor rot are two emerging postharvest diseases of mandarin fruit in California and that postharvest disease-control programs for mandarin fruit should target not only common postharvest diseases such as green mold, blue mold, and sour rot, but also emerging diseases Mucor rot and gray mold.

Technical Abstract: In recent years, storing mandarin fruit in cold facilities has become a common practice to retain fruit quality and expand the marketing window, but postharvest diseases can limit the storage of the fruit. To determine major postharvest diseases affecting mandarins, decayed fruit were collected from 20 and 46 grower lots either at pre-sorting or after cold storage in 2015 and 2016, respectively. Fungal isolation and identification were attempted for all decayed fruit. Alternaria rot caused by Alternaria spp. was most prevalent on the non-stored fruit that were collected at pre-sorting, accounting for 53.5% and 83.1% in 2015 and 2016, respectively. On the stored fruit that were collected after cold storage, green mold caused by Penicillium digitatum (36.3%) was most prevalent followed by Mucor rot caused by Mucor piriformis (27.7%) and blue mold caused by P. italicum (23.3%) in 2015, while gray mold caused by Botrytis cinerea (29.7%) was most prevalent followed by Mucor rot (27.1%) and sour rot caused by Geotrichum citri-aurantii (18.7%) in 2016. Our results indicate that gray mold and Mucor rot are two emerging postharvest diseases of mandarin fruit in California and that postharvest disease-control programs for mandarin fruit should target not only common postharvest diseases such as green mold, blue mold, and sour rot,but also emerging diseases Mucor rot and gray mold.