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Poster: Diseases of Plants: New & Emerging Diseases


Mucor Rot – An Emerging Postharvest Disease of Mandarin Fruit Caused by Mucor piriformis and other Mucor spp. in California.
S. SAITO (1), T. Michailides (2), C. Xiao (1) (1) USDA-ARS, San Joaquin Valley Agricultural Sciences Center, U.S.A.; (2) Kearney Agricultural Research & Extension Center, UC-Davis, Division of Agriculture and Natural Resources, U.S.A.

In recent years, an emerging, undescribed postharvest disease was observed on mandarin fruit after extended storage in California. We collected decayed mandarin fruit from three citrus packinghouses in the Central Valley of California in 2015 and identified this disease as Mucor rot caused by Mucor spp. Mucor rot occurred in 11 of the 15 grower lots sampled, and the incidence of the disease in the total decayed fruit varied among affected grower lots, ranging from 3.3 to 93.1% with an average of 49.2%. In total, 197 isolates of Mucor spp. were obtained from decayed mandarin fruit and identified based on ITS sequence and morphological characteristics. Of the 197 isolates, 92.4%, 3.6%, 2.0%, 1.5%, and 0.5% were identified as M. piriformis, M. circinelloides, M. racemosus, M. hiemalis, and M. mucedo, respectively. Pathogenicity tests on mandarin fruit showed that M. piriformis was the most virulent among all tested species. Our results indicated that Mucor rot of mandarins in California is caused by Mucor species consisting of M. piriformis, M. circinelloides, M. racemosus, M. hiemalis, and M. mucedo, with M. piriformis being the most prevalent species. Previously, M. racemosus was reported on citrus. This is the first report of Mucor rot on citrus caused by M. piriformis, M. circinelloides, M. hiemalis, and M. mucedo.