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ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Publications at this Location » Publication #373189
Research Project: Integrate Pre- and Postharvest Approaches to Enhance Fresh Fruit Quality and Control Postharvest Diseases

Location: Commodity Protection and Quality Research

Title: Phylogenetic, morphological, and pathogenic characterization of Alternaria species associated with fruit rot of mandarin in California

Author
item WANG, FEI - Kearney Agricultural Center
item SEIYA, SAITO - Former ARS Employee
item MICHAILIDES, THEMIS - Kearney Agricultural Center
item Xiao, Chang-Lin

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/24/2020
Publication Date: 10/24/2021
Citation: Wang, F., Seiya, S., Michailides, T.J., Xiao, C. 2021. Phylogenetic, morphological, and pathogenic characterization of Alternaria species associated with fruit rot of mandarin in California. Plant Disease. 105(9):2606-2617. https://doi.org/10.1094/PDIS-10-20-2145-RE.
DOI: https://doi.org/10.1094/PDIS-10-20-2145-RE

Interpretive Summary: Alternaria rot caused by Alternaria species is one of the major postharvest diseases of mandarin fruit in California. In this study, we obtained 177 Alternaria isolates from decayed mandarin fruit exhibiting Alternaria rot symptoms to determine which Alternaria spp. are responsible for Alternaria fruit rot using morphological and DNA fingerprinting approaches. Of the 177 isolates, 49.7% were identified as A. alternata, 30.0 % were A. arborescens, and 20.3% were A. tenuissima. Pathogenicity tests showed that all three Alternaria species were able to cause Alternaria rot on mandarin fruit at both 5°C and 20°C. Our results indicated that Alternaria alternata, A. arborescens, and A. tenuissima are the primary causal agents of Alternaria rot of mandarin fruit in California with A. arborescens causing fruit rot on mandarin being reported for the first time.

Technical Abstract: Alternaria rot caused by Alternaria species is one of the major postharvest diseases of mandarin fruit in California. The aims of this study were to identify these Alternaria species using phylogenetic analyses and morphological characteristics and test their pathogenicity to mandarin fruit. In 2015 and 2016, decayed mandarin fruit exhibiting Alternaria rot symptoms were collected from three citrus fruit packinghouses in the Central Valley of California. In total, 177 Alternaria isolates were obtained from decayed fruit and classified into three species, A. alternata, A. arborescens and A. tenuissima. The identification was based on DNA sequences of the second largest subunit of RNA polymerase II (RPB2), plasma membrane ATPase and Calmodulin gene regions in combination with morphological characters. Of the 177 isolates, 88 isolates (49.7%) were identified as A. alternata, 53 isolates (30.0 %) were A. arborescens, and 36 isolates (20.3%) were A. tenuissima. Mycelial growth rate and sporulation varied among the selected isolates of the three species. Pathogenicity tests showed that all three Alternaria species were pathogenic on mandarin fruit at both 5°C and 20°C. Our results indicated that three Alternaria species, A. alternata, A. arborescens, and A. tenuissima, were responsible for Alternaria rot of mandarin fruit in California with A. arborescens causing fruit rot on mandarin being reported for the first time.