Skip to main content
ARS Home » Pacific West Area » Parlier, California » San Joaquin Valley Agricultural Sciences Center » Commodity Protection and Quality Research » Research » Publications at this Location » Publication #317247
Title: Phylogenetic, morphological and pathogenic characterization of Alternaria species associated with fruit rots of blueberry in California

Author
item ZHU, X - China Agricultural University
item Xiao, Chang-Lin

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/26/2015
Publication Date: 12/1/2015
Citation: Zhu, X.Q., Xiao, C. 2015. Phylogenetic, morphological and pathogenic characterization of Alternaria species associated with fruit rots of blueberry in California. Phytopathology. 105:1555-1567. doi: 10.1094/PHYTO-05-15-0122-R.

Interpretive Summary: Recent establishment of low-chill southern highbush blueberry cultivars in California’s warm climate has significantly increased the acreage of blueberry production in Central California, which is now a major southern highbush blueberry production region in the United States. However, fruit rot caused by Alternaria spp. is one of the most important factors affecting the postharvest quality and shelf life of blueberry fruits. In this study, we obtained 283 isolates of Alternaria spp. from decayed blueberry fruits to determine which Alternaria spp. are responsible for Alternaria fruit rot using morphological and DNA fingerprinting approaches. Of the 283 isolates, 61.5% were identified as A. alternata, 32.9% were A. arborescens, 5.0% were A. tenuissima, and only one isolate of A. infectoria and one isolate of A. rosae were found. All five Alternaria spp. were able to cause decay on the fruit inoculated with the fungus. Previously A. tenuissima has been reported to be the major causal agent of Alternaria fruit rot of blueberry worldwide. Our results indicate that the species composition of Alternaria responsible for Alternaria fruit rot in blueberry can be dependent on geographical region and that A. alternata and A. arborescens are the primary causal agents of Alternaria fruit rot in blueberry in California.

Technical Abstract: Fruit rot caused by Alternaria spp. is one of the most important factors affecting the postharvest quality and shelf life of blueberry fruits. Alternaria spp. isolates were collected from decayed fruits of blueberry in the Central Valley of California during 2012 and 2013. The aims of this study were to characterize these isolates using morphological and molecular approaches and test their pathogenicity to blueberry fruits. In total, 283 isolates were identified as Alternaria spp. based on DNA sequences of the Plasma membrane ATPase, Alt a1, and Calmodulin gene regions in combination with morphological characters of the culture and sporulation. Five species of Alternaria, including Alternaria alternata, A. tenuissima, A. arborescens, A. infectoria, and A. rosae were identified. Of the 283 isolates, 61.5% were identified as A. alternata, 32.9% were A. arborescens, 5.0% were A. tenuissima, and only one isolate of A. infectoria, and one isolate of A. rosae were found. These fungi were able to grow at temperatures from 0 to 35°C, and mycelial growth was arrested at 40°C. Optimal radial growth occurred between 20 to 30°C. Pathogenicity tests showed that all five Alternaria spp. were pathogenic on blueberry fruit at 0, 4, and 20°C, with A. alternata, A. arborescens, and A. tenuissima being the most pathogenic species, followed by A. infectoria and A. rosae. Previously A. tenuissima has been reported to be the major causal agent of Alternaria fruit rot of blueberry worldwide. Our results indicated that the species composition of Alternaria responsible for Alternaria fruit rot in blueberry can be dependent on geographical region. A. alternata, A. arborescens, A. infectoria, and A. rosae are the first report on blueberry in California. This is also the first report of A. infectoria and A. rosae infecting blueberry fruit in the world.