Alternaria alternata sensu lato, casual agent of citrus brown spot, first identified in Yunnan
province in 2010 and subsequently found in Zhejiang, Hunan, Guangdong provinces,
Chongqing municipality andGuangxi autonomous region in China. During 2010e2012, 86
isolates were collected from diseased citrus, of which 85 % isolates were pathogenic to Ponkan
tangerine. Phylogenetic analyses of Chinese and worldwide isolates using partial sequences
of an endopolygalacturonase gene (endoPG) and combined dataset ofendoPG and
two anonymous loci (OPA1-3, OPA2-1) found that Chinese isolates fell into two of three previously
described clades. One clade (‘clade 3’) contained isolates from Turkey and Israel,
and the other clade (‘clade 1’) contained isolates from Florida, USA. None of the isolates
from China fell into the last previously described clade (‘clade 2’). However, 24 isolates
from Hunan, Guangdong and Guangxi fell into a fourth clade (‘clade 4’) not previously reported
to be associated with citrus brown spot. This clade included multilocus haplotypes
known to infect Japanese pear and strawberry. The observation that Chinese brown spot
isolates fell into only two of three known worldwide lineages suggests that this fungus
may not have co-evolved with its host in China but elsewhere in Southeast Asia and introduced
to China.