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Two isolates ( CVd- WHw and CVn- WHg) recovered from Verticillium-wilt-symptomatic cotton grown in Hubei Province of China were identified based on their morphology, growth characteristics in culture, specific amplification and identification of internal transcribed spacer ( ITS) r DNA sequence. According to the morphological characteristics, specific PCR amplification and ITS sequences, CVd- WHw was identified as V. dahliae and CVn- WHg as Gibellulopsis nigrescens. In bioassays, the two isolates had significantly lower pathogenicity to cotton plant than V. dahliae isolate CVd- AYb. Cotton pre-inoculated with isolate CVn- WHg or CVd- WHw exhibited reduced disease indices of Verticillium wilt compared with those inoculated with CVd- AYb alone. Cotton co-inoculated with CVn- WHg or CVd- WHw and CVd- AYb provided increased protection from subsequent CVd- AYb inoculation. These results suggest that the two isolates have the potential to be developed as biocontrol agents for the control of Verticillium wilt in cotton. To our knowledge, this is the first report of a cross-protection phenomenon using Gibellulopsis nigrescens against Verticillium wilt caused by V. dahliae on cotton. [ABSTRACT FROM AUTHOR]