Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: August 1, 2004
Publication Date: September 30, 2004
Citation: Chen, W., Sharma, K.D., Wheeler, M.H., Muehlbauer, F.J. 2004. The role of melanin production in ascochyta blight of chickpea.. Phytopathology. 94:S132. Technical Abstract: Ascochyta blight caused by Ascochyta rabiei is an important disease of chickpea. Two pathotypes of the pathogen are identified in the US. A. rabiei produces melanin in culture and in infected plants. The role of melanin production by A. rabiei in pathogenicity was investigated. Albino mutants of A. rabiei, in contrast to wild types, lost pathogenicity on chickpea. The mutants were able to convert scytalone, a precursor of the 1, 8-dihydroxalnapathalene (DHN) melanin, into a dark compound similar to melanin. Specific melanin-inhibitors, pyroquilon and tricyclazole, blocked melanin production by wild types, suggesting that A. rabiei uses the DHN pathway for melanin synthesis. The same specific melanin-inhibitors when applied to plants significantly reduced disease severity caused by wild type strains. Transcripts of scytalone dehydratase, an intermediate enzyme in the DHN-melanin pathway, were detected in conidia using RT-PCR. Data suggest that melanin biosynthesis is operative during spore germination, and melanin production plays important roles in pathogenesis of A. rabiei on chickpea.