Abstract
Five Curvularia strains isolated from diseased leaves of lemongrass (Cymbopogon citratus) in Guangxi Province, China, were examined. NCBI-Blast searches of ITS sequences suggested a high degree of similarity (99–100%) to Curvularia akaii, C. akaiiensis, C. bothriochloae, C. heteropogonis and C. sichuanensis. To accurately identify these strains, we further analysed their morphology and phylogenetic relationships based on combinations of ITS, GAPDH, and tef1 gene sequences. Morphological observations indicated that the key character differing from similar species was conidial size, whereas phylogenetic analyses indicated that the five strains represent one species that is also distinct from C. akaii, C. akaiiensis and C. bothriochloae by conidial size and conidiophore length. Thus, the strains examined are found to represent a new species described herein as Curvularia nanningensis. The pathogenicity test on the host and detached leaves confirmed the new species to be pathogenic on Cymbopogon citratus leaves. Standardised requirements for reliable identification of Curvularia pathogens are also proposed.
Highlights
Cymbopogon citratus Stapf, believed to be a native of Malaysia, is widely distributed in all continents and in America, China, Guatemala and Southeast Asia
In the ITS gene region, for C. akaiiensis, the base sequence was identical to our strains; only 1 difference for C. bothriochloae; base differences were 8 for C. akaii, 9 for C. deightonii and 5 for C. sichuanensis
Phylogenetic analysis based on combined DNA sequences of ITS, GAPDH and tef1 showed that our strains were related to three Curvularia species named C. akaii (Tsuda & Ueyama) Sivan., C. akaiiensis Sivan. and C. bothriochloae Sivan., Alcorn & R.G
Summary
Cymbopogon citratus Stapf (lemongrass), believed to be a native of Malaysia, is widely distributed in all continents and in America, China, Guatemala and Southeast Asia. Guatemala is known to be the main exporter of lemongrass with about 250 tons per year. China produces 80 to 100 tons of lemongrass annually and the USA and Russia each imports about 70 tons per year (DAFF 2012). Lemongrass can be severely infected with a rust disease caused by Puccinia nakanishikii Dietel in Hawaii and California (Gardner 1985; Koike and Molinar 1999). In Brazil, a rust on lemongrass caused by another Puccinia species named P. cymbopogonis Massee has been reported (Vida et al 2006). Joy et al (2006) summarised the various disease symptoms and their causal agents of lemongrass In Brazil, a rust on lemongrass caused by another Puccinia species named P. cymbopogonis Massee has been reported (Vida et al 2006). Joy et al (2006) summarised the various disease symptoms and their causal agents of lemongrass
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