INTERNATIONAL JOURNAL OF AGRICULTURAL TECHNOLOGY

Volume 14, No. 06, Month NOVEMBER, Year 2018, Pages 845 - 860

Morphological and molecular based identification of corn downy mildew distributed in thailand.

Janruang, P. and Unartngam, J.

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In Thailand, corn downy mildews are reported to cause by six species of fungi including Peronosclerospora sorghi, P. philippinensis, P. sacchari, P. spontanea, Sclerophthora rayssiae var. zeae and P. maydis. The fungal species of corn downy mildew distributed in different geographic areas of Thailand based on morphological and molecular identification was determined. The disease samples were collected for morphological and DNA sequence observations. The results showed that all fungal isolates possessed various conidial shapes with 15.0-19.8×15.0-32.0 µm in size and different conidiophore types using septum position. Therefore, morphological characteristics of conidia and conidiophore type were similar in range to P. maydis and P. sorghi. Phylogenetic analysis was carried out using the 28S rDNA gene and internal transcribed spacer 1 (ITS1) region. The results of ITS1 region analysis indicated that 31 sequences were grouped together with P. maydis obtained from the GenBank database (NCBI) at a 99% similarity coefficient and separated from other sequences. Therefore, the present study suggested that four species in Pest List of Thailand should be removed from the list of corn downy mildew, including P. philippinensis, P. sacchari, P. spontanea and Sclerophthora rayssiae var. zeae.

Keywords

Corn downy mildew, Peronosclerospora, 28S rDNA, ITS1 region

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