Universal Journal of Plant Science Vol. 2(7), pp. 121 - 127
DOI: 10.13189/ujps.2014.020702
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Molecular and Pathogenic Diversity of the Causal Agents of Onion Leaf Twister Disease in Batticaloa District of Sri Lanka

Vengadaramana, A. ^1,2,*, D. M. De Costa ^3
1 Postgraduate Institute of Agriculture, University of Peradeniya, Sri Lanka
² Department of Botany, Faculty of Science, University of Jaffna, Sri Lanka
³ Department of Agricultural Biology, Faculty of Agriculture, University of Peradeniya, Sri Lanka

ABSTRACT

Leaf Twister disease (LTD) is a major disease of onion (Allium ascalonicum L.) cultivated in Sri Lanka. The present study was aimed to determine molecular and pathogenic variations among the causal agents of onion leaf twister disease. The pathogens causing the LTD have been identified as Colletotrichum and Fusarium spp. Pathogenic variations of the fungal isolates, in terms of pathogenicity and virulence were determined in vivo by inoculation assays using red onion (variety Vethalan). LTD-infected plants were collected from farmer fields of four locations of Batticaloa district, Sri Lanka. Possible causal organism/s of LTD were isolated from three different parts of the infected plants, namely leaves, pseudostem and bulb. Morphologically-different six isolates of Colletotrichum and seven Fusarium isolates were obtained by isolations. Virulence of the Colletotrichum and Fusarium varied significantly among the isolates in terms of rapidity and extent of disease spread. Variety Vethalan was not completely resistant to any isolate of the two fungal genera tested. Genomic DNA of 13 isolates was extracted from each purified isolate using a modified CTAB method. PCR amplification was done with ITS1 and ITS4 primers to amplify the 5.8S-ITS subunit of the Colletotrichum isolates. The ITS2-rDNA subunit of Fusarium isolates was amplified by ITS-Fu1f and ITS-Fu1r primers. As expected 590 bp and 466 bp PCR products were resulted in by all Colletotrichum and Fusarium isolates, respectively. Colletotrichum isolates showed two polymorphic groups based on PCR-RFLP by RsaI, Hae III and Msp I. Fusarium isolates showed no polymorphism based on PCR-RFLP by Rsa I, Hae III and Msp I. Findings of the present study revealed that molecular and pathogenic variations exist among different isolates of Colletotrichum and pathogenic variations only exist among Fusarium isolates infecting red onion in Batticaloa district of Sri Lanka.

KEYWORDS
Allium Ascalonicum L., Genomic DNA, ITS Regions, PCR-RFLP, Polymorphism

Cite This Paper in IEEE or APA Citation Styles
(a). IEEE Format:
[1] Vengadaramana, A. , D. M. De Costa , "Molecular and Pathogenic Diversity of the Causal Agents of Onion Leaf Twister Disease in Batticaloa District of Sri Lanka," Universal Journal of Plant Science, Vol. 2, No. 7, pp. 121 - 127, 2014. DOI: 10.13189/ujps.2014.020702.

(b). APA Format:
Vengadaramana, A. , D. M. De Costa (2014). Molecular and Pathogenic Diversity of the Causal Agents of Onion Leaf Twister Disease in Batticaloa District of Sri Lanka. Universal Journal of Plant Science, 2(7), 121 - 127. DOI: 10.13189/ujps.2014.020702.