PCR-RAPD profiling of Fusarium spp. causing guava wilt disease in India

Epitypification of Fusarium oxysporum - clearing the taxonomic chaos

Fusarium oxysporum is the most economically important and commonly encountered species of Fusarium. This soil-borne fungus is known to harbour both pathogenic (plant, animal and human) and non-pathogenic strains. However, in its current concept F. oxysporum is a species complex consisting of numerous cryptic species. Identification and naming these cryptic species is complicated by multiple subspecific classification systems and the lack of living ex-type material to serve as basic reference point for phylogenetic inference. Therefore, to advance and stabilise the taxonomic position of F. oxysporum as a species and allow naming of the multiple cryptic species recognised in this species complex, an epitype is designated for F. oxysporum. Using multi-locus phylogenetic inference and subtle morphological differences with the newly established epitype of F. oxysporum as reference point, 15 cryptic taxa are resolved in this study and described as species.

PCR - RFLP patterns for the differentiation of the Fusarium species in virtue of ITS rDNA

BACKGROUND AND PURPOSE

The Fusarium species are among the most important fungi in the medical, veterinary and agricultural fields.

MATERIALS AND METHODS

In the present study, 172 strains of these fungi have been analyzed. The high molecular weight DNAs were extracted from 23 reference strains as well as from 149 isolated Fusarium species. Using the designed nucleotide primers from rDNA of Fusarium species, PCR analysis was performed for the amplification of ITS regions. Afterwards, the location of the effective endonuclease enzymes has been evaluated within approximately 930 bp of rDNA sequence.

RESULTS

Through the selected enzymes including; HhaI, MspI, TaqI and FaqI, the mentioned Fusarium species have been divided into 33 groups. The first three enzymes were able to classify Fusarium species into 23 groups of which 19 groups included one member, one group included two members and three groups included three members of the Fusarium species. This study also revealed the possibility in the identification of F. semitectum, F. solani complex, F. pseudograminearum, F. nisikadoi, F. coeruleum and F. acuminatum species by one unique enzyme. In addition, our study indicated the ability of the differentiation of F. Compactum from F. equiseti.

CONCLUSION

As Compared to previous studies with more endonuclease enzymes and with limited in identifications, the ITS-RFLP patterns reported here an attempted to evaluate most of the Fusarium species successfully.

Molecular detection and genotyping of Fusarium oxysporum f. sp. psidii isolates from different agro-ecological regions of India

Twenty one isolates of Fusarium oxysporum f. sp. psidii (Fop), causing a vascular wilt in guava (Psidium guajava L.), were collected from different agro-ecological regions of India. The pathogenicity test was performed in guava seedlings, where the Fop isolates were found to be highly pathogenic. All 21 isolates were confirmed as F. oxysporum f. sp. psidii by a newly developed, species-specific primer against the conserved regions of 28S rDNA and the intergenic spacer region. RAPD and PCR-RFLP were used for genotyping the isolates to determine their genetic relationships. Fifteen RAPD primers were tested, of which five primers produced prominent, polymorphic, and reproducible bands. RAPD yielded an average of 6.5 polymorphic bands per primer, with the amplified DNA fragments ranging from 200-2,000 bp in size. A dendrogram constructed from these data indicated a 22-74% level of homology. In RFLP analysis, two major bands (350 and 220 bp) were commonly present in all isolates of F. oxysporum. These findings provide new insight for rapid, specific, and sensitive disease diagnosis. However, genotyping could be useful in strain-level discrimination of isolates from different agro-ecological regions of India.