Partial characterization of toxins associated with stem end rot of mango caused by Lasiodiplodia theobromae

In this study, the toxicity of liquid culture media from different isolates of Lasiodiplodia theobromae was characterized and some properties of the toxic metabolites were distinguished. In this work toxin producing ability of L. theobromae was revealed by studying the physical parameters viz., osmotic potential, toxin concentration, pH, temperature and biological parameter like host specificity and wilting index. The obtained results showed that the optimal toxin-production conditions for L. theobromae in potato dextrose broth under pH 6.0, at 25-35°C for 7 days. The liquid culture from all isolates were toxic to mango plants and induced the rapid wilting. The toxin obtained from the liquid culture has thermal, acid base stability and a broad range of toxicity to main host and non-host plants. Moreover, the direct bioassay for two components of the liquid filtrates precipitated by ethanol showed that the active ingredient of the toxin is a kind of non protein substance, which was further endorsed by the papain hydrolysis analysis. Our results confirmed the chemical nature of toxic compound elucidating the favorable environmental conditions for toxin production of L. theobromae and proved potential role of toxic metabolites in the mechanism of disease development

Detection of banana streak virus (BSV) Tamil Nadu isolate (India) and its serological relationship with other badna viruses

Banana streak virus (BSV) is of quarantine significance since Musa is a vegetatively propagated crop. Diagnosis by symptomatology is unreliable because the symptoms are variable or absent. Hence, reliable and sensitive diagnostic tests are of major significance. Such sensitive diagnostic tests are also required for virus indexing of germplasm collections. Hence, attempts were made for diagnosis of BSV and to study the serological relationship with other badna viruses. BSV particles were purified from BSV infected plants, collected from the locality of Tamil Nadu, India. Immunosorbent electron microscopy studies revealed bacilliform viral particles with a size of 120 x 30 nm. Polyclonal antiserum raised against BSV reacted with the rice tungro bacilliform virus and sugarcane bacilliform virus in TAS ELISA. In PCR assays, the primers designed to amplify DNA of BSV Onne isolate amplified DNA of BSV Tamil Nadu isolate producing amplicons of about 644 bp in size. The primers used in PCR to amplify the BSV did not amplify other badna viruses tested such as Rice tungro bacilliform virus and Sugarcane bacilliform virus. Our results suggest that the BSV isolate from Tamil Nadu is closely related to Nigerian BSV (Onne) isolate.Keywords: Triple Antibody sandwich Enzyme linked immunosorbent Assay (TAS ELISA), banana streak virus (BSV), polymerase chain reaction (PCR), polyclonal antiseru