Occurrence of Cucumber mosaic virus on vanilla (Vanilla planifolia Andrews) in India.

Cucumber mosaic virus (CMV) causing mosaic, leaf distortion and stunting of vanilla (Vanilla planifolia Andrews) in India was characterized on the basis of biological and coat protein (CP) nucleotide sequence properties. In mechanical inoculation tests, the virus was found to infect members of Chenopodiaceae, Cucurbitaceae, Fabaceae and Solanaceae. Nicotiana benthamiana was found to be a suitable host for the propagation of CMV. The virus was purified from inoculated N. benthamiana plants and negatively stained purified preparations contained isometric particles of about 28 nm in diameter. The molecular weight of the viral coat protein subunits was found to be 25.0 kDa. Polyclonal antiserum was produced in New Zealand white rabbit, immunoglobulin G (IgG) was purified and conjugated with alkaline phosphatase enzyme. Double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) method was standardized for the detection of CMV infection in vanilla plants. CP gene of the virus was amplified using reverse transcriptase-polymerase chain reaction (RT-PCR), cloned and sequenced. Sequenced region contained a single open reading frame of 657 nucleotides potentially coding for 218 amino acids. Sequence analyses with other CMV isolates revealed the greatest identity with black pepper isolate of CMV (99%) and the phylogram clearly showed that CMV infecting vanilla belongs to subgroup IB. This is the first report of occurrence of CMV on V. planifolia from India.

Plasmodium falciparum: detection and strain identification of Indian isolates by polymerase chain reaction.

The polymerase chain reaction (PCR) was employed for detection and strain identification of P. falciparum in a comparative field study of Indian isolates. The primers were selected from highly conserved regions flanking the variable, tandemly repeated regions of highly polymorphic cell surface antigens, major merozoite surface antigen-1 (MSP-1), major surface antigen-2 (MSP-2), circumsporozoite surface antigen (CSP) and ring-infected erythrocyte surface antigen (RESA). Out of the 52 microscopically positive P. falciparum infected field samples, 47 samples were positive by PCR. Variation in the size of the amplified products was observed using MSP-1, MSP-2 specific primers respectively in different field isolates of P. falciparum, but CSP and RESA did not exhibit any variation in size of the amplified product. The multiplex PCR results demonstrated that amplified products from these surface antigens vary in size and there is a specific pattern for each strain and this could be utilized to identify a particular field isolate. One P. falciparum infected field sample detected by the above PCR method was found to be a mixed infection by two different strains. Five microscopically positive P. vivax infeced samples were also analyzed by PCR method using P. falciparum cell surface antigen (MSP-2) specific primers. PCR results showed one P. vivax infected sample was positive when P. falciparum specific primers were used, this could be due to inaccurate and reduced limit of detection of Plasmodial species by microscopic examination.