Biotechnological approaches to determine the impact of viruses in the energy crop plant Jatropha curcas.

BACKGROUND: Geminiviruses infect a wide range of plant species including Jatropha and cassava both belonging to family Euphorbiaceae. Cassava is traditionally an important food crop in Sub - Saharan countries, while Jatropha is considered as valuable biofuel plant with great perspectives in the future. RESULTS: A total of 127 Jatropha samples from Ethiopia and Kenya and 124 cassava samples from Kenya were tested by Enzyme-Linked Immunosorbent Assay (ELISA) for RNA viruses and polymerase chain reaction for geminiviruses. Jatropha samples from 4 different districts in Kenya and Ethiopia (analyzed by ELISA) were negative for all three RNA viruses tested: Cassava brown streak virus (CBSV), Cassava common mosaic virus, Cucumber mosaic virus, Three cassava samples from Busia district (Kenya) contained CBSV. Efforts to develop diagnostic approaches allowing reliable pathogen detection in Jatropha, involved the amplification and sequencing of the entire DNA A molecules of 40 Kenyan isolates belonging to African cassava mosaic virus (ACMV) and East African cassava mosaic virus - Uganda. This information enabled the design of novel primers to address different questions: a) primers amplifying longer sequences led to a phylogenetic tree of isolates, allowing some predictions on the evolutionary aspects of Begomoviruses in Jatrophia; b) primers amplifying shorter sequences represent a reliable diagnostic tool. This is the first report of the two Begomoviruses in J. curcas. Two cassava samples were co - infected with cassava mosaic geminivirus and CBSV. A Defective DNA A of ACMV was found for the first time in Jatropha. CONCLUSION: Cassava geminiviruses occurring in Jatropha might be spread wider than anticipated. If not taken care of, this virus infection might negatively impact large scale plantations for biofuel production. Being hosts for similar pathogens, the planting vicinity of the two crop plants needs to be handled carefully.

Characterization of a Phytoplasma Associated with Frogskin Disease in Cassava.

Cassava frogskin disease (CFSD) is an economically important root disease of cassava (Manihot esculenta) in Colombia and other South American countries, including Brazil, Venezuela, Peru, Costa Rica, and Panama. The roots of severely affected plants are thin, making them unsuitable for consumption. In Colombia, phytoplasma infections were confirmed in 35 of 39 genotypes exhibiting mild or severe CFSD symptoms either by direct or nested polymerase chain reaction (PCR) assays employing ribosomal (r)RNA operon primer pairs. The CFSD-associated phytoplasmas were identified as group 16SrIII strains by restriction fragment length polymorphism (RFLP) and sequence analyses of amplified rDNA products, and results were corroborated by PCRs employing group 16SrIII-specific rRNA gene or ribosomal protein (rp) gene primers. Collectively, RFLP analyses indicated that CFSD strains differed from all phytoplasmas described previously in group 16SrIII and, on this basis, the strains were tentatively assigned to new ribosomal and ribosomal protein subgroups 16SrIII-L and rpIII-H, respectively. This is the first molecular identification of a phytoplasma associated with CFSD in cassava in Colombia.

'Candidatus Phytoplasma omanense', associated with witches'-broom of Cassia italica (Mill.) Spreng. in Oman.

Samples from plants of Cassia italica exhibiting typical witches'-broom symptoms (Cassia witches'-broom; CWB) were examined for the presence of plant pathogenic phytoplasmas by PCR amplification using universal phytoplasma primers. All affected plants yielded positive results. RFLP analyses of rRNA gene products indicated that the phytoplasmas detected were different from those described previously. Phylogenetic analysis of 16S rRNA gene sequences confirmed that CWB represents a distinct lineage and shares a common ancestor with 'Candidatus Phytoplasma phoenicium'. Molecular comparison revealed that the 16S rRNA gene sequences of the four CWB strains (IM-1, IM-2, IM-3 and IM-4) identified in symptomatic C. italica samples were nearly identical (99.6-100 % similarity). The closest relatives were members of the pigeon pea witches'-broom phytoplasma ribosomal group (16SrIX; 95-97 % sequence similarity). On the basis of unique 16S rRNA gene sequences and biological properties, the phytoplasma associated with witches'-broom of C. italica in Oman represents a coherent but discrete novel phytoplasma, 'Candidatus Phytoplasma omanense', with GenBank/DDBJ/EMBL accession number EF666051 representing the reference strain.