Molecular survey of the Texas Phoenix decline phytoplasma population in Florida, USA

A nested polymerase chain reaction (PCR) assay was used to amplify 16S-23S intergenic spacer (IGS) region from DNA samples individually extracted from 25 Sabal palmetto (cabbage palms) showing symptoms of Texas Phoenix decline (TPD) in West Central Florida. The IGS region was also amplified from DNA from other palm species showing symptoms of TPD and lethal yellowing (LY). A subset of the  aforementioned phytoplasma DNA samples (Sabal and other palm species) together with additional samples from various hosts collected from different geographical localities were further studied to compare the collected phytoplasma strains using sequence analysis of the glycoprotease (gcp) genes. Restriction fragment length polymorphisms (RFLP) analysis of the PCR-amplified 16S-23S IGS region and the gcp gene using a three restriction enzymes showed that the population of the phytoplasmas infecting S. palmetto in West Central Florida is probably homogenous. The S. palmetto phytoplasma also appeared similar to all the 16SrIV-D phytoplasmas infecting other palm species and different from all phytoplasmas belonging to the 16SrIV-A subgroup. We recommend more work using genes or genomic regions other than the 16S-23S IGS region and the gcp gene to be done.Keywords: 16S-23S intergenic spacer region, glycoprotease gene, phytoplasma, Texas Phoenix decline, lethal yellowingAfrican Journal of Biotechnology Vol. 12(40), pp. 5814-582

Fungicide sensitivity in <I>Tapesia yallundae </I>populations collected from 15 wheat fields in the Western Cape province of South Africa

AgriwetenskappePlantpatologiePlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Fungicide sensitivity of Tapesia yallundae populations collected from 15 wheat fields in the Western Cape of South Africa

In the Western Cape province of South Africa, eyespot disease (Tapesia yallundae) of wheat is primarily controlled by fungicide applications. Previous studies have shown, however, that isolates of T. yallundae vary in their response to fungicides. In the present study, 20 isolates from each of 15 fields with different fungicide histories were screened against carbendazim at 1 ¿g/ml; propiconazole, tebuconazole and flutriafol each at 0.1, 0.5, 1 and 2 ¿g/ml; and flusilazole and bromuconazole each at 0.05, 0.1, 0.5 ¿g/ml. No isolates were resistant to carbendazim. Flusilazole proved to be most effective of all the triazole fungicides tested. Based on the analysis of EC50 values compared to that of a field at Gouda that is at baseline sensitivity, shifts in sensitivity were detected to all triazoles. This suggests that measures for prevention of build-up of resistance need to be employed

Phytoplasma transmission by seed

The transmission of phytoplasmas by seed was reported in several herbaceous and some woody plant species. The seedlings were usually analyzed for the presence of phytoplasmas in different stages of growth by nested-PCR/RFLP analysis and phytoplasmas belonging to different ribosomal groups according with species and geographical distribution were detected. The phytoplasma isolation from corn seedlings confirms the seed transmission of viable phytoplasma cells. The sudden epidemic events associated with the presence of phytoplasmas molecularly undistinguishable, in very distant geographic areas, on the same herbaceous species, provides further indications of transmission of these prokaryotes also by seeds. In all the analysed species, the phytoplasma detected in seedlings belong to different ribosomal groups, in some cases they are found also in mixed infection. Since phytoplasma presence is not contemplated in propagation material by the any of the worldwide plant protection quarantine protocols nor by seed producers, the movement of seeds from infected plants implies a wide dissemination of the pathogens and therefore of the associated diseases in still uncontaminated areas