Determination of the Putative Insect Vector of Napier Grass Stunt Phytoplasma using Molecular and Bioassay techniques in Western Kenya

Abstract

Sampling insects in and around Napier grass fields revealed that 21 Homopteran insect species exploit Napier Grass (Pennisetum purpureum Schumach 1827) canopy. Leafhopper Cicadulina sp., and plant hoppers; Leptodelphax dymas Young, and Sogatella manentho Horvath, are the most dominant Napier canopy insects. This study developed a Loop Mediated Isothermal Amplification of DNA (LAMP) for rapid detection of phytoplasma 16S rDNA. LAMP was simple, sensitive, specific, robust and very rapid Napier Grass Stunt phytoplasma (Ngs-phytoplasma) detection technique. After a 20 days of phytoplasma Acquisition Access Period (AAP) on diseased Napier grass and 30 days latency period on healthy grasses, Cicadulina sp., Exitianus sp 5., and Cofana spectra Distant tested positive for Ngs-phytoplasma indicating that they interact with Ngs-phytoplasma in circulative manner. The ability of these Napier Canopy insects to vector Ngs-phytoplasma was confirmed by Membrane feeding and Natural transmission experiments, incriminating the white leafhopper, Cofana spectra Distant to be the leading insect vector of Ngs-phytoplasma though Cicadulina sp., and Exitianus sp 5 cannot be ruled out as additional vector(s)