Insect vectors transmission of phytoplasma to vegetables in Eastern Visayas Philippines

Abstract

Phytoplasma diseases are found affecting vegetables in Eastern Visayas, Philippines. Identifying the insect vectors that transmit phytoplasma in the field is necessary for the management of this disease. This study was conducted to identify the vectors of phytoplasma affecting bitter gourd, loofah, and string beans. Insects associated with these vegetables that had shown phytoplasma symptoms in the field were collected, mass-reared, and the progenies of mass reared insects were used for transmission to healthy host plants. Phytoplasma detection was done through PCR and nest PCR assays. Phytoplasma was positively transmitted to healthy bitter gourd plants by a cicadellid leafhopper, Hishimonus sp. and brown planthopper, Ricania speculum. The ~ 1.25Kb phytoplasma-specific band was amplified in these insects. The phytoplasmas transmitted by the Hishimonus sp. and R. speculum produced two different types of symptoms to the bitter gourd, and rDNA sequence analysis separated them into two clusters which confirmed that the phytoplasmas belong to two different strains. Although the Aphis gossypii and Aphis craccivora also produced symptoms in bitter gourd and string beans, and the pathogen was detected in the insects, whether they vectored phytoplasma to their respective hosts needs further study, since the symptoms produced were quite different from the ones produced by the cicadellid leafhopper and Ricania speculum.