Diagnosis of potato stunting disease in Central Java, Indonesia

Potatoes are one of the highest economic value of horticulture crops in Indonesia. Survey at potato central production in Wonosobo and Banjarnegara regency, Central Java was conducted and found two type stunting symptoms on potatoes with disease incidence ranging from 5%-40%. The research aimed to identify the symptom-causing pathogens. The pathogens are identified by bioassay, serological detection, RT-PCR/PCR, and DNA sequencing. The mechanical transmission of both types of stunting symptoms showed different symptoms found in the fields. However, by grafting transmission, the stunting type 1 showed chlorosis, mosaic, and leaf curling, while the type 2 showed stunting and leaf rugose. These indicate those symptoms caused by viruses and other pathogens. The serology tests showed those samples positively reacted against Potato virus Y, and Potato virus X antisera. RT-PCR using universal primer Potyvirus and Potexvirus confirmed the existence of both viruses. Nested PCR by using universal primer of phytoplasma confirmed its existence in type 2 stunting symptoms. Nucleotide sequence analysis results confirmed serological tests that the stunting type 1 caused by double infection of PVY strain O and PVX. The stunting type 2 was caused by double infection of PVY and Sweet potato little leaf phytoplasma (SPLL); the members of 16SrII group.