Acquisition, Transmission, and Multiplication of Rice Grassy Stunt Virus (RGSV) in Brown Plant Hopper Evaluated by RT-LAMP

Abstract

INTRODUCTION

For two million families, rice farming is the source for over half of its household income, making rice as one of the most extensively grown crops in the country. Unfortunately, several factors threaten the future of rice production, the leading cause of which is rice diseases. It is important to know the extent of damage brought by these diseases and to be keen on identifying the shifting disease problems associated with technological changes. This study focuses on early information on crop health and disease detection as these can facilitate the control of diseases. Through proper management strategies such as vector control through pesticide applications, fungicide applications, and disease-specific chemical applications, these can improve productivity.

METHODS

A protocol was followed in various processes such as preparation of plant material, acquisition, and inoculation (access periods are 0, 4, 24, 48, and 72 hrs) of the virus via the vector and RNA extraction on both plant and insect material. Reverse-transcriptase Loop-mediated Isothermal Amplification (RT-LAMP) was used for the diagnosis and confirmation of the RGSV. Prior to amplification, the quality and quantity of the extracted RNA were checked using gel electrophoresis and Reverse Transcriptase Polymerase Chain Reaction (RT-PCR).

RESULTS

Results show that 36.67 % of insects acquired RGSV and the brown plant hopper can obtain the virus in as early as 4 hours. Moreover, there is a direct relationship between the acquisition period and the concentration of the virus as well as the amplification time. For insect-plant transmission, 7.14% of the infected insects were able to transfer the virus to the plants. However, disease symptoms such as stunted growth and active tillering which gives it a "grassy' appearance first appeared on the 24hours acquisition period. With this, it suggests that the successful transmission of the virus can be achieved in a day.

DISCUSSIONS

Further tests will be performed to evaluate the speed rate by which the insect can acquire the virus between 0 hours to 4hours. This rate is alarming as the early disease detection relies primarily on scouting or visual inspection of disease symptoms in the field which is too late in the way that yield loss has already been incurred. Recently, RT-LAMP has been adapted, with a lateral-flow assay that is low-cost, simple, and rapid, having portable detection devices which offer potentials for on-site diagnosis by non-specialists.