Revealing differences in the viral transmission mechanism between viruliferous and nonviruliferous Tagosodes orizicolus using transmission electron microscopy

The rice delphacid, Tagosodes orizicolus, presents a threat to the Texas rice industry by causing feeding and oviposition damage on leaves and by transmitting Rice hoja blanca virus (RHBV) to rice. The rice delphacid is one of the most destructive pests of rice in Latin America, causing up to 100% yield loss when combined with RHBV. This insect was found in the United States in the 1950s and 1980s and was not detected in the US again until 2015 in rice fields near Houston, TX, when outbreaks caused up to 25% yield loss. RHBV is a negative-sense single-stranded RNA virus and viral transmission by the insect vector is under genetic control. In addition, RHBV has deleterious effects on T. orizicolus such as increased mortality and reduced oviposition. The details on how and if RHBV affects T. orizicolus are unknown along with transmission barriers RHBV faces in the insect vector. In this study, transmission electron microscopy (TEM) is used to explore potential transmission barriers for RHBV in nonviruliferous T. orizicolus by assessing presence of virions, viral inclusion bodies, and viroplasms. Nonviruliferous and viruliferous adults were examined under TEM. Nonviruliferous had abundant inclusion bodies in the gut and salivary glands while viruliferous only a relatively low concentration in salivary glands, possibly representing a ‘dead-end’ for RHBV in salivary glands of nonviruliferous insects. Ultimately, this study increases the knowledge of this pathosystem and could lead to development of control methods for this insect and virus threatening the rice industry in Texas.