RT-PCR based detection of Pepper mild mottle virus from capsicum seeds and seed transmission assay

Pepper mild mottle virus (PMMoV), a Tobamovirus from Virgaviridae family, is highly contagious and transmitted by seeds as well as soil in nature. PMMoV has become a greater threat to capsicum cultivation worldwide. To develop an indigenous, rapid, and sensitive protocol for routine detection of PMMoV from seeds, the sensitivity of DAS-ELISA and RT-PCR was compared in the present study. The infected seeds of California Wonder were included in the study. Through DAS-ELISA the virus was successfully detected from 20 mg of seeds. However, using RT-PCR, we were able to detect the virus even from one infected seed with reproducibility. In the present study, vertical seed transmission of the test virus was investigated by employing a grow-out test under greenhouse conditions as well as directly through RT-PCR omitting the grow-out test in three capsicum cultivars. Based on symptoms observations in grow out test, seed transmission was observed in the 3 capsicum cultivars viz., California Wonder (63.04%), Yolo Wonder (33.80%) and Doux des LAndes (33.30%). Through RT-PCR it was estimated to be 55.56% (California Wonder), 28.96% (Yolo Wonder), and 40.64% (Doux des Landes), respectively. Thus, indicating 100% seed-to-seedling PMMoV transmission and reliability of RT-PCR in direct PMMoV detection from seeds. Even a small percentage of infected seed has the potential to greatly increase the PMMoV inoculum in the field and result in 100% plant infection. Therefore, we suggest using the established procedure for PMMoV detection right from the seed. © 2023, The Author(s), under exclusive licence to Indian Virological Society.