Chapter 18 - Enigmatic emergence of seed transmission of geminiviruses

Abstract

Geminiviruses are the largest group of plant viruses causing diseases in a wide diversity of crop plants. These are predominantly transmitted by phloem-feeding insects which include various species of leafhoppers, a treehopper, and specifically the polyphagous Bemisia tabaci (Gennadius). The other means of transmission is through grafting and to some extent through sap. There was no record of seed transmission of geminiviruses until 2015. In recent years the seed transmission of virus species belonging to the genera Begomovirus, Becurtovirus, and Curtovirus of the family Geminiviridae has been recorded. Sweet potato leaf curl virus was the first geminivirus reported to be transmitted through seed. Subsequently detailed studies demonstrated seed transmission in 10 viruses, that is, tomato yellow leaf curl virus in tomato, sweet pepper and white soybean, mungbean yellow mosaic virus in blackgram, tomato leaf curl New Delhi virus in chayote and Zucchini squash, beet curly top virus, beet curly top Iran virus in petunia, dolichos yellow mosaic virus in lab lab bean, bittergourd yellow mosaic virus in bitttergourd, Sweet potato symptomless virus 1 in sweet potato, Okra yellow mosaic Mexico virus in weeds, and pepper yellow leaf curl Indonesia virus in chilli capsicum. This chapter will provide focused information on these seed-transmitted geminiviruses. The mechanism of seed transmission and its impact on active spread of the virus will also be briefly discussed.