Insights into Emerging Begomovirus–Deltasatellite Complex Diversity: The First Deltasatellite Infecting Legumes

SIMPLE SUMMARY: Legumes play an important nutritional role in the diets of millions of people, mainly in developing countries, but their productivity is seriously affected by a variety of pathogens including viruses. In the last few decades, a number of whitefly-transmitted viruses have emerged mainly in tropical and subtropical areas worldwide including the DNA-containing begomoviruses. A survey of leguminous plants for the presence of begomoviruses was conducted in Venezuela, an understudied country in this regard, even when a variety of symptoms resembling those caused by begomoviruses has been observed in leguminous crops for 20 years. As a result, begomoviruses belonging to four novel species have been discovered and molecularly characterized. In addition, a novel deltasatellite, a small DNA molecule associated with some begomoviruses, has been found to be associated with cabbage leaf curl virus. This is the first time that a deltasatellite has been found to infect legumes. Our results illustrate the increasing complexity faced by researchers and breeders looking to develop control strategies against these emerging pathogens. ABSTRACT: Begomoviruses and associated DNA satellites are involved in pathosystems that include many cultivated and wild dicot plants and the whitefly vector Bemisia tabaci. A survey of leguminous plants, both crops and wild species, was conducted in Venezuela, an understudied country, to determine the presence of begomoviruses. Molecular analysis identified the presence of bipartite begomoviruses in 37% of the collected plants. Four of the six begomoviruses identified constituted novel species, and two others had not been previously reported in Venezuela. In addition, a novel deltasatellite (cabbage leaf curl deltasatellite, CabLCD) was found to be associated with cabbage leaf curl virus (CabLCV) in several plant species. CabLCD was the first deltasatellite found to infect legumes and the first found in the New World to infect a crop plant. Agroinoculation experiments using Nicotiana benthamiana plants and infectious viral clones confirmed that CabLCV acts as a helper virus for CabLCD. The begomovirus–deltasatellite complex described here is also present in wild legume plants, suggesting the possible role of these plants in the emergence and establishment of begomoviral diseases in the main legume crops in the region. Pathological knowledge of these begomovirus–deltasatellite complexes is fundamental to develop control methods to protect leguminous crops from the diseases they cause.