Recent developments in the molecular biology of rice tungro viruses

Abstract

The most important viral disease of rice in South and Southeast Asia is called tungro. This causes severe yellowing and stunting of the plant, leading to almost total yield loss. This disease has been recognised as an important constraint in obtaining the desired yield of rice in many states of India and other neighbouring countries and is of major agricultural importance. Due to the above reason, it has received steady attention from virologists, epidemiologists as well as breeders to understand the disease spread, pathogenesis and to look for sources of genetic resistance. For a review, the reader is referred to an excellent book on this topic, namely, Anjaneyulu et al., 1994. Since late eighties, however, the causative agents of this disease, namely the tungro viruses have been intensively studied using the tools of molecular biology with the exciting prospect of genetically modifying the rice plant with genes derived from the viruses to engineer resistance, as has been already successfully done for a number of host-virus systems in crop plants. This has not only resulted in the production and testing of several lines of transgenic rice plants containing various combinations of the viral genes, but has also unravelled novel facets of the molecular biology of the viruses themselves. A need has been felt to review these recent developments, which have not been covered in the previous publications. This review is an attempt to bring together the recent findings on the molecular biology of tungro viruses and discuss its implications on future disease control strategies.