Barley yellow dwarf disease: recent advances and future strategies

Abstract

Given the complex nature of the disease known as barley yellow dwarf (BYD), it is essential that researchers working to combat it come together periodically to share what they have learned about the virus pathogen and its vectors, report on the use of new methodologies, and present the latest findings in different regions of the world. The latter is especially important given that individual strains of the pathogens classified as Barley yellow dwarf virus (BYDV) and Cereal yellow dwarf virus behave differently in different regions of the world, a fact that must be taken into account when breeding crop varieties that will provide farmers with effective BYD control. Since the last time involved researchers came together was at a meeting held at the International Center for Agricultural Research in the Dry Areas (ICARDA) in Aleppo, Syria, in 1989, a BYD symposium was long overdue. The incidence of BYD in any given year is very unpredictable. It depends not only on host-pathogen dynamics and environmental conditions that favor disease development, but also on fluctuations in the aphid populations that vector the disease. This unpredictability makes it very difficult to know when it makes sense to apply control measures—for example, insecticide applications to reduce aphid populations. Expensive and not always effective, insecticides should almost never be applied except in places where it is fairly certain that both vector and virus will be endemic each year. Moreover, in wheat-producing areas of the developing world where BYD is a problem (parts of North Africa, the Eastern African Highlands, several Asian countries, China included, and parts of Latin America), most farmers cannot afford chemical control methods. For all these reasons, durable genetic resistance and/or tolerance to BYDV is the best and most cost-effective option for bringing this unpredictable disease under control. However, in affected countries there has been limited progress in developing crop varieties that are BYD resistant/tolerant and also agronomically appealing to the farmer. As yet, no progress has been made on developing methods to combat the virus directly. It is obvious that large advances remain to be made in combating BYD. Progress in controlling the disease is more likely to accelerate if BYD researchers from all over the world pool the latest data and insights they have gleaned. CIMMYT and, more specifically, the Wheat Program, is happy to organize and host an occasion for doing just that, and hopes that it will also serve to make funding sources aware that there are still wide gaps in the knowledge about this complex disease. We expect these proceedings will allow researchers who did not attend the event to access the wealth of information that we were privileged to share during the symposium.