Epidemiology and integrated management of persistently transmitted aphid-borne viruses of legume and cereal crops in West Asia and North Africa.

ABSTRACT

Cool-season food legumes (faba bean, lentil, chickpea and pea) and cereals (bread and durum wheat and barley) are the most important and widely cultivated crops in West Asia and North Africa (WANA), where they are the main source of carbohydrates and protein for the majority of the population. Persistently transmitted aphid-borne viruses pose a significant limitation to legume and cereal production worldwide. Surveys conducted in many countries in WANA during the last three decades established that the most important of these viruses are Faba bean necrotic yellows virus (FBNYV genus Nanovirus; family Nanoviridae), Bean leafroll virus (BLRV genus Luteovirus; family Luteoviridae), Beet western yellows virus (BWYV genus Polerovirus; family Luteoviridae), Soybean dwarf virus (SbDV genus Luteovirus; family Luteoviridae) and Chickpea chlorotic stunt virus (CpCSV genus Polerovirus; family Luteoviridae) which affect legume crops, and Barley yellow dwarf virus-PAV (BYDV-PAV genus Luteovirus; family Luteoviridae), Barley yellow dwarf virus-MAV (BYDV-MAV genus Luteovirus; family Luteoviridae) and Cereal yellow dwarf virus-RPV (CYDV-RPV genus Polerovirus; family Luteoviridae) which affect cereal crops. Loss in yield caused by these viruses is usually high when infection occurs early in the growing season. Many aphid vector species for the above-mentioned viruses are reported to be prevalent in the WANA region. In addition, in this region many wild species (annual or perennial) were found infected with these viruses and may play an important role in their ecology and spread. Fast spread of these diseases was always associated with high aphid vector populations and activity. Although virus disease management can be achieved by combining several control measures, development of resistant genotypes is undoubtedly one of the most appropriate control methods. Over the last three decades barley and wheat genotypes resistant to BYDV, faba bean genotypes resistant to BLRV, and lentil genotypes resistant to BLRV, FBNYV and SbDV have been successfully identified. Moreover, progress has been made in disease management of some of these viruses using a combination of management options. Experience gathered over the last few decades clearly showed that no single method of virus disease control suffices to reduce yield losses in legume and cereal crops.