Occurrence And Management Of Bean Leafroll Virus In Food Legume Crops In West Asia And North Africa Region

Safaa G. Kumari and Khaled M
Makkouk, Virology Laboratory, International Center for Agricultural Research in the Dry Areas (ICARDA), P.O. Box 5466, Aleppo, Syria
E-mail: S.Kumari@cgiar.org

Abstract

Bean leafroll virus (BLRV, family Luteoviridae) is an economically important disease affecting several legume crops in many countries of West Asia and North Africa (WANA). The main symptoms produced by the virus are leaf yellowing, plant stunting, reddening, thickening of the leaves and suppression of flowering and pod set. BLRV is persistently transmitted by aphid species. Surveys made in nine countries in WANA (Ethiopia, Iran, Iraq, Jordan, Pakistan, Tunisia, Turkey, Syria and Yemen) during the period of 1996-2001 indicated that BLRV was the most common in Iran, Iraq, Syria and Tunisia. Although virus disease management can be achieved through combination of several approaches, development of resistant genotypes is undoubtedly one of the most promising control component. A total of 222 lentil and 360 faba bean genotypes were evaluated for their reaction to BLRV using artificial inoculation with the pea aphid Acyrthosiphon pisum under field conditions. Repeated inoculation and continuing reselection during four growing seasons lead to the identification of resistant genotypes. Six lentil genotypes (ILL 74, 75, 85, 213, 214, 6816) and 15 faba bean genotypes (from BPL 5271 until 5285) were found resistant to BLRV. The effectiveness of using seed treatment with imidacloprid (Gaucho®) to reduce BLRV incidence in faba bean and lentil was investigated. BLRV Incidence in faba bean was reduced from 92% in untreated plots to 23 and 13% in plots treated with 1.4 and 2.8 g a.i./kg, respectively. Moreover, the yield loss was reduced from 80% (untreated plots) to 14 and 7%, respectively. Results indicated that imidacloprid at 2.8 g a.i./kg reduced virus incidence in faba bean plants from 91.6% in untreated plots to 0.0%, when inoculated with BLRV two months after sowing. However, no effect was observed when virus inoculation was done three months after sowing. Moreover, imidacloprid seed treatment significantly improved lentil yield of moderately resistant and susceptible lentil genotypes, but had no effect on the yield of resistant genotypes.