Screening of lentil genotypes for resistance to Bean yellow mosaic virus and effect of mixed infection on the susceptibility of some resistant lentil genotypes

A total of 100 lentil genotypes were evaluated for their reaction to a Syrian isolate (SV205-85) of Bean yellow mosaic virus (BYMV, genus Potyvirus, family Potyviridae) under field conditions during 2010/2011 growing season. All plants were inoculated mechanically before flowering stage and selection of resistance was based on: (i) visual symptoms incidence and severity, and (ii) virus movement in the plant tissues based on tissue-blot immunoassay (TBIA) test. Only one genotype (ILL1949) was highly resistant to BYMV and another three (ILL518, ILL1935 and ILL7470) were found resistant. Sixteen lentil genotypes with different levels of susceptibility to BYMV were selected to study the effect of mixed virus infection of BYMV and Faba bean necrotic yellows virus (FBNYV, genus Nanovirus, family Nanoviridae) under plastic house conditions. All plants studied were inoculated mechanically with BYMV followed by FBNYV using viruliferous pea aphids (Acyrthosiphon pisum Harris), and were tested 28 days after inoculation by TBIA. Serological results showed that inoculation with FBNYV did not alter the resistance to BYMV of two lentil resistant genotypes (ILL518 and ILL5005), whereas inoculation with FBNYV increased the susceptibility to BYMV in three lentil genotypes (ILL336, ILL4736 and ILL1949). Three genotypes (ILL74, ILL75 and ILL213) were found highly resistant to BYMV and FBNYV with single virus infection and became moderately resistant to BYMV and resistant to FBNYV following mixed virus infection.