Effect of the Site of Infection Source and Some Onion Genotypes on Management of Onion Yellow Dwarf Virus in the River Nile State, Sudan

Abstract

Field experiments were carried out at Hudeiba Research
Station Farm during 2004/ 05 and 2005/06 seasons to evaluate the effect
of the location of infection source on the spread of onion yellow dwarf
virus (OYDV) and to screen 18 onion genotypes for resistance to the
virus. Disease incidence was assessed in blocks of 60 x 6 m planted with
disease-free onion seedlings and located upwind and downwind of the
disease source at distances of 0, 6, 12, 18, 24 and 30 m. Average
incidence of 33.7% and 57.8% was recorded in downwind blocks
compared to 8.0% and 9.9% in upwind blocks, irrespective of the distance
from the disease source, in 2004/05 and 2005/06, respectively. The blocks
located downwind and adjacent to the disease source had the highest
disease incidence of 93.4% and 95.5% compared with 7.8% and 18.9% in
blocks located at a distance of 30 m away from the source during the two
seasons, respectively. In upwind blocks, disease incidence of 15.4% and
20.2% was recorded in blocks adjoining the disease source, while
incidence of 3.7% and 4.85% was recorded in blocks located at a distance
of 30 m in the two seasons, respectively. None of the genotypes tested
was resistant to the OYDV infection; however, Baftaim Red genotype
proved to be tolerant to the virus.