Irrigated hybrid maize crop yield losses due to barley yellow dwarf virus-PAV luteovirus

PAV, one of the luteoviruses inducing the barley yellow dwarf disease, grea tly reduces yield of cereal crops and has been reported to cause reddening in several varieties of maize (Zea may's L.). However, there have been no r eports that the virus causes significant reductions in size or yield of irr igated maize. Trials to assess the effect of PAV on maize fields were condu cted for 3 yr with two hybrids ('Dea' and 'Nobilis') and two isolates of PA V (2t and L14), These two isolates differed in geographic origin and virule nce on barley (Hordeum vulgare L.), but they multiplied similarly to wild i solates in leaves of maize hybrids. The virus was detected in maize leaves during the same period after inoculation in two out of three Sears. The rea son for low le,els of virus in leaves in the 1996 season may have been high temperatures (>30 degrees C) following inoculation. Under these renditions , the virus was restricted to the roots for long periods. This blocking of virus migration and/or foliar multiplication was accompanied bg less redden ing. and there was almost no decrease in grain yield. High early leaf infec tion of the virus had little effect on the vegetative development of the hy brids (<10% reduction in plant height), but grain yield was between 15 and 20% lower for a production of 10 to 12 t ha(-1). This drop in yield was due to fewer kernels of maize per ear, while the 1000 kernel mass was unaffect ed. The loss in yield was not affected by either the virus isolate or the m aize hybrid, although the intensity of symptoms differed between hybrids. T he data show that there are potential losses incurred by PAV on maize yield . Therefore, these findings justify the establishment of a breeding program .