Incidence of and yiel loss caused by maize rayado fino virus in maize cultivars in Ecuador

Description: Three sowing date trials, each planted with one cultivar, were performed to measure the natural in¬cidence of the Maize rayado fino virus (MRFV). The lowest incidences (1-6%) were obtained at the sowing dates normally practised in the tested regions. Earlier or later sowing dates had higher to much higher inci¬dences (up to 18 and 32%). Two cultivar trials, one with four cullivars and one with eight cultivars, showed sig¬nificant differences in incidence, ranging from 14.0% in ‘Iniap-160’ to 2.0% in 'Cadet-2’. In one trial with plots of 1000m2, the cultivar Iniap-122 was sown at three sowing dates. In each plot, plants that developed MRFV symptoms at the 8-10 leaf stage, at the 12-14 leaf stage and at the emergence of tassels were marked. Marked MRFV-al'fected plants were compared with non-MRFV-affected plants in their neighbourhood to estimate yield loss due to MRFV. The yield losses at the three sowing dates were 2.5, 1.6 and 4.8%, respec¬tively. It was concluded that the yield loss due to MRFV is quite small provided sowing is restricted to the nor¬mal sowing period.