Incidence and Prevalence of Verticillium Wilt of Olives in Jordan

A study of the incidence of Verticillium wilt disease in olive groves and the prevalence of V. dahliae races in the olive major producing regions in Jordan was started in 1997. For the race typing of V. dahliae, three tomato cultivars were used as differential hosts. From irrigated fields, 48% of the samples collected showed Verticillium infections, while only 7.4% of the samples collected from non-irrigated olive groves showed positive fungal isolations. Some olive groves showed symptoms of Verticillium wilt during spring months, but leaf and vascular necrosis was mainly clear in October and November. Both races of V. dahliae were reported for the first time in Jordan. Race 2 appeared in 63% of the total collected isolates, while race 1 constituted 32% among the tested isolates. The ratio of race 2 to race 1 isolates obtained from infected olive fields was nearly 2:1. The highest disease severity was observed in irrigated fields. The proportion of infected petioles sampled from the bottom of tomato plants was greater than that of infected stem segments sampled from the mid part of inoculated seedlings. For precise disease evaluation, isolation must be done from the lower petioles of the infected or inoculated plants. Tomato seedlings cv. AR Tom 001 inoculated with the isolates of V. dahliae race 1 produced no fruits during the whole experimental period. Isolation of the pathogen was successful from fallen olive leaves but unsuccessful from the seed flesh or embryo of olive fruits collected from infected trees