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Terminal shoot susceptibility of new Polish apple cultigens to fire blight

Piotr Sobiczewski, Edward Żurawicz, Stanisław Berczyński, Mariusz Lewandowski

Research Institute of Pomology and Floriculture
Pomologiczna 18, 96-100 Skierniewice, Poland
e-mail: psobicz@insad.pl

In 2000-2001 the following apple cultivars and clones, bred at Research Institute of Pomology and Floriculture in Skierniewice, Poland (grafted on M.9 and P 22 rootstocks), were evaluated: ‘Early Freegold’, ‘Egeria’, ‘Free Redstar’, ‘Ligol’, ‘Ligolina’, ‘Medea’, ‘Melfree’, ‘Odra’, D-13, and J-79. ‘Freedom’ and ‘Florina’ were included as standards. Tips of terminal shoots of young trees growing in pots in a greenhouse, were inoculated with a highly virulent strain (Ea 691) of E. amylovora (107 cfu ml-1). Observations and measurements of the development and severity of fire blight, performed 6 weeks after inoculation, showed that ‘Free Redstar’ and J-79 on the P 22 rootstock appeared to be the most resistant, while ‘Egeria’, ‘Ligol’, and ‘Ligolina’ were the most susceptible. Also on M.9 ‘Free Redstar’ and J-79 showed the lowest susceptibility among the evaluated cultigens while ‘Ligolina’ was the most susceptible. These findings corresponded to the distribution of the tested trees amongst 5 susceptibility classes. 40-46.7% of the individuals of ‘Free Redstar’ on both rootstocks and 80% of J-79 on P 22 were classified as susceptibility class 1 (the most resistant). On the other hand, none of ‘Ligol’ on P 22 and ‘Ligolina’ on M.9 and only 6.7% of ‘Ligolina’ on P 22 trees belonged to that class.

Sobiczewski P., Żurawicz E., Berczyński S., Lewandowski M., 2004. Terminal shoot susceptibility of new Polish apple cultigens to fire blight. Folia Horticulturae 16/2: 149-157.