Monitoring of <Emphasis Type="Italic">Phytophthora</Emphasis> species on fruit trees in Bulgaria |
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| Authors: | Mariana Nakova |
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| Institution: | (1) Department of Phytopathology, Agricultural University Plovdiv, 12 Mendeleev St., Plovdiv, 4000, Bulgaria |
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| Abstract: | Disease on fruit trees in Bulgaria caused by Phytopthora cactorum and P. citrophthora was found in the period 1998–1999. Leaves of some trees become reddish during July, and later in the season fall off. Infected
trees die during the same season, or the next season. Observations on symptom development and spread of Phytophthora root and crown rot of fruit trees was undertaken from 1999 to 2009. Disease incidence is between 2% and 14% in some gardens
and nurseries. The disease was registered in the regions of Plovdiv, Kjustendil, Sliven, Yambol, Karnobat, Bourgas and Svishtov.
Samples from infected plant tissues were taken and isolations were done on selective PARP media, or by applying a baiting
bioassay. Based on morphological and cultural characteristics and temperature requirements the following Phytophthora species have been identified: Phytophthora cactorum, P. citrophthora, P. drechsleri, P. cryptogea, hybrid and Pythium. Pathogenicity of the isolates was tested on green apple fruits or one-year-old apple rootstocks. Laboratory studies of the
effect of temperature on mycelia growth showed that most isolates can grow from 5° up to 30°C, with an optimum from 18° to
25°C. Only three strains grew at 35–36°C, two developed slowly, one grew well. The optimal pH for mycelia development was
tested. Aiming at control of disease, in vivo pot trials have been carried out for studying resistance of rootstocks to P. cactorum. At the end of the growing season a good level of resistance has been shown in the rootstocks M29C, Gizela 6, and MAXMA 14. |
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