Monitoring of Phytophthora species on fruit trees in Bulgaria

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 oneyear-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.

Pathogenicity, Fungicide Resistance, and Genetic Variability ofPhytophthora rubiIsolates from Raspberry (Rubus idaeus) in the Western United States

“…When directly comparing all three isolation methods, direct cane isolation proved the most successful and least labor intensive method; more Phytophthora isolates were isolated using the direct cane method compared to root isolation or soil baiting. Cane isolation has also been used for the isolation of several Phytophthora species that cause root rot in woody plant/tree species, such as P. lateralis on Chamaecyparis lawsoniana (8), P. gonapodyides and P. lacustris isolated from Alder (Alnus glutinosa) (25), and P. cactorum and P. citrophthora on fruit trees in Bulgaria (24). Isolating directly from the cane is a simple and clean method that would be useful for other soilborne Phytophthora species where root lesions lead up to the crown root or cane/stem.…”

Effects of some commercial products on root and crown rot caused by Phytophthora cactorum in apple cultivation

“…However, Phytophthora species are among the most destructive soil-borne pathogens causing economic losses in orchards in fruit production (Erwin and Ribeiro 1996;Sánchez et al 2019). For example, in Bulgaria, it was reported that Phytophthora species caused drying the plants up to 10% in some orchards (Nakova 2010), while they caused considerable losses, 2.5 -24.5% death in nurseries and 0.2 -77.5% in apple orchards in India (Sharma et al 2014). Among Phytophthora species, Phytophthora cactorum (Lebert & John) Schröeter is the most frequently reported species in apple-growing regions (Jones and Aldwinckle 1997;Ebrahimzadeh and Dolar 2019).…”

Pathocomplex of root rot of apple tree in nurseries and young orchards of the South of Russia

“…This disease affects many fruit and berry crops: apple, pear, plum, peach, apricot, cherry, strawberry, etc. [1][2][3][4][5][6][7][8]. The causative agents of root rot are obligate and facultative pathogens, some of which become xylotrophs when the tree dies; as a result of pathogenesis, roots rot, the wood turns brown and cracks, the bark turns black, the branches weaken, the leaves turn yellow and crumble, the plant stops fruiting and eventually dies [9][10].…”

“…Depending on the conditions of humidity, air temperature, illumination and the predecessor in the crop rotation, seedlings and young plants of fruit crops are affected by such root rot pathogens as Rhizoctonia solani Kühn (teleomorph: Thanatephorus cucumeris) [11,12], species from genus Pythium Pringsheim [6,11,13], Cylindrocarpon Wollenw [14], Fusarium Link [10,11,15] and Phytophthora de Bary [6,7,8,9]. Pythiosis, late blight, fusarium, rhizoctonia, the prevalence of which can vary from 10 to 100 %, weaken the root system, affect the development of plants, and can cause their complete death [1].…”