Apple burrknots involved in trunk canker initiation and dying of young trees

Abstract

Conditions associated with an unusually high occurrence of burrknots in two young commercial apple orchards at two locations, Těšetice and Stošíkovice, South Moravia, the Czech Republic, were analysed. In the first orchard, planted in spring 2003, the occurrence of burrknot on trees of cvs. Early Smith, Jonagold and Gala on M.9 rootstock was evaluated. In the second orchard, planted in autumn 2002, cv. Gala on M.9 rootstock was assessed. Planting material used at each location was obtained from the same commercial propagator and had been established from the same propagation stock materials. Of 60 trees per cultivar surveyed in the first orchard, incidence of burrknots in cvs. Early Smith, Jonagold and Gala trees was 98, 97 and 92%, respectively. The burrknot severity (mean number of burrknots on above portion of rootstock) was significantly higher on Jonagold trees, i.e. 3.65, than on the other two cultivars. Of 60 Gala trees in the second orchard, symptoms of burrknot appeared on 73.3% of trees planted on a slight slope and 70.0% of trees planted on a plane. The burrknot severity was significantly higher on the Gala trees planted in the Těšetice orchard than in the Stošíkovice location. Burrknot incidence and incidence of root-suckers were the highest on Jonagold trees at Těšetice. However, correlations between burrknot number and number of root-suckers were not statistically significant. Five years after the tree planting, increased dying of Jonagold trees was recorded at Těšetice. Of 290 trees examined, 5.5% had died. On the rootstock portion of trunk, each dead tree exhibited burrknots associated with bark cankers that more or less girdled the trunks. Only sporadic occurrence of canker symptoms and no premature dying of young trees were observed at Stošíkovice. Attempts at isolation of the fire blight bacterium, <I>Erwinia amylovora</I>, and oomycete <I>Phytophthora</I> spp. from necrotic tissue surrounding burrknots on rootstocks were not successful. The stem associated apple tree viruses <I>Apple stem pitting virus</I> (ASPV) and <I>Apple stem grooving virus</I> (ASGV) were detected frequently in the rootstock and scion parts of cvs. Jonagold and Early Smith and less frequently in Gala cultivar. The virus positive trees included individuals both with various burrknot severity and without symptoms of burrknots. There were no correlations between the incidence of burrknots and the presence of ASPV and ASGV.

Reaction of selected apple cultivars to wilt pathogen Verticillium dahlia

“…Delicious Anbari, however scions of the other four apple cultivars (Royal Gala, Double Red, Golden Delicious, and Granny Smith) did not show any disease symptoms. Similarly, the stem associated apple tree viruses such as Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV) were detected frequently in the rootstock and scion parts SFW -shoot fresh weight; RFW -root fresh weight; SDW -shoot dry weight; RDW -root dry weight; DS -disease severity (%) *correlation is significant at the 0.05 probability level; **correlation is significant at the 0.01 probability level of Jonagold and Early Smith cultivars and to the lower extent in Gala cultivar (Kůdela et al 2009). Therefore, cv.…”

Advances in fruit crop propagation in Brazil and worldwide-apple trees

“…The occurrence of burrknots is peculiar to the genetic constitution of the cultivar, not being due to infection by biological agents (KUDELA et al, 2009). Rootstocks differ in the sensitivity degree to this disorder, being very marked in MM-111, MM-106, M-7 and M-26.…”

Yield performance of apple rootstocks of the Geneva series on replanting soil

“…In the present study, 1.46 and 1.26 burrknots were present along the tree trunks of M.9 and of the combination Marubakaido/M.9, respectively, which are significantly higher averages than those of the Geneva rootstocks. Studies conducted in the Czech Republic suggested that burrknots on apple tree trunks can restrict the development of the plant, affecting fruit production, and may also facilitate the introduction of canker diseases, which could cause premature tree death (Küdela et al, 2009).…”