Apples are widely consumed by people all over the world due to their taste and nutritional value. However, apple trees are prone to various environmental stresses, including fungal diseases. Among them, Cytospora canker (or Valsa canker) can cause dieback of branches and twigs. Although Kazakhstan is well known as an origin of apples, very little is known about canker diseases that spread across all commercial orchards. Therefore, an accurate identification of the causal agents of those diseases is needed for further application of informed disease management strategies. In this study, eleven isolates belonging to four Cytospora species were isolated from multiple cultivars, grown in six different orchards within the Almaty region, Kazakhstan. As a result of a multilocus phylogenetic analysis using ITS, LSU and tef1-α marker genes and morphological characterization, these isolates were described as Cytospora parasitica, Cytospora sorbina, Cytospora pruinopsis and Cytospora chrysosperma. Moreover, a pathogenicity test was conducted on detached twigs, and it demonstrated that two of these fungi were highly virulent. Overall, this paper is a first report of the causal agents of apple canker disease in Kazakhstan and could be a trigger for conducting future studies to better understand the disease epidemiology, as well as build management strategies.

Plant viruses can cause substantial yield losses, yet disease severity often varies between seasons because plants frequently experience heat or cold episodes before infection. In this study, we tested whether such temperature conditions affect the plant’s redox balance and alter its response to Tomato bushy stunt virus (TBSV) infection in Nicotiana benthamiana. Plants were exposed to short-term heat and cold stress, after which they recovered before virus inoculation. Following this, we assessed the reactive oxygen species (ROS) content, lipid peroxidation (LPO), oxidative DNA damage, stress-related proteins, redox-associated enzymes, and antioxidant metabolites. TBSV led to non-parallel ROS responses during infection, with consistently elevated hydrogen peroxide in infected plants but reduced superoxide relative to corresponding mock controls. Heat pre-exposure caused pronounced LPO that decreased further after infection, whereas cold pre-exposure stabilized malondialdehyde near levels observed at 25 °C. Both thermal stress and infection increased 8-oxo-dG and were associated with distinct changes in 8-oxoguanine glycosylase abundance. Infection strongly induced heat shock protein 90 (and moderately heat shock protein 70), while prior heat limited further chaperone induction by TBSV. These results indicate that viral infection develops within and is limited by the host’s oxidative state, where redox homeostasis may restrict infection-related processes, and infection leads to changes in this redox environment that are favorable for its development.

This study provides a morphological description of Cytospora spp. isolates collected from apple tree branches affected by Cytospora canker. Cytospora canker is a globally widespread disease caused by highly aggressive pathogens that induce cankers in woody plants within both natural and agro-ecosystems. In severe cases, cankers can lead to the dieback of branches and trees. This article presents the first report of Cytospora sorbina and Cytospora parasitica species identified in intensive apple orchards of Almaty region, Kazakhstan. Notably, the species composition, as well as the morphological and genetic characteristics of Cytospora spp. pathogens causing Cytospora canker in Kazakhstan, remain understudied. Consequently, this study examined the cultural and morphological properties of Cytospora canker pathogens, including determining optimal growth media and temperature conditions for these pathogens. For microbiological analysis, samples were collected from five intensive apple orchards in the Almaty region, yielding 15 fungal isolates from the following apple varieties: Gala, Granny Smith, Golden Delicious, Golden Rush and Fuji. Based on morphological and cultural characteristics, the isolates were identified as Cytospora sorbina and Cytospora parasitica. The results showed optimal growth conditions at 27°C on potato dextrose agar (PDA). This study provides insights into the host-pathogen biological interactions, potentially facilitating improvements in early diagnostics and the development of integrated disease management strategies against Cytospora-related diseases to protect apple orchards.