Anatomical Alterations and Management Strategies of Diplocarpon rosae Infection in Rosa centifolia

Abstract

Black spot caused by Diplocarpon rosae is a serious issue of rose. Current study was conceived to assess antifungal potency of five different phyto-extracts including Cinnamon, Turmeric, Black pepper, Ginger and Aloe vera against D. rosae under laboratory and in planta conditions. All the phyto-extracts were evaluated at three concentrations under completely randomized design (CRD) with three replications of each treatments under laboratory conditions. However, the most effective treatments (cinnamon and turmeric) under lab conditions were further examined in planta against black spot of rose. The results revealed that, cinnamon was the most effective treatment against D. rosae under lab conditions with least mycelial growth (4.61 mm) followed by Turmeric (6.50 mm), Black pepper (7.24 mm), Ginger (8.06 mm) and Aloe vera (7.60 mm). While, the combined application of cinnamon and turmeric exhibited least disease incidence (32.63%) under in-vivo conditions. Being an airborne pathogen, D. rosae affects the anatomy of the infected tissues. So, the contemporary study was designed to investigate the anatomical alterations including Midrib thickness (MIT) (µm), Vascular bundle area (VBA) (µm²), Adaxial epidermal thickness (ADET) (µm), Abaxial epidermal thickness (ABET) (µm) and Parenchymatous cell area (PCA) (µm²) of rose leaf cells infected with D. rosae. The analysis was comprised of three main targets such as among healthy & infected, treated & untreated and at different inoculation stages of rose leaf cells. The samples of rose plants were gathered from Horticulture Area of UAF. Following typical anatomical procedures, the leaf samples were examined under digital compound microscope. All the observations exposed that there was no abnormality found in healthy leaf sample, while the infected sample showed an expanded MIT, ruptured ABET, sclerified ADET, decreased VBA and larger PCAs. Furthermore, at different inoculation stages the MIT was found expanded in all three stages, PCAs began increased in size and VBA become shrunk in second stage of inoculation. While after treatment with cinnamon and turmeric alone and in combination, the anatomical observation showed that combination of cinnamon and turmeric exhibited positive effect on normalizing the measurements of investigated parameters, whereas individual application of turmeric only reduced PCAs to normal size.