First Report of Puccinia thaliae Causing leaf rust on Canna indica in Malaysia

Canna indica L. (family Cannaceae), locally known as Bunga Kana, is a perennial plant grown as a source of starch and for ornamental purposes in Malaysia. During June 2021, Bunga Kana with rust symptoms and signs were collected from the Universiti Malaysia Sabah in the province of Sabah. The severity was 95%, and the incidence was 90%. Yellow uredinia were observed primarily on the abaxial surface of the leaves. As the disease progressed, leaves were covered with coalescing pustules, and chlorosis and brown necrosis developed. Microscopic examination of pustules revealed the presence of urediniospores and teliospores. Urediniospores were round to ovoid in shape, yellow, and echinulate, 17.7 to 24.6 x 26.8 to 45.2 μm, with two equatorial pores. Teliospores were elongate-clavate, with rounded apex, yellow contents, 18.3 x 20.2 to 45.8 x 53.9 μm, with a short pedicel. Yellow urediniospores were collected using a fine brush, and genomic DNA was extracted using lysis buffer [Tris-HCl (0.1M, pH 9.5), NaCl (1M), EDTA (0.5M, pH 8)] prior to heating at 95°C for 10 min. KOD One PCR master mix containing hot-start modified KOD DNA polymerase was used for PCR amplification. The 28S ribosomal RNA gene was amplified using primers Rust28SF (Aime et al. 2018) and LR5 (Vilgalys and Hester 1990). BLASTn analysis of the newly generated 28S ribosomal RNA gene (OK462969) in GenBank revealed a 99% sequence identity to Puccinia thaliae Dietel (JX206994 of 28S ribosomal RNA gene). The morphological and molecular characterization of the rust fungus matched P. thaliae described by Padamsee and McKenzie (2012). Koch's postulates were performed with spray inoculations of urediniospores suspended in water (106 spores/ml) on leaves of three healthy Bunga Kana plants, while water was sprayed on three additional Bunga Kana plants which served as control. The inoculated Bunga Kana plants were covered with plastics for 48 h at 25°C in the dark, and then placed in the greenhouse. Symptoms and signs similar to those of the field collection occurred after 13 days post inoculation. No symptoms occurred on controls. Leaf rust on Bunga Kana plants caused by P. thaliae has been reported in Europe (Talhinhas et al. 2016), Hawaii (Nelson 2013), India (Gopi et al. 2014), Mexico (Cedas de Jesús et al. 2018), Nepal (Adhikari and Durrieu 2016), New Zealand (Padamsee and McKenzie 2012), Singapore (Neo and Tham 2010) and South Africa (van Jaarsveld et al. 2006) over the past fifteen years. To our knowledge, this is the first report of P. thaliae causing leaf rust on C. indica in Malaysia. Our findings expand the geographic range of P. thaliae and indicate it could be a potential threat limiting the starch production of C. indica in Malaysia.

Performance Evaluation of Laboratory Scale Vegetated Vermifilter for Domestic Wastewater

Locally as well as globally, the Collection and treatment of wastewater are seen to have an impact on the environment and economy in one way or the other. Designing a system that minimizes this effect to the best possible scenario is of paramount importance, adding to greater sustainability in terms of economic, environmental, and social terms. The solutions such as on-site treatment of wastewater, local recycling, and reuse of resources contained in domestic wastewater (predominantly water itself) can be best summed up as Decentralized treatment of sewage which appears to be a coherent solution to address sustainability. Vermifiltration is a low-cost aerobic decentralized wastewater treatment option. Two lab-scale vertical flow filters are designed in this project, with both being assisted by Canna indica (MAVF), but only one introduced with Eisenia fetida. The experimental phase continued for 5 weeks with a hydraulic loading rate of 0.14 m3 m -2 day-1 with an acclimatization period of 15 days. The results depicted that MAVF has a better organic degradation capacity than the one without earthworms alone. The quality of wastewater is determined by Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) to a great extent. Removal efficiencies of COD were 67 % for MAVF and 55 % for MAF, while for BOD, it was 80 % for MAVF and 69 % for MAF, respectively. The BOD and COD tests were assisted by other parameters like pH, and turbidity. Keywords: Domestic wastewater, Decentralized treatment, Aerobic treatment, Macrophyte Assisted Vermifilter (MAVF), Macrophyte Assisted Filter (MAF), Sustainability, Low-Cost Treatment, Canna Indica, Eisenia Fetida

Effects of Supplemental Cations on Growth and Nitrogen Accumulation in Canna indica L.

The effects of supplemental cations on growth, nitrogen, and mineral accumulation were assessed in Canna indica L. Similar sized 45 days-old plants were grown on a nutrient solution modified from Hoagland and Arnon (1950). The different cations were added to generate 6 treatments (n=4): (i) control (no cation added), (ii) 2.5 mM K+, (iii) 2.5 mM Ca2+, (iv) 75 mM Na+, (v) 1.25 mM K+ + 1.25 mM Ca2+ and (vi) 2.5 mM Ca2+ + 75 mM Na+, respectively. An experiment was carried out in the greenhouse for 49 days. The study found that supplemental K+ and K++ Ca2+ increased plant growth and total biomass. The highest SER was found in plants receiving supplemental K+. In contrast, SERs, leaf areas, and total biomass decreased in Na+ or Na++Ca2+ supplemented plants. The accumulated NO3- concentration (at the whole plant level) was also highest in the plants with supplemental K+ and K++Ca2+. The total nitrogen accumulation was higher in the K+, Ca2+, and K++Ca2+ supplemented plants than in the control plants. The results suggest that supplemental cations particularly K+ can enhance plant growth and nitrogen accumulation in C. indica. Therefore, cation supplementation could be an alternative technique to stimulate plant growth and improve nitrate removal in constructed wetlands. Keywords: Constructed wetland, Nitrate removal, Potassium, Tropical wetland plants

Effects of Dissolved O2 and Fe Availability on Growth, Morphology, Aerenchyma Formation and Radial Oxygen Loss of Canna indica L. and Heliconia psittacorum L.f.

In constructed wetlands (CWs), plants are usually affected by low O2 levels. Under such conditions, most soluble iron is reduced to ferrous (Fe2+) which is highly soluble, and toxic to plants as well. As a consequence of excessive ferrous iron with low O2 supply, plant growth is reduced, leading to declining nutrient removal efficiency. This study was conducted to determine the effects of different dissolved oxygen levels (normoxia and hypoxia) with Fe supplied on growth, morphology, and root anatomy of two wetland plants (Canna indica and Heliconia psittacorum). The plants were grown on a nutrient solution modified from Smart and Barko (1985) under normoxic and hypoxic conditions. All plants were grown in greenhouse conditions for 42 days. Plant growth rates and biomass accumulation were drastically reduced under hypoxia while leaf number was not affected. Under hypoxia, root diameter and root porosity also increased in C. indica, whereas H. psittacorum had greater aerenchyma formation. Moreover, C. indica showed adaptive traits to cope with hypoxia and Fe stress by increasing radial oxygen loss (ROL), releasing O2 to the rhizosphere to resist toxic effects of ferrous iron under hypoxia. In contrast, H. psittacorum had no ROL under hypoxia. Moreover, the plants showed leaf chlorosis, leaf roll, and root rotting. Hence, it is suggested that C. indica could have better performance than H. psittacorum to treat wastewater in CWs as this species can adapt to hypoxic conditions and releases O2 into rhizosphere which improves dissolved oxygen (DO) in the wastewater. Keywords: Aerenchyma, Dissolved oxygen, Iron, Root porosity, Wetland emergent plant

Effects of Light Environments on Leaf Traits and Phenotypic Plasticity of Canna indica

Canna indica L (African arrowroot), is a beneficial, multi-use tropical perennial with a worldwide distribution, but relatively unexplored. This plant has the potential to be developed as a food crop in an intercropping system, utilizing idle land under commercial plantations such as rubber or teak. This study aimed to determine the best light-growing conditions for C. indica. A completely randomized design was used with growth light as the treatment consisting of 25%, 50%, and 100% of natural light, respectively. Leaf traits, growth characteristics, and phenotypic plasticity were used to measure C. indica’s response to different treatments. The results of this study showed that C. indica grown in low light has the best growth with increased height, leaf area, root and shoot dry weights, but decreased leaf thickness, which caused the increase in specific leaf area, leaf area ratio, and leaf weight ratio, but decreased root to shoot ratio. Based on leaf traits and biomass allocation, the phenotypic plasticity index was 0.23, a typical number for shade tolerant species. These findings were the first time to be reported for C. indica. For agroforestry practices, it can be recommended that C. indica be used as an intercropping plant under tree canopies.