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Effect of Partially Uv-blocking Films on Xanthomonas Axonopoides Pv. Citri Causing Citrus (citrus Aurantifolia) Canker

Abul Hasnat Muhammad Solaiman
Department of Horticulture, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh

Takashi Nishizawa
Faculty of Agriculture, Yamagata University, Tsuruoka, Japan

Shahran Ahmed Nayem
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh

Sayed Mohammad Mohsin
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh

Salahuddin M. Chowdhury
Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh

Abstract/ Executive Summary:

Citrus canker caused by Xanthomonas axonopoides pv citri is currently the most devastating disease impacting world citrus production. An experiment was conducted to testify the hypothesis that partially UV-blocking film has the ability to suppress the development of canker disease of citrus. The quantified variables were latent period of the pathogen, temperature, relative humidity, partially UV-blocking conditions, disease incidence and disease severity. The mini houses were constructed and covered with four types of polyolefin films that have the ability to block solar UV-irradiation shorter than UV-A of (<400 nm), (<360 nm), (<350 nm) and (<340 nm) and the results were compared with UV-transmitting and outdoors. The result showed that the leaves under <400 nm and <360 nm UV-blockings took less time (8 days) to express the symptom than outdoors (13 days). The lowest incidence (66.7%) was recorded in outdoors and highest incidence (100%) was recorded under <400 nm at 45 days after inoculation. Similarly, lowest severity (10%) was recorded in outdoors and the highest severity (43.3%) was recorded under <400 nm at 45 days after inoculation. Disease incidence and severity gradually decreased as the UV blocking rates decreased. Solar radiation with contains combination of different UV-radiation may be detrimental for multiplication of the bacteria Xanthomonas axonopoides pv citri.

Keywords: Citrus canker, Disease management, Incidence and severity, Partially UV-blocking

Location: Plant Disease Diagnostic Laboratory, Department of Plant Pathology, Sher-E-Bangla Agricultural University, Dhaka

Start Date:

End Date:

Program Area: Pest Management

Commodity: Fruit

Objectives:

To investigate the effect of partially UV-blocking films shorter than UV-A on citrus canker disease

Methodology:

Preparation of Mini House: Effect of partially UV-blocking shorter than UV-A on citrus canker was observed during 10 August to 30 September in 2014. Laboratory experiments were conducted in Plant Disease Diagnostic Laboratory, Department of Plant Pathology, Sher-E-Bangla Agricultural University, Dhaka, Bangladesh and field experiments were conducted in the Horticultural farm, Department of Horticulture, Sher-E-Bangla Agricultural University, Dhaka. Fifteen plastic mini houses of 1.8 m × 1.9 m × 0.6 m (L×B×H) with different PO films (0.13-mm thickness) were prepared for experimentation (Plate 1. A). Mini houses were covered with different PO films which can block UV-radiations shorter than 400 nm (<400 nm, T₁), 360 nm (<360 nm, T₂), 350 nm (<350 nm, T₃) and 340 nm (<340 nm, T₄), respectively (PO film collected from Mitsubishi Plastics Agri. Dream, Tokyo, Japan) and the results were compared with that of UV-transmitting (T₅) and outdoors (T₆). A bamboo bench was used above three feet of the soil level for each tunnel to protect soil heat. The first 60 cm (33%) of the tunnel from the soil level remained open to control the heat of the tunnels and allow the invasion by insects. Earthen pots with citrus plants (one year old) were transferred in those mini houses and three plants were put under each tunnel. Measurement of Environmental Conditions: Temperature, humidity, visible and UV-light irradiations were measured in daily basis during the experiment. Both temperature and humidity were recorded at 8:00, 12:00 and 24:00, while visible and UV-light irradiations were measured at 12.00. Cultivation of Citrus Seedling and Inoculation with Bacteria: Citrus seedling (1 year old) collected from Krishibid Nursery, Bangladesh were used for this assay. The seedlings were planted in 25 × 25 cm² earthen pots (one plant pot^-1). Sterile loamy soil and sand (2:1) were used as potting media. Seedlings were irrigated with tap water once a day. There is no additional nutrient was supplied during the study period. Seedlings were inoculated with bacterial suspension (5 μl, OD: 0.5) containing 10⁸ CFU/ml by injection method using 1 ml syringe after 15 days of transplantation. Five leaves of each plant were inoculated. Plants were covered with polythene bag after inoculation for 24 hours to maintain suitable moisture condition. Then the plants were transferred under the UV-blocking films to observe the post inoculation effect of UV-A on citrus canker. Isolation and Identification of the Causal Organism: Leaves were collected from infected citrus (Kagji lebu; C. aurantifolia) field and surface sterilized by 0.1% HgCl₂solution for 30 seconds and then thoroughly washed with distilled water thrice to remove any trace amounts of HgCl₂. The excess moisture was removed by placing these pieces in between two folds of sterilized blotter paper. Then the causal bacterium, Xanthomonas axonopodis pv. citri was isolated using the techniques described by Goszczynska and Serfontein. Colonies of bacteria were purified on NA and SX media plates. The causal organism of citrus canker, Xanthomonas axonopodis pv. citri was identified by following gram’s staining reaction, potassium hydroxide (3% KOH) test, starch hydrolysis test, catalase testand oxidase test. Pathogenicity Test: A bacterial suspension (5 μl, OD: 0.5) containing 108 colony forming units per ml (CFU/ml) was inoculated into the lower surface of citrus leaf with a sterile syringe by injection method and observed for 15 days. Visual symptoms were recorded and examined. To confirm Koch’s postulates, bacteria reisolated from diseased leaves were streaked on NA plate and re-identified using the methods outlined by Lin et al.,.Recording of Data: Data on disease incidence and severity were collected after 15, 30 and 45 days of inoculation. Assessment of disease incidence and severity was calculated using the formula. Experimental Design: The experiment was laid out following randomized complete block design (RCBD) design with three replications. Six treatments were used in the experiment including control. Statistical Analysis: Data were subjected to analysis of variance and significant differences of the means among treatments were analyzed using MSTAT-C software (East Lansing, MI, USA).

Source of Information: World Journal of Agricultural Sciences 11 (4): 202-209, 2015

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Thus, disease incidence and severity increase with high temperature, humidity and low UV intensity and vice-versa. From the findings of this study, it can conclude that higher UV-A Radiations are suitable to avoid canker disease of citrus in tropical and subtropical regions. However, further similar investigations are needed to clarify the individual effect of UV-B against the disease.

Knowledge Management: Journal