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Chitosan for Plant Growth Promotion and Disease Suppression Against Anthracnose in Chilli

Jahanara Akter
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

Rayhanur Jannat*
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

Md. Motaher Hossain
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

Jalal Uddin Ahmed
Department of Crop Botany, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

Md. Tanbir Rubayet
Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh

Abstract/ Executive Summary:

Chitosan is naturally occurring compound potentially used in sustainable agriculture to control plant diseases and enhance growth. An attempt was made to control anthracnose or ripen fruit rot of chilli caused by Colletotrichum capsici in the field under inoculated condition and to increase the growth and yield of chilli by different concentrations of chitosan as seed treatment and foliar application methods. C. capsici isolate “So” was found to be the most virulent against chilli at the time of pathogenicity test. Chitosan at 1% concentration was found to be most effective against the radial growth of C. capsici. Subsequently, seed treatment or foliar spray was done with C. capsici spore suspension (5×106 ml-1 ) and different concentrations of chitosan as per requirement of the treatments. Anthracnose or ripen fruit rot of chilli and postharvest disease incidence (DI) and percent disease index (PDI) were significantly lowest in the treatment T8, where seeds were treated with 1% chitosan combination with foliar spray of chitosan (0.5%) in pathogen inoculated condition. On the contrary, anthracnose or ripen fruit rot of chilli and post-harvest DI and PDI were significantly highest in the treatment T1, where seeds were treated with C. capsici. Germination percentage, growth promoting components, yield and thousand seed weight (TSW) were also highest in treatment T8 compared to all other treatments. As a result, the combined use of chitosan as seed treatment (1%) and foliar spray (0.5%) appeared to be most effective in controlling anthracnose of chilli and increased yield and yield contributing characters.

Keywords: Anthracnose, Biological control, Chitosan, Colletotrichum capsici, Yield.

Location: Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh

Start Date: 00-03-2016

End Date: 00-08-2017

Program Area: Pest Management

Commodity: Chilli

Objectives:

This study was undertaken to select the most effective dose of chitosan in reducing the mycelial growth of C. capsici and to evaluate the effect of chitosan in controlling the disease and progress growth and yield of chilli.

Methodology:

2.1 Experimental site and materials A field experiment was carried out at Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh, during the period from March 2016 - August 2017. Seeds sample of chilli variety “BARI Morich 3” was collected from the Bangladesh Agricultural Research Institute (BARI), Gazipur, Bangladesh. 2.2 Collection, isolation and identification of C. capsici Three isolates of C. capsici were collected from infected region of chilli fruits following standard phytopathological procedures (Dasgupta, 1981; Agostini and Timmer, 1992). Disease samples were collected from the field and carried to the laboratory in polythene bags. The infected plant parts were cut into small pieces (1 cm2 ) in advance lesion margin where healthy and disease tissues remain together. The cut plant parts and fruit tissues were surface sterilized by 1% sodium hypochloride (NaOCl) solution for 2-3 minutes then washed three times with sterile deionized water to remove the NaOCl. The cut pieces were then placed onto sterilized agar (20 ml) in glass petridishes and incubated at room temperature (25±2 °C ) until acervuli formation. Conidia produced in acervuli came out in the form of ooze and were placed onto PDA and incubated at room temperature for seven days. The fungal pathogen was identified by observing the morphological feature, acervuli formation, presence or absence of setae, cultural and conidial characters under compound microscope (Barneet and Hunter, 1972). 2.3 Preparation of spore suspension Ten days old culture grown on PDA was flooded with 10 ml of sterilized distilled water. Acervuli and conidia along with mycelial mass were separated from the substratum by scrapping with a narrow edge sterilized glass slide (Sharif and Bhuiyan, 2005). The suspension was sieved through double layer cheese cloth to discard acervuli and mycelial mass. The spore suspension was adjusted to 5x106 ml-1 by adding sterilized distilled water and counting under compound microscope using counting slide (haemocytometer). Seeds were submerged in spore suspension with gentle stirring for 5 minutes. The wetted seeds were air dried in a sterile cabinet and prepared for further treatment. 2.4 Pathogenicity test for the selection of virulent isolate of the test pathogen in pot culture Three isolates of C. capsici named as So, Mo and Ba were evaluated for their pathogenicity test in the pot culture experiment under the shade condition. Each earthen pot was filled with 2.0 kg sterilized soil. Twenty-five pieces of chilli seeds for each pot were inoculated with spore suspension of So, Mo and Ba isolate of C. capsici. Then, the inoculated seeds were sown in each pot and in control pot healthy seeds were sown without inoculation. Disease development was observed regularly and recorded at 10 to 20 days after sowing to estimate the effect of pathogens in causing preemergence and post-emergence seedling mortality. The causal agent of seedling mortality was confirmed after reisolation of the pathogen from un-germinated seeds. 2.5 Pathogenicity test of the test pathogen on detached chilli fruit Pathogenicity test with three selected isolates of the pathogen C. capsici was conducted by inoculating harvested chilli fruit. Each isolate of C. capsici was grown on PDA plates separately. Inoculation was made by puncturing the tissue with small sterilized needle and then spore suspension (5×106 spore ml-1 ) of C. capsici sprayed over the chilli fruit. After inoculation, chilli fruits were kept in a separate transparent polyethylene bag to avoid drying. Inoculated chillies were incubated for four days at room temperature. After four days, percent disease index (PDI) was rated following 0-4 scale, where 0=No visible sign or symptoms, 1=1-25%, 2=26-50%, 3=51-75% and 4=76-100% infection on chilli fruits (Abraham et al., 1996). 2.6 Collection of chitosan Chitosan was collected from Bangladesh Atomic Energy Commission (BAEC), Dhaka, Bangladesh. Chitosan was derived from the cover of quick growing sea shrimp. The solution was extracted from sea shrimp and then it was irradiated with γ-ray (20 kD) which acts as a plant growth promoter. 2.7 In-vitro evaluation of chitosan for their inhibitory effect on the radial growth of C. capsici Several preliminary evaluations of chitosan were done with different concentration of chitosan such as 0.4%, 0.6%, 0.8%, 1% and 1.2% on PDA plate against the C. capsici. Plates were individually challenged at the center with equal agar plug (5 mm in diameter) taken from 7 days old culture of the pathogen and incubated at 250C. Mean colony diameter was measured when the control plate (without chitosan) reached full growth. The radial growths of C. capsici in three replications were recorded separately and there averages were taken. The percent inhibition of the radial growth was calculated as described by Sundaret al., (1995).

Source of Information: International Journal of Environment, Agriculture and Biotechnology (IJEAB) Vol-3, Issue-3, May-June- 2018, ISSN: 2456-1878

Article Link (Online Journal): http://dx.doi.org/10.22161/ijeab/3.3.13

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present study showed that seed treatment with 1% chitosan combined with foliar spray of 0.5% chitosan was appeared to be excellent in controlling post-emergence seedling mortality, anthracnose or ripen fruit rot of chilli, post-harvest disease incidence (DI) and percent disease index (PDI) with the significant increase of growth, yield and thousand seed weight. Moreover, Chitosan at 1% concentration completely inhibited the mycelial growth of C. capsici in in vitro evaluation. Growers can adopt eco-friendly control measures against anthracnose or ripen fruit rot of chilli through the seed treatment with 1% chitosan combined with foliar spray of 0.5% chitosan as an alternative to chemical fungicides.

Knowledge Management: Journal