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Effect of Seed Infection Levels and Population Density on Seedling Infection and Incidence of Bipolaris Sorokiniana of Wheat Cv. Shatabdi

F. Begum
Department of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh.

M.N. Islam
Department of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh.

F.M. Aminuzzaman
Department of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh.

M.R. Islam
Department of Plant Pathology, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh.

Abstract/ Executive Summary:

An experiment was conducted during March 2010-April 2011 to find out the influence of seed infection level by Bipolaris sorokiniana and population density on leaf blight development, healthy seed production and yield of wheat, cv. shatabdi. The seed infection level and the population density influenced the pathogenic activities through creating microclimate variability that modify the leaf blight/spot development by Bipolaris sorokiniana of wheat, six different seed infection levels viz.T₁= 0%, T₂ = 5.1-15%, T₃ = 15.1-25%, T₄ = 25.1-35%, T₅ = 35.1-45%, T₆ = 45.1-60% were tested. Using three different method namely blotter method, water agar method and rolled paper towel method the germination percentage, normal seedling percentage and vigor index was maximum at 0% seed infection and minimum at 45.1-60% seed infection. Number of infected seedlings and dead seed was higher at maximum seed infection level and lower at 0% seed infection level. In green house tray method seed germination and vigor index decreased with the increase of seed infection level by Bipolaris sorokiniana. Different seed infection increased the severity of Bipolaris sorokiniana up to 45.1-60% seed infection. Population density and seed infection levels had significant influence on plant growth parameters and yield and yield contributing character. Population density 300 seeds/m² showed best performance in case of grain and straw yield. The highest grain yield (2.64 t/ha) and straw yield (6.87 t/ha) was obtained from 300 seeds/m² population density. The highest grain yield (3.14 t/ha) was also produced from 0% seed infection, whereas, 45.1-60% seed infection produced the lowest grain yield (1.04 t/ha). The highest straw yield was observed with 300 seeds/m² and the lowest from 200 seeds/m². The influence of the development of leaf blight disease of wheat by Bipolaris sorokiniana with increased plant density attributed to favorable microclimate produced in the field condition.

Keywords: Wheat, Leaf blight, Fungi, Bipolaris, Seed infection

Location: Department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka

Start Date: 00-03-2010

End Date: 00-04-2011

Program Area: Seed Technology

Commodity: Fungal Disease, Wheat

Objectives:

To assess the effect of different seed infection level and population density on leaf blight development and yield of wheat.

Methodology:

The experiment was conducted during March 2010 to April 2011 in three steps. At first seed health test was done in the laboratory. Then leaf blight severity was examined in respect to different seed infection level and planting density in the field laboratory of the department of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka and finally seed health study was done after harvesting in the laboratory. Wheat cv. Shatabdi was used in this study were collected from the farm of Sher-e-Bangla Agricultural University. After collection the seeds were kept in a plastic container with air tight lid and the container was stored in normal room temperature in seed pathology laboratory. The seed sample was physically sorted out to prepare different level of seed infection. Six level of seed infection was prepared to assess the development of leaf blight/spot by B. sorokiniana of wheat. At first seed sample was collected and then sorted out of healthy looking seeds with bold golden color separated from black pointed seeds. Then, different level of seed infection was prepared by mixing of healthy seeds and black pointed seeds through laboratory test and counting the infection percentage. T₁ (0.00% infection of seeds) grade was prepared by treating healthy looking seeds with Provax-200. Then T₂, T₃, T₄, T₅ and T₆ seed sample with 5.1-15% seed infection, 15.1-25% seed infection, 25.1-35% seed infection, 35.1-45% seed infection and 45.1-60% seed infection was prepared, respectively, by mixing apparently healthy seeds with different levels of black pointed seed. The collected seed sample was divided into different grade and considered as treatment which has been done by physical sorting of seeds. Six treatments were used in this experiment. These treatments were- T₁= (0% seed infection), T₂= (5.1-15% seed infection), T₃= (15.1-25% seed infection), T₄= (25.1-35% seed infection), T₅= (35.1-45% seed infection) and T₆= (45.1 -60% seed infection). For studying the seed health different methods were used. Incidence of seed borne B. sorokiniana was recorded by using the Blotter method. In this method 3 layers of blotter were soaked in sterilized water and placed at the bottom of the glass petridish. Then 25 seeds were plated on the blotting paper in a petridish maintaining three replications. The petridish were incubated at 25±1°c under 12/12 hrs light and darkness cycle for 7 days. After 7 days of incubation the seeds were observed for the presence of seed-borne pathogen of B. sorokiniana under stereo binocular microscope following the key of Mathur and Kongsdal (2003) (Germination of the seeds was also recorded). The water agar test tube seedling symptom test developed by Khare et al. (1977) was used in the present evaluation. In this technique, test tube slants were prepared by pouring 10 ml of 1% water agar in each test tube (2 cm in diameter and 15 cm in length) and then sterilized in autoclave for 15 minute under 15 Ibs pressure at 121°C. The water agar in the test tube was solidified at an angle of 60° so that the seeds could be placed on the slanted agar conveniently and record of pathogens could be taken easily. One hundred seeds from each treatment were taken and one seed per test tube were placed on solidified water agar slant at the rate of one seed per tube. The seeded tubes were closed with cotton plugs and arranged in plastic racks. The tubes were then incubated at erect condition in an air cooled room (Temp. 22°C) under fluorescent day light tube. The cotton plugs were removed when the seedlings reached the rim of the test tube. Data on germination, number of normal seedlings, number of abnormal seedlings and number of dead seeds were recorded. Seedling infection and seedling vigor test was done in the Rolled Paper Towel Method (Warham 1990). In this method, 400 seeds were randomly taken from each treatment with three replications 50 seeds were placed uniformly between a pair of moist paper towels. The towels were rolled and the two ends were closed with rubber band as the moist could not remove easily. Then the rolled papers containing seeds were placed in an upright position for 7-10 days at room temperature under normal 12/12 light and darkness cycle. After incubation number of normal seedlings, number of abnormal seedlings and number of dead seeds were recorded. The number of normal and abnormal seedlings was recorded to ISTA rules (ISTA 1996). The shoot and root portions were blotted dry with fine tissue paper and fresh weight was taken before the materials could get desiccated. Length of shoot was measured from the base of the stem up to the growing point of the youngest leaf. Similarly, length of root was measured from the starting point of the root to the largest available lateral root apex. Vigor of the seedling was determined by the following formula (Baki and Anderson, 1972). Vigor Index = (Mean of root length + Mean of shoot length) X Seed germination (%). In tray method technique, plastic tray was used to test the germination, infection, dead seed and vigor of seedling in the soil. In this method, 400 seeds were randomly taken from each treatment maintaining there replications. There was 18 number of plastic tray for each treatment. Three tray soil was used to place 400 seeds in every tray. The tray was filled with mixed soil (soil + cow dung + sand) and then treated with formalin spray and covered with polythene sheet for 2 days. After that the soil was opened for five days under the bright sunlight to remove the toxicity of fumigation. Then 5 lines were made in each tray where 80 seeds were sown in each line. After that proper care was taken like irrigation was given properly. After 7-10, days data were recorded on the basis of different parameters. For determination of seedlings vigor, Fifty (50) seedlings were randomly selected from each tray and their individual shoot and root length were measured. Data were recorded on germination percentage, number of healthy seedling, number of infected seedling, number of dead seed, shoot length, root length and seedling weight following ISTA rules (1996) and Vigor index was determined following Baki and Anderson (1972). Two hundred seeds were randomly selected from each harvested samples and incubated for collection of data on germination and incidence of B. sorokiniana following Blotter method (ISTA 1996). The grading of seeds was done following the 0-5 rating scale of CIMMYT (Gilchrist 1985). The rating scale is: 0= Free from infection, 1= Only embryo blackish, 2= Embryo and its adjacent area slightly infected, 3= Embryo and less than ¼ of grains are discolored, 4= Embryo and ½ of grains are infected, 5= Grains are shriveled almost completely discolored or more than ½ of grains are discolored. The recorded data for different parameters were compiled and tabulated in proper form the data were subjected to arcsine transformation when needed. The treatment means were compared by Duncan's Multiple Range Test (DMRT), following Gomez and Gomez (1984).

Source of Information: Int. J. Sustain. Crop Prod. 12(3): 22-30 (November 2017)

Article Link (Online Journal): http://ggfjournals.com/e-journals archive

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The present investigation demonstrated that higher level of Bipolaris infected seed or greater population density can significantly increase the seedling infection and incidence of Bipolaris sorokiniana on wheat cv. shatabdi.

Knowledge Management: Journal