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 (5×10 6 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.
A new disease of Cosmos sulphureus Cav. causing external and internal stem discoloration, premature death, and wilting was observed in 27.8% of plants with an average disease severity rating of 4.4 in Gazipur, Bangladesh.Morphological, pathological, and molecular analyses identified the isolated fungus as Sclerotinia sclerotiorum (Lib) de Bary, the causative agent of white rot disease. The optimum growth and sclerotium formation of S. sclerotiorum occurred at 20°C and pH 5.0, while glucose, peptone, yeast extract, casein, and ascorbic acid were the appropriate nutrient sources. Furthermore, mycelial growth and sclerotial development were favored in media containing potassium, magnesium, calcium, and sodium. As many as 20 plant species of 10 families;
The fresh okras were analyzed for proximate composition whereas the developed pickles were analyzed for proximate composition, microbiological status, sensory attributes and overall storage stability of the pickles. The proximate composition fresh okra was moisture 87.5%, ash 0.89%, total solid 18%, vitamin-C 11.1 mg/100g. According to the processing method, the compositions of developed pickles were different. The range of moisture content varied from 59.28% to 69.20% for pickle in sugar, oil and combination of both. Since sugar and salt were used, resulting losses in moisture content were observed in all the samples. Vitamin-C content was decreased or lost by oxidation and heat following first-order kinetics which states that concentration has exponential relationship with time. The microbiological studies revealed that total viable counts (bacteria) were high in pickles which was processed in sugar and low which was processed in oil and oil-sugar mixed, respectively. The acceptability of processed pickles was organoleptically evaluated by the panelists using 1-9 hedonic scale assigned marks for colour, flavour, texture and overall acceptability. The test score indicated that among three samples, the pickle which was processed in sugar and oil mixed (sample-3) was the most acceptable. Storage studies were carried out for up to six months at room temperature (27ºC-33ºC) at an interval of 1 month up to first 2 months and at an interval of 2 months for the consecutive 4 months. The result showed that moisture content decreased slightly with time. All the pickles became softer with the passing of time.
Seasonal abundances of the sucking insects, namely mealy bug, white fly and scale insects, and chewing insect viz., fruit fly was monitored during September, 2016 to June, 2017 in a guava Psidium guajava orchard. Sucking insect was monitored by weekly observation on the leaves and chewing insect was captured using methyl eugenol trap. The mealy bug, white fly and scale insects were abundant during 4th week of November to 4th week of January and they showed fluctuations in their population. The mealy bug, white fly and scale insects had peak abundance in the 1st week of January, 4th week of November and 1st week of December, respectively. The scale insect revealed significantly higher abundance compared to other sucking insects. Two species of fruit fly, namely Bactrocera tryoni and B. dorsalis were found in the guava orchard and B. tryoni showed significantly higher abundance compared to B. dorsalis both in winter and summer seasons. In winter, B. tryoni reached the peak abundance in the 2nd week of January and their peak abundance in summer occurred in the 1st week of May. The daily mean temperature and relative humidity influenced the abundance of the sucking and chewing insects. Temperature individually contributed 30.0, 59.6, 59.3% abundance and temperature with relative humidity had 34.8, 60.9 and 73.5% abundance on mealy bug, white fly and scale insect, respectively. The effect of temperature on the abundance of fruit fly in winter and summer were 42.6 and 50.3%, respectively and the combined effect of temperature with relative humidity were 68.7% in winter and 61.9% in summer. Bangladesh J. Zool. 47(1): 97-105, 2019
An attempt was made for controlling of Rhizoctonia canker caused by Rhizoctonia solani and southern blight caused by Sclerotium rolfsii in pot and field experiments under inoculated condition and also to increase the growth promoting factors and yield of carrot through the application of chitosan. Before setting the experiments in the field, laboratory experiments were carried out to select virulent isolates of R. solani and S. rolfsii and effective dose of chitosan on mycelial growth inhibition of virulent isolates of test pathogens. In the pathogenicity test, R. solani isolate R-1 and S. rolfsii isolate S-1 were found to be the most virulent against carrot seedlings. In vitro application of 1.0% chitosan was found to inhibit 100% mycelial growth of both tested pathogens. The field experiment was laid out following randomized complete block design with four treatments, where no treatment was done in T1, pathogen was inoculated in T2 and seed treatment and soil amendment with 1.0% chitosan was done in T3 and T4, respectively, in pathogen inoculated condition. Application of 1.0% chitosan as seed treatment or soil amendment significantly reduced post-emergence seedling mortality, incidence of diseases and enhanced seedling growth and also yields of carrot. On the contrary, post-emergence seedling mortality, incidence of Rhizoctonia canker and southern blight of carrot were highest in treatment T2 where soil was inoculated with pathogens. Chitosan could be used as an alternative of fungicide to suppress Rhizoctonia canker and southern blight in sustainable agriculture and improvement the yield of carrot.
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