Chitosan is a biodegradable natural compound that has a great potentiality in agriculture for controlling plant diseases. An attempt was made to control Fusarium wilt caused by Fusarium oxysporum f. sp. melongenae under inoculated field condition and increase the growth and yield of brinjal by chitosan. Before setting the experiments in the field, preliminary laboratory experiments were carried out to select virulent isolate and effective dose of chitosan against the mycelial growth of the selected pathogen. F. oxysporum f. sp. melongenae isolate F-1 was found to be the most virulent on brinjal in pathogenicity test. Chitosan @ 1.0% concentration was appeared to be the highest inhibitory to the test pathogen at in vitro condition. Additionally, seed treatment with 1.0% chitosan for 12 hrs resulted in the highest increased in germination and seedling growth of brinjal. The field experiment was conducted following Randomized Complete Block Design (RCBD) with four treatments. No treatment was given in T1, the pathogen was inoculated in T2 and seed treatment and soil amendment with 1.0% chitosan was done in T3 and T4, respectively, in test pathogen inoculated condition. Application of 1.0% chitosan as a seed treatment (T3) or soil amendment (T4) significantly reduced pre- and post-emergence seedling mortality, incidence and severity of Fusarium wilt as well as enhanced germination percentage, plant growth and yield of brinjal. On the contrary, pre-emergence and post-emergence seedling mortality, disease incidence and severity of Fusarium wilt were highest in treatment T2 where the soil was inoculated with pathogen without chitosan. Therefore, chitosan could be used against this vascular disease as an alternative to inorganic fungicides and augment yield.

Rhizoctonia crown rot and canker caused by Rhizoctonia solani and southern blight caused by Sclerotium rolfsii are the two main devastating diseases that hamper carrot production greatly in Bangladesh. Indiscriminate use of chemical fungicides in controlling the pathogens also pollutes the environment, so an alternative bio-control agent was used to control the diseases. In the pathogenicity test, R-1 isolate of R. solani and S-1 isolate of S. rolfsii were found to be the most virulent against carrot seedlings and harvested carrots. T. harzianum isolate Pb-7 was appeared to be the most effective antagonist in the preliminary screening against both the selected pathogens. The field experiment was laid out following randomized complete block design with five treatments and three replications. In pathogen inoculated fields, 200g and 400g wheat grain colonized Trichoderma fortified compost, composted poultry refuges were mixed in the soil as per treatment before sowing carrot seeds. Pre- and post-emergence seedling mortality, incidence of Rhizoctonia crown rot and canker, and southern blight of carrot reduced significantly in treatments where soil was amended by wheat grain colonized Trichoderma fortified compost. On the contrary, pre- and post-emergence seedling mortality, incidence of Rhizoctonia crown rot and canker and southern blight of carrot was highest in pathogen inoculated fields. Trichoderma fortified compost enhanced germination percentage, growth promoting factors, yield and yield contributing components. The concentration of 400g wheat grain colonized Trichoderma fortified compost can be a suitable alternative to chemical fungicides used against these two devastating diseases of carrot.

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.DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16777 Progress. Agric. 21(1 & 2): 215 - 222, 2010

Rhizoctonia stem canker and black scurf of potato are the most prevalent and widespread soil-borne fungal diseases that cause notable reduction in the yield of potato globally. The purpose of the current study was to assess the effect of both Curtobacterium citreum and chitosan, either alone or in combination, on the prevention of potato Rhizoctonia diseases and its growth-promoting characteristics. The antagonistic capability of the endophytic bacteria C. citreum PLPL and chitosan against R. solani was evaluated and got potential responses. Following that, compatibility tests between C. citreum and chitosan were conducted, revealing compatibility between the natural agents. Prior to sowing, seed tubers were treated with C. citreum (108 colony forming units per mililiter) and chitosan at 1.0 % concentration. In comparison to pathogen-inoculated plots, all individual and combined treatments increased growth and yield while reducing disease incidence and severity. The combination of C. citreum and chitosan resulted in the significant reduction in disease incidence (79.95% for stem canker and 65.53% for black scurf) and percent disease index (85.14% for stem canker and 66.00% for black scurf) over the pathogen-inoculated plot. The combination of C. citreum with chitosan resulted in a maximum yield of 43.15 t/ha, with all growth parameters significantly increased. In addition to increasing potato yield, treating tubers with a combination of C. citreum and chitosan may be a sustainable and environment friendly method of managing stem canker and black scurf diseases. Ann. Bangladesh Agric. 28(2): 71-87

Rice blast caused by Pyricularia oryzae (syn. Magnaporthe oryzae) is one of the most devastating diseases in rice, resulting in substantial yield loss. Currently, the control of rice blast relies significantly on chemical fungicides, which raise numerous environmental concerns. However, silver nanoparticles (AgNPs) are emerging as innovative, non-resistant substitutes for conventional fungicides. This study aimed to synthesize AgNPs from banana flowers via a green approach and assess their antifungal activity against Pyricularia oryzae strain SP2 in vitro. The pathogen Pyricularia oryzae strain SP2 was identified by morphological features and study of the internal transcribed spacer (ITS) sequence. The AgNPs were characterized via UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive x-ray analysis (EDX). The optimal reaction conditions for the green synthesis of the AgNPs resulted in a rapid color change from light yellow to dark brown when the floral extract (15 ml) was added. A surface plasmon resonance peak was observed in the UV-visible spectrum at approximately 433 cm⁻¹, which was correlated with the synthesis of the AgNPs. The biogenic AgNPs had a spherical form with an average particle size of 47.63 nm, according to TEM and SEM examination. The greatest mycelial growth inhibition of P. oryzae (87.25%) was observed when it was exposed to biofabricated AgNPs at 40 μg ml⁻¹. The AgNPs successfully suppressed spore germination and germ tube development of P. oryzae, with increased doses demonstrating enhanced antifungal efficacy. Additionally, the appressorium formation rates decreased from 78.34% in the control to 41.67%, 16.45%, and 4% at increasing concentrations (20, 30, 40 μg ml⁻¹). Overall, this study demonstrated that bioinspired AgNPs have antifungal activity against the rice blast pathogen P. oryzae and can be used to control blast diseases in rice.