Ashok Kumar Misra

Biocontrol potential of Trichoderma species against mango malformation pathogens

Malformation disease of Mango (Mangifera indica L.) caused by Fusarium moniliforme var. subglutinans is one of the most destructive diseases, which is a major production constraint in the mango-growing regions of India. In this study, The bioagents Trichoderma viride (Tr1), Trichoderma virens (Tr2) and Trichoderma harzianum (Tr3) were evaluated in culture with the pathogens to monitor the antagonistic effect and their volatile compound and culture filtrates (non-volatile compound). It was found that all the three isolates of bioagents significantly checked the growth of F. moniliforme var. subglutinans. In dual culture, the best result was obtained with T. harzianum followed by T. virens and T. viride. A similar result was also observed in the case of culture filtrates ofTrichoderma spp. The results clearly showed that inhibition of the growth of the fusaria isolates by T. harzianum was significantly superior to T. viride andT.virens. In case of antifungal activity of volatile compounds released by Trichoderma isolates, it was also observed that T. virens was more superior to T.harzianum and T. viride.

Fusarium chlamydosporum, causing wilt disease of guava (Psidium guajava L.) in India

Wilt is a serious disease of guava crop in India. Fusarium oxysporum f. sp. psidii and F. solani have been reported as the main causative agents of this disease. Most recently a survey on guava plants affected with wilt disease was conducted in severely affected areas of India, and two new species of Fusarium viz. Fusarium proliferatum and Fusarium chlamydosporum were found to be associated with this disease. However, pathogenecity of Fusarium chlamydosporum was successfully conducted in the field trials. The culture of F. chlamydosporum was processed for DNA sequencing and DNA sequence was submitted to NCBI with GenBank accession no. HM102506. The submitted DNA sequence of F. chlamydosporum was compared for the genetic position in Fusarium spp. evolutionary phylogenic tree.

Histological changes in guava root during wilting induced by Fusarium spp.

Wilt is the most destructive disease of guava in India. Fusarium oxysporum f. sp. psidii and Fusarium solani are reported as most commonly isolated pathogens and are considered to be associated singly or in combination with roots of wilt affected plants of guava (Psidium guajava L.). Histopathological observations were made of the roots of wilt affected guava plants in the present investigation. The observations of wilted guava root showed disintegration/necrosis of the epidermal tissue, cortex tissue and vascular bundle cells. In T.S. of root of wilted plant the normal shape of the epidermis was disrupted and there was breaking and opening in the epidermis through which pathogen may enter in the host tissue. Necrosis of the internal tissue and vascular bundle restricts the movement of water and nutrient and thus results wilting.

Challenges in Dewatering of Indian Medium Coking Coals: Case Studies with Chemical Reagents

At the West Bokaro Washery of Tata Steel, India, the coarse coal is dewatered in a vibrating basket centrifuge and fine clean coal is dewatered in a screen bowl centrifuge. Due to the higher amount of fine fraction (0.038 mm) treated in the flotation circuit of the washery (about 9% of ROM), the moisture content of the clean coal fines is high. A polyacrylate surfactant reduced the fine coal moisture content by 8% and it was found to be the best among the various reagents tested in the laboratory. The chemical was found very effective for dewatering the coarse clean coal. Laboratory and plant trials showed that through treating only the coarse clean coal by the surfactant, the moisture in the composite clean coal could be reduced from 12.0% to 9.8%. The optimum dosage of the reagent was 0.24 kg/t dry coal. Laboratory-scale filtration using coagulant and surfactant increased filtration rate of centrifuge centrate. Also, the final moisture content was found to be 10% less than that obtained without addition of any reagents. For improving the clarity of thickener overflow, anionic polyacrylate based flocculant was found better than present plant flocculant based on polyamide. The optimum dosage of the recommended flocculant was 0.012–0.016 kg/t of dry fine coal.

Current Scenario of Mango Malformation and Its Management Strategies: An Overview

Malformation disease caused by the Fusarium species complex results in significant economic losses in the yield, production and export quality mango in tropical and subtropical mango growing countries. The disease is widespread in flowers and vegetative shoots of mango. It has a crippling effect on mango production, bringing in heavy economic losses. In spite of the highest area and production of mango in the world, the mango productivity is very low. This is because of the several abiotic and biotic factors, of which malformation is one of the most important problems. Early diagnosis of the pathogens and proper management strategies will help cultivators to protect the mango orchid and fruits from successive and secondary infection. The latent infection of budwood is common; a treatment that would eliminate the pathogen from budwood would be invaluable. In current chapter we give an overview on mango malformation disease, symptomology, epidemiology, molecular diversity and disease management strategies to control the pathogen and its incidence.

A REACTION–DIFFUSION MODEL FOR THE CONTROL OF CHOLERA EPIDEMIC

Understanding the spatio-temporal dynamics of cholera outbreaks may help in devising more effective control procedures. In this paper, we have considered a reaction–diffusion system for biological control of cholera epidemic. Firstly, we have focused on temporal evolution of cholera in a region and its control using lytic bacteriophage in the aquatic reservoirs. Then, we have explored the effect of spatial dispersion of populations on the disease dynamics. We have observed the onset of sustained oscillations via Hopf-bifurcation for the endemic state of temporal system. This onset of fluctuations in populations depends upon the phage adsorption rate. But in the spatially extended setting, all the populations stabilize i.e., the spatio-temporal distribution of all the populations becomes uniform. Some numerical computations have been done to verify analytical results.

Hisopathological Study of Healthy and Malformed Tissues of Mango (Mangifera indica L.)

Malformation is a serious threat to mango production in India and other mango growing countries (tropical and subtropical) of the world. The disease is widespread in flowers and vegetative shoots. It has a crippling effect on mango production causing heavy economic losses. Mango Malformation Disease is a fungal disease caused by Fusarium moniliforme var. subglutinans. Symptoms of the disease include loss of the apical dominance and swelling of vegetative buds, proliferation of leaves and flowers, phyllody and hypertrophy of panicle axes. Histopathological observations of malformed shoots and penical reveal occasional inter-and intracellular distribution of fungal hyphae in cortex, phloem and parenchymatous pith cell. Fungal mycelium has also been detected at the juncture of the shoot tip in malformed axillary buds, axes of petels and sepals of malformed buds, and in the degenerating embryos of mustard stage malformed fruits.