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20162
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End date: 2016 × Start date: 2016 × Type: Thesis × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    OCCURRENCE AND DISTRIBUTION OF ROOT-KNOT NEMATODE Meloidogyne incognita IN PATCHOULI Pogostemon cablin
    (AAU, Jorhat, 2016-07) Buragohain, Pallab; Gogoi, B.B.
    Patchouli [Pogostemon cablin (Blanco)] is an important aromatic plant belonging to family Lamiaceae, is a native of Philippines (Arpana et al., 2008). It is grown wild in Malaysia, Indonesia, Singapore and few other countries. Owing to high demand of its essential oil many countries have domesticated this crop. It has multiple uses, it is used in cosmetics, breath fresheners, flavouring baked foods, meat, sausages, etc. Patchouli is very susceptible to root -knot nematode and wilt causing pathogens. In moist and wet weather condition root knot infestation is high in plants which may lead to wilting of plant and kill the plant within 2-3 days due to secondary infection by fungal and bacterial pathogens. The study on “Occurrence and distribution of root-knot nematode Meloidogyne incognita in patchouli Pogostemon cablin” was carried out in the year 2014 -2016, in Golaghat, Nagaon, Jorhat and Sonitpur districts by conducting a survey programme. A total of 123 samples were collected randomly from the four districts. Root-knot infestation was recorded in most of the fields covering the four districts. Root and soil samples were found to be heavily infested by root-knot nematode. The maximum frequency was recorded in Nagaon districts i.e. 38.88 per cent whereas minimum frequency of 21.87 per cent was recorded in Golaghat district. Many fungal pathogens were found to be associated with most of the root-knot infested plants. In the present investigation, three fungal pathogens were found to be associated with root-knot infested plants. They are Fusarium sp., Rhizoctonia solani and Cercospora sp. It has been observed that the patchouli plants are also infested by different insect pests like leaf roller and grass hopper. These insect pests are voracious eater and almost eat up the green foliage leading to defoliation and heavy yield loss.
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    ThesisItemOpen Access
    Characterization and Identification of Potential Probiotic Lactic Acid Bacteria (LAB) Isolated from Fermented Dairy Product of Assam (Doi)
    (AAU, Jorhat, 2016-07) FATMA, JAIBA; Barooah, M.
    Probiotics are the health promoting viable microorganisms that exhibit a beneficial effect on the health of human being by improving the intestinal microbial balance. Lactic acid bacteria (LAB) are important and well known agents. Fermented milk products like Dahi are known source of probiotic organisms. In the present study, LAB was isolated from 25 different ‘Doi’ samples collected from 8 different districts of Assam viz, Tinsukia, Dibrugarh, Sivsagar, Jorhat, Lakhimpur, Udalguri, Morigaon and Bongaigaon. A total of 30 bacteria were isolated initially but only 20 bacteria isolated from Doi meet the classification of LAB as Gram-positive and catalase negative (Salminen et al., 1993). These 20 LAB isolates were characterized based on their phenotypic, biochemical and molecular characteristics. Further, the isolates were screened for their potential probiotic properties based on conditions simulating human gastrointestinal tract (GI). These isolates were able to survive at low pH 2.5 which is similar to the pH of the human GI tract and able to convert lactose into lactic acid. Further studies revealed that these isolates were able to grow in a temperature ranging from 15-40ºC and grow at 9 % NaCl concentration. The antimicrobial activity of these isolates were tested against six pathogenic bacteria viz, Escherichia coli, Pseudomonas putida, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella enterica and Bacillus cereus. Four isolates (ABT-Z2, ABT-Z3, ABT-Z4 and ABT-Z22) were able to inhibit the growth of all the tested six pathogenic bacteria. All the isolates produced Exopolysaccharide (EPS) whose production was maximum at pH-6. Seven best LAB isolates were characterized by 16S rRNA gene sequencing and sequence analysis using nBLAST revealed that five of the seven isolates belonged to Lactobacillus plantarum and two belonged to L. brevis. The results of the present analysis revealed that strain L. plantarum is the predominant species of LAB found in Assamese Doi. The strain also displayed the best probiotic potential among the tested isolates. In future, this strain of bacteria can be used in preparing probiotic milk based fermented product and can be developed as an efficient starter culture to make Doi.