Thumbnail Image

Theses

Browse

20202
Reset filters
Subject: Nematology × End date: 2020 × Start date: 2020 × Type: Thesis ×
Reset filters

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ThesisItemOpen Access
    Morphological and morphometric variations of Hoplolaimus and Helicotylenchus
    (AAU, Jorhat, 2020-08) Venkadesh, G; Das, Debanand
    Investigations were carried out to study the morphological and morphometric variations of genera Hoplolaimus and Helicotylenchus in relation to host plants and geographical locations of Assam. Total of 163 soil samples were collected from Rice, Maize, Banana, Mango, Jackfruit, Citrus, Pea and Tea, and from different geographical locations viz., Jorhat, Kokrajhar, Sivasagar, Kamrup, Lakhimpur, Dhemaji, Nagaon and KarbiAnglong district of Assam. The populations of both genera under survey were identified as Hoplolaimus columbus, Hoplolaimus indicus, Helicotylenchus crenacauda and Helicotylenchus dihystera. In the study no morphological variations have been observed in genera Hoplolaimus and Helicotylenchus in relation to both host plants and geographical locations. Results of morphometric characters showed that body length, a ratio, oesophagus length, b ratio, oesophageal gland overlapping length, bʹ ratio, ABW, MB, V, Vʹ, stylet length, SE and Pp (only in Hoplolaimus) were regards as least variable characters and considered highly stable in relation to host plants for genera Hoplolaimus and Helicotylenchus. The c ratio, number of tail annules and Pa of females were least variable characters; while, tail length and cʹ ratio were moderately variable characters in Hoplolaimus columbus. The c ratio, cʹ ratio, number of tail annules and Pa of females were regarded as moderately variable characters; while, tail length of females was regarded as highly variable character in Hoplolaimus indicus. In males of H. indicus, tail length, c ratio, cʹ ratio and Pa were regarded as least variable characters; while, bursa of males was regarded as moderately variable character. The tail length, c ratio, cʹ ratio and O of females were regarded as moderately variable characters in relation to host plants of Helicotylenchus dihystera. Influence of geographical locations on morphometric characters revealed that the body length, a ratio, oesophagus length, b ratio, oesophageal gland overlapping length, ABW, MB, V, Vʹ, stylet length and Pp (only in Hoplolaimus) were least variable characters and considered highly stable characters in relation to geographical locations for genera Hoplolaimus and Helicotylenchus. The bʹ ratio, c ratio, cʹ ratio, SE and number of tail annules were least variable characters; while, tail length and Pa of females were moderately variable characters in Hoplolaimus columbus. The bʹ ratio, c ratio, cʹ ratio, SE, number of tail annules and Pa of females were moderately variable characters; while, tail length of was highly variable character in females of Hoplolaimus indicus. In males of H. indicus, bʹ ratio, tail length, SE, Pp, spicule length and gubernaculum length were least variable characters; while, c ratio, cʹ ratio, Pa and bursa of males were moderately variable characters. In case of Helicotylenchus crenacauda the bʹ ratio and SE of females were regarded as least variable characters; while, tail length, c ratio, cʹ ratio and O of females were moderately variable characters. The bʹ ratio, tail length, c ratio and SE of females were regarded as least variable characters; while, cʹ ratio and O of females were regarded as moderately variable characters in relation to geographical locations of Helicotylenchus dihystera.
  • Thumbnail Image
    ThesisItemOpen Access
    ISOLATION, CHARACTERIZATION AND EVALUATION OF ENDOPHYTIC BACTERIA AGAINST ROOT-KNOT NEMATODES
    (AAU, Jorhat, 2020-09) Basumatary, Binita; Das, Debanand
    Fifteen endophytic bacteria were isolated from leaves and stems of Solanum lycopersicum and S pimpinellifolium. Morphological characterization of these endophytes revealed that 6 bacteria were gram positive and 9 bacteria were gram negative, 10 bacteria were rod shaped, 3 were coccus shaped and 2 were diplococcus in shape. All 15 bacteria were motile in nature. Biochemical characterization of the isolated endophytes revealed that 9 bacteria showed positive reaction to KOH test while, 6 were negative to KOH test, 11 bacteria showed positive reaction to Citrate and 4 were negative to citrate test. All the 15 bacteria were positive for Gelatine hydrolysis and Catalase test. Six endophytic bacteria showed positive reaction and 9 showed negative reactions for Starch hydrolysis test. Four potential isolates were structurally analysed by using scanning electron microscope and revealed that the length and breadth of BETLI, BETL2, BETL4 and BETS2 were 701.70nm × 348.30nm, 954.l0 nm x 303.10 nm, 984.10nm × 332.90nm and 1422.00nm × 742.00 nm, respectively. Five endophytic bacteria showing potentiality against root-knot nematode were identified by using 16S rRNA, and they were Microbacterium arborescens (BETLI), Bacillus marisflavi (BETL2), Bacillus altitudinis (BETL4), Exigobacterium indicum (BETS2) and Bacillus marisflavi (BETL6). Study on in vitro efficacy of bacterial endophytes against second stage juvenile of root-knot nematode (J2) revealed that all the isolates had the potentiality to significantly increase the mortality of nematodes however, the isolate BETL2 showed the best result on mortality rate (81.47%) of 2 stage juvenile (J2) of Meloidogyne incognita, followed by isolates BETL4 (81.43%) and BETLI (79.07%) Dose-response models were used to determine the concentration of bacterial culture filtrates required to kill 50 per cent juveniles of M. incognita. Four potential bacterial endophytes were tested with different methods of applications (seed treatment, seedling root dip treatment, soil application and their combinations) in pot condition against root-knot nematodes in tomato. All the tested endophytic bacteria significantly increased the plant growth parameters of tomato and reduced the nematode multiplication than untreated control. However, maximum increase in plant growth parameters and decrease in number of galls, egg mass and nematode population in soil was observed in combined application of seed treatment + root dip treatment + soil treatment of Bacillus marisflavi (BETL2) @ 1x 10 cfu/ml of crop.