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Theses

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2015 - 20163
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Subject: Nematology × End date: 2016 × Start date: 2010 × Type: Thesis ×
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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
    BIOLOGY AND MOLECULAR CHARACTERIZATION OF ROOT-KNOT NEMATODES OF ASSAM
    (AAU, Jorhat, 2015-08) Kshetrimayum, Sumita; Das, Debanand
    Investigations were carried out to find the molecular characterization of root-knot nematode of Assam, morphological and morphometric variations among the populations of root-knot nematode (s) of Assam and effect of temperature on the biology (embryogenesis, penetration and multiplication) of root-knot nematode, Meloidogyne incognita. PCR analysis using specific primer, MiF-MiR for M. incognita showed that all the populations of root-knot nematode collected from nine districts (Jorhat, Golaghat, Sibsagar, Lakhimpur, Dhubri, Nagaon, Dibrugarh, Kokrajhar and Kamrup) of Assam produced a PCR product of 399bp for all the root-knot nematode isolates. A representative of four different isolates from four districts viz., Jorhat, Lakhimpur, Nagaon and Kamrup were partially sequenced. Sequenced similarity of Mi isolates from four districts showed 89 per cent to 99 per cent homology. Results of molecular characterization using RAPD primers revealed that populations of root-knot nematode of nine districts of Assam formed three clusters with a bifurcation at 0.47 similarities. The first cluster had five isolates viz., Jorhat, Sibsagar, Kokrajhar, Kamrup and Dhubri. The second cluster comprised of three isolates viz., Golaghat, Lakhimpur and Dibrugarh, while Nagaon was found to be totally different from other isolates. Study on the morphological variations among the populations of Meloidogyne incognita from nine districts of Assam exhibited variations only in the tail shape, while other morphological characters showed similarities among the populations. Tail shape of second stage juveniles of M. incognita collected from Golaghat, Kokrajhar, Nagaon and Sibsagar district was similar in shape. Likewise, tail shape of second stage juvenile of Dibrugarh, Jorhat and Lakhimpur population showed similarity but, Dhubri and Kamrup population showed variation from other populations. No variation on perineal pattern was observed in size and shape of perineal pattern of M. incognita collected from nine districts of Assam. Studies on morphometric variations (body length, stylet length, lip height, lip width, MB, a, b, b´, c and c´) among the populations of M. incognita from nine districts of Assam showed no distinct variations in the major characters, except in MB value. MB value of Kamrup population was higher (61.79) than other populations. Present investigation on effect of temperature on the biology (embryogenesis, penetration and multiplication) of root-knot nematode, Meloidogyne incognita revealed that M. incognita completed embryogenesis within 4.468 days at 28°C, which was found to be the favorable temperature for embryogenesis than 31°C (5.168 days) and ambient temperature (7.645 days). Penetration was not affected by temperature but, migration and post-penetration inside the root tissue were influenced by temperature. At 27±1°C, M. incognita second stage juvenile took 5 days to reach stele region followed by 31±1°C and 23±1°C (7 days) while, at 21±1°C, it took 10 days. Multiplication of M. incognita was greatly affected by temperature. Maximum number of galls per root system (119.6), number of egg masses per root system (275.2), number of eggs per egg mass (343.6), final nematode population (1335.2) and reproduction factor of nematodes (2.67) was observed at 27±1°C followed by 31±1°C, 23±1°C and 21±1°C.
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    ThesisItemOpen Access
    DIVERSITY OF ENTOMOPATHOGENIC NEMATODES (EPN) IN ASSAM
    (AAU, Jorhat, 2015) Borgohain, Nivedita; Gogoi, B. B.
    An investigation was carried out to see the diversity and distribution of Entomopathogenic nematodes in Assam. EPNs were recovered at a frequency of 14.75 per cent from 45 samples out of the 305 number samples. The highest frequency of 30.00 per cent was recorded in Karbi-Anglong district and lowest of 10.00 per cent was from Dhubri district. Identification of EPNs isolates were made on the basis of morphological and morphometric studies on the developmental stages of the nematodes. Four species of EPN viz., Steinernema abbasi, Steinernema karii and Heterorhabditis bacteriophora and Heterorhabditis sonorensis were identified. Heterorhabditis sonorensis is for the first time reported from India. Among the identified species Steinernema abbasi is more prevalent, like Heterorhabditis sonorensis are more abundant in our ecosystem. Highest record of EPNs was in forest eco-system (20%) followed by perennial fruit crops (18.18), grass land (15.4%), ornamental crops (9.43%) and vegetables (6.00%). Steinernema spp. isolated from acidic to alkaline soil whereas Heterorhabditis spp. from acidic to alkaline soil with low to high organic matter content. On the basis of soil types, highest EPNs were recorded from sandy loam soil