PG Thesis

Permanent URI for this collectionhttp://localhost:4000/handle/123456789/2

Browse

Author: search.filters.author.KAUHas files: Yes

Search Results

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Prevalence of sesamum phyllody in Onattukara tract and evaluation of fungal root endophyte Piriformospora indica for its management
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2022) Gifty, K J; KAU; Radhika, N S
    The research work entitled ‘Prevalence of sesamum phyllody in Onattukara tract and evaluation of fungal root endophyte Piriformospora indica for its management’ was conducted during 2019-21 at Department of Plant Pathology, College of Agriculture, Vellayani and Onattukara Regional Agricultural Research Station with the objectives to study the symptomatology, molecular detection and characterization of phytoplasma inciting sesamum phyllody disease in AEU 3 (Onattukara tract); and evaluation of fungal root endophyte P. indica for its management. Phytoplasma infected sesamum samples were collected from D and F blocks of Onattukara Regional Agricultural Research Station and Karthikapally. Karthikapally recorded highest disease incidence (39.44 per cent) and vulnerability index (23.75). Chocolate weed, Melochia corchorifolia, was found to be exhibiting symptoms of shoot proliferation. Hoppers collected from the infected fields were identified as Orosius albicintus, Hishimonas phycitis and Nephotettix sp. Disease symptoms were observed at the stage of flowering of sesamum plants in all the sampled locations. The associated symptoms were reduction in internodal length of stem, axillary bud proliferation, thickening of the floral veins, phyllody and floral proliferation. Microtome sections of infected and healthy leaf, stem of sesamum stained with 4,6-diamidino-2-phenylindole (DAPI) stain, and observed under fluorescence microscope emitted diffuse fluorescence from the infected tissues, which was brighter than the one from the parenchymal cells indicating the presence of phytoplasma in the infected tissues. Studies on variations in the level of gibberellic acid (GA) and indole-3-acetic acid (IAA) in phyllody infected and healthy sesamum was undertaken. GA content was increased by 2.25 times and 10.46 times, and IAA content was decreased by 1.25 times and 1.97 times in leaves and flowers of infected samples compared to the healthy samples. Molecular characterization of sesamum phyllody was performed with leaf samples collected from ORARS lowland, ORARS upland, Vellayani and Karthikapally. Amplicons of 1.4kb was obtained by amplifying with universal primers P1/P6 for detection of phytoplasma. The sequences obtained were subjected to BLAST analysis and the 16S rDNA gene sequence showed that all the isolates shared more than 99 per cent similarity with that of the ‘Candidatus phytoplasma aurantifolia’ strains in GenBank data base. In the phylogenetic tree constructed, the sesamum phyllody phytoplasma under study clustered with the 16SrII group (Candidatus Phytoplasma aurantifolia) phytoplasmas causing sesamum phyllody in various regions. The virtual RFLP pattern generated by iPhyClassifier, derived from 16S rDNA fragment was found to be identical to the reference pattern of 16Sr group II, subgroup D (GenBank accession: Y10097). Based on the results obtained from sequence analysis and virtual RFLP pattern, the phytoplasma associated with sesamum phyllody was identified as ‘'Candidatus Phytoplasma aurantifolia”-related strain belonging to subgroup 16SrII-D. P. indica obtained from Department of Plant Pathology, College of Agriculture, Vellayani was mass multiplied in sterilized coir pith: FYM mixture (1:1) amended with 2 per cent gram flour and sesamum seeds were sown. Colonization was observed seven days after germination. Wedge grafting was standardized in sesamum at 30 days after germination. Pot culture experiment was conducted to evaluate the effect of P. indica against phytoplasma causing sesamum phyllody, by grafting the colonized and non-colonized plants with infected scion. P. indica colonization could significantly reduce the incidence and severity of infection. After 30 and 45 days of grafting, an incidence of 20 and 60 per cent, and severity of 5 and 50 were recorded in the colonized plants grafted with infected scion, whereas an incidence of 60 and 80 per cent and severity of 45 and 75 were recorded in non-colonized plants grafted with infected scion. In colonized plants, enhanced shoot and root length at 30 and 55 days after germination were recorded and also earliness in flowering compared to noncolonized plants. Hence the associated symptoms of phytoplasma infection in sesamum are virescence, thickening of floral veins, phyllody and floral proliferation. The study revealed the association of Candidatus phytoplasma aurantifolia group with sesamum phyllody prevalent in Onattukara tract. The evaluation of beneficial fungal root endophyte P. indica against phytoplasma revealed delayed expression of symptoms in the colonized plants.
  • No Thumbnail Available
    Item
    Eco-friendly management of major pests of yard long bean, vigna unguiculata subsp. sesquipedalis (L.) Verdcourt.
    (Department of Agricultural Entomology, College of Agriculture, Padannakkad, 2017) Vineetha, V; KAU; Ramesha, B
    The study entitled ′′Eco-friendly management of major pests of yard long bean, Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt′′ was carried out in the Instructional farm of College of Agriculture, Padannakkad, Kasaragod during two seasons viz., kharif (May to August) and rabi (September to December) in the year 2016. The vegetable cowpea variety ‘Lola’ released by KAU was selected for the study. The study was undertaken with an intention to find out the efficacy of different microbial agents, neem based and biorational insecticides. The experimental design was RBD with 9 treatments and three replications. The treatments included; T1- Beauveria bassiana (liquid formulation @ 107 spores/ml of water), T2- Metarhizium anisopliae (liquid formulation @ 107 spores/ml of water), T3- Lecanicillium lecanii (liquid formulation @ 107 spores/ml of water), T4- Bt formulation 2× 108 cfu/ml @ 1 ml/l of water, T5- Neem based insecticide (Azadirachtin 1 per cent @ 5 ml/l of water), T6- Neem oil emulsion 5 per cent (50 ml/l of water), T7- Spinosad 45 SC @ 0.4 ml/l of water, T8- Malathion 50 EC @ 2ml/l of water (standard check), T9- Absolute control. All the treatments were imposed at fortnightly intervals just after the initial attack of pest was seen and observations were recorded at weekly intervals corresponding to standard weeks. The data were subjected to square root transformation and analyzed using ANOVA. After three consecutive sprays of Spinosad 45 SC @ 0.4 ml/l of water at fortnightly intervals there was complete reduction of pod borer larvae during kharif and rabi season. The percentage of flowers and pods infested by pod borer larvae were also reduced completely and no infestation was noticed after three consecutive sprays of Spinosad during both seasons. Thus it was found that Spinosad 45 SC was effective in reducing the number of pod borers, percentage of flowers infested and percentage of pods infested. During kharif season, Beauveria bassiana was found to be the most effective treatment in reducing the nymphs and adults of pod bugs with minimum number of 0.56 bugs per plant followed by 0.63 bugs in T5 compared to T9 with 7.46 bugs per plant after three consecutive sprays. During rabi season, Azadirachtin 1 per cent showed no incidence of pod bugs after three sprays and Neem oil 5 per cent consistently reduced number of bugs to zero on 15 days after third spray whereas T9 exhibited maximum number of 4.26 bugs/plant. The effect of Beauveria bassiana was lowered during rabi season. It might be due to the inability of Beauveria spores to germinate and cause infection during that season because of inadequate humidity. Azadirachtin 1 per cent incessantly lowered the per cent of pods infested by pod bugs to zero even after two sprays during both seasons and leaf miner attacked leaves was also found minimum in plot treated with Azadirachtin 1 per cent (0.63 leaves/plant) compared to T9 (7.12 leaves/plant). The aphid population on shoots and per cent of aphid infestation on shoots were found to be zero after three consecutive sprays of Lecanicillium lecanii at fortnightly intervals during kharif season. Lecanicillium lecanii also lowered the aphid population on pods and caused exorbitant reduction in the percentage of infested pods during both seasons after three sprays. Though pod length is an inheriting character, maximum length of 42.30cm and 48.40cm was shown by T7 during kharif and rabi seasons respectively. During both seasons viz., kharif and rabi, the total and marketable yield was high in T7 with highest benefit – cost ratio of 1.50 and 2.26 respectively.
  • No Thumbnail Available
    Item
    Climate variability impact on water resources in the command area of a river diversion scheme
    (Academy of Climate Change Education and Research, Vellanikkara, 2017) Abhijith, V; KAU; Mary Regina, F
    Climate change is the major cause that affects water availability mainly due to variability in rainfall and temperature. The rising population and increasing food demands are imposing a further pressure on available water resources. Hence the efficient management of available water resource is of great concern. Irrigation is the largest sector that accounts for water use. In this situation a study was conducted in the command area of Left Bank Canal of Chalakudy River Diversion Scheme to assess the impact of climate variability on the water availability for the cropping systems and domestic demand during the irrigation period from December to May. The variability and trend in the rainfall was studied for the basin for a period from 1987 to 2016 and it is seen that the annual rainfall shows a declining trend. An investigation was done for finding out the cropping pattern of the canal commands. The crop water demand worked out using CROPWAT was used to estimate irrigation water demand. The domestic water demand calculated for the basin along with the irrigation water requirement constituted the net water demand. The total weekly water requirement was computed for all the branch canals for the irrigation period. The groundwater level analysis was done for wells along branch canals. Water recharge was observed in almost all the observation wells during supply periods. But no recharge was observed in wells in tail reaches during certain supply periods due to insufficient supply of water to tail ends. The weekly water supply for the branch canals were compared with the water demand. Most branches show a water deficit while a few exhibits water excess. Water deficit was observed mostly in longer and farther branches. The existing supply system was noted to be inefficient and works without considering proper branch wise water demand. The discharge from the main shutter was also obtained and was found to be almost about five times of the demand. Seepage losses, illegal withdrawal of canal water, and improper management are observed to be the reasons behind the insufficient water supply. Proper management of canals and supply based on demand has to be followed for efficient water management. A computer based model was developed for the calculation of weekly water demand based on crop and weather data. A comparison of supply with the demand can also be done in the model which indicates the efficiency of supply system on a weekly basis. Proper planning can be done for efficient water management through the canal system, under the given conditions using the model.
  • No Thumbnail Available
    Item
    Characterization of Mycosphaerella spp. causing sigatoka leaf spot disease complex of banana in Kerala and its management
    (Department of Plant Pathology College of Horticulture, Vellanikkara, 2019) Milsha George; KAU; Anita Cherian, K
  • No Thumbnail Available
    Item
    Breeding biology and cross compatibility of close wild relatives of brinjal (Solanum melongena L.)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2016) Neeraja Puthiamadom; KAU; Presanna Kumari, K T
    The present study entitled “Breeding biology and cross compatibility of close wild relatives of brinjal (Solanum melongena L.)” was carried out in the Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, during 2014 – 2016. The objective of the study was to elucidate the reproductive biology of the related wild species of brinjal and to ascertain their cross compatibility with the cultivated species. Four wild species variants of Solanum viz., viarum, gilo, incanum and indicum, collected from NBPGR, RS, Vellanikkara along with S. melongena varieties Haritha and Surya formed the material for the study. These genotypes were evaluated for various vegetative, floral and fruit characters following the descriptor developed by IPGRI (1988) and clustering was done. Study of the reproductive biology revealed that flowering was profuse in S. viarum, S.incanum and S. gilo. However S. indicum did not flower during the entire experiment period and hence could not be utilized in the programme. The flowers of Solanum species were found to be positively geotropic with a floral formula of ♀∕K(5)C(5)A(5)G(2). In all the species evaluated, flowers were pedicellate, zygomorphic, bisexual and complete. Irrespective of species, long, medium and short styled flowers were observed. However, the frequency of medium styled flowers were very low. Unlike in the case of S. gilo and S. melongena variety Haritha, a change in colour of the corolla was observed in S. viarum, S. incanum and S. melongena variety Surya on the day prior to anthesis. The time of anther dehiscence was found to vary with the species. The pollen grains dehisced nearly two to five hours after flower opening in S. viarum and S. incanum. However, in the cultivated varieties, Haritha and Surya, anther dehiscence commenced along with the opening of flowers. Among the different species protandry was observed only in S. gilo. The dehiscence continued for three days in all the species. Irrespective of species, pollen grains were remained fertile for three days. The change in the colour of the stigmatic surface from glossy green to deep yellow, at the time of initiation of stigma receptivity was a unique feature of S. gilo. In all the other wild species of Solanum as well as the cultivated varieties Haritha and Surya, the colour of the stigmatic surface was glossy green at the time of receptivity. The colour was found to fade with the decline in receptivity. Studies to assess the mode of pollination revealed that cross pollination is the rule in Solanum species. Cross compatibility studies were undertaken between the three wild species which flowered and the two cultivated types under S. melongena. Among the twelve crosses attempted, Surya x S. viarum, S. viarum x Surya, Surya x S. incanum, Haritha x S. incanum, S. incanum x Haritha, S. viarum x Haritha were the successful ones. Out of these, the progeny of three crosses viz., Surya x S. viarum, S. viarum x Surya and Surya x S. incanum established in the field. The progeny of the cross Surya x S. viarum was found to be superior with respect to fruit weight as well as absence of prickles on leaf and fruit pedicel. Even though one of the parents of this cross, Surya was susceptible to most of the common pests and diseases of brinjal, no incidence of pests and diseases was noticed in the progeny population
  • No Thumbnail Available
    Item
    Screening for leaf curl virus disease complex resistance, genetic evaluation and molecular characterization of bird chilli (Capsicum frutescens L.)
    (Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, 2006) Nicey Mathew; KAU; Abdul Khader, K M
    The investigation entitled “Screening for leaf curl virus disease complex resistance, genetic evaluation and molecular characterisation of bird chilli (C. frutescens L.)” was conducted at Department of Plant Breeding and Genetics, College of Agriculture, Vellayani, Thiruvananthapuram during 2003-2005. The data for the investigation were collected from two field experiments, each laid out in Randomized Block Design with three replications. The second experiment was conducted without taking any control measures against leaf curl virus disease. The 49 genotypes included in the study showed significant difference for all the 14 biometric characters. They all showed high heritability coupled with high genetic advance except days to first flowering for which the genetic advance was moderate. The maximum values for phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded for fruit yield per plant and individual fruit weight respectively and the minimum values for days to first flowering. Fruit yield per plant was positively correlated with number of fruit per plant, number of secondary branches, plant spread, 100-seed weight, number of primary branches, number of seeds per fruit, individual fruit weight, fruit length, fruit width and plant height. Path analysis revealed high positive direct effect of individual fruit weight and number of fruits per plant on yield per plant. Hence selection for these characters can improve the yield. The 49 genotypes were grouped into five clusters based on Mahalanobis D2 statistic. Cluster I was the largest with 29 genotypes while clusters IV and V had only one genotype each. Clusters II and III had 11 and eight genotypes respectively. Cluster I was found to be superior to the other clusters with respect to the desirable characters. The genotypes were ranked based on the selection indices. High yielding and superior genotypes had high selection indices while low yielding genotypes were having low selection indices. Field screening of 49 genotypes for leaf curl virus resistance (experiment II) showed that five genotypes were highly tolerant to the disease while 14 genotypes were susceptible and 30 were highly susceptible. Comparison of yield and vulnerability index in both the experiments showed that reduction in yield was less in tolerant varieties than in susceptible varieties. The yield performance of Karumukku local, Thavanur local 3 and Meenachil local were comparable under controlled and uncontrolled conditions. Correlation analysis showed negative association of yield with vulnerability index in both experiments indicating that susceptibility to the disease leads to reduction in yield. The high yielding and leaf curl tolerant types identified from the study can be used as parents in crop improvement programme to evolve high yielding, leaf curl tolerant varieties. RAPD analysis was performed using the random primers OPA-01, OPB-01, OPB-06 and OPB-10 and the 49 genotypes were characterized using Jaccard’s similarity coefficient analysis and a dendrogram was constructed to cluster the genotypes. The high yielding genotypes T1 (Karumukku local) and T15 (Thavanur local 3) came in the same cluster (cluster II) while the leaf curl virus tolerant genotypes T35 (Kayamkulam local 3) and T33 (Kayamkulam local 4) came in the other cluster (Cluster I).
  • No Thumbnail Available
    Item
    Molecular characterisation of Ralstonia solanacearum (Smith) Yabuuchi et al causing bacterial wilt in solanaceous vegetables
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2001) Deepa James; KAU; Girija, D
    Bacterial wilt incited by Ralstonia solanacearum is one of the most devastating diseases of solanaceous vegetable crops in Kerala. Crop losses due to the incidence of this disease may go upto 100 per cent. Existence of different strains, races and biovars has been responsible for breaking down of resistance of varieties evolved through breeding programmes. In view of wide variability, a study was undertaken to characterise the isolates of R. solanacearum collected from three different agro climatic zones ofKerala at molecular level. Nine isolates of R. solanacearum collected from three different locations from brinjal, chilli and tomato were used in the study. These were isolated, purified and maintained in sterile distilled water at room temperature. Inoculation techniques were standardised in brinjal, chilli and tomato plants for assessing the virulence and aggressiveness of the isolates. Virulence and aggressiveness of the isolates were studied on respective host plants and found them highly varying. Vellanikkara and Kumarakom isolates could cross inoculate, whereas Ambalavayal isolates did not. The isolates were characterised by various cultural, morphological and biochemical tests and the variability among them was studied. Biovars, III and IlIA and races, 1 and 3 were identified among the isolates. The isolates were resistant to ampicillin and sensitive to chloramphenicol. Plasmid DNA profile of the isolates were studied and no difference was found in the plasmid DNA profile of the nine isolates. Polymorphism among the isolates was studied using RAPD with ten decamer primers. RAPD profiles exhibited great diversity among biovars III and IlIA as well as among race 1 isolates. Race 3 isolates were less polymorphic with certain primers tested. OPF8 yielded a unique band specific to race 3 isolates. Dendrogram obtained from the pooled data of RAPD profiles also showed high genetic similarity between race 3 isolates. Dendrogram obtained from the pooled data of RAPD profiles also showed high genetic similarity between race 3 isolates. Restriction analysis could not characterise the isolates since no banding pattern was obtained with restricted DNA. No hybridization signal was detected after Southern hybridization in RFLP. Curing of plasmid DNA at high temperatures was found unsuccessful. Plasmid profiles of both mucoid and non-mucoid colonies were compared to assess the role of plasmid in EPS production and the plasmid could be observed in both types of colonies. In the latter, a reduction in size of the plasmid was noticed. Thus the study revealed that great diversity existed among strains of R. solanacearum at different locations of Kerala when molecular techniques, especially RAPD was used as a tool.