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ThesisItem Open Access Development and pharmacological evaluation of small molecular bioactives from marine algae associated heterotrophic bacteria(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Aneetta, Francis; KAU; Kajal, ChakrabortyIncreased incidences of microbial resistance and the development of drug-resistant pathogens have triggered an urge amongst researchers focusing on the discovery of potential anti-infective compounds. The present study conducted at Marine Biotechnology Division, ICAR-CMFRI, Kochi, highlights the cultivable diversity and bioactivities of heterotrophic bacteria associated with the intertidal macroalgae of Southeast coast of India. Among the 40 bacteria isolated, the majority of the isolates represented Gamma-proteobacteria (62 %) and the following 38 % resided in the phyla Firmicutes. The isolates were then screened for antibacterial activities against a wide spectrum of pathogens including methicillin-resistant Staphylococcus aureus by spot on lawn assay. Further, one of the most active strains belonging to the phyla Firmicutes isolated from Rhodophyceae macroalga, Laurencia papillosa, with a zone of inhibition ≥ 35 mm, was selected for bioprospecting studies. It was characterized as Bacillus velezensis MBTDLP1 (MT122835), based on integrated phenotypic and genotypic analysis. Type-I pks gene (MT394492) of 700 bp also could be amplified from the candidate bacterium. The bacterium exhibited siderophore production in CAS agar screening. The bacteria showed significant susceptibility to the commercially available antibiotics thus neglecting the chances of pathogenicity. The organic extract of the candidate bacterium was also found to display ferrous ion chelating capacity (IC50 4.2 mg/mL). The heterotrophic bacterium B. velezensis MBTDLP1 exhibited promising anti-infective properties against test pathogens which included multidrug- resistant pathogen methicillin-resistant S.aureus (MIC of 15 μg/mL). The organic extract showed antibacterial activity (MIC 7.5-15 μg/mL), antioxidant property with IC50 values from 0.1-0.9 mg/mL against ABTS and DPPH radicals, anti-inflammatory activity with IC50 0.01 mg/mL against 5-LOX, anti-diabetic property with IC50 0.1-0.4 mg/mL in correspondence to α-amylase and α-glucosidase. The organic extract also showed significant anti-cancer activity against Human breast cancer cells with IC50 0.032 mg/mL and less cytotoxicity to normal cells. Significant antibacterial activity against drug resistant bacteria together with considerable pharmacological activities combined with the presence of genes coding for bioactive secondary metabolites revealed that this marine symbiotic bacterium could be used against the dilemma.ThesisItem Open Access Development of multiple shoot culture of Ashwagandha (Whithania somnifera) for in vitro alkaloid stimulation studies(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Malavika, M R; KAU; Viji, M MThe study entitled “Development of multiple shoot culture of ashwagandha (Withania somnifera) for in vitro alkaloid stimulation studies” was conducted at the Department of Plant Biotechnology and Department of Plant Physiology, College of Agriculture, Vellayani, Thiruvananthapuram, during 2019-2020. The primary objective of the study was to establish multiple shoot cultures of ashwagandha (Withania somnifera) for in vitro alkaloid stimulation studies. The seeds of Withania somnifera, variety Arka ashwagandha procured from IIHR Bangalore were used for the study. The seeds were subjected to various treatments to enhance seed germination under in vitro condition. Among the different treatments studied, S5 (the treatment in which the seeds were soaked in water overnight, surface sterilized with 5% Tween 20 for 5 minutes followed by 0.1% HgCl2 treatment for 5 minutes and then inoculated in half strength MS media with 0.3% GA3) was found to be the best for seed germination (100%). But the treatment S1 (seeds soaked in water overnight, surface sterilized with 5% Tween 20 for 5 minutes followed by 0.1% HgCl2 treatment for 10 minutes and then inoculated to half strength MS media without hormones) failed to induce germination. Treatment S2 (seeds soaked in 250ppm GA3 overnight, surface sterilized with 5% Tween 20 for 5 minutes followed by 0.1% HgCl2 treatment for 10 minutes and then inoculated in half strength MS media without hormones) also failed to induce any germination. But in the treatment S3, 40% of germination was found on 14th day of inoculation and the seedlings showed an average shoot length of 3.75 cm in 28 days. In this treatment S3, the seeds were soaked in tender coconut water for 1hour and then soaked in 250ppm GA3 overnight and the next day surface sterilized with 5% Tween 20 for 5 minutes followed by 0.1% HgCl2 treatment for 10 minutes and then inoculated in half strength MS media with 0.3 ppm GA3.The growth of the seedlings was very slow and the yield was also very poor in the treatment S4 (in which the seeds were soaked in water overnight and the next day surface sterilized with 5% Tween 20 for 5 minutes followed by 0.1% HgCl2 treatment for 10 minutes and then inoculated in half strength MS media with 0.3 ppm GA3).In treatment S5, the time of exposure of the seeds to HgCl2 treatments was reduced to 5 minutes and the rest was the same as above. In S6, the concentration of HgCl2 was reduced to 0.05% but the time of exposure of the seeds to HgCl2 treatments was 10 minutes. In S7, the concentration of HgCl2 and time of exposure of the seeds to HgCl2 treatments were reduced as 0.05% and 5 minutes respectively. The treatments S4, S6 and S7 failed to give any response. Among these treatments, treatment S5 has shown maximum germination rate (100%) with an average shoot length of 5.87 cm. Germination was found within 6 days of inoculation. Compared to the rest of the treatments, S5 has shown not only maximum germination rate but also faster development of the seedlings. Nodal, leaf and shoot tip explants were taken from one month old in vitro grown seedlings and subjected to different shoot multiplication media for shoot induction. The explants were inoculated in plain MS media without any hormones in treatment T0 and this treatment failed to show any response. In the treatment T1 (MS+1mgNAA+3mgKn) shoot multiplication response of different explants viz. shoot tip (10%), leaf (10%) and nodal explants (16%) were very poor. Similarly in treatment T2 (MS+1.5mgNAA+1mgKn) also the response of shoot tip (10%), leaf (10%) and nodal (16%) explants were not satisfactory. In the treatment T3 (MS+1mgNAA+1.5mgKn), leaf explants showed shoot induction (10%) but there was no response in both shoot tip and nodal explants. But in the treatments T4 (MS+0.5mgBA+0.1mgIAA) and T7 (MS+3mgBA+1mgKn), 33% of shoot induction was found in both cases of shoot tip and nodal explants and callus development was found in case of leaf explants. Leaf explants showed 12% shoot induction in treatment T6 (MS+2.5mgBA) and no shoot induction was found in both shoot tip and nodal explants. Maximum response was found in treatment T5 (MS+2mgBA) with 80% shoot induction in nodal explants, 33% shoot induction in shoot tip explants and callus development was found in case of leaf explants. Among the treatments, T5 (MS+2mgBA) was found to exhibit both maximum shoot induction and faster development of the multiple shoots. Shoot induction was found after 30 days of inoculation. Among the three explants used, nodal explants showed maximum shoot induction (80%; the number of cultures showing multiplication-20±0.570, number of shoots per explant-15±0.670) with an average shoot length of 1.85±0.750cm in treatment T5 (MS+2mgBA). Hence in the present study, the use of in vitro derived nodal explants and subjecting them to treatment T5 (MS+2mgBA) is adjudged as the best protocol for establishing multiple shoots which can be used for in vitro propagation and alkaloid stimulation studies of Withania somnifera.ThesisItem Open Access Identification and expression profiling of Banana bract mosaic virus (BBrMV) responsive microRNAs in banana cultivar nendran (Musa AAB)(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Athira, Vijayan; KAU; Soni, K BThe study entitled “Identification and expression profiling of Banana bract mosaic virus (BBrMV) responsive microRNAs in banana cultivar Nendran (Musa AAB)” was conducted in the Department of Plant Biotechnology, College of Agriculture Vellayani, Thiruvananthapuram during 2018-2020. The objective of the study was to validate computationally predicted selected microRNAs (miRNAs) in banana cultivar Nendran (Musa AAB) and to study their expression in Banana bract mosaic virus (BBrMV) infection. In a previous study conducted in the Department of Plant Biotechnology, College of Agriculture Vellayani, 52 mature miRNAs were computationally predicted in the banana genome using NOVOMIR tool and their target genes identified. From them, three miRNAs were selected to study their response to BBrMV infection. The selection was done based on the possible role of their target genes in biotic stress responses. The miRNAs selected were miR-5417 (target: F Box family protein), miR- 1634 (target: Patatin like phospholipase family protein) and miR- 67 (target: Probable xyloglucan endotransglucosylase/hydrolase protein 33). The study was carried out in the BBrMV infected field grown banana plants of cv. Nendran. BBrMV infection in the infected plants were confirmed by RT-PCR using viral coat protein gene specific primers and the expected amplicon of size 745 bp was obtained. Uninfected plants served as control. For studying the expression of these miRNAs, RNA was isolated from the leaves of infected and control plants samples following the modified Rodrigues-Garcia protocol. Stem-loop primers were used for reverse transcribing miRNAs to cDNA. The primers for the amplification of miRNAs and their target genes were designed, synthesized and their specificity was analyzed. The expression profiling of miRNAs and their target genes was done by RT-qPCR and the results were analyzed using qBase plus software. The Raw Cq values obtained were normalized using a reference gene β-actin. The miRNAs and their target genes were analysed with reference to the uninfected control plants. RT-qPCR analysis confirmed the presence of all the three computationally predicted miRNAs in banana cv Nendran. All the BBrMV infected samples showed an elevated level of miR-1634 (2.95 and 6.52 fold) and miR-67 (4.46 and 5.04 fold) compared to the uninfected control. Similarly, their target genes Patatin like phospholipase family protein (target of miR-1634) showed 5 to 10 fold increase and Probable xyloglucan endotransglucosylase/hydrolase protein 33 (target of miR- 67) showed 6.95 and 9.45 fold increase in the infected plants. No considerable change in the expression of miR-5417 was observed in the infected samples. But its target gene (F Box family protein) was found upregulated by 6.3 to 9.2 folds in both BBrMV infected plants compared to the control. Hence an inverse correlation could be established between the miRNA and its target. The study showed that all the three miRNAs (miR-5417, miR-67 and miR-1634) respond to BBrMV infection and have a role in stress response of the plants. All the target genes showed upregulation in the BBrMV infected samples, showing their role in biotic stress response. miR-5417 showed an inverse correlation with its target.ThesisItem Open Access Genetic diversity analysis of Xanthosoma sagittifolium (L.) schott using molecular markers(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Krishnaveni, Vijayakumar; KAU; Asha Devi, AThe study entitled “Genetic diversity analysis of Xanthosoma sagittifolium (L.) Schott using molecular markers” was carried out at the Division of Crop Improvement, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2019-2020. The objective of the study was to analyze the genetic variation in tannia based on morphological and molecular characteristics. The knowledge can be exploited for crop improvement programs of Xanthosoma and can be used to develop a core collection. Thirty accessions were selected for the study. For morphological analysis, observations on all the below-ground characteristics of the plant viz., tuber characters were taken (using IPGRI descriptors). The recorded data were analyzed using various statistical methods such as diversity indices (percentage distribution of traits, Shannon's diversity index and Simpson's diversity index), PCA, similarity matrix, cluster analysis and ANOVA. The Shannon Weaver’s diversity index ranged from 0.24 to 0.98 whereas, the Simpson’s diversity index ranged from 0.13 to 0.62. The time of harvest, the position of the cormel apex and the exterior surface of the corm showed no variation and remained constant for the accessions studied. Cluster dendrogram resulted in four major clusters and one outlier. Cluster I had four sub clusters (Ia, Ib, Ic and Id) comprising seven, five, six and five accessions. Cluster II, III and IV consisted of two accessions each, while Xa-JG/2016-1, the only pink-fleshed accession in the set remained an outlier. Cluster II grouped the two accessions, TTn-14-6 and Xa-152 which produced elongated pencil-like cormels that were unmarketable. The rest of the accessions showed variability in tuber shape, size and colour as well as colour of corm apex. PCA revealed that accessions Xa-Ju/10-8, Xa-67, Xa- 152, and Xa-JG/2016-1 showed maximum variability. Based on the coefficient of variation, the degree of variability was found to be high for corm weight, number of cormels produced per plant and cormel weight. For molecular analysis, DNA was isolated by employing a slightly modified version of Dellaporta protocol. Good quality DNA ranging from 1.06 (TTn14-5) - 2.34 (Xa-HOB-T8-2) was obtained. A total of 24 ISSR primers were taken for screening of which, 14 were selected at an annealing temperature of 56.3oC. The selected primers were UBC 807, UBC 808,UBC 809, UBC 810, UBC811, UBC817, UBC818, UBC824, UBC825, UBC827, UBC834, UBC 836, UBC 845 and (GA)9 AC. The PCR products were resolved in 2% agarose and the polymorphic bands obtained were subjected to various analyses. The primers showed 91.64% polymorphism and the total number of bands ranged from 7 to 19. UBC 808, UBC 810, UBC 818 and UBC 824 showing 100% polymorphism. Cluster analysis was done based on Euclidean distance in which the thirty accessions were grouped into four major clusters with the maximum number of accessions in cluster I (22). It had two sub clusters Ia and Ib along with three divergent lines viz., TTn14-1, Xa-JG/2016-1 and Xa-AD/2014-18. One of the sub clusters comprised two duplicates TTn14-9 and Xa-MNS/14-1 as well as TTn14-5 and Xa-MTS-local which showed 100% similarity. Of the three accessions grouped under cluster IV, TTn14-6 and Xa-152 produced elongated pencil like cormels, whereas, Xa-AD/2014-17 produced normal cylindrical cormels. Cluster II had two accessions collected from the Northeast region pooling together. Apart from ISSR markers, cross compatibility of taro SSR markers with tannia accessions was also checked using nine SSR markers (Ce1 B03, Ce1 F04, Ce1 F12, Uq73-164, Uq84-207, Uq97- 256, Uq110-283, Uq132- 147 and Uq201-302) using various temperature regimes and PCR conditions. However, specific bands were not obtained and it was found to be incompatible in accordance with previous studies. The morphological and molecular assessment aided in identification of duplicates and variants present among the germplasm collection whereas the characters which were found contributing to major variability can be used to identify good yielding varieties and eliminate undesirable ones. The data generated from this study is useful for formation of core collection, effective conservation, exploitation of the germplasm as well as breeding and improvement programmes.ThesisItem Open Access Morphological and molecular analysis for assessing intraspecific variation in sweet potato (Ipomea batatas (L.) Lam.) and interspecific divergence in Ipomoea spp.(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Sasilekha, S; KAU; Shirly Raichal, AnilThe study entitled “Morphological and molecular analysis for assessing intraspecific variation in sweet potato (Ipomoea batatas (L.) Lam.) and interspecific divergence in Ipomoea spp.” was carried out in the Division of Crop Improvement, ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during 2019-2020 with an objective to analyse the intraspecific variation in sweet potato and interspecific divergence in Ipomoea spp. based on morphological and molecular markers. Forty one Ipomoea batatas accessions from the National Active sweet potato germplasm site at ICAR-CTCRI and 6 wild species collected from ICAR-CTCRI campus and KAU, Vellayani (Ipomoea aquatica, Ipomoea palmata, Ipomoea obscura, Ipomoea vitifolia, Ipomoea nil and Ipomoea triloba) were used for the study. Morphological analysis was performed by using eighteen sweet potato descriptors as provided by IPGRI (CIP et al., 1991). The recorded data were analyzed statistically by various tools such as PCA and cluster dendrogram using Multivariate statistical package (MVSP 3.22). The dendrogram separated the accessions into two principal clusters at a Euclidean distance of 1.7. The PCA analysis revealed predominant vine colour, leaf lobes type, shape of central leaf lobe, immature leaf colour and petiole pigmentation as the major variables that contributed to the clustering of the sweet potato accessions. . Molecular characterisation was performed using ISSR markers. The genomic DNA was isolated from young leaves using Dellaporta et al. (1983) method. 11 ISSR primers were used for screening of forty seven accessions. PCR amplicons obtained using selected primers were resolved on 2% agarose and polymorphic bands were scored. The selected primers showed 100% polymorphism and the number of bands ranged from 12 to 23 with a mean value of 19.2 polymorphic bands per primer. A total of 211 polymorphic bands were obtained. The data analysed using NTSYS PC 2.02 program generated a dendrogram, which grouped the forty seven accessions into two principal clusters bas, ed on Jaccard‟s similarity coefficient. All the sweet potato accessions were included in the first principal cluster which was subdivided into seven sub-clusters and there was a lot of intra-cluster variation. The second principal cluster consisted of all the 6 wild species with Ipomoea palmata as an outlier. The clustering was also found similar in morphological characterization. The similarity between the different accessions ranged between 50-85%. The accessions S623 and S632 (Iba 3 and Iba 5) were 85% similar. The least similar accessions were AR-2017-2 (Iba 19) and I.vitifolia (35%). Three Ipomoea batatas [S 823 (Iba 38), S 663(Iba 24) and SD- 11 (Iba 31)] showed maximum similarity (72%) with the wild Ipomoea spp. Ipomoea triloba and Ipomoea aquatica were the most similar ones among all the wild species by 72%. The least similar accessions among wild species were Ipomoea palmata, I. aquatica and Ipomea vitifolia (59%). Among all the wild species I.triloba showed maximum similarity (72%) with sweet potato (Iba 31). Mantel‟s test also showed a significant correlation (r = 0.4365; p = 0.0001) between the molecular and morphological distance matrices indicating that the morphological characters that were used in this study are genetically controlled and not affected by the environment. The hexaploid nature of the crop, self-incompatibility, along with the outcrossing nature together might have contributed to the high variation observed among the accessions.ThesisItem Open Access Evaluation of anti inflammatory and antioxidant potentials of Zingiber wightianum Thwaites (Malayayinchi) an ethnomedicinal plant of Kerala(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Meera, T S; KAU; Suja, S RThe thesis entitled ‘Evaluation of anti-inflammatory and antioxidant potentials of Zingiber wightianum Thwaites (Malayinchi), an Ethnomedicinal plant of Kerala.’ was carried out in the Ethnomedicine and Ethnopharmacology Division of Jawaharlal Nehru Tropical Botanic Garden and Research Institute (JNTBGRI), Palode, Thiruvananthapuram during the academic year 2019-2020. The objective of the study was to scientifically evaluate anti-inflammatory and antioxidant properties of an ethnomedicinal plant Zingiber wightianum Thwaites (Malayinchi). Zingiber wightianum Thwaites (Malayinchi), herbaceous plant of the family Zingiberaceae, is one of the important medicinal plants seen in dense tropical forests of the southern Indian peninsula. The rhizomes of Zingiber wightianum were collected from the hills of Western Ghats and maintained at JNTBGRI to conduct pharmacological studies. Extraction procedures were carried to prepare the drugs of different doses for the study. Acute oral toxicity studies in mice and anti-inflammatory studies in rats, were done as pharmacological analysis. In the preliminary phytochemical investigation, rhizomes of Zingiber wightianum have shown the presence of secondary metabolites like phenols, saponins, flavonoids, glycosides, phlobatannins, anthocyanins and steroids which may be responsible for its medicinal properties. The total phenolic content in the ethanolic, hydro ethanolic and aqueous extract of Zingiber wightianum, expressed as gallic acid equivalents per gram of dry extract, was 10.3, 9.9 and 9.1 mg per gram of the extract respectively. The total flavonoid content of EZW, HZW and AZW was found to be 7.5, 6.8 and 6.5 mg GAE/g of extract. Oral administration of 50, 150, 450, 1000 and 2000 mg/kg body weight of rhizome extract to Swiss albino mice for 14 days did not produce any toxic symptoms, even at the highest dose. Anti-inflammatory potential of rhizome extract was investigated in vivo by carrageenan induced paw oedema and formalin induced paw oedema methods and in vitro by Albumin denaturation assay and HRBC membrane stabilization assay. The extracts were administered at doses of 50, and 100 mg/kg body weight orally in adult wistar rats and the maximum percentage inhibition of paw oedema in the right hind limb was shown by EZW 100 mg/kg in both the methods. EZW at higher concentration protected significantly the hypotonicity induced haemolysis of HRBC and prevented the denaturation of albumin by in vitro anti-inflammatory analysis. The antioxidant effect of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 121.83 μg/mL, 123.67 μg/mL and 132.66 μg/mL in hydroxyl radical scavenging assay, 86.27 μg/mL, 69.85 μg/mL, 135.82 μg/mL in nitric oxide radical scavenging assay. While in superoxide radical scavenging assay, ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 21.32μg/mL, 53.15 μg/mL and 44.28 μg/mL. In ABTS radical scavenging assay, of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 132.77 μg/mL, 180.28 μg/mL and 190.86 μg/mL. While in DPPH radical scavenging assay, ethanolic, hydro ethanolic and aqueous extract of Z. wightianum showed IC50 of 71.02 μg/mL, 137.48 μg/mL and 137.94 μg/mL. Total antioxidant capacity of ethanolic, hydro ethanolic and aqueous extract of Z. wightianum was found to be 83 μg AAE/g, 81 μg AAE/g and 69 μg AAE/g of dry extract. The ferric reducing ability of ethanolic, hydro ethanolic and aqueous extracts of Z. wightianum were found to be 414 mg, 410 mg and 385.25 mg /g dry weight. The antioxidant potential of Z. wightianum was compared with a standard and the outcome portrayed a significant impact. These results may offer assistance to set up a comprehensive investigation utilizing the drug as the reference. Thus the above findings scientifically validated the traditional claim of Zingiber wightianum for its medicinal use.ThesisItem Open Access Diversity analysis of Murraya koenigii (L) Spreng in Kerala through phytochemical and genetic profiling(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Aswani Sureshbabu, T; KAU; Rameshkumar, K BThe research work entitled ―Diversity analysis of Murraya koenigii (L.) Spreng in Kerala through phytochemical and genetic profiling‖ was carried out at Phytochemistry and Phytopharmacology Division, and Biotechnology and Bioinformatics Division of KSCSTE-JNTBGRI, Palode, during 2019-2020. Murraya koenigii (L.) Spreng.is the leafy spice plant commonly known as curry leaf. The plant, belonging to the family Rutaceae, is native to India, Sri Lanka and other South Asian countries. It is widely used for culinary purposes and medicinal purposes in Ayurveda. To find the diversity within species through phytochemical and genomic analysis level, different accessions were collected from various biogeographical regions, seasons and different maturity stages. The essential oil was isolated from the samples by hydrodistillation using Clevenger type apparatus, and the oils were analyzed using GCMS. The results show considerable variation in the oil yield in different seasons, maturity stages and biogeography. Total oil yield varies from 0.10%v/w to 0.48%v/w. From this study, the major compounds were identified as E-caryophyllene, β-phellandrene, E-β- ocimene, α-humulene, α-selinene and α-pinene. Accession collected from Kannur was distinct from other accessions in statistical analysis. Seasonal variation analysis revealed that the oil yield was higher in the rainy season. Further, mature leaves possess a higher amount of essential oil compared to younger leaves. Genetic diversity was checked by isolating DNA from samples taken from various locations of Kerala and their diversity is analyzed by SCoT Primer PCR amplification. The SCoT markers showed an average of 92.96% polymorphism. This study provides a diversity profile of Murraya koenigii in Kerala. It can be further elaborated by analyzing more number of plant samples and soil samples from different places to develop a variety of high volatile content yield for farmers.ThesisItem Open Access Role of mixed infection of cassava mosaic viruses in cassava mosaic disease development(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Akhila, J; KAU; Makeshkumar, TA study on “Role of mixed infection of Cassava mosaic viruses in cassava mosaic disease development” was conducted at ICAR-Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram, during 2019- 2020. The important findings of the above studies are summarised in this chapter. Fifty samples randomly collected from the five varieties of cassava (Kochangamuttan, Kariyilappothiyan, Karutha gandharipadappan, H226, Manja noorumuttan), showed high score (>4) symptoms scale of very severe mosaic having distorted and misshapen leaves with stunted growth of plants. Multiplex PCR could differentially detect the presence of ICMV and SLCMV from the infected leaves. Among the five varieties of cassava, leaf samples collected from only one variety (Kariyilappothiyan) had ICMV infection as confirmed by PCR. Whereas, the samples from the variety Manja noorumuttan, did not show any PCR amplification. The mosaic symptoms appeared in the leaves of the variety may be due to physiological disorders such as nutritional deficiency. But the rest of the varieties showed amplification and had SLCMV infection. Out of five varieties, Manja noorumuttan variety is free from both ICMV and SLCMV. Out of rest four cassava varieties, Kariyilappothiyan was found infected with ICMV and other three varieties were infected with SLCMV. None of the varieties showed mixed infection of ICMV and SLCMV. Using chip bud grafting, both the SLCMV and ICMV infected plants were used as stock and scion for mixed infection. The grafted cassava plants showed yellow mosaic patterns on newly appeared leaves after two weeks. No substantial changes in the symptoms were observed in the plants grafted with buds from ICMV on SLCMV infected plants. But severe symptoms were observed in ICMV infected plants grafted with buds from SLCMV infected plants. This reveals that SLCMV is more severe than ICMV. Agroinoculation of Nicotiana tabacum was done with a partial dimer of DNA A and DNA B of both SLCMV and ICMV, in order to study the symptom appearance during the mixed infection. The plants inoculated with DNA A components of SLCMV and ICMV individually, showed curling of young leaves and mild mosaic symptoms respectively. The plants infiltrated with both components of SLCMV, showed severe stunting, thickening of mild veins, curling of leaves. However, the plants inoculated with both components of ICMV showed mild mosaic and mild curling of leaves and reduction in size. In the case of mixed infection of DNA A and DNA B components of both SLCMV and ICMV in Nicotiana plants showed symptoms including curling on the newly emerged leaves, yellow mosaic pattern on older leaves and severe stunting, resembling a mild SLCMV infection. Similarly, Agrobacterium strains with infectious clones were injected in the axillary buds of cassava plants to analyse the symptomatology during the mixed infection of SLCMV and ICMV. But the cassava plants did not show any mosaic symptoms in leaves with the infectious clones until 60 days after inoculation. The study reveals that agro- inoculation method is more effective in N. tabacum than cassava.ThesisItem Open Access Screening of cassava genotype for cassava mosaic disease resistance(Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Preeja, P S; KAU; Makeshkumar, TThe study on “Screening of cassava genotype for cassava mosaic disease resistance” was conducted at the ICAR- Central Tuber Crop Research Institute, Sreekariyam, Thiruvananthapuram during 2019-2020. The objective of the study was to screen the cassava breeding lines for resistance to cassava mosaic disease. The screening was carried out in fifteen selected cassava breeding lines from the breeding programme to analyze their resistance to cassava mosaic disease (CMD). For the analysis of resistance, virus inoculum was introduced into the fifteen breeding lines by grafting. Chip bud grafting method was carried out to analyze the resistance of breeding lines. The Sri Lankan cassava mosaic virus (SLCMV) infected plants, confirmed through multiplex PCR were selected as the inoculum source (scion) for grafting. Periodic observations were carried out in grafted plants by morphological (symptom appearance) as well as molecular analysis by means of ELISA and PCR. None of the grafted cassava plants showed any mosaic symptoms in the new shoots developed. PCR, ELISA and qPCR results revealed that the presence of SLCMV was only confirmed to the control plants (susceptible cv. H-226) and were absent in the breeding lines tested. This confirmed the 15 breeding lines screened are resistant to cassava mosaic disease caused by SLCMV. CMD resistant cassava varieties have an effective role in minimizing the damage caused by the virus. The success of grafting suggests this technique as the most efficient one for virus transmission and the resistant screening programme. The rapid selection of CMD resistance lines can be offered by this technique. The CMD resistance breeding lines have a better role in on-farm production as well as in the breeding programme.
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