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    Plant growth promotion and stress mitigation mediated by the root endophytic fungus Piriformospora indica In Cassava (Manihot esculenta Crantz)
    (Department of Microbiology, College of Agriculture, Vellayani, 2025-12-12) Akhila P Subhash; Anith, K N
    The study entitled “Plant growth promotion and stress mitigation mediated by the root endophytic fungus Piriformospora indica in cassava (Manihot esculenta Crantz)” was conducted in the Department of Microbiology, College of Agriculture, Vellayani, Thiruvananthapuram and in the ICAR–Central Tuber Crops Research Institute (CTCRI), Sreekariyam, Thiruvananthapuram during 2021-2024, with an objective to investigate the effects of the root endophytic fungus P. indica in cassava on productivity, nutrient acquisition and disease suppression against major pathogens. Other microbial agents used in the study were arbuscular mycorrhizal fungus Glomus mosseae, and the biocontrol bacterium Pseudomonas fluorescens PN026. Initially, the pathogens causing stem and root rot disease in cassava were isolated from the naturally infected plants. Three fungal isolates were obtained from the infected cassava samples, and these isolates were identified as Lasiodiplodia theobromae, Fusarium sp. and Cunninghamella elegans with morphological studies and by molecular identification using internal transcribed spacer region (ITS) sequence-based technique. Among them, L. theobromae and Fusarium sp. were identified as the major pathogens and C. elegans as a minor pathogen causing the disease. Pathogenicity of the isolates was verified by proving Koch’s postulates by inoculating the isolated pathogens separately, sequentially and in different combinations in freshly harvested healthy cassava tubers. Treatment with the combination of pathogens L. theobromae and Fusarium sp. was identified as the one showing highest infectivity with high percentage of weight loss and with least number of days taken for the symptom development. This inoculum combination was used for further studies. Direct and indirect antagonism of P. indica against the cassava stem and root rot fungal pathogens was evaluated on potato dextrose agar (PDA) plates. Direct antagonism was evaluated through dual culture plate assay and indirect antagonism through agar well diffusion method using the culture filtrate of P. indica. However, in both the tests P. indica did not inhibit these fungal pathogens in vitro. In vivo studies included cassava root colonization and root initiation, nutrient acquisition and plant growth promotion experiment as well as stem and root rot disease and cassava mosaic disease suppression. An experiment was conducted in protray to evaluate the root colonization abilities of P. indica in Sree Suvarna, Sree Jaya and Aswathy varieties of cassava in both sterile and unsterile planting medium. Fungal structures were detected by trypan blue staining, WGA-AF 488 (Wheat germ agglutinin- Alexa flour 488) staining and confocal imaging. Pear shaped chlamydospores were observed within the root cortical tissues at 14 days after inoculation. Further confirmation was done by molecular detection with the help PiTEF gene primer using a PCR reaction. This is the first report of successful colonization of P. indica in cassava. The root colonization ability of the AM fungus G. mosseae in all the three varieties of cassava in sterile planting medium was also evaluated using trypan blue staining method. The percentage of root colonization was 100 percent in all these varieties, where AM fungal vesicles as well as arbuscles were observed in the roots at 14 days after inoculation. Root initiation tests in minisetts were carried out in Sree Jaya and Aswathy cassava varieties by applying P. indica and Pseudomonas fluorescens in both sterile and unsterile planting medium. When P. indica and P. fluorescens colonized plants were compared to control plants, all root growth parameters were observed to be higher. However, most of parameters were found significant in unsterile planting medium when compared to the sterile planting medium which may be due to the insufficient root colonization of both the beneficial microbes in cassava minisetts in the sterile medium. A field experiment was conducted by applying P. indica and AM fungus G. mosseae, along with different doses of NPK fertilizers in cassava variety Sree Suvarna to evaluate the abilities of both beneficial fungi to promote growth and acquire nutrients. Different biometric, physiological, yield as well as quality parameters were analyzed. The application with a combination of 75 percent of the recommended dose of NPK along with P. indica was found to be the best treatment that improved growth and yield attributes, whereas the combination of 75 percent NPK along with G. mosseae recorded significant improvement in total dry matter contents as well as tuber quality parameters. The results showed that the chemical fertilizer dose could be reduced to a level of 75 percent of the recommended dose, without compromising the growth and yield, if the fertilizers are applied together with the bio-inoculants, either P. indica or G. mosseae. The same treatments also resulted in higher total nitrogen uptake while the combination of 100 percent NPK and G. mosseae resulted in better phosphorous and potassium uptake by the cassava plants. A grow bag experiment was conducted to examine the stem and root rot disease suppressing ability of P. indica in the local disease-prone cassava variety Aswathy. The treatment combination of pathogens, L. theobromae and Fusarium sp. was selected for the inoculation purpose. An increase in the growth and yield and decrease in disease incidence was noted in P. indica and G. mosseae inoculated plants, even when the plants were challenged with the stem and root rot pathogens. The pathogen inoculated control plants recorded the least number of days taken for the initial symptom development (6 months after planting), highest percentage of tubers affected per plant (53.33%) and extent of damage in each tuber (50%) followed by the chemical control plants. Simultaneously another grow bag experiment was also conducted, in the mosaic susceptible variety Sree Jaya to assess the cassava mosaic virus disease suppression by P. indica. Natural incidence of cassava mosaic virus in the cassava plants was monitored by visual scoring from 4 MAP till harvest (7 MAP). The plants from absolute control recorded highest visible symptoms of mosaic disease which was on par with G. mosseae treated plants, and least symptoms were recorded in the P. indica treated plants. Viral load in the cassava leaves estimated by quantitative polymerase chain reaction (qPCR) showed highest viral copy number in the G. mosseae treated plants and least in the P. indica treated plants. However, the G. mosseae treated plants showed maximum yield parameters compared to all other treatments. From the results of the present study, it can be inferred that the combined application of P. indica (vermiculite based inoculum one percent w/v @ 20 g/pit) or AM fungus G. mosseae (@ 5 g/pit) along with 75 percent recommended dosage of NPK fertilizers at the time of planting helps to reduce the amount of chemical fertilizers as well as enhance the growth and yield parameters of cassava plants. The study also suggests that P. indica as well as AM fungus G. mosseae can be utilized as biocontrol agents to combat stem and root rot disease of cassava. Effective colonization of P. indica also reduces the incidence of cassava mosaic virus. The combined application of these two beneficial endophytic fungi might have the potential to improve the growth and yield parameters of cassava with positive effects on disease control.
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    Nutrient management in cassava (Manihot esculenta Crantz) variety Vellayani Hraswa for southern laterites (Agro ecological unit 8)
    (Department of Agronomy, College of Agriculture ,Vellayani, 2024-06-01) Aparna, R A.
    Phosphorus transformation in acid sulphate rice soils of Kerala Acid sulphate soils are lowland soils situated below the mean sea level along the coastal tracts of Kottayam, Alappuzha, Thrissur and Malappuram districts of Kerala, spread in two agro-ecological units namely Kuttanad (AEU 4) and Kole lands (AEU 6). These soils are characterised by high levels of organic matter, low pH and toxicity of iron (Fe) and aluminium (Al) with wide variability in available phosphorus (P) content. Acid sulphate soils generally contain substantial quantities of Fe sulphide minerals or the oxidation reaction products of these sulphidic minerals and the protonated/non-protonated surfaces of Al/Fe hydroxides and oxides, resulting in P sorption and formation of the complexes, thus decreasing P availability in soil. However, the recent fertility evaluations across the state showed high available P status due to solubilization of the accumulated applied P. To develop an economically viable phosphorus nutrient management strategy, a pioneer study on P transformations in acid sulphate soils is highly required. The study aimed to understand seasonal variation of nutrients and transformations of phosphorus in acid sulphate soils. The investigation was conducted at Radiotracer laboratory, College of Agriculture, Vellanikkara, with four experiments viz., collection and characterization of soil samples from the acid sulphate soils of Kerala in two seasons, fractionation of phosphorus, adsorption study and an incubation study. In the first experiment, 125 representative soil samples from Kuttanad (AEU 4) (15 each from Upper Kuttanad, Lower Kuttanad, Vechur Kari, Purakkad Kari and Kayal lands) and Kole lands (25 each from Thrissur and Ponnani Kole) in pre-monsoon (April) and post-monsoon (November) were collected and characterised. The experiments on the fractionation and adsorption of phosphorus were done in thirty-five samples ie., five each from the seven selected locations with varying available P status. Phosphorus fractionation was carried out to quantify different fractions of phosphorus and their contribution to the available pool. The inorganic P fractions includes saloid bound P, Fe-P, Al-P, reductant soluble P and Ca-P. Adsorption study was carried out to work out the quantity/ intensity (Q/I) relationship of phosphorus and the pattern of adsorption in acid sulphate soils. Finally, an incubation experiment of 90 days duration was conducted to understand the effect of phosphatic fertilisers, lime and farmyard manure at different levels in low and high available P soils collected from Kuttanad and Kole lands. The treatment details of the incubation study were three levels of phosphatic fertilisers (as SSP - 0, 35 and 70 kg ha-1), two levels of lime (as CaO - without lime and lime as per POP recommendations) and two levels of farmyard manure (0 t ha-1 and 5 t ha-1). The observations were made on 30th, 60th and 90th days of incubation. Seasonal characterisation of soil samples during the two seasons revealed that among the collected samples, 50 per cent was sandy clay loam and 40 per cent was sandy loam in texture. The acidity characterisation of soil samples reaffirmed the extreme acidity condition of acid sulphate soils with 40 per cent of samples coming under extremely acidic class and 20 per cent under very strongly acidic. Among the collected soil samples, 37.60 per cent was low in available P, 23.20 per cent and 39.20 per cent under medium and high P respectively. The soil sample from Vechur Kari region showed the highest value of organic carbon (11.46 %). The available micronutrients viz., Fe and Mn showed very high concentrations. Among the acidity fractions, potential acidity was dominant followed by pH-dependent acidity in both seasons. Seasonal variation in electrochemical properties like pH and EC was noticed between two seasons. Ultra acidic soil reaction with high electrical conductivity was noticed during pre-monsoon period which reaffirm the salt water intrusion in these locations. Oxidation of pyrite mineral resulted in high amount of available sulphur as well as potential acidity during pre-monsoon. Reduced condition prevailing in the post monsoon resulted in high concentration of available iron. The fractionation study of phosphorus indicated that the per cent distribution of different phosphorus fractions followed the order, Fe- P > organic P > reductant soluble P > calcium P > aluminium P > saloid bound P. The contribution of dominant fraction (Fe-P) to the available P is mainly through saloid bound P. The phosphorus fixing capacity was significantly and positively correlated with clay, organic matter content, and negatively correlated with the available P. In the adsorption study, high buffer power indicated the ability of acid sulphate soils to replenish the depleted available P. Freundlich adsorption isotherm was found to be the best to explain P adsorption followed by Langmuir and Temkin adsorption isotherms. The Freundlich adsorption constant, KF was found to be correlated with organic matter which confirmed the fixation of phosphorus by organic matter in acid sulphate soils. In most of the soils, Langmuir adsorption constant (KL) increased with rise in temperature, indicates chemisorption behaviour of P adsorption. The incubation study affirmed that in soils with low available P, the addition of SSP at doses of 70 kg ha-1 and 35 kg ha-1 along with lime and FYM showed a significant increase in pH. In these soils, the addition of SSP (70 kg ha-1) along with lime and FYM registered the highest available P of 51.63 and 73.33 kg ha-1 respectively in Kuttanad and Kole soils at 60th day of incubation. In the same treatment, Fe bound P fraction was found to be highest with a decreasing trend towards 60th day of incubation, which increased after that. In the case of soils with high available P, the treatment combination with the addition of the highest dose of SSP (70 kg ha-1) along with lime and FYM showed the highest pH with an increasing trend towards 60th day. On the contrary to low P soils, in high P soils, the addition of SSP at 35 kg ha-1 along with lime and FYM registered the highest available P of 309.44 and 126.94 kg ha-1 respectively in Kuttanad and Kole at 30th day of incubation followed by a reduction towards 60th day of incubation. Phosphorus, a widely varying nutrient in acid sulphate soils is prone to high adsorption and fixation in soil depending upon the type of clay, organic matter content and amount of oxides and hydroxides of Fe and Al. There was no significant seasonal variation of P in soil samples from AEU 4 and AEU 6. In acid sulphate soils, the most dominant fraction, Fe-P contributed to available P mainly through saloid bound P, which is the water-soluble and loosely bound P fraction. The reduction of available P with the increase in P fixing capacity necessitates its estimation at least for the grouping of soils for the efficient management of phosphorus. In soils with high available P, addition of lower dose of SSP (35 kg ha-1) along with organic manure (FYM @ 5 t ha- 1) and lime (POP recommendations) is sufficient to enhance the P availability. Where as, in soils with low available P, addition of higher dose of SSP (70 kg ha-1) along with organic manure (FYM @ 5 t ha-1) and lime (POP recommendations) enhanced the P availability than its sole application. In this regard, field experiments in acid sulphate soils have to be conducted to confirm the results of incubation study in rice under natural system and more investigation is needed to know the interaction between organic matter and organic P fraction. As the organic matter plays the dual function in the environment- as a link and as a bottleneck for phosphorus availability, detailed study should be undertaken to know the complex formed by P fixation and its degree of crystallinity for developing better P management strategies in acid sulphate soils.
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    Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)
    (Department of Agronomy, College of Agriculture, Vellanikkara, 2021) Dayana Samson; Sindhu, P V
    Kerala is considered a treasure house of medicinal and aromatic plants, however, due to indiscriminate harvesting; the existence of most of these plants is under threat. Cultivation is the only option to ensure the continual supply of high quality raw materials without diminishing natural resources. Due to small holding size and a greater focus on cash crops, the scope for commercial production of medicinal plants as a pure crop in Kerala is restricted. So, the practical alternative is to bring them under intercropping with priority crops such as food and commercial crops. Cassava (Manihot esculenta Crantz) is the most important starchy root crop grown in the tropics. The wide spacing, together with slow initial growth and development, makes cassava compatible to intercropping with short duration annual crops. The present study entitled “Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)” was carried out at the Agronomy farm, Department of Agronomy, College of Agriculture, Vellanikara from September 2020 to April 2021 to assess the feasibility of intercropping cassava with the medicinal plants Indigofera tinctoria, Plectranthus vettiveroides and Sida alnifolia. The experiment was laid out in Randomized Block Design (RBD) with 10 treatments replicated thrice. The treatments included sole crops of cassava and medicinal plants, cassava + single row of medicinal plants, and cassava + double rows of medicinal plants. The observations on growth, yield and yield attributes of main and intercrops, and quality parameters of medicinal plants were recorded. Competitive indices and economics of cultivation were also computed. Intercropping significantly influenced the growth and yield attributes of both main and intercrops. With respect to plant height of cassava, significant variation was observed only at later stages of crop growth. Shorter cassava plants were observed when intercropped with Sida alnifolia (162.84 cm). In general, medicinal plants grown under intercropping system recorded taller plants, except for Indigofera, where sole cropping resulted in taller plants.The sole crop of cassava produced higher per plant tuber yield of 3.24 kg (32417 kg/ha) and was at par with cassava with single row of Plectranthus (3.12 kg/plant). The lowest tuber yield was recorded when cassava was intercropped with double row of Sida (1.77 kg/plant). Similar trend was observed in itop yield and dry matter production per plant. The yield of medicinal plants was the highest in sole crops, followed by single row intercropping and double row intercropping. Same trend was observed for quality parameters of medicinal plants. The quality of Indigofera tinctoria, expressed by indican content, was higher in sole crop (1.40 per cent) and was on par with single row inter crop (1.39 per cent). Sole crop of Plectranthus vettiveroides registered the highest essential oil content of 0.60 per cent, followed by cassava + single row of Plectranthus (0.40 per cent). Sole crop of Sida alnifolia produced highest total alkaloid (3.07 per cent) and was at par with single row intercrop (2.94 per cent). Cassavas intercropped with double rows of medicinal plants were more efficient in controlling weeds than sole crop of cassava or cassava + single row of medicinal plants. Sole crop of cassava recorded the highest total weed density and dry matter production at 30 DAP, 60 DAP and 90 DAP. Sida alnifolia controlled the weeds more effectively than other medicinal plants, both as sole crop or as intercrop with cassava. Competition indices like land equivalent ratio (LER), relative crowding coefficient (K or RCC), competitive ratio (CR), cassava equivalent yield (CEY) and aggressivity were assessed for evaluating intercropping efficiency. All intercropping systems recorded LER of values greater than one, indicating the yield advantage over sole cropping. The highest LER (1.41) was recorded when cassava was intercropped with double row double row of Plectranthus vettiveroides and LER was lower when Sida alnifolia was intercropped either as single row or as double rows (1.01 and 1.05 respectively). Higher RCC and CR values and positive aggressivity values for cassava indicated dominance of cassava over medicinal plants. K (RCC) of all treatments was greater than one, indicating yield advantage of the system. The highest CEY was recorded for cassava + Indigofera as double row, with cassava equivalent yield of 43895 kg/ha, and the lowest CEY was for sole crop of Sida alnifolia (3000 kg/ha). Among the medicinal plants evaluated, Indigofera tinctoria, either as double row or as single row, could be recommended as the best medicinal intercrop for cassava. Intercropping cassava with single row Plectranthus vettiveroides was the next best alternative.
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    Investigaiton on extraction of starch from cassava (Manihot esculenta Crantz) stem
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2019) Hasmi Sulain, K K; Saravanan Raju
    The study entitled “Investigation on extraction of starch from cassava (Manihot esculenta Crantz) stem” was carried out at the Division of Crop Utilization, ICAR- Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during the year 2018- 2019. Cassava stem starch is an ideal source to increase the availability of starch without using additional land, water and fertilizers. Hence understanding the structural and functional properties of stem starch is an important aspect before substituting with root starch because there is a lack of knowledge of starch properties when compared to root starch. In this study, starch from cassava stem were extracted by four different methods such as extraction using water, extraction using chemicals such as Sodium hydroxide and sodium meta bi sulphate, microwave assisted extraction and ultra sound assisted extraction. The cassava genotypes suitable for extraction of starch from stem and functional properties of this stem starches were investigated. In the present study, the physiological characters of such as stem length, stem girth, stem fresh weight and stem dry weight and stem moisture content were measured in the selected genotypes of cassava. The results showed that stem length of cassava ranges from 100-300cm and the stem girth ranges from 2.5-8cm. The fresh weight and dry weight of cassava stem ranges from 0.4-2Kg and 0.2-0.7Kg respectively.The moisture content of cassava stem varies from 62-72% but the moisture content was less than 2% in all stem starches. The swelling volume was same for all the stem starches (15ml) and the solubility was less than 10%. Starches with high swelling volume and solubility and low gelatinization temperature has various applications in food industry. The water binding capacity varied from 46.09% to 77.50% for different cassava stem starches. The in vitro starch digestibility of cassava stem starches ranges from 0.1-0.3 g/g. The starch yield from cassava stem ranges from 17% to 30% and the starch content was found to be 38-55% on dry weight basis. The starch yield was found to be maximum for H-1687 and minimum for Quintal. 64 The peroxidase content in cassava stem starches ranges from 0.05-0.13ng/mg and the poly phenol oxidase content ranges from 10-30mg/g. Both this enzyme content was found to be lowest in Black Thailand and maximum for Sree Swarna and Quintal. It was found that extraction using ultra sound and micro wave assistance could increase the extractability of starch from cassava stem and the genotypes H1687 and H-226 was found to be high starch yielding varieties and thus it could be used for the extraction of starch from cassava stem. Cassava stem contain more than 30% of starch (dry mass), hence the wasted cassava stem starch can be utilized for both food and non-food applications. More over cassava can increase both food and fuel resources where cassava roots are for food and stems for fuel and even reduce poverty without using additional land.
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    Meta-analysis of QTLs associated with pest and disease resistance genes in cassava
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2019) Reshma Parveen, J; Sreekumar, J
    Plant disease resistance is a complex trait which is controlled by quantitative trait loci (QTLs). Several QTLs have been found for cassava disease resistance. Meta-analysis provides a simple, reliable, and economical method for integrating information from multiple QTL studies across various environmental and genetic backgrounds, detecting consistent QTLs powerfully and estimating their genetic positions precisely. The study entitled "META-ANALYSIS OF QTLs ASSOCIATED WITH PEST AND DISEASE RESISTANCE GENES IN CASSAVA" was conducted at the ICAR-CTCRI, Sreekaryam, Thiruvanathapuram during October 2018 to August 2019. The objectives of this study was to combine the results of QTL detection studies conducted on Cassava Mosaic Disease (CMD) resistance genes in cassava, to integrate this data with genomic information of cassava and to validate the results obtained using resistant and susceptible varieties. 61 QTLs from 6 different published QTL mapping studies related to Cassava Mosaic Disease (CMD) and Cassava Brown Streak Disease (CBSD) were selected. A consensus map was constructed by integrating individual linkage maps of these QTLs with a reference map (Cassava genetic linkage map). 58 QTLs from the initial 61 QTLs were then projected to this consensus map. Using Biomercator V.4 software meta-analysis of these projected QTLs were carried out. Meta-analysis of CMD and CBSD-RN resistance QTLs were done separately. 11 MQTLs for CMD resistance and 10 MQTLs for CBSD-RN resistance were obtained. For mining candidate genes and for identifying their functional information the QTLs within the MQTLs with confidence interval less than 2cM and physical length less than1Mb were selected. A total of 38 candidate genes associated with CMD resistance and 30 genes associated with CBSD-RN resistance were annotated. Defence related civ 104 protein and transcription factors were found to be associated with these genes. Validation of the identified QTLs was done by using real time PCR and the genes were found to be expressed in resistant variety of cassava. The MQTLs found in this study that have small physical and genetic intervals are useful for marker-assisted selection for developing disease resistance varieties of cassava.
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    Modeling of cassava-cassava mosaic vrus interactions with computational biology and bioinformatics approach
    (Department of Plant Biotechnology, College of Agriculture,Vellayani, 2019) Rajani, K R; Sreekumar, J
    Every year pathogenic organisms cause billions of dollars’ worth damage to crops and livestock. In agriculture, study of plant-microbe interactions is demanding a special attention to develop management strategies for the destructive pathogen induced diseases that cause huge crop losses every year worldwide. Cassava Mosaic Virus (CMV) is a major viral leaf pathogen that causes disease in cassava. Protein-Protein Interactions (PPIs) play a critical role in initiating pathogenesis and maintaining infection. Understanding the PPI network between a host and pathogen is a critical step for studying the molecular basis of pathogenesis. The experimental study of PPIs at a large scale is very scarce and also the high throughput experimental results show high false positive rate. Hence, there is a need for developing efficient computational models to predict the interaction between host and pathogen in a genome scale, and find novel candidate effectors and/or their targets. In this study, interacting proteins in cassava-CMV interaction is predicted using interolog-based method. The interolog method relies on protein sequence similarity to conduct the PPI prediction. Using this method, 114 PPIs have been predicted between 114 proteins of cassava and 10 proteins of CMV. Functional annotation of the predicted proteins showed the presence of 10 disease resistance protein in cassava that interacts with CMV. The subcellular location of the predicted proteins was found and it showed that major interactions occur in nucleus and chloroplast region. This can be a useful resource to the plant community to characterize the host-pathogen interaction in cassava and CMV. Further, these prediction models can be applied to the agriculturally relevant crops.
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    Investigations on nutritional aspects of Cassava (Manihot esculenta Crantz) Leaf and its enrichment
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2019) Reshma, A; Saravanan Raju
    The study entitled “Investigations on nutritional aspects of cassava (Manihot esculenta Crantz) leaf and its enrichment” was carried out at the Division of Crop Utilization, ICAR – Central Tuber Crops Research Institute, Sreekariyam, Thiruvananthapuram during the year 2018 – 2019. Cassava (Manihot esculenta Crantz) is a major stable food crop for sustainable agricultural practice and food security in both developing and under developed countries. Cassava leaves are rich in protein, carotenes, vitamins B1, B2, and C, and minerals such as calcium, magnesium and also rich in anti-nutritional factors such as cyanogens. Efficient use of cassava products resulted in reduced feed costs. With proper processing the inclusion levels of cassava leaves in diets can be increased and can be used as an alternative energy source. The total fresh weight and dry weight (in grams), and number of leaves (per plant) were studied. For the ten different genotypes the fresh weight and dry weight of the leaves ranged from 168.33 g – 398.77 g plant-1 and 129.67 to 44.57 g plant-1. The number of leaves per plant also varied greatly in number per plant of each genotypes. The crude fibre content of the leaves ranged from 6.4 to 10.3% (Oke, 1966). In the present study the fibre content of leaves was obtained ranging from 18.73 to 48.67% for different genotypes. The lignin content in cassava leaves determines its anti nutritional quality. Higher content of lignin in feed limits its consumption. The lignin content obtained from the study ranges from 0.06 – 0.15 g/g for different genotypes. The linamarin content present in the leaves of the ten cassava genotypes were analysed and it ranged from 0.75 to 6.04 mg g-1 on a fresh weight basis. On a dry weight basis the content ranges from 0.34 to 1.2 mg g-1. The linamarin content at 7th day and 20th day of enrichment of the genotypes H1687 was found to be 0.3549 and 0.3504 mg g-1 while for the genotype Malayan 4 it was found to be 0.3631 and 0.355 mgg-1 respectively. The content can be reduced greatly as the duration of fermentation increases. The rapid reduction in the level of cyanide 75 after ensiling implies that ensiling is an effective way of reducing HCN in cassava leaves and roots before feeding them to dairy animals. In the present study, different genotypes of cassava leaves showed that the content of trypsin inhibitors reaches up to a maximum value of 33.41% for the genotype Sree Jaya (three month old plants). The protein content of the cassava leaves was found to be higher in all genotypes. The protein content of the enriched samples was found to be reduced at 7th day and 20th day when compared to the samples at 0th day. Addition of additives such as molasses resulted in reduction of protein content in the silage, The presence of high content of mineral elements particularly Ca, Mg, K elements in cassava leaves confirms its importance as a rich source of mineral elements. The mineral elements Cu, Zn, Fe, Mn, P present in leaves ranges between 24.7 to 29.7 (mg/L), 123.2 to 230.9 (mg/L), 420 (mg/L) to 476.7 (mg/L), 151.3 (mg/L) – 385.9 (mg/L) and 1.53395 (mg/L) -2.9466 (mg/L) respectively. The mineral elements was found to have a slight decrease in the content on enrichment at 7th and 20th day when compared to initial days. For the present study urea was added as N source, yeast and molasses are also added into the silage for the enrichment purposes which enhance the fermentation rate of the silage that resulted in a characteristic odour, flavour and colour of the silage. The H1687 and Malayan 4 (M4) genotypes having high dry matter and protein content is suitable for use as leaf meal and preparation of silage from cassava leaves.
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    Comparative evaluation of tools for gene regulatory network prediction and network reconstructioon using genomic data
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Reshma Bhasker, T; Sreekumar, J
    Developing regulatory network of genes controlling traits which are of importance economically and commercially are gaining much significance in present times. GRN’s provide an insight into the transcriptional mechanisms that regulate the robust and stochastic gene expression and their relationship with the phenotypic variability that can be utilized for better crop improvement strategies. The former approaches for Gene Regulatory Network construction mainly rely on using gene expression data as input, but the time consumption and high cost of expression analysis paved way for developing new methodologies that make GRN prediction easier. The integration of genomic information along with gene expression data, could make the process of Gene Regulatory Network (GRN) construction more reliable than using expression data alone as input source. Using this approach, we have tried to develop the regulatory network of genes controlling immunity in cassava with special context to Bacterial blight resistance. Initially the immunity related genes in cassava were identified by protein domain search and analysis using HMMER. Cassava specific genes were further filtered for high competency, mapped and annotated to determine its biological role and function. A set of 1919 immunity related genes in cassava were identified, out of which 22 of them were specifically conferring virus resistance, 727 of them were screened for bacterial blight resistance by microarray data integration and a network was created using they predicted interactions identified from 324 genes using STRING. The networks obtained was visualized using Cytoscape and cross validated with simulated dataset generated from SynTReN. The generated network if immunity related genes in cassava could give more insight into the defence mechanism in cassava that can help in adapting better crop improvement and management strategies. A comparison of various approaches used for GRN prediction like probabilistic method, mutual information-based method, correlation-based approaches etc was also done and various tool like ARACNE, WGCNA etc were evaluated. Networks with different sizes, 50, 100 and 150 was generated and the network parameters like clustering coefficient, network density etc were compared. Clustering coefficient does not seem to vary with increase in network size but network heterogeneity and density were observed to increase. The statistical analysis of the performance of different methods resulted into a conclusion that the mutual information based approaches are better tools for Gene Regulatory Network construction than the other methods and it performed with a specificity of 75.7% and a sensitivity of 79.4%.
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    Development of infectious clones of cassava mosaic virus and their validation
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2018) Vishnu Narayanan; Makeshkumar, T
    The study entitled “Development of infectious clones of cassava mosaic virus and their validation” was conducted at the ICAR- Central Tuber Crop Research Institute (ICAR-CTCRI), Sreekariyam, Thiruvananthapuram during 2017- 2018. The major objectives of the study were cloning and characterisation of SLCMV/ICMV infected leaf samples, construction of infectious clones of SLCMV/ICMV and agroinoculation of Nicotiana benthaminana with the partial dimers constructed in order to check the infectiousness of the viral clones. The whole genome amplification of SLCMV/ICMV DNA samples were done and cloned in pUC19 vectors to obtain pSLCMV A7 (2746 bp), pSLCMV B2 (2738 bp) and pICMV A5 (2739 bp) full length clones. The sequence of pSLCMV A7 showed maximum similarity of 99 % with ‘SLCMV-[TVM1]’ sequence in NCBI blast. While the sequence of pSLCMV B2 showed maximum similarity of 99 % with ‘SLCMV-[Ker20]’ sequence in NCBI blast. The sequence of pICMV A5 showed maximum similarity of 95 % with ‘ICMV-[Mah]’ sequence in NCBI blast. In order to develop infectious clones, partial dimers were constructed for SLCMV DNA-A and SLCMV DNA-B and cloned in binary vector pPZP201. These infectious clones were successfully transformed into wild type A. tumefaciens, Ach5 strain by triparental method. Then agroinoculation of N. benthamiana with the constructed partial dimers was found to be successful. After 14 days post inoculation, plants infected with DNA-A + DNA-B partial dimers showed severe symptoms like leaf curling, stunting. The plants infected with partial dimer of DNA-A alone showed mild symptoms like upward leaf curling which confirmed its monopartite lineage. While those plants agroinoculated with partial dimer of DNA-B alone did not show any symptoms. These efficient infectious clones of cassava mosaic virus and their subsequent inoculation technique would provide a major advancement to the resistance development in cassava.
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    Identification of graft transmissible resistant factors and development of si RNA mediated resistance in cassava against cassava mosaic geminivirus
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Asha B Nair; Umamaheswaran, K