1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Bioefficacy of entomopathogenic fungi against cassava mealybug, phenacoccus manihotti matile-ferrero (Hemiptera: Pseudococcidae)
    (Department of Agricultural Entomology, College of Agriculture,Vellanikkara, 2024-02-21) Fasna, Sherin, K.; Smitha Ravi; Gowri Priya
    Cassava mealybug (CMB), Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae) is a major insect pest of cassava. It causes severe damage by stunting the growth points of cassava plants, sometimes totally defoliating the plants. Level of infestation and yield loss by cassava mealybug varied from 30 to100 and 30 to 90 per cent respectively. In India, the occurrence of this pest was first noticed on cassava in Thrissur, Kerala during April 2020. Control of mealybugs commonly relies on the use of insecticides. But, it is difficult to control mealybugs using insecticides, due to their cryptic life cycle, presence of waxy coating, and formation of dense colonies. Management of insect pests using entomopathogens has received considerable importance in recent times. As part of AICRP programme of 2020-22, AICRP on BCCP, Thrissur centre conducted survey in cassava growing fields of Thrissur and Palakkad district to assess the species composition of mealybugs, damage intensity and associated natural enemies. During the survey, mycosed cadavers were collected and seven isolates of entomopathogenic fungi were obtained. Out of seven, five entomopathogenic fungal isolates were selected, characterized and evaluated under the present study entitled “Bioefficacy of entomopathogenic fungi against cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae)”. The identity of five isolates was confirmed through morphological, cultural and molecular characterization. The fungal isolates were identified as two isolates of Simplicillium aogashimaense (EPF 2 and EPF 4), two isolates of Purpureocillium lilacinum (EPF 3 and EPF 7) and one isolate of Lecanicillium psallioate (EPF 5). Pathogenicity of these fungal isolates was tested against second instar nymphs of cassava mealybug, P. manihoti in the laboratory. A preliminary screening bioassay was carried out initially, and the superior isolates were subjected to dose-response and exposure-time response bioassay. In the preliminary screening bioassay, P. lilacinum isolates (EPF 7 and EPF 3) recorded more than 90.0 per cent mortality. S. aogashimaense (EPF 4) and L. psalliotae (EPF 5) registered mean mortality of 82.5 and 75.0 per cent respectively. S. aogashimaense (EPF 2) recorded the lowest mortality of 70.0 per cent, which was significantly lower than all other isolates. The best four isolates in the pre-screening were subjected to dose-response and exposure time- response bioassay. Spore suspensions of five different concentrations ranging from109 to 105 spores ml-1 were tested against mealybug. Ten days after treatment, two isolates of P. lilacinum (EPF 7 and EPF 3) recorded more than 80.0 per cent reduction in population of mealybug at the concentration of 109 spores ml-1 . The same isolates showed low LC50 and LT50 values. Efficacy of these two superior isolates of P. lilacinum (EPF 7 and EPF 3) at concentration of 1×108 spores ml-1 was evaluated in a pot culture experiment. The isolates were compared with a standard biocontrol check, NBAIR isolate of Lecanicillium lecanii @ 1×108 spores ml-1 , a botanical insecticide (neem oil emulsion @ 2%) and a chemical insecticide, dimethoate 30 EC @ 1.5 ml L-1 . Maximum reduction in the mealybug population was observed in dimethoate treated plants (99.86%). Even though, the neem oil emulsion (2%) showed significant effect on mealybugs, certain signs of phytotoxicity were observed in treated plants. Among three fungal isolates, significantly higher reduction in population was observed in P. lilacinum, EPF 7 (78.55%) followed by P. lilacinum, EPF 3 (74.92%), and both being on par with each other. In conclusion, the present study revealed that biological control of cassava mealybug, P. manihoti using two promising isolates of P. lilacinum could be a viable component in the integrated pest management. Two rounds of foliar application of any of the two isolates of P. lilacinum (EPF 3 and EPF 7), at 15 days interval at the dosage of 1×108 spores ml-1 was found effective against cassava mealybug, P. manihoti.
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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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    Process optimization of fruit blended boba tea pearls from cassava (Manihot esculenta)
    (Department of community science, college of agriculture,Vellayani, 2023-11-09) Gayathri, D.; Anitha, Chandran
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    Technology adoption behaviour cassava growers in Kollam district
    (Department of Agricultural Extension, College of Agriculture, Vellayani, 2020) Kavya, V S; Bindu, Podikunju
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    Role of mixed infection of cassava mosaic viruses in cassava mosaic disease development
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Akhila, J; Makeshkumar, T
    A 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.
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    Screening of cassava genotype for cassava mosaic disease resistance
    (Department of Plant Biotechnology, College of Agriculture, Vellayani, 2020) Preeja, P S; Makeshkumar, T
    The 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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    Formulating fermented cassava food products
    (Department of Home Science, College of Agriculture, Vellayani, 1989) Sathyalakshmi, C; Chellammal, S
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    Crop-weather-nutrient relations in cassava under drought stress
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2020) Sreelakshmi, K; Meera Menon, V
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    In vitro mutagenesis and evaluation of somatic embryo derived plantlets in cassava (Manihot esculenta Crantz.)
    (Department of Plant Breeding and Genetics, College of Horticulture, Vellanikkara, 2016) Riya Antony; Jiji Joseph
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    Pre-harvest forecasting models and instability in production of cassava (manihot esculenta crantz.)
    (Department of Agricultural Statistics, College of Agriculture, Vellayani, 2017) Neethu Kumar, S; Brigit Joseph