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

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    Strain improvement of Trichoderma spp.for management of foot rot of black pepper caused by phytophthora capsici
    (Department of plant pathology, College of Agriculture, Vellanikkara, 2025-09-22) Alby John; Susha S Thara
    The research work entitled ‘Strain improvement of Trichoderma spp. for management of foot rot of black pepper caused by Phytophthora capsici’ was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2022-2025 with an objective of enhancing the antagonistic potential and growth promotion of Trichoderma strains by protoplast fusion and mutagenesis; studying the biochemical and molecular mechanisms underlying antagonism and evaluation of its efficacy for managing P. capsici. Five promising isolates of Trichoderma spp.: TRMW-2, TRKR-2, TRPN-3, TRPN-11 and TRPN-17, previously collected from different agroclimatic zones of Kerala, along with Trichoderma asperellum, the reference culture from KAU were used as the parental isolates. Molecular characterization using species-specific primers (TEF1 and RPB2) and multi-gene phylogenetic analysis identified TRMW-2, TRKR-2, TRPN 3, TRPN-11 and TRPN-17 as Trichoderma brevicompactum [Tb], Trichoderma koningiopsis [Tk], Trichoderma pholiotae (PN3) [Tp (PN3)], T. pholiotae (PN11) [Tp(PN11)] and Trichoderma guizhouense [Tg], respectively. A total of 15 protoplast fusion combinations were performed using the six parental isolates and 30 fusants with a colony diameter exceeding 8.5 cm at 48 h were screened. Among these, the 10 most effective fusants, exhibiting a growth inhibition rate of 85.73% to 92.13% against P. capsici were selected based on their mycelial growth suppression. Simple sequence repeat (SSR) marker analysis was performed using 15 primers to determine whether the selected fusants were interspecific. Similar amplification patterns were observed between the fusants Ta × Tk-1, Tk × Tp (PN3)-1, Ta × Tp (PN3)-1 and Ta × Tp (PN3)-5 and their respective parental strains for the markers PRB ATC, TV1, KON 700, TA4, TA9 and TH5, confirming them as interspecific fusants. Strain improvement through UV irradiation (5, 10 and 15 min) exhibited an inverse correlation between exposure time and the number of regenerated colonies. Among 140 mutants screened, 30 with a colony diameter greater than 7.5 cm at 48 h were selected, which were further narrowed down to 10 with the highest inhibition rates of 80.87% - 84.47% against P. capsici. Similarly, gamma irradiation (150, 200, 250 and 300 Gy) showed a negative correlation between colony regeneration and radiation dose. Among 180 mutants screened, 10 superior mutants with a growth inhibition of 81.67% - 90.40% were selected. From the 30 improved Trichoderma spp. strains obtained through three distinct strain improvement techniques, the 10 most effective strains exhibiting significant pathogen inhibition (83.73% to 93.60%) were identified and subjected to genetic stability assessment via ten successive subculturing rounds, followed by dual culture assay against P. capsici. The five most promising Trichoderma strains: T. asperellum × T. koningiopsis-1 [Ta × Tk-1], T. koningiopsis ×T. pholiotae (PN3)-1 [Tk × Tp(PN3)-1], T. pholiotae (PN11) fifth UV mutant colony irradiated for 5 min [Tp(PN11).5m5], T. pholiotae sixth gamma mutant colony irradiated at 200 Gy [Tp(PN3).200m6] and T. asperellum first gamma mutant colony irradiated at 250 Gy [Ta.250m1] with superior mycelial growth suppression (83% to 91.27%) were selected. Culture filtrate assay at 50% concentration revealed maximum mycelial inhibition of P. capsici by Tk × Tp(PN3)-1 (98.33%) and Tp(PN11).5m5 (97.92%). Additionally, Ta × Tk-1 (76.13%) and Tp(PN3).200m6 (72.25%) exhibited significant volatile metabolite activity against P. capsici, outperforming T. asperellum (59.88%). The potential of the selected Trichoderma spp. strains to produce lytic enzymes, including β-1,3 glucanase, protease, chitinase and lipase was evaluated. Ta × Tk-1, Tk × Tp(PN3)-1, Tp(PN11).5m5 and Ta.250m1 exhibited higher enzymatic activity than T. asperellum, signifying enhanced antagonistic potential. Growth promoting attributes, including IAA (174.41 μg ml-1) and siderophore production (77.09%) were highest in the interspecific fusant Ta × Tk-1, while phosphate solubilization was most pronounced in the gamma mutant Ta.250m1(1326.90 μg ml-1). Cultural and morphological characterization of the improved strains revealed distinct variations in conidiation, pigmentation, hyphal width and conidial and phialide size compared to their parental isolates. Notably, Tp(PN3).200m6 exhibited deep yellow pigmentation, while Ta × Tk-1 and Ta.250m1 showed dense sporulation. Pot culture experiments were conducted to evaluate the biocontrol efficacy and plant growth promoting potential of five promising Trichoderma spp. along with T. asperellum in black pepper var. Panniyur - 1. Biometric characters (plant height, number of leaves, nodes and internodal length) were highest in plants treated with Ta × Tk-1, followed by Ta.250m1. Upon challenge inoculation with P. capsici, lesion size was smallest in plants treated with Tk × Tp(PN3)-1 and Tp(PN11).5m5, corresponding to a percent disease index of 20.19% and 35.44% respectively, compared to 83.57% in control plants. Elevated activity of defense related enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, catalase and superoxide dismutase) was recorded in plants treated with Tk × Tp(PN3)-1, Tp(PN11).5m5 and Ta × Tk-1. The relative expression of antagonism associated genes from different functional groups; chitinase, β-1,3-endoglucanase, subtilisin-like protease and terpene synthase were analyzed in both improved Trichoderma strains and their respective parental isolates using semi-quantitative RT-PCR. Expression levels were significantly upregulated in Tk × Tp(PN3)-1 and Tp(PN11).5m5 across all four genes compared to the parental isolates. This study identified three improved Trichoderma strains; Ta × Tk-1, Tk × Tp(PN3)-1 and Tp(PN11).5m5 that exhibited enhanced antagonistic potential, biochemical characteristics, plant growth promoting traits and defense enzyme activities, surpassing the reference strain T. asperellum. Therefore, following multi-locational field trials across different crops and comprehensive toxicological studies, these strains could be released as efficient biocontrol agents in the future.
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    Development of robotic black pepper harvesting system
    (Department of Farm Machinery and Power Engineering, Kelappaji College of Agricultural Engineering and Technology, Tavanur, 2022-07-25) Amsuja V Ajayan.; Sindhu Bhaskar
    Black pepper is a perennial crop and one of India's most economically significant spices. It has a high commercial value in the market all around the world. Its fruit is harvested, dried, and powdered for many cuisines and processed for many value-added products. Black pepper is a flowering vine growing on supporting stakes. The berries turn from green to red on maturity and are harvested when it starts to turn red. For achieving good quality and good-sized pepper, it should be harvested at its correct maturity stage. Generally, black pepper spikes were harvested manually by climbing on supporting trees using bamboo poles. It is a tedious task because there are chances of falling from ladders while harvesting and also causes some musculoskeletal diseases to the labours. For their time saving and heavy work intensity, farmers harvest almost all the fruits in a range of maturity along with the real matured ones. This practice eventually affects the crop yield and quality. Through robotic harvesting, black pepper spikes can be harvested at correct maturity and also helps to overcome the difficulties faced by the labours. The main functions of robotic harvesting are identification, plucking, depositing, and controlling. KAU developed a machine vision system with the camera as sensor, Raspberry pi 4 model B as the processor, and LCD as the display unit to identify matured black pepper spikes. The programing code was written in python language, and the Tensorflow-faster RCNN platform was used for the detection. Hence, a robotic black pepper harvesting system was developed in the present study, and its performance evaluation was carried out. The physical properties of black pepper relevant to design and develop a robotic black pepper harvesting system were determined. The developed robotic black pepper harvesting system consists of a machine vision system to identify matured black pepper spikes, a manipulator with 2 DOF, an end-effector with 1 DOF, and a control unit. Servo motors actuated the shoulder and elbow joints of the manipulator and the cutting blades. Shear-type cutting was employed for detaching pepper spikes from the pepper vine. The entire system was controlled by the microprocessor Raspberry pi 4 Model B. For controlling the servo motors, the library RPi.GPIO was installed on raspberry pi, and the programming code was 180 written in python language. Two lead-acid batteries with a voltage of 12 V and a current 9Ah were connected in parallel to power the entire system. The overall dimension of the developed unit was 59 × 18 × 162 cm, and it weighs 2.1 kg. The performance evaluation parameters of the machine vision system viz., sensitivity, specificity, and accuracy were respectively as 85 %, 77 %, and 82 % in Karimunda variety and 84 %, 77 %, and 82 % in Panniyur 1 variety. Time taken for detection is 0.43 seconds. Also, the capacity of the developed robotic black pepper harvesting system is 3.5 kg h-1 and 562 spikes h-1 in the Karimunda variety, whereas 4.6 kg h -1 and 683 spikes h -1 in Panniyur 1 variety. The effectiveness index, time taken for the entire operation, harvesting loss, and drying loss was 81%, 6.6 seconds, 4.9 %, and 39 % in the Karimunda variety and 82 %, 6.3 seconds, 7%, and 66 % in Panniyur 1 variety respectively. The system takes 0.18 seconds for a single cut for both varieties; it was fixed in the program. A study was also carried out for manual harvesting and found that manual harvesting has a capacity of 1052 spikes h-1 and 6.3 kg h -1 in the Karimunda variety and 1654 spikes h -1 and 10.8 kg h -1 in the Panniyur 1 variety, which is higher than robotic harvesting. The effectiveness index of the manual harvesting was 40% in Karimunda and 38 % in Panniyur 1, which is lower than robotic harvesting. The harvesting loss and drying loss of manual harvesting are 15.3 % and 56 % in Karimunda and 17.5 % and 81 % in Panniyur 1, which is higher than robotic harvesting. It was statistically verified and found a significant difference between manual and robotic harvesting in terms of capacity, effectiveness index, harvesting loss, and drying loss at a 5 % level of significance.
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    Management of a major fungal disease in black pepper (Piper nigrum L.)
    (Department of Plant Pathology, College of Agriculture,Padanakkad, 2022) Pranavya, A P; Sajeesh P K
    Black pepper (Piper nigrum L.) is one of the major spice crops and plantation crops that grow as the sole crop or intercrop in Kerala. In nurseries of black pepper major biotic stress are caused by bacteria, fungus, virus and nematode, out of this fungal infection are the leading one. The seedling blight, anthracnose and collar rot were found to be more severe in the nursery. With this background, the present study was conducted to identify the major fungal pathogen associated with black pepper nursery and formulate disease management strategies against that pathogen. A survey was carried out in black pepper growing nurseries to record the different diseases. Seedling blight, anthracnose and collar rot were observed. The fungal isolates associated with seedling blight in nurseries at Padannakkad and Kanakappalli were designated as Pc1 and Pc2 respectively. Anthracnose affected seedlings were collected from Padannkkad, Balal, Panniyur and Periya black pepper nurseries and the fungal isolates associated were designated as Cg1, Cg2, Cg3 and Cg4 respectively. The collar rot samples were collected from Padannakkad, Periya and Panniyur and isolates were designated as Sr1, Sr2 and Sr3. In the case of seedling blight infection, highest disease incidence (DI) (74%) was recorded in Pc1. The highest percent disease index (PDI) in case seedling blight (32%) was recorded in Pc1 as compared to Pc2 isolate. In the case of anthracnose, higher DI (30%) and PDI (25%) were recorded in Cg1 in comparison with Cg2, Cg3 and Cg4. In case of collar rot, higher DI (20%) was recorded in case of Sr1 isolate. All the isolates were tested for its pathogenicity; in case of seedling blight, the isolate Pc1 recorded higher radial growth (7.90 cm) and recorded lesser time (2days) for the symptom development as compared to Pc2 isolate. In case of anthracnose, isolate Cg1 recorded higher radial growth (8.0 cm) and took lesser time (5days) for the symptom development in comparison with Cg2, Cg3 and Cg4. In case of collar rot isolate Sr1 recorded higher radial growth (8.96 cm) and recorded lesser time (2days) for the symptom development as compared to Sr2 and Sr3. A trial was laid out to identify the most susceptible variety of black pepper as well as the most virulent strain of the pathogen among different isolates on pepper varieties viz., Panniyur (P) 1-6, P8, P9, Vijay and Karimunda. Panniyur 2 was identified as most susceptible variety and Pc1 was the virulent isolate. Based on cultural and morphological characters and molecular characterization, Pc1 was identified as Phytophthora capsici. In vitro evaluation of biocontrol agents, chemical fungicides and organic preparations were carried out to study the efficacy against P. capsici. Under in vitro conditions biocontrol agent T. harzianum (2%) exhibited maximum inhibition (55.56%) followed by P. fluorescens (53.33%). Among the chemical fungicides copper oxychloride (0.3%) and metalaxyl (8%) + mancozeb (64%) at 0.3 percent recorded 100 per cent inhibition. Among the organic preparations, ready to use neem oil garlic soap (3%) and garlic extract at 0.3 percent recorded maximum inhibition 31.11% percent and 28.88% percent respectively in the mycelial growth of the pathogen. The best-performing treatments from the in vitro evaluation were selected for pot culture experiment on variety Panniyur 2. After 7 days of inoculation, the least PDI (0.00 %) as well as the least lesion development (0.00%) was recorded in case of metalaxyl (8%) + mancozeb (64%) at 0.6 per cent. The higher PDI (86.66%), as well as maximum lesion development (46.66%), was recorded in ready to use neem oil garlic soap (3%). The study reveals that, the seedling blight caused by Phytophthora capsici can be effectively managed with the foliar application of metalaxyl (8%) + mancozeb (64%) at 0.6 per cent.
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    Biocontrol of anthracnose of black pepper (Piper nigrum L.) caused by Colletotrichum spp. using mycoparasites
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2002) Anoop Sankar; Santhakumari, P
    An investigation was done for exploiting potential biocontrol agents for the management of anthracnose of black pepper. Survey conducted on the incidence of anthracnose disease in eleven different locations of the state during February - July 2000 revealed that Colletotrichum gloeosporioides was the most common pathogen associated with this disease. Distinct variability in morphological characters and pathogenicity was exhibited by the di"fferent isolates of the pathogen. The most virulent isolate was isolate C6 from Perinthalmanna. The pathogen survived for three months on infected leaves in the soil and upto five months on infected leaves under laboratory conditions. A study was conducted to isolate potential mycoparasites of C. gloeosporioides from the rhizosphere and phyllosphere of both healthy and diseased black pepper plants from the various locations surveyed. Among the fungi isolated, two isolates of Trichoderma harzianum Rifai (T I and T 2) and two isolates of Aspergillus niger van Tieghem (A, and A2) were found to be most effective in' inhibiting C. gloeosporioides in vitro. After mass multiplication, the selected fungal antagonists were formulated in talc, which was found to be the best carrier material for maintaining the viability of the antagonists. The shelf life of the talc based formulations were 150 days and 180 days for the T. harzianum isolates and A. niger isolates respectively. The antagonistic fungi were tested separately under greenhouse conditions by a combination of two methods of application viz., soil application and foliar spray. Greenhouse studies indicated that all the four isolates were equally effective In suppressing the development of the disease in black pepper cuttings. Application of the talc based formulations of the four isolates in the soil @ 109 / kg soil followed by foliar spray with one per cent suspension of the talc based formulations twice at 15 days interval starting from 10 days after pathogen inoculation was very effective in controlling the disease under greenhouse conditions. In general, application of the fungal antagonists promoted the growth of black pepper cuttings. Isolate Al produced maximum shoot length, root length and fresh weight in the treated black pepper cuttings. The results of the study assigned dual roles as biocontrol agents and plant growth promoters for all the four fungal antagonists.
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    Evaluation of pathogenesis related proteins in relation to phytophthora foot rot in black pepper [Piper Nigrum L.]
    (Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 2000) Parab, G V; Nazeem, P A
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    Effect of biofertilizers on early rooting, growth and nutrient status of black pepper (Piper nigrum L.)
    (Department of Agronomy, College of Horticulture, Vellenikkara, 2001) Ashithraj, N; Prameela, K P
    With an objective of studying the effect of vanous biofertilizers on establishment and growth of pepper cuttings, an experiment was conducted in the College of Horticulture, Vellanikkara during 1999-2000. Both lateral and runner cuttings were inoculated with five species of Glomus and three strains each of A.lipoferum and A.chroococcum. Observations were taken on germination and different growth parameters. Based on the early performance two species of Glomus and two strains each of A.chroococcum and Alipoferum were selected. Single, double and triple combinations of these selected microbes were studied further. Multiple inoculation was found to be supenor over single inoculations. Combinations involving AMF and nitrogen fixing bacteria were showing better results compared to two nitrogen fixing bacteria. Comparing the two species of AMF, Gfosciculatum was more effective in improving overall growth characters. Among nitrogen fixers, Alipoferum was more promising. Combination effect of Gfasciculatum and Alipoferum was appreciably good. However, addition of A.chroococcum with A.lipoforum and AMF further improved the growth performance of crop.
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    Variability analysis in calliclones of black pepper (Piper nigrum L.)
    (Department of Plantation Crops and Spices, College of Horticulture, Vellanikkara, 2000) Sanchu, C R; Shylaja, M R
    The investigations on 'Variability analysis ID calliclones of black pepper' were carried out in the Department of Plantation Crops and Spices, College of Horticulture, Kerala Agricultural University, Vellanikkara from October, 1998 to July, 2000. Thirty calliclones of black pepper regenerated from axenic seedling of the cultivar Cheriakanyakkadan planted in Pepper Research Scheme of the Department during June, 1995 were utilised for the study. The objective of the study was to assess the variability among the calliclones of black pepper based on morphological, yield and quality attributes and reaction to Phytophthora foot rot disease. Morphological descriptions of the thirty clones were made based on the mPGR descriptor. The variation at the phenotypic level was measured using the procedure described by Deklerk (I 990). Screening of calliclones for Phytophthora foot rot resistance/tolerance was carried out as per the procedure reported by Kueh and Khew (1980). Wide variability was observed for morphological characters like leaf shape, leaf area, internodal length of laterals, number of runner shoots and lateral branches in the different calli clones studied. The calliclones also exhibited variations for yield and yield contributing characters like the number of spikes per lateral, spike length and number of berries per spike. The dry recovery percentage recorded was generally high in all the calliclones and the clones exhibited less variation for the character. The eontent of essential oil and piperine showed more variation than the content of oleoresin in the different calliclones studied. The assessment of Phytophthora foot rot disease reaction of the calliclones revealed that the clones CC 43, CC 58 and CC 60 were highly tolerant. Five elite clones viz. CC 58, CC 43, CC 60, CC 56 and CC 57 with desirable traits like high yield, quality and tolerance to Phytophthora capsid were identified. Based on overall attributes, the calliclone 'CC 60' was selected as the superior clone with high yield, quality and high tolerance to Phytophthora foot rot. The superior and elite clones with desirable attributes can be further exploited in crop improvement/production programmes.
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    Influence of soil moisture regimes on growth and yield in bush pepper (Piper nigrum L.)
    (Department of Agronomy, College of Horticulture, Vellenikkara, 2000) Thankamani, C K; Ashokan, P K