Browsing by Author "Radhakrishnan, N V"

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Biopriming and foliar apllication of biocontrol agents and endophytes for the management of major foliar fungal diseases of bush cowpea
(Department of Plant Pathology, College of Agriculture , Vellayani, 2023-05-26) Aswathy ,V S.; Radhakrishnan, N V
The study entitled “Biopriming and foliar application of biocontrol agents and endophytes for the management of major foliar fungal diseases of bush cowpea” was conducted at College of Agriculture, Vellayani and Coconut Research Station, Balaramapuram during 2020-2022. The objective was to develop best ecofriendly management practice involving biopriming, foliar application of endophytes and biocontrol agents for the control of major foliar fungal diseases in bush cowpea with special emphasis on Cercospora leaf spot and anthracnose. Symptomatology and etiology of anthracnose and Cercospora leaf spot were studied under field condition from different locations in Trivandrum district viz., Vellayani, Pappanchani, Venganoor, Balaramapuram, Nedumangad and Parassala. The pathogens were isolated and studied their morphological characteristics. Bush cowpea seeds were collected from five agro-ecological zones of Kerala viz., Northern, High range, Central, Special problem and Southern zones and the seeds were assessed for both externally and internally seed borne microflora. Percentage of infection was calculated by blotter method. The lowest percentage of infection was found in seed samples collected from Wayanad (16.7%) and the highest in Thrissur (38.2%). The diseased leaf samples showing anthracnose were collected from five locations of Thiruvananthapuram district and isolated Colletotrichum gloeosporioides from each location. Pathogenecity of isolated pathogen was proved by detached leaf assay and seedling assay. Vellayani isolate (C1) was found to be the most virulent pathogen and recorded lesion size of 4.33cm and 1.82cm in detached leaf assay and seedling assay on seventh day respectively. The isolate C1 was used for further studies. In vitro evaluation of biocontrol agents like Trichoderma asperellum T6 (KAU), Trichoderma koningiopsis (TRKR2), Trichoderma harzianum (TRMW2), Piriformospora indica (No. INBA 3202001787), Bacillus amyloliquiefaciens VLY 24, Bacillus velezensis (CBRE5), Bacillus amyloliquefaciens (CBSE5) and Pseudomonas fluorescens PN026 (KAU isolate) against Colletotrichum gloeosporioides and Cercospora sp. were carried out. Dual culture method of Colletotrichum gloeosporioides against biocontrol agent recorded highest percentage inhibition of mycelia by T. asperellum (64.76) followed by Trichoderma strain TRKR2 (52.63) which was on par with bacterial strain CBRE5 and least for Psuedomonas fluorescens. In vitro pathogen suppression by spore germination assay on Cercospora sp. by 145 biocontrol agents revealed that maximum inhibition of conidia germination was by T. asperellum (36.25 %) followed by Trichoderma strain TRKR2 and Trichoderma strain TRMW2 whereas least inhibition percentage was observed with Piriformospora indica (14.96). Peroxidase and polyphenol oxidase assay on bush cowpea pods and seeds showed that fungus infected tissues had relatively higher activity of these oxidase enzymes in comparison to healthy pods. Enzyme activities were higher in pods and seeds treated with Bacillus strain CBRE5, T. asperellum and Trichoderma strain TRKR2. Standardization of priming techniques revealed that soaking of seeds for 2h was found effective for Trichoderma asperellum, Bacillus velezensis (CBRE5) and Bacillus amyloliquiefaciens VLY 24 and 4h for Trichoderma strain TRKR2. The soaking duration is followed for the treatments in in vivo studies. Based on the in vitro studies, the best three treatments viz., Trichoderma asperellum, Trichoderma strain TRKR2 and Bacillus strain CBRE5 were taken for in vivo studies. In vivo studies on the effect of seed biopriming and spraying of biocontrol agent suspension at 4 leaf, 50 per cent, flowering and pod set stages revealed lowest disease severity of anthracnose was recorded for Trichoderma asperellum treated plants with disease suppression over control 41.74 per cent followed by carbendazim, Trichoderma strain TRKR2 and Bacillus strain CBRE5. In the case of Cercospora leaf spot Trichoderma asperellum treated plants shown highest disease suppression (63.47%) over control followed by carbendazim, Trichoderma strain TRKR2 and Bacillus strain CBRE5. Bacillus strain CBRE5 recorded least disease suppression over control in anthracnose and Cercospora leaf spot while comparing other treatments. Highest number of pods per plant (34.75), seeds per pod (15.25), plant height (46.05 cm) and yield (232.47 g) were shown by bacterial strain CBRE5 treated plants. Thus, the present study indicated that the seed biopriming for 2 h along with foliar application of Trichoderma asperellum suspension at 4 leaf , 50 per cent flowering and pod set stages was most effective treatment for the management of major foliar fungal diseases like anthracnose and Cercospora leaf spot of bush cowpea whereas seed biopriming for 2 h along with foliar application of Bacillus velezensis suspension at 4 leaf stage, 50 per cent flowering stage and pod set was the best treatment in plant growth promotion in vivo which could be used as an eco-friendly measure to produce safe to eat crop.
Characterization of fungal pathogen associated with leaf rot disease of coconut (Cocos nucifere L.) and in vitro evaluation of phylloplane microflora as biocontrol agents
(Department of Plant Pathology, College of Agriculture, Vellayani, 2020) Deena Sebastian; Radhakrishnan, N V
Leaf rot disease (LRD) is a major foliar disease affecting coconut plantations of Southern Kerala especially in root (wilt) affected areas. In this context, the study entitled ‘Characterization of fungal pathogen associated with leaf rot disease of coconut (Cocos nucifera L.) and in vitro evaluation of phylloplane microflora as biocontrol agents’ was conducted in the Department of Plant Pathology, College of Agriculture, Vellayani during the year 2018-2020, with the objective to identify and characterize the major fungal pathogens associated with the LRD of coconut and in vitro evaluation of phylloplane microflora of coconut against the pathogens. The isolation of LRD pathogens was carried out from six taluks of Thiruvananthpuram district such as Thiruvananthapuram, Neyyattinkara, Nedumangad, Chirayinkeezhu, Kattakada and Varkala. Three locations were selected from each taluk and a total of eighteen samples were collected during the study. The results revealed that the disease in Thiruvananthapuram district was caused by a spectrum of pathogens such as Colletotrichum gloeosporioides, Fusarium spp., Gliocladium sp., and Scytalidium sp. The LRD was caused either by a single pathogen or by combinations of pathogens. C. gloeosporioides and Fusarium spp. were found as the major pathogens of LRD based on the frequency of isolation. Each and every isolate of the same pathogen differed from one another in cultural characters and virulence. All the pathogens produced water soaked brown lesion on artificial inoculation on detached spindle leaves; though the days taken for symptom initiation and size of the lesion developed varied. The isolate C3 (Isolate from Anayara, Thiruvananthapuram taluk) was found to be more virulent among the C. gloeosporioides isolates; and among the Fusarium spp. isolates, the isolate F5 (Isolate from Alamkode, Chirayinkeezhu taluk) was found to be more virulent. By observing the spore characters of the isolates, it was found that the spore size and pigmentation of the culture haven’t any significance to the virulence of the pathogen. Dual inoculation of the major pathogens on detached spindle leaves caused severe incidence of the disease compared to the individual inoculation of the pathogens. This result indicated that the LRD caused by fungal complex is more severe than that caused by individual fungal isolates. There are phylloplane fungi existing on healthy leaves of the infected palm with enough inhibition potential to LRD. The phylloplane fungal isolate PF5 showed more per cent inhibition to mycelial growth of C. gloeosporioides (54.44%) followed by the isolate PF4 (43.33%); and the isolate PF4 showed more inhibition to Fusarium sp. (64.44%) followed by the isolate PF5 (45.55%) in the dual culture assay. The detached spindle leaf assay also supported the same fact that the isolate PF5 was observed to be more suppressive to the disease caused by C. gloeosporioides (28.77%) and the isolate PF4 was reported to have more suppression to the disease caused by Fusarium sp. (34.56%). These pre-treatment effects are more promising than Pseudomonas fluorescens PN026, but inferior to copper oxy chloride (0.2%). Thus, the present study revealed that the LRD of coconut in Thiruvananthapuram district is caused by a combination of pathogenic fungi viz., C. gloeosporioides, Fusarium spp., Gliocladium sp., and Scytalidium sp. Prophylactic application of the phylloplane fungal isolates PF4 and PF5 could reduce the LRD severity in vitro to a promising level and these isolate can be further tested for in vivo biocontrol potential before going for the development of a formulated product.
Fungal pathogens associated with button shedding in coconut and its management using antagonistic microorganisms
(Department of Plant Pathology, College of Agriculture , Vellayani, 2022-03-08) Aparnna Shaju; Radhakrishnan, N V
The research work entitled ‘Fungal pathogens associated with button shedding in coconut and its management using antagonistic microorganisms’ was conducted during 2019-21 at Department of Plant Pathology, College of Agriculture, Vellayani and Coconut Research Station, Balaramapuram with the objectives to isolate the fungal pathogens associated with button shedding in coconut, in vitro screening of the isolated pathogens and spraying of antagonists on the field for the management of the disease. Fallen infected nuts were collected from College of Agriculture, Vellayani and Coconut Research Station, Balaramapuram. The percentage disease incidence and intensity were high during monsoon season with highest value in the month of May in both locations. The disease was highly prevalent in Coconut Research Station, Balaramapuram compared to College of Agriculture, Vellayani. The samples collected were grouped into different age groups based on their maturity and found that the fungal infection was more prevalent in two month old nuts (88.57 %) and 3-4 month old nuts (87.00 %) while five month or above old nuts recorded lower fungal infection (40.00 %). The fungal pathogens isolated from both locations include Phytophthora palmivora, Lasiodiplodia theobromae, Fusarium oxysporum, Colletotrichum gloeosporioides and Thielaviopsis paradoxa. Regardless of the pathogen isolated from the samples, the fallen nuts displayed brown to black lesions extending from the perianth regions to the distal end. The isolated fungi vary in their morphological and microscopical characteristics which forms the basis for their identification. P. palmivora isolates were white to dull white in colour with stellate or irregular pattern. Lasiodiplodia theobromae cultures were initially white in colour which later turned grey and eventually became black in colour. F. oxysporum produced whitish colony growth with yellow or pink colour on the rear side. Colletotrichum gloeosporioides isolates showed white colony growth with white or greyish white colour on the rear side. T. paradoxa isolates had whitish colony growth with black pigmentation. The sporangia of P. palmivora were elongated, papillate and pedicellate while L. theobromae had dark brown, septate conidia with longitudinal striations. F. oxysporum produced oval micro conidia and sickle shaped macro conidia. Spores of C. gloeosporioides were cylindrical in shape with oil globule in the center. Dark brown conidia in chains without any septa were the characteristics of T. paradoxa. When cultured on Potato Dextrose Agar medium, the isolates varied in the time taken to fully cover the 9 cm Petri plate. T. paradoxa and L. theobromae took only three days to attain full growth. P. palmivora and C. gloeosporioides isolates attained full growth within 10 to 12 days. F. oxysporum took more than 12 days to reach full growth. The isolated pathogens when inoculated on two month old healthy nuts resulted in the formation of brown to black lesions. The lesion size varied with the inoculated fungus. T. paradoxa and L. theobromae were the most virulent and caused severe rotting of nuts within 15 days of inoculation. The combined inoculation of isolates obtained from Coconut Research Station, Balaramapuram resulted in much more severe rotting than isolates obtained from College of Agriculture, Vellayani. The isolated pathogens were screened in vitro against antagonistic microorganisms obtained from Department of Agricultural Microbiology, College of Agriculture, Vellayani which include Pseudomonas fluorescens PN026, Trichoderma sp. (KAU strain), Bacillus amyloliquefaciens VLY24 and Bacillus velezensis PCSE10. The antagonists exhibited lysis or overgrowth or antibiosis in dual culture plates depending on the pathogen tested. Among these antagonists, Trichoderma sp. (KAU strain) showed higher inhibition percentage and antagonistic index. Among the bacterial antagonists, B. amyloliquefaciens VLY24 and B. velezensis PCSE10 recorded wider inhibition zone with higher percentage inhibition and antagonistic index. P. fluorescens had the lowest percentage of inhibition and antagonistic index. The antagonistic microorganisms tested in vitro were cultured in liquid broth and adjusted to 108 colony forming units per ml. The antagonists are then sprayed on two to seven month old bunches of button shedding affected palms in Coconut Research Station, Balaramapuram. Copper oxychloride (0.2 %) was used as chemical check. The number of nuts in the treated bunches were noted down at the time of spraying and also at fortnightly intervals. The percentage nut fall for each interval was calculated. After 70 days of spraying, the percentage of nut fall was much lower in bunches sprayed with B. amyloliquefaciens VLY24 (42.71 %) followed by Copper oxychloride treatment (47.54 %). The nut fall percentage exhibited a declining trend which could be attributed to the decrease in fungal infection in mature nuts.
Genetic variation in tomato for yield and resistance to bacterial wilt
(Kerala Agricultural University, Vellanikara, 2001) Pradeepkumar, T; Dijee, Bastian; Joy, M; Radhakrishnan, N V; Aipe, K C
Integrated management of rhizoctonia leaf blight of amaranthus (Amaranthus tricolor L.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2016) Gireesh; Radhakrishnan, N V
Integrated management of sigatoka leaf spot disease of banana caused by Mycosphaerella musicola R. leach ex J. L. mulder
(Department of plant pathology, College of agriculture,Vellayani, 2015) Nayana, K; Radhakrishnan, N V
Management of cercospora leaf spot of vegetable cowpea (Vigna unguiculata subsp. sesquipedalis (L.) Verdcourt.)
(Department of Plant Pathology, College of Agriculture, Vellayani, 2017) Chinnu Ravi; Radhakrishnan, N V
Mango varietal response to Anthracnose disease and its post-harvest management
(Department of Plant Pathology, College of Agriculture , Vellayanikkara, 2025-02-15) Nikiru Lamare.; Radhakrishnan, N V
The study entitled “Mango varietal response to anthracnose disease and its post-harvest management” was done to evaluate the incidence and severity of anthracnose in different mango varieties during post-harvest storage and assess the efficacy of certain post-harvest management techniques controlling anthracnose on the quality of fruits in different mango varieties. A survey was conducted in two agro-ecological units – 1 (Southern coastal plain) and 8 (Southern laterites) covering Kollam and Thiruvananthapuram districts. Mango varieties with anthracnose symptoms were collected from the surveyed locations, and pathogen isolates were obtained. The isolates were subjected to pathogenicity testing, morphological characterization, and virulence rating. The cultural and morphological studies showed that isolates displayed fluffy or sparse mycelial growth with white to grey pigmentation and had regular margins. The conidia of all isolates were oblong, dumbbell shaped, measuring 9.2 × 3.5 to 11.4 × 3.6 μm. Upon artificial inoculation on the fruits, the isolates showed the typical anthracnose symptoms, with black or brown sunken lesions. Upon virulent rating, it was revealed that isolate C10 proved to be the most virulent, with a lesion development rate of 1.30 cm/day and PDI of 46.67%. The virulent isolate was molecularly characterized with ITS primers and confirmed as Colletotrichum gloeosporioides (accession no. PQ475860) by phylogenetic analysis. Five mango varieties, Kottukonam, Neelum, Priyur, Rumani, and Totapuri, were obtained and subjected to screening by artificial inoculation of the anthracnose pathogen and assessed the varietal variation in symptom development, lesion growth and susceptibility. Symptoms were developed in 2 days for Kottukonam and Priyur, while Neelum, Rumani, and Totapuri showed symptoms after 3 days. Kottukonam showed the highest susceptibility with a PDI of 72.33%, while Totapuri had the lowest at 45.40%. In vitro evaluation of the antagonistic potential post-harvest management strategies against anthracnose pathogens was studied. Two bacterial cultures of Bacillus velezensis PCSE-10 and B. amyloliquifaciens VLY24 were obtained from the Department of Agricultural Microbiology. The dual culture assay of the biocontrol agents against the anthracnose pathogen revealed that B. amyloliquifaciens VLY24 showed 37.08% inhibition, while B. velezensis PCSE-10 had 32.87% inhibition. Poisoned food assay of carbendazim 50% WP against the pathogen revealed that 0.1% and 0.2% concentration showed 100% inhibition while 0.05% showed 76.67% inhibition. In vitro evaluation of bacterial suspension and cell free culture filtrate (CFC) of biocontrol agents against the pathogen mycelial growth at different concentrations showed that bacterial suspensions were more effective than CFC. In both the strains highest inhibition of mycelial growth was shown in the bacterial suspension of 100% concentration with 78.78% inhibition with B. amyloliquifaciens VLY24 and 76.83% inhibition with B. velezensis PCSE-10. The evaluation of various post-harvest management strategies for controlling anthracnose disease was conducted in five mango varieties in a two-factorial Completely Randomized Design (CRD). It revealed that the combination of hot water treatment (HWT) (52°C for 10 minutes) + B. amyloliquefaciens VLY24 (BA VLY24) (100% suspension) and carbendazim (CBZ) (0.1%) resulted in the lowest per cent disease index (PDI) of 17.04%, followed by the combination of HWT (52°C for 10 minutes) + B. velezensis PCSE-10 (BV PCSE-10) (100% suspension) + CBZ (0.1%), which had a PDI of 18.68%. Among the varieties, the lowest PDI was observed in Totapuri (38.26%), while the highest was recorded in Kottukonam (46.56%). Regarding total soluble solids (TSS), the combination of HWT+ BA VLY24 + CBZ recorded the lowest TSS content (12.86 °Brix). Across varieties, Priyur exhibited the highest TSS content (17.63 °Brix), followed by Neelum (14.65 °Brix). The effects of the interaction of treatments on lesion size and PDI across all varieties were not significantly different, which implies that treatments applied across all varieties have the same relative effect, whereas the impact on TSS varied significantly among varieties as TSS content varies with varieties. A combination treatment of hot water (52°C for 10 minutes) +B. amyloliquefaciens VLY24 (100% bacterial suspension) + Carbendazim 50% WP (0.1%) was applied to five mango varieties (Kottukonam, Neelum, Priyur, Rumani, and Totapuri). The response of treated fruits was compared with untreated controls. On the 7DAI, no symptoms were observed in treated fruits except for Kottukonam, whereas untreated fruits displayed symptoms as early as the 4th or 5th day. PDI was significantly higher in untreated fruits, with the highest PDI recorded in untreated Kottukonam (50.67%) and the lowest in untreated Totapuri (22%). Biochemical analysis revealed that peroxidase and polyphenol oxidase activities were higher in treated fruits than untreated ones on the 7 DAI. Treated fruits also exhibited an extended shelf life, and Totapuri recorded the longest duration (9.33 days). Physiological loss of weight was higher in untreated fruits than in treated fruits. Sensory evaluation revealed that treated fruits exhibited superior internal and external sensory quality in terms of appearance, colour, flavour, and overall acceptability. Among the varieties, Totapuri received the highest overall acceptability score of 8.08. Biochemical assessments indicated that treated fruits had higher titratable acidity whereas, total soluble solids (TSS) and reducing sugar content were lower in treated fruits across all varieties tested. This study concluded that C. gloeosporioides was the pathogen responsible for mango anthracnose. Among the varieties, when subjected to screening by artificial inoculation, it revealed that Kottukonam was the most susceptible mango variety, followed by Priyur, while Totapuri was the least susceptible, followed by Rumani and Neelum. Effective post-harvest management of mango anthracnose can be achieved using a combination of hot water treatment (52°C for 10 minutes), B. amyloliquefaciens VLY24 (100% suspension), and carbendazim 50% WP (0.1%).
Prevalence variability and characterisation of Phytophthora palmivora Butl. inciting bud rot of coconut and its management using endophytes in seedlings
(Department of Plant Pathology, College of Agriculture, Vellayani, 2024-08-30) Aswathi, M S.; Radhakrishnan, N V
The research work entitled “Prevalence, variability and characterisation of Phytophthora palmivora Butl. inciting bud rot of coconut and its management using endophytes in seedlings” was carried out in the Department of Plant Pathology, College of Agriculture, Vellayani, Thiruvananthapuram during 2019-2024 with the following objectives; assessment of the prevalence of bud rot in different agroecological units; characterisation of Phytophthora palmivora causing coconut bud rot and its variability; and to evaluate fungal root endophyte Piriformospora indica and the bacterial foliar endophyte Bacillus amyloliquefaciens VLY24 in its management. The survey was conducted in three selected agroecological units of Kerala viz., AEU 8 (Southern laterites), AEU 9 (South central laterites) and AEU 11 (Northern laterites) to study the prevalence of bud rot and to collect the diseased samples. The highest (38.09%) and lowest (4.44%) disease incidence was recorded from the locations of AEU 11. The bud rot incidence in AEU 8 varied from 5.79 per cent to 28 per cent. The disease incidence of AEU 9 varied from 5.00 per cent to 34.28 per cent. The varieties, WCT, CGD, COD, Komadan and other dwarf palms belonging to the age group 2-50 years old were observed with disease incidence during the survey. Characteristic symptoms of bud rot noticed at survey locations were rotting, withering and drooping of spear leaves followed by its complete rotting with a foul smell. Ten isolates of Phytophthora spp. were obtained from infected palms of surveyed locations. Based on the molecular characterisation seven isolates were identified as P. palmivora, two as P. nicotianae and one P. meadii.A screening was carried out to identify the most virulent isolate of Phytophthora spp. based on the lesion size produced on the detached spear leaves and nuts of West Coast Tall variety upon the inoculation with mycelium disc and zoospore suspension. The screening was done for 13 Phytophthora isolates, including ten isolates from surveyed locations and three isolates obtained from ICAR-Central Plantation Crops Research Institute, Kasaragod. P. palmivora isolate 8APp from Kottukal (AEU 8) was identified as the most virulent isolate which produced largest lesions on detached leaves and nuts with a fastest lesion growth. This isolate was selected for further studies, dual culture, pot culture and field studies against P. palmivora.Variability of 13 Phytophthora isolates was studied based on the cultural, morphological characters and molecular analysis through RAPD. Significant variability was found in all the observed characters among different isolates. Phytophthora isolates exhibited a variety of growth patterns like stellate, semi-starry, chrysanthemum, light rosette and also without any specific pattern. Phytophthora palmivora isolate 8APp (Kottukal, AEU 8) showed the highest growth rate (1.33 cm/day). The lowest growth rate was observed for the isolate 9APn (Attingal, AEU 9; 0.89 cm/day).Phytophthora isolates produced hyaline coenocytic hyphae. Significant variation in width of hypha was noticed among isolates and it varied from 4.08 - 6.34 µm. The chlamydospore dimensions varied from 19.39- 31.52 µm x 18.90 - 30.65 µm which significantly varied among the isolates. Phytophthora produced ovoid, pyriform, ellipsoid and limoniform shaped sporangia and significant variation in sporangial size was noticed among the isolates. Length of sporangia varied from 24.56 - 55.56 µm; breadth varied from 19.55 - 28.58 µm and L/B ratio varied from 1.26 – 2.20.The genetic variability among Phytophthora isolates was studied by RAPD. Analysis of the RAPD pattern produced by four decamer primers revealed intra specific variability in isolates and also the variability existing in morphologically similar isolates. Evaluation of P. indica and B. amyloliquefaciens VLY24 against P. palmivora was done by dual culture assay. B. amyloliquefaciens VLY24 inhibited the mycelial growth of P. palmivora by 50.22 per cent at 10 DAI in dual culture plate. P. indica restricted the mycelial growth of P. palmivora by 36 per cent. In the interaction between B. amyloliquefaciens and P. palmivora, an inhibition zone of 1.64 cm was produced by B. amyloliquefaciens against P. palmivora; while, the type of interactions like lysis, inhibition zone and over growth was absent in the interaction between P. indica and P. palmivora. Antagonistic potential of B. amyloliquefaciens was comparatively higher than P. indica against P. palmivora. Evaluation of P. indica and B. amyloliquefaciens VLY24 against P. palmivora was carried out by pot culture studies. Colonization of B. amyloliquefaciens alone in coconut seedlings reduced the lesion size by 69.15 and 63.68 per cent in pot culture study1 and 2 respectively. Piriformospora indica + B. amyloliquefaciens colonized seedlings reduced the lesion size by 57.71 and 59.69 per cent in pot culture study1 and 2 respectively. The per cent reduction in lesion size over control in pot culture study1 and 2 by P. indica alone colonized seedlings was 20.89 and 25.85 respectively. Colonization of P. indica and B. amyloliquefaciens enhanced the growth of coconut seedlings by improving seedling height, girth, number of leaves and also early splitting of leaves. In the pot culture study 1 and 2, P. indica + B. amyloliquefaciens colonization improved the seedling height by 42 and 49 per cent, girth by 46 per cent, number of leaves by 18 per cent respectively. Colonization of P. indica alone increased the seedling height by 37 and 30 per cent, girth by 58 and 41 per cent, number of leaves by 31 and 24 per cent in pot culture 1 and 2 respectively. B. amyloliquefaciens alone colonized seedlings improved the seedling height by 23 and 24 per cent, girth by 22 and 30 per cent, number of leaves by 18 and 15 per cent respectively in pot culture 1 and 2. The highest splitting per cent of leaf (80 per cent) at 12th month stage was noticed in P. indica alone colonized seedlings and P. indica + B. amyloliquefaciens colonized seedlings in pot culture study 1. The early splitting of leaf was observed in B. amyloliquefaciens alone colonized seedlings and P. indica + B. amyloliquefaciens colonized seedlings at 9th month stage itself in pot culture study 2 and the highest splitting per cent (60%) was noticed in B. amyloliquefaciens alone colonized seedlings. The field experiments were conducted to evaluate P. indica and B. amyloliquefaciens VLY24 against natural incidence of bud rot disease in colonized seedlings. Lowest disease incidence was recorded in B. amyloliquefaciens alone colonized seedlings (11.11% and 0% in field 1 and 2 respectively), followed by P. indica+ B. amyloliquefaciens colonized seedlings (22.22% and 0 % in field 1 and 2 respectively). P. indica alone colonized seedlings recorded 22.22 per cent and 11.11 per cent DI in field 1 and 2 respectively. In field study 1 and 2, P. indica + B. amyloliquefaciens colonization improved the height by 20 and 15 per cent, girth by 27 and 25 per cent, number of leaves by 9 per cent respectively. P. indica alone colonized seedlings increased the height by 21 and 16 per cent, girth by 24 and 22 per cent, number of leaves by 13 per cent respectively in field experiment 1 and 2. B. amyloliquefaciens alone colonized seedlings did not significantly improved the growth parameters viz., height, girth and number of leaves compared to control. However, the leaf splitting per cent was significantly improved at the 18th month stage under field conditions. Biochemical mechanism of disease tolerance in B. amyloliquefaciens and P. indica colonized seedlings was studied at 24 and 72 hours after inoculation (HAI). Increased activity of defense related enzymes viz., phenylalanine ammonia lyase, peroxidase, polyphenol oxidase, catalase and superoxide dismutase was noticed in B. amyloliquefaciens and P. indica colonized coconut seedlings. Moreover, B. amyloliquefaciens and P. indica reduced the bud rot symptoms in coconut seedlings by inhibiting the accumulation of ROS and hydrogen peroxide. The relative expression of genes involved in salicylic acid and jasmonic acid pathway was studied in B. amyloliquefaciens and P. indica colonized seedling upon P. palmivora inoculation. B. amyloliquefaciens and P. indica reduced the bud rot symptoms in colonized seedlings by the upregulation of genes involved in salicylic acid signalling (NPR1 and PR5) pathway. Upregulation of LOX2 gene involved in jasmonic acid pathway was observed in B. amyloliquefaciens and P. indica colonized coconut seedlings at 72 HAI of P. palmivora. Relative expression of OPR3 gene involved in jasmonic acid pathway was less in B. amyloliquefaciens and P. indica colonized seedlings at 24 and 72 HAI of P. palmivora compared to control diseased seedlings. The bud rot disease of coconut caused by Phytophthora spp. is widely distributed in Kerala. Variability in cultural, morphological and genetic characters exist among different Phytophthora spp. isolates obtained from three selected agroecological units of Kerala viz., AEU 8, AEU 9 and AEU 11. Sowing of coconut seed nuts in P. indica enriched medium (106 cfu g-1) followed by a foliar spray (108 cfu ml-1) of B. amyloliquefaciens VLY24 in 6 months old seedlings is effective in reducing the bud rot incidence and enhancing the growth by improving seedling height, girth, number of leaves and early splitting of the leaves. P. indica and B. amyloliquefaciens VLY24 enhance the tolerance of coconut seedlings against P. palmivora by increasing the antioxidant enzyme activity and inducing the expression of genes in salicylic acid and jasmonic acid pathways.