PG Thesis

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    Etiology of cushion gall disease of Cacao (Theobroma cacao L.)
    (Department of Plant Pathology, College of Agriculture,Padannakkad, 2025) Nissi Christeena Mannam.
    The study entitled “Germplasm collection and diversity analysis of Kiriyathu [Andrographis paniculata (Burm. F.) Wall. ex. Nees] ecotypes of Southern districts of Kerala” was carried out in the Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Agriculture, Vellayani, during the period 2023- 2024 with the objective of collecting Kiriyathu ecotypes, estimation of morphological and genetic variation using Simple Sequence Repeat (SSR) markers. Kiriyathu ecotypes, 35 nos. viz., Kalakkode, Chirakkara, Perinad, Karicode, Vellimon, Kundara, Karunagappally, Kayamkulam, Thamarakkulam, Mavelikkara, Chengannur, Alappuzha, Thiruvalla, Kottayam, Chottanikkara, Ernakulam, Mala, Kodungallur, Vellayani, Kattakkada, Neyyattinkara, Parassala, Kachani, Karakulam, Bharanikkavu, Sasthamcotta, Adoor, Vellanad, Kadakkal, Pathanamthitta, Odakkali, Palode, Aryanad, Vithura and Nedumkandam were collected from nine different Agro Ecological Units (AEUs) of Kerala. The indigenous traditional uses of Kiriyathu gathered from the inhabitants/ localities/traditional medicinal practitioners include its utilisation for curing fever, malaria, jaundice, snake/insect bite, wounds, dysmenorrhea, digestive ailments and managing diabetes. Genetic variation of the Kiriyathu ecotypes using SSR primers identified seven polymorphic primers viz., Ando 4-26, Ando 4-27-2, Ando 4-43/1, Ando 5-12-1, Ando 5-14-2, Ando 5-26-2 and Ando 5-29. The polymorphism percentage was 64.08 per cent and the Polymorphism Information Content (PIC) value ranged from 0.11 to 0.64. Among the primers, Ando 4-27-2 recorded high PIC value and hence, considered to be more informative for diversity analysis. The dendrogram developed using molecular data could group Kiriyathu ecotypes into three major clusters - Cluster I containing seven subclusters (I to VII) and 27 ecotypes, Cluster II consist of five ecotypes and Cluster III having three ecotypes. In addition, the scatter plot developed using Principal Coordinate Analysis (PCoA) could identify a genetically diverse ecotype viz., Chirakkara belonging to AEU 1, Southern Coastal Plain. Morphological diversity of nine Kiriyathu ecotypes, one each selected from the subclusters of Cluster I, Cluster II and Cluster III respectively were studied by raising its seeds in pro-trays, transplanting it into polybags containing soil and cow dung powder (2:1) and maintained up to harvest at 50 per cent flowering. Seedling characteristics such as seedling height (15 DAT) and no. of leaves per seedling were maximum for Bharanikkavu (16.33 cm) and Thamarakkulam (14.33) respectively. Plant characteristics viz., days to 50 percent flowering, no. of primary branches, no. of secondary branches, plant duration up to seed set (days) and plant height were maximum in Chirakkara (141.66), Alappuzha (7.33), Thamarakkulam (5.66), Chirakkara (161.66) and Vellanad (75.06 cm) ecotypes respectively. Maximum leaf length and leaf girth were recorded for Chirakkara, 9.23 cm and 3.50 cm respectively. However, maximum stem girth was recorded by Vellanad, 2.53 cm. Yield characteristics such as herbage yield per plant (g) and leaf/stem ratio were maximum in Chirakkara (12.93g) and Vellanad (1.10) respectively. The study concluded that the 35 Kiriyathu ecotypes collected from nine different AEUs in the Southern districts of Kerala varied genetically. Chirakkara ecotype (AEU 1, Southern Coastal Plain) showed higher genetic variation and it showed superior morphological characteristics too - maximum days to 50 per cent flowering (141.66), plant duration up to seed set (161.66 days), leaf length (9.23 cm), leaf girth (3.50 cm) and herbage yield per plant (12.93g).
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    Etiology and management of sheath rot disease of rice
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2023-03-16) Boya Sreekanth.; Surendran, M
    The study entitled "Etiology and management of sheath rot disease of rice" was conducted at Department of Plant Pathology, College of Agriculture Vellayani and Rice Research Station, Moncompu during 2020-2022, with the objective to isolate and characterize the pathogen associated with sheath rot disease of rice and evaluate the efficacy of the available Bacillus sp.and commercial fungicides against sheath rot disease of rice. Purposive sampling survey conducted in four rice growing districts of Kerala during 2021-2022 to collect the sheath rot infected panicles and to access the disease incidence (DI) and disease severity (DS). Among the surveyed locations, maximum DI (49.23 per cent) and DS (46.32 per cent) were recorded from Neelamperoor and Palakkad. S. oryzae was isolated from the collected specimens; a total of five pure cultures of S. oryzae (Isolate I1 to Isolate I5) were obtained and Koch's postulates were proved for all the isolates in rice var. Uma. All the S. oryzae isolates were screened for its virulence and pathogenicity in rice var. Uma. The isolate I5, from Thrithala produced the symptom within 24 h of artificial inoculation. On 4th day of artificial inoculation, isolate I5 recorded a maximum lesion size of 2.50 cm; and thus, concluded as the most virulent isolate. The cultural characters of these 5 isolates were whitish orange with some radial foldings and morphological characters of hyphae was septate and whitish orange in color and spores single celled and cylindrical in shape. Average size of the spore was 5.53 x 1.66 µm. Dual culture assay of Bacillus sp. B15, Bacillus sp. B17, Bacillus sp. B33, Bacillussp. B42 and Pseudomonasfluorescens(PN026) in potato dextrose agar (PDA) medium indicated that the beneficial endophytic bacteria significantly inhibited the growth of the pathogen through multiple antagonistic properties. Maximum growth inhibition of S. oryzae (70.95 per cent) by P. fluorescens (PN026) followed by Bacillus sp. B17 (64.45 per cent) and Bacillus sp. B 42 (50.95 per cent) were observed on 12 th day of dual culturing. Among the four commercial fungicides tested in vitro, trifloxystrobin 25%+tebuconazole 50 % 75 WG (400ppm), propineb 50 WP (2500ppm) and hexaconazole 5EC (2000ppm) completely inhibited (100%) the sheath rot pathogen compared to copper hydroxide 77 WP (2000ppm) which inhibited the growth of the sheath rot pathogen by 86.42% per cent. Considering the overall performance, recommended doses of trifloxystrobin 25%+tebuconazole 50 % 75 WG (400ppm), propineb 50 WP (2500ppm) and hexaconazole 5 EC (2000ppm) were more effective against sheath rot pathogen. The isolation of DNA from sheath rot pathogen was carried out by using CTAB (cetyltrimethyl ammonium bromide) method of DNA isolation. Quality and quantity of sample DNA were 1.73 and 60 µg ml-1 . Size of the amplicon is 608bp. This sheath rot associated pathogen was identified from Rajiv Gandhi Centre for Biotechnology (RGCB), Thiruvananthapuram as Sarocladium oryzae through molecular characterization (GenBank Accession no. OP716814). This sheath rot pathogen was used for further studies. Pot culture experiment was conducted for screening rice varieties (20 numbers) for resistance to sheath rot pathogen. Artificial inoculation was done at panicle initiation stage. Aathira and Shreyas showed tolerant reaction to sheath rot disease whereas Uma variety showed the highest susceptibility nature. The biocontrol agents and fungicides were evaluated in the field against sheath rot disease of rice during Kharif 2022 at RRS, Moncompu. Management of disease before panicle emergence is very much essential. Prophylactic application of talc-based formulation of Bacillus sp. B15, Bacillus sp. B17, Bacillus sp. B33, Bacillus sp., B42, B 15+ B17+ B 33+ B 42 consortium and Pseudomonas fluorescens (PN026) as seed treatment (10g kg-1 ) + soil application (1kg/acre) + foliar spray (20g L-1 of water at booting stage) for the management of sheath rot disease of rice and thereby improving the yield. Among all the bioagent treatments, the application of B 15+ B 17+ B 33+ B 42 consortium showed more efficacy nature for the management of sheath rot disease of rice and improving the yield. Four commercial fungicides viz., copper hydroxide 77 WP @ 2 g L-1 , trifloxystrobin25%+tebuconazole 50 % 75 WG @ 0.4 g L -1 , propineb 50 WP @ 2.5 g L -1 and hexaconazole 5 EC@2 ml L-1 were given as foliar spraying at booting stage. Among all the fungicides tested in the field, trifloxystrobin 25%+tebuconazole 50 % 75 WG @ 0.4 g L -1 and hexaconazole 5 EC@ 2 ml L-1 applied as foliar spraying were significantly superior in reducing the disease and increasing the yield followed by propineb 50 WP @ 2.5 g L-1 and copper hydroxide 77 WP @ 2 g L-1 . Benefit cost ratio was also more in case of B 15+ B 17+ B 33+ B 42 consortium and trifloxystrobin 25%+tebuconazole 50 % 75 WG @ 0.4 g L-1 . Thus, the present study revealed that sheath rot of rice could be managed by using Bacillus sp. B 15+ B 17+ B 33+ B 42 consortium as seed treatment (10g kg-1 ) + soil application (1kg/acre) + foliar spray (20g L-1 of water at booting) and commercial fungicide, trifloxystrobin 25%+tebuconazole 50 % 75 WG @ 0.4 g L -1 and hexaconazole 5 EC at 2 ml L -1 . The results may be subjected to multi-location and multi- seasonal field trails before recommendation. The compatibility of Bacillus sp. consortium with new generation fungicides and the residue of fungicides in grain may further be studied.
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    Etiology and management of bacterial wilt of yard long bean
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2023) Talla Sushmitha; Sajeena A
    The study entitled “Etiology and management of bacterial wilt of yard long bean” was conducted at College of Agriculture, Vellayani and Integrated Farming System Research Station (IFSRS), Karamana during 2020-2022 with an objective to identify and characterize the bacterium inciting wilt disease in yard long bean and management of the disease. Bacterial wilt infected yard long bean plant samples were collected from Vamanapuram (8.7226° N, 76.8971° E) and Nanniyode panchayat (8.6988° N, 77.0262° E) of Thiruvananthapuram district, Kerala. The disease incidence was 85 to 90 per cent. The disease symptoms included drooping and wilting of green leaves, collapse of stem followed by death of plants. The bacterium was isolated on triphenyl tetrazolium chloride (TZC/TTC) medium and three methods of pathogenicity tests viz., root dip, root dip and stem injection as well as soil inoculation were undertaken to prove Koch's postulates. The symptoms were observed within three to seven days after inoculation and complete wilting was observed in 7, 10 and 14 days in root dip, root dip and stem injection and soil inoculation respectively. Cultural studies revealed the bacterial colonies to be white or cream, circular, smooth, convex in casamino acid peptone glucose agar (CPG) and white, circular, smooth, convex, fluid like with pink colouration at centre in TZC medium which were the best media for the bacterial growth. Morphological and biochemical studies revealed the bacteria as gram negative, rod-shaped and facultative anaerobic. Molecular characterization using the universal primers of 16S rRNA viz., 27F/1492R revealed 99.83 per cent identity with several isolates of Enterobacter spp. and Kosakonia oryzae and the gene amplified using CM7F/CM31b primers of rpoB, one of four house-keeping genes of Enterobacteriaceae revealed 99.72 per cent identity with Kosakonia oryzae strain Ola51. The 16S rRNA and rpoB sequence were deposited in NCBI database (Acc. no. OP321041 and Acc. no. OP321041 respectively). Further, phylogenetic analysis and biochemical characterization using Enterobacteriaceae specific kit confirmed the pathogen to be K. oryzae. 142 In vitro evaluation of various chemicals by poisoned food technique and filter paper assay revealed that streptocycline (250 ppm) was the most effective bactericide resulting in a mean inhibition zone of 27.67 mm, followed by copper oxychloride 50 % WP (0.30 %) (17.00 mm) and copper hydroxide 77% WP (0.20 %) (15.33 mm). Among the various botanicals screened for antibacterial effect in vitro by paired plate technique, bulbs of Allium sativum revealed the highest inhibition of bacterial growth followed by leaves of Mansoa alliaceae. In agar well diffusion method, bulbs of A. sativum (15 %) followed by leaves of Boerhavia diffusa (20 %) and M. alliacea (20 %) resulted in maximum inhibition (inhibition zone of 20.33, 18.83, 16 mm respectively) of the bacterial growth. An in vivo study was undertaken at IFSRS, Karamana for the management of bacterial wilt disease in yard long bean (var. Geethika) using the best three treatments viz., bulbs of A. sativum (10g per pit), copper oxychloride 50% WP (0.30 %) and copper hydroxide 77 % WP (0.20 %) selected from in vitro studies along with streptocycline (250 ppm), bacteria inoculated and uninoculated treatments as checks. The inoculated control revealed 100 per cent disease incidence whereas soil application of crushed garlic bulbs (10 g/pot at one week before transplanting) followed by immediate covering with cow dung and soil mixture, seedling treatment and soil application of crushed garlic bulbs at 10, 20 and 30 days after transplanting (DAT) registered the minimum disease incidence (13.33 %) with the maximum number of pods (43), pod length (46.82 cm), pod weight (21.67 g) and pod yield (815.13 g) followed by soil application of copper oxychloride 50 % WP (0.3 %) (754.77 g pod yield) with 20 per cent disease incidence. Treatment application at 10, 20 and 30 DAT with 10 days interval (DI) was more effective than at 15, 30 and 45 DAT with 15 days interval. Biochemical studies on identifying the mechanism of disease tole
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    Etiology and immuno- molecular detection of the virus causing mosaic disease in snake gourd
    (Department of Plant Pathology, College of Agriculture,Vellayani, 2024-01-23) Ammu Asok, A; Krishnapriya, P J
    The study entitled “Etiology and immuno-molecular detection of the virus causing mosaic disease in snake gourd” was carried out at College of Agriculture, Vellayani during 2021-2023 with the objectives of symptomatology, maintenance of virus in systemic and local lesion host, host range studies, seed transmission, aphid transmission, immunological diagnosis, molecular diagnosis and host pathogen interaction of the viruses causing mosaic disease in snake gourd (Trichosanthes anguina). Mosaic diseased snake gourd samples were collected from three taluks of Thiruvananthapuram district (Thiruvananthapuram, Neyyattinkara and Varkala) of Kerala during January-March and July-September of 2021-23. The characteristic symptoms of snake gourd mosaic disease were mosaic, mosaic mottling, vein banding, blistering, distortion, puckering on leaves and deformed fruits. The disease incidence in majority of the fields was found to be over 25.0 per cent and disease severity progressed with age of the crop. In the surveyed locations, the highest disease incidence of 94.0 to 100 per cent and vulnerability index of 72.9 to 82.7 were observed in commercial variety Kaumudi from fields of College of Agriculture, Vellayani. In snake gourd variety Baby, disease incidence of 28.5 per cent and vulnerability index of 46.6 were observed. Similar symptoms of mosaic were observed on weeds like Hemidesmus indicus (F: Apocynaceae) and Synedrella nodiflora (F: Asteraceae) in snake gourd field. The snake gourd mosaic viruses were sap transmissible and maintained in systemic host viz., snake gourd varieties Kaumudi and Baby and also in local lesion hosts viz., Chenopodium amaranticolor and Nicotiana tabacum var. Samsun. Local lesion assay revealed that viruses associated with snake gourd mosaic disease were Potyviruses and Cucumoviruses. Based on host range studies, virus was mechanically transmissible to plants of family Cucurbitaceae viz., pumpkin, bitter gourd, cucumber, ridge gourd, bottle gourd, water melon and family Solanaceae viz., Nicotiana glutinosa and Nicotiana tabacum var. Samsun. However, no symptoms were produced in tomato, chilli, brinjal and papaya. Host range studies identified viruses associated with the snake gourd mosaic disease as Papaya ring spot virus (PRSV) Type W and Cucumber mosaic virus (CMV). No seed transmission was recorded in snake gourd plants raised from seeds produced by snake gourd mosaic viruses infected plant. Aphid transmission of the virus of 30.0 per cent was observed with Aphis craccivora and 50.0 per cent was observed with A. gossypii. The viruses causing snake gourd mosaic disease were immunologically detected using Double antibody sandwich-Enzyme linked immunosorbent assay (DAS-ELISA) and Direct antigen coating-ELISA (DAC-ELISA) with polyclonal antibodies specific to PRSV and CMV respectively. Dot immunobinding assay (DIBA) detected CMV from snake gourd mosaic diseased samples. Reverse transcriptase-Polymerase chain reaction (RT-PCR) was carried out and amplicons of sizes 1200 bp and 400 bp were obtained with primers specific to coat protein of PRSV and 2a protein of CMV respectively. Comparative nucleotide sequence alignment of the isolates revealed an 86.5 and 93.8 per cent homology with PRSV and CMV isolates from Tamil Nadu respectively. Comparative amino acid sequence alignment of the isolates revealed an 88.9 and 97.8 per cent homology with coat protein of PRSV-W and 2a protein of CMV respectively. The sequences were deposited in NCBI GenBank with accession numbers viz., OR601008 and OR601007. Phylogenetic tree was constructed and PRSV isolate grouped in the same clade along with other reported PRSV type-W isolates, thus the isolate was identified as PRSV Type-W. CMV isolate from snake gourd grouped in the same clade along with other CMV isolates from snake gourd and Musa sp. Virus inoculated snake gourd plants showed a significant reduction in total chlorophyll content (0.61 mg g-1) and increase in protein content (13.79 mg g-1) at 5 weeks after transmission. The activities of defense related enzymes (peroxidase, polyphenol oxidase, phenylalanine ammonialyase, superoxide dismutase and catalase) were higher in inoculated plants compared to healthy plants. Thus, the present study revealed that snake gourd mosaic disease is caused by the combined infection of PRSV-W and CMV in the surveyed locations of Thiruvananthapuram district. Synedrella nodiflora was identified as the suitable weed host and viruses were transmitted through Aphis gossypii and Aphis craccivora.
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    Etiology of bud proliferation in vegetable cowpea
    (Department of Plant Pathology, College of Agriculture, Vellayani, 2022-02-11) Devika, S; Radhika, N S
    The study entitled „Etiology of bud proliferation in vegetable cowpea‟ was conducted at Department of Plant Pathology, College of Agriculture, Vellayani during 2019-2021 with an objective of studying the symptomatology, immuno-molecular detection and characterization of incitant/(s) of bud proliferation in vegetable cowpea. Bud proliferation disease of cowpea has been observed in different varieties in different locations. Purposive sampling was carried out in different locations of Thiruvananthapuram, Kollam, Alappuzha and Thrissur and collected symptoms were used for further studies. The characteristic symptom of the disease is the abnormal proliferation of bud which showed an increase in number of buds up to 16-35. The proliferated buds also showed pinkish- brown patches in it. Noticeable symptoms were also seen in the leaves of the diseased plant. They were smaller, crinkled and unusually dark in colour. The fasciation of stem has also been observed in the fields of Onattukara and Chavara. The infected plants were stunted and completely sterile. The highest disease incidence was found to be in the variety Bhagyalakshmy cultivated in Mannuthy (6.57 per cent). The population of hoppers was observed in the field and the insects identified were Exitanus sp., Balclutha sp., Nilaparvata lugens, Ptoleria sp., Nisia nervosa. The weeds Phyllanthus, Neer-grampu and Jack bean were found to be showing similar symptoms near the diseased cowpea fields. The graft transmission was successful from cowpea to periwinkle with 40 per cent efficiency. The leaves of the graft inoculated periwinkle plants showed severe interveinal chlorosis and later on yellowing. Graft transmission was unsuccessful from cowpea to cowpea. The transmission studies for viruses from cowpea to cowpea and cowpea to Chenopodium revealed the absence of viruses. The DAPI staining of diseased and healthy plants affirmed the presence of phytoplasma in the diseased samples. Small fluorescent-coloured bodies were seen in the stem and leaf of infected plants compared to healthy. The hormonal analysis of the symptomatic plants compared to the healthy ones showed significant difference. The GA content in diseased leaf and bud was increased by 20.88 and 17.46 per cent respectively. The IAA content in diseased leaf (older) and bud was increased by 61.55 and 46.52 per cent respectively. The serological detection for viruses using monoclonal antibodies of CABMV and BICMV and polyclonal antibodies of TSWV and WSMoV divulged the absence of viruses in the diseased samples. The graft inoculated periwinkle plants also showed no presence of viruses. The molecular detection of phytoplasma with nested PCR was carried out. The first primers P1/P7 amplified a 1.8kb fragment and the second set of primers; R16F2n/R16R2 amplified a 1.2kb fragment, giving positive results. The final amplified product was sequenced and by BLAST analysis it was found that the 16S rDNA sequence shared 99.80 per cent similarity with that of the „Candidatus Phytoplasma asteris‟ reference strain (GenBank accession: M30790). Hence the phytoplasma under study is a „Candidatus Phytoplasma asteris‟-related strain. The virtual RFLP pattern derived from the query 16S rDNA F2nR2 fragment was identical (similarity coefficient 1.00) to the reference pattern of 16Sr group I, subgroup B (GenBank accession: AP006628). The phytoplasma under study was found to be a member of 16SrI-B.
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    Etiology and characterization of diseases of Anthurium (Anthurium andraeanum L.) in Kerala
    (Department of Plant Pathology, College of Agriculture, Vellanikkara, 2021) Nitha Rafi; Anita Cherian, K
    Anthurium (Anthurium andraeanum L.), a native of Tropical America is a perennial herbaceous plant commercially grown for its attractive coloured spathe and green shiny foliage. These have great economic value in the global flower trade that led to the budding of many urban and rural anthurium entrepreneurs in the countryside, particularly in the state of Kerala. During the recent past, the cultivation of this high valued cut flower crop is challenged by many biotic factors and the changes in climate scenario occurred recently led to the emergence of various new pests and diseases. Hence the present study was undertaken to identify and document the diseases affecting anthurium grown in the state of Kerala and the characterization of associated pathogens. Purposive sampling surveys were conducted in the anthurium cultivated locations of six districts viz. Thrissur, Ernakulam, Palakkad, Malappuram, Kozhikode and Wayanad during the period from October, 2020 to July, 2021. The incidence and severity of various symptoms were assessed and collected the samples for further studies. Twelve leaf spots (KMALS, PBALS, VFNLS, VCNLS1, VCNLS2, IJKLS, KKYLS, OKMLS, OLRLS, TLRLS, TBMLS and NLBLS) two leaf blights (VFNLB and OLKLB), one root rot (VCNRR), one wilt (MNTLW) four inflorescence rots (MNTSR, CKDSR, PNMSR and ALVSR) and one mosaic symptom (VCNML) were collected during the survey. Among the leaf spots, PBALS recorded the highest per cent disease severity (PDS) of 58.23 followed by NLBLS (46.66 %) and ALVSR recorded the highest severity of 32 per cent among inflorescence rots. Isolation and pathogenicity studies of the associated pathogens yielded 18 fungal and two bacterial isolates. Symptomatology of these diseases were studied both under natural and artificial conditions. The fungal pathogens were characterized and identified by studying cultural and morphological characteristics. Based on these characters, leaf spot pathogens were identified as Colletotrichum gloeosporioides, Lasiodiplodia theobromae, Phoma sp., Phomopsis sp., Corynespora sp., Pestalotiopsis sp. and those causing inflorescence rot as Colletotrichum gloeosporioides and Phomopsis sp. and root rot pathogen as Phytopythium sp. and wilt pathogen as Fusarium sp. The bacterial isolates causing leaf blight were identified as Xanthomonas sp. based on cultural, morphological and biochemical characteristics. The viral like symptoms subjected to electron microscopy revealed the absence of any virus particles. PCR amplification of Internal Transcribed Spacer (ITS) region of the fungal genome followed by sequencing and in silico analysis confirmed that the pathogen associated with TBMLS as C. queenslandicum, VCNRR as Phytopythium vexans, IJKLS as Diaporthe phaseolarum, KKYLS and OKMLS as Phomopsis heveicola, NLBLS as Lasiodiplodia theobromae, TLRLS as Pseudopestalotiopsis thea, VCNLS2 and OLRLS as Corynespora cassiicola, MNTLW as Fusarium fujikuroi. The pathogens associated with KMALS, PBALS, VFNLS, MNTSR, PNMSR and ALVSR belong to Colletotrichum gloeosporioides species complex. The bacterial isolates (VFNLB and OLKLB) were confirmed as Xanthomonas axonopodis through the amplification of 16S rRNA region of the genome followed by sequencing and in silico analysis. An in vitro experiment was conducted to study the efficacy of fungicides and biocontrol agents/bioformulations against major fungal pathogens. Fungicides viz. propineb, difenoconazole, carbendazim 12 % + mancozeb 64 %, cymoxanil 8% + mancozeb 64 % and Bordeaux mixture were highly effective against L. theobromae and Colletotrichum sp. (PBALS) as it resulted in cent per cent inhibition of these two pathogens at all the three doses. In the case of P. vexans, fungicides viz. propineb, azoxystrobin, carbendazim 12 % + mancozeb 64 %, cymoxanil 8% + mancozeb 64 % and Bordeaux mixture were found to be effective even at a lower dose. Among the three chemicals tested against Xanthomonas axonopodis, maximum inhibition was recorded in the case of streptocycline. Dual culture and filter paper disc method revealed that the biocontrol agents/formulations viz. Trichoderma sp., PGPR-II and PGPM were effective against all the tested fungal and bacterial pathogens. Pseudomonas fluorescens was found effective against three fungal and the bacterial pathogen.
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    Etiology and management of die back disease of mango grafts in nursery
    (Department of Plant Pathology, College of Horticulture, Vellanikkara, 2009) Sangeetha, C; Beena, S