Browsing by Author "Anita Cherian, K"
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ThesisItem Open Access Characterization and documentation of diseases of passion fruit (Passiflora edulis Sims.)(Department of Plant Pathology, College of Horticulture,Vellanikkara) Karthika, Mohan; KAU; Anita Cherian, KPassion fruit (Passiflora edulis Sims.), a native of Brazil is an emerging high value crop with fruits of great export potential. It is a woody, climbing vine which is valued for its fruits with unique flavor and aroma as well as for its nutritional and medicinal properties. During the recent past, there is tremendous increase in the cultivation of passion fruit, particularly in the state of Kerala. This is because of its importance as an assured source of income to small and marginal farmers. But, the longevity and productivity of passion fruit vines are often challenged by many biotic stress especially diseases. Even though many diseases are reported internationally, no systematic study has been conducted in the country particularly in Kerala due to the recent introduction of this crop in the agricultural scenario of the state. Hence, the present study was undertaken to identify the diseases affecting passion fruit occurring in Kerala, documentation of the same and characterization of associated pathogens. Purposive sampling surveys were conducted in the passion fruit growing tracts of five districts viz. Thrissur, Ernakulam, Palakkad, Wayanad and Ernakulam during the period of March, 2019 to January, 2020. Eight leaf spots (VKALS, MDKLS, NELLS, NENLS, MNPLS, MVPLS, THNLS and AMBLS), two leaf blights (NENLB and MVPLB), four fruit rots (MDKFR, NELFR, MVPFR and PAZFR), one bud blight (KLYBB), two wilts (MNPWt and KANWt) and one leaf malformation (VKALM) were observed during the survey. Among the foliage diseases, leaf blight (MVPLB) recorded the highest per cent disease incidence (PDI) of 78 per cent with a severity of 63.9 per cent. Among the fruit diseases, PAZFR recorded the highest incidence of 53.59 per cent disease with a severity of 26.47 per cent. The disease incidence of wilt; MNPWt and KANWt were 37.64 and 33 per cent respectively. Isolation and pathogenicity studies of the associated microorganisms yielded 15 fungal isolates (leaf spots, leaf blights and fruit rots), two bacterial isolates (wilt) and one virus isolate (leaf malformation). Symptoms of the different diseases were studied both under natural and artificial conditions. The fungal isolates were characterized and identified by studying the cultural and morphological characteristics. Based on these characters, Colletotrichum sp., Alternaria sp. and Lasiodiplodia sp. were identified as leaf spot pathogens, Rhizoctonia sp. as leaf blight pathogen, Phomopsis (Diaporthe) sp. as the bud blight pathogen and Colletotrichum sp., Alternaria sp. and Sclerotium sp. as fruit rot pathogens infecting passion fruit. The bacterial isolates (MNPWt and KANWt) causing wilt disease in passion fruit was identified as Ralstonia solanacearum Yabuuchi et al. based on cultural, morphological and biochemical characters. The differential host inoculation test conducted for race identification of the bacteria revealed that it belongs to Race 1. Morphological and biological characterisation of virus associated with leaf malformation revealed the association of Potyvirus as the causal organism of leaf and fruit malformation. Molecular characterization was carried out by genomic DNA isolation and amplification of specific region of fungal genome by Polymerase Chain Reaction (PCR) for the species level identification of the isolates. Amplification of Internal Transcribed Spacer (ITS) region of the fungal isolates followed by ITS sequencing and in silico analysis confirmed that the pathogen causing VKALS, NELLS, MVPLS, THNLS, AMBLS, NELFR and MVPFR as Colletotrichum brevisporum, MDKLS and MDKFR as Alternaria porri, NENLS as Colletotrichum queenslandicum, MNPLS as Lasiodiplodia theobromae, MVPLB and NENLB as Rhizoctonia solani, KLYBB as Diaporthe phaselorum and PAZFR as Sclerotium rolfsii. The bacterial isolates (MNPWt and KANWt) causing wilt disease in passion fruit was further confirmed as R. solanacearum through the amplification of 16 S rRNA region of the genome followed by sequencing and in silico analysis. The molecular characterization of Potyvirus associated with passion fruit was carried out using RNA extraction followed by cDNA synthesis and amplification of gene corresponding Cylindrical Inclusion (CI) protein using degenerate primers (Ha et al., 2008). The PCR yielded the expected band size of 680 bp, thus confirming Potyvirus as the causal organism of fruit and leaf malformation. An in vitro experiment was conducted to study the efficacy of fungicides and biocontrol agents against major fungal pathogens viz. C. brevisporum and S. rolfsii. Fungicides viz. copper hydroxide, hexaconazole, propineb, difenoconazole, carbendazim 12% + mancozeb 64%, azoxystrobin and Bordeaux mixture were found to be very effective against C. brevisporum at recommended dose and showed cent per cent inhibition of fungal growth. In the case of S. rolfsii, fungicides viz. hexaconazole and azoxystrobin were found to be effective even at a lower dose. Dual culture studies revealed that the biocontrol agent, Trichoderma sp. was effective against both the pathogens viz. C. brevisporum and S. rolfsii whereas Pseudomonas fluorescens was effective only against C. brevisporum.ThesisItem Open Access Characterization and integrated management of Fusarium oxysporum f.sp. cubense (E.F. Smith) synder and hansen causing fusarium wilt disease of banana(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2020) Lishma, N P; KAU; Anita Cherian, KFusarium wilt of banana caused by the soil borne fungus Fusarium oxysporum f. sp. cubense (Foc) is a serious constraint to banana cultivation in Kerala. The fungal species constitute four pathogenic races, of which Race 1 is the prevalent one in our country and Race 4 is one of the emerging threats, though not reported from Kerala yet. The present study was undertaken to characterize the associated pathogenic races and to develop an integrated package for the disease management. The project initiated with purposive sampling surveys in various districts viz., Thiruvananthapuram, Ernakulam, Thrissur, Palakkad, Kozhikode and Wayanad representing different agroclimatic zones of Kerala. The per cent disease incidence (PDI) and the per cent disease severity (PDS) ranged from 1.52 to 43.65 per cent and 20.34 to 49.57 per cent. The correlation analysis of PDI with weather parameters showed a positive correlation with rainfall. However, it was negatively correlated with temperature. The study on symptoms under natural as well as artificial conditions showed characteristic external and internal symptoms. The number of days taken for complete wilting under artificial inoculation was 29.67 in Rasthali (AAB), 47.99 in Njalipoovan (AB), 31 in Kadali (AA) and 37.67 in Chenkadali (AAA). Among the thirty isolates of the Foc collected, twenty three isolates were from Rasthali variety, four isolates from Kadali, two isolates from Njalipoovan and one from Chenkadali. Studies on identification of Foc races with the differential host assay revealed that the varieties such as Cavendish (assay host to Race 4), Nendran (assay host to Race 4), Heliconia sp. (assay to Race 3) and Monthan (assay to Race 2) did not produce any type of symptoms whereas, all the isolates produced symptoms on Rasthali (assay host to Race 1) variety. A non polymerase chain reaction (PCR) based quick molecular diagnostic technique with loop mediated isothermal amplification (LAMP) assay was developed for the detection of Races of the pathogen. All isolates showed positive reaction to the LAMP assay for Race 1 and negative for Race 4. A PCR was also standardised for the confirmation of the races. It is concluded that all the isolates collected from different agroclimatic zones belonged to the Race 1 category of the pathogen only. Cultural and morphological characterization of the isolates revealed white coloured aerial mycelium with pink pigmentation and cottony and fluffy mycelial mat. The mycelial growth rate in half strength potato dextrose agar (PDA) medium ranged from 0.83 to 2.40 cm/day and the length and breadth of macroconidia and microconidia measured about 15.01 - 20.20 μm x 2.14 - 5.07 μm and 4.49 - 7.42 μm x 1.35 - 3.13 μm respectively. The inter-septal length and breadth of hyphae ranged from 16.14 to 22.94 μm and 4.22 to 6.57 μm respectively and the size of chlamydospores varied from 5.68 to 9.58 μm in diameter. The PCR based molecular characterization of isolates using ITS (internal transcribed spacer) primers produced single bands of size approximately 580 bp. In silico analysis of the sequences showed 96 to 100 per cent homology to Foc. Based on cultural, morphological and molecular characters, the pathogen was identified as Fusarium oxysporum f. sp. cubense. The screening of accessions maintained in the germplasm of Banana Research Station (BRS), Kannara was done to assess their disease resistance to Foc Race 1 and were grouped into six categories. Fifteen immune varieties viz., Attunendran, Zanzibar, Big Ebanga, Nedunendran, Nendran, BRS II, Thiruvananthapuram, Pachanadan I, Cultivar Rose, Pisang Lilin, Pisang Jari Buaya, Yangambi Km5, Grand Naine, Chinese Cavendish and Nendran Hybrid and four highly susceptible varieties viz., Cheriya Poovan, Valiya Poovan, Kadali and Rasakadali were identified. The estimation of biochemical parameters for the assessment of host plant disease resistance against Foc Race 1 revealed that the activity of total phenols and defense related enzymes was more in resistant varieties compared to susceptible varieties and the activity of reducing and non reducing sugars was more in susceptible varieties. An in vitro experiment was conducted for the evaluation of chemical fungicides, biocontrol agents and botanicals for control of the pathogen. The effective treatments from in vitro evaluation were carried over to pot culture and field experiments for the disease management. Among the various treatments, an integrated package comprising of Pseudomonas fluorescens + arbuscular mycorrhizal fungi and Trichoderma enriched cow dung + tebuconazole (T6) was proved to be the best for yield and disease management. It is concluded that the present study has enlightened our knowledge on characterization, race identification and management of Fusarium wilt pathogen infecting banana.ThesisItem Open Access Characterization of Mycosphaerella spp. causing sigatoka leaf spot disease complex of banana in Kerala and its management(Department of Plant Pathology College of Horticulture, Vellanikkara, 2019) Milsha George; KAU; Anita Cherian, KSigatoka leaf spot disease complex caused by Mycosphaerella spp. is a serious constraint to banana cultivation in Kerala. The present study was undertaken to characterize the associated pathogen and to develop an integrated management package against this disease. The project initiated with purposive sampling surveys conducted in various districts representing different agroclimatic zones of Kerala viz. Malappuram (Northern zone), Palakkad (Northern zone), Thrissur (Central zone), Ernakulam (Central zone), Wayanad (High range zone) and Trivandrum (Southern zone). The percent disease severity (PDS) ranged from 3.33 to 43.90%. The correlation analysis of PDS with weather parameters showed a positive correlation with rainfall however, it was found to be negatively correlated with temperature. The study on symptomatology revealed that there were six types of symptoms noticed on banana var. Nendran (AAB), two types each on Palayankodan (AAB) and Njalipoovan (AB), while only one type of symptom was recorded on Robusta (AAA) and Kadali (AA). Isolation of the pathogen could be achieved on potato dextrose agar medium after 10- 12 days of incubation at very specific conditions. The fungal colony was slightly raised with irregular margin and greyish velvety appearance. Studies on morphological structures revealed that the conidia were hyaline to olivaceous brown in colour which measured about 24.29 - 71.89 µm length x 0.91 - 2.40 µm width with 3-8 septations. The sexual structures were flask shaped perithecia containing long asci bearing eight ascospores. Based on cultural and morphological characters, the pathogen was identified as Mycosphaerella eumusae. The identity of the pathogen was further confirmed by PCR based molecular characterization. In silico analysis of the sequences of the isolates showed 99 -100% homology to Mycosphaerella eumusae. Hence, it is concluded that the pathogen associated with Sigatoka leaf spot disease of banana in Kerala is identified as Mycosphaerella eumusae Crous & Mourichon (anamorph Pseudocercospora eumusae Crous & Mourichon). The screening of accessions maintained in the Germplasm of Banana Research Station, Kannara was done to assess their disease reaction and were grouped into six categories. Five resistant varieties viz., Pisang Lilin, BRS 1, BRS 2, FHIA 01 and FHIA 23 and susceptible varieties viz., Nendran, Grand Naine, Robusta, Moris and Kadali were further selected to investigate the anatomical, biochemical and molecular basis of host plant resistance. Anatomical studies revealed that the resistant varieties were characterized by thicker cuticle, epidermis and mesophyll tissues compared to the susceptible varieties. The number of stomata and the stomatal pore width were more in susceptible varieties compared to the resistant varieties. The biochemical basis of resistance was assessed by quantifying phenols, reducing sugars, non reducing sugars and the activity of defense related enzymes viz., peroxidase, polyphenol oxidase and phenylalanine ammonia lyase in both resistant and susceptible varieties. The results revealed that the phenols, reducing sugars and the defense related enzymes were higher in resistant varieties compared to susceptible ones. The amplification of genomic DNA of resistant and susceptible varieties using Sequence characterized amplified region (SCAR) markers yielded an amplicon of size 644bp in resistant cultivars while the bands were absent in susceptible cultivar. The BLASTn analysis of the sequence of the amplicons showed 90 per cent sequence homology to genomic sequences of Kanthali SCAR marker OPA1363 which is tightly linked to Sigatoka leaf spot disease resistance. Field experiments were conducted to evaluate the efficacy of chemical fungicides and organic / inorganic preparations for disease management. Among the various chemical fungicides, foliar spraying with trifloxystrobin (25%) + tebuconazole (50%), 0.4g/l) was found to be the best followed by copper hydroxide, hexaconazole (5%) + captan (70%), 2g/l) and Bordeaux mixture (1%), without leaving any toxic residues in the harvested fruits. The results of the experiment on disease management using organic / inorganic preparations revealed the effectiveness of PGPR mix II (consortium of Pseudomonas fluorescens and Bacillus subtilis), 2% followed by Pseudomonas fluorescens (2%) given as foliar spray. It is concluded that the present study has enlightened our knowledge on the etiology and management of Sigatoka leaf spot disease of banana cultivation in Kerala.ThesisItem Open Access Characterization, host range and management of papaya ringspot virus (PRSV)(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2018) Atheena Harish; KAU; Anita Cherian, KPapaya is an important fruit crop which is cultivated extensively both in tropics and subtropics. During the last decade, the area under papaya cultivation has dramatically increased due to the introduction of superior varieties. A major setback subsequent to the introduction of such new varieties has been the incidence of papaya ringspot disease caused by Papaya ringspot virus (PRSV) which leads to almost 100 per cent yield loss. Considering the importance of the disease, the project was undertaken with the objectives of characterization of the virus, molecular and immunodiagnosis along with disease management. The research project was initiated with purposive sampling surveys conducted in different papaya orchards of Thrissur district in order to document the symptoms under natural conditions, to assess the incidence and severity of the disease and to collect infected samples for further studies. The maximum disease incidence and disease severity recorded were 99.6 and 96.67 per cent on papaya variety Red Lady from Vellikulangara and Puthur respectively. The development of symptoms was studied under artificial conditions also through mechanical inoculation of healthy papaya seedlings with virus inoculum maintained in insect proof net house conditions. The salient diagnostic symptoms of the disease observed on leaves were chlorotic spots, mottling, vein thickening, puckering, leaf distortion, shoestring symptom along with presence of oily streaks on the petiole. The fruits of infected plants presented typical oily concentric or broken ringspots on fruit surface along with malformation. Histopathological studies of infected leaves revealed disruption of the epidermis, disorganization of parenchyma, disintegration of chloroplasts and deposition of crystalline bodies. The studies on virus transmission confirmed that it is transmitted through plant sap from infected to healthy papaya plants. Seed transmission studies revealed that PRSV is not seed -borne. Twenty one plant species including weeds seen in and around papaya orchards were tested for studying the host range of the virus and only five plant species viz., Cucumis sativus, Cucurbita moschata, Trichosanthes cucumerina, Momordica charantia and Chenopodium amaranticolor developed symptoms after artificial inoculation of PRSV and thus proved to be the hosts of the virus. Morphological characterization done using electron microscopy showed the presence of typical flexuous rod particles of size 807.74 nm x 12 nm which indicated that the virus belongs to genus Potyvirus and the etiology of the disease was confirmed as Papaya ringspot virus. Immunodiagnostic technique was validated using Direct Antigen Coating - Enzyme Linked Immuno Sorbent Assay (DAC-ELISA) and infected samples showed positive reaction to PRSV antiserum and could be detected at 1:200 dilution of primary antibody and 1:10,000 dilution of secondary antibody. Molecular characterization of PRSV was also carried out through Reverse Transcription Polymerase Chain Reaction (RT-PCR). The nuclear inclusion b (NIb) gene and the coat protein (CP) gene were amplified using reported primer pairs which yielded amplicons of approximate size of 1700 bp. The PCR products were outsourced for sequencing and in silico analysis of the sequences obtained revealed that the isolates of present study are more similar to Calicut isolate of PRSV, PRSV- Ca (DQ666640.1) A pot culture experiment under insect proof conditions was also conducted to evaluate the effects of selected botanicals, chemicals and biocontrol agents for disease management. Among the fourteen treatments, Bougainvillea leaf extract, 10 per cent (T7) was the most effective with lowest disease severity (6.67%) followed by foliar spray and soil drenching with Pseudomonas fluorescens 2 per cent (T3) with a disease severity of 11.11 per cent as against 97.77 per cent recorded in untreated control plants. Plant height recorded after each treatment application revealed that both 10 per cent Bougainvillea leaf extract (T7) and 2 per cent P. fluorescens are equally superior to all other treatments. However, with respect to mean girth of stem, maximum value (2.91 cm) was recorded in P. fluorescens (T3) The data on virus titre of all treated plants assessed through DAC-ELISA revealed that the concentration of virus particles was minimum in plants treated with T7 and T3. The outcome of this study would facilitate early detection and elimination of source of virus infection and thereby prevent the spread of disease in the field. The information generated on molecular characterization of PRSV isolates under could be applied in genetic engineering. The project also revealed the potential of botanical, Bougainvillea spectabilis leaf extract and biocontrol agent, Pseudomonas fluorescens for the ecofriendly management of papaya ringspot disease.ArticleItem Open Access Collar rot and wilt of clove seedlings incited by Cylindrocladium Camelliae Venkitaramani and Venkata ram – A new record from India(Kerala Agricultural University, 1994) Beena, S; Anita Cherian, K; Varma, A S; James Mathew; KAUArticleItem Open Access Collar rot of murraya koenigii L. by corticium rolfsii curzi(Kerala Agricultural University, 1994) Anita Cherian, K; Beena, S; Koshy Abraham; KAUThesisItem Open Access Etiology and characterization of diseases of Anthurium (Anthurium andraeanum L.) in Kerala(Department of Plant Pathology, College of Agriculture, Vellanikkara, 2021) Nitha, Rafi; KAU; Anita Cherian, KAnthurium (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.ThesisItem Open Access Etiology and Management of Rhizome Rot Disease of Banana(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2003) Usha, N K; KAU; Anita Cherian, KRhizome rot disease of banana is one of the most serious diseases of banana In Kerala.The pathogen was isolated from infected rhizomes of banana var. Nendran and the pathogenicity was established after standardising the method of inoculation .. The symptomatology of the disease was studied in detail under natural field conditions and under artificially inoculated controlled conditions. The salient symptoms of the disease were flaccidity and yellowing of leaves and soft rotting of the rhizome. Based on the morphological, cultural, biochemical, physiological and molecular characters, coupled with its pathogenicity, the pathogen causing rhizome rot disease of banana var. Nendran was identified as Erwinia carotovora. Studies were conducted on the host range of the pathogen on five hosts viz. heliconia, canna, ginger, turmeric and colocasia under field conditions. The results revealed that the pathogen failed to infect these hosts. Studies on soil survival of the pathogen revealed that the pathogen survived in the sterilized soil in the presence of diseased rhizomes for 180-185 days. Out of the 240 accessions of banana screened for resistance to rhizome rot disease under natural field conditions, the genome AAB is found to be the most susceptible one among the genornes screened. The variety Poppoulu (AAB) was found to be the most severely infected one. The commercial variety of Kera1a viz; endran was also found to be highly susceptible to the disease. In vitro inhibitory effect of antibiotics, fungicides, botanicals, and bioagents on the growth of the pathogen was tested. Among the fungicides, fytolan at 0.4 per cent concentration gave the maximum inhibition followed by fytolan at 0.3 per cent. Among the antibiotics tried, streptocycline at 300 ppm was found to be the most superior one. Garlic extract at 100 per cent concentration was the best botanical for inhibiting the pathogen. Pot culture experiment on the management of the disease revealed that among the six treatments given, fytolan at 0.4 per cent and streptocycline at 300 ppm were found to be the most effective treatments in controlling the rhizome rot disease of banana. Garlic extract at 100 percent concentration was also found to be effective in managing the disease under field conditions, which was on par with Pseudomonas flourescens (T2) and bleaching powder (Tl).ThesisItem Open Access MANAGEMENT OF TOMATO LEAF CURL VIRUS IN TOMATO THROUGH THE CONTROL OF ITS WHITEFLY VECTOR, Bemisia tabaci Genn. BY ENTOMOPATHOGENIC FUNGI(University of Agricultural Science, Dharwad, 1999) Anita Cherian, K; Muniyappa, VABSTRACT NOT AVAILABLEThesisItem Open Access Molecular characterization of virus causing infectious chlorosis disease of banana(Department of Plant Pathology, College of Horticulture Vellanikkara, 2017) Ahamed Mujtaba, V; KAU; Anita Cherian, KThe experiment entitled “Nutrient management in strawberry (Fragaria x ananassa Duch.)” was undertaken at Regional Agricultural Research Station, Ambalavayal, Wayanad during the year 2016-17. Performance of strawberry variety Winter Dawn was evaluated under nine treatments and a control in the open field viz., FYM 10 t ha-1 + NPK 50:20:50 kg ha-1 (T1); FYM 10 t ha-1 + NPK 75:30:75 kg ha-1 (T2 ); FYM 10 t ha-1 + NPK 100:40:100 kg ha-1 (T3); FYM 20 t ha-1 + NPK 50:30:100 kg ha-1 (T4); FYM 20 t ha-1 + NPK 75:40:50 kg ha-1 (T5); FYM 20 t ha-1 + NPK 100:20:75 kg ha-1 (T6); FYM 30 t ha-1 + NPK 50:40:75 kg ha-1 (T7); FYM 30 t ha-1 + NPK 75:20:100 kg ha-1 (T8); FYM 30 t ha-1 + NPK 100:30:50 kg ha-1 (T9) and an absolute control (T10), without any nutrient application. All the treatments were on par and superior over the control (T10) in case of plant height. In case of plant spread, T2, T3, T5, T6, T7, T8 and T9 were on par and superior over the control while T1 and T4 were on par with each other but differs with other treatments. All the treatments except T2 were on par and superior over the control with respect to number of leaves per plant. Application of treatments had no significant effect on days to first flowering. In case of number of flowers and clusters per plant, T1, T2, T3, T5, T6, T7, T8 and T9 were on par and superior over the control while T4 was on par with the control (T10). Days to first harvest was minimum in T6, T7, T8 and T9 which were on par while all other treatments were on par with the control (T10).In case of number of fruits and yield per plant, T7 (FYM 30 t ha-1 + NPK 50:40:75 kg ha-1) and T8 (FYM 30 t ha-1 + NPK 75:20:100 kg ha-1) were on par and superior over other treatments including T1, T2, T3, T4, T5, T6 and T9 which were on par and superior over the control. Average fruit weight recorded under T3, T5, T6, T7, T8 and T9 were on par which was followed by T2 on par with T4 and T1. Days to final harvest was not found to be influenced by the application of different treatments. Biochemical characters of fruits viz., TSS, acidity and TSS/acidity ratio were not having any significant effect due to the application of treatments. In case of total sugars, T3, T7, T8 and T9 were having the highest content and were on par which was followed by T5 on par with T1, T2, T4, T6 and T10. The overall sensory score was highest in T7 followed by T8. Application of different treatments had no significant effect on the shelf life of strawberry fruits. N, P, K and Ca content in the plant were not significantly affected by any treatment while Mg content was found to be on par in all treatments and superior over the control. Soil analysis after the harvest of the crop revealed that the values for soil EC, available P, K, Mg and S were found to be elevated while soil pH, organic carbon and available Ca content were found to be at lower levels than the initial values before planting. It was concluded that among different nutrient combinations evaluated, T7 (FYM 30 t ha-1 + NPK 50:40:75 kg ha-1) with a BC ratio of 3.06 can be recommended for further optimization and refinement.ThesisItem Open Access Molecular characterization, host range and integrated management of bhindi yellow vein mosaic disease(Department of Plant Pathology, College of Horticulture, Vellanikkara, 2019) Chinju, E A; KAU; Anita Cherian, KBhindi (Abelmoschus esculentus (L.) Moench) is one of the most important vegetable crops cultivated across the globe. However, its cultivation is often hindered by biotic stresses like incidence of pests and diseases. Among the diseases, yellow vein mosaic disease is one of the major constraints in bhindi cultivation which leads to 100 per cent yield loss especially when infected at an early stage of the crop. In recent years, the evolution of new viral strains is a serious problem especially among Begomoviruses belonging to the family Geminiviridae which has an adverse effect on the host plant resistance. Considering these facts, the present study was undertaken to carry out the molecular characterization of the virus causing bhindi yellow vein mosaic disease (BYVMD), to study the host range and seed transmission of the virus and to develop a sustainable disease management strategy. The project was initiated with purposive sampling survey conducted in elevan different locations of Thrissur district, Kerala. The disease incidence recorded during the survey ranged from 61.20 to 98.16 per cent while the disease severity ranged from 48 to 90 per cent. The predominant symptoms observed on the leaves of infected plants under natural conditions were vein clearing, vein thickening, reduction in leaf area, bleached appearance and marginal necrosis. A novel type of symptom observed during the survey was general yellowing of leaves with severe puckering along the veins and upward curling of leaves. Linear cholorotic striations were observed on the calyx of the flower buds. The immature fruits produced by the infected plants showed linear chlorotic striations, while the mature fruits were bleached in appearance along with reduction in fruit size. The plants infected during the early vegetative stage were extremely stunted. The major symptoms developed under artificial conditions were vein clearing, vein thickening and puckering of leaves. xxiv Histopathological studies of the infected leaf revealed disruption of parenchymtous cells in the epidermis, disintegration of chloroplast, reduction in number of metaxylem and protoxylem along with abnormality of phloem vessels. The studies on virus transmission confirmed that it is transmitted through grafting and insect vector, Bemisia tabaci. The presence of virus inside the insect body was also confirmed through polymerase chain reaction (PCR) based molecular technique. The studies on seed transmission revealed that BYVMD is not seed-borne. Host range studies revealed that weed species Synedrella nodiflora and Hemidesmus indicus were proved to be hosts of the begomovirus. Molecular detection of the virus causing BYVMD was standardized through PCR, using universal primer specific to the core coat protein gene of Begomovirus which yielded amplicons at expected size of about 550 bp. The amplification was also carried out using primers specific to coat protein gene of bhindi yellow vein mosaic virus (BYVMV) and okra enation leaf curl virus (OELCuV) which yielded amplicons at expected band size of about 770 bp. The molecular characterization of the elevan isolates was carried out through in silico analysis to identify the virus associated with BYVMD and for diversity analysis. The results revealed that all the isolates showed 99-100 per cent nucleotide homology to OELCuV. BLASTp analysis of the isolates also showed 100 per cent identity with coat protein of OELCuV and thus confirming that the virus causing yellow vein mosaic disease in bhindi in Kerala is okra enation leaf curl virus. The identity was further confirmed through DNA barcoding technique and species demarcation analysis. A field experiment was also conducted to develop a disease management package against BYVMD. Among the seven treatments, T5 i.e., integrated management with early seedling protection using insect proof net + yellow sticky trap + seed bio-priming and foliar spray of PGPR mix II + alternate foliar spray of Bougainvillea spectabilis and azadiractin was found to be most effective with xxv lowest disease incidence and severity, least whitefly population and maximum yield. It is concluded that yellow vein mosaic disease affecting bhindi cultivation in Kerala is caused by okra enation leaf curl virus, an evolved strain of BYVMV. This virus is transmitted through grafting and the insect vector Bemisia tabaci and not though seeds. The outcome of the study would also facilitate early detection and elimination of sources of infection so as to reduce the spread of the disease. An integrated disease management package was also developed for the benefit of farming community.ThesisItem Open Access Molecular cloning and characterisation of coat protein gene of banana bract mosaic virus(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2016) Darshan Gowda, M R; KAU; Anita Cherian, KBanana (Musa spp.), identified as ‘tropical treasure’ is grown extensively in the tropical and sub tropical regions of the world. Diseases, especially those caused by viruses are major constraints for the profitable cultivation of banana. Among the viral diseases, banana bract mosaic is one of the most important, which leads to an yield reduction ranging from 52 to 75 per cent. This disease is caused by Banana bract mosaic virus (BBrMV) which is a member of genus Potyvirus and family Potyviridae. In case of any viral disease, early diagnosis is very important since symptomless hosts carry the viral inoculum. Development of molecular clones of viral genome has immense application in the field of disease diagnostics and management. Hence, the present study was carried out with the objective to develop molecular clones of coat protein (CP) gene of BBrMV and to characterize it.The infected suckers were collected from Banana Research Station (BRS), Kannara and maintained in the insect proof net house of Department of Plant Pathology. The symptoms developed on different plant parts under natural field conditions were documented which included longitudinal, irregular, reddish streaks of varying sizes on the base of pseudostem, mosaic pattern on bracts, fan like orientation of leaves, spindle shaped lesions on leaves, reduced bunch size and malformed fingers.The serodiagnostic technique namely, Direct Antigen Coating-Enzyme linked immuno sorbent assay (DAC-ELISA) was validated by determining the antibody titre with different dilutions of primary antibody viz., 1:100, 1:200, 1:300, 1:500 and it was found that BBrMV could be best detected at 1:200 dilution along with 1:500 dilution of secondary antibody. Later, the presence of virus particles in the samples were confirmed by DAC-ELISA using the standardized combination of primary and secondary antibody dilutions. Dot Immuno Binding Assay (DIBA) was validated to detect BBrMV and showed positive reaction for infected leaf sample which was detected by the development of purple coloured spots on nitrocellulose membrane.The genome of BBrMV is RNA and hence, molecular detection of virus was standardized by Reverse Transcription- PCR (RT-PCR). Total RNA was isolated by two different protocols using different reagents. Among the two methods, the one with Ambion Purelink RNA Reagent was the most appropriate for RNA isolation from banana since it provided highest quality and quantity of RNA compared to the protocol with TRIzol reagent. The isolated RNA was converted into complementary DNA (cDNA) using First Strand cDNA synthesis kit. RTPCR amplification of coat protein gene was standardized using gene specific reported primer (B1/B2) and designed primer (BCPF1/R1) which yielded amplicons of approximate size, 605 bp and 850 bp respectively. The molecular cloning of CP gene was done in Escherichia coli (DH5- alpha). The presence of gene insert in transformed colonies were confirmed by colony PCR using plasmid specific primer (T7 and SP6) which yielded amplicons of expected band size of 1150 bp. The amplified colony PCR products were sequenced to obtain CP gene sequence of BBrMV. The characterization of cloned CP gene of BBrMV was carried out by in silico analysis. The blast analysis revealed that the CP gene sequence of the virus showed maximum homology of 99 per cent to KER2 isolate from Kasargod, Kerala (Accession no. KF385491). The sequence exhibited significant nucleotide identity (99 to 96 per cent) and amino acid identity (95 to 83 per cent) with other nucleotide and protein sequences of BBrMV available in the database of Genbank. The phylogenetic analysis by the alignment of CP gene sequences of selected 22 isolates also revealed that the present isolate was more similar to KER2 isolate and the Indian isolates did not show any relationship based on geographical origin.The recombinant clones developed in the present study could be applied in serodiagnosis and genetic engineering. This could be also used as disease diagnostic probes for more sensitive molecular diagnostic techniques like Nucleic acid spot hybridization.ThesisItem Open Access Molecular cloning and characterization of virus causing leaf curl disease of capsicum spp.(Centre for Plant Biotechnology and Molecular Biology, College of Horticulture, Vellanikkara, 2019) Niranjana Menon, C; KAU; Anita Cherian, KChilli is one of the most important crops cultivated across the globe, as vegetable, spice and for industrial purposes. According to the statistics of National Horticulture Board (2017), the crop covers an area of 1860 ha in the state of Kerala with an average production of 12470 tonnes. During the last decade, the threats posed by the emerging begomoviruses infecting solanaceous crops have affected the economic cultivation of chilli. Chilli leaf curl disease caused by Chilli leaf curl virus belonging to the genus Begomovirus and family Geminiviridae is a serious constraint to chilli production in India which causes upto 100 per cent yield loss especially when infected at an early stage of the crop. Considering the importance of the disease, the present study was undertaken with the objective to study the incidence and symptomatology of chilli leaf curl disease and to characterize and clone the coat protein gene of the Chilli leaf curl virus isolates. The project initiated with purposive sampling surveys conducted in eleven different locations of Thrissur district, Kerala to document the incidence and symptomatology of leaf curl disease on chilli plants. The disease incidence recorded during the survey ranged from 43.30 to 85.00 per cent under open field conditions and from 45.75 to 79.40 per cent under protected conditions while the disease severity ranged from 43.60 to 81.54 per cent and from 49.40 to 87.50 per cent, respectively under open field conditions and protected conditions. The symptomatology of chilli leaf curl disease on different parts of the plant such as leaves, internodes, fruits and the whole plant under natural conditions was documented during the survey. The symptoms observed on the leaves of infected chilli plants under natural conditions include upward curling, crinkling, puckering, vein banding, interveinal chlorosis, size reduction of leaf lamina and leaf malformation. The fruits produced by the infected plants showed size reduction and deformation. The infected plants were stunted and bushy in appearance. The transmission of the virus by insect vector, Bemisia tabaci and grafting was studied and the symptoms were documented. The newly emerged leaves after artificial inoculation expressed symptoms such as curling, puckering and crinkling along with stunting of plant growth. Molecular characterization of the four virus isolates collected from various locations of Thrissur district viz., VKA1 VKA2, KAR1 and KOD4 and two isolates viz., VLNY1 and PKD1 collected from Vellayani, Thiruvanathapuram district and from Vithinasseri, Palakkad district, respectively were undertaken. The total genomic DNA from virus infected chilli leaf samples was isolated and subjected to PCR amplification of viral coat protein gene to confirm the presence of virus infection. PCR amplification of the isolated DNA was carried out using two Begomovirus specific degenerate (universal) primers, namely, AV494 / AC1048 (Wyatt and Brown, 1996) and Deng 540 / 541 (Deng et al., 1994). The amplicons of size 550 bp were obtained and were sequenced. The partial coat protein gene of size 550bp were also cloned into the vector pTZ57R/T and transformed into DH5α strain of Escherichia coli and the true recombinants with desirable insert were confirmed by colony PCR. The sequence data obtained in the study were subjected to in silico analysis to assess the diversity of the isolates. The nucleotide BLAST (BLASTn) analysis revealed more than 90 per cent sequence identity with Chilli leaf curl Vellanad virus isolate (Accession No. NC038442.1) from Vellanad region of Thiruvanathapuram district, Kerala. The translated nucleotide - protein BLAST (BLASTx) analysis of the viral sequences revealed more than 96 per cent sequence identity with Chilli leaf curl Vellanad virus coat protein sequence (accession no. YP_009506391.1). The coat protein sequences of all the six isolates were translated into corresponding amino acid sequence by ExPASy Translate tool and were used for further analysis and interpretation. The phylogenetic analysis revealed that, the isolates VKA2, KAR1 and KOD4 had very distinct sequence alignment when compared to other Chilli leaf curl virus isolates from India. The results indicated that, the three isolates viz., VKA2, KAR1 and KOD4 could be new strains of Chilli leaf curl virus infecting chilli. Three, possibly new strains of Chilli leaf curl virus infecting chilli have been identified and hence the study highlights the need for monitoring the emergence of new strains of plant viruses especially begomoviruses infecting solanaceous crops grown in Kerala. As this disease is one of the most important challenges to chilli cultivation, the information generated from the study could also be applied for the timely detection and effective disease managementArticleItem Open Access New leaf spot disease of kodampuli (Garcinia Cambogia) desr.(Kerala Agricultural University, 1996) Anita Cherian, K; Beena, S; Koshy Abraham; KAUThesisItem Open Access Post harvest deterioration of fruits by microbes and their control(Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Anita Cherian, K; KAU; Susamma PhilipSeveral fungi and bacteria was isolated from decayed fruits like banana, mango, pineapple and orange collected from the local markets of Trivandrum city over a period of six months, Among these Botryodiplodia theobromas was the most common fungus with its occurrence on all fruits. Other pathogenic fungi isolated from each fruit