1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
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Item Management of collar rot of elephant foot yam (Amorphopallus paeoniifolius) using biocontrol agents and fungicides(Department of Plant Pathology, College of Agriculture , Vellayani, 2025-01-25) Sreechithra, M S; Sherin A SalamThe research titled "Management of collar rot of elephant foot yam (Amorphophallus paeoniifolius (Dennst.)) using biocontrol agents and fungicides" was conducted in the Department of Plant Pathology, College of Agriculture, Vellayani, Thiruvananthapuram during 2022-2024 with the objectives of characterizing the pathogen causing collar rot and to manage it using biocontrol agents and fungicides. As part of the study, a survey was conducted at Thiruvananthapuram, Kollam, and Alappuzha districts, belonging to two agro-ecological units (AEU 8 and 9) of Kerala. Koch’s postulate of the ten isolates obtained during the survey was confirmed. Isolate I3 obtained from Venganoor area of Thiruvananthapuram district was found to be the most virulent and fast-growing. Cultural and morphological studies revealed that the isolates took only 3-5 days to complete its growth in Petri dish (9cm). The colony colour was white with no pigmentation. The colony texture of all isolates was fan-like except I6 and I10 which were fluffy and sparse towards the center respectively. The isolates took 6-12 days for sclerotial formation and the number of sclerotia ranged between 0 and 180. The isolate I3 produced the highest number of sclerotia (180) within 15 days, while I6 failed to produce any sclerotia. The hyphal width and septal distance ranged from 1.14 to 3.68 μm and 81.01 to 129.70 μm respectively. The size of sclerotia varied from 1.20 to 1.96 mm and isolate I3 recorded the largest sclerotial size of 1.96 mm. Based on cultural, morphological, and pathogenic characteristics, I3 was found to be the most virulent among the ten isolates. The identity of the pathogen was confirmed molecularly using ITS primers as Athelia rolfsii (Accession no. PQ268968) (teleomorph of Sclerotium rolfsii) with 100% homology. In order to isolate beneficial antagonistic bacteria against S. rolfsii, 82 collections were made from the soil with healthy elephant foot yam. Out of this, 15 were short listed based on the primary screening and from this two (B57 and B 43) showing the best antagonistic property was used for further studies. These antagonists were molecularly identified as Bacillus amyloliquefaciens (B57) (Accession no. PQ268963) (100% similarity) and B. velezensis (B43) (Accession no. PQ268964) (99.87% similarity). Both the isolates tested positive for cellulase and pectinase activity with B57 producing significantly higher quantities of NH3, IAA, siderophore and volatile compounds compared to isolate B43. Antagonistic property of B57 and B43 was compared with the widely used biocontrol agents in Kerala and it was found that B57 (64.16%) was on par with biocontrol check Trichoderma asperellum (KAU T6) (62.78 %), followed by B. velezensis (B43) (57.22 %). Among the fungicides assessed, mancozeb (75% WP) and trifloxystrobin (25%) + tebuconazole (50%) 75 WG inhibited the pathogen completely at all concentrations tested and performed better than other treatments even at a lower concentration of 0.005%. In the in vivo study, the treatments trifloxystrobin (25%) + tebuconazole (50%) 75 WG @ 0.05% and @0.1% gave 100% control followed by the treatments B57, Trichoderma enriched neem cake and FYM and mancozeb 75 WP (0.2%) which were found to be on par. Plants treated with B57 and Trichoderma enriched neem cake and FYM inhibited the pathogen without producing any symptoms for up to 160 days and produced smaller lesions compared to others. It also gave better yield compared to other treatments. The chemical fungicides failed to enhance any biometric parameters and yield. The findings of the study confirmed that the collar rot of EFY in Kerala is caused by Sclerotium rolfsii (T: Athelia rolfsii). During the course of the study, a promising rhizobacterial antagonist (B. amyloliquefaciens (B57) (PQ268963)) was obtained. In vivo studies confirmed that, corm treatment and soil application of B. amyloliquefaciens (B57) (PQ 268963)) @20g/l at the time of planting and 30 and 45 DAP could enhance plant growth and yield and inhibit collar rot disease. Among the fungicides tried, corm treatment and soil application of trifloxystrobin (25%) + tebuconazole (50%) 75 WG at the time of planting, 30 and 45 days after planting could effectively inhibit the collar rot pathogen even at a lower dose of 0.05%.Item Identification of virus(es) and phytoplasma associated with mixed infection of mosaic and yellowing disease in elephant foot yam(Department of Plant Biotechnology, College of Agriculture , Vellayani, 2022-11-16) Jancy ,C S; Makeshkumar,TThe present research work entitled Identification of virus(es) and phytoplasma associated with mixed infection of mosaic and yellowing disease in Elephant foot yam was carried out at ICAR CTCRI, Sreekaryam during the year 2021-2022, with the primary objective of identification and characterization of virus(es) / phytoplasma causing mixed infection of mosaic and yellowing in elephant foot yam. Elephant foot yam (EFY) plants having symptoms such as mosaic, yellowing, vein yellowing, mosaic with yellowing, curling etc. were collected from different fields of CTCRI as well as from KVK (Kottayam) and Erode (Tamil Nādu). Genomic DNA and RNA were isolated from symptomatic leaf samples using CTAB method. Detection of phytoplasma was carried out by PCR using universal primers P1/P7 followed by nested PCR using R16F2n/ R16R2. The expected band size of 1.2kb has not been obtained from any of the infected leaf samples. Detection of DNA virus was carried out using primers CLTY F / CLTY R which are begomovirus specific. The expected band size of 500bp was obtained. RNA virus was detected using RT PCR. The cDNA synthesized using Verso cDNA synthesis kit was amplified using different sets of primers viz., GBNV F/GBNV R, MKTOSPOSGF/MKTOSPOSGR, DsMV RPA1 F/ DsMV RPA1 R, MKGNNSF/WEICNR, PRSF8313/PRSR9420, ChVMCPF/ChVMCPR, ChVMF2393/ChVMF3560 and BCWZ F/BCWZ R. An amplicon size of 400bp was obtained from symptomatic leaf samples collected from CTCRI, KVK Kottayam and Tamil Nadu using DsMV RPA primers. A specific band of 1.2kb size and nonspecific band of size 500bp was obtained using potyvirus genus specific primer MKGNNSF/WEICNR and nonspecific band of size 300bp was obtained using Groundnut bud necrosis virus (GBNV) specific primer GBNVF/GBNVR . Positive amplicons were eluted from the gel and sequenced. Eluted amplicons were also ligated to pTZ57R/T vector, cloned to competent DH5α E.coli cells and screened through Blue-white screening on LB ampicillin/X-Gal plate. The white transformed colonies that gave an expected band size in Colony PCR were chosen forsequencing. 87 BLASTn analysis revealed that the DNA virus sequences isolated from the infected leaf samples from CTCRI had 91.77 per cent similarity with Sri Lankan cassava mosaic virus (SLCMV). PCR analysis was carried out using different sets of primers viz., SL RPA F/R, SLRP Rep F/R for further confirmation of SLCMV and an amplicon of size 1000bp and 734 bp was obtained respectively. BLASTn analysis of RNA viral sequences obtained by using BCWZ F and BCWZ R primers revealed that the infected leaf samples from CTCRI, Tamil Nadu and KVK had only 74 per cent identity with Moroccan watermelon mosaic virus and those obtained by using potyvirus genus specific primers MKGNNSF/WEICNR had only 74 per cent similarity with Dasheen Mosaic Virus. Phytoplasma has not been detected in any of the collected symptomatic samples. In conclusion, the characterization of DNA and RNA viruses from EFY leaf samples revealed that the Elephant foot yam plants were subjected to mixed infection. The Sequence information of DNA virus isolate reveals the infection of SLCMV in leaf samples and that of RNA virus isolates obtained from leaf samples reveals the probability of infection with viruses that belong to families other than potyviridae.Item Integrated nutrient management in minisett cultivation of elephant foot yam {Amorphophallus paeoniifolius (Dennst.) Nicolson}(Department of Agronomy, College of Agriculture ,Vellayani, 2022-11-18) Dhanalakshmi V N; Rajasree GThe study entitled “Integrated nutrient management in minisett cultivation of elephant foot yam [Amorphophallus paeoniifolius (Dennst.) Nicolson]” was conducted at the Instructional Farm, College of Agriculture, Vellayani, Thiruvananthapuram to standardise the minisett size in elephant foot yam and to investigate the effect of integrated nutrient management practices on growth, yield, quality and economics of cultivation and to study the rooting and tuberisation pattern of minisett planted elephant foot yam. The investigation consisted of two experiments; standardisation of minisett corm size and integrated nutrient management practices (field experiment) and rooting and tuberisation pattern study (pot culture) and was undertaken during April to November 2018 and 2019. The first experiment was laid out in RBD with 15 treatment combinations and a control, replicated thrice. The treatments comprised three minisett corm sizes (s1-200 g, s2-300 g and s3-400 g) and five integrated nutrient management practices (i1-100 per cent NPK, i2-75 per cent NPK with 50 per cent N substitution through coir pith compost, i3-75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF, i4-50 per cent NPK with 50 per cent N substitution through coir pith compost, i5-50 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF). The minisett corms and control corms (1 kg) of elephant foot yam var. Gajendra were planted at a spacing of 60 x 60 cm and 90 x 90 cm respectively. The recommended dose of N, P and K (100:50:150 kg NPK ha-1 ) for elephant foot yam was modified based on soil test data. Substitution of N with coir pith compost was carried out on N equivalent basis, and P and K were given through chemical sources. The pot culture experiment was laid out in CRD with 14 plants per treatment with the same treatments as the field experiment. The number of days taken for 100 per cent sprouting of seed corms varied between minisett corms and control corms and the latter sprouted early. The minisett corm s3 (400 g) recorded taller plants, higher leaf area index, pseudostem 281 girth and canopy spread. Application of 100 per cent NPK (i1) as chemical fertilizer produced taller plants and higher canopy spread during later stages compared to INM practices. Among the INM treatments, i3 (75 % NPK with 50 % N substitution through coir pith compost + PGPR mix-I + AMF) found superior with respect to growth attributes such as plant height and canopy spread. The treatment combination s3i1 (400 g + 100 % NPK as chemical fertilizer) produced taller plants and recorded higher canopy spread. Among the interactions including INM practices, taller plants were produced by s3i3 and s3i5 and higher canopy spread was recorded with s3i2, s3i3 and s3i5. Control plants (1 kg) showed taller plants, higher pseudostem girth and canopy spread at all stages of observation. The s3 recorded higher yield attributes, corm yield (48.81 and 50.57 t ha-1 during first year and second year, respectively) and pooled corm yield (49.69 t ha1 ). The treatments, i1 (100 % NPK) recorded significantly the highest yield attributes and yield. Among the different INM practices, i3 recorded higher yield attributes and corm yield (38.26 and 45.37 t ha-1 during first year and second year, respectively), while corm yield in pooled mean analysis (41.82 t ha-1 ) was also higher in this treatment. The s3i1 (400 g + 100 % NPK as chemical fertilizer) produced significantly the highest yield attributes and yield among all the treatments. Among the INM combinations, s3i3 recorded higher yield attributes, corm yield and higher pooled mean of corm yield (51.29 t ha-1 ). Control recorded higher yield attributes than minisetts. Pooled analysis of corm yield ha-1 indicated that s3i1, s3i2, s3i3 and s3i5 were superior to control and s2i1, s2i2, s2i3 and s3i4 were on par with control. Quality attributes like starch, total sugar, crude protein and crude fibre content of corm were non significant with respect to the treatments. Higher dry matter content was obtained in i4 (50 % NPK with 50 % N substitution through coir pith compost). The lower content of oxalic acid was recorded with i5 and i4 and the higher content was in i1 (100 % NPK). The minisett corm s3 recorded superior results for nutrient content, uptake and nutrient harvest indices. The INM treatment, i3 recorded higher nutrient content and uptake, however the highest was recorded in i1 among all the treatments. The treatment s3i1 (400 g + 100 % NPK 282 through chemical fertilisers) recorded significantly the highest K uptake. Among the combinations including INM practices, s3i3 recorded higher K uptake during second year. The combinations, s3i1, s3i2, s3i3, s3i4 and s3i5 were found superior to control in case of nutrient uptake. Soil chemical properties after the field experiments were not significantly affected by the treatments. The treatment s3i1 (400 g + 100 % NPK) recorded the highest net income and BCR during both the years. The highest net income and BCR were recorded from s3i2 during first year and s3i3 during second year, and the two year mean of net income and BCR were also highest in the case of INM treatment s3i3. In pot culture study, chemical properties of potting medium at monthly intervals up to harvest were not significantly affected by the treatments except for organic carbon content. The treatment i3 (75 % NPK with 50 % N substitution through coir pith compost + PGPR mix-I + AMF) recorded higher organic carbon content at 5 MAP. The minisett corm s3 excelled in rooting pattern and root anatomical parameters. Higher number of roots per plant was recorded in i2 and i3, however, these treatments were on par with i1 (100 % NPK). Higher weight of roots per plant was observed in i5, i4 and i3 and, root anatomical parameters were superior in i3. The interactions, s3i5, s3i4 and s3i3 recorded the highest weight of roots per plant. Higher root parameters were recorded in control than in minisetts and, in case of number of roots per plant s3i1, s3i2 and s3i3 at 4, 6 MAP and harvest, and s3i1 at 5 MAP recorded on par results with control. In the case of weight of roots per plant, s3i3 was on par with control at harvest. The roots of plants applied with AMF showed mycelial network from 3 MAP up to the harvest, and in the maximum growing stage of 5 MAP, vesicles were found in between the cells of the roots of AMF applied plants. Higher root colonization was observed in s3i3 at 5 MAP. Corm initiation was observed between 1 MAP and 2 MAP in control and between 2 MAP and 3 MAP in all other treatments. The s2 (300 g) during 3-4 MAP and s3 (400 g) during all other stages had significantly the highest corm bulking rate (CBR). Higher corm bulking efficiency (CBE) was recorded in s2 during 3-4 MAP, s1 during 4-5 MAP and 6 MAP-harvest and s3 during 5-6 MAP. 283 The INM treatment i3 showed superior results for CBR and CBE, however, higher CBR and CBE were recorded in i1 (100 % NPK) among all the treatments. The s3i1 (400 g + 100 % NPK)showed the highest CBR and CBE during 4-5 MAP and 5-6 MAP among all the treatments. Among the INM interactions, s3i3 during 3-4 MAP and 5-6 MAP; s3i2 during 4-5 MAP and s3i4 during 6 MAP-harvest recorded higher CBR. The s2i3 during 3-4 MAP, s1i3 during 4-5 MAP, s3i3 during 5-6 MAP and s1i5 during 6 MAP-harvest recorded higher CBE. Higher corm weight per plant was recorded with s3. The i1 recorded the higher corm weight per plant among all the treatments, and at 5 MAP, i1 was on par with i3. Among the INM treatments i2 at 3 MAP and i3 at all other stages recorded higher corm weight per plant. Among interactions, s3i3 produced higher corm weight, however, among all the treatments the highest corm weight was noted in s3i1 at all stages except at 4 MAP. Control produced significantly higher corm weight per plant than minisetts. Uptake of nitrogen at 3 MAP and uptake of phosphorus at harvest were higher in s3. The INM treatment i3 recorded higher microbial population and dehydrogenase activity in the potting medium and among the interactions, higher dehydrogenase activity was recorded with s3i3. Significant and positive correlations were observed between corm weight per plant vs. root anatomical parameters and nutrient uptake vs. root anatomical parameters. It is evident from the present study that planting of 400 g minisett corm resulted in better growth, yield and quality of elephant foot yam. Application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I [@ 10 g per pit (dry cow dung: PGPR mix-I in 50:1 proportion) - at planting and 2 MAP] + AMF (@ 10 g per pit - at the time of planting) in elephant foot yam resulted in superior growth, yield and quality under INM system. Planting of 400 g minisett and application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF under an INM system could be recommended for economic production of minisett elephant foot yam. Rooting and tuberisation of elephant foot yam were found superior in planting of 400 g minisett corm with application of 75 per cent NPK with 50 per cent N substitution through coir pith compost + PGPR mix-I + AMF.