Browsing by Author "Surendran, M"

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Assessment and Management of rice sheath blight disease in Kuttanad
(Department of Plant Pathology, College of Agriculture , Vellayani, 2025-01-30) Archana Gilbert; Surendran, M
The study entitled “Assessment and management of rice sheath blight disease in Kuttanad” was conducted at Department of Plant Pathology, College of Agriculture, Vellayani and M. S. Swaminathan Rice Research Station, Moncompu during 2022-2024 with the objectives of assessment of extent of rice sheath blight disease incidence caused by Rhizoctonia solani in Kuttanad region, screening for host plant resistance and evaluation of different management strategies. A survey was conducted in forty locations of agro ecological unit (AEU) – 04 (Kuttanad) in Alappuzha, Kottayam and Pathanamthitta districts to assess the extent of sheath blight disease incidence in rice. The symptomatology was studied and plants with grey water soaked lesions with brown margins were observed on leaf sheath near the water level. Presence of brown coloured sclerotia were observed in severely infected plants. Disease parameters such as disease incidence and disease severity were recorded. The highest disease incidence (72.73%) and disease severity (80.19%) were observed in Neelamperoor region of Alappuzha district. The diseased samples were collected for the isolation of the pathogen and 40 isolates were obtained. The pathogenicity was confirmed by artificially inoculating the isolates in rice variety, Uma. Days taken for symptom development and sclerotia formation was recorded and isolate from Neelamperoor region took least number of days for symptom development (3 days) and sclerotia formation (5 days). Cultural and morphological studies of the isolates were conducted and the colony colour varied from white to dark brown in PDA medium. The mycelia formed were aerial and flat type. The number of days for complete growth in Petri plate (90 mm) and for sclerotia formation was 3 to 11 days and 3 to 9 days respectively. The isolate from Neelamperoor took least number of days for complete growth in Petri plate (3 days) and for the formation of sclerotia (3 days). Pattern of sclerotia formation was scattered or confined to centre or periphery. Sclerotia was white to dark brown in colour with smooth and rough surface. Size of sclerotia varied from 1.05 – 1.48 mm. The mycelia were hyaline and septate with right angled branching. Hyphal width ranged from 1.12 – 1.98 μm. The molecular characterization of the virulent isolate was done using ITS primers. The DNA sequence comparison showed similarity with R. solani. The sequences obtained was submitted in GenBank and was allotted with accession number PQ658187. In vitro evaluation of biocontrol agents in growth inhibition of R. solani was tested by dual culture technique. Biocontrol agents Bacillus amyloliquefaciens (B15) and Pseudomonas fluorescens (PN026) were tested and highest mycelial growth inhibition (68.64%) was observed in B. amyloliquefaciens. Efficacy of fungicides in growth inhibition of R. solani at different concentrations was tested under in vitro conditions by poisoned food technique. Fungicides, azoxystrobin 18.2% + difenoconazole 11.4% SC, kresoxim methyl 40% + hexaconazole 8% WG and trifloxystrobin 25% + tebuconazole 50% 75 WG were evaluated against virulent isolate of R. solani. Complete mycelial inhibition was recorded with azoxystrobin 18.2% + difenoconazole 11.4% SC at 1 mlL-1 and in Kresoxim methyl 40%+ Hexaconazole 8% WG at 0.5 gL-1 and 1 gL-1. Fifteen varieties released by KAU were subjected to screening for host plant resistance against sheath blight disease. The disease parameters were analyzed and among these, Aiswarya and Kanchana were observed to be resistant with least disease severity (15.55% and 20.01% respectively) whereas varieties Uma, Jyothi and Karishma were found to be more susceptible exhibiting disease severity of 80.11%, 77.78% and 72.23% respectively. In vivo evaluation of efficacy of biocontrol agents and fungicides along with different fertilizer dose for the management of sheath blight disease was conducted in rice variety Uma in split plot design. Highest per cent reduction in disease over control was observed in treatment combination kresoxim methyl 40% + hexaconazole 8% WG at 1 gL-1 with 75%N, 100%P, 125%K of recommended dose of fertilizers (RDF) (73.93%) followed by treatment combination of kresoxim methyl 40% + hexaconazole 8% WG at 1 gL-1 with 100% RDF (70.31%). Among biocontrol agents, treatment combination of B. amyloliquefaciens (B15) and 75%N, 100%P, 125%K of RDF had better control with 38.79% reduction in disease severity. Highest per cent increase in grain yield was recorded in treatment combination of kresoxim methyl 40% + hexaconazole 8% WG at a concentration of 1 gL-1 and 75%N, 100%P, 125%K of RDF (97.23%) followed by kresoxim methyl 40% + hexaconazole 8% WG at 1 gL-1 and 100% RDF (90.10%). The present study concludes that sheath blight disease incidence ranged from 15.39 to 72.73% in AEU – 04 (Kuttanad). The varieties Aiswarya and Kanchana exhibited resistance to the disease. Sheath blight disease can be effectively managed by foliar spraying of commercial fungicide kresoxim methyl 40% + hexaconazole 8% WG at a concentration of 1 gL-1 at maximum tillering stage along with 75%N, 100%P, 125%K of RDF. Biocontrol agent B. amyloliquefaciens (B15) given as seed treatment (10 gkg-1 seed), soil treatment (1 kg acre-1) at 35 days after planting and foliar spray (20 gL-1) at maximum tillering stage combined with 75%N, 100%P, 125%K of RDF also reduces the disease incidence along with increasing yield parameters
Characterization and management of major pathogens associated with grain discolouration disease of rice
(Department of plant pathology, college of agriculture,Vellayani, 2023-11-16) Amrith, P K.; Surendran, M
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.
Transmission, physical properties and host range of brinjal mosaic virus
(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Surendran, M; Rajagopalan, B