BIOPOLYMER BASED MULTILAYER SEED COATINGS WITH TRICHODERMA, RHIZOBIUM OR BACILLUS AND COMPATIBLE FUNGICIDES AGAINST SEED AND SOIL BORNE DISEASES IN SESAMUM, GROUNDNUT AND SOYBEAN

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Date
2023-01-09
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PROFFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
Sesamum, groundnut and soybean are important oilseed crops grown in many parts of the world. Among different fungal diseases, Macrophomina phaseolina in sesamum and soybean, Sclerotium rolfsii in groundnut are common, widespread and causing significant yield losses. M. phaseolina in sesamum and soybean, S. rolfsii in groundnut were isolated from infected plant parts and purified by hyphal tip method. Pathogenicity test was conducted on susceptible sesamum cv. Swetha Til, groundnut cv. K-6 and soybean cv. JS-335. Pathogen was re-isolated from artificially inoculated plants and found similar in all aspects thus fulfilling Koch’s postulates. The efficacy of six bioagents viz., T. asperellum (TaDOR 7316), Trichoderma sp. (T16), T harzianum (Th), T. asperellum (Ta10), T. asperellum (Ta11) and T. harzianum (Th4d) were evaluated against M. phaseolina isolates of sesamum and soybean and S. rolfsii of groundnut. The results revealed that among six bioagents tested, T. harzianum (Th4d) was found effective in inhibiting the mycelial growth of M. phaseolina of sesamum (66.3 %), S. rolfsii of groundnut (71.9 %) and M. phaseolina of soybean (67.0 %), respectively. The efficacy of five fungicides viz., carboxin 37.5 % + thiram 37.5 %, tebuconazole 25 % EC, mancozeb 75 %WP, penflufen 13.28 % w/w + trifloxystrobin 13.28 % w/w FS and chlorothalonil 75 % WP were evaluated under in vitro by poisoned food technique against M. phaseolina isolate of sesamum, S. rolfsii of groundnut and M. phaseolina isolate of soybean. Among five fungicides tested, penflufen + trifloxystrobin, chlorothalonil and tebuconazole were found effective at all the concentrations with 100 % inhibition in M. phaseolina of sesamum. Similarly, penflufen + trifloxystrobin fungicide was found highly effective at all the concentrations tested and inhibited 100 % growth of S. rolfsii in groundnut and M. phaseolina of soybean when compared with control. In-vitro compatibility of carboxin 37.5 % + thiram 37.5 %, tebuconazole 25 % EC, mancozeb 75 %WP, penflufen 13.28 % w/w + trifloxystrobin 13.28 % w/w FS and chlorothalonil 75 % WP at 20, 50, 100, 250, 500, 750 and 1000 ppm concentrations were tested with three Trichoderma isolates i.e., T. harzianum (Th4d), T. asperellum (TaDor 7316), T. harzianum (Th) and Bradyrhizobium sp., B. subtilis. Among five fungicides, penflufen + trifloxystrobin was found compatible with T. harzianum (Th4d) at all the concentrations of 20, 50, 100, 250, 500, 750 and 1000 ppm with 90 mm growth was observed. In case of bacterial bioagents, penflufen + trifloxystrobin was found compatible with Bradyrhizobium sp. and recorded OD value of 1.188 at 1000 ppm concentration. Compatibility among three Trichoderma isolates with Bradyrhizobium sp. and B. subtilis indicated that Trichoderma was over grew on Bradyrhizobium sp. and without formation of inhibition. Whereas, the growth of Trichoderma isolates were inhibited by B. subtilis isolate. Characterization of chitosan films were done by Fourier-Transform Infrared Spectroscopy (FTIR) and variation was observed in presence of fungicides and bioagents. Scanning Electron Microscope (SEM) microphotographs showed rough texture of chitosan blend film and undulation were observed in chitosan blended film with T. harzianum (Th4d) and Bradyrhizobium sp. was due to presence of spores of both bioagents. Standardization of multilayer seed coating with combination of biopolymer chitosan, fungicide and bioagents with different concentrations were tested in groundnut cv. K-6 under in vitro by using small pots and kept in growth chamber at 25± 20C with 90 per cent relative humidity. Among different seed treatment combinations tested, the double layer seed coating consisting of chitosan + fungicide + T. harzianum Th4d and chitosan + Bradyrhizobium sp. showed higher germination percentage and seedling vigour index - I and seedling vigour index - II as compared to three layer and single layer seed coating in all the concentrations tested. Combination of effective fungicide (penflufen + trifloxystrobin) with potential biocontrol agents (T. harzianum (Th4d) and (Bradyrhizobium sp.) and seed coat biopolymer chitosan and their combinations were tested against M. phaseolina of sesamum and soybean and S. rolfsii of groundnut by rolled paper towel method. Among different treatments, T5 treatment with double layer seed coating with chitosan 5 ml + fungicide 7.5 ml + Th4d 0.1 g as inner layer and chitosan 5 ml + Bradyrhizobium sp. 0.5 g as outer second layer was significantly enhanced seed germination per cent in sesamum and soybean (86.7 %) and groundnut (100%) as compared with untreated control (without pathogen) recorded germination of 71 %, 70 % and 80 %, respectively. Whereas under inoculated conditions with pathogen, the per cent seed germination was significantly enhanced in sesamum (83.8 %), soybean (83.1 %) and groundnut (94.0 %) as compared to untreated control with 59.0 %, 66.2 % and 64.0 %, respectively. In pot culture studies, the maximum per cent germination in sesamum and groundnut was recorded in T5 treatment with 80.0 % and 94.0 %, respectively. Whereas in soybean, the highest germination per cent was recorded in T5 and T7 treatments with 82.5 % of germination which was on par with each other. Disease incidence was low in T5 treatment with 21.6 %, 11.7 % and 13.1 % in sesamum, groundnut and soybean, respectively. Storability and shelf studies in seed coatings with biopolymer chitosan, fungicide and bioagents and their combinations in sesamum, groundnut and soybean at four months storage period revealed that seed quality parameters viz., seed germination and seed vigour index-I and seed vigour index II were gradually decreased with increase in period of seed storage. Maximum seed germination per cent of 81.4 %, root length (11.9 cm), shoot length (4.7 cm), SVI-I (1351), SVI-II (5.4) and dry weight (0.066 g) in sesamum were recorded in T5 treatment at the end of four months period of seed storage. The data on shelf life (Log CFUs) of T. harzianum (Th4d) and Bradyrhizobium sp. on coated seeds of sesamum recorded more number of colony forming units in T3 treatment (chitosan 5 ml + fungicide 7.5 ml + Th4d 0.1 g) + (chitosan 5 ml + Bradyrhizobium sp. 0.5 g) with 4.92 and 2.94 Log CFU g seed-1 of both T. harzianum (Th4d) and Bradyrhizobium sp., respectively. At the end four months period of seed storage in groundnut, recorded maximum germination per cent of 86.7 %, root length (19.6 cm), shoot length (10.1 cm), SVI-I (2254), SVI-II (49.8) and dry weight (0.33 g) in T5 treatment. The results on shelf life of T. harzianum (Th4d) and Bradyrhizobium sp. on coated seeds of groundnut recorded more number of colony counts in T3 treatment with 2.86 Log CFU g seed-1 and 4.69 Log CFU g seed-1 , respectively. Maximum germination of 78.8 %, root length (24.9 cm), shoot length (15.0 cm), SVI I (3137), SVI-II (41.1) and dry weight (0.52 g) were recorded in T5 treatment. The results on shelf life (Log CFUs) of T. harzianum (Th4d) and Bradyrhizobium sp. on coated seeds of soybean recorded more number of colony counts in T3 treatment with 2.86 Log CFU g seed-1 and 4.79 Log CFU g seed-1 , respectively at the end of four months period of seed storage in soybean. The results on persistence of T. harzianum (Th4d) and Bradyrhizobium sp. in chitosan and fungicide film after application in sterilized red and black soils in absence of plants over 120 days period revealed that maximum colony forming units of T. harzianum (Th4d) were recorded in T3 treatment with 3.54 and 3.50 Log CFUs/g. Whereas in Bradyrhizobium sp. the maximum colony forming units were observed in T3 treatment with 5.34 and 5.27 Log CFUs/ g at 90 days after application (DAA). Root colonization efficacy of T. harzianum (Th4d) and Bradyrhizobium sp. in sesamum, groundnut and soybean crop in red and black soil types were assessed at 15, 30 and 45 DAS. The maximum number of T. harzianum (Th4d) and Bradyrhizobium sp. colony forming units were observed in red soils in sesamum and groundnut crops whereas black soils in soybean crop at 45 DAS. In sesamum and soybean crops, the influence of seed coatings with effective fungicide (penflufen + trifloxystrobin), potential biocontrol agent (T. harzianum (Th4d), Bradyrhizobium sp.) and seed coat biopolymer (chitosan) and their combination under glasshouse were studied. The highest germination per cent, plant height (cm), number of pods per plant, hundred seed weight (g), seed yield per plant (g), number of seeds per pod and seed yield per ha (q) and low disease incidence (%) were recorded in T5 seed treatment. Effect of seed coating on biochemical parameters viz., oil content, protein and fatty acid content in sesamum and soybean were differed. In groundnut, the influence of seed coatings with effective fungicide (penflufen + trifloxystrobin), potential biocontrol agents (T. harzianum (Th4d), Bradyrhizobium sp.) and seed coat biopolymer (chitosan) and their combinations were tested under field conditions. The results indicated that highest germination per cent was recorded in T5 seed treatment with 91.9 %, field emergence index (84.8 %), plant height (42.8 cm), nodules (279.0), number of pods per plant (40.7), hundred seed weight (38.5 g), seed yield per plant (22.40 g), number of seeds per pod (1.84), seed yield per ha (21.1 q), haulm yield (4760.0 kg), B:C ratio (1:2.41) and low disease incidence (5.2 %) and AUDPC (102.8). Effect of seed coatings on biochemical parameters viz., oil content, protein and fatty acid content in groundnut were significantly different. Among seed treatments the higher oil content, protein content were recorded in T5 treatment with 52.85 % and 23.6 %.
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