Development of integrated disease management modules for major fungal disease of Basmati rice and fungicide residue analysis

Abstract

Rice (Oryza sativa L.) is the world’s most important crop and considered as a staple food for more than half of the world’s population. Rice is affected by many fungal, bacterial, viral and nematode diseases. Among them, blast, brown spot and sheath blight disease are the most frequent and ferocious fungal diseases were observed in western U.P. Therefore, the present investigation was carried out to development an integrated management module against major fungal diseases of Basmati rice with the aim to ensure the food safety. For this purpose different fungicides, leaf extract and bio-agents were tested against M. grisea, B. oryzae and R. solani in vitro. The results revealed that, in case of fungicides maximum 87.41% mycelial growth inhibition of M. grisea was recorded in tricyclazole at 100 ppm concentration followed by 76.30% in propiconazole at 50 ppm. While, maximum mycelial growth inhibition of B. oryzae 57.04% was recorded in hexaconazole at 100 ppm followed by 51.10% in carbendazim at 50 ppm concentration. However, the maximum 68.15% mycelial growth inhibition of R. solani was recorded in propiconazole 100 ppm. In case of leaf extract, maximum 66.56%, 68.31% and 63.10% mycelium growth inhibition of M. grisea, B. oryzae and R. solani respectively was recorded in Bael leaf extract at 10% concentration. In case of Bio-agents, Pseudomonas fluorescens was found most effective compared to Trichoderma harzianum which inhibited 66.56% mycelial growth of M. grisea, 68.31% of B. oryzae and 63.10% of R. solani. The trial was conducted subsequently in year 2018-19 and 2019-20 for development of integrated disease management module in Basmati rice in field condition. 18 modules were evaluated and the result evinced that the maximum plant height 116.33 cm and 117.00 cm was recorded in module M2 and numbers of tillers 18.33 and 15.67 was recorded in module M1 during both consecutive years. The lowest disease intensity AUDPC of blast was recorded 382.20 and 348.90, brown spot 473.35 and 406.70, sheath blight 171.45 and 197.25 in module M6, M9 and M17 during 2018-19 and 2019-20 respectively. The maximum test weight was 29.91 g and 29.90 g while grain yield 43.69 q/ha and 40.06 q/ha was recorded in module M6 during both consecutive years. The investigations concerning the residues of fungicides in Basmati rice will help in generating information regarding the level of residue present in grains whether it is safe for consumption as per the guidelines of Codex Alimentarius, European Union Directives, Food Safety and Standards Authority of India. The fungicide residue analysis was done by using HPLC system. The minimum residue of carbendazim, tricyclazole, propiconazole, hexaconazole, isoprothiolane was 0.04 ppm, 0.97 ppm, 0.46 ppm, 0.05 ppm, 0.45 ppm and 0.03 ppm, 0.07 ppm, 0.31 ppm, 0.06 ppm, 0.43 ppm found in module M3, M7, M5, M4 and M7 respectively during both consecutive years. For confirmation of cultural and morphological identification of M. grisea, B. oryzae and R. solani, molecular characterization has been done by PCR amplification of ITS region of rDNA. PCR amplification of ITS region of genomic DNAs extracted from pathogens was done using the universal ITS1 and ITS4 primers. The ITS region of rDNAs of pathogens were amplifying PCR products of approximately ~600bp as estimated by agarose gel electrophoresis. The PCR-amplified ITS region (ITS1, 5.8S rDNA, and ITS4) of pathogens were sequenced. The sequence obtained were subjected to BLAST search for identify and confirmation, and subsequently submitted to National Centre for Biotechnology Information (NCBI) Genebank. The accession number of sequence of ITS region of pathogens is MW287325.1, MW309505.1 and MW009705.1 of Magnaporthe grisea, Bipolaris oryzae and Rhizoctonia solani respectively.