Evaluation of aromatic rice genotypes against blast and its biointensive management under rainfed condition
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Date
2021
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AAU, Jorhat
Abstract
Rice blast caused by Pyricularia oryzae, has gained the status of major disease of rice, and it infects almost all the rice growing areas throughout the world. And it is predicted as a major disease in India and in the recent times, the disease has been observed to show an increasing trend in rice fields of Assam, and it causes yield losses varies from 1 to 100%. In the present study evaluation of aromatic rice varieties for resistance and susceptibility against blast was done and studied the effect of management strategies under field condition in Assam. Among the thirty varieties tested with artificial inoculation, none of the varieties shows highly resistance (ie., completely free from the disease) and highly susceptibility whereas, fourteen varieties showed resistant reaction, while five varieties showed moderately resistant, eight varieties showed moderately susceptibility and three varieties shows susceptibility reaction. Addition to that total genomic DNA was extracted from the blast culture were subjected to PCR assay using ITS 1 and ITS 4 primers. BLAST analysis of the samples showed the similarity percentage of 99-98% with the other isolates. Phylogenetic analysis was done with the help of Mega X software, it was found that the samples were closely related with Pyricularia oryzae Meghalaya isolate JX469384. Biochemical analysis was evaluated in both healthy and infected leaves of resistant and susceptible aromatic rice genotypes. The resistant entries possess a higher amount of phenols and lower amount of total proteins and total soluble sugars as compared to the susceptible one. After the infection the phenols content was increased in infected leaf as compared to the healthy one in all the entries whereas the total proteins and total soluble sugars were decreased in infected leaf as compared to the healthy one in all the entries. Among the different date of sowing, highest incidence of blast disease (30.35% and 32.81%) were recorded in crop showed on 13th July of 2019 and 2020 respectively. Whereas lowest incidence of blast disease (6.72% and 7.14%) were recorded in crop showed on 15th June of 2019 and 2020 respectively. Correlation studies on the influence of weather parameters on blast disease development revealed that maximum and minimum temperature, evening relative humidity, rainfall and rainy day were negatively correlated with disease development whereas, relative humidity morning and bright sun shine hours shows positive correlation with the disease development. Multiple regression analysis indicates that, by using max temperature, relative humidity evening and bright sun shine hours could predict the blast disease incidence up to 98% in future in that area. In vitro
ABSTRACT
evaluation of Botanical viz., Mustard oil cake (MOC) and compost materials viz., Farm yard Manure (FYM) and Vermi compost (VC) against blast revealed that MOC at 0.2% concentration showed highest inhibition of pathogen over control ie., 46.27% after 7th day followed by MOC at 0.1% shows 39.02% and VC at 0.2% concentration shows 36.67 % inhibition over control respectively. Among the three different bio agents ie., Trichoderma harzianum, T. viride and T. koningii, all of them showed significantly inhibition of the pathogen in vitro but higher percentage inhibition over control showed by T. harzianum, ie., 97.41%. In vivo condition, Seed treatment with Trichoderma harzianum amended with MOC (20%) + cow urine (5%) shows less percent disease incidence ie., 4.30% and 5.73% after 15 and 30 days after sowing in the nursery respectively. Whereas, in field condition, Trichoderma harzianum amended Extract of MOC at 20% concentration showed less percent disease incidence ie., 5.64 %, 9.85 % and 24.31 % and less percent disease severity ie., 3.74%, 7.96% and 9.67% after 45, 60, 75 days after showing respectively. Followed by Trichoderma harzianum amended Extract of MOC at 10% and Trichoderma harzianum amended Extract of VC at 20% concentration respectively.