Evaluation of aromatic rice genotypes against blast and its biointensive management under rainfed condition

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...