Blast Disease Behavior in Some Boro Rice Varieties of Bangladesh and Development of Induced Resistance System Against Blast Disease through Selected Novel Chemicals

Chronologically two experiments have been conducted during the period from October 2018 to May 2019 and July 2019 to June 2020 at Sher-e-Bangla Agricultural University, Bangladesh for the identification of one of the best rice varieties and chemicals against blast disease. In a field experiment, eight boro rice varieties were evaluated (five inbreed varieties, two high-yielding varieties, and one wild variety) to observe varietal performances against blast disease. A pot experiment was also performed to study the resistance behavior of the tested varieties in an in-vitro condition by applying silica powder, K2SiO3, salicylic acid, cattle urine (both normal and pregnant cows), and PPN. Field study revealed that the wild variety was highly resistant (incidence and severity 0%) whereas BRRI dhan58 was susceptible (incidence 21.48% and severity 60.48%). Wild variety was also characterized by the highest tiller number (20.73), panicle length (24.90 cm), fresh grain weight (62.30 g), and dry grain weight (51.70 g). The highest number of panicles was recorded in BRRI dhan28 (18.40) which was statistically like the wild variety (17.50). Though wild variety performed best in another parameter it gave the lowest amount of yield (4.77 kg/plot). In morphological studies of pathogen, pyriform-shaped conidia were found in a sympodial fashion on conidiophores whose size varied from 22.13 to 28.47 μm × 9.13 to 11.72 μm (average 25.30×10.43 μm). The second experiment revealed that all selected novel chemicals showed some extent of resistance but the cattle urine, PPN, and K2SiO3 showed a promising effect. Koch’s postulate test for the experiment confirmed the causal organism of blast disease is Magnaporthe oryzaein artificially inoculated plants.