STUDY ON ISOLATION OF Pyricularia oryzae CAUSED BLAST DISEASE OF RICE AND ITS MANAGEMENT BY USING POTASSIUM SILICATE

Abstract

Blast of rice caused by Pyricularia oryzae fungus which played vital roles in reducing yield of rice in Bangladesh from last two years. The prevalence of rice blast was remarkable in greater Dinajpur district including Thakurgaon and Rangpur. The blast samples were collected from the farmers field of selected area of Dinajpur, Thakurgaon and Rangpur districts which were reported to have blast infection by the regional agricultural extension centers during Boro season 20172018.

Blast infected leaf, node and neck samples were collected for the in-vitro study. The in-vitro study was carried out at the Molecular biology and Plant virology laboratory, Dept. of Plant Pathology, Sher-e-Bangla Agricultural University, Dhaka. The main objectives of this experiment was to isolate the blast pathogen and to identify the best culture media for pathogenic growth and sporulation of Pyricularia oryzae, to study its morphological and pathogenic characteristics. From the study, it was revealed that Carrot Rice straw Dextrose Agar (CRDA) was found for the best mycelial growth and sporulation of pathogen. The morphological study of the derived three isolates from the field samples, it was evident that the disease was caused by Pyricularia oryzae, as the isolates produced hyaline, pyriform three celled conidia (average 16.45 × 7.46 µm) from leaf sample and CRDA media, respectively. They were able to reestablish

the disease in in-vitro pathogenicity test. In-vivo study was also carried out by using Blast susceptible rice variety BRRI dhan 28 to assess the efficacy of Potassium Silicate (K 2 SiO 3 ) in different doses (0, 1, 2, 4, 8, or 10 g L Si), number of sprayings at pH 5.5. Silicon (Si) is known as a “beneficial element” for plants. The direct and indirect benefits of the element for crops (especially grasses) are related to resistance to diseases, pests a drought. From this study it was found that spraying of K 2 SiO 3 ii

at 4 g L -1 significantly reduce the blast disease incidence and severity.