Status of Grain Discoloration Disease in Paddy Growing Ecosystems of Karnataka, India

Among different diseases that affect rice crops, grain discoloration disease (GD) is one of the emerging diseases in all rice cultivating areas around the world. Though the disease has recently emerged, it is catching the attention of the scientific and farming community due to its qualitative and quantitative loss. Since the disease is a highly complex disease caused by multiple pathogens, thus its management is challenging. As the disease is still in the emerging stage, its incidence and severity in different rice ecosystems are still not available. Assessment of disease incidence, severity, and yield loss is very crucial for disease management. We carried out an intensive roving survey to assess the incidence of GD across Karnataka. An intensive roving survey was conducted across 130 villages, covering 192 paddy-growing locations and 14 districts of six major rice-growing ecosystems in Karnataka state, India. The highest disease incidence (98) was recorded in Sutturu village of Nanjanagud Taluk of Mysuru District of Kaveri ecosystem. In contrast, the lowest disease incidence (3) was recorded in the Kadakal village of Shahpur taluk of Yadgir District of Upper Krisha Project (UKP) of Karnataka state. Among six distinct ecosystems, the highest mean disease incidence was recorded in the coastal ecosystem (85.11), followed by the Kaveri ecosystem (74.34), which is considered a hot spot for GD incidence. Upper Krishna Project (UKP) and Thunga Bhadra Project (TBP) are considered less risky regions for GD. Analyzing hotspots for GD in Karnataka aids in formulating ecosystems and ecologically specific disease management practices. This study also helps to identify rice cultivars distributed and the disease incidence observed. The highest disease incidence was recorded in bold-seeded cultivars such as Jyothi, KCP-1, Sahyadri Panchamukhi, MO-4, MTU-1001, Kempu Jyothi, Kaje 25-9, Kaje Jaya, Godavari, IR-64, Meenakshi, Sahyadri Kempumukthi, Abhilash, Guttasale, Gandhasale, Uma with more than 90 disease incidence. Whereas the lowest disease incidence was recorded in small and slender seeded cultivars such as Cross Sona, Sona and Gandu Sona, RNR-15048, Nellore Sona, MTU-1010, BPT-5204 recording < 10 disease incidence. This is the first intensive study to document the status of GD in the distinct rice ecosystems of Karnataka.