Potential of Fungicidal Sprays On an Emerging Bakanae Disease Management in Basmati Rice and Seed Health Assessment Through Real Time PCR

Abstract

Bakanae disease is widespread in rice cultivation areas globally, presenting a significant challenge to basmati rice farming in India. Chemical seed and seedling treatment methods are commonly employed for managing bakanae disease, however, very less information is available on spray treatments. Our study aimed to assess the effectiveness of various fungicidal spray in field conditions for managing bakanae disease and their impact on basmati rice yield and related characteristics. Seven fungicides, along with a pathogen-inoculated control, were evaluated as foliar treatments during the Kharif season of the year 2021 and 2022. A combined analysis of data from two years showed that T₁ (Carbendazim 50% WP) had the lowest disease incidence at 44.68%, demonstrating a significantly high percentage disease inhibition of 44.08%. Following closely was T₄ (Tebuconazole 50% + Trifloxystrobin 25% WG) with a disease incidence of 50.00% and a corresponding percentage disease inhibition of 37.37%, while, maximum disease incidence of 79.84% was recorded in control treatment (T₈) followed by T₅ (Copper oxychloride 50% WP). Further, significantly high grain yield was obtained in Carbendazim 50% WP treatments (219.37 g/m²) followed by Tebuconazole 50% + Trifloxystrobin 25% WG (212.00 g/m²). Additionally, a quantitative polymerase chain reaction assay on harvested grains with Fusarium fujikuroi specific marker revealed least pathogen colonization in harvested seeds of Carbendazim 50% WP treatment (T₁), with a Ct value of 33.763 (copy no. 4.88E + 10), followed by Tebuconazole 50% + Trifloxystrobin 25% WG (Ct value 33.752, copy no. 4.94E + 10), conversely, Copper oxychloride (T₅) demonstrated the least effectiveness with highest pathogen load (copy no. 9.44E + 13). Based on our findings, we recommend the use of Carbendazim 50% WP or Tebuconazole 50% + Trifloxystrobin 25% WG for the management of bakanae disease as foliar spray (2 sprays) treatments (First spray after 15 days of transplanting; second spray at maximum tillering stage (around 25–30 days post I^st spray)) showing low AUDPC and high yield compared to inoculated control. Further, fungicidal spray reduced the infected seed percentage and carried less inoculum in next season. Therefore, these investigations will be valuable for management of bakanae disease after symptom appearance in field conditions. Findings could be further helpful in developing and validating an integrated approach to manage bakanae disease effectively in near future.