Spot blotch caused by fungal pathogen Bipolaris sorokiniana (Sacc.) Shoemaker is an important fungal disease in warm and humid wheat growing condition. Study on pathogenic variability of B. sorokinianana isolates is limited in Nepal. Information based on host × pathogen interaction is a useful tool to devise the disease management strategy. Therefore, aggressiveness of total 36 single spore isolates of B. sorokiniana (27 isolates from terai, 7 isolates from mid hill and 2 isolates from high hill) of Nepal were evaluated on 14 days old seedling of RR-21 (susceptible check), Guatam (moderate resistant) and Chirya 3 (resistant check) under polyhouse condition. Results revealed highly significant isolate-by-variety interaction (P<0.001) for all the disease development traits, suggesting substantial variability in the pathogenicity of the isolates. Moreover, days to disease appearance, number of lesions per leaf and disease severity was highly correlated to Area Under Disease Progress Curve (AUDPC), illustrating those traits as an important indicator of disease development and pathogen aggressiveness. RR-21 exhibited susceptible to overall isolates response followed by Gautam and Chirya 3. On the basis of AUDPC value, top ten aggressive isolates were identified (N-BS24, N-BS7, N-BS28, N-BS36, N-BS27, N-BS37, N-BS15, N-BS38, N-BS19 and N-BS16). Among them, N-BS24 and N-BS28 were able to show high disease against resistant check Chirya 3, so aggressiveness of these two isolates can be further validated through adult plant screening and genetic study and utilize it for resistant breeding program in Nepal.
L. Aryal, S. Shrestha, H. Manandhar et al.· Nepal Agriculture Research J...· 0 citations
Brown spot, caused by Bipolaris oryzae, is an important constraint to rice production under favourable disease conditions. This study evaluated the field efficacy of eight fungicides against brown spot and assessed disease severity among rice genotypes cultivated in farmers’ fields. A randomised complete block design with three replications was established at Rampur, Chitwan, using the susceptible cultivar Sankharika. Eight fungicide treatments and an untreated control were compared following three foliar applications at seven-day intervals. Disease severity and the area under the disease progress curve (AUDPC) were determined, and grain yield was correlated with AUDPC. A roving survey was also conducted at 21 locations in Chitwan and Nawalparasi districts. All fungicide treatments reduced final disease severity relative to the untreated control. Metalaxyl 8% + mancozeb 64% WP recorded the lowest mean AUDPC (436.85), followed by carbendazim (470.50) and hexaconazole (482.20). Hexaconazole recorded the lowest final disease severity (28.90%), whereas the untreated control recorded 45.20%. The association between grain yield and AUDPC was weak and not statistically significant (r = −0.031). The survey identified six genotypes, with maximum severity of 78% in Samba Mansuli and Sabitri and minimum severity of 26% in Kalo Basmati. These findings indicate differential fungicide performance and genotype responses under the evaluated field conditions and support further multilocation and multiseason validation.
Rajan Lamsal, Surakshya Ghimire, Gautam Thapa et al.· Asian Journal of Biology· 0 citations
We use cookies to run the site and, with your consent, for analytics and to show ads.
See our Cookie Policy.
