Stripe rust, caused by Puccinia striiformis f. sp. hordei, is economically an important disease of barley (Hordeum vulgare L.) and causes a significant yield loss in major barley-growing countries, including Nepal, where the growing season is relatively cool and wet. A worldwide collection of 340 barley genotypes was evaluated over three years for stripe rust resistance at the research field of the Agricultural Research Station, Dailekh, western Nepal. In addition, resistant and susceptible checks for stripe rust, 'Bonus' and 'Solu Uwa', were repeated in an augmented block design. When comparing disease severity over three years, significant variation among barley genotypes was observed in disease resistance. Among 342 genotypes, 99 (29%), 120 (35%), and 130 (38%) were resistant to stripe rust in 2016, 2017, and 2018, respectively. A total of 49 genotypes were found to be resistant in all three years. These identified resistant barley genotypes can serve as a source of stripe rust resistance in barley breeding programs in Nepal and other stripe rust-prone regions in South Asia and similar environments.
B. Pokharel, L. Aryal, S. Gurung et al.· Nepal Agriculture Research J...· 0 citations
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
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