Field Experiment to Evaluate the Response of Different Varieties of Wheat against Spot Blotch (Bipolaris sorokiniana) at Bhairahawa, Nepal

Spot blotch incited by Bipolaris sorokiniana is one of the most important foliar disease limiting wheat production in Nepal. A field experiment was conducted from 13 December 2017 to 12 April 2018 in the research field of National Wheat Research Program (NWRP), Padsari-1 Rupandehi, Nepal to evaluate response of 12 wheat varieties against spot blotch caused by Bipolaris sorokiniana. The experiment was laid out in Randomized complete block design (RCBD) with 12 treatments and three replications. Individual treatment plot was 2 m2 and total research field area was 152.5 m2. Disease scoring was done by double digit scoring starting from heading stage in which 4 scorings were done at 7 days interval following Zadok scale. Different traits taken for scoring were lesion size, lesion mimic, leaf tip necrosis, spike length, peduncle extrusion at different growth stages. Days to heading, days to maturity, 50 spike yield, and plot yield and test weight were recorded. The mean AUDPC was calculated and analyzed. Varieties differed significantly in mean AUDPC values. On the basis of mean AUDPC value, the varieties were categorized under four categories i.e., resistant, moderately resistant, susceptible and highly susceptible. Furthermore, the correlation of 12 varieties with AUDPC and various traits was analyzed. There was negative correlation between AUDPC and yield i.e. -0.62050. Among 12 varieties, RR-21 showed highest level of disease increment with AUDPC value 974.897 and found to be the most susceptible while least was observed in Danphe with AUDPC value 383.7 and found to be resistant. Badhganga with the AUDPC value of 396.517 was also found to be resistant to spot blotch. No varieties were found highly resistant. Similarly, Swargadwari, Gautam, NL 971, Tilottama, Aditya, Dhaulagiri and Vijaya appeared moderately resistant to spot blotch of wheat. Bhrikuti and WK 1204 were susceptible to spot blotch. Wheat grain yield varied among the varieties. Maximum yield was recorded in Danphe (5.7 t/ha) and minimum yield was recorded in RR-21 (3.5 t/ha). Similarly, highest value of test weight was recorded in Danphe (53.43 gm) and the lowest value was in Bhrikuti (34.53 gm). So, Danphe showing better performance at Bhairahawa can be taken as the source of tolerance in upcoming experiments and RR-21 can be used as susceptible check and these varieties can be suggested to incorporate into breeding program.