Studies on Spot Blotch of Tetraploid Wheat Caused by Bipolaris sorokiniana Sacc Shoem

Abstract

Spot blotch is an important disease in warm and humid regions of India and newlineother South Asian countries due to its widespread prevalence and increasing severity. newlineCultural characters of 24 isolates of Bipolaris sorokiniana (Sacc.) Shoem. representing newlinesix agro-ecological zones of India cultured on PDA revealed five different colony newlinecolours. The frequency of white (29.2 %) was maximum, while lowest (4.2 %) was newlineblack type. The maximum and minimum colony diameter of 89.5 and 39.3 mm recorded newlinein Varanasi (V-2) and Powerkheda isolate respectively. The size of the conidia varied newlinefrom 15.3-126.0 and#956;m and#61620; 6.3-36.1 and#956;m with 1-6 septa, colour differed from dark brown to newlineolivaceous, ovate to elliptical in shape and germination pattern was by unipolar or newlinebipolar. Variability of isolates through virulence study and SSR markers had showed newlinehigh distinction. Similarity co-efficients were ranged from 0.64 to 0.98 representing less newlinethan 64 per cent genetic variability among isolates. newlineThirty one genotypes out of 121 were consistent in their disease response newlineshowing resistant to moderately resistance during both the years (2013-15). Among 31 newlinegenotypes, 45IDYN27, 45IDYN36, PDW291 and other 16 performed superior over best newlinechecks with regards to AUDPC and yield. Genotypes showing lowest AUDPC newlineexhibited higher SPAD and NDVI value. The two markers, Xgwm 312-2A and Xgwm newline114- 3B contributed to phenotypic variation (22.3 %) for spot blotch resistance. newlineThe stomatal frequency was higher in susceptible genotypes. The resistant newlinegenotypes showed higher activity of peroxidase and lower polyphenol oxidase activity newlinethan susceptible ones. The higher reducing sugar and total phenol content was noticed newlinein resistant genotypes. Quality parameters viz., GPC, SDV and YP were more in newlinediseased condition rather than in protected situation, while exactly opposite trend was newlinenoticed with respect to starch and gluten content. The fungicide, Pyraclostrobin 13.3 % newline+ Epoxiconazole 5 % (0.1 %) proved to be better alternative to triazoles. newline