Variability and characterization of host response to Helminthosporium sativum, incitant of spot blotch of wheat
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Authors
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MOHD. AKRAM and AMERIKA SINGH*
Centre of Advanced Studies in Plant Pathology, College of Agriculture. G.B. Pant University of Agriculture and
Technology, Pantnagar 263 145
Keywords:
Monoconidial, Helminthosporium sativum, spot blotch, virulence, detached leaf cultureAbstract
Nine monoconidial isolates of Helminthosporium sativum were tested for their variability. The maximum linear growth (96.5 mm) was recorded in isolate PHSI followed by PHS5 (89.6), PHS4 (88.7), PHS7 (53.9), PHS2 (48.6), KHS9 (20.9), PHS6 (16.4), PHS8 (15.9) and PHS3 (14.4) grown on PDA for 10 days. The shape of the colony of different isolates also varied from circular with aerial mycelium to circular and irregular with moderate aerial mycelium and circular with abundant aerial mycelium. Average conidial length was maximum in isolate PHS5 (81.3 u), followed by PHS2, PHS3, PHSI, PHS8, PHS4, PHS6, KHS9 and PHS7 (56.4 u), The maximum average width of conidia was associated with PHS7 (21.4 u) followed by PHSI (20.2), PHS3 (18.9), PHS2 (18), KHS9 (17.1), PHS5 (17.1), PHS4 (16.8), PHS8 (15.4) and PHS6 (15.1 u), Conidial germination was highest in PHS3 (96.2) while lowest in PHSI (64.4). All the isolates showed the bipolar germination pattern. Pathogenic variability studied by the inoculations of 9 isolates of H. sativum on 24 wheat genotypes using "detached leaf culture" test, revealed significant differences in incubation period (IP), lesion length (LL) and sporulation, Among 9 isolates the maximum IP (3.4 days), minimum LL (2.4 mm) and moderate sporulation (12.2 spore/rum" of disease leaf area) were associated with isolate PHSt. However, IP (2.2), the maximum LL (lt.5 mm) and highest sporulation (17.3) was observed in PHS3. The isolate PHS3 was found highly virulent and PHSI was least virulent on 24 wheat genotypes. The other isolates varied between the highly virulent and the least virulent isolate for their virulence. Based on incubation period, lesion length and sporulation 24 wheat genotypes were characterized by inoculating with the spores suspension of 9 isolates on detached leaf in Petridishes. Only 5 genotypes namely VL738, BOW'S', HW2023, PATO (R) TZ PPSN 64 NAR and HD 2206 x HORK S' were categorized as resistant due to comparatively higher incubation period and reduced lesion length and sporulation.
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