Thumbnail Image

Thesis

Browse

20151
Reset filters
Subject: Plant Pathology × Author: Heflish, Ahmed Ibrahim Abdelbary Ibrahim × End date: 2018 × Start date: 2010 × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    ThesisItemRestricted
    Management of Sheath Blight of Rice Using Native Strains of Biocontrol Agents and Cloning of Antifungal Gene
    (PAU, 2015) Heflish, Ahmed Ibrahim Abdelbary Ibrahim; Singh, Narinder
    Sheath blight of rice caused by Rhizoctonia spp. is one of the most important rice diseases worldwide including India. Thirty isolates of Rhizoctonia were isolated from infected rice plants. Genetic diversity of the pathogen was determined by using 11 simple sequence repeats (SSR) molecular markers. The isolates were identified with specific primers at species level. Twenty nine isolates were identified as Rhizoctonia solani while one isolate was found to be as Rhizoctonia oryzae. Native biocontrol agents were isolated from rice rhizospheric soils. Twenty seven isolates of Trichoderma and seventeen isolates of Pseudomonas fluorescens were isolated and screened in vitro against R. solani and R. oryzae causing sheath blight of rice through dual culture technique, effect of volatile and non volatile compounds. Among all tested isolates under in vitro conditions Trichoderma T19 showed the maximum inhibition for R. solani and R. oryzae (65.80 and 74.44 % respectively). Volatile metabolites from Trichoderma T19 also caused maximum inhibition of R. solani (56.91 %) and R. oryzae (91.23%). In case of non-volatile compounds inhibition of the pathogens increased with the increase of culture filtrate concentration from 10 to 50 per cent and T19 with 50 per cent concentration showed the highest percentage of inhibition against R. solani (95.80 %) and R. oryzae (90.74%). P. fluorescens (Pf14) reduced the mycelial growth of R. solani by 60.49 per cent (inhibition zone 9.67 mm) and of R. oryzae by 74.94 per cent with 12.78 mm inhibition zone. Volatile compounds from P. fluorescens (Pf14) showed inhibition of mycelial growth of R. solani and R. oryzae (76.79 and 66.79 % respectively), while in case of non volatile the inhibition by Pf14 using 50 per cent concentration of culture filtrate against R. solani and R. oryzae was 82.47 and 93.46 per cent respectively. Biochemical tests for estimation of cell wall degrading enzymes showed the ability of T19 and Pf14 to produce high level of chitinase (22.1 and 17.5 unit/ml respectively) and β-1,3-glucanase (1.92 and 1.76 unit/ml respectively). Pf14 also presented high activity of siderophore production (20.5 mm halo zone). Fingerprinting of the most effective seven isolates of Trichoderma and of P. fluorescens using SSR marker showed variation between the isolates at molecular level. Efficacy of talc based bioformulations of Trichoderma T19 and P. fluorescens Pf14 applied individually as well as in combination under greenhouse and field conditions was seen against sheath blight of rice. Trichoderma T19 when applied as seed + soil + foliar spray showed the maximum reduction of disease incidence (67.49 %) and disease severity (82.92 %). It also acted as plant growth promoter and increased the number of tillers/hill (12.20), plant height (72.71 cm) and finally the yield of the crop (71.3 q/ha). Molecular identification of Trichoderma T19 using ITS1 and ITS4 universal primers showed 100 per cent similarity with T. asperellum. Cloning of endochitinase42 gene from T. asperellum T19 (potent strain) and Trichoderma T5 (mild strain) showed no difference in the gene sequence between the two Trichoderma isolates, while the difference in the antagonistic activity may be was due to the difference in the promoter region of the gene. Study of shelf life of bioformulations revealed that antagonists T. asperellum T19 and P. fluorescens Pf14 can remain potent for 6 months when stored at room temperature, while at low temperature storage (4oC) these can remain potent up to one year. For mass multiplication sugarcane pressmud and rice leaves supported rapid, maximum growth and sporulation of T. asperellum T19.