Biological control of the fungus Drechslera in rice and genetic engineering for host resistance gene
Shimaa Ahmed Gouda;
Abstract
Drechslera species are among most common fungal pathogens of rice, causing brown spot disease. Infection by Drechslera species attacks the plant at any growth stage and it appears on the foliage as scattered brown spot that coalesces and result in withering and yellowing of the leaves. This fungal disease reduce yield by 16% to 43%.
In the present study, rice rhizosphere mould and yeast fungi were isolated from El-Dakahlia and El-Qaliubiya governorates. Thirty five fungal isolates belonging to 12 genera of filamentous (mould) fungi and 4 genera of yeast were isolated. Results indicated that in case of mould fungi Fusarium and Aspergillus were the most dominant isolates (520 and 410 CFU, respectively) while Monodictys and Phaeodactylium represented the lowest ones (10 CFU for each). Concerning yeast fungi, Stephomoascus and Candida gave the highest CFU count (90 and 60 CFU respectively).
Isolation of pathogens from infected rice leaves and grains from El-Dakahlia and El-Qaliubiya governorates indicated that Drechslera spicifera gave the highest frequency percentages (56 % and 53.33 % respectively) while Drechslera rostrata gave 33 % and 26.66 % for both governorates respectively.
Out of 35 rhizosphere isolates, fourteen isolates showed antagonistic activity against the pathogenic fungi were tested for control two Drechslera species isolated from infected leaves and grains of rice plants of the same governorates. Penicillium decumbens has the highest antagonistic activity against Drechslera spicifera (83.9 %) and Aspergillus terrus against Drechslera rostrata (82.3%).
Drechslera spicifera was tested for pathogenicity under different treatment as salicylic acid and hydrogen peroxide spraying with Drechslera spicifera only and with Drechslera spicifera and Penicillium decumbens. Results of the pathogenicity tests indicated that spraying of salicylic acid decrease percentages of disease incidence (DI) from 77.3 to 64% during pathogen treatment only and from 64 to 55.3% during pathogen with antagonist treatment compared to control, results also indicated that there was decreasing in disease severity index (DSI) was from 65 to 25% and from 35 to10 % in both treatment pathogen and pathogen with antagonist respectively.
In contrast to salicylic acid, hydrogen peroxide spraying increased percentages of disease incidence (DI) from 77.3 to 81% with treatment of pathogen and from 64 to 79.6% in treatment of pathogen with antagonist compared to control while there was a decreasing in disease severity index (DSI) from 65 to 45% and from 35 to 15% with the treatment with pathogen only and pathogen with the antagonist respectively.
Salicylic acid spraying had an effect in up regulation of β -1,3-glucanase 1 (Gns1) and β-1,3-glucanase 5 (Gns5) 36 fold and 15.5 fold respectively after 72 hour from treatment while hydrogen peroxide spraying had an effect in down regulation of β -1,3-glucanase 1 (Gns1) and β-1,3-glucanase 5 (Gns5) than in salicylic acid spraying 6.2 fold and 0.8 fold after 72 hour from treatment respectively.
Key words: Rice plant, Drechslera spp., brown spot, salicylic acid, hydrogen peroxide, β-1,3-glucanase, up regulation and down regulation of PR genes
In the present study, rice rhizosphere mould and yeast fungi were isolated from El-Dakahlia and El-Qaliubiya governorates. Thirty five fungal isolates belonging to 12 genera of filamentous (mould) fungi and 4 genera of yeast were isolated. Results indicated that in case of mould fungi Fusarium and Aspergillus were the most dominant isolates (520 and 410 CFU, respectively) while Monodictys and Phaeodactylium represented the lowest ones (10 CFU for each). Concerning yeast fungi, Stephomoascus and Candida gave the highest CFU count (90 and 60 CFU respectively).
Isolation of pathogens from infected rice leaves and grains from El-Dakahlia and El-Qaliubiya governorates indicated that Drechslera spicifera gave the highest frequency percentages (56 % and 53.33 % respectively) while Drechslera rostrata gave 33 % and 26.66 % for both governorates respectively.
Out of 35 rhizosphere isolates, fourteen isolates showed antagonistic activity against the pathogenic fungi were tested for control two Drechslera species isolated from infected leaves and grains of rice plants of the same governorates. Penicillium decumbens has the highest antagonistic activity against Drechslera spicifera (83.9 %) and Aspergillus terrus against Drechslera rostrata (82.3%).
Drechslera spicifera was tested for pathogenicity under different treatment as salicylic acid and hydrogen peroxide spraying with Drechslera spicifera only and with Drechslera spicifera and Penicillium decumbens. Results of the pathogenicity tests indicated that spraying of salicylic acid decrease percentages of disease incidence (DI) from 77.3 to 64% during pathogen treatment only and from 64 to 55.3% during pathogen with antagonist treatment compared to control, results also indicated that there was decreasing in disease severity index (DSI) was from 65 to 25% and from 35 to10 % in both treatment pathogen and pathogen with antagonist respectively.
In contrast to salicylic acid, hydrogen peroxide spraying increased percentages of disease incidence (DI) from 77.3 to 81% with treatment of pathogen and from 64 to 79.6% in treatment of pathogen with antagonist compared to control while there was a decreasing in disease severity index (DSI) from 65 to 45% and from 35 to 15% with the treatment with pathogen only and pathogen with the antagonist respectively.
Salicylic acid spraying had an effect in up regulation of β -1,3-glucanase 1 (Gns1) and β-1,3-glucanase 5 (Gns5) 36 fold and 15.5 fold respectively after 72 hour from treatment while hydrogen peroxide spraying had an effect in down regulation of β -1,3-glucanase 1 (Gns1) and β-1,3-glucanase 5 (Gns5) than in salicylic acid spraying 6.2 fold and 0.8 fold after 72 hour from treatment respectively.
Key words: Rice plant, Drechslera spp., brown spot, salicylic acid, hydrogen peroxide, β-1,3-glucanase, up regulation and down regulation of PR genes
Other data
| Title | Biological control of the fungus Drechslera in rice and genetic engineering for host resistance gene | Other Titles | المقاومة الحيوية لفطر دركسلرا فى الأرز والهندسة الوراثية لجين المقاومة فى العائل | Authors | Shimaa Ahmed Gouda | Issue Date | 2017 |
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