| Wheat is one of the most important staple crops.Tilletia controversa Kühn is the causal agent of wheat dwarf bunt.Dwarf bunt of wheat,with soil-borne teliospores and infection through tiller initials,and infection occurs through the coleoptile shortly after seed germination and goes to reproductive parts of the crop.Yield losses due to T.controversa have reached 70-80% in cold wheat growing areas of the world.Controlling of dwarf bunt by using pesticides is harmful for humans and create the pollution in the environment.Therefore,there is a need to develop ecofriendly approach to control dwarf bunt of wheat.The results of first experiments showed that resistant wheat cultivars displayed significantly higher expression of pathogenesis-related genes than a susceptible cultivar at different days post inoculation with T.controversa.Similarly,expression was also high in the resistant cultivars after exogenous application of phytohormones,including salicylic acid.The expression of pathogenesisrelated genes,especially chitinase 4,was high in the resistant cultivar,while LPT-1 was down regulated after T.controversa infection.Callose deposition was greater in the resistant cultivar than in the susceptible cultivar at 10 days post inoculation.The anthers and ovaries of the susceptible cultivar were infected by T.controversa at 7 and 15 days post inoculation.There were no fungal hyphae in anther and ovary cells in the resistant cultivar until 10 and 23 days post inoculation,respectively.Moreover,anther length and width were negatively influenced by T.controversa at 16 days post inoculation.The plant height was also affected by fungal infection.Similarly,the results of second experiment showed that defence genes PR-10 a,Catalase,COI1-1,COII-2 and HRin1 was upregulated by methyljasmonate,salicylic acid and methyljasmonate + salicylic acid treatments,but methyljasmonate induced high level of expression compared to salicylic acid and methyljasmonate+ salicylic acid at 1,2,and 3 weeks in roots and coleoptiles,respectively.The severity of T.controversa effects in roots was greater at 1 week,but it decreased at 2 weeks in all treatments.Additionally,confocal microscopy was used to track the fungal hyphae in resistant and susceptible cultivars in coleoptiles,anther and ovary cells.The results showed that no hyphae were present in the coleoptiles and anthers of methyljasmonate,salicylic acid and methyljasmonate,salicylic acid treated plants,while the hyphae were located on epidermal and sub-epidermal cells of anthers.In addition,the severity of hyphae increased with the passage of time as anthers matured.Bunted seeds were observed in the T.controversa inoculated plants,while no disease symptoms were observed in the phytohormones treatments and control plants.Likewise,the results of third experiment showed that the relative expression of Ta LHY and Ta PR-4 and Ta PR-5 genes was higher in a resistant and moderately resistant cultivars rather than susceptible cultivar at 72 h post inoculation with T.controversa.Similarly,the expression of defensin,Ta PR-2 and Ta PR-10 genes was observed higher in resistant and moderately resistant cultivars after exogenous application of phytohormones,including methyl jasmonate,salicylic acid,and abscisic acid.There were no fungal hyphae in tapetum cells in susceptible cultivar after methyl jasmonate,salicylic acid and abscisic acid treatments during the tracking of fungal hyphae through confocal microscopy.Moreover,after T.controversa infection,the pollen germination was of 80.06,58.73,and 0.67% in resistant,moderately resistant and susceptible cultivars,respectively.In summary,the resistance to T.controversa was achieved in cultivars via the regulation of the expression of defense-related and pathogenesis-related genes.Additionally,methyljasmonate and salicylic acid display a distinct role in activation of defence genes in the roots and coleoptiles and that they eliminate the fungal pathogen movement to upper parts of the plants with the passage of time as the anthers mature.The above results suggested that the using of resistant cultivar and application of phytohormones is a good option against the dwarf bunt disease. |
PDF Full Text Request