Application of Mycorrhizae for Controlling Root Diseases of Sesame

Application of Mycorrhizae for Controlling Root Diseases of Sesame Vesicular arbuscular mycorrhizae fungi (VAM) was evaluated as a biotic agent for controlling wilt and root-rot diseases of sesame caused by Fusarium oxysporum f. sp. sesami (Zap.) Cast and Macrophomina phaseolina (Moubl) Ashby pathogens can infect sesame plant at any growth stage causing considerable losses of seed yield. Spores of VA mycorrhizae fungi (Glomus spp.) were collected from the soil around the root systems of sesame plants then propagated on roots of Suddan grass (Sorghum vulgare var. sudanese). Under green house and field conditions, two hundreds sporocarps of Glomus spp. were added as a soil drench beside the sesame plant. Glomus spp. (VA mycorrhizae) significantly reduced wilt and root-rot incidence of sesame plants. Lums spp. (VA mycorrhizae) also significantly increased plant morphological characters such as plant height, number of branches and number of pods for each plant. Application of Glomus spp. to protect sesame plants by colonizing the root system, significantly reduced colonization of fungal pathogens in sesame rhizosphere as well as pathogenic activity of fungal pathogens increased lignin contents in the sesame root system were also observed. Furthermore, mycorrhizae treatment provided selective bacterial stimulation for colonization on sesame rhizosphere. These bacteria belonging the Bacillus group showed highly antagonistic potential to fungal pathogens. Application of mycorrhizae together with other biocontrol agent such as Trichoderma viride or Bacillus subtilis significantly effected than individual treatments for controlling these diseases incidences and increasing morphological characters and seed yield of sesame.

Symbiotic Vesicular-Arbuscular Mycorrhizae Influence Maximum Rates of Photosynthesis in Tropical Tree Seedlings Grown Under Elevated CO2

To investigate the importance of phosphorus and carbohydrate concentrations in influencing photosynthetic capacity of tropical forest tree seedlings under elevated CO2, we grew seedlings of Beilschmiedia pendula (Sw.) Hemsl. (Lauraceae) under elevated CO2 concentrations either with or without vesicular-arbuscular (VA) mycorrhizae. VA-mycorrhizae increased phosphorus concentrations in all plant organs (leaves, stems and roots). Maximum rates of photosynthesis (Amax) measured under saturating levels of CO2 and light were correlated with leaf phosphorus concentrations. VA-mycorrhizae also increased leaf carbohydrate concentrations, particularly under elevated CO2, but levels were low and within the range observed in naturally occurring forest species. Root carbohydrate concentrations were reduced in VA-mycorrhizal plants relative to non-mycorrhizal plants. These results indicate an important role for VA-mycorrhizae in controlling photosynthetic rates and sink strength in tropical trees, and thus in determining their response to future increases in atmospheric CO2 concentrations.