Figure 4.
Quantitative analysis of fungal colonization in mycorrhizal M. truncatula roots treated with different CO solutions. A general promotion of fungal colonization was induced by all treatments. In more detail, the application of 1 g/L COs from P. ostreatus (Po 1 g/L) induced a significant increase in colonization frequency (F%) and arbuscule abundance in the whole root system (A%) compared to water-treated controls. A comparable increase in F% was also obtained using a 1 mg/L solution (Po 1 mg/L), which also produced a significant increase in arbuscule abundance in the colonized areas (a%). By contrast, shrimp-derived COs produced a significant increase in A% and M% (representing the average extension of fungal colonization in the root system), as well as a relevant but statistically non significant elevation of F%, when applied at high concentration (SH 1 g/L), but SH 1 mg/L produced the lowest increase in F% and only a significant increase in arbuscule abundance in the colonized areas (a%). No significant differences were observed in the intensity of the mycorrhization in colonized parts of the root system (m%). In short, P. ostreatus COs resulted to be more efficient promoters of AM colonization than shrimp COs, especially when used at low dosage. A minimum of four biological replicates were evaluated for each treatment. Asterisks indicate significant differences (Student’s t test: P < 0.05).