Forbidden lines emission in T Tauri stars is a powerful probe of the presence of high velocity jets and slow winds originating from the inner region of the circumstellar disc. Such phenomena are strictly linked to mass accretion, contributing to the disc evolution and dispersal.
We summarize here the results of a survey on the [OI]6300A line emission in 131 T Tauri stars of nearby star forming regions, observed with the X-shooter spectrograph at the Very Large Telescope (VLT). The line profile was deconvolved into a low velocity component (LVC, $\mid$V$_r \mid$ $<$ 40 km/s) and a high velocity component (HVC, $\mid$V$_r \mid$ $>$ 40 km/s ), originating from slow winds and high velocity jets, respectively.
We found a strong correlation between the [OI]6300A luminosity of both the LVC and HVC, and the stellar and accretion parameters of the central sources, with similar slopes for the two components.
Mass ejection rates ($\dot{M}_{jet}$) measured from the HVC [OI]6300A line luminosity span from $\sim$ 10$^{-13}$ to $\sim$ 10$^{-7}$ M$_{\odot}$/yr , and the corresponding $\dot{M}_{jet}$/$\dot{M}_{acc}$ ratio ranges from $\sim$0.01 to $\sim$0.5, with an average value of 0.07. However, considering the upper limits on the non-detected HVC, we infer a $\dot{M}_{jet}$/$\dot{M}_{acc}$ ratio $<$ 0.03 in more than 40\% of sources. We argue that most of these sources might lack the physical conditions needed for an efficient magneto-centrifugal acceleration in the star-disc interaction region.