  Studies of beryllium abundance in large samples of solar-type stars show a
small fraction of extremely beryllium-deficient stars, which challenges our
current understanding of light element depletion in these stars. We suggest two
possible scenarios that may explain this high level of Be depletion: early
accretion and rotational mixing. We show that in both cases, the conditions
required to reach the observed level of Be depletion are quite extreme, which
explains the very small fraction of detected Be outliers. We suggest that
substantial Be depletion can be obtained in stars if they were fast rotators in
the past, with high initial rotational velocities and short disc lifetimes. Our
analysis suggests that rotational mixing may not be efficient enough to deplete
Be in less than 10 Myr. Consequently, the detection of strongly Be-deficient
stars in clusters younger than $\sim$ 10 Myr may provide a genuine signature of
accretion process and the proof that some protostars may undergo many extreme
bursts of accretion during their embedded phases of evolution.

Solar and Stellar Astrophysics