  It is shown that substantially enhanced Higgs to diphoton rate induced by
light staus with large left-right mixing in MSSM requires at the GUT scale
non-universal gaugino masses with bino and/or wino lighter than gluino. The
possibility of such enhancement is investigated in MSSM models with arbitrary
gaugino masses at the GUT scale with additional restriction of top-bottom-tau
Yukawa unification, as predicted by minimal SO(10) GUTs. Many patterns of
gaugino masses leading to enhanced Higgs to diphoton rate and the Yukawa
unification are identified. Some of these patterns can be accommodated in a
well-motivated scenarios such as mirage mediation or SUSY breaking F-terms
being a non-singlet of SO(10). Phenomenological implications of a scenario with
non-universal gaugino masses generated by a mixture of the singlet F-term and
the F-term in a 24-dimensional representation of SU(5) $\subset$ SO(10) are
studied in detail. Possible non-universalities of other soft terms generated by
such F-terms are discussed. The enhancement of Higgs to diphoton rate up to 30%
can be obtained in agreement with all phenomenological constraints, including
vacuum metastability bounds. The lightest sbottom and pseudoscalar Higgs are
within easy reach of the 14 TeV LHC. The LSP can be either bino-like or
wino-like. The thermal relic abundance in the former case may be in agreement
with the cosmological data thanks to efficient stau coannihilation.
