  The main purpose of this article is to establish moderate deviation
principles for additive functionals of bifurcating Markov chains. Bifurcating
Markov chains are a class of processes which are indexed by a regular binary
tree. They can be seen as the models which represent the evolution of a trait
along a population where each individual has two offsprings. Unlike the
previous results of Bitseki, Djellout \& Guillin (2014), we consider here the
case of functions which depend only on one variable. So, mainly inspired by the
recent works of Bitseki \& Delmas (2020) about the central limit theorem for
general additive functionals of bifurcating Markov chains, we give here a
moderate deviation principle for additive functionals of bifurcating Markov
chains when the functions depend on one variable. This work is done under the
uniform geometric ergodicity and the uniform ergodic property based on the
second spectral gap assumptions. The proofs of our results are based on
martingale decomposition recently developed by Bitseki \& Delmas (2020) and on
results of Dembo (1996), Djellout (2001) and Puhalski (1997).
