An overview of the endogenous and environmental factors related to the Coffea arabica flowering process

The transition of vegetative meristems to a reproductive state followed by floral development and flowering is a complex process regulated by many regulatory pathways that integrate(epi)genetic and environmental factors to guarantee the reproductive success in angiosperms.In woody and perennial species,such as coffee trees,the extended life cycle reflects adaptive strategies,i.e.,two-year cycle,sequential flowering and bud latency during the winter,that ensure reproductive success in a variable environment.The dynamics of coffee flowering integrate multiple stimuli to induce morpho-physiological changes,especially during the reproductive phase.We discussed diverse stimuli which are directly and indirectly associated with molecular pathways related to the reproductive meristem transition and floral development until anthesis.Here,we propose to redefine some concepts regarding coffee floral development,such as:i)a summary of genes possibly involved in the flowering pathways;ii)a new classification of buds by position in the node(B1-B4)to avoid misunderstandings with the uneven developmental stages;iii)comparative ABC model to Arabidopsis and tomato to allow evolutionary discussions of whorls development in Coffea sp.From this,we expect to collaborate to drive future studies towards coffee breeding and production,for example,improving floral bud activation,controlling the flowering time,anthesis synchronization to produce more homogeneous ripening fruits,reducing abortion or early flower openings,and increasing fruitification.Moreover,we think that the explored relationship between physiological and molecular approaches during the coffee flowering may be extended to understand other tropical perennial species,especially those with asynchronous flowering behavior,and to understand evolutive aspects in Rubiaceae.