Severe modifications in source‐sink ratio influence the susceptibility of bananas to crown rot and its phenolics content

Abstract

AbstractBanana susceptibility to crown rot is influenced by many biotic and abiotic preharvest factors, which include source‐sink (So‐Si) ratio modifications through trimming of leaves and fruit. Banana plant's resistance to biotic stress has been previously correlated to its phenolic content; it is hypothesized that the crown's phenolic content may influence the fruit's susceptibility. The aim of this work was to investigate the influence of severe So‐Si ratio modifications, via the removal of leaves and fruit, and the involvement of phenolics in the fruit's susceptibility to crown rot. Fruit susceptibility was evaluated 13 days postinoculation (13 dpi) with Colletotrichum musae. Banana crowns obtained on the day of harvest before inoculation (dhbi) and 13 dpi were analysed for changes in phenolics using GC‐MS, HPLC, and LC‐MS devices. Severe So‐Si ratio modifications had a significant effect (p <.001) on susceptibility, fruits of low So‐Si ratio being most susceptible. It also significantly influenced (p < .001) some tree and fruit characteristics. The less susceptible (S−) crowns had higher amounts of phenolics compared to the more susceptible (S+) ones. Catecholamines were identified as the major phenolics in banana crown, notably dopamine compared to norepinephrine and normetanephrine. Hydroxycinnamic acids (ferulic acid and its derivatives) were significantly accumulated (p <.001) the dhbi in S− crowns compared to S+ crowns, but decreased 13 dpi. Phenolics have a possible role in the biochemical defence of banana crown and could be used by producers as a chemical criterion for estimation of the level of banana's susceptibility to crown rot.