Reference : Study of the physiological component involved in the development of crown rot in bana...
Dissertations and theses : Doctoral thesis
Life sciences : Agriculture & agronomy
Study of the physiological component involved in the development of crown rot in bananas and the role of phenolics in susceptibility variation mechanisms
[fr] Étude de la composante physiologique impliquée dans le développement des pourritures de couronne de bananes et rôle des composés phénoliques dans les mécanismes de variation de sensibilité
Ewane, Cécile mailto [Université de Liège - ULiège > > > Doct. sc. agro. & ingé. biol.]
GxABT-ULg, ​Gembloux, ​​Belgique
Doctorat en Sciences Agronomiques et Ingénierie Biologique
VIII, 112
Lepoivre, Philippe mailto
de Lapeyre de Bellaire, Luc mailto
Francis, Frédéric mailto
Jijakli, Haissam mailto
Lognay, Georges mailto
Baudoin, Jean-Pierre mailto
Lassois, Ludivine mailto
[en] Banana ; Crown rot ; susceptibility variation ; biotic and abiotic preharvest factors ; phenolic compounds
[en] Crown rot is a post-harvest disease caused by a broad unspecific and opportunistic parasitic complex, which affects the quality of export bananas in Cameroon, as well as in most of the production areas around the world. The originality of this research is that it is sets out, not only to investigate on the conditions surrounding the development of the disease and the variable factors of fruit’s susceptibility, but equally to characterize the phenolic content of the banana crown with differential susceptibility levels. The study therefore aims at showing the influence of abiotic and biotic factors on the fruit’s physiological component at harvest and the involvement of phenolic compounds in the mechanism staked in fruit’s susceptibility variations to this pathology.
At the end of this study, it appears that abiotic and biotic factors influence the fruit’s physiological component at harvest, affecting thus its susceptibility level and therefore favours the development of crown rot disease. The reliability of internal necrosis surface (INS) assessments method was improved. The influence of abiotic factors (production area and harvest date) on fruit susceptibility was demonstrated without season influence. Fruits grown in high altitudes (Ekona, 500 m) were less susceptible to crown rot than the ones grown in low altitudes (Dia-Dia, Koumba, 80 m). It was noticed that at certain harvest dates within the rainy season, fruit susceptibility was higher in plantations with low altitudes. Concerning biotic factors, Mycosphaerella leaf spot disease’s influence was shown in two geographical areas. In Cameroon, black leaf streak disease significantly influenced banana’s sensitivity to crown rot (P< 0.001). In Guadeloupe, Sigatoka disease had no effect (P> 0.05) on banana’s susceptibility to the development of crown rot disease. The influence of the source-sink ratio variations, an abiotic factor, on fruit physiology could explain these differences.
The influence of severe source-sink ratio modification on fruit susceptibility to crown rot was shown. Fruits with low source-sink ratio were the most susceptible. Bananas of extreme modalities (12leaves/1hand, 1leaf/8hands) and with differential susceptibility (S-, S+) to crown rot were used for the biochemical characterization of their phenolic content at two stages: the day of harvest before inoculation (dhbi) and 13 days post-inoculation (13dpi) by chromatographic methods (GC-MS, HPLC, LC-MS). Dopamine was identified as the major secondary metabolite (phenolic alkaloid) in banana crown. Norepinephrine and normetanephrine levels were high in the dhbi, especially in the S+ crowns. Hydroxycinnamic acids (ferulic acid, coumaric acid and their derivatives) and other unidentified compounds were accumulated in highly significant quantities (P <0.001) in the dhbi in the less susceptible crown (S-) as compared to the susceptible ones (S+), with decreased 13dpi mostly in the susceptible fruits (S+). These results suggest a possible role of these phenolics in banana crown biochemical defense. However, the main role of each phenolic detected in the susceptibility variations mechanism remains unclear. This study is the starting point to understanding the function(s) of phenolics in banana crown defense.
This is a pioneer study on the influence of abiotic and biotic factors on the banana fruit’s physiological component at harvest through the assessment of their incidence on crown rot development. This work appears to be the first to link the level of fruit’s susceptibility at two stages (dhbi and13dpi) with their crown phenolic content.

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