Biocontrol Of Postharvest Brown Rot And Its Effects On Peach Puree Quality PDF Download

Peach quality development and fungal infections after harvest are issues of concern in the fruit value chain. Their examination would benefit from an integrated approach that considers the processes involved, their interactions, and their drivers. In this context, the general objectives of the thesis were (i) to create a modeling framework to simulate peach quality development and brown rot infections and their control by pre-harvest (cultural practices) and post-harvest (storage) conditions; and (ii) to use this model to investigate ways to improve fruit quality and to reduce losses. In this study, we focused on the nectarine (Prunus persica var. nucipersica) case. We first defined and calibrated, using experimental data, a mathematical model to simulate the combined effect of fruit growth and storage conditions (temperature and relative humidity) on nectarine quality-related traits. We modeledthe seasonal course of fruit surface conductance to water vapor, fruit mass loss during storage, and sugar concentration dynamics in fruit pulp. The observed data suggested an increase of sweetness with an increase of fruit mass loss during storage, which was also shown by model simulations. Moreover, the model put forward that fruit from late harvest dates could have higher sweetness at the end of storage than fruit harvested earlier. Second, we studied the spread of brown rot during storage. We verified experimentally that there were no secondary infections (without direct contact between fruit) by Monilinia laxa. Then, we used experimental results to test the effect of pre-harvest (including meteorology) and post-harvest conditionson the time-to-infection by brown rot, using a survival model with parametric estimates. Several conditions were found to be significant in explaining the disease incidence, notably the mean storage temperature, the fruit mass and the prevalence of brown rot at harvest, and the mean wetness duration in the week before harvest. Finally, we integrated the above-mentioned models within a fruit crop model that takes explicitly into account the role of pre-harvest practices on the development of fruit characteristics at the tree scale. We studied, via a sensitivity analysis and model exploration, the model behavior in relation to some orchard practices (irrigation and fruit load) and storage conditions (temperature and relative humidity). Model simulations correctly reproduced the well-known effects of practices on fruit quality criteria, such as the increase of fruit size under well-irrigated conditions and low fruit load, and the increase of sweetness under water-stressed regimes. The model was able to support that fruit properties are controlled by storage conditions, notably fruit mass loss increases with increasing temperature and decreasing relative humidity, and the brown rot infections increase with temperature. Simulations also highlighted the influence of interactions between pre- and post-harvest conditions on the brown rot prevalence and the fruit yield at the end of storage. We finally used the modeling framework to search for the combinations of pre- and post-harvest conditions thatoptimize a performance score encompassing fruit quality and yield. The relative importance assigned to the fruit quality criteria largely affected the choice of the optimal scenarios. The results also pointed out a trade-off between quality criteria, and in particular sweetness, and the fruit yield. The use of this modeling framework could support the dialogue between the actors of the fruit value chain, by suggesting scenarios of pre-harvest practices and storage conditions that satisfy their expectations, without prejudging the subsequent behavior of the fruit after storage.