Abscisic acid plays a key role in the regulation of date palm fruit ripening.

The date palm (Phoenix dactylifera L.) fruit is of major importance for the nutrition of broad populations in the world's desert strip; yet it is sorely understudied. Understanding the mechanism regulating date fruit development and ripening is essential to customise date crop to the climatic change, which elaborates yield losses due to often too early occurring wet season. This study aimed to uncover the mechanism regulating date fruit ripening. To that end, we followed the natural process of date fruit development and the effects of exogenous hormone application on fruit ripening in the elite cultivar 'Medjool'. The results of the current study indicate that the onset of fruit ripening occurre once the seed had reached maximum dry weight. From this point, fruit pericarp endogenous abscisic acid (ABA) levels consistently increased until fruit harvest. The final stage in fruit ripening, the yellow-to-brown transition, was preceded by an arrest of xylem-mediated water transport into the fruit. Exogenous ABA application enhanced fruit ripening when applied just before the green-to-yellow fruit color transition. Repeated ABA applications hastened various fruit ripening processes, resulting in earlier fruit harvest. The data presented supports a pivotal role for ABA in the regulation of date fruit ripening.

Characterizing the Fungal Microbiome in Date (Phoenix dactylifera) Fruit Pulp and Peel from Early Development to Harvest.

Date palm (Phoenix dactylifera) is considered to be a highly important food crop in several African and Middle Eastern countries due to its nutritional value and health-promoting properties. Microbial contamination of dates has been of concern to consumers, but very few works have analyzed in detail the microbial load of the different parts of date fruit. In the present work, we characterized the fungal communities of date fruit using a metagenomic approach, analyzing the data for differences between microbial populations residing in the pulp and peel of "Medjool" dates at the different stages of fruit development. The results revealed that Penicillium, Cladosporium, Aspergillus, and Alternaria were the most abundant genera in both parts of the fruit, however, the distribution of taxa among the time points and tissue types (peel vs. pulp) was very diverse. Penicillium was more abundant in the pulp at the green developmental stage (Kimri), while Aspergillus was more frequent in the peel at the brown developmental stage (Tamer). The highest abundance of Alternaria was detected at the earliest sampled stage of fruit development (Hababauk stage). Cladosporium had a high level of abundance in peel tissues at the Hababauk and yellow (Khalal) stages. Regarding the yeast community, the abundance of Candida remained stable up until the Khalal stage, but exhibited a dramatic increase in abundance at the Tamer stage in peel tissues, while the level of Metschnikowia, a genus containing several species with postharvest biocontrol activity, exhibited no significant differences between the two tissue types or stages of fruit development. This work constitutes a comprehensive metagenomic analysis of the fungal microbiome of date fruits, and has identified changes in the composition of the fungal microbiome in peel and pulp tissues at the different stages of fruit development. Notably, this study has also characterized the endophytic fungal microbiome present in pulp tissues of dates.