Project description:The transcriptional response of the Mexican Lime to two different isolates of the Citrus Tristeza Virus was evaluated. Virus Isolates were T305, which provokes severe symptoms in Lime plants, and isolate T385 which does not result in any visible symptoms. Five Lime plants were inoculated with each virus isolate, and four healthy plants were used to create a pooled control. Citrus custom arrays were hybridized with an infected sample and the pooled control, using a dyeswap design. In total, the experiment comprised hybridizations with twenty microarrays, ten for each virus isolate, including five biological replicates, each technically duplicated by dye-swapping.
Project description:Key lime (Citrus aurantiifolia) is an emerging crop in Italy, especially in the Southern regions, where the environmental conditions are suitable for its cultivation. A field survey in Sicily in a commercial orchard of Key lime revealed the widespread presence of water-soaked spots and sunken/dry lesions at the stylar-end, mainly in pre-harvest condition. Water-soaked spots were attributed to Geotrichum citri-aurantii, an agent of sour rot on Citrus spp., whereas the sunken/dry lesion was attributed to the physiological disorder known as stylar-end breakdown. Sour rot and stylar-end breakdown are usually considered post-harvest diseases and rarely found in the field on fruit still attached to the tree. Although Geotrichum citri-aurantii is not responsible for the stylar-end breakdown, its association with this alteration reveals the importance of the environmental conditions and the agronomic practices in diseases/disorders development. In addition, to our knowledge, this is the first report of Geotrichum citri-aurantii on Key lime in Europe.
Project description:Background: Witches’ broom disease of Mexican lime (Citrus aurantifolia L.), which is caused by the phytoplasma “Candidatus Phytoplasma aurantifolia”, is a devastating disease that results in significant economic losses. Plants adapt to abiotic stresses by regulating gene expression at the transcriptional and post-transcriptional levels. MicroRNAs (miRNAs) are a recently identified family of molecules that regulate plant responses to environmental stresses through post-transcriptional gene silencing. Methods: Using a high-throughput approach to sequence small RNAs, we compared the expression profiles of miRNAs in healthy Mexican lime trees and in plants infected with “Ca. Phytoplasma aurantifolia”. Results: Our results demonstrated the involvement of different miRNAs in the response of Mexican lime trees to infection by “Ca. Phytoplasma aurantifolia”. We identified miRNA families that are expressed differentially upon infection with phytoplasmas. Most of the miRNAs had variants with small sequence variations (isomiRs), which are expressed differentially in response to pathogen infection. Conclusions: It is likely that the miRNAs that are expressed differentially in healthy and phytoplasma-infected Mexican lime trees are involved in coordinating the regulation of hormonal, nutritional, and stress signalling pathways, and the complex interactions between them. Future research to elucidate the roles of these miRNAs should improve our understanding of the level of diversity of specific plant responses to phytoplasmas.
Project description:Iron chlorosis is one of the major abiotic stresses affecting fruit trees and other crops in calcareous soils. The most evident symptoms are connected to a reduction in growth and yield and in the interveinal chlorosis of leaves. A custom CombiMatrix 90K microarray was used to identify candidate genes involved in the citrus response to iron deficiency stress, comparing Tarocco Scirè orange [Citrus sinensis (L.) Osbeck] grafted on two different rootstocks, Swingle citrumelo (C. paradisi × Poncirus trifoliata), high sensitive, and Carrizo citrange (C. sinensis × P. trifoliata), tolerant. RNA was extracted from roots of plants grown in two different soils, one volcanic (0% of active lime) used as control, and the other calcareous (10% of active lime).