Riccardo Russo
Ciclo: XXXIII
Data inizio: 31/10/2017
Curriculum: Agroalimentari
Borsa: UniCT - senza borsa
Titolo tesi: Traditional and advanced methods to detect resistant genotypes to mal secco disease
Abstract: Mal secco is the most severe disease that caused impressive yield losses to the Italian lemon industry. It is a tracheomycotic disease caused by the fungus Plenodomus tracheiphilus (Petri) Gruyter, Aveskamp & Verkley. Since the first reported disease in the Sicilian lemon orchards, the main goal for breeders and lemon growers was to identify lemon clones resistant to Mal Secco Disease (MSD). Different genetic improvement methods were used to resolve this challenging, but none had fully achieved the results. Although some less susceptible lemon (C. limon L. Burm. f.) clones with high fruit quality have been selected (Femminello Zagara Bianca, Femminello Continella), the high pressure of the pathogen allows the growers to use only the Monachello clone. This lemon clone has guaranteed the survival of lemon orchards in many areas afflicted by the disease, but it does not guarantee the Italian lemon industry's competitivity. The project's main goal was to enhance the knowledge about gene involved in MDS tolerance, resistance, and sensibility, with two combined different approaches, based on traditional techniques and transcriptomic analysis. So, a phenotypic survey, founded on the evaluation of the different level of tolerance or resistance to MSD, has been performed in a germplasm field planted at CREA, Italy, in an area of high pathogen pressure combined with a molecular screening based on real-time PCR. The results revealed sources of tolerance in lemon and citron hybrids. The molecular screening identified P. tracheiphilus in all lemon clones and clones without apparent symptoms, indicating their ability to tolerate the disease. Based on the survey result, we selected the most suitable parents to generate two segregating populations.to introduce the resistance genes in lemon genotypes, which may help to detect possible Quantitative Trait Locus (QTLs) involved into the resistance to MSD. Thanks to the utilization of molecular markers, Simple Sequence Repeats (SSRs), these populations were screened to discard the F1 hybrids from selfing crosses. A genome-wide mapping of QTLs controlling the resistance to MSD will be a desirable tool to use in the next years, with the final purpose to identify the most valuable molecular markers suitable for marker-assisted selection (MAS) in the breeding programs. This project also provides a reliable method for MSD detection by RT-PCR analysis by which a significant correlation with disease symptoms was calculated. With the main aim of identifying candidate genes involved in the defence response of citrus plants to "mal secco", we performed a de novo transcriptome analysis of rough lemon (Citrus jambiri Lush.) seedlings subjected to artificial inoculations of P. tracheiphilus in comparison with plants inoculated with water. This work's main findings are that, under fungus challenge, rough lemon significantly down-regulated the genes involved in the light-harvesting and the photosynthetic electron flow, thus probably inducing a shortage of energy for cellular functions. Moreover, the systemic acquired resistance (SAR) is activated through the induced salicylic acid cascade, probably preparing the plants to a successive pathogen attack. Interestingly, RPM1 interacting protein 4, an essential positive regulator of plant defence, and BIR2, which is a negative regulator of the basal level of immunity (namely PTI, pathogen-associated molecular patterns triggered immunity) have been identified thus representing useful targets for genetic breeding of target genes. The application of new plant breeding techniques (NPBTs), specifically genome editing and cisgenesis, can offer an alternative method for advancing resistance to mal secco and other biotic and abiotic stresses. NPBTs produce targeted and minimal modifications to selected genotypes without altering the genetic background. These techniques will be essential for a cultivar, Femminello Siracusano 2Kr, which is highly valued by growers for fruit quality and productivity, but it is very susceptible to MSD.
Tutor: Nicolosi-Lo Piero
Data Conseguimento Titolo: 29/03/2021
Linkedin: Indicate il link
Email: riccardo.russo.1991@gmail.com
Periodi all'estero- Sede e data: Presso il Citrus Reaserch and Education Center (CREC), Florida (USA), dal 03-02-2020 al 30-07-2020, dal 27-10-2020 al 17-12-2020 e dal 27-01-2021 al 31-05-2021
Esperienze post-Dottorato ed attuale occupazione: Vincitore di una borsa annuale finanziata dalla “Fondazione Umberto Veronesi” (2023-2024) presso Di3A