Evaluation of tolerance to brown rot caused by monilinia laxa (aderhold and ruhland) honey, in peach germplasm (prunus persica (l.) batsch)

Resumen

The peach is one of the most important global tree crops within the economically important Rosaceae family. The crop is faced with numerous pest and disease, especially fungal pathogens that infect stone fruits in the field, on transit and in the store. Over 50 % postharvest, global loss has been ascribed to the brown rot disease of the species of Monilinia and in the recent years the disease has been so critical in the orchard that some stone fruits were abandoned. And in Spain, particularly, the disease has been associated with well over 60 % fruit losses after harvest. Although, there exist different control options, the breeding for resistance remains an ideal management option for brown rot disease control considering the uniqueness of its sustainability in the chain of crop production and environmental compatibility. The thesis aims at phenotyping peach germplasm of the Aula Dei-CSIC tolerant cultivars and progenies to brown rot of Monilinia laxa with good quality. The study focuses on peach breeding within the Ebro valley of the Mediterranean eco-zone, through the use of tolerant variety or genotypes with good quality characteristics in brown rot disease management. Chapter I sets an evaluation method, by optimizing the available protocols, to screen tolerance to brown rot by Monilinia spp. in peach germplasm. This was enhanced and achieved with the comprehensive bibliographic review and compilation of information currently available on peach and the resultant effect of interaction (brown rot) with species of Monilinia and available management options. Chapter II examines the effect of physicochemical factors of pH and titratable acidity (TA) in the host-pathogen interaction of peach and M. laxa in-vitro and in-vivo. This study encompasses the necessity to know the evolution of fruit maturity in new and old varieties in relation to potential Monilinia infection in immature fruits. Chapter III is a screening test based upon artificial fruit inoculation to validate on several parental lines of the peach breeding program (‘Crown Princess’, ‘Big Top’, ‘Andross’, and ‘BabyGold 9’). In addition, cultivars with different phenolic content and early (‘Tebana’) or late harvested, as the Spanish traditional non-melting flesh cultivars (‘Miraflores’, ‘Calanda Tardío’ and ‘Calante’), were included in the study. The correlation of pathogenic factors with their biochemical composition concerning acids, phenolic contents in flesh-fruit is also discussed. Chapter IV screens sixty eight progenies from the ‘Babygold 9’ × ‘Crown Princess’ population of the breeding program of EEAD-CSIC for susceptibility to brown rot of Monilia laxa. Physicochemical traits, such as fruit firmness and soluble solids content were recorded before and after storage. Titratable acidity, pH, and antioxidant composition were also measured at harvest for correlation with pathogenic factors. Key words: Prunus persica; Monilinia spp; host; pathogen; stone fruits; crop protection; plant breeding; ex-situ; in-situ; germplasm; fungus; alkaline; physicochemical; genetic tolerance, bioactive, susceptibility; brown rot; phytochemicals; plant improvement; necrotrophic fungi; infection; introgression; genotypes; firmness.