Inheritance of Fruit Red-Flesh Patterns in Peach

Fruit color is an important trait in peach from the point of view of consumer preference, nutritional content, and diversification of fruit typologies. Several genes and phenotypes have been described for peach flesh and skin color, and although peach color knowledge has increased in the last few years, some fruit color patterns observed in peach breeding programs have not been carefully described. In this work, we first describe some peach mesocarp color patterns that have not yet been described in a collection of commercial peach cultivars, and we also study the genetic inheritance of the red dots present in the flesh (RDF) and red color around the stone (CAS) in several intra- and interspecific segregating populations for both traits. For RDF, we identified a QTL at the beginning of G5 in two intraspecific populations, and for CAS we identified a major QTL in G4 in both an intraspecific and an interspecific population between almond and peach. Finally, we discuss the interaction between these QTLs and some other genes previously identified in peach, such as dominant blood flesh (DBF), color around the stone (Cs), subacid (D) and the maturity date (MD), and the implications for peach breeding. The results obtained here will help peach germplasm curators and breeders to better characterize their plant materials and to develop an integrated system of molecular markers to select these traits.info:eu-repo/semantics/publishedVersio

Construction of a NIL collection of P. davidiana into the peach genetic background

Resumen del trabajo presentado en X International Peach Symposium, celebrado en Naoussa (Grecia) del 30 de mayo al 3 de junio de 2022.MAI is a breeding strategy used to increase the genetic variability of a species by introgressing new traits from closely related compatible species in a short period of time. The proof of concept of the MAI strategy has been recently described using a cross between peach and almond. This led to the identification of several almond genes with a potential use in peach breeding programs. In this study, MAI was applied in interespecific crosses between peach and P. davidiana. Two BC1 populations (NT1Ba and NT1Ca), derived from a cross between the peach cultivar ‘Nectatop’ and two P. persica x P. davidiana hybrids (‘Cadaman’ and ‘Barrier’), have been developed and are under analysis. Both populations have been genotyped and individuals having a low number of introgressions of P. davidiana covering the whole P. davidiana genome were selected. These individuals have been backcrossed to ‘Nectatop’ and this BC2 progenies were or are being selected using a new LSQUO96.96 Genotyping IFC’ Fluidigm SNP array developed from the resequencing data of the parental lines. In one population, 32 prILs (pre introgression lines; lines with 2-4 introgressed fragments) covering practically the entire genome of P. davidiana have been selected. In this population, a new powdery mildew resistance gene was mapped. For the other population, NT2Ca, the crosses have been done and next year a prILs collection will be selected. These populations are being phenotyped for phenology, fruit quality, leaf morphology and resistance traits to identify useful genes from P. davidiana. QTL analysis identified several genomic regions involved in the genetic control of leaf shape, maturity date and bitter flesh taste, among others. These materials will be useful for the identification of new alleles of interest for its use in peach breeding programs

Introgresión asistida por marcadores (MAI) en Prunus: estado actual

Trabajo presentado al X Congreso de Mejora Genética de Plantas, celebrado en Pontevedra (España) entre el 19 y el 22 de septiembre de 2022.Una de las principales limitaciones en la mejora genética del melocotón es el bajo nivel de variabilidad genética presente en las variedades comerciales. La introgresión de nueva variabilidad genética procedente de especies silvestres del género Prunus o de variedades exóticas de melocotón, puede proporcionar nuevos alelos útiles para mejorar la calidad de la fruta o el estrés biótico o abiótico. De hecho, la mayoría de las fuentes de resistencia a diferentes plagas y enfermedades se han identificado en estos materiales genéticos. Para introgresar toda esta variabilidad de forma eficiente y en un tiempo razonable, desarrollamos una estrategia llamada introgresión asistida por marcadores (MAI), que permite la integración de sólo un fragmento de ADN procedente de germoplasma exótico en una variedad de melocotón en dos generaciones después del híbrido. Utilizando esta estrategia, desarrollamos una colección de líneas de introgresión (ILs) a partir de un cruce entre melocotón ('Earlygold') y almendro ('Texas') y una colección de pre-ILs (PrILs) a partir de un cruce entre melocotonero y P. davidiana. En estos materiales ya se han identificado algunos alelos interesantes para la mejora del melocotón que proporcionan resistencia al oídio, color rojo de la pulpa o piel verde. Algunos de estos genes ya se están utilizando en el programa de mejora de melocotón del IRTA. Estas colecciones serán una herramienta muy útil para estudiar la variación cuantitativa y pueden ser consideradas como material de pre-mejora para los programas de mejora del melocotón

New insights into flowering date in Prunus: fine mapping of a major QTL in sweet cherry

Flowering date is an important trait in Prunus fruit species, especially for their adaptation in a global warming context. Numerous quantitative trait loci (QTLs) have been identified and a major one was previously located on LG4. The objectives of this study were to fine-map this QTL in sweet cherry, to identify robust candidate genes by using the new sweet cherry genome sequence of the cultivar “Regina” and to define markers usable in marker-assisted selection (MAS). We performed QTL analyses on two populations derived from crosses using cultivars “Regina” and “Garnet” as parents. The first one (n = 117) was phenotyped over ten years, while the second one (n = 1386) was evaluated during three years. Kompetitive allele specific PCR (KASP) markers located within the QTL region on LG4 were developed and mapped within this region, consisting in the first fine mapping in sweet cherry. The QTL interval was narrowed from 380 kb to 68 kb and candidate genes were identified by using the genome sequence of “Regina”. Their expression was analyzed from bud dormancy period to flowering in cultivars “Regina” and “Garnet”. Several genes, such as PavBOI-E3, PavSR45a and PavSAUR71, were differentially expressed in these two cultivars and could be then considered as promising candidate genes. Two KASP markers were validated using a population derived from a cross between cultivars “Regina” and “Lapins” and two collections, including landraces and modern cultivars. Thanks to the high synteny within the Prunus genus, these results give new insights into the control of flowering date in Prunus species and pave the way for the development of molecular breeding strategies.info:eu-repo/semantics/publishedVersio