Fine mapping and identification of candidate genes for the peach powdery mildew resistance gene Vr3

Powdery mildew is one of the major diseases of peach (Prunus persica), caused by the ascomycete Podosphaera pannosa. Currently, it is controlled through calendar-based fungicide treatments starting at petal fall, but an alternative is to develop resistant peach varieties. Previous studies mapped a resistance gene (Vr3) in interspecific populations between almond (‘Texas’) and peach (‘Earlygold’). To obtain molecular markers highly linked to Vr3 and to reduce the number of candidate genes, we fine-mapped Vr3 to a genomic region of 270 kb with 27 annotated genes. To find evidence supporting one of these positional candidate genes as being responsible of Vr3, we analyzed the polymorphisms of the resequences of both parents and used near-isogenic lines (NILs) for expression analysis of the positional candidate genes in symptomatic or asymptomatic leaves. Genes differentially expressed between resistant and susceptible individuals were annotated as a Disease Resistance Protein RGA2 (Prupe2G111700) or an Eceriferum 1 protein involved in epicuticular wax biosynthesis (Prupe2G112800). Only Prupe2G111700 contained a variant predicted to have a disruptive effect on the encoded protein, and was overexpressed in both heterozygous and homozygous individuals containing the Vr3 almond allele, compared with susceptible individuals. This information was also useful to identify and validate molecular markers tightly linked and flanking Vr3. In addition, the NILs used in this work will facilitate the introgression of this gene into peach elite materials, alone or pyramided with other known resistance genes such as peach powdery mildew resistance gene Vr2.info:eu-repo/semantics/publishedVersio

Biochemical and genetic implications of the slow ripening phenotype in peach fruit

The peach [Prunus persica L. (Batsch)] slow ripening (SR) trait is a mutation preventing the normal fruit ripening process. It is determined by a single Mendelian gene (Sr/sr) located on linkage group 4, where only homozygous individuals for a recessive allele (sr) show the SR phenotype and are generally discarded from breeding programs. Ripening-related traits such as fruit weight, firmness loss, ethylene production, ACO activity, sugars and organic acids composition, malondialdehyde, antioxidant capacity and total phenolic content were evaluated in a segregating population for the SR trait during two consecutive harvest seasons and at different maturity stages. Although there is no commercial value for the slow ripening (srsr) individuals, our results demonstrate that a heterozygous combination involving sr and another allele at this locus (Sr2) showed interesting traits including a longer harvest window and improved postharvest behaviour if harvested at the appropriate maturity (IAD ≥ 2). All these traits seem to be linked to a delayed ripening behaviour mediated, in turn, by a lower ethylene production capacity and an altered sugar (mainly sucrose) and organic acid accumulation/utilisation on-tree. The selection of this allelic combination could be an easy and efficient strategy to obtain new peach cultivars with potentially improved shelf life.info:eu-repo/semantics/acceptedVersio

When teaching works and time helps: Noun modification in L2 English school children

Producción CientíficaThe study focuses on the interaction between length of exposure and instruction in the L2 English acquisition process of L1 Spanish school children. Two target structures involving noun premodification are targeted: noun–noun (NN) compounds and adjective–noun (AN) strings. Four groups of participants have been studied for 3 years: a group that has been exposed to a specifically designed teaching program targeting NN compounds and a group that has received the regular English instruction program which does not address this structure as part of the curriculum. Two age subgroups appear in each case. The longitudinal judgment data elicited show that performance improves in the cooperation between length of exposure and the exposure to the NN instruction program. Furthermore, it is this last issue that actually takes the lead in that the NN instruction program directly impacts on not only NN compounds but also AN strings. This points to instruction being determinant in the L2 learning process; that is, a consciously and carefully directed instruction is proven to be more effective than length of exposure itself. This study on longitudinal experimental data contributes to shed light on the factors involved in instructed L2 acquisition.Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA009P17)Ministerio de Ciencia, Innovación y Universidades - Fondo Europeo de Desarrollo Regional (project PGC2018-097693-B-I00

A Decision Support System Based on Degree-Days to Initiate Fungicide Spray Programs for Peach Powdery Mildew in Catalonia, Spain

The incidence of peach powdery mildew (PPM) on fruit was monitored in commercial peach orchards to i) describe the disease progress in relation to several environmental parameters and ii) establish an operating threshold to initiate a fungicide spray program based on accumulated degree-day (ADD) data. A beta-regression model for disease incidence showed a substantial contribution of the random effects orchard and year, whereas relevant fixed effects corresponded to ADD, wetness duration, and ADD considering vapor pressure deficit and rain. When beta-regression models were fitted for each orchard and year considering only ADD, disease onset was observed at 242 ± 13 ADD and symptoms did not develop further after 484 ± 42 ADD. An operating threshold to initiate fungicide applications was established at 220 ADD, coinciding with a PPM incidence in fruit around 0.05. A validation was further conducted by comparing PPM incidence in i) a standard, calendar-based program, ii) a program with applications initiated at 220 ADD, and iii) a nontreated control. A statistically relevant reduction in disease incidence in fruit was obtained with both fungicide programs, from 0.244 recorded in the control to 0.073 with the 220-ADD alert program, and 0.049 with the standard program. The 220-ADD alert program resulted in 33% reduction in fungicide applications.info:eu-repo/semantics/acceptedVersio

Inheritance and QTL analysis of chilling and heat requirements for flowering in an interspecific almond x peach (Texas x Earlygold) F2 population

Blooming in temperate fruit species is triggered by chilling and heat requirements (CR and HR), with a wide range of requirements within the same species. CR for flower bud dormancy release has become a limiting factor for geographical adaptation of fruit trees in warmer regions. The present study investigated the genetic basis of CR and HR to break dormancy and flowering time (FT) in an almond x peach F2 progeny. FT, HR and CR were evaluated over two consecutive years (2015/2016 and 2016/2017). Seven out of the eight identified quantitative trait loci (QTLs) were found in both periods of analysis. They affected eight traits, and included a consistent QTL for breaking dormancy, CR and HR. Two of them, affecting FT and HR for FT (GDHF), colocalized in G1, and the remaining QTLs, affecting chilling and heat requirements, both influenced by dormancy breaking (DB), were located in G6. These results indicate that factors not related to DB affect flowering time in this population. Implications of the results in peach breeding are discussed.info:eu-repo/semantics/acceptedVersio

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

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

Inheritance and QTL analysis of chilling and heat requirements for flowering in an interspecific almond x peach (Texas x Earlygold) F2 population

Altres ajuts: Generalitat de Catalunya/CERCA programmeBlooming in temperate fruit species is triggered by chilling and heat requirements (CR and HR), with a wide range of requirements within the same species. CR for flower bud dormancy release has become a limiting factor for geographical adaptation of fruit trees in warmer regions. The present study investigated the genetic basis of CR and HR to break dormancy and flowering time (FT) in an almond x peach F2 progeny. FT, HR and CR were evaluated over two consecutive years (2015/2016 and 2016/2017). Seven out of the eight identified quantitative trait loci (QTLs) were found in both periods of analysis. They affected eight traits, and included a consistent QTL for breaking dormancy, CR and HR. Two of them, affecting FT and HR for FT (GDHF), colocalized in G1, and the remaining QTLs, affecting chilling and heat requirements, both influenced by dormancy breaking (DB), were located in G6. These results indicate that factors not related to DB affect flowering time in this population. Implications of the results in peach breeding are discussed

A qPCR-based method for the detection and quantification of the peach powdery mildew (Podosphaera pannosa) in epidemiological studies

[EN] A qPCR-based method was developed to detect and quantifyPodosphaera pannosa, the main causal agent of peach powdery mildew. A primer pair was designed to target part of the ITS region of the fungal ribosomal DNA, which proved to be highly specific and sensitive. A minimum of 2.81 pg mu L(- 1)ofP. pannosaDNA and 6 conidia mL(- 1)in artificially-prepared conidia suspensions were found to be the limit of detection. Moreover, a quantification of conidia placed on plastic tapes commonly used in volumetric air samplers was performed. Regression equations on conidia quantification obtained either from aqueous conidia suspensions or conidia placed on plastic tapes were similar. The protocol was further validated in field conditions by estimating the number ofP. pannosaconidia obtained with an air sampler, by both microscopic and molecular quantification. Both techniques detected the peaks of conidia production during a 4-month sampling period, and a significant correlation (r = 0.772) was observed between both quantification methods. Additionally, the molecular method was applied to detect latent fungal inoculum in different plant parts of peach trees. The pathogen was detected mainly on the bark of affected twigs, and to a lesser extent, in foliar buds. The method developed here can be applied in the study ofP. pannosaepidemiology and can help in improving the management of this pathogen through its early detection and quantification.This research was funded by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Spain, project RTA2013-00004-C03-01, and with matching funds from the European Regional Development Fund (ERDF). Jordi Luque was supported by the CERCA Programme, Generalitat de Catalunya. Neus Marimon was supported by INIA with a predoctoral grant (CPD-2015-0142). The authors thank Dr Josep Girbal (Univ. Autònoma de Barcelona, Bellaterra, Spain) for kindly providing us with herbarium vouchers of different powdery mildew species.Marimón, N.; Eduardo, I.; León Santana, M.; Berbegal Martinez, M.; Armengol Fortí, J.; Luque, J. (2020). A qPCR-based method for the detection and quantification of the peach powdery mildew (Podosphaera pannosa) in epidemiological studies. European Journal of Plant Pathology. 158(4):1005-1016. https://doi.org/10.1007/s10658-020-02136-0S100510161584Amano, K. (1986). Host range and geographical distribution of the powdery mildew fungi (p. 741). Tokyo: Japan Scientific Societies Press.Armbruster, D. A., & Pry, T. (2008). Limit of blank, limit of detection and limit of quantitation. The Clinical Biochemist Reviews, 2(suppl. 1), 49–52.Braun, U. (1987). A monograph of the Erysiphales (powdery mildews). Nova Hedwigia, 89, 1-700. Stuttgart: J. Cramer.Braun, U., Cook, R. T. A., Inman, A. J., & Shin, H. D. (2002). 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High-density mapping suggests cytoplasmic male sterility with two restorer genes in almond x peach progenies

Peach (Prunus persica) and almond (Prunus dulcis) are two sexually compatible species that produce fertile offspring. Almond, a highly polymorphic species, is a potential source of new genes for peach that has a strongly eroded gene pool. Here we describe the genetics of a male sterile phenotype that segregated in two almond (‘Texas’) 3 peach (‘Earlygold’) progenies: an F2 (T3E) and a backcross one (T1E) to the ‘Earlygold’ parent. High-density maps were developed using a 9k peach SNP chip and 135 simple-sequence repeats. Three highly syntenic and collinear maps were obtained: one for the F2 (T3E) and two for the backcross, T1E (for the hybrid) and E (for ‘Earlygold’). A major reduction of recombination was observed in the interspecific maps (T3E and T1E) compared to the intraspecific parent (E). The E map also had extensive monomorphic genomic regions suggesting the presence of large DNA fragments identical by descent. Our data for the male sterility character were consistent with the existence of cytoplasmic male sterility, where individuals having the almond cytoplasm required the almond allele in at least one of two independent restorer genes, Rf1 and Rf2, to be fertile. The restorer genes were located in a 3.4 Mbp fragment of linkage group 2 (Rf1) and 1.4 Mbp of linkage group 6 (Rf2). Both fragments contained several genes coding for pentatricopeptide proteins, demonstrated to be responsible for restoring fertility in other species. The implications of these results for using almond as a source of novel variability in peach are discussed.info:eu-repo/semantics/publishedVersio