Inheritance of esters and other volatile compounds responsible for the fruity aroma in strawberry.

Cultivated strawberry, Fragaria × ananassa, has a complex aroma due to the presence of more than 350 volatile organic compounds (VOCs). However, a mixture of only 19 compounds, called Key Volatile Compounds (KVC), can impart the main strawberry aroma. The octoploid nature of the cultivated strawberry species (2n = 8x = 56) adds complexity to the heritance of the accumulation of the volatiles responsible for aroma. An F1 population cross between two breeding parental lines, FC50 and FD54, was phenotyped for aroma by SPME GCMS during six harvests. A total of 58 compounds were identified: 33 esters, nine terpenes, seven aldehydes, four lactones, two furans, one acid, one alkane and one alcohol, of which 16 were KVCs. A total of 179 QTLs were found, and 85 of these were detected in at least three harvests, of which 50 QTLs were considered major (LOD > 4.0) and detected in five or six analyzed harvests. Several clusters of ester QTLs associated with fruity aroma were discovered, such as QTLs for esters that share hexanoate group that were mapped in LG4A (Hexanoate_4A), those that share acetate and octyl groups in LG6A (Acetate_6A and Octyl_6A) or those with the same methyl group in LG7B (Methyl_7B). Different terpene QTLs associated with floral aroma appear grouped in a cluster in LG3C (Terpene_3C). Some of these clusters of QTLs were validated in a second F2 population, a cross of "Camarosa" and "Dover," that was also phenotyped for three years. Selected SNPs from floral and fruity aroma QTLs were tested in a third population, which will most likely be useful for marker-assisted breeding (MAB).

Shape, firmness and fruit quality QTLs shared in two non-related strawberry populations.

The cultivated strawberry (Fragaria x ananassa) is an octoploid species (2n = 8x = 56), appreciated widely for its fruit. There have been very few studies on fruit quality traits, which are known to be mostly polygenic and environmentally dependent. To identify higher genetic variability, two non-related populations were genotyped: an F1 population cross between 'FC50' and 'FD54' and an F2 population cross between 'Camarosa' and 'Dover', hybridizing both with IStraw35k and IStraw90k SNP arrays, respectively. The F1 genetic map was constructed with 14595 SNPs and the F2 map with 7977 SNPs. High collinearity was observed when comparing one genetic map with the other and on comparing both with the octoploid genome. To assess fruit variability, both populations were phenotyped for shape, firmness, taste and other fruit traits over the 2016-2019 period. With QTL analyses, 33 stable QTLs were mapped in the 'FC50xFD54' population, and three hotspot regions were found for shape traits in LG3A, LG4D and LG6D. In the '21AF' population, only eight stable QTLs were detected. Despite that, two major and stable QTLs were mapped in the same interval of confidence for both populations. A shared fruit shape ratio QTL which explained around 25 % of trait variance was mapped in LG3A, and a shared firmness QTL explaining 26.9 % of trait variance in LG7C. For the first time, two QTLs were discovered in LG3A and LG4A for a phenotype neck without achenes. When analysing two different mapping populations, in addition to finding specific QTL regions for the studied traits, a narrowing down of the interval of confidence for the shared QTLs is achieved. As a result of this study, a new set of SNPs for fruit firmness and shape is now available for use in MAS in strawberry breeding programs.

Pedigree analysis of 220 almond genotypes reveals two world mainstream breeding lines based on only three different cultivars.

Loss of genetic variability is an increasing challenge in tree breeding programs due to the repeated use of a reduced number of founder genotypes. However, in almond, little is known about the genetic variability in current breeding stocks, although several cases of inbreeding depression have been reported. To gain insights into the genetic structure in modern breeding programs worldwide, marker-verified pedigree data of 220 almond cultivars and breeding selections were analyzed. Inbreeding coefficients, pairwise relatedness, and genetic contribution were calculated for these genotypes. The results reveal two mainstream breeding lines based on three cultivars: "Tuono", "Cristomorto", and "Nonpareil". Descendants from "Tuono" or "Cristomorto" number 76 (sharing 34 descendants), while "Nonpareil" has 71 descendants. The mean inbreeding coefficient of the analyzed genotypes was 0.041, with 14 genotypes presenting a high inbreeding coefficient, over 0.250. Breeding programs from France, the USA, and Spain showed inbreeding coefficients of 0.075, 0.070, and 0.037, respectively. According to their genetic contribution, modern cultivars from Israel, France, the USA, Spain, and Australia trace back to a maximum of six main founding genotypes. Among the group of 65 genotypes carrying the Sf allele for self-compatibility, the mean relatedness coefficient was 0.125, with "Tuono" as the main founding genotype (24.7% of total genetic contribution). The results broaden our understanding about the tendencies followed in almond breeding over the last 50 years and will have a large impact into breeding decision-making process worldwide. Increasing current genetic variability is required in almond breeding programs to assure genetic gain and continuing breeding progress.

Two Loci, RiAF3 and RiAF4, Contribute to the Annual-Fruiting Trait in Rubus.

Most Rubus species have a biennial cycle of flowering and fruiting with an intervening period of winter dormancy, in common with many perennial fruit crops. Annual-fruiting (AF) varieties of raspberry (Rubus idaeus and Rubus occidentalis L.) and blackberry (Rubus subgenus Rubus) are able to flower and fruit in one growing season, without the intervening dormant period normally required in biennial-fruiting (BF) varieties. We used a red raspberry (R. idaeus) population segregating for AF obtained from a cross between NC493 and 'Chilliwack' to identify genetic factors controlling AF. Genotyping by sequencing (GBS) was used to generate saturated linkage maps in both parents. Trait mapping in this population indicated that AF is controlled by two newly identified loci (RiAF3 and RiAF4) located on Rubus linkage groups (LGs) 3 and 4. The location of these loci was analyzed using single-nucleotide polymorphism (SNP) markers on independent red raspberry and blackberry populations segregating for the AF trait. This confirmed that AF in Rubus is regulated by loci on LG 3 and 4, in addition to a previously reported locus on LG 7. Comparative RNAseq analysis at the time of floral bud differentiation in an AF and a BF variety revealed candidate genes potentially regulating the trait.

Construction of an almond linkage map in an Australian population Nonpareil x Lauranne.

BACKGROUND: Despite a high genetic similarity to peach, almonds (Prunus dulcis) have a fleshless fruit and edible kernel, produced as a crop for human consumption. While the release of peach genome v1.0 provides an excellent opportunity for almond genetic and genomic studies, well-assessed segregating populations and the respective saturated genetic linkage maps lay the foundation for such studies to be completed in almond. RESULTS: Using an almond intraspecific cross between 'Nonpareil' and 'Lauranne' (N x L), we constructed a moderately saturated map with SSRs, SNPs, ISSRs and RAPDs. The N x L map covered 591.4 cM of the genome with 157 loci. The average marker distance of the map was 4.0 cM. The map displayed high synteny and colinearity with the Prunus T x E reference map in all eight linkage groups (G1-G8). The positions of 14 mapped gene-anchored SNPs corresponded approximately with the positions of homologous sequences in the peach genome v1.0. Analysis of Mendelian segregation ratios showed that 17.9% of markers had significantly skewed genotype ratios at the level of P < 0.05. Due to the large number of skewed markers in the linkage group 7, the potential existence of deleterious gene(s) was assessed in the group. Integrated maps produced by two different mapping methods using JoinMap® 3 were compared, and their high degree of similarity was evident despite the positional inconsistency of a few markers. CONCLUSIONS: We presented a moderately saturated Australian almond map, which is highly syntenic and collinear with the Prunus reference map and peach genome V1.0. Therefore, the well-assessed almond population reported here can be used to investigate the traits of interest under Australian growing conditions, and provides more information on the almond genome for the international community.

Self-incompatibility genotypes in almond re-evaluated by PCR, stylar ribonucleases, sequencing analysis and controlled pollinations.

As part of the almond breeding programme at IRTA, we investigated the S genotypes of several cultivars using a combination of RNase zymograms, testcrosses, pollen-tube growth analysis and molecular identification by PCR analysis. For some of the cultivars examined, discrepancies appeared between their S alleles as reported in the literature and those found in this investigation, leading to a re-evaluation of their S genotypes. Analysis of the stylar ribonucleases (RNases), which are known to correlate with S alleles, of cvs. Achaak, Ardechoise, Desmayo Largueta, Ferrastar, Gabaix, Garbi, Glorieta, Languedoc, Primorskiy and Texas revealed inconsistencies with respect to the S5 and S10 alleles. However, PCR with the conserved primer pair AS1II/AmyC5R failed to detect any of these inconsistencies. When the S alleles from Desmayo Largueta, Gabaix, Primorskiy and Texas were sequenced, Texas and Primorskiy were found to carry the reported S5 allele, while Desmayo Largueta and Gabaix carried a new allele, which has been tentatively denoted as S25 This new S allele, previously reported to be S10, was also identified in Achaak, Ardechoise and Ferrastar. The proposed new S genotypes are Achaak (S2S25), Ardechoise (S1S25), Desmayo Largueta (S1S25), Ferrastar (S2S25) and Gabaix (S10S25). The S alleles of Garbi, Glorieta, Languedoc, Texas and Primorskiy remain as reported in the literature. Testcrosses in the field and laboratory confirmed the new S genotypes. One cultivar (Gabaix) could be assigned to the existing cross-incompatibility group O of unique genotypes, and two new groups were established (XVI and XVII) consisting of two cultivars each. The clarification of these S alleles will be useful in almond breeding programmes and for planning new commercial orchards in the future.