Júlia Halász

New self-incompatibility alleles in apricot (Prunus armeniaca L.) revealed by stylar ribonuclease assay and S-PCR analysis

Apricot (Prunus armeniaca L.) shows gametophytic self-incompatibility controlled by a single locus with several allelic variants. An allele for self-compatibility (SC) and seven alleles for self-incompatibility (S1–S7) were described previously. Our experiments were carried out to ascertain whether the number of allelic variants of apricot S-locus was indeed so small. Twenty-seven apricot accessions were analysed for stylar ribonucleases by non-equilibrium pH gradient electrofocusing (NEpHGE) to determine their S-genotype. To validate the results of electrofocusing, the applicability of the S-gene-specific consensus PCR primers designed from sweet cherry sequences was tested. NEpHGE revealed 12 bands associated with distinct S-alleles in newly genotyped cultivars. Cherry consensus primers amplified 11 alleles out from 16 ones, which indicated that these primers could also recognize most of the S-RNase sequences in apricot, and provided an efficient tool to confirm or reject NEpHGE results. By combining the protein and DNA-based methods, complete or partial S-genotyping was achieved for 23 apricot accessions and nine putatively new alleles (provisionally labelled S8–S16) were found. Their identity needs to be confirmed by pollination tests or S-allele sequencing. This study provides evidence that similarly to other Prunus species, the S-locus of apricot is more variable than previously believed.

Molecular typing of the self-incompatibility locus of Turkish sweet cherry genotypes reflects phylogenetic relationships among cherries and other Prunus species

Self-incompatibility of sweet cherry (Prunus avium L.) is controlled by the multiallelic S-locus. While many cultivars and wild accessions have been S-genotyped, only limited data are available on accessions native to the center of origin of this species. Therefore, this study was carried out to determine the S-genotype of 11 landrace cultivars and 17 local genotypes selected from populations growing wild at the Black Sea coast. Eleven sweet cherries (S1–S7, S10, and S12–S14) and some wild cherries (S17–S19, S21/25, and S31) S-RNase alleles were detected. The results indicate that Turkish cultivars represent a broader gene pool as compared with international cultivars. A new (S37) and a doubtful allele (provisionally labelled as S7m) as well as the sour cherry S34-allele were identified in sweet cherry. These data and others (SSR variants within the S13-RNase introns) confirmed that allele pools of sweet and sour cherries in the Black Sea region are overlapping. A new cross-incompatibility group, XLV (S2S18), was also proposed. Allele-specific primers were designed for S17–S19, S21/25, S34, and S37. A phylogenetic analysis of the cherry S31-RNase and its trans-specific sister alleles reliably mirrored the assumed length of the time period after the divergence of species in the subgenera Cerasus and Prunophora. Most variations (insertions/deletions and single-nucleotide polymorphisms) in the S-RNase gene were silent and, hence, have not been exposed to natural selection. The results are discussed from the aspects of S-allele evolution and phylogenetic relationships among cherries and other Prunus species.

S-genotyping of old apple cultivars from the Carpathian basin: methodological, breeding and evolutionary aspects

Apple exhibits self-incompatibility controlled by the multiallelic S-locus. Twenty-three old apple cultivars were S-genotyped using three different approaches (allele-specific polymerase chain reaction (PCR) + cleaved amplified polymorphic sequences (CAPS), consensus PCR + sequencing and consensus PCR + CAPS) to compare the robustness and reliability of these techniques and characterise genotypes from the Carpathian basin that might be useful in resistance breeding. Best results were obtained using the ASPF3 and ASPR3S consensus primer pair that detected 96% of all alleles carried by the 23 cultivars tested. Flow cytometry analysis was also needed to control the completeness of the genotypes as was seen in case of a tetraploid cultivar with only three assigned S-alleles. The genetic disparity between the old Carpathian basin and modern apple cultivars was indicated by differences in allele frequency data (S9, S24 and S26) as well as single nucleotide polymorphisms in S1, S2, S7S24 and S26 and indels in S20 and S26 alleles. An alignment of partial genomic sequences indicated trans-specific and trans-generic evolution of S-ribonuclease alleles in the Maloideae subfamily (S26 and S28) and a possibly recent introgression event (S1) between Malus × domestica and Malus sylvestris. These data suggest that the genome of old cultivars from the Carpathian basin was enriched by several Malus taxa and are free from the consequences of modern breeding. These cultivars may contribute to the widening of the genetic basis of cultivated apple and prevent genetic erosion in future commercial cultivars.

Self-(in)compatibility genotypes of Moroccan apricots indicate differences and similarities in the crop history of European and North African apricot germplasm

BackgroundAllelic diversity of the S-locus is attributed to the genetic relationships among genotypes and sexual reproduction strategy. In otherwise self-incompatible Prunus species, the emergence of loss-of-function in S-haplotypes has resulted in self-compatibility. This information may allow following major stages of crop history. The genetic diversity in the S-locus of local apricots (Prunus armeniaca L.) from different oasis ecosystems in Morocco and the comparison of the occurrence and frequency of S-alleles with other regions may allow testing the validity of previous theories on the origin and dissemination of North African apricots.ResultsThe S-genotypes of 55 Moroccan apricot accessions were determined, resulting in 37 self-compatible genotypes, from which 33 were homozygotes for self-compatibility. SC was the most frequent S-allele in this germplasm, followed by S13, S7, S11, S2, S20, S8, and S6. New approaches (CAPS or allele-specific PCR) were designed for a reliable verification of the rare or unexpected alleles. The frequency and distribution of the S-alleles differed among the oases. Some of these alleles, S8, S11, S13 and S20, were formerly detected only in the Irano Caucasian germplasm and are not present in Europe.ConclusionsOur data supports the Irano-Caucasian origin of the Moroccan apricots and their original introduction by Phoenicians and Arabs through the North African shore. North Africa seems to have preserved much higher variability of apricot as compared with Europe. The loss of genetic diversity in apricot might be explained by the occurrence of self-compatibility and the length of time that apricot has spent with this breeding system in an environment without its wild relatives, such as the Moroccan oases or Central Europe.

Identification of a recently active Prunus‐specific non‐autonomous Mutator element with considerable genome shaping force

Miniature inverted-repeat transposable elements (MITEs) are known to contribute to the evolution of plants, but only limited information is available for MITEs in the Prunus genome. We identified a MITE that has been named Falling Stones, FaSt. All structural features (349-bp size, 82-bp terminal inverted repeats and 9-bp target site duplications) are consistent with this MITE being a putative member of the Mutator transposase superfamily. FaSt showed a preferential accumulation in the short AT-rich segments of the euchromatin region of the peach genome. DNA sequencing and pollination experiments have been performed to confirm that the nested insertion of FaSt into the S-haplotype-specific F-box gene of apricot resulted in the breakdown of self-incompatibility (SI). A bioinformatics-based survey of the known Rosaceae and other genomes and a newly designed polymerase chain reaction (PCR) assay verified the Prunoideae-specific occurrence of FaSt elements. Phylogenetic analysis suggested a recent activity of FaSt in the Prunus genome. The occurrence of a nested insertion in the apricot genome further supports the recent activity of FaSt in response to abiotic stress conditions. This study reports on a presumably active non-autonomous Mutator element in Prunus that exhibits a major indirect genome shaping force through inducing loss-of-function mutation in the SI locus.

Identification of self-(in)compatibility S-alleles and new cross-incompatibility groups in Tunisian apricot (Prunus armeniaca L.) cultivars

Summary Local Tunisian apricot (Prunus armeniaca L.) cultivars are characterised by having abundant flowering and floral self-incompatibility. In this study, PCR amplification provided definitive data on the S-genotypes of eight local and four new Tunisian apricot cultivars. These results were confirmed by field evaluations. Eight local cultivars (‘Oud Rhayem’, ‘Oud Hmida’, ‘Bouthani Ben Friha’, ‘Bedri Ahmar’, ‘Oueld El Oud’, ‘Hamidi’, ‘Bouk Ahmed’, and ‘Adedi Ahmar’) were found to be self-incompatible and three of four INRAT cultivars (‘Sayeb’, ‘Asli’, and ‘Raki’) were self-compatible, as described previously. The INRAT cultivar ‘Ouardi’ was self-incompatible, although it was previously described as a self-compatible cultivar.We also propose three new cross-incompatibility (CIG) groups: CIG XV (S7S8), CIG XVI (S7S11), and CIG XVII (S8S12) which include Tunisian and other cultivars.

Self-(in)compatibility and fruit set in 19 local Moroccan apricot (Prunus armeniaca L.) genotypes

Summary Self-compatibility and fruit set were assessed in 19 local apricot (Prunus armeniaca L.) genotypes identified in four different oasis ecosystems in southern Morocco. Observations on pollen tube growth, as well as examinations of the fruit-set percentages obtained after self-pollination in the field, established the compatibility of their pollen. Fourteen genotypes from different geographical origins were self-compatible, with fruit set percentages ranging from 14.8 – 42.2%, whereas five were self-incompatible, with no fruit set. Consequently, almost all the local apricot genotypes propagated by seed in oasis ecosystems in southern Morocco proved to be self-compatible. In addition, the fruit-set percentages after open-pollination showed high variability among genotypes from the same oasis, among locations, and in the 2 years of study, with medium-to-high fruit set percentages for all genotypes, ranging from 11.9 – 30.1%. Self-compatibility has therefore been identified for the first time, not only in Moroccan apricot genotypes, but also in the North African Prunus gene pool.