Article Addendum: The paradox of clonality and the evolution of self-incompatibility

In the January issue of New Phytologist Vallejo-Marín and O’Brien documented that in the genus Solanum (Solanaceae) clonality and self-incompatibility, a common genetic mechanism enforcing cross-fertilization, co-occur more often than expected by chance. Using a phylogenetic approach the authors showed that the statistical association between clonality and self-incompatibility persists even after taking into account phylogenetic relationships among species, uncertainty in the phylogenetic reconstruction, and associations between clonality and life history (annual/perennial). Vallejo-Marín and O’Brien suggest that clonality and self-incompatibility tend to co-occur because clonality, by allowing the persistence and propagation of a genotype in environments with limited pollinator or mate availability, reduces the selective pressure favoring the breakdown of self-incompatibility. In addition to promoting the maintenance of self-incompatibility, when clonality results in the spatial aggregation of genetically identical individuals, clonality may promote its breakdown by restricting pollen transfer between different genotypes. Here I call attention to these contradictory predictions of the effects of clonality on the evolution of self-incompatibility, and suggest that the outcome of this paradox depend on both the extent to which clonal propagation compensates for limited seed production, and on the extent to which clonality reduces pollen transfer between genotypes

DNA-based S-genotyping of Japanese plum and pluot cultivars to clarify incompatibility relationships

Diploid japanese plum (Prunus salicina Lindl.) cultivars are commonly self-incompatible. To date, 14 incompatibility alleles (S-alleles) have been identified and labeled with alphabetical (S-a-S-n) and 5 with numeric codes (S-1, S-3-S-6). We applied polymerase chain reaction amplification of the S-RNase alleles with degenerate and allele-specific primers in 10 japanese plum cultivars and two pluots of unknown incompatibility alleles. Besides DNA sequencing, an additional method for the exact length determination of the first intron region was used for the first time for S-genotype japanese plums. The S-3-allele was shown to correspond to S-k in the alphabetic nomenclature, S-4 to S-c, S-5 to S-e, and S-6 to S-f. The S-5-allele-specific primer can be used as a reliable marker for self-compatibility in japanese plum. 'Black Amber', 'October Sun', 'TC Sun', and 'Super Giant' share the SbSc genotype, which was confirmed by test crosses. These cultivars belong to the widest incompatibility group currently known in japanese plum. An additional incompatibility group (ScSh) was established, including 'Green Sun' and 'Queen Rosa', a cultivar formerly known as a universal donor. By incorporating all previous and recent results, a table was assembled including 49 cultivars assigned to I-VII incompatibility groups, to the self-compatible group and to the group O of unique genotypes. These data may considerably contribute to further growing and breeding activities

Identification of self-incompatibility alleles and pollen incompatibility groups in sweet cherry by PCR based s-allele typing and controlled pollination

A total of 17 pollen incompatibility groups in sweet cherry (Prunusavium L.) were identified among 46 accessions by PCR based S-alleletyping analysis and by controlled test pollinations. Two putativeS-alleles different from S 1 to S 6,S z and S y were identified. Five S-genotypes, S 1 S 5, S 1 S 6,S 2 S 6, S 4 S 6, andS 5 S 6, combinations of S 1 toS 6 alleles that had not previously been identified from cultivars in NYSAES, were positively confirmed by PCR based S-genotyping analysis. Also, the S-genotypes of cultivars in some pollen incompatibility groups that had previously been incorrectly reported have been clarified. Several popular cultivars, which were previously used as testers for S-allele typing analysis, were found to have been inaccurately genotyped. In addition, the S-genotypes and self-incompatibility groups of some relatively recentlyintroduced cultivars were identified. The molecular typing system ofS-genotypes based on PCR is a useful and rapid method for identifying newS-alleles and incompatibility groups in sweet cherr

S-Genotype Profiles of Turkish Apricot Germplasm

In flowering plants, gametophytic self-incompatibility, controlled by a single locus with several allelic variants, is one of the major problems preventing self-fertilization. Among fruit trees, apricots show to a high degree self-incompatibility, especially in Middle-Asian and Iranian-Caucasian eco-geographical groups. In the present study, self-(in)compatibility characteristics of a total of 236 apricot genotypes (218 Turkish and 18 foreign) found within the National Apricot Germplasms of Apricot Research Institute in Malatya, Turkey was studied. Analyses were carried out by using four primer pairs (SRc-F and SRc-R, EM-PC2consFD and EM-PC3consRD, AprSC8-R and PaConsI-F, AprFBC8-F and AprFBC8-R). A total of 11 S-RNase alleles (S2, S3, S6, S7, S8, S9, S11, S12, S13, S20 and Sc) were determined in the 236 apricot genotypes. As Turkish and foreign apricot genotypes are determined mostly self-incompatible, the data obtained hereby might be of good use for apricot breeding programs and more practically, for apricot new plantations; thus pollinator cultivars should be considered when self-incompatible apricot cultivars are being used

Controlling for genetic identity of varieties, pollen contamination and stigma receptivity is essential to characterize the self-incompatibility system of Olea europaea L.

open7siBervillé et al. express concern about the existence of the diallelic self-incompatibility (DSI) system in Olea europaea, mainly because our model does not account for results from previous studies from their group that claimed to have documented asymmetry of the incompatibility response in reciprocal crosses. In this answer to their comment, we present original results based on reciprocal stigma tests that contradict conclusions from these studies. We show that, in our hands, not a single case of asymmetry was confirmed, endorsing that symmetry of incompatibility reactions seems to be the rule in Olive. We discuss three important aspects that were not taken into account in the studies cited in their comments and that can explain the discrepancy: (i) the vast uncertainty around the actual genetic identity of vernacular varieties, (ii) the risk of massive contamination associated with the pollination protocols that they used and (iii) the importance of checking for stigma receptivity in controlled crosses. These studies were thus poorly genetically controlled, and we stand by our original conclusion that Olive tree exhibits DSI.openSaumitou-Laprade, Pierre; Vernet, Philippe; Vekemans, Xavier; Castric, Vincent; Barcaccia, Gianni; Khadari, Bouchaib; Baldoni, LucianaSaumitou-Laprade, Pierre; Vernet, Philippe; Vekemans, Xavier; Castric, Vincent; Barcaccia, Gianni; Khadari, Bouchaib; Baldoni, Lucian

Assessment of Almond (Prunus dulcis L.) for Self-Compatibility and Stigma Receptivity Period Based on Fruit Set Index

Regarding to the self-compatibility test the 6 genotypes under the study show low self-fertilization and categorized in self-incompatible group, in evaluating the best time for hand pollination, the emasculated genotypes in the same day show significantly difference in responding to the hand pollination in  the days After emasculation which the highest fruit set percentage recorded in 3 days after emasculation and decreased in other days when considering the 0 day to 8  days after emasculation the study shows the importance and emphasis of choosing the overlapping varieties in an orchard and considering the self- incompatibility of genotypes and pollinator in reform and development of new almond orchard

Current advances in genomics and breeding of leaf chicory (Cichorium intybus L.)

This review gives an overview of agricultural topics on a non-model species, in other words, leaf chicory. Often classified as a minor crop, \u201cRadicchio\u201d, the Italian name of leaf chicory, is assuming a very important role at both a local and national level, as it characterizes a high proportion of the agricultural income of suited areas. Botanical classification along the genus Cichorium is reported and a detailed description of the most important cultivated biotypes typical of northern Italy is presented. A special consideration is reserved to breeding aspects, from molecular marker-assisted selection to the implementation of the first genome draft and leaf transcriptomes. Sexual barriers, for example, self-incompatibility or male-sterility, are described in great detail with the aim to be utilized for breeding purposes. The main aspects of seed production are also critically presented. In conclusion, the present work is a sort of handbook to better understand this orphan crop and it is mainly directed to breeders and seed producers dealing with leaf chicory

Inheritance of self-And graft-incompatibility traits in an F 1 apricot progeny

Floral self-incompatibility affecting yearly yield in a weather-dependent manner and graft incompatibility affecting longevity of mature trees are two important traits for apricot production. However, genetic control of graft compatibility and relationship between these traits are unknown. Here, we analyzed its inheritance in an F 1 apricot progeny from a cross between self- and graft- incompatible and self- and graft-compatible cultivars. Hybrid individuals were genotyped for establishing self-incompatibility status and grafted on the plum rootstock ‘Marianna 2624’. Phenotyping of graft incompatibility was done at two time points, one month and one year after grafting. Anatomical (necrotic layer, bark and wood discontinuity for two consecutive years) and cytomorphological (cell proliferation, cell arrangement and cell shape one month after grafting) characteristics related to graft compatibility displayed continuous variation within the progeny, suggesting a polygenic inheritance. Using the Pearson correlation test, strong and significant correlations were detected between anatomical and cytomorphological traits that may reduce the number of characters for screening genotypes or progenies for graft compatibility in segregating crosses. Furthermore, no correlation existed between self- and graft incompatibility traits suggesting that they are independent inheritance traits. Hence, screening an extended hybrid population is required for pyramiding these traits in breeding programs

Asymmetrical hybridization and gene flow between Eisenia andrei and E. fetida lumbricid earthworms

Uniformly pigmented Eisenia andrei (Ea) and striped E. fetida (Ef) lumbricid earthworms are hermaphrodites capable of self-fertilization, cross-fertilization, and asymmetrical hybridization. The latter was detected by genotyping of F1 and F2 progeny of the controlled Ea+Ef pairs by species-specific sequences of maternal mitochondrial COI genes and maternal/paternal nuclear S28 rRNA genes. Among F1offspring there were self-fertilized Ea (aAA), Ef (fFF), and cross-fertilized fertile Ea-derived hybrids (aAF); the latter mated with Ea and gave new generation of Ea and hybrids, while mated with Ef gave Ea, Ef, Ea-derived hybrids and sterile Ef-derived hybrids (fFA). Coelomic fluid of Ea exhibits unique fluorescence spectra called here the M-fluorescence considered as a molecular biomarker of this species. Since similar fluorescence was detected also in some Ef (hypothetical hybrids?), the aim of present investigations was to identify the M-positive earthworms among families genotyped previously. It was assumed that factor/s responsible for metabolic pathways leading to production of undefined yet M-fluorophore might be encoded/controlled by alleles of hypothetical nuclear gene of Eisenia sp. segregating independently from species-specific S28 rRNA nuclear genes, where 'MM' or 'Mm' alleles determine M-positivity while 'mm' alleles determine M-negative phenotypes. Spectra of M-fluorescence were detected in all 10 Ea (aAAMM) and 19 Ea-derived hybrids (aAFMm), three of four Ef-derived hybrids (fFAMm) and one 'atypical' Ef (fFFMm) among 13 Ef earthworms. Among progeny of 'atypical' M-positive Ef (fFFMm) reappeared 'typical' M-negative Ef (fFFmm), confirming such hypothesis. Alternatively, the M-fluorescence might be dependent on unknown gene products of vertically-transmitted Ea-specific symbiotic bacteria sexually transferred to the Ef partner. Hypotheses of intrinsic and external origin of M-fluorescence might complement each other. The presence/absence of M-fluorophore does not correspond with body pigmentation patterns; Ef-characteristic banding appeared in posterior parts of hybrids body. In conclusion, Ea/Ef hybridization may serve for further studies on bi-directional gene flow

The effect of sheltered load on reproduction in Solanum carolinense, a species with variable self-incompatibility

In previous studies, we have investigated the strength of self-incompatibility (SI) in Solanum carolinense, a highly successful weed with a fully functional SI system that inhabits early successional and other disturbed habitats. We have found that the SI response in S. carolinense is a plastic trait—its strength being affected by the age of the flowers, and the presence of developing fruits and that there are genetic differences among families in their self-fertility. However, in species with a fully functional SI response, selfing would not be that common. As a result, deleterious recessives scattered though the genome of horsenettle are only occasionally exposed to selection. It has been suggested that deleterious recessives accumulate near S-alleles in strong SI species because the S-locus is located in a non-recombining region of the genome and because strong S-alleles are never in the homozygous state, thus sheltering some of the genetic load near the S-locus from selection. We performed a series of laboratory and greenhouse experiments to determine the extent to which sheltered load adds to the overall magnitude of inbreeding depression in horsenettle. Specifically, we amplified and sequenced the S-alleles from 16 genets collected from a large population in Pennsylvania and performed a series of controlled self-pollinations. We then grew the selfed progeny in the greenhouse; recorded various measures of growth and reproductive output; and amplified and sequenced their S-allele(s). We found that the heterozygous progeny of self-pollinations produce more flowers and have a greater ability to set both self and cross seed than S-homozygous progeny. We also found evidence of variation in the magnitude of load among S-alleles. These results suggest that sheltered load might slow the fixation of weak (partially compatible) S-alleles in this population, thus adding to the maintenance of a mixed mating system rather than leading to the fixation of the selfing allele