Inbreeding and true seed in tetrasomic potato. I. Selfing and open pollination in Andean landraces (Solanum tuberosum Gp. Andigena)

 True potato seed (TPS) may be an alternative method of potato production in developing countries. A breeding method for the sexual propagation of this vegetatively propagated crop should consider the development of parental lines and the type of cultivar to be released. Open-pollinated (OP) cultivars seem to be an inexpensive procedure to produce potato from true seed. However, OP progenies are the result of selfing and outcrossing in male-fertile tetraploid potatoes. The aim of the present research was to establish the effect of inbreeding and open pollination in TPS. Ten Andigena clones were used as parental material to derive hybrid (S₀), inbred (S₁ and S₂), and open-pollinated (OP₁ and OP₂) generations. Significant differences among generations were found for pollen production, pollen viability (as determined by its stainability with aceto-carmine glycerol), number of flowers and berries plant^-1, number of seeds berry^-1, weight of 1000 seeds, and tuber yield plant^-1. The parental populations were significantly different for most of the traits, but not for flower production and berry weight. The interaction of population ×generation was significant for pollen and seed production as well as for weight for 1000 seeds. All the traits evaluated except seed weight showed a strong inbreeding depression, while the OP progenies had intermediate values between the S₀ and the S₁. This demonstrates that open pollination in potatoes is not exclusively the product of selfing; it also results from outcrossing. Received: 10 November 1997 / Accepted: 3 March 1998     

Genetic analysis of incompatibility in the diploid Ipomoea species closely related to the sweet potato

Summary In order to identify the genotypic constitutions of incompatibility in the diploid species, Ipomoea leucantha Jacq. (K221), which is most closely related to the sweet potato, the progenies derived from the reciprocal crosses, backcrosses and testcrosses were analysed. All the plants examined were self-incompatible, and pollen germination was inhibited on the stigma after incompatible pollinations. No reciprocal differences were found in the incompatibility reactions. In the progenies three incompatibility groups were observed which showed the rather simple segregation ratios. The homozygous plants for incompatibility alleles were obtained in the progenies. The experimental results demonstrated a sporophytic type of incompatibility controlled by a single locus with multiple S-alleles exhibiting a dominance relationship in both the pollen and the stigma. The plants obtained in the progenies had the following genotypes: S ₁ S ₂, S ₁ S ₃, S ₂ S ₂, S ₂ S ₃ and S ₃ S ₃.     

Molecular and Genetic Analyses of Four Nonfunctional S Haplotype Variants Derived from a Common Ancestral S Haplotype Identified in Sour Cherry (Prunus cerasus L.)

Tetraploid sour cherry (Prunus cerasus) has an S-RNase-based gametophytic self-incompatibility (GSI) system; however, individuals can be either self-incompatible (SI) or self-compatible (SC). Unlike the situation in the Solanaceae, where self-compatibility accompanying polyploidization is often due to the compatibility of heteroallelic pollen, the genotype-dependent loss of SI in sour cherry is due to the compatibility of pollen containing two nonfunctional S haplotypes. Sour cherry individuals with the S₄S₆S_36aS_36b genotype are predicted to be SC, as only pollen containing both nonfunctional S_36a and S_36b haplotypes would be SC. However, we previously found that individuals of this genotype were SI. Here we describe four nonfunctional S₃₆ variants. Our molecular analyses identified a mutation that would confer loss of stylar S function for one of the variants, and two alterations that might cause loss of pollen S function for all four variants. Genetic crosses showed that individuals possessing two nonfunctional S₃₆ haplotypes and two functional S haplotypes have reduced self-fertilization due to a very low frequency of transmission of the one pollen type that would be SC. Our finding that the underlying mechanism limiting successful transmission of genetically compatible gametes does not involve GSI is consistent with our previous genetic model for Prunus in which heteroallelic pollen is incompatible. This provides a unique case in which breakdown of SI does not occur despite the potential to generate SC pollen genotypes.GAMETOPHYTIC self-incompatibility (GSI) is a widespread mechanism in flowering plants that prevents self-fertilization and promotes out-crossing (De Nettancourt 2001). In GSI plants, pollen tube growth is arrested if there is a match between the genes at the S-locus that control pollen and stylar specificity. The gene controlling stylar specificity in the Solanaceae, Rosaceae, and Plantaginaceae is known to encode a ribonuclease (S-RNase) (for a review see McClure 2009), while the gene controlling pollen specificity encodes an F-box protein [S haplotype-specific F-box protein (SFB) or S-locus F-box protein (SLF)] (Lai et al. 2002; Entani et al. 2003; Ushijima et al. 2003; Sijacic et al. 2004). As these two specificity genes are tightly linked and recombination between these two genes has never been observed (Ikeda et al. 2005), these two S-locus specificity genes are collectively termed the S haplotype.Characterization of the S haplotype is most advanced in Prunus (Rosaceae) due to the small physical size of the S haplotype region and the close proximity of the stylar S (S-RNase) and pollen S (SFB) genes (Entani et al. 2003; Ushijima et al. 2003; Yamane et al. 2003b; Ikeda et al. 2005). Within Prunus, sweet cherry (Prunus avium) and sour cherry (P. cerasus) represent a model diploid–tetraploid series that has been used to investigate the effects of polyploidy on GSI. Tetraploid sour cherry is considered to have arisen through hybridization between sweet cherry and tetraploid ground cherry (P. fruticosa) (Olden and Nybom 1968). Like sweet cherry, sour cherry exhibits an S-RNase-based GSI system (Yamane et al. 2001; Hauck et al. 2002; Tobutt et al. 2004) and interspecific crossing studies have demonstrated that sour cherry shares eight sweet cherry S haplotypes: S₁, S₄, S₆, S₉, S₁₂, S₁₃, S₁₄, and S₁₆ (Bošković et al. 2006; Hauck et al. 2006a,b; Tsukamoto et al. 2006, 2008). However, in contrast to sweet cherry, natural sour cherry selections include both self-incompatible (SI) and self-compatible (SC) types. A genetic model demonstrating that the genotype-dependent loss of SI in sour cherry is due to the accumulation of a minimum of two nonfunctional S haploytpes within a single individual was developed and validated (Hauck et al. 2006b). These nonfunctional S haplotypes were characterized as either pollen-part mutants or stylar-part mutants, depending on whether the pollen S or stylar S specificity was disrupted. In Prunus, pollen-part and stylar-part mutants are denoted by a prime symbol “′” or a subscribed “m,” respectively, following the S haplotype number (Tsukamoto et al. 2006). Molecular characterizations of five of the nonfunctional S haplotypes from sour cherry characterized to date support the genetic results because mutations were identified that affected the S-RNase and/or SFB. These changes in coding or regulatory regions included mutations within the S-RNase and/or SFB causing premature stop codons, transposable element insertions within SFB and upstream of the S-RNase, and a 23-bp deletion in a conserved region of the S-RNase (Yamane et al. 2003a; Hauck et al. 2006a; Tsukamoto et al. 2006).According to the genetic model, termed the “one-allele-match model,” sour cherry pollen is rejected if one or both of the functional S haplotypes in the 2x pollen grain match an S haplotype in the style (Hauck et al. 2006b). Therefore, only pollen containing two nonfunctional S haplotypes would be SC; thus, a sour cherry genotype is SC if it has a minimum of two nonfunctional S haplotypes. We previously tested the one-allele-match model using 92 sour cherry selections from four progeny populations (Hauck et al. 2006b). For all the progeny except three, their S genotype correctly predicted whether they were SI or SC. The three progeny individuals that were the exception all had the same genotype: S₄S₆S_aS_d. These individuals were predicted to be SC as the S_a and S_d haplotypes were shown to be nonfunctional in genetic studies and therefore S_aS_d pollen should be SC. However, these progeny were classified as SI on the basis of observations of self-pollen tube growth in the styles. The S_a and S_d haplotypes were originally distinguished on the basis of different RFLP fragment sizes using an S-RNase probe; the HindIII fragment sizes for S_a and S_d differed by ∼200 bp, 6.4-kb and 6.2-kb, respectively (Yamane et al. 2001; Hauck et al. 2002). However, partial S-RNase and SFB sequences from the S_a and S_d haplotypes were identical (N. R. Hauck and A. F. Iezzoni, unpublished results), suggesting that S_a and S_d represented different mutations of the same S haplotype. Therefore, we hypothesized that the SI phenotype of the S₄S₆S_aS_d individuals resulted from complementary pistil S and pollen S mutations in the nonfunctional S_a and S_d haplotypes, thus behaving genetically as one functional S haplotype.We previously reported that heteroallelic sour cherry pollen containing two different functional pollen S haplotypes is incompatible (Hauck et al. 2006b). This finding is counter to the well-documented phenomenon in the Solanaceae where SC accompanying polyploidization is frequently due to the SC of heteroallelic pollen (Lewis 1943; Golz et al. 1999, 2001; Tsukamoto et al. 2005; Xue et al. 2009). Therefore, models explaining the molecular basis of self-recognition in Prunus and the Solanaceae must be consistent with these differing genetic expectations. Recently, Huang et al. (2008) reported competitive interaction in a SC selection of tetraploid P. pseudocerasus, raising the possibility that the SC mechanism between these two tetraploid Prunus species could be different. However, although the data in Huang et al. (2008) are consistent with heteroallelic pollen being SC, homoallelic pollen (e.g., S₁S₁, S₅S₅, or S₇S₇) was not shown to be successful in compatible crosses and unsuccessful in incompatible ones. Therefore, it is possible that the SC in P. pseudocerasus could be caused by mutations in other genes critical for the SI reaction. Because of the importance of these differing genetic expectations for understanding S-RNase-based GSI, we sought to investigate our previously identified exceptions to the one-allele-match model. Specifically, our objective was to test our prior hypothesis that the nonfunctional S_a and S_d haplotypes interact in a complementary manner and therefore behave together genetically as a single functional S haplotype. In this work, the S_a and S_d haplotypes were renamed S_36a and S_36b, respectively, following the order of previously published S haplotypes (Tsukamoto et al. 2008; Vaughan et al. 2008) for reasons explained in the results.     

Inheritance of Hetero-Diploid Pollen S-Haplotype in Self-Compatible Tetraploid Chinese Cherry (Prunus pseudocerasus Lindl)

The breakdown of self-incompatibility, which could result from the accumulation of non-functional S-haplotypes or competitive interaction between two different functional S-haplotypes, has been studied extensively at the molecular level in tetraploid Rosaceae species. In this study, two tetraploid Chinese cherry (Prunus pseudocerasus) cultivars and one diploid sweet cherry (Prunus avium) cultivar were used to investigate the ploidy of pollen grains and inheritance of pollen-S alleles. Genetic analysis of the S-genotypes of two intercross-pollinated progenies showed that the pollen grains derived from Chinese cherry cultivars were hetero-diploid, and that the two S-haplotypes were made up of every combination of two of the four possible S-haplotypes. Moreover, the distributions of single S-haplotypes expressed in self- and intercross-pollinated progenies were in disequilibrium. The number of individuals of the two different S-haplotypes was unequal in two self-pollinated and two intercross-pollinated progenies. Notably, the number of individuals containing two different S-haplotypes (S₁- and S₅-, S₅- and S₈-, S₁- and S₄-haplotype) was larger than that of other individuals in the two self-pollinated progenies, indicating that some of these hetero-diploid pollen grains may have the capability to inactivate stylar S-RNase inside the pollen tube and grow better into the ovaries.     

Self-incompatibility in passion fruit: evidence of two locus genetic control

 The self-incompatibility in yellow passion fruit was previously described as homomorphic sporophytic with monofactorial inheritance. Five progenies were obtained by bud-selfing. The plants of these progenies were selfed, reciprocally crossed within each progeny and crossed with known incompatible phenotypes to identify their phenotypic group. Fruit set was evaluated at the 7th day after pollination. Two progenies consisted of two self-incompatible groups, the other three formed three suck groups. The groups were identified as S₁, S₂, S₃, S₄, S₅ and S₆. The results provide evidence that the self-incompatibility of passion fruit is controlled by two loci, the S-gene and another, whose expression needs to be investigated. Received: 20 June 1998 / Accepted: 13 July 1998     

Fine Mapping of ui6.1, a Gametophytic Factor Controlling Pollen-Side Unilateral Incompatibility in Interspecific Solanum Hybrids

Unilateral incompatibility (UI) is a prezygotic reproductive barrier in plants that prevents fertilization by foreign (interspecific) pollen through the inhibition of pollen tube growth. Incompatibility occurs in one direction only, most often when the female is a self-incompatible species and the male is self-compatible (the “SI × SC rule”). Pistils of the wild tomato relative Solanum lycopersicoides (SI) reject pollen of cultivated tomato (S. lycopersicum, SC), but accept pollen of S. pennellii (SC accession). Expression of pistil-side UI is weakened in S. lycopersicum × S. lycopersicoides hybrids, as pollen tube rejection occurs lower in the style. Two gametophytic factors are sufficient for pollen compatibility on allotriploid hybrids: ui1.1 on chromosome 1 (near the S locus), and ui6.1 on chromosome 6. We report herein a fine-scale map of the ui6.1 region. Recombination around ui6.1 was suppressed in lines containing a short S. pennellii introgression, but less so in lines containing a longer introgression. More recombinants were obtained from female than male meioses. A high-resolution genetic map of this region delineated the location of ui6.1 to ∼0.128 MU, or 160 kb. Identification of the underlying gene should elucidate the mechanism of interspecific pollen rejection and its relationship to self-incompatibility.FLOWERING plants have evolved several reproductive barriers for preventing illegitimate hybridization with related species. These barriers may be expressed prefertilization and/or postfertilization. Unilateral incompatibility or incongruity (UI) is a prefertilization barrier that occurs when pollen of one species is rejected on pistils of a related species, while no rejection occurs in the reciprocal cross (De Nettancourt 1977). In theory, unilateral incompatibility should reinforce species identity in natural, sympatric populations of related taxa. This barrier also impedes the efforts of plant breeders to transfer traits from wild species into related crop plants. For example, the transfer of cytoplasmic traits from species with maternally inherited chloroplasts and mitochondria may be prevented by unilateral crossing barriers. Nuclear-encoded traits may also be inaccessible if F₁ interspecific hybrids are both male sterile and incompatible as female parents.In the Solanaceae, unilateral incompatibility is observed in crosses between cultivated tomato (Solanum lycopersicum, formerly Lycopersicon esculentum) and some related wild species. In general, pistils of the cultivated tomato act as a “universal acceptor,” in that they fail to recognize and reject pollen of other tomato species. In the reciprocal crosses, pollen of S. lycopersicum is rejected on styles of virtually all of the green-fruited species, but not on styles of other red or orange-fruited species (reviewed by Mutschler and Liedl 1994). This pattern is mostly consistent with the “SI × SC” rule, wherein pollen of self-compatible (SC) species (including cultivated tomato) are rejected on pistils of self-incompatible (SI) species, but not in the reverse direction (Lewis and Crowe 1958). Exceptions to the SI × SC rule in the tomato clade include species or populations that have lost self-incompatibility but retain the ability to reject pollen of tomato. This is the case for the facultative outcrossing species S. chmielewskii, the autogamous S. neorickii (formerly L. parviflorum), as well as marginal SC populations of normally SI species such as S. pennellii and S. habrochaites (formerly L. hirsutum). An SC accession of S. pennellii, LA0716, is exceptional in having lost the ability to reject self pollen, while retaining the ability to serve as pollen parent on styles of SI accessions of this species (and other SI species, including S. peruvianum and S. lycopersicoides) (Hardon 1967; Rick 1979; Quiros et al. 1986). In this regard, S. pennellii LA0716 conforms to the Lewis and Crowe (1958) model in that it behaves like a transitional form lacking SI function in the pistil but not in the pollen.Unilateral incompatibility may also occur in crosses between populations or races of a single species. In S. habrochaites for example, pollen from SC biotypes located at the northern or southern margins of its geographic range is rejected on pistils of the central, SI populations (Martin 1961, 1963). Furthermore, pollen from the northern SC group is rejected by styles of the southern SC populations. Yet pistils of both SC biotypes are able to reject pollen of cultivated tomato. Thus there appear to be at least three distinct unilateral crossing barriers, just within S. habrochaites, possibly indicating different pollen tube recognition and rejection systems. The F₁ N × S hybrid is SC, as expected, but SI plants are recovered in the F₂ generation, suggesting that the loss of SI occurred via independent mutations in the north and the south (Rick and Chetelat 1991).Interspecific F₁ hybrids between SI wild species and SC cultivated tomato are self-incompatible and reject pollen of cultivated tomato, indicating both traits are at least partially dominant (McGuire and Rick 1954; Martin 1963; Hardon 1967). Interestingly, pollen of the F₁ hybrids is incompatible on pistils of the wild species parent (i.e., including other individuals of the same accessions, but with nonmatching S alleles). This observation suggests that there are dominant factors from cultivated tomato that lead to pollen rejection on styles of the wild species, regardless of the pollen genotype. This apparent sporophytic effect contrasts with the purely gametophytic nature of pollen SI specificity in the Solanaceae (De Nettancourt 1977).Early studies of the inheritance of unilateral incompatibility in tomato suggested the involvement of several genes controlling the pistil response; however, the genetics of pollen responses have received little attention. In F₂ S. habrochaites (northern SC accession) × S. habrochaites (central SI accession), the rejection of pollen from the SC parent segregated as if controlled by one to two dominant genes from the SI accession (Martin 1964). In crosses of S. lycopersicum to both SI and SC accessions of S. pennellii, the intra- and interspecific crossing relations were largely consistent with the Lewis and Crowe (1958) model of stepwise mutation at the S locus (Hardon 1967); there was also evidence of a second barrier in the SC S. pennellii accession. In F₁ and BC₁ hybrids of S. lycopersicum × S. habrochaites, the segregation of unilateral and self-incompatibilities was consistent with the action of two major genes, with minor polygenes indicated as well (Martin 1967). More recently, several QTL underlying pistil-side unilateral and self-incompatibilities were mapped in BC₁ S. lycopersicum × S. habrochaites (Bernacchi and Tanksley 1997); the major QTL for both forms of pollen rejection was located at or near the S locus on chromosome 1, which controls SI specificity (Tanksley and Loaiza-Figueroa 1985).There are little data on pollen-side unilateral incompatibility factors in the tomato clade, or any other system. Our previous work identified two to three genetic loci from S. pennellii that are required for pollen to overcome incompatibility on pistils of S. lycopersicum × S. lycopersicoides or S. lycopersicum × S. sitiens hybrids (Chetelat and Deverna 1991; Pertuze et al. 2003). One of these factors mapped to the S locus, the other two were on chromosomes 6 and 10. In this system the female tester stocks were either diploid or allotriploid hybrids, the latter containing one genome of the wild, SI parent, plus two genomes of cultivated tomato; both types of hybrids reject pollen of cultivated tomato. The pollen parents were either F₁ S. lycopersicum × S. pennellii or bridging lines developed by backcrossing the F₁ to cultivated tomato and selecting for the ability to overcome stylar incompatibility. In the progeny, distorted segregation ratios were observed in which the S. pennellii alleles were preferentially transmitted, indicating linkage to gametophytic factors required forcompatibility.This experimental system has several advantages for detecting pollen (gametophytic) unilateral incompatibility genes. First, pollen-expressed factors are readily distinguished from pistil factors because only the former show linkage to S. pennellii specific markers. Second, pollen rejection is by unilateral, not self-incompatibility, since both species contributing to the pollen genotype, S. lycopersicum and S. pennellii, are SC. Finally, as we describe herein, the rejection of tomato pollen by pistils of the interspecific hybrids is weakened by the decreasing dosage of the S. lycopersicoides genome, which reduces the number of pollen factors required for compatibility. Thus, the gametophytic factors on chromosomes 1 and 6 (denoted hereinafter ui1.1 and ui6.1), when present in the same pollen, are sufficient for full compatibility on pistils of allotriploid interspecific hybrids, whereas they confer only partial compatibility on diploid hybrids.Our overall objectives are to identify the genes underlying both the chromosome 1 and chromosome 6 pollen-specific unilateral incompatibility factors from S. pennellii and to determine the nature of their interaction. Toward this goal, we report herein the high-resolution genetic and physical mapping of the ui6.1 region.     

Genetic Diversity of Some Pear Cultivars and Genotypes Using Simple Sequence Repeat (SSR) Markers

The genetic diversity and relationships among 47 pear cultivars and genotypes (Pyrus spp.), including 4 Japanese pears (Pyrus pyrifolia), 40 European pears (Pyrus communis), 1 Chinese pear (Pyrus bretschneideri) as well as 2 wild relatives (Pyrus salicifolia and Pyrus mazandaranica) were studied using 28 microsatellite primer pairs. A total of 174 alleles were produced at the 28 SSR loci with their sizes ranging from 81 to 290?bp. The number of observed alleles for each locus ranged from 3 (TsuENH014 and TsuENH046) to 12 (NB103a), with an average of 6.21 alleles per locus. In some SSR loci, more than two alleles were amplified in some cultivars and genotypes, suggesting that duplication has occurred in those accessions. This information suggests that at least two genomic regions exist for these loci in the pear genome. The observed heterozygosity (H _o) values of amplified loci ranged from 0.17 (TsuENH006) to 0.97 (NB103a). Shannon's information index (I) value was observed to be highest (2.14) in the NB103a locus, while the TsuENH006 locus had the lowest value with an average of 1.37 among SSR loci. The Dice genetic similarity coefficient ranged from 0.29 (??Nijisseiki?? and P. mazandaranica) to 0.91 (??Chojuro?? and ??Nijisseiki??) among samples. UPGMA cluster analysis showed two major groups corresponding to the Japanese and European pears.     

CoNi2S4‐Graphene‐2D‐MoSe2 as an Advanced Electrode Material for Supercapacitors

3D CoNi₂S₄‐graphene‐2D‐MoSe₂ (CoNi₂S₄‐G‐MoSe₂) nanocomposite is designed and prepared using a facile ultrasonication and hydrothermal method for supercapacitor (SC) applications. Because of the novel nanocomposite structures and resultant maximized synergistic effect among ultrathin MoSe₂ nanosheets, highly conductive graphene and CoNi₂S₄ nanoparticles, the electrode exhibits rapid electron and ion transport rate and large electroactive surface area, resulting in its amazing electrochemical properties. The CoNi₂S₄‐G‐MoSe₂ electrode demonstrates a maximum specific capacitance of 1141 F g^?1, with capacitance retention of ≈108% after 2000 cycles at a high charge–discharge current density of 20 A g^?1. As to its symmetric device, 109 F g^?1 at a scan rate of 5 mV s^?1 is exhibited. This pioneering work should be helpful in enhancing the capacitive performance of SC materials by designing nanostructures with efficient synergetic effects.     

Evaluation of photosynthetic electron flow using simultaneous measurements of gas exchange and chlorophyll fluorescence under photorespiratory conditions

Simultaneous measurements of leaf gas exchange and chlorophyll fluorescence for Koelreuteria paniculata Laxm. at 380 ± 5.6 and 600 ± 8.5 ??mol mol^?1 were conducted, and the photosynthetic electron flow via photosystem II (PSII) to photosynthesis, photorespiration, and other electron-consuming processes were calculated. The results showed that the photosynthetic electron flow associated with carboxylation (J _c), oxygenation (J _o), and other electron-consuming processes (J _r) were 72.7, 45.7, and 29.4 ??mol(e^?) m^?2 s^?1 at 380 ??mol mol^?1, respectively; and 86.1, 35.3, and 48.2 ??mol(e^?) m^?2 s^?1 at 600 ??mol mol^?1, respectively. Our results revealed that other aspects associated with electronconsuming processes, except for photosynthesis and respiration, were neither negligible nor constant under photorespiratory conditions. Using maximum net photosynthetic rate (P _max), day respiration (R), photorespiration rate (R _l), and maximum electron flow via PSII (J _max), the use efficiency of electrons via PSII at saturation irradiance to fix CO₂ was calculated. The calculated results showed that the use efficiency of electrons via PSII to fix CO₂ at 600 ??mo^l mol^?1 was almost as effective as that at 380 ??mol mol^?1, even though more electrons passed through PSII at 600 ??mol mol^?1 than at 380 ??mol mol^?1.     

Expression of CMS in Zygotic and Apozygotic Progenies of Sugar Beet Beta vulgaris L.

Zygotic and apozygotic progenies of sugar beet exhibit high phenotypic variation with respect to cytoplasmic male sterility (CMS). There are progenies with completely sterile, semisterile, semifertile, and fertile pollen. The proportions of semifertile and fertile plants in zygotic and apozygotic progenies varied from zero to 28% and from zero to 17.8%, respectively. Comparison of the phenotypic distributions in zygotic and apozygotic progenies did not reveal significant differences in the CMS expression, although the latter is determined by the maternal S-plasmotype and both maternal and paternal (pollinator) genotypes in zygotic progenies and only by the maternal S-plasmotype and genotype in apozygotic progenies. It has been hypothesized that the instability of the CMS expression in apozygotic progenies is determined by epigenetic variation in the activities of the genes that control the maintenance of the pollen-grain sterility. Inactivated dominant alleles R f ⁰ ₁ and R f ⁰ ₂ in homozygous state may function as sterility maintenance genes, whereas activation of these alleles during ontogeny results in a partial or complete restoration of pollen-grain fertility. It was demonstrated that pollen fertility of mother plants withS cytoplasm did not affect the CMS expression in two sib progenies. Conversely, in two other progenies, the proportion of fertile plants was significantly higher in the sib progenies of mother plants with fertile pollen and S cytoplasm (inheritance of epigenetic variation).     

A farnesyl pyrophosphate synthase gene expressed in pollen functions in S‐RNase‐independent unilateral incompatibility

Multiple independent and overlapping pollen rejection pathways contribute to unilateral interspecific incompatibility (UI). In crosses between tomato species, pollen rejection usually occurs when the female parent is self‐incompatible (SI) and the male parent self‐compatible (SC) (the ‘SI × SC rule’). Additional, as yet unknown, UI mechanisms are independent of self‐incompatibility and contribute to UI between SC species or populations. We identified a major quantitative trait locus on chromosome 10 (ui10.1) which affects pollen‐side UI responses in crosses between cultivated tomato, Solanum lycopersicum, and Solanum pennelliiLA0716, both of which are SC and lack S‐RNase, the pistil determinant of S‐specificity in Solanaceae. Here we show that ui10.1 is a farnesyl pyrophosphate synthase gene (FPS2) expressed in pollen. Expression is about 18‐fold higher in pollen of S. pennellii than in S. lycopersicum. Pollen with the hypomorphic S. lycopersicum allele is selectively eliminated on pistils of the F₁ hybrid, leading to transmission ratio distortion in the F₂ progeny. CRISPR/Cas9‐generated knockout mutants (fps2) in S. pennelliiLA0716 are self‐sterile due to pollen rejection, but mutant pollen is fully functional on pistils of S. lycopersicum. F₂ progeny of S. lycopersicum × S. pennellii (fps2) show reversed transmission ratio distortion due to selective elimination of pollen bearing the knockout allele. Overexpression of FPS2 in S. lycopersicum pollen rescues the pollen elimination phenotype. FPS2‐based pollen selectivity does not involve S‐RNase and has not been previously linked to UI. Our results point to an entirely new mechanism of interspecific pollen rejection in plants.     

Revised dominance hierarchy for S-alleles in Corylus avellana L.

Pollen-stigma compatibility was studied in cultivars and more than 1800 seedlings of the European hazelnut (Corylus avellana L). Four new S-alleles were identified, bringing the total to 25 unique alleles within C. avellana. The new alleles are the recessive alleles in ‘Tonda di Giffoni’ and ‘Segorbe’ (S₂₃), in ‘Neue Riesennuss’ (S₂₅), in ‘Gasaway’ (S₂₆), and a dominant allele in a seedling of Turkish origin (S₂₄). Dominance relationships in 233 of the possible 300 pairs of alleles were determined in both pistil and pollen. All alleles exhibited independent action in the pistil, whereas in the pollen either dominance or codominance was exhibited. The dominance hierarchy of alleles in the pollen was revised in light of the new information obtained. All 25 alleles have been assigned to a level in the hierarchy that is linear and now has eight levels. S₆ and S₉ were reassigned to lower levels in the hierarchy. Thirteen of the alleles are on the level of S₁, while S₄, S₆, S₁₁, and S₂₃ occupy unique positions in the hierarchy. Improved pollen tester clones were identified for several S-alleles. The alleles in 55 cultivars were determined. The alleles identified in ‘DuChilly’ (S₁₀ S₁₄) did not agree with previous reports. Four cultivars have the same alleles as ‘Römische Nuss’ (S₁₀ S₁₈) and are morphologically indistinguishable from it: ‘Frutto-grosso’, ‘Istarski Okrogloplodna’, ‘Payrone’, and ‘Romai’. ‘Belle di Giubilino’ and ‘Tonda di Biglini’ are both S₁ S₁₀ and appear to be synonyms for the same cultivar.     

Ubiquitination of S4-RNase by S-LOCUS F-BOX LIKE2 Contributes to Self-Compatibility of Sweet Cherry ‘Lapins’

Recent studies have shown that loss of pollen-S function in S₄′ pollen from sweet cherry (Prunus avium) is associated with a mutation in an S haplotype-specific F-box4 (SFB4) gene. However, how this mutation leads to self-compatibility is unclear. Here, we examined this mechanism by analyzing several self-compatible sweet cherry varieties. We determined that mutated SFB4 (SFB4ʹ) in S4′ pollen (pollen harboring the SFB4ʹ gene) is approximately 6 kD shorter than wild-type SFB4 due to a premature termination caused by a four-nucleotide deletion. SFB4′ did not interact with S-RNase. However, a protein in S4′ pollen ubiquitinated S-RNase, resulting in its degradation via the 26S proteasome pathway, indicating that factors in S4′ pollen other than SFB4 participate in S-RNase recognition and degradation. To identify these factors, we used S₄-RNase as a bait to screen S4′ pollen proteins. Our screen identified the protein encoded by S₄-SLFL2, a low-polymorphic gene that is closely linked to the S-locus. Further investigations indicate that SLFL2 ubiquitinates S-RNase, leading to its degradation. Subcellular localization analysis showed that SFB4 is primarily localized to the pollen tube tip, whereas SLFL2 is not. When S₄-SLFL2 expression was suppressed by antisense oligonucleotide treatment in wild-type pollen tubes, pollen still had the capacity to ubiquitinate S-RNase; however, this ubiquitin-labeled S-RNase was not degraded via the 26S proteasome pathway, suggesting that SFB4 does not participate in the degradation of S-RNase. When SFB4 loses its function, S₄-SLFL2 might mediate the ubiquitination and degradation of S-RNase, which is consistent with the self-compatibility of S4′ pollen.

In sweet cherry (Prunus avium), self-incompatibility is mainly controlled by the S-locus, which is located at the end of chromosome 6 (Akagi et al., 2016; Shirasawa et al., 2017). Although the vast majority of sweet cherry varieties show self-incompatibility, some self-compatible varieties have been identified, most of which resulted from the use of x-ray mutagenesis and continuous cross-breeding (Ushijima et al., 2004; Sonneveld et al., 2005). At present, naturally occurring self-compatible varieties are rare (Marchese et al., 2007; Wünsch et al., 2010; Ono et al., 2018). X-ray-induced mutations that have given rise to self-compatibility include a 4-bp deletion (TTAT) in the gene encoding an SFB4′ (S-locus F-box 4′) protein, located in the S-locus and regarded as the dominant pollen factor in self-incompatibility. This mutation is present in the first identified self-compatible sweet cherry variety, ‘Stellar’, as well as in a series of its self-compatible descendants, including ‘Lapins’, ‘Yanyang’, and ‘Sweet heart’ (Lapins, 1971; Ushijima et al., 2004). Deletion of SFB3 and a large fragment insertion in SFB5 have also been identified in other self-compatible sweet cherry varieties (Sonneveld et al., 2005; Marchese et al., 2007). Additionally, a mutation not linked to the S-locus (linked instead to the M-locus) could also cause self-compatibility in sweet cherry and closely related species such as apricot (Prunus armeniaca; Wünsch et al., 2010; Zuriaga et al., 2013; Muñoz-Sanz et al., 2017; Ono et al., 2018). Much of the self-compatibility in Prunus species seems to be closely linked to mutation of SFB in the S-locus (Zhu et al., 2004; Muñoz-Espinoza et al., 2017); however, the mechanism of how this mutation of SFB causes self-compatibility is unknown.The gene composition of the S-locus in sweet cherry differs from that of other gametophytic self-incompatible species, such as apple (Malus domestica), pear (Pyrus spp.), and petunia (Petunia spp.). In sweet cherry, in addition to a single S-RNase gene, the S-locus contains one SFB gene, which has a high level of allelic polymorphism, and three SLFL (S-locus F-box-like) genes with low levels of, or no, allelic polymorphism (Ushijima et al., 2004; Matsumoto et al., 2008). By contrast, the apple, pear, and petunia S-locus usually contains one S-RNase and 16 to 20 F-box genes (Kakui et al., 2011; Okada et al., 2011, 2013; Minamikawa et al., 2014; Williams et al., 2014a; Yuan et al., 2014; Kubo et al., 2015; Pratas et al., 2018). The F-box gene, named SFBB (S-locus F-box brother) in apple and pear and SLF (S-locus F-box) in petunia, exhibits higher sequence similarity with SLFL than with SFB from sweet cherry (Matsumoto et al., 2008; Tao and Iezzoni, 2010). The protein encoded by SLF in the petunia S-locus is thought to be part of an SCF (Skp, Cullin, F-box)-containing complex that recognizes nonself S-RNase and degrades it through the ubiquitin pathway (Kubo et al., 2010; Zhao et al., 2010; Chen et al., 2012; Entani et al., 2014; Li et al., 2014, 2016, 2017; Sun et al., 2018). In sweet cherry, a number of reports have described the expression and protein interactions of SFB, SLFL, Skp1, and Cullin (Ushijima et al., 2004; Matsumoto et al., 2012); however, only a few reports have examined the relationship between SFB/SLFL and S-RNase (Matsumoto and Tao, 2016, 2019), and none has investigated whether the SFB/SLFL proteins participate in the ubiquitin labeling of S-RNase.Although the function of SFB4 and SLFL in self-compatibility is unknown, the observation that S4′ pollen tubes grow in sweet cherry pistils that harbor the same S alleles led us to speculate that S4′ pollen might inhibit the toxicity of self S-RNase. In petunia, the results of several studies have suggested that pollen tubes inhibit self S-RNase when an SLF gene from another S-locus haplotype is expressed (Sijacic et al., 2004; Kubo et al., 2010; Williams et al., 2014b; Sun et al., 2018). For example, when SLF2 from the S₇ haplotype is heterologously expressed in pollen harboring the S₉ or S₁₁ haplotype, the S₉ or S₁₁ pollen acquire the capacity to inhibit self S-RNase and break down self-incompatibility (Kubo et al., 2010). The SLF2 protein in petunia has been proposed to ubiquitinate S₉-RNase and S₁₁-RNase and lead to its degradation through the 26S proteasome pathway (Entani et al., 2014). If SFB/SLFL in sweet cherry have a similar function, the S4′ pollen would not be expected to inhibit self S₄-RNase, prompting the suggestion that the functions of SFB/SLFL in sweet cherry and SLF in petunia vary (Tao and Iezzoni, 2010; Matsumoto et al., 2012).In this study, we used sweet cherry to investigate how S4′ pollen inhibits S-RNase and causes self-compatibility, focusing on the question of whether the SFB/SLFL protein can ubiquitinate S-RNase, resulting in its degradation.     

Inheritance and interactions of incompatibility alleles in the tetraploid sour cherry

Three progenies of sour cherry (Prunus cerasus) were analysed to correlate self-(in)compatibility status with S-RNase phenotype in this allotetraploid hybrid of sweet and ground cherry. Self-(in)compatibility was assessed in the field and by monitoring pollen tube growth after selfing. The S-RNase phenotypes were determined by isoelectric focusing of stylar proteins and staining for RNase activity and, for the parents, confirmed by PCR. Seedling phenotypes were generally consistent with disomic segregation of S-RNase alleles. The genetic arrangements of the parents were deduced to be ‘Köröser’ (self-incompatible) S ₁ S ₄ .S _B S _D , ‘Schattenmorelle’ (self-compatible) S ₆ S ₁₃ .S _B S _B , and clone 43.87 (self-compatible) S ₄ S ₁₃ .S _B S _B , where “.” separates the two homoeologous genomes. The presence of S ₄ and S ₆ alleles at the same locus led to self-incompatibility, whereas S ₁₃ and S _B at homoeologous loci led to self-compatibility. The failure of certain heteroallelic genotypes in the three crosses or in the self-incompatible seedlings indicates that S ₄ and S ₆ are dominant to S _B . However, the success of S ₁₃ S _B pollen on styles expressing corresponding S-RNases indicates competitive interaction or lack of pollen-S components. In general, the universal compatibility of S ₁₃ S _B pollen may explain the frequent occurrence of S ₁₃ and S _B together in sour cherry cultivars. Alleles S _B and S _D , that are presumed to derive from ground cherry, and S ₁₃ , presumably from sweet cherry, were sequenced. Our findings contribute to an understanding of inheritance of self-(in)compatibility, facilitate screening of progenies for self-compatibility and provide a basis for studying molecular interactions in heteroallelic pollen.     

Complexes of N-thiophosphorylthioureas RNHC(S)NHP(S)(OiPr)2 (HL) (R = pyridin-2-yl, pyridin-3-yl, 6-amino-pyridin-2-yl) with copper(I): Crystal structures of Cu(PPh3)nL (n = 1, 2)

Reaction of the potassium salts of N-thiophosphorylated thioureas of common formula RNHC(S)NHP(S)(OiPr)₂ [R = pyridin-2-yl (HL^a), pyridin-3-yl (HL^b), 6-amino-pyridin-2-yl (HL^c)] with Cu(PPh₃)₃I in aqueous EtOH/CH₂Cl₂ leads to mononuclear [Cu(PPh₃)₂L^a,b-S,S′] (1, 2) and [Cu(PPh₃)L^c-S,S′] (3) complexes. Using copper(I) iodide instead of Cu(PPh₃)₃I, polynuclear complexes [Cu_n(L-S,S′)_n] (4-6) were obtained. The structures of these compounds were investigated by IR, ¹H, ³¹P{¹H} NMR spectroscopy, ES-MS and elemental analyses. The crystal structures of Cu(PPh₃)₂L^b (2) and Cu(PPh₃)L^c (3) were determined by single-crystal X-ray diffraction.     

Self-Incompatibility in Petunia inflata: The Relationship between a Self-Incompatibility Locus F-Box Protein and Its Non-Self S-RNases

The highly polymorphic S (for self-incompatibility) locus regulates self-incompatibility in Petunia inflata; the S-RNase regulates pistil specificity, and multiple S-locus F-box (SLF) genes regulate pollen specificity. The collaborative non-self recognition model predicts that, for any S-haplotype, an unknown number of SLFs collectively recognize all non-self S-RNases to mediate their ubiquitination and degradation. Using a gain-of-function assay, we examined the relationships between S₂-SLF1 (for S₂-allelic product of Type-1 SLF) and four S-RNases. The results suggest that S₂-SLF1 interacts with S₇- and S₁₃-RNases, and the previously identified S₁- and S₃-RNases, but not with S₅- or S₁₁-RNase. An artificial microRNA expressed by the S₂-SLF1 promoter, but not by the vegetative cell-specific promoter, Late Anther Tomato 52, suppressed expression of S₂-SLF1 in S₂ pollen, suggesting that SLF1 is specific to the generative cell. The S₂ pollen with S₂-SLF1 suppressed was compatible with S₃-, S₅-, S₇-, S₁₁-, and S₁₃-carrying pistils, confirming that other SLF proteins are responsible for detoxifying S₅- and S₁₁-RNases and suggesting that S₂-SLF1 is not the only SLF in S₂ pollen that interacts with S₃-, S₇-, and S₁₃-RNases. Petunia may have evolved at least two types of SLF proteins to detoxify any non-self S-RNase to minimize the deleterious effects of mutation in any SLF.     

Ultrathin and Porous Ni3S2/CoNi2S4 3D‐Network Structure for Superhigh Energy Density Asymmetric Supercapacitors

3D‐networked, ultrathin, and porous Ni₃S₂/CoNi₂S₄ on Ni foam (NF) is successfully designed and synthesized by a simple sulfidation process from 3D Ni–Co precursors. Interestingly, the edge site‐enriched Ni₃S₂/CoNi₂S₄/NF 3D‐network is realized by the etching‐like effect of S^2? ions, which made the surfaces of Ni₃S₂/CoNi₂S₄/NF with a ridge‐like feature. The intriguing structural/compositional/componental advantages endow 3D‐networked‐free‐standing Ni₃S₂/CoNi₂S₄/NF electrodes better electrochemical performance with specific capacitance of 2435 F g^?1 at a current density of 2 A g^?1 and an excellent rate capability of 80% at 20 A g^?1. The corresponding asymmetric supercapacitor achieves a high energy density of 40.0 W h kg^?1 at an superhigh power density of 17.3 kW kg^?1, excellent specific capacitance (175 F g^?1 at 1A g^?1), and electrochemical cycling stability (92.8% retention after 6000 cycles) with Ni₃S₂/CoNi₂S₄/NF as the positive electrode and activated carbon/NF as the negative electrode. Moreover, the temperature dependences of cyclic voltammetry curve polarization and specific capacitances are carefully investigated, and become more obvious and higher, respectively, with the increase of test temperature. These can be attributed to the components' synergetic effect assuring rich redox reactions, high conductivity as well as highly porous but robust architectures. This work provides a general, low‐cost route to produce high performance electrode materials for portable supercapacitor applications on a large scale.