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Identification of the S-genotypes in landraces is a crucial step in the molecular characteri- zation of Serbian autochthonous sweet cherry germplasm. It is also of enormous significance for bre- eders and growers, as this fruit species exhibits a gametophytic self-incompatibility, controlled by the multi-allelic two genes of the S-locus. The aim of this study was to summarize known information and reveal new data on the S-alleles in 23 sweet cherry landraces originating in the Republic of Ser- bia. The use of polymerase chain reaction (PCR) with consensus primers for the second intron of S- RNase, primers specific for S-RNase and certain SFB alleles, along with DNA fragment analysis using fluorescently labelled forward primers to amplify both the S-RNase first intron and the SFB in- tron, revealed 10 alleles (S1 to S6, S9, S12, S13 and S22) that generated the following 13 S-genotypes: S1S2 (one landrace), S1S4 (one landrace), S1S5 (one landrace), S2S3 (four landraces), S3S4 (two lan- draces), S3S5 (two landraces), S3S6 (three landraces), S3S9 (two landraces), S3S12 (two landraces), S4S5 (one landrace), S4S13 (one landrace), S5S22 (one landrace) and S6S9 (two landraces). The most frequent S-allele and S-genotype in this sweet cherry material were S3 and S2S3, with occurrence fre- quencies of 32.6% and 17.4%, respectively. Based on the obtained results, the sweet cherry landraces were assigned to 12 incompatibility groups and one group of universal donors (‘0’). These results pro- vide important information about their cross-compatibility and the diversity of the S-locus in Serbian sweet cherry germplasm.

In the last years, an important renewal of plant material is taking place in apricot, with the introduction of new cultivars from different breeding programs. The pollination requirements of many of these cultivars are unknown. In this work, the self-(in)compatibility and the S-alleles have been studied in 40 apricot cultivars. Self-(in)compatibility was analysed by self- and cross-pollination experiments followed by the observation of pollen tube growth through the pistil under the microscope. The S-alleles of the cultivars analysed were determined by PCR amplification of the S-RNase gene. The self-(in)compatibility and the S-RNase genotype of 31 cultivars are firstly reported here, identifying one new apricot S-RNase allele. These results, combined with information from previous studies, allow allocating the cultivars in their corresponding incompatibility group.

[ES] Los sistemas de autoincompatibilidad (SI) en angiospermas evitan la autofecundación promoviendo la polinización cruzada que favorece la generación de diversidad genética. En solanáceas, rosáceas y plantagináceas la SI está controlada por un sistema gametofítico controlado por la interacción entre un determinante del polen (SFL) y un determinante femenino (S-RNasa). Se sabe que los dos genes que codifican para estas proteínas se encuentran en un locus hipervariable llamado locus-S. En solanáceas las S-RNasas presentan cinco dominios conservados, dos regiones hipervariables y un intrón. Se ha descrito que estos genes presentan un amplio número de alelos que varían tanto en sus regiones hipervariables como en el tamaño del intrón. La detección de estos alelos permite conocer de antemano qué plantas van a ser compatibles entre sí, permitiendo una mejor planificación de los programas de mejora. Se ha visto en especies como tomate que la transición de la auto-incompatibilidad a la auto-compatibilidad es un rasgo característico de la domesticación, ya que una planta autocompatible facilita enormemente la fijación de caracteres de interés. Esto suele ser debido a la selección de individuos que presentan mutaciones en alguno de los dos determinantes, permitiendo así saltarse el control de rechazo del polen. En el marco de los programas de mejora es común el uso de especies silvestres que aporten nuevos caracteres de interés en las especies cultivadas. Sin embargo, estas especies suelen ser autoincompatibles, lo que dificulta su uso para el desarrollo de nuevos materiales. El pepino dulce (Solanum muricatum Aiton) es un cultivo herbáceo de origen andino que es cultivado por sus frutos comestibles, jugosos y aromáticos. Pertenece a la familia de las solanáceas, estando filogenéticamente cercano a otras importantes especies como el tomate y la patata. El pepino dulce es autocompatible pero dentro la sección Basarthrum a la que pertenece, encontramos tanto especies autoinco, [EN] The self-incompatibility (SI) systems in angiosperms avoid selfing, promoting cross-pollination and the generation of genetic diversity. In Solanaceae, Rosaceae and Plantaginaceae self-incompatibility is controlled by a gametophytic system controlled by the interaction between a male determinant (SFL) and a female determinant (S-RNase). It is known that both genes codifying these proteins are located in a hipervariable locus named the S-locus. In Solanaceae, S-RNases comprise five conserved domains, two hipervariable regions and an intron. It has been described that these gens show a wide number of alleles that vary in their hipervariable regions as well as in the size of their intron. The detection of these alleles allows to know beforehand which plants are going to be incompatible, allowing for a better planning of breeding programs. It has been observed in species such as tomato that transition from self-incompatibility to selfcompatibility is a characteristic trait of domestication, as a self-compatible plant makes the fixation of interesting traits much easier. This is usually due to the selection of plants that have mutations in one of the two determinants, allowing them to bypass the rejection of pollen control. In breeding programs is common to use wild species that contribute with new interesting traits for the cultivated species. However, these species usually are self-incompatible, which makes their use in the development of new materials difficult. Pepino (Solanum muricatum Aiton) is a species of shrub of Andean origin cultivated for its edible, juicy and aromatic fruits. It belongs to the Solanaceae family, and is phylogenetically close to other relevant species such as tomato and potato. The pepino is self-compatible, but inside the section Basarthrum, to which it belongs, there are self-incompatible species as well as self-compatible species. The main objective of this work was to determine different incompatibility alleles by amplifying regions

[ES] Los sistemas de autoincompatibilidad (SI) en angiospermas evitan la autofecundación promoviendo la polinización cruzada que favorece la generación de diversidad genética. En solanáceas, rosáceas y plantagináceas la SI está controlada por un sistema gametofítico controlado por la interacción entre un determinante del polen (SFL) y un determinante femenino (S-RNasa). Se sabe que los dos genes que codifican para estas proteínas se encuentran en un locus hipervariable llamado locus-S. En solanáceas las S-RNasas presentan cinco dominios conservados, dos regiones hipervariables y un intrón. Se ha descrito que estos genes presentan un amplio número de alelos que varían tanto en sus regiones hipervariables como en el tamaño del intrón. La detección de estos alelos permite conocer de antemano qué plantas van a ser compatibles entre sí, permitiendo una mejor planificación de los programas de mejora. Se ha visto en especies como tomate que la transición de la auto-incompatibilidad a la auto-compatibilidad es un rasgo característico de la domesticación, ya que una planta autocompatible facilita enormemente la fijación de caracteres de interés. Esto suele ser debido a la selección de individuos que presentan mutaciones en alguno de los dos determinantes, permitiendo así saltarse el control de rechazo del polen. En el marco de los programas de mejora es común el uso de especies silvestres que aporten nuevos caracteres de interés en las especies cultivadas. Sin embargo, estas especies suelen ser autoincompatibles, lo que dificulta su uso para el desarrollo de nuevos materiales. El pepino dulce (Solanum muricatum Aiton) es un cultivo herbáceo de origen andino que es cultivado por sus frutos comestibles, jugosos y aromáticos. Pertenece a la familia de las solanáceas, estando filogenéticamente cercano a otras importantes especies como el tomate y la patata. El pepino dulce es autocompatible pero dentro la sección Basarthrum a la que pertenece, encontramos tanto especies autoinco, [EN] The self-incompatibility (SI) systems in angiosperms avoid selfing, promoting cross-pollination and the generation of genetic diversity. In Solanaceae, Rosaceae and Plantaginaceae self-incompatibility is controlled by a gametophytic system controlled by the interaction between a male determinant (SFL) and a female determinant (S-RNase). It is known that both genes codifying these proteins are located in a hipervariable locus named the S-locus. In Solanaceae, S-RNases comprise five conserved domains, two hipervariable regions and an intron. It has been described that these gens show a wide number of alleles that vary in their hipervariable regions as well as in the size of their intron. The detection of these alleles allows to know beforehand which plants are going to be incompatible, allowing for a better planning of breeding programs. It has been observed in species such as tomato that transition from self-incompatibility to selfcompatibility is a characteristic trait of domestication, as a self-compatible plant makes the fixation of interesting traits much easier. This is usually due to the selection of plants that have mutations in one of the two determinants, allowing them to bypass the rejection of pollen control. In breeding programs is common to use wild species that contribute with new interesting traits for the cultivated species. However, these species usually are self-incompatible, which makes their use in the development of new materials difficult. Pepino (Solanum muricatum Aiton) is a species of shrub of Andean origin cultivated for its edible, juicy and aromatic fruits. It belongs to the Solanaceae family, and is phylogenetically close to other relevant species such as tomato and potato. The pepino is self-compatible, but inside the section Basarthrum, to which it belongs, there are self-incompatible species as well as self-compatible species. The main objective of this work was to determine different incompatibility alleles by amplifying regions

[ES] Los sistemas de autoincompatibilidad (SI) en angiospermas evitan la autofecundación promoviendo la polinización cruzada que favorece la generación de diversidad genética. En solanáceas, rosáceas y plantagináceas la SI está controlada por un sistema gametofítico controlado por la interacción entre un determinante del polen (SFL) y un determinante femenino (S-RNasa). Se sabe que los dos genes que codifican para estas proteínas se encuentran en un locus hipervariable llamado locus-S. En solanáceas las S-RNasas presentan cinco dominios conservados, dos regiones hipervariables y un intrón. Se ha descrito que estos genes presentan un amplio número de alelos que varían tanto en sus regiones hipervariables como en el tamaño del intrón. La detección de estos alelos permite conocer de antemano qué plantas van a ser compatibles entre sí, permitiendo una mejor planificación de los programas de mejora. Se ha visto en especies como tomate que la transición de la auto-incompatibilidad a la auto-compatibilidad es un rasgo característico de la domesticación, ya que una planta autocompatible facilita enormemente la fijación de caracteres de interés. Esto suele ser debido a la selección de individuos que presentan mutaciones en alguno de los dos determinantes, permitiendo así saltarse el control de rechazo del polen. En el marco de los programas de mejora es común el uso de especies silvestres que aporten nuevos caracteres de interés en las especies cultivadas. Sin embargo, estas especies suelen ser autoincompatibles, lo que dificulta su uso para el desarrollo de nuevos materiales. El pepino dulce (Solanum muricatum Aiton) es un cultivo herbáceo de origen andino que es cultivado por sus frutos comestibles, jugosos y aromáticos. Pertenece a la familia de las solanáceas, estando filogenéticamente cercano a otras importantes especies como el tomate y la patata. El pepino dulce es autocompatible pero dentro la sección Basarthrum a la que pertenece, encontramos tanto especies autoinco, [EN] The self-incompatibility (SI) systems in angiosperms avoid selfing, promoting cross-pollination and the generation of genetic diversity. In Solanaceae, Rosaceae and Plantaginaceae self-incompatibility is controlled by a gametophytic system controlled by the interaction between a male determinant (SFL) and a female determinant (S-RNase). It is known that both genes codifying these proteins are located in a hipervariable locus named the S-locus. In Solanaceae, S-RNases comprise five conserved domains, two hipervariable regions and an intron. It has been described that these gens show a wide number of alleles that vary in their hipervariable regions as well as in the size of their intron. The detection of these alleles allows to know beforehand which plants are going to be incompatible, allowing for a better planning of breeding programs. It has been observed in species such as tomato that transition from self-incompatibility to selfcompatibility is a characteristic trait of domestication, as a self-compatible plant makes the fixation of interesting traits much easier. This is usually due to the selection of plants that have mutations in one of the two determinants, allowing them to bypass the rejection of pollen control. In breeding programs is common to use wild species that contribute with new interesting traits for the cultivated species. However, these species usually are self-incompatible, which makes their use in the development of new materials difficult. Pepino (Solanum muricatum Aiton) is a species of shrub of Andean origin cultivated for its edible, juicy and aromatic fruits. It belongs to the Solanaceae family, and is phylogenetically close to other relevant species such as tomato and potato. The pepino is self-compatible, but inside the section Basarthrum, to which it belongs, there are self-incompatible species as well as self-compatible species. The main objective of this work was to determine different incompatibility alleles by amplifying regions

[ES] Los sistemas de autoincompatibilidad (SI) en angiospermas evitan la autofecundación promoviendo la polinización cruzada que favorece la generación de diversidad genética. En solanáceas, rosáceas y plantagináceas la SI está controlada por un sistema gametofítico controlado por la interacción entre un determinante del polen (SFL) y un determinante femenino (S-RNasa). Se sabe que los dos genes que codifican para estas proteínas se encuentran en un locus hipervariable llamado locus-S. En solanáceas las S-RNasas presentan cinco dominios conservados, dos regiones hipervariables y un intrón. Se ha descrito que estos genes presentan un amplio número de alelos que varían tanto en sus regiones hipervariables como en el tamaño del intrón. La detección de estos alelos permite conocer de antemano qué plantas van a ser compatibles entre sí, permitiendo una mejor planificación de los programas de mejora. Se ha visto en especies como tomate que la transición de la auto-incompatibilidad a la auto-compatibilidad es un rasgo característico de la domesticación, ya que una planta autocompatible facilita enormemente la fijación de caracteres de interés. Esto suele ser debido a la selección de individuos que presentan mutaciones en alguno de los dos determinantes, permitiendo así saltarse el control de rechazo del polen. En el marco de los programas de mejora es común el uso de especies silvestres que aporten nuevos caracteres de interés en las especies cultivadas. Sin embargo, estas especies suelen ser autoincompatibles, lo que dificulta su uso para el desarrollo de nuevos materiales. El pepino dulce (Solanum muricatum Aiton) es un cultivo herbáceo de origen andino que es cultivado por sus frutos comestibles, jugosos y aromáticos. Pertenece a la familia de las solanáceas, estando filogenéticamente cercano a otras importantes especies como el tomate y la patata. El pepino dulce es autocompatible pero dentro la sección Basarthrum a la que pertenece, encontramos tanto especies autoinco, [EN] The self-incompatibility (SI) systems in angiosperms avoid selfing, promoting cross-pollination and the generation of genetic diversity. In Solanaceae, Rosaceae and Plantaginaceae self-incompatibility is controlled by a gametophytic system controlled by the interaction between a male determinant (SFL) and a female determinant (S-RNase). It is known that both genes codifying these proteins are located in a hipervariable locus named the S-locus. In Solanaceae, S-RNases comprise five conserved domains, two hipervariable regions and an intron. It has been described that these gens show a wide number of alleles that vary in their hipervariable regions as well as in the size of their intron. The detection of these alleles allows to know beforehand which plants are going to be incompatible, allowing for a better planning of breeding programs. It has been observed in species such as tomato that transition from self-incompatibility to selfcompatibility is a characteristic trait of domestication, as a self-compatible plant makes the fixation of interesting traits much easier. This is usually due to the selection of plants that have mutations in one of the two determinants, allowing them to bypass the rejection of pollen control. In breeding programs is common to use wild species that contribute with new interesting traits for the cultivated species. However, these species usually are self-incompatible, which makes their use in the development of new materials difficult. Pepino (Solanum muricatum Aiton) is a species of shrub of Andean origin cultivated for its edible, juicy and aromatic fruits. It belongs to the Solanaceae family, and is phylogenetically close to other relevant species such as tomato and potato. The pepino is self-compatible, but inside the section Basarthrum, to which it belongs, there are self-incompatible species as well as self-compatible species. The main objective of this work was to determine different incompatibility alleles by amplifying regions

Solanaceae, Rosaceae, and Plantaginaceae exhibit the S-RNase-based gametophytic self-incompatibility (GSI) system. This type of GSI is controlled by a single polymorphic locus (S locus) containing the pistil S determinant gene, S-ribonuclease (S-RNase), and the pollen S determinant, the S locus F-box gene (SFB/SLF). In addition to these determinant genes, non-S factors, called modifier genes, are required for the GSI reaction. Here, we conducted large-scale transcriptome analysis of unpollinated, self-pollinated, and cross-pollinated pistils of Japanese apricot (Prunus mume Sieb. et Zucc. cv. Nanko) to capture all of the molecular events induced by the GSI reaction in Prunus, using next-generation sequencing technologies. We obtained 40,061 unigenes from 77,521,310 reads from pollinated and unpollinated pistils and pollen grains. Among these unigenes, 29,985 and 27,898 unigene sequences showed at least one hit against the NCBI nr and TAIR10 protein databases, respectively, in BLASTX searches using an E-value cutoff of 1e-6. Digital expression analysis showed that 8,907 and 10,190 unigenes were expressed at significantly different levels between unpollinated (UP) and cross-pollinated (CP) pistils and between UP and self-pollinated (SP) pistils, respectively. The expression of 4,348 unigenes in both CP and SP pollination was commonly and significantly different from that in UP, while the expression of 4,559 and 5,842 unigenes in CP and SP, respectively, was specifically and significantly different from UP. The expression of 2,227 unigenes was up-regulated both in CP and SP compared with UP. Genes supposedly involved in S-RNase-based GSI were included among the unigenes up-regulated by pollination, while no unigenes homologous to the solanaceous pistil modifiers HT-B or 120K were included among the unigenes up-regulated by pollination or in the whole unpollinated/pollinated pistil transcriptome. We discuss the distinct molecular mechanism of S-RNase-based GSI in Prunus

Peach (Prunus persica) as a species is self-compatible (SC), although most other Prunus fruit tree species are partially or fully self-incompatible. We previously identified 3 mutated Shaplotypes, S[1], S[2], and S[2m], that confer self-compatibility on commercial peach cultivars for fruit production. In this report, we identified 2 novel SC S haplotypes, S[3] and S[4], among 130 peach cultivars and strains consisting mainly of ornamental cultivars and wild strains. The S[3]haplotype was found only in ornamental cultivars, while the S[4] haplotype was found mainly in wild strains. S-RNases in the S[3] and S[4] haplotypes appeared to have no defects in their primary structures. S haplotype-specific F-box (SFB) sequences were also present in the Slocus downstream of the S[3]- and S[4]-RNases. These SFB sequences were in a reverse transcriptional orientation as has been reported in most other functional Prunus S haplotypes; however, both SFB[3] and SFB[4] appeared to be mutated. DNA sequencing of the entire downstream region of SFB[3], extending about 12 kbp to the stop codon of S-RNase, revealed the presence of a premature stop codon 975 bp downstream from the SFB[3] start codon. No sequence homologous to SFB downstream of the stop codon was found. There was a 4946 bp insertion in the middle of SFB[4]. The original SFB[4] sequence, obtained by removing the inserted sequence, encodes a typical SFB. Based on the 3 previously identified peach Shaplotypes, we supposed that the S[3] and S[4] haplotypes were also SC pollen part mutant (PPM) S haplotypes. Here, we also discuss possible reasons for all peach S haplotypes identified so far having the PPM SC S haplotype.

Due to the gametophytic self-incompatibility of European pear (Pyrus communis), S-compatible cultivars that flower synchronically are required in commercial pear orchards to ensure effective pollination and fruit production. The gametophytic self-incompatibility is controlled by a single locus (S-locus) encoding a polymorphic stylar ribonuclease (S-RNase) and pollen-specific expressed F-box genes (SFBB). Both the S-RNase and the SFBB genes are multi-allelic and are ideal markers for molecular S-genotyping. In the present study, we genotype the S-locus of thirteen North Western European pear cultivars by sequencing their S-RNases. All the described cultivars diverged by their S-allele combinations and six of them had unique S-genotype so that they are at least semi-compatible with all the 150 previously described cultivars and could be potentially interesting pollinator cultivars for commercial orchards.

To avoid endogamy many flowering plants evolved a mechanism to recognize and reject their self-pollen, which is known as self-incompatibility (SI) system. In many cases the SI is genetically controlled by a single and highly polymorphic locus known as the S-locus. This DNA region carries two tightly linked transcriptional units. One of them encodes the female determinant (pistil expressed) and the second one the male determinant (pollen expressed). In this review, we discuss the most relevant advances in the SI mechanism in S-RNase based systems, which are present in Solanaceae, Rosaceae and Plantaginaceae. In these families, the female determinant encodes a ribonuclease named S-RNase and the male determinant encodes a protein called SLF/SFB (S-locus F-Box). We finally describe the role of the role of modifier genes, not coded by S-locus, in the pollen rejection response and propose a model including the main events so far described., Para evitar la endogamia muchas plantas con flores hermafroditas evolucionaron con un mecanismo para reconocer y rechazar su propio polen y que se conoce como sistema de autoincompatibilidad (AI). En muchos casos la AI está controlada genéticamente por un solo locus altamente polimórfico, conocido como locus S. Esta región del DNA incluye dos unidades transcripcionales fuertemente ligadas. Una de ellas codifica la determinante femenina (expresada en el pistilo) y la otra a la determinante masculina (expresada en el polen). En esta revisión se discuten los principales avances en el mecanismo de AI gametofítica dependiente de S-RNasas, el cual está presente en Solanaceae, Rosaceae y Plantaginaceae. En estas familias, la determinante femenina codifica una ribonucleasa (S-RNasa) y la determinante masculina una proteína con caja F (SLF/SFB). Además, se describe la participación de genes modificadores no codificados en el locus S y que son esenciales en la AI, así como la posible función de sus productos en el mecanismo de rechazo del polen. Finalmente, proponemos un modelo que incluye los principales sucesos descritos a la fecha.

To avoid endogamy many flowering plants evolved a mechanism to recognize and reject their self-pollen, which is known as self-incompatibility (SI) system. In many cases the SI is genetically controlled by a single and highly polymorphic locus known as the S-locus. This DNA region carries two tightly linked transcriptional units. One of them encodes the female determinant (pistil expressed) and the second one the male determinant (pollen expressed). In this review, we discuss the most relevant advances in the SI mechanism in S-RNase based systems, which are present in Solanaceae, Rosaceae and Plantaginaceae. In these families, the female determinant encodes a ribonuclease named S-RNase and the male determinant encodes a protein called SLF/SFB (S-locus F-Box). We finally describe the role of the role of modifier genes, not coded by S-locus, in the pollen rejection response and propose a model including the main events so far described., Para evitar la endogamia muchas plantas con flores hermafroditas evolucionaron con un mecanismo para reconocer y rechazar su propio polen y que se conoce como sistema de autoincompatibilidad (AI). En muchos casos la AI está controlada genéticamente por un solo locus altamente polimórfico, conocido como locus S. Esta región del DNA incluye dos unidades transcripcionales fuertemente ligadas. Una de ellas codifica la determinante femenina (expresada en el pistilo) y la otra a la determinante masculina (expresada en el polen). En esta revisión se discuten los principales avances en el mecanismo de AI gametofítica dependiente de S-RNasas, el cual está presente en Solanaceae, Rosaceae y Plantaginaceae. En estas familias, la determinante femenina codifica una ribonucleasa (S-RNasa) y la determinante masculina una proteína con caja F (SLF/SFB). Además, se describe la participación de genes modificadores no codificados en el locus S y que son esenciales en la AI, así como la posible función de sus productos en el mecanismo de rechazo del polen. Finalmente, proponemos un modelo que incluye los principales sucesos descritos a la fecha.

To avoid endogamy many flowering plants evolved a mechanism to recognize and reject their self-pollen, which is known as self-incompatibility (SI) system. In many cases the SI is genetically controlled by a single and highly polymorphic locus known as the S-locus. This DNA region carries two tightly linked transcriptional units. One of them encodes the female determinant (pistil expressed) and the second one the male determinant (pollen expressed). In this review, we discuss the most relevant advances in the SI mechanism in S-RNase based systems, which are present in Solanaceae, Rosaceae and Plantaginaceae. In these families, the female determinant encodes a ribonuclease named S-RNase and the male determinant encodes a protein called SLF/SFB (S-locus F-Box). We finally describe the role of the role of modifier genes, not coded by S-locus, in the pollen rejection response and propose a model including the main events so far described., Para evitar la endogamia muchas plantas con flores hermafroditas evolucionaron con un mecanismo para reconocer y rechazar su propio polen y que se conoce como sistema de autoincompatibilidad (AI). En muchos casos la AI está controlada genéticamente por un solo locus altamente polimórfico, conocido como locus S. Esta región del DNA incluye dos unidades transcripcionales fuertemente ligadas. Una de ellas codifica la determinante femenina (expresada en el pistilo) y la otra a la determinante masculina (expresada en el polen). En esta revisión se discuten los principales avances en el mecanismo de AI gametofítica dependiente de S-RNasas, el cual está presente en Solanaceae, Rosaceae y Plantaginaceae. En estas familias, la determinante femenina codifica una ribonucleasa (S-RNasa) y la determinante masculina una proteína con caja F (SLF/SFB). Además, se describe la participación de genes modificadores no codificados en el locus S y que son esenciales en la AI, así como la posible función de sus productos en el mecanismo de rechazo del polen. Finalmente, proponemos un modelo que incluye los principales sucesos descritos a la fecha.

Loquat (Eriobotrya japonica Lindl.; Pyrinae, Rosaceae) is an evergreen fruit tree which is acquiring increasing importance as an alternative crop in warm-temperate and subtropical regions. Recent pollination studies suggest that crop intensification has resulted in a reduction of fruit productivity in different locations. Loquat exhibits gametophytic self-incompatibility (GSI) and, consequently, fruit set strongly depends on cross-pollination between intercompatible cultivars. S-genotyping and incompatibility group assignment is therefore essential for adequate loquat orchard design. This study reports the molecular characterization of the S-RNase allele composition of 31 loquat cultivars grown in Spain. PCR with primers developed from loquat S-RNase sequences was used in combination with high-performance capillary polyacrilamide electrophoresis for the fine-evaluation of length polymorphisms at the S-RNase gene. This approach allowed to uncover a new S-RNase allele (S5), whose sequence is reported and to characterize the first six cross-incompatibility groups (I-VI) in loquat, resulting from the combination of five S-alleles (S1 to S5)

Tetraploid sour cherry (Prunus cerasus L.) exhibits gametophytic self-incompatibility (GSI) whereby the specificity of self-pollen rejection is controlled by alleles of the stylar and pollen specificity genes, S-RNase and SFB (S haplotype-specific F-box protein gene), respectively. As sour cherry selections can be either self-compatible (SC) or self-incompatible (SI), polyploidy per se does not result in SC. Instead the genotype-dependent loss of SI in sour cherry is due to the accumulation of non-functional S-haplotypes. The presence of two or more non-functional S-haplotypes within sour cherry 2x pollen renders that pollen SC. Two new S-haplotypes from sour cherry, S(33) and S(34), that are presumed to be contributed by the P. fruticosa species parent, the complete S-RNase and SFB sequences of a third S-haplotype, S(35), plus the presence of two previously identified sweet cherry S-haplotypes, S(14) and S(16) are described here. Genetic segregation data demonstrated that the S(16)-, S(33)-, S(34)-, and S(35)-haplotypes present in sour cherry are fully functional. This result is consistent with our previous finding that 'hetero-allelic' pollen is incompatible in sour cherry. Phylogenetic analyses of the SFB and S-RNase sequences from available Prunus species reveal that the relationships among S-haplotypes show no correspondence to known organismal relationships at any taxonomic level within Prunus, indicating that polymorphisms at the S-locus have been maintained throughout the evolution of the genus. Furthermore, the phylogenetic relationships among SFB sequences are generally incongruent with those among S-RNase sequences for the same S-haplotypes. Hypotheses compatible with these results are discussed.

Tetraploid sour cherry (Prunus cerasus L.) exhibits gametophytic self-incompatibility (GSI) whereby the specificity of self-pollen rejection is controlled by alleles of the stylar and pollen specificity genes, S-RNase and SFB (S haplotype-specific F-box protein gene), respectively. As sour cherry selections can be either self-compatible (SC) or self-incompatible (SI), polyploidy per se does not result in SC. Instead the genotype-dependent loss of SI in sour cherry is due to the accumulation of non-functional S-haplotypes. The presence of two or more non-functional S-haplotypes within sour cherry 2x pollen renders that pollen SC. Two new S-haplotypes from sour cherry, S(33) and S(34), that are presumed to be contributed by the P. fruticosa species parent, the complete S-RNase and SFB sequences of a third S-haplotype, S(35), plus the presence of two previously identified sweet cherry S-haplotypes, S(14) and S(16) are described here. Genetic segregation data demonstrated that the S(16)-, S(33)-, S(34)-, and S(35)-haplotypes present in sour cherry are fully functional. This result is consistent with our previous finding that 'hetero-allelic' pollen is incompatible in sour cherry. Phylogenetic analyses of the SFB and S-RNase sequences from available Prunus species reveal that the relationships among S-haplotypes show no correspondence to known organismal relationships at any taxonomic level within Prunus, indicating that polymorphisms at the S-locus have been maintained throughout the evolution of the genus. Furthermore, the phylogenetic relationships among SFB sequences are generally incongruent with those among S-RNase sequences for the same S-haplotypes. Hypotheses compatible with these results are discussed.

Many species of Prunus display an S-RNase-based gametophytic self-incompatibility (SI), controlled by a single highly polymorphic multigene complex termed the S-locus. This comprises tightly linked stylar- and pollen-expressed genes that determine the specificity of the SI response. We investigated SI of Prunus tenella, a wild species found in small, isolated populations on the Balkan peninsula, initially by pollination experiments and identifying stylar-expressed RNase alleles. Nine P. tenella S-RNase alleles (S1–S9) were cloned; their sequence analysis showed a very high ratio of non-synonymous to synonymous nucleotide substitutions (Ka/Ks) and revealed that S-RNase alleles of P. tenella, unlike those of Prunus dulcis, show positive selection in all regions except the conserved regions and that between C2 and RHV. Remarkably, S8-RNase, was found to be identical to S1-RNase from Prunus avium, a species that does not interbreed with P. tenella and, except for just one amino acid, to S11 of P. dulcis. However, the corresponding introns and S-RNase–SFB intergenic regions showed considerable differences. Moreover, protein sequences of the pollen-expressed SFB alleles were not identical, harbouring 12 amino-acid replacements between those of P. tenella SFB8 and P. avium SFB1. Implications of this finding for hypotheses about the evolution of new S-specificities are discussed.

Cross-compatibility relationships in almond are controlled by a gametophytically expressed incompatibility system partly mediated by stylar RNases, of which 29 have been reported. To resolve possible synonyms and to provide data for phylogenetic analysis, 21 almond S-RNase alleles were cloned and sequenced from SP (signal peptide region) or C1 (first conserved region) to C5, except for the S 29 allele, which could be cloned only from SP to C1. Nineteen sequences (S 4 , S 6 , S 11 –S 22 , S 25 –S 29 ) were potentially new whereas S 10 and S 24 had previously been published but with different labels. The sequences for S 16 and S 17 were identical to that for S 1 , published previously; likewise, S 15 was identical to S 5 . In addition, S 4 and S 20 were identical, as were S 13 and S 19 . A revised version of the standard table of almond incompatibility genotypes is presented. Several alleles had AT or GA tandem repeats in their introns. Sequences of the 23 distinct newly cloned or already published alleles were aligned. Sliding windows analysis of Ka/Ks identified regions where positive selection may operate; in contrast to the Maloideae, most of the region from the beginning of C3 to the beginning of RC4 appeared not to be under positive selection. Phylogenetic analysis indicated four pairs of alleles had ‘bootstrap’ support > 80%: S 5 /S 10 , S 4 /S 8, S 11 /S 24 , and S 3 /S 6 . Various motifs up to 19 residues long occurred in at least two alleles, and their distributions were consistent with intragenic recombination, as were separate phylogenetic analyses of the 5′ and 3′ sections. Sequence comparison of phylogenetically related alleles indicated the significance of the region between RC4 and C5 in defining specificity.