Self-compatible Research Articles

Analysis of S-locus and expression of S-alleles of self-compatible rapid-cycling Brassica oleracea 'TO1000DH3'.

Brassica oleracea is a strictly self-incompatible (SI) plant, but rapid-cycling B. oleracea 'TO1000DH3' is self-compatible (SC). Self-incompatibility in Brassicaceae is controlled by multiple alleles of the S-locus. Three S-locus genes, S-locus glycoprotein (SLG), S-locus receptor kinase (SRK) and S-locus protein 11 or S-locus cysteine-rich (SP11/SCR), have been reported to date, all of which are classified into class I and II. In this study, we investigated the molecular mechanism behind alterations of SI to SC in rapid-cycling B. olerace 'TO1000DH3'. Class I SRK were identified by genomic DNA PCR and PCR-RFLP analysis using SRK specific markers and found to be homozygous. Cloning and sequencing of class I SRK revealed a normal kinase domain without any S-domain/transmembrane domain. Moreover, S-locus sequencing analysis revealed only an SLG sequence, but no SP11/SCR. Expression analysis showed no SRK expression in the stigma, although other genes involved in the SI recognition reaction (SLG, MLPK, ARC1, THL) were found to have normal expression in the stigma. Taken together, the above results suggest that structural aberrations such as deletion of the SI recognition genes may be responsible for the breakdown of SI in rapid-cycling B. oleracea 'TO1000DH3'.

Molecular Phylogenetics and Reproductive Biology of <I>Oenothera</I> section <I>Kneiffia</I> (Onagraceae)

Abstract Oenothera, the evening primrose genus, is a model system for studying the evolution of flowering plant reproductive biology. Members of this group vary in the species of pollinator that visit their flowers and in breeding systems, including both self-compatible (SC) and self-incompatible (SI) species. Here, we examine the evolutionary relationships among the six species of Oenothera section Kneiffia using sequences from two nuclear and four chloroplast genes. Through field studies we describe the effective pollinators for four species that had not been previously reported, and experimentally test for pollen limitation. Three of the six species are SC, and three are SI. The phylogeny strongly supports three separate transitions from SI to SC. Despite the expectation that SC species evolved the ability to self because of pollen limitation, or that pollen limitation evolves among SC species, we found no significant differences in pollen limitation between the SI and SC species in this study. Our res...

Pseudo-self-compatibility in Centaurea cyanus L

Agricultural intensification has resulted in drastic regression of several arable land-dependent weeds. This decrease, along with reduced pollinator abundance, could lead to population-level extinction of self-incompatible species. Alternatively, it could drive adaptation to self-compatibility through selection on standing genetic variation. We investigated whether pseudo-self-compatible (PSC) or self-compatible (SC) plants are present in populations of the rarified weed Centaurea cyanus in the species’ extreme western distribution limits in Europe. We compared seed production of isolated plants and of pairs of plants in cages with or without pollinators. We showed that pollinators are necessary for self-fertilization. The majority of plants were self-incompatible (SI), but about 12% were PSC, and one was SC. Reproductive traits of PSC plants were not different from those of other plants. There was no difference between plants from two regions that differed in C. cyanus abundance. We conclude that the genetic variation necessary to transition to selfing is present in C. cyanus; this could help to maintain endangered populations, but the transition to selfing does not appear to have happened in nature yet.

TRANSMISSION ADVANTAGE FAVORS SELFING ALLELE IN EXPERIMENTAL POPULATIONS OF SELF-INCOMPATIBLEWITHERINGIA SOLANACEA(SOLANACEAE)

The evolution of self-fertilization is one of the most commonly traversed transitions in flowering plants, with profound implications for population genetic structure and evolutionary potential. We investigated factors influencing this transition using Witheringia solanacea, a predominantly self-incompatible (SI) species within which self-compatible (SC) genotypes have been identified. We showed that self-compatibility in this species segregates with variation at the S-locus as inherited by plants in F1 and F2 generations. To examine reproductive assurance and the transmission advantage of selfing, we placed SC and SI genotypes in genetically replicated gardens and monitored male and female reproductive success, as well as selfing rates of SC plants. Self-compatibility did not lead to increased fruit or seed set, even under conditions of pollinator scarcity, and the realized selfing rate of SC plants was less than 10%. SC plants had higher fruit abortion rates, consistent with previous evidence showing strong inbreeding depression at the embryonic stage. Although the selfing allele did not provide reproductive assurance under observed conditions, it also did not cause pollen discounting, so the transmission advantage of selfing should promote its spread. Given observed numbers of S-alleles and selfing rates, self-compatibility should spread even under conditions of exceedingly high initial inbreeding depression.

Characterization of self-incompatibility genes in the intergeneric hybrid xBrassicoraphanus

Brassica rapa and Raphanus sativus are strictly self-incompatible (SI) plants; however, xBrassicoraphanus (baemoochae) is an intergeneric hybrid synthesized following hybridization of B. rapa and R. sativus that is self-compatible (SC). Self-incompatibility in Brassicaceae is controlled by multiple alleles of the S-locus. Two S-locus genes, SRK (S-locus receptor kinase) and SP11/SCR (S-locus protein 11 or S-locus cysteine-rich), have been reported to date, both of which are classified into class I and II. In this study, we investigate if there is an alteration in the structure or the expression in SRK or SP11 genes behind the alteration of SI to SC in baemoochae. Class I and II SRK were identified by PCR of the genomic DNA of baemoochae using SRK-specific universal primers. Cloning and sequencing of both classes of SRK was conducted and compared with SRK genes of parental species. Comparison analysis showed no genomic alterations and both of them showed expression in the stigma. Similarly, SP11 genes also showed no genomic alterations and normally are expressed in the anther. Other SI-related genes (MLPK, ARC1, THL) also showed normal expression in the stigma and anther. Taken together, these results revealed that no structural/gene expression change in these genes was responsible for the breakdown of SI in baemoochae. Rather, the transformation from SI parents to SC descendants could be responding to epigenetic mechanisms.

Restoring pistil‐side self‐incompatibility factors recapitulates an interspecific reproductive barrier between tomato species

Interspecific reproductive barriers are poorly understood, but are central to the biological species concept. The pre-zygotic barriers between red- and green-fruited species in the tomato clade of the genus Solanum provide a model to better understand these barriers in plants. Compatibility usually follows the SIxSC rule: pollen from self-compatible (SC) red-fruited species is rejected on pistils of the predominantly self-incompatible (SI) green-fruited species, but the reciprocal crosses are compatible. This suggests that the interspecific reproductive barrier may be linked to the intraspecific SI mechanism. However, pollen from the SC red-fruited species is also rejected by SC accessions of green-fruited species that lack S-RNase, a key protein expressed in pistils of SI Solanum species. Thus, multiple mechanisms may contribute to the barrier between red- and green-fruited species. We tested whether an S-RNase-dependent barrier is sufficient for rejection of pollen from red-fruited species by introducing functional S-RNase, HT-A and HT-B genes from SI species into Solanumlycopersicum (cultivated tomato). We found that expressing S-RNase in combination with either HT-A or HT-B in the pistil is sufficient to cause rejection of pollen from all four red-fruited species. Thus, redundant mechanisms must operate side by side to prevent crosses between red- and green-fruited species in the clade, underlining the complexity of interspecific pollination barriers. Our results also have implications for mating system transitions. We suggest that these transitions must occur in a specific sequence, and that the transition from SI to SC also affects interspecific compatibility.

The Role of a Pollen-Expressed Cullin1 Protein in Gametophytic Self-Incompatibility in Solanum

We previously isolated a pollen factor, ui6.1, which encodes a Cullin1 protein (CUL1) that functions in unilateral interspecific incompatibility (UI) in Solanum. Here we show that CUL1 is also required for pollen function in self-incompatibility (SI). We used RNA interference (RNAi) to reduce CUL1 expression in pollen of Solanum arcanum, a wild SI tomato relative. Hemizygous T0 plants showed little or no transmission of the transfer DNA (T-DNA) through pollen when crossed onto nontransgenic SI plants, indicating that CUL1-deficient pollen are selectively eliminated. When crossed onto a related self-compatible (SC) accession lacking active S-RNase, pollen transmission of the T-DNA followed Mendelian ratios. These results provide further evidence for functional overlap between SI and UI on the pollen side and suggest that CUL1 mutations will reinforce SI-to-SC transitions in natural populations only if preceded by loss of pistil S-RNase expression.

Maintenance of self-incompatibility in peripheral populations of a circumboreal woodland subshrub.

Compared with self-incompatible (SI) species, species that shift to self-compatibility (SC) are more likely to colonize a new habitat. Self-incompatibility and fruit-set failure have been widely reported in European populations of Linnaea borealis (twinflower), whereas at the eastern margin of its North American distribution it showed potential SC. We investigated the breeding system of L. borealis in northwestern China, the eastern margin of the species' distribution in Eurasia. Pollinators, breeding system and pollen limitation were examined in a nature reserve with thousands of L. borealis individuals. To investigate whether fruit set was limited by mating opportunity, we compared fruit set in high-, medium- and low-density patches of L. borealis. To examine whether clonal reproduction resulted in higher fruit-set failure, we compared fruit set among different sizes of clonal ramets. Flies contributed most pollinator visits in the studied population. It was strictly SI and natural fruit set depended on insect visits. Patch density comparisons showed that L. borealis was not pollen limited in low-density patches that had significantly fewer flowers. However, it produced significantly fewer fruits per flower when clonal ramet size increased, suggesting that the high failure of fruit set in larger clones with more flowers may be caused by geitonogamy. Generalist pollinators and clonal reproduction may help L. borealis to colonize in marginal areas without the transition of the breeding system from SI to SC, but experiencing fruit-set failure resulting from geitonogamy within clones.

Mapping a New Source of Self-fertility in Perennial Ryegrass (Lolium perenne L.)

There is a rising interest of moving towards hybrid breeding in outcrossing species. Self-compatibility (SC), which occurs at low rates in self-incompatible species, could be used to develop inbred lines, a key requirement for hybrid breeding programs. In perennial ryegrass, the existence of SC independent from the self-incompatibility (SI) loci S and Z has been reported. In this study, we used 98 F2 individuals from a cross between a self-compatible ecotype and an individual of the VrnA mapping population that were tested with markers for two candidate linkage groups 3 and 5 as well as markers for candidate regions at the S and Z locus. We were able to determine a tentative location of a SC locus and tested the possible interaction to other loci involved in SI and SC. This information will help to fine map the SC locus, and for marker-assisted selection.

Different expression of S-locus cysteine-rich protein (SCR) alleles in self-incompatible and self-compatible Brassica napus breeding lines and cultivars: Can be SCR/SP11 used as a selectable marker in breeding?

There are several approaches available for hybrid breeding in oil seed rape, Brassica napus, as cytoplasmic male sterility (CMS), genic male sterility (GMS), self-incompatibility (SI), and chemical hybridizing agens (CHA). In comparison with others, SI is regarded as one of the most valuable strategies in hybrid breeding. Unlike self-incompatible (SI) B. rapa and B. oleracea, two ancestor species, B. napus is naturally self-compatible (SC). However, occasionally SI also occurs in rapeseed cultivars. SI in Brassicaceae plants is sporophytically controlled by a single multi-allelic locus (S-locus), which contains at least three highly polymorphic genes expressed in the stigma (S locus glycoprotein, SLG and S receptor kinase, SRK) and in the pollen (SCR/SP11). In segregating population derived from crosses between DH SI lines and 00-quality donors we found two recessive alleles of a SCR class II gene. We developed new primers for detection of unique cv. Tandem derived allele and this allele was successfully amplified in SI donor plants and SI plants after first cycle of crossing. Analyses of other accessions (SI donor different from cv. Tandem) and varieties did not show so clear pattern of segregation and different expression of both alleles does not correspond to phenotypic manifestation of self-incompatibility and we can assume that it is caused by the presence of repressor gene that does not lie on the S-locus. Key words: Self-incompatibility, Brassica napus, S receptor kinase (SRK), S locus glycoprotein (SLG), S locus cysteine-rich protein (SCR).

Self-(in)compatibility inheritance and allele-specific marker development in yellow mustard (Sinapis alba)

Yellow mustard (Sinapis alba) has a sporophytic self-incompatibility reproduction system. Genetically stable self-incompatible (SI) and self-compatible (SC) inbred lines have recently been developed in this crop. Understanding the S haplotype of different inbred lines and the inheritance of the self-(in)compatibility (SI/SC) trait is very important for breeding purposes. In this study, we used the S-locus gene-specific primers in Brassica rapa and Brassica oleracea to clone yellow mustard S-locus genes of SI lines Y514 and Y1130 and SC lines Y1499 and Y1501. The PCR amplification results and DNA sequences of the S-locus genes revealed that Y514 carried the class I S haplotype, while Y1130, Y1499, and Y1501 had the class II S haplotype. The results of our genetic studies indicated that self-incompatibility was dominant over self-compatibility and controlled by a one-gene locus in the two crosses of Y514 × Y1499 and Y1130 × Y1501. Of the five S-locus gene polymorphic primer pairs, Sal-SLGI and Sal-SRKI each generated one dominant marker for the SI phenotype of Y514; Sal-SLGII and Sal-SRKII produced dominant marker(s) for the SC phenotype of Y1501 and Y1499; Sal-SP11II generated one dominant marker for Y1130. These markers co-segregated with the SI/SC phenotype in the F2 populations of the two crosses. In addition, co-dominant markers were developed by mixing the two polymorphic primer pairs specific for each parent in the multiplex PCR, which allowed zygosity to be determined in the F2 populations. The SI/SC allele-specific markers have proven to be very useful for the selection of the desirable SC genotypes in our yellow mustard breeding program.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9943-8) contains supplementary material, which is available to authorized users.

Effects of pollen availability and the mutation bias on the fixation of mutations disabling the male specificity of self‐incompatibility

The evolution of self-compatibility (SC) by the loss of self-incompatibility (SI) is regarded as one of the most frequent transitions in flowering plants. SI systems are generally characterized by specific interactions between the male and female specificity genes encoded at the S-locus. Recent empirical studies have revealed that the evolution of SC is often driven by male SC-conferring mutations at the S-locus rather than by female mutations. In this study, using a forward simulation model, we compared the fixation probabilities of male vs. female SC-conferring mutations at the S-locus. We explicitly considered the effects of pollen availability in the population and bias in the occurrence of SC-conferring mutations on the male and female specificity genes. We found that male SC-conferring mutations were indeed more likely to be fixed than were female SC-conferring mutations in a wide range of parameters. This pattern was particularly strong when pollen availability was relatively high. Under such a condition, even if the occurrence of mutations was biased strongly towards the female specificity gene, male SC-conferring mutations were much more often fixed. Our study demonstrates that fixation probabilities of those two types of mutation vary strongly depending on ecological and genetic conditions, although both types result in the same evolutionary consequence-the loss of SI.

Self-compatibility in loquat (Eriobotrya japonica Lindl.) is possibly due to S6-RNase mutation

Loquat (Eriobotrya japonica Lindl.), a member of the Rosaceae, carries the RNase-dependent gametophytic self-incompatibility (GSI) fertilization system. However, cultivars that carry the S6 allele are self-compatible (SC). In the present study, the S6ins-RNase and four S6-SFB genes were analyzed. Near the 3′ end of the S6ins-RNase open reading frame, a 24-nucleotide in-frame insertion was identified. Transcription of S6ins-RNase mRNA in SC cultivars Avri, Yehuda and Akko 1 was lower than that of the coupled S-RNase (S2, S3 and S4, respectively). Computer modeling of the putative S6ins-RNase protein positioned the 8-amino acid insertion as an external ring on the protein's surface, facing the catalytic site, and possibly preventing RNA degradation. Accordingly, RNase activity gel analysis showed no activity for the S6ins-RNase protein. In the four cloned S6-SFBs (EjSFBB1a-S6, EjSFBB1b-S6, EjSFBB4-S6 and EjSFBB8-S6), which correspond to three SFB brother subtypes, no mutation was observed. Thus, the SC of the loquat S6 haplotype is due to inactivity of the S6ins-RNase.

THE ROLE OF INBREEDING DEPRESSION AND MATING SYSTEM IN THE EVOLUTION OF HETEROSTYLY

We investigated the role of morph-based differences in the expression of inbreeding depression in loss of the mid-styled morph from populations of tristylous Oxalis alpina. The extent of self-compatibility (SC) of reproductive morphs, the degree of self-fertilization, and the magnitude of inbreeding depression were investigated in three populations of O. alpina differing in their tristylous incompatibility relationships. All three populations exhibited significant inbreeding depression. In two populations with highly modified tristylous incompatibility, manifested as increased reciprocal compatibility between short- and long-styled morphs, substantial SC and self-fertilization of mid-styled morphs were detected, and expected to result in expression of inbreeding depression in the progeny of mid-styled morphs in the natural populations. In contrast, significant self-fertility of the mid-styled morph was absent from the population with typical tristylous incompatibility, and no self-fertilization could be detected. Although self-fertilization and expression of inbreeding depression should result in selection against the mid-styled morph in the later stages of the transition from tristyly to distyly, in O. alpina selection against the mid-styled morph in the early phases of the evolution of distyly is likely due to genic selection against mid-alleles associated with modified tristylous incompatibility, rather than expression of inbreeding depression.

Pollen Tube Growth and Self-Compatibility in Almond.

Although pollen tube growth has been an important criterion for self-compatibility evaluation in almond, there is not a clear-cut separation between positive and negative growth of pollen tubes in the different genotypes. The examination of pollen tube growth after selfing almond seedlings has allowed establishing different levels of compatibility, but not a clear-cut separation between self-compatible (SC) and self-incompatible (SI) genotypes, related to the presence of pseudo-self-compatibility in almond. Consequently, a relationship between pollen tube growth and self-compatibility in almond may be established for evaluating the seedlings in breeding programs.

An S-Locus Independent Pollen Factor Confers Self-Compatibility in ‘Katy’ Apricot

Loss of pollen-S function in Prunus self-compatible cultivars has been mostly associated with deletions or insertions in the S-haplotype-specific F-box (SFB) genes. However, self-compatible pollen-part mutants defective for non-S-locus factors have also been found, for instance, in the apricot (Prunus armeniaca) cv. ‘Canino’. In the present study, we report the genetic and molecular analysis of another self-compatible apricot cv. termed ‘Katy’. S-genotype of ‘Katy’ was determined as S 1 S 2 and S-RNase PCR-typing of selfing and outcrossing populations from ‘Katy’ showed that pollen gametes bearing either the S 1- or the S 2-haplotype were able to overcome self-incompatibility (SI) barriers. Sequence analyses showed no SNP or indel affecting the SFB 1 and SFB 2 alleles from ‘Katy’ and, moreover, no evidence of pollen-S duplication was found. As a whole, the obtained results are compatible with the hypothesis that the loss-of-function of a S-locus unlinked factor gametophytically expressed in pollen (M’-locus) leads to SI breakdown in ‘Katy’. A mapping strategy based on segregation distortion loci mapped the M’-locus within an interval of 9.4 cM at the distal end of chr.3 corresponding to ∼1.29 Mb in the peach (Prunus persica) genome. Interestingly, pollen-part mutations (PPMs) causing self-compatibility (SC) in the apricot cvs. ‘Canino’ and ‘Katy’ are located within an overlapping region of ∼273 Kb in chr.3. No evidence is yet available to discern if they affect the same gene or not, but molecular markers seem to indicate that both cultivars are genetically unrelated suggesting that every PPM may have arisen independently. Further research will be necessary to reveal the precise nature of ‘Katy’ PPM, but fine-mapping already enables SC marker-assisted selection and paves the way for future positional cloning of the underlying gene.

Pollinator scarcity drives the shift to delayed selfing in Himalayan mayapple Podophyllum hexandrum (Berberidaceae)

Recent molecular phylogenetics have indicated that American mayapple (mainly self-incompatible, SI) and Himalayan mayapple, which was considered to be self-compatible (SC), are sister species with disjunct distribution between eastern Asia and eastern North America. We test a hypothesis that the persistence of this early spring flowering herb in the Himalayan region is attributable to the transition from SI to SC, the capacity for selfing in an unpredictable pollination environment. Pollinator observations were conducted in an alpine meadow with hundreds of Himalayan mayapple (Podophyllum hexandrum Royle) individuals over 2 years. To examine autogamy, seed set under different pollination treatments was compared. To clarify whether automatic self-pollination is achieved by movement of the pistil as a previous study suggested, we measured incline angles of the pistil and observed flower movement during anthesis using video. Floral visitors to the nectarless flowers were very rare, but solitary bees and honeybees could be potential pollinators. Seed set of bagged flowers was not significantly different from that of open-pollinated, self- or cross-pollinated flowers. However, removal of petals or stamens lowered seed yield. The angles of inclination of pistils did not change during the process of pollination. Automatic self-pollination was facilitated by petals closing and stamens moving simultaneously to contact the stigma. Stigmatic pollen load increased little during the day time, in contrast to a sharp increase when the flowers closed during the night-time. These observations indicated that Himalayan mayapple was SC and delayed self-pollination was facilitated by the movement of petals rather than the pistil. Compared with SI American mayapple, no obvious inbreeding depression in SC Himalayan mayapple may contribute its existence in the uplifting zone. A scarcity of pollinators may have driven the shift to delayed selfing in P. hexandrum.

A Self-compatible Pollen-part Mutant of Japanese Pear Produced by Crossing ‘Kosui’ with Pollen from Gamma-irradiated ‘Kosui’

The self-incompatible (SI) Japanese pear cultivar ‘Kosui’ was pollinated with pollen collected from a chronically gamma-irradiated ‘Kosui’ tree, and a progeny was obtained. This progeny resulted in the identification of self-compatible (SC) breeding selection, designated 415-1, which showed 74.4% fruit set in a self-pollination test. PCR-based genetic analysis revealed that 415-1 has S-RNase genotype S4S5, which is the same as that of the parent, ‘Kosui’. Pollination trials were used to investigate whether 415-1 harbors a stylar-part mutation or a pollen-part mutation in its SI locus. When 415-1 was pollinated with pollen from cultivars of the same genotype (‘Syuugyoku’ and ‘Oushuu’), no seed-containing fruit were set, indicating that 415-1 contains functional S4- and S5-RNase alleles. On the other hand, when ‘Syuugyoku’ and ‘Oushuu’ were pollinated with pollen from 415-1, fruit-bearing seeds were produced; therefore, we conclude that 415-1 carries a pollen-part mutation at the SI locus. This new self-compatible breeding selection will be useful for the development of new Japanese pear cultivars with SC.

Developmental onset of reproductive barriers and associated proteome changes in stigma/styles of Solanum pennellii.

Although self-incompatibility (SI) in plants has been studied extensively, far less is known about interspecific reproductive barriers. One interspecific barrier, known as unilateral incongruity or incompatibility (UI), occurs when species display unidirectional compatibility in interspecific crosses. In the wild tomato species Solanum pennellii, both SI and self-compatible (SC) populations express UI when crossed with domesticated tomato, offering a useful model system to dissect the molecular mechanisms involved in reproductive barriers. In this study, the timing of reproductive barrier establishment during pistil development was determined in SI and SC accessions of S. pennellii using a semi-in vivo system to track pollen-tube growth in developing styles. Both SI and UI barriers were absent in styles 5 days prior to flower opening, but were established by 2 days before flower opening, with partial barriers detected during a transition period 3–4 days before flower opening. The developmental expression dynamics of known SI factors, S-RNases and HT proteins, was also examined. The accumulation of HT-A protein coincided temporally and spatially with UI barriers in developing pistils. Proteomic analysis of stigma/styles from key developmental stages showed a switch in protein profiles from cell-division-associated proteins in immature stigma/styles to a set of proteins in mature stigma/styles that included S-RNases, HT-A protein and proteins associated with cell-wall loosening and defense responses, which could be involved in pollen–pistil interactions. Other prominent proteins in mature stigma/styles were those involved in lipid metabolism, consistent with the accumulation of lipid-rich material during pistil maturation.

The genetic characterization of self-incompatibility in a Brassica napus line with promising breeding potential

The aim of this study was to study hybrid breeding through the self-incompatibility (SI) pollination control system. To this end, we characterized the SI of a Brassica napus line ‘S-1300’. ‘S-1300’ was found to have two class II S haplotypes, namely BnS-1300 and BnS-6 located on the A and C genome, respectively. A self-compatible line ‘8400’ had one class I S haplotype (BnS-1) on the A genome and one class II S haplotype (BnS-6) on the C genome. Genetic analysis revealed that SI in ‘S-1300’ was recessive to SC (self-compatibility) in ‘8400’ and controlled by BnS-1300 on the A genome. BnSP11-1300 and BnSRK-1300 were cloned by the homology-based candidate gene method and found to share 100 % identity of coding sequence with BrS-60. The expression of BnSP11-1300 was detected only in ‘S-1300’, while the transcripts of BnSRK-1300 were detected in both ‘S-1300’ and ‘S-1300 × 8400’, which further confirmed that the class II S haplotype BnS-1300 controls the SI in ‘S-1300’. The potential of using ‘S-1300’ in research directed at elucidating the SC mechanism and in hybrid breeding of B. napus was discussed.