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ABSTRACT The development of mapping populations and quantitative trait loci (QTL) analysis face constraints, in crops exhibiting male sterility and self‐incompatibility under field conditions. Addressing these challenges requires the integration of advanced techniques, including the temporal alteration or excision of centromere histone H3 (CENH3) protein and the use of gene editing tools such as MATRILINEAL (MTL) knockout. Specifically, this can be achieved through Cas9/gRNA‐mediated mutagenesis or Cas9/gRNA‐driven promoter expression systems. These technologies offer efficient means to advance mapping populations and QTL analysis in male sterile and self‐incompatible crops within controlled ecosystems. The doubled haploid (DH) mapping population, traditionally requiring 3 years of generation time via anther culture method, can now be expedited to 2–3 years of generation time using gene editing techniques within controlled environmental systems. Notably, DH mapping populations can be efficiently generated in various crops, including rice, wheat, maize, barley and oats by leveraging gene editing tools. Among these tools, the novel approach of CENH3 protein temporal alteration/excision emerges as highly efficient compared to MTL knockout using Cas9/gRNA‐mediated mutation or Cas9/gRNA promoter expression. However, further investigation is warranted to optimise the regeneration of double haploid populations and enhance QTL analysis in male sterile and self‐incompatible crops under controlled systems. [ABSTRACT FROM AUTHOR]

Self-incompatibility (SI) poses a significant reproductive barrier, severely impacting the yield, quality, and economic value of Camellia oleifera. In this study, methyl jasmonate (MeJA) was employed as an exogenous stimulus to alleviate SI in C. oleifera. The research findings revealed that an exogenous dose of 1000 μmol·L−1 MeJA enhanced the germination and tube growth of C. oleifera self-pollen and greatly improved ovule penetration (18.75%) and fertilization (15.81%), ultimately increasing fruit setting (18.67%). It was discovered by transcriptome analysis that the key genes (CAD, C4H) involved in the lignin production process exhibited elevated expression levels in self-pistils treated with MeJA. Further analysis showed that the lignin concentration in the MeJA-treated pistils was 31.70% higher compared with the control group. As verified by pollen germination assays in vitro, lignin in the appropriate concentration range could promote pollen tube growth. Gene expression network analysis indicated that transcription factor bHLH may be pivotal in regulating lignin biosynthesis in response to MeJA, which in turn affects pollen tubes. Further transient knockdown of bHLH (Co_33962) confirmed its important role in C. oleifera pollen tube growth. In summary, the application of MeJA resulted in the stimulation of self-pollen tube elongation and enhanced fruit setting in C. oleifera, which could be associated with the differential change in genes related to lignin synthesis and the increased lignin content. [ABSTRACT FROM AUTHOR]

Summary: Plants employ a diversity of reproductive safeguarding strategies to circumvent the challenge of pollen limitation. Focusing on southern African Lachenalia (Asparagaceae: Scilloideae), we test the hypothesis that the evolution of reproductive safeguarding traits (self‐compatibility, autonomous selfing, bird pollination and clonal propagation) is favoured in species occupying conditions of low insect abundance imposed by critically infertile fynbos heathland vegetation and by flowering outside the austral spring insect abundance peak.We trace the evolution of these traits and selective regimes on a dated, multi‐locus phylogeny of Lachenalia and assess their evolutionary associations using ordinary and phylogenetic regression.Ancestral state reconstructions identify an association with non‐fynbos vegetation and spring flowering as ancestral in Lachenalia, the transition to fynbos vegetation and non‐spring flowering taking place multiple times. They also show that self‐compatibility, autofertility, bird pollination and production of multiple clonal offsets have evolved repeatedly.Regression models suggest that bird pollination and self‐compatibility are selected for in fynbos and in non‐spring flowering lineages, with autofertility being positively associated with non‐spring flowering. These patterns support the interpretation of these traits as reproductive safeguarding adaptations under reduced insect pollinator abundance. We find no evidence to support the interpretation of clonal propagation as a reproductive safeguarding strategy. See also the Commentary on this article by Burd, 244: 7–9. [ABSTRACT FROM AUTHOR]

Self-incompatibility (SI) is a complex mechanism that prevents plants from self-fertilizing to preserve and promote genetic variability. The angiosperm species have developed two different SI systems, the sporophytic (SSI) and the gametophytic (GSI) systems. SI is a significant impediment to steady fruit production in fruit tree species of the Rosaceae. In Rosaceae, GSI is genetically regulated via a single locus, named the 'S-locus', which includes a minimum of two polymorphic and relatively intercorrelated S genes: a pistil-expressed S-RNase gene and several pollen-expressed SFBB (S-locus F-Box Brothers) or SFB (S haplotype-specific F-box protein). This necessitates the interaction of S-RNases with the male determinants. Although genetic and molecular analyses of S genes have shown that mutations in both pistils and pollen-specific components induce self-compatibility in many species and cultivars, other genes or molecules outside the S-locus can co-participate in the male gamete rejection in GSI. However, we highlight and synthesize the most recent knowledge on different mechanisms of GSI in Rosaceae in this current review. [ABSTRACT FROM AUTHOR]

Cyperus esculentus seeds are often considered irrelevant for C. esculentus spread as their fragile seedlings would not establish or survive in agricultural soils. However, the ever-increasing spread and upsurge of genetically different clonal populations in NW-Europe raises questions about the establishment of C. esculentus seeds and the reproductive performance of seedlings. Indeed, little is known about the potential of C. esculentus seedlings to grow and propagate under outdoor conditions relative to plants grown from tubers. Seeds from different clonal populations were sown outdoors in various soil types and under different irrigation levels (rainfed, irrigated) to assess seed germination and seedling establishment. Additionally, two pot experiments were conducted with three different plant types (plants originating from mother tubers and from seeds harvested on open- or self-pollinated plants) obtained from eight clonal populations. Plant performance was investigated by measuring vegetative and generative parameters. Germination under outdoor conditions was significantly affected by clonal population and was highest in irrigated sand (5.3%). Germination in sand was 4.1 times higher in irrigated plots than in rainfed plots. In irrigated plots, germination was 3.8 and 4.7 times higher in sand than in sandy loam and clay, respectively. Depending on the year, three out of five to five out of six clonal populations produced more tubers when grown from mother tubers than from seeds. Maximal tuber reproduction factors of 1:965, 1:752, and 1:618 were achieved for plants from mother tubers and seeds from open- and self-pollinated flowers, respectively. Plants originating from open-pollinated seedlings have the potential to equal or exceed the vegetative reproductive capacity of plants originating from mother tubers. As a result of their ability to establish in situ and their substantial vegetative reproductive capacity, C. esculentus seedlings are highly relevant for agriculture and merit appropriate attention in any integrated weed management system targeting C. esculentus. [ABSTRACT FROM AUTHOR]

Pollination success of alpine plants is often restricted by low and unpredictable pollinator activity because of harsh and unstable weather conditions, where nocturnal pollination is rare. The alpine orchid, Platanthera tipuloides (Orchidaceae), has inconspicuous greenish yellow flowers with a sweet scent and a long spur that contains nectar. These floral traits are expected to be related to nocturnal moth pollination. To elucidate the pollination mode and reproductive characteristics of this species, we measured floral traits (spur length, nectar content in the spur, floral scent), documented flower visitors using camera traps, and quantified self‐compatibility and the degree of pollen limitation through controlled pollinations at two study plots in the Taisetsu Mountains, northern Japan. It was revealed that P. tipuloides is self‐incompatible and pollen limitation was absent at one of the study plots. The flowers emitted more volatile substances during the night, including lilac aldehyde isomers, which are known to attract moths. A nocturnal moth, Entephria amplicosta, was observed foraging nectar from the flowers, while no diurnal visitors were observed. The proboscis of E. amplicosta was shorter than the spur length, but it was long enough to access the accumulated nectar in the spurs. These results suggest that nocturnal pollination by moths is possible and can be efficient even in an alpine ecosystem with harsh environmental conditions. [ABSTRACT FROM AUTHOR]

Summary Only very limited information is available on why some nonsynonymous variants severely alter gene function while others have no effect. To identify the characteristic features of mutations that strongly influence gene function, this study focused on SRK which encodes a highly polymorphic receptor kinase expressed in stigma papillary cells that underlies a female determinant of self‐incompatibility in Brassicaceae. A set of 300 Arabidopsis thaliana transformants expressing mutated SRKb from A. lyrata was constructed using error‐prone PCR and the genotype and self‐incompatibility phenotype of each transformant were determined. Almost all the transformants showing the self‐incompatibility defect contained mutations in AlSRKb that altered localization to the plasma membrane. The observed mutations occurred in amino acid residues that were highly conserved across S haplotypes and whose predicted locations were in the interior of the protein. Our findings suggested that mutations causing the self‐incompatibility defect were more likely to result from changes to AlSRKb biosynthesis than from loss of AlSRKb function. In addition, we examined whether the RandomForest and Extreme Gradient Boosting methods could predict the self‐incompatibility phenotypes of SRK mutants. [ABSTRACT FROM AUTHOR]

Pollination by deception is assumed as the general rule among pleurothallid orchids. However, considering the exceptional diversity of this group (44 genera and over 5100 species) and the relatively limited number of available studies (pollination ecology has been assessed in only 17 genera), generalized trends about their pollination systems might disregard a wide variety of specific life-history traits and inconspicuous honest signals/rewards for pollinators. The few known associations of pleurothallid orchids with a large assortment of fly taxa further support the assumption of generalized pollination by deception. We investigated the natural pollination system of Masdevallia hortensis, a strictly endemic species of cloud forests in the Western Andes of Colombia. This species exhibited a sophisticated and unique pollination mechanism, producing sugary secretions in the lateral sepals along purple dotted patches, fed upon by different visiting species of fruit flies (Drosophilidae). The sucrose concentration in these secretions varied throughout the day and significantly decreased after pollinaria removal. Visiting fruit flies appeared to be guided towards a chamber between the mobile lip and the column, by dotted lines in the lateral sepals. During visitations, individuals of the most abundant species in our observations (Drosophila sp. 1) were singly entrapped in the chamber until eventually freeing themselves with the pollinaria attached to their bodies. We also demonstrated that M. hortensis is strictly self-incompatible, which makes fly pollination an essential process for the maintenance of natural populations of the species. The flowers of M. hortensis offer rewards for visiting insects, an aspect that should be thoroughly evaluated before making generalizations. In this way, we urge integrative ecological studies to understand the reproductive evolutionary patterns in this group of orchids. [ABSTRACT FROM AUTHOR]

Although self-incompatibility in apples (Malus × domestica Borkh.) is regulated by a single S-locus with multiple S-haplotypes that comprise pistil S (S-RNase) and pollen S genes, it is not desirable in commercial orchards because it requires cross-pollination to achieve stable fruit production. Therefore, it is important to identify and characterize self-compatible apple cultivars. However, little is known about self-compatibility (SC) and its underlying molecular mechanisms in apples. In this study, we discovered that ‘Vered’, an early maturing and low chilling-requiring apple cultivar, exhibits stable SC, which was evaluated via self-pollination tests. The S-genotype of ‘Vered’ was designated as S24S39sm. Results of genetic analysis of selfed progeny of ‘Vered’ revealed that SC is associated with the S39sm-haplotype, and molecular analyses indicated that it is caused by alternative splicing and a 205-bp deletion in S39sm-RNase. These events induce frameshifts and ultimately produce the defective S39sm-RNase isoforms that lack their C-terminal half. These results enabled us to develop a 117-bp DNA marker that can be used to assist in the selection of self-compatible apples with the dysfunctional S39sm-RNase. Thus, analysis of ‘Vered’ provided insights into the molecular mechanism of the very rare trait of natural stylar-part SC. Moreover, ‘Vered’ is a valuable genetic resource for breeding cultivars with SC and/or low chilling requirement in apple. Our findings contribute to a better understanding of self-compatible molecular mechanisms in apple and provide for the accelerated breeding of self-compatible apple cultivars.Key message: This study identifies the apple cultivar, ‘Vered’, as a stylar-part self-compatible genetic resource. We reveal the molecular mechanism underlying self-compatibility and develop an efficient selection marker for the self-compatibility. [ABSTRACT FROM AUTHOR]

Abstract Utilizing 32 previously identified S ribonuclease (S-RNase) gene sequences and abundant citrus resources, this study designed specific primers for 10 S-RNase genes. A total of 32 pairs of primers were used to analyze the self-incompatibility genotypes (S-genotypes) of 241 citrus resources, encompassing 105 mandarins, 47 pummelos, 69 oranges, and 20 lemons and citrons. These results provide theoretical guidance for parent selection in production and breeding programs. Among the 215 samples analyzed, two normal S-genotypes were identified, while no S-genotypes were detected in three samples. Notably, 21 samples, primarily citrons, exhibited amplification of only one S-genotype. Additionally, two pummelo samples showed amplification of three S-genotypes each. The integration of S-genotype and selfing phenotype identification revealed five newly discovered self-compatible mutated materials: Changsha ‘Shatian’ pummelo, large-fruited red pummelo, slender leaf ‘Mangshanyegan’, ‘Shatangju’, and W. Murcott. These findings provide valuable resources for investigating the self-compatibility mechanism in citrus.

• Specialised plant pollination systems can suffer reduced fertility if they receive insufficient pollinator service. • The Cape endemic Cyanella alba possess specialised floral adaptations – mirror-image flowers and dimorphic anthers – usually associated with buzz pollination by bees. • Experimental pollinations demonstrated that plants possess ovarian self-incompatibility and depend on pollinators for cross-pollination. • Chronic pollen limitation of seed set owing to the near absence of visitation by buzz pollinating bees was evident in several natural populations. • Land use and climate change may explain the paucity of buzz pollination with implications for ecology and evolution of plant populations. Plants with specialised pollination systems may be susceptible to reduced fertility if they are incapable of autonomous self-pollination and are visited infrequently by pollinators capable of promoting effective cross-pollination. Here, we investigate this question by examining the reproductive ecology of the Cape endemic Cyanella alba subsp. flavescens (Tecophilaeaceae), which has mirror-image flowers (enantiostyly) and dimorphic anthers (heteranthery). These traits are usually associated with buzz pollination mediated by bees that extract pollen from the poricidal anthers of flowers through vibration. We quantified insect visitation to flowers in three populations over two years in the vicinity of the Biedouw Valley, Western Cape, South Africa to determine whether plants were visited by buzz-pollinating bees. We also recorded visits by pollinators to other co-flowering species at each site and constructed a network on insect visitation. We conducted controlled hand pollinations and bagging experiments to determine whether plants were self-compatible and capable of autonomous self-pollination, and compared natural levels of fruit and seed set with those obtained from hand cross-pollination to evaluate evidence for pollen limitation of seed fertility. Despite 74 h of field observations, only two actively buzz-pollinating bees were recorded visiting flowers, although they were observed visiting other species in the community. The most frequent visitors to C. alba were opportunistic pollen-consuming beetles although we obtained no direct evidence that they were effective in promoting cross-pollination. Plants in each population exhibited chronic pollen limitation of seed set. Controlled pollinations demonstrated that plants were moderately self-sterile and incapable of autonomous self-pollination. Although fruit set was high following self-pollination, few seeds were evident within developing fruit. Observations of pollen-tube growth following controlled hand self- and cross-pollination revealed abundant pollen tubes at the base of styles in both treatments. Thus, self-sterility in C. alba probably results from late-acting ovarian self-incompatibility, and possibly also the abortion of developing seed due to inbreeding depression. We discuss the possible causes of scarce buzz pollination in C. alba and consider its ecological and evolutionary consequences. [ABSTRACT FROM AUTHOR]

The shift from outcrossing to self-fertilization is one of the main evolutionary transitions in plants and has broad effects on evolutionary trajectories. In Brassicaceae, the ability to inhibit self-fertilization is controlled by 2 genes, SCR and SRK , tightly linked within the S -locus. A series of small non-coding RNAs also encoded within the S -locus regulates the transcriptional activity of SCR alleles, resulting in a linear dominance hierarchy between them. In Brassicaceae, natural allopolyploid species are often self-compatible (SC) even when one of the progenitor species is self-incompatible, but the reason why polyploid lineages tend to lose self-incompatibility (SI) and the timing of the loss of SI (immediately after ancestral hybridization between the progenitor species, or at a later stage after the formation of allopolyploid lineages) have generally remained elusive. We used a series of synthetic diploid and tetraploid hybrids obtained between self-fertilizing Capsella orientalis and outcrossing Capsella grandiflora to test whether the breakdown of SI could be observed immediately after hybridization, and whether the occurrence of SC phenotypes could be explained by the dominance interactions between S -haplotypes inherited from the parental lineages. We used RNA-sequencing data from young inflorescences to measure allele-specific expression of the SCR gene and infer dominance interactions in the synthetic hybrids. We then evaluated the seed set from autonomous self-pollination in the synthetic hybrids. Our results demonstrate that self-compatibility of the hybrids depends on the relative dominance between S -alleles inherited from the parental species, confirming that SI can be lost instantaneously upon formation of the ancestral allopolyploid lineage. They also confirm that the epigenetic regulation that controls dominance interactions between S -alleles can function between subgenomes in allopolyploids. Together, our results illustrate how a detailed knowledge of the mechanisms controlling SI can illuminate our understanding of the patterns of co-variation between the mating system and changes in ploidy. [ABSTRACT FROM AUTHOR]

SUMMARY: The successful interaction between pollen and stigma is a critical process for plant sexual reproduction, involving a series of intricate molecular and physiological events. After self‐compatible pollination, a significant reduction in reactive oxygen species (ROS) production has been observed in stigmas, which is essential for pollen grain rehydration and subsequent pollen tube growth. Several scavenging enzymes tightly regulate ROS homeostasis. However, the potential role of these ROS‐scavenging enzymes in the pollen‐stigma interaction in Brassica napus remains unclear. Here, we showed that the activity of ascorbate peroxidase (APX), an enzyme that plays a crucial role in the detoxification of hydrogen peroxide (H2O2), was modulated depending on the compatibility of pollination in B. napus. We then identified stigma‐expressed APX1s and generated pentuple mutants of APX1s using CRISPR/Cas9 technology. After compatible pollination, the BnaAPX1 pentuple mutants accumulated higher levels of H2O2 in the stigma, while the overexpression of BnaA09.APX1 resulted in lower levels of H2O2. Furthermore, the knockout of BnaAPX1 delayed the compatible response‐mediated pollen rehydration and germination, which was consistent with the effects of a specific APX inhibitor, ρ‐Aminophenol, on compatible pollination. In contrast, the overexpression of BnaA09.APX1 accelerated pollen rehydration and germination after both compatible and incompatible pollinations. However, delaying and promoting pollen rehydration and germination did not affect the seed set after compatible and incompatible pollination in APX1 pentuple mutants and overexpression lines, respectively. Our results demonstrate the fundamental role of BnaAPX1 in pollen rehydration and germination by regulating ROS homeostasis during the pollen‐stigma interaction in B. napus. Significance Statement: Our research found that self‐incompatibility in Brassica napus requires the accumulation of reactive oxygen species (ROS) levels in the stigma. We identified the importance of BnaAPX1 in regulating ROS homeostasis, which is critical for pollen rehydration and germination in B. napus. [ABSTRACT FROM AUTHOR]

Self-incompatibility (SI) is a genetic mechanism that promotes out-breeding and maintains genetic diversity in plant species. The inhibition of pollen germination and pollen tube growth is one of the major characteristics of SI response. The involvement of Ca2+ signaling mediated by Ca2+ sensors in the SI response has been demonstrated to affect the germination of incompatible pollen and the normal elongation of pollen tubes. In this study, the calmodulin-like 49 (BrCML49) gene in Chinese cabbage (Brassica rapa L. ssp. pekinensis) was down-regulated expression during the SI process, indicating that BrCML49 may participate in the regulation of SI response. The transient suppression of BrCML49 gene induced the abnormal germination of pollen in vitro, which showed the putative positive roles of BrCML49 in regulating pollen germination. The inhibited germination of self- and cross-pollen in BrCML49-suppressed stigma was also observed, which revealed the activated SI response. After BrCML49 suppression, the increases in Ca2+ level in stigmatic papilla cells were consistent with the increases in ROS/H2O2 contents in the stigma, which may be essential for the occurrence of SI response. Furthermore, heterologous overexpression of BrCML49 in Arabidopsis validated the positive regulation of BrCML49 in pollen germination and pollen tube growth. In addition, BrCML49 overexpressed Arabidopsis exhibited an enhanced tolerance of pollen germination to high Ca2+ condition. These results will provide valuable information for understanding the roles of BrCML49 in regulating pollen germination and pollen tube growth during SI process in Chinese cabbage. [ABSTRACT FROM AUTHOR]

As self-incompatibility is a major issue in pummelo breeding and production, its mechanism in citrus was analyzed to improve breeding efficiency and reduce production costs. Rutaceae belongs to S-RNase type of gametophytic self-incompatibility. While the function of S-RNase/SLF and the mechanism of self-incompatibility have been studied extensively, the transcriptional regulation of S-RNase has been less studied. We performed transcriptome sequencing with the styles of ‘Shatian’ pummelo on the day of anthesis and 1–5 days before anthesis, and found that the transcript level of S-RNase gradually decreased with flower development. By analyzing differentially expressed genes and correlation with the expression trend of S-RNase, we identified a candidate gene, CgHSFB1, and utilized biochemical experiments such as yeast one-hybrid assay, electrophoretic mobility shift assay and dual-luciferase assay, as well as transient transformation of citrus calli and Citrus microcarpa and demonstrated that CgHSFB1 could directly bind to the S1-RNase promoter and repress the expression of S1-RNase, which is involved in the pummelo self-incompatibility response. In contrast, CgHSFB1 did not bind to the promoter of S2-RNase, and there was specificity in the regulation of S-RNase.Key message: Transcription factor CgHSFB1 regulates the expression of S -RNase and is thus involved in self-incompatibility in citrus. [ABSTRACT FROM AUTHOR]

Olive (Olea europaea L.) is an important Mediterranean tree species with a longstanding history of cultivation, boasting a diverse array of local cultivars. While traditional olive orchards are valued for their cultural and aesthetic significance, they often face economic sustainability challenges in the modern context. The success of both traditional and newly introduced cultivars (e.g. those obtained by cross-breeding) is hindered by self-incompatibility, a prevalent issue for this species that results in low fruit set when limited genetic diversity is present. Further, biological, environmental, and agronomic factors have been shown to interlink in shaping fertilization patterns, hence impacting on the final yield. Climatic conditions during pollination, such as excessive rainfall or high temperatures, can further exacerbate the problem. In this work, we provide an overview of the various factors that trigger the phenomenon of suboptimal fruit set in olive trees. This work provides a comprehensive understanding of the interplay among these factors, shedding light on potential mechanisms and pathways that contribute to the observed outcomes in the context of self-incompatibility in olive. [ABSTRACT FROM AUTHOR]

This article discusses effective strategies for creating self-compatible Brassica rapa (Chinese cabbage) plants by introducing mutated SRK and SCR/SP11 genes from Brassica napus (rapeseed). Self-incompatibility (SI) is a common trait in Brassica vegetable crops, but it hinders the development and propagation of inbred lines. The manipulation of SI genes, such as SRK and SCR/SP11, can lead to the creation of self-compatible materials. The researchers used CRISPR/Cas9 technology to mutate the BnSRK-1 gene in B. napus and then employed distant hybridization to introduce the mutated gene into B. rapa, resulting in the generation of self-compatible materials. This research has important implications for improving the breeding process of Brassica vegetable crops. [Extracted from the article]

Trendy high-density olive fields are often monovarietal orchards, mostly using the cultivar Arbequina. However, Arbequina shows a strong self-incompatibility response, and its yields depend on wind cross-pollination, which is not always available. With the aim of finding suitable self-compatible cultivars that can replace Arbequina, we evaluated pollen–pistil interaction, fruit set and seed paternity in Arbosana under different pollination treatments: self-pollination, open-pollination and three cross-pollination treatments: × Arbequina, × Sikitita and × Koroneiki. All these cultivars are low-vigor cultivars suitable for high-density orchards, making them potential pollinizers for Arbosana. The results show that Arbosana is also self-incompatible with a strong reduction in fruit set due to a lower fertilization level caused by a strong inhibition of pollen tube growth in self-pollinated flowers. Seed-paternity analyses confirmed the self-incompatibility response of Arbosana and suggest that some fruit obtained in bagged shoots under self-pollination were, in fact, a product of cross-fertilization. In conclusion, we recommend against the use of Arbosana in large monovarietal orchards. On the contrary, good results were obtained under cross-pollination with Sikitita, Arbequina and Koroneiki pollen, allowing us to recommend them as pollinizers for Arbosana in appropriate pollination designs. This is the first time Arbosana self-incompatibility has been reported. [ABSTRACT FROM AUTHOR]

In Brassicaceae self‐incompatibility (SI), self‐pollen rejection is initiated by the S‐haplotype specific interactions between the pollen S cysteine‐rich/S‐locus protein 11 (SCR/SP11) ligands and the stigma S receptor kinases (SRK). In Brassica SI, a member of the Plant U‐Box (PUB) E3 ubiquitin ligases, ARM‐repeat containing 1 (ARC1), is then activated by SRK in this stigma and cellular events downstream of this cause SI pollen rejection by inhibiting pollen hydration and pollen tube growth. During the transition to selfing, Arabidopsis thaliana lost the SI components, SCR, SRK, and ARC1. However, this trait can be reintroduced into A. thaliana by adding back functional copies of these genes from closely related SI species. Both SCR and SRK are required for this, though the degree of SI pollen rejection varies between A. thaliana accessions, and ARC1 is not always needed to produce a strong SI response. For the A. thaliana C24 accession, only transforming with Arabidopsis lyrataSCR and SRK confers a strong SI trait (SI‐C24), and so here, we investigated if ARC1‐related PUBs were involved in the SI pathway in the transgenic A. thaliana SI‐C24 line. Two close ARC1 homologs, PUB17 and PUB16, were selected, and (Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) technology was used to generate pub17 and pub16 mutations in the C24 accession. These mutants were then crossed into the transgenic A. thaliana SI‐C24 line and their potential impact on SI pollen rejection was investigated. Overall, we did not observe any significant differences in SI responses to implicate PUB17 and PUB16 functioning in the transgenic A. thaliana SI‐C24 stigma to reject SI pollen. [ABSTRACT FROM AUTHOR]

Summary: Nicotiana attenuata styles preferentially select pollen from among accessions with corresponding expression patterns of NaS‐like‐RNases (SLRs), and the postpollination ethylene burst (PPEB) is an accurate predictor of seed siring success. However, the ecological consequences of mate selection, its effect on the progeny, and the role of SLRs in the control of ethylene signaling remain unknown.We explored the link between the magnitude of the ethylene burst and expression of the SLRs in a set of recombinant inbred lines (RILs), dissected the genetic underpinnings of mate selection through genome‐wide association study (GWAS), and examined its outcome for phenotypes in the next generation.We found that high levels of PPEB are associated with the absence of SLR2 in most of the tested RILs. We identified candidate genes potentially involved in the control of mate selection and showed that pollination of maternal genotypes with their favored pollen donors produces offspring with longer roots. When the maternal genotypes are only able to select against nonfavored pollen donors, the selection for such positive traits is abolished.We conclude that plants' ability of mate choice contributes to measurable changes in progeny phenotypes and is thus likely a target of selection. [ABSTRACT FROM AUTHOR]

Yield in many crops is affected by abscission during the early stages of fruitlet development. The reasons for fruitlet abscission are often unclear but they may include genetic factors because, in some crops, self-pollinated fruitlets are more likely to abscise than cross-pollinated fruitlets. Pollen parentage can also affect final fruit size and fruit quality. Here, we aimed to understand the effects of pollen parentage on fruitlet retention and nut quality in orchards of macadamia (Macadamia integrifolia Maiden & Betche). We identified the pollen parent of macadamia 'cultivar '816' embryos by analysing single nucleotide polymorphisms (SNPs) in their DNA using customised MassARRAY and Single Allele Base Extension Reaction (SABER) methods. This allowed us to determine the proportions of self-fertilised and cross-fertilised progeny during premature fruit drop at 6 weeks and 10 weeks after peak anthesis, as well as at nut maturity. We determined how pollen parentage affected nut-in-shell (NIS) mass, kernel mass, kernel recovery, and oil concentration. Macadamia trees retained cross-fertilised fruitlets rather than self-fertilised fruitlets. The percentage of progeny that were cross-fertilised increased from 6% at 6 weeks after peak anthesis to 97% at nut maturity, with each tree producing on average 22 self-fertilised nuts and 881 cross-fertilised nuts. Three of the four cross-pollen parents provided fruit with significantly higher NIS mass, kernel mass, or kernel recovery than the few remaining self-fertilised fruit. Fruit that were cross-fertilised by '842', 'A4', or 'A203' had 16–29% higher NIS mass and 24–44% higher kernel mass than self-fertilised fruit. Nuts that were cross-fertilised by 'A4' or 'A203' also had 5% or 6% higher kernel recovery, worth approximately $US460–540 more per ton for growers than self-fertilised nuts. The highly selective abscission of self-fertilised fruitlets and the lower nut quality of self-fertilised fruit highlight the critical importance of cross-pollination for macadamia productivity. [ABSTRACT FROM AUTHOR]

The continuously refined genome assembly of the Chinese cabbage accession Chiifu is widely recognized as the reference for Brassica rapa. However, the high self-incompatibility of Chiifu limits its broader utilization. In this study, we report the development of self-compatible Chiifu lines through a meticulous markerassisted selection (MAS) strategy, involving the substitution of the Chiifu allele of MLPK (M-locus protein kinase) with that from the self-compatible Yellow Sarson (YS). A YS-based marker (SC-MLPK) was employed to screen 841 B. rapa accessions, confirming that all eight accessions with the mlpk/mlpk (mm) genotype exhibited self-compatibility. Additionally, we designed 131 High-Resolution Melting (HRM) markers evenly distributed across the B. rapa genome as genomic background selection (GBS) markers to facilitate the introgression of self-compatibility from YS into Chiifu along with SC-MLPK. Genome background screening revealed that the BC3S1 population had a proportion of the recurrent parent genome (PR) ranging from 93.9% to 98.5%. From this population, we identified self-compatible individuals exhibiting a high number of pollen tubes penetrating stigmas (NPT) (>25) and a maximum compatibility index (CI) value of 7.5. Furthermore, we selected two individuals demonstrating significant similarity to Chiifu in both genetic background and morphological appearance, alongside self-compatibility. These selected individuals were self-pollinated to generate two novel lines designated as SCChiifu Lines. The development of these self-compatible Chiifu lines, together with the SC-MLPK marker and the set of HRM markers, represents valuable tools for B. rapa genetics and breeding. [ABSTRACT FROM AUTHOR]

Key message: Through a multidisciplinary study we found that Gymnocalycium bruchii, an endemic cactus from central Argentina, acts as a dioecious species, which is the first record in this genus. Cactaceae species are typically hermaphroditic; however, about 2% have other different reproductive systems. These non-hermaphroditic species may develop sexual dimorphism in flowers or other reproductive, vegetative or ecological traits, besides a specific breeding system and floral ontogeny. Therefore, multidisciplinary research is necessary to fully understand reproduction in those species. For this purpose, we studied Gymnocalicium bruchii, a globose cactus endemic to central Argentina that is presumably dioecious or gynodioecious. We made observations in two natural and two cultivated populations. We made morphological observations of plants and flowers, and performed quantitative analyses to determine the sex ratio, size of plants and flowers, flower production, fruiting, among other variables. We performed hand-pollination, self-fertilization and free-pollination tests to determine the breeding system. Finally, we studied the anatomy and ontogeny of the reproductive organs using permanent histological slides of flower morphs at different stages. Our results confirm that Gymnocalicium bruchii is a dioecious species. Female flowers have atrophied anthers and a functional gynoecium that produces fruits and seeds. Male flowers are bigger and have a functional androecium but a sterile gynoecium. In the cultivated population, the sex ratio was 1/1, whereas the number of male individuals was higher in both natural populations. Pollination tests corroborated dioecy. Ontogenetic studies revealed that in female flowers the anthers collapse before microspore maturation, while in male flowers the gynoecium shows normal development of the ovary, style, stigma, and ovules; however, the latter are never fertilized. [ABSTRACT FROM AUTHOR]

Main conclusion: Self-incompatibility studies have revealed a potential use of Tunisian apple resources for crop improvement and modern breeding programs and a likely correlation between the pollen tube growth and flowering period. Apples [Malus domestica. Borkh] exhibit an S-RNase-based gametophytic self-incompatibility (GSI) system. Four primer combinations were used to S-genotype eighteen Tunisian local apple accessions and twelve introduced accessions that served as references. Within the Tunisian local accessions, S2, S3, S7, and S28 S-alleles were the most frequent and were assigned to 14 S-genotypes; among them, S7S28, S3S7, S2S5, and S2S3 were the most abundant. PCA plot showed that population structuring was affected by the S-alleles frequencies and revealed a modern origin of the Tunisian varieties rather than being ancient ones. Nonetheless, the results obtained with 17 SSR markers showed a separate grouping of local Tunisian accessions that calls into question the hypothesis discussed. Pollination experiments showed that the pollen started to germinate within 24 h of pollination but 48 h after pollination in the “El Fessi” accession. The first pollen tubes arrived in the styles within 36 h of pollination in two early flowering accessions known as “Arbi” and “Bokri”, and after 72 h of pollination in late flowering “El Fessi” and 48 h after pollination in remaining accessions. The first pollen tube arrests were observed in accessions “Arbi” and “Bokri” within 84 h of pollination, within 108 h of pollination in “El Fessi” and within 108 h of pollination in remaining accessions. In the apple accession called “Boutabgaya,” the pollen tubes reached the base of the style within 120 h of pollination without being aborted. Nevertheless, the self-compatible nature of “Boutabgaya” needs more studies to be confirmed. However, our results revealed the malfunction of the female component of the GSI in this accession. To conclude, this work paved the path for further studies to enhance the insight (i) into the relation between the flowering period and the pollen tube growth, (ii) self-compatible nature of “Boutabgaya”, and (iii) the origin of the Tunisian apple. [ABSTRACT FROM AUTHOR]

The productivity of many tree crops is limited by low yield, partly due to high rates of fruitlet abscission during early fruit development. Early studies suggested that cross-pollinated fruitlets may be selectively retained during fruit development, although paternity testing of fruitlets to test this hypothesis was technically challenging. We used MassARRAY genotyping to determine the effects of pollen parentage on fruitlet retention and fruit quality of Hass avocado. We identified the paternity of abscised and retained fruitlets at 6 and 10 weeks, and mature fruit at 36 weeks, after peak anthesis. We measured the embryo mass, pericarp mass, total mass and nutrient concentrations of fruitlets, and the seed mass, flesh mass, total mass, diameter, length, nutrient concentrations and fatty-acid composition of mature fruit. The percentages of progeny on the tree that were cross-fertilised increased from 4.6% at 6 weeks after peak anthesis to 10.7% at fruit maturity. Only 1.0% of freshly abscised fruitlets on the ground at 10 weeks after peak anthesis were cross-pollinated even though 6.5% of retained fruitlets on the tree were cross-pollinated. At this stage, cross-pollinated fruitlets had similar nutrient concentrations to self-pollinated fruitlets, but they had higher total contents of P, K, Al, Ca, Fe, Mn and Zn due to having greater fruitlet mass. At maturity, cross-pollinated fruit were 6% heavier and had 2% greater diameter than self-pollinated fruit, without significant differences in flesh nutrient concentrations or fatty acid composition. The results demonstrate that Hass avocado trees selectively retain cross-pollinated fruitlets, which are larger than self-pollinated fruitlets and ultimately produce larger mature fruit. Avocado growers can increase fruit size and yield by improving the opportunities for cross-pollination, possibly by closely interplanting type A and type B cultivars and introducing more beehives into orchards. [ABSTRACT FROM AUTHOR]

Background: The Myrtaceae family represents one of the most diverse groups in South America. Yet, there are few studies on their reproductive characteristics. Among the species with limited information on their reproductive behavior are Myrceugenia euosma (O. Berg) D. Legrand and Siphoneugena reitzii D. Legrand. Questions: What are the floral attractions and resources of M. euosma and S. reitzii for pollinators? Who are the pollinators of these species? What is the predominant reproductive system in both species? Studied species: M. euosma and S. reitzii, two sympatric Myrtaceae from southern Brazil. Study site and dates: Urubici, Painel, and Rio Rufino, Santa Catarina state, southern Brazil. November 2021 - February 2022. Methods: Information was obtained on morphological aspects, anthesis time, stigmatic viability, floral resources, structures attractive to visitors, olfactory testing, observation and identification of floral visitors, and reproductive system testing. Results: The flowers of M. euosma opens between 11 am and 17 pm (- 20 pm), with full opening occurring mostly at night; S. reitzii flowers open between 4 a.m. and 6 a.m., with a highest peak by 8 a.m. Flowers of both species have receptive stigmas until senescence. Pollen is the primary floral reward and the scent coming from the anthers combined with the floral display attract native bees and Apis mellifera, legitimate pollinators of both species. The lack of fruit development in the self-pollination tests support cross reproduction in both taxa. Conclusions: Both species exhibit traits consistent with melittophily syndrome and potential self-incompatibility. These results are essential for conservation efforts.

Studying the signatures of evolution can help to understand genetic processes. Here, we demonstrate how the existence of balancing selection can be used to identify the breeding systems of fungi from genomic data. The breeding systems of fungi are controlled by self-incompatibility loci that determine mating types between potential mating partners, resulting in strong balancing selection at the loci. Within the fungal phylum Basidiomycota, two such self-incompatibility loci, namely HD MAT locus and P/R MAT locus, control mating types of gametes. Loss of function at one or both MAT loci results in different breeding systems and relaxes the MAT locus from balancing selection. By investigating the signatures of balancing selection at MAT loci, one can infer a species breeding system without culture-based studies. Nevertheless, the extreme sequence divergence among MAT alleles imposes challenges for retrieving full variants from both alleles when using the conventional read-mapping method. Therefore, we employed a combination of read-mapping and local de novo assembly to construct haplotypes of HD MAT alleles from genomes in suilloid fungi (genera Suillus and Rhizopogon). Genealogy and pairwise divergence of HD MAT alleles showed that the origins of mating types predate the split between these two closely related genera. High sequence divergence, trans-specific polymorphism, and the deeply diverging genealogy confirm the long-term functionality and multiallelic status of HD MAT locus in suilloid fungi. This work highlights a genomics approach to studying breeding systems regardless of the culturability of organisms based on the interplay between evolution and genetics.

Abstract Background Goji (Lycium barbarum L.) is a perennial deciduous shrub widely distributed in arid and semiarid regions of Northwest China. It is highly valued for its medicinal and functional properties. Most goji varieties are naturally self-incompatible, posing challenges in breeding and cultivation. Self-incompatibility is a complex genetic trait, with ongoing debates regarding the number of self-incompatible loci. To date, no genetic mappings has been conducted for S loci or other loci related to self-incompatibility in goji. Results We used genome resequencing to create a high-resolution map for detecting de novo single-nucleotide polymorphisms (SNP) in goji. We focused on 229 F1 individuals from self-compatible ‘13–19’ and self-incompatible ‘new 9’ varieties. Subsequently, we conducted a quantitative trait locus (QTL) analysis on traits associated with self-compatibility in goji berries. The genetic map consisted of 249,327 SNPs distributed across 12 linkage groups (LGs), spanning a total distance of 1243.74 cM, with an average interval of 0.002 cM. Phenotypic data related to self-incompatibility, such as average fruit weight, fruit rate, compatibility index, and comparable compatibility index after self-pollination and geitonogamy, were collected for the years 2021–2022, as well as for an extra year representing the mean data from 2021 to 2022 (2021/22). A total of 43 significant QTL, corresponding to multiple traits were identified, accounting for more than 11% of the observed phenotypic variation. Notably, a specific QTL on chromosome 2 consistently appeared across different years, irrespective of the relationship between self-pollination and geitonogamy. Within the localization interval, 1180 genes were annotated, including Lba02g01102 (annotated as an S-RNase gene), which showed pistil-specific expression. Cloning of S-RNase genes revealed that the parents had two different S-RNase alleles, namely S1S11 and S2S8. S-genotype identification of the F1 population indicated segregation of the four S-alleles from the parents in the offspring, with the type of S-RNase gene significantly associated with self-compatibility. Conclusions In summary, our study provides valuable insights into the genetic mechanism underlying self-compatibility in goji berries. This highlights the importance of further positional cloning investigations and emphasizes the importance of integration of marker-assisted selection in goji breeding programs.

Self-incompatibility (SI) is a mechanism for preventing self-fertilization in flowering plants. SI is controlled by a single S-locus with multiple haplotypes (S-haplotypes). When the pistil and pollen share the same S-haplotype, the pollen is recognized as self and rejected by the pistil. This review introduces our research on Brassicaceae and Solanaceae SI systems to identify the S-determinants encoded at the S-locus and uncover the mechanisms of self/nonself-discrimination and pollen rejection. The recognition mechanisms of SI systems differ between these families. A self-recognition system is adopted by Brassicaceae, whereas a collaborative nonself-recognition system is used by Solanaceae. Work by our group and subsequent studies indicate that plants have evolved diverse SI systems.

Identification of the S genotype of Malus plants will greatly promote the discovery of new genes, the cultivation and production of apple, the breeding of new varieties, and the origin and evolution of self-incompatibility in Malus plants. In this experiment, 88 Malus germplasm resources, such as Aihuahong, Xishuhaitang, and Reguanzi, were used as materials. Seven gene-specific primer combinations were used in the genotype identification. PCR amplification using leaf DNA produced a single S-RNase gene fragment in all materials. The results revealed that 70 of the identified materials obtained a complete S-RNase genotype, while only one S-RNase gene was found in 18 of them. Through homology comparison and analysis, 13 S-RNase genotypes were obtained: S1S2 (Aihuahong, etc.), S1S28 (Xixian Haitang, etc.), S1S51 (Hebei Pingdinghaitang), S1S3 (Xiangyangcun Daguo, etc.), S2S3 (Zhaiyehaitang, etc.), S3S51 (Xishan 1), S3S28 (Huangselihaerde, etc.), S2S28 (Honghaitang, etc.), S4S28 (Bo 11), S7S28 (Jiuquan Shaguo), S10Se (Dongchengguan 13), S10S21 (Dongxiangjiao) and SeS51 (Xiongyue Haitang). Simultaneously, the frequency of the S gene in the tested materials was analyzed. The findings revealed that different S genes had varying frequencies in Malus resources, as well as varying frequencies between intraspecific and interspecific. S3 had the highest frequency of 68.18%, followed by S1 (42.04%). In addition, the phylogenetic tree and origin evolution analysis revealed that the S gene differentiation was completed prior to the formation of various apple species, that cultivated species also evolved new S genes, and that the S50 gene is the oldest S allele in Malus plants. The S1, S29, and S33 genes in apple-cultivated species, on the other hand, may have originated in M. sieversii, M. hupehensis, and M. kansuensis, respectively. In addition to M. sieversii, M. kansuensis and M. sikkimensis may have also played a role in the origin and evolution of some Chinese apples.

Background: Goji (Lycium barbarum L.) is a perennial deciduous shrub widely distributed in arid and semiarid regions of Northwest China. It is highly valued for its medicinal and functional properties. Most goji varieties are naturally self-incompatible, posing challenges in breeding and cultivation. Self-incompatibility is a complex genetic trait, with ongoing debates regarding the number of self-incompatible loci. To date, no genetic mappings has been conducted for S loci or other loci related to self-incompatibility in goji. Results: We used genome resequencing to create a high-resolution map for detecting de novo single-nucleotide polymorphisms (SNP) in goji. We focused on 229 F1 individuals from self-compatible '13–19' and self-incompatible 'new 9' varieties. Subsequently, we conducted a quantitative trait locus (QTL) analysis on traits associated with self-compatibility in goji berries. The genetic map consisted of 249,327 SNPs distributed across 12 linkage groups (LGs), spanning a total distance of 1243.74 cM, with an average interval of 0.002 cM. Phenotypic data related to self-incompatibility, such as average fruit weight, fruit rate, compatibility index, and comparable compatibility index after self-pollination and geitonogamy, were collected for the years 2021–2022, as well as for an extra year representing the mean data from 2021 to 2022 (2021/22). A total of 43 significant QTL, corresponding to multiple traits were identified, accounting for more than 11% of the observed phenotypic variation. Notably, a specific QTL on chromosome 2 consistently appeared across different years, irrespective of the relationship between self-pollination and geitonogamy. Within the localization interval, 1180 genes were annotated, including Lba02g01102 (annotated as an S-RNase gene), which showed pistil-specific expression. Cloning of S-RNase genes revealed that the parents had two different S-RNase alleles, namely S1S11 and S2S8. S-genotype identification of the F1 population indicated segregation of the four S-alleles from the parents in the offspring, with the type of S-RNase gene significantly associated with self-compatibility. Conclusions: In summary, our study provides valuable insights into the genetic mechanism underlying self-compatibility in goji berries. This highlights the importance of further positional cloning investigations and emphasizes the importance of integration of marker-assisted selection in goji breeding programs. [ABSTRACT FROM AUTHOR]

Summary: Self‐incompatibility (SI) is a widespread prezygotic mechanism for flowering plants to avoid inbreeding depression and promote genetic diversity. Citrus has an S‐RNase‐based SI system, which was frequently lost during evolution. We previously identified a single nucleotide mutation in Sm‐RNase, which is responsible for the loss of SI in mandarin and its hybrids. However, little is known about other mechanisms responsible for conversion of SI to self‐compatibility (SC) and we identify a completely different mechanism widely utilized by citrus. Here, we found a 786‐bp miniature inverted‐repeat transposable element (MITE) insertion in the promoter region of the FhiS2‐RNase in Fortunella hindsii Swingle (a model plant for citrus gene function), which does not contain the Sm‐RNase allele but are still SC. We demonstrate that this MITE plays a pivotal role in the loss of SI in citrus, providing evidence that this MITE insertion prevents expression of the S‐RNase; moreover, transgenic experiments show that deletion of this 786‐bp MITE insertion recovers the expression of FhiS2‐RNase and restores SI. This study identifies the first evidence for a role for MITEs at the S‐locus affecting the SI phenotype. A family‐wide survey of the S‐locus revealed that MITE insertions occur frequently adjacent to S‐RNase alleles in different citrus genera, but only certain MITEs appear to be responsible for the loss of SI. Our study provides evidence that insertion of MITEs into a promoter region can alter a breeding strategy and suggests that this phenomenon may be broadly responsible for SC in species with the S‐RNase system. [ABSTRACT FROM AUTHOR]

Self‐incompatibility (SI) is an intraspecific reproductive barrier widely present in angiosperms. The SI system with the broadest occurrence in angiosperms is based on an S‐RNase linked to a cluster of multiple S‐locus F‐box (SLF) genes found in the Solanaceae, Plantaginaceae, Rosaceae, and Rutaceae. Recent studies reveal that non‐self S‐RNase is degraded by the Skip Cullin F‐box (SCF)SLF‐mediated ubiquitin–proteasome system in a collaborative manner in Petunia, but how self‐RNase functions largely remains mysterious. Here, we show that S‐RNases form S‐RNase condensates (SRCs) in the self‐pollen tube cytoplasm through phase separation and the disruption of SRC formation breaks SI in self‐incompatible Petunia hybrida. We further find that the pistil SI factors of a small asparagine‐rich protein HT‐B and thioredoxin h together with a reduced state of the pollen tube all promote the expansion of SRCs, which then sequester several actin‐binding proteins, including the actin polymerization factor PhABRACL, the actin polymerization activity of which is reduced by S‐RNase in vitro. Meanwhile, we find that S‐RNase variants lacking condensation ability fail to recruit PhABRACL and are unable to induce actin foci formation required for pollen tube growth inhibition. Taken together, our results demonstrate that phase separation of S‐RNase promotes SI response in P. hybrida, revealing a new mode of S‐RNase action. [ABSTRACT FROM AUTHOR]

DNA marker technology, being an alternative to classical hybrid selection approach, is a rapid method for identifying genes and loci associated with breeding-important traits at the early stages of ontogenesis, and, consequently, represents an approach for intensifying the breeding process. This review presents an overview of the studies on the identification of the economically important traits in the pear genome, as well as the development and use of marker-assisted selection (MAS) techniques. To date, a number of genetic factors have been identified in the pear genome, including the resistance to diseases and pests, namely, the resistance to European pear scab (V. pirina Aderh) and Asian pear scab (V. nashicola), to black spot (Alternaria alternata (Fr.) Keissler) and brown spot (Stemphylium vesicarium) disease, fire blight (Erwinia amylovora), pear psylla (Cacopsylla pyri), pear slug (Caliroacerasi), pear blister mite (Eriophyes pyri), self-incompatibility locus, and dwarf trait gene. Major genes and quantitative trait loci (QTLs) for the fruit quality characteristics have also been identified, namely those controlling fruit skin color and fruit russeting, fruit size and weight, taste, the level of ethylene production, and harvest time. It should be noted that Russian studies in this field are limited to the validation and use of MAS techniques developed abroad. According to the experience of Japanese researchers, the use of MAS for several key traits had considerably increased the efficiency of breeding process. Despite the currently limited list of MAS techniques for pears, the high pace of genome research guarantees fairly rapid development of new methods in the future. In combination with new breeding technologies (NBT), the use of MAS for pear is a promising trend in breeding. [ABSTRACT FROM AUTHOR]

European hazelnut (Corylus avellana L.) cultivation has grown worldwide in recent years, even though the world's production is still fulfilled by a few dozen cultivars well adapted to the local environments of their selection. After Turkey, Italy is the second largest producer of hazelnuts, and the province of Viterbo, in central Italy, is recognized as one of the most suitable districts for hazelnut cultivation. The production in this area relies almost entirely on local cultivar 'Tonda Gentile Romana', whereas cultivar 'Nocchione' is used as the main pollinizer. More recently, cultivar 'Tonda di Giffoni' has been introduced in new local plantations. Cultivation of many cultivars in different areas is of fundamental importance to test their adaptability to different environmental conditions, a need currently accentuated by ongoing climate change. With this aim, a European hazelnut collection field was established in 2000 in Caprarola municipality (Viterbo province), where plants of twelve hazelnut cultivars were observed over four growing seasons for their phenological, agronomic and nut traits. The cultivars studied, namely 'Barcelona', 'Camponica', 'Ennis', 'Merveille de Bollwiller', 'Negret', 'Nocchione', 'Riccia di Talanico', 'San Giovanni', 'Tombul', 'Tonda di Giffoni', 'Tonda Gentile' and 'Tonda Gentile Romana', showed a high diversity in their phenological behaviour, yield efficiency and nut and kernel traits. Cultivars 'Negret', 'Tombul' and 'Tonda Gentile', with poor yields over the years of research, do not seem suitable to be cultivated as main cultivars in the studied environment, contrary to 'Camponica' and 'San Giovanni', which produced abundantly, reaching a total of almost 30 and 25 kg plant—1 of in–shell hazelnuts, respectively. Cultivars 'Tonda Gentile Romana' and 'Nocchione' confirmed their yield consistency, whereas 'Ennis', 'Barcelona' and 'Tombul' seem suitable to be introduced as pollinizers thanks to their male blooming overlapping with the female blooming of the main cultivar 'Tonda Gentile Romana'. Cultivar 'Tonda di Giffoni' did not perform well in the studied environment, despite being recognized as one of the highest-yield cultivars. [ABSTRACT FROM AUTHOR]

Self-incompatibility is a widespread genetic mechanism found in flowering plants. It plays a crucial role in preventing inbreeding and promoting outcrossing. The genes that control self-incompatibility in plants are typically determined by the S-locus female determinant factor and the S-locus male determinant factor. In the Solanaceae family, the male determinant factor is often the SLF gene. In this research, we cloned and analyzed 13 S2-LbSLF genes from the L. barbarum genome, which are located on chromosome 2 and close to the physical location of the S-locus female determinant factor S-RNase, covering a region of approximately 90.4 Mb. The amino acid sequence identity of the 13 S2-LbSLFs is 58.46%, and they all possess relatively conserved motifs and typical F-box domains, without introns. A co-linearity analysis revealed that there are no tandemly repeated genes in the S2-LbSLF genes, and that there are two pairs of co-linear genes between S2-LbSLF and the tomato, which also belongs to the Solanaceae family. A phylogenetic analysis indicates that the S2-LbSLF members can be divided into six groups, and it was found that the 13 S2-LbSLFs are clustered with the SLF genes of tobacco and Petunia inflata to varying degrees, potentially serving as pollen determinant factors regulating self-incompatibility in L. barbarum. The results for the gene expression patterns suggest that S2-LbSLF is only expressed in pollen tissue. The results of the yeast two-hybrid assay showed that the C-terminal region of S2-LbSLFs lacking the F-box domain can interact with S-RNase. This study provides theoretical data for further investigation into the functions of S2-LbSLF members, particularly for the identification of pollen determinant factors regulating self-incompatibility in L. barbarum. [ABSTRACT FROM AUTHOR]

Self-compatibility (SC) in a naturally self-incompatible fruit tree species is an incredibly interesting trait for breeding objectives and a valuable tool to investigate the mechanism of the gametophytic self-incompatibility system. We focused on an apple (Malus × domestica Borkh.), in which studies on the SC remain largely unexplored because of a lack of spontaneous and/or induced self-compatible mutants, and performed gamma-ray mutagenesis and succeeded in producing several pollen-part self-compatible mutants. We revealed that SC in the mutants was not caused by a dysfunctional pollen S factor in either of the S-haplotypes but presumably by a translocation of an S-haplotype to a non-homologous chromosome, which allowed the mutants to produce S-heteroallelic pollen grains that overcome self-incompatibility through the competitive interaction between the two different S-factors in the pollen grain. The results from our study demonstrate that duplication of the pollen-S in a pollen grain causes the breakdown of the pollen function in Malus, like Pyrus of Rosaceae and Solanaceae, but not in the mutation of the pollen-S itself, like Prunus. The mutants and our finding will be useful for apple breeding programs. [ABSTRACT FROM AUTHOR]

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Mating type (sex) plays a crucial role in regulating sexual reproduction in most extant eukaryotes. One of the functions of mating types is ensuring self-incompatibility to some extent, thereby promoting genetic diversity. However, heterothallic mating is not always the best mating strategy. For example, in low-density populations or specific environments, such as parasitic ones, species may need to increase the ratio of potential mating partners. Consequently, many species allow homothallic selfing (i.e., self-fertility or intraclonal mating). Throughout the extensive evolutionary history of species, changes in environmental conditions have influenced mating strategies back and forth. However, the mechanisms through which mating-type recognition regulates sexual reproduction and the dynamics of mating strategy throughout evolution remain poorly understood. In this study, we show that the Cip1 protein is responsible for coupling sexual reproduction initiation to mating-type recognition in the protozoal eukaryote Tetrahymena thermophila. Deletion of the Cip1 protein leads to the loss of the selfing-avoidance function of mating-type recognition, resulting in selfing without mating-type recognition. Further experiments revealed that Cipl is a regulatory subunit of the Cdk19--Cyc9 complex, which controls the initiation of sexual reproduction. These results reveal a mechanism that regulates the choice between mating and selfing. This mechanism also contributes to the debate about the ancestral state of sexual reproduction. [ABSTRACT FROM AUTHOR]

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (CRISPR-Cas9) system has been widely applied in cultivated crops, but limited in their wild relatives. Nicotiana alata is a typical wild species of genus Nicotiana that is globally distributed as a horticultural plant and well-studied as a self-incompatibility model. It also has valuable genes for disease resistance and ornamental traits. However, it lacks an efficient genetic transformation and genome editing system, which hampers its gene function and breeding research. In this study, we developed an optimized hypocotyl-mediated transformation method for CRISPR-Cas9 delivery. The genetic transformation efficiency was significantly improved from approximately 1% to over 80%. We also applied the CRISPR-Cas9 system to target the phytoene desaturase (NalaPDS) gene in N. alata and obtained edited plants with PDS mutations with over 50% editing efficiency. To generate self-compatible N. alata lines, a polycistronic tRNA-gRNA (PTG) strategy was used to target exonic regions of allelic S-RNase genes and generate targeted knockouts simultaneously. We demonstrated that our system is feasible, stable, and high-efficiency for N. alata genome editing. Our study provides a powerful tool for basic research and genetic improvement of N. alata and an example for other wild tobacco species. [ABSTRACT FROM AUTHOR]

Despite the potential for mechanical, developmental and/or chemical mechanisms to prevent self-fertilization, incidental self-fertilization is inevitable in many predominantly outcrossing species. In such cases, inbreeding can compromise individual fitness. Unquestionably, much of this inbreeding depression is maladaptive. However, we show that when reproductive compensation allows for the replacement of inviable embryos lost early in development, selection can favour deleterious recessive variants that induce 'self-sacrificial' death of inbred embryos. Our theoretical results provide numerous testable predictions which could challenge the assumption that inbreeding depression is always maladaptive. Our work is applicable any species that cannot fully avoid inbreeding, exhibits substantial inbreeding depression, and has the potential to compensate embryos lost early in development. In addition to its general applicability, our theory suggests that self-sacrificial variants might be responsible for the remarkably low realized selfing rates of gymnosperms with high primary selfing rates, as gymnosperms exhibit strong inbreeding depression, have effective reproductive compensation mechanisms, and cannot evolve chemical self-incompatibility. [ABSTRACT FROM AUTHOR]

Alfalfa (Medicago sativa L.) is an important forage crop worldwide, but molecular genetics and breeding research in this species are hindered by its self-incompatibility (SI). Although the mechanisms underlying SI have been extensively studied in other plant families, SI in legumes, including alfalfa, remains poorly understood. Here, we determined that self-pollinated pollen tubes could germinate on the stigma of alfalfa, grow through the style, and reach the ovarian cavity, but the ovules collapsed ~48 h after self-pollination. A transcriptomic analysis of dissected pistils 24 h after self-pollination identified 941 differently expressed genes (DEGs), including 784 upregulated and 157 downregulated genes. A gene ontology (GO) analysis showed that the DEGs were highly enriched in functions associated with the regulation of pollen tube growth and pollen germination. A Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that pentose and glucuronate interconversion, plant hormone signal transduction, the spliceosome, and ribosomes might play important roles in SI. Our co-expression analysis showed that F-box proteins, serine/threonine protein kinases, calcium-dependent protein kinases (CDPKs), bHLHs, bZIPs, and MYB-related family proteins were likely involved in the SI response. Our study provides a catalog of candidate genes for further study to understand SI in alfalfa and related legumes. [ABSTRACT FROM AUTHOR]

Radish (Raphanus sativus L.), a root vegetable belonging to the Brassicaceae family, is considered one of the representative crops displaying sporophytic self-incompatibility (SSI). The utilization of a self-incompatibility system in F1 breeding can improve the efficiency of cross-combinations, leading to a reduction in breeding time and aiding in the development of novel F1 varieties. The successful implementation of this system necessitates the rapid and accurate identification of S haplotypes in parental lines. In this study, we identified a total of nine S haplotypes among 22 elite radish lines through Sanger sequencing. Subsequently, we obtained sequences for showing a 95% similarity to nine S haplotypes, along with sequences identified by other researchers using BLAST. Following this, multiple sequence alignment (MSA) was conducted to identify SRK and SLG sequence similarities, as well as polymorphisms within the class I and II groups. Subsequently, S haplotype-specific marker sets were developed, targeting polymorphic regions of SRK and SLG alleles. These markers successfully amplified each of the nine S haplotypes. These markers will play a crucial role in the rapid and precise identification of parental S haplotypes in the radish F1 breeding process, proving instrumental in the radish F1 purity test. [ABSTRACT FROM AUTHOR]

Global fruit and nut yields are affected by shortfalls in pollinator populations, and pollen limitation is most prevalent among tropical, bee-pollinated and self-incompatible plants. Macadamia is a subtropical, bee-pollinated crop in which some cultivars have been found to be highly outcrossing. We aimed to determine the extent of outcrossing and its effects on nut quality across a wide range of international macadamia cultivars in three countries. We sampled fruit from 19 macadamia cultivars across 23 sites in Australia, Brazil and South Africa. We used genotype-by-sequencing and MassARRAY methods to assign paternity to individual fruit and we assessed pollen-parent effects on nut quality. Macadamia was highly outcrossing, producing 80–100% of fruit by cross-pollination, at 17 of the 23 sites. Mixed mating (41–72% outcrossing) was identified at five sites, and low outcrossing (10%) was identified in one cultivar at one site where it was isolated from other flowering macadamia trees. Outcrossed fruit often had significantly better quality than selfed fruit, with 1.61–3.39 g higher nut-in-shell mass, 0.53–1.55 g higher kernel mass, 3.3–6.4% higher kernel recovery, and 3.0–3.5% higher oil concentration. The differences in kernel recovery equated to differences in value of USD 433–841 per ton of nut-in-shell at prices of USD 3000 per ton. In summary, macadamia cultivars were mostly highly outcrossing, and outcrossed nuts often had higher quality than selfed nuts. Growers should consider interplanting different cultivars more closely and distributing bee hives more widely to maximise cross-pollination, produce high yields, and optimise nut quality. [ABSTRACT FROM AUTHOR]

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Abstract In Brassicaceae self‐incompatibility (SI), self‐pollen rejection is initiated by the S‐haplotype specific interactions between the pollen S cysteine‐rich/S‐locus protein 11 (SCR/SP11) ligands and the stigma S receptor kinases (SRK). In Brassica SI, a member of the Plant U‐Box (PUB) E3 ubiquitin ligases, ARM‐repeat containing 1 (ARC1), is then activated by SRK in this stigma and cellular events downstream of this cause SI pollen rejection by inhibiting pollen hydration and pollen tube growth. During the transition to selfing, Arabidopsis thaliana lost the SI components, SCR, SRK, and ARC1. However, this trait can be reintroduced into A. thaliana by adding back functional copies of these genes from closely related SI species. Both SCR and SRK are required for this, though the degree of SI pollen rejection varies between A. thaliana accessions, and ARC1 is not always needed to produce a strong SI response. For the A. thaliana C24 accession, only transforming with Arabidopsis lyrata SCR and SRK confers a strong SI trait (SI‐C24), and so here, we investigated if ARC1‐related PUBs were involved in the SI pathway in the transgenic A. thaliana SI‐C24 line. Two close ARC1 homologs, PUB17 and PUB16, were selected, and (Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) technology was used to generate pub17 and pub16 mutations in the C24 accession. These mutants were then crossed into the transgenic A. thaliana SI‐C24 line and their potential impact on SI pollen rejection was investigated. Overall, we did not observe any significant differences in SI responses to implicate PUB17 and PUB16 functioning in the transgenic A. thaliana SI‐C24 stigma to reject SI pollen.

Abstract Due to self-incompatibility (SI) prevents self-fertilization, natural or artificial cross-pollination has been conducted in many orchards to stabilize fruit yield. However, it is still puzzled which routes of self S-RNase arresting pollen tube growth. Herein, 17 COBRA genes were isolated from pear genome. Of these genes, the pollen-specifically expressed PbCOB.A.1 and PbCOB.A.2 positively mediates pollen tube growth. The promoters of PbCOB.A.1 and/or PbCOB.A.2 were bound and activated by PbABF.E.2 (an ABRE-binding factor) and PbC2H2.K16.2 (a C2H2-type zinc finger protein). Notably, the expressions of PbCOB.A.1, PbCOB.A.2, and PbC2H2.K16.2 were repressed by self S-RNase, suggesting that self S-RNase reduces the expression of PbCOB.A.1 and PbCOB.A.2 by decreasing the expression of their upstream factors, such as PbC2H2.K16.2, to arrest pollen tube growth. PbCOB.A.1 or PbCOB.A.2 accelerates the growth of pollen tubes treated by self S-RNase, but can hardly affect level of reactive oxygen species and deploymerization of actin cytoskeleton in pollen tubes and cannot physically interact with any reported proteins involved in SI. These results indicate that PbCOB.A.1 and PbCOB.A.2 may not relieve S-RNase toxicity in incompatible pollen tube. The information provides a new route to elucidate the arresting pollen tube growth during SI reaction. Graphical Abstract

Cyperus esculentus seeds are often considered irrelevant for C. esculentus spread as their fragile seedlings would not establish or survive in agricultural soils. However, the ever-increasing spread and upsurge of genetically different clonal populations in NW-Europe raises questions about the establishment of C. esculentus seeds and the reproductive performance of seedlings. Indeed, little is known about the potential of C. esculentus seedlings to grow and propagate under outdoor conditions relative to plants grown from tubers. Seeds from different clonal populations were sown outdoors in various soil types and under different irrigation levels (rainfed, irrigated) to assess seed germination and seedling establishment. Additionally, two pot experiments were conducted with three different plant types (plants originating from mother tubers and from seeds harvested on open- or self-pollinated plants) obtained from eight clonal populations. Plant performance was investigated by measuring vegetative and generative parameters. Germination under outdoor conditions was significantly affected by clonal population and was highest in irrigated sand (5.3%). Germination in sand was 4.1 times higher in irrigated plots than in rainfed plots. In irrigated plots, germination was 3.8 and 4.7 times higher in sand than in sandy loam and clay, respectively. Depending on the year, three out of five to five out of six clonal populations produced more tubers when grown from mother tubers than from seeds. Maximal tuber reproduction factors of 1:965, 1:752, and 1:618 were achieved for plants from mother tubers and seeds from open- and self-pollinated flowers, respectively. Plants originating from open-pollinated seedlings have the potential to equal or exceed the vegetative reproductive capacity of plants originating from mother tubers. As a result of their ability to establish in situ and their substantial vegetative reproductive capacity, C. esculentus seedlings are highly relevant for agriculture and merit appropriate attention in any integrated weed management system targeting C. esculentus.