Male-sterile Flowers Research Articles

Identification of male sterility-related genes in Saccharum officinarum and Saccharum spontaneum.

Candidate male sterility genes were identified in sugarcane, which interacts with kinase-related proteins, transcription factors, and plant hormone signaling pathways to regulate stamen and anther development. Saccharum officinarum is a cultivated sugarcane species that its predominant feature is high sucrose content in stems. Flowering is necessary for breeding new cultivars but will terminate plant growth and reduce sugar yield. The wild sugarcane species Saccharum spontaneum has robust and viable pollen, whereas most S. officinarum accessions are male sterile, which isa desirable trait of a maternal parent in sugarcane breeding. To study male sterility and related regulatory pathways in sugarcane, we carried out RNAseq using flowers in different developmental stages between male-sterile S. officinarum accession 'LA Purple' and fertile S. spontaneum accession 'SES208'. Gene expression profiles were used to detect how genes are differentially expressed between male sterile and fertile flowers and to identify candidate genes for male sterility. Weighted gene correlation networks analysis (WGCNA) was conducted to investigate the regulatory networks. Transcriptomic analyses showed that 988 genes and 2888 alleles were differentially expressed in S. officinarum compared to S. spontaneum. Ten differentially expressed genes and thirty alleles were identified as candidate genes and alleles for male sterility in sugarcane. The gene Sspon.03G0007630 and two alleles of the gene Sspon.08G0002270, Sspon.08G0002270-2B and Sspon.08G0014700-1A, were involved in the early stamen or carpel development stages, while the remaining genes were classified into the post-meiosis stage. Gibberellin, auxin, and jasmonic acid signaling pathways are involved in the stamen development in sugarcane. The results expanded our knowledge of male sterility-related genes in sugarcane and generated genomic resources to facilitate the selection of ideal maternal parents to improve breeding efficiency.

Where are volatiles produced in the highly synorganised inflorescence of Arum maculatum L.?

Floral scents vary spatially within flowers and inflorescences, with effects on pollinator behaviour. Here, we restudied the spatial scent pattern of Arum maculatum, an Araceae, with a higher spatial resolution than previously. The inflorescence of this species consists of a spadix, whose distal part is a sterile osmophore called the appendix, whereas its basal part bears sterile and fertile male and female flowers. This spadix is surrounded by a spathe, which forms a floral chamber around the flowers. So far, it was known that the appendix is responsible for the emission of most of the volatiles, but some volatiles were specifically found within the floral chamber, with the organ(s) responsible for their emission being unclear. By repeatedly collecting (dynamic headspace) and analysing (gas chromatography/mass spectrometry) the scent of whole inflorescences and of inflorescences with the spathe and the various zones of the spadix sequentially removed, we determined and quantified all scent compounds of the major units of the inflorescence of A. maculatum. We confirm that the inflorescence scent is mainly composed of scents released by the appendix, and we for the first time provide evidence that the male flower zone of the spadix also contributes to the inflorescence scent. Future studies are needed to test whether, and if, how, this spatial scent pattern in A. maculatum affects the movement of pollinators within the inflorescence and their pollination effectiveness.

Floral nectary structure, nectar presentation and morpho-anatomical analysis of male‐fertile and male‐sterile anthers in onion (Allium cepa, Amaryllidaceae)

Background and aims: The onion (Allium cepa var. cepa) is an allogamous species in which male-sterile lines have been developed. However, the structure of the flower and floral nectaries have only been briefly described. The objective of this study is to update the floral anatomy data, comparing the gynoecium and androecium of male-fertile and male-sterile lines, and to analyze the three-dimensional structure of the floral nectary. M&M: Conventional optical and scanning electron microscopy techniques were used. Results: Fertile and sterile male flowers have the same structural organization. The septal or gynopleural nectary is organized in three zones: 1) production area formed by the glandular tissue arranged radially in the septa of the ovary, 2) discharge zone: a small channel at the apex connects the nectariferous tissue with the pocket formed between the ovary wall and the overlying ridge, and 3) presentation and harvest zone, where the excreted nectar accumulates, formed between the widened base of the inner staminal filaments opposite the ovary. Conclusions: The only anatomical differences in the flowers sterile male lines are the lack of pollen production and the absence of dehiscence, despite having a normal stomium and anther wall. The floral nectaries of onion are a clear example of secondary presentation of nectar.

SEXUAL POLYMORPHISM OF <i>RANUNCULUS CASSUBICUS</i> (RANUNCULACEAE) IN MOSCOW REGION

For the first time, gynodioecy is described in a perennial herbaceous polycarpic plant Ranunculus cassubicus L. (Kashubian buttercup) in the Moscow Region. It was revealed that R. cassubicus forms three types of flowers differing in the androecium structure: perfect (with fertile stamens and carpels), partially male-sterile (the number of stamens varies greatly and is much less than in perfect flowers), and pistillate ones (stamens completely missing). The sizes of flowers and their parts decrease in many studied parameters in the following row: perfect – partially male-sterile – pistillate. The studied 12 populations included six types of individuals forming: 1) only perfect flowers (83.1–89.2% of the total number of generative plants); 2) perfect and partially male-sterile flowers (4.0–6.5%); 3) only partially male-sterile flowers (2.8–3.9%); 4) perfect and pistillate flowers (1.4–2.6%); 5) pistillate and partially male-sterile flowers (1.2–2.9%); 6) only pistillate flowers (0.6–1.5%). It is established that over three years of observations (2020–2022), individuals of different sexual forms did not change the sex of flowers, and the sexual structure of populations remained stable, without sharp fluctuations.

ЧАСТИЧНАЯ СТЕРИЛЬНОСТЬ МУЖСКОЙ РЕПРОДУКТИВНОЙ СИСТЕМЫ ОДНОДОМНОЙ КОНОПЛИ

In 2018–2020, the authors examined causes of partial sterility of the male reproductive system in monoecious hemp. Male flowers of the dioecious hemp variety Igorkin and the monoecious hemp variety Diana were studied. The buds and open flowers were fixed with aceto-alcohol based on the Krnau method and with chromaceto-formalin according to the Navashin method. The procedure involved staining 5–10 µm thick sections with iron hematoxylin according to Heidenhain’s prescription and with basic fuchsin dye combining a licht-grun tint according to the Modilevsky technique. Many researchers have found that the flowering rate in male monoecious hemp flowers is much lower than in the dioecious variety. Some monoecious hemp plants cannot produce pollen grains as the species can form monoclinous flowers that drop at the bud stage. Studies have also established inherited male sterility and partial male sterility in monoecious hemp. It can be found within a plant, a flower and even an anther. The study aimed to identify the causes of partial sterility of male monoecious hemp flowers. It employed a microscopic analysis of the anther development in monoecious and dioecious hemp varieties. The study has established that the partial sterility of the male reproductive system of monoecious hemp is caused by the tapetum degeneration. Degeneration of the tapetum at any stage brings about sterile and semi-sterile male flowers in monoecious hemp

SEXUAL POLYMORPHISM OF <i>RANUNCULUS ACRIS</i> (RANUNCULACEAE) IN THE MOSCOW REGION

The gynodioecy of the polycarpic Ranunculus acris L. was studied in the Moscow Region. This plant has three types of flowers that differ in androecium structure: perfect flowers (with fertile stamens and carpels), partially male-sterile ones (some of the stamens become staminodes to form sterile pollen), and pistillate ones (an extreme reduction of stamens and the complete absence of fertile pollen). These three types of flowers form a size gradient from the largest perfect to the smallest pistillate ones. Each flower type is formed on separate plants. The share of plants with perfect flowers in 10 studied coenopopulations varied from 43.9 to 53.0%, that of the plants with partially male-sterile flowers from 45.5 to 54.4%. Plants with pistillate flowers are extremely rare (1.5–2.0%). Over three years of observations (2020–2022), we found that the sexual forms of the plants did not change the sex of their flowers, and the sex ratio in the coenopopulations remained stable, without significant fluctuations.

Virus-induced gene silencing for in planta validation of gene function in cucurbits.

Virus-induced gene silencing (VIGS) is a powerful tool for high-throughput analysis of gene function. Here, we developed the VIGS vector pCF93, from which expression of the cucumber fruit mottle mosaic virus genome is driven by the cauliflower mosaic virus 35S promoter to produce viral transcripts in inoculated plants. To test the utility of the pCF93 vector, we identified candidate genes related to male sterility (MS) in watermelon (Citrullus lanatus), which is recalcitrant to genetic transformation. Specifically, we exploited previously reported reference-based and de novo transcriptome data to define 38 differentially expressed genes between a male-sterile line and its fertile near-isogenic line in the watermelon cultivar DAH. We amplified 200- to 300-bp fragments of these genes, cloned them into pCF93, and inoculated DAH with the resulting VIGS clones. The small watermelon cultivar DAH enabled high-throughput screening using a small cultivation area. We simultaneously characterized the phenotypes associated with each of the 38 candidate genes in plants grown in a greenhouse. Silencing of 8 of the 38 candidate genes produced male-sterile flowers with abnormal stamens and no pollen. We confirmed the extent of gene silencing in inoculated flowers using reverse transcription-qPCR. Histological analysis of stamens from male-fertile and male-sterile floral buds and mature flowers revealed developmental defects and shrunken pollen sacs. Based on these findings, we propose that the pCF93 vector and our VIGS system will facilitate high-throughput analysis for the study of gene function in watermelons.

High-temperature stress suppresses allene oxide cyclase 2 and causes male sterility in cotton by disrupting jasmonic acid signaling

Cotton (Gossypium spp.) yield is reduced by stress. In this study, high temperature (HT) suppressed the expression of the jasmonic acid (JA) biosynthesis gene allene oxide cyclase 2 (GhAOC2), reducing JA content and causing male sterility in the cotton HT-sensitive line H05. Anther sterility was reversed by exogenous application of methyl jasmonate (MeJA) to early buds. To elucidate the role of GhAOC2 in JA biosynthesis and identify its putative contribution to the anther response to HT, we created gene knockout cotton plants using the CRISPR/Cas9 system. Ghaoc2 mutant lines showed male-sterile flowers with reduced JA content in the anthers at the tetrad stage (TS), tapetum degradation stage (TDS), and anther dehiscence stage (ADS). Exogenous application of MeJA to early mutant buds (containing TS or TDS anthers) rescued the sterile pollen and indehiscent anther phenotypes, while ROS signals were reduced in ADS anthers. We propose that HT downregulates the expression of GhAOC2 in anthers, reducing JA biosynthesis and causing excessive ROS accumulation in anthers, leading to male sterility. These findings suggest exogenous JA application as a strategy for increasing male fertility in cotton under HT.

Transcriptomic analysis reveals candidate genes for male sterility in Prunus sibirica.

BackgroundThe phenomenon of male sterility widely occurs in Prunus sibirica and has a serious negative impact on yield. We identified the key stage and cause of male sterility and found differentially expressed genes related to male sterility in Prunus sibirica, and we analyzed the expression pattern of these genes. This work aimed to provide valuable reference and theoretical basis for the study of reproductive development and the mechanisms of male sterility in Prunus sibirica.MethodThe microstructures of male sterile flower buds and male fertile flower buds were observed by paraffin section. Transcriptome sequencing was used to screen genes related to male sterility in Prunus sibirica. Quantitative real-time PCR analysis was performed to verify the transcriptome data.ResultsAnther development was divided into the sporogenous cell stage, tetrad stage, microspore stage, and pollen maturity stage. Compared with male fertile flower buds, in the microspore stage, the pollen sac wall tissue in the male sterile flower buds showed no signs of degeneration. In the pollen maturity stage, the tapetum and middle layer were not fully degraded, and anther development stopped. Therefore, the microspore stage was the key stage for anther abortion , and the pollen maturity stage was the post stage for anther abortion. A total of 4,108 differentially expressed genes were identified by transcriptome analysis. Among them, 1,899 were up-regulated, and 2,209 were down-regulated in the transcriptome of male sterile flower buds. We found that “protein kinase activity”, “apoptosis process”, “calcium binding”, “cell death”, “cytochrome c oxidase activity”, “aspartate peptidase activity”, “cysteine peptidase activity” and other biological pathways such as “starch and sucrose metabolism” and “proteasome” were closely related to male sterility in Prunus sibirica. A total of 331 key genes were preliminarily screened.ConclusionThe occurrence of male sterility in Prunus sibirica involved many biological processes and metabolic pathways. According to the results of microstructure observations, related physiological indexes determination and transcriptome analysis, we reveal that the occurrence of male sterility in Prunus sibirica may be caused by abnormal metabolic processes such as the release of cytochrome c in the male sterile flower buds, the imbalance of the antioxidant system being destroyed, and the inability of macromolecular substances such as starch to be converted into soluble small molecules at the correct stage of reproductive development, resulting in energy loss. As a result, the tapetum cannot be fully degraded, thereby blocking anther development, which eventually led to the formation of male sterility.

Comparative analysis of morphology, cytology, and mitochondrial transcriptome of sterile male flowers of rubber tree

AbstractRubber tree [Hevea brasiliensis (Willd. ex A. Juss.) Müll. Arg.] is the exclusive commercial source of natural rubber. Male‐sterile (MS) germplasm has proven to be valuable for rubber tree hybrid breeding, but its male sterility mechanism remains unclear. Here, morphological observations of a new MS clone Reyan93‐114 showed shriveled anthers, short filaments, and withered male flowers. Transmission electron microscopy revealed the tapetal cells of the anthers were hypertrophic and vacuolated. Microspore protoplasts reduced in size, and the microspore wall had obvious defects: the incomplete intine and the insufficiently deposited exine. Organelles had disappeared in both tapetal cells and microspores. Comparative mitochondrial transcriptome analysis identified three differentially expressed genes in the MS clones: orf126, orf51, and atp8. In particular, orf126 and orf51 were unique insertions in the MS mitochondrial genomes. The former was an unknown open reading frame, and the latter was a fusion gene that contained a portion of atp9. These two genes should be studied as candidate male sterility genes in rubber tree. These results clarified the cytological causes of male sterility and expanded to understand the relationship between mitochondrial genes and male sterility in rubber tree.

Comparative transcriptome between male fertile and male sterile alfalfa (Medicago varia).

The online version contains supplementary material available at 10.1007/s12298-021-01026-x.

Male sterility significantly elevates shape variation and fluctuating asymmetry of zygomorphic corolla in gynodioecious Glechoma hederacea (Lamiaceae)

Female flowers of gynodioecious plants usually have smaller corollas than bisexual flowers. This difference is explained as a developmental consequence of stamen abortion and as a result of stronger selection for larger corolla size in hermaphroditic flowers that solely ensure male function within populations. This study evaluated whether the size difference of zygomorphic corollas in a widely distributed gynodioecious herb Glechoma hederacea is accompanied by variation in shape and bilateral fluctuating asymmetry of sexually differentiated flowers. Geometric morphometric analyses of bilateral symmetry in the shapes of corolla lower lips showed that male-sterile flowers were significantly more plastic and asymmetric, implying that they may be subjected to weaker stabilizing selection for corolla shape in comparison to hermaphrodites. These results illustrated that sexual differentiation may be an important factor contributing to bilateral fluctuating asymmetry in the shape of zygomorphic flowers.

The Mitochondrial Genome Assembly of Fennel (Foeniculum vulgare) Reveals Two Different atp6 Gene Sequences in Cytoplasmic Male Sterile Accessions.

Cytoplasmic male sterility (CMS) has always aroused interest among researchers and breeders, being a valuable resource widely exploited not only to breed F1 hybrid varieties but also to investigate genes that control stamen and pollen development. With the aim of identifying candidate genes for CMS in fennel, we adopted an effective strategy relying on the comparison between mitochondrial genomes (mtDNA) of both fertile and sterile genotypes. mtDNA raw reads derived from a CMS genotype were assembled in a single molecule (296,483 bp), while a draft mtDNA assembly (166,124 nucleotides, 94 contigs) was performed using male fertile sample (MF) sequences. From their annotation and alignment, two atp6-like sequences were identified. atp6−, the putative mutant copy with a 300 bp truncation at the 5’-end, was found only in the mtDNA of CMS samples, while the wild type copy (atp6+) was detected only in the MF mtDNA. Further analyses (i.e., reads mapping and Sanger sequencing), revealed an atp6+ copy also in CMS samples, probably in the nuclear DNA. However, qPCRs performed on different tissues proved that, despite its availability, atp6+ is expressed only in MF samples, while apt6− mRNA was always detected in CMS individuals. In the light of these findings, the energy deficiency model could explain the pollen deficiency observed in male sterile flower. atp6− could represent a gene whose mRNA is translated into a not-fully functional protein leading to suboptimal ATP production that guarantees essential cellular processes but not a high energy demand process such as pollen development. Our study provides novel insights into the fennel mtDNA genome and its atp6 genes, and paves the way for further studies aimed at understanding their functional roles in the determination of male sterility.

Male Sterility is linked to the Flavonoid Biosynthesis Pathways in Prunus mira.

Sterility plays an important role in plant adaptation and evolution and has contributed to the development of high yielding crop hybrids. We used the widely targeted metabolomics profiling to survey the metabolites and biological pathways associated with male sterility in Prunus mira by comparing flowers from fertile and sterile trees. Male sterile flowers displayed abnormal stamen, uncolored anthers, and distorted and shrunken pollen grains with an apparent lack of turgidity. We report 566 metabolites in six flower samples and 140 differentially accumulated metabolites (DAMs) between both flower types. Most of the DAMs belong to the phenyl propanoid biosynthesis pathway, particularly flavonoid, flavone and flavonol biosynthesis pathways, implying that alterations in these key pathways link to male sterility in P. mira. The known link between low levels of flavonoid metabolites, weak expression levels of several structural genes from the phenyl propanoid biosynthesis pathway and hyper accumulation of reactive oxygen species were highlighted for understanding the underlying mechanism leading to the abnormal or aborted pollen grains observed in the sterile flowers. Data on the molecular mechanism of male sterility in Prunus mira will facilitate further in-depth investigations on this important agronomic and ecological trait.

Biological characteristics and cytological studies on anther abortion of male sterile <italic>Camellia crassocolumna</italic>

The purpose of this study was to explore the flower morphology, anther and pollen abortion time and its cytological characteristics in male sterile plants of C. crassocolumna . The flowering process, floral morphology, anther structure, meiosis and microsporogenesis of male sterile (M350) and fertile plants (M352) of C. crassocolumna were observed by stereomicroscopy, paraffin section, chromosome preparation and DAPI staining. The results showed that the wild tea plant had a perfect flower, its anthers were tetrasporangiate shaped like a butterfly, with an anther wall development of basic type. It tapetal cells were binuclear, forming secretory cells at the tetrad stage, and degrading during mononuclear pollen stage. After the meiosis I, meiosis II and cytokinesis, pollen mother cells developed into tetrahedral tetrads. Microspores were triangular, and mature pollen was two-celled. The stamens of male sterile flowers developed normally in the early stage of flower bud development, and there was no difference between sterile and fertile flowers, while in the late stage of flower bud development, filaments were curved, anthers adhered and shriveled, anthers could not release pollen. The tapetal cells of male sterile flowers were proliferation abnormally and disordly at the meiosis of stage pollen mother cells, and the degradation of tapetum was delayed during the mononuclear and binucleate pollen periods. During meiosis of pollen mother cells of male sterile flowers, there were some abnormal appearances, such as chromosome ring, lagging chromosomes, chromosome bridges, chromosomal deletion, scattered chromosomes, unequal separation, micronucleus and abnormal tetrad. In sterile plants, the microspore cytoplasm was disorder, pollen grains adhered to each other at the mononuclear stage, pollen wall crumpled and deformed, cytoplasm and nucleus of pollen were blurred, the mature pollen cells were hollow and sunken. Taken together, the floral organ morphology of male sterile plants in C. crassocolumna belongs to stamen collapse type and anther abnormality type. The development of anthers is blocked from meiosis of pollen mother cells to uninucleate pollen stage, belonging to pollen mother cell abortion type and uninucleate pollen abortion type. Mononuclear period is the main period of anther abortion. Tapetum degradation delayed, chromosomal abnormalities of pollen mother cells in meiosis, and abnormal development of microspores and pollens, might be the main reasons for anther abortion in male sterile plants of C. crassocolumna .

Identification and development of male sterile and their maintainer lines in short-day onion (Allium cepa L.) genotypes

The performance of different onion genotypes was assessed for bolting traits because of identification and isolation of male sterile lines, significant results were revealed for number of bolts per plant, bolt length, umbel height, umbel diameter, number of flowers per umbel and number of flowers per plant. The male-sterile plants were spotted among the genotypes, which was phenotypically male sterile, in which flowers had the longer style with the narrow stigmatic knob, does produce functionally non-viable pollens, perianths of the male-sterile flower was not open fully. The anthers were light green to slightly yellowish translucent, shrivelled, seldom empty anther without pollen grains and were fused with anther sacs. The male-sterile plants were confirmed by acetocarmine assay and orf725 molecular marker. The identified male sterile lines will be used as parental material in future heterosis breeding to increase the onion bulb productivity.

Limited Cross Plant Movement and Non-Crop Preferences Reduce the Efficiency of Honey Bees as Pollinators of Hybrid Carrot Seed Crops.

Pollination rates in hybrid carrot crops remain limited after introduction of honey bee hives. In this study, honey bee foraging behaviour was observed in commercial hybrid carrot seed crops. Significantly more visits were made to male-fertile (MF) rather than cytoplasmically male-sterile (CMS) flowers. Pollen was collected from bees returning to a hive, to determine daily variation in pollen loads collected and to what level the bees were foraging for carrot pollen. Honey bees visited a wide range of alternative pollen sources and made relatively few visits to carrot plants throughout the period of flowering. Visitation rates to other individual floral sources fluctuated but visitation to carrot was consistently low. The underlying rate of carrot pollen visits among collecting trips was modelled and estimated to be as low as 1.4%, a likely cause of the limited success implementing honey bee hives in carrot crops.

Progressive programmed cell death inwards across the anther wall in male sterile flowers of the gynodioecious plant Plantago lanceolata.

A cell death signal is perceived and responded to by epidermal cells first before being conveyed inwards across the anther wall in male sterile Plantago lanceolata flowers. In gynodioecious plants, floral phenotype is determined by an interplay between cytoplasmic male sterility (CMS)-promoting factors and fertility-restoring genes segregating in the nuclear background. Plantago lanceolata exhibits at least four different sterilizing cytoplasms. MS1, a "brown-anther" male sterile phenotype, segregates with a CMSI cytoplasm and a non-restoring nuclear background in P. lanceolata populations. The aim of this study was to investigate the cytology of early anther development in segregating hermaphrodite and male sterile flowers sharing the same CMSI cytoplasm, and to determine if the sterility phenotype correlates with any changes to the normal pattern of programmed cell death (PCD) that occurs during anther development. Cytology shows cellular abnormalities in all four anther wall layers (epidermis, endothecium, middle layer and tapetum), the persistence and enlargement of middle layer and tapetal cells, and the failure of microspore mother cells to complete meiosis in male sterile anthers. In these anthers, apoptotic-PCD occurs earlier than in fertile anthers and is detected in all four cell layers of the anther wall before the middle layer and tapetal cells become enlarged. PCD is separated spatially and temporally within the anther wall, occurring first in epidermal cells before extending radially to cells in the inner anther wall layers. This is the first evidence of a cell death signal being perceived and responded to by epidermal cells first before being conveyed inwards across the anther wall in male sterile plants.

THE STEPS OF OBTAINING HETEROTIC F1 HYBRIDS OF WATERMELON

The article deals with the stages of obtaining heterosis hybrids F1 watermelon. To solve the problem of creating heterosis hybrids watermelon allocated parent line with nuclear (gene) male sterility, which has a marker recessive trait – a single leaf blade. On the basis of this line, we create F1 watermelon hybrids that meet the requirements of modern production. The characteristic of the maternal line (line HMS) having sterile male flowers (gene ms) and wholeness (nl), light green color of the fruit (g), which is also a recessive trait. Also, the assessment on complex resistance to Fusarium and Anthracnose in linear hybrids F1 watermelon showed their superiority over the parent lines and a significant excess of the standard. Determined the combining ability of hybrid combinations of watermelon were evaluated for yield. According to the results of the evaluation of the ability to combine, a positive effect on productivity showed a combination with the paternal lines: Uspeh, Nice, Medunok, Vostorg, Favorite, Stimul, Icar, Rubyn, Pamyat Kholodova. The effect of more than 20 t / ha showed paternal lines Pamyat Kholoova, Favorite, Ikar. The optimal variant of the parent forms ratio is o: m: o: m: o (1:2), this scheme provides a higher hybridity of the obtained seeds. Hybridity of the obtained seeds was determined in the nurseries of preliminary and competitive variety testing. Hybridity of seeds was from 84.2 to 96.3%, which is satisfactory for industrial crops, where non-hybrid plants will be removed at breakthrough on the marker basis. Separated hybrids Line Cms x Rubyn, Line Cms x Medunok, the Line Cms x Favorite, Line Cms x Vostorg, Line Cms x Icar. The aim of the research was to develop the stages of obtaining heterosis hybrids F1 watermelon.

Potential usability of CMS rucola for the breeding process

Rucola is a leafy vegetable from the Brassicaceae family with continuously increasing economic demand. Under this name rocket salad (Eruca sativa) as well as the perennial wall rocket (Diplotaxis tenuifolia) are commercially distributed. So far, for both species no hybrid system is available. Therefore, breeding lines of both species were used to pollinate cytoplasmic male sterile (CMS) cauliflower (Brassica oleracea) plants. Intergeneric Fi-hybrids were achieved by manual crosses and embryo rescue. Allotetraploid plants obtained after colchicine treatment were recurrently backcrossed with the respective rucola parent. The elimination of Brassica genomic DNA was verified using molecular markers, GISH analysis, flow cytometry and chromosome analysis. All backcross plants from BC2 up to the BC6 generation of the B. oleracea x E. sativa (BE) cross showed male sterility and full seed set compared to the E. sativa parent. No further incompatibilities were noticed between the CMS inducing cytoplasm and the E. sativa genome. Agronomical traits such as plant vigor, biomass production, flowering and seed set were recorded for the different backcross generations. The developed alloplasmic lines are diploid with 2n=2x=22 chromosomes and could be introduced without any problems into the breeding process. Also BC1 plants of the cross B. oleracea x D. tenuifolia (BD) had completely male sterile flowers. The phenotype was similar to that of the D. tenuifolia parent. Unlike the BE combination, for BD combination embryo rescue was necessary to establish BC2 plants. The flowers of all BC2 plants of BD combination showed besides the male sterility a pronounced female sterility, expressed by the abort of ovaries and failed seed set. Hence, this combination seems to be not applicable for the breeding process. Reasons for this strikingly different behaviour are under investigation.