Male Sterile Genotypes Research Articles

The establishment of the anther somatic niche with single cell sequencing.

The anther is the developmental housing of pollen and therefore the male gametes of flowering plants. The meiotic cells from which pollen are derived must differentiate de novo from somatic anther cells and synchronously develop with the rest of the anther. Anthropogenic control over anther development has become crucial for global agriculture so as to maintain inbred lines and generate hybrid seeds of many crops. Understanding the genes that underlie the proper differentiation, developmental landmarks, and functions of each anther cell type is thus fundamental to both basic and applied plant sciences. We investigated the development of the somatic niche of the maize (Zea mays) anther using single-cell RNA-seq (scRNA-seq). Extensive background knowledge on the birth then pace and pattern of cell division of the maize anther cell types and published examples of cell-type gene expression from in situ hybridization allowed us to identify the primary cell types within the anther lobe, as well as the connective cells between the four lobes. We established the developmental trajectories of somatic cell types from pre-meiosis to post-meiosis, identified putative marker genes for the somatic cell types that previously lacked any known specific functions, and addressed the possibility that tapetal cells sequentially differentiate. This comprehensive scRNA-seq dataset of the somatic niche of the maize anther will serve as a baseline for future analyses investigating male-sterile genotypes and the impact of environmental conditions on male fertility in flowering plants.

Genomic insights into the clonal reproductive Opuntia cochenillifera: mitochondrial and chloroplast genomes of the cochineal cactus for enhanced understanding of structural dynamics and evolutionary implications.

The cochineal cactus (Opuntia cochenillifera), notable for its substantial agricultural and industrial applications, predominantly undergoes clonal reproduction, which presents significant challenges in breeding and germplasm innovation. Recent developments in mitochondrial genome engineering offer promising avenues for introducing heritable mutations, potentially facilitating selective sexual reproduction through the creation of cytoplasmic male sterile genotypes. However, the lack of comprehensive mitochondrial genome information for Opuntia species hinders these efforts. Here, we intended to sequence and characterize its mitochondrial genome to maximize the potential of its genomes for evolutionary studies, molecular breeding, and molecular marker developments. We sequenced the total DNA of the O. cochenillifera using DNBSEQ and Nanopore platforms. The mitochondrial genome was then assembled using a hybrid assembly strategy using Unicycler software. We found that the mitochondrial genome of O. cochenillifera has a length of 1,156,235 bp, a GC content of 43.06%, and contains 54 unique protein-coding genes and 346 simple repeats. Comparative genomic analysis revealed 48 homologous fragments shared between mitochondrial and chloroplast genomes, with a total length of 47,935 bp. Additionally, the comparison of mitochondrial genomes from fourCactaceae species highlighted their dynamic nature and frequent mitogenomic reorganizations. Our study provides a new perspective on the evolution of the organelle genome and its potential application in genetic breeding. These findings offer valuable insights into the mitochondrial genetics of Cactaceae, potentially facilitating future research and breeding programs aimed at enhancing the genetic diversity and adaptability of O. cochenillifera by leveraging its unique mitochondrial genome characteristics.

Identification of sources of male sterility in the Colombian Coffee Collection for the genetic improvement of Coffea arabica L.

In coffee (Coffea arabica L.), male sterility is a prerequisite for the exploitation of heterosis since it provides an efficient and reliable method for the production of hybrid seeds. Given its relevance, the objective of this study was to identify male-sterile genotypes within the Colombian Coffee Collection that can be used in genetic improvement. For this purpose, Ethiopian germplasm and progenies derived from hybrids between C. arabica x C. canephora were explored between 2017 and 2021. In the first stage, genotypes without visual presence of pollen were preselected in the field, followed by selection through staining and verification of male sterility and female fertility through directed crosses (directed, reciprocal and selfing). In this stage, 9,753 trees were explored, preselecting 2.4% due to visual absence of pollen. The staining of structures allowed us to confirm the lack or sporadic production of pollen in 23 individuals of Ethiopian origin. The results of the directed crosses led to the identification of 11 male-sterile and 12 partially male-sterile genotypes belonging to 15 accessions. In all cases, the individuals were characterized by the presence of anthers but with an absence or low content of pollen, which is why the male sterility is possibly of the sporogenic type. The female receptivity values were between 2.9% and 72.6%, being higher than 30% in five genotypes. These genotypes are a valuable tool for the genetic improvement of C. arabica with the potential to facilitate the use of heterosis and to allow a deeper understanding the development of male gametophytes in the species.

Morphological characteristics of pollen from triploid watermelon and its fate on stigmas in a hybrid crop production system

Hybrid crop production is more reliant on pollinators compared to open-pollinated crops because they require cross-pollination between a male-fertile and a male-sterile line. Little is known about how stigma receipt of pollen from male-sterile genotypes affects reproduction in hybrids. Non-viable and non-compatible pollen cannot fertilise plant ovules, but may still interfere with pollination success. Here we used seedless watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) as a model hybrid plant, to evaluate the morphology, physiology, and movement of pollen from inter-planted genotypes (diploids and triploids). We found that pollen from triploids (‘Exclamation’ and ‘Royal Armada’) and diploids (‘SP-6’, ‘Summer Flavor 800’, and ‘Tiger’) was visually distinguishable. Pollen in triploids had more deformities (42.4–46%), tetrads (43–44%), and abnormal growth of callose plugs in pollen tubes. The amount of pollen in triploids to germinate on stigmas was low (8 ± 3%), and few pollen grains produced pollen tubes (6.5 ± 2%). Still, contrary to previous reports our results suggest that some viable pollen grains are produced by triploid watermelons. However, whilst honey bees can collect and deposit pollen from triploids onto stigmas, its effect on hybrid watermelon reproduction is likely to be minimal due to its low germination rate.

An Improved and Simplified Propagation System for Pollen-Free Sugi (Cryptomeria japonica) via Somatic Embryogenesis.

Sugi (Japanese cedar, Cryptomeria japonica) is the most important forestry tree species in Japan, covering 44% of the total artificial forest area. Large amounts of pollen released from these forests each spring cause allergic reactions in approximately 40% of the population, which are a serious social and public health problem in Japan. As a countermeasure, there is an urgent need to reforest using male-sterile plants (MSPs; pollen-free plants); however, the production of MSPs via conventional methods is inefficient, time consuming, and requires considerable resources in terms of labor and space. In the present paper, we described an improved and simplified methodology for the efficient propagation of pollen-free Japanese cedar, combining the use of genetic markers (marker-assisted selection or marker-aided selection) for the early selection of male-sterile genotypes and the use of somatic embryogenesis (SE) for the clonal mass propagation of seedlings. We describe all the stages involved in the production process of somatic seedlings. Our results demonstrated that this methodology easily and efficiently produces MSPs with a discrimination rate of 100% in a short period of time. Production of 243.6 ± 163.6 cotyledonary embryos per plate, somatic embryo germination, and plantlet conversion frequencies of 87.1 ± 11.9% and 84.8 ± 12.6%, respectively, and a 77.6 ± 12.1% survival rate after ex vitro acclimatization was achieved. Moreover, we also describe an easy method for the collection of somatic embryos prior to germination, as well as an efficient and practical method for their storage at 5°C. Finally, a representative schedule for the propagation of pollen-free sugi somatic seedlings is presented as a reference for practical uses. This methodology will definitively help to accelerate the production of C. japonica MSPs across Japan.

The anther-specific CYP704B is potentially responsible for MSG26 male sterility in barley.

Plant male sterility is a valuable trait in breeding and hybrid seed production. The barley male-sterility gene msg26 was mapped to a 0.02-cM region that anchors to a 506-kb low-quality assembly between two cleaved amplified polymorphic sequence (CAPS) markers, SP1M14 and SP1M49. The barley gene HORVU4Hr1G074840, which encodes a putative cytochrome P450 CYP704B protein, appears to be a strong candidate for the MSG26 trait. Barley (Hordeum vulgare L.) is an important cereal crop worldwide. Traditional breeding in barley is time-consuming and labor-intensive. The use of male-sterile genotypes may significantly improve the efficacy of hybrid breeding and seed production. The barley accession 'GSHO745' is a spontaneous male-sterile mutant from the barley variety, 'Unitan'. The male sterility in 'GSHO745' is controlled by the recessive gene, msg26 (originally named as ms-u). We revealed that the barley plants homozygous for msg26 proceeded normally through Meiosis II until the tetrad stage, but became fully defective in the late uninucleate microspores and developed pollen-less anthers. Using seven barley F2 populations, we mapped MSG26 to a 0.02-cM region that anchored to a 506-kb low-quality assembly between two cleaved amplified polymorphic sequence markers, SP1M14 and SP1M49. The HORVU4Hr1G074840 gene that encodes a putative cytochrome P450 protein (CYP704B) was identified as the most plausible candidate for MSG26. First, HORVU4Hr1G074840 is located in a collinear region of the rice CYP704B2 and the maize CYP704B1. Both of these genes are essential for male gamete production. Second, the male-sterile allele of HORVU4Hr1G074840 in GSHO745 contained a 4-bp deletion in the last exon. The resulting frame shift causes a Gly436Gln substitution, scrambles the sequence of the remainder of the protein, and forms a new termination site at the 70th triplet of the shifted reading frame. We thus called the variant protein CYP704B:p.G436Qfs*70. Third, the barley HORVU4Hr1G074840 gene was specifically expressed in anthers. Altogether, HORVU4Hr1G074840 represents a strong candidate for MSG26 in barley.

Calcium distribution in fertile and sterile anthers of thermosensitive male-sterile wheat

Calcium distribution in fertile and sterile anthers of a thermosensitive male-sterile wheat genotype was investigated using an antimonate precipitation method. During fertile anther development, before meiosis of the microspore mother cells, calcium precipitates were apparent in tapetal cells of the anther wall. After meiosis, precipitates were detected in the early microspores and accumulated in the large vacuole of late microspores. After microspore division, following decomposition of the large vacuole, precipitates decreased in the bicellular pollen. The earliest abnormality in calcium precipitate distribution detected during sterile pollen development was the greater accumulation of precipitates in the cytoplasm and nucleus of late microspores. The sterile microspore can divide to form bicellular pollen, but the large vacuole of sterile bicellular pollen did not decompose and greater abundance of precipitates was retained in the large vacuole. Abnormal distribution of calcium precipitates in sterile pollen precedes structural changes, suggesting that abnormal calcium metabolism is associated with pollen abortion.

Metabolic Alterations in Male-Sterile Potato as Compared to Male-Fertile.

The common potato, Solanum tuberosum L., is the fourth most important agricultural crop worldwide. Until recently, vegetative propagation by tubers has been the main method of potato cultivation. A shift of interest to sexual potato reproduction by true botanical seeds is due to the appearance of a new hybrid seed breeding strategy whose successful application for many crop species has been supported by male sterility. This investigation was focused on the study of differences in the metabolite profiles of anthers at the mature pollen stage from male-fertile and male-sterile genotypes of S. tuberosum. Application of gas chromatography coupled with a mass spectrometry method allowed detection of metabolic profiles for 192 compounds. Further data analysis with several libraries fully identified 75 metabolites; a similar amount was defined up to the classes. Metabolic profiles in the anthers of fertile genotypes were significantly distinguished from male-sterile ones by the accumulation of carbohydrates, while the anthers of sterile genotypes contained a higher amount of amino acids. In comparison with male-fertile plants, male-sterile genotypes had undeveloped pollen grain characters; i.e., smaller grain size, a thicker exine, “permanent tetrads” that failed to disintegrate into microspores, and the absence of pollen apertures that might be due to a disorder in the metabolism of carbohydrates and fatty acids.

Application of herbicides on parental lines (A clearfield® and R) of hybrid rice at post-flowering stage for production

The hypothesis of this study is based on the fact that parental line A-Clearfield® (male-sterile genotype) (Clearfield provide has tolerance to imidazolinone herbicides) and line R (male-fertile genotype - pollinator) is sensitive to the herbicide. So after flowering, we may apply an imidazolinone herbicide (Kifix®) to the plantings to kill line R, and harvesting only the hybrid seeds. The objective was to test the use of imidazolinone herbicide on parental lines (A-Clearfield® which is resistant to Kifix herbicide) and R no Clearfield® (non-resistant to Kifix genotype) as a strategy to improve production of hybrid seed in rice. Two trials were conducted to evaluate (A) the use of doses of imidazolinone herbicide in line R (plant control, number of grains per panicles, grain yield and seed germination; and (B) the use of different doses of imidazolinone herbicide in line A Clearfield® grain yield and seed germination. Trials were conducted in the tropical region of Brazil in randomized complete block design in factorial scheme 5 x 2 x 2. The treatments were the combination of five Kifix (Imazapyr, 525 g kg-1 + Imazapic, 175 g kg-1) rates applied on two no Clearfield® rice genotypes (first trial) or Clearfield® rice genotypes (second trial) in two growing seasons. The results showed application of herbicide doses higher than 150 g ha-1 after full flowering stage can cause reduction in growth and development of no Clearfield® rice. The use of Kifix herbicide in CL (Clearfield®) rice cultivars did not affect the grain yield, mass of 1000 grains, seed germination, first count germination, seedling emergence and seedling length. New researches should be done to define plant arrangement suitable for line R (no Clearfield®) and line A Clearfield® to find the optimum condition to produce hybrid seeds. From our results, we could see that the use of parental line A Clearfield® with a line R no Clearfield®, after flowering, provided the production of only hybrid seeds in the area, without reduction in seed quality.

Chloroplast Genome Sequence of Pigeonpea (Cajanus cajan (L.) Millspaugh) and Cajanus scarabaeoides (L.) Thouars: Genome Organization and Comparison with Other Legumes.

Pigeonpea (Cajanus cajan (L.) Millspaugh), a diploid (2n = 22) legume crop with a genome size of 852 Mbp, serves as an important source of human dietary protein especially in South East Asian and African regions. In this study, the draft chloroplast genomes of Cajanus cajan and Cajanus scarabaeoides (L.) Thouars were generated. Cajanus scarabaeoides is an important species of the Cajanus gene pool and has also been used for developing promising CMS system by different groups. A male sterile genotype harboring the C. scarabaeoides cytoplasm was used for sequencing the plastid genome. The cp genome of C. cajan is 152,242bp long, having a quadripartite structure with LSC of 83,455 bp and SSC of 17,871 bp separated by IRs of 25,398 bp. Similarly, the cp genome of C. scarabaeoides is 152,201bp long, having a quadripartite structure in which IRs of 25,402 bp length separates 83,423 bp of LSC and 17,854 bp of SSC. The pigeonpea cp genome contains 116 unique genes, including 30 tRNA, 4 rRNA, 78 predicted protein coding genes and 5 pseudogenes. A 50 kb inversion was observed in the LSC region of pigeonpea cp genome, consistent with other legumes. Comparison of cp genome with other legumes revealed the contraction of IR boundaries due to the absence of rps19 gene in the IR region. Chloroplast SSRs were mined and a total of 280 and 292 cpSSRs were identified in C. scarabaeoides and C. cajan respectively. RNA editing was observed at 37 sites in both C. scarabaeoides and C. cajan, with maximum occurrence in the ndh genes. The pigeonpea cp genome sequence would be beneficial in providing informative molecular markers which can be utilized for genetic diversity analysis and aid in understanding the plant systematics studies among major grain legumes.

Garlic (Allium sativum L.) fertility: transcriptome and proteome analyses provide insight into flower and pollen development.

Commercial cultivars of garlic, a popular condiment, are sterile, making genetic studies and breeding of this plant challenging. However, recent fertility restoration has enabled advanced physiological and genetic research and hybridization in this important crop. Morphophysiological studies, combined with transcriptome and proteome analyses and quantitative PCR validation, enabled the identification of genes and specific processes involved in gametogenesis in fertile and male-sterile garlic genotypes. Both genotypes exhibit normal meiosis at early stages of anther development, but in the male-sterile plants, tapetal hypertrophy after microspore release leads to pollen degeneration. Transcriptome analysis and global gene-expression profiling showed that >16,000 genes are differentially expressed in the fertile vs. male-sterile developing flowers. Proteome analysis and quantitative comparison of 2D-gel protein maps revealed 36 significantly different protein spots, 9 of which were present only in the male-sterile genotype. Bioinformatic and quantitative PCR validation of 10 candidate genes exhibited significant expression differences between male-sterile and fertile flowers. A comparison of morphophysiological and molecular traits of fertile and male-sterile garlic flowers suggests that respiratory restrictions and/or non-regulated programmed cell death of the tapetum can lead to energy deficiency and consequent pollen abortion. Potential molecular markers for male fertility and sterility in garlic are proposed.

Effects of different temperature regimes on flower development, microsporogenesis and fertility in bolting garlic (Allium sativum).

Garlic (Allium sativum L.) cultivars do not develop fertile flowers and seeds. Therefore, garlic production and improvement depend exclusively on vegetative propagation. Recent advances in garlic research have enabled fertility restoration and the discovery of fertile and male-sterile genotypes; however, the environmental regulation of the reproductive process is still not clear. Garlic seeds are successfully produced in the Mediterrenean region, where the photoperiod is relatively short, whereas spring and summer temperatures are high. We hypothesise that, in bolting garlic, various stages of florogenesis are differentially regulated by temperature and that high temperatures might obstruct pollen production. The effects of eight combinations of controlled growth temperatures on fertile and male-sterile garlic clones were studied. In both genotypes, a gradual temperature increase before and during anthesis favoured intact flower development. Surprisingly, continuous exposure to moderate temperatures during the entire growth period resulted in poor flowering, anther abortion and reduced pollen production. In the male-sterile genotype, no growth regime improved pollen production, which is controlled by genetic mechanisms. In the male-fertile genotype, gradual temperature increase supported pollen production but a sharp transition to high temperatures resulted in rapid flower senescence and pollen abortion, thus supporting our research hypothesis. In both fertile and male-sterile plants, the most vulnerable phase of microsporogenesis is the unicellular microspore stage. Tapetal malformation is the major cause for malnutrition of the microspores, with consequent production of nonviable pollen grains.

The effect of environmental factors and plant genotype on the severity of Claviceps purpurea in winter rye

Claviceps purpurea causes ergot, a serious disease of rye and grasses. Resistance genes to the pathogen have not been found in the genome of rye so far. Therefore we evaluated 90 rye genotypes in two seasons at three locations and analyzed the ergot incidence. In one location (Smolice) the same genotypes were also used to assess the influence of water spraying during rye flowering on ergot occurrence. Moreover, 29 cytoplasmic male-sterile genotypes of rye were used in Poznan, where within a 5 km distance there were no rye plants. In the first two experiments the source of the pathogen consisted of its sclerotia introduced into the soil, whereas in the third experiment a suspension of conidiospores was used to spray the plants from the moment of first flowering. Percentage of sclerotia in grain by weight in the first two experiments and sclerotia weight per ear in the third experiment were used as a measure of rye susceptibility to C. purpurea. Both rye genotype and location (weather conditions) showed significant variation for both traits. Low temperature and rainfall during rye flowering increased the occurrence of ergot. Water spraying of rye during flowering also boosted the occurrence of ergot. In another experiment, with sclerotia of C. purpurea used as inocula, ergot occurrence varied from 0 to 4.73 % in 2011/12 and from 0 to 5.22 % of sclerotia in grain yield in 2012/13. Cytoplasmic male-sterile rye inoculation with conidia of C. purpurea resulted in sclerotia presence which ranged from 0.10 to 0.26 g per ear.

The generative propagation and quality of new male-sterile cauliflowers with the Ogu-INRA and Brassica nigra cytoplasm

ABSTRACT In the years of 2012-2013 male-sterile cauliflower genotypes with the Brassica nigra cytoplasm and their maintainers were tested with respect to their ability for generative propagation and the quality of agronomical traits in comparison to male-fertile inbreeds and sterile genotypes with the Ogu-INRA cytoplasm. The ability for the generative propagation for male-sterile genotypes with the B. nigra cytoplasm was diversified and lower than for the maintainer, fertile lines and lines with the Ogu-INRA cytoplasm. Generative stalks of cauliflowers with the B. nigra cytoplasm usually had a higher number of buds and flowers in comparison to the fertile genotypes and to the sterile Ogu-INRA lines. The most desired commercial characteristics, such as circular shape, compactness of curd and intermediate or strong coverage by leaves, were noticed for sterile lines with the Ogu-INRA cytoplasm and their fertile complementary lines. Three experimental F1 hybrids showed good quality in comparison to commercial F1 cultivars.

Development of male sterile broccoli lines with raphanus sativus cytoplasm and assessment of their value for breeding purposes

ABSTRACT The aim of this study was to obtain new broccoli lines with cytoplasmic male sterility trait for the development of the modern F1 hybrids. CDT70 cauliflower line obtained in the Research Institute of Horticulture, formerly Research Institute of Vegetable Crops, Skierniewice, Poland, with the reliable cytoplasmic male sterility from Raphanus sativus (Ogu-INRA) was selected as a source of this trait. Three broccoli lines: BMi, BCr1 and BCr2 were used as donors of commercial characters in all cross combinations with sterile components. Selected fertile broccoli genotypes were characterized by good quality, uniformity and high level of self-compatibility. The breeding procedure included three consecutive back crosses of male sterile genotypes with fertile broccoli lines that lasted from 2008 to 2012. In each generation, self-compatibility level, the stability of the male sterility trait and ability for the generative propagation of back-crossed genotypes were tested in comparison with donor broccoli lines in the greenhouse. The agronomical and morphological characters of the back-crossed progeny were also evaluated in the field. As a result, three CMS broccoli lines of Bc3 generation with good quality and high seeding index, suitable for the breeding purposes, were obtained.

A recessive gene controlling male sterility sensitive to short daylength/low temperature in wheat (Triticum aestivum L.)

Utilization of a two-line breeding system via photoperiod-thermo sensitive male sterility has a great potential for hybrid production in wheat (Triticum aestivum L.). 337S is a novel wheat male sterile line sensitive to both short daylength/low temperature and long daylength/high temperature. Five F(2) populations derived from the crosses between 337S and five common wheat varieties were developed for genetic analysis. All F(1)'s were highly fertile while segregation occurred in the F(2) populations with a ratio of 3 fertile:1 sterile under short daylength/low temperature. It is shown that male sterility in 337S was controlled by a single recessive gene, temporarily designated as wptms3. Bulked segregant analysis (BSA) coupled with simple sequence repeat (SSR) markers was applied to map the sterile gene using one mapping population. The wptms3 gene was mapped to chromosome arm 1BS and flanked by Xgwm413 and Xgwm182 at a genetic distance of 3.2 and 23.5 cM, respectively. The accuracy and efficiency of marker-assisted selection were evaluated and proved essential for identifying homozygous recessive male sterile genotypes of the wptms3 gene in F(2) generation.

Exploitation of nuclear and cytoplasm variability in Hordeum chilense for wheat breeding

Hordeum chilense Roem. et Schultz. is a diploid wild barley native to Chile and Argentina. The high crossability of this species with other members of the Triticeae tribe promoted the development of the new species × Tritordeum Ascherson et Graebner. Hexaploid tritordeum was developed from the hybrid derived from the cross between H. chilense (used as female parent) and durum wheat. The interest of H. chilense is based on the presence of traits potentially useful for wheat breeding, including high endosperm carotenoid content, septoria tritici blotch resistance and abiotic stress tolerance. Besides, the variability at cytoplasm level is also important in this species. The development of common wheat–H. chilense alloplasmic lines (nucleus from wheat and cytoplasm from H. chilense) results in fertile or male sterile genotypes, depending on the accession donating the cytoplasm. Furthermore, these alloplasmic lines constitute an ideal system for deepening our knowledge on nuclear–cytoplasm interactions. In conclusion, H. chilense is an interesting source of variability for wheat breeding.

In vitro culture of various genotypes of male sterile Japanese cedar (Cryptomeria japonica D. Don)

The pollen allergy problem of Japanese cedar has been a nation-wide problem in spring time in Japan. It is said that about 20% of people suffer Japanese cedar pollinosis in urban areas. New projects substituting Japanese cedar forest stands with low-pollen or sterile male Japanese cedar trees started from 2008. The propagation of male sterile Japanese cedar genotypes is one of the most important steps in that project. We developed a micropropagation technique using an in vitro culture of male sterile Japanese cedar genotypes. Leafy shoot segments were used for explants. There was a genotypic difference in tissue culture response. Among the cytokinin tested, zeatin and 6-benzylaminopurine (BAP) were relatively effective for bud induction. More buds were induced in the medium containing zeatin than that containing BAP with the male sterile genotype Fukushima 5. Shoots developed from buds on the medium 1/2 LP containing 5 g l−1activated charcoal. Shoots produced roots on a medium containing 23.8 μM (5 mg l−1) 4-chloroindole-3-acetic acid and 0.044 μM (0.01 mg l−1) BAP. Rooted plantlets were successfully habituated and cultured in pots outside. The in vitro cultured materials will be used for the micropropagation of male sterile Japanese cedar in order to reduce the pollen in the air.

Paternal effects on seed mass in Arabidopsis thaliana

Who is in control of seed size, and do some fathers sire bigger seeds than others? We used isogenic male-sterile genotypes of the Arabidopsis thaliana accessions Col and Ler. By fertilising flowers side-by-side with either pollen from the same accession ('self-pollination') or pollen from another accession (outcrossing), we compared, on the same mother plant, seed set of flowers that were very similar in resource status. Some paternal genotypes had a significant effect on seed mass, with the most extreme father siring seeds 15.3% heavier than seeds resulting from 'self-pollination'. There was no correlation between seed mass of paternal parents and the seeds they sired. We discuss the evolution of seed size as a tug-of-war between parent and offspring.

CYTOLOGICAL PECULIARITIES IN TOMATO (SOLANUM LYCOPERSICUM) NUCLEAR MALE STERILITY

A cytological investigation for identification of the meiotic stages and mechanism of male sterility expression in nuclear male sterile tomato line No. 6944aa (msms1035) was performed in “Maritsa” Vegetable Crops Research Institute, Plovdiv, Bulgaria. The male sterile genotypes from second backcross progenies (BC1P2 and BC3P2) of the hybrid between line No. 6944aa and line No. 1 were cytologically characterized. The purpose was – to study the heritage and stability of the male sterility in creation of new sterile tomato line. The meiotic analysis in the pollen mother cells of sterile genotypes from line No. 6944aa revealed, that 12 bivalents were formed during the diakinesis and metaphase one in 74.1% of the cells. In parallel with bivalents 1 to 2 quadrivalents were observed in 15.8% of PMC and in case of desynapsis and early bivalent and quadrivalent separation 2 to 22 univalents in 10.1% of the cells were established. The normal pairing of homologous chromosomes of sterile msms 1035 plants from the different backcross progenies was described in 73.6 and 75.9% of PMC. The similar formation of multivalents and univalets, as in the mother sterile plants, was observed in backcross msms 1035 plants. The chromosomes have been distributed visually regular toward the spindle poles during the anaphase one both in the mother and in the backcross sterile genotypes in about 91–92% of the meiocytes. The cells lethality took place after second telophase, as the expression of the gene responsible for cytokinesis was blocked and we did not observe tetrad stage and microspore formation in msms 1035 plants. The cytological mechanism of nuclear male sterility in tomato, determined by gene ms 1035 probably is the presence of reciprocal, symmetric heterozygous translocations, as the disruptions of chromosomes destroyed expression of the genes which defined normal initiation, running and termination of the some meiotic stages. As a result of meiotic abnormalities chromosomes and gene unbalanced nuclei were formed, which reflected in pollen mother cell lethality.