Asynapsis and unreduced gamete formation in a Trifolium interspecific hybrid

Background Unreduced gametes, a driving force in the widespread polyploidization and speciation of flowering plants, occur relatively frequently in interspecific or intergeneric hybrids. Studies of the mechanisms leading to 2n gamete formation, mainly in the wheat tribe Triticeae have shown that unreductional meiosis is often associated with chromosome asynapsis during the first meiotic division. The present study explored the mechanisms of meiotic nonreduction leading to functional unreduced gametes in an interspecific Trifolium (clover) hybrid with three sub-genomes from T. ambiguum and one sub-genome from T. occidentale. Results Unreductional meiosis leading to 2n gametes occurred when there was a high frequency of asynapsis during the first meiotic division. In this hybrid, approximately 39% of chromosomes were unpaired at metaphase I. Within the same cell at anaphase I, sister chromatids of univalents underwent precocious separation and formed laggard chromatids whereas paired chromosomes segregated without separation of sister chromatids as in normal meiosis. This asynchrony was frequently accompanied by incomplete or no movement of chromosomes toward the poles and restitution leading to unreduced chromosome constitutions. Reductional meiosis was restored in progeny where asynapsis frequencies were low. Two progeny plants with approximately 5 and 7% of unpaired chromosomes at metaphase I showed full restoration of reductional meiosis. Conclusions The study revealed that formation of 2n gametes occurred when asynapsis (univalent) frequency at meiosis I was high, and that normal gamete production was restored in the next generation when asynapsis frequencies were low. Asynapsis-dependent 2n gamete formation, previously supported by evidence largely from wheat and its relatives and grasshopper, is also applicable to hybrids from the dicotyledonous plant genus Trifolium. The present results align well with those from these widely divergent organisms and strongly suggest common molecular mechanisms involved in unreduced gamete formation.

Study and development of methods for obtaining intergeneric hybrids of salmonids (Salmonidae (Jarocki or Schinz, 1822)) for achieving the effect of heterosis and increasing their productivity

Purpose. To study the possibility of obtaining highly productive intergeneric salmonid hybrids between rainbow trout and brook trout; brown trout and brook trout; rainbow trout and brown trout, as well as to develop methodological approaches and determine of optimal variants of hybrid crosses. Findings. In order to obtain intergeneric hybrids, we used six variants of hybrid crosses with brood fish of three salmonids belonging to three families (Salmo, Oncorhynhus, Salvelinus). The study used age-4 female rainbow trout with average body weight of 3296.8 g, Fork length was 62.6 cm, and the average working fecundity was 7420 eggs. Age-3 rainbow trout males had an average body weight of 1613 g and an average body length of 49.8 cm; age-3 brown trout females had an average body weight of 453.8 g and average working fecundity of 1540 eggs, and males had an average weight of 458.7 g; age-3 brook trout females had an average weight of 809.7 g and a length of 38.9 cm with working fecundity of 1732 eggs, and age-4 males had an average weight of 1212.8 g and an average body length of 46.0 cm. Twelve variants of fertilization were used: six variants at normal water temperature and six variants after a temperature shock. Under natural conditions, the creation of intergeneric hybrids is almost impossible, except for variants between brown trout and brook trout, which is due to the similarity of their biology. However, the efficiency of this cross is low and economically impractical for fish farmers. When applying the temperature shock during fertilization, hybrids proved to be the most effective, where females were rainbow trout, and males were brook trout and brown trout. The average weight of young-of-the-year intergeneric hybrids was, depending on the species of fish, from 8 to 54 g. The highest results were obtained for the creation of hybrids where following broodstock was used: ♂brook trout Х ♀brown trout; ♂brown trout Х ♀rainbow trout. In these variants of crossbreeding, the survival rate of young-of-the-year during the period of cultivation was 94.8 and 92.8%, respectively. In particular, the above hybrids did not suffer from infectious diseases during the growing period. Originality. New data on the development of methods for obtaining viable offspring of newly created hybrids were obtained, and the optimal variants of crossing between females and males of these salmonids were determined. Practical value. The results can be used for artificial breeding of salmonids in specialized farms that will allow obtaining high quality products and reducing their costs. Key words:rainbow trout, brown trout, brook trout, incubation, free embryos, larvae, fry, young-of-the-year.

Genome-wide unbalanced expression bias and expression level dominance toward Brassica oleracea in artificially synthesized intergeneric hybrids of Raphanobrassica

Raphanobrassica (RrRrCrCr, 2n = 4x = 36), which is generated by distant hybridization between the maternal parent Raphanus sativus (RsRs, 2n = 2x = 18) and the paternal parent Brassica oleracea (C°C°, 2n = 2x = 18), displays intermediate silique phenotypes compared to diploid progenitors. However, the hybrid shares much more similarities in silique phenotypes with those of B. oleracea than those of R. sativus. Strikingly, the silique of Raphanobrassica is obviously split into two parts. To investigate the gene expression patterns behind these phenomena, transcriptome analysis was performed on the upper, middle, and lower sections of pods (RCsiu, RCsim, and RCsil), seeds in the upper and lower sections of siliques (RCseu and RCsel) from Raphanobrassica, whole pods (Rsi and Csi) and all seeds in the siliques (Rse and Cse) from R. sativus and B. oleracea. Transcriptome shock was observed in all five aforementioned tissues of Raphanobrassica. Genome-wide unbalanced biased expression and expression level dominance were also discovered, and both of them were toward B. oleracea in Raphanobrassica, which is consistent with the observed phenotypes. The present results reveal the global gene expression patterns of different sections of siliques of Raphanobrassica, pods, and seeds of B. oleracea and R. sativus, unraveling the tight correlation between global gene expression patterns and phenotypes of the hybrid and its parents.

Nothospecies ×Sorbaronia fallax (Rosaceae) in the flora of Ukraine

×Sorbaronia fallax is a complex of artificially bred intergeneric hybrids. It is one of the non-traditional fruit crops. Fruits of the nothospecies are used in as food and medicinal raw materials. ×Sorbaronia fallax is sporadically grown in orchards, forest crops, forest belts used in landscaping. In many contries, e.g. United Kingdom, Norway, Sweden, Finland, Belgium, Netherlands, Czech Republic, Estonia, Latvia, Lithuania, Poland, Belarus, some regions of Russian Federation, and the United States (Connecticut), ×S. fallax belongs to invasive species. During our field trips in 2018 and 2020, we noted several cases of occurrence this nothospecies outside of culture. The aim was to generalize information about the spontaneous spread of ×S. fallax outside the cultivation sites and outline its secondary area in Ukraine. We discuss the problem of taxonomy and nomenclature of "chokeberry", which is common in Ukraine and is apomictic microspecies. In our opinion, it would be appropriate to use the name ×Sorbaronia mitschurinii for this nothotaxon, but this would contradict the International Code of Nomenclature for algae, fungi, and plants. The central part of the publication is devoted to analyzing available sources on the cultivation and spontaneous distribution of ×S. fallax in Ukraine. This nothotaxon now spontaneously grows in Lviv, Ivano-Frankivsk, Volyn, Rivne, Zhytomyr, Kyiv, and Sumy regions, as well as in the vicinity of Kyiv. It spreads spontaneously on forest frinnges, on glades, along forest roads, on pastures, meadows, swamps, and peatlands. ×Sorbaronia fallax is eukenophyte and ergasiophyte. Local spontaneous populations of ×S. fallax are primarily small, but some of them consist a few dozen to several hundred individuals. We assumed that there is reason to consider ×S. fallax as a potentially invasive nothospecies in the northern and western regions of Ukraine. In the appendices, we provide both lists of ×S. fallax location in culture and list its records outside culture. Keywords: black chokeberry, Aronia, Sorbus, invasive species, expansion. ×Sorbaronia fallax – комплекс штучно виведених міжродових гібридів. Це одна з нетрадиційних плодових культур. Її плоди використовуються в харчуванні та як лікарська сировина. ×Sorbaronia fallax спорадично вирощують у плодових садах, лісових культурах, лісосмугах, використовують в озелененні. У багатьох країнах – Великій Британії, Норвегії, Швеції, Фінляндії, Бельгії, Нідерландах, Чехії, Естонії, Латвії, Литві, Польщі, Білорусі, окремих суб’єктах Російської Федерації та в США (Коннектикут) ×S. fallax є інвазійною. Під час експедиційних досліджень у 2018 і 2020 роках нами відмічено кілька випадків зростання цього нотовиду поза культурою. Нашою метою було узагальнити відомості про спонтанне поширення ×S. fallax поза місцями культивування і окреслити її вторинний ареал в Україні. У статті обговорюємо проблему таксономії і номенклатури “чорноплідної горобини”, яка розповсюджена в Україні і є апоміктичним мікровидом. На нашу думку, для цього нототаксону доцільно було б використовувати назву ×Sorbaronia mitschurinii, проте це б суперечило International Code of Nomenclature for algae, fungi, and plants. Основна частина публікації присвячена аналізу наявних джерел про вирощування і спонтанне поширення ×S. fallax в Україні. Поза культурою цей нототаксон нині росте у Львівській, Івано-Франківській, Волинській, Рівненській, Житомирській, Київській та Сумській областях, а також в околицях Києва. Він спонтанно поширюється на узліссях, вирубках, вздовж лісових доріг, на пасовищах, болотистих і заплавних луках, болотах та торфовищах. ×Sorbaronia fallax є еукенофітом, ергазіофітом. Локальні спонтанні популяції ×S. fallax переважно малочисельні, але деякі з них нараховують від кількох десятків до кількох сотень особин. Показуємо, що є підстави розглядати ×S. fallax як потенційно інвазійний нотовид у північних і західних областях України. У додатках наведено перелік відомостей про поширення ×S. fallax у культурі та поза нею. Ключові слова: чорноплідна горобина, Aronia, Sorbus, інвазійний вид, експансія

Identification of Parental Genome Construction and Inherited Morphological Characteristics in Triploid and AneuploidIntergeneric Hybrids from a Diploid−Diploid Cross between Citrus and Fortunella

We previously obtained two intergeneric hybrids with different ploidies, i.e., aneuploid (2n = 28) and eutriploid, from diploid−diploid crosses between ‘Kiyomi’ tangor (Citrus unshiu Marcow. × C. sinensis (L.) Osbeck) and Meiwa kumquat (Fortunella crassifolia Swingle) as novel breeding materials for a seedless kumquat. In this study, we attempted to clarify the construction of the parental genomes of these hybrids by SSR genotyping and genomic in situ hybridization (GISH)−chromomycin A3 (CMA) analysis. SSR genotyping in NSX43 (LG5) and CiBE2227 (LG8) loci revealed that both hybrids inherited one allele from ‘Kiyomi’ tangor and two heterozygous alleles from Meiwa kumquat. The GISH analysis failed due to the high genomic homology between Citrus and Fortunella. At the same time, the CMA karyotype compositions of the two intergeneric hybrids (H15-701: 2A + 1B + 3C + 13D + 7E + 1F + 1Dst; H15-702: 3A + 1B + 2C + 15D + 4E +1F + 1Dst) and both parents (‘Kiyomi’ tangor: 1A + 2B + 2C + 6D + 7E; Meiwa kumquat: 2A + 2C + 12D + 1F + 1Dst) were completely revealed. We identified the parental genome construction and polyploidization processes in both intergeneric hybrids on the basis of these SSR genotypes and CMA karyotype compositions according to the following theory: the SSR genotypes and chromosome compositions were the same as those of the somatic chromosome and two-fold after the first division (even number) in unreduced gametes caused by first-division restitution (FDR) and second-division restitution (SDR), respectively. Consequently, we determined that both intergeneric hybrids may have had two genomes derived from the 2n male unreduced gamete as a result of the FDR of the Meiwa kumquat. In addition, most horticultural traits of the leaves, flowers, and fruits of both hybrids showed intermediate traits of the parents, but the fruit sizes and flowering habits were more like those of the two inherited genomes of Meiwa kumquat.

Phenotypic Characterization and RT-qPCR Analysis of Flower Development in F1 Transgenics of Chrysanthemum × grandiflorum

Gene silencing is the epigenetic regulation of any gene in order to prevent gene expression at the transcription or translation levels. Among various gene silencing techniques, RNA silencing (RNAi) is notable gene regulation technique that involves sequence-specific targeting and RNA degradation. However, the effectiveness of transgene-induced RNAi in F1 generation of chrysanthemum has not been studied yet. In the current study, we used RNAi-constructed CmTFL1 (white-flowered) and CmSVP overexpressed (yellow flowered) transgenic plants of previously conducted two studies for our experiment. Cross hybridization was performed between these intergeneric transgenic and non-transgenic plants of the winter-growing chrysanthemum selection “37” (light pink flowered). The transgene CmSVP was confirmed in F1 hybrids by RT-PCR analysis, whereas hybrids of CmTFL1 parental plants were non-transgenic. Besides this, quantitative real-time PCR (qPCR) was used to explain the molecular mechanism of flower development using reference genes. Intergeneric and interspecific hybrids produced different colored flowers unlike their respective parents. These results suggest that generic traits of CmSVP overexpressed plants can be transferred into F1 generations when crossed with mutant plants. This study will aid in understanding the breeding phenomenon among intergeneric hybrids of chrysanthemum plants at an in vivo level, and such transgenics will also be more suitable for sustainable flower yield under a low-light production system.

Pre- and Postzygotic Barriers Associated with Intergeneric Hybridization between Aronia melanocarpa (Michx.) Elliott x Pyrus communis L. and ×Sorbaronia dippelii (Zabel) CK Schneid. x Pyrus communis

Intergeneric hybridization between Aronia and Pyrus may provide a pathway for developing novel fruit types with larger, sweeter fruits, while maintaining the high levels of biologically health-promoting compounds present in Aronia fruits. Here we describe a deleterious genetic incompatibility, known as hybrid necrosis or hybrid lethality, that occurs in intergeneric F1 hybrids of Aronia melanocarpa x Pyrus communis and ×Sorbaronia dippelii x Pyrus communis. Pollination experiments revealed that maternal A. melanocarpa and ×S. dippelii pistils are compatible with pollen from P. communis. Controlled pollinations using different mating combinations resulted in varying levels of fruit and seed set. Because every combination produced at least some viable seeds, prezygotic incompatibility does not appear to be present. We attempted to recover putative intergeneric progeny via either in vitro germination or in vitro shoot organogenesis from cotyledons. Progeny of putative hybrids from A. melanocarpa x P. communis only survived for a maximum of 14 days before succumbing to hybrid lethality. Regeneration of ×S. dippelii x P. communis was successful for two seedlings that have been maintained for an extended time in tissue culture. These two seedlings have leaf morphologies intermediate between the two parental genotypes. We also confirmed their hybrid status by using AFLPs and flow cytometry. Putative intergeneric hybrids were grown out ex vitro before showing symptoms of hybrid necrosis and dying after 3 months. Eventually micrografts failed, ultimately showing the same symptoms of hybrid necrosis. These results show that intergeneric hybridization is possible between Aronia and related genera in the Rosaceae, but there are postzygotic barriers to hybridity that can prevent the normal growth and development of the progeny.