Search

Reduction to a haploid state followed by chromosome doubling is an established method for the production of inbred lines for diploid-hybrid true seed production. In potato, the focus on haploid induction has been to use haploid inducers to develop primary dihaploids from tetraploid breeding clones via maternal haploid induction. Further reduction of diploid breeding lines into true monoploids via haploid induction is also possible but has not been explored extensively. PL-4, a diploid potato line developed as an improved haploid inducer, was crossed as female in a limited number of crosses with a diploid breeding line derived from Solanum tuberosum Group Phureja-stenotomum. Embryo rescue resulted in two offspring below the guard cell count threshold, and SNP analysis identified one offspring as a monoploid derived from PL-4. [ABSTRACT FROM AUTHOR]

Embryo rescue technology has been widely applied in seedless grape breeding, but its success depends on many factors. Here, two Vitis vinifera seedless varieties 'Qinhong No.2' and 'Qinhong No.10' were used as research objects, the inflorescences were sprayed with 0.5 mg·L−1 thidiazuron 10 days before flowering, and then the ovules from open- and self-pollination of them were cultured in solid–liquid biphase MM3 media to investigate the effect of thidiazuron on embryo rescue. Under natural condition, the ovules of open- and self-pollination were inoculated onto three solid–liquid biphase media NN, ER, and MM3 to compare the efficiency of embryo rescue. The results showed that pre-bloom spraying thidiazuron significantly promoted ovule development and further improved the effect of embryo rescue in vitro. After applying thidiazuron, the embryo development rate, germination rate, and seedling rate of the four combinations reached 30.77%–42.62%, 29.36%–41.64%, and 22.02%–40.33%, respectively. Open-pollination of the two varieties provided better effects for culturing than their self-pollination, and the MM3 medium was always more suitable for embryo development than either the ER or NN medium. Furthermore, the germination rate of bare embryos of 'Qinhong No. 10' open-pollination on solid WPM medium surpassed that of ovules (without embryo stripping) on solid NN medium. HIGHLIGHTS: Pre-bloom spraying TDZ could improve the effect of embryo rescue of seedless grape. The embryo rescue effect was better in open- than self-pollinated seedless grapes. Solid–liquid biphase MM3 was more suitable for embryo rescue than an ER or NN medium. The seedling rate of bare embryos on WPM medium exceeded that of ovules on NN medium. Overall, 2312 hybrids from the four combinations were obtained via embryo rescue. [ABSTRACT FROM AUTHOR]

The major factors affecting the in vitro immature embryo rescue efficiencies from Prunus persica or P. armeniaca accessions have been identified, along with improving the feasibility. Variations in the woody plant medium (WPM) were used depending on the embryo size. Embryos less than 5 mm long were cultured in WPM supplemented with 1 μM BAP and 1 μM GA3, while embryos bigger than 5 mm long were cultured in hormone-free medium, with or without vermiculite. The environmental in vitro culture conditions consisted of three phases: a (I) stratification at 4 °C during a 3- to 5-month-long period in the dark, followed by (II) growth of germinated embryos at 14 °C for a 4-week-long period, with 12 h light a day, which favors plantlet development, and finally, (III) growth at 24 °C, with 16 h light a day, until the plantlets were acclimatized in the greenhouse. The germination of smaller embryos, at the end of phase I, ranged from 82.2% to 22.1% for apricots and flat peaches, respectively, whereas for bigger embryos, the germination varied from 97.3% to 53.2% for the same species. The embryo germination for peaches and nectarines ranged from 40.1% to 30.3% for smaller embryos, and from 91.9% to 63.0% for bigger embryos. Endo- and epiphytic contamination, affecting from 7.4% to 52.9% of cultured embryos, depending on the fruit type and conservation conditions, and the capacity to acclimate to soil conditions, ranging from 50.4% to 93.2%, were the two most important factors influencing the protocol's efficiency and feasibility. Considering the overall efficiencies, expressed as hardened plants transferred to field plots over clean uncontaminated embryo, the values ranged from 55.8% for nectarines, 54.0% for peaches, 45.6% for apricots, and 23.3% for flat fruits. The addition of vermiculite to the culture medium significantly improved the plantlet development, avoiding subculture to fresh medium when an extension of phase III was required before acclimatization. Compared to laboratory glassware, the use of food glass containers with air-permeable sealing film, along with vermiculite-containing medium, significantly reduced the costs when handling the large number of embryos required for breeding programs. [ABSTRACT FROM AUTHOR]

Hardy geranium is a popular ornamental plant with a high market demand. As a result, there is a strong need for continuous innovation to improve its ornamental qualities. Interspecific hybridization is a widely used technique for introducing desirable traits and creating new cultivars with added value. To explore the possibilities of creating novelty within the Geranium genus, we conducted 2438 interspecific crosses over three flowering seasons, resulting in the successful harvest of 445 seeds and the final production of 82 seedlings. Using embryo rescue increased the germination rate of a seedling from 0.17% to 1.01%. To validate the paternal genetic contribution in the new seedlings, we used amplified fragment length polymorphism (AFLP) to assess the proportion of uniquely inherited paternal markers in all seedlings. AFLP analysis confirmed that 54 of the 82 seedlings were indeed true hybrids (65.8% hybridization success rate). A morphological evaluation of the flowers and leaves, including flower diameter (mm), style length (mm), number of flowers, flowering period (weeks), and color of both flowers and leaves, provided further confirmation of the F1 hybrid status of the seedlings. The results of our interspecific breeding demonstrated the efficiency of interspecific hybridization in hardy geraniums and its potential to create distinctive and novel cultivars for the ornamental market. [ABSTRACT FROM AUTHOR]

The production of the common bean (Phaseolus vulgaris L.), one of the most important sources of protein and minerals and one of the most consumed grain legumes globally, is highly affected by heat and drought constraints. In contrast, the tepary bean (Phaseolus acutifolius A. Gray), a common bean-related species, is adapted to hot and dry climates. Hybridization to introduce complex traits from the tepary bean into the common bean has been challenging, as embryo rescue is required. In this study, we report three novel interspecific lines that were obtained by crossing lines from prior common bean × tepary bean hybridization with Phaseolus parvifolius Freytag in order to increase the male gametic diversity to facilitate interspecific crosses. These interspecific lines enhanced the crossability of the common bean and tepary bean species while avoiding the embryo rescue process. Crossing these three interspecific lines with tepary beans resulted in 12-fold more hybrid plants than crossing traditional common beans with tepary beans. Whole-genome sequencing analysis of these three interspecific lines shows large introgressions of genomic regions corresponding to P. parvifolius on chromosomes that presumably contribute to reproductive barriers between both species. The development of these lines opens up the possibility of increasing the introgression of desirable tepary bean traits into the common bean to address constraints driven by climate change.

Embryo rescue is a vital technique in cucurbit breeding and propagation, addressing challenges such as embryo abortion, poor seed viability, and incompatibility barriers. This method involves the excision of immature embryos from seeds followed by their in vitro culture on a nutrient medium, providing an environment conducive to their growth and development. In cucurbits, embryo rescue has been extensively utilized to overcome barriers to hybridization, enabling the production of interspecific and intergeneric hybrids with desired traits. Various factors, including genotype, developmental stage of embryos, and culture conditions, influence the success of embryo rescue in cucurbits. Optimal nutrient formulations, growth regulators, and culture techniques are critical for promoting embryo germination, shoot elongation, and subsequent plantlet establishment. Additionally, embryo rescue facilitates the recovery of valuable genetic material from wild and exotic cucurbit species, expanding genetic diversity and developing novel cultivars with improved traits such as disease resistance, yield, and quality. This review highlights the principles, applications, and advancements in embryo rescue technology in cucurbits, emphasizing its significance in cucurbit breeding programs and crop improvement efforts. [ABSTRACT FROM AUTHOR]

Embryo rescue is an effective method and has been widely applied in the breeding of seedless grape. In this study, we conducted eight cross combinations involving five stenospermocarpic seedless grape varieties, with the male parents being the variety ‘Beichun’ and a seedless variety ‘Venus Seedless’. The young fruits of the resulting hybrid plants were harvested at the optimal sampling time for each female parent and subjected to in vitro ovule culture. To enhance the efficiency of the seedless grape embryo rescue technology system, we conducted a comparative analysis on the impact of solid and solid-liquid diphasic MM3 embryo development medium, various parental genotypes, and the duration of ovule culture on embryo rescue. Additionally, marker assisted-selection (MAS), was employed on the hybrids using the seedless gene molecular marker SCF27-2000. Results revealed variability in the impact of medium phase on the successful rescue of embryos across different cross combination. Cultivars ‘Perlette’ and ‘Qinhong No.1’ emerged as suitable female parents for successful embryo rescue. Notably, the influence of the maternal genotype on embryo rescue exceeded that of the paternal genotype and medium phase. The rates of embryo development, growth, and seedling formation for the combinations ‘Perlette’ × ‘Venus Seedless’ and ‘Qinhong No.1’ × ‘Venus Seedless’ peaked at 10 weeks of ovule culture. A total of 894 hybrid strains resulting from eight cross combinations were obtained through embryo rescue, which 559 strains exhibiting a seedless marker, yielding an average seedless rate of 62.53%.Key message: The study investigated the influencing factors in embryo rescue for seedless grapes, resulting in the identification of 559 strains carrying the seedless gene molecular marker SCF27-2000. [ABSTRACT FROM AUTHOR]

Embryo rescue is essential for the breeding of seedless grapes, but current protocols are inefficient and limit practical application. Here, we documented factors influencing embryo rescue efficiency using crosses of a cold-resistant seeded hybrid 00-1-5 ('Muscat Hamburg' × Vitis amurensis) as the paternal parent with four stenospermocarpic seedless grape cvs., 'Flame Seedless', 'Qinhong No. 2', 'Qinhong No. 10', and 'Ruby Seedless'. The results showed that treatment of inflorescences with 30∼50 mg·L−1 IBA 14 days before flowering significantly increased the embryo development, germination, and transition to seedling for progeny of each of the four crosses. 'Qinhong No. 2' × 00-1-5 and 'Qinhong No. 10' × 00-1-5, with a large number of ovules, were cultured on solid and solid–liquid biphase MM3 media respectively, the embryo development rate on solid medium was significantly better than that on solid–liquid biphase medium. 'Ruby Seedless', 'Qinhong No. 2' and 'Qinhong No. 10' are more suitable for embryo rescue as maternal parent. The optimal medium for transforming deformed seedlings into normal seedlings was 2 × MS medium containing 0.2 mg·L−1 6-BA, 0.1 mg·L−1 IAA, and 1.6 mg·L−1 ZnSO4. In total, 311 embryos were rescued successfully, which were considered as potential cold-resistant seedless hybrids. [ABSTRACT FROM AUTHOR]

The major factors affecting the in vitro immature embryo rescue efficiencies from Prunus persica or P. armeniaca accessions have been identified, along with improving the feasibility. Variations in the woody plant medium (WPM) were used depending on the embryo size. Embryos less than 5 mm long were cultured in WPM supplemented with 1 μM BAP and 1 μM GA3, while embryos bigger than 5 mm long were cultured in hormone-free medium, with or without vermiculite. The environmental in vitro culture conditions consisted of three phases: a (I) stratification at 4 °C during a 3- to 5-month-long period in the dark, followed by (II) growth of germinated embryos at 14 °C for a 4-week-long period, with 12 h light a day, which favors plantlet development, and finally, (III) growth at 24 °C, with 16 h light a day, until the plantlets were acclimatized in the greenhouse. The germination of smaller embryos, at the end of phase I, ranged from 82.2% to 22.1% for apricots and flat peaches, respectively, whereas for bigger embryos, the germination varied from 97.3% to 53.2% for the same species. The embryo germination for peaches and nectarines ranged from 40.1% to 30.3% for smaller embryos, and from 91.9% to 63.0% for bigger embryos. Endo- and epiphytic contamination, affecting from 7.4% to 52.9% of cultured embryos, depending on the fruit type and conservation conditions, and the capacity to acclimate to soil conditions, ranging from 50.4% to 93.2%, were the two most important factors influencing the protocol’s efficiency and feasibility. Considering the overall efficiencies, expressed as hardened plants transferred to field plots over clean uncontaminated embryo, the values ranged from 55.8% for nectarines, 54.0% for peaches, 45.6% for apricots, and 23.3% for flat fruits. The addition of vermiculite to the culture medium significantly improved the plantlet development, avoiding subculture to fresh medium when an extension of phase III was required before acclimatization. Compared to laboratory glassware, the use of food glass containers with air-permeable sealing film, along with vermiculite-containing medium, significantly reduced the costs when handling the large number of embryos required for breeding programs.

The development of seedless cultivars is a primary goal in grapevine breeding. Since grapes are stenospermic and tend to abort their embryos before development, traditional breeding methods often yield seedless cultivars at a low frequency. Therefore, embryo rescue has emerged as a promising approach for creating seedless grape cultivars. This study aimed to optimize the ideal sampling time and protocol for efficient embryo rescue in grapes. Ovules from immature berries collected at various days after pollination (20DAP, 30DAP, 40DAP, and 50DAP) were cultured on Nitsch and Nitsch (NN) medium with different concentrations of Benzyl aminopurine (BAP) (0.1, 0.2, and 0.5 mg/L) and Activated Charcoal (AC) (1.5, 2, and 2.5 g/L). Several parameters were assessed, including maximum ovule growth, the percentage of enlarged ovules, percentage of collapsed ovules, callus formation percentage, and embryo germination percentage. The study’s results indicated that berries collected at 40 DAP yielded the best outcomes across all parameters. Regarding treatments, the most favorable results were achieved when ovules were cultured on NN medium supplemented with 0.5 mg/L BAP and 2 g/L AC. In conclusion, the study underscores the significance of choosing the right sampling time and treatments to ensure efficient embryo rescue in grapes. The protocol standardized from this research is recommended for effectively rescuing embryos and developing seedless hybrids. [ABSTRACT FROM AUTHOR]

The union of unreduced female and male gametes leads to spontaneous chromosome doubling, which is not only an important way of the origin of polyploid species but also an essential tool for enhancing crop doubled haploid breeding efficiency. A major quantitative trait locus QTug.sau-3B responsible for unreduced gametes formation was discovered in tetraploid Triticum turgidum wheat and was further transferred to elite common wheat lines using synthetic hexaploid wheat as a bridge. This objective of this study is to make wheat/wheat F1 hybrids between the elite lines with this gene region and commercial cultivars and to evaluate the efficiency of QTug.sau-3B gene leading to spontaneous chromosome doubling. Wheat/wheat F1 hybrids and their parents were pollinated with the fresh pollen of Imperata cylindrica to produce wheat haploid through chromosome elimination of I. cylindrica. Doubled haploid (DH) were then developed by spontaneous chromosome doubling in haploids because of the union of unreduced female and male gametes. In this experiment, 5 F1 hybrid materials and 3 I. cylindrica materials were used for distant hybridization. 4610 florets were pollinated, 1965 seeds were produced, 244 embryos were obtained, and 50 wheat haploid plants were obtained. In different temperature treatments, the haploid plant numbered H31 set seeds at 25°C/18°C (18 h/6 h) and 25°C/10°C (18 h/6 h), and the self-fertilization rate was 4.35% and 2.41%, respectively. The results of this study provide a reference for the establishment of wheat haploid breeding technology of chromosome elimination based on wheat-I. cylindrica hybridization and automatic chromosome doubling based on unreduced gamete genes. [ABSTRACT FROM AUTHOR]

Diploid Citrus × Poncirus hybrids have significantly contributed to citrus rootstock evaluation. In Türkiye, common sour orange rootstock is used in many different climates and soil conditions at almost 85% of citrus plantations, but this rootstock is susceptible to Citrus tristeza virus disease. This study was conducted to improve new rootstock genotypes by traditional hybridization. Common sour orange (CSO) and Common mandarin (Citrus deliciosa Ten.) (CM) were crossed with Troyer citrange (TC) while King mandarin (KM) was crossed with Carrizo citrange (CC). Embryos obtained from crosses were taken on 110, 120 and 130 days after artificial pollination (DAP), and were germinated on MT culture media. The embryos of 120 DAP of combinations had the highest germination rate within CSO×TC, 95.15%; CM×TC, 96.25%; KM×CC, 95.23%. The trifoliate rates for each combination at subculture (CSO×TC, 17.40%; CM×TC, 11.11%; KM×CC; 6.17%) were obtained from 110 DAP embryos. Survival rates of the genotypes were ranged between 72.13% and 90.28% in subculture and varied from 40.17% and 64.71% in the greenhouse. As a result of the ploidy analysis by flow cytometry, the nuclear DNA content of diploid genotypes were found between 0.78 pg/2C and 0.93 pg/2C. One of the genotypes derived from CM×TC hybridization on 120 DAP was determinated as a triploid plant. [ABSTRACT FROM AUTHOR]

Hardy geranium is a popular ornamental plant with a high market demand. As a result, there is a strong need for continuous innovation to improve its ornamental qualities. Interspecific hybridization is a widely used technique for introducing desirable traits and creating new cultivars with added value. To explore the possibilities of creating novelty within the Geranium genus, we conducted 2438 interspecific crosses over three flowering seasons, resulting in the successful harvest of 445 seeds and the final production of 82 seedlings. Using embryo rescue increased the germination rate of a seedling from 0.17% to 1.01%. To validate the paternal genetic contribution in the new seedlings, we used amplified fragment length polymorphism (AFLP) to assess the proportion of uniquely inherited paternal markers in all seedlings. AFLP analysis confirmed that 54 of the 82 seedlings were indeed true hybrids (65.8% hybridization success rate). A morphological evaluation of the flowers and leaves, including flower diameter (mm), style length (mm), number of flowers, flowering period (weeks), and color of both flowers and leaves, provided further confirmation of the F1 hybrid status of the seedlings. The results of our interspecific breeding demonstrated the efficiency of interspecific hybridization in hardy geraniums and its potential to create distinctive and novel cultivars for the ornamental market.

Brassica juncea (L.) Czern. & Coss. (Indian mustard) is an economically important edible oil crop. Over the years, plant breeders have developed many elite varieties of B. juncea with better yield traits, but research work on the introgression of stress resilience traits has largely been lagging due to scarcity of resistant donors. Crop wild relatives (CWRs) are the weedy relatives of domesticated plant species which are left unutilized in their natural habitat due to the presence of certain undesirable alleles which hamper their yield potential, and thus, their further domestication. CWRs of B. juncea namely include Sinapis alba L. (White mustard), B. tournefortii Gouan. (African mustard), B. fruticulosa Cirillo (Twiggy turnip), Camelina sativa L. (Gold-of-pleasure), Diplotaxis tenuisiliqua Delile (Wall rocket), D. erucoides L. (White wall rocket), D. muralis L. (Annual wall rocket), Crambe abyssinica R.E.Fr. (Abyssinian mustard), Erucastrum gallicum Willd. (Common dogmustard), E. cardaminoides Webb ex Christ (Dogmustard), Capsella bursa-pastoris L. (Shepherds purse), Lepidium sativum L. (Garden Cress) etc. These CWRs have withstood several regimes of biotic and abiotic stresses over the past thousands of years which led them to accumulate many useful alleles contributing in resistance against various environmental stresses. Thus, CWRs could serve as resourceful gene pools for introgression of stress resilience traits into Indian mustard. This review summarizes research work on the introgression of resistance against Sclerotinia stem rot (caused by Sclerotinia sclerotiorum), Alternaria blight (caused by Alternaria brassicae), white rust (caused by Albugo candida), aphid attack, drought and high temperature from CWRs into B. juncea. However, various pre- and post-fertilization barriers due to different ploidy levels are major stumbling blocks in the success of such programmes, therefore, we also insightfully discuss how the advances made in -omics technology could be helpful in assisting various breeding programmes aiming at improvisation of stress resilience traits in B. juncea. [ABSTRACT FROM AUTHOR]

The new trends in the consumption of table grapes and the growing interest in the environmental impact of this crop have pushed breeders toward the development of seedless cultivars endowed with resistance, through crossbreeding programs. To obtain seedless grapes, the use of embryo-rescue techniques is fundamental. In this research, a grape embryo-culture protocol was optimized and validated by using 39 cultivars and 41 cross-combinations carried out in the framework of a large private table grape program of the private network Italian Variety Club in the period 2017–2021 evaluating several factors, such as the improvement in embryo formation, germination and growth, and plantlet development. The embryo culture attitude of crosses between different combinations of seedless parents was assessed, and the rates of embryo development from the extracted ovules mostly ranged from 3.5 to 35.5% with 5 out of 43 genotypes outliers. Experiments conducted at different sampling times, in a range of 43–62 days after pollination (DAP), did not show significant differences between the samples analyzed, while the rate of embryos developed with the applied protocol proved its employability on multiple genotypes, although the grapevine genotype significantly influenced the technique efficiency. [ABSTRACT FROM AUTHOR]

Tomato (Solanum lycopersicum L.) is the most important vegetable crop grown in India after potato. Root-knot nematodes (RKNs) (Meloidogyne spp.) cause yield loss between 11 and 35% in tomato. RKNs are also known to be involved in the tomato wilt disease complex in association with Fusarium oxysporum sp. lycopersici and Ralstonia solanacearum. The nematode resistance gene, Mi1 from Solanum peruvianum, is currently the only source of RKN resistance in modern tomato cultivars. Mi1 mediated resistance is temperature sensitive and ineffective above 28 °C soil temperature. Nematode resistance gene, Mi-9 found in S. arcanum accession LA2157 is heat-stable and is located on the short arm of chromosome 6. In our study, LA2157 was crossed with tomato cultivar Kashi Amrit. The inter-specific hybrid was successfully developed through embryo rescue. The hybridity of embryo rescued plants was confirmed by morphological features and molecular marker assay. LA2157 and F1 hybrid showed immune reaction to M. incognita under the high inoculation pressure of 2000s stage infective juveniles per plant, while cv. Kashi Amrit exhibited a highly susceptible reaction. Among hundred F3 plants from ten F2s, ten F3 plants each of two separate F3 families (43 and 119) have shown resistance and no segregation was observed within the family for resistance during April–May, 2020 (high temperature). All F4 plants derived from 43F3 also gave an immune reaction to M. incognita indicating homozygous nature of 43F2 plant for Mi-9 gene. We believe that this set of resistant plants can be utilized to transfer heat-stable nematode resistance in the background of cultivated tomatoes. Key message: Inter-specific tomato hybrid of Kashi Amrit and LA2157 was developed through embryo rescue from fruits of 33–34 days after pollination. The identified F4 family homozygous for Mi-9 can be used to transfer heat-stable nematode resistance to cultivated tomatoes. [ABSTRACT FROM AUTHOR]

O. ficus-indica (prickly pear cactus) is an important forage and food source in arid and semiarid ecosystems and is the most important cactus species in cultivation globally. The high degree of apomixis in the species is a hindrance in plant breeding programs where genetic segregation is sought for the selection of superior genotypes. To understand if in ovulo embryo rescue could increase the proportion of zygotic seedlings, we compared the mature seed-derived seedlings with those regenerated from in vitro embryo rescue at 20, 25, 30, 35, and 40 post-anthesis days (PADs) in four Italian cultivars. The seedlings were classified as apomictic or zygotic based on molecular marker analysis using inter-sequence single repeat (ISSR) primers. Multiple embryos were recovered from all the cultured immature ovules, and plantlets were regenerated and acclimatized to the field post hardening, with success rates ranging from 62% ('Senza spine') to 83% ('Gialla'). The level of polyembryony differed among cultivars and recovery dates, with the highest being 'Rossa', producing 4.8 embryos/ovule at 35 PADs, and 'Gialla', the lowest, with 2.7 at 40 PADs. The maximum number of embryos observed within a single ovule was 14 in 'Trunzara bianca'. ISSR analysis revealed that ovule culture at 35 PADs produced the highest percentage of zygotic seedlings in all the cultivars, from 51% ('Rossa') to 98% ('Gialla'), with a high genotype effect as well. Mature seeds produced much fewer seedlings per seed, ranging from 1.2 in 'Trunzara bianca' to 2.0 in 'Rossa' and a lower percentage of zygotic seedlings (from 14% in 'Rossa' to 63% in 'Gialla'). Our research opens a pathway to increase the availability of zygotic seedlings in O. ficus-indica breeding programs through in ovulo embryo culture. [ABSTRACT FROM AUTHOR]

Brassica juncea (L.) Czern. & Coss. (Indian mustard) is an economically important edible oil crop. Over the years, plant breeders have developed many elite varieties of B. juncea with better yield traits, but research work on the introgression of stress resilience traits has largely been lagging due to scarcity of resistant donors. Crop wild relatives (CWRs) are the weedy relatives of domesticated plant species which are left unutilized in their natural habitat due to the presence of certain undesirable alleles which hamper their yield potential, and thus, their further domestication. CWRs of B. juncea namely include Sinapis alba L. (White mustard), B. tournefortii Gouan. (African mustard), B. fruticulosa Cirillo (Twiggy turnip), Camelina sativa L. (Gold-of-pleasure), Diplotaxis tenuisiliqua Delile (Wall rocket), D. erucoides L. (White wall rocket), D. muralis L. (Annual wall rocket), Crambe abyssinica R.E.Fr. (Abyssinian mustard), Erucastrum gallicum Willd. (Common dogmustard), E. cardaminoides Webb ex Christ (Dogmustard), Capsella bursa-pastoris L. (Shepherds purse), Lepidium sativum L. (Garden Cress) etc. These CWRs have withstood several regimes of biotic and abiotic stresses over the past thousands of years which led them to accumulate many useful alleles contributing in resistance against various environmental stresses. Thus, CWRs could serve as resourceful gene pools for introgression of stress resilience traits into Indian mustard. This review summarizes research work on the introgression of resistance against Sclerotinia stem rot (caused by Sclerotinia sclerotiorum), Alternaria blight (caused by Alternaria brassicae), white rust (caused by Albugo candida), aphid attack, drought and high temperature from CWRs into B. juncea. However, various pre- and post-fertilization barriers due to different ploidy levels are major stumbling blocks in the success of such programmes, therefore, we also insightfully discuss how the advances made in -omics technology could be helpful in assisting various breeding programmes aiming at improvisation of stress resilience traits in B. juncea.

The creation of homozygous plants is essential for both genetic studies and the production of hybrid seeds, particularly in plants that were pollinated by an alien species. Dihaploid (DH) technology is an important application in obtaining homozygous lines used to plant speed breeding programs. The generation of haploid embryos by pollen irradiation and pollination of female flowers with irradiated pollen has been successfully applied. The influence of irradiated pollen on the induction of haploids in sunflower (Helianthus annuus L.) has been evaluated on 16 different sunflower lines from Turkey's National Sunflower Breeding Program. In this study, pollen grains were irradiated with varying dosages of Gamma rays (500-1000 Gy) to generate parthenogenetic haploid embryos in oilseed sunflowers. At a period of 12-20 days following the process of pollination, embryos were plated into modified MS culture media under a 16/8 h photoperiod and a temperature of 25°C. Parthenogenetic 18457 embryos at different developmental stages were rescued in vitro and 650 were germinated. The ploidy analysis of regenerants was made with chromosome count and flow cytometry. Except for 500 Gy, all dosages were effective for inducing embryos and haploid plants. Obtained results indicate that parthenogenetic haploid embryos can be produced in K3AD SN:8, IMI 069, and IMI 044 sunflower genotypes by selecting the appropriate Gamma ray dose and embryonic developmental stage. This study was focused to recover sunflower doubled haploids to accelerate the production of non-segregating lines for breeding. [ABSTRACT FROM AUTHOR]

Doubled haploid (DH) technology has become integral to maize breeding programs to expedite inbred line development and increase the efficiency of breeding operations. Unlike many other plant species that use in vitro methods, DH production in maize uses a relatively simple and efficient in vivo haploid induction method. However, it takes two complete crop cycles for DH line generation, one for haploid induction and the other one for chromosome doubling and seed production. Rescuing in vivo induced haploid embryos has the potential to reduce the time for DH line development and improve the efficiency of DH line production. However, the identification of a few haploid embryos (~10%) resulting from an induction cross from the rest of the diploid embryos is a challenge. In this study, we demonstrated that an anthocyanin marker, namely R1-nj, which is integrated into most haploid inducers, can aid in distinguishing haploid and diploid embryos. Further, we tested conditions that enhance R1-nj anthocyanin marker expression in embryos and found that light and sucrose enhance anthocyanin expression, while phosphorous deprivation in the media had no affect. Validating the use of the R1-nj marker for haploid and diploid embryo identification using a gold standard classification based on visual differences among haploids and diploids for characteristics such as seedling vigor, erectness of leaves, tassel fertility, etc., indicated that the R1-nj marker could lead to significantly high false positives, necessitating the use of additional markers for increased accuracy and reliability of haploid embryo identification. [ABSTRACT FROM AUTHOR]

The frequency of death from miscarriage is very high, greater than the number of deaths from induced abortion or major diseases. Berg (2017 , Philosophical Studies 174:1217–26) argues that, given this, those who contend that personhood begins at conception (PAC) are obliged to reorient their resources accordingly—towards stopping miscarriage, in preference to stopping abortion or diseases. This argument depends on there being a basic moral similarity between these deaths. I argue that, for those that hold to PAC, there are good reasons to think that there is no such similarity. There is a morally relevant difference between preventing killing and letting die, giving PAC supporters reasons to prioritize reducing abortion over reducing miscarriage. And the time-relative interest account provides a morally relevant difference in the badness of death of miscarriages and deaths of born adults, justifying attempts to combat major diseases over attempts to combat miscarriage. I consider recent developments in the literature and contend that these new arguments are unsuccessful in establishing moral similarities between deaths from miscarriage and abortion, and deaths from miscarriage and disease. [ABSTRACT FROM AUTHOR]

Embryo rescue is a vital technique in cucurbit breeding and propagation, addressing challenges such as embryo abortion, poor seed viability, and incompatibility barriers. This method involves the excision of immature embryos from seeds followed by their in vitro culture on a nutrient medium, providing an environment conducive to their growth and development. In cucurbits, embryo rescue has been extensively utilized to overcome barriers to hybridization, enabling the production of interspecific and intergeneric hybrids with desired traits. Various factors, including genotype, developmental stage of embryos, and culture conditions, influence the success of embryo rescue in cucurbits. Optimal nutrient formulations, growth regulators, and culture techniques are critical for promoting embryo germination, shoot elongation, and subsequent plantlet establishment. Additionally, embryo rescue facilitates the recovery of valuable genetic material from wild and exotic cucurbit species, expanding genetic diversity and developing novel cultivars with improved traits such as disease resistance, yield, and quality. This review highlights the principles, applications, and advancements in embryo rescue technology in cucurbits, emphasizing its significance in cucurbit breeding programs and crop improvement efforts.

The creation of homozygous plants is essential for both genetic studies and the production of hybrid seeds, particularly in plants that were pollinated by an alien species. Dihaploid (DH) technology is an important application in obtaining homozygous lines used to plant speed breeding programs. The generation of haploid embryos by pollen irradiation and pollination of female flowers with irradiated pollen has been successfully applied. The influence of irradiated pollen on the induction of haploids in sunflower (Helianthus annuus L.) has been evaluated on 16 different sunflower lines from Turkey’s National Sunflower Breeding Program. In this study, pollen grains were irradiated with varying dosages of Gamma rays (500-1000 Gy) to generate parthenogenetic haploid embryos in oilseed sunflowers. At a period of 12–20 days following the process of pollination, embryos were plated into modified MS culture media under a 16/8 h photoperiod and a temperature of 25◦C. Parthenogenetic 18457 embryos at different developmental stages were rescued in vitro and 650 were germinated. The ploidy analysis of regenerants was made with chromosome count and flow cytometry. Except for 500 Gy, all dosages were effective for inducing embryos and haploid plants. Obtained results indicate that parthenogenetic haploid embryos can be produced in K3AD SN:8, IMI 069, and IMI 044 sunflower genotypes by selecting the appropriate Gamma ray dose and embryonic developmental stage. This study was focused to recover sunflower doubled haploids to accelerate the production of non-segregating lines for breeding.

The success of seedless grape embryo rescue depends on many factors. To study the effects of parental genotypes on embryo rescue, we conducted 11 hybridisation combinations using nine stenospermocarpic seedless grapes as female parents and three seedless or seeded grapes as male parents. At the optimal sampling time of each mother plant, the hybrid ovules were inoculated and cultured on a solid–liquid biphasic MM3 medium. Then, the bare embryos were removed and inoculated on a WPM medium for germination and seedling formation. The results showed that when ‘Jupiter’ (seedless) was the male parent, ‘Perlette’ had the highest rates of embryo development, germination and seedling formation, followed by ‘Kunxiang Seedless’; when ‘Su-67’ (seedless) was the male parent, ‘FZ42’ had the highest embryo development rate; when ‘Beichun’ (seeded) was the male parent, ‘Fresno Seedless’ had the best embryo rescue results, followed by ‘Qinhong No.10’. These suggest that ‘Perlette’, ‘Kunxiang Seedless’, ‘Fresno Seedless’ and ‘Qinhong No.10’ are suitable female parents for embryo rescue. When ‘FZ42’ was the female parent, ‘Su-67’ was better than ‘Jupiter’ as the male parent; when ‘Perlette’ was the female parent, ‘Jupiter’ and ‘Su-67’ as male parents had no significant difference, indicating that paternal genotype has a certain effect on embryo rescue. HIGHLIGHTS The maternal genotype has a significant effect on the embryo rescue of seedless grapes. The paternal genotype has a certain effect on embryo rescue of seedless grapes. ‘Perlette’, ‘Kunxiang Seedless’, ‘Fresno Seedless’ and ‘Qinhong No.10’ are suitable female parents. A total of 345 hybrids from 11 cross-combinations were obtained by embryo rescue. The maternal genotype has a significant effect on the embryo rescue of seedless grapes.The paternal genotype has a certain effect on embryo rescue of seedless grapes.‘Perlette’, ‘Kunxiang Seedless’, ‘Fresno Seedless’ and ‘Qinhong No.10’ are suitable female parents.A total of 345 hybrids from 11 cross-combinations were obtained by embryo rescue. [ABSTRACT FROM AUTHOR]

Seedless grapes play an important role in fresh food and dry production. New varieties breeding by hybridization with seedless varieties as female parents is the most effective way to cultivate seedless varieties. However, the embryos of seedless varieties cannot develop normally, so it is difficult to obtain hybrid offspring as hybrid female parent. Moreover, grape is a perennial tree species with highly heterozygous genes, with long breeding cycle and low efficiency. In this study, embryo rescue technique was used to cultivate hybrid offspring by crossing with 'Ruby Seedless' as female parent and 'Hongqitezao' as male parent, so as to solve the problem that seedless varieties cannot be female parent; and molecular markers technology was used to carry out assisted breeding research to solve the problems of long cycle and low efficiency. TP-M13-SSR technique was used to carry out authenticity breeding. SCAR marker SCF27 was used to detect the seedless traits of hybrid plants, phenotypic traits was used to verify the results of molecular markers, and seedless trait-related SSR markers VMC7F2, VrSD10 and P3_VvAGL11 was used to detect and verify the genotypes of individual plants with inconsistent detection results by the two methods. The results showed that a total of 384 hybrid offspring were finally obtained, and the hybridization rate was 84.43%. The seed phenotypes of 163 fruit-bearing plants were identified, and the coincidence rate of genotypic and phenotypic analyses was 95.71%. Additionally, 305 F1 plants were detected using the SCF27 marker, and the abortion rate was 64.92%. This study shows that embryo rescue is an effective method for breeding seedless grape cultivars, and the application of molecular markers could facilitate the early identification of hybrid traits, and improve breeding efficiency. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agriculturae Zhejiangensis is the property of Acta Agriculturae Zhejiangensis Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Common buckwheat (Fagopyrum esculentum) is an annual self-incompatible plant that is widely grown. The genus Fagopyrum comprises more than 20 species, including F. cymosum, a perennial that, unlike common buckwheat, is highly resistant to excess water. In this study, we developed interspecific hybrids between F. esculentum and F. cymosum via embryo rescue, to improve undesirable traits of common buckwheat, such as low tolerance to excess water. The interspecific hybrids were confirmed by genomic in situ hybridization (GISH). We also developed DNA markers to confirm the identity of the hybrids and if genes derived from each genome were inherited by the next generation. Observations of pollen indicated that the interspecific hybrids were essentially sterile. Unpaired chromosomes and abnormal segregation during meiosis were likely responsible for the pollen sterility of the hybrids. These findings could facilitate buckwheat breeding to produce lines that can withstand harsh environments with wild or related species in the genus Fagopyrum. [ABSTRACT FROM AUTHOR]

SUMMARY: The Arabidopsis thaliana genome harbors more than 450 nuclear genes encoding pentatricopeptide repeat (PPR) proteins that operate in the RNA metabolism of mitochondria and/or plastids. To date, the molecular function of many PPR proteins is still unknown. Here we analyzed the nucleus‐encoded gene At4g19440 coding for a P‐type PPR protein. Knockout of this gene interferes with normal embryo development and seed maturation. Two experimental approaches were applied to overcome lethality and to investigate the outcome of At4g19440 knockout in adult plants. These studies revealed changes in the abundance of several mitochondria‐encoded transcripts. In particular, steady‐state levels of dicistronic rpl5‐cob RNAs were markedly reduced, whereas levels of mature ccmC and rpl2‐mttB transcripts were clearly increased. Predictions according to the one repeat to one nucleotide code for PPR proteins indicate binding of the At4g19440 protein to a previously detected small RNA at the 3′ termini of the dicistronic rpl5‐cob transcripts. This potential interaction indicates a function of this protein in 3′ end formation and stabilization of these RNA species, whereas the increase in the levels of the ccmC mRNA along with other mitochondria‐encoded RNAs seems to be a secondary effect of At4g19440 knockout. Since the inactivation of At4g19440 influences the stability of several mitochondrial RNAs we call this gene MITOCHONDRIAL TRANSCRIPT STABILITY FACTOR 4 (MTSF4). This factor will be an interesting subject to study opposing effects of a single nucleus‐encoded protein on mitochondrial transcript levels. Significance Statement: The nucleus‐encoded gene MITOCHONDRIAL TRANSCRIPT STABILITY FACTOR 4 is essential for accumulation of rpl5‐cob dicistronic transcripts in mitochondria of Arabidopsis thaliana. Knockout of this nuclear gene interferes with the formation of viable seeds and leads to a severe reduction in rpl5‐cob mRNAs but concomitantly induces an increase in other mitochondrial RNAs. [ABSTRACT FROM AUTHOR]

This experiment was carried out at the High Rainfall Station of the International Institute of Tropical Agriculture (IITA) in Onne, Rivers State, Nigeria, to investigate if secondary triploid plantains established using in-vitro excised zygotic embryo propagules and tissue culture will differ significantly from those established by using ex-vitro propagules such as seeds obtained from open or hand pollinated parents. Seeds of secondary triploid plantain hybrids were obtained by crossing tetraploid female hybrids TMP4x 2796-5 and TMP4x 4698-1 by hand pollination with pollen from known diploid males TMP2x 1297-3 and TMP2x 1448-1. Another set of these female hybrids were exposed to open pollination. At maturity, seeds from ripened mature fruits from both methods of pollination had their zygotic embryos extracted and cultured in-vitro. Another set of seeds were grown ex-vitro in the soil. Both in-vitro and ex-vitro derived propagules obtained from open and hand pollinated parents were raised in the tissue culture laboratory and the nursery respectively. Three replications of the 12 treatments of eight-week-old secondary triploids were planted in the field at 3m x 2m spacing using an RCB (randomized complete block) design. Data collected were: number of days to 50% flowering (DTF), time to fruit filling (TFF), plant height and number of leaves at 50% flowering, bunch weight, number of hands/bunches, fingers/ bunch and total yield. Collected data were analysed using ANOVA in RCB design at (P = 0.05) while means were compared with Duncan’s Multiple Range Test at (P = 0.05). Inconsistent individual genotypically significant differences were found in some phenological and vegetative characters, yield constituents and total yield between ex-vitro and in-vitro derived secondary triploids indicating no definitive pattern in responses of the secondary triploids. However, only days to flowering (DTF) showed consistent significant notable differences out of all these traits. Generally, the ex-vitro derived secondary triploids flowered significantly later than in-vitro derived ones. The secondary triploids from open pollinated parental crosses flowered significantly earlier than those obtained from the hand pollinated parental crosses. [ABSTRACT FROM AUTHOR]

Coconut (Cocos nucifera L.) is widely recognized as one of nature's most beneficial plants. Makapuno, a special type of coconut with a soft, jelly-like endosperm, is a high-value commercial coconut and an expensive delicacy with a high cost of planting material. The embryo rescue technique is a very useful tool to support mass propagation of makapuno coconut. Nevertheless, transplanting the seedlings is a challenge due to poor root development, which results in the inability of the plant to acclimatize. In this study, primary root excision was used in makapuno to observe the effects of primary root excision on lateral root development. The overall results showed that seedlings with roots excised had a significantly higher number of lateral roots, and shoot length also increased significantly. Using de novo transcriptome assembly and differential gene expression analysis, we identified 512 differentially expressed genes in the excised and intact root samples. ERF071, encoding an ethylene-responsive transcription factor, was identified as a highly expressed gene in excised roots compared to intact roots, and was considered a candidate gene associated with lateral root formation induced by root excision in makapuno coconut. This study provides insight into the mechanism and candidate genes involved in the development of lateral roots in coconut, which may be useful for the future breeding and mass propagation of makapuno coconut through tissue culture. [ABSTRACT FROM AUTHOR]

Daylily (Hemerocallis) is a perennial with high ornamental value. It is difficult to obtain innovative daylily germplasm by conventional crossbreeding. To enrich the genetic variation of Hemerocallis, daylily was used as male parent to cross with lycoris (Lycoris). Artificial pollination and embryo rescue were performed to overcome reproductive isolation. Cross‐compatibility and pollen germination were analysed to investigate interfamily reproductive isolation. Leaf morphological analysis and inter‐simple sequence repeat (ISSR) were performed to identify the hybrid at seedling stage. Results showed that most pollen grains failed to adhere to stigmas, and pollen tubes germinated in a disordered direction. Ten days after pollination, 77.19% of ovaries aborted. Ovaries were harvested only in 10 hybridization combinations, the fruit setting rates were 7.69%–42.86%, and the ovule numbers were 0–6.0 per ovary. One embryo developed into plantlets eventually, whose parental combination was L. aurea × H. 'My Complementary'. The hybrid was identified and exhibited both intermediate and novel characteristics of parents. This research is the first attempt to explore a protocol to obtain interfamily hybrid between daylily and lycoris. [ABSTRACT FROM AUTHOR]

Citrus rootstock breeding is important to improve their resistance to diseases, pests and adverse environmental conditions. The majority of citrus species have nuceller embryony. Although Clementine mandarin is monoembryonic, in some cases (intercrossing etc.) abortive seed formation can be seen frequently. In this study, Clementine mandarin × Carrizo citrange were crossed. In the study, interspecies hybridization (Citrus × Poncirus) was used. Embryo rescue technique was used to prevent the loss of hybrid individuals due to abortive seed formation. The seeds were gathered from the crossed plants 80, 100, and 120 days after pollination. The immature embryos were removed from the seeds and these embryos were transferred to control, 0.5, and 1.0 mg l-1 GA3 containing medium to germination. The highest germination rate with 100% was observed from 1.0 mg l-1 GA3 containing media harvested 120 days after pollination. Additionally, the highest rate of trifoliate seedlings was obtained from embryos gathered after 120 days of the pollination. [ABSTRACT FROM AUTHOR]

Immature lentisk (Pistacia lentiscus L.) seeds from plants grown in Liguria (Italy) were collected and surface sterilized with ethanol (70%) and then NaOCl (1%). The outer pericarp of the immature fruits was removed and shells were opened. Enhancement of Embryo germination was examined through the use of five sucrose concentrations (0, 15, 30, 45, and 60 g L-1) combined with five concentrations of GA3 (0, 0.1, 0.3, 0.5, and 0.7 mg L-1). After 14 days, the germination frequency was detected and after 16 days, seedling development was evaluated. The embryo development into plantlets increased up to 54.37% when 45 g L-1 of sucrose was supplied; at this concentration, all the parameters, such as plantlet weight, height, and root length were high, while at 60 g L-1 of sucrose, the plantlets showed many lateral root formations. The root shape was completely different among the treatments. The percentage of embryo germination, plantlet weight and height, root length, and main lateral root number were enhanced when GA3 was used in the concentration of 0.7 (mg L-1). No rooting at all was observed when GA3 was used in a concentration of 0.3 or 0.5 (mg L-1) or medium without GA3. This research increases the possibility to obtain a massive number of plants to be used as rootstock for pistachio cultivation in difficult soils.

Abstract The production of the common bean (Phaseolus vulgaris L.), one of the most important sources of protein and minerals and one of the most consumed grain legumes globally, is highly affected by heat and drought constraints. In contrast, the tepary bean (Phaseolus acutifolius A. Gray), a common bean‐related species, is adapted to hot and dry climates. Hybridization to introduce complex traits from the tepary bean into the common bean has been challenging, as embryo rescue is required. In this study, we report three novel interspecific lines that were obtained by crossing lines from prior common bean × tepary bean hybridization with Phaseolus parvifolius Freytag in order to increase the male gametic diversity to facilitate interspecific crosses. These interspecific lines enhanced the crossability of the common bean and tepary bean species while avoiding the embryo rescue process. Crossing these three interspecific lines with tepary beans resulted in 12‐fold more hybrid plants than crossing traditional common beans with tepary beans. Whole‐genome sequencing analysis of these three interspecific lines shows large introgressions of genomic regions corresponding to P. parvifolius on chromosomes that presumably contribute to reproductive barriers between both species. The development of these lines opens up the possibility of increasing the introgression of desirable tepary bean traits into the common bean to address constraints driven by climate change.

The new trends in the consumption of table grapes and the growing interest in the environmental impact of this crop have pushed breeders toward the development of seedless cultivars endowed with resistance, through crossbreeding programs. To obtain seedless grapes, the use of embryo-rescue techniques is fundamental. In this research, a grape embryo-culture protocol was optimized and validated by using 39 cultivars and 41 cross-combinations carried out in the framework of a large private table grape program of the private network Italian Variety Club in the period 2017–2021 evaluating several factors, such as the improvement in embryo formation, germination and growth, and plantlet development. The embryo culture attitude of crosses between different combinations of seedless parents was assessed, and the rates of embryo development from the extracted ovules mostly ranged from 3.5 to 35.5% with 5 out of 43 genotypes outliers. Experiments conducted at different sampling times, in a range of 43–62 days after pollination (DAP), did not show significant differences between the samples analyzed, while the rate of embryos developed with the applied protocol proved its employability on multiple genotypes, although the grapevine genotype significantly influenced the technique efficiency.

Interspecific hybridization is a significant plant evolutionary process and, concomitantly, a frequently used method to broaden the genetic variability of species and genetically improve crops. However, in distant crosses, many prezygotic and postzygotic barriers are encountered that prevent free, uncontrolled gene flow between species. Therefore, various experimental methods exploiting tissue culture, such as in vitro fertilization, embryo rescue, and protoplast fusion, have been developed to raise hybrids that cannot be obtained naturally through conventional approaches. Professor Maciej Zenkteler of the Adam Mickiewicz University in Poznań pioneered the use of tissue culture in Poland to overcome barriers to sexual crossing. In the mid-1960s, he employed in vitro pollination in which pollen grains were directly applied onto the surface of exposed ovules as the primary method to bypass prezygotic barriers and in vitro culture of isolated ovules and developing embryos (embryo rescue) to overcome post-zygotic barriers. These approaches proved effective for species possessing numerous ovules and large placentas, such as representatives of the families Caryophyllaceae, Solanaceae, and Brassicaceae. Soon thereafter, these methods were extended to other Polish institutes and universities and applied for crop improvement, such as for the production of intergeneric hybrids between Salix and Populus species, resynthesis and broadening of the genetic variability of oilseed rape (Brassica napus L.), and the generation of new interspecific hybrids of Allium. In the late 1970s, Professor Zenkteler was the first to undertake protoplast fusion. At that time, it appeared that no incompatibility could exist at the fusion level and that somatic hybridization would supersede the possibilities offered by sexual hybridization; however, the reality turned out to be slightly harsh. Nonetheless, successful regeneration of different interspecific hybrids of potato, tomato, or gentians has been achieved by Polish research groups thus far.

Seedlessness is one of the most desirable traits for table and raisin grapes. Stenospermocarpic cultivars are desirable because they have large berries with superior quality. Embryo rescue techniques have been widely used to get progeny seedling populations from crosses using seedless mother plants. Selection of the female parent, sampling time, and the growth medium are the most crucial to the success of this technique. This study investigated the effect of best sampling time and media composition on embryo rescue efficiency in a cold-hardy hybrid grape breeding program. We sampled ovules 5 to 9 weeks after flowering, and we tested four media compositions. The greatest percentages of embryo germination and normal seedlings were obtained when ovules were harvest at 8 weeks after flowering, indicating that it is suitable to harvest ovules at veraison, when the extraction of ovules is easier as a result of softer berry flesh. For the media composition experiment, all ovules were harvested at 8 weeks after flowering. Nitsch & Nitsch culture medium had very low germination, and the resulting seedlings performed the lowest compared with the other treatments. Lloyd & McCown Woody Plant Basal Medium (WPM) increased the number of embryos germinated significantly, and a number of normal seedlings and plantlets developed. Although there was no significant difference among the other three media containing WPM supplemented with different doses of plant regulators, the WPM Plus medium [with cytokinin (6-benzlaminopurine), indole-3-butyric acid, gibberellin, and casein hydrolysate] promoted the greatest percentage of established plants (46.98%). Therefore, the 8-weeks-after-flowering harvest time and the WPM Plus medium were selected for use in the embryo rescue protocol at the University of Minnesota grape breeding program.

O. ficus-indica (prickly pear cactus) is an important forage and food source in arid and semiarid ecosystems and is the most important cactus species in cultivation globally. The high degree of apomixis in the species is a hindrance in plant breeding programs where genetic segregation is sought for the selection of superior genotypes. To understand if in ovulo embryo rescue could increase the proportion of zygotic seedlings, we compared the mature seed-derived seedlings with those regenerated from in vitro embryo rescue at 20, 25, 30, 35, and 40 post-anthesis days (PADs) in four Italian cultivars. The seedlings were classified as apomictic or zygotic based on molecular marker analysis using inter-sequence single repeat (ISSR) primers. Multiple embryos were recovered from all the cultured immature ovules, and plantlets were regenerated and acclimatized to the field post hardening, with success rates ranging from 62% (‘Senza spine’) to 83% (‘Gialla’). The level of polyembryony differed among cultivars and recovery dates, with the highest being ‘Rossa’, producing 4.8 embryos/ovule at 35 PADs, and ‘Gialla’, the lowest, with 2.7 at 40 PADs. The maximum number of embryos observed within a single ovule was 14 in ‘Trunzara bianca’. ISSR analysis revealed that ovule culture at 35 PADs produced the highest percentage of zygotic seedlings in all the cultivars, from 51% (‘Rossa’) to 98% (‘Gialla’), with a high genotype effect as well. Mature seeds produced much fewer seedlings per seed, ranging from 1.2 in ‘Trunzara bianca’ to 2.0 in ‘Rossa’ and a lower percentage of zygotic seedlings (from 14% in ‘Rossa’ to 63% in ‘Gialla’). Our research opens a pathway to increase the availability of zygotic seedlings in O. ficus-indica breeding programs through in ovulo embryo culture.

Doubled haploid (DH) technology has become integral to maize breeding programs to expedite inbred line development and increase the efficiency of breeding operations. Unlike many other plant species that use in vitro methods, DH production in maize uses a relatively simple and efficient in vivo haploid induction method. However, it takes two complete crop cycles for DH line generation, one for haploid induction and the other one for chromosome doubling and seed production. Rescuing in vivo induced haploid embryos has the potential to reduce the time for DH line development and improve the efficiency of DH line production. However, the identification of a few haploid embryos (~10%) resulting from an induction cross from the rest of the diploid embryos is a challenge. In this study, we demonstrated that an anthocyanin marker, namely R1-nj, which is integrated into most haploid inducers, can aid in distinguishing haploid and diploid embryos. Further, we tested conditions that enhance R1-nj anthocyanin marker expression in embryos and found that light and sucrose enhance anthocyanin expression, while phosphorous deprivation in the media had no affect. Validating the use of the R1-nj marker for haploid and diploid embryo identification using a gold standard classification based on visual differences among haploids and diploids for characteristics such as seedling vigor, erectness of leaves, tassel fertility, etc., indicated that the R1-nj marker could lead to significantly high false positives, necessitating the use of additional markers for increased accuracy and reliability of haploid embryo identification.

Copyright of Acta Agriculturae Zhejiangensis is the property of Acta Agriculturae Zhejiangensis Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Turkey is one of the major exporters of mandarins in the Mediterranean region. Seedlessness in citrus, which is one of the most desired fruit quality traits, especially in fresh mandarin export markets, can be obtained via triploidy as in many fruit species. Triploid plants can be recovered by 2x × 2x hybridizations in citrus, as well as 2x × 4x and 4x × 2x crosses. Hence, we aimed to develop local triploid hybrids by using the embryo rescue technique in five crosses using eight different citrus varieties in the present study. Methods and results: Embryos isolated from abortive seeds derived by 135 days after pollinations were cultured on modified Murashige and Tucker (MT) medium by adding different levels of GA3 to achieve a high germination rate. A population of 574 plants was developed as a result of embryo rescue. After screening the ploidy levels of this 574-plant population with the aid of flow cytometry, 4 triploids from 'Encore' × 'Murcott', 8 triploids from 'Fortune' × 'Willow leaf', 1 triploid from 'Kiyomi' × 'Murcott', and 1 triploid from 'Ortanique' × 'Murcott' hybridization were recovered. Triploid hybrid plants and related parents were analyzed with SSR markers heterozygotic for parental mandarin varieties. In addition, we evaluated stomatal characteristics of diploid and triploid hybrids obtained from different crosses. Stomatal traits of diploid and triploid hybrids in all crosses significantly differed except the stomata index. Conclusions: Genotyping of triploid plants confirmed using Simple Sequence Repeat (SSR) molecular markers and five SSRs were able to identify three alleles of triploid hybrids. Selected triploid mandarin hybrids have been grafted on several rootstocks for field trials and are in the process of yield and quality performances. [ABSTRACT FROM AUTHOR]