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The present study was the first report on the somatic embryogenesis of the Tunisian chickpea (Cicer arietinum L.) particularly supposed to be recalcitrant and difficult to manipulate in vitro. An efficient protocol has been developed for inducing indirect somatic embryogenesis derived from immature zygotic embryo axis, young leaflet and hypocotylar explants. Callogenesis was achieved on full-strength Murashige and Skoog's (1962) (MS) basal medium supplemented with two auxin/cytokinin combinations; 2,4- dichlorophenoxyacetic acid (2,4-D) and 6-furfurylamonopurine (KIN) or 1-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) to establish the phytohormones requirement to promote the best induction of friable calli. For somatic embryos induction, embryogenic calli developed from zygotic embryo axes, leaflet and hypocotylar explants were cultured on MS full strength and MS/2, half strength, free of phytohormones media. This study found that all explants exhibited high frequency of callus induction. For immature zygotic embryo axes and young leaflet explants, media containing the combination of 2,4-D and KIN were best effective for inducing callogenesis and friable calli. The most important embryogenic callus percentages were obtained on the culture medium containing the highest concentrations of 2,4-D (2 mg L-1) and KIN (0.5 mg L-1). However, media containing the combination NAA and BAP were best effective for inducing embryogenic calli on hypocotylar explants. A maximal rate of embryogenic calli was reached on medium containing 3 mg L-1 NAA and 1 mg L-1 BAP. The highest number of somatic embryos was obtained with embryogenic calli derived from embryo axis explants and cultured on MS half strength free phytohormones medium. About 56% of somatic embryos converted successfully into fertile plantlets. [ABSTRACT FROM AUTHOR]

Cryopreservation is a reliable technique for the long-term storage and preservation of embryogenic cells, maintaining their viability without loss of their embryogenic capacity. However, the large-scale conservation of grapevine embryogenic lines in cryobanks remains limited. A significant challenge is understanding somatic cell rejuvenation. Here, we investigate the encapsulation/dehydration and encapsulation/vitrification for cryopreserving embryogenic material. Cell rejuvenation and enhanced embryogenic competence were observed after cryopreservation, as evidenced through structural cellular changes observed by histology and electron scanning microscopy. Results showed that cryopreserved samples of 110-Richter, Riesling, and Tempranillo using encapsulation/dehydration had better survival rates, averaging 81%, 62%, and 48%, respectively, while encapsulation/vitrification yielded lower survival rates, averaging 58%, 42%, and 32%, respectively. Cryopreservation also improved post-thaw recovery and regeneration efficiency assessed through regrowth of proembryogenic masses and somatic embryo conversion reaching 54–72% against 11–17% in control samples. Cryopreservation triggered changes in gene expression patterns and exhibited considerable increase at genotype-specific basis of 1.5- to 4.5-fold in SERK1, BBM, and WOX associated to embryogenic competence as well as in ChitIV and LEA involved in stress response. Membrane stability index, hydrogen peroxide, and proline contents were used as indicators of oxidative stress uncovering a key role of an osmotic trans-priming effect leading to cryotolerance. Our finding highlighted that cryopreservation enhances embryogenic capacity in senescent callus and probably acts as a screening process allowing safe maintenance of proembryogenic cells and promoting their recovery. This study provides a high throughput innovation to set up cryolines for cell rejuvenation of grapevine and other important plant species. [ABSTRACT FROM AUTHOR]

When constrained by in vitro culture conditions, microspores from Opuntia ficus-indica (L.) Mill. (Barbary fig) anthers were forced to stall out their gametophytic pathway and switch towards androgenesis. Five microspore stages were characterized based on cellular architecture. A relationship was also established between anthers and bud flower features. Anthers were cultured on three culture media containing 2,4-dichlorophenoxyacetic acid, thidiazuron and gibberellic acid at 22°C for 4 wk, followed by heat shock treatment at 32°C or 42°C for 2 wk, and the stressed material was recultured at 22°C for 24 wk in the dark. When anthers were heat shocked at 32°C and 42°C, the cultivated anthers swelled and burst, followed by the microspores flowing onto the explant surface. Androgenesis occurred directly and indirectly at uni- and binucleate stages. The micromorphology of multicellular, proembryos, globular, torpedo and cotyledonary-like-shaped structures from dehisced anthers was confirmed by environmental scanning electron microscopy. Furthermore, at 42°C, microscopic analysis demonstrated that the non-responsive microspores achieved pollen maturation and more rarely, the emission of a pollen tube. However, 11.4 to 14.4% of the mature pollen grains were converted into pollen embryos. The established system may serve, for the first time, as a protocol to produce microspore embryos in O. ficus-indica. Nevertheless, more efforts are needed to complete the development of diplo-haploid plantlets. [ABSTRACT FROM AUTHOR]