Soybean, a major legume crop, is the source of vegetable oil and protein. There is a need for transgenic approaches to breeding superior soybean varieties to meet future climate challenges. Efficient plant regeneration is a prerequisite for successful application of genetic transformation technology. Soybean cultivars are classified into different maturity groups based on photoperiod requirements. In this study, nine soybean varieties belonging to different maturity group were regenerated successfully from three different explants: half split hypocotyl, complete hypocotyl, and cotyledonary node. All the genotypes and explant types responded by producing adventitious shoots. Shoot induction potential ranged within 60–87%, 50–100%, and 75–100%, and regeneration rate ranged within 4.2–10, 2.7–4.2, and 2.6–10.5 shoots per explant using half split hypocotyl, complete hypocotyl, and cotyledonary explants, respectively, among all the tested genotypes. Bunya variety showed the best regeneration response using half split and complete hypocotyl explants and the PNR791 with cotyledonary node. The regenerated shoots were successfully rooted and acclimatized to glasshouse conditions. This study shows that commercial varieties of soybean are amenable to shoot regeneration with high regeneration frequencies and could be exploited for genetic transformation. Further, our results show no correlation between shoots regeneration capacity with the maturity grouping of the soybean cultivars tested.

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The efficient regeneration of plants from commercial genotypes is a pre-requisite for successful genetic transformation, to apply modern crop improvement techniques such as CRISPR-based genome editing. Plant regeneration through the somatic embryogenesis pathway offers an advantage over the organogenesis approach, avoiding the risk of developing chimeras. Plant genotype, explant type, and media compositions play an essential role in the in-vitro regeneration of plants. This study aimed to characterize the commercially grown Australian soybean genotypes for their potential to induce somatic embryos, embryo proliferation, maturation, germination, and plant regeneration. Overall, nine soybean cultivars belonging to different maturity groups were evaluated. Immature cotyledon ranging from 2–4 and 4–6 mm in size were used as explants for somatic embryogenesis induction. Maximum somatic embryo induction frequency (86%) was observed from 4–6 mm immature cotyledons of the cv. Jack (MG III), followed by 66%, 26%, 21%, and 6% in cultivars Williams (MG III), Snowy (MG III), MoonB1 (MG V), and PNR791 (MG V), respectively. On the other hand, cv. Snowy showed maximum somatic-embryo-inducing potential (67%) in 2–4 mm immature cotyledons followed by Williams, Jack, MoonB1, and PNR791. Somatic embryos from Jack, Williams, and Snowy cultivars were further tested for embryo proliferation, maturation, and germination. Maximum proliferation and maturation were observed in cv. Jack, followed by Snowy and Williams. However, cv. Snowy showed a significantly higher conversion of cotyledonary stage embryos to plantlets (85%), than both Jack and Williams cultivars (53% each). In conclusion, this study outlined a protocol for somatic embryogenesis and plant regeneration from three soybean cultivars. Our findings suggest commercial cv. Snowy could be a good candidate for developing transgenic plants through somatic embryogenesis.

This study investigated the integration of Arabidopsis vacuolar H +-pyro-phosphatase (H +-PPase) (AVP1) transgene in transgenic sugarcane plants for drought tolerance. The gene integration was confirmed by polymerase chain reaction (PCR) and Southern blotting. Transgene expression was estimated by Western blotting. When sugarcane plants were grown on soil under 50% reduced water supply, the transgenic sugarcane overexpressing AVP1 produced higher shoot biomass based on cane height, number of millable canes, and Brix (%) compared with wild-type. The overexpression of AVP1 in transgenic sugarcane plants increased tolerance to drought stress, as demonstrated by increased relative water content (RWC) and leaf water (Ψ w), osmotic (Ψ s), and turgor potential (Ψ p). Physiological parameters such as photosynthetic rate (P n), stomatal conductance (C), and transpiration rate (E) were less affected by water-deficit stress in transgenic AVP1 plants compared with wild-type plants. In conclusion, our results indicated that AVP1 conferred tolerance to drought or water-deficit stress, highlighting potential use of this gene for crop improvement through biotechnological applications.

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The genus Saccharum is composed of species with high polyploidy and highly varied chromosome numbers, laying a challenge for uncovering its genomic structure and evolution. We developed a chromosome 2 painting (CP2) probe by designing oligonucleotides covering chromosome 2 of Saccharum spontaneum (2n = 8x = 64). Fluorescence in situ hybridization (FISH) using this CP2 probe revealed six types of ploidies from twenty S. spontaneum clones, including 6x, 8x, 10x, 11x, 12x, and 13x clones. The finding of S. spontaneum clones with uneven of ploid suggested that certain S. spontaneum clones come from hybridization. It renews our knowledge that S. spontaneum is derived from autopolyploidization. Combined with a S. spontaneum-specific probe, chromosome 2-derived chromosome or fragments from either S. spontaneum or Saccharum officinarum can be identified in sugarcane modern cultivars. We revealed unexpected high level of interspecific recombination from introgressive S. spontaneum chromosomes (>50.0%) in cultivars ROC22 and ZZ1, indicating frequent chromosome exchange in cultivars. Intriguingly, we observed interspecific recombination recurring among either homoeologous or non-homoeologous chromosomes in sugarcane cultivars. These results demonstrated that chromosome painting FISH is a powerful tool in the genome dissection of sugarcane and provide new insights into the genome structure and evolution of the complex genus Saccharum.

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