The effect of genotype and culture medium on somatic embryogenesis and plant regeneration from mature embryos of fourteen apomictic cultivars of buffel grass (Cenchrus ciliaris L.)

Abstract

Buffel grass (Cenchrus ciliaris L.) is an important apomictic grass used as forage for ruminant livestock. Biotechnological methods provide opportunities for producing new germplasm. Mature embryos of fourteen buffel grass apomictic cultivars (2n = 4x = 36) were used to induce embryogenic callus formation using a basal medium supplemented with 3% sucrose and with the testing of five concentrations of 2,4‐dichlorophenoxyacetic acid (2,4‐D) and four concentrations of 6‐benzylaminopurine (BAP). The effects of cultivar and culture medium on callus induction and plant regeneration were evaluated. Significant differences were observed among the fourteen cultivars and the five concentrations of 2,4‐D (P < 0·01). Values for embryogenic callus production varied from 0 to 86·7. Most cultivars showed the highest level of embryogenic callus production on the medium with the concentration of 3 mg L−1 2,4‐D. The addition of different BAP concentrations in combination with 2,4‐D in the medium inhibited embryogenic callus growth and did not permit plant regeneration. The data clearly demonstrated that the genotype and concentrations of 2,4‐D had significant effects both on the frequency of embryonic callus formation from mature embryos and on the subsequent efficiency of plant regeneration of apomictic cultivars of buffel grass. Cultivars Biloela and Nunbank showed the greatest efficiency in in vitro culture response.

Somatic embryogenesis and regeneration of Cenchrus ciliaris genotypes from immature inflorescence explants

“…While seeds showed highest callus growth at 2 mg dm -3 2,4-D, shoot tips and immature inflorescences recorded highest callus growth at 3 mg dm -3 2,4-D (Table 1). Our results are consistent with the results of Colomba et al (2006) who demonstrated significant differences between various concentrations of 2,4-D on callus induction, embryogenic callus and somatic embryo formation. The morphogenic potential of the induced callus was assessed on the same induction medium.…”

“…Auxin was required in our study at a very low concentration for achieving higher rate of shoot regeneration, in contrast to earlier study by Kackar and Shekhawat (1991) who reported plant regeneration in an auxin free medium. But our results are partially corroborated by Colomba et al (2006) who obtained shoot regeneration in 3 -4 weeks after embryogenic cultures were transferred to regeneration medium containing NAA and BA. Significant genotypic differences were also observed in shoot differentiation and maintenance of regeneration capacity in sorghum (Cai and Butler 1990), barley (Hanzel et al 1985) and wheat (Rajyalakshmi et al 1991).…”

Optimization of somatic embryogenesis and in vitro plant regeneration of Urochloa species using picloram

“…Llanero were highly recalcitrance to the in vitro conditions tested here. Some cultivars of the apomictic grass Pennisetum ciliare showed recalcitrant behavior when mature embryos were used as the initial explant (Colomba et al 2006). When anthers of the same cultivars were used as explants, embryogenic calluses were observed in up to 44% of the explants, and normal plants were regenerated (Carloni et al 2014).…”

“…High auxin concentrations rapidly change the metabolism of cells resulting in the development of callus (Dudits et al 1995). The auxin 2,4-D alone or in combination with other plant growth regulators has been widely used for the induction of somatic embryogenesis in many grasses such as Cenchrus ciliares (Colomba et al 2006), Chloris gayana (Gondo et al 2007), Cynodon dactylon (Zhang et al 2007), Zoysia matrella (Dhandapani et al 2008), Eremochloa ophiuroids (Barampuram et al 2009), Pogonatherum paniceum (Wang et al 2008), and U. brizantha (Cabral et al 2011). However, other synthetic auxins such as picloram have not been tested for regeneration of tropical grasses from the Urochloa genus.…”

Genetic Transformation of Apomictic Grasses: Progress and Constraints

“…Several morphogenic regulators are able to modify calli responsiveness to embryogenesis, transformation, and regeneration (Fehér, 2019;Gordon-Kamm et al, 2019). Also, it is commonly observed that even the genotype and explant source might condition these callus responses (Echenique et al, 1996;Colomba et al, 2006;Yadav et al, 2009;Seo et al, 2010;Cabral et al, 2011;Kumar and Bhat, 2012;Takamori et al, 2015). As genotype effects are unavoidable, different explants, culture conditions, and morphogenic regulators should be assayed to improve the transformation and regeneration efficiencies.…”