Optimization of Barley Mature Embryo Regeneration and Comparison with Immature Embryos of Local Cultivars

The improvement of the in vitro plant regeneration in barley with the epigenetic modifier of histone acetylation, trichostatin A

Genotype-limited plant regeneration is one of the main obstacles to the broader use of genetic transformation in barley breeding. Thus, developing new approaches that might improve responses of in vitro recalcitrant genotypes remains at the center of barley biotechnology. Here, we analyzed different barley genotypes, including "Golden Promise," a genotype commonly used in the genetic transformation, and four malting barley cultivars of poor regenerative potential. The expression of hormone-related transcription factor (TF) genes with documented roles in plant regeneration was analyzed in genotypes with various plant-regenerating capacities. The results indicated differential expression of auxin-related TF genes between the barley genotypes in both the explants and the derived cultures. In support of the role of auxin in barley regeneration, distinct differences in the accumulation of free and oxidized auxin were observed in explants and explant-derived callus cultures of barley genotypes. Following the assumption that modifying gene expression might improve plant regeneration in barley, we treated the barley explants with trichostatin A (TSA), which affects histone acetylation. The effects of TSA were genotype-dependent as TSA treatment improved plant regeneration in two barley cultivars. TSA-induced changes in plant regeneration were associated with the increased expression of auxin biosynthesis-involved TFs. The study demonstrated that explant treatment with chromatin modifiers such as TSA might provide a new and effective epigenetic approach to improving plant regeneration in recalcitrant barley genotypes.

Effects of salt and heat pre-treatment factors on efficient regeneration in barley (Hordeum vulgare L.)

An efficient callus induction and plant regeneration system has been developed using salt and heat as pre-treatment factors for three barley genotypes viz. BB-3, BB-6 and BHL-18. Different concentrations of NaCl (1.5, 2.5, 3.5, 4.5, 5.5 and 6.5 g/L) were used and its effects were determined on the basis of the viability of callus (CV), plant regeneration (PR), relative growth rate (RGR) and tolerance index (TI). The BB-6 showed highest performance on tolerance based on CV (14.72%), PR (7.69%), RGR (0.91%) and TI (0.42%) at 6.5 g/L NaCl. Various NaCl concentrations displayed significantly differences at P < 0.01 level as compared with the control. Plant regeneration capability was recorded after heat pre-treatment using calli at 30, 35 and 40 °C. In this study, BHL-18 produced highest callus induction (59.71%) after desiccated at 40 °C for BB-6. Highest regeneration was recorded around 41.66% when 4 weeks old calli were pre-treated at 35 °C. Furthermore, heat pre-treatment factors were very effective for enhancing plant regeneration (25-41.66%) which was 1.8-2.14 fold higher compared to the control (13.88-19.44%). Hence, heat treated calli displayed higher tolerance level to survive in NaCl-induced treatment for determining abiotic stress and increased regeneration rate at 35 °C temperature in BB-6 barley genotype.