Abstract
Sorghum, a naturally drought tolerant crop, is genetically diverse and provides a wide gene pool for exploitation in crop breeding. In this study, we experimentally assessed friable callus induction rates of seven sorghum varieties using shoot explant for the generation of cell suspension cultures. The cell suspensions were characterized in terms of cell growth and viability profiles as well as gene expression following 400 mM sorbitol-induced osmotic stress for 72 h. Only ICSB 338, a drought susceptible variety, was readily amenable to friable callus formation. Cell culture growth plots of both ICSB 338 and White sorghum (used as a reference line) depicted typical sigmoidal curves. Interestingly, Evans blue assay showed that ICSB 338 cell cultures are more susceptible to osmotic stress than the White sorghum cells. The osmotic stress treatment also triggered differential expression of eight target genes between the two cell culture lines. Overall, these results suggest that the genetic diversity of sorghum germplasm influences friable callus induction rates and molecular responses to osmotic stress, and could be further exploited in plant stress biology studies. Therefore, we have developed a valuable resource for use in molecular studies of sorghum in response to a range of biotic and abiotic stresses.
Highlights
Sorghum (Sorghum bicolor) is the fifth most important cereal crop worldwide after maize (Zea mays), rice (Oryza sativa), wheat (Triticum aestivum), and barley (Hordeum vulgare) [1]
Because White sorghum had previously been used in callus production procedures [27], this variety
The calculated callus variety was excluded from callus induction rate calculations in the current study
Summary
Sorghum (Sorghum bicolor) is the fifth most important cereal crop worldwide after maize (Zea mays), rice (Oryza sativa), wheat (Triticum aestivum), and barley (Hordeum vulgare) [1]. Biotechnological studies aimed at understanding a range of fundamental processes in plants require, amongst others, in vitro experimental systems utilizing callus and cell suspension cultures. Sorghum is considered to be one of the most recalcitrant cereal crops for in vitro experiments [8], possibly due to the accumulation of phenolics, low callus induction frequencies, and a long callus generation period [9]. In another sorghum study, the addition of lipoic acid to callus induction media greatly improved the callus induction frequency of immature embryos for plant regeneration and transformation systems [10]. Some callus cultures show organ regeneration with root- and shoot-like structures developing on the callus masses [15]
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