| In terms of production and planting areas, sorghum is the fifth most important cereal, after wheat, rice, maize, and barley. About 90% of the area in the world where sorghum is grown is in developing countries where drought, salinity, acidity and other abiotic stresses are limiting production and quality. The search for quality inbred lines is important in enriching heterotic pools in hybrid sorghum breeding. However little is known about the genetic and epigenetic control of grain quality parameters and how they relate to sorghum productivity. Boron and Sodium Chloride toxicity have been an unnoticed problem in sorghum production especially in Africa and Asia. In this study we investigated morphological and genomic changes due to Boron (B) and the combination of B and Sodium Chloride (NaCl) toxicity on an inbred line, YN267 (D) of Sorghum bicolor.The preliminary experiment involved the subjection of germinating sorghum seeds into different concentrations (10, 25, 50, 100, 150, 200, 250, 300 and 350 mM) of NaCl and selecting a concentration (100 mM) where morphology was significantly affected but not inhibited. In the first phase of study, the sorghum inbred line seeds were exposed to various concentrations of B: 10, 50, 100, 150, 200, 300 mM at the germination stage and were transferred into soil after 14 days of treatment. Morphological analysis at maturity revealed an increase in panicle length as well as yield at 150mM. Methylation-sensitive Amplification Polymorphism (MSAP) was used to determine the DNA cytosine methylation levels and patterns. Treatments at 150 mM and 300 mM both had a higher CG methylation level of 13.59% but CNG methylation level of 5.95% was detected for 150 mM while 5.59% was detected in 300mM. CG hypo methylation of 0.19% was observed in all treatments but CG hyper methylation of 0.75% was highest at 150 mM. CNG hyper methylation of 0.19% was detected in 100 mM, 150 mM and 300 mM while CNG hypo methylation of 0.19% and 0.37% was detected in 10 mM and 300 mM respectively.The second phase involved treatment of the sorghum seeds in concentrations of B beyond the tolerable level (300 and 400 mM) in combination with NaCl concentration of 100 mM in all treatments. Morphological analysis revealed a reduction of all traits but a gradual increase in yield was observed at 300 mM and 400 mM. MSAP analysis also showed a higher CG methylation level of 19.88% at 300 mM, while a lower level of 13.26% was detected in 400 mM. CNG methylation for 300 mM was 5.26% while for 400 mM, 4.68% was observed. CG hyper methylation was 5.47% and 0.78% for 300 mM and 400 mM respectively while CG hypomethylation was 0.78% and 2.73% for both treatments respectively. CNG hyper methylation of 0.20% was detected in 300 mM while CNG hypo methylation of 0.39% was detected in 400 mM. The BLASTN results of the 4 sequenced DNA fragments showed that an orthologue of an amino acid transporter family which is involved in stress tolerance, a putative transposon protein, a methyl-CpG-binding domain (MBD10) and a glycosyl transferase family 43 protein expressions were triggered in these abiotic stresses. These results altogether show that the effects of NaCl and Boron toxicity as reflected on the morphology of the treated sorghum inbred line plants invoked epigenetic changes in cytosine DNA methylation which occurred at the critical embryonic period of growth and were somatically transmitted in adult plants.
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