Drought is one of the main environmental factors affecting growth and yield of sorghum in arid and semi-arid areas of the world. In vitro selection of Sorghum bicolor for drought tolerance was undertaken by the use of somaclonal variation. The experiment was carried out with a collection of sixteen sorghum genotypes and tested in a completely randomized design. Data were recorded at five different PEG 6000 (polyethylene glycol) levels (0, 0.5, 1.0, 1.5, 2.0% (w/v) treatments)) on coleoptile length (CL), root length (RL), shoot dry weight (SDW), root dry weight (RDW), root number (RN) and statistically analyzed for significant differences. Significant differences were observed among the genotypes, treatments and their interactions for the evaluated plant traits suggesting a great amount of variability for drought tolerance in sorghum. In general, embryogenic callus induction and plantlet regeneration was found to be indirectly proportional to increased PEG concentrations. By taking into consideration all the measured traits, Mann Whitney rank sum test revealed that 76T1#23 and Teshale followed by Gambella-1107 and Melkam showed better drought stress tolerance while Chelenko appeared to be drought sensitive.

The anthocyanin biosynthesis attracts strong interest due to the potential antioxidant value and as an important morphological marker. However, the underlying mechanism of anthocyanin accumulation in plant tissues is not clearly understood. Here, a rice mutant with a purple color in the leaf blade, named pl6, was developed from wild type (WT), Zhenong 41, with gamma ray treatment. By map-based cloning, the OsPL6 gene was located on the short arm of chromosome 6. The multiple mutations, such as single nucleotide polymorphism (SNP) at −702, −598, −450, an insertion at −119 in the promoter, three SNPs and one 6-bp deletion in the 5′-UTR region, were identified, which could upregulate the expression of OsPL6 to accumulate anthocyanin. Subsequently, the transcript level of structural genes in the anthocyanin biosynthesis pathway, including OsCHS, OsPAL, OsF3H and OsF3′H, was elevated significantly. Histological analysis revealed that the light attenuation feature of anthocyanin has degraded the grana and stroma thylakoids, which resulted in poor photosynthetic efficiency of purple leaves. Despite this, the photoabatement and antioxidative activity of anthocyanin have better equipped the pl6 mutant to minimize the oxidative damage. Moreover, the contents of abscisic acid (ABA) and cytokanin (CK) were elevated along with anthocyanin accumulation in the pl6 mutant. In conclusion, our results demonstrate that activation of OsPL6 could be responsible for the purple coloration in leaves by accumulating excessive anthocyanin and further reveal that anthocyanin acts as a strong antioxidant to scavenge reactive oxygen species (ROS) and thus play an important role in tissue maintenance.

No abstract

No abstract