Genetic variability of tissue cultured Sorghum bicolor (L) Moench as revealed by morphological traits and simple sequence repeats (SSR) markers
To evaluate their performance for seedling traits at seedling stage (under hydroponics), plant water relations under water stress and ultimately grain yield, and to estimate the genetic variability of the regenerates, the parent plants of local sorghum cultivars in Kenya using simple sequence repeats (SSR) markers were analyzed. The research involved Seredo, El Gardam and Mtama 1 sorghum cultivars. The TC (Tissue culture) regenerates were produced through somatic embryogenesis in Linsmaier and Skoog (LS) media augmented with an osmoticum, NaCl (100 mM) in attempt to improve the parent plant for water stress tolerance. The genetic variability was investigated using five SSR markers and seven morphological traits associated with water stress tolerance. The amplified DNA fragments were screened by gel electrophoresis using 2% agarose. Cluster and principal component analysis (PCA) were done using NTSYS-pc version 2.2. The SSR detected 11 alleles with an average of 2.2 alleles per locus. The number of alleles per locus ranged from two to three and the allelic polymorphism information content (PIC) value ranged from 0.344 for Xcup14 to 0.730 for Xgap72 with an average of 0.559. These results show that the cultivars differed for morphological and SSR markers. The average genetic similarity based on the morphological traits (0.922 with a range of 0.845 to 0.989) was higher than SSR markers (0.625 with a range of 0.306 to 0.944). The results also show that the classification of these sorghum cultivars may be useful to the breeders to plan crosses for preferred traits. The results also show that the sorghum microsatellites can be used to distinguish the cultivars and to estimate genetic diversity due to somaclonal variation. Overall, this study shows that tissue culture technique might not add value in producing somaclonal variation in sorghum.
Key words: Cultivars, tissue culture regenerates, water stress tolerance, simple sequence repeats.