No abstract

The independent target region amplification polymorphism (TRAP) and single-nucleotide polymorphism (SNP) markers were used for genetic evaluation of different selected 47 sugarcane genotypes. A total of 23 pairs of TRAP markers generated 925 alleles, of which 74% alleles were polymorphic. Polymorphism was generally high (>50%), ranging from 54 to 98%. The polymorphism information content (PIC) values 0.20 varied among the primer combination ranging from 0.17 in SAI + Arbi 2 to 0.31 in GL 2+ Arbi 1 with an average of 0.24. However, the Pearson correlation between PIC and power of discrimination (PD) was found to be less significant. Single-nucleotide polymorphisms were used first time for the assessment of genetic diversity among different species of Saccharum and cultivated sugarcane varieties. The SNPs were detected from 454 sequencing. A total of 245 SNP markers were assayed across the 47 genotypes, and 167 SNPs were found to be polymorphic. The PIC values ranged from 0.04 to 0.38 with an average of 0.21, and their respective PD varied from 0.58 to 0.04 with an average value of 0.31. The obtained results relatively significant were compared with the other marker systems through genetic similarity and the clusters formed in different unweighted pair group method with arithmetic mean clustering dendrogram. The clustering analysis established genetic relationship in the order of Erianthus > Sclerostachya > Narenga > Saccharum spontaneum > S. robustum > S. barberi > S. officinarum/cultivars. These results ratify TRAP and SNP marker systems for assessing genetic diversity studies, and more diversified Erianthus spp. can contribute substantially towards sugarcane varietal improvement through breeding with Saccharum spp. or hybrid cultivars.

Sugarcane (Saccharum spp.) is a dynamic C4 polyploidy grass used as a major source of sucrose and an alternative for ethanol, food, and energy. Despite growing scientific interest, various sucrose metabolism regulatory aspects have been limited. Biochemical and gene expression studies were conducted on developmental stages, 240-420 days of planting (DAP) in mature leaves of three high and three low sucrose sugarcane cultivars. Sucrose synthase (SS) and sucrose phosphate synthase (SPS) activities were found to be remarkably higher at 240-360 DAP but decrease at 420 DAP. Twofold increases of SS activity was estimated at 240-360 DAP while SPS activity trend was found to be lower than the SS activity. In comparing SS and SPS activities with the brix of respective DAP, results show that these activities are significant and positively correlated with 'r' values of 0.69 and 0.68 for SS and SPS, respectively. However, the soluble acid invertase (SAI) and neutral invertase (NI) activities were found to decrease significantly with the maturity of cultivars, negatively correlating with brix at 'r' values 0.83 and 0.89 for SAI and NI, respectively. The antioxidant enzyme activity was modulated similar to the invertases activity. Of the six genes, ESAS 11 and 23 associated with sucrose accumulation and ESTS 34 and 41 associated with sugar transport in sugarcane were differentially expressed among the selected high and low sugarcane cultivars. Hence, these findings reinforce the selection of diverse sugarcane cultivars for gene expression studies targeting to quantitative traits and candidate marker determination.

Sugarcane is an important crop producing around 75 % of sugar in world and used as first generation biofuel. In present study, the genomic and gene based microsatellite markers were analyzed by low cost Single Strand Confirmation Polymorphism technique for genetic evaluation of 22 selected sugarcane genotypes. Total 16 genomic and 12 Expression Sequence Tag derived markers were able to amplify the selected sugarcane genotypes. Total 138 alleles were amplified of which 99 alleles (72 %) found polymorphic with an average of 4.9 alleles per locus. Microsatellite marker, VCSSR7 and VCSSR 12 showed monomorphic alleles with frequency 7.1 % over the average of 3.5 obtained for polymorphic locus. The level of Polymorphic Information Content (PIC) varied from 0.09 in VCSSR 6 to 0.88 in VCSSR 11 marker respectively with a mean of 0.49. Genomic SSRs showed more polymorphism than EST-SSRs markers on selected sugarcane genotypes whereas, the genetic similarity indices calculated by Jaccard's similarity coefficient varied from 0.55 to 0.81 indicate a high level of genetic similarity among the genotypes that was mainly attributed to intra specific diversity. Hence, the SSR-SSCP technique helped to identify the genetically diverse clones which could be used in crossing program for introgression of sugar and stress related traits in hybrid sugarcane.