Antioxidants and Phenolic Secretion in Sugarcane Genotypes Shoots Culture

Secretion of phenolic compounds is a major limitation for sugarcane in vitro shoot culture, causing a loss of regenerative capacity and subsequent cell death. In this study, micropropagation and phenolic secretion of four Saccharum genotypes were evaluated in presence of different antioxidants. Aseptic cultures of S. officinarum (PI 184794 and PI 88652), S. sinense (PI 29109) and S. robustum (UNK R65P35) were propagated on medium containing antioxidants, citric acid (100 mg/L), L-cysteine (100 mg/L), polyvynylpirrolidone (300 mg/L) and L-glutathione (50 mg/L) in two consecutive subculture cycles. Interaction between genotypes and antioxidants was significant in both cycles. All genotypes showed good shoot formation, shoot vigor and color, except in PI 88652 which had less shoot development in both the presence and absence of the antioxidants tested. PI 184794 displayed the highest shoot proliferation in the presence of citric acid, and UNK R65P35 produced more shoots per explant in the 2nd subculture. For S. sinense (PI 29109), in both subcultures, most shoots were observed in the presence of polyvynylpirrolidone. Medium discoloration due to phenolic secretion was reduced in the presence of citric acid and polyvynylpirrolidone. The type of secreted phenolic compounds differed with genotype as the Principal Component Analysis of cultivation media separated PI 88652 from PI 29109 and UKN R65P35. Phenolic compounds varied in composition and were secreted at various levels as a function of genotype and antioxidant type. Loadings plots indicated the genotype and antioxidant separations were broadly driven by flavonoid compounds.