Total phenol content of guava fruit and development of an in vitro regeneration protocol amenable to genetic improvement

Total soluble phenolics in two white (‘Allahabad Safeda’ and ‘Lucknow-49’), two pink (‘Beaumont’ and ‘Gushiken Sweet’), and three red fleshed (‘Ka Hua Kola’, ‘Ruby Supreme’ and ‘Red Fleshed’) guava ( Psidium guajava L.) fruits were assessed using the Folin-Ciocalteu procedure. ‘Allahabad Safeda’ and ‘Ruby Supreme’ contained the highest level of phenols (1,967.5 and 1,921.25 μg/g gallic acid equivalents). No significant difference in phenolic content was observed between white and red fleshed guava fruits. An in vitro method was developed for clonal propagation of ‘Lucknow-49’ and ‘Gushiken Sweet’ cultivars. Five concentrations of six-benzylaminopurine (BAP) and kinetin (KIN) plant growth regulators were tested for in vitro regeneration. A maximum of 4.5 shoots per explant was produced on Murashige and Skoog medium supplemented with 8.9 μM BAP + 9.4 μM KIN. These studies indicate that guava, a rich source of natural phenolic antioxidants, can be efficiently micropropagated for genetic studies to enhance its nutraceutical value.