Alleviating shoot tip necrosis during in vitro propagation of grape cv. Red Globe

In vitro propagation plays a key role in mass production and is an important tool in breeding fruit crops. However, the major limiting factor for in vitro propagation of fruit crops is shoot tip necrosis (STN). STN is a physiological disorder characterized by browning, senescence and death of the apical buds which later progress basipetally resulting in complete drying of cultures under in vitro. It is commonly manifested during the stages of multiplication, elongation or at rooting at different intensities. During the course of refinement of micro propagation protocol for grape cultivar 'Red Globe' severe loss of cultures was observed immediately after first subculturing due to STN. This necessitated to alleviate the STN during in vitro propagation of grapes. To manage and overcome STN, the influence of subculturing intervals and different concentrations (1, 2 and 3 mg L-1) of Benzyl amino purine (BAP) and different concentrations of calcium (Ca) and boron (B) in full and half strength Murashige and Skoog (MS) media were studied. The positive effect of three concentrations (120.12, 180.18, and 240.24 mg L-1) of Ca and B (1.08, 2.17 and 3.25 mg L-1) were observed on occurrence of STN suggest the influential role of elevated calcium levels on maintenance of cellular integrity leading to strong recovery from STN. It is suggested to grow the cultures in half strength MS media supplemented with BAP at 1 mg L-1, 180.18 mg L-1 of Ca and 1.08 mgL(-1) of B with 2 weeks subculture interval in the initial subculture phase could effectively manage the incidence of STN in grape cv. 'Red Globe'.