EFFECT OF VARIOUS CULTURE CONDITIONS ON PROLIFERATION AND SHOOT TIP NECROSIS IN THE PEAR CULTIVARS €˜WILLIAM'S’ AND €˜HIGHLAND’ GROWN IN VITRO

In vitro Shoot Regeneration and Control of Shoot Tip Necrosis in Tissue Cultures of Soymida febrifuga (Roxb.) A. Juss.

“…Some report that the use of higher concentrations of Ca alleviates or controls the STN (Dyson and Digby 1975, Vieitez et al 1989, Singha et al 1990, Barghchi and Alderson 1996, Piagnani et al 1996, Wang and Van Staden 2001, Chang and Miller 2005, Martin et al 2007). In contrast, other reports show that high Ca concentrations in the culture media significantly increase the percentage of STN (Grigoriadou et al 2000). Increasing Ca concentrations in macadamia rooting experiments failed to stop STN with concentrations higher than 6 mM aggravating the problem (Bhalla and Mulwa 2003).…”

“…The symptoms of nutrient deficiency of less mobile elements such as calcium (Ca) and boron (B) (Raven 1977) first appear in the meristematic regions and young leaves whereas symptoms of excessive amounts of these minerals are first observed on the older leaves (Barghchi and Alderson 1996). The problem of non-pathogenic dieback or shoot necrosis in vitro has been associated with complex set of factors such as salt formulation, growth regulators, use of additives like charcoal to medium, sugar source, frequency of subculturing affecting it, physiological disorders associated with rooting, sulphur content and NH4/NO3 ratio and pH fluctuations (Vieitez et al 1989, De Block 1990, Kataeva et al 1991, Lakshmi and Raghava 1993, Mackay et al 1995, Piagnani et al 1996, Grigoriadou et al 2000, Seling et al 2000, Wang and Van Staden 2001and Jain et al 2009). …”

Factors contributing to in vitro shoot-tip necrosis and their physiological interactions

“…Medium type, high Ca in half strength MS medium, duration in culture Choice of medium was cultivar dependent. Use low Ca level Grigoriadou et al (2000) Pistachio nut Pistacia vera L. Ca and/or B deficiency Increasing Ca and B to a certain level, CaCl 2 was preferred Ca source Barghchi and Alderson (1996) The flame of the forest Butea monosperma (Lam.) Taub.…”

“…Mexican redbud plants cultured on a medium supplemented with isopentenyladenine (iP), kinetin or thidiazuron (TDZ) showed excessive yellowing of leaves and necrosis at the higher concentrations (Mackay et al 1995). On the other hand BA had no effect on STN in the pear cultivars 'William's' and 'Highland' grown in vitro while STN increased with increasing BA concentrations in Quercus ruber suggesting that response to BA could also be genotype dependent (Grigoriadou et al 2000). In Harpagophytum procumbens, STN increased with increasing cytokinin concentrations.…”

Changes in endogenous cytokinin profiles in micropropagated Harpagophytum procumbens in relation to shoot-tip necrosis and cytokinin treatments

“…Bairu et al (2009b) for example, observed gradual recovery from necrotic symptoms when Harpagophytum procumbens cultures were transferred to cytokinin-free rooting medium. Others suggest that the effect of CKs on STN is influenced by the type and concentration of CKs used (Mackay et al 1995;Bairu et al 2009b) and genotype dependent responses (Grigoriadou et al 2000). This investigation was aimed at providing a better explanation and understanding of the effect of CKs on STN.…”