|Authors: ||H. Pathak, V. Dhawan|
|Keywords: ||axillary branching, genotypic, micropropagation, apple rootstocks, carbohydrates, hyperhydricity |
The influence of five different carbohydrate sources, fructose, glucose, mannitol, sorbitol and sucrose on in vitro shoot proliferation of apple (Malus × domestica Borkh.) rootstocks, M 7 and MM 111 was compared.
Type and concentration of carbohydrate had a significant effect on the multiplication rate and length of shoots and was found to vary with the rootstock.
In M 7, maximum multiplication of 4.57 and shoot length of 2.54 cm was obtained at 4% sucrose.
The second best response was observed with 5% glucose.
Although, the effect of glucose was not significantly different from sorbitol, elongation of shoots was more enhanced on medium with glucose.
On the contrary, in MM 111, 4% sorbitol resulted in the best multiplication rate (3.31) and shoot length (2.30 cm), followed by 4% sucrose.
Mannitol and fructose lead to inadequate quality and growth of shoots of both the rootstocks.
Carbohydrates, besides, affecting the proliferation rate were also correlated with the occurrence of hyperhydricity.
At lower concentrations of all the carbohydrates tested, severe hyperhydricity and stunting of shoots was observed in M 7 as well as MM 111. Hyperhydricity was highest with mannitol and fructose.
The results indicate a genotype dependent response of shoot cultures of apple rootstocks to different carbohydrates.
Thus, the present study suggests the identification and optimization of the most effective carbohydrate for the multiplication of each cultivar as a necessary step for the development of an efficient micropropagation protocol.
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