Question

Virus-free plants are formed by?
A. Meristem Culture
B. Callus structure
C. Somatic cell structure
D. Protoplast fusion

Answer 1

Hint:A plant will be referred to as virus-free plants if it tests negative for a selected type of well known Virus. The virus-free clones are obtained by a virus affected by plant tissue culture as the virus is translocated through sieve tubes. The apical meristem of the virus-infected plant remains free.

Complete answer: When the plant breeders need to re-generate plants that are virus-free using asexual multiplication (to receive clones of the first unhealthy plant), they usually collect the apical
meristem or the top of the infected plant and cultivate inappropriate media, to that a new, complete and virus-free plantlets develop. Virus-free plants can be formed by meristem culture because the viruses spread systematically in the whole plant except the meristems when they colonize a new plant host, through phloem vascular element.

So the right answer is Option A (meristem culture).

Additional Information:
The meristem Culture method uses the proven fact that the virus is localized within the infected plant body, that is, either the virus does not exist in the apical meristem system or the virus concentration is less in a certain area of the plant. A small area of the apical meristem is then cut and cultivation of the virus-free plant is carried out in an agar medium and a healthy virus-free plant is obtained from the infected plant. As for the extraction course, the isolation, culture, and raising of the apical meristem system, and examination of the virus are common procedures to be taken. The extraction and culture of plant meristem are done in a sterilized room, by carefully avoiding miscellaneous fungus.

Note: Morel and Martin in 1952 were the first to demonstrate that virus-free plants were obtained from virus-infected plants using the method of meristem culture. In addition to that, some other systemic pathogens such as mycoplasma, fungi, and bacterial diseases can also be removed by using this technique.