Disease-Free Plants

Manufacturing of disease-free plants

Many plant species are infected with pathogens — viruses, microorganism, fungi, mycoplasma and nematodes that purpose systemic diseases. Although these diseases do not continually result in the demise of the plant, they lessen the first-rate and yield of plants. The plants inflamed with microorganism and fungi frequently respond to chemical treatment by bactericides and fungicides.

However, it is very hard to therapy the virus-infected plant culture. Further, viral disease is effortlessly transferred in seed- propagated in addition to vegetatively propagated plant species. Plant breeders are always interested in expanding disease-free plant life, in particular, viral disease-free plant culture. This has come to be a fact through tissue cultures.

Apical Meristems with Low number of Viruses

In fashionable, the apical meristems of the pathogen inflamed and disorder harbouring flora are both loose or convey a low attention of viruses, for the subsequent motives:

• The absence of vascular tissue in the meristems through which viruses with ease pass within the plant frame.
• Hastily dividing meristematic cells with excessive metabolic activity do now not allow viruses to multiply.
• Virus replication is inhibited via a high attention of endogenous auxin in shoot apices. Tissue culture strategies using meristem are effectively used for the manufacturing of disease-free plants, due to numerous pathogens — viruses, bacteria, fungi, mycoplasmas.

Techniques to produce Viruses free plants

In widespread, plant life is infected with many viruses; the nature of a number of them may be unknown. The utilization virus-free plant means that the given plant is unfastened from all the viruses, despite the fact that this will now not be continually authentic. The usually used techniques for virus removal in plants are indexed beneath, and in short described subsequently.

• Heat control of plant
• Meristem-tip subculture
• Chemical treatment of media
• Different in vitro techniques

Heat control (Thermotherapy) of plants

In the early days, earlier than the advent of meristem cultures, in the vivo eradication of viruses from plants become finished through heat control, of entire plant life. The underlying principle is that many viruses in plant tissues are either partially or absolutely inactivated at higher temperatures with minimum damage to the host plant. Thermotherapy (at temperatures 35-forty°C) changed into executed with the aid of using hot water or hot air for an elimination of viruses from developing shoots and buds.

There are two obstacles of viral elimination by using heat control:

• Maximum of the viruses is not touchy to heat
• Many plant species do now not live on after thermotherapy

With the above dangers, heat control has not come to be famous for virus removal.

Meristem-Tip subculture

A trendy description of the method adopted for meristem and shoot tip cultures has been described in above texts.For viral elimination, the size of the meristem used in cultures is very crucial. This is due to the fact that maximum of the viruses exists by using establishing a gradient in plant tissues.

Actually, the regeneration of virus-free plants through cultures is inversely proportional to the dimensions of the meristem used. The meristem-tip explant used for viral elimination cultures is just too small. A stereoscopic microscope is usually employed for this purpose.

Meristem-tip cultures are stimulated by way of the following factors:

• Physiological condition of the explant — actively developing buds are extra effective.
• Thermotherapy previous to meristem-tip culture — for the positive plant (possessing viruses in the meristematic regions), heat control is first given and then the meristem-guidelines are removed and cultured.
• Culture medium —MS medium with low concentrations of auxins and cytokinins is right.

Chemical treatment of Media

Some workers have attempted to get rid of viruses from infected flowers by the chemical remedy of the tissue culture media. The commonly used chemical compounds are growth substances (e.g. cytokinins) and antimetabolites (e.g thiouracil, acetylsalicylic acid).

There are conflicting reviews on the elimination of viruses via chemical remedy of the media. As an instance, an addition of cytokinin suppressed the multiplication of certain viruses even as for some different viruses, it truly inspired.

Other in Vitro techniques

Besides meristem-tip culture, different in vitro methods also are used for raising virus-free plants. On this regard, callus cultures have been successful to a degree. The callus derived from the inflamed tissue does not carry the pathogens during the cells. In reality, the uneven distribution of tobacco mosaic virus in tobacco leaves changed into exploited to broaden virus-free flowers of tobacco. Somatic cell hybridization, gene transformation and somaclonal variations additionally beneficial to raise disease-free plant life.

Removal of Pathogens except for Viruses

Except for the removal of viruses, meristem-tip cultures and callus cultures also are beneficial for an eradication of bacteria, fungi, and mycoplasmas. Some examples are given below:

• The fungus Fusarium roseum has been efficiently removed through meristem cultures from carnation flowers.
• Certain microorganism (Pseudomonas carophylli, Pectobacterium parthenii) are eradicated from carnation plants through using meristem cultures.

Merits and Demerits of disease-free Plant production

A few of the culture strategies, meristem-tip culture is the maximum reliable approach for virus and other pathogen removals. This requires excellent knowledge of plant pathology and tissue culture.

Virus-free plants show extended growth and development of vegetation, higher yield (e.g. potato), increased flower length (e.g. Chrysanthemum), and progressed rooting of stem cuttings (e.g. Pelargonium)

Virus-free plants are greater susceptible to the equal virus whilst uncovered once more. That is the fundamental quandary. Reinfection of sickness disease free plants may be minimized with good information of greenhouse renovation.

References

Cassida, L.E Jr.Industrial microbiology.New age into publishers, 1996.

I, Stever.Biochemistry.new york Wall freeman company, 1995.

JE, Smith.Biotechnology.Sinauer Association, 2000.

Nelson, D L and M M Cox.Leininger Principle of Biochemistry.Fifth. Freeman publication, 2004.