ADVERTISEMENTS:
In this article we will discuss about the mycoplasmal diseases of potato.
(a) Purple Top Roll:
The disease occurs particularly in North America but reported for the first time in India which can cause 15 to 20% of loss of Potato yield.
ADVERTISEMENTS:
Symptoms:
The disease is characterised by rolling and purple or pink coloration of the basal part of leaflets of top leaves. Certain varieties develop only rolling and no coloration. Stunting, chlorosis, profuse axillary shoots with aerial tubers and swelling of nodes are other symptoms. No wilting or necrosis of tuber takes place.
Causal Organism:
Mycoplasma like organisms belonging to “Aster Yellows”.
ADVERTISEMENTS:
Disease Cycle:
Vector Orosius albicinctus transmits the disease. Infected tubers are the most important source of transmission. The disease has been transmitted to clove, tomato, datura and tobacco also.
Control Measures:
No effective control measure has been reported.
(b) Marginal Flavescence of Potato:
ADVERTISEMENTS:
It is another mycoplasmal disease reported from India which is prevalent in hills and plateau areas where cool weather prevails for a longer duration during the crop season. The crop loss due to this disease varies between 40-75%.
ADVERTISEMENTS:
Symptoms:
Chlorosis on the margins of upper young leaves is the main symptom of the disease. In rare cases, the severely affected plants after exhibiting flavescence of leaf margins for quite some time develop pinkish coloration on leaflets bases and start rolling. Hairy root symptoms on tubers of 60-65% plants affected with marginal flavescence has been observed.
ADVERTISEMENTS:
Disease Cycle:
The disease is transmitted by leaf hopper and grafting. 5-35% tubers carry the pathogen and serve as source of primary inoculum.
Control Measures:
Hot water treatment of potato tubers at 50°C for 10-15 minutes eliminates the pathogen without adversely affecting the tubers (Sangav & Singh, 1985).
ADVERTISEMENTS:
(c) Witcties’ Broom:
ADVERTISEMENTS:
The disease results in extreme stunting of plants and numerous filaments stems with simply leaves. Very small tubers are produced by the affected plant resulting in total loss of the plant.
Disease Cycle:
Mode of transmission is similar to other two disease control measures.
Control Measure:
No effective control measure has so far been suggested.
