pathology diseases caused by mlo's

here we are having the topic such as diseases caused by MLO;s and management

1. Topic :Diseases Caused by MLO’s

2. Prepared By : T. Bhanu Krishna M. Rukmini Kapil Attri Amman Preet kaur K. Nikhilesh Submitted to : Dr. Adesh kumar

3. History of discovery of MLO ’ S The year 1967 began a new era for plant pathology, as Japanese researchers reported the discovery of pathogens here to fore unknown in plants. These were called mycoplasm like organisms, or MLO. Several diseases thought to be caused by viruses were reported the

4. discovery of pathogens heretofore unknown in plants. These were called mycoplasma like organisms, or MLO. Several diseases thought to be caused by viruses were subsequently reexamined, and MLO were identified as the true causal agents. The significance of this discovery is shown by the wide host range of MLO: 700 herbaceous and woody plants in 424 genera within 99 families.

5. Definition : In simple terms MLO are single-celled, non motile organisms somewhat smaller than bacteria. They are the smallest known living cells. More technically, they are wall-less prokaryotes, consisting of an elastic, triple layered membrane enclosing cytoplasm that contains ribosome's and strands of DNA.

6. Detection of MLO: As plant pathogens, MLO occur only in the phloem sieve tube elements of leaves, shoots, and roots. Their direct study in the phloem has been by electron microscopy , but a fluorescence test for MLO has simplified the process of infection diagnosis .

7. Symptoms of Disease attack: Mycoplasmal pathogens can induce reduction and stimulation of growth in their hosts simultaneously. Growth reduction is expressed as stunted and misshapen leaves and floral parts, shortened internodes, and decreased annual ring width.

8. Transmission of the disease: One difficulty in achieving control of mycoplasmal pathogens is that they are easily spread . MLO are transmitted from plant to plant by phloem-feeding insects, such as leafhoppers, spittle bugs, and psyllids. The wide host range of these pathogens in woody and herbaceous plants makes the acquisition and spread of MLO by insect vectors more likely.

9. Vegetative propagation materials such as cuttings, grafting scions and stocks, and shoot tips for micro-propagation can readily carry MLO. Control: Practical control measures are essentially limited to exclusion of the pathogen by the use of disease-free stock or by roguing infected plants out of the ground. Injecting trees with tetracycline

10. antibiotics results in a temporary remission of symptoms in some hosts, but these treatments are not curative. Peach rosette Peach rosette (Figure 1A) is characterized by a lack of shoot elongation with dormant buds producing a compacted growth habit somewhat reminiscent of the basal rosettes seen in some herbaceous biennials and perennials. Shortened internodes result in a large number of leaves over a very short distance.

11. LITTLE PEACH Little peach symptoms (Figure 3) may resemble some aspects of the symptoms of yellows and rosette and, like rosette and yellows, only one or two branches of whole trees may be affected. Apical dominance is lost and all buds on an infected limb develop thin, willowy shoots with small leaves. The shoots are longer than on rosette-affected trees but shorter than on yellows-affected trees

12. No fruit is produced on limbs displaying little peach symptoms. Fruit maturity is delayed and fruit is smaller than normal.

13.   SUGARCANE : MAJOR DISEASE : GRASSY SHOOT     Symptoms The disease appears nearly two months after planting. The disease is characterized by the production of numerous lanky tillers from the base of the affected shoots. Leaves become pale yellow to completely chlorotic, thin and narrow. The plants appear bushy and ‘grass-like’ due to reduction in the length of internodes premature and continuous tillering .

14. Cane formation rarely occurs in the affected clumps, if formed, thin with shorter internodes having aerial roots at the lower nodes.

15. Disease cycle The primary spread of the phytoplasma is through diseased setts and cutting knifes. The pathogen is transmitted secondarily by aphids viz .  Rhopalosiphum maydis, Melanaphi sacchari and M. idiosacchari.  Sorghum and maize serves as natural and collateral hosts

16. Management Eradication of diseased parts as soon as symptoms are seen. Avoid selection of setts from diseased area. Pre-treating the healthy setts with hot water at 52°C for 1 hour before planting Treating them with hot air at 54°C for 8 hours. Spraying the crop twice a month with insecticides

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