The disease of Foliar Yellowing Syndrome of Sugar Cane (YLS) is found in many sugarcane countries and it produces losses of 60% in the susceptible varieties.

This work is the first report of YLS in Cuba and it is offered very complete data, until the moment, of these pathogens' genetic variability.

It is informed for the first time the association with phytoplasmas' disease belonging to the clade of aster yellowing (AY).

With this work, it has been made a contribution to determine the disease's origin, which is an unveiled problem in the world.

There were determined the effects on the host and on the components of sugar cane yield. Likewise, there were studied the measures that can help to minimize their negative effects.

It is offered a methodology for field diagnosis, being proven that the increment of leaves’ brix is an inherent characteristic to this disease, being very reliable the obtained data.

It was determined that the identification of phytoplasmas related with the disease should be made by molecular methods, since it is impossible through the symptomatology.

It was reached the conclusion that the disease's nature is not due to the presence of luteoviruses, fungi or nematodes.

The main alterations induced by this disease were identified, being reported for the first time the affectation on the quality of juices.

It is offered a disease evaluation scale for the varieties, being previously evaluated the existent germoplasm from cane and being demonstrated that 48% of genotypes has not presented disease symptoms. This disease affects the main commercial varieties of the country with a propagation of 23%. The results have generated very useful recommendations for the program of national improvement and the management of varieties and seeds.

The report of this disease and its association with phytoplasms, appear in prestigious international magazines such as the International Journal Plant Diseases; likewise other works are reported on the topic in other prestigious magazines and they have been presented in international events.