Sugarcane grassy shoot disease

Sugarcane grassy shoot disease
Common names	SCGS, Sugarcane grassy shoot phytoplasma, grassy shoot of sugarcane
Causal agents	Phytoplasma
Hosts	sugarcane
Vectors	leafhoppers (Saccharosydne saccharivora, Matsumuratettix hiroglyphicus,Deltocephalus vulgaris and Yamatotettix flavovittatus)
EPPO code	PHYP48
Distribution	Southeast Asia and India

Sugarcane grassy shoot disease (SCGS), caused by small, parasitic bacteria, contributes to losses of 5% to 20% in the main crop of sugarcane, and these losses are higher in the ratoon crop. A higher incidence of SCGS has been recorded in some parts of Southeast Asia and India, resulting in 100% loss in cane yield and sugar production.

Sugarcane is a vegetatively propagated crop, so the pathogen is transmitted via seed material and by phloem-feeding leafhopper vectors.Saccharosydne saccharivora,Matsumuratettix hiroglyphicus,Deltocephalus vulgaris and Yamatotettix flavovittatus have been confirmed as vectors for phytoplasma transmission in sugarcane. Unconfirmed reports also suggest a spread through the steel blades (machetes) used for sugarcane harvesting..

Phytoplasma-infected sugarcane plants show a proliferation of tillers, which give it typical grassy appearance, hence the name grassy shoot disease. The leaves of infected plants do not produce chlorophyll, and therefore appear white or creamy yellow. The leaf veins turn white first as the phytoplasma resides in leaf phloem tissue. Symptoms at the early stage of the plant life cycle include leaf chlorosis, mainly at the central leaf whorl. Infected plants do not have the capacity to produce food in the absence of chlorophyll, which results in no cane formation. These symptoms can be seen prominently in the stubble crop. The eye or lateral buds sprout before the normal time on growing cane. A survey of various fields of western Maharashtra showed grassy shoot with chlorotic or creamy white leaves was the most prevalent phenotype in sugarcane plants infected with SCGS.

Symptoms of iron deficiency (interveinal chlorosis) are very similar to those of SCGS. It shows creamy leaves, but no chlorosis occurs in leaf veins, and they remain green. In the case of severe iron deficiency, veins may lose chlorophyll in the absence of iron and appear similar to SCGS disease. Iron deficiency is caused by a lack of iron nutrients in the soil; therefore, one may observe several plants showing symptoms of iron deficiency in localized patches in a field. Phytoplasma-infected plants, though, may occur anywhere in the field in a more random distribution. Treatment with 0.1% ferrous sulfate, either by spraying or supplying it through fertilizer cures iron deficiency, but phytoplasma-infected sugarcane does not respond to any treatment. Phytoplasma-infected plants growing in vitro show sensitivity to tetracycline.

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