Yellow leaf disease of sugarcane: symptom, etiology, epidemiology, impact on sugarcane, diagnosis and management

Abstract

Yellow leaf disease (YLD) caused by Sugarcane yellow leaf virus is recorded in almost all the sugarcane growing countries in the world. The disease was observed during 1999 in India for the first time and later its wide spread occurrence throughout country was found. In popular varieties, the disease intensity varied from0 to 100% and the disease incidence varied from 0 to 75.0% under field conditions. The expression of symptoms under field conditions was influenced to a limited extent by different biotic and abiotic factors. Severe infection of YLD was found to significantly affect cane yield and juice quality in certain cultivars. YLD infected sugarcane plants recorded lesser photosynthetic activity and reduced mobilization of photosynthates from the leaves to sink, thereby reducing the sucrose accumulation in the affected stalks. Planting of setts from virus infected canes has been found as the chief source of disease introduction in the field and secondary transmission of the disease occurs through aphid vectors to varying extent. Precise diagnostic techniques like tissue-blot, ELISA and RT-PCR have been standardized to detect the associated pathogen sugarcane yellow leaf virus (SCYLV) from the suspected sugarcane. Although association of SCYLV has been reported from many countries there are also evidences of sugarcane yellows phytoplasmas (ScYP) causing the disease in few countries. Efforts are being made to identify the disease-resistant sources to YLD in sugarcane germplasm and to breed YLD-resistant varieties in different countries. Among the different management approaches, clean seed programme is found to be the most effective to control the disease. Elimination of the virus through meristem culture has been demonstrated to purify the virus from the infected planting materials and this technique needs to be adopted to supply disease-free planting materials which would sustain sugarcane production. Attempts to develop transgenic sugarcane for SCYLV resistance have been found successful and this strategy also holds promise to manage the disease in the future.