Impact of Sugarcane yellow leaf virus (ScYLV) infection on physiological efficiency and growth parameters of sugarcane under tropical climatic conditions in India

Yellow leaf (YL) of sugarcane caused by Sugarcane yellow leaf virus (ScYLV, a Polerovirus of the Luteoviridae family) is a serious disease affecting the crop production and productivity in India. Although impact of the disease on cane growth is observed, no systematic study has been done so far from the tropical Asian region to establish its impact on various physiological parameters, cane yield and juice quality. We have assessed physiological parameters in symptomatic and asymptomatic plants of ten different cultivars and a genotype. In addition, similar comparisons were made between virus-infected and virus-free plants derived through meristem culture. Our studies established that among several physiological parameters, photosynthetic rate (A), stomatal conductance (g _s) and SPAD metre values were significantly reduced in cultivars severely infected with ScYLV. Virus-infected cultivars exhibited significant reduction in growth/yield parameters, viz. stalk height, stalk thickness and number of internodes. Plant growth reductions were found to be 42.9, 42.3 and 38.9 % in susceptible cultivars CoPant 84211, Co 86032 and CoC 671, respectively. In addition to reduction in stalk weight, height and girth, YL disease also reduced juice yield in the affected canes up to 34.15 %. Similarly, comparison of diseased (virus-infected) and virus-free plants derived through meristem culture also revealed a drastic reduction in cane growth/physiological parameters and juice yield due to virus infection. The present study is the first comprehensive report demonstrating that YL disease caused by ScYLV seriously affects cane and juice yield in major sugarcane varieties under tropical climatic conditions (India). Consequently, this situation warrants a massive programme to provide healthy seed material and initiate breeding for YL resistance in sugarcane.