Present status and future management strategies for sugarcane yellow leaf virus: A major constraint to the global sugarcane production

Abstract

Sugarcane yellow leaf virus (SCYLV), a distinct virus species belongs to the genus Polerovirus, family Luteoviridae. SCYLV is one of the major constraints in sugarcane production worldwide and widely distributed in almost all the sugarcane growing countries. SCYLV is known to have great genetic diversity within the species and presently ten genotypes are known to occur in the world. SCYLV is predominantly occurring in most of sugarcane growing states in India. Virion comprised of 180 coat protein units and are icosahedral, non-enveloped ranged from 24 – 29 nm in diameter. As like other poleroviruses, SCYLV genome is monopartite, single stranded positive sense linear RNA of about 6 kb. SCYLV genome is composed of six open reading frames (ORFs), ORF0 encodes a viral suppressor, ORF1 encodes a multifunctional protein, ORF2 encodes RNA-dependent RNA polymerase, ORF3 encodes a viral coat protein, and ORF4 encodes a movement protein and ORF5 is translated by the peptide encoded by ORF3 as a read-through protein via translational read-through mechanism. SCYLV is a phloem limited and predominantly transmitted by sugarcane aphid (Melanaphis sacchari), while other aphid species are known to transmit the virus in a circulative manner viz., corn leaf aphid (Rhopalosiphum maidis), rice root aphid (R. rufiabdominalis), and sugarcane wholly aphid (Ceratovacuna lanigera). SCYLV is not transmitted by sap therefore, its transmission through M. sacchari have been achieved in different crop plants including, wheat (Triticum aestivum L), oats (Avena sativa L.), barley (Hordeum vulgare L.), rice (Oryza sativa L.), and corn (Zea mays L.) under protected conditions. SCYLV shares a limited natural host range and mainly found to infect sugarcane (Sachharum hybrid), grain sorghum (Sorghum bicolor), and columbus grass (Sorghum almum). SCYLV induces mild to prominent yellowing of the midrib, smaller leaves, bunching of leaves at the crown region of the plants, shortened internodes, yellowing across the leaf lamina, and necrosis from the leaf tip towards the leaf base along the midrib. Subsequently, complete drying of leaves and stunted growth during the severe infection. In India, yellow leaf disease (YLD) severity is varying with different genotypes cultivated in different agro–climatic conditions. Therefore, integrated disease management (IDM) approaches needs to adapt to cope up with huge economic loss due to this virus.