Sugarcane mosaic virus (SCMV) is a plant pathogen that targets sugarcane and related grasses. First identified in Puerto Rico in 1916, it rapidly spread throughout the southern United States in the early 1920s. This virus has a considerable economic impact on global agriculture, particularly for sugarcane and maize crops.
Understanding Sugarcane Mosaic Virus
Sugarcane mosaic virus belongs to the Potyviridae family of plant viruses. It is a positive-sense, single-stranded RNA virus, characterized by flexible, filamentous rod-shaped particles. The virus replicates within host plant cells, interfering with normal plant functions. Sugarcane is its primary host, but SCMV also infects other crops like maize and sorghum, and wild grasses such as Johnson grass. Warmer, humid conditions favor its spread and impact.
Identifying the Symptoms
SCMV infection in sugarcane is identified by a distinct mosaic pattern on the leaves. This pattern appears as irregular light green, yellowish, or whitish streaks and blotches alternating with normal green leaf tissue. These symptoms are more prominent on the younger, basal portions of new foliage. The severity and appearance of symptoms can vary depending on the sugarcane variety, virus strain, and environmental conditions. Infected plants may also exhibit stunted growth, reduced stalk diameter, and decreased sugar content, impacting crop yield and quality.
How the Virus Moves
SCMV primarily spreads through aphid vectors, which transmit the virus in a non-persistent manner. This means aphids acquire the virus quickly from an infected plant and transmit it to a healthy plant within a short feeding period. The virus also spreads through mechanical means, such as contaminated farm tools, machinery, and human handling during agricultural practices. A major pathway for spread is the use of infected planting material, specifically sugarcane setts. If infected stalks are used for propagation, the virus can accumulate and spread to new fields.
Protecting Sugarcane Crops
Managing Sugarcane mosaic virus involves a combination of strategies. Using disease-free planting material, such as clean sugarcane setts, prevents new infections. Prompt removal, or rogueing, of infected plants from fields reduces the source of viral inoculum. Controlling aphid populations through integrated pest management practices also limits virus spread by these vectors.
A long-term solution involves developing and deploying sugarcane varieties resistant to SCMV. Plant breeders select and breed varieties with genes providing resistance or tolerance. For instance, varieties with genetic backgrounds from Saccharum spontaneum and Saccharum barberi exhibit resistance to mosaic. Crop rotation or fallow periods are complementary strategies, helping to break the disease cycle by removing host plants. An integrated disease management approach, combining these methods, is the most sustainable way to protect sugarcane production.