Pigeonpea sterility mosaic virus

Pigeonpea sterility mosaic virus (PPSMV) is a devastating viral disease affecting pigeonpea (Cajanus cajan) crops globally, particularly in tropical regions. It is caused by a virus belonging to the genus Emaravirus. This disease is unique in its transmission method, as it does not spread through seeds or mechanical sap contact but is vectored exclusively by the eriophyid mite Aceria cajani.

The primary host for this pathogen is the pigeonpea plant. The disease is most prevalent in areas where pigeonpea is grown continuously, providing a constant reservoir for the viral vector throughout the year. The mite facilitates the rapid spread of the virus during the growing season.

Symptoms of the infection include mosaic patterns on leaves, leaf size reduction, and chlorosis. The most critical symptom is "sterility," where the plant fails to produce pods or the pods remain stunted and empty. Affected plants often exhibit a bushy appearance due to excessive proliferation of secondary shoots, preventing normal maturation.

Development and spread of the virus are highly dependent on the lifecycle of Aceria cajani. Hot and dry weather conditions, followed by moderate rains, favor the rapid multiplication and wind-assisted dispersal of these mites. Early-season infestation leads to severe crop damage, often resulting in total loss of reproductive potential for the entire field.

Management strategies are essential to mitigate losses, as there is no chemical cure for the virus once the plant is infected. The focus remains on preventative measures:

• Planting disease-resistant or tolerant cultivars.
• Ensuring a crop-free period to break the life cycle of the mite vector.
• Eradicating volunteer plants and wild hosts that harbor the virus.
• Applying systemic acaricides to control mite populations in early crop stages.
• Implementing appropriate spatial isolation between successive plantings.