Status of Citrus aurantifolia infected with Witches' Broom Disease of Lime in Oman

Production of lime (Citrus aurantifolia) in Oman has been significantly reduced in recent years. The reduction in yield has been attributed to a combination of biotic and abiotic factors that adversely affected tree growth and productivity. Lime cultivation area has lost 50% of its acreage compared to 1990, mainly due to tree loss caused by Witches' Broom Disease of Lime (WBDL) associated with Candidatus Phytoplasma aurantifolia. The disease that originated in the Sultanate and spread to neighboring countries has the potential to devastate lime production throughout the entire regions of western Asia and North Africa thus affecting fruit imports to Oman as well. Infection with WBDL has been worsened by increasingly stressful abiotic conditions, mainly frequent drought and soil and water salinity that ultimately led to the decline of lime production in the country. This decline subsequently resulted in loss of lime acreage and profitability and reduced income from largely traditional farming systems. The unsustainable lime production has eventually led to abandonment of many farms, to conversion of fruit farms to forage farms, or to a complete change of the land use into other commercial projects. While the causal agent of WBDL has long been identified, there have been no practical solutions to control the disease thus far and these challenges remain decades later. This review will address the current status of lime in Oman and propose some solutions to enhance productivity of infected trees.