Citrus as a Pioneer “Clean” Plant

In 1932, Citrus was the first crop in which a disease was associated with a virus (Citrus psorosis virus). This led to the establishment in California of a program to supply budwood of citrus that was free of the psorosis virus. As more graft-transmissible diseases of citrus were described, budwood sources free of the causal pathogens became necessary and led to the establishment of the Citrus Varietal Improvement Program in the 1950's in California. The concept of using only clean sources of citrus budwood spread from California into other citrus-producing states and was eventually incorporated into the APHIS protocol for interstate movement of citrus propagative materials.

The use of clean source propagative materials in citrus was well established when the National Clean Plant Network (NCPN) was implemented starting in 2009, so it was natural to include citrus as an NCPN commodity. The NCPN promotes a distributed model of service from geographically diverse clean plant centers. It brings the Centers, industry, researchers, State and Federal regulatory personnel together to discuss issues. Within the NCPN, citrus has the largest number of clean plant centers, highest number of accessions maintained, and second highest number of propagative units distributed annually.

More information on the origins of clean citrus and its status in the NCPN is available at: 

https://ucanr.edu/sites/default/files/2024-12/Topics_in_Subtropics104004.pdf