Cracking symptoms of Sweet potato feathery mottle virus- Russet Crack strain.
The first clean seed program for sweetpotato was started in the 1960s in California. At that time, it was well known in the industry that new seed stock was required to prevent Russet Crack and “variety decline,” or the gradual loss of yield that occurred in many varieties. The use of virus-tested seed is one of the reasons for substantial sweetpotato yield increases. Clean material, coupled with higher yielding, disease-resistant varieties has resulted in marked increases in yield in recent decades. In 1967, average yields in California were 5 tons/acre; in 2001 average yield had more than doubled to 12 tons/acre.
The Southeastern Experience
Today, North Carolina is the leading producer of sweetpotato in the United States. In the 1990s, prior to implementing a clean seed program, the sweetpotato crop was devastated by a virus disease - Sweetpotato feathery mottle virus – Russet Crack strain. Yields were reduced more than 50% in affected fields. In Louisiana yield decline was up to 40%. In response, the Micropropagation Unit at North Carolina State University and the LSU AgCenter virus-tested seed program were started in 1999 to "clean up" and provide clean seed and plant material to growers. Simultaneously, both states began programs to certify sweetpotato plant material. Due to the fact that the use of certified seed varies greatly between states, NCPN education and outreach efforts are focused on educating sweetpotato producers about the value of using certified planting material.
Sweetpotato clean seed programs are established in California, Louisiana, North Carolina, and Mississippi. Other sweetpotato producing states are interested in developing clean seed programs.