|Yokomi, Raymond - Ray|
Submitted to: Society of Citrus Nurserymen International Congress
Publication Type: Abstract only
Publication Acceptance Date: 1/18/2014
Publication Date: 2/16/2014
Citation: Silvestre, P., Bederski, K., Roistacher, C., Giampetruzzi, A., Loconsole, G., Hartung, J.S., Saponari, M., Yokomi, R.K. 2014. Genetic diversity of citrus tristeza virus from cross-protected and unprotected citrus trees after 20 years of natural challenge in Peru. In: Abstract Book of the 10th Congress, International Society of Citrus Nurseries, Feb 14-19, 2014, Mazatlan, Sinaloa, Mexico. Interpretive Summary:
Technical Abstract: Quick decline, caused by Citrus tristeza virus (CTV), devastated Peruvian citrus on sour orange rootstock between 1950 and 1965. A second epidemic occurred between 1965 to 1985 due to spread of CTV strains causing severe stem pitting (SP) on branches and trunks, regardless of rootstock. SP weakens trees and results in reduced size, quantity and quality of fruit. The Vivero Topara Nursery (180 km south of Lima, Peru) identified and tested symptomless CTV isolates that confer cross-protection (XP) against SP symptoms in sweet orange, grapefruit and Mexican (key) limes. Use of these CTV isolates may be, in part or wholly, responsible for revitalization of sweet orange production in coastal areas where climatic conditions are favorable for severe symptom expression. Twenty CTV isolates were selected from cross-protected and non-protected trees after >20 years of natural field challenge with SP strains transmitted by the brown citrus aphid, Toxoptera citricida (Kirkaldy). Sequence-based molecular evaluation of the coat protein gene from source plants showed that a mixture of CTV genotypes was present. Eighteen of 20 samples tested had a genotype associated with severe CTV strains in combination with a Poncirus trifoliata CTV resistance-breaking (RB) genotype. Studies to correlate presence and accumulation of different CTV strains with regard to symptom phenology and XP are now underway. The data collected should provide critical knowledge on CTV XP and help to identify isolates that can mitigate disease losses caused by severe strains of CTV.