Annual disease testing for Citrus tristeza virus (CTV)  is nearly complete at LREC.  Each year we test all field trees for presence of the virus using the Direct Tissue Blot Immunoassay method, which is a form of ELISA.  This year we have more than 11,000 trees to test.  CTV is found in the phloem tissues of citrus plants, and virus titer is typically highest during April in the San Joaquin Valley. 

Field technicians Cody McCarter and Jessica Seymore work as a team to collect the tissue, which can be in the form of young flushing stalks or leaf petioles.  The stalks or leaves are taken from the tree and the ends snipped with a cigar cutter for a smooth cut that is pressed onto a nitrocellulose membrane.  The leaf material is then discarded, as the blots made onto the membrane contain enough phloem to reveal presence of the virus.  Membranes are processed in-house in a laboratory, and results are obtained within four hours.  Trees that are found to be infected are removed in order to protect research plots and foundation trees from infection.

Dr. Mikeal Roose (Dept. of Botany and Plant Sciences, UC Riverside) attends the first harvest of a new rootstock trial located south of LREC in a private orchard.  The research trial consists of 300 trees of Tango mandarin on many different rootstocks.  The fruit was picked into the small totes shown here, which prevents delicate mandarin varieties from being crushed, as compared to oranges which are normally picked into 24-carton fruit bins weighing 900 lbs.  After harvest, the trees were measured for size and an overall tree health rating was given.  Additional data generated from the LREC packline includes individual fruit size, weight, °Brix, color, and texture.  These measurements help the researcher gauge the performance of specific rootstocks for Tango mandarin.

This week Beth Grafton-Cardwell's entomology research team harvested 288 3-year-old 'Tango' mandarin trees, and ran the fruit over the Lindcove fruit grading system.  Her group is studying the long-term effects of reducing citrus leafminer densities with insecticides and what impact that has on the development of the trees and the number, size, color, and Brix of the fruit.

The UC ANR Program Council held their February business meeting at Lindcove REC, where they were able to taste a selection of the more than 400 citrus varieties grown at the Center.