|Schnell ii, Raymond|
Submitted to: European Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/23/2004
Publication Date: 1/1/2005
Citation: Suarez, I.E., Schnell II, R.J., Kuhn, D.N., Litz, R.E. 2005. Avocado sunblotch viroid (ASBVd) is persistent in embyogenic cultures derived from the nucellus of an ASBVd-infected tree. European Journal of Plant Pathology. 111:317-326. Interpretive Summary: Avocado sunblotch viroid (ASBVd) was detected in embyogenic avocado cultures induced from the nucellus of infected 'Vero Beach' SE2. Nucellar cultures were induced on semisolid medium consisting of B5 major salts, MS minor salts and organics, 45 g of sucrose and 0.41 uM picloram. Embryogenic cultures consisting of polyembryonic masses were maintained in suspension cultures of MS medium with 0.41 uM picloram. Suspension cultures of 'Vero Beach' SE2 proliferated more rapidly than ASBVd-free 'Hass' 11.4.3 and developed more somatic embryos on maturation medium. Indexing of PEMs and somatic embryos using RT-PCR one year after induction demonstrated that 'Vero Beach' SE2 remained ASBVd positive. Nine ASBVd variants were isolated from 17 sequenced clones, three of which have not been previously reported. Three of the 4 variants isolated from somatic embryos showed variation either at the right terminal loop or in the stem area, indicating a possible association between nucleotide variation and developmental stage of the embryogenic tissue.
Technical Abstract: Avocado sunblotch viroid is similar to a virus and causes blemishes on the avocado fruit and a decline in the health of avocado trees. This viroid has been difficult to study because the titer, the amount of the viroid in a tree at a particular time, fluctuates greatly. This research reports on the persistence of the viroid in tissue culture and demonstrates that variants found in the original plant are also found in the cell culture derived polyembryonic masses. It also demonstrates that new variants arise during the tissue culture process. As a result of this research we will be able to use tissue culture systems to further investigate the biology of the viroid. Using tissue culture we can control the growth and environmental conditions of the cells which gives us the ability to sutdy gene silencing among these small RNA molecules.