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Reliable detection of Peach latent mosaic viroid (PLMVd) by real-time RT-PCR

Carmen Martínez: Instituto Valenciano Investigaciones Agrarias (IVIA)

<div><em>Peach latent mosaic viroid</em> (PLMVd) is a worldwide-distributed pathogen that causes leaf mosaics, delays in foliation, flowering and ripening, irregularly-shaped and discolored fruits with cracked sutures and, in a few cases, albinism (peach calico). PLMVd variants are clustered into two different classes, I and II, with the latter presenting multiple changes with respect to the former in the region delimited by positions 161-197 (stems p6a and p6b). We have developed a real-time RT-PCR method able to detect PLMVd variants. Three different TaqMan probes were designed: P1 and P2 specific for class I and II variants, and P3 for all PLMVd variants deposited in databases. Our real-time RT-PCR approach has been used to characterize PLMVd populations present in the peach indicator GF305 after independent inoculation of representative variants of class I and II, and co-inoculation with both variants. Plants were analyzed by hybridization with a full-length PLMVd riboprobe, sequencing of conventional RT-PCR products, and real-time RT-PCR. Under greenhouse conditions the results showed a strong competition between both variants during host colonization, since only class II variants were detected in the co-inoculated plants. These results point to a higher biological fitness of class II PLMVd variants.</div>