The molecular characterization of the virus and virus-line agents present in Ta Tao 5 germplasm of Prunus persica

Abstract

Peach production in the southeastern United States is limited by late spring freezes. Ta Tao 5 germplasm, used either as an interstem or by chip bud inoculation, has been shown to delay bloom and avoid the effects of these late freezes. The growth modification is graft transmissible and the germplasm has been found to be infected with ACLSV, APruV-3, and PLMVd. Using a combination of PCR, cloning, and sequencing techniques, a molecular characterization of the three graft-transmissible agents present in Ta Tao 5 has been completed. The complete nucleotide sequence of the genome of the isolate of ACLSV (ACLSV-Ta Tao 5) was determined. The genomic organization was typical of other isolates of ACLSV, but the sequence showed only 73% nucleotide identity to the Batalon1 isolate of ACLSV. This distant relationship with characterized isolates of ACLSV explains why primers recommended for PCR reactions used to identify the virus failed to detect the isolate from Ta Tao 5 reliably. This is the first complete genomic sequence of an isolate of ACLSV from peach. The 3' terminal third of the complete sequence of APruV-3 isolated from Ta Tao 5 was obtained. Four ORFs and one long 819 nt NCR region were identified. The ORFs encoded for the TGB proteins and the CP, respectively. The aa sequence of the CP showed 94% identity with the corresponding published sequence of APruV- 3. The genome of the isolate of PLMVd present in Ta Tao 5 was 337 nt in length and showed no obvious insertions or variations. The sequence showed more than 96% sequence identity with PLMVd isolates found in other parts of the world. Reliable and sensitive techniques for the detection of the agents infecting Ta Tao 5 are described in this study. One Step PCR was used to detect all three agents, and PLMVd also was detected readily by dot blot hybridization. The further studies necessary to determine the relationship between these three agents found in Ta Tao 5 and the bloom delay phenomenon now can be completed.