3. Results
3.1. Detection of PMTV through soil-bait tests
Root and leaves samples from each of the four N. debneyi plants
(in one pot/location) were tested after 6–8 weeks by symptomatology,
ELISA, RT-PCR and back inoculation of sap to indicator plants.
The bait plants (N. debneyi) exhibited v-shaped yellow leaf markings
(Fig. 1a). A total 20/26 locations soil samples from seven
zones showed PMTV infected bait plants on the basis of symptoms
(Table 1). In TAS/DAS-ELISA, PMTV was detected in bait plants
grown in putative viruliferious soils from 25/26 locations. The Avalues in samples considered positive was quite higher than that
of the values of healthy sap (Table 1).
RT-PCR analysis of pooled samples of all four N. debneyi bait
plants indicated that out of 26 locations, PMTV was detected in
25 and 24 roots and leaves of bait plants, respectively. The root sample of bait plants of one location (Mankyal) was positive while
virus was not detected in leaves samples using RT-PCR (Table 1 and
Fig. 2). A 566 bp band was visible in agarose gels from both roots
and leaves of baited plants (Fig. 2). The results were further con-
firmed by back inoculation of sap from both roots and leaves of bait
plants on indicator plants [N. debneyi or N. benthamiana (Fig. 1b)].
The root samples of bait plants grown in soils of 25 locations and
leaves of 24 locations reproduced systemic infection on indicator
host upon back indexing (Table 1). Both roots and leaves samples
of bait plants from two locations (Ashrait-zone C and Kalam-zone
E) produced mosaic symptoms similar to PVX and infected indicator
plants were killed 2 weeks after back inoculation. However, no
specific PVX symptoms were observed in bait plants (N. debneyi)
grown in infested soils of both locations