Incidence, Distribution and Characteristics of Major Tomato Leaf ...

Incidence, distribution and characteristics of major tomato leaf curl and mosaic virus diseases
Samples IG1 and K1 (Table 3.2) tested positively to TYLCV-Is with degenerate primers
PAL1v 1978 and PAR1c 715 (Rojas et al., 1993; Nakhla et al., 1993; Wyatt and Brown,
1996), whereas seven more samples, i.e. IG2, IG3, RL1, RL2, K1, K3, and MB8 were
positive with degenerate primers PARAv 494 and PARAc 1048 in PCR (Figure 3.12
A,B, C, Dand G), and were therefore identified to be geminiviruses.
In another experiment where specific primers to TYLCV-Is were used to test for
TYLCV, 5 samples were positive with primers PTYCRv 21 and PTYIRc 287 (Figure
3.12 F), while 3 samples tested positive with primers PTYCR2v 1499 and PTYAL1c
2196 (Figure 3.12 G). No isolate was positive with primers PTYC2c 1814 and PTYV2v
466, as indicated in Figure 3.10 H. Samples ISOPOT and MB8, which clearly tested
positive with primers PTYC2v 1499 and PTYAL1c 2196, did not form clear expected
bands in this PCR reaction with specific TYLCV primers PTYCRv 21and PTYIRc 287,
even though earlier on they were positive to the same primers in PCR (Table 3.11). Of
the 10 samples tested with specific primers PTLCV-UGrep2r and cp1f, only three
isolates tested positive, as indicated in Figure 3.12 I. Results of both DNA Hybridisation
and PCR are summarised in table 3.11. Samples that tested negative in all experiments
were disregarded in this report.
Genetic Identity of Tomato Yellow Leaf Curl Samples IGI, KI and RL5
Yellow leaf curl samples IGI, KI and RL5 taken in 1998 (Table 3.2), and which
consistently tested positively in DNA hybridisation and PCR experiments, were selected
for further analysis. Further more, sample IG1 drew our attention because it also reacted
to the general probe, while many other samples did not (Figure 3.9A). As such, cloning
and sequencing was done for IG1, KI and RL5 isolates. Partial sequences of IG1 and RL5
isolates were successfully generated. The sequence for K1 had many uncertain
nucleotides and was therefore disregarded.
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