Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
Whitefly and whitefly-borne viruses in the tropics : Building a ... - cgiar
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potyvirus, most likely transmitted by<br />
aphids. The BGYMV isolates from<br />
Honduras did not react with <strong>the</strong> MAB-<br />
BS prepared <strong>in</strong> 1993 to <strong>the</strong><br />
Guatemalan isolate. The orig<strong>in</strong>al<br />
Guatemalan isolate reacted to this<br />
monoclonal when used as a control <strong>in</strong><br />
this test. This result suggests that <strong>the</strong><br />
present Honduran BGYMV isolates<br />
also have altered <strong>the</strong>ir capsid prote<strong>in</strong><br />
composition, probably <strong>in</strong> response to<br />
<strong>the</strong> arrival of a more ubiquitous<br />
vector, <strong>the</strong> B biotype of B. tabaci.<br />
The deoxyribonucleic acid (DNA)<br />
of <strong>the</strong> BGYMV isolates found <strong>in</strong>fect<strong>in</strong>g<br />
common bean was amplified by<br />
polymerase cha<strong>in</strong> reaction (PCR) for<br />
clon<strong>in</strong>g <strong>and</strong> partial sequenc<strong>in</strong>g. These<br />
results (Table 2) show that <strong>the</strong><br />
Honduran BGYMV isolate is a stra<strong>in</strong><br />
206<br />
Whiteflies <strong>and</strong> <strong>Whitefly</strong>-<strong>borne</strong> Viruses <strong>in</strong> <strong>the</strong> Tropics<br />
Table 1. Results of various diagnostic assays performed on selected plant samples from <strong>the</strong><br />
Comayagua Valley, Honduras.<br />
Sample Crop Diagnostic assay a<br />
EM MAB-BS MAB-GA PTY1 CMV PCR<br />
1 Common bean nt + - nt nt +<br />
2 Cucumber + - nt + nt nt<br />
3 Cundeamor nt - nt nt nt nt<br />
4 Common bean nt + - nt nt +<br />
5 Common bean - - - - - nt<br />
6 Tomato nt + nt nt nt nt<br />
7 Tomato nt + nt nt nt nt<br />
8 Tomato nt + nt nt nt nt<br />
a. EM, electron microscopy; MAB-BS, a broad spectrum monoclonal antibody used to detect bi-partite<br />
begomo<strong>viruses</strong>; MAB-GA, a monoclonal antibody used to detect <strong>the</strong> orig<strong>in</strong>al Middle American<br />
isolates of Bean golden yellow mosaic virus-Guatemala; PTY1, monoclonal antibody to detect<br />
poty<strong>viruses</strong>; CMV, monoclonal antibody aga<strong>in</strong>st cucumo<strong>viruses</strong>; PCR, polymerase cha<strong>in</strong> reaction;<br />
<strong>and</strong> nt, not tested.<br />
of <strong>the</strong> BGYMV species found <strong>in</strong> Middle<br />
America. In order to test <strong>the</strong> hypo<strong>the</strong>sis<br />
that <strong>the</strong> differences <strong>in</strong> nucleotide<br />
sequence homology at <strong>the</strong> coat prote<strong>in</strong><br />
level (AV1) may have occurred <strong>in</strong><br />
response to <strong>the</strong> presence of <strong>the</strong> new<br />
B. tabaci biotype.<br />
Eight <strong>whitefly</strong> samples from<br />
common bean, four samples from<br />
cucumber, three samples from tomato<br />
<strong>and</strong> one sample from chilli were<br />
biotyped by r<strong>and</strong>om amplified<br />
polymorphic DNA (RAPD) analysis. The<br />
results from <strong>the</strong>se tests (Table 3) do not<br />
support <strong>the</strong> hypo<strong>the</strong>sis of coat prote<strong>in</strong><br />
changes <strong>in</strong> <strong>the</strong> Honduran BGYMV<br />
isolate due to <strong>the</strong> emergence of a new<br />
<strong>whitefly</strong> biotype, because only <strong>the</strong><br />
A biotype of B. tabaci biotype was<br />
detected <strong>in</strong> <strong>the</strong>se samples.<br />
Table 2. Partial sequence homology (%) between a Bean golden yellow mosaic virus (BGYMV) isolate<br />
from Honduras (HD) <strong>and</strong> related BGYMV/Bean golden mosaic virus (BGMV) isolates<br />
characterized <strong>in</strong> <strong>the</strong> early 1990s.<br />
ORF a<br />
Isolates b<br />
BGYMV-DR BGYMV-PR BGYMV-GA BGMV-BR BGYMV-HD<br />
AC1 91.1 89.5 92.0 66.8 100<br />
AV1 93.8 91.8 94.2 78.0 100<br />
a. ORF, open read<strong>in</strong>g frame; AC1, viral replicase gene; <strong>and</strong> AV1, coat prote<strong>in</strong> gene.<br />
b. DR, Dom<strong>in</strong>ican Republic; PR, Puerto Rico; GA, Guatemala; <strong>and</strong> BR, Brazil.