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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.

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