Monci F, Navas-Castillo J, Moriones E
Estación Experimental "La Mayora," CSIC, 29750 Algarrobo-Costa, Málaga, Spain.
Plant Dis. 2001 Dec;85(12):1289. doi: 10.1094/PDIS.2001.85.12.1289A.
Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV, formerly TYLCV-Sar) are geminivirus species of the genus Begomovirus that cause the disease known as tomato yellow leaf curl. In Spain, TYLCV and TYLCSV have coexisted in field and greenhouse tomato (Lycopersicon esculentum) crops since 1996 (2). TYLCV is also the causal agent of the leaf crumple disease of common bean (Phaseolus vulgaris) (1), a species that TYLCSV is unable to infect (2). Analysis of field samples from common bean plants affected by leaf crumple disease collected in Almería (southeastern Spain) during 1999 showed that, unexpectedly, several samples hybridized with TYLCV- and TYLCSV-specific probes prepared to the intergenic region (IR) as previously described (1). Polymerase chain reactions (PCR) performed with total nucleic acids extracted from one of these samples (ES421/99) using primer pairs specific to the IR of TYLCV (MA-30/MA-31) or TYLCSV (MA-14/MA-15) (1) gave no amplification product. However, the combination of MA-30 (5' end of TYLCV IR) and MA-15 (3' end of TYLCSV IR) produced a PCR DNA product of the expected size (351 bp). Direct DNA sequencing of this product (GenBank Accession No. AF401478) indicated the presence of a chimeric IR in ES421/99. Comparison of the obtained sequence with those available for isolates reported from Spain showed that the 5' side (149 nt) from the stem-loop structure conserved in the IR of all geminiviruses was 99% identical to the corresponding region of TYLCV (GenBank Accession No. AF071228) and only 62% identical to TYLCSV (GenBank Accession No. Z25751). In contrast, the 3' side (124 nt) from the stem-loop was 98% identical to the corresponding region of TYLCSV and only 57% identical to TYLCV. The 33-nt region involved in the stem-loop was 100% identical to TYLCV and showed one nucleotide change in the loop with respect to TYLCSV. Therefore, this DNA sequence data showed evidence of the occurrence in ES421/99 of a natural recombination between TYLCV and TYLCSV. The biological and epidemiological consequences of the presence of this new interspecific recombinant have yet to be determined. References: (1) J. Navas-Castillo et al. Plant Dis. 83:29, 1999. (2) S. Sánchez-Campos et al. Phytopathology 89:1038, 1999.
番茄黄化曲叶病毒（TYLCV，原TYLCV-Is）和番茄黄化曲叶撒丁岛病毒（TYLCSV，原TYLCV-Sar）是菜豆金色花叶病毒属的双生病毒，可引发番茄黄化曲叶病。自1996年起，TYLCV和TYLCSV在西班牙的露地和温室番茄（Lycopersicon esculentum）作物中共存（2）。TYLCV也是普通菜豆（Phaseolus vulgaris）叶皱病的病原体（1），而TYLCSV无法感染该物种（2）。对1999年在西班牙东南部阿尔梅里亚采集的受叶皱病影响的普通菜豆植株的田间样本进行分析，结果意外发现，一些样本与先前所述的针对基因间隔区（IR）制备的TYLCV和TYLCSV特异性探针发生了杂交（1）。使用针对TYLCV的IR（MA-30/MA-31）或TYLCSV的IR（MA-14/MA-15）的引物对（1），对从其中一个样本（ES421/99）中提取的总核酸进行聚合酶链反应（PCR），未得到扩增产物。然而，MA-30（TYLCV IR的5'端）和MA-15（TYLCSV IR的3'端）的组合产生了预期大小（351 bp）的PCR DNA产物。对该产物进行直接DNA测序（GenBank登录号AF401478）表明，ES421/99中存在嵌合IR。将获得的序列与西班牙报道的分离株的可用序列进行比较，结果显示，在所有双生病毒的IR中保守的茎环结构的5'侧（149 nt）与TYLCV的相应区域有99%的同一性，与TYLCSV的相应区域只有62%的同一性。相比之下，茎环的3'侧（124 nt）与TYLCSV的相应区域有98%的同一性，与TYLCV的相应区域只有57%的同一性。参与茎环的33 nt区域与TYLCV 100%相同，相对于TYLCSV，其环中有一个核苷酸变化。因此，该DNA序列数据证明了ES421/99中发生了TYLCV和TYLCSV之间的自然重组。这种新的种间重组体存在的生物学和流行病学后果尚待确定。参考文献：（1）J. Navas-Castillo等人，《植物病害》83:29，1999年。（2）S. Sánchez-Campos等人，《植物病理学》89:1038，1999年。
