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Curtovirus Infection of Chile Pepper in New Mexico

Chile pepper-producing areas of southern New Mexico (NM) were surveyed during 2001 and 2002 to identify which curtoviruses were infecting chile peppers and to determine the distribution of the viruses among fields. Plants with symptoms resembling Beet curly top virus (BCTV) were collected from 10 fields and tested for the presence of curtoviruses by polymerase chain reaction using primers designed to detect a portion of the coat protein (cp) gene, and tested for specific curtoviruses using primers designed to detect to a portion of the replication-associated protein (rep) gene. All amplicons were sequenced and compared with curtoviruses for which complete sequences were available. Amplification was successful from 79.5% of the chile pepper samples. Analysis of the CP sequences showed that more than 92% of the NM field isolates shared high (98 to 100%) amino acid identity with well-characterized curtoviruses. However, eight NM isolates displayed a distinct CP sequence that shared only 86 to 88% amino acid identity with those curtoviruses. Comparison of the rep gene sequence showed that 18.5% of the NM field isolates tested shared 98 to 100% amino acid identity with Beet mild curly top virus (BMCTV), 48% shared 96 to 97% amino acid identity with Beet severe curly top virus (BSCTV), and 32% shared 93 to 97% amino acid identity with BMCTV and BSCTV. Although the distribution of curtoviruses was not identical among all fields sampled, little or no spatial patterns were found among the field isolates. This study revealed the complexity of curtoviruses in a single crop and limited geographical area.