Sida leaf curl virus associated with Sida cordifolia in Northern Thailand

Diseases caused by Begomovirus species are playing a crucial role in Thai agriculture. Effective disease management requires an understanding of the viruses that associate with weeds as alternative hosts. Sida spp. (Malvaceae) are a prevalent weed in Thailand that has been mostly associated with symptoms similar to viral infections. Globally, there are 38 begomoviruses known to exist from Sida species. Sida cordifolia L. samples that showed yellowing, vein clearing, and upward leaf curling or cupping were collected in Mueang Chiang Mai District. The partial coat protein (CP) gene of DNA-A was amplified using degenerate primers, Deng A and Deng B. Sequences of Sida samples (CM-BM01; OQ459361 and CM-BM02; OQ459362) showed greater similarities with those of the Sida leaf curl virus (SiLCV) isolates (MW465952: SiLCV-[HN] - 97%; AM050731: SiLCV-[Hn60] - 93%; and AM050730: SiLCV-[Hn57] - 93%). CM-BM01 and CM-BM02 clustered with SiLCV isolates and were sister to SiLCV-[HN] in the maximum likelihood phylogeny. SiLCV has been reported in China in association with S. cordifolia. A Sida species with an unidentified begomovirus and a SiLCV associated with Abutilon indicum L. (Malvaceae) have both been found in Thailand. This is the first known report of the SiLCV associated with S. cordifolia from Thailand. The potential of Sida weeds as alternate hosts and the effectiveness of virus transmission to crop plants are currently unresolved. Continued research into the role of weeds as alternative hosts for vector-borne viruses is vital for successful disease management.