A Geminivirus-Satellite Complex is Associated with Leaf Deformity of Mentha (Mint) Plants in Punjab

Abstract

A widespread leaf deformity disease of mentha (mint), accompanied by whiteflies, the vectors of begomoviruses, was observed in Punjab in the last few years. The presence of begomovirus was indicated by DNA dot-blot analysis using the conserved coat protein and replicationassociated protein genes of another begomovirus, Sri Lankan cassava mosaic virus (SLCMV). A DNA fragment (2.0 kb), representing a partial genomic DNA of a begomovirus, amplified from the symptomatic mentha leaves was used to design end-primers and further amplify an additional 0.9 kb fragment, representing the remaining portion of the resident viral DNA. The two sequences, assembled together (2.7 kb), showed that they represented the complete sequence of an isolate of Tomato leaf curl Karnataka virus (ToLCKV) DNA. Using universal betasatellite primers, a 1.4 kb fragment was amplified from the same sample. This cloned DNA fragment showed complete sequence identity with the previously reported Cotton leaf curl Multan betasatellite (CLCuMB). Majority of the symptomatic mentha leaf samples, collected from four districts of Punjab, showed cross-hybridization in DNA dot-blot using cloned SLCMV and CLCuMB DNA, indicating the presence of one or more begomoviruses related to SLCMV and the betasatellite, CLCuMB. The begomovirus and betasatellite could be mechanically transmitted to Nicotiana benthamiana. Whitefly transmission of the resident begomovirus could also be demonstrated on mentha. The evidence indicates the association of ToLCKV and CLCuMB, a hitherto new combination of a begomovirus and a betasatellite associated with a leaf deformity disease in mentha in Punjab.

Two Novel DNAs That Enhance Symptoms and Overcome CMD2 Resistance to Cassava Mosaic Disease

“…In support of this idea, the direct repeats (GCTGCA) at the ends of genomic sequence related to SEGS-1 coincide with the junction sequence of the SEGS-1 episome. A sequence related to SEGS-1 (98% identity) was cloned using betasatellite primers from begomovirus-infected Mentha plants showing severe leaf deformation ( 61 ), suggesting that an SEGS-1 episome underwent lateral transfer, possibly in association with geminivirus infection. However, the failure to detect SEGS-1 episomes in virions is not consistent with this possibility, and the source of SEGS-1 in Mentha remains elusive.…”

“…These differences suggest that SEGS-1 and SEGS-2 target distinct processes involved in geminivirus infection or host defense. However, the enhancement of CMB infection by SEGS-2 in N. benthamiana and the presence of an SEGS-1-related sequence in infected Mentha plants showing severe leaf deformation ( 61 ) suggest that both have the potential to alter infection in diverse plant species.…”