Figure 1.
Symptoms of cotton leaf curl disease affected cotton in Sindh, Pakistan.
A field of cotton in Sindh showing near complete infection (A). Close up of a severely infected cotton plant showing leaf curling and stunting (B). Underside of a cotton leaf from an infected plant showing vein swelling, enations and leaf-like growths (C).
Figure 2.
The begomovirus affecting cotton in Sindh likely originates from Egypt.
Neigbour-joining phylogenetic dendrogram based upon an alignment of all complete genome nucleotide sequences of Cotton leaf curl Gezira virus (CLCuGV) available in the databases and the two available sequences of Hollyhock leaf crumple virus (the virus species most closely related to CLCuGV) with the sequences isolated from Pakistan. In each case the database accession number is given. The numbers at nodes represent percentage bootstrap confidence scores (1000 replicates). The alignment was arbitrarily rooted on outgroup, the sequence of Tomato pseudo curly top virus (TPCTV), a distantly related geminivirus. The plant species from which viruses were isolated and their geographical origins are indicated; Burkina Faso (BFA). Additionally, the viruses originating from north Africa (N) and from Africa south of the Sahara (S) are indicated.
Table 1.
Percentage nucleotide sequence identities of begomovirus clones isolated from Sindh with Malvaceae-infecting viruses from Africa.
Figure 3.
The Chilli leaf curl betasatellite detected in cotton is distinct from the majority of ChLCB detected in other plant species.
Neigbour-joining phylogenetic dendrogram based upon an alignment of all full-length nucleotide sequences of ChLCuB available in databases with that isolated from cotton in Sindh (NGVB). In each case the database accession number is given. The numbers at nodes represent percentage bootstrap confidence scores (1000 replicates). The alignment was arbitrarily rooted on outgroup, the sequence of Tomato yellow leaf curl Thailand alphasatellite (TYLCTHA), an unrelated molecule of a similar size. The plant species from which betasatellites were isolated and their geographical origins are indicated. The northern (N) and southern (S) “strains” of ChLCB identified by Hussain et al. [34] are indicated.
Figure 4.
CLCuGV from Sindh replicates in the presence of both CLCuMB and ChLCB in Nicotiana benthamiana.
Southern blot analysis of DNA extracted from N. benthamiana probed for the presence of CLCuGV. Samples were extracted from a healthy plant (H) and plants inoculated with CLCuGV (GA), CLCuGV and CLCuMB (GA+CB) and CLCuGV and ChLCB (GA+ChB). The positions of open circular (oc), supercoiled (sc) and single stranded (ss) viral DNA forms are indicated. Approximately 10 µg of DNA was loaded in each well.
Figure 5.
Symptoms induced by virus and betasatellite clones in Nicotiana benthamiana.
Shown are pictures of plants (upper panels) and close-up views of the undersides of leaves using transmitted light (lower panels). Shown are a healthy plant (panels A and B) and plants inoculated with CLCuMV and CLCuMB (panels C and D), CLCuGV (panels E and F), CLCuGV and ChLCB (panels G and H), CLCuGV and CLCuMB (panels I and J) and CLCuGV, ChLCB and CLCuMB (panels K and L).
Table 2.
Infectivity of CLCuGV in the presence of betasatellites to Nicotiana benthamiana.
Figure 6.
Geographic distribution of CLCuGV and possible routes for spread from Africa to Asia.
Countries from which sequences of CLCuGV are available are coloured. Only a small amount of sequence of CLCuGV, forming part of a recombinant Tomato yellow leaf curl virus isolate, is available from Iran. The separate map of Pakistan shows Hala and Tando Adam, in Sindh province, from which the CLCuGV clones were obtained. The dashed lines show the possible overland (via the Middle East) and sea routes for the introduction of CLCuGV from North Africa to Pakistan.