Molecular diversity of Cotton leaf curl Gezira virus isolates and their satellite DNAs associated with okra leaf curl disease in Burkina Faso

Abstract

Okra leaf curl disease (OLCD) is a major constraint on okra (Abelmoschus esculentus) production and is widespread in Africa. Using a large number of samples representative of the major growing regions in Burkina Faso (BF), we show that the disease is associated with a monopartite begomovirus and satellite DNA complexes. Twenty-three complete genomic sequences of Cotton leaf curl Gezira virus (CLCuGV) isolates associated with OLCD, sharing 95 to 99% nucleotide identity, were cloned and sequenced. Six betasatellite and four alphasatellite (DNA-1) molecules were also characterized. The six isolates of betasatellite associated with CLCuGV isolates correspond to Cotton leaf curl Gezira betasatellite (CLCuGB) (88 to 98% nucleotide identity). One isolate of alphasatellite is a variant of Cotton leaf curl Gezira alphasatellite (CLCuGA) (89% nucleotide identity), whereas the three others isolates appear to correspond to a new species of alphasatellite (CLCuGA most similar sequence present 52 to 60% nucleotide identity), provisionally named Okra leaf curl Burkina Faso alphasatellite (OLCBFA). Recombination analysis of the viruses demonstrated the interspecies recombinant origin of all CLCuGV isolates, with parents being close to Hollyhock leaf crumple virus (AY036009) and Tomato leaf curl Diana virus (AM701765). Combined with the presence of satellites DNA, these results highlight the complexity of begomoviruses associated with OLCD.

Begomovirus disease complex: emerging threat to vegetable production systems of West and Central Africa

“…Beside the WATIBs, others such as Tomato yellow leaf curl Mali virus (TYLCMLV), Pepper yellow vein Mali virus (PepYVMLV), and Tomato leaf curl Mali virus (ToLCMLV) have been identified infecting tomato and pepper in the region [49][50][51][52][53][54][55][56][57] (Figure 3 arrows). Apart from the pepper and tomato-infecting begomoviruses, others such as Cotton leaf curl Gezira virus (CLCuGeV), Okra leaf curl Cameroon virus (OLCuCMV), and Okra yellow crinkle virus (OYCrV) have been identified infecting okra in West and Central Africa [49,52,56,58] (Figure 3). Putative recombination events were detected in begomovirus genomes for all three plant species studied, indicating that recombination is an important mechanism for their evolution.…”

“…The presence of DNA satellites in Africa was first shown in a survey for alphasatellites in samples from Asia and Africa, where they were found in different plants from both Egypt and Kenya [29] (Figure 4). Recently, one betasatellite, Cotton leaf curl Gezira betasatellite (CLCuGB), initially identified in the Nile basin, has been identified in West and Central Africa, associated with diseased okra and tomato [52,55,56,58,64] (Figure 5). Two new betasatellites, Ageratum leaf curl Cameroon betasatellite (ALCCMB) and Tomato leaf curl Togo betasatellite (ToLCTGB), have been identified infecting A.…”

“…Also, new types of alphasatellites, Ageratum leaf curl Cameroon alphasatellite (ALCCMA), Tomato leaf curl Cameroon alphasatellite (ToLCCMA), Okra leaf curl Mali alphasatellite (OLCuMLA), Okra leaf curl Burkina Faso alphasatellite (OLCuBFA), and Okra yellow crinkle alphasatellite (OYCrA), have been identified infecting A. conyzoides, okra, and tomato [50][51][52][53]56,58] in West Africa and the lone Central African state, Cameroon.…”

“…In addition to the conventional breeding, different transgenic approaches for achieving resistance or tolerance have been tested against begomoviruses infecting tomato and pepper [80][81][82] and this may be a way forward for obtaining durable resistance. In West and Central Africa, leaf curl disease is regarded as the most important biotic stress for okra, and there is a lack of viral resistance/tolerance [58,83]. However, okra has been regarded as a crop of minor importance, and the breeding efforts for okra in the region have been limited.…”

First report of an alphasatellite associated with Okra enation leaf curl virus

“…Okra or bhendi (Abelmoschus esculentus) is cultivated in tropical, subtropical, and warm temperate regions around the world. In Africa, the leaf curl diseases of okra are caused by a complex of begomoviruses consisting of Cotton leaf curl Gezira virus (CLCuGV), Okra yellow crinkle virus (OYCrV), and Hollyhock leaf crumple virus (HoLCrV), associated with Cotton leaf curl Gezira betasatellite (CLCuGB) and Cotton leaf curl Gezira alphasatellite (CLCuGA) [12]. In India, bhendi yellow vein mosaic disease is caused by Bhendi yellow vein mosaic virus associated with Bhendi yellow vein mosaic betasatellite [5].…”