Analysis of the resistance of Gossypium herbaceum to cotton leaf curl kokhran virus strain burewala and cotton leaf curl multan betasatellite

Gossypium herbaceum is resistant to cotton leaf curl disease but the nature of the resistance is poorly characterized. The reaction of G. herbaceum cv. Co Tiep Khac to infection by the Burewala strain of cotton leaf curl Kokhran virus (CLCuKoV-Bur) and cotton leaf curl Multan betasatellite (CLCuMuB) was characterized following whitefly-mediated inoculation and grafting. The CLCuKoV-Bur and CLCuMuB isolates used in this study had 97–100% nucleotide sequence identity with other isolates for which sequence information is accessible in databases. A high level of resistance was demonstrated in cv. Co Tiep Khac using 200 whiteflies per plant with no apparent disease symptoms even 90 days post-inoculation, and no detection of the virus-betasatellite complex, as shown by polymerase chain reaction (PCR) and rolling circle amplification (RCA)/PCR. Following graft-inoculation, mild foliar disease symptoms were observed in leaves proximal to the grafting sites of most of cv. Co Tiep Khac plants but not in apical leaves. The presence of CLCuKoV-Bur and CLCuMuB was detected by RCA/PCR but not by PCR and Southern hybridization in symptomless apical leaves of cv. Co Tiep Khac. In addition, less virus accumulated in cv. Co Tiep Khac compared to G. hirsutum cv. CIM-496. These results provided insights into the resistance of G. herbaceum cv. Co Tiep Khac to CLCuKoV-Bur and CLCuMuB.