Abstract
Cotton leaf curl virus disease (CLCuD) is an important constraint to cotton production. The resistance of G. arboreum to this devastating disease is well documented. In the present investigation, we explored the possibility of transferring genes for resistance to CLCuD from G. arboreum (2n = 26) cv 15-Mollisoni into G. hirsutum (2n = 52) cv CRSM-38 through conventional breeding. We investigated the cytology of the BC1 to BC3 progenies of direct and reciprocal crosses of G. arboreum and G. hirsutum and evaluated their resistance to CLCuD. The F1 progenies were completely resistant to this disease, while a decrease in resistance was observed in all backcross generations. As backcrossing progressed, the disease incidence increased in BC1 (1.7–2.0%), BC2 (1.8–4.0%), and BC3 (4.2–7.0%). However, the disease incidence was much lower than that of the check variety CIM-496, with a CLCuD incidence of 96%. Additionally, the disease incidence percentage was lower in the direct cross 2(G. arboreum)×G. hirsutum than in that of G. hirsutum×G. arboreum. Phenotypic resemblance of BC1 ∼BC3 progenies to G. arboreum confirmed the success of cross between the two species. Cytological studies of CLCuD-resistant plants revealed that the frequency of univalents and multivalents was high in BC1, with sterile or partially fertile plants, but low in BC2 (in both combinations), with shy bearing plants. In BC3, most of the plants exhibited normal bearing ability due to the high frequency of chromosome associations (bivalents). The assessment of CLCuD through grafting showed that the BC1 to BC3 progenies were highly resistant to this disease. Thus, this study successfully demonstrates the possibility of introgressing CLCuD resistance genes from G. arboreum to G. hirsutum.
Highlights
Cotton production is biotically constrained by various diseases, which lead to yield instability and reduced seed quality
There are seven such virus species, all belonging to the Begomovirus genus, and DNA-b satellites are associated with Cotton leaf curl disease (CLCuD) in these regions [5,6,7,8]
The F1 CLCuDresistant progeny involving these parents, which was developed by Ahmad et al [44], comprising direct cross [2(G. arboreum)6G. hirsutum] and its reciprocal cross (G. hirsutum6G. arboreum), was utilized to directly backcross with G. hirsutum
Summary
Cotton production is biotically constrained by various diseases, which lead to yield instability and reduced seed quality. CLCuD is caused by a pathogen complex of a virus and a DNA beta satellite (DNAb) molecule [4]. CLCuD was first recorded in 1967 in the Multan district, Pakistan, on scattered Gossypium hirsutum plants [9,10,11], and it has spread rapidly to all cotton growing areas of Pakistan and throughout the Indian subcontinent. Two epidemics of this disease have been observed during the past three decades due to a loss of host-plant resistance in existing cotton varieties [12,13]
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