Genetic inheritance and resistance patterns of cotton leaf curl disease in upland cotton (Gossypium hirsutum L.)

Abstract

Cotton Leaf Curl Disease (CLCuD) has been causing substantial yield losses to the cotton crop in South Asia since its first epidemic in the early 1990s. Researchers face several problems while screening and breeding for CLCuD-resistant varieties due to absence of a reliable screening system, controversial inheritance data, limited genetic information about resistance sources, rapid evolution of viral strains, recombination between two virus groups, narrow plant genetic base, poor management practices, and reliance on small segregating populations. These factors have led to the failure of several cotton varieties that were initially released as resistant to Cotton Leaf Curl Virus (CLCuV). Hence, in the present study, a highly CLCuV-susceptible breeding line, Stoneville-47, tagged with a herbicide resistance marker gene (Round-Up-ready cotton), was crossed with newly discovered resistant accessions, Mac-07 and USG13_1087, to gain insights into the genetic inheritance patterns of resistance against CLCuD. Screening of breeding material against CLCuD resulted in thirty-each resistant (S-0), and susceptible plants (S1-S4) upon grafting with susceptible scions. The qPCR further validated the results, as no viral or betasatellite DNA was detected in resistant plants, unlike the susceptible ones. The Chi-square test of F₁ and F₂ generations revealed the presence of a single dominant gene or closely linked QTLs with involvement of certain modifying factors or suppressors, controlling CLCuD resistance. These findings suggest that backcross breeding is a suitable method to introduce disease resistance. The circumvention of the suppressors of resistance from the selected progenies can be achieved by raising larger plant populations. However, there is still a need to fine-map the resistance loci, identify key haplotypes, and validate them across diverse genetic backgrounds. Moreover, pyramiding these clusters maybe a straightforward approach to advancing the development of CLCuD-resistant cotton varieties.