Genetics and Genomics of Cotton Leaf Curl Disease, Its Viral Causal Agents and Whitefly Vector: A Way Forward to Sustain Cotton Fiber Security

Abstract

Cotton leaf curl disease (CLCuD) after its first epidemic in 1912 in Nigeria, has spread to different cotton growing countries including United States, Pakistan, India, and China. The disease is of viral origin—transmitted by the whitefly Bemisia tabaci, which is difficult to control because of the prevalence of multiple virulent viral strains or related species. The problem is further complicated as the CLCuD causing virus complex has a higher recombination rate. The availability of alternate host crops like tomato, okra, etc., and practicing mixed type farming system have further exaggerated the situation by adding synergy to the evolution of new viral strains and vectors. Efforts to control this disease using host plant resistance remained successful using two gene based-resistance that was broken by the evolution of new resistance breaking strain called Burewala virus. Development of transgenic cotton using both pathogen and non-pathogenic derived approaches are in progress. In future, screening for new forms of host resistance, use of DNA markers for the rapid incorporation of resistance into adapted cultivars overlaid with transgenics and using genome editing by CRISPR/Cas system would be instrumental in adding multiple layers of defense to control the disease—thus cotton fiber production will be sustained.

The Tale of Cotton Plant: From Wild Type to Domestication, Leading to Its Improvement by Genetic Transformation

“…Crossing (test cross and back cross) is considered as an effective way to get a plant of interest. Mac7 is identified as resistant cultivar against CLCuD Burewala strain and it was released as a germplasm line by the USDA [81]. It is also an effective measurement for development of plant for better traits.…”

Population structure, linkage disequilibrium and association mapping for cotton leaf curl disease incidence in cotton (Gossypium hirsutum L.)

“…CLCuD is the major cause of huge loss to world cotton production, especially in Pakistan, India, and China [37]. In Pakistan, there is considerable reduction in cotton crop area due to non-availability of CLCuD resistant elite cotton cultivars and cotton farmers were forced to cultivate alternative crops for sustainable earnings from their agricultural lands [3].…”

Introductory Chapter: Updates on Achieving Sustainable Cotton Production

“…Other than releasing cotton varieties expressing high yield potential by growing in high input environments-progressive farmers can afford, there is a need to open R&D fronts for developing cotton varieties which can withstand the impact of changing climate and produce sustainable yields in low input or in optimum input environments [11]. Deployment of high-tech genomic tools in breeding is one of the approaches to initiate breeding by design aiming at the development of resilient cotton cultivars [12,13].…”

“…For addressing this issue, collaborative and coordinated research programs including sharing of cotton germplasm for screening in the hotspot regions would help in tackling such issues. USDA screened >5000 accessions of cotton in hotspot regions of Pakistan, and more than a dozen of asymptomatic cotton genotypes were identified [11,13,19]. This information and genetic material are useful for Pakistan and also for the whole cotton-growing community as the threat is spreading to other countries (reported in India and China).…”