Lessons learned and future strategies for combating cotton leaf curl disease

Structural Genomics

oral

Rahman, Mehboob-ur-; Abas, Ammad; Abbas, Hasan; Zafar, Yusuf

Rahman, Mehboob-ur-

Rahman, Mehboob-ur-

Cotton leaf curl disease, a disease of viral origin transmitted by a vector (whitefly, Bemisia tabaci), was first reported in 1912 in Nigeria, and spread to many other major cotton-growing countries like Egypt, Sudan, India and Pakistan, and recently in China. Pakistan played a substantial role in understanding the multiple virus components, and also developed cotton varieties showing resistance and or tolerance to cotton leaf curl disease. Also, various fingerprinting assays like SSRs were used for understanding about the extent of genetic diversity within the cotton germplasm—appeared to be narrow, and also identified few potential markers associated with the old strain of cotton leaf curl virus. Efforts for the identification of DNA markers associated with tolerance to the Burewala strains are going on through an umbrella Pak-US “Cotton Germplasm Enhancement Project (managed by ICARDA, Paksitan)”. In Pakistani cotton germplasm/genotypes, narrow genetic diversity (estimated among 85 cotton genotypes) alone is not a decisive factor for the large-scale infection of the disease. Complete elimination of cultivation of locally evolved G. arboreum genotypes coupled with intensification in agriculture during the last three decades provided the congenial condition for the occurrence of the epidemic. The genetics of resistance to the disease is not simple at intraspecific level, however, could be categorized in to three groups at interspecific level. Experimentation on pyramiding of various sources of resistance for developing a single super genotype did yield any kind of enhanced resistance in the cotton genotypes. New technologies, such as exploiting pathogen derived resistance, still are not successful for improving resistance in the transgenic cotton. Our study demonstrated the need for bringing new wild genetic sources for fueling the cultivated cotton species, bridging through genomic efforts, would pave the way for developing resistant cultivars – a long term strategy to combat the emergence of new strains of virus in future.