Cotton Leaf Curl Disease is among the most destroying viral catastrophe that causes tremendous loss to cotton yield particularly in Pakistan during the past 20 years. Seven different types of Begomoviruses have been discovered related with the disease. It was first revealed in Nigeria (1912) on Gossypium Peruvianum and Gossypium Vitifolia, Sudan (1924), Tanzania (1926), Philippine (1959) however in Pakistan CLCuD was first recorded in the 1967 in Multan region on scattered hirsutum plants. Cotton Leaf Curl Disease (CLCuD) contaminated plants may show many different symptoms relying upon the extent of this disease, normally the symptoms were thickening and yellowing of small veins on the lower surface of young leaves. Under serious attack of the infection, leaves twist or curl downward or upward. The plant growth stunted because of decrease of inter-nodal distance. The severity of disease also produces a cup shape outgrowth on the lower side of the curled leaves that is known as Enation. The significant vector for spreading of this sickness is white fly. So by controlling white fly, this disease can be controlled in real terms.
The wild species of Gossypium are potential sources of resistance to biotic (insect and diseases) and abiotic (salinity, cold, drought, heat) stresses. The species, G. thurberri, G. anomalum, G. raimondii, G. armourianum and G. tomentosum are the best sources for resistance of insect pests including whitefly which is the main vector for the inoculation of CLCuD. These wild species can be used to transfer this resistance character in to our cultivated cotton varieties. Either biotechnological methods or conventional methods of breeding can be used to make varieties with greater resistance. The effect of CLCUV can also be minimized by applying some agronomic practices and non-biotechnological methods. Cotton leaf curl disease spread from the primary inoculum that is available in the off season as weeds and different hosts.
The CLCuD can be managed by control of vector whitefly and eradication of weeds that contribute as a host of cotton leaf curl virus. Different agronomic practices like sowing time and use of supplements (Nitrogen and Potassium) can minimize the disease impact. Appropriate sowing time ideally mid-April to mid-May brings about reduction of disease impact. In the case of planting later than 15th of June, the recommended plant to plant spacing is 15 cm in order to manage CLCuD. The influence of Potassium (K) application on disease through specific metabolic functions alters the relationship of host-parasite interaction. An investigation indicated that by increased use of Potassium up to 250kg/ha brings about the reduction of this viral attack from 12 to 38%. Also the seed cotton yield increased up to 37% by increased application as compared to Zero-K. All the previously mentioned measures of controlling CLCuD can be implemented relying on the conditions. Development of resistance varieties alongside Agronomic, fertilizer, insecticidal control and biotechnological techniques can be utilized alone and in combination to control this extreme disease impact which is yet a challenge even after twenty years of broad research.
This article is collectively authored by Bilal Ahmed1, Muhammad Abu Bakar2 and Hafiz Muhammad Bukhsh3-1Department of Plant Breeding Genetics, University of Agriculture, Faisalabad, 2World Wide Fund Rahim Yar Khan, 3 World Wide Fund Rahim Yar Khan.