INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY ISSN Print: 1560–8530; ISSN Online: 1814–9596 17–0232/2017/19–5–1149–1155 DOI: 10.17957/IJAB/15.0403 http://www.fspublishers.org Full Length Article To cite this paper: Hussain, F., R. Ahmad, A. Jabbar and G. Murtaza, 2017. Infestation of cotton leaf curl virus in two Bt cotton cultivars under different sowing methods and plant spacing systems. Int. J. Agric. Biol., 19: 1149‒1155 Infestation of Cotton Leaf Curl Virus in two Bt Cotton Cultivars under Different Sowing Methods and Plant Spacing Systems Fida Hussain 1 , Riaz Ahmad 1 , Abdul Jabbar 1 and Ghulam Murtaza 2 ¹Department of Agronomy, University of Agriculture, Faisalabad-38040, Pakistan 2 Institute of Soil and Environmental sciences, University of Agriculture Faisalabad-38040, Pakistan * For Correspondence: fida_51214@yahoo.com Abstract Cotton production is integral to economic development of Pakistan. However, cotton leaf curl virus (CLCuV) infestation affects the growth and productivity of cotton, and has been causing serious yield losses for the last two decades. Transgenic Bt varieties have resistance against CLCuV and can produce the high yield. This experiment was conducted to evaluate the effect of different sowing methods (flat sowing and bed sowing) and plant spacing (22.5 and 30 cm) on CLCuV infestation, whitefly population and growth and yield of two Bt cultivars viz. AA-703 and FH-113 during 2010 and again in 2011. The experiment was laid out in a split-split plot design with three replications. The average of the two years’ results showed that there was 78% CLCuV incidence in 30 cm spacing as compared to 85% incidence in 22.5 cm spacing. However, cotton crop grown at narrow spacing with higher plant population (44444 plants ha -1 ) produced 17% higher seed cotton yield than wider spacing with lower plant population (33333 plants ha -1 ). The sowing methods did not significantly affect the disease incidence nonetheless the seed cotton yield of bed sown crop was 21% higher than the flat sown cotton crop. Cultivar AA-703 produced 14% higher seed cotton yield than cultivar FH-113 due to low disease infestation, higher boll weight and more number of bolls. The net profit (Rs. 102577 ha -1 ) and benefit cost ratio (1.65) indicated that cotton cultivar AA-703 sown on beds at plant spacing of 22.5 cm could produce the maximum seed cotton yield. © 2017 Friends Science Publishers Keywords: Cotton leaf curl virus; Number of enations; Number of whitefly; Plant spacing; Sowing methods Introduction Cotton (Gossypium hirsutum L.) is the main cash crop of Pakistan which contributes substantially to the national economy. However, several problems, particularly the cotton leaf curl virus (CLCuV) is severe threat to the growth and productivity of cotton crop (Farooq et al., 2014). In Punjab, the highest losses due to Begomovirus were observed during 1992 (Iqbal et al., 1997). During the last decade, about 60-90% of cotton fields in Pakistan were infested with CLCuV (Iqbal and Khan, 2010); moreover, CLCuV caused the cumulative losses of $1.2 billion in Punjab (Hussain et al., 2012). From 1988 to 2002, more than 7.7 million bales of cotton were lost due to CLCuV attack (Akhtar et al., 2005). The major symptoms of CLCuV are leaf-curling either towards lower side or upper side, swallowing of midribs and veins, color darkening, stunted growth and occasionally the development of tiny leaf structure “enation” on the lower side of leaf (Briddon and Markham, 2001; Qazi et al., 2007). Different management practices and development of resistant or tolerant cultivars reduces the CLCuV induced yield losses (Akhtar et al., 2004). For example, the use of resistant cultivars, control of whitefly, eradication of weeds and proper nutrient management might be the viable options to reduce the CLCuV attack in cotton (Narula et al., 1999). Different plant spacings also affect the CLCuV incidence; its infestation is increased at plant spacing of 45 cm (Singh et al., 2012). In this context, Iqbal and Khan (2010) reported that increased plant spacing for early sown cotton and decreased plant spacing under late-sown conditions was effective for the management of CLCuV. In another study, the number of whitefly was decreased from 4 to 3 per leaf with increase in plant spacing from 23 to 30 cm (Arif et al., 2006). In a study, cotton grown in plant spacing of 23 cm produced better yield than 30 and 38 cm (Khan et al., 2005). The changing temperature and precipitation patterns cause shift in some pests (white fly) from one population to other population thus affecting the epidemiology of CLCuV disease (Farooq et al., 2014). The low temperature during growing season and wind speed have adverse effect, while sunshine has a positive impact on the whitefly population (Khan et al., 2010). On the other hand, the morphological characteristics of the host plants like hair density and hair length on midrib vein and lamina enhance the population of