RESUMO
Cotton (Gossypium hirsutum L.), being a cash and fiber crop is of high significance in Pakistan. Numerous insect pests and viral diseases in Pakistan and around the world attack cotton crop. Genetically modified cotton (transgenic, resistant to lepidopteran insects), hereafter written as 'Bt-cotton' has been introduced in many regions of the world to combat bollworms. However, cultivars differ in their pest susceptibility, yield response and fiber quality traits. Nonetheless, recent studies have indicated that lepidopteran pests are evolving resistance against 'Bt-cotton'. Several 'Bt-cotton' cultivars have been developed in Pakistan in the past decade; however, limited is known about their pest susceptibility, seed-cotton yield and fiber quality traits. This two-year field study evaluated pest susceptibility, yield and fiber quality traits of thirteen newly developed 'Bt-cotton' cultivars in Pakistan. The cultivars differed in their susceptibility to sucking insects during both years of study. The cultivars 'FH-647', 'SLH-8', 'FH-Lalazar' and 'IUB-013' were more susceptible to jassid, whereas 'BS-52' exhibited higher susceptibility to whitefly during both years of study. Similarly, cultivars 'AGC-999' and 'MNH-992' proved highly susceptible to thrips during each study year. Although 'Bt-cotton' is resistant to bollworms, cultivars 'SLAH-8', 'VH-305' and 'BH-184' were susceptible to spotted bollworm, while 'SLAH-8', 'RH-647' and 'VH-305' were infested by American bollworm. The most susceptible cultivars to cotton leaf curl virus (CLCuV) attack were 'RH-647', 'IR-NIBGE-7' and 'VH-305'. The highest seed-cotton yield was recorded for 'FH-Lalazar' during both years of study. Similarly, the highest ginning out turn was recorded for cultivars 'BS-52', 'VH-305', 'RH-647', 'IUB' and 'AA-919'. The cultivar 'FH-Lalazar' exhibited low pest susceptibility and CLCuV infestation compared to the rest of cultivars. The highest and the lowest gross and net incomes and benefit:cost ratio were noted for 'FH-Lalazar' and 'RH-647, respectively. Keeping in view the low pest susceptibility and high seed-cotton yield, 'FH-Lalazar' could be recommended for higher yield and economic returns in Multan, Pakistan. Nonetheless, regional trials should be conducted for site-specific or region-specific recommendations.