Baig et al., Biological Forum – An International Journal 13(4): 1129-1133(2021) 1129 ISSN No. (Print): 0975-1130 ISSN No. (Online): 2249-3239 Evaluation of Newly Developed Bt Cotton (Cry 1Ac) Genotypes for Seed Cotton Yield under Ultra High Density Planting System in Cotton (Gossypium hirsutum L.) Baig K.S. * , Gaikwad A.R., Chinchane V.N., Pandagale A.D. and Surewad S.V. Cotton Research Station, Nanded (VNMKV, Parbhani), Vasantrao Naik Marathawada Krishi Vidyapeeth, Parbhani, (Maharashtra), India. (Corresponding author: Baig K.S.*) (Received 03 October 2021, Accepted 24 November, 2021) (Published by Research Trend, Website: www.researchtrend.net) ABSTRACT: Cotton being cash crop of rainfed growers have low productivity urging genotype wise change in plant density in particular. Bt cotton varieties having ‘Cry1Ac’ gene will reduce the cost of production of resource poor farmers. Hence, a field experiment was conducted to evaluate newly developed Bt cotton (BG I) genotypes of Gossypium hirsutum under Ultra High Density Planting System during kharif season 2019-20 at Cotton Research Station, Nanded. The experiment was laid out in FRBD design consisting of two factors of plant densities viz. 45 × 10 cm 2 (2.22 lakh plants/ha), 45 × 15 cm 2 (1.48 lakh plants/ha) and 45 × 22.5 cm 2 (0.98 lakh plants/ha) in main plots and seven genotypes of Gossypium hirsutum cotton in sub plots with three replications. Density 0.98 lakh/ha (spacing 45 × 22.5 cm) out yielded significantly over density 2.22 lakh/ha (spacing 45 × 10 cm) for seed cotton yield. Genotype NH 1901 Bt (1458 kg/ha) and NH 1904 Bt (1458 kg/ha) were found significant over checks, NH 615 (1286 kg/ha) and Suraj (1076 kg/ha) for seed cotton yield. Genotypes NH 1901 Bt, NH 1902 Bt and NH 1904 Bt performed better under spacing 45 × 22.5 cm (0.98 lakh/ha), genotypes NH 1903 Bt, NH 1905 Bt and NH 615 performed better under 45 × 15 cm (1.48 lakh/ha) whereas spacing 45 × 10 (2.22 lakh/ha) was found significant for Suraj. Keywords: Ultra high density planting, seed cotton yield, Bt cotton genotype, spacing. INTRODUCTION Cotton, the king of fibres, occupies a pre-eminent position as a commercial crop in India. Cotton also known as ‘white gold’ as it is preferred by farmers as a cash crop. It is grown commercially in the temperate and tropical regions of more than 70 countries. India is perhaps the first country to make use of cotton. Cotton enjoys a pre-eminent status among all cash crops in the country. Specific areas of production include countries such as China, USA, India, Pakistan, Uzbekistan, Turkey, Australia, Greece, Brazil, Egypt etc. Among the various factors responsible for low yield of cotton crop in the country, low plant population, use of low potential varieties and suitable agronomic requirement of genotypes are of primary importance. Various techniques like maintaining suitable plant density, use of optimum dose of fertilizers, growth regulators, etc. are being used to overcome these constraints in cotton production. Moreover, the availability of labour for clean picking is also a serious constraint. At present in India, entire cotton is picked manually which is labour intensive and is becoming expensive day by day. On the contrary, about 30 per cent of world cotton production in Australia, Israel and USA is machine picked. Under these circumstances, compact cotton genotypes are ideally suited. They offer great scope for reducing not only row width, but also necessitates spacing between the plants in a row. Ultra narrow row (UNR) cotton production is considered as a potential strategy for reducing production costs by shortening the growing season. Compact genotypes provide the scope for increasing plant population per unit area by virtue of their shorter stature. It provides scope for double cropping and mechanical harvesting. These compact types have the added advantage of requiring few pickings only. Therefore, reduces the labour cost as well as seed cost as farmers can use the varietal seeds during next sowing for two to three seasons. Cultivation of hirsutum cotton varieties may be an option to high seed cost which further can reduce production cost with Biological Forum – An International Journal 13(4): 1129-1133(2021)