2. Evaluation of Adaptability and Yielding Ability of BT Cotton Varieties under Arid Region of Bahawalpur.

3. Introduction Cotton: Cotton being a non ‐ food cash crop contributes significantly in foreign exchange earning. Cotton accounts for 8.6 percent of the value added in agriculture and about 1.8 percent to GDP. In the year 2009-10 total production was 12698 thousands bales. Crop was sown on the area of 3106 thousand hectares (GOP,2010). Conti…..

4. Bt Cotton Bt cotton is developed by Genetic Engineering techniques (Biotechnology). Bt cotton contains Genes from bacteria Bacillus thuringiensis (Bt.) Eight countries commercially grew Bt cotton (USA, Australia, China, India etc.). Protein of this gene is deadly for the Chewing Pests. There may be 30% increase in cotton yield due to resistance against chewing pest and hence additional income to poor farmers. Conti…..

5. The Bt. cotton varieties including Bt hybrids currently grown in Pakistan are from exotic sources which are given to farmers for cultivation without validating these performance and without providing production technologies based on research conducted according to local environment. (Economic survey of Pakistan 2009-2010) All the Bt. cotton varieties grown are susceptible to Cotton Leaf Curl Virus (CLCV) and sucking pest i.e. mealy bug, Jassid and White fly which are a major threat to cotton crop.

6. Review of Literature Among the comparative growth and yield performance of four cotton varieties, Bt-121 had maximum value for seed cotton weight per boll and maturity percentage and produced 26% higher seed cotton yield than all other cultivars (Aziz et al). Seed cotton is mainly a function of boll number per plant. The significant difference in boll number per plant among different cotton cultivars observed might be due to inherent capacity. and inability of some genotypes to provide photosynthates to large number of bolls (Nisar et al., 2007 and Tahira at et al 2007). Conti…..

7. Maximum seed cotton yield was produced when cotton was sown from 15 th April to 1 st May in Nawabshah (Arain et al.,2002). The yield decreased significantly in mid and end June sowing dates (Muhammad et al.,2002). Cotton yield is affected by different sowing dates under the various climatic condition (Ali et al.,2004). Conti…..

8. Short season cultivars produced more dry matter than long season cultivars due to greater radiation use efficiency and light interception. It is only due to earlier canopy development (Bang and Milory.,2000). Early sowing (20 th May) produced 10% more flowers,23% more open bolls, 18% more seed cotton yield and 13% more ginning out turn (GOT) than the late sowing (10 th June) (Arshad.,2005).

9. Objectives To study the impact of sowing time on phenology and growth of Bt cotton cultivars. To study the yield performance of Bt cotton sown at various sowing dates.

10. Materials and Methods The experiment was conducted in 2011 at Regional Agriculture Research Institute, Bahawalpur. Design: RCBD with split plot arrangement. plot size: 3m ×7m R×R: 75cm P×P: 22cm Seed rate: 25kg ha -1 Other cultural practices were kept normal.

11. Materials and Methods Treatments: Factor A: Sowing dates SD 1 =15 February SD 2 =15March SD 3 =15April SD 4 =15May SD 5 =15June Factor B: BT Varieties V 1 =886 V 2 =121 V 3 =3701 V 4 =703

12. Crop growth data Leaf Area Index LAI= Leaf area / Land area Crop Growth Rate CGR=W 2 -W 1 / T 2 -T 1 Leaf Area Duration LAD=(LAI 1 +LAI 2 )×(T 2 -T 1 )/2 Net Assimilation Rate NAR=TDM / LAD

13. Yield and yield component No. of plants per plot. Plant height(cm). Total number of bolls per plant. Number of un opened boll per plant. Number of opened boll per plant. Average boll weight. Seed cotton yield Kg per hactere. Ginning out turn. Harvest index.

14. Number of plants m -2 at harvest Total number of plants in each plot was counted and it was divided to total plot area to get plants m -2.

15. Plant height(cm) Plant height was determined at maturity with the help of a meter rod. The heights of three randomly selected plants plot -1 was measured from soil surface to the tip of the plant and then averaged.

16. No. of monopodial branches plant -1 Number of monopodial branches plant -1 were counted from 5 randomly selected plants from each plot and then averaged in each treatment.

17. Number of sympodial branches plant -1 Number of sympodial branches per plant were also counted from 5 randomly selected plants from each plot and average number of sympodial branches was calculated.

18. Number of boll plant -1 For number of bolls per plant,5 plants were selected randomly from each plot and then averaged.

19. Number of un-opened boll plant -1 For un-opened bolls, 5 selected plants were examined and un- opened bolls were calculated and then averaged.

20. Number of opened bolls plant -1 The selected 5 plants were picked separately, counted the number of opened bolls plant -1,and then the average was calculated.

21. Average boll weight(g) Average boll weight was obtained by dividing the total yield of seed cotton per plant by the total number of bolls picked from that particular plant. Then the average boll weight plant -1 was computed for each plot.

22. 100-cotton-seed weight(g) 100-cotton seed were selected randomly from each plot and weighed.

23. Seed cotton yield(kg ha -1 ) Crop was picked three times at present. Seed cotton weight plot -1 was weighed in addition.

24. References Ahsan, A., N. Akhtar, M. Afzal, M. Ashraf, A. Tanveer, R. Ahmad and M. Ehsan. 2011. Comparative performance of Bt cotton with some elite conventional cotton cultivars under arid to semi-arid Conditions. African J. of Agricultural Research. 5(6): 1600-1606. Ali. M., Ghulam mohy-ud-din, M. Anjam ali, S. Bashir and L. ali 2004. Response of cotton genotypes to time of sowing. Asian J. of Plant. Sci., 1 (5): 538-539. Arain, M.H., M.J.Baloach, C.K. Kalwar, and A.A. Memon. 2002. performance of new developed cotton strains under different sowing dates. Pak. J.Bio. Sci., supplementary Issue No. 1.

25. Arshad, M. 2006. Modeling the growth, development and radiation use efficiency of four cotton, cultivars with two sowing dates under the climatic conditions of Faisalabad. Msc. thesis Dept. of Agron. Univ. of Agri. Faisalabad. Bang, M.P., and S.P. Milory. 2000. Timing of crop maturity in cotton. Impact of dry matter production and partioning. CSIRO. Plant Industery, Australian Cotton cooperation Reseach center, Fid. Crop Res., 68(1): 143-155. Economic Survey of Pakistan. 2009-10. Ministry of Finance, Government of Pakistan.