Dry matter partitioning and plant growth response of transgenic Bt and non Bt cotton

Field experiment was conducted at Parbhani during kharif season of 2004 and 2005 to study the effects of nutrient and pest management on growth and development of Bt cotton (Gossypium hirsutum L) with special reference to dry matter production and its partitioning towards sinks. The Bt cotton recorded significantly less dry matter/plant than non Bt (NBt) cotton hybrids during both years. Green boll was found to be the major sink for photosynthate in Bt cotton at 120 days after sowing and it was to the extent of 37.28 and 51.68 per cent of total dry matter during first and second season crop respectively. It was observed that MECH 184 Bt produced significantly higher seed cotton yield (1658 Kg/ha) over it NBt counterpart (1071 Kg/h). The performance of MECH 184 Bt was exceedingly superior and it produced 54.20 and 52.77% more seed cotton yield than NBt counterparts MECH 184 and PHH 316, respectively. Moreover, the transgenic MECH 184 Bt cotton hybrid recorded significantly higher harvest index, matured earlier as compared to both MECH 184 and PHH 316 NBt cotton. The MECH 184 Bt cotton hybrid was found quite effective in reducing the insecticidal spray to the extent of 60% over its NBt counterpart. The insecticidal pest management in cotton was found promising in managing cotton pest complex and finally realized significantly higher seed cotton yield than biopesticidal pest management. The application of graded level of chemical fertilizer, i.e. 80, 40 and 40 kg per ha of N, P and K and 100, 50 and 50 kg per ha of NPK under rainfed condition were equally effective in enhancing growth and yield attributes. Moreover, the improvement in growth and yield attributes was significantly superior over application of FYM (10 t/ha). Thus, it was concluded that due to increased retention of bolls, the crop growth pattern and biomass partitioning has changed substantially in Bt cotton.