Exploiting Recombinational Variability for Combining Ability to Improve Performance of Cotton Hybrids Based On UASD Cry 1Ac Transgenic Event No 78

Abstract

A study on creation of recombinational variability for combining ability along newlinewith incorporation of UASD 78 Bt gene for development of UASD 78 based improved newlineBt hybrids was conducted. Fifteen non Bt inbred lines were crossed with the four non Bt newlinetesters and one Bt tester UASD 78 to derive sixty non Bt and fifteen Bt hybrids, newlinerespectively during kharif, 2018 at UAS, Dharwad. The non Bt hybrids were ranked for newlinetheir per se performance and specific combining ability effects with respect to seed newlinecotton yield as a prime trait. Testers, DHIRS 15 and DHIRS 10 were selected as top newlineperforming non Bt testers which combined well with female parents of top five non Bt newlinehybrids for seed cotton yield. Top two UASD 78 based crosses DHIRS-67 × UASD 78 newlineand DHIRS-69 × UASD 78 for seed cotton yield were selected and used as benchmark newlinecrosses for comparison in the evaluation program of UASD 78 based improved Bt newlinehybrids during kharif, 2021. DHIRS 67 and DHIRS 69 (best combiners with Bt tester) newlinewere used as testers to cross with F3 recombinant Bt lines. The Bt tester UASD 78 and newlineits derived Bt hybrids and Bt checks were devoid of bollworm infestation The higher newlineinfestation of boll worm was observed in non Bt parental genotypes and hybrids. In newlineorder to exploit recombinational variability for combining ability in F3 generation along newlinewith incorporation of UASD 78 Bt gene, two top performing testers were crossed with newlineUASD 78 and the selection for combining ability was done in F3 generation. The newlineidentification of Bt positive plants in the two F2 populations viz., DHIRS 15 X UASD78 newlineand DHIRS 10 X UASD78 was performed through ELISA and the positive plants were newlineadvanced to F3 generation. Each of the F3 plant in both the populations was subjected to newlineELISA and zygosity testing to identify homozygous Bt plants. F3 Bt positive newlinehomozygous plants were tagged and used for crossing program as females with DHIRS- newline67 and DHIRS-69 as testers. During the evaluation program of UASD 78 based newlineimproved Bt hybrids, it was noticed that many of the F3 recombina