Analysis of transgene(s) (psy+crtI) inheritance and its stability over generations in the genetic background of indica rice cultivar Swarna

Abstract

Rice the major staple food crop which feeds more than half of the world’s population but, lacks pathway to synthesize and accumulate provitamin A in endosperm therefore rice eaters particularly children, and pregnant women suffer due to vitamin A deficiency. The pathway for provitamin A synthesis in rice endosperm has been engineered and transgenic rice lines have yellow endosperm, called ‘Golden Rice’. The present study aimed at studying the inheritance of transgene(s) in six transgenic events of ‘Golden Rice’ and transfer of provitamin A trait from transgenic lines to a widely grown mega rice variety Swarna. The events E1, R1 and W1 showed normal Mendelian inheritance in F2, BC1F1 and BC1F2 generations. The event W1 was studied in BC1F3 as well and showed normal Mendelian inheritance of 3:1. The inheritance pattern in L1 event in BC1F1 and BC1F2 showed normal Mendelian inheritance following expected ratio 1:1 and 3:1 respectively. The two events G1 and T1 showed distorted segregation in BC1F2 and BC2F2 respectively in Swarna genetic background. In G1 event, transgene inheritance showed segregation distortion in BC1F2 in favour of transgene negative plants. In T1 event, inheritance followed expected Mendelian segregation in BC1F1, BC2F1 and BC2F2, generations. However, when tested against co-dominant inheritance 1:2:1 pattern in BC2F2, segregation distortion was observed with less than the expected transgene homozygotes. While against 3:1 ratio, it showed the expected segregation pattern in BC2F2 generation. Segregation distortion probably due to differential transmission of transgene positive/negative gametes through either/both parents which needs further study.