Marker assisted introgression of opaque 2 allele for development of quality protein maize inbred lines in Sri Lanka

Maize (Zea mays L.) plays a very important role in human and animal nutrition in many developed and developing countries, worldwide. Tryptophan and Lysine content of maize, which is normally deficient, can be enhanced by transfer of the opaque 2 (O₂) gene along with several other modifier genes. Marker assisted breeding is the most effective and efficient way to develop quality protein maize (QPM). Crosses were made between recurrent parent CML 20 with different QPM donor parents CML 194, CML 193, CML 161, CML 164 and CML 171. The cross combination CML 20 / CML193 cross was selected for further study. According to the light table selection index, phenotypic selection for kernel modification was around 22-28% seeds out of BC1F2 population contributing to 2^nd and 3^rd categories were used to generate BC₂F₁ and BC₂F₂. Marker assisted selection was done using SSR marker phi 057 in BC₂F₂ generation. Out of 210 plants, 30 plants were identified with opaque 2 genes. Those thirty plants selected from BC₂F₂, were advanced to BC₂F₆ and then subjected to PCR amplification. The results, showed that 10 plants as homozygous for opaque 2 recessive allele. Selected 10 lines were further evaluated for yield and agronomic traits. Among the new QPM lines, MIQPM 6, and 9 showed a grain yield more than 4 t ha⁻¹, which was comparable with two CIMMYT QPM lines of CML 194 and CML 161. Except MIQPM 5, other tested lines showed acceptable grain yield about 3-4 t ha⁻¹. Shelling percentage of inbred lines varied from 70 -80%. Further, both newly developed MIQPM 6 and MIQPM 9 showed higher number of average tassel branches as eight compared to other lines. Thus, based on the yield, plant and ear characteristic’s the new QPM lines, MIQPM 6 and MIQPM 9 can be identified as promising lines possessing O₂O₂ genotypes. Extensive review of literature indicates that, this is the first report of a study in Sri Lanka where quality protein maize lines were developed using marker assisted breeding.