Marker-assisted breeding for introgression of opaque-2 allele into elite maize inbred line BML-7

Improvement of quality protein maize (QPM) along with high content of lysine and tryptophan had foremost importance in maize breeding program. The efficient and easiest way of developing QPM hybrids was by backcross breeding in marker aided selection. Hence, the present investigation aimed at conversion of elite maize inbred line BML-7 into QPM line. CML-186 was identified to be a donor variety as it revealed high-quality polymorphism with BML-7 for opaque-2 gene specific marker umc1066. Non-QPM inbred line BML-7 was crossed with QPM donor CML-186 and produced F₁ followed by the development of BC₁F₁ and BC₂F₁ population. Foreground selection was carried out with umc1066 in F₁, and selected plants were used for BC₁F₁ and BC₂F₁ populations. Two hundred plants were screened in both BC₁F₁ and BC₂F₁ population with umc1066 for foreground selection amino acid modifiers. Foreground selected plants for both opaque-2 and amino acid modifiers were screened for background selection for BML-7 genome. Recurrent parent genome (RPG) was calculated for BC₂F₁ population plants. Two plants have shown with RPG 90-93% in two generation with back cross population. Two BC₂F₂ populations resulted from marker recognized BC₂F₁ individuals subjected toward foreground selection followed by tryptophan estimation. The tryptophan and lysine concentration was improved in all the plants. BC₂F₂ lines developed from hard endosperm kernels were selfed for BC₂F₂ lines and finest line was selected to illustrate the QPM version of BML-7, with 0.97% of tryptophan and 4.04% of lysine concentration in protein. Therefore, the QPM version of BML-7 line can be used for the development of single cross hybrid QPM maize version.